JP2016199088A - Control device of four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a four-wheel drive vehicle that comprises two connection/disconnection mechanisms which are released during two-wheel driving and can suppress corotation of a rotational element between the two connection/disconnection mechanisms during the two-wheel driving.SOLUTION: In a state where a clutch 50 for driving front wheels and a front-side clutch 36 are disconnected, a clutch hub 76 rotates integrally with a rear-wheel output shaft 44, and an inner hub 79, a clutch drum 78, friction plates 80 and plates 81 are brought into non-rotating states. Therefore, the friction plates 80 and the plates 81 do not relatively rotate, so that dragging torque caused by friction is generated exclusively between the clutch hub 76 and one of plates 81 adjacent to the clutch hub 76. This allows the dragging torque to be reduced remarkably in comparison with when dragging torque is generated between a plurality of friction plates 80 and plates 81 which are laminated with each other, improving fuel economy.SELECTED DRAWING: Figure 3

Description

  The present invention relates to control of a four-wheel drive vehicle including a connection / disconnection mechanism that switches between two-wheel drive travel and four-wheel drive travel.

  First provided on a power transmission path between an input rotation member connected to a main drive wheel provided in a vehicle so as to transmit power and an output rotation member connected to a sub drive wheel so as to transmit power. There is known a four-wheel drive vehicle including a connection / disconnection mechanism and a second connection / disconnection mechanism on a power transmission path between the output rotation member and the auxiliary drive wheel. For example, in the four-wheel drive vehicle of Patent Document 1, the transfer 5 is provided with the 2-4 switching mechanism 7 configured by a meshing clutch that connects and disconnects between the differential case 39 and the propeller shaft. Is provided with a clutch mechanism 71 composed of a multi-plate clutch that connects and disconnects between the outer case 65 and the inner case 67. In the four-wheel drive vehicle of Patent Document 1, the connection between the 2-4 switching mechanism 7 and the clutch mechanism 71 is canceled by releasing the connection between the 2-4 switching mechanism 7 and the clutch mechanism 71 during two-wheel drive traveling. The drag (rotation) of the rotating member (propeller shaft 21 or the like) constituting the power transmission path is suppressed to improve fuel efficiency.

JP 2002-370557 A

  However, in the above-described four-wheel drive vehicle of Patent Document 1, since the clutch mechanism 71 is constituted by a frictional multi-plate clutch, even if the clutch mechanism 71 is released, the clutch mechanism 71 is configured alternately. Drag torque is generated between the plurality of laminated friction plates and the plurality of plates due to the viscosity of oil in the clutch mechanism 71. As a result, there is a problem that even if the clutch mechanism 71 is released, the propeller shaft 21 and the like are rotated, and the effect of improving fuel consumption is reduced.

  The present invention has been made in the background of the above circumstances, and its object is to provide an input rotating member connected to the main drive wheel so as to be able to transmit power, and a power transmission member to the sub drive wheel. A first connecting / disconnecting mechanism provided on the power transmission path between the output rotating member and the output rotating member coupled to transmit power, and a power transmission path between the power transmission member and the auxiliary driving wheel. It is an object of the present invention to provide a control device for a four-wheel drive vehicle that can suppress accompanying movement that occurs during two-wheel drive traveling in a four-wheel drive vehicle equipped with a two-connection mechanism.

  In order to achieve the above object, the gist of the first invention is that: (a) an input rotating member connected to the main drive wheel so as to be able to transmit power and rotating about an axis; An output rotating member that is coupled so as to be able to transmit power and rotates about the same axis as the input rotating member, and a first connection / disconnection provided on a power transmission path between the input rotating member and the output rotating member In a four-wheel drive vehicle configured to include a mechanism and a second connection / disconnection mechanism provided on a power transmission path between the power transmission member and the sub drive wheel, (b) the first A control device for a four-wheel drive vehicle that controls a driving state of a vehicle by switching a connection state of a connection / disconnection mechanism and the second connection / disconnection mechanism, and (c) the first connection / disconnection mechanism includes the input A hub connected to the rotating member so as to be able to transmit rotation; and (d) the output A drum that is connected to the rolling member so as to be able to transmit rotation; (e) an inner hub disposed on the inner peripheral side of the drum so as to be rotatable relative to the hub; and (f) an outer peripheral surface of the inner hub that is not relatively rotatable. And a plurality of friction plates that are movably engaged in the axial direction, and (g) are non-rotatable relative to the inner peripheral surface of the drum and are movably engaged in the axial direction and alternately with the friction plates. A plurality of stacked plates; (h) a piston that presses the plurality of friction plates and plates in the axial direction; and (i) a non-rotatable engagement with the inner hub at all times. A sleeve that is movably provided at an axial position that engages with the hub and that is biased to a position that engages with the hub in conjunction with the piston, and (j) The first connecting / disconnecting machine by controlling the magnitude of the pressing force (K) the control device is configured such that (l) the first connecting / disconnecting mechanism and the second connecting / disconnecting mechanism are disconnected in a two-wheel drive traveling state. When connecting the one connecting / disconnecting mechanism, (m) operating the piston to press the friction plate and the plate, and determining that the rotational speeds of the drum and the hub are synchronized, When the transmission torque is reduced and the rotation speed of the drum is reduced, it is determined that the sleeve and the hub are not engaged, and (n) even if the transmission torque of the first connecting / disconnecting mechanism is reduced, When the rotational speed of the drum does not decrease, it is determined that the sleeve and the hub are engaged.

  According to the control device for a four-wheel drive vehicle of the first invention, in the four-wheel drive vehicle configured as described above, the hub is input when the first connecting / disconnecting mechanism and the second connecting / disconnecting mechanism are disconnected. The inner hub, the drum, the friction plate, and the plate rotate in unison with the rotating member. Therefore, the friction plate and the plate do not rotate relative to each other, and a drag torque due to friction is generated only between the hub and one plate adjacent to the hub. As a result, the drag torque is greatly reduced as compared with the case where drag torque is generated between the plurality of friction plates and the plates stacked on each other, thereby improving fuel efficiency.

  In addition, since the piston moves in the axial direction and presses the friction plate and the plate, a frictional force is generated between the hub and one plate adjacent to the hub. And the relative rotational speed gradually decreases. Since the drum, the inner hub, and the sleeve rotate integrally, the sleeve and the hub can be engaged when the rotation speeds of the drum and the hub are synchronized. At this time, the sleeve is moved to a position where the sleeve engages with the hub in conjunction with the piston, and the sleeve and the hub are engaged with each other, whereby the hub and the inner hub are connected via the sleeve.

  Here, when the rotational speeds of the drum and the inner hub are synchronized and moved in the axial direction toward the position where the sleeve engages with the hub in conjunction with the piston, the tip of the engagement tooth of the sleeve and the engagement tooth of the hub There is a possibility that the tip of the contactor will come into contact and will not be normally engaged (not engaged). In this state, if torque distribution control of the front and rear wheels is performed by adjusting the transmission torque of the first connecting / disconnecting mechanism, a desired torque distribution cannot be obtained, or sliding engagement between the engagement teeth of the sleeve and the hub may occur. There is a possibility of causing a decrease in durability.

  In contrast, when the electronic control unit determines that the rotation speeds of the drum and the hub are synchronized, the electronic control unit decreases the transmission torque of the first connecting / disconnecting mechanism. At this time, when the sleeve and the hub are engaged, the rotational speed of the drum does not decrease even if the transmission torque decreases, and the relative rotational speed between the drum and the hub does not increase. On the other hand, when the sleeve and the hub are not normally engaged, when the transmission torque of the first connecting / disconnecting mechanism decreases, the rotational speed of the drum decreases and the relative rotational speed of the drum and hub also increases. Therefore, the electronic control unit reduces the transmission torque of the first connecting / disconnecting mechanism, and when the rotational speed of the drum decreases at this time, or when the relative rotational speed of the drum and the hub increases, the sleeve and the hub Are not engaged, and if the rotational speed of the drum does not decrease or the relative rotational speed does not increase, it can be determined that the sleeve and the hub are engaged.

  Further, the gist of the second invention is that, in the control device for a four-wheel drive vehicle of the first invention, the sleeve and the hub are not engaged when the transmission torque of the first connecting / disconnecting mechanism is reduced. If it is determined that the transmission is correct, the transmission torque of the first connecting / disconnecting mechanism is increased again. As described above, when it is determined that the sleeve and the hub are disengaged after the transmission torque of the first connection / disconnection mechanism is reduced, the transmission torque of the first connection / disconnection mechanism is increased again. The rotational speed is again synchronized, at which time the sleeve and hub can be engaged. Here, when the rotation speeds of the hub and the drum are synchronized, the transmission torque is reduced again, and it is determined again whether or not the sleeve and the hub are engaged. At this time as well, if it is determined that the sleeve and the hub are disengaged, the transmission torque of the first connecting / disconnecting mechanism is increased, and the rotation synchronization and the engagement determination due to the increase of the transmission torque are performed. In this manner, the rotation synchronization between the hub and the drum and the engagement determination after the rotation synchronization are repeatedly executed until it is determined that the sleeve and the hub are engaged. Can be judged.

