JP2023068564A - Control device for four-wheel drive vehicle - Google Patents

Abstract

To make it possible to appropriately control the distribution of driving force according to the friction coefficient of a road surface in a four-wheel drive vehicle capable of traveling in a driving state through a control method in which the distribution of driving force to sub-driving wheels is increased when the occurrence of a slip is detected.SOLUTION: A control device 100 includes a slip determination section 102. The control device 100 increases the distribution of driving force transmitted to front wheels 14L and 14R relative to driving force transmitted to rear wheels 16L and 16R on condition that the occurrence of a slip is determined by the slip determination section 102. The slip determination section 102 determines the occurrence state of the slip while making it part of or the whole of a criterion that a wheel slip ratio S in a vehicle 10 exceeds a threshold L. The slip determination section 102 sets the threshold L such that the threshold L becomes higher as lateral acceleration acting on the vehicle 10 becomes higher.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 inventors select a first clutch that selectively disconnects or connects the power transmission path between the driving force source and the power transmission member, and the power transmission path between the power transmission member and the auxiliary drive wheel. In a four-wheel drive vehicle equipped with a second clutch that automatically disengages or engages, we investigated possible problems in the case of a control system that detects the occurrence of slip and increases the distribution of driving force to the auxiliary drive wheels. .

As a result, even on so-called high-μ roads, where the coefficient of friction is high and slips are unlikely to occur, a sharp turn reduces the ground contact load of the inner wheel in the turning radius direction, causing slips to occur. We have found that there is a possibility. In such a case, if the occurrence of slip is detected and control is performed to increase the distribution of the driving force to the auxiliary drive wheels, the slip will be suppressed, but on the other hand, the so-called It was found that there is a concern that the tight corner braking phenomenon may occur.

Therefore, the present invention provides a four-wheel drive vehicle that can run in a drive state by a control system that detects the occurrence of slip and increases the distribution of the driving force to the auxiliary drive wheels, and appropriately adjusts the driving force according to the friction coefficient of the road surface. The object is to provide a controller for a four-wheel drive vehicle capable of controlling the distribution of

Here, the inventors of the present invention conducted extensive studies and found that the lateral acceleration acting on the vehicle can serve as an index that accurately reflects the road surface conditions. We have come to the knowledge that it is possible to control the distribution of force. Specifically, the higher the lateral acceleration, the higher the coefficient of friction and the less likely it is to slip. We have come to the knowledge that it is possible to accurately grasp and appropriately control the distribution of the driving force.

(1) A control device for a four-wheel drive vehicle of the present invention provided based on such knowledge includes 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 wheels, wherein at least one of the first clutch and the second clutch is released to release the A two-wheel drive state in which driving force is transmitted from the driving force source to the left and right main driving wheels, and by engaging the first clutch and the second clutch, the driving force source can also be transmitted to the left and right auxiliary driving wheels. Changing the degree of engagement of the first clutch on the condition that the occurrence of slip in the four-wheel drive vehicle is detected while the second clutch is engaged in a four-wheel drive state in which driving force is transmitted. , the driving state can be switched between a drive distribution variable state in which drive control is performed by a standby control system that increases the distribution of the driving force transmitted to the auxiliary driving wheels with respect to the driving force transmitted to the main driving wheels. A slip determination used in a wheel drive vehicle for determining whether a slip has occurred in a variable drive distribution state by using, as part or all of the determination condition, the slip rate of the wheels of the four-wheel drive vehicle exceeding a threshold value. drive transmitted to the auxiliary drive wheels relative to the driving force transmitted to the main drive wheels, provided that the slip determination unit determines that a slip has occurred as part or all of the condition. The slip determination unit sets the threshold using a part or all of the lateral acceleration acting on the four-wheel drive vehicle as an index, and the lateral acceleration increases. The threshold value is set so that the threshold value increases as the

