JP2528006B2 - Power distribution device for four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power distribution device for a four-wheel drive vehicle, and more specifically, to a front and rear wheels via a hydraulic multi-plate clutch and a pair of helical gears provided in a transfer case. The present invention relates to a power distribution device for a four-wheel drive vehicle that is configured to transmit power so that power can be distributed.

[Conventional technology]

As a power distribution device for such a four-wheel drive vehicle,
There is one that automatically controls the transmission torque of the hydraulic multi-plate clutch as in Japanese Patent No. 63-12815, and as a control method thereof, the operating hydraulic pressure of the hydraulic multi-plate clutch is changed according to the running state and the road surface condition of the automobile. There is something that can be changed (JP-A-61)
-155027).

Here, a pair of transfer gears for transmitting power from the transmission output shaft to the front wheels are arranged in the transfer case in which the hydraulic multi-plate clutch is arranged, and a bearing for rotatably supporting the transmission gears is provided. .

As the transfer gear, a helical gear having a relatively large meshing ratio is generally used for the purpose of ensuring strength and reducing noise.

[Problems to be Solved by the Invention]

By the way, in such a conventional example, since the transfer gear is composed of a helical gear, a large thrust load acts on the helical drive gear in addition to the radial load. For this reason, the load on the bearing becomes large, and the bearing structure becomes large in size in order to secure sufficient strength and life, and consequently the transfer device also becomes large and the weight increases.

A hydraulic multi-disc clutch generally has a structure in which a piston is arranged in a clutch drum, which is a rotating member. Therefore, centrifugal hydraulic pressure is generated in a hydraulic chamber of the hydraulic multi-disc clutch, and the hydraulic multi-disc clutch operates. There is also a problem that the control accuracy of hydraulic pressure is lowered.

Therefore, the present invention reduces the load on the bearing that rotatably supports the helical drive gear, thereby reducing the size and weight of the bearing structure, which in turn reduces the size and weight of the transfer device, and reduces centrifugal force in the hydraulic chamber of the hydraulic multi-plate clutch. An object of the present invention is to prevent hydraulic pressure from being generated, improve control accuracy of operating hydraulic pressure of a hydraulic multi-plate clutch, and appropriately distribute torque to front and rear wheels.

[Means for solving the problem]

To this end, the present invention provides a power distribution device for a four-wheel drive vehicle in which the front and rear wheels are power-transmittable via a hydraulic multi-plate clutch and a pair of helical gears provided in a transfer case. Is a stationary member that is slidably fitted in a transfer case to form a hydraulic chamber between the transfer case and a piston that presses the clutch plate through a relays bearing and is regulated in rotation. The helical drive gear is provided with a clutch drum coupled to a drive gear, and the helical drive gear has a twist angle set so that the direction of the thrust load during forward traveling is opposite to the direction of the pressing force of the piston.

[Action]

With such a means, the direction of the thrust load acting on the helical drive gear when the vehicle is traveling forward is
The direction is opposite to the direction of the pressing force of the piston of the hydraulic multi-plate clutch, and the thrust load is offset according to the pressing force of the piston. Therefore, the load on the bearing that rotatably supports the helical drive gear is reduced. Therefore, the bearing structure can be made smaller and lighter, and the transfer device can be made smaller and lighter.

Further, since the piston of the hydraulic multi-disc clutch is restricted in rotation and forms a hydraulic chamber with the transfer case, centrifugal hydraulic pressure is not generated in the hydraulic chamber even when the hydraulic multi-disc clutch is rotated. Therefore, the control accuracy of the operating hydraulic pressure of the hydraulic multi-disc clutch is improved, and the torque can be appropriately distributed to the front and rear wheels.

〔Example〕

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

In FIG. 3, reference numeral 1 is an automatic transmission 1, and an engine output is input from a crankshaft 2 to a input shaft 4 via a torque converter 3. The power is transmitted from the input shaft 4 to the output shaft 7 via the front planetary gear 5 and the rear planetary gear 6. The front planetary gear 5 and the rear planetary gear 6 include a brake band 8 for gear shift operation, a reverse clutch 9, a high clutch 10, a forward clutch 11, an overrunning clutch 12, a low and reverse brake.
13 are attached.

Here, a transfer drive gear 14 composed of a helical gear as shown in FIG. 4 is spline-coupled to the output shaft 7, while a drive pinion shaft 15 arranged in parallel below the output shaft 7.
A transfer driven gear 16 meshing with the transfer drive gear 14 is fixed to the drive drive gear 14, and the power is constantly transmitted from the output shaft 7 to the front wheel side via the drive pinion 17 and the front differential device 18.

Further, between the rear drive shaft 19 coaxially arranged behind the output shaft 7 and the transfer life gear 14, a pressing multi-plate clutch 20 as a transfer clutch is interposed, and the hydraulic multi-plate clutch 20 is The power of the output shaft 7 according to the transmitted torque is distributed to the rear wheels via the rear drive shaft 19, the propeller shaft 21, and the rear differential device 22.

