JPS61155027A - Four wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To enhance the running performance of a four wheel-drive vehicle, by disposing wet-type friction clutch means between the output shaft of a transmission and a front wheel drive shaft and between the former and a rear wheel- drive shaft, respectively, and changing the hydraulic pressure to the clutch means in accordance with the running condition of the vehicle. CONSTITUTION:In such an arrangement that the output torque of an engine which is transmitted through an output shaft 31 is distributed to front and rear propeller shafts 7, 9 by means of a transfer 5 at a predetermined ration, wet-type friction clutches 54, 55 for front and rear wheels are fitted on the outer periphery of a drive shaft 53 coaxially coupled to the output shaft 31 and disposed in a casing 51 for the transfer 5. A driven shaft 56 to which the propeller shaft 7 is coupled is connected to the other end of the drive shaft 53 through the rear wheel clutch 55. The clutches 54, 55 are controlled such that flow control valves 13, 14 controls hydraulic oil fed into hydraulic operating chambers 54b, 55b in the clutches 54, 55 by means of a control unit 15 in accordance with the running condition of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel drive vehicle that is capable of distributing driving force to front wheels and rear wheels at an appropriate ratio depending on driving conditions.

(Prior Art) In a four-wheel drive vehicle, a rotation difference occurs between the front and rear wheels when turning, etc., which causes a braking phenomenon and impairs driving stability. For this reason, some vehicles are equipped with a differential device between the front and rear vehicles to absorb this difference in rotation. For example, JP-A-57-41
Publication No. 216 discloses a power transmission device for a four-wheel drive vehicle equipped with this differential device.

In a four-wheel drive vehicle equipped with such a differential device, the difference in rotation between the front and rear wheels is absorbed, and driving force (driving torque) is distributed to the front and rear wheels at a predetermined distribution ratio (usually 50:50). ) will be distributed.

(Problem to be solved by the invention) However, the driving force is always forwarded by a fixed distribution ratio.
Distribution to the rear wheels may be inappropriate depending on driving conditions. For example, during acceleration and deceleration, even though the center of gravity of the vehicle shifts, if drive torque is distributed to the front and rear wheels at the same rate, it is not possible to improve acceleration performance or braking efficiency. . In view of these points, an object of the present invention is to change the distribution of drive torque to the front and rear wheels depending on driving conditions. Our goal is to provide four-wheel drive vehicles.

(Means for Solving the Problems) Therefore, in view of the fact that in a hydraulically operated friction clutch, the torque transmitted changes depending on the pressure of the hydraulic oil applied thereto, the present invention provides a solution to such friction, The output shaft of the transmission and the front wheel drive shaft, and the output shaft and the rear wheel drive shaft are connected via the clutch means, and the hydraulic pressure applied to the friction clutch means is changed depending on the driving conditions, thereby causing the output shaft to move from the output shaft to the rear wheel drive shaft. It changes the torque transmitted to the front and rear drive shafts.

The hydraulic control means for changing the pressure of the hydraulic oil applied to the friction clutch means detects the torque of the transmission output shaft, for example, detects the deflection angle, acceleration, accelerator opening, etc., and calculates these detected values. Based on the previous,
The torque distribution ratio to the rear wheels is determined, and the pressure of hydraulic oil applied to the friction clutch means is controlled so that the torque is distributed to the front and rear wheels at the determined distribution ratio.

For example, in normal constant speed driving conditions, the distribution ratio is set to 50.
: 50, and when the vehicle is accelerated, the greater the degree of acceleration, the greater the torque distribution to the rear wheels. When such control is performed, the driving torque of the rear wheels increases in accordance with the extent to which the center of gravity of the vehicle moves rearward during start-up acceleration, that is, in accordance with the extent to which the road surface friction force increases.

(Effects of the Invention) As described above, according to the present invention, drive torque can be distributed to the front and rear wheels depending on the driving conditions.

In other words, it is possible to change the torque distribution to the front and rear wheels depending on the degree of acceleration/deceleration, degree of deflection, etc., thereby improving acceleration performance, braking efficiency, steering stability during turns, etc. I can do it.

(Example) Examples of the present invention will be described below with reference to the drawings.

1 to 3 show one embodiment of the present invention. First, as shown in FIG. 2, in the driving force transmission system of this example, a transmission 3 is connected to an engine 1, and the transmission 3 is connected to a transfer 5. The output torque of the engine 1 is shifted by the transmission 3 and then distributed to a predetermined ratio by the transfer 5, and the distributed driving torque is transmitted to the rear wheels 11 and the front wheels 1 through the propeller shafts 7 and 9, respectively.
3.

