JPS62253530A - Power transmitting device - Google Patents

Abstract

PURPOSE:To prevent the fuel consumption rate from being deteriorated at the time of the high-speed travel by providing a relief valve regulating the maximum liquid pressure in the hydraulic chamber of a sliding clutch on a member rotated integrally with an input shaft and decreasing the relief pressure as the input rotating speed is increased. CONSTITUTION:When a slip is generated on rear wheels 9, a difference in the rotating speed is generated between an input shaft 13 and an output shaft 18, and an oil pump 60 is driven in response to this relative rotating speed. Thereby, the oil pressure in a hydraulic chamber 45 is increased, the coupling force between clutch plates 41, 42, is increased, and the torque of the input shaft 13 is distributed to the output shaft 18. A relief valve 46 regulating the maximum oil pressure in the hydraulic chamber 45 decreases the relief oil pressure as the input rotating speed is increased. Therefore, the torque transmitted by a clutch 40 is decreased, and finally the clutch 40 is cut off. Accordingly, at the time of the high-speed travel, two-wheel driving is performed to improve the fuel consumption rate, a slip between the clutch plates 41, 42 is eliminated, and the life is improved.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to power transmission devices that automatically transmit torque according to the relative rotational speed between an input shaft and an output shaft, particularly transfer devices and differentials of four-wheel drive vehicles. The present invention relates to a power transmission device suitable as a restriction device.

Conventional technology and its problems Conventionally, viscous couplings are widely known as power transmission devices that automatically transmit torque according to the relative rotation between an input shaft and an output shaft. A disc with many slits fitted into the spline on the side and a disc with many round holes fitted into the spline inside the drum are stacked alternately, and high viscosity silicone oil is sealed inside the drum. When there is no relative rotation between the input and output sides, no torque is transmitted, and as the relative rotation speed increases, torque is transmitted by shearing resistance between the silicone oil and the disk. .

The above-mentioned viscous coupling allows extremely smooth power transmission and does not require any switching operations, so for example
When used as a transfer device for a wheel drive vehicle, it can achieve efficient driving similar to a two-wheel drive during normal driving, and fully demonstrate the characteristics of a four-wheel drive when driving on rough or snowy roads.

However, viscous coupling has the following two drawbacks. The first is that the torque-relative rotational speed characteristic of viscous force/7bring shows an upwardly convex curve, and the transmitted torque is relatively large even when the relative rotational speed is small. For example, this may cause tight braking during low-speed cornering, and when there is a difference in rotational speed between the front and rear wheels due to an unbalance in the effective diameter of the front and rear wheels, the product of the relative rotational speed and the transmitted torque Since the loss of energy increases proportionally, fuel efficiency is adversely affected, especially in the region where the relative rotational speed is small during high-speed driving. Second, the processing of the disk is complicated and requires high precision, and
Since a large number of disks are required for each viscous coupling, the cost is high.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a power transmission device that eliminates the drawbacks of the viscous coupling described above, improves fuel efficiency during high-speed running, and extends the life of clutch plates.

Structure of the Invention In order to achieve the above object, the present invention provides a power transmission device that transmits torque according to the relative rotation speed between the input shaft and the output shaft. It is equipped with a hydraulic pump to be driven and a sliding clutch that engages an input and output shaft by the discharged hydraulic pressure of the hydraulic pump, and a relief valve that regulates the maximum hydraulic pressure in the hydraulic chamber of the sliding clutch. The relief valve, which is provided on a member that rotates integrally with the input shaft, automatically adjusts the pressure so that the maximum hydraulic pressure decreases as the input rotational speed increases.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an example in which the present invention is applied to a transfer device for a four-wheel drive vehicle.A transmission 2 is connected to the rear of an engine 1, and the way the transmission 2 comes out is similar to that of a transfer device 3. Power is distributed to two transmission shafts 4.5 via the transmission shaft. and,
One transmission shaft 4 drives the front wheels 7 via a differential device 6,
The other transmission shaft 5 drives rear wheels 9 via a differential gear 8.

