JP2023047212A - Four-wheel drive vehicle control device - Google Patents

Abstract

To provide a four-wheel drive vehicle control device capable of curbing a large shock even when a four-wheel drive state is switched to a two-wheel drive state with a drive train undergoing torsion.SOLUTION: A control device 100 comprises: a torsion determination section 102 which determines generation of torsion in a drive train; and a first clutch control section 104 which controls magnitude of first clutch transmission torque transmitted through a front wheel driving clutch 46. When the first clutch control section 104 switches a four-wheel drive state to a two-wheel drive state, the control device 100 executes torque reduction control to reduce the first clutch transmission torque. When the drive train undergoes torsion, the control device 100 executes the torque reduction control so that the first clutch transmission torque is reduced more gradually than when the drive train does not undergo torsion.SELECTED DRAWING: Figure 1

Description

The present invention relates to a controller for a four-wheel drive vehicle.

Conventionally, a control system for an all-wheel drive vehicle disclosed in Patent Document 1 below has been provided as a control device for a four-wheel drive vehicle. The control system of Patent Document 1 below includes a first axle that is driven by a prime mover for a limited period of time, a second axle that is always connected to the prime mover via a propeller shaft, the propeller shaft and the first axle. a subshaft in driving communication with a motor for controlling the connection between the prime mover and the first axle. This control system includes a first clutch that disconnectably connects the propeller shaft and the sub-shaft, a second clutch that disconnectably connects the sub-shaft and the first axle, and the second clutch. synchronization determination means for determining whether the second clutch can be connected; and connection determination means for determining whether the second clutch is connected. With such a configuration, the control system of Patent Document 1 attempts to quickly switch between the 2WD mode and the AWD mode while preventing impulsive or vibrational fluctuations in the transmission torque. .

Japanese Patent Application Laid-Open No. 2020-032773

Here, the present inventors have made intensive studies and found that a first clutch for selectively disconnecting or connecting the power transmission path between the driving force source and the power transmission member, power between the power transmission member and the sub-driving wheel In a four-wheel drive vehicle equipped with a second clutch that selectively disconnects or connects a transmission path, when switching from the four-wheel drive state to the two-wheel drive state, the torque that can be transmitted by the first clutch (first After adjusting the connection state of the first clutch so that the clutch transmission torque) is lower than before switching to the two-wheel drive state by a predetermined value, the first clutch transmission torque is gradually reduced. It was found that the shock caused by the opening of the first clutch can be minimized without significantly lengthening the time required for the clutch to be released.

However, when the inventors of the present invention conducted further intensive studies, it was found that twisting occurs in the drive system consisting of the propeller shaft, drive shaft, etc., such as when so-called tight corner braking occurs or after sudden braking. In this state, if the first clutch is released to switch from four-wheel drive to two-wheel drive, there is a concern that the torsion of the drive train will suddenly release, resulting in a large shock. was gotten.

Therefore, in the present invention, even if the four-wheel drive state is switched to the two-wheel drive state in a state where the drive system is twisted, such as when so-called tight corner braking occurs or after sudden braking. An object of the present invention is to provide a controller for a four-wheel drive vehicle capable of suppressing occurrence of a large shock.

(1) A controller for a four-wheel drive vehicle according to the present invention comprises a first clutch for selectively disconnecting or connecting a power transmission path between a driving force source and a power transmission member; and a second clutch that selectively disconnects or connects the power transmission path between the drive power source to the left and right main drive wheels by disengaging the first clutch and the second clutch, respectively. A two-wheel drive state in which driving force is transmitted, and a four-wheel drive state in which driving force is also transmitted from the driving force source to the left and right sub-driving wheels by engaging the first clutch and the second clutch, respectively. , a four-wheel drive vehicle control device for use in a four-wheel drive vehicle capable of switching between the a transmission torque control unit that controls the magnitude of the first clutch transmission torque transmitted through the power transmission path, wherein the transmission torque control unit switches from the four-wheel drive state to the two-wheel drive state. At this time, torque reduction control is performed to reduce the magnitude of the first clutch transmission torque, and on the condition that the torsion determination unit determines that torsion is occurring in the drive system, The torque reduction control is performed so that the first clutch transmission torque is gently reduced compared to when it is not determined that the twist in the drive system is occurring.

In the control device for a four-wheel drive vehicle of the present invention, the transmission torque control section performs torque reduction control to reduce the magnitude of the first clutch transmission torque when switching from the four-wheel drive state to the two-wheel drive state. ing. As a result, the controller for a four-wheel drive vehicle of the present invention minimizes the time required to disengage the first clutch and the shock associated with the disengagement of the first clutch when switching from the four-wheel drive state to the two-wheel drive state. can be suppressed. Further, the controller for a four-wheel drive vehicle of the present invention determines that a twist has occurred in the drive system on the condition that the twist determination unit has determined that a twist has occurred in the drive system. Torque reduction control is performed so that the first clutch transmission torque is reduced more gently than when the determination is not made. As a result, the controller for a four-wheel drive vehicle according to the present invention can operate the four-wheel drive system in a state where the drive system is twisted, such as when a so-called tight corner braking occurs or after sudden braking. Even if the state is switched to the two-wheel drive state, it is possible to minimize the shock caused by the release of the first clutch while suppressing an increase in the shock caused by the release of the torsion of the drive system.

