1. Field of the Invention
The present invention relates to a bearing unit with sensor which detects the condition (including vibration, temperature, rotation speed and the like) of a bearing, a gear box, a spindle or the like incorporated in machinery (for example, a movable body such as a railway vehicle, a car or a guided vehicle, or a mechanical equipment such as a continuous-casting machine or a rolling mill), so that preventive maintenance can be achieved thereon.
In addition, the invention relates to a linear motion unit with sensor which detects the condition (including vibration, temperature, speed and the like) of a ball screw, a linear guide or the like incorporated in a lathe, a machining center, an injection molder, semiconductor manufacturing equipment or the like, so that preventive maintenance can be achieved thereon.
In addition, the invention relates to a wireless sensor attached to an industrial machine or a vehicle such as a car or a railway vehicle so as to transmit signals showing running condition by wireless; a bearing unit or a linear motion unit having the wireless sensor; a management apparatus for receiving the transmitted signals; and a monitoring system using these.
2. Description of the Related Art
Bearings for supporting rotating shafts as axles of vehicle such as cars and railway vehicles, or linear motion units such as ball screws or linear guides and bearings applied to industrial machines such as processing machines or assembling machines may produce vibration (that is, a change of acceleration) due to motion or heat due to friction. Such vibration or temperature does not only affect the lives of the bearings or the linear motion units but also takes part in the accuracy of the industrial machines, the safety of the vehicles, and soon. It is therefore desired to measure the vibration and the temperature appropriately and monitor whether they are in the rated condition. In addition, the rotation speed of bearings is often monitored constantly or reported with constant period because the rotation speed is important to grasp the running condition of apparatus or the like to which the bearings are attached.
Therefore, a general-purpose vibration sensor with an accelerometer, a general-purpose temperature sensor with a thermocouple or the like, a rotation sensor for detecting rotation speed, or the like, is attached to a housing of a bearing or a movable element of a linear motion unit that is a target. Such a sensor is connected to a measuring device through a cable so as to monitor vibration, temperature or the like.
In a related-art bearing unit, for example, as shown in FIG. 30, a temperature sensor 1104 and a rotation speed sensor 1106 are disposed separately and independently on a housing 1102 in which a rolling bearing 1100 has been set. The running condition (a change of temperature, a change of rotation speed, and so on) of the rolling bearing 1100 is detected by the temperature sensor 1104 and the rotation speed sensor 1106 .
Actually, the running condition of the rolling bearing 1100 includes not only the change of temperature, the change of rotation speed and the like but also impact vibration caused by an impact load from external force applied to the rolling bearing and abnormal vibration generated with abrasion, flaking, cracking or the like in the rolling bearing by way of example. When only the temperature sensor 1104 and the rotation speed sensor 1106 are provided as in the related-art bearing unit, it takes much time for temperature to be transmitted to a temperature measuring portion even if abnormality such as flaking occurs in the bearing. Further, when abnormality is slight, it is difficult to detect the abnormality in an early stage of the abnormality occurrence in which the bearing temperature does not increase so much.
In addition, when the temperature sensor 1104 and the rotation speed sensor 1106 are disposed separately and independently, it is necessary to secure a space therefor in the bearing unit. As a result, it is difficult to make the unit compact.
In addition, for example as a railway vehicle, signals of the temperature, the rotation speed and so on detected by the sensors 1104 and 1106 are transmitted to a control unit attached to the vehicle body side 10-20 m distant. Here, the rotation speed signal is a digital signal, and the temperature signal is an analog signal.
However, since the distance between the sensors 1104 and 1106 attached to the bearing unit and the control unit attached to the vehicle body side is 10-20 m, the signals of the rotation speed, the temperature and so on detected by the sensors 1104 and 1106 are easily distorted in their output waveforms or affected by noise due to the signal transmission. Particularly, the analog temperature signal is easily distorted in its output waveform or affected by noise, so as to cause the deterioration of measuring accuracy. In addition, when the temperature signal which is an analog signal is transmitted through a cable together with the rotation speed signal which is a digital signal, noise from the rotation speed signal may be superimposed on the analog temperature signal due to electromagnetic coupling (coupling based on electrostatic coupling, electromagnetic induction or electromagnetic waves).
Further, in such a related-art bearing unit with sensor, for example, as shown in FIG. 31, a vibration sensor 2104 and a temperature sensor 2106 are disposed on a housing 2102 in which a rolling bearing 2100 has been set. The vibration sensor 2104 and the temperature sensor 2106 are connected (wire-connected) to a monitor 2112 and a thermometer 2114 through cables 2108 and 2110 respectively. In this case, changes of condition in vibration and temperature appearing during the operation of the rolling bearing 2100 are detected by the vibration sensor 2104 and the temperature sensor 2106 respectively. The respective detection data is transmitted to the monitor 2112 and the thermometer 2114 through the cables 2108 and 2110 . Then, on the basis of the detection data transmitted to the monitor 2112 and the thermometer 2114 , a recorder 2116 performs recording/tabulating processing about the vibration condition and the temperature condition, while an alarm device 2118 performs monitoring/alarming processing about the change of vibration and the change of temperature.
In the related-art bearing unit with sensor, detection data from the vibration sensor 2104 and the temperature sensor 2106 is transmitted (wire-transmitted) through the cables 2108 and 2110 to the monitor 2112 , the thermometer 2114 and so on installed externally. In this case, when the number of the vibration sensors 2104 and the temperature sensors 2106 installed increases, the number of the cables 2108 and 2110 for external transmission has to be increased so much. As a result, the wiring processing of the cables 2108 and 2110 becomes troublesome while the number of parts for the wiring processing increases so that the manufacturing cost of the unit increases. Further, a space for wiring the cables 2108 and 2110 has to be secured in the unit. Thus, the unit increases so much in scale. In addition, when great vibration is given externally, the cables 2108 and 2110 may be disconnected so that signals cannot be transmitted/received.
In addition, when the bearing 2100 and the housing 2102 move as those in a railway vehicle or a car, the monitor 2112 or a measuring instrument 2116 has to be mounted on the movable body of the railway vehicle or the like.
Further, even in the case of a fixed machine, when the bearing housing 2102 is removed frequently, the cables 2108 and 2110 have to be removed whenever the bearing housing 2102 is removed.
Since there is a limit in the frequency band of vibration waves that can be detected by the vibration sensor 2104 disposed in the related-art bearing unit, the vibration waves cannot be detected sensitively when vibration waves generated in the unit are infinitesimal. For example, the related-art vibration sensor 2104 can detect deformation or failure of a member generating comparatively great vibration waves. However, since initial symptoms of abnormal vibration such as infinitesimal deformation, microcrack, abrasion, flaking or peeling appear before the deformation or failure of the member, and the vibration at this time has a form of infinitesimal elastic waves (high frequency vibration) with a high-frequency component of 10 kHz or higher, the vibration condition cannot be detected sensitively. As a result, even if abnormality begins to appear in the rolling bearing 2100 , the symptoms of the abnormality cannot be detected in an early stage. Thus, it is difficult to plan preventive maintenance for the unit.
Particularly, when the rolling bearing 2100 rotates at a low speed, vibration waves generated in the unit become infinitesimal. It is therefore difficult for the vibration sensor 2100 described above to detect the vibration waves accurately. As a result, it is impossible to grasp the abnormality of the bearing in an early stage. In addition, temperature increase in the unit rarely appears in the thermometer, either. Thus, it is impossible to grasp the symptoms of abnormality such as seizure in an early stage.
It is therefore a first object of the invention to provide a wireless sensor, a rolling bearing unit or a linear motion unit having no need of wiring for sending sensor signals; a management apparatus for receiving the signals; and a monitoring system used in combination of the wireless sensor, the rolling bearing unit or the linear motion unit with the management apparatus.
It is a second object of the invention to provide a bearing unit and a linear motion unit in which signals of rotation speed, temperature, vibration (acceleration) and so on can be transmitted to a control unit attached to the vehicle body side in the condition that there is negligible distortion in the output waveform or negligible influence of noise.
It is a third object of the invention to provide a bearing unit with sensor with a compact sensor in which the vibration condition of bearings can be detected with high accuracy.
It is a fourth object of the invention to provide a low-price and compact bearing unit with sensor and a low-price and compact linear motion unit with sensor in which the condition of vibration ranging from a low frequency to a high frequency can be detected.
In order to attain the foregoing objects, the invention is configured as follows.
(1) A wireless sensor for detecting normal condition or abnormality in one of a rolling bearing, a ball screw and a linear guide, having:
a detection unit for detecting a subject of detection;
a data processing unit for processing data detected by the detection unit; and
a communication unit for transmitting, by wireless, detection data processed by the processing unit.
(2) A wireless sensor according to (1), wherein:
the communication unit transmits, by wireless, the detection data processed by the processing unit together with identification information peculiar to the detection unit.
(3) A wireless sensor according to (1) or (2), wherein:
the detection unit includes at least one of a vibration sensor for detecting vibration, a temperature sensor for detecting temperature, and a rotation speed sensor for detecting rotation speed.
(4) A wireless sensor according to any one of (1) to (3), wherein:
in response to an instruction signal corresponding to identification information of the detection unit, the communication unit for performing transmission and reception transmits the detection data of the detection unit specified by the instruction signal together with the identification information.
(5) A wireless sensor according to any one of (1) to (4), wherein:
the communication unit converts one of information detected by the detection unit and information involved therein into digital information, and transmits the digital information.