  Further, the gist of the third invention is that in the control device for a four-wheel drive vehicle of the first invention or the second invention, when switching from two-wheel drive travel to four-wheel drive travel, the sleeve, the hub, After the engagement is determined, the second connecting / disconnecting mechanism is connected. In this way, in the state where the sleeve and the hub are engaged, the rotating element that constitutes the power transmission path between the output rotating member and the second connecting / disconnecting mechanism is rotated, so that the second connecting / disconnecting state is achieved. The rotational speeds of the two rotating elements connected by the mechanism are synchronized, and the second connecting / disconnecting mechanism can be connected.

  According to a fourth aspect of the present invention, there is provided a control device for a vehicle connecting / disconnecting mechanism according to the third invention, comprising: a display device that indicates a driving state of the four-wheel drive vehicle; It is characterized by displaying that the vehicle is in a four-wheel drive running state after the connection of the two-connection mechanism is determined. In this way, since the display device indicates that the vehicle is in the four-wheel drive traveling state when the vehicle is surely switched to the four-wheel drive traveling, it is possible to prevent the actual drive state from being different from the display drive state. it can.

It is a figure explaining the schematic structure of the four-wheel drive vehicle to which this invention is applied, and is a figure explaining the principal part of the control system for the various controls in a vehicle. FIG. 2 is a skeleton diagram illustrating a schematic configuration of the transfer of FIG. 1. FIG. 3 is an enlarged view of a main part for explaining the configuration of a clutch mechanism used for switching between a two-wheel drive running state and a four-wheel drive running state in the transfer of FIG. 2, and shows a disconnected state of the clutch mechanism. FIG. 3 is an enlarged view of a main part for explaining a configuration of a clutch mechanism used for switching between a two-wheel drive running state and a four-wheel drive running state in the transfer of FIG. 2, and showing an engaged state of the clutch mechanism. . It is a functional block diagram explaining the principal part of the control function of the electronic control apparatus of FIG. It is a flowchart explaining the principal part of control action of the electronic controller of FIG. It is a time chart which shows the operation result by the control operation of the electronic control unit of FIG. It is a flowchart explaining the principal part of the control action of the electronic control apparatus corresponding to the other Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a diagram illustrating a schematic configuration of a four-wheel drive (4WD) vehicle 10 to which the present invention is applied, and also illustrates a main part of a control system for various controls in the vehicle 10. In FIG. 1, a vehicle 10 includes an engine 12 as a driving force source, left and right front wheels 14L and 14R (referred to as front wheels 14 unless otherwise specified), and left and right rear wheels 16L and 16R (respectively referred to as rear wheels unless otherwise specified). 16), a power transmission device 18 for transmitting the power of the engine 12 to the front wheel 14 and the rear wheel 16, respectively. The rear wheel 16 that functions as a main drive wheel is a main drive wheel that serves as a drive wheel during two-wheel drive (2WD) travel and four-wheel drive (4WD) travel. The front wheels 14 functioning as auxiliary driving wheels are auxiliary driving wheels that are driven wheels when traveling in 2WD and are driving wheels when traveling in 4WD. Accordingly, the vehicle 10 is a four-wheel drive vehicle based on a front engine rear wheel drive (FR).

  The power transmission device 18 includes a transmission 20 connected to the engine 12, a transfer 22 that is a front and rear wheel power distribution device connected to the transmission 20, a front propeller shaft 24 and a rear propeller shaft 26 connected to the transfer 22, respectively. Front wheel differential gear device 28 connected to the front propeller shaft 24, rear wheel differential gear device 30 connected to the rear propeller shaft 26, left and right front wheel axles 32L connected to the front wheel differential gear device 28, 32R (referred to as front wheel axle 32 unless otherwise specified), left and right rear wheel axles 34L and 34R (referred to as rear wheel axle 34 unless otherwise specified), etc. ing. In the power transmission device 18 configured as described above, the power of the engine 12 transmitted to the transfer 22 via the transmission 20 is transmitted from the transfer 22 to the rear propeller shaft 26, the rear wheel differential gear device 30, and the rear wheel. The power is transmitted to the rear wheel 16 via the power transmission path on the rear wheel side such as the axle 34. Further, a part of the power of the engine 12 transmitted to the rear wheel 16 side is distributed to the front wheel 14 side by the transfer 22, and the front wheels such as the front propeller shaft 24, the front wheel differential gear device 28, the front wheel axle 32, and the like. The power is transmitted to the front wheels 14 sequentially through the power transmission path on the side.

  The front wheel differential gear device 28 includes a front side clutch 36 on the front wheel axle 32R side (that is, between the front wheel differential gear device 28 and the front wheel 14R). The front side clutch 36 is an electrically (electromagnetic) controlled dog clutch (that is, meshing) that connects or disconnects the power transmission path between the front wheel differential gear device 28 and the front wheel 14R according to the traveling state of the vehicle. Type clutch). The front side clutch 36 may further include a synchronization mechanism (synchronization mechanism). The front side clutch 36 corresponds to the second connecting / disconnecting mechanism of the present invention.

  FIG. 2 is a skeleton diagram illustrating a schematic configuration of the transfer 22. In FIG. 2, the transfer 22 includes a transfer case 40 as a non-rotating member. In the transfer case 40, the transfer 22 includes an input shaft 42, a rear wheel output shaft 44 that outputs power to the rear wheel 16 as the main drive wheel, and a drive side that outputs power to the front wheel 14 as the auxiliary drive wheel. A sprocket 46, a high / low switching mechanism 48 serving as a sub-transmission for shifting the rotation of the input shaft 42 and transmitting it to the rear wheel side output shaft 44, and a transmission torque transmitted from the rear wheel side output shaft 44 to the drive side sprocket 46 A front wheel drive clutch 50 as a multi-plate clutch to be adjusted is provided around a common axis C1 (of the input shaft 42 and the rear wheel output shaft 44). In the transfer case 40, the transfer 22 has a common front wheel side output shaft 52 and a driven sprocket 54 provided integrally with the front wheel side output shaft 52 (the front propeller shaft 24 and the front wheel side output shaft). 52) and a front wheel drive chain 56 for connecting the drive side sprocket 46 and the driven side sprocket 54, the rear wheel side output shaft 44, and the drive side sprocket 46 integrally. A differential lock mechanism 58 is provided as a dog clutch to be connected. In this embodiment, the front wheel drive clutch 50 corresponds to the first connecting / disconnecting mechanism of the present invention, the rear wheel side output shaft 44 corresponds to the input rotation member of the present invention, and the drive side sprocket 46 corresponds to the output rotation of the present invention. It corresponds to the member.

  The input shaft 42 is connected to an output rotating member (not shown) of the transmission 20 via a spline fitting joint or the like, and is driven to rotate by receiving the driving force transmitted from the engine 12 via the transmission 20. It is done. The rear wheel side output shaft 44 is connected to the left and right rear wheels 16 functioning as main drive wheels via the rear propeller shaft 26, the rear wheel differential gear device 30, the left and right rear wheel axles 34 and the like so as to be able to transmit power. Yes. The drive-side sprocket 46 is a sub-drive wheel via a front-wheel drive chain 56, a driven sprocket 54, a front propeller shaft 24, a front-wheel differential gear device 28, left and right front-wheel axles 32, a front-side clutch 36, and the like. It is connected to the left and right front wheels 14 so that power can be transmitted. The front wheel side output shaft 52 is connected to the front propeller shaft 24. The front propeller shaft 24 corresponds to the power transmission member of the present invention.

  The transfer 22 configured in this manner cuts off torque transmitted to the drive side sprocket 46, for example, and transmits power transmitted from the transmission 20 only to the rear wheels 16 to enter a two-wheel drive running state, or Power is transmitted to the drive-side sprocket 46, and torque is distributed to each of the front wheels 14 and the rear wheels 16 to achieve a four-wheel drive running state. In addition, the transfer 22 establishes, for example, either a high-speed gear stage (high-speed gear stage) H or a low-speed gear stage (low-speed gear stage) L to reduce or reduce the rotation from the transmission 20 as it is. Transmit to the subsequent stage.