(2) In the control device for a four-wheel drive vehicle of the present invention, the transmission torque reduction control reduces the magnitude of the first clutch transmission torque to a level lower than before switching from the four-wheel drive state to the two-wheel drive state. After decreasing stepwise or continuously to the sweep start torque, the first clutch transmission torque is decreased stepwise or continuously from the sweep start torque, and the torsion in the drive system is detected by the torsion determination unit. On the condition that it is determined that the torsion has occurred, the sweep start torque is set higher than when it is not determined that the torsion has occurred in the drive system, and the torque It is preferable that the feature is that reduction control is performed.

The controller for a four-wheel drive vehicle according to the present invention sets the sweep start torque higher when a twist occurs in the drive train than when the twist does not occur, thereby changing the four-wheel drive state to the two-wheel drive state. Minimize the shock that occurs immediately after switching to the state. Further, the controller for a four-wheel drive vehicle of the present invention reduces the first clutch transmission torque to a sweep start torque suitable for the presence or absence of torsion in the drive system, and then gradually or continuously reduces the first clutch transmission torque. is reduced, the time required for disengaging the first clutch is minimized, and the shock that occurs during the period in which the first clutch transmission torque is reduced from the sweep start torque can also be minimized.

(3) In the control device for a four-wheel drive vehicle of the present invention, the transmission torque reduction control reduces the magnitude of the first clutch transmission torque to be lower than when switching from the four-wheel drive state to the two-wheel drive state. After decreasing stepwise or continuously to the sweep start torque, the first clutch transmission torque is decreased stepwise or continuously from the sweep start torque, and the torsion in the drive system is detected by the torsion determination unit. On the condition that it is determined that the torsion has occurred, the decrease per unit time from the sweep start torque compared to when it is not determined that the torsion has occurred in the drive system It is preferable that the torque reduction control is performed by disengaging the first clutch so that the decrease rate of the first clutch transmission torque becomes small.

The four-wheel drive vehicle control device of the present invention reduces the first clutch transmission torque to the sweep start torque when switching from the four-wheel drive state to the two-wheel drive state, and then stepwise or continuously It is supposed that the first clutch transmission torque is reduced immediately. As a result, the four-wheel-drive vehicle control device of the present invention can minimize the time required to release the first clutch and minimize the shock associated with the release of the first clutch. Further, the four-wheel drive vehicle control device of the present invention reduces the first clutch transmission torque to the sweep start torque and further reduces it, depending on whether or not torsion occurs in the drive system, per unit time. is to change the decrease rate of the first clutch transmission torque at . Specifically, in the four-wheel drive vehicle control device of the present invention, when the drive system is twisted, the reduction rate of the first clutch transmission torque is smaller than when the drive system is not twisted. The release control of the first clutch is performed so that Therefore, the control device for a four-wheel drive vehicle of the present invention can minimize the occurrence of a shock due to the disengagement of the first clutch even when twisting occurs in the drive system.

(4) The controller for a four-wheel drive vehicle of the present invention sets the sweep start torque higher when the torsion of the drive system is large than when the torsion of the drive system is small, so that the torque reduction control can be performed. It should be characterized by:

The controller for a four-wheel drive vehicle according to the present invention has the above-described configuration, so that when the torsion of the drive train is large, compared with when the torsion of the drive system is small, the four-wheel drive state can be changed to the two-wheel drive state. It is possible to reduce the amount of decrease in the first clutch transmission torque immediately after switching. As a result, the controller for a four-wheel drive vehicle according to the present invention can perform torque reduction control by setting an appropriate sweep start torque according to the degree of torsion of the drive system, thereby changing from the four-wheel drive state to the two-wheel drive state. The shock that occurs immediately after switching to the state can be suppressed to a minimum.

(5) In the control device for a four-wheel drive vehicle of the present invention, when the torsion of the drive system is large, the first clutch decreases per unit time from the sweep start torque more than when the torsion of the drive system is small. It is preferable that the torque reduction control is performed by disengaging the first clutch so that the rate of decrease in transmission torque becomes small.

The control device for a four-wheel drive vehicle according to the present invention, having the above-described configuration, gently reduces the first clutch transmission torque when the torsion of the drive system is large compared to when the torsion of the drive system is small. be able to. As a result, even when the torsion of the drive system is large, it is possible to minimize the shock caused by switching from the four-wheel drive state to the two-wheel drive state.

(6) In the control device for a four-wheel drive vehicle of the present invention, the twist determination unit can determine the magnitude of twist in the drive system using a steering angle as a part or all of an index, and the twist determination unit Preferably, the torque reduction control is performed based on the determined magnitude of torsion in the driving system.

With the configuration described above, the controller for a four-wheel drive vehicle according to the present invention switches from the four-wheel drive state to the two-wheel drive state in consideration of the torsion of the drive system that occurs according to the magnitude of the steering angle. Torque reduction control can be performed so as to minimize the shock that occurs along with the

(7) In the control device for a four-wheel drive vehicle of the present invention, the first clutch is a wet multi-plate clutch capable of adjusting the degree of engagement according to the magnitude of hydraulic pressure, and the transmission torque control section It is preferable that the magnitude of the first clutch transmission torque is controlled according to the magnitude of the hydraulic pressure acting on the first clutch.

