JP2010058684A - Drive force transmission device for four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive force transmission device for a four-wheel drive vehicle enabling switching of two-wheel drive and four-wheel drive during transmission of torque to a drive wheel, preventing generation of tight corner braking phenomenon during switching and preventing reduction of fuel consumption at the two-wheel drive. <P>SOLUTION: The drive force transmission device for the four-wheel drive vehicle is provided with a central differential device 100; a first clutch mechanism 124 for controlling differential restriction of the central differential device 100; a second clutch mechanism 134 capable of disconnecting/connecting transmission of output of the central differential device 100 to a front wheel output shaft 98; and a disconnection/connection mechanism 76 capable of disconnecting/connecting connection of the front wheel differential device 22 and a left front wheel drive shaft 68. When it is switched from the four-wheel drive to the two-wheel drive, the first clutch mechanism 124 is fastened, the second clutch mechanism is released, and connection of the disconnection/connection mechanism 76 is further disconnected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a driving force transmission device for a four-wheel drive vehicle including a central differential, and more particularly to a driving force transmission device for a four-wheel drive vehicle that can switch between two-wheel drive and four-wheel drive even during transmission of the driving force.

  Conventionally, in a four-wheel drive vehicle based on a rear-wheel drive vehicle that can be switched between a four-wheel drive and a two-wheel drive by a rear wheel by an operation of an in-vehicle changeover switch or the like by a driver, the distribution control of the driving force to the front wheels is centrally controlled. As a driving force transmission device for a four-wheel drive vehicle performed by a moving device (center differential), for example, the one shown in FIG. 20 is known.

  In FIG. 20, the driving force transmission device 500 is provided in the four-wheel drive vehicle 502, and the driving force from the engine 504 is shifted by the transmission 506 and input to the driving force distribution device 508 in the driving force transmission device 500.

  When the switching mechanism provided in the central differential 510 during two-wheel drive traveling is disconnected from the front wheel drive system, the driving force is transmitted as it is to the rear wheel differential 518 via the rear wheel propeller shaft 514, The rear wheel differential 518 absorbs the rotational speed difference between the left rear wheel 520 and the right rear wheel 522, and rotates the left rear wheel 520 and the right rear wheel 522 with equal torque.

  When the switching mechanism provided in the central differential device 510 is connected to the front wheel drive system during four-wheel drive traveling, the driving force is applied to the chain belt mechanism 512 and the front wheel propeller shaft 516 coupled to the central differential device 510. The front wheel differential device 524 absorbs the rotational speed difference between the left front wheel 526 and the right front wheel 528 and applies the same torque to the left front wheel 526 and the right front wheel 528 to rotate.

  The central differential 510 properly rotates with a predetermined torque distribution ratio while absorbing the difference in rotational speed between the rear wheels 520 and 522 and the front wheels 526 and 528.

  FIG. 21 is an explanatory diagram showing an example of the central differential 510 of FIG. 20 in a skeleton. In FIG. 21, a central differential 510 is rotatably supported by an input shaft 532 for inputting a driving force from a transmission 506, a planetary carrier 546 constituting a planetary gear mechanism 544 connected to the input shaft 532, and the planetary carrier 546. Planetary gear 548, outer gear 550 that engages with planetary gear 548, sun gear 552, rear wheel output shaft 534 that is connected to outer gear 550 and outputs driving force to rear wheel propeller shaft 514, and outer ring portion 558 of outer gear 550 And a sun gear shaft 554 are provided with a fluid coupling 560 (viscous coupling) that functions as a differential limiting mechanism.

  Further, a sprocket 540 that outputs a driving force to the front wheel output shaft 536, a sprocket 538 connected to the tooth portion 568 via the sprocket shaft 556, and a chain belt mechanism 512 constituted by a chain belt 542, and a tooth portion connected to the input shaft 532 564 and a tooth portion 566 connected to the sun gear 552 via the sun gear shaft 554.

  Further, a sleeve 570 that can be spline-engaged with the tooth portions 564, 566, and 568, and a shift shaft 572 that slides the sleeve 570 and switches the coupling between the tooth portions 564, 566, and 568 and the sleeve 570 are provided. The sleeve 570 and the shift shaft 572 constitute a switching mechanism 562 (sliding clutch). Shift shaft 572 is driven by an actuator (not shown).

  FIG. 21A shows a four-wheel drive state where the sleeve 570 engages with the teeth 566 and 568, and the sun gear 552 connected to the teeth 566 and the sprocket 538 connected to the teeth 568 are fixed. Rotate in state.

  That is, the driving force input from the input shaft 532 to the planetary carrier 546 is output to the rear wheel output shaft 534 via the planetary gear 548 and the outer gear 550, and the planetary gear 548, the sun gear 552, the sun gear shaft 554, and the tooth portion 566. , The sleeve 570, the tooth portion 568, the sprocket 538, the chain belt 542, and the sprocket 540 are also output to the front wheel output shaft 536.

  When the rear wheels 520, 522 or the front wheels 526, 528 slip and a difference in rotational speed occurs between the rear wheel drive shaft 534 and the front wheel drive shaft 532, that is, the outer gear 550 and the sun gear 552, the fluid coupling 560 functions as a differential limiting mechanism. The idling of the rear wheels 520 and 522 or the front wheels 526 and 528 is prevented.

  FIG. 21B shows a two-wheel drive state where the sleeve 570 engages with the tooth portions 564 and 566, and the planetary carrier 546 and the sun gear 552 rotate in a fixed state, so that the planetary gear 548 does not rotate. The outer gear 550 rotates at the same speed as the sun gear 552 because the planetary gear 548 does not rotate. That is, the central differential 510 is in a differential lock state.

  Since the tooth portion 568 is not engaged with the sleeve 570, the driving force input from the input shaft 532 to the planetary carrier 546 is not transmitted to the sprocket 538, and is transmitted to the rear wheel output shaft 534 via the planetary gear 548 and the outer gear 550. Is output only.

In addition, as shown in FIG. 20, there is also a system in which a connection / disconnection mechanism 576 capable of disconnecting the connection between the front wheel differential 524 and the front wheel drive shaft 574 is provided. In such a system, an ECU (Electronic control unit) switches the central differential unit 510 from the four-wheel drive state of FIG. 21A to the two-wheel drive state of FIG. By subsequently disconnecting the connection / disconnection mechanism 576, the rotation of the components of the front wheel differential 524 and the front wheel driving force transmission section 530 can be stopped.
JP 2002-264677 A

  However, in the conventional power transmission device for a four-wheel drive vehicle as shown in FIG. 20, even if a driver tries to switch from a four-wheel drive to a two-wheel drive by operating a changeover switch or the like, the accelerator is turned on to change the front and rear wheels. When the driving force is transmitted, as shown in FIG. 21A, the switching mechanism 562 slides the sleeve 570 as a switching operation because the sleeve 570 is transmitting torque from the tooth portion 566 to the tooth portion 568. Cannot be switched to the state shown in FIG.

  Therefore, switching from the four-wheel drive state shown in FIG. 21 (A) to the two-wheel drive state shown in FIG. 21 (B) first turns off the accelerator, the transmission 506 interrupts transmission of the driving force, etc. The sleeve 570 has to be slid after the driving force is not transmitted to the front and rear wheels, which increases the switching time.

  In addition, even when the driver switches to four-wheel drive by operating the changeover switch or the like when the road surface condition changes suddenly during traveling by two-wheel drive and the rear wheels 520 and 522 as drive wheels slip. If the rotational speeds of the tooth portion 566 interlocked with the rear wheel output shaft 534 and the tooth portion 568 interlocked with the front wheel output shaft 536 do not match, the sleeve 570 and the tooth portion 568 are not smoothly engaged.

  In a state where slip occurs in the rear wheels 520 and 522, there is a difference in rotational speed between the tooth portions 566 and the tooth portions 568, and the two-wheel drive state shown in FIG. 21B changes to the four-wheel drive state shown in FIG. In order to switch between them, the sleeve 570 must be slid after the rotational speeds of the tooth portions 566 and the tooth portions 568 are made to coincide with each other by the synchronization mechanism. If this occurs, it may be difficult to switch to four-wheel drive.

  Further, when switching from four-wheel drive to two-wheel drive, or when switching from two-wheel drive to four-wheel drive, the engagement between the sleeve 570 and the tooth portion 564 or 568 is released and then the tooth portion 568 or 564 is engaged. As a result, the sleeve 570 engages only with the tooth portion 566, and in this case, the sun gear 552, the tooth portion 566, and the sleeve 570 are idled, making it difficult to synchronize the sleeve 570 and the tooth portion 568.

  Therefore, before the engagement between the sleeve 570 and the tooth portion 564 or 568 is completely released, the engagement with the tooth portion 568 or 564 is started. In this case, the tooth portions 564, 566, and 568 are simultaneously attached to the sleeve 570. When engaged, that is, when the central differential 510 is in a differential lock state during four-wheel drive, even if it is temporary, cornering in this state causes tight corner braking phenomenon, and driving performance Adversely affects.

  Further, in the conventional power transmission device for a four-wheel drive vehicle as shown in FIG. 20, the front left wheel 526 and the right front wheel 528 rotate even when the rear wheels are driven by two wheels, so that the front wheel differential 524, the front wheels Each component of the front wheel driving force transmission section 530 including the propeller shaft 516 and the chain belt mechanism 512 rotates, and the element has a loss due to oil viscosity resistance and friction of the bearing, and rotation inertia of the front wheel propeller shaft 516 and the like. There is a problem that fuel consumption is reduced due to energy loss for accelerating / decelerating the rotation of the engine.

  Further, even in a system in which a connection / disconnection mechanism 576 is provided to stop the rotation of each component of the front wheel driving force transmission section 530 during two-wheel driving, switching to two-wheel driving is entrusted to the driver's operation. As long as the vehicle is traveling in the four-wheel drive position even when the vehicle is not required, the components of the front wheel driving force transmission section 530 are rotating, and the oil is similar to the system without the connection / disconnection mechanism 574. The loss due to the viscous resistance and the friction of the bearing portion, and the energy loss for accelerating and decelerating the rotation of the elements having the rotational inertia such as the front wheel propeller shaft 516 cause a reduction in fuel consumption.

The present invention provides a driving force transmission device for a four-wheel drive vehicle that enables switching between two-wheel drive and four-wheel drive during torque transmission to the drive wheels, and prevents the occurrence of a tight corner braking phenomenon during switching. The purpose is to do.

  In order to achieve this object, the present invention is configured as follows. First, the present invention includes a central differential that inputs a driving force from a power source and outputs the driving force to a first driving wheel and a second driving wheel, and transmits the driving force to the first driving wheel and the second driving wheel. In a four-wheel drive vehicle driving force transmission device capable of switching between driving and two-wheel driving for transmitting driving force only to the first driving wheel, a first clutch mechanism for controlling differential limitation of the central differential device; And a second clutch mechanism capable of connecting / disconnecting output transmission to the second driving wheel driving force transmission system of the central differential.