  The high / low switching mechanism 48 includes a single pinion type planetary gear device 60 and a high / low sleeve 62. The planetary gear device 60 is disposed substantially concentrically with the sun gear S connected to the input shaft 42 so as not to rotate relative to the axis C1, and is connected to the transfer case 40 so as not to rotate about the axis C1. And a carrier CA that supports the sun gear S and a plurality of pinion gears P meshing with the ring gear R so as to be capable of rotating and revolving around the sun gear S. Therefore, the rotational speed of the sun gear S is constant with respect to the input shaft 42, and the rotational speed of the carrier CA is decelerated with respect to the input shaft 42. High side gear teeth 64 are fixed to the inner peripheral surface of the sun gear S, and low side gear teeth 66 having the same diameter as the high side gear teeth 64 are fixed to the carrier CA. The high-side gear teeth 64 are spline teeth that are involved in the establishment of the high-speed side gear stage H that outputs a rotation at the same speed as the input shaft 42. The low-side gear teeth 66 are spline teeth that are involved in the establishment of the low-speed side gear stage L that outputs rotation at a lower speed side than the high-side gear teeth 64. The high / low sleeve 62 is spline-fitted to the rear wheel side output shaft 44 so as to be relatively movable in a direction parallel to the axis C1, and is integrally provided adjacent to the fork connecting portion 62a and the fork connecting portion 62a. The rear wheel side output shaft 44 has outer teeth 62b that mesh with the high gear teeth 64 and the low gear teeth 66, respectively, by movement in the direction parallel to the axis C1. The high side gear teeth 64 and the outer peripheral teeth 62b mesh with each other, whereby the rotation of the input shaft 42 and the rotation at the same speed are transmitted to the rear wheel side output shaft 44, and the low side gear teeth 66 and the outer peripheral teeth 62b mesh with each other. The rotation decelerated with respect to the rotation of the input shaft 42 is transmitted to the rear wheel output shaft 44. The high side gear teeth 64 and the high / low sleeve 62 function as a high speed side gear stage clutch that forms the high speed side gear stage H, and the low side gear teeth 66 and the high / low sleeve 62 form the low speed side gear stage L. Functions as a low speed gear clutch. The high / low switching mechanism 48 enters a power transmission cut-off state (neutral state) when the high / low sleeve 62 does not mesh with either the high side gear teeth 64 or the low side gear teeth 66, and the high speed side gear stage H and the low speed side gear stage. When the gear stage is switched with L, it is switched after passing through this power transmission enabled state.

  The diff lock mechanism 58 is spline-fitted to a lock tooth 68 fixed on the inner peripheral surface of the drive side sprocket 46 and a rear wheel side output shaft 44 so as to be relatively movable in a direction parallel to the axis C1. An outer peripheral tooth 70a meshing with the lock tooth 68 by movement in a parallel direction has a lock sleeve 70 fixed to the outer peripheral surface. In the transfer 22, in the engaged state of the differential lock mechanism 58 in which the outer peripheral teeth 70 a of the lock sleeve 70 and the lock teeth 68 are engaged, the rear wheel side output shaft 44 and the drive side sprocket 46 are integrally rotated, A differential lock state is formed.

  The high / low sleeve 62 is provided in a space on the drive side sprocket 46 side with respect to the planetary gear device 60. The lock sleeve 70 is separately provided adjacent to the high / low sleeve 62 in the space between the high / low switching mechanism 48 and the drive side sprocket 46. The transfer 22 includes a first spring 72 between the high / low sleeve 62 and the lock sleeve 70 that urges the high / low sleeve 62 and the lock sleeve 70 toward the side away from each other. The transfer 22 abuts against the convex portion 44 a of the rear wheel side output shaft 44 and the lock sleeve 70 between the drive side sprocket 46 and the lock sleeve 70 and biases the lock sleeve 70 away from the lock teeth 68. A second spring 74 is provided. The convex portion 44 a is a flange portion of the rear-wheel-side output shaft 44 that protrudes toward the lock tooth 68 in the radially inner space of the drive-side sprocket 46. The high-side gear teeth 64 are provided at positions farther from the lock sleeve 70 than the low-side gear teeth 66 when viewed in the direction parallel to the axis C1. The outer peripheral teeth 62b of the high / low sleeve 62 mesh with the high side gear teeth 64 on the side where the high / low sleeve 62 is separated from the lock sleeve 70 (left side in FIGS. 2 and 3), and the side where the high / low sleeve 62 approaches the lock sleeve 70 ( In FIG. 2 and FIG. The outer peripheral teeth 70a of the lock sleeve 70 mesh with the lock teeth 68 on the side where the lock sleeve 70 approaches the drive side sprocket 46 (right side in FIGS. 2 and 3). Accordingly, the outer peripheral teeth 70 a of the lock sleeve 70 mesh with the lock teeth 68 at a position where the high / low sleeve 62 meshes with the low-side gear teeth 66.

  The front-wheel drive clutch 50 is on a power transmission path between the rear-wheel output shaft 44 and the drive-side sprocket 46 and is switched between high and low with respect to the outer periphery of the rear-wheel-side output shaft 44 and the drive-side sprocket 46. It is arranged on the opposite side to the mechanism 48. Is provided. As shown in FIGS. 3 and 4, the front-wheel drive clutch 50 includes a clutch hub 76 that is spline-fitted to the rear-wheel output shaft 44 so as to be relatively non-rotatable, and is connected to be able to transmit rotation, and a drive-side sprocket. 46, a clutch drum 78 connected to be able to transmit rotation, a cylindrical inner hub 79 disposed on the inner peripheral side of the clutch drum 78 so as to be rotatable relative to the clutch hub 76, and an inner peripheral portion of the inner hub 79. A plurality of disk-like friction plates 80 that are relatively non-rotatable to the outer circumferential surface of the clutch drum 78 and that are movable in the axial direction, and the outer circumferential portion is relatively unrotatable to the inner circumferential surface of the clutch drum 78 and is axial And a plurality of disk-like plates 81 arranged alternately with the friction plates 80, and the plurality of friction plates 80 and the plurality of plates 81 are pushed in the axial direction. The piston 82 is engaged with the inner hub 79 so as not to rotate relative to the inner hub 79 at all times, and is movably provided in an axial position where the clutch hub 76 is engaged. It is a wet multi-plate friction clutch mechanism capable of adjusting the transmission torque by controlling the magnitude of the pressing force of the piston 82, and comprising a sleeve 83 biased to the engaging position. The clutch hub 76 corresponds to the hub of the present invention, and the clutch drum 78 corresponds to the drum of the present invention.

  The front-wheel drive clutch 50 is moved to the non-pressing side (the right side in FIGS. 2 and 3), which is the side where the piston 82 moves away from the driving-side sprocket 46 in the axis C1 direction (hereinafter referred to as the axial direction). When the friction plate 80 and the plate 81 are not pressed, the release state is established. On the other hand, the front-wheel drive clutch 50 is moved to the pressing side (the left side in FIGS. 2 and 3) that is close to the driving-side sprocket 46 in the direction of the axis C <b> 1 to press the friction plate 80 and the plate 81. In this state, the transmission torque of the front wheel drive clutch 50 is adjusted according to the pressing force of the piston 82, and the slip state or the engaged state is established.

  The clutch hub 76 has a disk shape extending in the radial direction, and an inner peripheral portion thereof is spline-fitted to the rear wheel output shaft 44 so that the clutch hub 76 is not rotatable relative to the rear wheel output shaft 44. . That is, the clutch hub 76 is rotated integrally with the rear wheel output shaft 44. A bottomed cylindrical clutch drum 78 is disposed so as to cover the clutch hub 76 and open in one axial direction. The bottomed portion of the clutch drum 78 is disposed on the drive side sprocket 46 side in the axial direction and is connected to the drive side sprocket 46. A plurality of plates 81 are spline-fitted on the inner peripheral surface of the portion of the clutch drum 78 formed in a cylindrical shape so as not to rotate relative to the clutch drum 78 and to move relative to the axial direction. .

  An inner hub 79 that is rotatable relative to the clutch hub 76 is disposed on the inner peripheral side of the clutch drum 78. The inner hub 79 is formed in a cylindrical shape, and a plurality of friction plates 80 are spline-fitted to the outer peripheral surface of the inner hub 79 so as not to rotate relative to the inner hub 79 and to be relatively movable in the axial direction. Yes. The friction plates 80 and the plates 81 are alternately stacked in the axial direction, and the plurality of friction plates 80 and the plurality of plates 81 constitute a friction engagement element 89 of the front-wheel drive clutch 50. A piston 82 is disposed on the back side of the drive side sprocket 46 in the axial direction of the friction engagement element 89.

  The piston 82 is configured to be movable in the axial direction. When the piston 82 is moved toward the drive side sprocket 46 in the axial direction, the piston 82 presses the friction engagement element 89 (the friction plate 80 and the plate 81). It becomes. The mechanism (piston drive device PD1) that moves the piston 82 in the axial direction will be described later.

  A cylindrical sleeve 83 is disposed on the inner peripheral side of the inner hub 79. Engagement teeth 83 a are formed on the outer peripheral surface of the sleeve 83. Further, on the inner peripheral portion of the inner hub 79, engagement teeth 79a that are always engaged with the engagement teeth 83a of the sleeve 83 are formed. Further, the clutch hub 76 is formed with an engagement tooth 76a adjacent to the engagement tooth 79a in the axial direction and at the same position as the engagement tooth 79a in the radial direction. The engagement teeth 76a are configured to be engageable with the engagement teeth 83a of the sleeve 83. When the sleeve 83 moves toward the drive side sprocket 46 in the axial direction, the engagement teeth 83a of the sleeve 83 are moved to the clutch hub 76. It engages with the engaging teeth 76a. At this time, the clutch hub 76 is connected to the inner hub 79 via the sleeve 83, and the clutch hub 76, the inner hub 79, and the sleeve 83 are integrally rotated.

