JP2721977B2 - Power distribution device for four-wheel drive vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a power distribution device for a four-wheel drive vehicle equipped with a wet hydraulic multi-plate clutch that distributes power to front and rear wheels.

[Prior art]

As such a power distribution device for a four-wheel drive vehicle, Japanese Patent Application Laid-Open
The thing described in 61-155027 is known conventionally. This is one in which two wet-type hydraulic multi-plate clutches for front wheel drive and rear wheel drive are arranged in a case of a transfer device that transmits power by branching from a transmission output shaft to front and rear wheels,
According to the hydraulic control, power can be continuously distributed to the front and rear wheels at an arbitrary ratio. Here, these wet hydraulic multi-plate clutches are configured such that the hydraulic oil is shared with the lubricating oil of gears and bearings in the transfer device, and the hydraulic piston for pressing the clutch plate rotates together with the clutch drum. ing. In such a case, it is necessary to provide a seal member on the hydraulic piston so as to effectively use the control oil pressure acting on the hydraulic piston.

[Problems to be solved by the invention]

Since the hydraulic piston rotates together with the clutch drum in this way, centrifugal hydraulic pressure is generated in the hydraulic chamber for driving the hydraulic piston with the rotation of the clutch drum, and this is added to the control hydraulic pressure and acts on the hydraulic piston. I will be. Therefore, the wet hydraulic multi-plate clutch cannot perform desired hydraulic control because the transmission torque is excessively larger than the set value corresponding to the control hydraulic pressure, and when the vehicle reaches a middle to high speed range and the centrifugal hydraulic pressure is large, the linear The internal hydraulic torque generated by the difference in the effective weight of the front and rear wheels due to the difference in the axle weight distribution of the vehicle during running and the shift of the center of gravity during acceleration running cannot be sufficiently absorbed by the wet hydraulic multi-plate clutch as a torque limiter. In addition, there are inconveniences such as deterioration of acceleration performance, deterioration of fuel efficiency, generation of vibration noise, and the like. In addition, since the wet-type hydraulic multi-plate clutch uses lubricating oil exclusively for gears as its operating oil, it is not possible to obtain an appropriate friction characteristic when a large steering is performed and a slipping action occurs in a four-wheel drive running state. Therefore, there is a problem that a stick-slip is caused to generate vibration noise. Further, since the transfer device accommodates two wet-type hydraulic multi-plate clutches and lengthens, the rigidity of the transfer device is reduced, so that vibration and noise of the drive system are increased, or the space in the vehicle compartment is reduced. In view of the above, the present invention provides a transfer-side device that has a compact structure, and enables the torque distribution to the front and rear wheels to be set to an arbitrary ratio. An object of the present invention is to prevent stick-slip from occurring.

[Means for Solving the Problems]

For this purpose, the present invention relates to a four-wheel drive vehicle in which power is distributed between front and rear wheels according to the pressure of hydraulic oil to two wet hydraulic multi-plate clutches. The two wet hydraulic multi-plate clutches are separately arranged in the front wheel independent differential and the rear wheel independent differential, respectively. The hydraulic pistons in these wet-type hydraulic multi-plate clutches are fixedly slidably fitted to the case members of the independent differential devices, which are non-moving members, as cylinders. And the working end opposite to the operating hydraulic chamber is pressed through a bearing to a retainer plate fitted inside the end of the clutch drum of the wet hydraulic multi-plate clutch. Those configured to press the clutch plates in the clutch drum.

[Action]

In such a means, even if the clutch plate in the clutch drum rotates due to the rotation of the transmission shaft, the hydraulic piston in each wet-type hydraulic multi-plate clutch does not rotate, and between these and the case member of the independent differential. Does not generate centrifugal oil pressure. In addition, since the hydraulic piston does not rotate, abnormal wear of the seal member due to rotation of the hydraulic piston can be suppressed. Power is distributed to the front and rear wheels at a desired ratio by hydraulic control of each wet hydraulic multi-plate clutch. Here, each wet hydraulic multi-plate clutch can obtain a desired friction characteristic by using an appropriate hydraulic oil having a predetermined composition, and when the internal circulation torque between the front and rear wheels is generated or in the four-wheel drive state. When the steering wheel is largely turned, the clutch plate smoothly slides without stick-slip.