  Here, the driving force transmission device for a four-wheel drive vehicle of the present invention includes a clutch drive mechanism that drives both the first clutch mechanism and the second clutch mechanism, and constantly presses the second clutch mechanism in the fastening direction. A fastening spring is provided.

  In addition, when switching from four-wheel drive to two-wheel drive, the driving force transmission device for a four-wheel drive vehicle according to the present invention starts fastening the first clutch mechanism at the same time as the completion of the release of the second clutch mechanism.

  Alternatively, when switching from four-wheel drive to two-wheel drive, the driving force transmission device for a four-wheel drive vehicle of the present invention starts fastening the first clutch mechanism before the completion of opening the second clutch mechanism.

  A driving force transmission device for a four-wheel drive vehicle according to the present invention includes a connecting / disconnecting mechanism capable of connecting / disconnecting the second driving wheel differential device and either one or both of the left and right second driving wheel drive shafts. During driving, the drag torque of the second clutch mechanism is made smaller than the rotational resistance of the second driving wheel driving force transmission section from the second clutch mechanism to the connecting / disconnecting mechanism, and the connecting / disconnecting mechanism and the second driving wheel differential device are The connection with either one or both of the second drive wheel drive shafts is cut, and the rotation of the second drive wheel drive force transmission section is stopped.

  Here, the second clutch mechanism has a plurality of clutch plates that can be displaced in the axial direction of the second clutch mechanism, and lubricates to stop or limit the supply of lubricating oil to the clutch plates when the second clutch mechanism is released. An oil limiting mechanism is provided.

Alternatively, the second clutch mechanism includes a plurality of clutch plates that can be displaced in the axial direction of the second clutch mechanism, and includes a spacer that urges the clutch plates in a direction that increases the interval between the clutch plates.

  According to the present invention, the first clutch mechanism for controlling the differential limitation of the central differential, and the second clutch mechanism capable of connecting / disconnecting output transmission to the second drive wheel driving force transmission system of the central differential By driving both the first clutch mechanism and the second clutch mechanism with a single clutch drive mechanism, it is possible to switch between two-wheel drive and four-wheel drive during torque transmission to the drive wheels with a lightweight and small device And

  In addition, by constantly pressing the second clutch mechanism in the fastening direction with a fastening spring, switching from two-wheel drive to four-wheel drive can be performed quickly, and when switching from four-wheel drive to two-wheel drive, the first clutch mechanism is fastened. Is started simultaneously with the completion of the release of the second clutch mechanism, so that the tight corner braking phenomenon does not occur even if the switching operation is during cornering.

Further, during two-wheel drive, the connection between the second drive wheel differential device and the left and right second drive wheel drive shafts is cut by a connecting / disconnecting mechanism, and the ring gear of the second drive wheel differential device accompanying the rotation of the second drive wheel Is provided with a lubricating oil limiting mechanism that stops or restricts the supply of lubricating oil to the clutch plate of the second clutch mechanism, and uses a spacer to secure the interval between the clutch plates. By making the drag torque smaller than the friction torque of the second driving wheel driving force transmission section, the rotation of the components of the second driven wheel driving force transmission section is stopped, the oil viscosity resistance and friction loss in this section, and the propeller shaft It is possible to reduce energy loss for accelerating / decelerating the rotation of an element having a rotational inertia such as a reduction in fuel consumption.

  FIG. 1 is an explanatory view showing an embodiment of a driving force transmission device for a four-wheel drive vehicle according to the present invention, which is applied to a vehicle in which a rear wheel is driven during two-wheel drive. In FIG. 1, the driving force transmission device 10 of this embodiment is provided in a four-wheel drive vehicle 12, and includes a driving force distribution device 18, a rear wheel differential device 20 (first drive wheel differential device), and a front wheel differential device 22. (Second drive wheel differential).

  The driving force distribution device 18 can connect and disconnect the central differential device 100, the first clutch mechanism 124 that controls the differential limitation of the central differential device 100, and the output transmission from the central differential device 100 to the front wheel output shaft 98. The rear wheel differential device 20 and the front wheel differential device 22 are connected to the driving force distribution device 18 via the rear wheel propeller shaft 24 and the front wheel propeller shaft 26, respectively.

  The driving force from the engine 14 is shifted by the transmission 16 and input from the input shaft 94 of the driving force distribution device 18. The input driving force is output to the rear wheel output shaft 96 via the central differential 100 regardless of the four-wheel drive or the two-wheel drive, and is passed through the universal joint 28, the rear wheel propeller shaft 24, and the universal joint 30. This is transmitted to the drive pinion 36 of the rear wheel differential 20.

  The drive pinion 36 drives the left rear wheel drive shaft 48 and the right rear wheel drive shaft 50 via the ring gear 38, the pinions 40 and 42, and the side gears 44 and 46, and the left rear wheel drive shaft 48 and the right rear wheel drive shaft. 50 rotates the left rear wheel 52 and the right rear wheel 54 to transmit the driving force to the road surface. Even if a difference in rotational speed occurs between the left rear wheel 52 and the right rear wheel 54 due to cornering or changes in road surface conditions, the rear wheel differential 20 absorbs the rotational speed difference, and the left rear wheel 52 and the right rear wheel 54 Can be rotated by applying a torque equal to.

  During four-wheel drive, the ECU fastens the second clutch mechanism 134 and connects the connecting / disconnecting mechanism 76, so that the driving force input to the input shaft 94 is transmitted to the left front wheel via the second clutch mechanism 134. 72 and the right front wheel 74 can also be transmitted. When the second clutch mechanism 134 is engaged, the sprocket 164 connected coaxially rotates the sprocket 170 via the chain belt 168, so that the driving force is also transmitted to the front wheel output shaft 98.

  The driving force output from the front wheel output shaft 98 is transmitted to the drive pinion 56 of the front wheel differential 22 through the universal joint 32, the front wheel propeller shaft 26, and the universal joint 34. The drive pinion 56 includes a ring gear 58 and a pinion 60. 62, side front gears 64 and 66, the left front wheel drive shaft 68 and the right front wheel drive shaft 70 are driven. The left front wheel drive shaft 68 and the right front wheel drive shaft 70 rotate the left front wheel 72 and the right front wheel 74, respectively, to drive the driving force. To the road surface.

  The connection / disconnection mechanism 76 connects the side gear 64 and the left front wheel drive shaft 68 during four-wheel drive, and the rotation of the side gear 64 is transmitted to the left front wheel drive shaft 68 as it is. Even if a difference in rotational speed occurs between the left front wheel 72 and the right front wheel 74 due to cornering or changes in road surface conditions, the front wheel differential 22 absorbs the rotational speed difference and gives equal torque to the left front wheel 72 and the right front wheel 74. Can be rotated.

  At the time of four-wheel drive, the ECU opens the first clutch mechanism 124 so that the central differential 100 is in an open differential state. 74, the central differential 100 can absorb the rotational speed difference and rotate the rear wheels 52 and 54 and the front wheels 72 and 74 by applying appropriate torque.

  When switching from four-wheel drive to two-wheel drive, or even if the driver does not operate the changeover switch, when detecting the vehicle state and automatically switching to two-wheel drive when there is no need for four-wheel drive according to ECU judgment, The ECU fastens the first clutch mechanism 124 and opens the second clutch mechanism 134, and then disconnects the connection / disconnection mechanism 76. In this case, the ECU may first engage the first clutch mechanism 124 and release the second clutch mechanism 134 after disconnecting the connection / disconnection mechanism 76 first.

  The connection / disconnection mechanism 76 disconnects the connection between the side gear 64 and the left front wheel drive shaft 68, and prevents the rotational force received by the left front wheel 72 and the right front wheel 74 from the road surface from rotating the ring gear 58. Accordingly, it is possible to solve the accompanying problem that the front wheel driving force transmission section 78 from the ring gear 58 to the sprocket 126 rotates even when the two wheels are driven without driving the front wheels, which is a factor that causes a decrease in fuel consumption when the two wheels are driven.

  In FIG. 1, if the side gear 64 and the left front wheel drive shaft 68 are connected during two-wheel drive, for example, when the side gears 64 and 66 rotate at the same speed in the same direction, the pinions 60 and 62 rotate (spin). Without this, the ring gear 58 rotates. Even if there is a difference in rotational speed between the side gears 64 and 66, if the rotational speed is the same, the rotational speed will change, but the ring gear 58 will rotate, and the ring gear 58 will rotate. The joint 34, the front wheel propeller shaft 26, the universal joint 32, the front wheel output shaft 98, the sprocket 170, the chain belt 168, and the sprocket 164 rotate.

  Although the front wheel driving force transmission section 78 from the ring gear 58 to the sprocket 164 is a portion that does not need to be rotated during two-wheel drive, the rotation of this portion reduces the viscous resistance of the oil, the friction loss of the bearing portion, and the like. cause. That is, the driving force transmitted from the rear wheels 52 and 54 to the road surface rotates the front wheels 72 and 74, thereby rotating the front wheel driving force transmission section 78 that does not need to be rotated during two-wheel drive, resulting in a loss of driving force and a reduction in fuel consumption. Will be invited.

  Therefore, in the present invention, during the two-wheel drive, the connection and disconnection mechanism 76 disconnects the side gear 64 and the left front wheel drive shaft 68, and the drag torque of the second clutch mechanism 134 is determined by the friction torque of the front wheel drive force transmission section 78. Also, the rotation of the front wheel driving force transmission section 78 is prevented. A method for reducing the drag torque will be described later in detail.

  When the connection between the side gear 64 and the left front wheel drive shaft 68 is broken, the rotation of the left front wheel 72 is not transmitted to the side gear 64, so the rotation of the side gear 66 by the right front wheel 74 causes the side gear 64 to move in the opposite direction via the pinions 60 and 62. Since the rotational resistance from the drive pinion 56 connected to the ring gear 58 to the sprocket 164 is larger than the rotational resistance of the pinions 60 and 62 and the side gear 64, the ring gear 58 does not rotate.

  The fact that the ring gear 58 does not rotate means that the front wheel driving force transmission section 78 does not rotate. In this case, the driving force is lost only in the portion where the pinions 60 and 62 and the side gear 64 are rotated. The fuel consumption can be improved compared to the case where the front wheel driving force transmission section 78 rotates.

  In the present embodiment, the connection / disconnection mechanism 76 is installed between the side gear 64 and the left front wheel drive shaft 68 in the front wheel differential 22, but the position where the side gear 64 and the left front wheel drive shaft 68 are intermittently connected, or It does not matter whether the side gear 66 and the right front wheel drive shaft 70 are intermittently installed, or both of them are installed in the front wheel differential 22 or outside. Further, another mechanism such as a system in which the unit constituted by the pinions 60 and 62 and the side gears 64 and 66 is separated from the ring gear 58 and the connection thereof is interrupted may be used.