  A fourth spring 85 is interposed between the piston 82 and the sleeve 83 in the axial direction on the inner peripheral side of the inner hub 79 in a loaded state. A fifth spring 87 having a smaller biasing force than the fourth spring 85 is interposed between the sleeve 83 and the inner hub 79 in the axial direction on the inner peripheral side of the cylindrical portion of the inner hub 79 in a loaded state. Has been. As a result, the front-wheel drive clutch 50 is disengaged (non-engaged), and the piston 82 is positioned at a position (non-engagement position) away from the friction engagement element 89 in the axial direction. The sleeve 83 is positioned away from the drive-side sprocket 46 in the axial direction by the urging force of the five springs 87, that is, in the non-engagement position of the sleeve 83 (with the hub 76). Further, the urging force of the fourth spring 85 urges the piston 82 to the non-actuated position that moves away from the drive-side sprocket 46 in the axial direction.

  2 and 3 show the released state (non-engaged state). In this state, since the engagement teeth 76a of the clutch hub 76 and the engagement teeth 83a of the sleeve 83 are not engaged, the clutch hub 76 and the inner hub 79 are relatively rotated, and the clutch drum 78 and the inner hub 79 are rotated. Are not relatively rotated, and there is no drag between the plurality of friction plates 80 and the plates 81 that are alternately engaged with the clutch drum 78 and the inner hub 79 so as not to be relatively rotatable, and the clutch hub 76 and the clutch hub 76 Since only slight drag occurs between the adjacent plates 81, the drag torque of the front-wheel drive clutch 50 is significantly reduced. Thus, in traveling in the two-wheel drive traveling state in which the front side clutch 36 and the front wheel drive clutch 50 are disconnected, the drive side sprocket 46 to the front wheel drive chain 56, the driven side sprocket 54, the front wheel side output shaft 52, Since the front propeller shaft 24 and the front-wheel differential gear device 28 are in a non-rotating state, the front-propeller shaft 24 is connected in a disengaged state, and the fuel consumption of the vehicle running in the two-wheel drive running state is greatly increased. Improved.

  In the disengaged state of the front wheel drive clutch 50 and the disengaged state of the differential lock mechanism 58 in which the outer peripheral teeth 70a of the lock sleeve 70 and the lock teeth 68 are not engaged with each other, the transfer 22 moves between the rear wheel side output shaft 44 and the drive side sprocket 46. The power transmission path therebetween is cut off, and the power transmitted from the transmission 20 is transmitted only to the rear wheels 16. The transfer 22 distributes the power transmitted from the transmission 20 to each of the front wheels 14 and the rear wheels 16 when the front wheel drive clutch 50 is in a slip state or an engaged state. In the slip state of the front-wheel drive clutch 50, the transfer 22 is allowed to have a rotational differential between the rear-wheel output shaft 44 and the drive-side sprocket 46, thereby forming a differential state (non-center differential lock state). . When the front wheel driving clutch 50 is engaged, the transfer 22 is rotated integrally with the rear wheel side output shaft 44 and the driving side sprocket 46 to form a center differential lock state. The front-wheel drive clutch 50 can continuously change the torque distribution between the front wheels 14 and the rear wheels 16, for example, between 0: 100 and 50:50 by controlling the transmission torque.

  The transfer 22 is a device that operates the high / low switching mechanism 48, the front wheel drive clutch 50, and the differential lock mechanism 58, and a screw that converts the rotational motion of the motor 84 and the motor 84 into linear motion via a worm gear 90 that is a speed reducer. A mechanism 86 and a transmission mechanism 88 for transmitting the linear motion force of the screw mechanism 86 to the high / low switching mechanism 48, the front wheel drive clutch 50, and the differential lock mechanism 58 are further provided. The piston drive device PD1 includes the motor 84, the worm gear 90, and the screw mechanism 86.

  When the front wheel drive clutch 50 is engaged to change from the two-wheel drive running state to the four-wheel drive running state, the piston 82 is biased by the fourth spring 85 by the motor 84, the worm gear 90, and the screw mechanism 86. In addition, it is moved forward in the axial direction toward the drive side sprocket 46 against the urging force of the fifth spring 87. At this time, the piston 82 presses the friction engagement element 89, and the sleeve 83 is urged toward the drive side sprocket 46 in the axial direction by the fourth spring 85 in conjunction with the movement of the piston 82. That is, the sleeve 83 is moved to the drive side sprocket 46 side in the axial direction in conjunction with the piston 82. When the friction engagement element 89 is pressed by the piston 82 and the rotation speeds of the clutch hub 76 and the sleeve 83 are synchronized (rotation synchronization), the engagement teeth 83 a of the sleeve 83 are engaged with the engagement teeth of the clutch hub 76. 76a is engaged. Further, the piston 82 is moved forward to press the friction engagement element 89, whereby the front wheel drive clutch 50 is engaged by the frictional force between the friction plate 80 and the plate 81.

  In the forward movement process of the piston 82, the engagement teeth 76 a of the clutch hub 76 and the engagement teeth 83 a of the sleeve 83 are not engaged when the rotational speeds of the clutch hub 76 and the sleeve 83 are not synchronized. At this time, the fourth spring 85 is compressed and deformed, and the movement of the sleeve 83 is prevented regardless of the forward movement of the piston 82. Thereafter, when the rotational speeds of the clutch hub 76 and the inner hub 79 are synchronized, the engagement teeth 83a of the sleeve 83 are engaged with the engagement teeth 76a of the clutch hub 76 by the elastic return force (biasing force) of the fourth spring 85. Until the sleeve 83 is moved in the axial direction. Accordingly, the clutch hub 76, the inner hub 79, and the sleeve 83 are engaged with each other. In this state, the clutch hub 76, the inner hub 79, and the sleeve 83 are integrally rotated, and power is transmitted with a transmission torque corresponding to the pressing force of the piston 82. FIG. 4 shows this state.

  The screw mechanism 86 is disposed around the same axis C1 as the rear-wheel-side output shaft 44, and a cylindrical screw member 92 indirectly connected to the motor 84 via a worm gear 90 provided in the transfer 22, A nut member 94 as a linear motion member connected to the screw shaft member 92 so as to be movable in a direction parallel to the axis C1 as the cylindrical screw member 92 rotates is provided. The screw mechanism 86 is a ball screw in which a cylindrical screw member 92 and a nut member 94 are operated via a large number of small-diameter balls 96. The worm gear 90 is a gear pair including a worm 98 formed integrally with the motor shaft of the motor 84, and a worm wheel 100 formed around the axis C1 and formed integrally with the cylindrical screw member 92. . For example, the rotation of the motor 84, which is a brushless motor, is decelerated and transmitted to the cylindrical screw member 92 via the worm gear 90. The screw mechanism 86 converts the rotation of the motor 84 transmitted to the cylindrical screw member 92 into a linear motion of the nut member 94.

  The transmission mechanism 88 is provided around another axis C3 parallel to the axis C1 of the cylindrical screw member 92, and is operatively connected to the nut member 94, and is fixed to the fork shaft 102. And a fork 104 connected to the high / low sleeve 62. The transmission mechanism 88 transmits the linear motion force of the nut member 94 in the screw mechanism 86 to the high / low sleeve 62 of the high / low switching mechanism 48 via the fork shaft 102 and the fork 104. A force is applied between the high / low sleeve 62 and the lock sleeve 70 via the first spring 72, and the lock sleeve 70 applies a force from the convex portion 44 a of the rear wheel side output shaft 44 via the second spring 74. Has been. Accordingly, the transmission mechanism 88 transmits the linear motion force of the nut member 94 in the screw mechanism 86 to the lock sleeve 70 of the differential lock mechanism 58 via the high / low sleeve 62. Therefore, the first spring 72 and the second spring 74 function as members that constitute part of the transmission mechanism 88.

  The screw mechanism 86 is disposed on the side opposite to the driving sprocket 46 with respect to the front wheel driving clutch 50. The piston 82 of the front-wheel drive clutch 50 is connected to the nut member 94 of the screw mechanism 86 so as not to be relatively movable in a direction parallel to the axis C1 and to be relatively rotatable around the axis C1. Therefore, the linear motion force of the nut member 94 in the screw mechanism 86 is transmitted to the friction engagement element 89 (friction plate 80, plate 81) of the front wheel drive clutch 50 via the piston 82. Therefore, the piston 82 is a pressing member that is connected to the nut member 94 and presses the friction engagement element 89 of the front wheel driving clutch 50, and also functions as a member that constitutes a part of the transmission mechanism 88. Thus, the transmission mechanism 88 transmits the linear motion force of the nut member 94 in the screw mechanism 86 to the friction engagement element 89 (friction plate 80, plate 81) of the front wheel drive clutch 50.

  The transmission mechanism 88 includes a connecting mechanism 106 that connects the nut member 94 and the fork shaft 102. The coupling mechanism 106 is disposed around the axis C3 so as to be slidable with the fork shaft 102 in a direction parallel to the axis C3, and the two flanged cylindrical members 108a, 108b, 2 provided at one end face each other. The cylindrical spacer 110 interposed between the two flanged cylindrical members 108a and 108b, the third spring 112 disposed on the outer peripheral side of the spacer 110, and the two flanged cylindrical members 108a and 108b are connected to the axis C3. A gripping member 114 that slidably grips in a parallel direction and a connecting member 116 that connects the gripping member 114 and the nut member 94 are provided. The gripping member 114 slides the flanged cylindrical members 108a and 108b on the fork shaft 102 by coming into contact with the flanges of the flanged cylindrical members 108a and 108b. The length of the collar in the state where the collars of the flanged cylindrical members 108 a and 108 b are in contact with the gripping member 114 is longer than the length of the spacer 110. Therefore, the state in which the scissors are in contact with the gripping member 114 is formed by the biasing force of the third spring 112.

