JPH0829686B2 - 4-wheel drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel drive device for transmitting power to front wheels and rear wheels in a four-wheel drive vehicle, and particularly to a first rotary shaft and a second rotary shaft. A differential pump that operates by the relative rotation of
A clutch having a pressing member that moves in the axial direction according to the fluid pressure discharged from the differential pump and frictionally engaging the first rotating shaft and the second rotating shaft by the axial movement of the pressing member is provided. The front wheel connected to the first rotating shaft and the second wheel.
It tried to limit the differential of the rear wheels connected to the rotating shaft. 4
Wheel drive device.

[Conventional technology]

A four-wheel drive system of this type is proposed in, for example, Japanese Patent Laid-Open No. 61-102329. Therefore, in the device proposed in the publication, the differential pump operates due to the differential (relative rotation) of the front wheel and the rear wheel, and the fluid pressure obtained by this causes the pressing member (piston) to move in the axial direction. The clutch engagement force (differential limiting force) is obtained by moving.

[Problems to be solved by the invention]

In the above-described conventional device, the clutch engagement force is obtained when the differential pump operates due to the differential between the front wheels and the rear wheels, but when there is no differential between the front wheels and the rear wheels, the differential pump does not operate and the clutch The engagement force cannot be obtained. Therefore, for example, when attempting to start at the time of starting from a deep sandy place, slippage occurs in the front wheels or the rear wheels (two-wheel drive state), and the tires scrape up the sand and accumulate in the sand. Although a sufficient differential is generated in the rear wheels to bring the vehicle into a four-wheel drive state, at this time, there may be a problem that the vehicle is already in the stuck state. This is because
The biggest problem was that the four wheels were not driven at the start of the vehicle, that is, when there was no differential (slip).

The present invention has been made in view of the above problems, and provides a four-wheel drive device that can obtain a clutch engagement force according to an operation by operating a shift mechanism even when there is no differential between front wheels and rear wheels. Is intended.

[Means for solving the problem]

In order to achieve the above object, in the present invention,
A differential pump that operates by relative rotation of the first rotating shaft and the second rotating shaft, and a pressing member that has a pressing member that moves in the axial direction according to the fluid pressure discharged from the differential pump. A clutch that frictionally engages the first rotating shaft and the second rotating shaft by directional movement is provided to limit a differential between a front wheel connected to the first rotating shaft and a rear wheel connected to the second rotating shaft. In the four-wheel drive device configured as described above, the discharge passage of the differential pump is narrowed by the movement in the axial direction to increase the pressure of the fluid pressure discharged from the differential pump, and the pressing member is pushed in the axial direction. A moving spool is provided, and a shift mechanism for axially pushing the spool is provided.

[Action]

In the four-wheel drive system according to the present invention, when the spool is not pushed by the shift mechanism, the discharge passage of the differential pump is not throttled and the pressing member is not pushed. Therefore, in this state, even if the differential pump operates due to the differential between the front wheel and the rear wheel, the fluid pressure discharged from the differential pump is not increased by the spool, but is increased by the same fluid pressure (low pressure). The pressing member is moved in the axial direction, and the clutch engagement force corresponding to the fluid pressure is obtained.

Further, when the spool is pushed by the shift mechanism and the discharge passage of the differential pump is throttled, the fluid pressure discharged from the differential pump is pressure-controlled by the spool, and the pressure member is pushed by the increased fluid pressure. The clutch engagement force corresponding to the fluid pressure increased in the clutch by being moved in the axial direction is obtained. At this time, if the spool presses the pressing member, the clutch engaging force is also obtained by this pressing force, and a large clutch engaging force is obtained.

By the way, the action of the spool pushing the pressing member is obtained by pushing the spool by the shift mechanism regardless of the operation of the differential pump, and even when there is no differential between the front wheels and the rear wheels, the shift mechanism operates. A clutch engagement force corresponding to the operation by is obtained.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a four-wheel drive system according to the present invention, in which the first rotating shaft 10 is splined to the right end of a connecting shaft 11, and the connecting shaft 11 is shown in FIG. Thus, it is connected to the left side gear A1 of the center differential A. The second rotary shaft 12 of the device is rotatable relative to the first rotary shaft 10 and is connected to the right side gear A2 of the center differential A as shown in FIG. The outer shell member 13 is fixed. In addition, the left side gear A1 of the center differential A is connected to both front wheels through the front wheel differential B.
The right side gear A2 is connected to the WF so as to be able to transmit power, and the right side gear A2 is connected to both rear wheels WR through the housing C, the ring gear D, the propeller shafts E and F and the rear wheel diff G, and the case A3. Is connected to the engine K via a transmission H and a clutch J so that power can be transmitted.

