JP2010025141A - Drive force transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive force transmission device capable of quickly suppressing generation of frictional heat by drag torque. <P>SOLUTION: The drive force transmission device 6 is provided with a bottomed-cylinder-like front housing 22, a shaft-like inner shaft 23 coaxially and rotatably arranged in a front housing 22 and a main clutch 41 arranged in a clutch storing chamber 34 for connecting a front housing 22 and the inner shaft 23 in a torque-transmittable manner. In the clutch storing chamber 34, a lubricating oil is filled at a predetermined filling ratio and a cam mechanism 42 for facilitating a main cam 46 pressing the main clutch 41 by operation of a pilot clutch 43. With a hydraulic pump 61 operated by rotation difference between the front housing 22 and the inner shaft 23, a pressing force that the main cam 46 applies to the main clutch 41 is reduced by the lubricating oil discharged from the hydraulic pump 61. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force transmission device that transmits a driving force by frictionally engaging a plurality of clutch plates.

  2. Description of the Related Art Conventionally, a cylindrical first rotating member and a shaft-shaped second rotating member coaxially disposed in the first rotating member so as to be rotatable are provided between the first rotating member and the second rotating member. There is a driving force transmission device in which a first rotating member and a second rotating member can be connected so as to be able to transmit torque by an arranged clutch mechanism. In addition, a cam mechanism is provided in which a pilot clutch is juxtaposed in the axial direction of the clutch mechanism (main clutch), and between the main clutch and the pilot clutch, the main clutch is pressed in the axial direction by the operation of the pilot clutch. The main clutch is frictionally engaged.

  Many of these types of driving force transmission devices are configured as so-called wet clutches in which lubricating oil is interposed between the clutch plates of the main clutch and the pilot clutch, so even when the pilot clutch is in an inoperative state, A so-called drag torque is generated due to the engaging force based on the viscosity of the interposed lubricating oil. The drag torque is converted into an axial pressing force by the cam mechanism and amplified to frictionally engage the main clutch, so that the main clutch generates heat due to friction between the clutch plates. In particular, when only the auxiliary driving wheel to which torque is transmitted via the driving force transmitting device is towed in a grounded state (so-called two-wheel towed), the first rotating member connected to the main driving wheel side does not rotate. However, only the second rotating member connected to the auxiliary drive wheel side rotates. As a result, there is a problem that a large rotational difference occurs between the first rotating member and the second rotating member, and the main clutch is overheated.

Therefore, Patent Document 1 discloses a direction in which the contact portion of the inner shaft (the axial end surface of the spline fitting portion) weakens the fastening force of the main clutch based on an increase in the internal pressure of the clutch storage chamber in which the main clutch is stored. A driving force transmission device configured to push the cam member back is disclosed. Thereby, the generation of frictional heat between the clutch plates is suppressed, and the main clutch is prevented from overheating.
Japanese Patent Laid-Open No. 2005-16698

  By the way, in Patent Document 1, the inner shaft moves so as to push back the cam member based on the increase in the internal pressure in the clutch housing chamber, that is, pushes back the cam member after the internal pressure rises due to heat generated in the main clutch. Move to. Therefore, there is a possibility that the main clutch and the like may be overheated until the internal pressure in the clutch housing chamber rises. Therefore, there is still room for improvement in this respect, and the protection of the driving force transmission device is made more reliable. It was demanded.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a driving force transmission device capable of quickly suppressing the generation of frictional heat due to drag torque.

  In order to achieve the above object, the invention described in claim 1 includes a cylindrical first rotating member, a shaft-shaped second rotating member that is coaxially disposed in the first rotating member, and the first rotating member. Torque can be transmitted between the first rotating member and the second rotating member by being arranged in a clutch housing chamber partitioned liquid-tightly between the first rotating member and the second rotating member and being pressed in the axial direction. A driving force transmission device comprising: a clutch mechanism coupled to the clutch mechanism; a pressing member that presses the clutch mechanism; and a lubricating oil filled in the clutch housing chamber at a predetermined filling rate. A hydraulic pump that operates according to a rotational difference from the two-rotating member, and an overheat protection mechanism that reduces the pressing force that the pressing member applies to the clutch mechanism by the lubricating oil discharged from the hydraulic pump. Summary .

  According to the above configuration, the overheat protection mechanism can reduce the pressing force of the pressing member by the lubricating oil supplied from the hydraulic pump. For example, when the two wheels are towed, the frictional heat between the clutch plates is generated. And the overheating of the main clutch can be prevented. Since the hydraulic pump operates based on the difference in rotation between the first rotating member and the second rotating member, the hydraulic pump is pressed more quickly than in the case where the pressing member is pushed back based on the increase in the internal pressure in the clutch chamber as in the prior art. The pressing force of the member can be reduced, and the driving force transmission device can be more reliably protected.

  According to a second aspect of the present invention, in the driving force transmission device according to the first aspect, the overheat protection mechanism is a hollow portion formed by being recessed in the second rotating member, the clutch housing chamber and the liquid The gist is to provide a tightly partitioned hydraulic chamber and reduce the pressing force applied to the clutch mechanism by the hydraulic pressure of the lubricating oil pumped to the hydraulic chamber by the hydraulic pump.