Based on the findings described above, the controller for a four-wheel drive vehicle of the present invention sets the threshold value using the lateral acceleration as a part or all of the index. Further, the controller for a four-wheel-drive vehicle according to the present invention sets the threshold value, which is the criterion for slip determination, higher as the lateral acceleration increases. Therefore, the controller for a four-wheel drive vehicle according to the present invention sets the threshold value higher for a road surface condition in which the coefficient of friction is high and slippage is less likely to occur. As a result, the controller for a four-wheel drive vehicle according to the present invention can suppress slip determination when the vehicle is traveling on a so-called high μ road. As a result, the controller for a four-wheel drive vehicle of the present invention suppresses the control to increase the transmission distribution of the driving force to the auxiliary drive wheels when traveling on a high μ road, and the tight corner braking is performed. It is possible to suppress the occurrence of the ringing phenomenon.

Here, when the vehicle is turned sharply, the inner wheel (inner wheel) tends to slip earlier than the outer wheel (outer wheel) in the turning radius direction. Further, when the control system for a four-wheel drive vehicle of the present invention performs the above-described control, it is preferable to be able to grasp the occurrence of slip as soon as possible. Therefore, in the control device for a four-wheel drive vehicle of the present invention, it is preferable that the slip determination section determines the state of occurrence of slip based on the slip ratio of the inner wheels.

(2) Based on this finding, the above-described control device for a four-wheel drive vehicle according to the present invention is such that the slip judging unit determines the degree of slip based on the slip rate of the wheels on the inner side of the turning radius direction of the four-wheel drive vehicle. It is preferable that it determines the occurrence state.

Based on the knowledge described above, the controller for a four-wheel drive vehicle of the present invention determines the state of occurrence of slip based on the slip rate of the wheels on the inside in the turning radius direction of the four-wheel drive vehicle. Therefore, the controller for a four-wheel drive vehicle according to the present invention can quickly and appropriately grasp the state of occurrence of slip and perform appropriate control.

Here, in the four-wheel drive vehicle control system of the present invention described above, in order to grasp the road surface condition more accurately and set the threshold value that is the criterion for determining the slip to an appropriate value, the lateral acceleration In addition to the above, it is good to add other factors suitable for grasping the road surface condition as indicators. For example, it is assumed that the larger the force acting on the four-wheel drive vehicle due to the influence of the lateral acceleration and the wheel drive force, the higher the coefficient of friction and the less likely it is to slip. Therefore, the controller for a four-wheel drive vehicle of the present invention sets the threshold using the force acting on the four-wheel drive vehicle due to the influence of the lateral acceleration and the wheel drive force as an index, thereby more accurately determining the road surface condition. It is considered that distribution control of the driving force reflecting the

(3) Based on this knowledge, the four-wheel drive vehicle control device of the present invention is configured such that, instead of or in addition to the magnitude of the lateral acceleration acting on the four-wheel drive vehicle, the slip determination unit The magnitude of the force acting on the four-wheel drive vehicle due to the influence of the lateral acceleration and the wheel drive force is used as an index for setting the threshold value, and the slip determination unit determines the lateral acceleration and the wheel It is preferable that the threshold value is set so that the threshold value increases as the force acting on the four-wheel drive vehicle increases due to the influence of the driving force.

The four-wheel drive vehicle control device of the present invention acts on the four-wheel drive vehicle by the influence of the lateral acceleration and the wheel driving force instead of or in addition to the magnitude of the lateral acceleration acting on the four-wheel drive vehicle. The threshold is set using the magnitude of the force as an index. Further, the four-wheel-drive vehicle control device of the present invention can be operated in a road surface state where the coefficient of friction increases and slippage is less likely to occur as the force acting on the four-wheel drive vehicle due to the influence of lateral acceleration and wheel drive force increases. Assuming that there is, the threshold is set high. Therefore, the control device for a four-wheel drive vehicle of the present invention more reliably suppresses the control to increase the distribution of the driving force to the auxiliary drive wheels when traveling on a high μ road. , it is possible to suppress the occurrence of the tight corner braking phenomenon.

