JPH0547865Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) This invention relates to a power transmission device used in, for example, a four-wheel drive vehicle.

(Prior Art) As a conventional viscous coupling device, there is, for example, one described in Japanese Patent Application Laid-open No. 65918/1983. This viscous coupling device is
A pressure chamber is formed on one side of a working chamber formed between the case side and the shaft side, and a free piston is fitted between the pressure chamber and the working chamber so as to be slidable in the axial direction. When hydraulic oil is supplied to the pressure chamber, the free piston slides toward the working chamber,
The transmission torque is increased by reducing the gap between the resistance plates on the case side and the shaft side.

(Problem to be solved by the invention) However, in such a conventional power transmission device, there is an oil pump for supplying hydraulic oil to the pressure chamber, and the pressure of the hydraulic oil supplied from this oil pump. A control unit, etc. is required to adjust the oil pressure, and the oil pump on the stationary side and the viscous cut spring on the rotating side must be connected via piping, etc., making the device complex and large, as well as having poor sealing performance. There were also problems with this.

Therefore, the purpose of this invention is to provide a power transmission device that can omit external devices such as an oil pump, yet can reliably adjust the transmitted torque and has highly reliable sealing performance. .

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, this invention includes a first rotating body and a second rotating body that are relatively rotatable, and a first rotating body and a second rotating body that are rotatable relative to each other. a hermetically sealed working chamber formed between the working chamber and the viscous fluid sealed in; In a power transmission device comprising a plurality of resistance plates, a pressure chamber filled with a working fluid is provided on one side of the working chamber, and a first end facing the pressure chamber and the other end facing the working chamber.
A piston and a second piston are provided, and the cross-sectional area of one end of each piston facing the pressure chamber is larger than the cross-sectional area of the other end.

(Function) According to the above configuration, when the viscous fluid expands, the first piston and the second piston move relative to each other in the axial direction due to the increase in internal pressure in the working chamber and the difference in the cross-sectional area of the working chamber side of both pistons, and one piston moves in the axial direction. Move towards the working chamber. Therefore, the resistance plates in the working chamber are pressed by the piston, the gap between the resistance plates is narrowed, and the torque transmission force is increased.

(Example) Hereinafter, an example of this invention will be described based on FIG. 1.

FIG. 1 shows a sectional view of a so-called viscous coupling device according to an embodiment of the power transmission device of this invention. This device is, for example, attached to the drive system of one of the front and rear wheels of a four-wheel drive vehicle.

An input member 1, which is a first rotating body that receives a rotational input, is spline-engaged with an output shaft 3 of the transfer shaft. A housing 5 is fitted to one end of the input member 1 by a spline, and an output member 7, which is a second rotating body, is fitted inside the housing 5 so as to be relatively rotatable. A hermetically sealed working chamber 9 is provided between the housing 5 and the output member 7.

The working chamber 9 is filled with a viscous fluid such as silicone oil. Inside the working chamber 9, there are a plurality of first resistance plates 11 formed on the outer periphery of the output member 7 and a plurality of first resistance plates 11 which are engaged in the circumferential direction by meshing with splines formed on the inner periphery of the housing 5 and are movable in the axial direction. Second resistance plates 13 which are engaged in the circumferential direction and are movable in the axial direction by meshing with the splines are alternately arranged.

An annular disc spring 15 is inserted between the first resistance plates. This disc spring 15 is connected to the first resistance plate 11
and the second resistance plate 13 are provided so as to be pushed apart,
A constant gap is maintained between both resistance plates 11 and 13. The disc spring 15 can also be made of a web washer or an elastic body such as rubber. Further, the disc spring 15 may be inserted between the second resistance plates 13 or both between the first resistance plates 11 and between the second resistance plates 13.

An annular pressure chamber 17 is formed in the input member 1, and a first piston 19 and a second piston 21 are respectively movable in the axial direction within the pressure chamber 17.
is fitted. Therefore, the pressure chamber 17 is provided on one side of the working chamber 9, and the pressure chamber 17
The inside is filled with oil as a working fluid. The first piston 19 is formed of an annular body having an inverted L-shaped cross section and has a large cross-sectional area portion 19a with a small inner diameter and a small cross-sectional area portion 19b with a large inner diameter, with the large cross-sectional area portion 19a facing the working chamber 9 side. , small cross-sectional area part 19
b is arranged toward the pressure chamber 17 side. The second piston 21 is formed of an annular body having an L-shaped cross section and a large diameter part 21a and a small diameter part 21b having different outer diameters, with the large diameter part 21a facing the pressure chamber 17 and the small diameter part 21b acting. It is arranged toward the room 9 side. Therefore, the configuration is such that the first piston 19 and the second piston 21 are provided, one end of which faces the pressure chamber 17 and the other end of which faces the working chamber 9. The cross-sectional area is larger than the cross-sectional area of the other end.