  According to the above configuration, the lubricating oil discharged from the hydraulic pump is pumped to the hydraulic chamber partitioned by the hollow portion formed in the second rotating member so as to suppress an increase in the size of the driving force transmission device. However, the pressing force of the pressing member can be reduced using the hydraulic pressure of the lubricating oil.

  According to a third aspect of the present invention, in the driving force transmission device according to the second aspect, the second rotating member is engaged with an outer peripheral surface of the second rotating member such that the inner clutch plate of the clutch mechanism is not relatively rotatable and is movable in the axial direction. A large-diameter portion in which the hollow portion is formed, and a small-diameter portion having a smaller diameter than the large-diameter portion, and the overheat protection mechanism is formed in the second rotating member, A through hole penetrating the step surface between the small diameter portion and the hydraulic chamber; a high pressure chamber in which the lubricating oil is discharged from the hydraulic pump; and a low pressure chamber in which the through hole is opened. And a plunger that is inserted into the through-hole and has a base end fixed to the low-pressure chamber side of the piston and a tip that engages the pressing member. To do.

  According to the above configuration, since the piston partitions the high pressure chamber and the low pressure chamber, the hydraulic pressure of the lubricating oil supplied to the hydraulic chamber (high pressure chamber) by the hydraulic pump acts on the piston. Thereby, since a piston moves to the low-pressure chamber side, a pressing member is pressed by the plunger in the direction in which the frictional engagement of the clutch mechanism is released. For this reason, for example, the pressing force of the pressing member can be surely reduced as compared with a case where the pressing force of the pressing member is decreased by jetting lubricant to the pressing member.

The gist of a fourth aspect of the present invention is that, in the driving force transmission device according to the third aspect, an elastic member for controlling movement of the piston by the hydraulic pressure of the lubricating oil is provided.
According to the above configuration, the movement of the piston by the hydraulic pressure of the lubricating oil is controlled by the elastic member, that is, when the hydraulic pressure is less than the elastic force of the elastic member, the pressing force applied to the clutch mechanism by the pressing member is reduced by the hydraulic pressure. If the hydraulic pressure is greater than the elastic force of the elastic member, the pressing force applied to the clutch mechanism by the pressing member is reduced by the hydraulic pressure. Therefore, by making the elastic force of the elastic member suitable, for example, when the rotation difference between the first rotating member and the second rotating member is small, such as when the rear wheel slips, the pressing force of the pressing member by hydraulic pressure If the rotational difference between the first rotating member and the second rotating member is large, such as when the two-wheel is towed, etc., the pressing force of the pressing member can be reduced by hydraulic pressure. As a result, when the control device distributes torque to the auxiliary drive wheels according to the traveling state of the vehicle, the pressing force of the pressing member that is reduced by the hydraulic pressure, that is, the torque transmission capacity of the driving force transmission device that is reduced by the hydraulic pressure is reduced. The control of the driving force transmission device can be prevented from becoming complicated, and the driving force transmission device can be controlled by a control method similar to the conventional method.

  According to a fifth aspect of the present invention, in the driving force transmission device according to the second aspect, the second rotating member is engaged with the inner clutch plate of the clutch mechanism so that the inner clutch plate is relatively unrotatable and axially movable. A large-diameter portion in which a hollow portion is formed, and a small-diameter portion having a smaller diameter than the large-diameter portion, and the pressing member is opposed to a step surface between the large-diameter portion and the small-diameter portion. The gist of the overheat protection mechanism is provided in the second rotating member, and has a through hole that opens to the hydraulic chamber and the step surface.

  According to the above configuration, since the pressing force of the pressing member is reduced by the lubricant ejected from the through hole, the overheat protection mechanism can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, the drive force transmission device which can suppress rapidly generation | occurrence | production of the frictional heat by drag torque can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, the vehicle 1 is a four-wheel drive vehicle based on a front-wheel drive vehicle, and an engine 2 is mounted on the front portion (left side in FIG. 1) of the vehicle 1 and assembled to the engine 2. A pair of front axles 4 are connected to the transaxle 3. A propeller shaft 5 is connected to the transaxle 3 together with the front axles 4, and the propeller shaft 5 can be connected to a pinion shaft (drive pinion shaft) 7 via a driving force transmission device 6. ing. The pinion shaft 7 is connected to a pair of rear axles 9 via a rear differential gear 8. Accordingly, the torque of the engine 2 is transmitted from the transaxle 3 to the front wheel 10f through the front axle 4, and from the transaxle 3, the propeller shaft 5, the driving force transmission device 6, the pinion shaft 7, the rear differential gear 8, and the various It is transmitted to the rear wheel 10r via the rear axle 9. In addition, the ECU 11 is connected to the driving force transmission device 6. The ECU 11 supplies a driving current to the driving force transmission device 6 in accordance with the running state of the vehicle, and controls the operation of the driving force transmission device 6 through this current supply, whereby a torque capacity that can be transmitted to the rear wheel 10r, that is, a torque. The transmission capacity is controlled. The driving force transmission device 6 is housed in the differential carrier 12 together with the rear differential gear 8.

