JP2017172763A - Friction engaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction engaging device capable of detecting wear of a friction engaging member with a simple structure.SOLUTION: In an oil chamber 20 formed by a housing 10 and a piston 17 of a friction engaging device 1, a communication passage 10e is provided. In the communication passage 10e, a relief valve 23 is arranged. A valve piston 23a of the relief valve 23 is energized in an opening direction by a hydraulic pressure of the oil chamber 20, and energized in a closing direction by an energization force of a valve spring 23b. The valve spring 23b moves further into the opening direction as the piston 17 comes closer to an end plate 15a. The energization force of the valve spring 23b is lower than the hydraulic pressure in the oil chamber 20, when the piston 17 moves further to the end plate 15a side than the normal time.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a friction engagement device that transmits rotation of an input member to an output member by friction engagement.

  Conventionally, like a multi-plate clutch used in a transmission, an input member, a first plate that rotates integrally with the input member, a second plate that frictionally engages with the first plate, and a second plate are integrated. There is known a friction engagement device that includes an output member that rotates in a rotating manner and that frictionally engages a first plate and a second plate to transmit the rotation of the input member to the output member.

  As this type of friction engagement device, there is a configuration in which the plates are brought into contact with each other and frictionally engaged by a pressing force from a piston movable in the axial direction. Such a piston is moved by a return spring disposed between the housing and the piston of the friction engagement device and a hydraulic pressure supplied to an oil chamber formed between the housing and the piston. There is something.

  In such a friction engagement device including a piston, a configuration is known in which a relief valve is provided in the oil chamber, thereby preventing an excessive pressing force from being applied to the piston (and hence a plate that is a friction engagement member). (For example, refer to Patent Document 1).

JP 2001-032861 A

  In the conventional frictional engagement device as described in Patent Document 1, a plate that is a frictional engagement member is worn and thinned when used for a certain period of time. If the thickness of the plate is reduced, the stroke amount of the piston necessary for the pressing force of the plate (that is, the movement amount of the piston required until the pressing force is applied from the piston to the plate) increases. As a result, there is a problem that the responsiveness of the friction engagement device is lowered.

  On the other hand, the structure which measures the stroke amount of a piston by providing a stroke sensor etc., and judges whether abnormal wear has generate | occur | produced on the friction engagement member based on the measured value is also considered. However, when the stroke sensor is installed, there is a problem that the entire apparatus becomes large or the production cost increases.

  The present invention has been made in view of the above points, and an object thereof is to provide a friction engagement device capable of detecting wear of a friction engagement member with a simple configuration.

  In order to achieve the above object, the friction engagement device of the present invention includes an input member (I) that is rotated by a driving force transmitted from a drive source, and a first friction that rotates integrally with the input member (I). An engagement member (15), a second friction engagement member (16) disposed so as to overlap the first friction engagement member (15) in the axial direction, and the second friction engagement member (16) An output member (O) that rotates integrally with and outputs rotation, and is movable in the axial direction, and is connected to one of the first friction engagement member (15) and the second friction engagement member (16). A piston (17) that applies a pressing force in a direction approaching the other side, a first biasing member (22) that biases the piston toward one side in the axial direction, and a housing in which the piston (17) is disposed. An oil chamber (10) between the piston (17) and the housing (10). 0) is formed, and the piston (17) is a friction engagement device (1) that is pressed to the other side in the axial direction in accordance with the hydraulic pressure supplied to the oil chamber (20). 20) a hydraulic pressure sensor (HS) for detecting the hydraulic pressure supplied to the oil chamber, a communication path (10e) for communicating the inside and the outside of the oil chamber (20), and a relief provided in the communication path (10e). The relief valve (23) includes a valve piston (23a) capable of closing the communication passage (10e), and a second urging member (23b) that urges the valve piston (23a). The valve piston (23a) is urged in the opening direction by the hydraulic pressure of the oil chamber (20), and is urged in the closing direction by the urging force of the second urging member (23b). The second biasing member (23b) When the stone (17) moves toward the first friction engagement member (15) and the second friction engagement member (16), it moves in the opening direction, and the second biasing member (23b) The urging force is generated when the piston (17) moves toward the first friction engagement member (15) and the second friction engagement member (16) with respect to the maximum movement position in a normal state. The oil pressure is lower than the oil pressure of (20).

