Title:
FLUID ENTRAPMENT DETECTION
Kind Code:
A1


Abstract:
A washing machine includes a cabinet, a wash tub supported within the cabinet, a spin basket for holding a wash load, the spin basket rotatable in the wash tub by a motor, and a controller for driving the motor to rotate the spin basket. The controller is adapted to detect water entrapment within a wash load in a spin basket of a washing machine by measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed, controlling the spin basket to dewater a wash load in the spin basket, measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed, comparing the first and second parameters, and detecting whether there is water entrapped in the wash load based on the comparison between the first and second parameters.



Inventors:
Darby, Adam John (AUCKLAND, NZ)
Cheung, Man Kit (AUCKLAND, NZ)
Application Number:
12/023428
Publication Date:
07/31/2008
Filing Date:
01/31/2008
Primary Class:
Other Classes:
68/12.02
International Classes:
D06F37/00; D06F23/00
View Patent Images:
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Primary Examiner:
PERRIN, JOSEPH L
Attorney, Agent or Firm:
IP Docket (Chicago, IL, US)
Claims:
We claim:

1. A washing machine comprising: a cabinet, a wash tub supported within the cabinet; a spin basket for holding a wash load, the spin basket rotatable in the wash tub by a motor, a controller for driving the motor to rotate the spin basket, the controller adapted to detect water entrapment within a wash load in a spin basket of a washing machine by: measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed, controlling the spin basket to dewater a wash load in the spin basket, measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed, comparing the first and second parameters, and detecting whether there is water entrapped in the wash load based on the comparison between the first and second parameters.

2. A washing machine according to claim 1 wherein if the controller detects that there is water entrapped in the wash load, the controller operates the motor to rotate the spin basket a second spin speed, and wherein the controller detects that there is no water entrapped in the wash load, the controller operates the motor to rotate the spin basket at a third spin speed, the third spin speed being greater than the second spin speed.

3. A washing machine according to claim 1 wherein it is detected that there is water entrapped if the rotational inertia indicated by the second parameter is greater than the rotational inertia indicated by the first parameter.

4. A washing machine according to claim 1 wherein measuring the first parameter comprises: a) the controller operating the motor to apply a torque to the spin basket to rotate spin basket at the first spin speed, b) the controller operating the motor to remove the torque and allow the spin basket to decelerate to an idle spin speed, and c) the controller measuring a first time for the spin basket to decelerate to the idle speed, wherein the measured first time is the first parameter.

5. A washing machine according to claim 4 wherein the step of measuring the second parameter comprises: a) the controller operating the motor to apply a torque to the spin basket to rotate spill basket at the first spin speed, b) the controller operating the motor to remove the torque and allow the spin basket to decelerate to a idle spin speed, and c) the controller measuring a second time for the spin basket to decelerate to the idle speed, wherein the measured second time is the second parameter,

6. A washing machine according to claim 5 wherein it is detected that there is water entrapped if the second time is larger than the first time.

7. A washing machine according to claim 1 wherein the step of measuring the first parameter comprises: a) the controller operating the motor to apply a torque to the spin basket to rotate spin basket at the first spin speed, b) the controller operating the motor to remove the torque and allow the spin basket to decelerate to a idle spin speed, c) the controller measuring a time for the spin basket to decelerate to the idle speed, d) the controller repeating steps a)-c) at least once to obtain one or more additional measured times, and e) the controller calculating the average of the measured times, wherein the average of the measure times is the first parameter.

8. A washing machine according to claim 7 wherein the step of measuring the second parameter comprises: a) the controller operating the motor to apply a torque to the spin basket to rotate spin basket at the first spin speed, b) the controller operating the motor to remove the torque and allow the spin basket to decelerate to a idle spin speed, c) the controller measuring a time for the spin basket to decelerate to the idle speed, d) the controller repeating steps a)-c) at least once to obtain one or more additional measured times, and e) the controller calculating the average of the measured times, wherein the average of the measure times is the first parameter.

9. A washing machine according to claim 1 wherein the first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed is the time taken for the spin basket to decelerate from the first speed to an idle speed.