  The fork shaft 102 is provided with stoppers 118a and 118b on the outer peripheral surface which make the flanged cylindrical members 108a and 108b non-slidable in the direction parallel to the axis C3. By making the flanged cylindrical members 108 a and 108 b non-slidable by the stoppers 118 a and 118 b, the transmission mechanism 88 causes the linear motion force of the nut member 94 to be changed from the high-low switching mechanism 48 via the fork shaft 102 and the fork 104. Can be communicated to.

  The outer peripheral teeth 70a of the lock sleeve 70 mesh with the lock teeth 68 at a position where the fork shaft 102 meshes the outer teeth 62b of the high / low sleeve 62 with the low gear gear 66 (referred to as a low gear position). The friction plate 80 of the front-wheel drive clutch 50 is pressed by the piston 82 at a position where the fork shaft 102 meshes the outer peripheral teeth 62b of the high / low sleeve 62 with the high side gear teeth 64 (referred to as a high gear position). It is not pressed by the piston 82 at the low gear position.

  At the high gear position of the fork shaft 102, the length between the flanges of the flanged cylindrical members 108a and 108b is changed between the length when the flanges are in contact with the gripping member 114 and the length of the spacer 110. Can do. Accordingly, the coupling mechanism 106 remains in the high gear position of the fork shaft 102, and between the position where the friction plate 80 of the front wheel drive clutch 50 is pressed by the piston 82 and the position where it is not pressed, Allows movement in parallel directions.

  The transfer 22 includes a gear position holding mechanism 120 that holds the high gear position of the fork shaft 102 and holds the low gear position of the fork shaft 102. The gear position holding mechanism 120 includes an accommodation hole 122 formed on the inner peripheral surface of the transfer case 40 on which the fork shaft 102 slides, a lock ball 124 accommodated in the accommodation hole 122, and an accommodation hole 122 accommodated in the lock. A locking spring 126 that biases the ball 124 toward the fork shaft 102, a recess 128 h that is formed on the outer peripheral surface of the fork shaft 102 and receives a part of the lock ball 124 at the high gear position of the fork shaft 102, and the fork shaft 102 And a recess 128l for receiving a part of the lock ball 124 in the low gear position. Each gear position of the fork shaft 102 is held by the gear position holding mechanism 120, so that each gear position of the fork shaft 102 is held even when the output from the motor 84 is stopped at each gear position.

  The transfer 22 includes a low gear position detection switch 130 that detects the low gear position of the fork shaft 102. The low gear position detection switch 130 is, for example, a ball-type contact switch. The low gear position detection switch 130 is fixed to a through hole 132 formed in the transfer case 40 at a position where the low gear position detection switch 130 contacts the fork shaft 102 moved to the low gear position. When the low gear position is detected by the low gear position detection switch 130, for example, an indicator for notifying the driver that the center differential lock state is in the low-speed gear stage L is lit.

  Returning to FIG. 1, the vehicle 10 is provided with an electronic control unit (ECU) 200 including a control device of the vehicle 10 that switches between a 2WD state and a 4WD state, for example. The electronic control device 200 includes a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like, for example. Various controls of the vehicle 10 are executed by performing signal processing. For example, the electronic control unit 200 executes output control of the engine 12, switching control of the driving state of the vehicle 10, and the like, and is configured separately for engine control, driving state control, and the like as necessary. The

  As shown in FIG. 1, the electronic control device 200 (control device) includes various sensors (for example, an engine rotation speed sensor 202, a motor rotation angle sensor 204, wheel speed sensors 206, an accelerator opening sensor) provided in the vehicle 10. 208, H range selection switch 210 for selecting the high-speed gear stage H by the driver's operation, 4WD selection switch 212 for selecting the 4WD state by the driver's operation, the center differential lock state is selected by the driver's operation Various actual values (for example, engine rotational speed Ne, motor rotational angle) based on detection signals from the differential lock selection switch 214, the output shaft rotational speed sensor 216 of the rear wheel output shaft 44, the rotational speed sensor 218 of the front propeller shaft 24, etc. θm, wheel speeds Nwfl and Nwfr of front wheels 14L and 14R and rear wheels 16L and 16R , Nwrl, Nwrr, accelerator opening θacc, H range request Hon which is a signal indicating that the H range selection switch 210 has been operated, 4WD request 4WDon which is a signal indicating that the 4WD selection switch 212 has been operated, diff lock selection LOCKon which is a signal indicating that the switch 214 has been operated, the rotational speed Nr of the rear wheel output shaft 44, the rotational speed Nf of the front propeller shaft 24, etc.) are supplied.

  As shown in FIG. 1, for example, an engine output control command signal Se for controlling the output of the engine 12, an operation command signal Sd for switching the state of the front clutch 36, and the rotation amount of the motor 84 are sent from the electronic control unit 200. A motor drive command signal Sm for controlling the vehicle, a signal Sw (see FIG. 5) indicating that the driving state of the vehicle 10 indicates two-wheel drive travel “2WD” or four-wheel drive travel “4WD”, and the like are used. Are output to the actuator of the front side clutch 36, the motor 84, the indicator 256 (see FIG. 5) functioning as a display device, and the like.

  In the vehicle 10 configured as described above, the movement amount (stroke) of the nut member 94 and the piston 82 is controlled by controlling the rotation amount of the motor 84. Driving the front wheel by driving the motor 84 by a predetermined amount of rotation from the position where the piston 82 contacts the friction plate 80 at the high gear position of the fork shaft 102 and moving the nut member 94 by a predetermined stroke to the non-pressing side. The position where the clutch 50 is in the disengaged state is the position for bringing the vehicle 10 into the 2WD traveling state in which only the rear wheel 16 is driven at the high speed side gear stage H. When the front-side clutch 36 is released at the H2 position, each rotating element (drive-side sprocket 46, drive-side sprocket 46,. No rotation is transmitted from the engine 12 side or the front wheel 14 side to the front wheel driving chain 56, the driven side sprocket 54, the front wheel side output shaft 52, the front propeller shaft 24, and the front wheel differential gear unit 28). Accordingly, during the 2WD traveling, each of these rotating elements stops rotating, the rotation of each rotating element is prevented, and traveling resistance is reduced.

  Further, in the high gear position of the fork shaft 102, the front wheel drive clutch 50 is slipped by controlling the amount of rotation of the motor 84 from the position where the piston 82 contacts the friction plate 80 and moving the nut member 94 to the pressing side. This position is a position for bringing the vehicle 10 into a 4WD traveling state in which power is transmitted to both the front wheels 14 and the rear wheels 16 at the high speed side gear stage H. In this H4 position, the torque distribution between the front wheels 14 and the rear wheels 16 is adjusted as necessary by controlling the transmission torque (torque capacity) of the front wheel drive clutch 50.

  As shown in FIG. 2, the position where the front wheel drive clutch 50 is engaged by controlling the amount of rotation of the motor 84 from the H4 position and further moving the nut member 94 to the pressing side is the vehicle 10. Is a position for setting the 4WD running state in the center differential lock state at the high speed side gear stage H.

  Further, at the low gear position of the fork shaft 102, the front wheel drive clutch 50 is disengaged and the differential lock mechanism 58 is engaged, so that the vehicle 10 is driven at 4 WD in the center differential lock state at the low speed gear stage L. It is a position for making a state.

  In the vehicle 10 configured as described above, when switching from 2-wheel drive travel to 4-wheel drive travel, the front wheel drive clutch 50 is first connected, and then the front side clutch 36 is connected. When the front-wheel drive clutch 50 is first connected, a rotating member (drive-side sprocket 46, front-wheel drive) that constitutes a power transmission path between the front-wheel drive clutch 50 and the front-side clutch 36 that has stopped rotating. The rotation is transmitted to the rotating elements connected by the front side clutch 36, and the connection of the front side clutch 36 is achieved. The rotation is transmitted to the chain 56, the driven side sprocket 54, the front wheel side output shaft 52, the front propeller shaft 24, etc. Is possible. Here, in the front-wheel drive clutch 50, when the friction engagement element 89 is pressed by the piston 82, the clutch hub 76 and the clutch hub 76 are in a state where the clutch hub 76 and the sleeve 83 are not engaged. A transmission torque is generated due to a frictional force between one adjacent plate 81. At this time, since the clutch drum 78, the inner hub 79, and the sleeve 83 fitted to the plate 81 are integrally rotated, the relative rotational speed between the clutch hub 76 and the clutch drum 78, the inner hub 79, and the sleeve 83 gradually increases. When the rotational speed of the clutch hub 76 and the sleeve 83 is synchronized, the sleeve 83 is moved toward the drive sprocket 46 in the axial direction by the elastic return force (biasing force) of the fourth spring 85, and the clutch hub 76 is engaged. The teeth 76a and the engagement teeth 83a of the sleeve 83 are engaged. Thereby, the clutch hub 76 and the sleeve 83 are engaged.