Here, the inventors of the present invention conducted extensive research and found that, in addition to the above-described lateral acceleration, for example, the yaw rate can serve as an index that accurately reflects the road surface condition. Specifically, it is assumed that the higher the yaw rate, the higher the coefficient of friction and the less likely it is for slippage to occur. We have come to the knowledge that we can appropriately control the distribution of the driving force.

(4) In the control device for a four-wheel drive vehicle of the present invention, the slip determination unit sets the threshold using the yaw rate as a part or all of the index instead of the lateral acceleration or in addition to the lateral acceleration. It is preferable that the threshold is set so that the threshold increases as the yaw rate increases.

The controller for a four-wheel drive vehicle according to the present invention uses the yaw rate as a part or all of the index in addition to the lateral acceleration or in place of the lateral acceleration to set the threshold value for determining the state of slip occurrence. ing. Therefore, the control device for a four-wheel drive vehicle of the present invention performs control to increase the transmission distribution of the driving force to the auxiliary drive wheels when traveling on a so-called high μ road, thereby preventing the tight corner braking phenomenon. You can prevent it from happening.

(5) In the four-wheel drive vehicle control device of the present invention described above, the slip determination unit grasps one or both of the wheel driving force and the vehicle speed as indicators in addition to the yaw rate. It is preferable that the threshold is set so that the threshold increases as the magnitude of the force acting on the vehicle increases.

Since the controller for a four-wheel drive vehicle according to the present invention is configured as described above, the magnitude of the force acting on the four-wheel drive vehicle is increased by taking into consideration the effects of the wheel driving force and vehicle speed in addition to the yaw rate. Based on the result, it is possible to perform transmission distribution control of the driving force according to the road surface condition.

According to the present invention, in a four-wheel drive vehicle that can run in a drive state by a control system that detects the occurrence of slip and increases the distribution of driving force to the auxiliary drive wheels, the vehicle can be driven appropriately according to the friction coefficient of the road surface. A controller for a four-wheel drive vehicle can be provided that can control the distribution of force.

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 flowchart showing a control flow that is performed when the driving state of the vehicle shown in FIG. 1 is a variable drive distribution state; FIG. 3 is a timing chart corresponding to the control flow according to FIG. 2; 4 is a timing chart showing changes in the slip ratio and changes in drive distribution to the auxiliary drive wheels, together with changes in the vehicle speed, the steering angle, and the lateral acceleration, when the threshold is kept constant without being changed.

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. The vehicle 10 employs a front engine/rear drive system. 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 engagement (engagement pressure). 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 engagement 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 rotatable integrally 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 at least one of the front wheel drive clutch 46 and 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 a state. 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 vehicle 10 includes a changeover switch 140 for switching driving states. The change-over switch 140 can be set to any one of three driving states of "2WD", "4WD LOCK", and "4WD AUTO". When the selector switch 140 is set to "2WD", one or both of the front wheel drive clutch 46 and dog clutch 94 are disengaged. As a result, the vehicle 10 is driven in a two-wheel drive state. When the changeover switch 140 is set to "4WD LOCK", the dog clutch 94 is engaged and the front wheel drive clutch 46 is completely engaged. As a result, the vehicle 10 is driven in a four-wheel drive state.

When the changeover switch 140 is set to "4WD AUTO", the degree of engagement of the front wheel drive clutch 46 is adjusted under the condition that the occurrence of slippage in the vehicle 10 is detected while the dog clutch 94 is engaged. By changing the ratio, a state (drive distribution variable state) in which drive control by a standby control method that increases the distribution of the drive force transmitted to the front wheels 14L, 14R with respect to the drive force transmitted to the rear wheels 16L, 16R is enabled (drive distribution variable state). be. Specifically, when the changeover switch 140 is set to "4WD AUTO", the dog clutch 94 is engaged, and the front wheel drive clutch 46 is engaged at a predetermined standby engagement degree in preparation for the occurrence of a slip. It is set to a standby state in the engaged state at S. When the changeover switch 140 is set to "4WD AUTO", if the rear wheels 16L and 16R, which are the main drive wheels, slip, the mesh clutch 94 is maintained in the engaged state and the front wheel drive gear is switched. By fully engaging the clutch 46, the drive state of the vehicle 10 is switched.