10. A washing machine according to claim 1 wherein the second parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed is the time taken for the spin basket to decelerate from the first speed to an idle speed.

11. A washing machine according to claim 2 wherein the second spin speed is less 670 rpm.

12. A washing machine according to claim 2 wherein the third spin speed is greater than 670 rpm.

13. A washing machine according to claim 1 wherein the first speed is between 15 rpm and 150 rpm.

14. A washing machine according to any one of claims 4, 5, 7 or 8 wherein the idle speed is between 35 rpm and 0 rpm.

15. A method of detecting water entrapment within a wash load in a spin basket of a washing machine, comprising the steps of: measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed, dewatering the wash load, measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed, comparing the first and second parameters, and determining whether there is water entrapped in the wash load based on the comparison between the first and second parameters.

16. A method according to claim 15 wherein if it is determined that there is water entrapped in the wash load, rotating the spin basket a second spin speed, and wherein if it is determined that there is no water entrapped in the wash load, rotating the spin basket at a third spin speed, the third spin speed being greater than the second spin speed.

17. A method according to claim 15 wherein it is determined that there is water entrapped if the rotational inertia indicated by the second parameter is greater than the rotational inertia indicated by the first parameter.

18. A method according to claim 15 wherein the step of measuring the first parameter comprises: a) applying a torque to the spin basket to rotate spin basket at the first spin speed, b) removing the torque and allowing the spin basket to decelerate to a idle spin speed, and c) measuring a first time for the spin basket to decelerate to the idle speed, wherein the measured first time is the first parameter.

19. A method according to claim 18 wherein the step of measuring the second parameter comprises: a) applying a torque to the spin basket to rotate spin basket at the first spin speed, b) removing the torque and allowing the spin basket to decelerate to a idle spin speed, and c) measuring a second time for the spin basket to decelerate to the idle speed, wherein the measured second time is the second parameter,

20. A method according to claim 19 wherein it is determined that there is water entrapped if the second time is larger than the first time.

21. A method according to claim 15 wherein the step of measuring the first parameter comprises: a) applying a torque to the spin basket to rotate spin basket at the first spin speed, b) removing the torque and allowing the spin basket to decelerate to a idle spin speed, c) measuring a time for the spin basket to decelerate to the idle speed, d) repeating steps a)-c) at least once to obtain one or more additional measured times, and e) calculating the average of the measured times, wherein the average of the measure times is the first parameter.

22. A method according to claim 21 wherein the step of measuring the second parameter comprises: a) applying a torque to the spin basket to rotate spin basket at the first spin speed, b) removing the torque and allowing the spin basket to decelerate to a idle spin speed, c) measuring a time for the spin basket to decelerate to the idle speed, d) repeating steps a)-c) at least once to obtain one or more additional measured times, and e) calculating the average of the measured times, wherein the average of the measure times is the second parameter.

23. A method according to claim 15 wherein the first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed is the time taken for the spin basket to decelerate from the first speed to an idle speed.

24. A method according to claim 15 wherein the second parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed is the time taken for the spin basket to decelerate from the first speed to an idle speed.

25. A method according to claim 16 wherein the second spin speed is less 670 rpm.

26. A method according to claim 16 wherein the third spin speed is greater than 670 rpm.

27. A method according to claim 15 wherein the first speed is between 15 rpm and 150 rpm.

28. A method according to any one of claims 18, 19, 21 or 22 wherein the idle speed is between 35 rpm and 0 rpm.

29. A method according to any one of claims 18, 19, 21 or 22 wherein measuring a first or second time for the spin basket to decelerate to an idle spin speed comprises: measuring the time taken for the spin basket to decelerate from an intermediate spill speed between the first and idle spin speed to the idle spin speed.

30. A washing machine according to any one of claims 4, 5, 7 or 8 wherein measuring a first or second time for the spin basket to decelerate to an idle spin speed comprises: measuring the time taken for the spin basket to decelerate from an intermediate spin speed between the first and idle spin speed to the idle spin speed.

