JPH076556B2 - Power transmission device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device that automatically transmits torque in accordance with the relative rotational speed between an input shaft and an output shaft, and more particularly to a transfer device and a differential device for a four-wheel drive vehicle. The present invention relates to a power transmission device suitable as a limiting device.

Conventional technology and its problems Conventionally, a viscous coupling is widely known as a power transmission device that automatically transmits torque according to the relative rotation speed between an input shaft and an output shaft. In this viscous coupling, a disc with a large number of slits fitted to the spline on the shaft side and a disc with a large number of round holes fitted to the spline on the inside of the drum are alternately superposed to form a high disc inside the drum. It is filled with viscous silicon oil.When there is no relative rotation between the input side and the output side, torque is not transmitted.As the relative rotation speed increases, the torque is increased due to the shear resistance between the silicon oil and the disc. It is a mechanism to transmit.

The viscous coupling can transmit power very smoothly and does not require any switching operation.
When used as a transfer device for a wheel drive vehicle, it can achieve the same efficient traveling as the two-wheel drive during normal traveling, and can sufficiently exhibit the characteristics as four-wheel drive during traveling on a rough road or a snowy road.

However, the viscous coupling has the following two drawbacks. The first is that the torque-relative rotation speed characteristic of the viscous coupling shows a curve with a convex shape, and the transmitted torque becomes relatively large even when the relative rotation speed is small. This means that, for example, a tight braking phenomenon may occur during low-speed cornering, and when there is a difference in the rotational speeds of the front and rear wheels due to imbalance of the effective diameters of the front and rear wheels, the product of the relative rotational speed and the transmission torque is Since the energy loss increases in proportion, the fuel consumption is adversely affected especially in the region where the relative rotation speed is small during high-speed traveling. Second,
The cost of the disk is high because the disk processing is complicated and requires high precision, and a large number of disks are required for one viscous coupling.

OBJECT OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the viscous coupling and to provide a power transmission device which can prevent overheating of the working liquid and has excellent durability.

In order to achieve the above object, the present invention is a power transmission device that transmits torque according to the magnitude of the relative rotation speed between the input shaft and the output shaft, by the relative rotation between the input shaft and the output shaft. It comprises a driven hydraulic pump and a sliding clutch that engages between the input and output shafts by the discharge hydraulic pressure of the hydraulic pump, and the working liquid rises above a predetermined temperature in the piston portion of the sliding clutch. A temperature sensitive member for forcibly engaging the clutch is sometimes provided.

Description of Embodiments FIG. 1 shows an example in which the present invention is applied to a transfer device of a four-wheel drive vehicle. A transmission 2 is connected to a rear portion of an engine 1, and an output of the transmission 2 is transferred via a transfer device 3. Power is distributed to the two transmission shafts 4 and 5. One of the transmission shafts 4 drives the front wheels 7 via the differential device 6, and the other transmission shaft 5 drives the rear wheels 9 via the differential device 8.

FIG. 2 shows the internal structure of the transfer device 3. The input shaft 13, which is the output shaft of the transmission 2, is directly connected to the center of the housings 10, 11, 12 and the input shaft 13 via a connector 14. A first output shaft 15 and a first output shaft 15 are rotatably supported by bearings 16 and 17, and the first output shaft 15 is connected to a transmission shaft 5 for driving a rear wheel 9. A cylindrical second output shaft 18 is rotatably supported on the outer periphery of the input shaft 13 via bearings 20 and 21, and a sprocket 22 is provided on the outer periphery of the right end portion of the second output shaft 18.
Are splined together, and this sprocket 22 is connected via a chain 23 to the transmission shaft 4 for driving the front wheels 7.