  As shown in FIG. 2, the driving force transmission device 6 has a bottomed cylindrical front housing 22 rotatably accommodated in a coupling case 21 of the differential carrier 12, and can rotate within the cylinder of the front housing 22. And an axial inner shaft 23 arranged coaxially therewith.

  The front housing 22 as the first rotating member is rotatable with respect to the coupling case 21 via the ball bearing 24 with the bottom 22a (left side in the figure) exposed to the outside of the coupling case 21. It is supported by. The front housing 22 is fitted with an annular rear housing 25 at its opening end 22b.

  In the front housing 22, an inner shaft 23 as a second rotating member is fitted and disposed in the rear housing 25. The inner shaft 23 has a large diameter portion 26 formed on the bottom 22a side (left side in FIG. 2) and a small diameter smaller than the large diameter portion 26 on the opening end 22b side (right side in FIG. 2) via the stepped surface 27. A cylindrical body having a portion 28 is formed. A large-diameter hollow portion 29 having an inner diameter larger than the outer diameter of the small-diameter portion 28 is formed in the large-diameter portion 26 so as to be recessed from the bottom-side end surface. On the other hand, the small-diameter portion 28 is formed with a small-diameter hollow portion 30 that is recessed from the end surface on the opening end side. The large-diameter hollow portion 29 and the small-diameter hollow portion 30 are partitioned liquid-tightly by a partition wall 31.

  The inner shaft 23 has a small-diameter portion 28 via a needle bearing 32 provided on the inner periphery of the rear housing 25, and a large-diameter portion 26 via a ball bearing 33 provided in the cylinder of the front housing 22. 22 and the rear housing 25 are rotatably supported. The clutch housing chamber 34 is partitioned by the inner peripheral surface of the front housing 22, the outer peripheral surface of the inner shaft 23, the axial inner side surface of the rear housing 25 (left side in FIG. 2), and a hydraulic pump 61 described later. Yes.

  The hydraulic chamber 35 is defined by the large-diameter hollow portion 29, the partition wall 31, the bottom portion 22 a of the front housing 22, and the hydraulic pump 61. That is, the large-diameter hollow portion 29 corresponds to the “hollow portion” of the present invention.

  The cylinder of the front housing 22 is sealed by a fitting portion between the front housing 22 and the rear housing 25 and seal members 36 and 37 provided between the inner periphery of the rear housing 25 and the outer periphery of the inner shaft 23. ing. As a result, the inside of the clutch housing chamber 34 is liquid-tightly sealed, and the lubricating oil is housed in the front housing 22 at a predetermined filling rate (80% in this embodiment), that is, the clutch housing chamber. 34 and the hydraulic chamber 35 are filled with lubricating oil.

  The bottom portion 22 a of the front housing 22 is connected to a flange portion (not shown) provided on the propeller shaft 5 by a bolt 38. Thereby, the front housing 22 rotates by the input of the torque which the engine 2 which is a drive source generate | occur | produces. Further, a connecting portion (spline fitting portion) 39 with the pinion shaft 7 is formed in the small diameter hollow portion 30 of the inner shaft 23. Therefore, when the driving force transmission device 6 is mounted on the vehicle 1, the front housing 22 is connected to the front wheel 10f side which is the main driving wheel, and the inner shaft 23 is connected to the rear wheel 10r side which is the auxiliary driving wheel. It is like that.

Further, the main clutch 41, the cam mechanism 42, and the pilot clutch 43 are arranged in this order from the left side in FIG.
The main clutch 41 as a clutch mechanism is a multi-plate friction clutch that connects the front housing 22 and the inner shaft 23 so that torque can be transmitted. The main clutch 41 has a plurality of outer clutch plates 44 provided so as to be movable in the axial direction and inner clutch plates 45 provided so as to be movable in the axial direction, and these plates 44, 45 are alternately arranged. Yes.

  Specifically, each outer clutch plate 44 is spline-fitted to the inner periphery of the front housing 22, and is supported with respect to the front housing 22 so as to be axially movable and not rotatable relative to the circumferential direction. Accordingly, each outer clutch plate 44 is provided so as to be able to rotate integrally with the front housing 22. On the other hand, each inner clutch plate 45 is spline-fitted to the outer periphery of the large-diameter portion 26 of the inner shaft 23, and is supported so as to be movable in the axial direction and not rotatable relative to the inner shaft 23, respectively. Yes. Therefore, each inner clutch plate 45 is provided so as to rotate integrally with the inner shaft 23.

  The main clutch 41 connects the front housing 22 and the inner shaft 23 so that torque can be transmitted by the outer clutch plates 44 and the inner clutch plates 45 being pressed in the axial direction and frictionally engaged with each other. It has become. At this time, the transmission torque between the front housing 22 and the inner shaft 23 changes according to the frictional engagement force of each outer clutch plate 44 and the inner clutch plate 45, that is, the axial pressing force.

