JP2023054724A - Control device for four-wheel drive vehicle - Google Patents

Abstract

To provide a control device for a four-wheel drive vehicle which permits travelling in a proper driving state in accordance with a situation even when malfunction of a switch for drive mode switching occurs.SOLUTION: A control device 100 includes a drive mode setting part 102 which sets a drive mode of a vehicle 10 on the basis of a signal outputted from a driving mode selection switch 140 provided in the vehicle 10, and a first clutch control part 104 and a second clutch control part 106 which operate and control a clutch 46 for driving front wheels and an engagement-type clutch 94 in accordance with the drive mode set on the drive mode setting part 102. The control device 100 performs such driving mode changing processing that a drive mode setting part 102 changes a driving mode from a two-wheel drive fixed mode to a driving type variable mode when malfunction of a driving mode selection switch 140 occurs in such a state that the vehicle 10 drives in the two-wheel drive fixed mode.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 4WD mode while preventing impulsive or vibrational fluctuations in the transmission torque. .

Japanese Patent Application Laid-Open No. 2020-032773

Here, the present inventors have proposed a drive mode (two-wheel drive fixed mode) in which power is transmitted only to the main drive wheels, such as the 2WD mode described above, and a drive mode in which power is transmitted not only to the main drive wheels but also to the auxiliary drive wheels, such as the 4WD mode. In addition to the drive mode (four-wheel drive fixed mode) that transmits the driving force, for example, as in the drive mode called 4WD AUTO, on the condition that the occurrence of slip is detected in the two-wheel drive state, the auxiliary drive wheel A four-wheel drive vehicle that can operate in a drive mode (variable drive mode) that performs drive control to increase the distribution of the transmitted driving force and change to a four-wheel drive state was studied.

As a result of the above study, there is a concern that if the drive mode switch used to switch the drive mode malfunctions, it will not be possible to drive in the 4WD state at the appropriate timing if the drive mode before the failure occurs is continued. I came to the knowledge that there is As a result of further intensive studies by the present inventors, for example, if a problem occurs in the switch while the drive mode is in the two-wheel drive state, the drive mode can be switched to four-wheel drive when driving in the four-wheel drive state is required. We have come to the knowledge that there is a possibility that problems such as being unable to switch to the wheel drive mode may occur.

SUMMARY OF THE INVENTION Therefore, the present invention provides a control device for a four-wheel drive vehicle that enables the vehicle to run in an appropriate driving state according to the situation, even if the switch for switching the driving mode malfunctions. aimed.

Here, in order to solve the above-mentioned problems, the inventors of the present invention conducted intensive studies and found that the drive mode was changed to the two-wheel drive fixed mode under the condition that the switch malfunctioned while the drive mode was in the two-wheel drive state. We considered switching from the four-wheel drive fixed mode to either the four-wheel drive fixed mode or the drive system variable mode.

As a result, it was found that if the drive mode is switched from fixed 2WD to fixed 4WD, tight corner braking may occur when turning at low speeds. It has been found that in such a state, there is a high possibility that a user who intends to drive in the two-wheel drive fixed mode will feel uncomfortable.

On the other hand, if the drive mode is switched from the two-wheel drive fixed mode to the drive system variable mode, the vehicle can normally run in the two-wheel drive state, and when a slip occurs, the drive mode is switched to the four-wheel drive state. As a result, even a user who intends to drive in the two-wheel drive fixed mode can drive without discomfort, and can drive in the four-wheel drive state when it is necessary to suppress slippage. Therefore, if the drive mode is switched from the two-wheel drive fixed mode to the drive system variable mode on the condition that the switch malfunctions while the drive mode is in the two-wheel drive state, four-wheel drive can be achieved in an appropriate situation. It was found that it is possible to run in the state.