A front case 30 is spline-coupled to the input shaft 13, an outer rear case 31 of the front case 30 is fitted, and a cylinder 32 and an oil pump body are provided between them.
The bolts 34 and 33 are integrally fastened together with the bolts 33 and 33 interposed. The internal space of the cases 30 and 31 is filled with hydraulic oil and sealed by oil seals 35 and 36. The hydraulic oil is filled through the bolt insertion hole 31a of the rear case 31, but especially the bolt hole 3 of the cylinder 32.
Since 2a is opened in a U shape on the outer peripheral side, if the oil is injected from the bolt insertion hole 31a of the rear case 31 with the bolt 34 pulled out, the cases 30 and 31 can be easily filled.

A slip clutch 40 and an oil pump 60 are arranged side by side with a cylinder 32 between the second output shaft 18 and the cases 30, 31. That is, the clutch hub 19 is integrally formed on the left end of the second output shaft 18, and the clutch plate 41 spline-engaged with the front case 30 and the clutch hub 19 is provided between the front case 30 and the clutch hub 19. , 42
Are alternately arranged. Inside the cylinder 32, a piston 43 for crimping the clutch plates 41, 42 is arranged movably in the axial direction, and the piston 43 has an orifice hole 44 for reducing the flow rate of hydraulic oil leaking from the hydraulic chamber 45. Has been formed. Further, as shown in FIG. 3, a relief valve 46 is provided in the thick outer peripheral portion of the cylinder 32, and when the internal pressure of the hydraulic chamber 45 becomes a predetermined value or more, it overcomes the spring 47 and opens the drain oil passages 48, 49. It is supposed to open. A cylindrical strainer 50 having a predetermined thickness is arranged on the outer peripheral side of the clutch plates 41, 42 to filter dust in the oil circulating inside the cases 30, 31 to protect the oil pump 60. There is.

As shown in FIG. 4, a corrugated plate temperature-sensitive member 51 made of a shape memory alloy is arranged inside the hydraulic chamber 45. The temperature-sensitive member 51 has a small wave undulation at a temperature lower than the transformation temperature. It is a two-transformation type that transforms so that the undulations of the waves increase when the temperature rises above the temperature. Therefore, if the oil temperature of the hydraulic chamber 45 is lower than the transformation temperature, the temperature sensitive member 51 does not pressurize the piston 43 at all, and if the temperature exceeds the transformation temperature, the piston 43 is moved to the clutch plates 41, 4.
Pressurize in 2 directions.

As shown in FIG. 5, an internal gear type oil pump 60 is provided inside the oil pump body 33, and a drive gear 61 thereof is spline-engaged with the outer periphery of the second output shaft 18 and a driven gear 62. Is rotatably fitted inside the oil pump body 33. Rear case facing the above oil pump 60
On the inner surface of 31, there are a discharge port 63 (which serves as a suction port during reverse rotation) and a suction port 64 (which serves as a discharge port during reverse rotation) when the oil pump 60 relatively rotates counterclockwise in FIG. The oil pump body 33 is formed at symmetrical positions, and the oil pump body 33 is provided with a pair of one-way valves 65 and 66 that communicate with the discharge port 63 and the suction port 64, respectively, and have different directions. Therefore, the hydraulic oil can be discharged to the hydraulic chamber 45 regardless of whether the oil pump 60 is driven in the forward or reverse direction. The hydraulic oil discharged from the oil pump 60 is discharged as shown by the arrow in FIG.
63 to one-way valve 66, communication hole 32b of cylinder 32, hydraulic chamber 45,
The orifice hole 44, the clutch plates 41 and 42, the strainer 50, the suction oil passage 67, and the one-way valve 65 circulate to the suction port 64, and in particular, the oil pump 60 is installed from the outer peripheral side of the cases 30 and 31. Since the working oil is sucked, the problem that air enters the suction port 64 due to the influence of the centrifugal hydraulic pressure and causes suction failure, and the suction oil passage is formed in the thin outer peripheral portion of the rear case 31, the working oil is Effectively cooled.