  Thus, the friction engagement device of the present invention urges the valve piston of the relief valve in the oil chamber, which is also provided in the conventional friction engagement device, in the closing direction by the urging force of the second urging member. ing. Therefore, when the urging force of the second urging member falls below the oil pressure from the oil chamber that urges the second urging member in the opening direction, the relief valve is opened, and the oil pressure in the oil chamber decreases.

  By the way, the second urging member moves in the opening direction when the piston moves toward the friction engagement member. That is, the urging force in the closing direction of the second urging member decreases as the piston moves toward the friction engagement member. Further, the urging force in the closing direction of the second urging member is set so as to be less than the load in the releasing direction due to the hydraulic pressure when the piston moves to the friction engagement member side from the maximum movement position in the normal state. .

  As a result, when abnormal wear occurs in the friction engagement member (that is, when the piston moves to the friction engagement member side from the maximum movement position in the normal state), the relief valve is opened, and the oil chamber Hydraulic pressure decreases. As a result, the abnormal wear of the friction engagement member can be detected only by measuring the hydraulic pressure with a hydraulic pressure sensor.

  Therefore, according to the friction engagement device of the present invention, the friction engagement can be achieved by using the relief valve and the hydraulic sensor which are also arranged in the conventional friction engagement device without using a dedicated member such as a stroke sensor. The wear of the member can be detected.

Sectional drawing which shows the structure of the friction engagement apparatus which concerns on embodiment. FIGS. 2A and 2B are enlarged cross-sectional views showing a main part when the friction engagement device of FIG. 1 is not worn, FIG. 2A shows a non-engagement state, and FIG. 2B shows an engagement state. FIGS. 3A and 3B are enlarged cross-sectional views showing a main part when the friction engagement device of FIG. 1 is worn, FIG. 3A shows a disengaged state, and FIG. 3B shows an engaged state. 4A and 4B are graphs showing the relationship between the amount of movement of the piston of the friction engagement device of FIG. 1 and the load applied from the piston to the relief valve. FIG. 4A shows the normal state and FIG. 4B shows the abnormal wear time. FIG. 5A is a graph showing the relationship between the hydraulic pressure supplied to the oil chamber of the friction engagement device of FIG. 1 and the load applied to the valve piston of the relief valve by the hydraulic pressure, FIG. 5A shows normal time, and FIG. 5B shows abnormal wear time. .

  Hereinafter, the friction engagement device according to the present embodiment will be described with reference to the drawings. In the present embodiment, the friction engagement device is used as a driving force transmission device for a vehicle or the like. However, the frictional engagement device according to the present invention can be mounted on other mechanisms such as a ship or the like, in addition to a driving force transmission device of another vehicle or an unmanned aircraft.

  First, with reference to FIG.1 and FIG.2, the structure of the friction engagement apparatus 1 which is what is called a wet multi-plate type clutch is demonstrated.

  As shown in FIG. 1, the friction engagement device 1 is configured as a cylindrical device. An input shaft I (input member) to which a driving force from a vehicle driving source is transmitted is inserted from one end side (right side in FIG. 1) of the opening of the friction engagement device 1. On the other hand, from the other end side (left side in FIG. 1), an output shaft O (output member) that transmits the driving force transmitted through the friction engagement device 1 to the driving wheels of the vehicle is inserted.