  FIG. 2 is a cross-sectional view showing an embodiment of the front wheel differential device 22 of FIG. In FIG. 2, the front wheel differential 22 is connected to a ring gear 58 fixed to the outer periphery of the differential case 80, a pinion 60 and a pinion 62 rotatably supported on a pinion shaft 82 fixed to the differential case 80, and a side gear shaft 84. A side gear 64 that is rotatably supported and meshes with the pinion 60 and the pinion 62 within the differential case 80, and a side gear 66 that is pivotally supported by the right front wheel drive shaft 70 and that meshes with the pinion 60 and the pinion 62 within the differential case 80.

  Further, the end portion 68b is spline-coupled to the left front wheel drive shaft 68, which is engaged with the side gear shaft 84 without being constrained in the rotational direction, the tooth portion 68a of the left front wheel drive shaft 68, and the tooth portion 84a of the side gear shaft 84. A sleeve 86 slidable at a position where the front wheel drive shaft 68 and the side gear shaft 84 are connected to each other and a position where the front gear shaft 84 is released; a fork 88 which slides the sleeve 86 by a tip end portion 88a slidably engaged with a groove 86a of the sleeve 86; A shift shaft 90 is provided that is fixed to the fork 88 and is driven in the axial direction by an actuator (not shown), and transmits the driving force from the drive pinion 56 that meshes with the ring gear 58 to the left front wheel 72 and the right front wheel 74 during four-wheel drive.

  In FIG. 2A, the connecting / disconnecting mechanism 76 at the time of two-wheel drive is in a non-connected state, and the sleeve 86 is not engaged with the tooth portion 84a of the side gear shaft 84. The rotation of the right front wheel drive shaft 70 is transmitted to the side gear 64 via the side gear 66, the pinion 60 and the pinion 62, and the ring gear 58 does not rotate, so that the side gear shaft 84 is rotated in the direction opposite to the right front wheel drive shaft 70.

  FIG. 2B shows a state in which the fork 88 moves in the C direction and the connecting / disconnecting mechanism 76 is connected during four-wheel drive, and the sleeve 86 is engaged with the tooth portion 84 a of the side gear shaft 84. The ring gear 58 is rotated by the drive pinion 56, and the left front wheel drive shaft 68 and the right front wheel drive shaft 70 are rotated in the same direction. When returning to the two-wheel drive, the fork 88 moves in the direction D, and the connection / disconnection mechanism 76 returns to the disconnected state.

  FIG. 3 is a cross-sectional view showing an embodiment of the driving force distribution device 18 of FIG. In FIG. 3, the driving force distribution device 18 has a housing 92 composed of a housing left side portion 92 a and a housing right side portion 92 b, and inputs the driving force from the engine 14 to the left side of the housing 92 via the transmission 16. On the right side of the input shaft 94 and the housing 92, a rear wheel output shaft 96 that outputs a driving force coaxially with the input shaft 94 is provided.

  In addition, a front wheel output shaft 98 that outputs a driving force in parallel to the input shaft 94 and on the opposite side of the rear wheel output shaft 96 is provided on the lower left side of the housing 92, and the driving force input to the input shaft 94 is a central differential. It is distributed by the planetary gear mechanism 102 functioning as 100 and transmitted to the rear wheel output shaft 96 and the front wheel output shaft 98.

  The planetary gear mechanism 102 includes a planetary carrier 104, a carrier cover 106, a carrier case 108, a planetary gear 112, a planetary gear shaft 114, an outer gear 116, an outer gear shaft 118, a sun gear 120, and a sun gear shaft 122. The planetary carrier 104 is formed by extending the right outer peripheral portion of the input shaft 94 in the radial direction, and holds the planetary gear 112 by the planetary gear shaft 114 so as to be rotatable.

  The carrier cover 106 supports the planetary gear shaft 114 together with the planetary carrier 104, and the carrier case 108 is positioned so as to fill a space other than the planetary gear 112 between the planetary carrier 104 and the carrier cover 106, and the planetary gear 112 freely rotates. Secure the spacing as you can. The planetary carrier 104, the carrier cover 106, and the carrier case 108 are fixed by bolts 110 (shown in FIG. 4) and rotate together, and this rotation causes the planetary gear 112 to revolve.

  On the right side of the input shaft 94 and the planetary gear mechanism 102 is provided an outer gear shaft 118 in which an outer gear 116 made of internal teeth is formed on the inner periphery of the large diameter portion at the left end, and the right end of the outer gear shaft 118 is It is directly connected to a rear wheel output shaft 96 arranged on the right side.

  The sun gear 120 is formed on the outer periphery of the right end of the sun gear shaft 122 that is rotatably provided on the outer periphery of the input shaft 94, and the driving force input to the input shaft 94 is transmitted through the planetary gear 112, the outer gear 116, and the sun gear 120. The output is distributed to the shaft 118 and the sun gear shaft 122 as the driving force on the rear wheel side and the front wheel side, respectively.

  FIG. 4 is a cross-sectional view showing the central differential device 100 of the present embodiment, and is a cross section taken along the line AA of the planetary gear mechanism 102 of FIG. In FIG. 4, the planetary gear 112 disposed between the planetary cases 108 meshes with the outer gear 116 and the sun gear 120, and rotates and revolves according to the rotational speed difference between the outer gear 116 and the sun gear 120.

  Referring again to FIG. 3, the first clutch mechanism 124 and the second clutch mechanism 134 are provided coaxially with the input shaft 94 on the left side of the planetary gear mechanism 102, and the first clutch mechanism 124 is connected to the input shaft 94. A first clutch hub 126 is formed on the outer periphery of the left end of the sun gear shaft 122 provided rotatably on the outer periphery, and a first clutch drum 128 is formed on the left end of the carrier cover 106 provided rotatably on the outer periphery of the sun gear shaft 122. ing.

  The first clutch mechanism 124 and the second clutch mechanism 134 in the first clutch drum 128 are displaced to the right of the first clutch mechanism 124 and the second clutch mechanism 134 in the axial direction, and the first clutch mechanism 124 is engaged. And a ring-shaped hydraulic piston 144 that opens the second clutch mechanism 134.

  The second clutch mechanism 134 has a second clutch drum 136 formed on the inner periphery of the first clutch hub 126 provided on the sun gear shaft 122, and a sprocket shaft 166 that rotatably supports the sprocket 164 with respect to the input shaft 94. And a second clutch hub 138 is formed at the right end.

  A second pressing member 156 that is displaced in the axial direction of the first clutch mechanism 124 and the second clutch mechanism 134 on the outer periphery of the sprocket shaft 166 and is urged by the fastening spring 162 to press in the direction of fastening the second clutch mechanism. Is provided.

  The first clutch mechanism 124 controls the connection between the planetary gear 112 and the sun gear 120 by opening and closing to switch the central differential 100 between an open differential state and a differential lock state, and the second clutch mechanism 134 is configured to connect the sun gear 120 and the sprocket 164. Switching between four-wheel drive and two-wheel drive by controlling the connection by fastening and releasing.

  A sprocket 170 is connected to the front wheel output shaft 98, and a chain belt 168 is hung and connected to the sprocket 164 on the second clutch mechanism 134 side.

  The lower right portion of the housing 92 includes a hydraulic pump 172 that supplies hydraulic pressure to the hydraulic piston 144, a servo motor 174 that drives the hydraulic pump 172, and a hydraulic sensor 176 that detects the hydraulic pressure. The hydraulic pressure from the hydraulic pump 172 is The oil is supplied to the hydraulic cylinder 148 via oil passages 178, 180, 182, 184, and 186 provided in a liquid-tight manner in the housing 92, outer gear shaft 118, input shaft 94, carrier case 108, and carrier cover 106.

  In addition, an oil pump 188 that is driven by the sprocket 164 and supplies oil for lubricating and cooling the second clutch mechanism 134 is provided on the left inner wall portion of the housing 92 between the outer periphery of the sprocket 164.

  In such a driving force distribution device 18, the driving force of the input shaft 94 is transmitted to the rear wheel output shaft 96 via the central differential device 100 regardless of the four-wheel driving or the two-wheel driving. At the time of four-wheel drive, the first clutch mechanism 124 is released to be in an open differential state, and the second clutch mechanism 134 is fastened, so that the driving force distributed by the central differential 100 is the second clutch mechanism 134. , The sprocket 164, the chain belt 168, and the sprocket 170 are also transmitted to the front wheel output shaft 96.

  At the time of two-wheel drive, the second clutch mechanism 134 is released and the sun gear shaft 122 and the sprocket 162 are disconnected, but the first clutch mechanism 124 is fastened and the central differential 100 is in the diff-lock state. The driving force input to the input shaft 94 is transmitted to the rear wheel output shaft 98 without causing the planetary carrier 104 to idle.

  5 is a cross-sectional view showing details of the first clutch mechanism 124 and the second clutch mechanism 134 of FIG. 3, and FIG. 5 (A) shows the upper part of the input shaft 94 in a four-wheel drive state. (B) shows the lower part of the input shaft 94 in a two-wheel drive state.

  In FIG. 5, for the first clutch mechanism 124, the hydraulic piston 144 that controls the fastening force of the first multi-plate clutch 130 provided between the first clutch hub 126 and the first clutch drum 128 is provided with the first clutch. Provided inside the drum 128.

  The hydraulic piston 144 has a pressing portion 146 and a thrust bearing 152, is fitted in a hydraulic cylinder 148 formed in the first clutch drum 128, and is movable in the axial direction of the first clutch drum. 150 is sealed.

  The first multi-plate clutch 130 is movable in the axial direction of the first clutch hub 126 and the first clutch drum 128 between the pressing portion 146 of the hydraulic piston 144 and the fixed pressure receiving plate 132 at the left end of the first clutch drum 128. Is retained.

  For the second clutch mechanism 134, a second pressing member 156 for controlling the fastening force of the second multi-plate clutch plate 140 provided between the second clutch drum 136 and the second clutch hub 138 is provided. The multi-plate clutch plate 140 is held movably in the axial direction of the second clutch drum 136 and the second clutch hub 138 between the pressure receiving portion 142 of the second clutch drum 136 and the pressing portion 158 of the second pressing member 156. ing.

  The second pressing member 156 has a pressing portion 158 and a thrust bearing 160, is fitted on the intermediate outer peripheral portion of the sprocket 164 of the sprocket shaft 166 and the second clutch hub 138, and is movable in the axial direction. The second clutch mechanism 134 is biased in the fastening direction by a fastening spring 162 provided therebetween.

  A plurality of connecting pins 154 pass through the intermediate portion of the first clutch hub 126 and the second clutch drum 136 formed integrally with the sun gear shaft 122 so as to be movable in the axial direction. The left end is engaged with the second pressing member 156 via the thrust bearing 160.

  Since the connecting pin 154 rotates together with the sun gear 120, the hydraulic piston 144 that rotates together with the planetary carrier 104 and the second pressing member 156 that rotates together with the sprocket 164 rotate relative to each other, but the rotational speed difference between the connecting pin 154 and the hydraulic piston 144. Is absorbed by the thrust bearing 152, and the rotational speed difference between the connecting pin 154 and the second pressing member 156 is absorbed by the thrust bearing 160.