With the configuration described above, the control device for a four-wheel drive vehicle according to the present invention is capable of four-wheel drive even when a wet multi-plate clutch is employed as the first clutch while the drive system is twisted. The shock generated by switching from the state to the two-wheel drive state can be minimized.

According to the present invention, even if the four-wheel drive state is switched to the two-wheel drive state in a state in which the drive system is twisted, such as in a so-called tight corner braking state or after sudden braking. Also, it is possible to provide a four-wheel drive vehicle control device capable of suppressing occurrence of a large shock.

It is an explanatory view showing a control device concerning one embodiment of the present invention, and vehicles carrying the same. FIG. 2 is a flow chart showing a control flow executed by a control device when the vehicle shown in FIG. 1 is switched from a four-wheel drive state to a two-wheel drive state; FIG. FIG. 2 is a timing chart showing changes in first clutch transmission torque when the vehicle shown in FIG. 1 switches from a four-wheel drive state to a two-wheel drive state; FIG.

A control device for a four-wheel drive vehicle (control device 100) according to an embodiment of the present invention will be described below with reference to the drawings, taking as an example a four-wheel drive vehicle (vehicle 10) employing the control device. In the following description, before referring to the specific configuration of control device 100 and the control by control device 100, the schematic configuration of vehicle 10 will be described.

FIG. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present invention is applied. As shown in FIG. 1, the vehicle 10 includes a driving force source 12, a pair of left and right front wheels 14L, 14R, a pair of left and right rear wheels 16L, 16R, a power transmission device 18, a control device 100, and the like. The vehicle 10 is in a two-wheel drive state in which the driving force is transmitted to the rear wheels 16L and 16R to travel, and a four-wheel drive state in which the driving force is transmitted to the front wheels 14L and 14R in addition to the rear wheels 16L and 16R. It is a four-wheel drive vehicle that can be switched as needed.

The driving force source 12 is for generating driving force for the vehicle 10 . The driving force source 12 can be configured by, for example, an engine, a motor, or the like. Further, the front wheels 14L and 14R constitute auxiliary driving wheels in the vehicle 10. As shown in FIG. The front wheels 14L and 14R function as drive wheels in the four-wheel drive state, and function as driven wheels in the two-wheel drive state. The rear wheels 16L and 16R constitute main driving wheels in the vehicle 10. As shown in FIG. The rear wheels 16L, 16R function as drive wheels in both the four-wheel drive state and the two-wheel drive state.

As shown in FIG. 1, the power transmission device 18 includes a transmission 20, a transfer 22, a front propeller shaft 24 (power transmission member), a rear propeller shaft 26, a front wheel differential gear device 28, and a rear wheel differential gear device. 30, a pair of left and right front wheel axles 32L and 32R, and a pair of left and right rear wheel axles 34L and 34R.

The power transmission device 18 has a power transmission path from the transmission 20 to the rear wheels 16L and 16R through the transfer 22, the rear propeller shaft 26, the rear wheel differential gear device 30, the rear wheel axles 34L and 34R, and the like. , the power generated in the driving force source 12 can be transmitted to the rear wheels 16L, 16R. Further, the power transmission device 18 can form a power transmission path that distributes and transmits part of the driving force transmitted from the driving force source 12 to the transfer 22 to the front wheels 14L, 14R. That is, by adjusting the connection state of a front wheel drive clutch 46, which will be described in detail later, the power transmission device 18 is configured to move from the transmission 20 via the transfer 22 to the front propeller shaft 24, the front wheel differential gear device 28, the front wheel axle, and the front propeller shaft 24. A part of the power generated in the driving force source 12 can be transmitted to the front wheels 14L, 14R by the power transmission path reaching the front wheels 14L, 14R through the 32L, 32R and the like in sequence.

The transmission 20 operates upon receiving an output from the driving force source 12, and is composed of, for example, a conventionally known MT (manual transmission), AT (automatic transmission), CVT (continuously variable transmission), or the like.

The transfer 22 includes an input shaft 38, a rear wheel side output shaft 40, a front wheel drive drive sprocket 42, and a front wheel drive clutch 46 (first clutch) inside a transfer case 36 around a first rotation axis C1. . Further, the transfer 22 includes a front-wheel-side output shaft 48 and a driven sprocket 50 for driving the front wheels around a second rotation axis C2 extending in a direction (substantially parallel in this embodiment) to the first rotation axis C1. ing. Further, the transfer 22 has a front-wheel drive chain 52 wound around the front-wheel drive drive sprocket 42 and the front-wheel drive driven sprocket 50 .

Input shaft 38 is connected to transmission 20 . This allows the input shaft 38 to receive power transmitted from the driving force source 12 . Also, the rear wheel output shaft 40 is connected to the rear propeller shaft 26 so as to be capable of power transmission. The front-wheel drive drive sprocket 42 is supported by the rear-wheel output shaft 40 so as to be relatively rotatable with respect to the rear-wheel output shaft 40 .