FIG. 2 shows the internal structure of the transfer device 3. In the center of the housing 10, 11, 12 is an input shaft 13 which is the output shaft of the transmission 2, and the input shaft 13 is directly connected to the input shaft 13 via a connector 14. A first output shaft 15 is rotatably supported by bearings 16 and 17, and the first output shaft 15 is rotatably supported by bearings 16 and 17.
It is connected to a transmission shaft 5 for driving. Further, a cylindrical second output shaft 18 is attached to a bearing 20 on the outer periphery of the input shaft 13.
, 21 so as to be relatively rotatable, and the second output shaft 1
A sprocket 22 is spline-coupled to the outer periphery of the right end of the wheel 8, and the sprocket 22 is connected via a chain 23 to a transmission shaft 4 for driving the front wheel 7.

A front case 30 is spline-coupled to the input shaft 13, and a rear case 31 is fitted on the outside of the front case 30, with a cylinder 32 and an oil pump body 33 interposed between them. are joined together by. The internal space of the case 30, 31 is filled with hydraulic oil, and the oil seal 35
, 36. The filling of hydraulic oil is carried out through the bolt insertion hole 31a of the rear case 31. In particular, since the bolt hole 32a of the cylinder 32 has a U-shaped opening on the outer circumferential side, the rear case 31 can be filled with the hydraulic oil with the bolt 34 pulled out. By injecting oil through the bolt insertion hole 31a, the case 30.31 can be easily filled.

A sliding clutch 40 and an oil pump 60 are connected to the cylinder 32 between the second output shaft 18 and the case 30.31.
They are placed in parallel with each other. That is, a clutch hub 19 is integrally formed at the left end of the second output shaft 18, and a clutch plate 41 is provided between the front case 30 and the clutch hub 19, which are spline-engaged with the front case 30 and the clutch hub 19, respectively. .42 is an alternating C? Multiple sheets are placed. A piston 43 for compressing the clutch plates 41 and 42 is disposed inside the cylinder 32 so as to be movable in the axial direction. It is formed.

As shown in FIG. 3, a relief valve 46 for regulating the maximum oil pressure in the hydraulic chamber 45 is arranged in the axial direction on the outer peripheral wall of the cylinder 32. As shown in FIG. This relief valve 46 has a ball 47
and a spring that urges the pole 47 in the valve closing direction, and when the oil pressure in the oil pressure chamber 45 exceeds a predetermined value (relief oil pressure), it overcomes the spring 48 and opens the drain oil path 49,
It is designed to open 50.

The seating surface 51 of the pawl 47 has a tapered shape as shown in detail in FIG. 4, and as the input rotation speed increases, the pawl 47 moves to the left in FIG. and lower the relief oil pressure. Here, the inclination angle of the seating surface 51 is α, the spring load is S, and the pole 47
F is the centrifugal load applied to F, and A is the opening area of the relief valve 46.
, when the relief oil pressure is P, the relational expression PA=S-F-tan cr holds true. In the above equation, the centrifugal load F is proportional to the square of the input rotation speed, so the relief oil pressure P is automatically regulated so as to decrease quadratically as the input rotation speed increases, as shown by the solid line in Figure 5. The input rotation speed is a predetermined value N
, the relief oil pressure P becomes zero. Note that when the inclination α of the seating surface 51 is increased, the change in the relief oil pressure P becomes steeper as shown by the broken line in FIG.
It can be adjusted so that the relief oil pressure P changes slowly as shown by the dashed line in the figure.

A cylindrical strainer 59 having a predetermined thickness is arranged on the outer circumferential side of the clutch 1% 241.42, and filters dirt in the oil circulating inside the case 30, 31 and protects the oil pump 60. ing.