【Example】

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 2 shows a power transmission system of a four-wheel drive vehicle to which one embodiment is applied, in which an engine 1, a clutch 2, a synchronous mesh type manual transmission 3, and a transfer device 4 are integrated from the front of the vehicle body. A front wheel differential device 7 and a rear wheel differential device 8, which are vertically arranged in the front-rear direction and are independent from a transfer device 4 via propeller shafts 5 and 6, respectively, are disposed at a front portion and a rear portion of the vehicle body. In the transfer apparatus 4, as shown in FIG. 1 (a), a transfer drive sprocket 11 and a transfer driven sprocket 12 are spline-fitted to a transmission output shaft 9 and a front drive shaft 10 arranged in parallel with the transmission output shaft 9, respectively. The transmission output shaft 9 and the front drive shaft 10
Are connected to propeller shafts 6, 5 via companion flanges 20, 21, respectively. As shown in FIG. 2, first and second wet hydraulic multi-plate clutches 22 and 28 are interposed in the transmission shafts in the front wheel differential 7 and the rear wheel differential 8. . And engine 1
Input to the manual transmission 3 through the clutch 2 from the transmission, the transmission is shifted to five forward and one reverse steps, and is transmitted from the transmission output shaft 9 to the transfer drive sprocket 11 and the chain 1.
3, input to the front wheel differential 7 via the transfer driven sprocket 12, front drive shaft 10, propeller shaft 5, and first wet hydraulic multi-plate clutch 22, from which power is transmitted to left and right front wheels 23. The transmission output shaft 9
The power taken from the rear of the transfer device 4 is input to the rear wheel differential device 8 via the propeller shaft 6 and the second wet hydraulic multi-plate clutch 28, from which power is transmitted to the left and right rear wheels 24. It is supposed to be. Here, the first and second two wet hydraulic multiple disc clutches 2
Reference numerals 2 and 28 denote oil pumps 14a and 14b, regulator valves 15a and 15b, and transfer clutch valves, respectively, as shown in FIG.
Appropriate control oil pressure is supplied according to the running state by a dedicated hydraulic control system having 16a, 16b, duty solenoid valves 17a, 17b, and pilot valves 18a, 18b. Since these hydraulic control systems have substantially the same configuration, one of them will be described. Duty pressure control is applied to a hydraulic circuit system which is adjusted to a predetermined hydraulic pressure from an oil pump 14a by a regulator valve 15a and reaches a wet hydraulic multi-plate clutch 22. A transfer solenoid valve 16a is interposed, and a duty solenoid valve 17a for discharge control is inserted into a pilot pressure circuit system having a pilot valve 18a. Then, the duty solenoid valves 17a and 17b in both hydraulic control systems adjust to the desired duty pressures respectively according to the duty signal from the control unit 19, so that the transfer clutch valves 16a and 16b are adjusted.
b are individually adjusted to a desired clutch pressure. The relationship between the duty ratio, the duty pressure and the clutch pressure is as shown in FIG. The first and second wet-type hydraulic multi-plate clutches 22 and 28 having such a hydraulic control system, together with the hydraulic control system, are differential members which are case members of the front wheel differential 7 and the rear wheel differential 8. Compacted in the carrier part. Here, the two-wet hydraulic multi-plate clutches 22, 28 and the differential devices 7, 8 have substantially the same configuration, and only one of them will be described. As shown in FIG. 1 (b), the differential carrier 29 includes a final gear on the rear wheel differential device 8 side.
The cylinder portion 33 which projects forward to cover the loosely fitted portion between the shaft portion 30a of the drive pinion 30 meshing with the input shaft 31 and the input shaft 31 on the propeller shaft 6 side and is connected to the extension case 32 around the input shaft 31 is an immovable member. The first is integrally formed as
As shown in FIG. 3C, a valve unit 2 in which the valves 15b, 16b, 17b and 18b are integrally formed on the lower surface of the cylinder 33