(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 Two-wheel drive fixed mode in which driving force is transmitted from the driving force source to the left and right main driving wheels, and from the driving force source to the left and right auxiliary driving wheels by respectively engaging the first clutch and the second clutch A four-wheel drive fixed mode that also transmits driving force, and by changing the degree of engagement of the first clutch when a predetermined condition is satisfied while engaging the second clutch, the main drive wheels The vehicle is drivable in a drive mode selected from a plurality of drive modes including a drive system variable mode that performs drive control to increase the distribution of the drive force transmitted to the auxiliary drive wheels with respect to the transmitted drive force, A control device for a four-wheel drive vehicle, which is used in a four-wheel drive vehicle and includes a drive mode selection switch that accepts selection of the drive mode, wherein the four-wheel drive vehicle is controlled based on a signal output from the drive mode selection switch. a driving mode setting unit that sets a vehicle driving mode; and a clutch control unit that controls the operation of the first clutch and the second clutch in accordance with the driving mode set by the driving mode setting unit. , the drive mode setting unit sets the drive mode setting unit as a partial or complete start condition that the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the two-wheel drive fixed mode. It is characterized by performing drive mode change processing for changing the mode from the two-wheel drive fixed mode to the drive system variable mode.

Based on the knowledge described above, the control device for a four-wheel drive vehicle of the present invention has a drive mode setting unit that sets the drive mode to two-wheel drive on the condition that the switch malfunctions while the drive mode is in the two-wheel drive state. Drive mode change processing for switching from the drive fixed mode to the drive method variable mode is performed. Therefore, the controller for a four-wheel drive vehicle according to the present invention can provide an appropriate drive state according to the situation even if the switch for switching the drive mode malfunctions while the drive mode is the two-wheel drive state. It is possible to control the operation of the four-wheel drive vehicle so that it can run with

(2) The four-wheel drive vehicle control device of the present invention described above has a stability determination unit that determines the stability of the four-wheel drive vehicle, and the drive mode setting unit determines whether the stability determination unit determines whether the stability of the four-wheel drive vehicle is stable. It is preferable that the drive mode change processing is performed with determination that the state is present as one of the start conditions.

As described above, the four-wheel drive vehicle control device of the present invention performs the drive mode change processing with the condition that the stability of the four-wheel drive vehicle is ensured as the starting condition. Drive mode change processing can be reliably performed in preparation for situations where driving is required.

(3) In the control device for a four-wheel drive vehicle of the present invention described above, the drive mode setting unit determines that (α) tire slip is occurring, (β) the vehicle is traveling on a low μ road, (γ) the outside air temperature is equal to or lower than a predetermined temperature, and the driving mode changing process is performed by satisfying at least one of the starting conditions.

With such a configuration, the controller for a four-wheel drive vehicle according to the present invention can control the four wheels as in the above (α) to (γ) even if the switch for switching the drive mode malfunctions. In a situation where the vehicle should be in the drive state, it is possible to run in the four-wheel drive state.

(4) The controller for a four-wheel drive vehicle according to the present invention is provided on the condition that the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the drive system variable mode. , and the drive mode setting unit maintains the drive mode in the drive method variable mode.

With such a configuration, the controller for a four-wheel drive vehicle of the present invention can enable the vehicle to travel in an appropriate driving state depending on the situation.

(5) The control device for a four-wheel drive vehicle according to the present invention is provided under the condition that the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the four-wheel drive fixed mode. Preferably, the drive mode setting unit maintains the drive mode at the four-wheel drive fixed mode.

The four-wheel drive vehicle controller of the present invention maintains the four-wheel drive fixed mode even after the drive mode selection switch malfunctions, thereby unexpectedly changing the drive mode to the two-wheel drive fixed mode. It is possible to suppress switching to the two-wheel drive state against the user's intention by changing the mode or drive system variable mode.

(6) In the four-wheel drive vehicle control device of the present invention described above, the stability determination unit determines that (A) the vehicle is stopped, and (B) acts on the vehicle in the front-rear direction and the left-right direction. Determination that the four-wheel drive vehicle is in a stable state based on at least one of (C) the yaw rate sensor value being within a predetermined range, and (C) the yaw rate sensor value being within a predetermined range. It is preferable that it is characterized by:

With such a configuration, the control device for a four-wheel drive vehicle of the present invention accurately grasps the stability of the four-wheel drive vehicle, and prepares for a situation in which four-wheel drive is required. Driving mode change processing can be performed in a state where the stability of the vehicle is high.

(7) In the four-wheel drive vehicle control device of the present invention described above, when the four-wheel drive vehicle is driven in the four-wheel drive fixed mode, the drive mode selection switch malfunctions, The drive mode setting unit changes the drive mode from the four-wheel drive fixed mode to the drive system variable mode on condition that the vehicle is assumed to be in a corner braking state. Good to have.