31. A washing machine comprising: a cabinet, a wash tub supported within the cabinet; a spin basket for holding a wash load, the spin basket rotatable in the wash tub by a motor, a controller for driving the motor to rotate the spin basket, the controller adapted to detect water entrapment within a spin basket of a washing machine by: measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed, controlling the spin basket to dewater a wash load in the spin basket, measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed, comparing the first and second parameters, and detecting whether there is water entrapped in the wash load based on the comparison between the first and second parameters.

Description:

CROSS-REFERENCE AND INCORPORATION BY REFERENCE

This application is a non-provisional of U.S. Provisional Patent Application Ser. No. 60/887,390, entitled “Fluid Entrapment Detection”, filed Jan. 31, 2007. U.S. Patent Provisional Patent Application Ser. No. 60/887,390 is hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to washing machine, and in particular to a control system used to modify the operation of the washing machine based on certain characteristics of the wash load.

BACKGROUND TO THE INVENTION

The typical washing machine has a washing basket, tub or receptacle that holds laundry for washing. The washing basket is coupled to a motor that is used to rotate the washing basket at various speeds during various operating cycles of the washing machine. A controller is used to control the operation of the motor depending on the various cycles of the washing cycle. Similarly, the controller receives feedback from a number of sensors and/or uses a number of algorithms to sense a number of conditions within the washing drum. This feedback is used to control the operating speed of the motor depending on the various operating conditions sensed during the washing cycle. Such conditions include wash basket imbalance conditions for example. This condition is predominantly sensed when the wash basket speed is being changed, for example, from an agitation cycle up to optimal spin speed where wash load dehydration occurs. As an example, an imbalance in the washing basket due to the load size and/or load distribution within the wash basket is magnified when the wash basket is rotated at high speeds. This will cause excessive vibration and may lead to washing machine malfunction.

US2005/0155159 to Gregory A Peterson discloses a method of operating a washing machine to detect a drum unbalance condition during the washing machine spin cycle. The washing machine is operated at fast speed to rotate the laundry basket. Load balance data is collected during the rotation of the basket. The received load balance data is then analysed and the washing machine is operated at a second high speed if it is determined that the load in the receptacle is balanced. This system includes a number of sensors which detect vibration of the washing machine drum to provide feedback to a controller which then analyses the data and modifies the operation of the washing cycle based on the information received from the sensors.

In this specification where reference has been made to patent specifications, other external documents, are other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise reference to such external documents is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

It is an object of the present invention to provide a washing machine or method for detecting water entrapped in a wash load.

SUMMARY OF THE INVENTION

In a first aspect, the present invention may broadly be said to be a washing machine comprising:

a cabinet,

a wash tub supported within the cabinet;

a spin basket for holding a wash load, the spin basket rotatable in the wash tub by a motor,

a controller for driving the motor to rotate the spin basket, the controller adapted to detect water entrapment within a wash load in a spin basket of a washing machine by:

measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed,

controlling the spin basket to dewater a wash load in the spin basket,

measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed,

comparing the first and second parameters, and

detecting whether there is water entrapped in the wash load based on the comparison between the first and second parameters.

In a second aspect, the present invention may broadly be said to be a method of detecting water entrapment within a wash load in a spin basket of a washing machine, comprising the steps of:

measuring a first parameter indicative of the rotational inertia of the spin basket when accelerated to a first spin speed,

dewatering the wash load,

measuring a second parameter indicative of the rotational inertia of the spin basket at the first speed,

comparing the first and second parameters, and

determining whether there is water entrapped in the wash load based on the comparison between the first and second parameters.

When interpreting statements in this invention which include “comprising”, the features prefaced by that term in each statement, all need to be present but other features can also be present.

This invention may also be said broadly to comprise in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention comprises the foregoing and also envisages constructions of which the following only gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described by way of example only and with reference to the accompanying drawings.

FIG. 1 shows in schematic form a washing machine according to one embodiment of the invention,

FIG. 2 shows in schematic form a wash load being engulfed by a waterproof item within the wash basket process of FIG. 1.

FIG. 3 shows in schematic form the position within a spin basket of a wash load engulfed by a waterproof item when the wash basket is spun.