  However, even when the rotational speeds of the clutch hub 76 and the sleeve 83 are synchronized, the tip of the engagement tooth 76a and the tip of the engagement tooth 83a may contact each other and may not engage normally. If it is determined that the front-wheel drive clutch 50 is connected in such a state and the torque distribution control during the four-wheel drive traveling is executed, the desired torque distribution is not executed or the engagement teeth 76a and 83a are not executed. There is also a possibility of causing wear due to sliding between them.

  Therefore, when the front wheel drive clutch 50 is connected, the electronic control unit 200 executes control described below to determine whether or not the sleeve 83 and the clutch hub 76 are engaged. It has. FIG. 5 is a functional block diagram illustrating a main part of the control function of the electronic control device 200.

  The electronic control unit 200 functionally includes a switching control unit 250 that switches between two-wheel drive traveling and four-wheel drive traveling. The switching control unit 250 controls the amount of movement of the nut member 94 and the piston 82 by controlling the amount of rotation of the motor 84 based on the motor rotation angle Am. The amount of movement of the nut member 94 is the amount of movement of the fork shaft 102 in the direction of the axis C3 and the amount of movement of the piston 82 in the direction of the axis C1. Therefore, the switching control unit 250 performs the switching operation of the high / low switching mechanism 48 and the adjustment of the transmission torque (torque capacity) of the front wheel driving clutch 50 based on the motor rotation angle Am. The switching control unit 250 stores in advance the relationship between the motor rotation angle Am and the transmission torque of the front wheel drive clutch 50, and sets the motor rotation angle Am so that the transmission torque of the front wheel drive clutch 50 becomes a desired value. adjust.

  When switching from two-wheel drive running to four-wheel drive running, the switching control unit 250 executes control to connect the front wheel driving clutch 50 and then connect the front side clutch 36. When the front-wheel drive clutch 50 is connected, the switching control unit 250 executes synchronous control that controls the amount of movement of the piston 82 to synchronize the rotational speed Nhub of the clutch hub 76 and the rotational speed Ndrum of the clutch drum 78. The switching control unit 250 executes feedback control based on, for example, the relative rotational speed ΔN (= Nhub−Ndrum) between the rotational speed Nhub of the clutch hub 76 and the rotational speed Ndrum of the clutch drum 78.

  The synchronization determination unit 252 determines whether the rotational speeds of the clutch hub 76 and the clutch drum 78 are synchronized. In other words, the synchronization determination unit 252 determines whether or not the rotational speeds of the clutch hub 76 and the sleeve 83 are synchronized. The synchronization determination unit 252 detects the rotational speed Nhub of the clutch hub 76 and the rotational speed Ndrum of the clutch drum 78, and determines whether these relative rotational speeds ΔN (= Nhub−Ndrum) are equal to or less than a predetermined value α. Determine whether. When the relative rotational speed ΔN is equal to or less than the predetermined value α, the synchronization determination unit 252 determines that the synchronization has been completed. The predetermined value α is set to such a minute value that it is determined that the rotational speeds of the clutch hub 76 and the clutch drum 78 are synchronized. The rotational speed Nhub of the clutch hub 76 is the same as the rotational speed Nr of the rear wheel output shaft 44 detected by the output shaft rotational speed sensor 216 because the clutch hub 76 is connected to the rear wheel output shaft 44 so as not to be relatively rotatable. Match. The rotational speed Ndrum of the clutch drum 78 is obtained by multiplying the rotational speed Nf of the front propeller shaft 24 detected by the rotational speed sensor 218 by a predetermined constant. The predetermined constant is a constant for converting the rotational speed Nf of the front propeller shaft 24 into the rotational speed Ndrum of the clutch drum 78, and in this embodiment, between the driving side sprocket 46 and the driven side sprocket 54. The gear ratio set mechanically corresponds. When the synchronization determination unit 252 determines that the synchronization of the clutch hub 76 and the clutch drum 78 has been completed, the clutch hub 76 and the sleeve 83 are also synchronized. Normally, the clutch hub 76 is urged by the urging force of the fourth spring 85. And the sleeve 83 are engaged with each other.

  When the synchronization determination unit 252 determines that the rotation speeds of the clutch hub 76 and the clutch drum 78 are synchronized, the engagement determination unit 254 is executed. The engagement determination unit 254 determines whether or not the clutch hub 76 and the sleeve 83 are engaged by the urging force of the fourth spring 85 when the rotational speeds of the clutch hub 76 and the clutch drum 78 (sleeve 83) are synchronized. judge. The engagement determination unit 254 moves the piston 82 to the non-pressing side that is the side away from the friction plate 80 (2WD side), and the transmission torque (torque capacity) of the front wheel driving clutch 50 is set to a predetermined value β. To lower. The predetermined value β is such that the front propeller shaft 24 connected to the clutch drum 78 so as to be able to transmit power even when the transmission torque of the front-wheel drive clutch 50 is reduced with the clutch hub 76 and the sleeve 83 engaged. Is set to a value larger than zero so that the rotational speed Ndrum of the clutch drum 78 does not decrease due to the rotational resistance.

  Here, when the clutch hub 76 and the sleeve 83 are engaged, the rotation synchronization of the clutch hub 76 and the clutch drum 78 is maintained regardless of the decrease in torque capacity. That is, the relative rotational speed ΔN between the rotational speed Nhub of the clutch hub 76 and the rotational speed Ndrum of the clutch drum 78 is maintained below the predetermined value α without increasing beyond the predetermined value α. On the other hand, when the clutch hub 76 and the sleeve 83 are not engaged (non-engaged), when the piston 82 moves away from the friction engagement element 89, the clutch hub 76 and the inner hub 79 rotate relative to each other. At this time, in the friction engagement element 89, the friction surface for generating the transmission torque is only the friction surface between the clutch hub 76 and the single plate 81, and the front propeller shaft 24 and other front wheel drive clutches. Since the transmission torque for maintaining the rotational speeds of the rotary elements constituting the power transmission path between the clutch 50 and the front clutch 36 at the time of synchronization cannot be obtained, the rotational speed Ndrum of the clutch drum 78 is set to the clutch hub 76. And the relative rotational speed ΔN (= Nhub−Ndrum) increases from a predetermined value α.

  Engagement determination unit 254 determines whether or not a predetermined time δ has elapsed since the transmission torque of front-wheel drive clutch 50 was reduced to a predetermined value β. When determining that the predetermined time δ has elapsed, the engagement determination unit 254 calculates a relative rotational speed ΔN (= Nhub−Ndrum) between the clutch hub 76 and the clutch drum 78. Then, the engagement determination unit 254 decreases the transmission torque of the front-wheel drive clutch 50 and, after a predetermined time δ has elapsed, the rotation speed Ndrum of the clutch drum 78 decreases, that is, the relative rotation speed ΔN (= Nhub−Ndrum) If the relative rotational speed ΔN at the start of the reduction of the transmission torque is increased, it is determined that the clutch hub 76 and the sleeve 83 are not engaged. In addition, the engagement determination unit 254 does not decrease the rotational speed Ndrum of the clutch drum 78 even if a predetermined time δ has elapsed since the transmission torque of the front-wheel drive clutch 50 is reduced, and the relative rotational speed ΔN is reduced by the transmission torque. When the relative rotational speed ΔN at the start of the decrease is maintained, it is determined that the clutch hub 76 and the sleeve 83 are engaged.

  When the engagement determination unit 254 determines that the clutch hub body 76 and the sleeve 83 are disengaged, the switching control unit 250 increases the transmission torque of the front wheel drive clutch 50 again and executes synchronous control. If it is determined by the synchronization determination unit 252 that the rotation is synchronized, the engagement determination unit 254 is executed again, and the engagement determination between the clutch hub 76 and the sleeve 83 is executed. In this way, the synchronization determination unit 252 and the engagement determination unit 254 are repeatedly executed until it is determined that the clutch hub 76 and the sleeve 83 are engaged.

  When the engagement determination unit 254 determines that the clutch hub 76 and the sleeve 83 are engaged, the switching control unit 250 connects the front side clutch 36 and puts the vehicle 10 into the four-wheel drive running state. Switch. Further, when the front wheel driving clutch 50 and the front side clutch 36 are connected, the switching control unit 250 displays the indicator 256 indicating the driving state of the vehicle 10 provided on the in-vehicle display from, for example, “2WD”. Switch to “4WD”.

  FIG. 6 is a flowchart for explaining a main part of the control operation of the electronic control device 200. This flowchart is executed when a command to switch to four-wheel drive traveling is output during two-wheel drive traveling in which the front-wheel driving clutch 50 and the front-side clutch 36 are disconnected.