Here, as shown in FIG. 1, the rear end of the output shaft 7 is rotatably supported by a mission case 24 via a ball bearing 23. The front end of the rear drive shaft 19 is a transmission case.
A transfer case 25 connected to the rear end of 24 is rotatably supported via a ball bearing 26, and its front end is rotatably fitted to the rear end of the output shaft 7 via a needle bearing 27. . The transfer drive gear 14 and the hydraulic multi-plate clutch 20 are arranged adjacent to each other in the front and rear in a transfer case 25 that covers a connecting portion between the output shaft 7 and the rear drive shaft 19.
Reference numeral 14 is in contact with the front end of the rear drive shaft 19 via a thrust bearing 28.

Transfer drive gear including the helical gear
The twist angle of the shaft 14 is set so that the thrust load acts on the rear hydraulic multi-plate clutch 20 side when the output shaft 7 is in the rotation direction of forward travel (see FIG. 4).

On the other hand, the hydraulic multi-plate clutch 20 has a hydraulic control system including a hydraulic pump 32 dedicated to power distribution, a control valve unit 34 that is duty-controlled by the output of the control unit 33, etc. The clutch hub 20a is supplied as shown in FIG.
Is spliced to the front end of the rear drive shaft 19,
The clutch drum 20b is the transfer drive gear 14
It is splined to a connecting ring 29 fixed at the end of the. A plurality of ring-shaped clutch plates 20c are spline fitted together with a pair of retainer plates 20d, 20e arranged at both ends of the clutch drum 20b, and one retainer plate 20d is the connecting ring 29. Is in contact with. Further, a plurality of ring-shaped clutch discs 20f are alternately arranged on the outer periphery of the clutch hub 20a and spline-fitted with the clutch plates 20c.

Here, the piston 20g of the hydraulic multi-plate clutch 20 has a ring shape, and is arranged on the side of the other retainer plate 20e and formed in the transfer case 25.
It is slidably fitted in 25a. And this piston 2
A plurality of return springs 20j, one end of which is supported by a tubular retainer 20h with a collar fixed to the transfer case 25, are urged to 0g, and a plurality of pins 20k fixed to the piston 20g are The rotation of the piston 20g is restricted by being inserted into the other end of the return spring 20j. The piston 20g is in contact with the other retainer plate 20e via the relay bearing 20m and the bearing retainer 20n.

In the four-wheel drive vehicle having the above-described configuration, the rotational power transmitted from the engine crankshaft 2 to the automatic transmission 1 via the torque converter 3 is appropriately changed there, and the transfer drive gear 14 on the output shaft 7 is changed.
From one side to the front differential device 18 via the transfer driven gear 16 and the other via the hydraulic multi-plate clutch 20 to the rear differential device.
Input to 22 to drive four wheels.

Here, when the vehicle is traveling forward, a thrust load directed to the rear hydraulic multi-plate clutch 20 side acts on the transfer drive gear 14.

For example, in a front-engine / front-drive (FF) -based 4-wheel drive vehicle in which the axle load distribution of the vehicle is 60% on the front wheel side and 40% on the rear wheel side, the torque transmission capacity of the hydraulic multi-plate clutch 20 is compared with the engine output. By always controlling the torque distribution equivalent to the axial load distribution, 40% of the output torque of the output shaft 7 is transmitted to the rear wheel side via the hydraulic multi-plate clutch 20, so that this thrust load is 60% of the front wheel. It depends on the torque. The thrust load is always increased / decreased in the same tendency as the driving force curve by performing the front / rear torque distribution control corresponding to the axial load distribution of the vehicle in accordance with the increase / decrease in the engine output.

On the other hand, the piston 20g of the hydraulic multi-plate clutch 20 is pressed in the direction opposite to this thrust load. This pressing force increases / decreases with the same tendency as the driving force curve because the hydraulic multi-plate clutch 20 transmits the torque according to the above-mentioned axial load distribution.

Therefore, by setting the relationship between the transmission torque capacity of the hydraulic multi-plate clutch 20 due to the piston pressing force and the thrust load to a predetermined value, the thrust load is offset by the pressing force of the piston. Therefore, the load on the ball bearing 23 that supports the output shaft 7 integrated with the transfer drive gear 14 and the ball bearing 26 that supports the rear drive shaft 19 integrated with the clutch hub 20a of the hydraulic multi-plate clutch 20 is reduced. Therefore, these ball bearings 23, 26 can be made smaller and lighter than conventional ones, and by doing so, the transfer case 25 can also be made smaller and lighter.

Further, since the hydraulic chamber 25a that applies hydraulic pressure to the piston 20g of the hydraulic multi-plate clutch 20 is formed between the transfer case 25, which is a stationary member, and the rotation-regulated piston 20g, the hydraulic multi-plate clutch 20 rotates at high speed. Even when you do, centrifugal oil pressure is not generated inside. Therefore, the control accuracy of the operating hydraulic pressure of the hydraulic multi-plate clutch 20 is improved, and the torque is appropriately distributed to the front and rear wheels.