  The cylindrical frictional engagement device 1 includes a case 10 (housing) that forms an outer peripheral surface and an end surface, and a first portion that is disposed inside the case 10, forms a part of the inner peripheral surface, and is coupled to the input shaft I. 1 clutch hub 11 and the 2nd clutch hub 12 which is arrange | positioned coaxially with the 1st clutch hub 11 inside the case 10, comprises the other part of an internal peripheral surface, and couple | bonds with the output shaft O. .

  The case 10 is provided on the cylindrical outer peripheral side wall 10a, the other end of the outer peripheral side wall 10a, an end surface 10b provided with an opening at the center, and the opening of the end surface 10b on one side in the axial direction. It has the cylindrical inner peripheral side wall part 10c extended.

  The first clutch hub 11 includes a cylindrical first boss portion 11a that forms a part of the inner peripheral surface of the friction engagement device 1, and a radially outward side from the first boss portion 11a (the outer peripheral surface side of the case 10). And a first guide portion 11c extending from the end of the first annular portion 11b opposite to the first boss portion 11a to the other end in the axial direction. ing.

  The second clutch hub 12 is a cylindrical second boss portion 12a that forms another part of the inner peripheral surface of the friction engagement device 1, and an annular shape that extends radially outward from the second boss portion 12a. The second annular portion 12b and a second guide portion 12c extending from the end of the second annular portion 12b opposite to the second boss portion 12a to the one side in the axial direction.

  The first boss portion 11a of the first clutch hub 11 includes a cylindrical small-diameter portion 11a1 and a cylindrical large-diameter portion 11a2 that is coaxial with the small-diameter portion 11a1 and has a larger diameter than the small-diameter portion 11a1. .

  The distal end portion of the input shaft I is inserted into the cylindrical small diameter portion 11a1 from one end side. The first clutch hub 11 and the input shaft I are spline-coupled at the distal end portion of the input shaft I and a part of the inner peripheral surface of the small diameter portion 11a1.

  A second boss portion 12a of the second clutch hub 12 is inserted into the cylindrical large diameter portion 11a2 from the other end side. A first ball bearing 13 is disposed between the inner peripheral surface of the large-diameter portion 11 a 2 of the first clutch hub 11 and a portion on one end side of the outer peripheral surface of the second boss portion 12 a of the second clutch hub 12. . Therefore, the first clutch hub 11 can rotate relative to the input clutch I integrally with the second clutch hub 12 (that is, the output shaft O).

  The 2nd boss part 12a of the 2nd clutch hub 12 is constituted cylindrical, and the tip part of output axis O is inserted from the other end side. The second clutch hub 12 and the output shaft O are spline-coupled at the distal end portion of the output shaft O and a part of the inner peripheral surface of the second boss portion 12a.

  A ball bearing 14 is disposed between the other end side portion of the outer peripheral surface of the second boss portion 12 a of the second clutch hub 12 and the inner peripheral surface of the inner peripheral side wall portion 10 c of the case 10. Therefore, the second clutch hub 12 can rotate integrally with the output shaft O with respect to the case 10.

  The 1st guide part 11c of the 1st clutch hub 11 is comprised by the cylinder shape. A plurality of first groove portions 11c1 extending in the axial direction are formed on the inner peripheral surface side of the first guide portion 11c. A plurality of annular outer plates 15 (first friction engagement members) are arranged on the inner peripheral surface side of the first guide portion 11c. The outermost plate on the other end side of the outer plate 15 is an end plate 15a that comes into contact with a thrust bearing 18 described later.

  A plurality of claw portions are formed on the outer peripheral side of the outer plate 15 so as to correspond to the first groove portion 11c1. Therefore, each outer plate 15 is movable in the axial direction on the inner peripheral surface side of the first guide portion 11c. On the other hand, the outer plate 15 rotates integrally with the first guide portion 11c (that is, the first clutch hub 11 and the input shaft I) in the circumferential direction.