FIG. 3 shows the configuration of the transfer 5. As shown in FIG. Referring to the figure, a drive shaft 53 is rotatably supported within a transfer case 51 via a bearing 52. One end of this shaft 53 is coaxially connected to the tip of the output shaft 31 of the transmission 3. Furthermore, a wet friction clutch 54 for the front wheels and a wet friction clutch 55 for the rear wheels are attached to the outer periphery of the drive shaft 53.

The other end of the drive shaft 53 is connected to a driven shaft 56 disposed coaxially with the drive shaft 53 via a rear wheel clutch 55. The driven shaft 56 is connected to a propeller shaft 7 for driving the rear wheels.

On the other hand, in the clutch 54 for the front wheels, the thalassocentric hub 54a is rotatably attached to the outer periphery of the drive shaft 53, and the hub 53a is the same (output gear 57 rotatably attached to the outer periphery of the drive shaft 53). The output gear 57 meshes with a transmission gear 59 fixed to an intermediate shaft 58 arranged parallel to the drive shaft 53.

The transmission gear 59 meshes with a gear 61 formed integrally with a driven shaft 60 arranged parallel to the drive shaft 53 . This driven shaft 60 is connected to a propeller shaft 9 for driving the front wheels via a universal joint. The clutches 54, 55 are hydraulically operated wet friction clutches, and their operating hydraulic chambers 54, b, 55 b 67 ?
When 'S hydraulic oil is supplied, the piston 54G due to the hydraulic pressure
, 55c moves. As a result, a large number of friction plates 5
4d and 55d are tightened, and the resulting frictional force causes the drive torque of the drive shaft 53 to be transmitted to the front wheels and the rear wheels, respectively. The torque transmitted by each clutch 54.55 is the piston 54C15
5c, and therefore the pressure of the hydraulic oil applied to the hydraulic chambers 54b and 55b.

FIG. 1 shows a hydraulic control system for changing the pressure of hydraulic oil applied to both clutches 54, 55 according to running conditions. As shown in the figure, the oil in the oil tank 11 is
It is sucked up by the pump 12, discharged at a predetermined pressure, and supplied to the working hydraulic chambers 54b, 55b of the respective clutches 54.55 via the variable flow rate control valves 13.14.

Both flow control valves 13, 14 are actuated by a control unit 15.

This control unit 15 receives detection outputs from a running state detection sensor 16 and a torque sensor 17 disposed on the transmission output shaft 31, and controls the flow rate control valves 13, 14 based on these input information. For example, if it is determined that the torque distribution to the rear wheels should be increased based on the output of the driving state detection sensor 16, the flow rate of the flow rate control valve 14 is increased, while the flow rate of the flow rate control valve 13 is decreased. Control signals are output to both valves 13 and 14, respectively, so as to cause the control to occur. As a result, a large amount of hydraulic oil is supplied to the hydraulic chamber 55b of the clutch 55 via the valve 14, and only a small amount of hydraulic oil is supplied to the hydraulic chamber 54b of the clutch 54 via the one-way valve 13. As a result, the pressure of the hydraulic oil on the clutch 55 side increases, and the piston 55c thereof moves more than the piston 54G of the clutch 54. That is, the torque transmitted by clutch 55 increases, and the torque transmitted by clutch 54 conversely decreases. In this way, the distribution of driving force torque to the front and rear wheels is determined depending on the driving condition.

Examples of the above-mentioned driving condition detection sensors include those shown in the left column of the table below. Also, in the right column of this table,
An example of control for a detected driving state is shown.

Acceleration performance can be improved by controlling the distribution of drive torque by using each sensor listed in the table singly or in combination.
Various driving performances such as control efficiency and cornering performance can be improved. Note that it is also possible to perform control by manual operation.

[Brief explanation of drawings]

FIG. 1 FIG. 1 is a configuration diagram showing a hydraulic control system in an embodiment of the present invention, FIG. 2 is a schematic diagram showing a drive system of a four-wheel drive vehicle,
FIG. 3 is a sectional view showing the transfer shown in FIG. 2. 7.9... Propeller shaft, 13.14... Flow rate control valve, 15... Control unit, 16... Running state detection sensor, 17... Torque sensor, 31... Transmission output shaft, 54.55...Clutch, 5
4b, 55b... Hydraulic working chamber, 54c, 55c...
piston.

Claims (1)

[Scope of Claims] A first wet friction clutch means that is installed between the output shaft of the transmission and the front wheel drive shaft, and that transmits torque from the output shaft to the front wheel drive shaft changes according to changes in working oil pressure. and a second wet friction/clutch means that is installed between the output shaft and the rear wheel drive shaft, and that changes the torque transmitted from the output shaft to the rear wheel drive shaft in accordance with changes in hydraulic pressure. A four-wheel drive vehicle characterized by comprising: hydraulic control means for changing the pressure of hydraulic oil to the first and second wet friction clutches according to driving conditions.