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 slip determination section 102 , a first clutch control section 104 and a second clutch control section 106 .

The slip determination unit 102 determines a slip occurrence state in the vehicle 10 . In the present embodiment, the slip determination unit 102 determines the occurrence state of slip using the slip rate S of the rear wheels 16L and 16R of the front wheels 14L and 14R and the rear wheels 16L and 16R as the wheels of the vehicle 10 as a determination condition. It is assumed that The slip determination unit 102 is preferably configured to determine the state of occurrence of slip based on the slip rate S of one or both of the rear wheels 16L and 16R. In the present embodiment, when the vehicle 10 turns, the inner wheel (inner wheel) in the turning radius tends to slip before the outer wheel (outer wheel). , 16R on the inner side in the turning radius direction of the vehicle 10, the occurrence state of the slip is determined based on the slip ratio S.

Here, the "slip rate S" is defined as S={Vb−Vw) when the vehicle 10 decelerates, where Vb is the speed of the vehicle 10 and Vw is the speed (wheel speed) calculated from the rotation speed of the wheel. /Vb}×100[%], and S={(Vw−Vb)/Vw}×100[%] when the vehicle 10 is accelerating.

The slip determination unit 102 determines that the slip rate S of the rear wheels 16L and 16R, which are the main drive wheels, exceeds a threshold value L in a drive distribution variable state (a state in which the changeover switch 140 is set to 4WD AUTO). is to determine the occurrence state of Further, when the vehicle 10 is turning, the slip determination unit 102 determines the state of occurrence of slip under the determination condition that the slip ratio S of the inner wheels of the rear wheels 16L and 16R exceeds the threshold value L. It is assumed that

The slip determination unit 102 sets the threshold value L using the lateral acceleration acting on the vehicle 10 as part or all of the index. In this embodiment, as can be seen from the timing chart of FIG. 3, the slip determination unit 102 sets the threshold value L so that the threshold value L increases as the lateral acceleration increases. .

The first clutch control section 104 controls transmission torque (degree of engagement of the first clutch) transmitted to the front propeller shaft 24 via 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 (engagement pressure) 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, when the changeover switch 140 is set to "4WD AUTO" and drive control is performed by the standby control method described above, the control device 100 described above appropriately controls the distribution of the driving force according to the friction coefficient of the road surface. It is characterized by performing control (driving force distribution control) for enabling. The control performed by the control device 100 when the selector switch 140 is set to "4WD AUTO" will be described in detail below in accordance with 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 the selector switch 140 of the vehicle 10 is set to "4WD AUTO", and is in a state (drive distribution variable state) in which drive control is performed by the standby control method. Check whether or not Here, when it is confirmed that the drive state of the vehicle 10 is in the variable drive distribution state, the control flow proceeds to step 2 .

(Step 2)
In step 2, the control device 100 prepares for setting the threshold value L for the slip determination unit 102 to determine whether or not the vehicle 10 is in a slipping state. ) is obtained. In this embodiment, the magnitude of the lateral acceleration acting on the vehicle 10 is used as the threshold setting index. Therefore, in step 2, the control device 100 obtains the magnitude of the lateral acceleration as an index value (threshold value setting index value) by obtaining an output signal from a sensor or the like provided in the vehicle 10 . After that, the control device 100 advances the control flow to step 3 .