  In FIG. 5A, the fastening spring 162 urges the second pressing member 156 to the right, and the pressing portion 158 presses the second multi-plate clutch 140, whereby the second clutch mechanism 134 is fastened. Further, the second pressing member 156 pushes the connecting pin 154 rightward through the thrust bearing 160, and further, the connecting pin 154 pushes the hydraulic piston 144 in the opening direction of the first multi-plate clutch 130 via the thrust bearing 152. Thus, the first clutch mechanism 124 is in an open state.

  Therefore, in the state of FIG. 5A, the first clutch mechanism 124 is opened and the central differential 100 is in an open differential state, so that the driving force input to the input shaft 94 is the gear ratio of the planetary gear mechanism 102. Accordingly, the outer gear 116 and the sun gear 120 are distributed via the planetary carrier 104 and the planetary gear 112.

  The driving force distributed to the sun gear 120 is transmitted from the sun gear shaft 122 to the sprocket shaft 166 because the second clutch mechanism 134 is engaged, and the rear wheel output shaft 98 is transmitted via the sprocket 164, the chain belt 168 and the sprocket 170. Further, the driving force distributed to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, so that four-wheel drive is performed.

  In FIG. 5B, the hydraulic piston 144 moves to the left by the hydraulic pressure supplied from the hydraulic pump 172 to the hydraulic cylinder 148 via the oil passages 182, 184, 186, and the pressing portion 146 is the first The first clutch mechanism 124 is engaged by pressing the plate clutch 130, the hydraulic piston 144 pushes the connecting pin 154 to the left via the thrust bearing 152, and the connecting pin 154 passes through the thrust bearing 160. Thus, the second clutch mechanism 134 is in the released state by pushing the second pressing member 156 against the fastening spring 162 in the opening direction of the second clutch mechanism 134.

  Therefore, in the state of FIG. 5B, the first clutch mechanism 124 is fastened, the relative position between the planetary gear 112 and the sun gear 120 is fixed, and the central differential 100 is in the differential lock state. Even if 134 is opened, the central differential 100 does not run idle, and the driving force input to the input shaft 94 is transmitted to the outer gear 116 and the sun gear 120 via the planetary carrier 104 and the planetary gear 112.

  The driving force transmitted to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, but the driving force transmitted to the sun gear 120 is output to the front wheel because the second clutch mechanism 134 is released. Since it is not transmitted to the shaft 98, it becomes a two-wheel drive by a rear wheel.

  FIG. 6 is a cross-sectional view showing another embodiment of the first clutch mechanism 124 and the second clutch mechanism 134 of FIG. 3 in the same manner as FIG. 5, and FIG. FIG. 6B shows the lower portion of the input shaft 94 as a two-wheel drive state.

  In FIG. 6, a hydraulic piston 145 that controls the fastening force of the first multi-plate clutch 130 provided between the first clutch hub 126 and the first clutch drum 128 is provided for the first clutch mechanism 124. Provided inside the drum 128.

  The hydraulic piston 145 has a pressing portion 146, is fitted in a hydraulic cylinder 148 formed on the first clutch drum 128, is movable in the axial direction of the first clutch drum, and is sealed by an O-ring 150. ing.

  The first multi-plate clutch 130 is arranged in the axial direction of the first clutch hub 126 and the first clutch drum 128 between the pressing portion 146 of the hydraulic piston 145 and the movable pressure receiving plate 133 located at the left end portion of the first clutch drum 128. It is held movable.

  For the second clutch mechanism 134, a second pressing member 157 for controlling the fastening force of the second multi-plate clutch plate 140 provided between the second clutch drum 136 and the second clutch hub 138 is provided. The multi-plate clutch plate 140 is held movably in the axial direction of the second clutch drum 136 and the second clutch hub 138 between the pressure receiving portion 142 of the second clutch drum 136 and the pressing portion 158 of the second pressing member 157. ing.

  The second pressing member 157 has a pressing portion 158 and a thrust bearing 161, is fitted to the intermediate outer peripheral portion of the sprocket shaft 166 and the second clutch hub 138, and is movable in the axial direction. The second clutch mechanism 134 is biased in the fastening direction by a fastening spring 162 provided therebetween.

  The thrust bearing 161 is engaged with the movable pressure receiving plate 133 and transmits the pressing force of the hydraulic piston 145 to the second pressing member 157 via the first multi-plate clutch 130.

  Since the movable pressure receiving plate 133 rotates together with the planetary carrier 104, it rotates relative to the second pressing member 157 rotating together with the sprocket 164, but the rotational speed difference is absorbed by the thrust bearing 161.

  In FIG. 6 (A), the fastening spring 162 urges the second pressing member 157 to the right, and the pressing portion 158 presses the second multi-plate clutch 140, whereby the second clutch mechanism 134 is fastened. The second pressing member 157 moves the movable pressure receiving plate 133 to the right via the thrust bearing 161. However, since the hydraulic piston 145 is in the standby position, the first multi-plate clutch 130 is pressed by the pressing portion 146. The first clutch mechanism 124 is in an open state.

  Therefore, in the state of FIG. 6A, the first clutch mechanism 124 is opened and the central differential 100 is in the open differential state, so that the driving force input to the input shaft 94 is the gear ratio of the planetary gear mechanism 102. Accordingly, the outer gear 116 and the sun gear 120 are distributed via the planetary carrier 104 and the planetary gear 112.

  The driving force distributed to the sun gear 120 is transmitted from the sun gear shaft 122 to the sprocket shaft 166 because the second clutch mechanism 134 is engaged, and the rear wheel output shaft 98 is transmitted via the sprocket 164, the chain belt 168 and the sprocket 170. Further, the driving force distributed to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, so that four-wheel drive is performed.

  In FIG. 6 (B), the hydraulic piston 145 moves to the left by the hydraulic pressure supplied from the hydraulic pump 172 to the hydraulic cylinder 148 via the oil passages 182, 184, 186, and the pressing portion 146 has the first multiplicity. The first clutch mechanism 124 is engaged by pressing the plate clutch 130. The hydraulic piston 145 pushes the movable pressure receiving plate 133 to the left via the first multi-plate clutch 130, and the movable pressure receiving plate 133 is thrust. By pressing the second pressing member 157 in the opening direction of the second clutch mechanism 134 against the fastening spring 162 via the bearing 161, the second clutch mechanism 134 is in an open state.

  Therefore, in the state of FIG. 6B, the first clutch mechanism 124 is engaged, the relative position between the planetary gear 112 and the sun gear 120 is fixed, and the central differential 100 is in the differential lock state. Even if 134 is opened, the central differential 100 does not run idle, and the driving force input to the input shaft 94 is transmitted to the outer gear 116 and the sun gear 120 via the planetary carrier 104 and the planetary gear 112.

  The driving force transmitted to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, but the driving force transmitted to the sun gear 120 is output to the front wheel because the second clutch mechanism 134 is released. Since it is not transmitted to the shaft 98, it becomes a two-wheel drive by a rear wheel.

  As shown in FIGS. 5 and 6, switching from four-wheel drive to two-wheel drive or from two-wheel drive to four-wheel drive is performed by controlling the first clutch mechanism 124 and the second clutch mechanism 134. Since the mechanism uses a multi-plate clutch, it can be freely engaged and disengaged even during torque transmission or when there is a difference in rotational speed, interrupting torque transmission like the conventional method using a sliding clutch, Factors that lengthen the switching time, such as synchronizing the rotation speed, are eliminated.

  That is, the switching time can be significantly shortened compared to the conventional case, and when switching from two-wheel drive to four-wheel drive, the second clutch mechanism 134 is engaged using the elasticity of the fastening spring 162. This can be performed much faster than the actuator used, and particularly when switching from two-wheel drive to four-wheel drive to avoid danger, the effect of high-speed switching is significant.

  FIG. 7 is an operation explanatory view schematically showing the states of the driving force distribution device 18 and the connection / disconnection mechanism 76 of the driving force transmission device 10 having the clutch mechanism of FIG. 5, and FIG. FIG. 7B shows a state during two-wheel drive. Further, the planetary gear mechanism 102, the first clutch mechanism 124, the second clutch mechanism 134, the hydraulic piston 144, and the sprocket 164 are shown by simplifying only the upper half of the cross section with respect to the input shaft 94, and the configuration shown in FIG. On the other hand, the front wheel differential device 22, the rear wheel differential device 20, and the connection / disconnection mechanism 76 have different directions and positions, but do not affect the requirements of the present invention.

  In FIG. 7A, the driving force from the engine 14 is transmitted to the planetary carrier 104 and the planetary gear 112 of the planetary gear mechanism 102 constituting the central differential device 100 via the input shaft 94 via the transmission 16. The outer gear 116 and the sun gear 120 are distributed.

  The driving force distributed to the outer gear 116 is transmitted to the rear wheels 52 and 54 via the rear wheel output shaft 96 and the rear wheel differential device 20, and the driving force distributed to the sun gear 120 is transmitted to the second clutch mechanism 134. Since it is fastened, it is transmitted to the front wheel differential device 22 via the sprocket 164, the chain belt 168, the sprocket 170, and the front wheel output shaft 98, and the driving force transmitted to the front wheel differential device 22 is transmitted to the connection / disconnection mechanism 76. Since they are connected, they are transmitted to the front wheels 72 and 74.

  Further, since the first clutch mechanism 124 is opened and the central differential 100 is in the open differential state, the central differential 100 absorbs the driving force while absorbing the rotational speed difference between the rear wheels 52 and 54 and the front wheels 72 and 74. By transmitting to the front and rear wheels at a predetermined distribution ratio set by the gear ratio of the planetary gear mechanism 102, the four-wheel drive vehicle 12 becomes four-wheel drive.

  Here, the opening of the first clutch mechanism 124 and the fastening of the second clutch mechanism 134 are held by the urging force of the fastening spring 162 in the R direction. In this state, the hydraulic pump 172 does not supply hydraulic pressure. When the ECU 198 determines that four-wheel drive is not necessary or when the driver operates the changeover switch to select two-wheel drive, the ECU 198 drives the servo motor 174 and starts supplying hydraulic pressure to the hydraulic pump 172. ) State.

  In FIG. 7B, the hydraulic pressure supplied from the hydraulic pump 172 to the hydraulic cylinder 148 drives the hydraulic piston 144 in the F direction, and the hydraulic piston 144 fastens the first clutch mechanism 124 against the fastening spring 162. The second clutch mechanism 134 is released.

  Here, the amount of hydraulic pressure supplied to the hydraulic cylinder 148 is controlled by the ECU 198 controlling the servo motor 174 that drives the hydraulic pump 172 based on the hydraulic pressure information detected by the hydraulic sensor 176.

  In the state of FIG. 7B, the driving force input from the input shaft 94 to the planetary gear mechanism 102 is transmitted to the outer gear 116 and the sun gear 120. The driving force transmitted to the outer gear 116 is transmitted to the rear wheels 52 and 54 via the rear wheel output shaft 96 and the rear wheel differential device 20, but the driving force transmitted to the sun gear 120 is the second clutch mechanism. Since 134 is open, it is not transmitted to the sprocket 164.