  The second guide portion 12c of the second clutch hub 12 is configured in a cylindrical shape, and the first guide portion 11c of the first clutch hub 11 and the outer plate 15 disposed on the inner peripheral side of the first guide portion 11c. It is arrange | positioned rather than the inner peripheral side. A plurality of second groove portions 12c1 extending in the axial direction are formed on the outer peripheral surface side of the second guide portion 12c. A plurality of annular inner plates 16 (second friction engagement members) are arranged on the outer peripheral surface side of the second guide portion 12c.

  A plurality of claw portions are formed on the inner peripheral side of the inner plate 16 so as to correspond to the second groove portion 12c1. Therefore, each inner plate 16 is movable in the axial direction on the outer peripheral surface side of the second guide portion 12c. On the other hand, the inner plate 16 rotates integrally with the second guide portion 12c (that is, the second clutch hub 12 and the output shaft O) in the circumferential direction.

  The plurality of outer plates 15 and the plurality of inner plates 16 are arranged so as to alternately overlap in the axial direction. When the outer plate 15 and the inner plate 16 are pressed toward one side in the axial direction by the piston 17, they are frictionally engaged with each other. In the frictionally engaged state, the outer plate 15 and the inner plate 16 rotate integrally, so that the rotation of the input shaft I causes the first clutch hub 11, the outer plate 15, the inner plate 16, and the second clutch hub. 12 to the output shaft O.

  In the friction engagement device 1, the outermost plate 15 (end plate 15 a) on the other end side is disposed closer to the piston 17 than the inner plate 16 on the other end side. However, the innermost plate 16 on the other end side may be disposed closer to the piston 17 side than the outermost plate 15 on the other end side. In that case, what is necessary is just to comprise the inner plate 16 of the other end side contact | abutted to the thrust bearing 18 as an end plate.

  Further, the friction engagement device 1 is disposed between an annular piston 17 disposed on the other end side of the outer plate 15 and the inner plate 16 inside the case 10, and between the piston 17, the outer plate 15 and the inner plate 16. And a thrust bearing 18 is provided.

  The outer peripheral surface of the piston 17 is slidable with the inner peripheral surface of the outer peripheral side wall portion 10a (specifically, an annular convex portion 10d described later) of the case 10. On the other hand, the inner peripheral surface of the piston 17 is slidable with the outer peripheral surface of the inner peripheral side wall portion 10 c of the case 10. The grooves 17a provided on the outer peripheral surface and inner peripheral surface of the piston 17 are liquid-tightly sealed between the piston 17 and the outer peripheral side wall portion 10a or between the piston 17 and the inner peripheral side wall portion 10c. A ring 19 is arranged; Thereby, an oil chamber 20 is formed between the piston 17 and the case 10.

  The hydraulic oil is supplied to the oil chamber 20 from an oil pressure control circuit HC including an oil pump and a plurality of valves through an oil passage. The hydraulic pressure of the hydraulic oil supplied from the hydraulic control circuit HC is detected by a hydraulic pressure sensor HS. The piston 17 moves to one end side in the axial direction in accordance with the increase in the volume of the oil chamber 20.

  A protrusion 17 b is provided on the surface on one end side of the piston 17. The protrusion 17b abuts on a protrusion receiving part 21a extending from the annular spring receiving part 21 provided on the inner peripheral side wall part 10c of the case 10 to the other side in the axial direction. Thereby, the rotation of the piston 17 around the axis is suppressed.

  A return spring 22 (first urging member) is disposed between the surface on the other end side on the radially inner side of the protrusion receiving portion 21 a of the spring receiving portion 21 and the surface on the one end side of the piston 17. Yes. The piston 17 is urged by a return spring 22 in a direction in which the volume of the oil chamber 20 is reduced (that is, the other end in the axial direction). Therefore, the piston 17 moves in the axial direction according to the hydraulic pressure supplied to the oil chamber 20 and the urging force of the return spring 22.