By engaging the front-wheel drive clutch 46, the front-wheel drive drive sprocket 42 can rotate integrally with the rear-wheel output shaft 40, and power is transmitted to the front-wheel output shaft 48 via the front-wheel drive chain 52. It becomes possible. Therefore, by engaging the front-wheel drive clutch 46, part of the driving force transmitted from the driving force source 12 to the rear propeller shaft 26 via the rear-wheel output shaft 40 is distributed. 42 and the front wheel drive chain 52 to the front wheel side output shaft 48 . On the other hand, by disengaging the front-wheel drive clutch 46, the driving force transmitted from the driving force source 12 to the rear-wheel output shaft 40 is not transmitted (distributed) to the front-wheel drive drive sprocket 42. It can be transmitted to the rear propeller shaft 26 .

The front wheel drive clutch 46 is composed of a wet multi-plate clutch. The front-wheel drive clutch 46 can adjust the transmission torque transmitted from the rear-wheel output shaft 40 to the front-wheel drive drive sprocket 42 by adjusting the degree of connection (engagement). That is, the front wheel drive clutch 46 is a clutch ( first clutch). The front wheel drive clutch 46 is operated by the action of hydraulic pressure, and the degree of connection can be adjusted by controlling the magnitude of the hydraulic pressure.

The front-wheel output shaft 48 is connected to the front propeller shaft 24 so as to be able to transmit power. The front-wheel drive driven sprocket 50 is provided so as to be integrally rotatable with the front-wheel output shaft 48 . The front-wheel drive chain 52 is wound around the front-wheel drive drive sprocket 42 and the front-wheel drive driven sprocket 50 so that power can be transmitted between the two sprockets.

The front wheel differential gear device 28 comprises a differential case 80, a pinion shaft 82, a pair of side gears 84L and 84R, a pair of pinions 86a and 86b, and a ring gear 90. As shown in FIG. The pinions 86 a and 86 b are attached to the differential case 80 while being arranged on both ends of the pinion shaft 82 . The side gears 84L, 84R are arranged to face each other inside the differential case 80 and mesh with the pinions 86a, 86b, respectively. The side gears 84L, 84R are connected to the front wheels 14L, 14R via front wheel axles 32L, 32R. Also, the ring gear 90 is integrally attached to the differential case 80 . A front drive pinion 25 connected to the front propeller shaft 24 is meshed with the ring gear 90 . The front-wheel differential gear device 28 also includes a dog clutch 94 (second clutch). The dog clutch 94 can be engaged by applying pressure (negative pressure). The dog clutch 94 selectively disconnects or connects a power transmission path between the front propeller shaft 24, which functions as a power transmission member to the front wheels 14L, 14R, and the front wheel axles 32L, 32R, which are auxiliary drive wheels. It functions as a two-clutch.

The rear wheel differential gear device 30 comprises a differential case 120, a pinion shaft 122, a pair of side gears 124L and 124R, a pair of pinions 126a and 126b, and a ring gear . The pinions 126a and 126b are attached to the differential case 120 while being arranged at both ends of the pinion shaft 122, respectively. The side gears 124L, 124R are arranged opposite to each other inside the differential case 120 and mesh with the pinions 126a, 126b, respectively. The side gears 124L, 124R are connected to the rear wheels 16L, 16R via rear wheel axles 34L, 34R. Also, the ring gear 130 is integrally attached to the differential case 120 . A rear drive pinion 27 connected to a rear propeller shaft 26 is meshed with the ring gear 130 .

Since the vehicle 10 is configured as described above, when both the front wheel drive clutch 46 and the dog clutch 94 are connected (engaged) so that torque can be transmitted, only the rear wheels 16L and 16R are engaged. Instead, the front wheels 14L and 14R are also in a state (four-wheel drive state) in which the power generated by the driving force source 12 can be transmitted. On the other hand, in the vehicle 10, when either the front wheel drive clutch 46 or dog clutch 94 is disengaged (disengaged), the power transmission path to the front wheels 14L and 14R is cut off, and torque cannot be transmitted. become. As a result, the vehicle 10 can transmit the power generated by the driving force source 12 to the rear wheels 16L and 16R, but cannot transmit the power to the front wheels 14L and 14R (two-wheel drive state).

The control device 100 can control the connected state (engaged state) of the front wheel drive clutch 46 and dog clutch 94 described above. The control device 100 includes, for example, a microcomputer having a CPU, RAM, ROM, input/output interface, and the like. The control device 100 includes a twist determination section 102 , a first clutch control section 104 (transmission torque control section), and a second clutch control section 106 .

The twist determination unit 102 is for determining the occurrence of twist in the driving system of the vehicle 10 . The twist determination unit 102 provides information such as steering angle, vehicle speed, lateral acceleration, yaw rate, pressure supplied to the brake booster (master cylinder pressure), brake pressure, tire rotation speed, rate of change in tire rotation speed, deceleration, etc. is acquired based on the detection signal of a sensor provided in the vehicle 10, and the occurrence of torsion in the driving system of the vehicle 10 can be determined using this information as part or all of the index.