  When a command to switch to four-wheel drive traveling is output during two-wheel drive traveling, step S1 (hereinafter, step is omitted) corresponding to the function of the switching control unit 250 is executed. In S1, the frictional engagement element 89 is pressed by the piston 82, whereby the rotational speed Ndrum of the clutch drum 78 is increased by the frictional force between the clutch hub 76 and the one plate 81 adjacent to the clutch hub 76. Thus, synchronous control for synchronizing the rotational speeds of the clutch hub 76 and the clutch drum 78 is executed. In S2 corresponding to the function of the synchronization determination unit 252, it is determined whether or not the synchronization of the rotational speeds of the clutch hub 76 and the clutch drum 78 has been completed. When S2 is denied, it returns to S1 and synchronous control is performed continuously. When the synchronization of the rotational speeds of the clutch hub 76 and the clutch drum 78 is completed, S2 is affirmed and the process proceeds to S3.

  In S3 corresponding to the function of the engagement determination unit 254, the piston 82 is controlled to move the piston 82 to the side away from the friction engagement element 89 (two-wheel drive travel side), and the transmission torque of the front-wheel drive clutch 50 is increased. Reduce to a predetermined value β. Next, in S4 corresponding to the function of the engagement determination unit 254, it is determined whether or not a predetermined time δ has elapsed since the transmission torque of the front wheel drive clutch 50 was reduced. If the predetermined time δ has not elapsed, the process returns to S4 again, and S4 is repeatedly executed until the predetermined time δ has elapsed. If it is determined that the predetermined time δ has elapsed, in S5 corresponding to the function of the engagement determination unit 254, whether or not the rotational speed Ndrum of the clutch drum 78 is lower than the rotational speed Nhub of the clutch hub 76, or a relative It is determined whether or not the rotational speed ΔN (= Nhub−Ndrum) has increased to be greater than a predetermined value α. When S5 is affirmed, that is, when the rotational speed Ndrum of the clutch drum 78 decreases, it is determined that the clutch drum 76 and the sleeve 83 are not engaged, and the process returns to S1. Therefore, the control in steps S1 to S5 is executed again. Steps S1 to S5 are repeatedly executed while S5 is affirmed.

  When S5 is negative, that is, when it is determined that the clutch hub 76 and the sleeve 83 are engaged by the urging force of the fourth spring 85, the front side clutch 36 is selected in S6 corresponding to the function of the switching control unit 250. Are connected and switched to four-wheel drive running.

  FIG. 7 is a time chart showing an operation result by the control operation of the electronic control device 200. When a command to switch from 2-wheel drive travel to 4-wheel drive travel is output at time t1, synchronous control by controlling the piston 82 is started, the transmission torque of the front-wheel drive clutch 50 increases, and the rotation is stopped. The existing rotational speed Ndrum of the clutch drum 78 is increased toward the rotational speed Nhub of the clutch hub 76 indicated by a one-dot chain line. When the completion of synchronization of the rotational speeds of the clutch hub 76 and the clutch drum 78 is determined at time t2, the piston 82 is moved to the side away from the friction plate 80 in order to determine the engagement between the clutch hub 76 and the sleeve 83. The transmission torque of the front wheel drive clutch 50 is reduced to a predetermined value β. At this time, when the clutch hub 76 and the sleeve 83 are engaged, as indicated by the solid line, the rotational speed of the clutch drum 78 also at the time t3 when a predetermined time δ has elapsed from the time t2 when the transmission torque is reduced. Ndrum does not decrease compared to the time point t2. In such a case, it is determined that the clutch hub 76 and the sleeve 83 are engaged with each other by the urging force of the fourth spring 85 at the time point t3, and the front side clutch 36 is connected at the time point t3 to drive the four-wheel drive. Can be switched to.

  On the other hand, when the clutch hub 76 and the sleeve 83 are not engaged, as shown by the broken line, the rotational speed Ndrum of the clutch drum 78 decreases and the relative rotational speed ΔN (= Nhub−Ndrum) reaches the time t2. Compared to increase. In such a case, it is determined that the clutch hub 76 and the sleeve 83 are not engaged at time t3. Then, at time t3, the synchronization control is executed again (resynchronization). When the rotation is synchronized at time t4, the transmission torque of the front-wheel drive clutch 50 decreases again at time t5, and whether or not the clutch hub 76 and the sleeve 83 are engaged at time t6 when a predetermined time δ has elapsed from time t5. Is determined again. When the rotational speed Ndrum of the clutch drum 78 does not decrease and the relative rotational speed ΔN does not increase at the time point t6, it is determined that the clutch hub 76 and the sleeve 83 are engaged, and at the time point t6, the front speed is increased. The side clutch 36 is connected to switch to four-wheel drive traveling.

  As described above, according to the present embodiment, when the front wheel drive clutch 50 and the front side clutch 36 are disconnected, the clutch hub 76 rotates integrally with the rear wheel output shaft 44, and the inner hub 79, the clutch drum 78, The friction plate 80 and the plate 81 are not rotated. Therefore, the friction plate 80 and the plate 81 do not rotate relative to each other, and a drag torque due to friction is generated only between the clutch hub 76 and one plate 81 adjacent to the clutch hub 76. Thereby, compared with the case where drag torque is generated between a plurality of friction plates 80 and plates 81 stacked on each other, drag torque is significantly reduced, and fuel efficiency is improved.

  Further, according to this embodiment, when it is determined that the rotation speeds of the clutch drum 78 and the clutch hub 76 are synchronized with each other, the transmission torque of the front-wheel drive clutch 50 is reduced. At this time, when the sleeve 83 and the clutch hub 76 are engaged, the relative rotational speed ΔN between the clutch drum 78 and the clutch hub 76 does not increase even if the transmission torque decreases. On the other hand, when the sleeve 83 and the clutch hub 76 are not normally engaged, when the transmission torque of the front wheel driving clutch 50 decreases, the relative rotational speed ΔN between the clutch drum 78 and the clutch hub 76 increases. As a result, when the transmission torque of the front-wheel drive clutch 50 is reduced and the relative rotational speed between the clutch drum 78 and the clutch hub 76 increases at this time, the sleeve 83 and the clutch hub 76 are not engaged. If the relative rotational speed does not increase, it can be determined that the sleeve 83 and the clutch hub 76 are engaged. As a result, it is possible to reliably determine whether or not the sleeve 83 and the clutch hub 76 are engaged. For example, torque distribution control for four-wheel drive traveling is executed in a non-engaged state, so that a desired distribution torque is obtained. Is not obtained, and it is possible to prevent a decrease in durability due to sliding between the engagement teeth of the sleeve 83 and the clutch hub 76.

  Further, according to the present embodiment, after the transmission torque of the front wheel clutch 50 is reduced, if it is determined that the sleeve 83 and the clutch hub 76 are not engaged, the transmission torque of the front wheel driving clutch 50 is increased again. Therefore, the rotational speeds of the clutch hub 76 and the clutch drum 78 are synchronized again, and at this time, the sleeve 83 and the clutch hub 76 can be engaged. Here, when the rotational speeds of the clutch hub 76 and the clutch drum 78 are synchronized, the transmission torque is reduced again, and it is determined again whether or not the sleeve 83 and the clutch hub 76 are engaged. When it is determined that the clutch hub 76 is disengaged, the transmission torque of the front wheel drive clutch 50 is increased. Thus, until it is determined that the sleeve 83 and the clutch hub 76 are engaged, the transmission torque of the front-wheel drive clutch 50 is reduced, and control for determining whether or not the sleeve 83 and the clutch hub 76 are engaged is performed. Is repeatedly executed, the engagement between the sleeve 83 and the clutch hub 76 can be reliably determined.

  Further, according to the present embodiment, when switching from the two-wheel drive traveling to the four-wheel drive traveling, the front side clutch 36 is connected after the engagement between the sleeve 83 and the clutch hub 76 is determined. In a state where the sleeve 83 and the clutch hub 76 are engaged, the rotating element constituting the power transmission path between the driving side sprocket 46 and the front side clutch 36 is rotated, so that the front side clutch 36 The rotational speeds of the two rotating elements to be connected are synchronized, and the front clutch 36 can be connected.

  Further, according to the present embodiment, since it is displayed that the vehicle is in the four-wheel drive running state after the connection of the front-wheel drive clutch 50 and the front side clutch 36 is determined, the four-wheel drive is surely switched to the four-wheel drive running. It is displayed on the indicator 256 that the vehicle is in a driving state, and it is possible to prevent the actual driving state from being different from the driving state based on the display.

  Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the above-described embodiment, the relative rotational speed ΔN (= Nhub−Ndrum) between the clutch hub 76 and the clutch drum 78 after a predetermined time δ has elapsed since the transmission torque of the front-wheel drive clutch 50 is reduced is calculated, and the relative In this embodiment, the clutch hub 76 is determined based on whether or not the rotational speed Ndrum of the clutch drum 78 has decreased. And the engagement of the sleeve 83 are determined.