(6) A bearing unit with sensor having:
outer and inner rings; and
a plurality of rolling elements disposed between the outer and inner rings; wherein:
one of the outer and inner rings is a stationary ring while the other is a rotating ring; and
a wireless sensor according to any one of (3) to (5), fixed integrally to one of the stationary ring and a member attached to the stationary ring, or provided to move integrally with one of the rotating ring and a member attached to the rotating ring.
(7). A bearing unit with sensor having:
a pair of first and second raceway rings rotating relatively through rolling elements;
a pulsar ring provided in the first raceway ring; and
a wireless sensor according to any one of (1) to (5), attached to the second raceway ring rotating relatively to the pulsar ring so as to be opposed to the pulsar ring.
(8) A bearing unit with sensor according to (7), wherein:
data about a periodic signal detected by the rotation speed sensor of the wireless sensor is transmitted in an FM modulation system in accordance with relative rotation between the pulsar ring and the wireless sensor.
(9) A bearing unit with sensor according to (7) or (8), wherein:
the communication unit transmits at least one of rotation number and rotation speed of the bearing unit obtained by the data processing unit on a basis of one of a wavelength and a frequency of a periodic signal generated in the rotation speed sensor in accordance with relative rotation between the pulsar ring and the wireless sensor.
(10) A bearing unit with sensor according to (7) or (8), wherein:
the communication unit transmits at least peculiar identification information at a breakpoint of each period of a periodic signal generated in the rotation speed sensor in accordance with relative rotation between the pulsar ring and the wireless sensor.
(11) A management apparatus having:
a communication tool for receiving a signal transmitted from one of a wireless sensor and a bearing unit having a detection unit for detecting a subject of detection; and
a signal processing unit for managing the received signal on a basis of identification information peculiar to at least one of the detection unit, the wireless sensor and the bearing unit, the identification information being included in the signal.
(12) A management apparatus having:
a communication unit for selectively receiving a signal transmitted from one of a wireless sensor and a bearing unit having a detection unit for detecting a subject of detection in accordance with identification information peculiar to the detection unit included in the signal, the selectively received signal including identification information registered in advance in the management apparatus.
(13) A management apparatus having:
a communication unit for receiving a signal transmitted from one of a wireless sensor and a bearing unit, and transmitting an instruction signal to make a request to one of the wireless sensor and the bearing unit for receiving the signal.
(14) A management apparatus according to any one of (11) to (13), wherein:
the management apparatus communicates with the wireless sensor and the bearing unit by digital signals.
(15) A monitoring system having:
one of a wireless sensor according to any one of (1) to (5) and a bearing unit according to any one of (6) to (10); and
a management apparatus according to any one of (11) to (14).
(16) A monitoring system having:
a plurality of wireless sensors according to any one of (1) to (5);
a plurality of bearing units according to any one of (6) to (10); and
management apparatus according to any one of (11) to (14);
wherein the management apparatus communicates with the wireless sensors and the bearing units by carrier waves of peculiar frequencies different from one another.
(17) A rolling bearing with sensor, having:
an outer ring and an inner ring which can rotate relatively to each other, one of the outer and inner rings being a stationary ring while the other is a rotating ring;
a plurality of rolling elements incorporated between the outer ring and the inner ring; and
a detection sensor unit provided in at least one of the stationary ring, a member attached to the stationary ring, the rotating ring and a member attached to the rotating ring, the detection sensor unit detecting condition of the rolling bearing;
wherein the detection sensor unit has a communication function for transmitting or transmitting/receiving data to or to/from outside by wireless.
(18) A rolling bearing with sensor according to (17), further having:
at least one relay unit which can transmit detection data detected by the detection sensor unit to outside by wireless.
(19) A rolling bearing with sensor according to (18), the relay unit including:
a communication unit which can convert the detection data from the detection sensor unit into a signal wave with a predetermined frequency component and transmit the signal wave to outside by wireless.
(20) A rolling bearing with sensor according to (18) or (19), wherein:
the detection sensor unit and the relay unit are electrically connected through a cable, and the detection data from the detection sensor unit is transmitted to the relay unit through the cable.
(21) A rolling bearing with sensor according to (18) or (19), the detection sensor unit including:
a communication unit which can convert the detection data of the detection sensor unit into a signal wave with a predetermined frequency component and transmit the signal wave to the relay unit by wireless.
(22) A rolling bearing with sensor according to any one of (19) to (21), wherein:
the signal wave is one of a radio wave, a light wave and an ultrasonic wave with a predetermined frequency component.
(23) A rolling bearing with sensor according to (18) or (19), wherein:
the detection sensor unit and the relay unit are electrically connected by use of electromagnetic induction; and
the detection sensor unit has a modulation circuit for modulating the detection data of the detection sensor unit into a predetermined modulated signal while the relay unit has a demodulation circuit for demodulating the modulated signal.
(24) A rolling bearing with sensor according to (17), wherein:
the detection sensor unit includes at least one of a vibration sensor, a temperature sensor, a rotation speed sensor and a pressure sensor.
(25) A rolling bearing with sensor according to (18), wherein:
signals from a plurality of detection sensor units having identification numbers respectively are relayed by relay units the number of which is smaller than the number of the detection sensor units.
(26) A rolling bearing with sensor according to (17), wherein:
the detection sensor unit has an acoustic detection sensor for detecting vibration condition of the rolling bearing; and
detection data detected by the acoustic detection sensor is transmitted to outside by wireless.
(27) A rolling bearing with sensor according to (26), wherein:
the acoustic detection sensor transduces a vibration wave generated mechanically into an electric signal.
(28) A rolling bearing with sensor according to (26) or (27), wherein:
the acoustic detection sensor having been incorporated in a sensor holder is set, and the sensor holder has an amplification circuit for amplifying an output of the acoustic detection sensor.
(29) A rolling bearing with sensor according to (28), wherein:
the sensor holder has a comparator for comparing the output of the acoustic detection sensor with a reference value and a counter for counting number of times of the output of the acoustic detection sensor exceeding the reference value within a predetermined time.
(30) A rolling bearing with sensor according to (28) or (29), wherein:
the sensor holder has a transmission circuit which can convert the output of the acoustic detection sensor into a signal wave with a predetermined frequency component and transmit the signal wave to output.
(31) A rolling bearing with sensor according to (31), wherein:
the signal wave is one of a radio wave, a light wave and an ultrasonic wave with a predetermined frequency component.
(32) A bearing unit with sensor having:
a rolling bearing having at least an outer ring, an inner ring and a plurality of rolling elements, at least one of the outer and inner rings being a rotating ring while the other is a stationary ring;
an integral-type sensor having at least one sensor for detecting condition of the bearing unit and a single sensor holder for including the sensor, the integral-type sensor being attached to one of the stationary ring and a member attached to the stationary ring; and
at least one relay unit provided near one of the integral-type sensor and the bearing, the relay unit amplifying an output signal from the integral-type sensor or converting the output signal into a signal suitable for long distance transmission so as to transmit the output signal to a control unit provided outside the bearing unit.
(33) A bearing unit with sensor according to (32), wherein:
at least one of a rotation speed sensor, a temperature sensor and a vibration sensor is provided as the sensor for detecting condition of the bearing unit.
(34) A bearing unit with sensor according to (32) or (33), wherein:
the signal from the relay unit is extracted from the bearing unit to outside by use of a cable.
(35) A bearing unit with sensor according to (32) or (33), wherein:
the signal from the relay unit is extracted from the bearing unit to outside by wireless.
(36) A rolling bearing with sensor having:
an outer ring and an inner ring which can rotate relatively to each other, one of the outer and inner rings being a stationary ring while the other is a rotating ring;
a plurality of rolling elements incorporated between the outer ring and the inner ring;
at least one sensor provided in at least one of the stationary ring, a member attached to the stationary ring, the rotating ring and a member attached to the rotating ring, the sensor measuring at least vibration condition of the rolling bearing; and
a board fixed to the sensor holder by screwing.
(37) A rolling bearing with sensor having:
an outer ring and an inner ring which can rotate relatively to each other, one of the outer and inner rings being a stationary ring while the other is a rotating ring;
a plurality of rolling elements incorporated between the outer ring and the inner ring; and
at least one sensor provided in at least one of the stationary ring, a member attached to the stationary ring, the rotating ring and a member attached to the rotating ring, the sensor measuring at least vibration condition of the rolling bearing;
a board in which a portion mounted with the sensor and various electronic elements is surrounded by one of flexible silicon rubber and forming rubber, and then molded with hard molding resin.
(38) A rolling bearing with sensor having:
an outer ring and an inner ring which can rotate relatively to each other, one of the outer and inner rings being a stationary ring while the other is a rotating ring;
a plurality of rolling elements incorporated between the outer ring and the inner ring; and
at least one sensor provided in at least one of the stationary ring, a member attached to the stationary ring, the rotating ring and a member attached to the rotating ring, the sensor measuring at least vibration condition of the rolling bearing;
wherein a bi-morpheme piezoelectric element having a double end support structure is used as the sensor.
(39) A bearing unit with sensor according to any one of (36) to (38), wherein:
the sensor includes at least one of a rotation speed sensor for measuring rotation speed of the rolling bearing and a temperature sensor for measuring temperature of the rolling bearing.