With such a configuration, the controller for a four-wheel drive vehicle according to the present invention can prevent a tight corner braking state when the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the fixed four-wheel drive mode. By changing to the drive system variable mode in such a situation, the operation of the four-wheel drive vehicle can be controlled so that the tight corner braking state can be resolved and the vehicle can run.

According to the present invention, there is provided a controller for a four-wheel drive vehicle that enables the vehicle to run in an appropriate driving state according to the situation, even when the switch for switching the driving mode malfunctions. can.

It is an explanatory view showing a control device concerning one embodiment of the present invention, and vehicles carrying the same. 2 is a flowchart showing an example of control performed in a state where a drive mode selection switch does not operate normally in the vehicle shown in FIG. 1; (a) to (c) are timing charts showing changes in the drive mode when the drive mode selection switch does not operate normally. (a) is a block diagram which shows the control apparatus based on a 2nd modification, (b) is a block diagram which shows the control apparatus based on a 3rd modification.

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 engagement (degree of 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 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 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 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 drive mode selection switch 140 for switching drive states. The drive mode selection switch 140 can select and set any of the three drive modes of "2WD", "4WD LOCK", and "4WD AUTO". When the drive mode selection 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 set to a drive mode (fixed two-wheel drive mode) in which it is driven in a two-wheel drive state. When the drive mode selection 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 set to a drive mode (four-wheel drive fixed mode) in which it is driven in a four-wheel drive state.

Further, when the drive mode selection switch 140 is set to "4WD AUTO", the degree of engagement of the front wheel drive clutch 46 is changed on the condition that the dog clutch 94 is engaged and slip occurrence is detected. A drive mode ( drive system variable mode). Specifically, when the drive mode selection switch 140 is set to "4WD AUTO", the dog clutch 94 is engaged, and the front wheel drive clutch 46 is placed in a predetermined standby state in preparation for the occurrence of a slip. It is in a standby state with the degree of engagement S engaged. When the drive mode selection switch 140 is set to "4WD AUTO", when the rear wheels 16L and 16R, which are the main drive wheels, slip, the front wheels are operated while the dog clutch 94 is maintained in the engaged state. By fully engaging the driving clutch 46, the driving 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 has a drive mode setting section 102 . In addition, the control device 100 serves as a clutch control section for controlling the operations of the front wheel drive clutch 46 and the dog clutch 94 in accordance with the drive mode set by the drive mode setting section 102. The first clutch control section 104 and a second clutch control unit 106 .

The driving mode setting section 102 sets the driving mode of the vehicle 10 based on the signal output from the driving mode selection switch 140 . Here, when the drive mode selection switch 140 is operating normally, the drive mode setting unit 102 can set the drive mode of the vehicle 10 by reflecting the operation of the drive mode selection switch 140 by the user. can. However, in a state where the drive mode selection switch 140 does not operate normally due to a failure of the drive mode selection switch 140 or a communication failure between the drive mode selection switch 140 and the drive mode setting unit 102, The setting of the drive mode selection switch 140 cannot be reflected. Therefore, the drive mode setting unit 102 performs drive mode change processing on the condition that the drive mode selection switch 140 does not operate normally, and automatically sets the drive mode.

Specifically, the drive mode setting unit 102 sets the drive mode to the two-wheel drive mode on the condition that the drive mode selection switch 140 malfunctions while the vehicle 10 is being driven in the fixed two-wheel drive mode. A process (drive mode change process) for changing from the drive fixed mode to the drive system variable mode is performed. On the other hand, the drive mode setting unit 102 keeps the drive mode in the variable drive system mode under the condition that the drive mode selection switch 140 malfunctions while the four-wheel drive vehicle is being driven in the variable drive system mode. maintain. Further, the drive mode setting unit 102 maintains the drive mode in the four-wheel drive fixed mode on condition that the drive mode selection switch 140 malfunctions while the vehicle 10 is being driven in the four-wheel drive fixed mode. process.

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 . The first clutch control unit 104 controls the operation of the front wheel drive clutch 46 according to the drive mode set by the drive mode setting unit 102 . 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 . The second clutch control section 106 controls the operation of the dog clutch 94 according to the drive mode set by the drive mode setting section 102 . 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 control device 100 described above is characterized by the control performed when the drive mode selection switch 140 does not operate normally. The control that is performed when the drive mode selection switch 140 does not operate normally 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 checks whether the drive mode selection switch 140 of the vehicle 10 is in an abnormal state due to a failure, poor communication, or the like. Here, if it is found that the drive mode selection switch 140 is in an abnormal state, the control flow proceeds to step 2 .