  When it is determined that the rotation synchronization between the clutch hub 76 and the clutch drum 78 is determined, the engagement determination unit 300 (see FIG. 5) of the present embodiment reduces the transmission torque of the front wheel driving clutch 50 and the front wheel driving clutch 50. It is determined whether or not a predetermined time δ has elapsed since the transmission torque was reduced. When determining that the predetermined time δ has elapsed, the engagement determination unit 300 detects the rotational speed Ndrum1 of the clutch drum 78 at that time, and the rotational speed Ndrum1 decreases the transmission torque of the front-wheel drive clutch 50. Whether or not the clutch hub 76 and the sleeve 83 can be engaged is determined based on whether or not the rotational speed Ndrum2 of the clutch drum 78 at the start time has decreased. Specifically, the engagement determination unit 300 determines a difference in rotational speed ΔNdrum (Ndrum2−) between the rotational speed Ndrum2 of the clutch drum 78 at the start of transmission torque reduction and the rotational speed Ndrum1 of the clutch drum 78 after a predetermined time δ has elapsed. Ndrum1) is calculated, and if the calculated rotational speed difference ΔNdrum is larger than a predetermined value ε set in advance, it is determined that the clutch hub 76 and the sleeve 83 are not engaged. On the other hand, when the calculated rotational speed difference ΔNdrum is a minute value equal to or smaller than the predetermined value ε, the engagement determination unit 300 determines that the clutch 76 and the sleeve 83 are engaged. The predetermined value ε is set in advance based on experiments and the like, and is set to a small value that can determine whether or not the clutch hub 76 and the sleeve 83 are engaged.

  FIG. 8 is a flowchart for explaining the control operation of the electronic control unit 302 (see FIG. 5) corresponding to the present embodiment. Comparing the flowchart of FIG. 8 with the flowchart of FIG. 6 corresponding to the above-described embodiment, in FIG. 8, in S5 (FIG. 6) in which the engagement determination is performed based on the increase of the relative rotational speed ΔN of the above-described embodiment. Instead, the process is changed to S10 in which the engagement determination is performed based on the decrease in the rotational speed Ndrum of the clutch drum 78. Further, the control operations of other steps are the same as those in the flowchart of FIG. Hereinafter, the control operation of S10 will be described, and detailed description of other steps will be omitted.

  S10 corresponding to the function of the engagement determination unit 300 in FIG. 8 is executed when it is determined in S4 that a predetermined time δ has elapsed since the decrease in the transmission torque of the front-wheel drive clutch 50 is started. In S10, the rotational speed Ndrum1 of the clutch drum 78 after the lapse of the predetermined time δ is detected, and the rotational speed Ndrum1 is compared with the rotational speed Ndrum2 of the clutch drum 78 when the transmission torque of the front wheel drive clutch 50 starts to decrease. It is determined whether or not it has decreased. For example, it is determined whether or not the rotational speed difference ΔN (Ndrum2−Ndrum1) between the rotational speed Ndrum2 at the time when the transmission torque starts to decrease and the rotational speed Ndrum1 after a predetermined time δ has elapsed is greater than a predetermined value ε. When the rotational speed difference ΔNdrum is larger than the predetermined value ε, that is, when the rotational speed Ndrum of the clutch drum 78 is decreased, it is determined that the clutch hub 76 and the sleeve 83 are not engaged, and the process returns to S1 and synchronization control is performed. Is executed again. On the other hand, if the rotational speed difference ΔNdrum is a minute value equal to or smaller than the predetermined value ε, it is determined that the clutch hub 76 and the sleeve 83 are engaged, and the process proceeds to S6. The engagement between the clutch hub 76 and the sleeve 83 can also be determined by determining a decrease in the rotational speed Ndrum of the clutch drum 78 as described above.

  Even when the engagement between the clutch hub 76 and the sleeve 83 is determined based on the decrease in the rotational speed Ndrum of the clutch drum 78, the time chart is the same as the time chart of FIG. . That is, when the reduction of the transmission torque is started at time t2 in FIG. 7, the rotational speed Ndrum1 of the clutch drum 78 at time t3 when the predetermined time δ has elapsed becomes equal to the clutch drum 78 at time t2, which is the transmission torque reduction start time. It is determined whether or not the rotational speed has decreased compared to Ndrum2. When it is determined that the rotational speed Ndrum of the clutch drum 78 has decreased at time t3, the transmission torque is increased again at time t3, and the synchronization control is executed again.

  As described above, the engagement between the clutch hub 76 and the sleeve 83 can be determined based on whether or not the rotational speed Ndrum of the clutch drum 78 has decreased, and the same effect as in the above-described embodiment can be obtained. it can.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in the above-described embodiment, the vehicle 10 is an FR type four-wheel drive vehicle in which the rear wheel 16 is the main drive wheel and the front wheel 14 is the auxiliary drive wheel. However, in the present invention, the front wheel 14 is the main drive. The present invention can also be applied to an FF type four-wheel drive vehicle in which the rear wheel 16 is a sub drive wheel.

  The rotational speed Nhub of the clutch hub 76 of the front-wheel drive clutch 50 is detected from the rotational speed Nf of the rear wheel output shaft 44 detected by the output shaft rotational speed sensor 216, and the rotational speed Ndrum of the clutch drum 78 is Although detected from the rotational speed Nf of the front propeller shaft 24 detected by the speed sensor 218, the present invention is not necessarily limited thereto. For example, the rotational speed Ndrum of the clutch drum 78 can also be obtained from the rotational speeds of the drive side sprocket 46, the driven side sprocket 54, and the front wheel differential gear device 28. That is, if the rotating member is connected to the clutch hub 76 and the clutch drum 78 so that power can be transmitted, the rotating speed of the clutch hub 76 and the rotating speed of the clutch drum 78 are detected by detecting the rotating speed of the rotating member. Ndrum can be obtained.

  In the above-described embodiment, the piston 82 is operated by the motor 84, the screw mechanism 86, and the like, but is not necessarily limited thereto. For example, as long as the movement amount of the piston 82 can be controlled, such as a hydraulic type or a ball cam, it can be applied as appropriate.

  The above description is only an embodiment, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art.

10: Four-wheel drive vehicle 14: Front wheel (sub-drive wheel)
16: Rear wheel (main drive wheel)
24: Front propeller shaft (power transmission member)
36: Front side clutch (second connecting / disconnecting mechanism)
44: Rear wheel output shaft (input rotation member)
46: Drive side sprocket (output rotating member)
50: Front wheel drive clutch (first connecting / disconnecting mechanism)
76: Clutch hub (hub)
78: Clutch drum (drum)
79: Inner hub 80: Friction plate 81: Plate 82: Piston 83: Sleeve 200, 302: Electronic control device (control device)
256: Indicator (display device)

Claims (4)

An input rotation member that is connected to the main drive wheel so as to be able to transmit power and rotates around an axis, and an output rotation that is connected to the sub drive wheel via a power transmission member so as to be able to transmit power and rotates about the same axis as the input rotation member A member, a first connecting / disconnecting mechanism provided on a power transmission path between the input rotation member and the output rotation member, and a power transmission path between the power transmission member and the auxiliary drive wheel. A second connecting / disconnecting mechanism provided;
In a four-wheel drive vehicle configured to include:
A control device for a four-wheel drive vehicle that controls a driving state of a vehicle by switching a connecting / disconnecting state of the first connecting / disconnecting mechanism and the second connecting / disconnecting mechanism,
The first connecting / disconnecting mechanism includes a hub coupled to the input rotating member so as to be capable of transmitting rotation;
A drum coupled to the output rotating member so as to be capable of transmitting rotation;
An inner hub disposed on the inner peripheral side of the drum so as to be rotatable relative to the hub;
A plurality of friction plates engaged with the outer peripheral surface of the inner hub so as not to rotate relative to each other and to be movable in the axial direction;
A plurality of plates that are disposed on the inner peripheral surface of the drum so as to be relatively non-rotatable and movable in the axial direction and are alternately stacked with the friction plates;
A piston for pressing the plurality of friction plates and the plate in the axial direction;
Engage with the inner hub at all times so that it cannot rotate relative to the inner hub, and is movably provided in an axial position that engages with the hub, and is biased to a position that engages with the hub in conjunction with the piston. A sleeve,
It is configured to be able to adjust the magnitude of the transmission torque of the first connection / disconnection mechanism by controlling the magnitude of the pressing force of the piston,
The controller is
When connecting the first connecting / disconnecting mechanism in a two-wheel drive running state in which the first connecting / disconnecting mechanism and the second connecting / disconnecting mechanism are disconnected,
When the piston is actuated to press the friction plate and the plate and it is determined that the rotation speeds of the drum and the hub are synchronized, the transmission torque of the first connecting / disconnecting mechanism is reduced, and the rotation speed of the drum is reduced. When lowered, it is determined that the sleeve and the hub are disengaged,
If the rotational speed of the drum does not decrease even when the transmission torque of the first connecting / disconnecting mechanism is decreased, it is determined that the sleeve and the hub are engaged. Control device.   When the transmission torque of the first connecting / disconnecting mechanism is reduced and the sleeve and the hub are determined to be disengaged, the transmission torque of the first connecting / disconnecting mechanism is increased again. The control device for a four-wheel drive vehicle according to claim 1.   3. When switching from two-wheel drive traveling to four-wheel drive traveling, the second connecting / disconnecting mechanism is connected after the engagement between the sleeve and the hub is determined. 4 wheel drive vehicle control device. A display device showing a driving state of the four-wheel drive vehicle;
4. The control device for a four-wheel drive vehicle according to claim 3, wherein a display indicating that the vehicle is in a four-wheel drive traveling state is displayed after the connection between the first connection / disconnection mechanism and the second connection / disconnection mechanism is determined.

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