Specifically, considering that a twist occurs in the drive system due to tight corner braking, for example, by combining one or a plurality of information such as the steering angle, vehicle speed, lateral acceleration, yaw rate, etc., the vehicle 10 can be driven. It may determine the occurrence of torsion in the system. Considering that twisting occurs due to sudden deceleration, information such as pressure supplied to the brake booster (master cylinder pressure), brake pressure, tire rotation speed, tire rotation speed change rate, deceleration, etc. By combining a plurality of them, occurrence of torsion in the driving system of the vehicle 10 can be determined. In the present embodiment, the twist determining unit 102 considers that twisting occurs in the drive system due to tight corner braking under conditions where the vehicle speed is low and the steering angle is large. It is determined that twisting occurs in the driving system of the vehicle 10 on the condition that the angle is greater than or equal to a predetermined size.

The first clutch control section 104 functions as a transmission torque control section that controls transmission torque (first clutch transmission torque) transmitted to the front propeller shaft 24 via the front wheel drive clutch 46 . The first clutch control unit 104 controls the amount of torque transmitted to the front propeller shaft 24 by controlling the degree of engagement of the front wheel drive clutch 46 . As described above, in this embodiment, the front wheel drive clutch 46 is a wet multi-plate clutch that can adjust the degree of engagement by controlling the magnitude of the hydraulic pressure. Therefore, the first clutch control unit 104 controls the magnitude of the torque transmitted to the front propeller shaft 24 by controlling the magnitude of the hydraulic pressure acting on the front wheel drive clutch 46 .

The second clutch control section 106 controls torque transmission from the front wheel drive clutch 46 to the front wheel differential gear device 28 by controlling the operation of the dog clutch 94 . As described above, the dog clutch 94 can be engaged by applying pressure (negative pressure). Therefore, the second clutch control unit 106 can switch the dog clutch 94 between the engaged state and the non-engaged state by controlling the magnitude of the pressure acting on the dog clutch 94 .

Here, the vehicle 10 described above is characterized by the control performed by the control device 100 when switching from the four-wheel drive state to the two-wheel drive state. Hereinafter, the control performed when the vehicle 10 is switched from the four-wheel drive state to the two-wheel drive state will be described in detail according to the flowchart of FIG. 2 and with reference to the timing chart of FIG.

(Step 1)
In step 1, the control device 100 confirms whether or not an instruction (two-wheel drive switching instruction) for switching the vehicle 10 from the four-wheel drive state to the two-wheel drive state has been input, for example, by operating a switch (not shown). Here, when the input of the two-wheel drive switching instruction is confirmed, the control flow proceeds to step 2 .

(Step 2)
In step 2, the control device 100 determines whether or not the twist determining section 102 causes the drive system of the vehicle 10 to twist. Here, if no twist has occurred, the control flow advances to step 3 . On the other hand, if a twist has occurred, the control flow proceeds to step 4;

(Step 3)
When the control flow advances from step 2 to step 3, the control device 100 causes the first clutch control unit 104 to release the front wheel drive clutch 46 step by step from step 5 onwards, so that the front propeller shaft 24 is engaged. initial setting (normal initial setting) for performing control (torque reduction control) to reduce the magnitude of the transmitted torque. Specifically, the control device 100 sets a predetermined value (normal sweep start torque) lower than the transmission torque transmitted via the front-wheel drive clutch 46 before switching from the four-wheel drive state to the two-wheel drive state. Set the sweep start torque as follows. In addition, after reducing the transmission torque of the front-wheel drive clutch 46 to the normal sweep start torque, the control device 100 sets the reduction rate of the transmission torque when reducing the transmission torque over time to a predetermined normal torque reduction rate. do. After that, the control device 100 advances the control flow to step 5 described later. In this embodiment, the transmission torque in the front-wheel drive clutch 46 is controlled by the hydraulic pressure acting on the front-wheel drive clutch 46 . Therefore, the control device 100 sets the normal sweep start oil pressure corresponding to the normal sweep start torque and the normal oil pressure decrease rate corresponding to the normal torque decrease rate. After that, the control device 100 shifts the control flow to step 5 .

(Step 4)
When the control flow advances from step 2 to step 4, the control device 100 performs initial settings for performing the torque reduction control described in step 3 above. Here, when the control flow proceeds from step 2 to step 4, considering that the drive train of the vehicle 10 is twisted, it is determined that the drive train is twisted. Initial setting is made so that the transmission torque (first clutch transmission torque) transmitted via the front wheel drive clutch 46 is gently reduced compared to when it is not performed (when the control flow advances from step 2 to step 3). (initial setting when twist occurs). Specifically, the control device 100 controls the normal sweep torque set in step 3 to be lower than the transmission torque transmitted via the front wheel drive clutch 46 before switching from the four-wheel drive state to the two-wheel drive state. The sweep start torque is set to a value higher than the start torque (sweep start torque when torsion occurs). Further, after the transmission torque in the front wheel drive clutch 46 is reduced to the sweep start torque at the occurrence of torsion, the reduction rate of the transmission torque when reducing the transmission torque over time is set to a lower torsional torque reduction rate than the normal torque reduction rate described above. Set the torque drop rate at occurrence. In this embodiment, since the transmission torque in the front-wheel drive clutch 46 is controlled by the hydraulic pressure acting on the front-wheel drive clutch 46, the torsion sweep start hydraulic pressure corresponding to the torsion sweep start torque, the torsion torque decrease rate Set the oil pressure decrease rate at the time of torsion corresponding to . After that, the control device 100 shifts the control flow to step 5 .