FIG. 4 is high level process flow showing how the wash load inertia sensing testing is applied during a typical wash cycle.

FIG. 5 is a process flow diagram showing one step of the wash load inertia sensing method.

FIG. 6 is a process flow diagram showing the implementation of the wash load inertia sensing as applied to the washing machine in FIG. 1.

DETAILED DESCRIPTION

Overview

The present invention will be described primarily with reference to a laundry washing machine. It has been found that if water is trapped inside a large waterproof item for example that surrounds or encloses around a number of other clothes items in the wash basket being cleaned, it is possible for the machine can reach a high spin speed, for example over 600 rpm, before the wash basket is forced violently out of balance. This type of situation is caused by water being trapped by the waterproof item and can result in the washing machine being damaged.

FIG. 1 shows in schematic form a washing machine 10 adapted to modify its operation based on the type or nature of a wash load 14 in the wash/spin basket 13. The washing machine 10 comprises an outer housing 11, an internal tub 12 and a spin basket 13 within the inner tub 12. The spin basket 13 is adapted to hold and wash items comprising the wash load 14. The washing machine 10 includes a motor 15 for an agitator 19 in order to wash the items in a wash load. A pump is required for recirculating water and delivering water from the spin basket. A motor is provided for introducing water into the wash tub 12. The machine also includes a controller 16 which is adapted to control various aspects of the function of the washing machine 10, including the motor 15 and pump for filling and draining wash water from the spin basket 13. The controller can also operate various other functions of the washing machine. These functions will be known to those skilled in the art and will not be described here.

Water Entrapment Condition

For a normal wash load it has been found that the inertia after spinning the wash load to 330 rpm for the first time should be noticeably less than the measured inertia straight after draining the wash water out of the wash load. This is due to water being extracted from the clothes while spinning the wash load at low speed. It has been found that a wash load would typically lose approximately 30% of its saturated mass after spinning the wash load to 330 rpm. However, if a waterproof item has engulfed the rest of the wash load thereby preventing water from escaping, then the water remaining in the wash bowl will be centrifuged outwards during spinning phase thereby increasing the rotational inertia. Water can also be trapped due to clogging of the spin basket (due to calcium deposits or the like). This can also cause imbalance issues. The present invention can alleviate this also by doing inertia testing and limiting spin speed if necessary.

A preferred embodiment of the invention will be described with reference to FIG. 2. This embodiment relates to a washing machine 10 with a low profile wash-plate 19 that has a mode that is part of the wash cycle process that determines if wash water 18 is being trapped within the spin basket 13.

It has been found that after draining the wash water 18 from the spin basket 13, excess wash water 18 can be trapped in the wash load 14. This has been found to be more likely to happen in a washing machine with a low-profile wash plate. FIG. 2 shows this particular condition whereby a waterproof item 40 has engulfed the rest of the wash load 41 thereby preventing all of the wash water from being drained from the wash load 41 and exiting the spin basket 13. Under these conditions, when the controller 16 initiates a spin cycle, the wash load items 41 that have retained the wash water are forced towards the circumference of the spin basket 13 due to the centrifugal force acting on the wash load 41 as shown in FIG. 3. An amount of the wash water will remain trapped in the wash load 41 during the spin cycle as a result of the waterproof item 40 engulfing the wash load 41 thereby preventing the excess water from being allowed to be removed and subsequently drain away from the wash load 41.

Hence, it has been found that when the spin basket 13 is spun up to a critical spin speed, the entrapped water within the wash load 41 suddenly shifts position within the wash bowl 13 causing a sudden and violent off-balance condition. This sudden shift of the entrapped water is believed to be due to the entrapped water being held by the wash load 41 in temporary “baffles” that compress against the walls of the spin basket 13 as the spin basket 13 accelerates up to spin speed. At the critical spin speed, the “baffles” compress enough to allow the water to overflow them.