As described above, since the insides of the cases 30 and 31 are almost filled with hydraulic oil, even if centrifugal oil pressure is generated inside the hydraulic chamber 45 due to the rotation of the cases 30 and 31, the inside and outside of the hydraulic chamber 45 are Therefore, there is no problem that the piston 43 erroneously engages the clutch plates 41 and 42 as the input rotation speed increases because the centrifugal oil pressure is canceled out. Also, the clutch plates 41, 42 are always in oil,
Moreover, since the oil is forcibly circulated by the oil pump 60, the heat generation of the clutch plates 41, 42 is suppressed, and the deterioration and wear of the clutch plates can be reduced.

Since the insides of the cases 30 and 31 are liquid-tightly sealed by the oil seals 35 and 36, there is no risk of oil leakage to the outside.
It is not limited to the case where it is provided inside 10, 11 and 12, and there is no problem even if it is exposed to the outside, and there is no restriction on the placement location.

Description of Operation The operation of the power transmission device having the above configuration will be described. Front wheel 7
And the rear wheel 9 are rotating at the same speed, the input shaft 13
Since there is no relative rotation between the second output shaft 18 and the second output shaft 18, the oil pump 60 is not driven at all, and the discharge hydraulic 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 the rear wheel 9 slips, the input shaft 13
A difference occurs in the rotational speeds of the (first output shaft 15) and the second output shaft 18, and the oil pump 60 is driven according to this relative rotational speed. Since the discharge hydraulic pressure of the oil pump 60 increases in accordance with the relative rotation speed, the hydraulic pressure in the hydraulic chamber 45 increases and the clutch plate 4
1, 42 increase the engagement force while sliding, and distribute 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 wheel 9 is reduced or eliminated. If the slip of the rear wheel 9 is reduced, the relative rotational speed of the first output shaft 15 and the second output shaft 18 is reduced, so that the discharge hydraulic pressure of the oil pump 60 is also reduced and the transmission torque is reduced.

When there is relative rotation between the input shaft 13 and the second output shaft 18, the clutch plates 41, 42 slip and generate heat, and this heat causes an increase in oil temperature. If the oil temperature is equal to or lower than the transformation temperature of the temperature sensitive member 51 (for example, hundreds of tens of degrees Celsius), the temperature sensitive member 51 does not apply any pressure to the piston 43, and the piston 43 operates only by the hydraulic pressure in the hydraulic chamber 45. To do. When the oil temperature rises above the transformation temperature, the temperature sensitive member 51 arranged in the hydraulic chamber 45 deforms and presses the piston 43 toward the clutch plates 41, 42,
The clutch 40 is forcibly engaged. For this reason the clutch plate
The slip between 41 and 42 is eliminated and the oil temperature rise is suppressed.
When the oil temperature falls below the transformation temperature, the temperature sensitive member 51 transforms back to the original state, and the pressure applied to the piston 43 is released. As described above, when the oil temperature rises above a predetermined temperature, the clutch is automatically engaged to prevent the oil temperature from rising, so damage to the facing portions of the clutch plates 41, 42 and deterioration of the hydraulic oil are prevented. .

The torque-relative rotation speed characteristic of the power transmission device of the present invention is the sixth.
As shown by the solid line in the figure, it shows a downward quadratic curve-like characteristic, and the characteristic of the conventional viscous coupling (dashed line in FIG. 6).
It is very different from the characteristic of being convex upward. In other words, in the case of viscous coupling, it has a relatively large transmission torque even when the relative speed is small, so when this is applied to a transfer device, a tight corner braking phenomenon is likely to occur during low speed cornering, and high speed running is also possible. When the relative rotation speed is relatively small as in the case of the above, the energy loss increases in proportion to the product of the relative rotation speed and the transmission torque, which deteriorates the fuel consumption especially at high speed. On the other hand, in the present invention, the transmission torque is small when the relative rotation speed is small, so that the tight corner braking phenomenon can be prevented, and the energy loss during high speed traveling can be reduced to improve the fuel consumption.