(40) A bearing unit with sensor according to any one of (36) or (39), wherein:
the sensor is incorporated in a single sensor holder together with various electronic elements for driving the sensor, and the sensor and the various electronic elements are mounted on a predetermined board.
(41) A bearing unit with sensor according to any one of (36) to (40), further having:
an amplification circuit for amplifying an output of the sensor.
FIG. 1 is a block diagram of a monitoring system according to a first embodiment of the invention;
FIG. 2 is a perspective view showing the state where the monitoring system in FIG. 1 has been applied to a machine tool;
FIG. 3 is a perspective view showing the state where the monitoring system in FIG. 1 has been applied to a plurality of processing machines;
FIG. 4A is a sectional view showing a bearing unit according to a second embodiment of the invention, and FIG. 4B is a side view of a sensor portion of the bearing unit, taken on line F 4 -F 4 in FIG. 4A;
FIG. 5 is a block diagram of the bearing unit in FIG. 4;
FIG. 6 is a schematic view showing the state where a monitoring system according to a third embodiment of the invention has been applied to an automobile;
FIG. 7 is a sectional view of a hub bearing unit for use in the monitoring system in FIG. 6;
FIG. 8 is a block diagram of the monitoring system in FIG. 6;
FIG. 9 is a waveform chart schematically showing a speed signal, a transmission signal, a digital signal of speed information and a digital signal of identification information output by a signal processing portion in FIG. 8;
FIG. 10 is a sectional view schematically showing the configuration of a bearing unit with sensor according to a fourth embodiment of the invention;
FIG. 11 is a block diagram showing the circuitry of a detection sensor unit and a relay unit shown in FIG. 10;
FIG. 12 is a block diagram showing the circuitry of a detection sensor unit and a relay unit according to a first modification of the fourth embodiment;
FIG. 13 is a block diagram showing the circuitry of a detection sensor unit and a relay unit according to a second modification of the fourth embodiment;
FIG. 14 is a block diagram showing the circuitry of a detection sensor unit and a relay unit according to a third modification of the fourth embodiment;
FIG. 15 is a sectional view schematically showing the whole configuration of a bearing unit with sensor according to a fifth embodiment;
FIG. 16 is a block diagram showing the circuitry of a detection sensor unit and a relay unit shown in FIG. 15;
FIG. 17 is a block diagram showing the circuitry of a detection sensor unit and a relay unit according to a first modification of the fifth embodiment;
FIG. 18 is a block diagram showing the circuitry of a detection sensor unit and a relay unit according to a second modification of the fifth embodiment;
FIG. 19 is a sectional view schematically showing the configuration of a bearing unit with sensor according to a sixth embodiment;
FIG. 20 is a sectional view schematically showing the configuration of a bearing unit with sensor according to a modification of the sixth embodiment;
FIG. 21 is a sectional view schematically showing the configuration of a bearing unit with sensor according to a seventh embodiment;
FIG. 22 is a block diagram showing the circuitry of a sensor holder in which an acoustic detection sensor (AE sensor) has been incorporated;
FIG. 23 is a block diagram showing the circuitry of a sensor holder according to a modification of the seventh embodiment;
FIG. 24 is a schematic view partially showing a bearing unit according to an eighth embodiment of the invention;
FIG. 25 is a schematic view partially showing a bearing unit according to a ninth embodiment of the invention;
FIG. 26 is a schematic view partially showing a bearing unit with sensor according to a tenth embodiment of the invention;
FIGS. 27A and 27B are plan views showing the configuration of a vibration sensor; FIG. 27A shows the state of a piezoelectric element during the absence of acceleration acting thereon, and FIG. 27B shows the state of the piezoelectric element during the presence of acceleration acting thereon;
FIG. 28 is a diagram showing the circuitry for a voltage output of the vibration sensor;
FIG. 29 is a diagram showing the circuitry for a current output of the vibration sensor;
FIG. 30 is a schematic view showing the configuration of a related-art bearing unit;
FIG. 31 is a schematic view showing the configuration of a related-art bearing unit with sensor;
FIG. 32 is a schematic view showing the configuration in which the sensor apparatus is applied to the linear guide device; and
FIG. 33 is a schematic view showing the configuration of the sensor holder using a resin mold.
A first embodiment of the invention will be described with reference to FIGS. 1 to 3 . A monitoring system 1 shown in FIG. 1 is constituted by a plurality of wireless sensors 2 and management apparatus 3 . Each of the wireless sensors 2 detects vibration or temperature as a subject of detection and transmits the detection data (signal) thereof. The management apparatus 3 receives signals R output from the plurality of wireless sensors 2 .
Each wireless sensor 2 has a vibration sensor module 4 , a temperature sensor module 5 , a multiplexer 6 , an A/D converter 7 , a RAM (Random Access Memory) 8 , a signal processing unit 9 and a communication unit 10 . The vibration sensor module 4 has a vibration sensor as a detection unit for detecting vibration as a subject of detection, so as to convert the change of vibration detected in the form of acceleration or the like into an electric signal, and output the electric signal. The temperature module 5 has a temperature sensor as a detection unit for detecting temperature as a subject of detection, so as to convert detected temperature into an electric signal and output the electric signal.
The multiplexer 6 multiplexes the signals output from the vibration sensor module 4 and the temperature sensor module 5 respectively so that the signals can be separated later as detection data independent of each other. Incidentally, the multiplexing by the multiplexer 6 may be based on either a multichannel system or a time-sharing system. In addition, when there is provided only one of the sensor modules 4 and 5 , the multiplexer 6 is dispensable. In addition, a plurality of A/D converters 7 may be provided instead of the multiplexer 6 .
The A/D converter 7 converts an analog signal from the vibration sensor module 4 or the temperature sensor module 5 into a digital signal. The RAM 8 is provided to store detection data converted by the A/D converter 7 temporarily before the detection data is processed. Incidentally, the RAM 8 is an example of a storage unit. Any storage unit may be used if it can store the detection data temporarily.
The signal processing unit 9 makes a sequential call for the detection data of the respective sensor modules 4 and 5 stored temporarily in the RAM 8 , and performs processing to compare the detection data with predetermined threshold values for vibration and temperature respectively. After that, the signal processing unit 9 supplies the detection data to the communication unit 10 together with the identification information peculiar to the respective sensor modules 4 and 5 . Incidentally, the value of vibration or temperature may be supplied directly to the communication unit 10 together with the identification information. Further, the A/D converter 7 , the RAM 8 and the signal processing unit 9 may be integrated into a processing unit.
When the sensor module 4 , 5 has a plurality of detection units, identification information may be issued for each detection unit that has detected its corresponding detection data. In addition, it is preferable that identification information for each wireless sensor 2 together with the identification information for each sensor module 4 , 5 is added to detection data to be transmitted. In this case, classification and management used for various purposes can be achieved on the side of the management apparatus 3 . Since the identification information is given to each detection unit, the identification information may be added to detection data and output together by the sensor module 4 , 5 .
The communication unit 10 can transmit and receive the signal. The communication unit 10 converts a signal supplied from the signal processing unit 9 into a radio-wave signal R, and transmits the signal R. Incidentally, in an environment where it is difficult to use radio waves, a communication unit 10 for converting a signal into an ultrasonic wave or light such as infrared light may be used.
In the wireless sensor 2 configured thus, the detection data detected by the respective sensor modules 4 and 5 is multiplexed by the multiplexer 6 , converted into a digital signal by the A/D converter 7 , and then stored in the RAM 8 temporarily. The stored detection data is read out sequentially by the signal processing unit 9 , subjected to processing such as calculation, and formed into a signal R added with identification information peculiar to each sensor module 4 , 5 . The signal R is transmitted from the communication unit 10 . Incidentally, it is preferable that the interval with which vibration, temperature and the like are detected is set to be a predetermined time interval, or an interval set up by a trigger using a predetermined threshold value. In this case, the amount of information corresponding to data can be reduced.
In such a manner, communication lines are dispensable because the wireless sensor 2 transmits the detection information by radio waves. Accordingly, when the wireless sensor 2 is attached to a movable shaft of a processing machine or the like, or a bearing unit of a vehicle, there is no trouble in the work of wiring. Thus, the use of the wireless sensor 2 results in avoiding the trouble in wiring and reduce the number of man-hours for wiring. In addition, identification information for each sensor module 4 , 5 is added to any signal R transmitted from the wireless sensor 2 . Thus, even if signals R are transmitted from a plurality of wireless sensors 2 at the same frequency, the signals R from the wireless sensors 2 can be identified individually. Accordingly, the management apparatus 3 receiving the signals R does not have to change the frequency for each wireless sensor 2 or each sensor module 4 , 5 . In addition, even when another wireless sensor 2 is added as a target of reception, reception can be carried out with the setting of the management apparatus 3 as it is. Then, detection data detected by the respective wireless sensors 2 or the respective sensor modules 4 and 5 can be classified easily on the basis of the identification information.
In addition, when the wireless sensor 2 receives an instruction signal Q corresponding to individual identification information, the wireless sensor 2 detects the latest condition of a sensor module specified by the instruction signal Q, and transmits the latest condition together with the identification information through the communication unit 10 . Thus, whenever a user wants to confirm detection data again, the user can obtain the latest detection data of a desired wireless sensor easily.
Incidentally, the instruction signal Q may be transmitted from the management apparatus 3 at any time interval so as to acquire the latest detection data of a desired wireless sensor. As a result, there is no case that a plurality of wireless sensors 2 transmit detection data perfectly simultaneously. Thus, transmitted data is prevented from in completion, and the reception accuracy is improved.