(Step 3)
At step 3 , the slip determination unit 102 of the control device 100 sets the threshold value L based on the threshold setting index value obtained at step 2 . In this embodiment, the threshold L is set based on the magnitude of lateral acceleration acting on the vehicle 10 . Here, the slip determination unit 102 determines the threshold L so that the threshold L increases as the lateral acceleration increases, as shown in the timing chart of FIG. set the value. When the setting of the threshold value L is completed, the control device 100 advances the control flow to step 4 .

(Step 4)
In step 4 , the control device 100 uses the slip determining section 102 to derive the slip ratio S of the rear wheels 16 L, 16 R of the vehicle 10 that is running, based on the speed Vb and the wheel speed Vw of the vehicle 10 . When the vehicle 10 is turning, the slip determination unit 102 derives the slip ratio S of the inner wheels of the rear wheels 16L and 16R. After that, the control device 100 advances the control flow to step 5 .

(Step 5)
At step 5 , the control device 100 uses the slip determination section 102 to determine whether or not the vehicle 10 is slipping. Specifically, the slip determination unit 102 compares the slip ratio S derived in step 4 described above with the threshold value L set in step 3 . If the slip ratio S is greater than the threshold value L (S>L), the slip determination unit 102 determines that a slip has occurred, and the control flow proceeds to step 6 . On the other hand, if it is confirmed that no slip has occurred, the control flow is returned to step 1.

(Step 6)
If the control flow proceeds from step 5 to step 6, the vehicle 10 is slipping. Therefore, the control device 100 increases the engagement degree of the front wheel drive clutch 46 from the standby engagement degree S under the control of the first clutch control section 104 . As a result, the distribution of the driving force transmitted to the front wheels 14L and 14R, which are auxiliary drive wheels, is increased.

Since the control device 100 mounted on the vehicle 10 described above has the following characteristic configurations (A) and (B), characteristic effects can be exhibited.

(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 mesh clutch 94 are released to transmit driving force from the driving force source 12 to the left and right rear wheels 16L, 16R (main driving wheels); 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 engaging the mesh type clutch 94, respectively, and slipping in the vehicle 10 while engaging the dog clutch 94. On the condition that the occurrence is detected, the degree of engagement of the front wheel drive clutch 46 is changed to increase the distribution of the driving force transmitted to the front wheels 14L, 14R with respect to the driving force transmitted to the rear wheels 16L, 16R. The vehicle 10 is used in a vehicle 10 capable of switching the drive state between a drive distribution variable state in which drive control is performed by a standby control method that allows the vehicle to switch between the drive state. The control device 100 has a slip determination unit 102 that determines whether a slip has occurred by setting the slip rate S of the wheels of the vehicle 10 exceeding the threshold value L as part or all of the determination condition in the drive distribution variable state. In addition, the control device 100 transmits the driving force transmitted to the rear wheels 16L, 16R to the front wheels 14L, 14R under the condition that the slip determination unit 102 determines that a slip has occurred. It is intended to increase the distribution of the driving force applied. In the control device 100, the slip determination unit 102 sets the threshold L using the lateral acceleration acting on the vehicle 10 as a part or all of the index, and the threshold L increases as the lateral acceleration increases. is characterized by setting a threshold L to

The control device 100 of this embodiment sets the threshold value L, which is the criterion for slip determination, higher as the lateral acceleration increases. Therefore, the control device 100 of the present embodiment sets the threshold value L higher as the road surface condition has a higher coefficient of friction and is less prone to slip. As a result, the control device 100 of the present embodiment can suppress slip determination when the vehicle is traveling on a so-called high μ road. As a result, the control device 100 of the present embodiment suppresses the control to increase the transmission distribution of the driving force to the front wheels 14L and 14R when traveling on a high μ road, thereby preventing the tight corner braking phenomenon. can be prevented from occurring.

More specifically, as in the comparative example shown in FIG. 4, when the threshold value L, which is the determination criterion for slip determination, is kept at a constant value without changing even if the lateral acceleration changes, the vehicle 10 does not slip. Control is performed to increase the transmission distribution of the driving force to the front wheels 14L and 14R in a period in which the slip ratio S exceeds the threshold value L as the lateral acceleration increases, even though the vehicle is in a state of being able to make a sharp turn without any movement. It will be. When such control is performed, there is a concern that a tight corner braking phenomenon may occur.