In this off-balance condition, the controller 16 will not continue to spin the spin basket 13 up to a maximum spin speed. The excess out of balance condition has been found to be so violent that the machine is at risk of being damaged if the spin cycle is not limited. As an example, this violent off-balance condition can cause damage to the washing machine suspension (not shown). It has been found that this sudden off-balance condition can occur when the spin speed reaches between 600 rpm and 1000 rpm. By limiting the spin basket spin speed to below a critical spin speed when an entrapped water condition has been detected, the sudden off-balance condition can be prevented. Typically, the critical spin speed has been found, through experimentation, to be no greater than 670 rpm.

The present invention is therefore directed to a system that can incorporated into a clothes washing cycle that can be used to detect when water within the wash load has been entrapped and subsequently limit the spin speed to below a threshold value for the remainder of the washing cycle.

Through experimentation it has been found that the most robust technique for detecting a water entrapment condition is based on a system that is capable of measuring the rotational inertia of a wash load when the wash load is placed into a spin condition. Furthermore, given that the out of balance condition has been found to occur at above a certain critical spin speed, it is preferable that the system employs a low speed rotational inertia detection system.

Rotational Inertia Detection

The more rotational inertia an object has, the less the object responds to being spun. In other words, the rotational inertia of an object is a measure of the object's resistance to a change of rotation. The low speed rotational inertia detection of a preferred embodiment of the present invention involves a wash load inertia sensing test being undertaken one or a number of times during each of the drain/spin sequences using the controller 16 to record and analyse the measured data. The spin basket/wash load rotational inertia is measured before dewatering of the wash load and is again measured again after dewatering has occurred. The relationship between the measured rotational inertia values before and after dewatering can be used to detect for water entrapment. For example, if the rotational inertia before dewatering is less than that after dewatering, it can be determined that water is entrapped in the wash load. This measured data is typically a measurement of the time taken for the spin basket 13 to decelerate from a first higher spin speed to a second lower spin speed when no rotational torque is applied by the motor 15 or other driving means. This measured data is recorded and stored in a memory device within the controller 16 one or more times during the wash load inertia sensing test sequence. The controller 16 then analyses the measured data to determine if water is being entrapped within the wash load 41. If the controller 16 determines that water is being entrapped, the controller 16 can modify the spin cycle to below a pre-determined threshold speed. This could be in any number of ways. Alternatively, another action may be taken such as stopping the cycle and issuing an alarm. This wash load inertia sensing test could be repeated during each drain/spin cycle undertaken throughout the entire wash cycle.

FIG. 4 shows a high level process flow showing how the wash load inertia sensing system testing incorporated in a typical wash cycle used in a washing machine. After the start of the wash cycle at step 90, the spin basket 13 is filled to a pre-determined water level at step 91 before the spin basket 13 is agitated at step 92 to wash the wash load of clothes. The spin basket 13 is then drained at step 93 before the wash load inertia sensing and detection process is undertaken at step 94. Depending on the result of the wash load inertia test at step 95 will determine the speed at which the spin basket 13 is to be rotated at during the spin cycle at step 96. Each step of the wash cycle from step 91 through to step 97 is repeated until the last spin cycle is undertaken step 97 after which the wash cycle is completed at step 98.

Wash Load Inertia Sensing Test Sequence

FIG. 5 shows a process flow diagram illustrating each of the wash load inertia sensing test steps. On completion of an agitation and drain phase of the wash cycle, a wash load inertia test is undertaken. This test sequence is undertaken one or more times before a spin speed for the particular wash load is determined. The entire inertia sensing test sequence is illustrated and discussed later.