The shape memory alloy is used as the material of the temperature sensitive member 51 in the above embodiment, but the present invention is not limited to this, and bimetal may be used, and the temperature sensitive member may be gas or volatilized inside as shown in FIG. An annular bellows 52 encapsulating a volatile substance may be used. In the case of shape memory alloy, since the pressing force at the time of deformation is large, it is possible to reliably engage the clutch, while in the case of bimetal or gas-filled bellows, the clutch engagement force continuously increases as the temperature rises, It is possible to avoid shock when the clutch is engaged.

Further, the position of the temperature-sensing member is not limited to the inside of the hydraulic chamber, but may be outside the hydraulic chamber.However, when the temperature-sensitive member is provided outside, the engagement is started after the piston has moved a predetermined stroke, so There will be some time lag. On the other hand, when provided internally, the piston does not need to make a stroke, and the sum of the clutch hydraulic pressure and the pressure applied by the temperature-sensitive member instantly acts as the clutch engaging force, so that the oil temperature rise can be reliably prevented.

The power transmission device of the present invention is not limited to the case where the working oil is enclosed in the case and the working oil circulates in the case, and the working oil may be supplied to the oil pump from the outside. Although the wet multi-plate clutch mechanism is shown as an example of the slip clutch, a cone clutch mechanism may be used, and the hydraulic pump is not limited to the gear type oil pump, but a vane pump or a piston pump may be used.

As is apparent from the above description, according to the present invention, the hydraulic pump driven by the relative rotation of the input / output shaft and the slip clutch for engaging the input / output shaft by the discharge hydraulic pressure of the hydraulic pump. As with the viscous coupling, it is possible to automatically switch the torque intermittently without inputting any external signal, and the transmission torque is small when the relative rotation speed of the input / output shaft is small. For,
It is possible to solve problems such as tight corner braking phenomenon in viscous coupling and deterioration of fuel consumption at high speed.

Further, in the present invention, since the existing technology can be used for both the hydraulic pump and the slip clutch, the product can be constructed at a lower cost than the viscous coupling and a highly reliable product can be provided.

In addition, a temperature sensitive member that forcibly engages the clutch when the temperature of the hydraulic fluid rises is placed in the piston part of the slip clutch, so an abnormal rise in the fluid temperature is automatically prevented without using any sensor or actuator. It is possible to improve the durability of the clutch plate and the hydraulic oil.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle to which the present invention is applied,
FIG. 2 is a sectional view of an example of a power transmission device according to the present invention,
3 is a partial sectional view of a portion of the apparatus different from that of FIG. 2, FIG. 4 is a perspective view of a first embodiment of the temperature sensitive member, and FIG. 5 is a sectional view taken along line VV of FIG. FIG. 6 is a characteristic comparison diagram of the present invention and a viscous coupling, and FIG. 7 is a perspective view of another embodiment of the temperature sensitive member. 3 ... Transfer device, 7 ... Front wheel, 9 ... Rear wheel, 13
...... Input shaft, 15 …… First output shaft, 18 …… Second output shaft, 3
0,31 …… Case, 32 …… Cylinder, 33 …… Oil pump body, 40 …… Slip clutch, 41,42 …… Clutch plate, 43 …… Piston, 44 …… Orifice hole, 45 …… Hydraulic chamber , 51, 52 …… Temperature sensitive member, 60 …… Oil pump, 63 ……
Discharge port, 64 …… Suction port, 65,66 …… One-way valve.

Claims (1)

[Claims] 1. A power transmission device for transmitting torque according to a relative rotational speed between an input shaft and an output shaft, a hydraulic pump driven by relative rotation between the input shaft and the output shaft, and the liquid pump. A slip-type clutch that engages between the input and output shafts by the discharge liquid pressure of the pressure pump, and a feeling that the clutch is forcibly engaged with the piston portion of the slip-type clutch when the working liquid rises above a predetermined temperature. A power transmission device comprising a temperature member.