(Step 2)
At step 2, the control device 100 checks whether or not the drive mode of the vehicle 10 before the abnormality of the drive mode selection switch 14 was confirmed at step 1 was the fixed two-wheel drive mode. Here, if the vehicle is in the two-wheel drive fixed mode, the control flow advances to step 3 . On the other hand, if the drive mode is a drive mode other than the fixed two-wheel drive mode, that is, the fixed four-wheel drive mode or variable drive system mode, the control flow proceeds to step 4 .

(Step 3)
When the control flow proceeds to step 3, the driving mode setting unit 102 of the control device 100 changes the setting of the driving mode from the conventional two-wheel drive fixed mode to the driving method variable mode. As a result, the control device 100 performs control to operate the vehicle 10 in the drive method variable mode regardless of the state of the drive mode selection switch 140 (see FIG. 3A). Specifically, the control device 100 brings the dog clutch 94 into the engaged state under the control of the second clutch control section 106 . In addition, under the control of the first clutch control section 104, the control device 100 engages the front wheel drive clutch 46 at a predetermined standby engagement degree S in preparation for the occurrence of a slip. As a result, when the rear wheels 16L and 16R, which are the main driving wheels, slip, the driving state of the vehicle 10 can be switched to the four-wheel drive state by fully engaging the front-wheel drive clutch 46. It is said that

(Step 4)
On the other hand, when the control flow advances from step 2 to step 4 described above, the drive mode setting unit 102 of the control device 100 maintains the drive mode in the state before the drive mode selection switch 140 malfunctioned. That is, if the drive mode before the drive mode selection switch 140 malfunctioned was the drive system variable mode, the drive mode is maintained in the drive system variable mode (see FIG. 3B). Also, if the drive mode before the drive mode selection switch 140 malfunctioned was the four-wheel drive fixed mode, the drive mode is maintained in the four-wheel drive fixed mode (see FIG. 3(c)).

Since the control device 100 mounted on the vehicle 10 described above has the following characteristic configurations (a) to (c), characteristic effects that cannot be achieved by the conventional technology described below can demonstrate

(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 dog clutch 94 are respectively released to engage the front wheel drive clutch 46 and dog clutch 94 in a two-wheel drive fixed mode in which driving force is transmitted from the driving force source 12 to the left and right main drive wheels. A four-wheel drive fixed mode 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 clutch 94, and when a predetermined condition is satisfied, a front-wheel drive mode is selected. and a drive system variable mode that performs drive control to increase 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 by changing the degree of engagement of the clutch 46. It is used in a vehicle 10 that can be driven in a drive mode selected from a plurality of drive modes, and is provided with a drive mode selection switch 140 that accepts selection of the drive mode. The control device 100 has a drive mode setting unit 102 that sets the drive mode of the vehicle 10 based on a signal output from the drive mode selection switch 140, and controls the front wheels according to the drive mode set in the drive mode setting unit 102. It has a clutch control section (first clutch control section 104 and second clutch control section 106 ) that controls the operation of the drive clutch 46 and dog clutch 94 . In the state where the vehicle 10 is driven in the two-wheel drive fixed mode, the drive mode setting unit 102 sets the drive mode setting unit 102 as a partial or complete starting condition that the drive mode selection switch 140 malfunctions. is changed from the fixed two-wheel drive mode to the variable drive mode.

In the control device 100, as described in (a) above, the drive mode setting unit 102 sets the drive mode to the two-wheel drive fixed mode on the condition that the switch malfunctions while the drive mode is in the two-wheel drive state. drive mode change processing for switching to the drive system variable mode. Therefore, the control device 100 of the present embodiment enables the vehicle to run in an appropriate driving state according to the situation when the switch for switching the driving mode malfunctions while the driving mode is the two-wheel drive state. Operation control of the vehicle 10 can be performed. Specifically, when the switch for switching the drive mode malfunctions while the drive mode is in the two-wheel drive state, the control device 100 prevents the switch from being switched to the four-wheel drive state due to, for example, a slip occurring. It is possible to switch to four-wheel drive when it is desirable, or switch to two-wheel drive when four-wheel drive is not required or when tight corner braking occurs.