For each inertia sensing test, the spin basket 13 is driven by the motor 15 up to a spin speed of preferably 45 rpm, step 50 and held at that speed for a period in the order of 2 seconds, step 51. Power is then removed from the motor 15 thereby allowing the spin basket 13 to decelerate, step 52. The motor 15 uses Hall effect sensors to provide rotor position sensing and rotor speed data as a data input to the controller 16. Whilst it is preferable to use Hall effect sensors to sense the rotor position other known techniques can be used such as back EMF sensing can also be used. Under the control of the controller 16, a timer integral with the controller 16 is started when the motor 15 drives the spin basket 13 by applying a torque. A first spin speed of 45 rpm has been determined as suitable but other spin speeds could be used within the range of between 15 rpm to 150 rpm. The idle state is considered to occur when the spin basket 13 rotation speed falls below a second speed such as 15 rpm or less at step 53. The time it takes for the spin basket 13 to decelerate from preferably 35 rpm or any other suitable speed less than or equal to the first spin speed of 45 rpm, down to 15 rpm is stored in a memory device within the controller 16 as a first timing value. Whilst it is preferable to time the deceleration of the spin basket 13 between 35 rpm down to 15 rpm, this range should be in no way limiting as other spin speed ranges could be used such as between 75 rpm to 20 rpm for example. The spin basket 13 is then allowed to continue to decelerate until the spin basket 13 and the motor 15 stops at step 54. The inertia sensing test is repeated again at step 55. A second timing value is obtained by repeating steps 50 through to 54. The controller 16 then retrieves the first timing value from the memory device and undertakes an averaging calculation on the first timing value and the second timing value to provide an averaged timing value as shown in step 56. The averaged timing value is then stored by the controller 16 in the memory device as a reference timing value. This provides a first parameter which is a parameter indicative of the rotational inertia of the spin basket 13/wash load 41 prior to at least partial dewatering. As will be appreciated by those skilled in the art, more than two timing values could be measured and averaged to obtain the first parameter indicative of the rotational inertia.

Entire Rotational Inertia Protection and Measurement

On completion of the wash load inertia sensing test sequence detailed above, the spin basket 13 is allowed to spin up to a speed of 330 rpm for approximately 30 seconds. This provides some dewatering of the wash load 41. Power is then removed from the motor 15 allowing the motor 15 to coast down to zero rpm indicating that the spin basket 13 has stopped spinning. The controller 16 then initiates a further wash load inertia sensing test sequence as illustrated with reference to FIG. 4.

The spin basket 13 is driven by the motor 15 up to a spin speed of preferably 45 rpm, step 50 and held at that speed for a period in the order of 2 seconds, step 51. Power is then removed from the motor 15 thereby allowing the spin basket 13 to decelerate, step 52. The motor 15 uses Hall effect sensors to provide rotor position sensing and speed data as a data input to the controller 16. Whilst it is preferable to use Hall Effect sensors to sense the rotor position other known techniques can be used such as back EMF sensing can also be used. Under the control of the controller 16, a timer that is integral with the controller is started when the motor 15 drives the spin basket 13 by applying a torque. A speed of 45 rpm has been determined as suitable but other spin speeds could be used within the range of 15 rpm to 150 rpm. The idle state is considered to occur when the spin basket 13 rotation speed falls below a second speed such as 15 rpm or less at step 53. The time it takes for the spin basket 13 to decelerate from 35 rpm down to 15 rpm is stored in a memory device within the controller 16 as a first timing value. The spin basket 13 is then allowed to continue to decelerate until the spin basket 13 and the motor 15 stops at step 54. The inertia sensing test is repeated again at step 55. A second timing value is obtained by repeating steps 50 through to 54. The controller 16 then retrieves the first timing value from the memory device and undertakes an averaging calculation on the first timing value and the second timing value to provide an averaged timing value as shown in step 56. The averaged timing value is then stored by the controller 16 in the memory device as a second reference timing vale. This provides a second parameter which is a parameter indicative of the rotational inertia of the spin basket 13/wash load 41 after a dewatering cycle has occurred.

The controller 16 then retrieves the first reference timing value from the memory device and compares the second reference timing value with the first reference timing value, that is, the second parameter is compared with the first parameter. Where the second reference timing value is greater than the first reference timing value indicates that the rotational inertia after dewatering is higher than the rotational inertia before dewatering indicating that water entrapped within the wash load. If this is the case, a water trapped flag is set to “1” by the controller 16 and the controller 16 will subsequently limit the spin speed to not exceed a critical value. This critical spin speed value is typically in the range of between 500 to 700 rpm. If the second reference timing value is less than the first reference timing value, the water trapped flag is set to “0” by the controller 16 allowing the motor 15 to be driven up to a maximum spin speed that is typically in the order of 1000 rpm.