  Accordingly, the driving force is not distributed to the front wheels 72 and 74 by the central differential device 100, and the first differential mechanism 100 is engaged and the central differential device 100 is in the differential lock state. Without driving, only the rear wheels 52 and 54 are driven, so that the four-wheel drive vehicle 12 is two-wheel drive.

  In the two-wheel drive state, the EUC 198 moves the sleeve 86 in the D direction by the actuator 200 to disconnect the connection / disconnection mechanism 76, thereby preventing the front wheel driving force transmission section 78 from being rotated and improving fuel efficiency. Let

  FIG. 8 is an operation explanatory view schematically showing the states of the driving force distribution device 18 and the connection / disconnection mechanism 76 of the driving force transmission device 10 including the clutch mechanism of FIG. The second clutch mechanism 134 is different, and other than that is the same as FIG. FIG. 8A shows a state during four-wheel drive, and FIG. 8B shows a state during two-wheel drive.

  Further, the planetary gear mechanism 102, the first clutch mechanism 124, the second clutch mechanism 134, the hydraulic piston 145, and the sprocket 164 are shown in a simplified manner in the upper half of the cross section with respect to the input shaft 94, and have the configuration shown in FIG. On the other hand, the front wheel differential device 22, the rear wheel differential device 20, and the connection / disconnection mechanism 76 have different directions and positions, but do not affect the requirements of the present invention.

  In FIG. 8A, the driving force from the engine 14 is transmitted to the planetary carrier 104 and the planetary gear 112 of the planetary gear mechanism 102 constituting the central differential device 100 via the input shaft 94 via the transmission 16. The outer gear 116 and the sun gear 120 are distributed.

  The driving force distributed to the outer gear 116 is transmitted to the rear wheels 52 and 54 via the rear wheel output shaft 96 and the rear wheel differential device 20, and the driving force distributed to the sun gear 120 is transmitted to the second clutch mechanism 134. Since it is fastened, it is transmitted to the front wheel differential device 22 via the sprocket 164, the chain belt 168, the sprocket 170, and the front wheel output shaft 98, and the driving force transmitted to the front wheel differential device 22 is transmitted to the connection / disconnection mechanism 76. Since they are connected, they are transmitted to the front wheels 72 and 74.

  Further, since the first clutch mechanism 124 is opened and the central differential 100 is in the open differential state, the central differential 100 absorbs the driving force while absorbing the rotational speed difference between the rear wheels 52 and 54 and the front wheels 72 and 74. By transmitting to the front and rear wheels at a predetermined distribution ratio set by the gear ratio of the planetary gear mechanism 102, the four-wheel drive vehicle 12 becomes four-wheel drive.

  Here, the fastening of the second clutch mechanism 134 is held by the urging force of the fastening spring 162 in the R direction. In this state, the hydraulic pump 172 does not supply hydraulic pressure, so the first clutch mechanism 124 is released. However, when the ECU 198 determines that four-wheel drive is not necessary or when the driver operates the changeover switch to select two-wheel drive, the ECU 198 drives the servo motor 174 and starts supplying hydraulic pressure to the hydraulic pump 172. Transition to the state of 8 (B).

  In FIG. 8B, the hydraulic pressure supplied from the hydraulic pump 172 to the hydraulic cylinder 148 drives the hydraulic piston 145 in the F direction, and the hydraulic piston 145 fastens the first clutch mechanism 124 against the fastening spring 162. The second clutch mechanism 134 is released.

  Here, the amount of hydraulic pressure supplied to the hydraulic cylinder 148 is controlled by the ECU 198 controlling the servo motor 174 that drives the hydraulic pump 172 based on the hydraulic pressure information detected by the hydraulic sensor 176.

  In the state of FIG. 8B, the driving force input from the input shaft 94 to the planetary gear mechanism 102 is transmitted to the outer gear 116 and the sun gear 120. The driving force transmitted to the outer gear 116 is transmitted to the rear wheels 52 and 54 via the rear wheel output shaft 96 and the rear wheel differential device 20, but the driving force transmitted to the sun gear 120 is the second clutch mechanism. Since 134 is open, it is not transmitted to the sprocket 164.

  Accordingly, the driving force is not distributed to the front wheels 72 and 74 by the central differential device 100, and the first differential mechanism 100 is engaged and the central differential device 100 is in the differential lock state. Without driving, only the rear wheels 52 and 54 are driven, so that the four-wheel drive vehicle 12 is two-wheel drive.

  In the two-wheel drive state, the EUC 198 moves the sleeve 86 in the D direction by the actuator 200 to disconnect the connection / disconnection mechanism 76, thereby preventing the front wheel driving force transmission section 78 from being rotated and improving fuel efficiency. Let

  FIG. 9 is an operation explanatory view showing the switching state of the first clutch mechanism 124 and the second clutch mechanism 134 of FIGS. 5 and 6. The torque curve of the drive force that can be transmitted is shown with the transmission torque T on the vertical axis. The horizontal axis is expressed as a pressing force F of the hydraulic piston 144 or 145.

  FIG. 9A shows a case where the tight corner braking phenomenon is avoided according to the embodiment of FIG. 5, and the first clutch torque curve 202 is transmitted from the first clutch mechanism 124 at the pressing force F1 to F3 of the hydraulic piston 144. The second clutch torque curve 204 indicates the torque that can be transmitted by the second clutch mechanism 134 at the pressing forces F0 to F2.

  FIG. 9B shows a case where the central differential 100 is caused to function as a limited slip differential during four-wheel drive according to the embodiment of FIG. 6, and the first clutch torque curve 202 is obtained from the pressing forces F1 to F3 of the hydraulic piston 145. The second clutch torque curve 204 indicates the torque that can be transmitted by the second clutch mechanism 134 at the pressing force F0 to F2.

  In FIG. 9A, the second clutch mechanism 134 is fastened with the maximum fastening force by the fastening spring 162 at the pressing force F0, so that the transmission torque to the front wheel is the maximum value T2, and this pressing force F0 is the driving force. This is the position of the four-wheel drive 206 of the distribution device 18. Further, since the first clutch mechanism 124 is completely released up to the pressing force F2, the central differential 100 is in the open differential state 208 in this section.

  When the hydraulic pressure is raised, the hydraulic piston 144 starts to release the pressure of the second clutch mechanism 134, becomes the pressing force F2, and starts to press the first clutch mechanism 124 at the same time as the release of the second clutch mechanism 134 is completed. Since the connection between the central differential 100 and the sprocket 164 is cut off, the pressing force F2 (F1) and thereafter is within the range of the two-wheel drive 212, and the range of the pressing force F0 to F2 is the transition zone from four-wheel drive to two-wheel drive. 214.

  At the pressing force F1 (F2), when the engagement of the first clutch mechanism 124 starts, the central differential 100 moves from the range of the open differential 208 to the differential limiting range 210 and functions as a limited slip differential. The maximum value F3 is the position of the differential lock 216 of the central differential 100.

  Thus, the tight corner braking phenomenon can be avoided by starting the engagement of the first clutch mechanism 124 simultaneously with the completion of the release of the second clutch mechanism 134.

  Here, when the start of engagement of the first clutch mechanism 124 is delayed from the completion of the release of the second clutch mechanism 134, that is, the pressing force F1 for starting the engagement of the first clutch mechanism 124 completes the release of the second clutch mechanism 134. If it is located to the right of the pressing force F2, the two-wheel drive in that range will be in an open differential state, and the central differential 100 will idle and the driving force will not be transmitted to both the front and rear wheels.

  In order to avoid this state, the engagement of the first clutch mechanism 124 may be started slightly earlier than the completion of the release of the second clutch mechanism 134, but in this state, a tight corner braking phenomenon may occur. Therefore, it is desirable that this overlap range is narrow.

  In FIG. 9B, the second clutch mechanism 134 is fastened with the maximum fastening force by the fastening spring 162 up to the pressing force F0, so that the transmission torque to the front wheel becomes the maximum value T2, and the pressing force F1 to F0 This is the range of the four-wheel drive 206 of the driving force distribution device 18.

  Further, since the first clutch mechanism 124 is completely opened at the pressing force F1, the central differential 100 is in the state of the open differential 208. However, the pressing force exceeds F1 to start the engagement, and the transmission torque T increases. Then, the central differential device 100 shifts from the open differential 208 state to the differential limiting range 210.

When the hydraulic pressure is raised, the hydraulic piston 145 starts to release the pressure of the first clutch mechanism 124. When the hydraulic pressure is increased to the pressing force F0, the second pressing member 157 is fastened via the first multi-plate clutch 130 and the movable pressure receiving plate 133. The second clutch mechanism 134 starts releasing the engagement as it begins to push against the spring 162. The transmission torque of the first clutch mechanism 124 is maintained at the transmission torque T1 at the pressing force F0 at which the transmission torque of the second clutch mechanism 134 starts to decrease.

  When the hydraulic pressure is further increased and the pressing force F2 is reached, the second clutch mechanism 134 is completely opened and the central differential 100 and the sprocket 164 are disconnected, so that the two-wheel drive is performed. It becomes the range. The range from the pressing force F0 to F2 is the transition section 214 from the four-wheel drive to the two-wheel drive, and the maximum value F3 of the pressing force F is the position of the differential lock 216 of the central differential 100.

  If the rear wheels 52 and 54 or the front wheels 72 and 74 slip during four-wheel drive, the ECU 198 controls the fastening force of the first clutch mechanism 124 to cause the central differential device 100 to generate a differential limiting force. It is also possible to enter a limited slip differential state. That is, the EUC 198 can prevent the slipping drive wheel from slipping by controlling the hydraulic pressure and setting the pressing force to an appropriate position between F1 and F2.

  However, when cornering the vehicle, especially when the turning radius is small, a tight corner braking phenomenon may occur if it encounters a section from this pressing force F1 to F2, but the tight corner braking phenomenon is prevented as much as possible. In order to achieve this, the value of the pressing force F0 may be reduced and the transmission torque T1 of the first clutch mechanism 124 may be maintained at a low value.

  Accordingly, the operation timing of the first clutch mechanism 124 and the second clutch mechanism 134 is set so that the fastening of the first clutch mechanism 124 starts simultaneously with the completion of the release of the second clutch mechanism 134 in order to avoid the tight corner braking phenomenon. In the case where the central differential 100 has a limited slip differential function, the first multi-plate clutch is configured so that the first clutch mechanism 124 starts to be engaged before the second clutch mechanism 134 is completely opened. What is necessary is just to set the clearance gap between the 130 and the second multi-plate clutch 140 and the end play.

  Further, when the tight corner braking phenomenon shown in FIG. 9A is avoided, if the torque generation at the start of the engagement of the first clutch mechanism 124 is delayed, the driving force cannot be transmitted smoothly to the front wheels. Therefore, for example, by using a non-linear portion of the load characteristic of the disc spring, it is possible to prevent the torque generation of the first clutch mechanism 124 from being delayed.