  In the friction engagement device 1, a coil spring is used as the first biasing member that biases the piston 17. However, the first biasing member is not limited to the coil spring. For example, rubber or the like may be used in addition to a disc spring or wave spring.

  A bearing support portion 17 c is provided at a position facing the end plate 15 a on the one end side of the piston 17. A thrust bearing 18 is disposed between the bearing support portion 17c and the end plate 15a so as to be movable in the axial direction. When the piston 17 moves to one end side, the pressing force from the piston 17 to the end plate 15 a is transmitted through the thrust bearing 18.

  Next, the frictional engagement between the outer plate 15 and the inner plate 16 will be described with reference to FIG.

  As shown in FIG. 2A, a state where sufficient hydraulic oil is not supplied from the hydraulic control circuit HC to the oil chamber 20 (that is, the hydraulic pressure supplied to the oil chamber 20 is sufficiently smaller than the urging force of the return spring 22. In the state), the piston 17 returns to a position where the urging force of the return spring 22 and the hydraulic pressure supplied to the oil chamber 20 are balanced.

  As a result, no pressing force is applied to the outer plate 15 and the inner plate 16, so that the outer plate 15 and the inner plate 16 are separated from each other (non-engaged state). As a result, the rotation of the input shaft I is not transmitted to the inner plate 16, the second clutch hub 12, and the output shaft O via the first clutch hub 11 and the outer plate 15.

  On the other hand, as shown in FIG. 2B, a state in which sufficient hydraulic oil is supplied from the hydraulic control circuit HC to the oil chamber 20 (that is, the hydraulic pressure supplied to the oil chamber 20 is more than the urging force of the return spring 22). 2), the piston 17 moves to one end side against the urging force of the return spring 22.

  As a result, a pressing force is applied to the outer plate 15 and the inner plate 16, so that the outer plate 15 and the inner plate 16 are frictionally engaged with each other (engaged state). As a result, the rotation of the input shaft I is transmitted to the inner plate 16, the second clutch hub 12 and the output shaft O via the first clutch hub 11 and the outer plate 15.

  By the way, the outer plate 15 and the inner plate 16 are engaged by friction. Therefore, if it continues to be used for a certain period of time, wear occurs on the surfaces in contact with each other, and the thickness in the axial direction gradually decreases.

  Therefore, as described below with reference to FIGS. 1 to 5, in the friction engagement device 1, abnormal wear occurs in the outer plate 15 and the inner plate 16 due to the communication path 10 e, the relief valve 23, and the hydraulic sensor HS. The determination mechanism for determining whether or not is being performed is configured.

  First, the schematic configuration of the determination mechanism will be described with reference to FIG. As shown in FIG. 1, the case 10 includes a cylindrical outer peripheral side wall 10a, an end surface 10b provided on the other end side of the outer peripheral side wall 10a, and an opening at the center, and an opening of the end surface 10b. And a cylindrical inner peripheral side wall portion 10c extending from the portion to one side in the axial direction.

  An annular convex portion 10d is provided on the inner peripheral surface of the end portion on the end surface portion 10b side of the outer peripheral side wall portion 10a so as to protrude toward the radially inner peripheral side. A communication passage 10e extending in the axial direction is formed in the annular convex portion 10d. The communication path 10e communicates the inside and the outside of the oil chamber 20. A relief valve 23 is disposed in the communication path 10e.

  The annular piston 17 slides with the inner peripheral surface of the annular convex portion 10d on the outer peripheral surface, and slides with the outer peripheral surface of the inner peripheral side wall portion 10c on the inner peripheral surface. Thereby, an oil chamber 20 is formed between the piston 17 and the case 10. The hydraulic pressure of the hydraulic oil supplied to the oil chamber 20 from the hydraulic control circuit HC is detected by a hydraulic pressure sensor HS.

  From the outer peripheral portion of the piston 17 in the radial direction so as to overlap the surface on one end side of the annular convex portion 10d in the axial direction (specifically, so as to cover a part of the opening portion on one end side of the communication passage 10e). An annular piston-side receiving portion 17d is extended toward the outer peripheral side.