Incidentally, at least one of the vibration sensor module 4 and the temperature sensor module 5 provided in the wireless sensor 2 in FIG. 1 may be provided, or a rotation speed sensor module for detecting rotation speed may be provided instead of both or one of the sensor modules 4 and 5 . Further, the vibration sensor module 4 , the temperature sensor module 5 and the rotation speed sensor module may be provided respectively.
Next, the management apparatus 3 will be described. The management apparatus 3 shown in FIG. 1 has a communication tool 11 , a signal processing unit 12 , an RAM 13 and an interface 14 . The communication tool 11 receives signals R transmitted from a plurality of wireless sensors 2 scattered around the management apparatus 3 by wireless, for example, by radio waves. The communication tool 11 sends the received signals R to the signal processing unit 12 . Incidentally, the radio waves used by the communication tool 11 may be of a single frequency. It is, however, preferable that at least two frequency bands can be used for transmission and reception.
The signal processing unit 12 classifies detection data included in the transmitted signals R on the basis of identification information peculiar to each wireless sensor 2 or each sensor module 4 , 5 included in the signals R. The RAM 13 has a memory capacity much larger than that of the RAM 8 of the wireless sensor 2 . The RAM 13 manages and stores the classified detection data (or the signals R) individually. Incidentally, the RAM 13 is an example of a storage unit. Any storage unit may be used if it can manage and store the received detection data (or the signals R) individually. The interface 14 is provided in parallel with the RAM 13 and from the signal processing unit 12 . The interface 14 outputs the detection data classified by the signal processing unit 12 to the outside.
In addition, the management apparatus 3 transmits an instruction signal Q through the communication tool 11 so as to make a request to a desired wireless sensor 2 or a desired sensor module 4 , 5 for the latest detection data. This instruction signal Q is added with information (data) corresponding to the identification information of the wireless sensor 2 or the sensor module 4 , 5 specified by the user, for example, the identification information peculiar to the desired wireless sensor 2 or the desired sensor module 4 , 5 .
The management apparatus 3 configured thus receives signals R transmitted from a plurality of wireless sensors 2 , classifies detection data on the basis of identification information of sensor modules 4 and 5 included in the signals R, records and stores the detection data in the RAM 13 . In addition, the management apparatus 3 outputs the detection data stored in the RAM 13 to the outside through the interface 14 in accordance with necessity. Accordingly, on the basis of the accumulated detection data of the respective wireless sensors 2 or the sensor modules 4 and 5 , the running conditions of respective machinery and equipment or the like can be analyzed by the signal processing unit 12 of the management apparatus 3 , or can be extracted to the outside through the interface 14 for the purpose of data processing. Thus, higher-level and more accurate analysis can be achieved.
Next, the monitoring system 1 constituted by the wireless sensors 2 and the management apparatus 3 makes the wireless sensors 2 detect vibration or temperature of subjects of detection at a predetermined interval or when the vibration or the temperature exceeds a threshold value set in the signal processing unit 9 of each wireless sensor 2 in advance. The monitoring system 1 adds identification information of each wireless sensor 2 or each sensor module 4 , 5 to the detection data, and transmits the detection data as signals R. Then, the monitoring system 1 makes the management apparatus 3 receive the signals R, classify the detection data for each identification information, store and manage the classified detection data.
In addition, the monitoring system 1 makes the management apparatus 3 transmit an instruction signal Q. The instruction signal Q corresponds to a desired wireless sensor 2 or a desired sensor module 4 , 5 . For example, the instruction signal Q includes identification information peculiar to the desired wireless sensor 2 or the desired sensor module 4 , 5 . Thus, the latest detection data of the respective sensor modules 4 and 5 of the wireless sensor 2 specified by the identification information included in the instruction signal Q or the sensor module ( 4 or 5 ) specified by the identification information can be transmitted (by return) as a signal R from the wireless sensor 2 . Accordingly, the latest detection data of any wireless sensor 2 or any sensor module 4 or 5 desired by the user can be acquired appropriately in the management apparatus 3 .
Then, the wireless sensors 2 of the monitoring system 1 are attached to spindle 22 and rotational shaft 23 of a machine tool 21 respectively as shown in FIG. 2, while the management apparatus 3 is provided in a body 24 of the machine tool. Then, vibrations, temperatures, or speeds of rotating shafts or moving shafts are detected by the wireless sensors 2 at a predetermined time interval. Detection data obtained by each wireless sensor 2 is received by the management apparatus 3 , and the detection data is classified and stored for each identification information.
When the monitoring system 1 is applied to the machine tool 21 , the wireless sensors 2 can be attached easily to the movable shafts 22 and 23 because the wireless sensors 2 make communication by wireless (radio waves). In addition, since there is no communication wiring, the wireless sensors 2 can be removed and attached easily when the peripheries of the wireless sensors 2 are disassembled for maintenance or the like. In addition, when another wireless sensor 2 is added, the wireless sensor 2 is attached easily. In addition, since detection data is transmitted as a signal R together with identification information, the detection data of the added wireless sensor 2 can be classified and managed by the management apparatus 3 in accordance with the identification information in the same manner as that of the other wireless sensors 2 . Further, when the user uses the management apparatus 3 to transmit an instruction signal added with identification information of the sensor module 4 or 5 of the wireless sensor 2 from which the user wants to obtain the latest detection data, the user can acquire the latest detection data of the desired sensor module 4 or 5 . Incidentally, to make the management apparatus 3 user-friendly, it will go well if the instruction signal is transmitted from the management apparatus 3 in response to an input to a control panel 25 of the machine tool 21 .
In addition, it is effective in self-diagnosis of the machine tool 21 or prevention of defects that the detection data stored in the management apparatus 3 is supplied to the control panel 25 of the machine tool 21 through the interface 14 (FIG. 1).
When the monitoring system 1 is used adjacently to other monitoring systems 1 , identification information of wireless sensors 2 to be received is set in the management apparatus 3 in advance so that detection data of the wireless sensors 2 to be received can be received selectively. Thus, crosstalk with signals of wireless sensors 2 for other machine tools can be prevented.
Further, when respective detection data of wireless sensors 2 provided in a plurality of processing machines 26 such as NC lathes or machining centers is received and managed together in the management apparatus 3 provided at a remote place, signals R output from the wireless sensors 2 attached to the respective processing machines 26 are once packed for each processing machine 26 , and the packed signals R are transmitted to the management apparatus 3 . In this case, detection data may be processed and accumulated for each processing machine 26 , and output in response to an instruction signal from the management apparatus 3 . Alternatively, on every occasion of detection in any wireless sensor 2 or any sensor module, detection data may be transmitted to the management apparatus 3 together with identification information of the wireless sensor 2 or the sensor module. When the output of the wireless sensor 2 is small, it is preferable to transmit the output via the relay unit 27 .
In such a manner, the user does not have to go to the respective processing machines 26 in order to check and monitor the running conditions of the processing machines 26 . In addition, since communication is performed by wireless between each of the wireless sensors attached to the processing machines 26 and the management apparatus 3 , it is not necessary to lay communication lines additionally. Thus, the monitoring system 1 is easy to introduce into existing equipment.
In addition, when mobile communication lines of portable telephone, PHS (Personal Handyphone System), satellite phone, or the like, is used for communication between each of the wireless sensors or each of the processing machines and the management apparatus 3 , the running conditions of bearings or gear boxes of cars or railway vehicles moving extensively can be managed and monitored under central control in real time. In this case, mobile communication lines may be used for communication between each of the wireless sensors 2 and the management apparatus 3 . Alternatively, signals R of the wireless sensors may be transmitted to a relay unit 27 close thereto, while mobile communication lines, serial-parallel communication (wire), general telephone lines (wire), LAN (Local Area Network), cables, radio transmission or the Internet is used for the communication between the relay unit 27 and the management apparatus 3 . Further, the management apparatus 3 may receive the signals R through general telephone lines (wire).
Assume that equipment in which wireless sensors 2 are installed is used movable among a plurality of buildings in accordance with the progress and schedule of work, or a plurality of pieces of such equipment are prepared and used to be replaced by one another for maintenance in order to increase the operating rates of lines. In such a case, pieces of management apparatus 3 installed in each building or each room may share management numbers or detection data of the wireless sensors through mobile communication or general telephone lines, LAN or the Internet. Thus, monitoring can be carried out without omission.
Incidentally, when mobile communication lines or general telephone lines are used for communication of the monitoring system 1 , the processing machine 26 , the car or the railway vehicle a wireless sensor is attached to may be judged to have need for maintenance and inspection on the basis of detection data transmitted by the wireless sensor and received by the management apparatus 3 . In such a case, the management apparatus 3 can be set to automatically give notice to mobile communication apparatus carried by a maintenance stuff. In addition, the maintenance stuff can use the mobile communication apparatus to search detection data of any wireless sensor.
Next, a second embodiment of the invention will be described with reference to FIGS. 4A to 5 . A rolling bearing unit 31 shown in FIG. 4A has a bearing unit 32 and a sensor unit 33 which is a wireless sensor. The bearing unit 32 has inner and outer rings 34 and 35 , rolling elements 36 disposed between these raceway rings 34 and 35 , a retainer 37 for the rolling elements 36 , and a seal or shield plate 351 . The sensor unit 33 has a detection unit 38 , a processing unit 39 , a communication unit 40 , and cells (batteries) 41 as shown in FIG. 4B. The detection unit 38 detects a subject of detection. The processing unit 39 processes detected data. The communication unit 40 transmits a signal output from the processing unit 39 by wireless. The cells 41 supply electric power to the detection unit 38 , the processing unit 39 and the communication unit 40 .