(Step 5)
In step 5, the control device 100, under the control of the first clutch control section 104, reduces the transmission torque of the front wheel drive clutch 46 to the sweep start torque set in step 3 or 4 described above. In this embodiment, the control device 100 reduces the transmission torque of the front wheel drive clutch 46 to the sweep start torque by lowering the oil pressure acting on the front wheel drive clutch 46 to the oil pressure corresponding to the sweep start torque. Here, as shown in FIG. 3, the sweep start torque when the drive system of the vehicle 10 is twisted (sweep start torque when twist is generated) is the torque when twist is not generated (normal sweep start torque). torque). Therefore, when the drive system is twisted, the reduction amount of the transmission torque when the torque transmitted by the front-wheel drive clutch 46 is reduced to the sweep start torque is smaller than when the twist is not generated. . When the transmission torque of the front wheel drive clutch 46 decreases to the sweep start torque in step 5, the control flow proceeds to step 6.

(Step 6)
In step 6, the control device 100 reduces the transmission torque of the front-wheel drive clutch 46 from the sweep start torque by the normal torque decrease rate set in step 3 or the torque decrease rate when twisting occurs set in step 4. control to allow In this embodiment, the control device 100 sets the hydraulic pressure acting on the front-wheel drive clutch 46 to the normal hydraulic pressure drop rate corresponding to the normal torque drop rate, or the torsional hydraulic pressure drop rate corresponding to the torsion occurrence torque drop rate. Lower. As a result, the transmission torque of the front wheel drive clutch 46 continuously decreases over time. Also, the torque reduction rate at the time of occurrence of torsion is set lower than the normal torque reduction rate. Therefore, when the drive system is twisted, the torque transmitted by the front wheel drive clutch 46 is reduced more gently than when the drive system is not twisted. When the transmission torque of the front wheel drive clutch 46 begins to decrease in step 6 , the control flow proceeds to step 7 .

(Step 7)
At step 7, the control device 100 confirms whether or not the front wheel drive clutch 46 is disengaged. Specifically, control device 100 confirms whether or not the hydraulic pressure acting on front-wheel drive clutch 46 has decreased to a predetermined value. Here, if the front wheel drive clutch 46 has not yet been disengaged, the control device 100 returns the control flow to step 6 . On the other hand, when the front wheel drive clutch 46 is disengaged, the control flow proceeds to step 8 .

(Step 8)
In step 8, the control device 100 performs processing for switching the dog clutch 94 to the disengaged state under the control of the second clutch control section 106 . As a result, the control device 100 completes a series of controls according to the control flow of FIG.

As described above, the control device 100 mounted on the vehicle 10 has the following characteristic configurations (a) to (e). Therefore, control device 100 can exhibit the following effects in vehicle 10 .

(a) The control device 100 of the present embodiment selectively disconnects or connects the power transmission path between the driving force source 12 and the front propeller shaft 24 (power transmission member). ), and a dog clutch 94 (second clutch) that selectively disconnects or connects the power transmission path between the front propeller shaft 24 and the front wheels 14L, 14R (auxiliary drive wheels), and a front wheel drive clutch 46 and the dog clutch 94 are respectively released to engage the front wheel drive clutch 46 and the dog clutch 94, respectively, in a two-wheel drive state in which driving force is transmitted from the driving force source 12 to the left and right rear wheels 16L and 16R. It is used for a vehicle 10 capable of switching between a four-wheel drive state and a four-wheel drive state in which driving force is also transmitted from the driving force source 12 to the left and right front wheels 14L and 14R by combining them. In addition, the control device 100 controls the twist determination unit 102 that determines the occurrence of twist in the drive train, and the degree of connection of the front wheel drive clutch 46, thereby increasing the first clutch transmission torque transmitted through the power transmission path. and a first clutch control section 104 (transmission torque control section) that controls the magnitude. Further, in the control device 100, the first clutch control unit 104 performs torque reduction control to reduce the magnitude of the first clutch transmission torque when switching from the four-wheel drive state to the two-wheel drive state. On the condition that the unit 102 has determined that a torsion has occurred in the drive system, the first clutch transmission torque is higher than when it is not determined that a torsion has occurred in the drive system. It is assumed that torque reduction control is performed so as to gently decrease.

The control device 100 of the present embodiment performs torque reduction control to reduce the magnitude of the first clutch transmission torque under the control of the first clutch control unit 104 when switching from the four-wheel drive state to the two-wheel drive state. It is assumed. Therefore, when switching from the four-wheel drive state to the two-wheel drive state, the control device 100 can minimize the time required to release the front-wheel drive clutch 46 and the shock caused by the release of the front-wheel drive clutch 46 . In addition to this, the control device 100 determines that a twist has occurred in the drive system on condition that the twist determination unit 102 has determined that a twist has occurred in the drive system. Torque reduction control is performed so that the first clutch transmission torque is gently reduced compared to when the first clutch is not engaged. Therefore, the control device 100 switches from the four-wheel drive state to the two-wheel drive state in a state in which the drive system is twisted, such as in a so-called tight corner braking state or after sudden braking. Even so, it is possible to minimize the increase in shock associated with the release of the torsion of the drive system.

