JP6973939B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for a vehicle that employs an active torque split 4WD.

Conventionally, an active torque split 4WD is widely known as a 4WD (four-wheel-drive) system for a four-wheel vehicle. In one example of an active torque split 4WD system, power from the engine is normally transmitted to the main drive wheels, such as the left and right front wheels. When the occurrence of tire slip is predicted from the road surface friction coefficient, etc., the power from the engine is actively distributed to the main drive wheel and the sub drive wheel by the electronically controlled coupling so that the tire slip does not occur. Will be done.

Japanese Unexamined Patent Publication No. 2015-9567

However, in order to prevent damage to parts that transmit power to the auxiliary drive wheels, such as the rear differential gear, there may be an upper limit on the power distributed from the electronically controlled coupling to the auxiliary drive wheels. .. In this case, even if a part of the power from the engine is distributed to the auxiliary drive wheels, the power that the main drive wheels must take is still excessive, and there is a possibility that tire slip of the main drive wheels may occur.

An object of the present invention is to provide a vehicle control device capable of satisfactorily suppressing the occurrence of tire slip.

In order to achieve the above object, the vehicle control device according to the present invention is a control used for a vehicle equipped with a power distribution device that distributes a part of the power transmitted from the drive source to the main drive wheels to the auxiliary drive wheels. If the device determines the distribution of power from the drive source to the main and sub-drive wheels and the determined distribution to the sub-drive wheels exceeds the upper limit that the sub-drive wheels can handle, at least. The output of the drive source is reduced by the amount of power exceeding the upper limit.

According to this configuration, when the distribution of the power from the drive source to the main drive wheel and the sub drive wheel is determined, the upper limit that the determined sub drive wheel can handle the distribution to the determined sub drive wheel is set. If it exceeds, the output of the drive source is reduced by at least the amount of power exceeding the upper limit. As a result, it is possible to suppress damage to parts that transmit power to the auxiliary drive wheels, and it is possible to satisfactorily suppress the occurrence of tire slip in the main drive wheels.

The control device subtracts the upper limit that the main drive wheel can handle from the power from the drive source, determines that the remaining power is distributed to the sub drive wheels, and the determined distribution to the sub drive wheels is subordinate. When the upper limit that the drive wheels can handle is exceeded, it is preferable that the output of the drive source is reduced by at least the power exceeding the upper limit, and the power that the auxiliary drive wheels are responsible for is reduced by the reduced amount.

As a result, it is possible to suppress the occurrence of tire slip on the auxiliary drive wheels while maximizing the grip of the main drive wheels.

According to the present invention, it is possible to suppress damage to parts that transmit power to the auxiliary drive wheels, and it is possible to satisfactorily suppress the occurrence of tire slip in the main drive wheels.

It is a top view of the vehicle which mounted the ECU which concerns on one Embodiment of this invention. It is a flowchart which shows the flow of power distribution control.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Active torque split 4WD system>
FIG. 1 is a plan view of a vehicle 1 on which an ECU 31 according to an embodiment of the present invention is mounted.

Vehicle 1 employs an active torque split 4WD system. The vehicle 1 includes an engine 2, a transmission 3, a front differential gear 4, a transfer 5, a propeller shaft 6, and a rear differential gear 7.

The engine 2 is mounted (mounted) horizontally on the front portion of the vehicle 1 so that the crankshaft faces sideways with respect to the front-rear direction of the vehicle 1, that is, the crankshaft extends in the vehicle width direction.

The transmission 3 may be a stepped automatic transmission (AT: Automatic Transmission) provided with a labigno type planetary gear mechanism, or may be a belt type continuously variable transmission (CVT). good. A torque converter with a lockup function is attached to the transmission 3.

A ring gear 12 is fixed to the differential case 11 of the front differential gear 4. The power of the engine 2 is changed and input to the ring gear 12 by the transmission 3. The power input to the ring gear 12 causes the differential case 11 to rotate integrally with the ring gear 12. Then, the rotation of the differential case 11 is converted into the rotation of each side gear 14 via the pinion gear 13, and the left and right front drive shafts 15L and 15R rotate integrally with each side gear, and the rotation of the front drive shafts 15L and 15R is the main. It is transmitted to the front wheels 16L and 16R, which are the drive wheels.

The transfer 5 includes, for example, a first bevel gear 17 that rotates integrally with the differential case 11 of the front differential gear 4, and a second bevel gear 18 that meshes with the first bevel gear 17. The front end of the propeller shaft 6 extending in the front-rear direction of the vehicle 1 is connected to the center of the second bevel gear 18.

An electronically controlled coupling 21 is interposed in the middle of the propeller shaft 6. As the electronically controlled coupling 21, a known one having a multi-plate friction clutch in which a plurality of input side clutch plates and output side clutch plates are alternately arranged is adopted.

The rear end of the propeller shaft 6 is connected to the drive pinion shaft of the rear differential gear 7. The power transmitted from the propeller shaft 6 to the rear differential gear 7 rotates the rear drive shafts 22L and 22R, and the rotations of the rear drive shafts 22L and 22R are transmitted to the rear wheels 23L and 23R, which are auxiliary drive wheels, respectively.

