JPH06211062A - Four-wheel drive power transmission - Google Patents

Abstract

PURPOSE:To enable four-wheel driving at the backing time in a forward four- wheel drive power transmission. CONSTITUTION:A one-way bearing allowing only forward rotation is provided between the front wheel axle side and a casing provided with a gear meshed with a driving gear to which the output from an engine is transmitted, and a friction clutch 16 is provided in parallel with the one-way bearing. A braking hydraulic circuit 22 is connected to the piston 17 of the friction clutch 16, and the hydraulic circuit 22 is provided with a solenoid valve 23 switched on when a shift lever 25 is placed in the reverse position so as to close the oil passage 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device for four-wheel drive during forward movement, which can achieve four-wheel drive even during reverse movement.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a power transmission device for four-wheel drive during forward movement of an automobile. In FIG. 2, 1 is an engine, 2
Is a transmission, 3 is a drive gear provided on the output side of the transmission 2, and 4 is a differential gear device.

In the differential gear device 4, reference numeral 5 is a casing provided with a gear 6 meshing with the drive gear 3, and a casing 8 is provided inside the casing via a one-way bearing 7 as a one-way power transmission means. A differential small gear 9 is rotatably supported on the casing 8, and a differential large gear 11 provided on the left and right front wheel axles 10 meshes with the differential small gear 9. The one-way bearing 7 allows only forward rotation. The drive gear 3 is connected to a rear wheel power transmission shaft 14 via gears 12 and 13.

Therefore, the driving force of the engine 1 is the front wheel axle 1.
0 and rear wheel axles are transmitted to achieve forward four-wheel drive,
Further, it is possible to prevent the braking phenomenon during turning.

In such a four-wheel drive system, when the foot brake is depressed, that is, when the brake is applied,
Since there is the one-way bearing 7, a situation occurs in which only the rear wheel side is locked. Therefore, as shown in FIG. 3, a friction clutch 16 as a friction engagement element operated by hydraulic pressure generated by stepping on the foot brake 15 is provided in parallel with the one-way bearing 7 between the casings 5 and 8. The four-wheel drive is maintained during braking.

[0006]

However, in the power transmission device as described above, only the rear wheels are driven when moving backward, and there is no particular problem when driving on a general road. There is a problem that you cannot escape.

[0007]

In order to solve the above-mentioned problems, in the present invention, a unidirectional power transmission means for allowing only forward rotation is provided in a power transmission path for transmitting a driving force from an engine to a front wheel axle. A frictional engagement element is provided in parallel with the power transmission means, an oil passage for generating hydraulic pressure by operating a foot brake is connected to an oil chamber of an actuator for operating the frictional engagement element, and when the reverse is selected, A valve for closing the oil passage was provided to constitute a four-wheel drive power transmission device.

[0008]

In the power transmission device of the above construction, if the foot brake is stepped on before retreating, the hydraulic pressure rises and the frictional engagement element is engaged. In this state, if backward movement is selected by the shift lever or the like, the valve is closed and the oil passage is closed, and the hydraulic pressure is maintained, so that the friction engagement element is maintained in the engaged state. Therefore, the front and rear wheels are directly connected, and four-wheel drive is achieved when moving backward.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the power transmission device according to the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a main part of a power transmission device according to an embodiment. The configurations of the engine, the transmission, the differential gear unit, etc. are the same as those shown in FIG.

Brake cylinder 2 of foot brake 15
The oil passage 22 connected to 1 is branched from the side that goes to the brake and the piston 17 that is the actuator of the friction clutch 16 is branched.
Is connected to the oil chamber. The oil passage 22 is branched in parallel on the way, and an electromagnetic valve 23 that is open when not energized is provided in one of the oil passages 22a. A one-way valve 24 that allows only the flow from the cylinder 21 toward the friction clutch 16 is provided in the other oil dividing passage 22b.

The electromagnetic bulb 23 is energized by a back lamp switching circuit. This circuit is provided with a reverse switch 26 that is turned on by moving the shift lever 25 backward. That is,
When the shift lever 25 selects backward movement, the electromagnetic valve 23 is energized and the oil passage 22a is shut off.

A manual switch 27 is provided in parallel with the reverse switch 26, and when the switch 27 is turned on, the electromagnetic valve 23 is energized.
In FIG. 1, 28 is a battery.

In this power transmission device, the electromagnetic valve 23 is turned off during normal forward traveling, and the oil dividing passage 22 is closed.
a is in an open state. Therefore, during forward braking, the hydraulic pressure generated by stepping on the foot brake 15 acts on the piston 17 of the friction clutch 16 through the oil passage 22 as before, and achieves four-wheel drive.

When moving backward, the foot brake 15 is first depressed. The friction clutch 16 is engaged by the hydraulic pressure that rises when the foot brake 15 is stepped on. When the shift lever 25 is shifted to the retracted position in this state, the reverse switch 26 is turned on to energize the electromagnetic valve 23 and close the oil dividing passage 22a. That is, the hydraulic pressure to the piston 17 is maintained and the friction clutch 16
Are held in the engaged state.

Therefore, even when the vehicle is moving backward, the direct drive four-wheel drive mode is established, and the four-wheel drive is achieved. Shift lever 2
If you set 5 to another position, the reverse switch 26 will turn off,
The electromagnetic valve 23 is de-energized, the oil dividing passage 22a is opened, and the hydraulic pressure to the piston 17 is released.

In this embodiment, since the manual switch 27 is provided, by depressing the foot brake 15 and turning on the switch 27, the direct connection four-wheel drive state can be always established. Further, the manual switch 27 may be used to both raise the hydraulic pressure and operate the electromagnetic valve.

[0017]

According to the power transmission device of the present invention, four-wheel drive is used when moving forward, and four-wheel drive is used even when moving backward in a four-wheel drive system capable of preventing the braking phenomenon during turning. In the case of a wheel, it is possible to escape backwards.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main part of a power transmission device according to an embodiment.

FIG. 2 is a schematic diagram of a power transmission device for forward four-wheel drive.

FIG. 3 is a schematic view of a friction clutch operating mechanism.

[Explanation of symbols]

 1 Engine 2 Transmission 3 Drive Gear 4 Differential Gear Device 7 One Way Bearing 10 Front Wheel Axle 15 Foot Brake 16 Friction Clutch 21 Brake Cylinder 22 Oil Path 23 Electromagnetic Valve 24 One Way Valve 25 Shift Lever 26 Reverse Switch 27 Manual Switch

Claims (1)

[Claims] 1. A foot brake comprising a one-way power transmission means for allowing only forward rotation in a power transmission path for transmitting a driving force from an engine to a front wheel axle, and a friction engagement element provided in parallel with the one-way power transmission means. Is connected to an oil chamber of an actuator that operates the friction engagement element, and a valve that closes the oil passage when reversing is selected is provided. Drive power transmission device.