  FIG. 10 is an explanatory diagram showing the relationship between the pressing force, transmission torque, and load characteristics of the fastening spring when a disc spring is used as the fastening spring. FIG. 10 (A) shows the coil spring of FIG. 5 (A). In the two-wheel drive state in which the first clutch mechanism 124 is fastened and the second clutch mechanism 134 is open, showing a cross section when a fastening spring 163 composed of a plurality of disc springs is used instead of the fastening spring 162 used. is there.

  FIG. 10B shows the first clutch torque curve 202 and the second clutch torque curve 204 on the left side, the front wheel transmission torque T on the vertical axis, and the pressing force F on the horizontal axis, and the load characteristic curve of the fastening spring 163 on the right side. 218 represents the spring load S on the vertical axis and the deflection amount δ on the horizontal axis, and the pressing forces F0, F2, and F3 correspond to the pressing forces F0, F2, and F3 in FIG. 9A, respectively.

  The fastening spring 163 obtains a load characteristic curve 218 by appropriately setting the plate thickness, free height, and number of disc springs. The disc springs can obtain various load characteristics depending on how they are combined. In the present embodiment, by utilizing such disc spring characteristics, a region where the amount of deflection per unit load is small (a linear region up to δ2). ) And a region with a large amount of deflection per unit load (non-linear region after δ2).

  As shown in FIG. 10 (B), the spring load S2 at the position of the bending amount δ2 of the fastening spring 163, or the position just before it, is matched with the pressing force F2 at the completion of opening of the second clutch mechanism 134, so that the hydraulic pressure When the pressing force F by the piston 144 is applied to the first clutch mechanism, the clearance of the first multi-plate clutch 130 can be reduced with a small increase in the pressing force, so that quick response can be obtained.

  FIG. 11 is a cross-sectional view showing another embodiment of the driving force distribution device 18 of FIG. 1, and includes a hydraulic piston 144, a hydraulic pump 172, a servo motor 174, and a hydraulic sensor 176 with respect to the cross-sectional view shown in FIG. The configuration is the same except that a first pressing member 220, a pressing pin 224, a ball cam mechanism 226, and a servo motor 228 are provided instead of the pressing mechanism.

  11, a ring-shaped first pressing member 220 is provided in the first clutch drum 128 instead of the hydraulic piston 144 of FIG. 3, and the first pressing member 220 is connected to a planetary gear mechanism via a plurality of pressing pins 224. It is connected to a ball cam mechanism 226 provided on the outer periphery of 102.

  The ball cam mechanism 226 holds + the ball 246 in the ball cam grooves 236 and 242 on the cam surfaces of the pair of fixed cam plate 234 and the rotating cam plate 240 that are provided coaxially with the input shaft 94 so as to be relatively rotatable. The fixed cam plate 234 is positioned on the opposite surface of the ball cam groove 236 by the housing 92, and the rotating cam plate 240 is engaged with the pressing pin 224 through the thrust bearing 248 on the opposite surface of the ball cam groove 242.

  FIG. 12 is an explanatory diagram of the ball cam mechanism 226 of FIG. 11, and FIG. 12A is located in front of the rotating cam plate 240 in a state where the rotating cam plate 240 is viewed from the direction of the rear wheel output shaft 96. The fixed cam plate 234 is indicated by an imaginary line (dashed line). 12B and 12C show the states of the fixed cam plate 234, the rotating cam plate 240, and the ball 246, and are cross sections taken along the line BB of FIG. 12A.

  In FIG. 12A, the fixed cam plate 234 has a plurality of ball cam grooves 236 in the circumferential direction, and a U-shaped arm portion 238 extending at the lower outer periphery is fitted to the outside of the holding portion 230 of the servo motor 228. The rotation is stopped by putting.

  The rotating cam plate 240 has a plurality of ball cam grooves 242 in the circumferential direction, and a sector gear 244 extending at the lower outer periphery and formed at the tip is meshed with the drive gear 232. In this embodiment, six sets of ball cam grooves 236, 242 and balls 246 are provided, and the number of sets is appropriately set according to various conditions.

  12B shows a state in which the rotating cam plate 240 does not press the pressing pin 224. FIG. 12C shows a state in which the rotating cam plate 240 is rotated by the servo motor 228, and the fixed cam plate 234 is moved. The relative position has moved in the R direction.

  When the rotating cam plate 240 moves in the R direction, the balls 246 move along the slopes of the ball cam grooves 236 and 242 in the S direction while rotating, thereby displacing the rotating cam plate 240 in the F direction.

  FIG. 13 is a cross-sectional view showing details of the first clutch mechanism 124, the second clutch mechanism 134, and the ball cam mechanism 226 of FIG. 11, and in contrast to the cross-sectional view shown in FIG. The configuration is the same except that the member 220, the pressing pin 224, the ball cam mechanism 226 and the like are provided. FIG. 13A shows the upper portion of the input shaft 94 in a four-wheel drive state, and FIG. 13B shows the lower portion of the input shaft 94 in a two-wheel drive state.

  In FIG. 13, a first pressing member 220 that controls the fastening force of the first multi-plate clutch 130 provided between the first clutch hub 126 and the first clutch drum 128 is provided for the first clutch mechanism 124. Provided inside one clutch drum 128.

  The first pressing member 220 has a pressing portion 222 and a thrust bearing 152, is fitted in a guide portion 250 formed on the first clutch drum 128, and is movable in the axial direction of the first clutch drum. The first pressing member 220 is connected to a ball cam mechanism 226 provided on the outer periphery of the planetary gear mechanism 102 via a pressing pin 224 that passes through the first clutch drum 128 and is movable in the axial direction.

  The first multi-plate clutch 130 moves in the axial direction of the first clutch hub 126 and the first clutch drum 128 between the pressing portion 222 of the first pressing member 220 and the fixed pressure receiving plate 132 at the left end of the first clutch drum 128. Held possible.

  Since the second clutch mechanism 134 and the connecting pin 154 are the same as those in FIG. 5, the description of the configuration and functions is omitted.

  In FIG. 13 (A), the fastening spring 162 urges the second pressing member 156 to the right, and the pressing portion 158 presses the second multi-plate clutch 140, whereby the second clutch mechanism 134 is fastened. The second pressing member 156 pushes the connecting pin 154 rightward through the thrust bearing 160, and the connecting pin 154 pushes the first pressing member 220 in the opening direction of the first multi-plate clutch 130 via the thrust bearing 152. By pushing, the first clutch mechanism 124 is in an open state.

  Therefore, in the state of FIG. 13A, the first clutch mechanism 124 is opened and the central differential 100 is in the open differential state, so that the driving force input to the input shaft 94 is the gear ratio of the planetary gear mechanism 2. Accordingly, the outer gear 116 and the sun gear 120 are distributed through the planetary carrier 104 and the planetary gear 112.

  The driving force distributed to the sun gear 120 is transmitted from the sun gear shaft 122 to the sprocket shaft 166 because the second clutch mechanism 134 is engaged, and the rear wheel output shaft 98 is transmitted via the sprocket 164, the chain belt 168, and the sprocket 170. Further, the driving force distributed to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, so that four-wheel drive is performed.

  In FIG. 13B, the ball cam mechanism 226 includes a ball cam groove 236 that is an inclined groove on an opposing surface, with the rotation cam plate 240 being rotated in a predetermined direction with respect to the fixed cam plate 234 by the drive gear 232 and the sector gear 244. The first pressing member 220 is moved to the left via the thrust bearing 248 and the pressing pin 224 in response to the pressing by the ball 246 sandwiched between the two.

  When the pressing portion 222 presses the first multi-plate clutch 130, the first clutch mechanism 124 is fastened, and the first pressing member 220 pushes the connecting pin 154 to the left via the thrust bearing 152, and the connecting pin 154 By pressing the second pressing member 156 in the opening direction of the second clutch mechanism 134 against the fastening spring 162 via the thrust bearing 160, the second clutch mechanism 134 is in an open state.

  Therefore, in the state of FIG. 13B, the first clutch mechanism 124 is engaged, the relative position between the planetary gear 112 and the sun gear 120 is fixed, and the central differential 100 is in the differential lock state. Even if 134 is opened, the central differential 100 does not run idle, and the driving force input to the input shaft 94 is transmitted to the outer gear 116 and the sun gear 120 via the planetary carrier 104 and the planetary gear 112.

  The driving force transmitted to the outer gear 116 is output to the rear wheel output shaft 96 via the outer gear shaft 118, but the driving force transmitted to the sun gear 120 is output to the front wheel because the second clutch mechanism 134 is released. Since it is not transmitted to the shaft 98, it becomes a two-wheel drive by a rear wheel.

  In such a driving force distribution device 18, the driving force of the input shaft 94 is transmitted to the rear wheel output shaft 96 via the central differential device 100 regardless of the four-wheel driving or the two-wheel driving. At the time of four-wheel drive, the first clutch mechanism 124 is released to be in an open differential state, and the second clutch mechanism 134 is fastened, so that the driving force distributed by the central differential 100 is the second clutch mechanism 134. , The sprocket 164, the chain belt 168, and the sprocket 170 are also transmitted to the front wheel output shaft 96.

  At the time of two-wheel drive, the second clutch mechanism 134 is released and the sun gear shaft 122 and the sprocket 162 are disconnected, but the first clutch mechanism 124 is fastened and the central differential 100 is in the diff-lock state. The driving force input to the input shaft 94 is transmitted to the rear wheel output shaft 98 without causing the planetary carrier 104 to idle.

  As another factor that causes the front wheel drive force transmission system to rotate when driving two wheels, the drag torque of the multi-plate clutch mechanism that switches the connection and disconnection of the drive force to the front wheel drive force transmission system is larger than the friction torque of the front wheel drive force transmission system And there is a problem that even if the multi-plate clutch mechanism is opened, the front wheel driving force transmission system is rotated.

  In the present embodiment, the oil generated by the relative rotational speed between the driving side (second clutch drum 136 side) and the driven side (second clutch hub 138 side) of the second multi-plate clutch 140 provided in the second clutch mechanism 134 is shown. The drag torque such as viscous resistance and friction loss due to contact between the clutch plates is made smaller than the friction torque of the front wheel driving force transmission section 78 to prevent this rotation.

  FIG. 14 is an explanatory view showing a lubricating oil limiting mechanism of the second clutch mechanism 134 of FIG. 3, and details of the first clutch mechanism 124, the second clutch mechanism 134 and the oil pump 188 shown in FIG. FIG. 14A shows the upper part in a two-wheel drive state, and FIG. 14B shows a four-wheel drive state.

  In FIG. 14A, an oil pump 188 is disposed between the housing 92 and the sprocket 164, receives power from the sprocket shaft 166, and hollows the input shaft 94 via an oil passage 252 provided in the sprocket shaft 166. Oil is supplied to the oil passage 256 of the part.