The cam mechanism 42 includes a main cam 46, a pilot cam 47, and a cam follower 48 interposed between the main cam 46 and the pilot cam 47.
The main cam 46 as a pressing member is formed in an annular shape and is disposed on the main clutch 41 side. The main cam 46 is spline-fitted into a spline groove (not shown) formed on the stepped surface 27 side of the large-diameter portion 26 of the inner shaft 23, and is movable in the axial direction with respect to the inner shaft 23. It is supported so that it cannot rotate relative to the circumferential direction. Therefore, the main cam 46 is provided so as to be able to rotate integrally with the inner shaft 23. The main cam 46 is configured such that its radially inner portion faces the step surface 27.

  On the other hand, the pilot cam 47 is formed in an annular shape and is disposed on the rear housing 25 side. The pilot cam 47 is supported so as to be rotatable relative to the small diameter portion 28 of the inner shaft 23 in the circumferential direction. The pilot cam 47 is slidably contacted with a needle bearing 49 provided between the pilot cam 47 and the rear housing 25. Accordingly, the pilot cam 47 is supported so as to be rotatable relative to the rear housing 25 at a constant interval.

  A plurality of U-shaped grooves inclined with respect to the circumferential direction are formed at equiangular intervals on the opposing surfaces of the main cam 46 and the pilot cam 47, and the cam follower 48 is disposed in each of the opposing U-shaped grooves. In this state, the main cam 46 and the pilot cam 47 are sandwiched. In the cam mechanism 42, when the main cam 46 and the pilot cam 47 rotate relative to each other, the main cam 46 and the pilot cam 47 are separated from each other, that is, the main cam 46 moves in the axial direction toward the main clutch 41, and the main cam 46 Applies a pressing force to the main clutch 41.

  The pilot clutch 43 is a multi-plate friction clutch that connects the front housing 22 and the pilot cam 47 so that torque can be transmitted. Like the main clutch 41, the pilot clutch 43 is arranged between a plurality (two in this embodiment) of outer clutch plates 51 that are movable in the axial direction, and between these outer clutch plates 51. And an inner clutch plate 52 movably provided in the axial direction.

  Specifically, each outer clutch plate 51 is spline-fitted to the inner periphery of the front housing 22, and is supported relative to the front housing 22 so as to be movable in the axial direction and not rotatable relative to the circumferential direction. . Therefore, each outer clutch plate 51 is provided so as to be able to rotate integrally with the front housing 22. On the other hand, the inner clutch plate 52 is splined to the outer periphery of the pilot cam 47, and is supported so as to be movable in the axial direction and not rotatable relative to the pilot clutch 43 in the circumferential direction. Therefore, the inner clutch plate 52 is provided so as to be able to rotate integrally with the pilot cam 47.

  The outer clutch plate 51 and the inner clutch plate 52 are pressed in the axial direction to be in an operating state in which they are frictionally engaged with each other. The pilot clutch 43 is configured to connect the front housing 22 and the pilot cam 47 so that torque can be transmitted when the outer clutch plate 51 and the inner clutch plate 52 are frictionally engaged with each other.

  That is, the pilot cam 47 rotates together with the main cam 46, that is, the inner shaft 23, when the pilot clutch 43 in which the outer clutch plate 51 and the inner clutch plate 52 are not frictionally engaged is in an inoperative state. At this time, a rotational difference corresponding to the rotational difference between the front housing 22 and the inner shaft 23 is generated between the front housing 22 and the pilot cam 47. More specifically, the pilot clutch 43 connects the front housing 22 and the pilot cam 47 so as to be able to transmit torque by this action, so that the torque based on the rotational difference between the front housing 22 and the inner shaft 23 (pilot cam 47). Is transmitted to the cam mechanism 42.

  That is, in the driving force transmission device 6, when the pilot clutch 43 is in an operating state, torque based on the rotational difference between the front housing 22 and the inner shaft 23 is transmitted to the cam mechanism 42, and the cam mechanism 42 is connected to the main cam 46. The main cam 46 is moved toward the axial main clutch 41 by the torque transmitted based on the rotational difference from the pilot cam 47. That is, the cam mechanism 42 converts the torque based on the rotational difference between the front housing 22 and the inner shaft 23 transmitted via the pilot clutch 43 into an axial pressing force and amplifies it. When the main cam 46 presses the main clutch 41, the outer clutch plate 44 and the inner clutch plate 45 of the main clutch 41 are frictionally engaged, and the front housing 22 and the inner shaft 23 are connected so as to transmit torque. It has become so.

  The pilot clutch 43 is configured as an electromagnetic clutch using the electromagnet 53 as a drive source. The electromagnet 53 is accommodated in an annular groove 54 formed outside the rear housing 25 (right side in FIG. 2). Specifically, the electromagnet 53 is surrounded by an annular yoke 55, and the inner surface of the yoke 55 is supported so as to be rotatable relative to the rear housing 25 via a ball bearing 56. Is arranged. A part of the outer peripheral surface of the yoke 55 is connected and fixed to the coupling case 21. Therefore, the electromagnet 53 (yoke 55) is supported so as to be rotatable relative to the rear housing 25 without being rotated.