  The relief valve 23 includes a valve piston 23a formed of a steel ball capable of closing the communication path 10e, and a valve spring 23b (second urging member) that urges the valve piston 23a.

  The valve piston 23a is biased toward one end side by the hydraulic pressure from the oil chamber 20 (that is, the opening direction (right direction in FIG. 1)), and toward the other end side by the biasing force of the valve spring 23b (that is, the valve piston 23a). , Is biased in the closing direction (left direction in FIG. 1).

  An end portion on one end side of the valve spring 23b is fixed to a surface on the other end side of the piston side receiving portion 17d of the piston 17. On the other hand, the other end of the valve spring 23b is fixed to the valve piston 23a. That is, the valve spring 23b can move integrally with the piston 17 when the piston 17 moves toward the end plate 15a (that is, the opening direction of the valve piston 23a).

  Therefore, the urging force (load) in the closing direction applied from the valve spring 23b to the valve piston 23a decreases as the piston 17 moves toward the end plate 15a (see FIG. 4). Further, the biasing force is set to be lower than the hydraulic pressure of the oil chamber 20 when the piston 17 moves to the end plate 15a side from the maximum movement position (piston position shown in FIG. 2B) in the normal state. .

  In the friction engagement device 1, a coil spring is used as the valve spring 23b as the second biasing member that biases the valve spring 23b. However, the second urging member is not limited to the coil spring. For example, rubber or the like may be used in addition to a disc spring or wave spring.

  Next, a method for determining abnormal wear by the determination mechanism will be described with reference to FIGS. FIG. 2 is an enlarged cross-sectional view showing a main part when the friction engagement device 1 is not worn, FIG. 2A shows a non-engaged state, and FIG. 2B shows an engaged state. FIG. 3 is an enlarged cross-sectional view showing a main part when the friction engagement device 1 is worn, FIG. 3A shows a non-engagement state, and FIG. 3B shows an engagement state.

  FIG. 4 is a graph showing the relationship between the amount of movement of the piston 17 and the load applied from the piston to the valve piston 23a of the relief valve 23. FIG. 4A shows the normal state and FIG. 4B shows the abnormal wear. FIG. 5 is a graph showing the relationship between the hydraulic pressure supplied to the oil chamber 20 and the load applied to the valve piston 23a of the relief valve 23 by the hydraulic pressure, FIG. 5A shows normal time, and FIG. 5B shows abnormal wear.

  When abnormal wear has not occurred on the outer plate 15 or the inner plate 16 (normal state), in the non-engaged state (the movement amount of the piston 17 is “0”), as shown in FIG. The urging force of the return spring 22 does not move from a position where no pressing force is applied to the end plate 15a against the hydraulic pressure of the oil chamber 20.

  At this time, as shown in FIG. 4A, a load F0 in the closing direction is applied to the valve piston 23a by the urging force of the valve spring 23b. On the other hand, at this time, the oil pressure in the oil chamber 20 is “0” or a very low value. Therefore, as shown in FIG. 5A, no load is applied to the valve piston 23a in the opening direction due to the oil pressure of the oil chamber 20 (load is “0”), or the valve spring 23b is not open in the opening direction. A load sufficiently smaller than the urging force is applied.

  As a result, a force in the closing direction is applied to the valve piston 23a, and the relief valve 23 maintains the closed state. Therefore, the value detected by the hydraulic sensor HS is a value as instructed from the hydraulic control circuit HC.

  Next, when there is no abnormal wear on the outer plate 15 or the inner plate 16 (normal state), in the engaged state (the movement amount of the piston 17 is “x1” (normal maximum movement position) state), FIG. As shown in 2B, the piston 17 moves against the urging force of the return spring 22 by the oil pressure of the oil chamber 20. Therefore, the piston 17 is positioned closer to the end plate 15a than the state of FIG. 2A so as to apply a pressing force to the end plate 15a.