The first rotary shaft 10 has a clutch inner hub 10 at its left end.
Also, a large number of friction discs 14 are spline-fitted to the clutch inner hub 10a so as to be movable in the axial direction. A rotor 15 is fitted to the right end of the first rotating shaft 10 via a ball spline 16 so as to be movable in the axial direction.

On the other hand, the outer shell member 13 has a clutch outer hub 13a at its left end portion, and a large number of spacer plates 17 are spline-fitted to the clutch outer hub 13a alternately with respect to the friction disc 14 so as to be axially movable. At the same time, a return spring 18 is assembled and a clip 19 prevents it from coming off. A cam ring 20 is fitted to the right end of the outer shell member 13 via a ball spline 21 so as to be movable in the axial direction.

Each friction disk 14 constitutes a wet multi-plate clutch L with each spacer plate 17 and return spring 18, etc., and is connected to the first rotary shaft 10 by the clutch engagement force obtained by this wet multi-plate clutch L. Front wheel
Rear wheel WR differential connected to WF and the second rotary shaft 12 (both shafts 10 and
12 relative rotation) is to be limited. The clutch engagement force of the wet multi-plate clutch L is determined by the axial pressing force transmitted from the hydraulic pump M.
This pressing force is the pressing force obtained by the hydraulic pressure discharged from the hydraulic pump M and the pressing force obtained by the spool 22.

The spool 22 has an annular groove 22a and is fitted in a holder 23 assembled in a liquid-tight manner between the first rotary shaft 10 and the right end portion of the outer shell member 13 so as to be movable in the axial direction. It is urged to the right by a coil spring 24 interposed therebetween. Further, the spool 22 is engaged with the shift fork 26 via the bearing 25 at the right end thereof, and the shift mechanism N including the shift fork 26 allows the spool 22 to be shown in (a), (b) and (c) of FIG.
It is adapted to be pushed in the axial direction to each position shown in. Then, the spool 22 at the position shown in FIG. 3 (a) sets the discharge passage Ma of the hydraulic pump M to the fully open state and separates from the hydraulic pump M, and in FIG. 3 (b). The spool 22 at the position shown is in a state where the discharge passage Ma of the hydraulic pump M is in a half-open state (semi-throttled state) and is in contact with the hydraulic pump M, and is in the position shown in FIG. 3 (c). 22 makes the discharge passage Ma of the hydraulic pump M fully closed (fully throttled) and pushes the hydraulic pump M axially to the left.

As shown in FIGS. 1 and 4 to 8, the hydraulic pump M is operated by the relative rotation of the first rotary shaft 10 and the second rotary shaft 12, that is, the differential between the front wheels WF and the rear wheels WR. The above-mentioned rotor 15 and cam ring 20, a pair of left and right bushes 27, 28 and cover plates 30, 31, and a valve plate 32 interposed between each bush 27, 28 and cover plates 30, 31. 33 and a large number of vanes 3 attached to the rotor 15
4 to 34, the rotor 15 has a cam ring 2
The suction port of the cover plate 30 whether rotated forward (in the direction indicated by the solid line in FIG. 4) or in reverse (rotated in the direction indicated by the broken line in FIG. 4) with respect to 0.
The hydraulic oil is configured to flow from 30a to the discharge port 31a of the cover plate 31. The hydraulic oil discharged from the hydraulic port M acts on the outer surface of the cover plate 31 to axially move the hydraulic pump M to the left in FIG. Ma and the first rotary shaft 10
It flows to the suction side of the hydraulic pump M through a passage Mb provided in the.

In the present embodiment constructed as described above, if the spool 22 is held at the position shown in FIG. 3A or 3B by the shift mechanism N, the hydraulic pump M is pushed axially by the spool 22. It will not be done. Then, when the hydraulic pump M is operated by the differential between the front wheels WF and the rear wheels WR while the spool 22 is held at the position shown in FIG. 3 (a), the hydraulic oil is discharged to the discharge passage Ma. In this state, since the discharge passage Ma is in the fully open state, the discharge pressure does not increase and the pressing force by the hydraulic pressure acting on the wet multi-plate clutch L via the hydraulic pump M is relatively small. Therefore, the relationship between the differential rotation speed (relative rotation speed) of the front wheels WF and the rear wheels WR and the torque transmitted via the wet multi-plate clutch L is the ninth.
It looks like the dashed line in the figure. The initial torque To in FIG. 1 is due to the mounting load of the return spring 18.

