Title:
Valve timing adjusting system
Kind Code:
A1


Abstract:
A valve timing adjusting system 1 includes a first valve timing adjusting device 6 changing a relative rotational of an intake camshaft S3 relative to a crank shaft S1, and also a second valve timing adjusting device 7 having a first rotor 71 transmitting the rotatory driving force derived from the crank shaft S1 to the device 6 via a chain 9a, and a second rotor 72 secured on an exhaust camshaft S4 rotating synchronously with the crank shaft S1.



Inventors:
Yamauchi, Makoto (Tokyo, JP)
Kinugawa, Hiroyuki (Tokyo, JP)
Application Number:
10/771304
Publication Date:
08/12/2004
Filing Date:
02/05/2004
Assignee:
MITSUBISHI DENKI KABUSHIKI KAISHA
Primary Class:
International Classes:
F01L1/34; F01L1/344; (IPC1-7): F01L1/34
View Patent Images:
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Primary Examiner:
CHANG, CHING
Attorney, Agent or Firm:
SUGHRUE MION, PLLC (2000 PENNSYLVANIA AVENUE, N.W. SUITE 900, WASHINGTON, DC, 20006, US)
Claims:

What is claimed is:



1. A valve timing adjusting system comprising: a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational position of the intake camshaft relative to a crank shaft of the internal combustion engine; and a second valve timing adjusting device having a first rotor transmitting rotatory driving force derived from the crank shaft to the first valve timing adjusting device, and having a second rotor secured on an exhaust camshaft rotating synchronously with the crank shaft.

2. The valve timing adjusting system according to claim 1, wherein the rotation regulating position of the first valve timing adjusting device is set at the most advanced position, and the rotation regulating position of the second valve timing adjusting device is set at the most lagged position.

3. A valve timing adjusting system comprising: a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational position of an intake camshaft relative to a crank shaft of an internal combustion engine; and a second valve timing adjusting device having a first rotor rotating synchronously with the crank shaft, and a second rotor secured on an exhaust camshaft of the internal combustion engine.

4. The valve timing adjusting system according to claim 3, wherein the rotation regulating position of the first valve timing adjusting device is set at the most advanced position, and the rotation regulating position of the second valve timing adjusting device is set at the most lagged position.

5. A valve timing adjusting system comprising: a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational angle of an intake camshaft relative to a crank shaft of the internal combustion engine; a second valve timing adjusting device provided on an exhaust camshaft of the internal combustion engine, and changing the relative rotational angle of the exhaust camshaft relative to the crank shaft; and a third valve timing adjusting device provided on the crank shaft side; wherein the third valve timing adjusting device is provided in series in the direction of the driving transmission relative to the first valve timing adjusting device and the second valve timing adjusting device.

6. The valve timing adjusting system according to claim 5, wherein among the plurality of valve timing adjusting devices provided in series, two are set at different rotation regulating positions, respectively.

7. The valve timing adjusting system according to claim 6, wherein among the two valve timing adjusting devices provided in series, one is set at the most advanced position, and the other is set at the most lagged position.

8. The valve timing adjusting system according to claim 7, wherein both of the two valve timing adjusting devices provided in series are of the vane type.

9. The valve timing adjusting system according to claim 7, wherein among the two valve timing adjusting devices provided in series, one is of the vane type, and the other is of the helical type.

10. The valve timing adjusting system according to claim 9, wherein the valve timing adjusting device whose rotation regulating position is set at the most advanced position is of the helical type, and the valve timing adjusting device whose rotation regulating position is set at the most lagged position is of the vane type.

11. The valve timing adjusting system according to claim 5, wherein the one valve timing adjusting device whose rotation regulating position is set at the most advanced position is provided in series relative to the two valve timing adjusting devices whose rotation regulating positions are set at the most lagged position, respectively.

12. The valve timing adjusting system according to claim 11, wherein the one valve timing adjusting device whose rotation regulating position is set at the most advanced position is coaxially connected directly with the crank shaft of the internal combustion engine.

13. The valve timing adjusting system according to claim 7, wherein two valve timing adjusting devices provided in series are made in combination of the vane type and the electric-powered type.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a valve timing adjusting system controlling opening and closing timing of an intake valve or an exhaust valve of an internal combustion engine such as an engine (hereinafter referred to simply as an “engine”).

[0003] 2. Description of the Related Art

[0004] A conventional valve timing adjusting system is generally known in which the system including a first rotor coupled with a crank shaft of an engine through a chain or belt and rotating synchronously with the crank shaft, and a second rotor integrally secured on an end face of the camshaft relatively rotatable only by a predetermined angle within the above first rotor are provided in an intake camshaft and an exhaust camshaft, respectively. In such a valve timing adjusting device, a relative rotational angle of the second rotor relative to the first rotor is changed by rotating the camshaft to an advance side or a lag side relative to the crank shaft by the aid of hydraulic pressure supplied by a hydraulic control valve such as an oil control valve (hereinafter referred to simply as an OCV).

[0005] Moreover, between the first rotor and the second rotor in the valve timing adjusting device is provided a rotation regulating mechanism composed of a lock pin to regulate a relative rotational angle between the first rotor and the second rotor, for instance, an engaging hole to receive therein the lock pin, and a coil spring to continuously urging the lock pin toward the engaging hole. This rotation regulating mechanism is for regulating a relative rotation between the first rotor and the second rotor by engaging the lock pin in the engaging hole by the aid of urging force of the coil spring, until sufficient hydraulic pressure is supplied to the valve timing adjusting device, in order to suppress noises produced by repeated abutment against the second rotor and separation from the rotor suffering from alternating reaction force derived from the camshaft when starting an engine. After that, upon sufficient hydraulic pressure is supplied to the valve timing adjusting device, the lock pin disengages from the engaging hole against the urging force of the coil spring by the action of the supplied hydraulic pressure. This removes the regulation of the relative rotation between the first rotor and the second rotor. Consequently, free control of a relative rotational angle between the first rotor and the second rotor can be get with the help of hydraulic pressure of the advance side, urging the second rotor to the advance side or with the help of hydraulic pressure of the lag side, urging the same to the lag side relative to the first rotor.

[0006] Incidentally, these valve timing adjusting devices are classified into three types depending on where the regulating position of the relative rotation (initial position) between the first rotor and the second rotor is placed when starting the engine. These types include the most lagged lock type for regulating the relative rotation between the rotors at the position where the second rotor is most lagged relative to the first rotor (hereinafter referred to as the most lagged position), the most advanced lock type for regulating the relative rotation between the rotors at the position where the second rotor is most advanced (hereinafter referred to as the most advanced position), and the intermediate lock type for regulating the relative rotation between the rotors at the nearly intermediate position between the most lagged position and the most advanced position.

[0007] In the valve timing adjusting device of the most lagged lock type, an engine can be stopped while pressing the second rotor against the most lagged position relative to the first rotor by only supplying thereto hydraulic pressure of the lag side from the above OCV. Therefore, the engine can be re-started with the lock pin engaged in the engaging hole, thereby suppressing production of noises.

[0008] Also, in the valve timing adjusting device of the most advanced lock type, the engine can be stopped while pressing the second rotor against the most advanced position relative to the first rotor by only supplying thereto the hydraulic pressure of the advance side from the above OCV. Accordingly, the engine can be re-started with the lock pin engaged in the engaging hole, thereby suppressing production of noises.

[0009] The valve timing adjusting device of the intermediate lock type focuses the spotlight of attention upon that the device of this type is easily controlled from the initial position to the advance side or the lag side when starting the engine, and has excellent responsiveness compared with the most advanced lock type and the most lagged lock type.

[0010] JP 10-131912 A discloses a combustion engine.

[0011] The problems to be solved by the present invention are as follows.

[0012] That is, in a case where a valve timing adjusting device of the intermediate lock type is adopted for a valve timing adjusting system, the second rotor is held at the nearly intermediate position relative to the first rotor by supplying the hydraulic pressure of the advance side and that of the lag side to the device from the OCV. Here, since when the engine is stopped, one cannot expect of balanced control of loss of the hydraulic pressure of the advance side and that of the lag side caused attended upon decrease in a rotational speed of the engine. As a result, the relative rotational angle between the rotors cannot be regulated at the nearly intermediate position. For this reason, upon starting the engine under such a condition, repeated mutual abutment and separation of the first rotor and the second rotor suffering from alternating reaction force from the camshaft produces noises. Moreover, an unstable initial position incurs improper opening and closing timing of the valve, thereby resulting in an unstable engine start.