The sensor unit 33 is attached to a flange 43 formed toward the center of an outer ring spacer 42 integrally fixed or closely contacted to the outer ring 35 of the bearing unit 32 . The detection unit 38 has a vibration sensor 44 for detecting vibration (that is, a change of acceleration) and a temperature sensor 45 for detecting temperature. The vibration sensor 44 and the temperature sensor 45 are attached to recess portions 46 a and 46 b provided in parts of the outer ring spacer 42 opposed to the bearing unit 32 , respectively, so as to detect vibration and temperature of the bearing unit 32 more accurately. Incidentally, the recess portions 46 a and 46 b to which the acceleration sensor 44 and the temperature sensor 45 are attached may be provided independently of each other, or provided integrally with each other. Incidentally, to detect the vibration or the temperature of the inner ring 34 of the bearing unit 32 aggressively, the sensor unit 33 may be attached to an inner ring spacer 47 integrally fixed or closely contacted to the inner ring 34 . In addition, the bearing unit may be designed so that the sensor unit 33 is incorporated directly in the inner ring 34 , the outer ring 35 , or the seal or shield plate 351 . Alternatively, the bearing unit may be designed so that the sensor unit 33 is incorporated in a member attached to the inner ring 34 or the outer ring 35 .
In addition, as shown in FIG. 5, the processing unit 39 has an amplifier 48 , a comparator 49 , a signal processing unit 50 and an ASK (Amplitude Shift Keying) modulator 51 . The amplifier 48 forms a signal of vibration detected by the vibration sensor 44 into an absolute value. The comparator 49 compares the signal of the vibration sensor 44 formed into an absolute value by the amplifier 48 and a signal output from the temperature sensor 45 with threshold values set in advance respectively. Thus, the comparator 49 outputs a result thereof. The signal processing unit 50 adds identification information peculiar to the vibration (acceleration) sensor 44 or the temperature sensor 45 outputting detection data to the detection data output from the comparator 49 . In addition, of the detection data, detection data judged to exceed the threshold value is added with an alarm signal, and output together. The ASK modulator 51 modulates the signal output from the signal processing unit 50 so as to digitize (binarize) the signal. Incidentally, any other system such as an FSK (Frequency Shift Keying) system may be adopted as the modulation system for communication. The communication unit 40 converts the signal digitized by the ASK modulator 51 into a radio wave, and transmits the radio wave as a signal R. In addition, the power supply to the detection unit 38 , the ASK modulator 51 , the communication unit 40 and soon may be controlled appropriately by the signal processing unit 50 so as to suppress power consumption with the exception of the detection time or the signal output time. In this case, the lives of the cells (batteries) 41 can be extended.
Incidentally, the sensor unit 33 may be incorporated in a portion in which the cells 41 cannot be exchanged, or vibration or temperature may be monitored constantly. In such a case, it is preferable that not-shown multi-polar magnets or spur-gear-like irregularities are provided in the inner ring spacer 47 , and a not-shown coil or a coil with magnets are provided in the flange 43 or the outer ring spacer 42 . Thus, a generator is formed to supply electric power to the detection unit 38 , the processing unit 39 and the communication unit 40 through a power supply circuit. Incidentally, it is more preferable that a storage battery is also used in the power supply circuit. In this case, the wireless sensor can be operated even when the generator is not operated.
The signal R transmitted from the bearing unit 31 is received by management apparatus 3 provided in a body of a processing machine or a vehicle the bearing unit 31 is attached to, or at a remote place. Incidentally, the management apparatus 3 is similar to the management apparatus 3 described in the first embodiment. Thus, the description thereof will be omitted.
In the bearing unit 31 configured thus, detection data is output by radio waves, and communication lines are dispensable. Thus, the bearing unit 31 can be attached easily as a bearing for a movable shaft of a processing machine, a vehicle, or the like. In addition, the signal R transmitted from the bearing unit 31 is added with identification information peculiar to the bearing unit 31 , the detection unit 38 of the bearing unit 31 , or the acceleration (vibration) sensor 44 or the temperature sensor 45 . Thus, even if each signal R is transmitted at the same frequency as other signals R, the management apparatus 3 receiving the signals R can identify the signal R easily individually for each bearing unit 31 , each detection unit 38 , each acceleration sensor 44 or each temperature sensor 45 . Incidentally, at least one of the vibration sensor 44 and the temperature sensor module 45 may be provided, or a rotation speed sensor may be provided instead of both or one of the sensors. Further, the vibration sensor 44 , the temperature sensor 45 and the rotation speed sensor may be provided respectively.
Further, another bearing unit 31 as a target of reception to be detected can be added easily because communication lines are dispensable. Then, a signal R transmitted therefrom has an identification signal for each detection data. Thus, even if each signal R is transmitted at the same frequency as other signals R, the signals R can be classified easily.
In addition, when the bearing unit 31 receives an instruction signal Q corresponding to identification information peculiar to the acceleration (vibration) sensor 44 or the temperature sensor 45 , the detection unit 38 or the bearing unit 31 , the bearing unit 31 detects latest data of the acceleration sensor 44 or the temperature sensor 45 , the detection unit 38 or all the detection units 38 of the bearing unit 31 specified by the instruction signal Q. Then, the bearing unit 31 transmits the detected latest data together with the identification information through the communication unit 40 . Accordingly, the user can acquire the latest data of a desired bearing unit 31 easily on a case-by-case basis. Then, when the bearing unit 31 is used together with the management apparatus 3 described in the first embodiment so as to form a monitoring system, effect similar to that of the monitoring system 1 in the first embodiment can be obtained.
In addition, the block diagram shown in FIG. 5 of the bearing unit 31 according to the second embodiment may be replaced by the block diagram shown in FIG. 1 of the wireless sensor 2 according to the first embodiment. On the contrary, the block diagram shown in FIG. 1 of the wireless sensor 2 according to the first embodiment may be replaced by the block diagram shown in FIG. 5 of the bearing unit 31 according to the second embodiment.
In addition, the block diagrams do not limit the embodiments. Any other block diagram may be used if it takes similar effect. Further, when the bearing unit 31 according to the second embodiment is used in attachment to the rotating shaft of the machine tool 21 in FIG. 2 or the processing machine in FIG. 3, similar effect can be obtained.
In addition, this embodiment is applicable not only to rolling bearings but also to linear guides or ball screws. In the case of a linear guide or a ball screw, its movable portion corresponds to a rotating ring of a rolling bearing.
A third embodiment of the invention will be described with reference to FIGS. 6 to 10 , using a monitoring system 63 by way of example. The monitoring system 63 is used for ABS (Anti-lock Braking System) to monitor the rotation speed or rotation numbers of wheels 62 of an automobile 61 . Incidentally, constituent parts the same as those in the wireless sensor, the bearing unit, the management apparatus and the monitoring system described in the first and second embodiments are referenced correspondingly, and the description thereof will be omitted.
The monitoring system 63 shown in FIG. 6 has hub bearing units 64 attached to the wheels 62 of the automobile 61 respectively, and management apparatus 66 attached to a body 65 . Each of the hub bearing units 64 has a wheel bearing 67 , a pulsar ring 68 and a wireless sensor 69 as shown in FIG. 7. The wheel bearing 67 has a set of raceway rings using an outer ring 70 , a first inner ring 71 and a second inner ring 72 , and two rows of rolling elements rolling on these raceway rings. The outer ring 70 has a flange 74 fixed to a knuckle portion K by a bolt. The first inner ring 71 has a flange 75 fixed to the wheel 62 through a brake disc by a bolt. A spline 71 a is formed in the inner surface of the first inner ring 71 so as to be fitted to a spline 76 a formed in the outer surface of an axle 76 . Thus, the first inner ring 71 is fixed to the axle 76 by a nut 77 . The second inner ring 72 is fitted to the first inner ring 71 . When the first inner ring 71 and the second inner ring 72 approach their rotating axes, the pre-load on the wheel bearing 67 increases.
In the pulsar ring 68 , convex portions 78 are formed circumferentially at an equal interval. The pulsar ring 68 is attached to the second inner ring 72 . Incidentally, it will go well if the pulsar ring 68 is attached to a position where the pulsar ring 68 rotates relatively to the wireless sensor 69 . Therefore, the pulsar ring 68 may be attached not to the second inner ring 72 but to the rotating side rotating with the axle 76 . In addition, when the wireless sensor 69 is attached to the rotating side, the pulsar ring 68 is attached to the fixed side.
The wireless sensor 69 is fixed to the outer ring 70 as shown in FIG. 7. The wireless sensor 69 has a speed sensor module 69 for detecting the rotation speed, a signal processing unit 80 , a communication unit 81 , and a power supply circuit 82 as shown in FIG. 8. Incidentally, it will go well if the wireless sensor 69 is attached in a position where the wireless sensor 69 rotates relatively to the pulsar ring 68 , so as to be opposed to the pulsar ring 68 . Therefore, the wireless sensor 69 may be attached to the knuckle portion K.