On the other hand, in the state where the spool 22 is held at the position shown in FIG. 3 (b), since the discharge passage Ma is half-opened by the spool 22, the discharge pressure generated by the operation of the hydraulic pump M is shown in FIG. The pressure is increased as compared with the case of (a). Therefore, the relationship between the differential rotation speed and the torque is the ninth.
As shown by the alternate long and short dash line in the figure, the torque transmitted via the wet multi-plate clutch L increases as compared with the case of FIG. 3 (a).

By the way, in the present embodiment, when the spool 22 is pushed to the position shown in FIG. 3 (c) by the shift mechanism N, the pressing force applied from the spool 22 in addition to the pressing force due to the hydraulic pressure described above is applied to the wet multi-plate clutch. Acts on L. Therefore, the relationship between the differential rotation speed and the torque is as shown by the chain double-dashed line in FIG. In the state of FIG. 3 (c), the discharge passage Ma is fully closed by the spool 22, so that the discharge pressure of the hydraulic pump M is increased as compared with the case of FIG. 3 (b). Thus, the relationship between the differential rotation speed and the torque actually becomes as shown by the solid line in FIG.

In the above embodiment, the torque transmitted via the wet multi-plate clutch L can be adjusted in three stages.
It is also possible to carry out the present invention such that it can be adjusted in multiple stages or steplessly. Further, in the above-mentioned embodiment, the present invention was carried out in the center differential, but the present invention replaces the viscous coupling provided in the portion corresponding to the propeller shafts E, F of the above-mentioned embodiment with a wet multi-plate clutch L,
It can also be implemented by providing the hydraulic pump M, the spool 22, and the like. Further, in the above embodiment, the hydraulic pump M is made movable in the axial direction so as to function also as a pressing member. However, for example, as in the device disclosed in Japanese Patent Laid-Open No. 61-102329, a pressing member is provided separately from the hydraulic pump. (Piston) is provided, and the same pressure member is used for pump discharge pressure and spool 22.
It is also possible to carry out the present invention by frictionally engaging the clutch by pushing with.

〔The invention's effect〕

In short, according to the present invention, the clutch engagement force can be obtained by the resultant force of the pressing force of the fluid pressure discharged from the differential pump and increased by the spool and the pressing force directly applied from the spool. Even if there is no wheel differential, the four-wheel drive can be made by engaging the clutch in preparation for the differential that may occur at the next moment, improving the ability to start and escape from sandy land or to drive on low μ roads. .

A large clutch engagement force can be obtained when the front wheels and the rear wheels are in a differential state, and running similar to direct drive four-wheel drive can be performed, so that running on rough roads is improved.

When the clutch engagement force is set to the same level as the conventional one, the differential pump can be made smaller and lighter, the cost can be reduced, and the mountability on the vehicle can be improved.

Such an effect can be expected.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part showing an example of a four-wheel drive system according to the present invention, FIG. 2 is an overall configuration diagram of the same, and FIG. 3 (a),
(B) and (c) are partially enlarged views of FIG. 1, FIG. 4 is a vertical sectional side view of the pump shown in FIG. 1, and FIGS. 5 and 6 are operation explanatory views of the pump, FIG. FIG. 8 is a view showing a bush, a cover plate and a valve plate in the pump,
FIG. 9 is a characteristic diagram showing the relationship between the differential rotation speed and the torque obtained in the four-wheel drive system shown in FIGS. 1 and 2. Explanation of reference numerals 10 ... First rotary shaft, 12 ... Second rotary shaft, 22 ... Spool, M ... Hydraulic pump (differential pump also serving as a pressing member), Ma ... Discharge path, L ... Wet type Multi-disc clutch, WF ...
Front wheel, WR ... rear wheel, N ... shift mechanism.

Claims (1)

[Claims] 1. A differential pump that is pumped by relative rotation of a first rotary shaft and a second rotary shaft, and a pressing member that moves in the axial direction according to the fluid pressure discharged from the differential pump. The first rotating shaft and the second rotating shaft are moved by the axial movement of the pressing member.
A four-wheel drive device, comprising a clutch for frictionally engaging a rotating shaft, for limiting a differential between a front wheel connected to the first rotating shaft and a rear wheel connected to the second rotating shaft,
A spool is provided which restricts the discharge passage of the differential pump by moving in the axial direction to increase the pressure of the fluid discharged from the differential pump, and pushes the pressing member in the axial direction. A four-wheel drive system characterized in that a shift mechanism for axially pushing is provided.