FIGS. 5 and 6 show another embodiment of the present invention applied to a four-wheel drive vehicle of the type in which power is always transmitted to the rear wheels and power is distributed to the front wheels via a hydraulic multi-plate clutch.

The difference from the embodiment shown in FIGS. 1 and 2 will now be described. In this embodiment, the output shaft 30 is formed integrally with the rear drive shaft 19 in the embodiment. The transfer drive gear 14 is rotatably fitted to the output shaft 30 via a needle bearing 31, and is rotatably supported by a transmission case 24 via a ball bearing 23. Also, the hydraulic multi-plate clutch 20 adjacent to the transfer drive gear 14 is
The clutch hub 20a is spline-coupled to the output shaft 30, and the clutch drum 20b is spline-fitted to the transfer drive gear 14 via a connecting ring 29.

Therefore, the rotary power from the automatic transmission 1 is transmitted from the output shaft 30 to the rear differential device 22 on one side.
And the other input to the front differential device 18 via the hydraulic multi-plate clutch 20, the transfer drive gear 14, and the transfer driven gear 16 to drive four wheels.

Even in such an embodiment, when the vehicle is traveling forward, a thrust load directed to the rear hydraulic multi-plate clutch 20 side acts on the transfer drive gear 14, and the piston 20g of the hydraulic multi-plate clutch 20 has this thrust load and The pressing force in the opposite direction acts.

Therefore, the thrust load is canceled according to the pressing force of the piston, and the load on the ball bearings 23 and 26 is reduced as in the previous embodiment.

It should be noted that in the above embodiment, the thrust load acting on the transfer drive gear 14 is in the opposite direction when the vehicle is running backward, and the load bearing on the ball bearing 23 increases. However, since the frequency of backward traveling is low, this problem can be solved by allowing the load capacity of the ball bearing 23 to have some margin.

〔The invention's effect〕

As described above, according to the present invention, the direction of the thrust load acting on the helical drive gear during forward running of the vehicle is opposite to the direction of the pressing force of the piston of the hydraulic multi-plate clutch, and the thrust load is It is offset according to the pressing force. Therefore, the load on the bearing that rotatably supports the helical drive gear is reduced. Therefore, the bearing structure can be made smaller and lighter, and the transfer device can be made smaller and lighter.

Further, since the piston of the hydraulic multi-disc clutch is restricted in rotation and forms a hydraulic chamber with the transfer case, centrifugal hydraulic pressure is not generated in the hydraulic chamber even when the hydraulic multi-disc clutch is rotated. Therefore, the control accuracy of the operating hydraulic pressure of the hydraulic multi-disc clutch is improved, and the torque can be properly distributed to the front and rear wheels.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a skeleton diagram corresponding to FIG. 1, FIG. 3 is a skeleton diagram showing the entire structure of an automobile transmission, and FIG. 4 is a transfer drive gear. FIG. 5 is a perspective view showing an assembled state of FIG. 5, FIG. 5 is a sectional view showing another embodiment of the present invention, and FIG. 6 is a skeleton diagram corresponding to FIG. 1 ... Automatic transmission, 2 ... Crank shaft, 3 ... Torque converter, 4 ... Input shaft, 5 ... Front planetary gear, 6 ... Rear planetary gear, 7 ... Output shaft, 8 ... Brake band, 9 ...... Reverse clutch, 10 …… High clutch, 11 …… Forward clutch, 12 …… Overrunning clutch, 13 …… Low and reverse brake, 14 …… Transfer drive gear, 15 …… Drive pinion shaft, 16 …… Transfer Driven gear, 17 …… Drive pinion, 18 …… Front differential device, 19 …… Rear drive shaft, 20 …… Hydraulic multi-plate clutch, 20a …… Clutch hub, 20b …… Clutch drum, 20c …… Clutch plate, 20d, 20e …… Retainer plate, 20f …… Clutch disc , 20g …… Piston, 20h …… Retainer, 20j …… Return spring, 20k …… Pin, 20m, Release bearing, 20n …… Bearing retainer, 21 …… Propeller shaft, 22 …… Rear differential device, 23 …… Ball Bearings, 24 …… Transmission case, 25 …… Transfer case, 26 …… Ball bearing, 27 …… Needle bearing, 28 …… Thrust bearing, 29 …… Connection ring. 30 …… output shaft, 31 …… needle bearing, 32 …… hydraulic pump, 33 …… control unit, 34 …… control valve unit.

Claims (1)

(57) [Claims] 1. A power distribution device for a four-wheel drive vehicle in which front and rear wheels are power-transmittable via a hydraulic multi-plate clutch and a pair of helical gears provided in a transfer case, wherein the hydraulic multi-plate clutch is stationary. A piston that presses the clutch plate through a release bearing, which is slidably fitted into the transfer case that is a member to form a hydraulic chamber between the member and the transfer case, and the drive gear of the helical gear. The power of a four-wheel drive vehicle is provided with a clutch drum to be coupled, and the helical drive gear has a twist angle set so that the direction of the thrust load during forward traveling is opposite to the direction of the pressing force of the piston. Distribution device.