(b) The control device 100 of the present embodiment reduces the magnitude of the first clutch transmission torque stepwise or continuously to a lower sweep start torque than before switching from the four-wheel drive state to the two-wheel drive state. Thereafter, the transmission torque reduction control can be performed by gradually or continuously reducing the first clutch transmission torque from the sweep start torque. Further, the control device 100, on the condition that the torsion determination unit 102 determines that the drive train is twisted, controls the control device 100 when it is not determined that the drive train is twisted. Torque reduction control is performed by setting the sweep start torque higher than in the case of As a result, the control device 100 can reduce the first clutch transmission torque to a suitable sweep start torque according to the presence or absence of torsion in the drive system, and then reduce the first clutch transmission torque stepwise or continuously. . In order to perform such control, the control device 100 minimizes the time required for releasing the front-wheel drive clutch 46 and minimizes the shock that occurs during the period in which the first clutch transmission torque is reduced from the sweep start torque. can be suppressed to a limited extent.

(c) The control device 100 of the present embodiment determines that a twist has occurred in the drive system on the condition that the twist determination unit 102 has determined that a twist has occurred in the drive system. Torque reduction control is performed by opening the front wheel drive clutch 46 so that the decrease rate of the first clutch transmission torque that decreases per unit time from the sweep start torque is smaller than when the control is not performed. It is By performing such control, the control device 100 can minimize the occurrence of a shock that accompanies the disengagement of the front wheel drive clutch 46 even when torsion occurs in the drive system.

(d) In the control device 100 of the present embodiment, the twist determination unit 102 determines the magnitude of the twist in the drive system using the steering angle as an index, and torque reduction control is performed based on the determination result. . As a result, the control device 100 takes into account the torsion of the drive system that occurs according to the magnitude of the steering angle, such as the above-described tight corner braking, when switching from the four-wheel drive state to the two-wheel drive state. Torque reduction control can be performed to minimize the shock that occurs. The torsion determination unit 102 may determine the magnitude of the torsion in the drive train using only the steering angle as an index. The magnitude of twist may be determined. Specifically, as described above, the torsion determination unit 102 determines, for example, the steering angle, vehicle speed, lateral acceleration, yaw rate, pressure supplied to the brake booster (master cylinder pressure), brake pressure, tire rotation speed, tire rotation speed, and so on. Information such as the rate of change in the number of wheels, deceleration, etc. is acquired based on the detection signal of a sensor provided in the vehicle 10, and this information is used as part or all of the index to determine the occurrence of twist in the drive system of the vehicle 10. shall be allowed.

(e) In the vehicle 10 in which the front-wheel drive clutch 46 is a wet multi-plate clutch that can adjust the degree of engagement according to the magnitude of the hydraulic pressure, the control device 100 of the present embodiment is such that the first clutch control unit 104 The magnitude of the first clutch transmission torque is controlled according to the magnitude of the hydraulic pressure acting on the front wheel drive clutch 46 . As a result, the control device 100 controls the hydraulic pressure acting on the front wheel drive clutch 46 in accordance with the timing chart shown in FIG. When switching from the drive state to the two-wheel drive state, it is possible to minimize the occurrence of a shock due to the release of the front-wheel drive clutch 46 .

Although the control device 100 exemplified in the above-described embodiment has exemplified a configuration including all the configurations according to the above (a) to (e), the present invention is not limited to this, and any one of these It may be one that does not have this configuration.

For example, as in (b) above, the control device 100 determines that a torsion has occurred in the drive system on the condition that the torsion determination unit 102 has determined that a torsion has occurred in the drive system. Compared to when the determination is not made, the sweep start torque is set higher, the torque reduction control is performed, and it is determined that the torsion in the drive system is occurring as in (c) above. The front-wheel drive clutch 46 is opened so that the rate of decrease in the first clutch transmission torque that decreases per unit time from the sweep start torque is smaller than when the clutch 46 is not engaged. However, the control device 100 does not vary the sweep start torque according to the presence or absence of twist in the drive system as in (b) above, but makes the sweep start torque the same regardless of the presence or absence of twist, while the above ( As in c), it is possible to vary the decrease rate of the first clutch transmission torque according to the presence or absence of torsion in the drive system. Conversely, the control device 100 changes the sweep start torque according to the presence or absence of torsion in the drive system as in (b) above, while not adopting the configuration in (c) above. It is possible to make the rate of decrease of the first clutch transmission torque the same after the first clutch transmission torque reaches the sweep start torque regardless of the presence or absence of torsion.

Further, the control device 100 is not limited to the one exemplified in the above embodiment, and the configuration can be changed as appropriate without departing from the scope of the present invention. As described above, the control device 100 not only changes the sweep start torque and the decrease rate of the first clutch transmission torque depending on the presence or absence of torsion in the drive system, but also, if there is torsion, starts the sweep according to the magnitude of the torsion. It is possible to vary the torque and the decrease rate of the first clutch transmission torque. Specifically, the control device 100 can be, for example, the following (f) or (g).

(f) The control device 100 can set the sweep start torque higher when the torsion of the drive system is large than when the torsion of the drive system is small, and perform torque reduction control. As a result, the control device 100 can perform torque reduction control in a state in which the first clutch transmission torque is reduced to an appropriate sweep start torque according to the magnitude of the torsion of the drive system.