  An armature 57 formed in an annular shape is disposed between the main cam 46 of the cam mechanism 42 and the pilot clutch 43. The armature 57 is spline fitted to the inner peripheral surface of the front housing 22 so as to be movable in the axial direction.

  The armature 57 is attracted by the electromagnetic force of the electromagnet 53 and moves so as to sandwich the outer clutch plate 51 and the inner clutch plate 52 between the armature 57 and the outer clutch plate 51 of the pilot clutch 43. And the inner clutch plate 52 are frictionally engaged.

  As described above, the driving force transmission device 6 can control the operation of the pilot clutch 43 through the current supply to the electromagnet 53. The operation of the main clutch 41, that is, the torque that can be transmitted between the front housing 22 and the inner shaft 23 can be controlled through the operation of the pilot clutch 43.

Next, a mechanism for preventing the driving force transmission device 6 from overheating will be described.
The driving force transmission device 6 includes a hydraulic pump 61 that generates a large hydraulic pressure based on an increase in the rotational difference between the front housing 22 and the inner shaft 23, and the main cam is based on the hydraulic pressure of the lubricating oil discharged from the hydraulic pump 61. 46 is configured to reduce the pressing force applied to the main clutch 41.

  Specifically, as shown in FIGS. 2 and 3, the hydraulic pump 61 is disposed between the clutch housing chamber 34 and the hydraulic chamber 35 and between the ball bearing 33 and the main clutch 41. The hydraulic pump 61 is immersed in the lubricating oil even when the vehicle 1 is towed with only the rear wheel 10r in contact with the ground (so-called two-wheel towed). The hydraulic pump 61 has a plurality of (through which the lubricating oil in the clutch housing chamber 34 is formed at equal intervals in the circumferential direction of the side wall of the large-diameter portion 26 due to the difference in rotation between the front housing 22 and the inner shaft 23. In the present embodiment, the pressure is fed to the large-diameter hollow portion 29 (hydraulic chamber 35) via four discharge ports 62. The hydraulic chamber 35 is sealed by seal members 63 and 64 provided between the hydraulic pump 61 and the inner peripheral surface of the front housing 22 and the outer peripheral surface of the inner shaft 23 (step surface 27), so that the clutch A space between the storage chamber 34 and the storage chamber 34 is liquid-tightly sealed.

  In the present embodiment, the hydraulic pump 61 is a known vane pump. The vane pump is fixed to the inner periphery of the front housing 22, and a plurality of vanes that can be projected and retracted along the radial direction are provided on the radially inner side. Further, on the outer peripheral surface of the inner shaft 23, a concave surface is formed which is recessed radially inward between the respective discharge ports 62 so that the vanes come into contact with each other. By doing so, the lubricating oil is pumped to the hydraulic chamber 35 by the hydraulic pump when the vane conveys the lubricating oil due to the rotational difference between the front housing 22 and the inner shaft 23.

  A plurality of through holes 65 (four in this embodiment) are formed in the inner shaft 23 at equal angular intervals in the circumferential direction through the partition wall 31 side bottom surface of the hydraulic chamber 35 and the step surface 27. In the present embodiment, each through-hole 65 is formed in a linear shape along the axial direction. Further, a disk-shaped piston 66 is disposed on the small diameter portion 28 side of the discharge port 62 of the hydraulic chamber 35 so as to be movable in the axial direction, and the hydraulic chamber 35 is moved by the piston 66 to the bottom 22a side (in FIG. 3). It is divided into a high-pressure chamber 67 on the left side and a low-pressure chamber 68 on the partition wall 31 side (right side in FIG. 3). Since the low pressure chamber 68 communicates with the clutch housing chamber 34 through the through-hole 65, the pressure in the low pressure chamber 68 and the pressure in the clutch housing chamber 34 are substantially equal. A seal member 69 is provided on the outer periphery of the piston 66, and lubricating oil cannot flow between the high-pressure chamber 67 and the low-pressure chamber 68 through the space between the inner peripheral surface of the large-diameter hollow portion 29 and the piston 66. It is like that.

  A discharge port 62 is disposed in the high-pressure chamber 67 so that lubricating oil pumped by the hydraulic pump 61 is introduced. A rod-like plunger 70 that passes through each through hole 65 is fixed to the side surface of the piston 66 on the low pressure chamber 68 side. Each plunger 70 has a base end portion 70 a fixed to the piston 66 and a tip end portion 70 b engaged with a radially inner portion of the main cam 46.

  Therefore, when the high pressure chamber 67 becomes higher than the low pressure chamber 68 by the hydraulic pressure of the lubricating oil pumped from the hydraulic pump 61 through the discharge port 62 and the piston 66 is moved to the partition wall 31 side, each plunger 70 is moved to the main cam. 46 is pressed to the pilot cam 47 side. As a result, the main cam 46 is pressed in the direction in which the friction engagement of the main clutch 41 is released (right side in FIG. 3, hereinafter referred to as the release direction), so that the pressing force applied to the main clutch 41 by the main cam 46 is reduced. It has come to be.