As shown in FIG. 6, an internal gear type oil pump 60 is provided inside the oil pump pod 33, and its driving gear 61 is spline-engaged with the outer periphery of the second output shaft 18, and the driven gear 62 is rotatably fitted inside the oil pump pod 33. On the inner surface of the rear case 31 facing the oil pump 60, there is a discharge port 63 (which becomes a suction port when the oil pump 60 rotates counterclockwise in FIG. The oil pump podium 33 is provided with a pair of one-way valves 65 and 66 in different directions that communicate with the discharge port 63 and the suction port 64, respectively. There is. Therefore, hydraulic oil can be discharged to the hydraulic chamber 45 even when the oil pump 60 is driven in either the forward or reverse direction. The hydraulic oil discharged from the oil pump 60 is transferred from the discharge port 63 as shown by the arrow in FIG.
, the suction oil passage 67, and the one-way valve 65 to the suction port 64. In particular, since the oil pump 60 sucks hydraulic oil from the outer circumferential side of the case 30, 31, the air is This eliminates the problem of oil entering the suction port 64 and causing suction failure, and since the suction oil passage is formed in the thin outer peripheral portion of the rear case 31, the hydraulic oil is effectively cooled.

As described above, the inside of the case 30.31 is almost filled with hydraulic oil, so even if centrifugal hydraulic pressure is generated inside the hydraulic chamber 45 due to the rotation of the case 30.31, the inside and outside of the hydraulic chamber 45 are not connected. Since the centrifugal oil pressure is offset, there is no problem of the piston 43 erroneously engaging the clutch 1/4L 42 as the input rotational speed increases. In addition, the clutch plate 41.
Since the clutch plates 41 and 42 are always in oil and the oil is forcibly circulated by the oil pump 60, heat generation of the clutch plates 41 and 42 is suppressed, and deterioration and wear of the clutch plates can be reduced.

In addition, the inside of the case 30.31 has an oil seal 35°3.
6, so there is no risk of oil leaking to the outside.Therefore, this power transmission device is not limited to being installed inside the housing 10, 11.12, and even if it is exposed to the outside. There are no problems and there are no restrictions on placement location.

Description of Operation The operation of the power transmission device having the above configuration will be explained. First, front wheel 7
When the rear wheels 9 and 9 are rotating at the same speed, the input shaft 1
3 and the second output shaft 18, the oil pump 60 is not driven at all, and the discharge oil pressure is zero. Therefore, the clutch 40 is not engaged, and the torque of the input shaft 13 is not distributed to the second output shaft 18.

If slip occurs in the rear wheel 9, the input shaft 13
There is a difference in the rotational speed between the first output shaft 15 and the second output shaft 13, and the oil pump 60 is driven according to this relative rotational speed. Since the discharge oil pressure of the oil pump 60 increases in accordance with the relative rotation speed, the oil pressure in the oil pressure chamber 45 increases and the clutch plate 4L 42 increases its engagement force while slipping, thereby transferring the torque of the input shaft 13 to the second output shaft. 18.

As a result, the rotation speed of the second output shaft 18 increases and approaches the rotation speed of the first output shaft 15, and the slip of the rear wheels 9 is reduced or eliminated.

If the slip of the rear wheel 9 decreases, the relative rotational speed between the first output shaft 15 and the second output shaft 18 decreases, so the discharge oil pressure of the oil pump 60 also decreases, and the transmitted torque decreases.

The torque-relative rotational speed characteristic of the power transmission device of the present invention is the seventh
As shown by the solid line in the figure, it exhibits a downwardly convex quadratic curve characteristic, which is significantly different from the upwardly convex characteristic of the conventional viscous coupling (broken line in Figure 7). In other words, in the case of a viscous coupling, it has a relatively large transmission torque even when the relative rotational speed is small, so if it is used in a transfer device, it is likely to cause tight corner braking during low-speed cornering, and it will be difficult to drive at high speeds. When the relative rotational speed is relatively small, such as when the vehicle is moving, the energy loss increases in proportion to the product of the relative rotational speed and the transmitted torque, which worsens fuel efficiency, especially during high-speed driving. In contrast, in the present invention, since the transmitted torque is minute when the relative rotational speed is small, it is possible to prevent the tight corner braking phenomenon, and also to reduce energy loss during high-speed driving and improve fuel efficiency.

Furthermore, as the input rotation speed increases, the relief pressure decreases as shown in FIG.
m), the hydraulic pressure in the hydraulic chamber 45 is drained and the clutch 40 is disconnected regardless of the relative rotation speed. This means that no torque is transmitted to the front wheels, resulting in two-wheel drive.