SUMMARY OF THE INVENTION

[0013] The present invention has been made to solve the above problems. An object of the present invention is to provide a valve timing adjusting system having a predetermined rotation range, and enabling a secure stop of an engine at a predetermined valve timing substantially within the middle of the rotation range, even under low hydraulic pressure when the engine is stopped.

[0014] A valve timing adjusting system according to the present invention includes a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational position of the intake camshaft relative to a crank shaft of the internal combustion engine; and a second valve timing adjusting device having a first rotor transmitting rotatory driving force derived from the crank shaft to the first valve timing adjusting device, and a second rotor secured on an exhaust camshaft rotating synchronously with the crank shaft.

[0015] According to the present invention, the above arrangement provides easy control of the relative rotational angle of the intake camshaft to a predetermined timing or the like substantially within the middle of a rotation range without changing the relative rotational angle of the exhaust camshaft relative to the crank shaft. Accordingly, the intake camshaft is securely stepped at the predetermined valve timing substantially within the middle of the rotation range, even under low hydraulic pressure when the engine is stopped. This removes uncertain factors of the conventional actuator of the intermediate lock type when starting the actuator. Moreover, the rotation range of the first valve timing adjusting device provided on the intake side is established by adding that of the second valve timing adjusting device with the result that a more wider rotation range is attained and this leads to an expansion of control range of the engine. Consequently, the arrangement provides an engine that can accommodate to a load varied depending on a variety of operating conditions.

[0016] Further, a valve timing adjusting system according to the present invention includes a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational position of the intake camshaft relative to a crank shaft of the internal combustion engine; and a second valve timing adjusting device having a first rotor rotating synchronously with the crank shaft, and a second rotor secured on an exhaust camshaft of the internal combustion engine.

[0017] According to the present invention, the above arrangement gives the first valve timing adjusting device provided on the intake side followed up by the second valve timing adjusting device provided on the exhaust side, which controls both valve timings of exhaust/intake to the lag side by the second valve timing adjusting device provided on the exhaust side. This easily controls the valve timing of the intake side to a predetermined timing substantially within the middle of the rotation range, and that of the exhaust side to the lag side. Accordingly, the intake camshaft is securely stopped at the predetermined valve timing substantially within the middle of the rotation range, even under low hydraulic pressure when the engine is stopped. This removes uncertain factors of the conventional actuator of the intermediate lock type when starting the actuator. Moreover, the rotation range of the first valve timing adjusting device provided on the intake side is obtained by adding that of the second valve timing adjusting device with the result that a more wider rotation range is attained and this leads to an expansion of control range of the engine. Consequently, the arrangement provides an engine that can accommodate to a load varied depending on a variety of operating conditions.

[0018] Moreover, a valve timing adjusting system according to the present invention includes a first valve timing adjusting device provided on an intake camshaft of an internal combustion engine, and changing a relative rotational angle of the intake camshaft relative to a crank shaft of the internal combustion engine; a second valve timing adjusting device provided on an exhaust camshaft of the internal combustion engine, and changing a relative rotational angle of the exhaust camshaft relative to the crank shaft; and a third valve timing adjusting device provided on the crank shaft side; wherein the third valve timing adjusting device is provided in series in the direction of the driving transmission relative to the first valve timing adjusting device and the second valve timing adjusting device.

[0019] According to the present invention, the above arrangement offers easy control to a predetermined timing or the like substantially within the middle of the rotation range. As a result, the valve timing adjusting system is securely stopped at the predetermined valve timing substantially within the middle of the rotation range, even under low hydraulic pressure when the engine is stopped. This removes uncertain factors of the conventional actuator of the intermediate lock type when starting the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic diagram showing a structure of a valve timing adjusting system using two valve timing adjusting devices according to a first embodiment of the present invention;

[0021] FIG. 2 is a radial sectional view showing the first valve timing adjusting device in the valve timing adjusting system shown in FIG. 1;

[0022] FIG. 3 is a radial sectional view showing the second valve timing adjusting device in the valve timing adjusting system shown in FIG. 1;

[0023] FIG. 4 is a schematic diagram showing respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 1;

[0024] FIG. 5 is a schematic diagram showing a structure of the valve timing adjusting system using two valve timing adjusting devices according to a second embodiment of the present invention;

[0025] FIG. 6 is a schematic diagram showing respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 5;

[0026] FIG. 7 is a schematic diagram showing a structure of the valve timing adjusting system using three valve timing adjusting devices according to a third embodiment of the present invention;

[0027] FIG. 8 is a circuit diagram showing a structure of the oil passages in the valve timing adjusting system shown in FIG. 7;

[0028] FIG. 9 is an axial sectional view showing the third valve timing adjusting device in the valve timing adjusting system shown in FIG. 7;

[0029] FIG. 10 is a radial sectional view showing the third valve timing adjusting device in the valve timing adjusting system shown in FIG. 7;

[0030] FIG. 11 is a radial sectional view showing the first valve timing adjusting device in the valve timing adjusting system shown in FIG. 7;

[0031] FIG. 12 is a radial sectional view showing the second valve timing adjusting device in the valve timing adjusting system shown in FIG. 7;

[0032] FIG. 13 is a schematic diagram showing the respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 7;

[0033] FIG. 14 is a schematic diagram showing a structure of the valve timing adjusting system using three valve timing adjusting devices according to a fourth embodiment of the present invention;

[0034] FIG. 15 is a circuit diagram showing a structure of the oil passages in the valve timing adjusting system shown in FIG. 14;

[0035] FIG. 16 is an axial sectional view showing the third valve timing adjusting device in the valve timing adjusting system shown in FIG. 14;

[0036] FIG. 17 is a radial sectional view showing the first valve timing adjusting device in the valve timing adjusting system shown in FIG. 14; and

[0037] FIG. 18 is a radial sectional view showing the second valve timing adjusting device in the valve timing adjusting system shown in FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

[0038] FIG. 1 is a schematic diagram showing a structure of a valve timing adjusting system using two valve timing adjusting devices according to the first embodiment of the present invention; FIG. 2 is a radial sectional view sowing a first valve timing adjusting device in the valve timing adjusting system shown in FIG. 1; FIG. 3 is a radial sectional view showing a second valve timing adjusting device in the valve timing adjusting system shown in FIG. 1; and FIG. 4 is a schematic diagram showing respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 1.

[0039] Referring to the FIGS. 1-4, reference numeral 1 denotes a valve timing adjusting system according to the first embodiment. The valve timing adjusting system 1 is generally composed of a first valve timing adjusting device 6 of the most lagged lock type provided on an intake camshaft S3, and changing a relative rotational angle of the intake camshaft S3 relative to a crank shaft S1 of an engine (not shown); and a second valve timing adjusting device 7 having a first rotor 71 transmitting the rotatory driving force derived from the crank shaft S1 to the first valve timing adjusting device 6 via a chain 9a, and a second rotor 72 secured on an exhaust camshaft S4 rotating synchronously with the crank shaft S1. Moreover,on the exhaust camshaft S4 is fixed a sprocket 8, and between the sprocket 8 and a sprocket 2 fixed on the crank shaft S1 is provided a chain 9b transmitting rotatory driving force derived from the crank shaft S1 to the former sprocket.

[0040] The structure of the first valve timing adjusting device 6 will now be described below.

[0041] The first valve timing adjusting device 6 is generally composed of a first rotor 11 rotating synchronously with the first rotor of the second valve timing adjusting device 7 through the chain 9a, and a second rotor 12 provided within the first rotor 11, and integrally secured on an end face of the intake camshaft S3.

[0042] As shown in FIG. 2, the first rotor 11 is generally composed of a housing 13 integrally having a sprocket 13a geared with the chain 9a, a case 14 provided adjacent to the housing 13, and having a plurality of shoes 14a radially inwardly projecting therefrom to form a plurality of spaces, and a cover (not shown) covering spaces formed within the case 14. These parts are integrally screwed and fastened by bolts 16.

[0043] The second rotor 12 is a rotor having a boss 12a integrally screwed and fastened on the end face of the intake camshaft S3 with a bolt 17 and a plurality of vanes 12b radially outwardly projecting from the periphery of the boss 12a (hereinafter the second rotor 12 is referred to as a “vane rotor 12”). Each of the vanes 12b of the vane rotor 12 divides the plurality of spaces formed by the shoes 14a of the case 14 into a plurality of advance side hydraulic rooms 18a and a plurality of lag side hydraulic rooms 19a. As shown in FIG. 2, one end of the first oil passage 18b formed in the interior of the intake camshaft S3 is connected to each of these advance side hydraulic rooms 18a, and similarly one end of the second oil passage (not shown) formed in the interior of the intake camshaft S3 is connected to each of the lag side hydraulic rooms 19a. Each of the other ends of the first oil passage (not shown) and the second oil passage (not shown) extends to an oil pump (not shown) and an oil pan (not shown) through an OCV (not shown).