  At this time, as shown in FIG. 4A, a load F1 in the closing direction is applied to the valve piston 23a by the urging force of the valve spring 23b. On the other hand, at this time, as shown in FIG. 5A, a load F2 in the opening direction is applied to the valve piston 23a in accordance with the change in the oil pressure of the oil chamber 20.

  At this time, since the load F1 in the closing direction is larger than the maximum load F2 in the opening direction, a force in the closing direction is applied to the valve piston 23a, and the relief valve 23 maintains the closed state. Therefore, the value detected by the hydraulic sensor HS is a value as instructed from the hydraulic control circuit HC.

  Next, when abnormal wear occurs in the outer plate 15 or the inner plate 16 (at the time of abnormal wear), as shown in FIG. 3A in the non-engaged state (the movement amount of the piston 17 is “0”). The piston 17 does not move from a position where no pressing force is applied to the end plate 15 a against the hydraulic pressure of the oil chamber 20 by the urging force of the return spring 22.

  At this time, as shown in FIG. 4B, a load F0 in the closing direction is applied to the valve piston 23a by the urging force of the valve spring 23b. On the other hand, at this time, the oil pressure in the oil chamber 20 is “0” or a very low value. Therefore, as shown in FIG. 5B, no load is applied to the valve piston 23a in the opening direction due to the hydraulic pressure of the oil chamber 20 (load is “0”), or the valve spring 23b is not open in the opening direction. A load sufficiently smaller than the urging force is applied.

  As a result, a force in the closing direction is applied to the valve piston 23a, and the relief valve 23 maintains the closed state. Therefore, the value detected by the hydraulic sensor HS is a value as instructed from the hydraulic control circuit HC.

  Next, when abnormal wear occurs in the outer plate 15 or the inner plate 16 (at the time of abnormal wear), the engagement state (the movement amount of the piston 17 is larger than “x1” (the maximum movement position at the normal time)). In the state of “x2”), as shown in FIG. 3B, the piston 17 moves against the urging force of the return spring 22 by the hydraulic pressure of the oil chamber 20. Therefore, the piston 17 is positioned closer to the end plate 15a than the state of FIG. 3A so as to apply a pressing force to the end plate 15a.

  Further, in this case, abnormal wear has occurred in the outer plate 15 and the inner plate 16, so that the stroke amount of the piston 17 (that is, the piston 17 required until the pressing force is applied from the piston 17 to the end plate 15a). The amount of movement) has increased. Therefore, the piston 17 has moved to the one end side from the pressing state in the normal state (the state of FIG. 2B).

  At this time, as shown in FIG. 4B, a load F3 in the closing direction is applied to the valve piston 23a by the urging force of the valve spring 23b. On the other hand, at this time, as shown in FIG. 5A, a load F2 in the opening direction is applied to the valve piston 23a in accordance with the change in the oil pressure of the oil chamber 20.

  The load F3 in the closing direction is a value lower than the load F1 due to the urging force at the time of pressing in accordance with the movement amount of the piston 17. The load F2 in the opening direction may exceed the load F3 (for example, a state corresponding to the position indicated by a dot in FIG. 5B). In this case, a force in the opening direction is applied to the valve piston 23a, and the relief valve 23 is opened. Therefore, hydraulic oil is discharged from the oil chamber 20 via the communication passage 10e, and the value detected by the hydraulic pressure sensor HS is lower than the instruction from the hydraulic pressure control circuit HC.

  Therefore, in the friction engagement device 1 including the determination mechanism configured by the communication path 10e, the relief valve 23, and the hydraulic pressure sensor HS, whether or not the hydraulic pressure of the hydraulic pressure sensor HS is lower than an instruction from the hydraulic pressure control circuit HC. It is possible to detect abnormal wear of the outer plate 15 and the inner plate 16 simply by detecting.