6 and the electric oil pump 14b is fixed to the side surface, and the second wet hydraulic multi-plate clutch 28 is disposed in the cylinder portion 33. Here, in the second wet hydraulic multi-plate clutch 28, the clutch drum 28a is welded and fixed to the flange 31a at the rear end of the input shaft 31, and the clutch hub 28b is spline-fitted to the shaft 30a of the drive pinion 30. Then, it is locked to the end of the input shaft 31 via a thrust washer 34. On the inner periphery of the clutch drum 28a, a plurality of ring-shaped clutch plates 28c are spline-fitted together with the retainer plates 28d at both ends, while on the outer periphery of the clutch hub 28b, a plurality of ring-shaped clutch disks 28e are provided. The clutch plate 28c, the retainer plate 28d, and the clutch disk 28e constitute a multi-plate clutch by being alternately arranged with the clutch plates 28c and spline-fitted. A ring-shaped piston 28f for applying a pressing force to the retainer plate 28d is provided on the cylinder portion 3 as an immovable member.
A hydraulic chamber 28g communicating with the transfer clutch valve 16b is formed between the partition wall 33a and the inner guide cylinder 33b so as to be slidably fitted in the inside 3 and an operating end opposite to the hydraulic chamber 28g. The portion is in contact with the retainer plate 28d via a release bearing 35 of an angular contact. The release bearing 35 is configured such that the outer race 35a abutting on the piston 28f is connected to the inner guide cylinder 33 via a claw 35b.
The inner race 35c is spline-fitted to the inner periphery of the clutch drum 28a, and the rotation of the outer race 35a prevents the piston 28f from rotating relative to the cylinder portion 33. . On the other hand, the shaft 30a of the input shaft 31 and the drive pinion 30
Are formed with oil passages 31b, 30b so as to communicate the outer peripheral side of the clutch drum 28a and the inner peripheral side of the clutch hub 28b. Then, the hydraulic oil in the cylinder section 33 is supplied to the clutch drum 28
The oil is drawn up on the outer periphery of a and supplied to the oil passage 30b by an oil guide (not shown), and the hydraulic oil is guided to the inner peripheral side of the clutch hub 28b through the oil passage 30b, so that the spline portion is provided in the radial direction (not shown). Through the oil passage, clutch plate
The multi-plate clutch such as the clutch disk 28e is lubricated. In order to prevent the hydraulic oil from leaking, the inner peripheral portion of the partition wall 33a of the cylinder portion 33 is attached to the inner peripheral portion of the front portion of the extension case 32 by oil seals 36, 3 respectively.
7 is installed. Further, since the characteristics of the lubricating oil for hypoid gears and the hydraulic oil in the differential device are different, the partition wall 33
aThe oil seal 36 on the inner peripheral portion is configured to maintain liquid tightness with each other. In the four-wheel drive vehicle having the above configuration, the power transmitted from the engine 1 to the manual transmission 3 via the clutch 2 is appropriately shifted there, and the transmission output shaft 9 transfers the power to the transfer device 4,
The signal is input to the front wheel differential 7 via a propeller shaft 5 and a first wet hydraulic multi-plate clutch 22, and the other is input to the rear wheel differential via a propeller shaft 6 and a second wet hydraulic multi-plate clutch 28. By inputting to 8, the vehicle is driven by four wheels. In this case, power is distributed to the front wheel side and the rear wheel side according to the transmission torque of each wet hydraulic multi-plate clutch 22, 28. And this distribution ratio is