[0044] Additionally, a receiving hole 23 penetrating through the shoe in a radial direction of the first valve timing adjusting device is formed in one of the shoes 14a of the case 14 provided in the first valve timing adjusting device 6. The receiving hole 23 is generally composed of a small portion 23a located inwardly in the radial direction of the device and a large portion 23b located more outwardly than the small portion 23a in the radial direction of the device. In the receiving hole 23 is axially, reciprocally, and slidably provided a lock pin 24. The lock pin 24 is generally composed of a small portion 24a located inwardly in the radial direction of the device and having an external diameter slidable relative to the small portion 23a of the receiving hole 23, a large portion 24b located more outwardly than the small portion 24a in the radial direction of the device and having an external diameter slidable relative to the large portion 23b of the receiving hole 23, and a non-penetrating hole 24c formed in the bottom of the large portion 24b. In addition, a bush 25 having a non-penetrating hole 25a is press-inserted into the receiving hole 23 from the outside of the device in the radial direction of the device, and the bush is secured therein by a stopper 26. A back-pressure exhausting hole 27 axially penetrating through the bottom thereof is formed in the non-penetrating hole 25a of the bush 25. Additionally, between the non-penetrating hole 25a of the bush 25 and the non-penetrating hole 24c of the lock pin 24 is provided a coil spring 28 continuously urging the lock pin 24 inwardly in the direction of the device.

[0045] Meanwhile, an engaging hole 29 is formed in the external periphery of the boss 12a of the vane rotor 12 in which the small portion 24a of the above lock pin 24 engages when the vane rotor 12 as the second rotor is in the most lagged position relative to the case 14 as the first rotor 11 (the most lagged lock).

[0046] A lock-maintaining hydraulic-pressure applying oil passage 30 is formed in the shoe 14a having the receiving hole 23 to apply the hydraulic pressure supplied from the lag side hydraulic room 19a to the back pressure space of the lock pin 24 among the spaces formed within the receiving hole 23 in order to hold the engagement between the lock pin 24 and the engaging hole 29 in the state of low hydraulic pressure when starting the engine. Furthermore, a lock-releasing hydraulic-pressure applying oil passage 31 is formed in the same shoe 14a to apply the hydraulic pressure supplied from each of the advance side hydraulic room 18a and the lag side hydraulic room 19a to a step 24d formed between the small portion 24a and the large portion 24b of the lock pin 24 in order to retreat the lock pin 24 against an urging force of the coil spring 28 and thereby push the lock pin out of the engaging hole 29. In addition, seal members 32 are provided in the tips of each of the vanes 12b of the vane rotor 12 and of each of the shoes 14a of the case 14 to prevent oil from flowing between the advance side hydraulic room 18a and the lag side hydraulic room 19a.

[0047] The structure of the second valve timing adjusting device 7 will now be described below.

[0048] Unlike the first valve timing adjusting device 6, the second valve timing adjusting device 7 has a structure of the most advanced lock type. The second valve timing adjusting device is generally composed of the first rotor 71 rotating synchronously with the first rotor 11 of the first valve timing adjusting device 6 through the chain 9a, and the second rotor 72 provided within the first rotor 71, and integrally secured on the end face of the exhaust camshaft S4.

[0049] As shown in FIG. 3, the first rotor 71 is generally composed of a housing 73 integrally having a sprocket 73a and a bearing (not shown) slidably contacting inside thereof the peripheral surface located in the proximity of the end face of the exhaust camshaft S4, a case 74 provided adjacent to this housing 73 and having a plurality of shoes 74a inside thereof radially inwardly projecting therefrom and thereby forming a plurality of spaces, and a cover (not shown) covering the spaces formed within the case 74. These parts are integrally fastened by bolts 76.

[0050] The second rotor 72 is a rotor having a boss 72a integrally screwed and fastened on the end face of the exhaust camshaft S4 with a bolt 77 and a plurality of vanes 72b radially outwardly projecting from the external periphery of the boss 72a (hereinafter the second rotor 72 is referred to as the “vane rotor 72”). Each of the vanes 72b of the vane rotor 72 divides the plurality of spaces formed by the shoes 74a of the case 74 into a plurality of advance side hydraulic rooms 78a and a plurality of lag side hydraulic rooms 79a. As shown in FIG. 3, one end of the first oil passage (not shown) formed in the interior of the exhaust camshaft S4 is connected to each of the advance side hydraulic rooms 78a, and similarly one end of the second oil passage (not shown) formed in the interior of the exhaust camshaft S4 is connected to each of the lag side hydraulic rooms 79a. Each of the other ends of the first oil passage (not shown) and the second oil passage (not shown) extends to an oil pump (not shown) and an oil pan (not shown) through an OCV (not shown).

[0051] Additionally, a receiving hole 83 penetrating through the shoe in the radial direction of the second valve timing adjusting device is formed in one of the shoes 74a of the case 74 provided in the second valve timing adjusting device 7. The receiving hole 83 is generally composed of a small portion 83a located inwardly in the radial direction of the device and a large portion 83b located more outwardly than the small portion 83a in the radial direction of the device. In this receiving hole 83 is axially, reciprocally, and slidably provided a lock pin 84. The lock pin 84 is generally composed of a small portion 84a located inwardly in the radial direction of the device and having an external diameter slidable relative to the small portion 83a of the receiving hole 83, a large portion 84b located more outwardly than the small portion 84a in the radial direction of the device, and having an external diameter slidable relative to the large portion 83b of the receiving hole 83, and a non-penetrating hole 84c formed in the bottom of the large portion 84b. In addition, a bush 85 having a non-penetrating hole 85a is press-inserted into the receiving hole 83 from the outside of the device in the radial direction of the device, and the bush is secured therein by a stopper 86. A back-pressure exhausting hole (not shown) axially penetrating the bottom thereof is formed in the non-penetrating hole 85a of the bush 85. Moreover, between the non-penetrating hole 85a of the bush 85 and the non-penetrating holes 84c of the lock pin 84 is provided a coil spring 88 continuously urging the lock pin 84 inwardly in the direction of the device.

[0052] On the other hand, an engaging hole 89 is formed in the external periphery of the boss 72a of the vane rotor 72 in which the small portion 84a of the above lock pin 84 engages when the vane rotor 72 as the second rotor is in the most advanced position relative to the case 74 as the first rotor 71 (the most advanced position lock).

[0053] A lock-maintaining hydraulic-pressure applying oil passage (not shown) is formed in the shoe 74a having the receiving hole 83 to apply the hydraulic pressure supplied from the lag side hydraulic room 79a to the back pressure space of the lock pin 84 among the spaces formed within the receiving hole 83 in order to hold the engagement between the lock pin 84 and the engaging hole 89 in the state of low hydraulic pressure when starting the engine. Additionally, a lock-releasing hydraulic-pressure applying oil passage 90 is formed in the same shoe 74a to apply the hydraulic pressure supplied from each of the advance side hydraulic room 78a and the lag side hydraulic room 79a to a step 84d formed between the small portion 84a and the large portion 84b of the lock pin 84 in order to retreat the lock pin 84 against an urging force of the coil spring 88 and thereby push the lock pin out of the engaging hole 89. In addition, seal members 91 are provided in the tips of each of the vanes 72b of the vane rotor 72 and each of the shoes 74a of the case 74 to prevent oil from flowing between the advance side hydraulic room 78a and the lag side hydraulic room 79a.

[0054] Moreover, between the vane 72b of the vane rotor 72 and the shoe 74a of the case 74 is provided an assistance link 92 continuously urging the vane rotor 72 to the advance side relative to the case 74 as the first rotor 71.

[0055] The operation of the valve timing adjusting system 1 will now be described below.

[0056] In this valve timing adjusting system 1, the relative rotational angle of the intake camshaft S3 relative to the crank shaft S1 is suitably determined depending on factors such as an water temperature, a rotation speed of the engine, an accelerator opening, and a load in engine operation, shown in Table 1, such that the opening and closing timing of the intake valve provided on the intake camshaft S3 becomes optimum, after settling the relative rotational angle of the exhaust camshaft S4 relative to the crank shaft S1.

[0057] First of all, when the engine is stopped, as mentioned above, the initial position of the first valve timing adjusting device 6 is being set at the most lagged position, and the initial position of the second valve timing adjusting device 7 is being set at the most advanced position.

