JP2688775B2 - Torque split type four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque split type four-wheel drive vehicle, and more particularly, to a torque split type four-wheel drive vehicle that facilitates steering when the steering force varies.

[Conventional technology]

The most common classification of automobiles, especially passenger cars, is where the engine is mounted and whether the drive wheels are front or rear. According to this classification, the engine is mounted in the front. It is well known that the rear wheels use the FR wheels as the driving wheels, and the front wheels use the front wheels as the driving wheels with the engine mounted in the front.

The former FR type vehicle has excellent turning performance but has a slight difficulty in straight running, and the latter FF type vehicle has some difficulty in turning performance but has excellent straight running property. There are advantages and disadvantages.

Therefore, by distributing the output torque of the engine to the four wheels of the front and rear wheels, so-called all wheels, it is possible to utilize the features of FR vehicles and FF vehicles according to the running environment of the vehicle, so-called torque split type four wheels. Proposals for driving vehicles have been made. Japanese Patent Application Laid-Open No. Sho 62-6813 is an example of this type of proposal.
No. 6 can be cited.

[Problems to be solved by the invention]

Among the above types of vehicles, FF type vehicles (other name FWD
Vehicle) and a 4WD vehicle with fixed torque distribution, the steering force fluctuation becomes large due to the driving force of the front wheels. .

In this way, when the steering force fluctuation greatly changes depending on the running state, it becomes difficult to keep the steering angle constant or steer as desired, and the vehicle behavior becomes unstable, resulting in a vehicle that is difficult to steer. there were.

Therefore, the present invention reduces the steering force fluctuation by reducing the front wheel drive torque by the torque split mechanism to prevent the front inner wheel slip in the situation where the front inner wheel slips and the steering force fluctuation easily increases. It is intended to provide a vehicle capable of exhibiting the performance as a four-wheel drive vehicle by shifting excess torque to the front wheels when a slip occurs on the wheels.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention provides a center differential to which an engine output is input, a front wheel transmission shaft that transmits power from the center differential to the front wheels, and a part of the transmission torque to the front wheels. A duty solenoid valve for driving the hydraulic multi-plate clutch, which includes a hydraulic multi-plate clutch for torque split that bypasses the differential and transmits to the rear wheel, and a rear-wheel transmission shaft that transmits power from the center differential to the rear wheel. In a torque split type four-wheel drive vehicle that has a torque split control unit that controls the output of the engine, the torque split control unit that drives the duty solenoid valve uses an accelerator opening sensor, a vehicle speed sensor, and a steering wheel based on a predetermined torque distribution. Accelerator opening during turning at medium and low vehicle speeds based on values calculated from angle sensors In this case, the torque distribution to the front wheels is reduced to reduce the fluctuation of the steering force, and when the rear wheels slip, the surplus torque is distributed to the front wheels so that the performance of the four-wheel drive vehicle can be exhibited. It is characterized by.

[Operation] When the ground load of the front inner wheel is reduced and the vehicle is slipping, such as in a turning state, the front wheel drive torque is reduced to reduce the steering force fluctuation.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In these figures, reference numeral 1 denotes an engine block, and reference numerals WFL, WFR, WRL, WRR denote front, rear, left and right wheels, and the output of the engine block 1 is formed by a planetary gear 31, a sun gear 32, etc. via a transmission 2. Input to the center differential 3 by the transmission shaft 33,
An output gear 34 constituting the center differential 3 meshes with a gear 61 provided on a transmission shaft 6 to a front wheel differential 5 described later, and a sun gear 32.
A transmission shaft 41 extending from the rear wheel differential 4 extends to the rear wheel differential 4.

A hydraulic multi-plate clutch 7 is provided closer to the rear wheel than the input gear 61 of the front wheel transmission shaft 6, and a gear 72 is attached to a transmission shaft 71 of the hydraulic multi-plate clutch 7. The gear ratio of the gear 42 and the gear 72, that is, the gear ratio k, is 1: 1.08 (k = 1.0).
8).