However, in the control device 100 of the present embodiment, as the lateral acceleration increases, the threshold value L, which is the criterion for slip determination, is set higher. Therefore, if the control by the control device 100 is performed, as shown in FIG. 3, even if the slip ratio increases, it is possible to suppress the control to increase the transmission distribution of the driving force to the front wheels 14L and 14R, which are the auxiliary drive wheels. can. As a result, when the vehicle is traveling on a high μ road, it is possible to suppress the occurrence of a tight corner braking phenomenon by suppressing slip determination.

In the present embodiment, the threshold value L is set using the lateral acceleration acting on the vehicle 10 as an index. An appropriate index can be used as a reference for setting the threshold L in . That is, if the vehicle speed is increased at the same lateral acceleration on a road surface with a high friction coefficient, the turning radius of the vehicle 10 becomes larger than when the vehicle speed is low. Of the 16Rs, the slip ratio S of the inner wheels is smaller than that at low vehicle speeds. Therefore, the controller 100 preferably lowers the threshold value L as the vehicle speed increases. From another point of view, at high vehicle speeds, the difference in turning radii between the front and rear wheels becomes smaller, so the tight corner braking phenomenon is less likely to occur. If this occurs, there is no problem even if the driving force distribution is increased, and there is no need to increase the threshold value L. Therefore, the control device 100 preferably lowers the slip determination threshold value L as the vehicle speed increases.

Based on the knowledge as described above, the control device 100 can add other elements such as the driving force acting on the wheels (wheel driving force), the yaw rate, and the vehicle speed to the lateral acceleration, as in a modified example described later. Alternatively, it can be used as an index for setting the threshold value L. FIG. By setting the threshold L using a plurality of indices in this way, it is possible to set the threshold L to a more appropriate value.

Further, in the present embodiment, an example is shown in which the wheel slip rate S of the vehicle 10 exceeding the threshold value L is set as all of the judgment conditions for judging the state of occurrence of slip, but the present invention is limited to this. It is also possible to add another element as a judgment condition for judging the state of occurrence of a slip instead of the above. If factors other than the slip rate S are taken into account in determining the slip occurrence state, it becomes possible to more accurately grasp the slip occurrence state.

(B) In the control device 100 of the present embodiment described above, the slip determination unit 102 determines the state of occurrence of slip based on the slip rate S of the wheels on the inner side of the vehicle 10 in the turning radius direction.

The control device 100 of the present embodiment is configured as in (B) above in view of the fact that the inner wheels slip earlier than the outer wheels when the vehicle 10 turns. Therefore, the control device 100 of the present embodiment can quickly and appropriately ascertain the occurrence state of slip and perform appropriate control.

In this embodiment, the state of occurrence of slip while the vehicle 10 is turning is determined by the slip rate S of the inner wheel (in this embodiment, the inner wheel of the rear wheels 16L and 16R). Although an example of focusing and understanding has been shown, the present invention is not limited to this. For example, the control device 100 may comprehend the occurrence of slip by comprehending the slip ratios S of both the inner wheel side and the outer wheel side.

The control device 100 described above is merely an example of the present invention, and various modifications are conceivable without departing from the gist of the present invention. For example, the control device 100 described above can also obtain a characteristic effect that cannot be achieved by the conventional technology by configuring as shown in (C) below.