[0058] Then, when starting the engine, the respective initial positions of the valve timing adjusting devices 6 and 7 are maintained as they are. However, at an idle state, when the water temperature is low because of fully closed accelerator opening in order to shift the valve timing on the intake camshaft S3 side in an advance direction, only the first valve timing adjusting device 6 is advance controlled while holding the control position of the second valve timing adjusting device 7 in the initial position (the most advanced position) as it is. Moreover, at the idle state, the control positions of the first valve timing adjusting device 6 and the second valve timing adjusting device 7 are put back to their initial positions, respectively, after the engine is warmed up by fully closing the accelerator opening.

[0059] Subsequently, in engine operation after the idle state is finished, where the accelerator opening is half closed, the second valve timing adjusting device 7a is lag controlled in order to shift the valve timing on the intake camshaft S3 side in the lag direction, after putting back the control position of the first valve timing adjusting device 6 to the initial position (the most lagged position), and the chain 9a is moved to the lag side. Further, where the accelerator opening is fully opened, when the load is low, the control positions of the first valve timing adjusting device 6 and the second valve timing adjusting device 7 are put back to their respective initial positions so as to shift the valve timing on the intake camshaft S3 side in the advance direction. Where the load is middle-level, the control position of the second valve timing adjusting device 7 is put back to the initial position (the most advanced position) in order to shift the valve timing on the intake camshaft S3 side in the advance direction, and further the first valve timing adjusting device 6 is advance controlled.

[0060] Further, where the load is high, the control positions of the first valve timing adjusting device 6 and the second valve timing adjusting device 7 are put back to their initial positions, respectively, in order to delay the valve timing of the intake camshaft S3.

[0061] As is evident from Table 1, in the valve timing adjusting system 1 according to the first embodiment with remaining the valve timing on the exhaust camshaft S4 side in the initial position (the most advanced position) unchanged, the second valve timing adjusting device 7 on the exhaust camshaft S4 side is rotated to the lag side depending on the operating conditions, thereby controlling the valve timing on the intake camshaft S3 side to the lag side as well.

[0062] Here, referring to FIG. 4, each of the rotation ranges of the first valve timing adjusting device 6 (the most lagged lock type) provided on the intake camshaft S3 and the second valve timing adjusting device 7 (the most advanced lock type) provided on the exhaust camshaft S4 will be described below. In FIG. 4, the exhaust camshaft S4 rotates synchronously with the crank shaft S1 and thus undergoes no change in the valve timing on the exhaust camshaft S4 side. In contrast, the valve timing on the intake camshaft S3 side can be controlled to the advance side and also to the lag side by using the first valve timing adjusting device 6 and the second valve timing adjusting device 7, thereby providing easy control of the valve timing on the intake camshaft S3 side to a predetermined timing located nearly in the middle of the rotation range. Arrow A1 of FIG. 4 indicates the rotation range to the advance side on the intake camshaft S3 side, and arrow A2 of FIG. 4 indicates the rotation range to the lag side on the intake camshaft S3 side.

[0063] As mentioned above, according to the first embodiment, the valve timing adjusting system 1 is arranged to include the first valve timing adjusting device 6 of the most lagged lock-type provided on the intake camshaft S3, and changing the relative rotational angle of the intake camshaft S3 relative to the crank shaft S1 of the engine (not shown); and the second valve timing adjusting device 7 having the first rotor 71 transmitting the rotatory driving force derived from the above crank shaft S1 to the first valve timing adjusting device 6 via the chain 9a, and the second rotor 72 secured on the exhaust camshaft S4 rotating synchronously with the crank shaft S1.

[0064] Through the arrangement thus structured of the first embodiment as above, the arrangement provides easy control of the relative rotational angle of the intake camshaft S3 to a predetermined timing located nearly in the middle of the rotation range of the intake camshaft without making a change in the relative rotational angle of the exhaust camshaft S4 relative to the crank shaft S1. Accordingly, even under low hydraulic pressure when the engine is stopped, the intake camshaft S3 can be securely stopped at a predetermined valve timing position located nearly in the middle of its rotation range. As a result, uncertain factors of the conventional actuator of the intermediate lock type are removed when starting the actuator.

[0065] According to the first embodiment, since the rotation range of the first valve timing adjusting device 6 provided on the intake side can be set up by adding the rotation range of the second valve timing adjusting device 7 provided on the exhaust side to the rotation range of the first valve timing adjusting device, the rotation range thereof can be widened, thereby making it possible to expand the control range of the engine. Consequently, the engine can accommodate to the load suffering changes depending on a variety of operating conditions.

Second Embodiment

[0066] FIG. 5 is a schematic diagram showing a structure of a valve timing adjusting system using two valve timing adjusting devices according to the second embodiment of the present invention, and FIG. 6 is a schematic diagram showing respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 5. In the second embodiment, the same components commonly used in the first embodiment are designated by the same reference numerals, and therefore explanation thereof is omitted for brevity's sake.

[0067] The valve timing adjusting system 1 according to the second embodiment is generally composed of a first valve timing adjusting device 6 of the most lagged lock type provided on an intake camshaft S3, and changing the relative rotational angle of the intake camshaft S3 relative to a crank shaft S1 of an engine (not shown); and a second valve timing adjusting device 7 having a first rotor 71 rotating synchronously with the crank shaft S1 via a chain 9b, and a second rotor 72 fixed on an exhaust camshaft S4. Moreover, on the exhaust camshaft S4 is secured a sprocket 8, and between the sprocket 8 and the first rotor 11 of the first valve timing adjusting device 6 is provided a chain 9a transmitting the rotatory driving force derived from the crank shaft S1 to the first valve timing adjusting device 6 side.

[0068] The operation of the valve timing adjusting system 1 will now be described below.

[0069] In this valve timing adjusting system 1, the relative rotational angle of the intake camshaft S3 and the exhaust camshaft S4 relative to the crank shaft S1 are suitably determined depending on factors such as an water temperature, a rotation speed of the engine, an accelerator opening, and a load, in engine operation, shown in Table 2 such that the opening and closing timings of the intake valve provided on the intake camshaft S3 and the exhaust valve provided on the exhaust camshaft S4 become optimum.

[0070] First of all, when the engine is stopped, as mentioned above, the initial position of the first valve timing adjusting device 6 is being set at the most lagged position, and the initial position of the second valve timing adjusting device 7 is being set at the most advanced position.

[0071] Then, when starting the engine, the respective initial positions of the valve timing adjusting devices 6 and 7 are maintained as they are. However, at an idle state, when the water temperature is low because of fully closed accelerator opening in order to shift the valve timing on the intake camshaft S3 side in the advance direction, only the first valve timing adjusting device 6 is advance controlled while holding the control position of the second valve timing adjusting device 7 in the initial position (the most advanced position) as it is. At the idle state, the control positions of the first valve timing adjusting device 6 and the second valve timing adjusting device 7 are put back to their initial positions, respectively, after the engine is warmed up by fully closing the accelerator opening.

[0072] Subsequently, in engine operation after the idle state is finished, where the accelerator opening is half opened, the second valve timing adjusting device 7 is lag controlled in order to shift both the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side in the lag direction, after putting back the control position of the first valve timing adjusting device 6 to the initial position (the most lagged position). Further, where the accelerator opening is fully opened, when the load is low, the control positions of the first valve timing adjusting device 6 and the second valve timing adjusting device 7 are put back to their initial positions, respectively, so as to shift the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side in the advance direction. Where the load is middle-level, the control position of the second valve timing adjusting device 7 is put back to the initial position (the most advanced position) in order to shift the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side in the advance direction, and further the first valve timing adjusting device 6 is advance controlled.

[0073] Further, where the load is high, the first valve timing adjusting device 6 is advance controlled in order to delay the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side, and at the same time the second valve timing adjusting device 7 is lag controlled.

[0074] As is evident from Table 2, since in the valve timing adjusting system 1 according to the second embodiment, the first valve timing adjusting device 6 provided on the intake camshaft S3 side follows up with the second valve timing adjusting device 7 provided on the exhaust camshaft S4 side, the first valve timing adjusting device 6 can be substantially operated to the lag side by lag controlling the second valve timing adjusting device 7.

[0075] Here, referring to FIG. 6, each of the rotation ranges of the first valve timing adjusting device 6 (the most lagged lock type) provided on the intake camshaft S3 and the second valve timing adjusting device 7 (the most advanced lock type) provided on the exhaust camshaft S4 will be described below. Arrow B of FIG. 6 indicates the rotation range from the initial position (the most advanced position) to the lag side, on the exhaust camshaft S4 side. In contrast, two-way arrow C1 indicates the rotation range from the initial position (the most lagged position) to the advance side, on the intake camshaft S3 side. This rotation range is shiftable followed up with the rotation of the second valve timing adjusting device 7 provided on the exhaust camshaft S4 to the lag side as shown with two-way arrow C2.