  That is, according to the friction engagement device 1, the outer plate 15 can be obtained by using the relief valve 23 and the hydraulic sensor HS that are also arranged in the conventional friction engagement device without using a dedicated member such as a stroke sensor. And abnormal wear of the inner plate 16 can be detected.

  Although the illustrated embodiment has been described above, the present invention is not limited to such a form.

  For example, in the above embodiment, the relief valve 23 is disposed in the communication path 10e extending in the axial direction. The relief valve 23 includes a valve piston 23a and a valve spring 23b (second urging member) that can close the communication passage 10e. Further, the valve spring 23 b is fixed to the piston side receiving portion 17 d of the piston 17 so as to move in conjunction with the movement of the piston 17.

  However, the relief valve of the present invention is not limited to such a configuration. For example, the piston and the second urging member do not need to be directly connected, and may be indirectly connected with another member interposed therebetween. If comprised in that way, it will become easy to make direction of a communicating path into directions other than an axial direction (for example, radial direction).

DESCRIPTION OF SYMBOLS 1 ... Friction engagement apparatus, 10 ... Case (housing | casing), 10a ... Outer peripheral side wall part, 10b ... End surface part, 10c ... Inner peripheral side wall part, 10d ... Annular convex part, 10e ... Communication path, 11 ... 1st clutch hub 11a ... first boss portion, 11a1 ... small diameter portion, 11a2 ... large diameter portion, 11b ... first annular portion, 11c ... first guide portion, 11c1 ... first groove portion, 12 ... second clutch hub, 12a ... second Boss part, 12b ... 2nd annular part, 12c ... 2nd guide part, 12c1 ... 2nd groove part, 13 ... 1st ball bearing, 14 ... 2nd ball bearing, 15 ... Outer plate (1st friction engagement member), 15a ... End plate, 16 ... Inner plate (second friction engagement member), 17 ... Piston, 17a ... Groove, 17b ... Projection, 17c ... Bearing support part, 17d ... Piston side receiving part, 18 ... Thrust bearing, DESCRIPTION OF SYMBOLS 9 ... O-ring, 20 ... Oil chamber, 21 ... Spring receiving part, 21a ... Projection receiving part, 22 ... Return spring (1st biasing member), 23 ... Relief valve, 23a ... Valve piston, 23b ... Valve spring ( (Second urging member), HC ... hydraulic control circuit, HS ... hydraulic sensor, I ... input shaft (input member), O ... output shaft (output member).

Claims (1)

An input member that is rotated by a driving force transmitted from a driving source;
A first friction engagement member that rotates integrally with the input member;
A second frictional engagement member arranged to overlap the first frictional engagement member in the axial direction;
An output member that rotates integrally with the second friction engagement member and outputs rotation;
A piston that is movable in an axial direction and applies a pressing force in a direction approaching the other to one of the first friction engagement member and the second friction engagement member;
A first urging member that urges the piston in one axial direction;
A housing in which the piston is disposed;
An oil chamber is formed between the piston and the housing,
The piston is a friction engagement device that is pressed to the other side in the axial direction according to the hydraulic pressure supplied to the oil chamber,
A hydraulic pressure sensor for detecting the hydraulic pressure supplied to the oil chamber;
A communication path communicating the inside and the outside of the oil chamber;
A relief valve provided in the communication path,
The relief valve has a valve piston capable of closing the communication path, and a second urging member that urges the valve piston,
The valve piston is biased in the opening direction by the hydraulic pressure of the oil chamber, and biased in the closing direction by the biasing force of the second biasing member,
The second urging member moves in the opening direction when the piston moves toward the first friction engagement member and the second friction engagement member.
The biasing force of the second biasing member is such that the piston of the oil chamber moves when the piston moves to the first friction engagement member and the second friction engagement member side with respect to the maximum movement position in a normal state. A friction engagement device characterized by being below hydraulic pressure.