JP2503686B2 - Power transmission device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device, and more particularly to a power transmission device, which is disposed between inner and outer rotary members coaxially and relatively rotatably arranged, and transmits torque between these rotary members. The present invention relates to a power transmission device.

(Prior Art) As a power transmission device of this kind formation, a special table Sho 61-501583
There is a power transmission device including a viscous fluid coupling (a viscous coupling) disclosed in Japanese Unexamined Patent Application Publication, No. 63-287631, a viscous coupling, a friction clutch, and a cam means for connecting both of them. . The power transmission device is disposed between the driving-side rotating member and the driven-side rotating member, and connects the two members so that power can be transmitted to each other when the both members relatively rotate to drive the driven-side rotating member. It is disposed between the driving side driven member and the driven side rotating member, between both driving side rotating members or between both driven side rotating members so that the difference in rotation between these two members when they rotate relative to each other is used. It is roughly classified into those used as an operation limiting mechanism for limiting. The former coupling mechanism is mainly disposed on one power transmission line in a real-time four-wheel drive vehicle, and the latter differential limiting mechanism is mainly disposed on each differential of the vehicle.

(Problems to be Solved by the Invention) By the way, in the former viscous coupling which is the former viscous fluid coupling, the viscosity caused by the shearing force of the viscous fluid existing between the inner and outer plates is relatively increased during relative rotation. Although friction torque enables torque transmission between both plates, the viscous friction torque is not so large and the rising characteristic of the torque is not good. Further, if a viscous coupling is formed to generate a large viscous friction torque, the shearing force becomes extremely large and the amount of heat generation increases, and the viscosity of the viscous fluid becomes high and its viscosity is greatly reduced. For this reason, the obtained viscous friction torque fluctuates and the torque transmission characteristic between both plates becomes unstable. Especially, when the rotational difference between both plates gradually increases and then gradually decreases, hysteresis occurs in the torque transmission characteristic. Therefore, when such a viscous coupling is used as a coupling mechanism for one power transmission system passage in a four-wheel drive vehicle, a differential limiting mechanism for each differential, etc., the transmission torque and differential limiting torque for one power transmission system passage Becomes unstable and affects the running performance of the vehicle.

In the latter power transmission device, torque is transmitted between the two rotating members by viscous friction torque generated by the viscous coupling, and the viscous friction torque is converted into thrust by cam means to generate friction. The clutch is engaged, and the torque is further transmitted between the two rotating members by the friction torque of the clutch. Therefore, such a power transmission device is based on the operation of the viscous coupling, and directly includes the above-mentioned problems of the viscous coupling.

The present applicant has proposed a power transmission device for solving these problems in Japanese Patent Application No. 63-114406. The power transmission device is disposed between the inner and outer rotary members coaxially and relatively rotatably positioned, and operates by relative rotation of the both rotary members to generate a frictional engagement force connecting the rotary members so that torque can be transmitted. And a friction clutch for increasing / decreasing the friction engagement force according to the applied thrust force, a viscous resistance generating means for generating a viscous resistance force according to the relative rotation of the rotating members, the viscous resistance generating means and the friction clutch. A cam member which is disposed between the cam members and which relatively rotates in response to the viscous resistance force generated by the viscous resistance force generating means and a plurality of cam surfaces of these two cam members are interposed to act to separate the cam members from each other. This is a configuration including a thrust converting means having a plurality of cam followers.

Such a power transmission device eliminates the above-mentioned viscous coupling and solves the above-mentioned problems caused by the viscous coupling. However, in the power transmission device, it is difficult to form the cam surface of the cam member with high accuracy, the contact state between each cam surface and each cam follower becomes uneven, and one-sided contact occurs. Overload is applied to the cam surface and cam follower, causing both to deform. As a result, the set torque transmission characteristics change and sufficient vehicle driving performance cannot be obtained.

Therefore, it is an object of the present invention to address such issues.

(Means for Solving the Problems) A power transmission device according to the present invention is disposed between both inner and outer rotary members that are coaxially and relatively rotatably positioned, and operates by the relative rotation of these both rotary members. A friction clutch that generates a frictional engagement force that connects the members in a torque-transmittable manner and that increases or decreases the frictional engagement force according to the applied thrust force, and a viscous resistance force that generates a viscous resistance force according to the relative rotation of the two rotary members. Generating means, a pair of cam members arranged between the viscous resistance generating means and the friction clutch and rotating relative to each other in accordance with the viscous resistance generated by the same viscous resistance generating means, and between a plurality of cam surfaces of these both cam members. And a thrust force conversion means having a plurality of cam followers that act to separate the cam members from each other. The cam member is composed of a plurality of cam forming members having a cam surface and a cam body member having a plurality of recesses into which the cam forming members are fitted, and the recesses are provided at the bottom thereof with the viscous resistance generating means. The cam forming member is liquid-tightly fitted in the recess of the cam body member and supported so as to be capable of advancing and retreating with respect to the other cam member. .