(b) In the control device 100 of the present embodiment described above, the drive mode setting unit 102 is set to , the drive mode is maintained in the drive system variable mode.

Since the control device 100 of the present embodiment is configured as described above, even after the drive mode selection switch 140 malfunctions, the drive mode is maintained in the drive method variable mode, and appropriate driving is performed according to the situation. It is possible to run in the state.

(c) The control device 100 of the present embodiment described above sets the drive mode setting unit 102 under the condition that the drive mode selection switch 140 malfunctions while the vehicle 10 is being driven in the fixed four-wheel drive mode. However, the drive mode is supposed to be maintained in the four-wheel drive fixed mode.

Since the control device 100 of the present embodiment is configured as described above, the drive mode is unexpectedly changed to the two-wheel drive fixed mode or the drive system variable mode after the drive mode selection switch 140 malfunctions. , it is possible to suppress switching to the two-wheel drive state against the user's intention.

In this embodiment, the control device 100 having the features (a) to (c) was exemplified, but the present invention is not limited to this. For example, it is possible not to have the configuration (b) or (c) or to have another configuration. Specifically, for example, it is possible to adopt a configuration as shown in the following first to third modifications. Each modification will be described below. In the following description, detailed descriptions of configurations common to the above-described embodiment will be omitted, and the same configurations will be described with the same reference numerals.

<First modification>
With the vehicle 10 being driven in the fixed two-wheel drive mode, the control device 100 sets the drive mode setting unit 102 to the fixed two-wheel drive mode on the condition that the drive mode selection switch 140 malfunctions as a starting condition. Although the process (driving mode change process) is performed to change the setting from the mode to the drive method variable mode, it is possible to add one or more other conditions as a start condition for performing the drive mode change process. be.

Specifically, the control device 100 of the first modified example sets, as a condition for starting the drive mode change process, that the drive mode selection switch 140 malfunctions while the vehicle 10 is being driven in the fixed two-wheel drive mode. In addition to , the drive mode setting unit 102 performs drive mode change processing on the condition that any one of the following conditions (α) to (γ) is satisfied as a start condition.
(α) Tire slip occurs.
(β) The vehicle is running on a low μ road.
(γ) that the outside air temperature is equal to or lower than a predetermined temperature;
According to this modified example, the following effect (d) can be obtained.

(d) In the control device 100 of this modification, the drive mode setting unit 102 performs the drive mode change process with the satisfaction of at least one of the above (α) to (γ) as one of the start conditions. be. Therefore, in the control device 100 of the present modified example, even if the drive mode changeover switch 140 malfunctions, the four-wheel drive state should be set as in (α) to (γ) above. Drive mode change processing is not performed until

With the configuration as described above, even if the drive mode changeover switch 140 malfunctions, the vehicle can run in the two-wheel drive fixed mode as intended by the user until the scene where the four-wheel drive mode is required occurs. Therefore, the user can drive the vehicle 10 without a sense of discomfort. In addition, after the situation where the configured four-wheel drive state is required as described above, it is possible to appropriately switch to the four-wheel drive state and travel in a situation where traveling in the four-wheel drive state is required.

In this modified example, an example is shown in which the satisfaction of any one of the following conditions (α) to (γ) is added as a start condition for the drive mode change process, but the present invention is not limited to this. Instead, conditions other than (α) to (γ) may be added, or any one of (α) to (γ) may be deleted from the conditions.

<Second modification>
When the vehicle 10 is driven in the fixed two-wheel drive mode, the control device 100 changes the drive mode from the fixed two-wheel drive mode to the variable drive system mode on the condition that the drive mode selection switch 140 malfunctions. (driving mode changing process), it is possible to add one or a plurality of other conditions as a starting condition for performing the driving mode changing process. For example, as shown in FIG. 4( a ), the control device 200 of the second modification includes the drive mode setting unit 102 , the first clutch control unit 104 , and the second clutch control unit 106 described above, as well as the stability control unit 106 . A determination unit 208 is provided, and the determination result of the stability determination unit 208 is taken into consideration as a start condition for performing the drive mode change processing.