By changing the clutch pressure according to the duty ratio signal from the control unit 19, the distribution on the rear wheel side is gradually increased from the FF state of 100% for the front wheels and 0% for the rear wheels, and the front and rear wheels pass through a direct-coupled 4WD state. It changes within the range of 0% and the rear wheel 100% FR state. Therefore, by inputting various signals such as a throttle opening signal, a rear wheel rotation signal, a front wheel rotation signal, and an idle signal to the control unit 19 and performing electronic control, the optimum front-rear power according to the traveling state of the automobile and road surface conditions is obtained. Distribution becomes possible, and running stability and drivability can be improved. If the difference in the axle weight distribution between the front and rear wheels of the vehicle, the sudden acceleration, and the movement of the center of gravity during climbing a hill causes a difference in the effective diameter of the front and rear wheels during the four-wheel drive, the difference between the front and rear wheels is determined. Relative rotation occurs. In such a case, the first or second wet hydraulic multi-plate clutches 22 and 28 function as a torque limiter by being controlled to a desired clutch pressure. For example, the clutch plate 28c on the clutch drum 28a side and the clutch plate 28c on the clutch hub 28b side Sliding occurs between the clutch disk 28e and the clutch disc 28e to absorb internal circulating torque caused by a rotation difference between the front and rear wheels. Therefore, acceleration performance and fuel efficiency during four-wheel drive traveling can be improved. Also, if you steer significantly while driving a four-wheel drive vehicle,
Internal circulation torque is generated between the front and rear wheels due to the difference between the turning radii of the front and rear wheels, and is especially large during low-speed maximum steering, requiring more driving force than necessary, and stalling occurs when entering a garage. Inconvenience occurs. In such a case, the first or second wet-type hydraulic multi-plate clutches 22 and 28 detect the aforementioned front-rear rotation speed and are controlled to reduce the pressure to a desired clutch pressure according to the rotation ratio or the rotation difference. In order to solve this problem, slippage occurs in the first or second wet hydraulic multiple disc clutches 22, 28. Therefore, the tight corner braking phenomenon at the time of turning can be avoided. When the first or second wet hydraulic multi-plate clutches 22 and 28 perform such sliding action, for example, the multi-plate clutches such as the clutch plate 28c and the clutch disk 28e are immersed in an appropriate hydraulic oil having a predetermined composition. As a result, desired friction characteristics are obtained, and no stick-slip occurs. Therefore, unpleasant vibrations and noises do not occur particularly at the time of low-speed maximum steering, and desired reliability and durability can be obtained for the friction material. Here, the behavior of each wet-type hydraulic multi-plate clutch 22, 28 itself is examined. As the input shaft 31 rotates, the clutch drum 28a
At the same time, even if the clutch plate 28c, the inner race 35c of the release bearing 35, and the like rotate, the piston 28f is prevented from rotating by the cylinder 33, which is an immovable member, and does not rotate. Therefore, no centrifugal oil pressure is generated in the hydraulic chamber 28g formed between the piston 28f and the cylinder portion 33, and unnecessary pressing force other than the pressing force by the control oil pressure is not applied to the clutch plate 28c and the like. Therefore, the hydraulic control of the hydraulic chamber 28g is accurate, and delicate hydraulic control is also possible. Moreover, since the piston 28f is not rotated as described above, occurrence of abnormal wear of the seal member is prevented. Further, since the wet type hydraulic multi-plate clutches 22 and 28 are arranged in the front wheel differential 7 and the rear wheel differential 8, the transfer device 4 does not become long and the device configuration is compact. As a result, the rigidity is maintained, and the vibration and noise of the drive system do not increase. Also, the space in the vehicle interior is not reduced. Although the above embodiment is based on a four-wheel drive vehicle with a front engine, it may be configured on a four-wheel drive vehicle with a rear engine. Although two oil pumps are provided corresponding to the first and second wet hydraulic multi-plate clutches, one oil pump may be shared by forming a hydraulic circuit with external piping or the like. The present invention can be applied to not only manual transmission vehicles but also automatic transmission vehicles and vehicles with continuously variable transmissions.