[0076] As described above, the valve timing adjusting system 1 according to the second embodiment is composed of the first valve timing adjusting device 6 of the most lagged lock type provided on the intake camshaft S3, and changing the relative rotational angle of the intake camshaft S3 relative to a crank shaft S1 of the engine (not shown); and the second valve timing adjusting device 7 having the first rotor 71 rotating synchronously with the crank shaft S1 via the chain 9b, and the second rotor 72 fixed on the exhaust camshaft S4.

[0077] Through the arrangement thus structured of the second embodiment as above, the arrangement provides control of both the valve timings of exhaust/intake to the lag sides by the second valve timing adjusting device 7 provided on the exhaust side, as the first valve timing adjusting device 6 provided on the intake side follows up with the second valve timing adjusting device 7 provided on the exhaust side. This easily controls the valve timing on the intake side to a predetermined timing located nearly in the middle of the rotation range, and the valve timing on the exhaust side to the lag side. Accordingly, even under low hydraulic pressure when the engine is stopped, the intake camshaft can be securely stopped at the predetermined valve timing located nearly in the middle of the rotation range. As a result, uncertain factors of the conventional actuator of the intermediate lock type are removed when starting the actuator.

[0078] According to the second embodiment, since the rotation range of the first valve timing adjusting device 6 provided on the intake side can be set up by adding the rotation range of the second valve timing adjusting device 7 provided on the exhaust side to the rotation range of the first valve timing adjusting device, the rotation range thereof can be widened, thereby making it possible to expand the control range of the engine. Consequently, the engine can accommodate to the load suffering changes depending on a variety of operating conditions.

Third Embodiment

[0079] FIG. 7 is a schematic diagram showing a structure of a valve timing adjusting system using three valve timing adjusting devices according to the third embodiment of the present invention; FIG. 8 is a circuit diagram showing a structure of the oil passages in the valve timing adjusting system shown in FIG. 7; FIG. 9 is an axial sectional showing a third valve timing adjusting device in the valve timing adjusting system shown in FIG. 7; FIG. 10 is a radial sectional view showing a third valve timing adjusting device in the valve timing adjusting system shown in FIG. 7; FIG. 11 is a radial sectional view showing the first valve timing adjusting device in the valve timing adjusting system shown in FIG. 7; FIG. 12 is a radial sectional view showing the second valve timing adjusting device in the valve timing adjusting system shown in FIG. 7; and FIG. 13 is a schematic diagram showing the respective operating ranges of the valve timing adjusting devices in the valve timing adjusting system shown in FIG. 7. In passing, the direction referred to herein simply as the “axial direction” or the “axial direction of the device ” indicates the axial direction of the valve timing adjusting device, and the direction referred to herein simply as the “radial direction” or the “radial direction of the device” indicates the radial direction of the valve timing adjusting device.

[0080] The valve timing adjusting system 1 according to the third embodiment is generally composed of a third valve timing adjusting device 10 of the most lagged lock type subjected to the rotatory driving force via a first chain 3 transmitted from a sprocket 2 integrally secured on the end face of a crank shaft S1 of an engine (not shown), rotating synchronously with the crank shaft S1, and provided on the end face of a control shaft S2; a first valve timing adjusting device 40 of the most advanced lock type subjected to the rotatory driving force via a second chain 5 transmitted from a sprocket 4 integrally secured on the above control shaft S2, and provided on the end face of an intake camshaft S3; and a second valve timing adjusting device 70 of the most advanced lock type subjected to the rotatory driving force via a second chain 5 transmitted from the above sprocket 4, and provided on the end face of an exhaust camshaft S4.

[0081] First of all, the structure of the third valve timing adjusting device 10 will now be described below.

[0082] The third valve timing adjusting device 10 is generally composed of a first rotor 11 rotating synchronously with the crank shaft S1 through the first chain 3, and a second rotor 12 provided within the first rotor 11, and integrally secured on the end face of the control shaft S2.

[0083] As shown in FIG. 9 and FIG. 10, the first rotor 11 is generally composed of a housing 13 integrally having a sprocket 13a subjected to the rotatory driving force derived from the crank shaft S1 and having more teeth than the sprocket 2 integrally fixed on the end face of the above crank shaft S1, and having inside thereof a bearing (not shown) slidably contacting the external peripheral surface located in the proximity of the end face of the control shaft S2; a case 14 provided adjacent to the housing 13 and having a plurality of shoes 14a inside thereof radially inwardly projecting and thereby forming a plurality of spaces; and a cover 15 covering the spaces formed within the case 14. These parts are integrally fastened and screwed by bolts 16.

[0084] The second rotor 12 is a rotor having a boss 12a integrally screwed and fastened on the end face of the control shaft S2 with a bolt 17 and a plurality of vanes 12b radially outwardly projecting from the external periphery of the boss 12a (hereinafter the second rotor 12 is referred to as the “vane rotor 12”). Each of the vanes 12b of the vane rotor 12 divides the plurality of spaces formed by the shoes 14a of the case 14 into a plurality of advance side hydraulic rooms 18a and a plurality of lag side hydraulic rooms 19a. As shown in FIG. 8 and FIG. 9, one end of a first oil passage 18b formed in the interior of the control shaft S2 is connected to each of the advance side hydraulic rooms 18a, and one end of a second oil passage 19b similarly formed in the interior of the control shaft S2 is connected to each of the lag side hydraulic rooms 19a. Each of the other ends of the first oil passage 18b and the second oil passage 19b extends to an oil pump 21 and an oil pan 22 through a first OCV 20.

[0085] Additionally, a receiving hole 23 penetrating through the shoe in the radial direction of the device is formed in one of the shoes 14a of the case 14 provided in the third valve timing adjusting device 10. The receiving hole 23 is generally composed of a small portion 23a located inwardly in the radial direction and a large portion 23b located more outwardly than the small portion 23a in the radial direction of the device. In the receiving hole 23 is axially, reciprocally, and slidably provided a lock pin 24. The lock pin 24 is generally composed of a small portion 24a located inwardly in the radial direction of the device, and having an external diameter slidable relative to the small portion 23a of the receiving hole 23; a large portion 24b located more outwardly than the small portion 24a in the radial direction of the device, and having an external diameter slidable relative to the large portion 23b of the receiving hole 23; and a non-penetrating hole 24c formed in the bottom of the large portion 24b. In addition, a bush 25 having a non-penetrating hole 25a is press-inserted into the receiving hole 23 from the outside of the device in the radial direction of the device, and the bush is secured therein by a stopper 26. A back-pressure exhausting hole 27 axially penetrating through the bottom thereof is formed in the non-penetrating hole 25a of the bush 25. Further, between the non-penetrating hole 25a of the bush 25 and the non-penetrating holes 24c of the lock pin 24 is provided a coil spring 28 continuously urging the lock pin 24 inwardly in the direction of the device.

[0086] Meanwhile, an engaging hole 29 is formed in the external periphery of the boss 12a of the vane rotor 12 in which the small portion 24a of the above lock pin 24 engages when the vane rotor 12 as the second rotor is in the most lagged position relative to the case 14 as the first rotor 11 (the most lagged lock). A lock-maintaining hydraulic-pressure applying oil passage 30 is formed in the shoe 14a having the receiving hole 23 to apply the hydraulic pressure supplied from the lag side hydraulic room 19a to the back pressure space of the lock pin 24 among the spaces formed within the receiving hole 23 in order to hold the engagement between the lock pin 24 and the engaging hole 29 in the state of low hydraulic pressure when starting the engine. Furthermore, a lock-releasing hydraulic-pressure applying oil passage 31 is formed in the same shoe 14a to apply the hydraulic pressure supplied from each of the advance side hydraulic room 18a and the lag side hydraulic room 19a to a step 24d formed between the small portion 24a and the large portion 24b of the lock pin 24 in order to retreat the lock pin 24 against an urging force of the coil spring 28 and thereby push the lock pin out of the engaging hole 29. In addition, seal members 32 are provided in the tips of each of the vanes 12b of the vane rotor 12 and each of the shoes 14a of the case 14 to prevent oil from flowing between the advance side hydraulic room 18a and the lag side hydraulic room 19a. The seal member 32 is generally composed of a seal 32a slidably contacting the internal peripheral surface of the case 14 or the external peripheral surface of the boss 12a of the vane rotor 12 and a blade spring 32b pressing the seal 32a against each of these peripheral surfaces.

[0087] The structure of the first valve timing adjusting device 40 will now be described below.

[0088] The first valve timing adjusting device 40 is generally composed of a first rotor 41 rotating synchronously with the control shaft S2 through the second chain 5, and a second rotor 42 provided within the first rotor 41, and integrally secured on the end face of the intake camshaft S3.