The stability determination section 208 determines the stability of the vehicle 10 . The stability determination unit 108 can determine the stability of the vehicle 10 based on one or more indices. In this modification, the stability determination unit 208 uses the following conditions (A) to (C) as indicators for determining the stability of the vehicle 10, and when any of the conditions is satisfied, the vehicle 10 Determine that it is in a stable state.
(A) The vehicle 10 is stopped.
(B) Both of the gravitational acceleration acting on the vehicle 10 in the longitudinal direction and the lateral direction are within a predetermined range.
(C) The yaw rate sensor value is within a predetermined range.

When the vehicle 10 is driven in the fixed two-wheel drive mode, the control device 200 of this modification causes the drive mode selection switch 140 to malfunction, and the stability determination unit 208 determines that the vehicle 10 is in a stable state. The start condition for performing the drive mode change process is that it is determined that the Therefore, even if drive mode selection switch 140 malfunctions while vehicle 10 is being driven in the fixed two-wheel drive mode, control device 200 determines that vehicle 10 is in a stable state by stability determination unit 208 . Until the determination is made, the drive mode change processing for changing the drive mode from the two-wheel drive fixed mode to the drive system variable mode is not performed, and the system waits.

Since the control device 200 of the second modified example has the following characteristic configurations (e) and (f), it can exhibit characteristic effects that cannot be achieved by the conventional technology described below. .

(e) The control device 200 of the second modification described above has a stability determination unit 208 that determines the stability of the vehicle 10, and the drive mode setting unit 102 determines that the stability determination unit 208 is in a stable state. The drive mode change process is performed with the determination of .

Since the control device 200 of the second modification performs the drive mode change process with the start condition that the stability of the vehicle 10 is ensured, the vehicle Drive mode change processing can be performed in a state where the stability of 10 is high. Note that, in this modified example, unlike the control device 100 exemplified in the above embodiment, an example was shown in which the stability of the vehicle 10 was added as a start condition for starting the drive mode change process. The present invention is not limited to this, and other conditions may be added as conditions for starting the drive mode change process.

(f) Further, in the control device 200 of the second modification, the stability determination unit 208 determines that the running state is stable based on at least one of the above conditions (A) to (C) as a determination criterion. Judgment is supposed to be made.

The control device 200 of the second modified example controls the vehicle 10 in a state where the vehicle 10 is stopped, a state where the gravitational acceleration acting on the vehicle 10 is within a predetermined value, or a state where the yaw rate sensor value is within a predetermined range. drive mode change processing can be performed in a stable state of In this modified example, the above-described (A) to (C) are exemplified as indicators for the stability determination unit 208 to determine the stability of the vehicle 10, but the present invention is not limited to these. Instead, the determination may be made in consideration of other determination conditions. In addition, in this modification example, it is determined that the vehicle 10 is in a stable state when at least one of the above conditions (A) to (C) is satisfied, but the present invention is not limited to this. Instead, it may not be determined that the vehicle 10 is in a stable state unless a plurality of conditions among (A) to (C) or other conditions are satisfied.

<Third modification>
The above-described control device 100 performs drive mode change processing on the condition that a malfunction of the drive mode selection switch 140 occurs while the vehicle 10 is being driven in the fixed two-wheel drive mode, and changes the drive mode to the fixed two-wheel drive mode. However, when the drive mode selection switch 140 malfunctions while the vehicle 10 is being driven in the four-wheel drive fixed mode, the drive mode is also changed. It is good as a thing. Based on this knowledge, the control device 300 of the third modified example is configured such that when the four-wheel drive vehicle is driven in the four-wheel drive fixed mode, the drive mode selection switch malfunctions and the tight corner braking state occurs. The drive mode is changed from the four-wheel drive fixed mode to the drive system variable mode on the condition that the estimated state is reached.

Specifically, as shown in FIG. 4B, the control device 300 of the third modification includes a vehicle state estimator 308 capable of estimating whether the vehicle 10 is in a tight corner braking state. there is The vehicle state estimator 308 may have any configuration as long as it can estimate whether the vehicle is in a tight corner braking state. can be used to estimate whether the vehicle is in a tight corner braking state.

More specifically, the vehicle state estimation unit 308 acquires information such as steering angle, vehicle speed, lateral acceleration, and yaw rate based on detection signals from sensors provided in the vehicle 10, and uses these information as indicators. Part or all of it may be possible to determine the occurrence of torsion in the drive system of the vehicle 10, and to estimate whether or not the vehicle is in a tight corner braking state based on the result. Specifically, the vehicle state estimating unit 308 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 can be assumed that the vehicle 10 is in a tight corner braking state on the condition that the steering angle is equal to or greater than a predetermined magnitude.