  In such a configuration, in the state where the second clutch mechanism 134 during two-wheel drive is opened and the second pressing member 156 is in the standby position farthest from the second multi-plate clutch 140, the second multi-plate clutch 140 Of the clutch plates, the one engaged with the second clutch hub 138 does not rotate, but the one engaged with the second clutch drum 136 rotates together with the sun gear shaft 122.

  However, since the second clutch hub 138 does not rotate, the sprocket shaft 166 does not rotate. Therefore, the oil pump 188 is not driven and oil is not discharged to the oil passage 252, so that the oil is supplied to the second multi-plate clutch 140. First, the drag of the second clutch hub 138 can be prevented by reducing the viscous resistance due to oil.

  In FIG. 14B, the two-wheel drive is switched to the four-wheel drive, and the hydraulic piston 144 moves to the right so that the second pressing member 156 presses the second multi-plate clutch 140 by the urging force of the fastening spring 162, In a state where the clutch plates of the second multi-plate clutch 140 are in contact with each other, the second clutch hub 138 rotates, so that the sprocket shaft 166 rotates. Accordingly, the oil pump 188 driven by the sprocket shaft 166 discharges oil to the oil passage 252 so that oil from the oil passage 252 is supplied to the second multi-plate clutch 140 via the oil passages 254, 256, and 258. Thus, seizure between the clutch plates is prevented.

  In the four-wheel drive, since the first clutch mechanism 124 is opened, it is not necessary to supply oil to the first multi-plate clutch 130. However, in this state, the lubrication and cooling of the first multi-plate clutch 130 are taken into consideration. In this case, for example, an oil passage 259 may be provided to supply oil to the first multi-plate clutch 130 side.

  FIG. 15 is an explanatory view showing a state in which the spacer 260 is installed in the second clutch mechanism 134 of FIG. FIG. 15 shows details of the second multi-plate clutch 140 in a state where the upper part of the input shaft 94 is in a two-wheel drive state, the second clutch mechanism 134 is opened, and the second pressing member 156 is farthest from the second multi-plate clutch 140. In the standby position.

  The second clutch mechanism 134 includes a second multi-plate clutch 140 that is movable in the axial direction, and the second multi-plate clutch 140 is spline-fitted with a plurality of outer clutch plates 140d on the inner periphery of the second clutch drum 136. A plurality of inner clutch plates 140h are spline-fitted to the outer periphery of the second clutch hub 138, and the outer clutch plates 140d and the inner clutch plates 140h are alternately arranged.

  The outer periphery of the outer clutch plate 140d is provided with a spacer 260, which is a leaf spring formed from a plate material, to ensure a gap between the adjacent inner clutch plates 140h on both sides and a friction surface that does not drag.

  The second multi-plate clutch 140 is movable in the axial direction between the pressure receiving surface 142a of the second clutch drum 136 and the pressing surface 158a of the second pressing member 156, and there is a gap E between the pressing surface 158a, but the spacer 260 If there is not, the clutch plates of the second multi-plate clutch 140 adhere to each other and are dragged without being separated. Since the spacer 260 secures a gap between the friction surfaces of the clutch plate, it is possible to prevent loss of driving force due to drag and improve fuel efficiency.

  Note that the value of the gap E when the pressing member 156 is in the standby position farthest from the second multi-plate clutch 140 is not necessarily constant depending on the state of the gap between the second multi-plate clutch 140.

  The spacer 260 can be installed on the outer periphery of the inner clutch plate 140h, but the inner side with a small torque loss is preferable. That is, if the friction resistance due to sliding between the inner clutch plate 140h adjacent to the outer clutch plate 140d on which the spacer 260 is installed and the spacer 260 is the same, the friction torque is lower when the inner clutch plate 140h is installed, and the friction torque is driven. This is because power loss occurs. Further, it is preferable that the spring load of the spacer 260 is small as long as the distance from the adjacent inner clutch plate 140h can be maintained.

  FIG. 16 is a perspective view showing the spacer of FIG. In FIG. 16, a spacer 260 is a leaf spring formed from a plate material, and includes a sandwiching portion 260a inserted into a recess 140c in the plate thickness direction provided on the inner peripheral portion of the outer clutch plate 140d, and an inner clutch plate adjacent to the sandwiching portion 260a. The elastic piece 260b which extends in the outer diameter direction of both surfaces of 140h and is deformable in the axial direction of the second multi-plate latch 140 is provided.

  In order to insert and fix the spacer 260 in the recess 140c in the direction indicated by the arrow, the interval between the clamping portions 2360a is set to be narrower than the thickness of the recess 140c.

  FIG. 17 is a cross-sectional view showing the spacer 260 of FIG. FIG. 17A shows a state in which the friction surfaces of the outer clutch plate 140d on which the spacer 260 is installed and the inner clutch plate 140h adjacent to each other are in close contact with each other and rotate while the second clutch mechanism 134 is engaged during four-wheel drive. is doing.

  FIG. 17B shows that the friction surfaces of the outer clutch plate 140d on which the spacer 260 is installed and the inner clutch plate 140h adjacent to each other are dragged by the spacer 260 when the second clutch mechanism 134 during two-wheel drive is opened. It is isolated in a gap that does not cause

  In FIG. 17B, since the outer clutch plate 140d rotates and the inner clutch plate 140h does not rotate, the tip of the elastic piece 260b of the spacer 260 slides with the adjacent inner clutch plate 140h. Therefore, the tip of the elastic piece 260b is preferably in contact with a portion that is not a friction surface.

  FIG. 18 is an explanatory view showing another embodiment of a driving force transmission device for a four-wheel drive vehicle according to the present invention, which is a case suitable for a vehicle of a system for driving front wheels during two-wheel drive. In FIG. 15, the driving force transmission device 300 of this embodiment is provided in a four-wheel drive vehicle 302, and includes a driving force distribution device 308, a front wheel differential device 320 (first drive wheel differential device), and a rear wheel differential device 322. (Second drive wheel differential).

  The driving force distribution device 308 connects and disconnects the central differential device 314, the first clutch mechanism 316 that controls the differential limitation of the central differential device 314, and the output transmission from the central differential device 314 to the rear wheel output shaft 330. The front wheel differential device 320 and the rear wheel differential device 322 are connected to the driving force distribution device 308 via the front wheel output shaft 312 and the propeller shaft 324, respectively.

  The driving force from the engine 304 is changed by the transmission 306 and is input from the drive gear 336 of the transmission 306 to the input gear 310 of the driving force distribution device 308, regardless of whether it is a four-wheel drive or a two-wheel drive. Is output to the front wheel output shaft 312 and transmitted to the differential case 338 of the front wheel differential 320.

  The differential case 338 drives the left front wheel drive shaft 348 and the right front wheel drive shaft 350 via the pinions 340 and 342 and the side gears 344 and 346. The left front wheel drive shaft 348 and the right front wheel drive shaft 350 are the left front wheel 352 and the right front wheel 354, respectively. To transmit the driving force to the road surface. Even if a difference in rotational speed occurs between the left front wheel 352 and all right wheels 354 due to changes in cornering, road surface conditions, etc., the front wheel differential device 320 absorbs the rotational speed difference and applies equal torque to the left front wheel 352 and the right front wheel 354. Can be fed and rotated.

  During four-wheel drive, the ECU engages the second clutch mechanism 318 and connects the connection / disconnection mechanism 376, so that the driving force input to the input gear 310 is left rear via the second clutch mechanism 318. Transmission to the wheel 372 and the right rear wheel 374 is possible.

  When the second clutch mechanism 318 is engaged, the driving force is transmitted to the rear wheel output shaft 330 by rotating the output pinion 328 via the bevel gear 326 that is coaxially connected.

  The driving force output from the rear wheel output shaft 330 is transmitted to the drive pinion 356 of the rear wheel differential device 322 via the universal joint 332, the propeller shaft 324, and the universal joint 334. The drive pinion 356 includes the ring gear 358, 360, 362 and side gears 364, 366 drive the left rear wheel drive shaft 368 and the right rear wheel drive shaft 370. The left rear wheel drive shaft 368 and the right rear wheel drive shaft 370 are respectively driven by the left rear wheel 372 and the right rear wheel. The wheel 374 is rotated to transmit the driving force to the road surface.

  The connection / disconnection mechanism 376 connects the side gear 364 and the left rear wheel drive shaft 368 during four-wheel drive, and the rotation of the side gear 364 is transmitted to the left rear wheel drive shaft 368 as it is. Even if a difference in rotational speed occurs between the left rear wheel 372 and the right rear wheel 374 due to cornering or changes in road surface conditions, the rear wheel differential 322 absorbs the rotational speed difference, and the left rear wheel 372 and the right rear wheel 374 Can be rotated by applying a torque equal to.

  During four-wheel drive, since the ECU opens the first clutch mechanism 316 to open the central differential 314, the left and right front wheels 352, 354 and the left and right rear wheels 352 and 354 are changed by cornering, road surface conditions, and the like. Even if a rotational speed difference occurs between the wheels 372 and 374, the central differential 314 can absorb the rotational speed difference and rotate the left and right front wheels 352 and 354 and the left and right rear wheels 372 and 374 with appropriate torque. .

  When switching from four-wheel drive to two-wheel drive, or even if the driver does not operate the changeover switch, when detecting the vehicle state and automatically switching to two-wheel drive when there is no need for four-wheel drive by ECU judgment, The ECU fastens the first clutch mechanism 316 and opens the second clutch mechanism 318, and then disconnects the connection / disconnection mechanism 376. In this case, the ECU may first engage the first clutch mechanism 316 and release the second clutch mechanism 318 after disconnecting the connection / disconnection mechanism 376 first.

  The connecting / disconnecting mechanism 376 disconnects the side gear 364 from the left rear wheel drive shaft 368 and prevents the rotational force received by the left rear wheel 372 and the right rear wheel 374 from the road surface from rotating the ring gear 358. As a result, it is possible to eliminate the accompanying problem that the rear wheel driving force transmission section 378 from the ring gear 358 to the bevel gear 326 rotates even during the two-wheel drive that does not drive the rear wheel, which is a factor that causes a reduction in fuel consumption during the two-wheel drive. .

  FIG. 19 is an operation explanatory diagram illustrating the states of the driving force distribution device 308 and the connection / disconnection mechanism 376 of the driving force transmission device 300 of FIG. 18, and illustrates a state during four-wheel drive. Further, the planetary gear mechanism 380, the first clutch mechanism 316, the second clutch mechanism 318, the hydraulic piston 390, and the input gear 310 are shown by simplifying only the upper half of the cross section with respect to the rotation axis.

  In FIG. 19, the driving force from the engine 304 is transmitted via the transmission 306 to the planetary carrier 382 and the planetary gear 384 of the planetary gear mechanism 380 constituting the central differential 314 via the drive gear 336 and the input gear 310. And distributed to the sun gear 386 and the outer gear 388.