The speed sensor module 79 has a coil 83 , a pole 84 , a magnet 85 and a rotation detection circuit 86 . The pole 84 penetrates the center of the coil 83 . The pole 84 is made of a member having a high magnetic permeability, for example, an iron core. One end 84 a of the pole 84 is close to the convex portions 78 formed in the pulsar ring 68 . The magnet 85 is attached to the other end 84 b of the pole 84 . The rotation detection circuit 86 detects a change of a current in the coil 83 . When the outer ring 70 and the second inner ring 72 rotate relatively, the convex portions 78 of the pulsar ring 68 change the magnetic flux density of the pole 84 . The coil 83 generates an induced current due to the change of the magnetic flux density of the pole 84 . Incidentally, it will go well if the pulsar ring 68 changes the magnetic flux density passing through the coil 83 . Therefore, the pulsar ring 68 may be a ring perforated at a fixed interval or a magnetic body such as a multi-polar magnet magnetized with N and S poles alternately at a fixed interval. When a multi-polar magnet is used for the pulsarring, the magnet 85 to be attached to the other end 84 b of the pole 84 is dispensable. In addition, the shape of the pole 84 is not limited to a rod-like shape, but it may be any other shape such as an annular shape if an induced current can be generated in the coil.
The signal processing unit 80 converts a continuous sine waveform signal detected by the rotation detection circuit 86 into a binarized rectangular speed signal 88 shown by the waveform (A) of FIG. 9. Incidentally, the waveform (A) of FIG. 9 schematically designates the speed signal output by the signal processing unit in FIG. 8; (B), a transmission signal in which a carrier wave is modulated with the speed signal of the waveform (A) in an FM modulation system by the communication unit; (C), a digital signal including identification information transmitted from the communication unit synchronously with the period of the speed signal of the waveform (A) and speed information associated with this identification information; and (D), a digital signal of the identification information transmitted synchronously with the period of the speed signal of the waveform (A). In addition, the signal processing unit 80 may have a counter 87 . In this case, the number of mountains or valleys of rectangular pulses is counted to obtain the rotation number or the rotation speed of the hub bearing unit 64 . Then, a digitized signal based on the rotation number or the rotation speed is output as a speed signal. By forming the rotation number or the rotation speed into a digitized signal, it is possible to prevent the speed signal 88 from varying due to noise in the process of transmission.
The communication unit 81 uses the speed signal 88 produced by the signal processing unit 80 to FM-modulate a carrier wave having a wavelength much longer than the frequency of the speed signal 88 , so as to form a transmission signal 89 as shown by the waveform (B) of FIG. 9. The transmission signal 89 is transmitted as a signal R. In this case, each hub bearing unit 64 uses a carrier wave at a different frequency from that of the other hub bearing units 64 so that the transmission signal 89 can be identified by the management apparatus 66 .
The power supply circuit 82 generates electric power by use of a current generated in the coil 83 , and supply the power to the speed sensor module 79 , the signal processing unit 80 and the communication unit 81 . In addition, the power supply circuit 82 has a storage battery 90 . The storage battery 90 stores surplus power when the rotation speed of the hub bearing unit 64 is stable. On the contrary, the storage battery 90 discharges the stored power when the rotation speed of the hub bearing unit 64 drops down so that power to be supplied cannot be generated sufficiently. Accordingly, the wireless sensor 69 has no need of power supply using a cable, and is mounted with no primary battery having need to be exchanged. Thus, the wireless sensor 69 is suitable for long time use. Incidentally, the power supply circuit 82 has a rectification circuit for rectifying an AC current generated in the coil 83 into a DC current, a charging circuit for monitoring the remaining electric energy of the storage battery 90 and controlling charge and discharge, and so on.
Incidentally, the wireless sensor 69 may have an amplifier for amplifying the detected signal or a waveform shaping circuit for shaping the signal waveform in order to transmit the signal more surely. In addition, when the frequency of the signal detected by the rotation detection circuit 86 is much higher than the frequency of the carrier wave, that is, when the rotation speed of the axle 76 is so high that the detected signal has a high frequency, the frequency of the detected signal may be close to the frequency of the carrier wave so that the carrier wave cannot be modulated well. In such a case, the signal processing unit 80 binarizes the signal detected by the rotation detection circuit 86 , counts the number of mountains or valleys of the rectangular waves in the counter 87 , and outputs a rectangular signal proportional to the rotation number or the rotation speed of the axle 76 as a speed signal. Then, the speed signal is used for modulating the carrier wave into a transmission signal 89 , and the transmission signal 89 is transmitted as a signal R.
The management apparatus 66 has a communication tool 11 , a signal processing unit 12 , a RAM 13 and an interface 14 as shown in FIG. 8. The communication tool 11 receives the signal R transmitted from each hub bearing unit 64 , and transmits an instruction signal Q to each hub bearing unit 64 . In addition, the communication tool 11 includes a splitter 91 . The splitter 91 splits transmitted transmission signals 89 on the basis of carrier waves differing from one hub bearing unit 64 to another. The signal processing unit 12 is provided for each hub bearing unit 64 so as to separate the speed signal 88 included in the transmission signal 89 transmitted from the hub bearing unit 64 . Incidentally, a plurality of communication tools 11 whose number is specifically corresponding to the number of the hub bearing units 64 may be provided instead of the splitter.
Incidentally, an FSK modulation, an AM modulation, an ASK modulation, and the like, other than the FM modulation, may be adopted as the modulation system for the signal used between the wireless sensor 69 and the management apparatus 66 .
In the monitoring system 63 configured thus, the first and second inner rings 71 and 72 , the axle 76 and the pulsar ring 68 of the hub bearing unit 64 rotate together with the wheel 62 when the automobile 61 runs. By the relative rotation to the wireless sensor 69 , the pulsar ring 68 fluctuates the magnetic flux density passing through the coil 83 provided in the speed sensor module 79 . When the magnetic flux density fluctuates, the coil 83 generates a current fluctuating like sine waves. By use of the generated current, the power supply circuit 82 supplies electric power to the signal processing unit 80 and the communication unit 81 . In addition, the signal processing unit 80 detects and binarizes the fluctuation of the current. Then, the signal processing unit 80 outputs a speed signal 88 . The communication unit 81 FM-modulates a carrier wave on the basis of the speed signal 88 so as to form a transmission signal 89 , and transmits the transmission signal 89 to the management apparatus 66 . In this case, the frequency of the carrier wave differs from one hub bearing unit 64 to another. Thus, signals transmitted from the hub bearing units 64 can be received by the management apparatus 66 without interference with one another.
The management apparatus 66 classifies the received transmission signals 89 for each hub bearing unit 64 , and stores them in the RAM 13 . In addition, in accordance with necessity, the information about speed signals stored in the RAM 13 is supplied through the interface 14 to the control unit controlling the running of the automobile 61 .
When the monitoring system 63 is applied to a vehicle such as a truck or a railway vehicle with many wheels, in which wheels to be managed are distant from one another, the communication tools 11 of the management apparatus 66 are disposed in the body 65 close to the wireless sensors 69 so as to make communication with the wireless sensors 69 respectively as shown by the portion A in FIG. 6. In this case, wires W between the communication tools 11 and the management tool 66 are attached along the body 65 so as not to be bent by the running of the automobile 61 . In such a manner, the communication tools 11 are disposed near their corresponding wireless sensors 69 of the hub bearing units 64 respectively. In addition, each communication tool 11 makes communication with the wireless sensor 69 of its corresponding hub bearing unit 64 by use of a transmission signal 89 output without interference with transmission signals 89 of the wireless sensors 69 of the other hub bearing units 64 which are attached to the other wheels 62 of the same automobile 61 . In such a case, the frequencies of the carrier waves set in the communication units 81 of the respective hub bearing units 64 may be identical to one another.
The wireless sensor 69 may convert information detected by the speed sensor module 79 as a detection unit of the hub bearing unit 64 or information involved therein into digital information, and transmits a digital signal 92 as the signal R as shown by the waveform (C) of FIG. 9. In this case, the information detected by the speed sensor module 79 or the information involved therein includes a speed signal 88 made up on the basis of the signal detected by the speed sensor module 79 , speed data 93 obtained by measuring the period of pulses of the speed signal 88 by the counter 87 and precise reference clock (not shown) and rearranging the period of pulses into a numeric value such as the rotation number or the rotation speed of the hub bearing unit 64 , identification information 94 corresponding to each sensor module, time when the speed data 93 was detected, and so on. Incidentally, the waveform (C) of FIG. 9 shows the case where the speed data 93 and the identification information 94 are transmitted as a digital signal 92 .
In such a manner, it becomes easy for the management apparatus 66 to identify the speed data 93 transmitted by the hub bearing unit 64 . In addition, when the speed signal 88 is transmitted as the digital signal 92 , the speed signal 88 can be reproduced on the reception side even if the digital signal 92 deteriorates due to ambient noise or the like. Thus, the speed signal 88 can be prevented from in completion. When the identification information 94 is added to the speed information 93 , the digital signal 92 from the respective hub bearing units 64 can be transmitted on the carrier waves at the same frequency. Thus, the splitter 91 can be omitted from the management apparatus 66 . In this case, in the management apparatus 66 , a circuit for processing the speed information 93 in accordance with the identification information 94 is included in the signal processing unit 12 . The speed information 93 may be information about the period of pulses of the speed signal 88 counted by the counter 87 and precise reference clock (not shown) of the signal processing unit 80 of the wireless sensor 69 , or may be information about the period of pulses converted into rotation speed or rotation number. When the speed information 93 is transmitted subsequently after the identification information 94 is transmitted, it is easy to associate the identification information 94 and the speed information 93 with each other. The digital signal 92 including the identification information 94 and the speed information 93 is output synchronously with each pulse of the speed signal 88 .