The differential method, whereby first and second reference timing values are obtained eliminates friction from the analysis which simplifies the process.

FIG. 6 show an entire wash cycle for a washing machine that incorporates the wash load inertia sensing and detection of the present invention. In this embodiment, two inertia sense tests are done to determine the final spin speed, one as part of the spray rinse cycle, and one as part of the deep rinse cycle (if there is one). The inertia sensing test is redone after a deep rinse because there is a chance that the water gets trapped during the deep rinse although it may not have happened during the wash. On commencement of the wash cycle at step 60, the spin basket 13 is filled with water to a predefined water level at step 61 and a first wash cycle, shown as an economy wash cycle at step 62 is undertaken. More water is added to the spin basket 13 at step 63 prior to the commencement of a wash load agitate cycle at step 64. The spin basket 13 is then drained at step 65 prior to the commencement of the first inertia sensing and detection process being undertaken at step 66 to provide the first reference timing value. This is determined as set out above. A first spray rinse cycle is then undertaken at step 67 before motor torque is removed allowing the spin basket to coast to a stop at step 68. Dewatering is included as part of the spray rinse cycle, step 67. Once the spin basket 13 has stopped rotating (after dewatering) the second step of the inertia sensing and detection is undertaken at step 69 enabling the second reference timing value to be determined (as set out above). A comparison of the first and second reference timing values is undertaken at step 70. If the second reference timing value is greater than the first reference timing signal then a flag is set to one which will cause the final spill speed to be limited to 670 rpm or lower. If second reference timing value is less than the first reference timing value the flag is set to zero which will cause the final spin speed not to be limited. The remainder of the rinse and drain steps are undertaken at step 71 until the spin basket 13 is dewatered. If one of the rinse steps was not a deep rinse at step 72 then the final spin speed of the spin basket 13 is limited to at or below the critical spin speed of between 500 to 700 rpm as shown at step 73 before the wash cycle is completed at step 74.

In the event that one of the rinse steps was a deep rinse at step 72, if the final spin speed is less than between 500 to 700 rpm, shown as 670 rpm by way of example in FIG. 6, the spin basket 13 is limited to at or below the critical spin speed of 670 rpm or within the range of between 500 and 700 rpm as shown at step 73 before the wash cycle is completed at step 74. However, if the final spin speed is determined to be greater that the critical speed shown as 670 rpm in step 75 then a further second inertia sensing and detection step is undertaken at step 76 to determine a second reference timing value (as set out above). The spin basket is then spun up to a speed of 330 rpm at step 77, motor torque is removed and the spin basket 13 is again allowed to coast to a stop at step 78. A further inertia sensing and detection test is undertaken at step 79 to provide a post dewater reference timing value parameter value. The controller 16 undertakes a second comparison test to determine if the second reference timing value is greater or less than the post dewatering reference timing value to provide a second parameter at step 78. The controller 16 then compares the first parameter with the second parameter to determine if water is entrapped at step 80 to determine if the spin basket spin speed is to be limited to a critical spin speed shown as 670 rpm at step 73 before the wash cycle is completed at step 74.

A number of tests were undertaken on different load sizes and fabric types implementing the wash load inertia sensing test as detailed above. To simulate a waterproof item engulfing a wash load, the wash load was enclosed in a plastic bag. The percentage difference between the first and second set of wash load inertia sensing test results are illustrated in Table 1 below. Each of the measured values was determined on the basis of averaging the result obtained from three consecutive wash load inertia sensing tests.

In order to provide a robust detection of potential water entrapment conditions, the controller 16 is programmed with a failure threshold value that is stored in the memory device within the controller 16. This failure threshold value sets a limit or trigger value as a limit above which will provide an indication that water is entrapped within the spin basket 13. It has been found that a failure threshold value in the order of +3% will provide a suitable threshold value level to provide a water trapped indication. Therefore, the results of the first and second reference timing value comparison test are also compared with the threshold value. If the threshold value is at or above 3% a water entrapment condition is initiated and the spin speed limited to below the critical spin speed. Otherwise, the wash cycle will initiate a normal dehydration spin speed.