In the present embodiment, the overheat protection mechanism is configured by the hydraulic chamber 35, the discharge port 62, the through hole 65, the piston 66, the plunger 70, and the like.
Further, an elastic member 71 made of a coil spring or the like is provided between the piston 66 and the partition wall 31. In this embodiment, the elastic coefficient of the elastic member 71 is equal to the elastic force of the elastic member 71 by the hydraulic pressure generated in the high pressure chamber 67 when the rotational difference between the front housing 22 and the inner shaft 23 is large (for example, 1000 rpm or more). The piston 66 is configured with an elastic coefficient so that the piston 66 can move to the partition wall 31 side. Accordingly, when the rotational difference between the front housing 22 and the inner shaft 23 is small (for example, about 200 to 300 rpm), the movement of the piston 66 toward the partition wall 31 causes the elastic force of the elastic member 71 to move. Regulated by

Next, the operation of the driving force transmission device 6 configured as described above will be described.
Since the pilot clutch 43 is configured as a so-called wet clutch, even when the pilot clutch 43 is in an inoperative state (when the electromagnet 53 is not energized), the pilot clutch 43 is caused by the engaging force based on the viscosity of the lubricating oil interposed therebetween. Thus, a so-called drag torque is generated. Then, this drag torque is converted into an axial pressing force by the cam mechanism 42 and amplified, and the main cam 46 tries to press the main clutch 41. Here, when the vehicle 1 is towed by two wheels, the front housing 22 connected to the front wheel 10f side is not rotated, while only the inner shaft 23 connected to the rear wheel 10r side is rotated. . As a result, a large rotational difference of about 1000 rpm occurs between the front housing 22 and the inner shaft 23. For this reason, when the main clutch 41 is frictionally engaged by the drag torque, the main clutch 41 and the like may be overheated due to friction between the outer clutch plate 44 and the inner clutch plate 45.

  In this regard, in the present embodiment, when a rotational difference is generated between the front housing 22 and the inner shaft 23, the hydraulic pump 61 is operated and the lubricating oil is hydraulically supplied from the clutch housing chamber 34 as indicated by arrows Y1 and Y2. A large hydraulic pressure generated when the rotational difference is large is supplied to the hydraulic chamber 35 by pressure. Then, the piston 66 moves toward the low pressure chamber 68 against the elastic force of the elastic member 71 and presses the main cam 46 in the release direction via the plunger 70. For this reason, when the two-wheel is towed, the main clutch 41 is prevented from being frictionally engaged by the drag torque generated in the pilot clutch 43, and the friction between the outer clutch plate 44 and the inner clutch plate 45 causes the main clutch 41 or Overheating of lubricating oil and the like is prevented. Since the hydraulic pump 61 operates based on the rotational difference between the front housing 22 and the inner shaft 23, the main cam is more quickly compared to the case where the main cam is pushed back based on the increase in the internal pressure in the clutch chamber as in the prior art. The pressing force 46 applies to the main clutch 41 is reduced.

  When the rotational difference between the front housing 22 and the inner shaft 23 disappears, the lubricating oil pumped into the hydraulic chamber 35 flows out into the clutch housing chamber 34 via the hydraulic pump 61.

  Further, when the vehicle 1 travels without being towed, for example, when the rear wheel 10r slips, the driving current is supplied from the ECU 11, the pilot clutch 43 is operated, and the main cam 46 presses the main clutch 41. . Thereby, the torque of the engine 2 is distributed to the rear wheel 10r, and the traction performance of the vehicle 1 is improved. Here, when the vehicle 1 travels without being towed, the front wheel 10f or the rear wheel 10r slips, so that the rotation difference generated between the front housing 22 and the inner shaft 23 is about 200 to 300 rpm. Therefore, even if the hydraulic pump 61 is operated by this rotational difference and the hydraulic pressure is applied to the piston 66, the movement of the piston 66 is restricted by the elastic force of the elastic member 71.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The driving force transmission device 6 is disposed in a bottomed cylindrical front housing 22, a shaft-like inner shaft 23 that is coaxially disposed rotatably inside the front housing 22, and a clutch housing chamber 34. And an inner shaft 23 are connected to each other so as to transmit torque. The clutch housing chamber 34 is provided with a cam mechanism 42 that is filled with lubricating oil at a predetermined filling rate, and the main cam 46 presses the main clutch 41 by the operation of the pilot clutch 43. A hydraulic pump 61 that is operated by the rotational difference between the front housing 22 and the inner shaft 23 is provided, and the pressing force that the main cam 46 applies to the main clutch 41 is reduced by the lubricating oil discharged from the hydraulic pump 61. For this reason, for example, when the vehicle 1 is towed by two wheels, the frictional engagement of the main clutch 41 is released. Therefore, the generation of frictional heat between the outer clutch plates 44 and the inner clutch plates 45 is suppressed, and the main clutch 41 is restrained. The clutch 41 can be prevented from overheating. In addition, since the hydraulic pump 61 operates based on the rotational difference between the front housing 22 and the inner shaft 23, the main cam 46 is more quickly compared to the case where the main cam 46 is pushed back based on the increase in the internal pressure in the clutch chamber as in the prior art. The driving force transmission device 6 can be more reliably protected.