[0089] As shown in FIG. 11, the first rotor 41 is generally composed of a housing 43 integrally having a sprocket 43a subjected to the rotatory driving force derived from the control shaft S2, and having more teeth than the sprocket 2 fixed on the above crank shaft S1, and having less teeth than the sprocket 13a provided on the housing 13 of the third valve timing adjusting device 10 and having a bearing (not shown) inside thereof slidably contacting the external peripheral surface located in the proximity of the end face of the intake camshaft S3; a case 44 provided adjacent to the housing 43, and having a plurality of shoes 44a inside thereof radially inwardly projecting and thereby forming a plurality of spaces; and a cover covering the spaces formed within the case 44. These parts are integrally fastened and screwed by bolts 46.

[0090] The second rotor 42 is a rotor having a boss 42a integrally fastened and screwed on the end face of the intake camshaft S3 with a bolt 47 and having a plurality of vanes 42b radially outwardly projecting from the external periphery of the boss 42a (hereinafter the second rotor 42 is referred to as the vane rotor 42). Each of the vanes 42b of the vane rotor 42 divides the plurality of spaces formed by the shoes 44a of the case 44 into a plurality of advance side hydraulic rooms 48a and a plurality of lag side hydraulic rooms 49a. As shown in FIG. 8, one end of a first oil passage 48b formed in the interior of the intake camshaft S3 is formed to each of the advance side hydraulic rooms 48a, and one end of a second oil passage 49b is connected to each of the lag side hydraulic rooms 49a similarly formed in the interior of the intake camshaft S3. Each of the other ends of the first oil passage 48b and the second oil passage 49b extends to the oil pump 21 and the oil pan 22 through a second OCV 50.

[0091] Additionally, a receiving hole 53 penetrating through the shoe in the radial direction of the device is formed in one of the shoes 44a of the case 44 provided in the first valve timing adjusting device 40. The receiving hole 53 is generally composed of a small portion 53a located inwardly in the radial direction and a large portion 53b located more outwardly than the small portion 53a in the radial direction. In the receiving hole 53 is axially, reciprocally, and slidably provided a lock pin 54. The lock pin 54 is generally composed of a small portion 54a located inwardly in the radial direction of the device, and having an external diameter slidable relative to the small portion 53a of the receiving hole 53; a large portion 54b located more outwardly than the small portion 54a in the radial direction of the device, and having an external diameter slidable relative to the large portion 53b of the receiving hole 53; and a non-penetrating hole 54c formed in the bottom of the large portion 54b. In addition, a bush 55 having a non-penetrating hole 55a is press-inserted into the receiving hole 53 from the outside of the device in the radial direction of the device, and the bush is secured therein by a stopper 56. Aback-pressure exhausting hole (not shown) axially penetrating through the bottom thereof is formed in the non-penetrating hole 55a of the bush 55. Furthermore, between the non-penetrating hole 55a of the bush 55 and the non-penetrating holes 54c of the lock pin 54 is provided a coil spring 58 continuously urging the lock pin 54 inwardly in the direction of the device.

[0092] At the same time, an engaging hole 59 is formed in the external periphery of the boss 42a of the vane rotor 42 in which the small portion 54a of the above lock pin 54 engages when the vane rotor 42 as the second rotor is in the most advanced position relative to the case 44 as the first rotor 41 (the most advanced lock).

[0093] A lock-maintaining hydraulic-pressure applying oil passage (not shown) is formed in the shoe 44a having the receiving hole 53 to apply the hydraulic pressure supplied from the lag side hydraulic room 49a to the back pressure space of the lock pin 54 among the spaces formed within the receiving hole 53 in order to hold the engagement between the lock pin 54 and the engaging hole 59 in the state of low hydraulic pressure when starting the engine. Furthermore, a lock-releasing hydraulic-pressure applying oil passage 60 is formed in the same shoe 44a to apply the hydraulic pressure supplied from each of the advance side hydraulic room 48a and the lag side hydraulic room 49a to a step 54d formed between the small portion 54a and the large portion 54b of the lock pin 54 in order to retreat the lock pin 54 against an urging force of the coil spring 58 and thereby push the lock pin out of the engaging hole 59. In addition, seal members 61 are provided in the tips of each of the vanes 42b of the vane rotor 42 and each of the shoes 44a of the case 44 to prevent oil from flowing between the advance side hydraulic room 48a and the lag side hydraulic room 49a.

[0094] Moreover, between of the vane 42b of the vane rotor 42 and the shoe 44a of the case 44 is provided an assistance link 62 continuously urging the vane rotor 42 to the advance side relative to the case 44 as the first rotor 41.

[0095] The structure of the second valve timing adjusting device 70 will now be described below.

[0096] The second valve timing adjusting device 70 has the same structure as one of the first valve timing adjusting device 40. That is, the second valve timing adjusting device is generally composed of a first rotor 71 rotating synchronously with the control shaft S2 through the second chain 5, and a second rotor 72 provided within the first rotor 71, and integrally secured on the end face of the exhaust camshaft S4.

[0097] As shown in FIG. 12, the first rotor 71 is generally composed of a housing 73 integrally having a sprocket 73a subjected to the rotatory driving force derived from the control shaft S2, and having more teeth than the above sprocket 2 fixed on the crank shaft S1 and having less teeth than the sprocket 13a provided on the housing 13 of the third valve timing adjusting device 10 and having a bearing (not shown) inside thereof slidably contacting the external peripheral surface located in the proximity of the end face of the exhaust camshaft S4; a case 74 provided adjacent to the housing 73 and having a plurality of shoes 74a inside thereof radially inwardly projecting and thereby forming a plurality of spaces; and a cover 75 covering the spaces formed within the case 74. These parts are integrally screwed and fastened by bolts 76.

[0098] The second rotor 72 is a rotor having a boss 72a integrally fastened and screwed on the end face of the exhaust camshaft S4 with a bolt 77 and a plurality of vanes 72b radially outwardly projecting from the external periphery of the boss 72a (hereinafter the second rotor 72 is referred to as the vane rotor 72). Each of the vanes 72b of the vane rotor 72 divides the plurality of spaces formed by the shoes 74a of the case 74 into a plurality of advance side hydraulic rooms 78a and a plurality of lag side hydraulic rooms 79a. As shown in FIG. 8, one end of a first oil passage 78b formed in the interior of the exhaust camshaft S4 is connected to each of the advance side hydraulic rooms 78a, and one end of a second oil passage 79b is connected to each of the lag side hydraulic rooms 79a similarly formed in the interior of the exhaust camshaft S4. Each of the other ends of the first oil passage 78b and the second oil passage 79b extends to the oil pump 21 and the oil pan 22 through a third OCV 80.

[0099] In addition, a receiving hole 83 penetrating through the shoe in the radial direction of the device is formed in one of the shoes 74a of the case 74 provided in the second valve timing adjusting device 70. The receiving hole 83 is generally composed of a small portion 83a located inwardly in the radial direction and a large portion 83b located more outwardly than the small portion 83a in the radial direction. In this receiving hole 83 is axially, reciprocally, and slidably provided a lock pin 84. The lock pin 84 is generally composed of a small portion 84a located inwardly in the radial direction of the device, and having an external diameter slidable within the small portion 83a of the receiving hole 83, a large portion 84b located more outwardly than the small portion 84a in the radial direction of the device, and having an external diameter slidable within the large portion 83b of the receiving hole 83, and a non-penetrating hole 84c formed in the bottom of the large portion 84b. In addition, a bush 85 having a non-receiving hole 85a is press-inserted into the receiving hole 83 from the outside of the device in the radial direction of the device, and the bush is secured therein by a stopper 86. A back-pressure exhausting hole (not shown) axially penetrating through the bottom thereof is formed in the non-penetrating hole 85a of the bush 85. Further, between the non-penetrating hole 85a of the bush 85 and the non-penetrating holes 84c of the lock pin 84 37. is provided a coil spring 88 continuously urging the lock pin 84 inwardly in the direction of the device.