In addition, the wireless sensor 69 may transmit only the identification information 94 as the signal R synchronously with the speed signal 88 as shown by the waveform (D) of FIG. 9. In this case, a counter is provided in the signal processing unit 12 of the management apparatus 66 so as to measure the period of the identification information 94 transmitted by each hub bearing unit 64 . Thus, the speed signal 88 detected by each hub bearing unit 64 is reproduced. In such a manner, the speed signal 88 of each hub bearing unit can be transmitted with a smaller amount of information (data) without interference. In addition, the identification information 94 may be transmitted whenever the hub bearing unit 64 rotates at one revolution. Alternatively, the identification information may be transmitted for every period of the current generated in the coil 83 of the speed sensor module 79 by the pulsar ring 68 , or for every desired period.
When the identification information 94 corresponding to each hub bearing unit 64 is applied to the monitoring system 63 , the management apparatus 66 can identify the hub bearing units 64 the number of which corresponds to the number of bits of the identification information 94 . Accordingly, the monitoring system 63 can be applied easily to a vehicle having a large number of wheels, such as a truck or a railway vehicle. In addition, when the number of the bits increases so as to increase the amount of information that the management apparatus 66 can identify, it is possible to prevent interference with speed information 93 transmitted from hub bearing units 64 in the other vehicles. In consideration of prevention of interference with signals or information transmitted from hub bearing units in the other vehicles, it is preferable that the practical number of bits of the identification information 94 is 16 bits, 32 bits, 64 bits, or more.
Incidentally, the speed sensor module 79 may have a coil 83 and a rod-like pole 84 disposed in the center of the coil 83 , or may be an annular coil twisted circumferentially at each convex portion 78 of the pulsar ring 68 . The pulsar ring 68 and the speed sensor module 79 may be disposed among the rolling elements 73 . In addition, the form of the speed sensor module may be either a passive type illustratively applied to the hub bearing unit in the third embodiment, or an active type. When an active type speed sensor module is used, a power generating coil is provided separately.
Although a ball bearing using balls as rolling elements is used for the hub bearing unit 64 shown in FIG. 7, a cylindrical roller bearing or a tapered roller bearing may be used. Alternatively, single row bearings may be used in combination. In addition, the vibration sensor module 4 and the temperature sensor module 5 shown in the first embodiment, and the vibration sensor 44 and the temperature sensor 45 shown in the second embodiment may be provided together with the speed sensor module 79 . The signal transmission system is not limited to radio waves. Ultrasonic waves, infrared rays, light, and the like, may be used.
Further, the invention is not limited to the bearing unit 64 , but it is also applicable to a ball screw 550 which is a linear motion unit for achieving linear motion by rolling of rolling elements as shown in FIG. 32.
In the ball screw 550 , a sensor unit 560 for a rolling unit is attached to a nut 551 so that abnormality such as flaking in the engagement portion between a screw shaft 552 and the nut 551 can be detected.
Incidentally, the partner to which the sensor unit 560 for a rolling unit is attached is not limited to the nut 551 . The sensor unit 560 for a rolling unit may be attached to a fixed-side support unit 553 or a simple-support-side support unit 554 supporting the screw shaft 552 . The screw shaft 552 is fixed axially to the fixed-side support unit 553 by a lock nut 555 so as to be rotated by a drive motor 557 coupled through a coupling 556 .
In addition, when the sensor unit 560 for a rolling unit is attached to a movable portion or a rail of a linear guide or any other linear motion unit as well as the ball screw, it is possible to detect abnormality such as flaking.
The wireless sensor or the bearing unit according the invention has a detection unit for detecting a subject of detection, an data processing unit for processing data detected by the detection unit, and a communication unit for transmitting, by wireless, detection data processed by the processing unit. Accordingly, the detected data can be transmitted by wireless using radio waves, ultrasonic waves, light, or the like. Thus, there is no need to arrange wiring for sending signals. In addition, when the detection unit is provided in a movable portion, there is no need to arrange wiring for sending signals. Accordingly, there occurs no problem that the wiring is disconnected. In addition, when the wireless sensor or the bearing unit is used in a movable body such as a vehicle, measuring instruments are mounted on the movable body while detection data thereof can be managed at a place other than the movable body.
Further, the wireless sensor or the bearing unit has a detection unit for detecting a subject of detection, a data processing unit for processing data detected by the detection unit, and a communication unit for transmitting, by wireless, the detection data processed by the processing unit together with identification information peculiar to the detection unit. Accordingly, signals transmitted from a plurality of wireless sensors can be identified easily. In addition, when an instruction signal corresponding to identification information, the subject of detection of the detection unit specified by the instruction signal is detected, and the identification signal of the detection unit is transmitted together with the detection data thereof. Accordingly, latest data of any wireless sensor or any bearing unit desired by the user can be acquired easily. When the detected information or information involved therein is converted into digital information and the digital information is transmitted, a signal which has deteriorated due to ambient noise can be reproduced easily. Thus, in completion of information can be prevented.
In the bearing unit according to the invention, a pulsar ring is provided on a first raceway ring of a pair of raceway rings rotating relatively through rolling elements, and a wireless sensor according to the invention is attached to the second raceway ring rotating relatively to the pulsar ring. According to this bearing unit, a detected signal is transmitted by wireless, while electric power can be supplied to a circuit in the wireless sensor by use of a current generated in a coil of a rotation speed sensor provided to be opposed to the pulsar ring. Accordingly, there is no need to arrange a signal line for transmitting the detected signal and a wire for supplying power to the circuit in the wireless sensor.
When a plurality of bearing units are used simultaneously, the bearing units according the invention transmitting data involved in detected signals in an FM modulation system can transmit the data using carrier waves differing from one bearing unit to another and peculiar to the individual bearing units. Accordingly, interference of the signals from the bearing units with one another can be prevented.
In the bearing unit according to the invention, at least one of the rotation number or the rotation speed obtained by the signal processing unit on the basis of a periodic signal generated in the rotation speed sensor is transmitted. Accordingly, digitized data is transmitted. Thus, it is possible to prevent the detection data from changing during the signal propagation.
In the bearing unit according to the invention, at least peculiar identification information is transmitted at a breakpoint of each period of the periodic signal generated in the rotation speed sensor. Accordingly, a signal detected by each bearing unit can be transmitted to the monitoring system with a smaller amount of information and without interference with signals detected by the other bearing units.
In addition, in the management apparatus according to the invention, a signal output from any wireless sensor or any bearing unit is classified on the basis of identification information peculiar to the detection unit included in the signal. Accordingly, signals from wireless sensors or bearing units can be managed easily. Then, in the management apparatus according to the invention, on the basis of the identification information peculiar to the detection units included in signals, signals including the identification information registered in advance in the management apparatus are selectively received. Accordingly, interference can be prevented more surely.
In addition, the monitoring system according to the invention uses wireless sensors or bearing units according to the invention, and management apparatus according to the invention. Accordingly, each wireless sensor or each bearing unit transmits not only detection data detected by its detection unit but also identification information peculiar to the detection unit. The management apparatus classifies and manages the detection data on the basis of the identification information. Thus, it is possible to monitor a plurality of wireless sensors or bearing units simultaneously.
In addition, the monitoring apparatus according to the invention uses a plurality of wireless sensors or bearing units simultaneously, and management apparatus making communication with the wireless sensors and the bearing units by use of carrier waves differing from one wireless sensor or one bearing unit to another and peculiar to each wireless sensor or each bearing unit. Thus, interference of signals between the wireless sensors and the monitoring system can be prevented.
A bearing unit with sensor according to a fourth embodiment of the invention will be described below with reference to the accompanying drawings. Although the following description will be made upon a double row tapered roller bearing by way of example, the bearing unit with sensor is not limited thereto and a single row tapered roller bearing may be used for the bearing unit with sensor. In addition, the kind of bearing unit is not limited if the bearing unit with sensor is a rolling unit such as a cylindrical roller bearing, a ball bearing, or a bearing unit.
As shown in FIGS. 10 and 11, the bearing unit with sensor according to this embodiment includes a rolling bearing 110 , detection sensor units 112 a and 112 b , and a relay unit 114 . The rolling bearing 110 is incorporated in a housing 102 . The rolling bearing 110 includes at least an outer ring 104 , an inner ring 106 and a plurality of rolling elements 108 . The outer and inner rings 104 and 106 can rotate relatively to each other. The rolling elements 108 are incorporated between the outer and inner rings 104 and 106 . The detection sensor units 112 a and 112 b are set in at least one of the outer ring 104 , a member attached to the outer ring 104 , the inner ring 106 and a member attached to the inner ring 106 so as to detect the condition of the rolling bearing 110 . The relay unit 114 can transmit detection data output from the detection sensor units 112 a and 112 b to the outside by wireless.
In this embodiment, the outer ring 104 is attached to the housing 102 while the inner ring 106 is attached to the shaft 116 . In this case, any system can be selected from an outer ring rotating (inner ring stationary) system for rotating the outer ring 104 , an inner ring rotating (outer ring stationary) system for rotating the inner ring 106 and a system for rotating the outer and inner rings 106 and 104 mutually. In addition, other constituent bearing members such as a retainer 119 , a sealing plate (contact or non-contact seal or shield) 118 , and so on, can be selected in accordance with necessity.