The large cross-sectional area portion 19a of the first piston 19
The inner circumference and the outer circumference of the small diameter portion 21b of the second piston 21,
The inner circumference of the small cross-sectional area portion 19b of the first piston 19 and the second
The outer periphery of the large diameter portion 21a of the piston 21 is in sliding contact, the outer periphery of the first piston 19 is in sliding contact with the inner periphery of the pressure chamber 17, and the inner periphery of the second piston 21 is in sliding contact with the outer periphery of the pressure chamber 17. It is kept liquid-tight.

The input member 1 and the first piston 19 have air holes 25a and 25 that communicate with the space 24 formed between the first piston 19 and the second piston 21.
b is provided.

Further, a pressing body 27 is interposed between the pistons 19 and 21 and the first resistance plate 11 on one side of the working chamber 9 so as to be movable in the axial direction.

Reference numeral 29 denotes an X-ring used as a highly pressure-resistant seal.

Next, the operation of the above embodiment will be described.

The rotational force input from the output shaft 3 to the input member 1 is transmitted to the housing 5, and the first resistance plate 11, which rotates integrally with the housing 5, and the housing 5
The resistance is transmitted to the second resistance plate 13 from the viscous resistance of the viscous fluid sealed in the working chamber 9 , and is transmitted to the output member 7 which rotates integrally with the second resistance plate 13 .

In the torque transmission carried out in this manner, the temperature of the liquid in the working chamber 9 rises during long-term differential rotation between the input member 1 and the output member 7, and as the liquid temperature rises, the liquid pressure rises. Then, this hydraulic pressure acts on the first piston 19 and the second piston 21, but the first piston 19 is stronger than the second piston 21.
Since the area on which the hydraulic pressure acts is large compared to the first piston 19, the first piston 19 slides toward the pressure chamber 17. This sliding movement of the first piston 19 increases the hydraulic pressure within the pressure chamber 17, and this hydraulic pressure causes the second piston 2 to
1 is slid in the direction of the working chamber 9 and presses the first resistance plate 11 and the second resistance plate 13 via the pressing plate 27,
The gap between the first resistance plate 11 and the second resistance plate 13 is reduced against the elasticity of the disc spring 15. As a result, the transmitted torque increases and an increase in the internal pressure of the working chamber 9 can be suppressed. Therefore, when the input rotation from the output shaft 3 is low, the torque transmission force is set low,
Tight corner braking phenomena such as parking in a garage can be prevented. Furthermore, when driving on a rough road, the hydraulic pressure increases due to long-term differential rotation, and the above-mentioned action allows stable driving with reliable torque transmission.

Note that the action by the second piston 21 may be such that both resistance plates 11 and 13 are fastened together. Additionally, air holes 25a and 25 communicate with the space 24 formed between the first piston 19 and the second piston 21.
b does not necessarily need to be provided.

[Effects of the invention] As is clear from the above explanation, according to the structure of this invention, when the internal pressure in the working chamber increases, the piston moves in response to this, increasing the torque transmission force and suppressing the increase in internal pressure. , to compensate for the decrease in the performance of the viscous coupling device due to the rise in liquid temperature, and to improve the durability.

Furthermore, since the gap between the resistance plates is reduced using the internal pressure within the working chamber, an external device such as an oil pump is not required, and the structure can be simplified and made more compact.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the upper half of a power transmission device according to an embodiment of the invention before operation and the lower half after operation. 1... Input member (first rotating body), 5... Housing, 7... Output member (second rotating body), 9... Working chamber, 11, 13... Resistance plate, 17... Pressure chamber,
19...first piston, 21...second piston.

Claims (1)

[Scope of utility model registration request] a first rotating body and a second rotating body that are relatively rotatable;
a closed working chamber formed between a first rotating body and a second rotating body and enclosing a viscous fluid; In a power transmission device comprising a plurality of resistance plates arranged alternately together, a pressure chamber filled with a working fluid is provided on one side of the working chamber, and one end faces the pressure chamber and the working chamber 1. A power transmission device comprising: a first piston and a second piston, the other end of which faces the pressure chamber; the cross-sectional area of one end of each piston facing the pressure chamber is larger than the cross-sectional area of the other end.