The hydraulic multi-plate clutch 7 is controlled by the pressure oil supplied from the oil pump 81 to the duty solenoid valve 8 via the output pipe 82 and the return pipe 83.

The output pressure of the duty solenoid valve 8 is controlled by an output signal from a torque split control unit 9, and this output pressure is
Is controlled.

In this torque split control unit 9,
The input torque is estimated from the accelerator position sensor 11 of the engine, the engine speed sensor 12, the position sensor 13 of the selector gear of the transmission, and further from the steering angle sensor 14, the vehicle speed sensor 15, each wheel speed sensor (four) 16 Is input and the transfer torque required to achieve the target torque split is calculated.

Then, the torque split control unit 9 first determines a basic torque distribution ratio based on an input signal from the steering angle sensor 14, and further, based on signals from the vehicle speed sensor 15 and the accelerator opening sensor 11, a medium / low vehicle speed (for example, 50km
/ h or less) and the accelerator opening is large, output to the duty solenoid valve 8 to correct the rear wheel drive tendency from the standard distribution.

Further, by comparing the signals from the wheel speed sensors 16 of all the wheels, the rear wheel slip occurring due to the correction of the rear wheel drive tendency (the road surface friction coefficient μ which may not occur) is detected, and the rear wheel slip occurs. If so, the surplus torque to the rear wheels is estimated based on the degree of rear wheel slip (slip ratio).

Excess torque = tire inertia x (rear wheel angular acceleration-average wheel angular acceleration) The relationship between the steering angle and the torque distribution described above is shown in Fig. 2, and the standard torque distribution is from the front wheel 6: the rear wheel 4 to the torque. The distribution is changed to ensure the performance as a four-wheel drive vehicle.

〔The invention's effect〕

As is apparent from the above description, the torque split type four-wheel drive vehicle of the present invention has a large accelerator opening degree when the vehicle is driven at a medium or low vehicle speed or when the vehicle is steered at a medium or low vehicle speed.
Since the torque distribution of the front wheels is reduced to make the rear wheel drive tendency more than the standard torque distribution to reduce the fluctuation of the steering force, and when the rear wheels slip, the surplus torque is distributed to the front wheels, It is possible to reduce the fluctuation and to exhibit the performance as a four-wheel drive vehicle.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a torque split type four-wheel drive vehicle of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between torque distribution and steering angle. 1 …… Engine block 2 …… Transmission 3 …… Center differential, 31 …… Planetary gear, 32 …… Sun gear, 33 …… Transmission shaft, 34 …… Output gear 4 …… Rear wheel differential, 42 …… Gear 5… ... front wheel differential 6 ... front wheel transmission shaft, 61 ... input gear 7 ... hydraulic multi-plate clutch, 71 ... transmission shaft, 72 ... gear 8 ... duty solenoid valve, 81 ... oil pump 9 ... torque split Control unit 11 …… Accelerator position sensor 12 …… Engine speed sensor 13 …… Position sensor 14 …… Steering angle sensor 15 …… Vehicle speed sensor 16 …… Wheel speed sensor

Claims (1)

(57) [Claims] 1. A center differential to which an engine output is input, a front wheel transmission shaft for transmitting power from the center differential to the front wheels, and a part of transmission torque to the front wheels is transmitted to the rear wheels by bypassing the center differential. A torque split control unit for controlling the output of a duty solenoid valve for driving the hydraulic multi-plate clutch is provided, which includes a hydraulic multi-plate clutch for torque splitting and a rear wheel transmission shaft for transmitting power from the center differential to the rear wheels. In a torque split type four-wheel drive vehicle that has a torque split control unit that drives a duty solenoid valve, based on a predetermined torque distribution, a value calculated from an accelerator opening sensor, a vehicle speed sensor, a steering angle sensor, etc. When the accelerator opening becomes large during turning at low vehicle speed, the torque distribution to the front wheels is reduced. A torque split type four-wheel drive characterized by reducing steering torque fluctuations and distributing surplus torque to the front wheels to exhibit the performance of a four-wheel drive vehicle when the rear wheels slip. car.