Further, the vehicle 1 is provided with an ECU (Electronic Control Unit) 31 having a configuration including a microcomputer (microcontroller unit). A wheel speed sensor 24 that outputs a pulse signal synchronized with the rotation of each of the front wheels 16L, 16R and the rear wheels 23L, 23R as a detection signal is connected to the ECU 31. The ECU 31 obtains each wheel speed of the front wheels 16L, 16R and the rear wheels 23L, 23R from the detection signal of each wheel speed sensor 24, and controls the electronically controlled coupling 21 based on this.

Although only one ECU 31 is shown in FIG. 1, a plurality of ECUs having the same configuration as the ECU 31 are mounted on the vehicle 1 in order to control each part. A plurality of ECUs including the ECU 31 are connected so as to be capable of bidirectional communication by a CAN (Controller Area Network) communication protocol.

<Power distribution control>
FIG. 2 is a flowchart showing the flow of power distribution control.

The ECU 31 executes the power distribution control shown in FIG. 2 in order to distribute the power from the engine 2 to the front wheels 16L and 16R and the rear wheels 23L and 23R.

In the power distribution control, first, it is determined whether or not to distribute the power from the engine 2 to the rear wheels 23L and 23R (step S1). In the ECU 31, the friction coefficient (μ) of the road surface in contact with each wheel is estimated from the wheel speeds of the front wheels 16L and 16R and the rear wheels 23L and 23R, and the occurrence of tire slip of the front wheels 16L and 16R is predicted from the road surface friction coefficient. NS. Then, when there is a possibility that tire slip of the front wheels 16L and 16R may occur, it is determined that the power from the engine 2 is distributed to the rear wheels 23L and 23R. On the other hand, if there is no possibility of tire slip occurring on the front wheels 16L and 16R, it is decided that the power from the engine 2 is not distributed to the rear wheels 23L and 23R, but is distributed only to the front wheels 16L and 16R ( NO) in step S1, the power distribution control is terminated. In this case, the electronically controlled coupling 21 remains open and is not engaged.

When it is determined to distribute the power from the engine 2 to the rear wheels 23L and 23R (YES in step S1), the distribution to the rear wheels 23L and 23R is determined (step S2). Specifically, the power component that the front wheels 16L and 16R can handle without causing tire slip is subtracted from the power from the engine 2, and the remaining power is determined to be distributed to the rear wheels 23L and 23R.

After that, it is determined whether or not the distribution to the rear wheels 23L and 23R exceeds the upper limit of the power that the rear wheels 23L and 23R can take charge of (step S3). The upper limit of the power that the rear wheels 23L and 23R can handle is obtained in advance from the strength of the rear differential gear 7 and the like, and is stored in the memory of the ECU 31.

When the distribution to the rear wheels 23L and 23R does not exceed the upper limit (NO in step S3), the engagement state of the electronically controlled coupling 21 is controlled so that the power of the distribution is transmitted to the rear wheels 23L and 23R. Then, the power distribution control is terminated.

When the distribution to the rear wheels 23L and 23R exceeds the upper limit (YES in step S3), the engine torque output by the engine 2 is reduced by the amount of power exceeding the upper limit (step S4). Then, the engagement state of the electronically controlled coupling 21 is controlled so that the upper limit power that the 23L, 23R can handle is transmitted to the rear wheels 23L, 23R, and the power distribution control is terminated.

<Action effect>
As described above, when it is decided to distribute the power from the engine 2 to the front wheels 16L, 16R and the rear wheels 23L, 23R, the determined distribution to the rear wheels 23L, 23R is to the rear wheels 23L, 23R. When the upper limit that can be handled by the engine is exceeded, the engine torque output from the engine 2 is reduced by the amount of power exceeding the upper limit. As a result, damage to parts that transmit power to the rear wheels 23L and 23R, such as the rear differential gear 7, can be suppressed, and the occurrence of tire slip on the front wheels 16L and 16R can be satisfactorily suppressed.

<Modification example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other embodiments.

For example, in the above-described embodiment, the main drive wheels to which the power is transmitted when the power is not distributed are the front wheels 16L and 16R, but the vehicle control device according to the present invention has the power when the power is not distributed. It can also be used for a vehicle having a configuration in which the main drive wheels to which the vehicle is transmitted are the rear wheels 23L and 23R.

Further, the transmission 3 may be a power split type continuously variable transmission. The power split type continuously variable transmission is provided with, for example, a belt-type continuously variable transmission mechanism that changes power steplessly by changing the gear ratio, and splits power into two paths between an input shaft and an output shaft. It is a transmission that can be transmitted.

In addition, various design changes can be made to the above-mentioned configuration within the scope of the matters described in the claims.

1: Vehicle 2: Engine (drive source)
16L, 16R: Front wheels (main drive wheels)
21: Electronically controlled coupling (power distribution device)
23L, 23R: Rear wheel (secondary drive wheel)
31: ECU (control unit)

Claims (1)

A control device used in a vehicle equipped with a power distribution device that distributes a part of the power transmitted from the drive source to the main drive wheels to the sub drive wheels.
Of the power from the drive source, the power that the main drive wheels can handle without causing tire slip is determined to be distributed to the main drive wheels, and the power is subtracted from the power from the drive source. to determine the residual power to distribution of the the auxiliary drive wheels,
When the determined distribution to the sub-drive wheels exceeds the upper limit that the sub-drive wheels can take charge of, the vehicle control device reduces the output of the drive source by at least the amount of power exceeding the upper limit.

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