Therefore, when the input rotational speed is high, such as when driving at high speed, the vehicle is driven in two wheels, which improves fuel efficiency and eliminates slippage of the clutch plate 4142, thereby extending the life of the vehicle.

Another Embodiment FIG. 8 shows another embodiment of the relief valve 46, in which a ball 52 and a spring 53 are arranged radially inside the cylinder 32, and the spring load of the spring 53 and the ball 52 are The pressure is adjusted to a relief pressure according to the difference between the centrifugal load and the applied centrifugal load. In this case, the relief valve 46
Since the valve port 54 is opened directly into the hydraulic chamber 45, there is no need to form a separate drain oil passage.

Note that the power transmission device of the present invention is not limited to the case in which hydraulic oil is sealed in the case and circulates within the case, and the hydraulic oil may be supplied to the oil pump from the outside. Although an example of a multi-plate clutch mechanism is shown, a cone clutch mechanism may also be used, and the hydraulic pump is not limited to a gear type oil pump, but a vane pump or a piston pump can also be used.

Effects of the Invention As is clear from the above explanation, according to the present invention, there is provided a hydraulic pump driven by the relative rotation of the input and output shafts, and a sliding clutch that engages the input and output shafts by the discharged hydraulic pressure of the hydraulic pump. By combining these, it is possible to automatically switch on and off the torque without inputting any external signals, similar to a viscous coupling, and the transmitted torque is also small when the relative rotational speed of the input and output shafts is small. For,
This solves the problems of viscous couplings such as tight corner braking and poor fuel efficiency when driving at high speeds.

Further, in the present invention, since existing technology can be used for both the hydraulic pump and the slip type clutch, it is possible to provide a product that is less expensive than a viscous coupling and has high reliability.

Furthermore, the relief valve that regulates the maximum oil pressure of the slip clutch is designed to lower the relief pressure as the input rotational speed increases due to the action of centrifugal load, so if the present invention is applied to a transfer device, the relative rotational speed will increase during high-speed driving. The system is in two-wheel drive mode regardless of the engine speed, resulting in improved fuel efficiency and longer clutch plate life.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle to which the present invention is applicable;
FIG. 2 is a sectional view of an example of a power transmission device according to the present invention;
Fig. 3 is a partial sectional view of a part of the above device that is different from Fig. 2, Fig. 4 is a partially enlarged view of Fig. 3, and Fig. 5 is a characteristic diagram showing the relationship between relief oil pressure and input rotation speed. , Fig. 6 is a sectional view taken along the line vr-vi in Fig. 2, Fig. 7 is a characteristic comparison diagram of the present invention and a viscous coupling, and Fig. 8 is a sectional view of another embodiment of the IJ IJ-F valve. . 3... Transfer device, 7... Front wheel, 9... Rear wheel, 13... Human power shaft, 15... First output shaft, 18...
...Second output shaft, 30.31...Case, 32...
Cylinder, 33...Oil pump pod, 40...
Slip type clutch, 41.42...Clutch plate, 43
... Piston, 44... Orifice hole, 45...
Hydraulic chamber, 46... Relief valve, 47... Ball, 4
8...Spring, 49.50...Drain oil path, 6
0...Oil pump, 63...Discharge port, 64...
Suction port, 65.66...one-way valve. Applicant Daihatsu Motor Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 1 Figure 3 Figure 6 - Figure 7

Claims (1)

[Claims] (1) In a power transmission device that transmits torque according to the relative rotation speed between the input shaft and the output shaft, there is a hydraulic pump driven by the relative rotation between the input shaft and the output shaft, and the hydraulic pump. a slip type clutch that engages between the input and output shafts using the discharge hydraulic pressure of the slip type clutch, and a relief valve that regulates the maximum hydraulic pressure in the hydraulic chamber of the slip type clutch is provided on a member that rotates integrally with the input shaft; A power transmission device characterized in that the valve automatically adjusts pressure so that the maximum hydraulic pressure decreases as the input rotation speed increases.