The detection sensor units 112 a and 112 b can be provided with a function for detecting the condition of the rolling bearing 110 such as vibration, temperature or rotation speed. In this embodiment, the detection sensor units 112 a and 112 b are provided with a function for detecting the vibration of the rolling bearing 110 and a function for detecting the rotation speed of the rolling bearing 110 respectively by way of example.
Each of the detection sensor units 112 a and 112 b has a sensor 120 and a signal processing circuit 122 for giving signal processing to the output from the sensor 120 (see FIG. 11).
For example, in the detection sensor unit 112 a having a function for detecting the vibration of the rolling bearing 110 , a piezoelectric element (not-shown) is applicable to the sensor 120 . In this case, when vibration acts on the sensor 120 during the operation of the rolling bearing 110 , the piezoelectric element is bent and deformed so that electric charge is generated in the piezoelectric element in accordance with the bending and deformation. Signal processing is given to the charge generated at this time by the signal processing circuit. Thus, the vibration condition of the rolling bearing 110 is detected. Then, the detection data is transmitted to the relay unit 114 as will described later.
On the other hand, as the detection sensor unit 112 b having a function for detecting the rotation speed of the rolling bearing 110 , for example, there can be used a hall element or hall IC using the Hall effect, or a magneto-resistance element whose resistance value changes in accordance with the change of magnetic flux, such as an MR element (magneto resistance element) or GMR element (giant magneto resistance element). In this case, the sensor 120 is disposed to be opposed to a speed detection ring (tone ring, pulsar ring or the like) 124 (see FIG. 15) attached to the outer circumference of the shaft 116 . For example, the change of magnetic flux density occurring during the operation of the rolling bearing 110 is transmitted to the signal processing circuit through the sensor 120 , and signal processing is given thereto. Thus, the rotation speed of the rolling bearing 110 is detected. Then, the detection data is transmitted to the relay unit 114 as will described later.
In this embodiment, the detection sensor units 112 a and 112 b are electrically connected to the relay unit 114 through cables 126 a and 126 b respectively. The detection data from the detection sensor units 112 a and 112 b is transmitted to the relay unit 114 through the cables 126 a and 126 b respectively.
A communication unit 128 is provided in the relay unit 114 (see FIG. 16). The communication unit 128 can convert the detection data from the respective detection sensor units 112 a and 112 b into signal waves with a predetermined frequency component, for example, by amplitude modulation (AM), frequency modulation (FM), phase modulation (PM) or the like, and transmit the signal waves to the outside by wireless. Further, the relay unit 114 is provided with a power supply 130 for driving the communication unit 128 and the respective detection sensor units 112 a and 112 b , and a transmitting antenna 132 for transmitting signal waves by wireless. In this case, radio waves, light waves, ultrasonic waves and the like with a predetermined frequency component can be used as the signal waves. Incidentally, the signal waves can be set to have various frequency components in accordance with the purpose, environment and so on in which the bearing unit with sensor will be used.
Incidentally, the method for setting the detection sensor units 112 a and 112 b is not limited especially if it can fix the sensor units 112 a and 112 b to the outer ring 104 , a member (housing 102 ) attached to the outer ring 104 , the inner ring 106 or a member (shaft 116 ) attached to the inner ring 106 surely. For example, any one of various methods such as a bonding method using an adhesive agent, a screwing method or a fitting method can be used. In this embodiment, the detection sensor units 112 a and 112 b are fixed to the outer ring 104 of the rolling bearing 110 respectively by way of example.
In addition, although the relay unit 114 is attached to the housing 102 in this embodiment, the attachment method thereof is not limited especially. For example, any one of various methods such as a bonding method using an adhesive agent, a screwing method or a fitting method can be used. Further, the position where the relay unit 114 is attached is not limited especially. The relay unit 114 may be attached to be planted in the housing 102 or attached to be exposed outside the housing 102 . In either case, it is preferable that the transmitting antenna 132 is disposed so that the forward end portion thereof projects over the housing 102 . When the forward end portion of the transmitting antenna 132 is made to project over the housing 102 in such a manner, the transmitting/receiving sensitivity of signal waves between the transmitting antenna 132 and a monitor 134 can be improved.
In the configuration described above, detection data output from the detection sensor units 112 a and 112 b is transmitted to the relay unit 114 through the cables 126 a and 126 b respectively during the operation of the bearing unit with sensor (rolling bearing 110 ). The detection data is converted into predetermined signal waves by the relay unit 114 , and then transmitted from the transmitting antenna 132 to the monitor 134 by wireless. At this time, a recorder 136 performs recording/tabulating processing about the vibration condition or the rotation speed condition of the rolling bearing 110 , while an alarm device 138 performs monitoring/alarming processing about the change of vibration or the change of rotation speed.
In such a manner, according to this embodiment, the detection data from the detection sensor units 112 a and 112 b is designed to be transmitted to the outside through the relay unit 114 by wireless so that the number of parts of the bearing unit with sensor can be reduced and the configuration of the unit can be simplified. As a result, it is possible to realize a low-cost and small-size bearing unit with sensor.
In addition, the detection sensor units 112 a and 112 b are electrically connected to the relay unit 114 through the cables 126 a and 126 b respectively. Accordingly, even when a communication function cannot be mounted on the respective detection sensor units 112 a and 112 b , or even when the use environment prevents wireless transmission to the relay unit 114 , wireless transmission from the relay unit 114 to the outside can be achieved.
Further, the power supply 130 is disposed in the relay unit 114 . Accordingly, the number of parts of each detection sensor unit 112 a , 112 b can be reduced and the configuration of the unit can be simplified. Thus, each detection sensor unit 112 a , 112 b can be downsized. As a result, the degree of freedom about the position (disposition) of each detection sensor unit 112 a , 112 b can be improved.
Furthermore, the forward end portion of the transmitting antenna 132 of the relay unit 114 is made to project over the housing 102 . Accordingly, the transmitting/receiving sensitivity of signal waves between the transmitting antenna 132 and the monitor 134 can be improved.
Incidentally, the invention is not limited to the aforementioned fourth embodiment. Various modification can be made as follows.
As a first modification, for example, as shown in FIG. 12, the signal processing circuit 122 may be incorporated in the relay unit 114 while the sensor 120 is mainly disposed in each of the detection sensor units 112 a and 112 b . According to this configuration, the respective detection sensor units 112 a and 112 b can be made smaller in size.
As a second modification, for example, as shown in FIG. 13, a passive type generator built-in sensor 120 a may be incorporated as a rotation sensor in each of the detection sensor units 112 a and 112 b instead of the sensor 120 so that the signal processing circuit 122 and the communication unit 128 are driven directly by the electric power from the generator built-in sensor 120 a . In this case, it is preferable that a storage battery 140 and a charging circuit 142 for charging the storage battery 140 are provided in the relay unit 114 . According to this configuration, the signal processing circuit 122 and the communication unit 128 can be driven directly by the electric power from the generator built-in sensor 120 a during the operation of the bearing unit with sensor (rolling bearing 110 ). Further, even when the operation of the bearing unit with sensor (rolling bearing 110 ) is suspended, the signal processing circuit 122 and the communication unit 128 can be driven continuously by the electric power accumulated in the storage battery 140 because the electric power from the generator built-in sensor 120 a has been accumulated in the storage battery 140 through the charging circuit 142 during the operation. In addition, a passive type sensor may be used merely as a rotation sensor.
As a third modification, for example, configuration may be made as shown in FIG. 14. In this example, it is assumed that no rotation sensor is used in each of the detection sensor units 112 a and 112 b or the rotation sensor is not provided with a function as a power generator. A sensor 120 and a generator 144 are incorporated in each of the detection sensor units 112 a and 112 b . In this case, electric power from the generator 144 is supplied to the storage battery 140 through the charging circuit 142 of the relay unit 114 so that the signal processing circuit 122 and the communication unit 128 are driven by the electric power of the storage battery 140 .
Incidentally, in the configurations of the fourth embodiment and its first to third modifications described above, an antenna (not shown) which can transmit and receive may be used instead of the transmitting antenna 132 of the relay unit 114 while the communication unit 128 has a transmitting/receiving function. According to this configuration, the signal processing circuit 122 can be controlled from the outside through the relay unit 114 . As a result, the condition (for example, vibration condition, temperature condition, rotation speed condition, and the like) of the rolling bearing 110 can be detected by remote control.
Next, a bearing unit with sensor according to a fifth embodiment of the invention will be described with reference to the accompanying drawings.
As shown in FIGS. 15 and 16, in the bearing unit with sensor according to this embodiment, each of detection sensor units 112 a and 112 b is provided with a communication unit 146 , a transmitting antenna 148 and a power supply (battery cell) 150 . By the communication unit 146 and the transmitting antenna 148 , detection data of the detection sensor units 112 a and 112 b can be converted into signal waves with a predetermined frequency component, and transmitted by wireless. The power supply 150 drives a sensor 120 , a signal processing unit 122 and the communication unit 146 . On the other hand, a relay unit 114 is provided with a receiving antenna 152 . By the receiving antenna 152 , the detection data of the detection sensor units 112 a and 112 b transmitted through the transmitting antenna 148 by wireless is received and sent to a communication unit 128 . In this case, radio waves, light waves, ultrasonic waves and the l