  (2) The hydraulic chamber 35 is partitioned by a bottom portion 22a formed by recessing the inner shaft 23. Accordingly, it is possible to reduce the pressing force of the main cam 46 by the hydraulic pressure of the lubricating oil while suppressing an increase in the size of the driving force transmission device 6.

  (3) The piston 66 is provided in the hydraulic chamber 35, and the piston 66 is moved by the oil pressure of the lubricating oil, so that the pressing force of the piston 66 directly acts on the main cam 46 via the plunger 70, and the main clutch 41 of the main cam 46 The pressing force against was reduced. Therefore, for example, the pressing force of the main cam 46 can be surely reduced as compared with the case where the pressing force of the main cam 46 is reduced by jetting the lubricating oil to the main cam 46.

  (4) An elastic member 71 is provided between the piston 66 and the partition wall 31 to control the movement of the piston 66 due to the oil pressure of the lubricating oil. The elastic member 71 restricts the movement of the piston 66 to the low pressure chamber 68 side when the rotation difference between the front housing 22 and the inner shaft 23 is small, and the piston 66 moves toward the low pressure chamber 68 when the rotation difference is large. The elastic modulus is such that it can move to the side. Accordingly, when the rotational difference between the front housing 22 and the inner shaft 23 is small, such as when the rear wheel 10r slips, the pressing force of the main cam 46 is not reduced by the hydraulic pressure, and the two wheels are towed. Thus, when the rotational difference is large, the pressing force of the main cam 46 can be reduced by hydraulic pressure. Thereby, when the ECU 11 distributes the torque to the rear wheels 10r according to the traveling state of the vehicle 1, the pressing force of the main cam 46 reduced by the hydraulic pressure, that is, the torque transmission capacity of the driving force transmission device 6 reduced by the hydraulic pressure. The control of the driving force transmission device 6 can be prevented from becoming complicated, and the driving force transmission device 6 can be controlled by the same control method as in the prior art.

In addition, you may implement this embodiment in the following aspects.
In the above embodiment, the overheat protection mechanism is configured by the hydraulic chamber 35, the through hole 65, the piston 66, and the plunger 70. However, the present invention is not limited to this, and the piston 66 and the plunger 70 are not provided. An overheat protection mechanism may be configured. By doing in this way, the main cam 46 presses the main clutch 41 by the lubricating oil pumped into the hydraulic chamber 35 being ejected from the through hole 65 due to the rotational difference between the front housing 22 and the inner shaft 23. Pressed in the opposite direction. Therefore, it is not necessary to provide the piston 66 and the plunger 70, and the overheat protection mechanism can be simplified.

  Alternatively, the lubricating oil may be pumped directly from the discharge port 62 to the through hole 65 without partitioning the hydraulic chamber 35. Even in this case, the overheat protection mechanism can be simply configured as described above.

  In the above embodiment, the main cam 46 is spline-fitted to the inner shaft 23 and the radially inner portion thereof is opposed to the step surface 27. However, the present invention is not limited to this. For example, the main cam 46 is configured to be spline-fitted to the front housing 22 so that the radially inner portion thereof does not face the stepped surface 27, and the distal end portion 70 b of the plunger 70 is provided with an extended portion bent radially outward. The main cam 46 may be engaged.

  In the above embodiment, the elastic member 71 is provided between the piston 66 and the partition wall 31 to restrict the movement of the piston 66 due to the oil pressure of the lubricating oil. An elastic member 71 may be provided between them to restrict the movement of the piston 66 when the rotational difference is small. Further, the elastic member 71 may not be provided.

  In the above embodiment, the gap between the clutch housing chamber 34 and the hydraulic chamber 35 is liquid-tightly sealed by sealing between the hydraulic pump 61 and the front housing 22 and the inner shaft 23 by the seal members 63 and 64. Partitioned. However, the present invention is not limited thereto, and instead of the seal members 63 and 64, for example, the opening end of the large-diameter hollow portion 29 is closed with a disk-like closing member, so that the space between the clutch housing chamber 34 and the hydraulic chamber 35 is closed. You may seal and partition liquid-tightly.

  In the above embodiment, the hydraulic chamber 35 is partitioned by the bottom 22 a of the front housing 22, the large-diameter hollow portion 29, and the partition wall 31, but is not limited thereto, and instead of the partition wall 31, for example, the small-diameter of the large-diameter hollow portion 29 The hydraulic chamber 35 may be partitioned by providing a seal member that closes the portion 28 side.

  In the above embodiment, the hydraulic pump 61 is disposed in the clutch housing chamber 34 formed between the front housing 22 and the inner shaft 23 and between the ball bearing 33 and the main clutch 41. Not limited to this. If the rotational difference between the front housing 22 and the inner shaft 23 is input to the hydraulic pump 61 and the hydraulic pump 61 is immersed in the lubricating oil when the two wheels are towed, the hydraulic pump 61 may be disposed at other positions. You may arrange. Further, the filling rate of the lubricating oil can be appropriately changed according to the arrangement of the hydraulic pump 61.