(Operation and effect of the invention) In the power transmission device having such a configuration, when relative rotation occurs between both rotary members, a viscous resistance force is generated in the viscous resistance force generating means according to the differential rotation speed, and the viscous resistance force is generated. Is converted into thrust for the friction clutch by the thrust converting means. Therefore, the friction clutch is pressed by the thrust, and torque is transmitted between both rotary members in proportion to the differential rotation speed. Therefore, the power transmission device functions as a connecting mechanism between the drive-side rotating member and the driven-side rotating member in one power-transmitting system path of the four-wheel drive vehicle, and also rotates between the drive-side and the driven-side rotating members and both drive-side rotating members. It functions as a differential control mechanism between members and between both driven side rotating members.

Then, in the power transmission device, when a viscous resistance force is generated in the viscous resistance force generating means, a pressure is generated in the viscous fluid chamber forming the means, and this pressure is fitted into each recess of one cam member. The cam forming member is pressed from the back surface to the other cam member side. As a result, the backlash and gap between each cam surface of both cam members and the cam followers disappear, and both of them come into a uniform contact state, and overload on some cam surfaces and cam followers is eliminated and deformation occurs in both. There is nothing to do. Therefore, the torque transmission characteristic is maintained at the set value and sufficient vehicle driving performance is obtained.

Further, according to such a configuration, the number of cam surfaces and cam followers for uniformly contacting each cam surface with all cam followers can be increased, which reduces the load applied to the set of cam surfaces and cam followers. ,
The cam follower can be downsized, and the device can be downsized.

(Example) To describe one example of the present invention with reference to the drawings,
FIG. 1 shows a power transmission device 10 according to the present invention. As shown in FIG. 5, the power transmission device 10 is arranged in a rear-wheel power transmission system passage of a rial time type four-wheel drive vehicle.

In the vehicle, the front wheel side is always driven and the rear wheel side is driven when necessary. The transaxle 22 mounted on one side of the engine 21 is equipped with a transmission and a transfer, and the power from the engine 21 is transmitted to the axle shaft 23.
To drive the front wheels 24 and output to the first propeller shaft 25. The first propeller shaft 25 is connected to the second propeller shaft 26 via the power transmission device 10. When both shafts 25, 26 can transmit power, power is output to the axle shaft 28 via the rear differential 27. , The rear wheels 29 are driven.

The power transmission device 10 is, as shown in FIGS. 1 and 2,
A friction clutch 10a, a viscous resistance generating means 10b, and a thrust converting means 10c are provided in an annular working chamber composed of an outer case 11 and an inner case 12. The outer case 11 is integrally connected to a first propeller shaft 25, and the inner case 12 is integrally connected to a second propeller shaft 26 and is coaxially and relatively rotatably assembled in the outer case 11. .

The friction clutch 10a is a wet multi-plate clutch and is composed of a large number of clutch plates 13a and clutch discs 13b. Each clutch plate 13a has its outer spline part fitted to the inner spline part 11a of the outer case 11 to be integrated with the case 11. The clutch discs 13b are assembled so as to be rotatable and movable in the axial direction, and the inner spline portion of each clutch disc 13b is fitted to the outer spline portion 12a of the inner case 12 so as to be integrally rotatable with the same case 12 and movable in the axial direction. Is installed in.

The viscous resistance generating means 10b is a bottom portion 11b in the outer case 11.
And a viscous fluid chamber R formed by a first cam member 14 forming a thrust converting means 10c described later, and an outer case 11.
The first fin 11c provided on the bottom 11b of the first cam member 14 and the second fin 14a provided on the first cam member 14. The first fin 11c is made of a material such as aluminum alloy that is lighter in weight and easier to process than the outer case 11.
11 is a bottom 11b integrally rotatable with the casing 11 is fitted to the large number of fins 11c ₁ are coaxially protruded a predetermined length are formed concentrically viscous fluid chamber R. 2nd fin
14a is integrally formed on the body member 14b of the first cam member 14 comprises a first fin 11c the same aluminum alloy lightweight and easily processed material and a number of fins 14a ₁
Are formed concentrically and project coaxially from the fluid chamber R by a predetermined length. The first cam member 14 is assembled so as to be liquid-tightly rotatable and axially slidable with respect to both cases 11 and 12, and each fin portion 14a ₁ is a fin portion 11c ₁ of each first fin 11c. They are fitted with each other with a predetermined minute gap therebetween and are polymerized with each other for a predetermined length. The liquid chamber R is filled with a predetermined amount of highly viscous fluid such as silicon oil.