【The invention's effect】

As described above, according to the present invention, even if the clutch drum rotates due to the rotation of the transmission shaft, the hydraulic pistons in each wet hydraulic multi-plate clutch do not rotate, and between these and the case member of the independent differential. No centrifugal oil pressure is generated in each of the hydraulic chambers. Therefore, each wet-type hydraulic multi-plate clutch distributes power at an arbitrary ratio to the front and rear wheels by an appropriate transmission torque according to the control oil pressure. In addition, since the hydraulic piston does not rotate, abnormal wear of the seal member can be prevented. This makes it possible to almost completely eliminate the occurrence of malfunction of the hydraulic piston and accurately set the control oil pressure required for proper power distribution. In addition, when the internal circulation torque is generated due to the rotation difference between the front and rear wheels, each wet-type hydraulic multi-plate clutch uses an appropriate operating oil having a predetermined composition, so that the wet-type hydraulic multi-plate clutch can perform the desired operation. By exhibiting the frictional characteristics of the tire, it smoothly absorbs without stick-slip and absorbs this enough to avoid tight corner braking when turning, acceleration performance and fuel economy when driving straight ahead And the generation of vibration noise can be prevented. In addition, the transfer device has a structure that does not include a wet-type hydraulic multi-plate clutch, and the structure is compact, so that the bending rigidity of the drive system is maintained to avoid increases in vibration and noise, and the space in the passenger compartment is also reduced. can do.

[Brief description of the drawings]

1 (a) and 1 (b) are cross-sectional views of an essential part showing an embodiment of the present invention, FIG. 1 (c) is a cross-sectional view taken along line CC of FIG. 1 (b), and FIG. FIG. 3 is a schematic configuration diagram of a transmission system of a four-wheel drive vehicle to which one embodiment is applied, FIG. 3 is a hydraulic circuit diagram used in one embodiment, and FIG. 4 is a characteristic diagram of duty pressure and clutch pressure. DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Clutch, 3 ... Synchronous mesh type manual transmission, 4 ... Transfer device, 5, 6 ... Propeller shaft, 7 ... Differential device for front wheels, 8 ... Rear wheels 9 differential transmission output shaft, 10 front drive shaft, 11 transfer drive sprocket, 12
Transfer driven sprocket, 13 …… Chain,
14a, 14b …… Oil pump, 15a, 15b …… Regulator valve, 16a, 16b …… Transfer clutch valve, 17a, 1
7b Duty solenoid valve, 18a, 18b Pilot valve, 19 Control unit, 20, 21 Companion flange, 22 First wet hydraulic multi-plate clutch,
23 ... front wheel, 24 ... rear wheel, 25 ... final gear, 26 ...
... Valve unit, 28 ... Second wet-type hydraulic multi-plate clutch, 28a ... Clutch drum, 28b ... Clutch hub, 28
c …… Clutch plate, 28d …… Retainer plate, 28
e… Clutch disk, 28f… Piston, 28g …… Hydraulic chamber, 29 …… Differential carrier, 30 …… Drive pinion, 30a …… Shaft, 30b …… Oil passage, 31 …… Input shaft, 31a …… Flange part, 31b ... oil passage, 32 ... extension case, 33 ... cylinder part, 33a ... partition wall, 3
3b …… Inner guide cylinder, 34 …… Thrust washer, 35 ……
Release bearing, 35a …… Outer race, 35b ……
Nail, 35c …… Inner race, 36,37 …… Oil seal, 43
a FF switch, 43b FR switch, 43c Control 4WD
switch.

Claims (1)

(57) [Claims] In a four-wheel drive vehicle in which power is distributed between front and rear wheels in accordance with the pressure of hydraulic oil to two wet-type hydraulic multi-plate clutches, power is transmitted from a transfer device via a propeller shaft. The vehicle includes a front wheel independent differential and a rear wheel independent differential, and the two wet hydraulic multi-plate clutches are separately arranged in the front wheel independent differential and the rear wheel independent differential, respectively, to transmit a transmission shaft. The hydraulic pistons in these wet-type hydraulic multi-plate clutches are fixedly slidably fitted to the case members of the independent differential devices, which are non-moving members, as cylinders, respectively. The working end opposite to the operating hydraulic chamber is pressed into contact with a retainer plate, which is fitted inside the end of the clutch drum of the wet-type hydraulic multi-plate clutch, via a bearing. Clutch plate configured four-wheel drive vehicle of the power distribution device in which to press the inside Chidoramu.