  In the above embodiment, the hydraulic pump 61 is constituted by a vane pump. However, the hydraulic pump 61 is not limited to this, and other hydraulic pumps such as a gear pump may be used as long as the hydraulic pump 61 is operated by a rotational difference between the front housing 22 and the inner shaft 23. May be.

  When a gear pump is used, for example, a pair of gears having different diameters are engaged with each other along the circumferential direction on the outer periphery of the large-diameter portion 26 in a state where the gears are engaged with each other. Each gear is arranged so that its axis is parallel to the axis of the inner shaft 23, and only the large-diameter gear is slid on the inner periphery of the front housing 22. By doing in this way, due to the difference in rotation between the front housing 22 and the inner shaft 23, these gears rotate in reverse to each other, and the lubricating oil is pumped.

  In each of the above embodiments, the present invention is applied to the driving force transmission device that frictionally engages the main clutch 41 with the cam mechanism 42. However, the present invention is not limited to this. The present invention may be applied to a driving force transmission device that is driven.

  In the above embodiment, the pilot clutch 43 is configured as an electromagnetic clutch, and current is supplied to the electromagnet 53. However, the present invention is not limited to this, and the pilot clutch 43 is operated by hydraulic pressure to control the current supplied to the hydraulic valve. The transmission torque may be controlled.

  In the above embodiment, the driving force transmission device 6 is mounted on the vehicle 1 having the front wheel 10f as the main driving wheel. However, the present invention is not limited thereto, and the driving force transmission device 6 may be mounted on a vehicle having the rear wheel 10r as the main driving wheel.

The schematic block diagram of the vehicle provided with the driving force transmission apparatus. Sectional drawing of a driving force transmission device. The expanded sectional view of the overheat protection mechanism in a driving force transmission device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 6 ... Driving force transmission device, 22 ... Front housing, 23 ... Inner shaft, 26 ... Large diameter part, 27 ... Step surface, 28 ... Small diameter part, 29 ... Large diameter hollow part, 34 ... Clutch accommodation chamber, 35 ... Hydraulic chamber , 41 ... main clutch, 45 ... inner clutch plate, 61 ... hydraulic pump, 65 ... through hole, 66 ... piston, 67 ... high pressure chamber, 68 ... low pressure chamber, 70 ... plunger, 70a ... base end, 70b ... tip 71 ... Elastic member

Claims (5)

A liquid-tight seal is formed between the cylindrical first rotating member, the shaft-shaped second rotating member coaxially disposed in the first rotating member, and the first rotating member and the second rotating member. A clutch mechanism that is arranged in a clutch housing chamber partitioned into two and is axially pressed to connect the first rotating member and the second rotating member so as to transmit torque, and a pressing member that presses the clutch mechanism; A driving force transmission apparatus comprising: a lubricating oil filled at a predetermined filling rate in the clutch housing chamber;
A hydraulic pump that operates by a rotational difference between the first rotating member and the second rotating member;
A driving force transmission device comprising: an overheat protection mechanism that reduces a pressing force applied by the pressing member to the clutch mechanism by the lubricating oil discharged from the hydraulic pump. The overheat protection mechanism includes a hydraulic chamber that is a hollow portion formed in a recessed manner in the second rotating member and is fluid-tightly partitioned from the clutch housing chamber,
2. The driving force transmission device according to claim 1, wherein a pressing force applied to the clutch mechanism is reduced by a hydraulic pressure of the lubricating oil pumped to the hydraulic chamber by the hydraulic pump. The second rotating member is engaged with an inner clutch plate of the clutch mechanism on the outer peripheral surface thereof so as not to be relatively rotatable and axially movable, and has a large diameter portion formed with the hollow portion, and a larger diameter portion than the large diameter portion. Having a small diameter portion with a small diameter,
The overheat protection mechanism is
A through hole formed in the second rotating member and penetrating the step surface between the large diameter portion and the small diameter portion and the hydraulic chamber;
A piston that divides the hydraulic chamber into a high-pressure chamber from which the lubricating oil is discharged from the hydraulic pump and a low-pressure chamber in which the through hole is opened;
3. The plunger according to claim 2, further comprising: a plunger that is inserted into the through hole, has a proximal end fixed to the low pressure chamber side of the piston, and a distal end engages with the pressing member. Driving force transmission device.   The driving force transmission device according to claim 3, further comprising an elastic member that controls movement of the piston by an oil pressure of the lubricating oil by an elastic force. The second rotating member includes a large diameter portion in which the inner clutch plate of the clutch mechanism is engaged so as not to be relatively rotatable and axially movable, and the hollow portion is formed, and a small diameter portion having a smaller diameter than the large diameter portion. And
The pressing member is disposed to face a step surface between the large diameter portion and the small diameter portion,
3. The driving force transmission device according to claim 2, wherein the overheat protection mechanism includes a through hole formed in the second rotating member and opening in the hydraulic chamber and the stepped surface.

Images