[0100] Meanwhile, an engaging hole 89 is formed in the external periphery of the boss 72a of the vane rotor 72 in which the small portion 84a of the above lock pin 84 engages when the vane rotor 72 as the second rotor is in the most advanced position relative to the case 74 as the first rotor 71, (the most advanced lock). A lock-maintaining hydraulic-pressure applying oil passage (not shown) is formed in the shoe 74a having the receiving hole 83 to apply the hydraulic pressure supplied from the lag side hydraulic room 79a to the back pressure space of the lock pin 84 among the spaces formed within the receiving hole 83 in order to hold the engagement between the lock pin 84 and the engaging hole 89 in the state of low hydraulic pressure when starting the engine. Additionally, a lock-releasing hydraulic-pressure applying oil passage 90 is formed in the same shoe 74a to apply the hydraulic pressure supplied from each of the advance side hydraulic room 78a and the lag side hydraulic room 79a to a step 84d formed between the small portion 84a and the large portion 84b of the lock pin 84 so as to retreat the lock pin 84 against an urging force of the coil spring 88 and thereby push the lock pin out of the engaging hole 89. In addition, seal members 91 are provided in the tips of each of the vanes 72b of the vane rotor 72 and each of the shoes 74a of the case 74 to prevent oil from flowing between the advance side hydraulic room 78a and the lag side hydraulic room 79a.

[0101] Moreover, between the vane 72b of the vane rotor 72 and the shoe 74a of the case 74 is provided an assistance link 92 continuously urging the vane rotor 72 to the advance side relative to the case 74 as the first rotor 71.

[0102] In the valve timing adjusting system 1 thus arranged as above, the first valve timing adjusting device 40, the second valve timing adjusting device 70, and the third valve timing adjusting device 10 are arranged such that the advance sides at which the second rotors 42, 72, and 12 are relatively rotatable relative to the first rotors 41, 71, and 11 are set to have the same angle totally with respect to the first rotors 41, 71, and 11, respectively.

[0103] The operation of the valve timing adjusting system 1 will now be described below.

[0104] In this valve timing adjusting system 1, the relative rotational angle of the intake camshaft S3 and the exhaust camshaft S4 relative to the crank shaft S1 are suitably determined depending on each of factors such as an water temperature, a speed of the engine rotation, an accelerator opening, and a load, in engine operation, shown in Table 3 so that the opening and closing timings of the intake valve provided on the intake camshaft S3 and the exhaust valve provided on the exhaust camshaft S4 become optimum.

[0105] First of all, when the engine is stopped, as mentioned above, the initial position of the third valve timing adjusting device 10 is being set at the most lagged position, and each of the initial positions of the first valve timing adjusting device 40 and the second valve timing adjusting device 70 is being set at the most advanced position.

[0106] Then, when starting the engine, respective initial positions of the valve timing adjusting devices 10, 40, and 70 are maintained as they are. However, at an idle state, when the water temperature is low because of fully closed accelerator opening, only the third valve timing adjusting device 10 is advance controlled in order to shift the valve timings both on the intake camshaft S3 side and the exhaust camshaft S4 side in the advance direction, while holding the control positions of the first valve timing adjusting device 40 and the second valve timing adjusting device 70 in the respective initial positions as they are. Moreover, at the idle state, after the engine is warmed up by fully closing the accelerator opening, while holding the control positions of the first valve timing adjusting device 40 and the second valve timing adjusting device 70 in the respective initial positions as they are, the advance side control performed on the third valve timing adjusting device 10 is stopped, and the control position of the device is put back to the initial position (the most lagged position).

[0107] Subsequently, in engine operation after the idle state finished, when the accelerator opening is half opened, the control position of the third valve timing adjusting device 10 is put back to the initial position (the most lagged position) in order to shift both the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side in the lag direction, and simultaneously the first valve timing adjusting device 40 and the second valve timing adjusting device 70 are advance controlled. Further, when the accelerator opening is fully opened, when the load is low, all of the control positions of the first, second, and third valve timing adjusting devices 40, 70, and 10 are put back to their initial positions, respectively in order to shift both the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side in the advance direction. When the load is middle-level, the third valve timing adjusting device 10 is advance controlled so as to shift the valve timing on the intake camshaft S3 side in the advance direction, the first valve timing adjusting device 40 is put back to the initial position (the most advanced position), and further the second valve timing adjusting device 70 is lag controlled. When attempting to shift only the valve timing on the intake camshaft S3 side in the advance direction, for instance, the exhaust camshaft S4 is turned back to the lag side to the amount of the lag control equal to that of the above advance control, thereby balancing the shifting of the valve timing. This prevents the valve timing on the exhaust camshaft S4 side from being advanced accompanied with the advance of the valve timing on the intake camshaft S3 side.

[0108] When the load is high, the first valve timing adjusting device 40 is put back to the initial position (the most advanced position) in order to retard the valve timing on the exhaust camshaft S4 side, and further the second valve timing adjusting device 70 is lag controlled after putting back the third valve timing adjusting device 10 to the initial position (the most lagged position).

[0109] As is evident from Table 3, there is no pattern to control the camshafts S3 and S4 at advance sides opposite to each other. For this reason, in this valve timing adjusting system 1, though it is not possible to move the intake camshaft S3 to the most advanced position and simultaneously the exhaust camshaft S4 to the most lagged position, the valve timing control in any control pattern other than this can be performed.

[0110] Referring to FIG. 13, the rotation ranges of the first valve timing adjusting device 40 and the second valve timing adjusting device 70, both of the most advanced lock type, provided on the intake camshaft S3 and the exhaust camshaft S4, respectively, will now be described below. In FIG. 13, because each of the initial positions (lock positions) of the first valve timing adjusting device 40 and the second valve timing adjusting device 70 is set at the most advanced position, two-way arrows D1 shown on the intake side and on the exhaust side indicate the rotation ranges thereof, respectively, from the initial position to the lag side. Moreover, two-way arrows D2 shown on the intake side and on the exhaust side indicate the rotation ranges of the intake camshaft S3 and the exhaust camshaft S4, respectively, shifted to the advance side by the movement of the third valve timing adjusting device 10 of the most lagged lock type. It can be seen from the fact that the above first valve timing adjusting device 40 and second valve timing adjusting device 70 is thereby relatively rotatable to the advance side relative to the crank shaft S1 by advance controlling the third valve timing adjusting device 10. Therefore, the intake camshaft S3 and the exhaust camshaft S4 is relatively rotatable not only to the lag side, but also to the advance side.

[0111] As mentioned above, according to the third embodiment, it is arranged such that the third valve timing adjusting device 10 is provided in series with the first valve timing adjusting device 40 and the second valve timing adjusting device 70. Through the arrangement of the third embodiment thus structured as above, the arrangement provides easy control of each of the valve timings on the intake camshaft S3 side and on the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position. Accordingly, even under low hydraulic pressure when the engine is stopped, the engine can be securely stopped at the predetermined valve timing located nearly in the middle of the rotation range, thereby removing uncertain factors of the conventional actuator of the intermediate lock type when starting the actuator.

[0112] According to the third embodiment, it is arranged such that the housing 13 including the sprocket 13a having more teeth than the sprocket 2 secured on the crank shaft S1 is provided on the third valve timing adjusting device 10, and the housing 43 or housing 73 including the sprocket 43a or sprocket 73a having more teeth than the sprocket 2 secured on the above crank shaft S1 and having less teeth than the sprocket 13a of the housing 13 of the third valve timing adjusting device 10 is provided on the first valve timing adjusting device 40 and the second valve timing adjusting device 70. Through the arrangement of the third embodiment thus structured as above, the arrangement provides slow rotation speed of the crank shaft S1 by the third valve timing adjusting device 10, thereby offering the small-sized sprocket 43a or 73a of the first valve timing adjusting device 40 and the second valve timing adjusting device 70, and reducing the size of the upper of the engine by virtue of reduction of the spacing between the intake camshaft S3 and the exhaust camshaft S4.

[0113] According to the third embodiment, it is arranged such that the third valve timing adjusting device 10, the first valve timing adjusting device 40, and the second valve timing adjusting device 70 is set so that their initial positions are different from each other. Through the arrangement of the third embodiment thus structured as above, the arrangement provides easy control of each of the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position.

[0114] According to the third embodiment, it is arranged that the third valve timing adjusting device 10 of the most lagged lock type, the first valve timing adjusting device 40, and the second valve timing adjusting device 70, both of the most advanced lock type are combined. Through the arrangement of the third embodiment thus structured as above, the arrangement provides easy control of each of the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position.

[0115] According to the third embodiment, it is arranged that the third valve timing adjusting device 10 of the vane type, the first valve timing adjusting device 40, and the second valve timing adjusting device 70, each of the vane type are combined. Through the arrangement of the third embodiment thus structured as above, the arrangement provides the large relative rotational angle and the valve timing held in a predetermined position using an intermediate-holding function of the valve timing adjusting devices of the vane type.