(C) In the above-described control device 100 of the present embodiment, the slip determination unit 102 determines the magnitude of the lateral acceleration acting on the vehicle 10 instead of or in addition to the lateral acceleration and the wheel driving force. The magnitude of the force acting on the vehicle 10 is used as an index for setting the threshold value L, and the slip determination unit 102 determines that the force acting on the vehicle 10 increases due to the influence of the lateral acceleration and the wheel driving force. The threshold L can be set so that the threshold L increases as the

The control device 100 according to the above (C), in order to more accurately grasp the road surface condition and set the threshold value L, which is the criterion for slipping, to an appropriate value, in addition to the lateral acceleration, the road surface This is based on the knowledge that it is good to add other factors suitable for grasping the situation as indicators. In the control device 100 according to (C) above, it is assumed that the greater the force acting on the vehicle 10 due to the influence of the lateral acceleration and the wheel drive force, the higher the coefficient of friction and the less likely it is to slip. Therefore, instead of or in addition to the magnitude of the lateral acceleration acting on the vehicle 10, the magnitude of the force acting on the vehicle 10 due to the influence of the lateral acceleration and the wheel driving force is used as an index to set the threshold value L. It is assumed. Therefore, by configuring the control device 100 as in (C) above, control is performed to increase the transmission distribution of the driving force to the front wheels 14L and 14R when the vehicle is traveling on a high μ road. can be more reliably suppressed, and the occurrence of the tight corner braking phenomenon can be suppressed.

Also, by configuring the control device 100 described above as in (D) below, it is possible to obtain a characteristic effect that cannot be achieved by the conventional technology.

(D) In the control device 100 described above, the slip determination unit 102 sets the threshold value L using the yaw rate as a part or all of the index instead of the lateral acceleration or in addition to the lateral acceleration, and the yaw rate increases. The threshold value L can be set so that the threshold value L increases as the number increases.

Here, it is assumed that the higher the yaw rate of the vehicle 10 when turning, the higher the coefficient of friction and the less likely it is to slip. Therefore, as in (D) above, the control device 100 uses the yaw rate as a part or all of the index in addition to the lateral acceleration or instead of the lateral acceleration, and sets the threshold value L for determining the slip occurrence state. good to do With such a configuration, the control device 100 performs control to increase the transmission distribution of the driving force to the front wheels 14L and 14R when traveling on a so-called high μ road, thereby causing the tight corner braking phenomenon. can be prevented from occurring.

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 driving 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: Slip Determination Unit 104: First Clutch Control Unit

Claims (3)

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 at least one of 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;
While engaging the second clutch, the drive transmitted to the main drive wheels is changed by changing the degree of engagement of the first clutch on the condition that occurrence of slip in the four-wheel drive vehicle is detected. a drive distribution variable state in which drive control is performed by a standby control method that increases the distribution of the drive force transmitted to the auxiliary drive wheels with respect to the force;
A control device for a four-wheel drive vehicle used in a four-wheel drive vehicle capable of switching the drive state to
a slip determination unit that determines whether or not a slip occurs based on a determination condition that a wheel slip ratio of the four-wheel drive vehicle exceeds a threshold in a variable drive distribution state;
The distribution of the driving force transmitted to the auxiliary driving wheels with respect to the driving force transmitted to the main driving wheels is increased under the condition that the slip determination unit determines that a slip has occurred, in part or in whole. and
The slip determination unit sets the threshold using a part or all of the lateral acceleration acting on the four-wheel drive vehicle as an index, and the threshold increases as the lateral acceleration increases. A control device for a four-wheel drive vehicle, characterized by: setting the threshold value. 2. The four-wheel drive system according to claim 1, wherein the slip determination unit determines a state of occurrence of slip based on a slip rate of a wheel on an inner side in a turning radius direction of the four-wheel drive vehicle. Vehicle controller. Instead of or in addition to the magnitude of the lateral acceleration acting on the four-wheel drive vehicle, the slip determination unit determines the magnitude of the force acting on the four-wheel drive vehicle due to the influence of the lateral acceleration and the wheel driving force. is used as an index for setting the threshold,
2. The threshold value is set so that the threshold value increases as the force acting on the four-wheel drive vehicle increases due to the influence of the lateral acceleration and the wheel drive force. 3. The controller for a four-wheel drive vehicle according to 2.

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