Since the control device 300 of the third modified example has a characteristic configuration as described in (g) below, it can exhibit characteristic effects that cannot be achieved with the conventional technology described below.

(g) In the state where the vehicle 10 is driven in the four-wheel drive fixed mode, the control device 300 of the present embodiment causes malfunction of the drive mode selection switch 140 and presumes a tight corner braking state. The drive mode setting unit 102 changes the drive mode from the four-wheel drive fixed mode to the drive system variable mode on the condition that the vehicle is in a state where

With the configuration as described above, the control device 300 of this modified example is configured such that when the drive mode selection switch 140 malfunctions while driving in the fixed four-wheel drive mode, tight corner braking is possible. By changing to the drive system variable mode when a state assumed to occur, it is possible to control the operation of the vehicle 10 so that the tight corner braking state can be resolved and the vehicle 10 can run.

The configurations shown in the above-described embodiment and the first to third modifications are merely examples of the present invention, and the configuration of each part can be changed as appropriate without departing from the gist of the present invention. For example, in the above-described embodiment, the wet multi-wheel clutch 46 (first clutch) for selectively disconnecting or connecting the power transmission path between the driving force source 12 and the front propeller shaft 24 (power transmission member) is used as the front wheel drive clutch 46 (first clutch). Although an example employing a plate clutch has been shown, the present invention is not limited to this. For example, the front wheel drive clutch 46 may employ various clutches whose degree of engagement can be controlled, such as an electrically controlled clutch or a clutch whose degree of 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 degree of engagement 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 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: Running state grasping unit 104: First clutch control unit (clutch control unit)
106: Second clutch control unit (clutch control unit)
108: Stability determination unit 200: Control device 208: Stability determination unit 300: Control device 308: Vehicle state estimation unit

Claims (5)

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 fixed mode in which driving force is transmitted from the driving force source to left and right main driving wheels by releasing at least one of the first clutch and the second clutch;
a four-wheel drive fixed mode 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;
By changing the degree of engagement of the first clutch when a predetermined condition is satisfied while engaging the second clutch, the driving force transmitted to the main driving wheels is transmitted to the sub-driving wheels. A drive system variable mode that performs drive control to increase the distribution of the driving force that
drivable by a drive mode selected from a plurality of drive modes including
A control device for a four-wheel drive vehicle used in a four-wheel drive vehicle comprising a drive mode selection switch for accepting selection of the drive mode,
a drive mode setting unit that sets a drive mode of the four-wheel drive vehicle based on a signal output from the drive mode selection switch;
a clutch control unit that controls the operation of the first clutch and the second clutch according to the drive mode set by the drive mode setting unit;
has
When the four-wheel drive vehicle is driven in the two-wheel drive fixed mode, the drive mode setting unit sets the drive mode selection switch to a state in which the drive mode selection switch malfunctions as a partial or complete start condition. A control device for a four-wheel drive vehicle, characterized in that a drive mode change process is performed to change from the two-wheel drive fixed mode to the drive system variable mode. Having a stability determination unit that determines the stability of the four-wheel drive vehicle,
2. The driving mode setting unit according to claim 1, wherein the driving mode setting unit performs the driving mode changing process using determination by the stability determination unit that the vehicle is in a stable state as one of the start conditions. A controller for a four-wheel drive vehicle as described. The driving mode setting unit determines at least one of (α) that the tire is slipping, (β) that the vehicle is traveling on a low μ road, and (γ) that the outside air temperature is equal to or lower than a predetermined temperature. 3. The controller for a four-wheel drive vehicle according to claim 1, wherein the drive mode changing process is performed with the satisfaction of the following as one of the start conditions. Under the condition that the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the drive system variable mode, the drive mode setting unit sets the drive mode to the drive system variable mode. 4. The controller for a four-wheel drive vehicle according to any one of claims 1 to 3, characterized in that: Under the condition that the drive mode selection switch malfunctions while the four-wheel drive vehicle is being driven in the four-wheel drive fixed mode, the drive mode setting unit changes the drive mode to the four-wheel drive mode. The four-wheel drive vehicle control device according to any one of claims 1 to 5, characterized in that the fixed mode is maintained.

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