(g) Further, the control device 100 controls the rate of decrease in the first clutch transmission torque, which decreases per unit time from the sweep start torque, to be smaller when the torsion of the drive system is large than when the torsion of the drive system is small. It is possible to perform torque reduction control by releasing the front wheel drive clutch 46 immediately. As a result, when the torsion of the drive system is large, the control device 100 gently reduces the first clutch transmission torque compared to when the torsion of the drive system is small, thereby switching from the four-wheel drive state to the two-wheel drive state. It is possible to minimize the shock caused by

In the above embodiment, a wet multi-plate clutch is used as the front wheel drive clutch 46 (first clutch) that selectively disconnects or connects the power transmission path between the driving force source 12 and the front propeller shaft 24 (power transmission member). is shown, the present invention is not limited to this. For example, the front-wheel drive clutch 46 may employ various clutches whose engagement can be controlled, such as an electrically controlled clutch or a clutch whose engagement can be adjusted by magnetic force. Further, in the present embodiment, the dog clutch 94 is employed as the second clutch for selectively disconnecting or connecting the power transmission path between the front propeller shaft 24 and the front wheels 14L, 14R (auxiliary driving wheels). However, the present invention is not limited to this, and an appropriate clutch such as a wet multi-plate clutch, an electrically controlled clutch, or a clutch whose connection state can be adjusted by magnetic force can be adopted as the second clutch. can be done.

The present invention is not limited to the above-described embodiments, modifications, and the like, and other embodiments are possible in accordance with the teachings and spirit of the claims without departing from the scope of the claims. The constituent elements of the above-described embodiments may be arbitrarily selected and combined. Any component of the embodiment and any component described in the means for solving the invention or a component embodying any component described in the means for solving the invention may be arbitrarily combined. may be configured We intend to acquire the rights for these as well in the amendment of the present application or in a divisional application.

The present invention includes a first clutch that selectively disconnects or connects a power transmission path between a driving force source and a power transmission member, and a power transmission path that selectively disconnects a power transmission path between the power transmission member and a sub-driving wheel. Alternatively, it can be suitably used in general controllers for four-wheel drive vehicles having a connected second clutch.

10: Vehicle (four-wheel drive vehicle)
12: Driving force source 14L, 14R: Front wheels (sub-driving wheels)
16L, 16R: Rear wheels (main drive wheels)
18: power transmission device 24: front propeller shaft (power transmission member)
46: Front wheel drive clutch (first clutch)
94: dog clutch (second clutch)
100: Control Device 102: Torsion Determining Section 104: First Clutch Control Section (Transmission Torque Control Section)

Claims (4)

a first clutch that selectively disconnects or connects a power transmission path between a driving force source and a power transmission member;
a second clutch that selectively disconnects or connects a power transmission path between the power transmission member and the auxiliary drive wheel;
a two-wheel drive state in which driving force is transmitted from the driving force source to left and right main driving wheels by disengaging the first clutch and the second clutch;
a four-wheel drive state in which driving force is also transmitted from the driving force source to the left and right sub-driving wheels by engaging the first clutch and the second clutch;
A four-wheel drive vehicle control device used in a four-wheel drive vehicle that can be switched to
a twist determination unit that determines the occurrence of twist in the drive system;
a transmission torque control unit that controls the magnitude of the first clutch transmission torque transmitted through the power transmission path by controlling the engagement state of the first clutch;
has
The transmission torque control unit performs torque reduction control to reduce the magnitude of the first clutch transmission torque when switching from the four-wheel drive state to the two-wheel drive state,
On the condition that the torsion determination unit has determined that a twist has occurred in the drive system, the first A controller for a four-wheel drive vehicle, characterized in that the torque reduction control is performed so that one-clutch transmission torque is gradually reduced. After the transmission torque reduction control gradually or continuously reduces the magnitude of the first clutch transmission torque to a sweep start torque lower than before switching from the four-wheel drive state to the two-wheel drive state, stepwise or continuously reducing the first clutch transmission torque from the sweep start torque,
On the condition that the torsion determination unit determines that a twist has occurred in the drive system, the above-described 2. A controller for a four-wheel drive vehicle according to claim 1, wherein said torque reduction control is performed with a sweep start torque set high. After the transmission torque reduction control gradually or continuously reduces the magnitude of the first clutch transmission torque to a lower sweep start torque than when switching from the four-wheel drive state to the two-wheel drive state, stepwise or continuously reducing the first clutch transmission torque from the sweep start torque,
On the condition that the torsion determination unit determines that a twist has occurred in the drive system, the above-described 2. The torque reduction control is performed by disengaging the first clutch so that the rate of decrease of the first clutch transmission torque that decreases per unit time from the sweep start torque becomes small. 3. The controller for a four-wheel drive vehicle according to 2. The first clutch is operated so that when the torsion of the drive system is large, the rate of decrease in the first clutch transmission torque that decreases per unit time from the sweep start torque is smaller than when the torsion of the drive system is small. 4. The control device for a four-wheel drive vehicle according to claim 2, wherein said torque reduction control is performed by opening.

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