  The driving force distributed to the sun gear 386 is transmitted to the front wheels 352 and 354 via the front wheel output shaft 312 and the front wheel differential device 320, and the driving force distributed to the outer gear 388 is engaged by the second clutch mechanism 318. Therefore, the driving force transmitted to the rear wheel differential device 322 via the bevel gear 326, the output pinion 328, and the rear wheel output shaft 330 is connected to the rear wheel differential device 322 by the connecting / disconnecting mechanism 376. Therefore, it is transmitted to the rear wheels 372 and 374.

  In addition, since the first clutch mechanism 316 is opened and the central differential 314 is in an open differential state, the central differential 314 absorbs the rotational speed difference between the front wheels 352 and 354 and the rear wheels 372 and 374 and generates driving force. By transmitting to the front and rear wheels at a predetermined distribution ratio set by the gear ratio of the planetary gear mechanism 380, the four-wheel drive vehicle 302 becomes four-wheel drive.

  Here, the opening of the first clutch mechanism 316 and the fastening of the second clutch mechanism 318 are held by the biasing force of the fastening spring 392. In this state, the hydraulic pump 398 does not supply hydraulic pressure, but the ECU 394 When it is determined that the wheel drive is not necessary, or when the driver selects the two-wheel drive by operating the changeover switch, the ECU 394 drives the servo motor 396, and when the hydraulic pump 398 starts to supply the hydraulic pressure, the ECU 394 shifts to the two-wheel drive state. .

  When the two-wheel drive state is entered, the hydraulic pressure supplied from the hydraulic pump 398 drives the hydraulic piston 390, and the hydraulic piston 390 engages the first clutch mechanism 316 against the fastening spring 36 and the second clutch mechanism 318. Open.

  Here, the control of the hydraulic pressure supply amount is performed by the ECU 394 controlling the servo motor 396 that drives the hydraulic pump 398 based on the hydraulic pressure information detected by the hydraulic sensor 400.

  In the two-wheel drive state, the driving force input from the input gear 310 to the planetary gear mechanism 380 is transmitted to the sun gear 386 and the outer gear 388. The driving force transmitted to the sun gear 386 is transmitted to the front wheels 352 and 354 via the front wheel output shaft 312 and the front wheel differential device 320, but the driving force transmitted to the outer gear 388 is released by the second clutch mechanism 318. Therefore, it is not transmitted to the bevel gear 326.

  Accordingly, the driving force is not distributed to the rear wheels 372 and 374 by the central differential device 314, and the first differential mechanism 316 is engaged and the central differential device 314 is in the differential lock state. Since only the front wheels 352 and 354 are driven without idling, the four-wheel drive vehicle 302 is two-wheel drive.

  In the two-wheel drive state, the EUC 394 moves the sleeve 404 by the actuator 402 to disconnect the connection / disconnection mechanism 376, thereby preventing the rear wheel driving force transmission section 378 from being rotated and improving fuel efficiency.

The present invention is not limited to the above embodiment, includes appropriate modifications without impairing the object and advantages thereof, and is not limited by the numerical values shown in the above embodiment.

Explanatory drawing which shows embodiment of the drive force transmission device for four-wheel drive vehicles by this invention Sectional drawing which shows embodiment of the front-wheel differential gear of FIG. Sectional drawing which shows embodiment of the driving force distribution apparatus of FIG. Sectional view showing the central differential of FIG. Sectional drawing which shows the clutch mechanism of FIG. Sectional drawing which shows other embodiment of the clutch mechanism of FIG. Operation | movement explanatory drawing which shows the drive state of a driving force transmission apparatus provided with the clutch mechanism of FIG. Operation | movement explanatory drawing which shows the drive state of a driving force transmission apparatus provided with the clutch mechanism of FIG. Operation explanatory diagram showing the switching state of the clutch mechanism of FIGS. Explanatory drawing which shows the relationship between the pressing force at the time of making the fastening spring of FIG. 5 into a nonlinear characteristic, and a spring load Sectional drawing which shows other embodiment of the driving force distribution apparatus of FIG. Explanatory drawing which shows the ball cam mechanism of FIG. Sectional drawing which shows the clutch mechanism of FIG. Explanatory drawing which shows the lubricating oil restriction | limiting mechanism of the 2nd clutch mechanism of FIG. Explanatory drawing which shows the state which installed the spacer in the 2nd clutch mechanism of FIG. The perspective view which shows the spacer of FIG. Sectional drawing which shows the spacer of FIG. Explanatory drawing which shows other embodiment of the driving force transmission apparatus for four-wheel drive vehicles by this invention. Operation explanatory diagram showing the driving state of the driving force transmission device of FIG. Explanatory drawing which shows the conventional driving force transmission device for four-wheel drive vehicles 20 is an explanatory diagram showing an embodiment of the central differential device of FIG.

Explanation of symbols

10, 300, 500: Driving force transmission devices 12, 302, 502: Four-wheel drive vehicles 14, 304, 504: Engines 16, 306, 506: Transmissions 18, 308, 508: Driving force distribution devices 20, 322, 518 : Rear wheel differential device 22, 320, 524: Front wheel differential device 24, 514: Rear wheel propeller shaft 26, 516: Front wheel propeller shaft 28, 30, 32, 34, 332, 334: Universal joint 36, 356: Drive Pinion 38, 358: Ring gear 40, 42, 360, 362: Pinion 44, 46, 364, 366: Side gear 48, 368: Left rear wheel drive shaft 50, 370: Right rear wheel drive shaft 52, 372, 520: Left Rear wheel 54, 374, 522: Right rear wheel 56: Drive pinion 58: Ring gear 60, 62, 340, 342: Pinion 64, 66 344, 346: Side gear 68, 348: Left front wheel drive shaft 70, 350: Right front wheel drive shaft 72, 352, 526: Left front wheel 74, 354, 528: Right front wheel 76, 376, 576: Connection mechanism 78, 530: Front wheel driving force transmission section 80, 338: Differential case 82: Pinion shaft 84: Side gear shaft 86, 404, 570: Sleeve 88: Fork 90: Shift shaft 92: Housing 94, 532: Input shaft 96, 330, 534: Rear wheel output Shaft 98, 312, 536: Front wheel output shaft 100, 314, 510: Central differential 102, 380, 544: Planetary gear mechanism 104, 382, 546: Planetary carrier 106: Carrier cover 108: Carrier case 110: Bolt 112, 384, 548: Planetary gear 114: Planetary gear shaft 116, 388, 5 0: outer gear 118: outer gear shaft 120, 386, 552: sun gear 122, 554: sun gear shaft 124, 316: first clutch mechanism 126: first clutch hub 128: first clutch drum 130: first multi-plate clutch 132 : Fixed pressure plate 133: movable pressure plate 134, 318: second clutch mechanism 136: second clutch drum 138: second clutch hub 140: second multi-plate clutch 142: pressure receiving portions 144, 145, 390: hydraulic piston 146, 158, 222: Pressing portion 148: Hydraulic cylinder 150: O-rings 152, 160, 161, 248: Thrust bearing 154: Connection pin 156, 157: Second pressing members 162, 163, 392: Fastening springs 164, 170, 538, 540: Sprocket 166, 556: Sprocket shaft 168 , 542: chain belt 172, 398: hydraulic pumps 174, 228, 396: servo motors 176, 400: hydraulic sensors 178, 180, 182, 184, 186: oil passage 188: oil pumps 190, 192, 194, 196: oil Roads 198, 394: ECU
200, 402: Actuator 202: First clutch torque curve 204: Second clutch torque curve 206: Four-wheel drive position 208: Open differential 210: Differential limit range 212: Two-wheel drive range 214: Transition section 216: Differential lock 218: Spring Load characteristic curve 220: first pressing member 224: pressing pin 226: ball cam mechanism 230: holding portion 232: drive gear 234: fixed cam plate 236: ball cam groove 238: arm portion 240: rotating cam plate 242: ball cam groove 244: fan shape Gear 246: Ball 250: Guide portion 252, 254, 256, 258, 259: Oil passage 260: Spacer 310: Input gear 324: Propeller shaft 326: Bevel gear 328: Output pinion 336: Drive gear 378: Rear wheel driving force transmission section 512: Chi Nberuto mechanism 558: the outer ring portion 560: fluid coupling 562: switching mechanism 564,566,568: teeth 572: shift shaft 574: front-wheel drive shaft

Claims (8)

A four-wheel drive for transmitting a driving force to the first driving wheel and the second driving wheel; a four-wheel driving for inputting a driving force from a power source and outputting the driving force to the first driving wheel and the second driving wheel; In a drive transmission device for a four-wheel drive vehicle capable of switching between two-wheel drive for transmitting drive force to only one drive wheel,
A first clutch mechanism for controlling a differential limit of the central differential;
A second clutch mechanism capable of connecting / disconnecting output transmission to the second driving wheel driving force transmission system of the central differential;
A driving force transmission device for a four-wheel drive vehicle.
The driving force transmission device for a four-wheel drive vehicle according to claim 1,
A driving force transmission device for a four-wheel drive vehicle, comprising a clutch drive mechanism for driving both the first clutch mechanism and the second clutch mechanism.
The driving force transmission device for a four-wheel drive vehicle according to claim 1,
A driving force transmission device for a four-wheel drive vehicle, comprising a fastening spring that constantly presses the second clutch mechanism in the fastening direction.
The driving force transmission device for a four-wheel drive vehicle according to claim 1,
When switching from four-wheel drive to two-wheel drive, engagement of the first clutch mechanism is started simultaneously with completion of disengagement of the second clutch mechanism.
The driving force transmission device for a four-wheel drive vehicle according to claim 1,
When switching from four-wheel drive to two-wheel drive, engagement of the first clutch mechanism is started before completion of disengagement of the second clutch mechanism.
The driving force transmission device for a four-wheel drive vehicle according to claim 1,
A connecting / disconnecting mechanism capable of connecting / disconnecting the second drive wheel differential device and either one or both of the left and right second drive wheel drive shafts;
During two-wheel drive, the drag torque of the second clutch mechanism is made smaller than the rotational resistance of the second driving wheel driving force transmission section from the second clutch mechanism to the connection / disconnection mechanism, and the second drive is performed by the connection / disconnection mechanism. For a four-wheel drive vehicle characterized in that the rotation of the second drive wheel drive force transmission section is stopped by disconnecting the connection between the wheel differential device and one or both of the left and right second drive wheel drive shafts. Driving force transmission device.
The drive force transmission device for a four-wheel drive vehicle according to claim 6, wherein the second clutch mechanism includes:
A plurality of clutch plates displaceable in the axial direction of the second clutch mechanism;
A driving force transmission device for a four-wheel drive vehicle, comprising: a lubricating oil limiting mechanism for stopping or limiting the supply of lubricating oil to the clutch plate when the second clutch mechanism is released.
The drive force transmission device for a four-wheel drive vehicle according to claim 6, wherein the second clutch mechanism includes:
A plurality of clutch plates displaceable in the axial direction of the second clutch mechanism;
A driving force transmission device for a four-wheel drive vehicle, comprising a spacer that biases the clutch plates in a direction to increase the interval between the clutch plates.

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