Fourth Embodiment

[0116] FIG. 14 is a schematic diagram showing a structure of the valve timing adjusting system using three valve timing adjusting devices according to the fourth embodiment of the present invention; FIG. 15 is a circuit diagram showing the structure of the oil passages in the valve timing adjusting system shown in FIG. 14; FIG. 16 is an axial sectional view showing the third valve timing adjusting device in the valve timing adjusting system shown in FIG. 14; FIG. 17 is a radial sectional view showing the first valve timing adjusting device in the valve timing adjusting system shown in FIG. 14; and FIG. 18 is a radial sectional view showing the second valve timing adjusting device in the valve timing adjusting system shown in FIG. 14. In the fourth embodiment, the same components commonly used in the third embodiment are designated by the same reference numerals, and therefore explanation thereof is omitted for brevity's sake.

[0117] The feature of the fourth embodiment is in that a third valve timing adjusting device 100 of the helical type and the most advanced lock type is provided on the end face of a crank shaft S1; a first valve timing adjusting device 200 of the vane type and the most lagged lock type is provided on the end face of an intake camshaft S3; and a second valve timing adjusting device 300 of the vane type and the most lagged lock type is provided on the end face of an exhaust camshaft S4.

[0118] The third valve timing adjusting device 100 according to the fourth embodiment is composed of a first rotor (hereinafter referred to as a “rotor”) 110 integrally screwed and fastened to a crank shaft S1 with a bolt 17 and having outside a helical spline (not shown); a second rotor 120 relatively rotatable through only a predetermined advance side relative to the first rotor 110, and having inside a sprocket 121 connecting with a first chain 3 and having the helical spline (not shown); a gear piston 130 axially slidable within the third valve timing adjusting device 100, and connected with both of the rotors 110, 120; an urging member 140 such as a coil spring axially urging the gear piston 130; a hydraulic room 150 generating a hydraulic force against an urging force of the urging member 140; and an oil passage 160 supplying oil from the crank shaft S1 to the hydraulic room 150, and discharging the oil from the room.

[0119] The second rotor 120 is composed of a housing 123 having outside the above sprocket 121, a case 124 axially provided adjacent to the housing 123, and a cover 125 covering an axial opening of the above hydraulic room 150, which is formed within the case 124. And these parts are integrally fastened and screwed to each other with bolts 16.

[0120] The urging member 140 urges the gear piston 130 such that the second rotor 120 can stop at the most advanced position relative to the first rotor 110 in the situation where there applied no hydraulic pressure when the engine is stopped. The oil passage 160 is connected with an oil pump 21 and also an oil pan 22 through a first OCV 20. Accordingly, after the engine is started, hydraulic pressure can be applied to the third valve timing adjusting device 100 from the oil pump 21 via the first OCV 20 and the oil passage 160.

[0121] Moreover, the relative rotational position between the first rotor 110 and the second rotor 120 is determined by the helical spline (not shown) included in both rotors and the gear piston 130, and the axial position of the gear piston 130 can be position-controlled by generating hydraulic force against an urging force with the oil supplied from the first OCV 20.

[0122] The first valve timing adjusting device 200 and the second valve timing adjusting device 300 have a common structure to that of the third valve timing adjusting device 10 according to the third embodiment. Moreover, each of the oil passages of the first valve timing adjusting device 200 is connected with the oil pump 21 and the oil pan 22 through a second OCV 50, and each of the oil passages of the second valve timing adjusting device 300 is connected with the oil pump 21 and the oil pan 22 through a third OCV 80.

[0123] In passing, because the engine is arranged such that while the crank shaft S1 rotates two turns, each of the intake camshaft S3 and the exhaust camshaft S4 rotates one turn, the gear ratio among the sprocket 121 of the third valve timing adjusting device 100, the sprocket of the first valve timing adjusting device 200, and the sprocket of the second valve timing adjusting device 300 is 1:2:2. Therefore, just as the case of the crank shaft S1 and both of the camshafts S3, S4, while the third valve timing adjusting device 100 rotates two turns, each of the first valve timing adjusting device 200 and the second valve timing adjusting device 300 rotates one turn.

[0124] In other words, the difference between the numbers of rotation makes equal the case where the valve timing of the third valve timing adjusting device 100 is relatively rotated by 2°, with the case where the phases of the first valve timing adjusting device 200 and the second valve timing adjusting device 300, and the intake camshaft S3 and the exhaust camshaft S4 are changed by 1°. For this reason, in the fourth embodiment, a relatively rotatable angle of the first valve timing adjusting device 200 and the second valve timing adjusting device 300 is one half of that of the third valve timing adjusting device 100. Yet in the third embodiment a similar effect can be exercised.

[0125] The operation will now be described below.

[0126] In the fourth embodiment as with the third embodiment, the relative rotational angle of the intake camshaft S3 and of the exhaust camshaft S4 relative to the crank shaft S1 are properly determined depending on factors such as an water temperature, a speed of the engine rotation, an accelerator opening, and a load, in engine operation, shown in Table 4 such that the opening and closing timings of the intake valve provided on the intake camshaft S3 and the exhaust valve provided on the exhaust camshaft S4 become optimum.

[0127] The fourth embodiment is different from the third embodiment in that the initial position of the first rotor 110 provided in the third valve timing adjusting device 100 is the most advanced position, and thereby the relative rotations of individual valve timing adjusting devices in the control pattern shown in Table 4 are different from that in the control pattern shown in Table 3. However, though it is not possible to move the intake camshaft S3 to the most advanced position and at the same time the exhaust camshaft S4 to the most lagged position as with the third embodiment, the valve timing control in any control pattern other than this can be performed.

[0128] As mentioned above, according to the fourth embodiment, it is arranged such that the third valve timing adjusting device 100 is provided in series with the first valve timing adjusting device 200 and the second valve timing adjusting device 300. Through the arrangement of the fourth embodiment thus structured as above, the arrangement provides easy control of each of the valve timings on the intake camshaft S3 side and the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position. Accordingly, even under low hydraulic pressure when the engine is stopped, the engine can be securely stopped at the predetermined valve timing located nearly in the middle of the rotation range, thereby removing uncertain factors of the conventional actuator of the intermediate lock type when starting the actuator.

[0129] According to the forth embodiment, the valve timing adjusting devices of the vane type is adopted as the first valve timing adjusting device 200, and the second valve timing adjusting device 300, respectively. Such an adoption provides the valve timing held at a predetermined position using an intermediate function of these valve timing adjusting devices of the vane type.

[0130] According to the fourth embodiment, the valve timing adjusting device of the helical type is adopted as the third valve timing adjusting device 100, in which it is not easy to put the device 100 to the most advanced position in the situation where there applied no hydraulic pressure. Such an adoption provides the valve timing adjusting device of the helical type embedded in the valve timing adjusting system where the device is permitted to run without restraint.

[0131] According to the fourth embodiment, it is arranged such that the third valve timing adjusting device 100 of the helical type is combined with the first valve timing adjusting device 200 and the second valve timing adjusting device 300 of the vane type. Through the arrangement of the fourth embodiment thus structured as above, the arrangement builds a valve timing adjusting system capable of controlling the system to the advance side or to the lag side from the state where the engine is started up.

[0132] According to the fourth embodiment, it is arranged such that the third valve timing adjusting device 100 of the most advanced lock type and the helical type is combined with the first valve timing adjusting device 200, and the second valve timing adjusting device 300 of the most lagged lock type and the vane type is combined. Through the arrangement of the fourth embodiment thus structured as above, the arrangement provides easy control of each the valve timings, taking advantages of the valve timing adjusting devices of each type on the intake camshaft S3 side and the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position.

[0133] According to the fourth embodiment, it is arranged such that the third valve timing adjusting device 100 of the most advanced lock type is combined with the first valve timing adjusting device 200, and the second valve timing adjusting device 300 of the most lagged lock type. Through the arrangement of the fourth embodiment thus structured as above, the arrangement provides easy control of each the valve timings, taking advantages of the valve timing adjusting devices of each type on the intake camshaft S3 side and of the exhaust camshaft S4 side to a predetermined timing located nearly in the middle of the rotation range including the most advanced position and the most lagged position.

[0134] According to the fourth embodiment, it is arranged such that the third valve timing adjusting device 100 is provided on the end face of the crank shaft S1. Through the arrangement of the fourth embodiment thus structured as above, the arrangement installs the device in the valve timing adjusting system without making a change in the layout of the conventional valve timing adjusting system.

[0135] The valve timing adjusting device of the vane type and the most lagged lock type is used as the third valve timing adjusting device in the valve timing adjusting system illustrated in the third embodiment, whereas the valve timing adjusting device of the helical type and the most advanced lock type is used the same illustrated in the fourth embodiment. The present invention may be advantageously adapted in motor-driven electric actuators of the worm gear type and the torsion spring type, for instance, because the amount of lubricant oil and the consumption of hydraulic pressure within the engine can be economized.