TABLE 1
WATER TRAPPED
NORMALLOAD
LOAD SIZE AND TYPELOAD(Plastic Bag)
2 kg Cotton−5%+14%
3.3 kg Cotton−4%+18%
6.2 kg Cotton−3%+13%
Small Synthetic Items−10%+11%
Med Synthetic Items−9%+12%
1 kg Towels−6% +9%
2 kg Towels−8%+13%
4 kg Towels−10%0.16

Implementation

In order to prevent any water entrapment from affecting the wash cycle and providing a fault type condition, the wash load inertia sensing system of the present invention is programmed into the wash cycle software residing in the controller 16. The wash load inertia sensing process steps are implemented each time an agitation cycle is completed and prior to a wash load dehydration spin cycle being undertaken. This will limit the occurrence of potentially damaging off-balance conditions occurring and therefore limit the potential risk of damage to the washing appliance 10.

The controller 16 will be programmed to detect small wash loads and as such the wash load inertia sensing system will be disabled. This condition will typically relate to a bowl float level that is measured to be less than 120 mm. Disabling the wash load inertia sensing system will avoid any false fault trips when the bowl is empty or where the is very little load in the washing machine 10.

The inertia sensing system is a multi-stage wash load inertia sensing system that is incorporated into and integral with a typical wash cycle set of events. The detection of a water entrapment condition preferably does not terminate a wash cycle and instead enables the wash cycle to resume and run to completion by limiting the spin speed at or below a critical speed level. In order to account for changing wash cycle conditions such as a power failure event or a user interrupting the wash cycle for example, the controller 16 has been programmed to deal with such situations. Some of the possible scenarios are outlined below.

a. Clearing the “Water Trapped” Status

The ‘water trapped’ status is cleared once each particular phase of the wash cycle has completed. Furthermore, the ‘water trapped’ status is clear when the washing machine 10 commences a further agitation phase a wash load inertia sensing cycle is undertaken before the wash cycle commences another drain/spin phase.

b. Power Cut

When a ‘water trapped’ situation is sensed by the wash load inertia sensing system, the ‘water trapped’ data indication is saved in the memory device within the controller 16 in the ‘brown out data’ area. Data stored in the ‘brown out data’ area is used as reference value information enabling this data to be retrieved once washing machine power is restored. This will enable the wash cycle to restart the wash cycle from the point where the washing machine 10 lost power.

c. Wash Load Sensing is Interrupted and the Wash Cycle is Advanced to a Different Stage.

The wash load inertia sensing system undertakes three distinct process steps to test for a ‘water trapped’ condition. The first two inertia test steps enable a reference ‘inertia’ value to be determined whilst the last stage of the inertia sensing test compares a further measured ‘inertia’ value with the reference ‘inertia’ value on completion of a 330 rpm spin phase. If a user pauses or advances the wash cycle while the wash load inertia sensing process is being performed, the process step count will be renumbered and the controller 16 will continue to undertake the remainder of the inertia sensing processing steps until the entire inertia sensing process has been competed.

d. Spray/Deep Rinse

Whilst it is not strictly necessary to perform inertia sensing during the spray rinse cycle after the main wash cycle as the machine is going to fill up again in the deep rinse cycle. However, if the wash cycle is interrupted during the spray rinse phase of the cycle and the wash cycle is advanced to a spin phase of the wash cycle, the wash load inertia sensing is performed for a mini aqua rinse cycle which is part of the spray portion of the deep rinse phase of the wash cycle.

Under normal operating conditions the washing machine will spin a wash load up to a maximum of 1000 rpm for a predetermined period of time allowing for a large amount of water to be removed from the wash load. In the event that a water entrapment condition is detected by the washing machine, thereby limiting the spin speed to at or below a critical spin speed, water entrapped spin cycle will run for the same time as that provided for normal spin operating conditions. As such, the wash load will be ‘wetter’ on completion of the ‘water trapped’ spin phase than if the wash load was spun at 1000 rpm. However, the level of wetness is insignificant given the risks involved in running the washing machine into an off-balance condition that will averted by implementing the wash load inertia sensing system of the present invention.