The thrust converting means 10c is composed of a first cam member 14, a second cam member 15, and a plurality of rollers 16 which are cam followers. The first cam member 14 is composed of the cam body member 14b and the cam forming member 14c. As shown in FIGS. 1 to 4, the cam body member 14b is provided with a plurality of recesses 14d formed on the surface facing the second cam member 15 at equal intervals in the circumferential direction. The cam forming member 14c is fitted into and supported by the recesses 14d through the rubber seal member 14e so as to be movable back and forth with respect to the second cam member 15. Also, each cam forming member 14c
Is a pair of cam surfaces 14 on the side facing the second cam member 15.
c _1, provided with a cam portion of the V shape composed of 14c _2, Similarly, the second cam member 15 is provided with a cam portion of the V shape consisting of a pair of cam surfaces 15b _1, 15b ₂ facing each cam formation member 14c There is.
The cam member 15 includes the first cam member 14 and the friction clutch 10.
It is integrally rotatably mounted on the outer circumference of the inner case 12 between the leftmost clutch disk 13b of a and the roller 16 between the cam members 15 and 14 of the first cam member 14. The rollers 16 are interposed and are in contact with the cam surfaces of the cam portions. Further, the first cam member 14 is formed with a communication hole 14f that opens to the center of the bottom of each recess 14d and the fluid chamber R.

In the power transmission device 10 having such a configuration, when relative rotation does not occur between the first and second propeller shafts 25, 26, torque is not transmitted between these shafts 25, 26, but both shafts 25, 26 When relative rotation occurs between 26, torque is transmitted between both shafts 25, 26. That is, when relative rotation occurs between the shafts 25 and 26, the outer case 11 and the first fin 11 that are integral with the first propeller shaft 25 are formed.
Inner case 1 integrated with c and the second propeller shaft 26
2. Relative rotation occurs between the second cam member 15 and the second fin 14a, and a viscous shear torque T represented by the following formula is generated between the fins 11c and 14a.

K: constant, μ: viscosity of viscous fluid, N: differential rotation speed, l: length of each fin section facing each other, h: gap between facing surfaces of each fin section,
ri: Each radius of the viscous shearing force generating portion This viscous shearing torque T acts as a resistance force that restricts the differential rotation of the first cam member 14, and this resistance force F is a roller.
If the arrangement radius of 16 is R, then F = T / R. This resistance is converted into a thrust for pressing the friction clutch 10a by the thrust conversion means 10c.
15 and the roller 16 operate as shown in FIG. 4, and the thrust S is S = Ftan θ, where θ is the contact angle between the roller 16 and each cam surface. As a result, in the friction clutch 10a, the clutch plate 13a and the clutch disc 13b are frictionally engaged according to the differential rotation speed, and torque is transmitted between both cases 11 and 12, that is, both shafts 25 and 26. The first cam member 14 slides toward the fluid chamber R by the action of each roller 16 to reduce the volume of the fluid chamber R, thereby increasing the filling rate of the viscous fluid and increasing the viscous shear torque. The decrease in the torque due to the decrease in the viscosity of the viscous fluid is supplemented.

Thus, in the power transmission device 10, the fluid chamber R
When the internal pressure rises, this pressure is applied to the back of each cam forming member 14c of the first cam member 14, and each cam forming member 1
4c is pressed toward the second cam member 15 side. As a result, the cam surfaces 14c ₁ , 14c ₂ and 15b ₁ , 15b of both cam members 14, 15 are formed.
_{Even if} there is play or gap between ₂ and each roller 16, they will be in a uniform contact with each other, and the overload condition on some cam surfaces and cam followers will be eliminated and deformation will occur in both. Absent. Therefore, the torque transmission characteristic is maintained at the set value and sufficient vehicle driving performance is obtained.

Further, according to such a configuration, since each cam surface and each cam follower uniformly abut, the number of cam surfaces and cam followers can be increased more than the three sets of this embodiment.
As a result, the load applied to the pair of cam surfaces and the cam followers is reduced, the cam followers can be reduced, and the device can be downsized.

Furthermore, according to this structure, the first cam member 14
Since a slight amount of viscous fluid exists on the back side of each cam forming member 14c in each recess 14d, the fluid absorbs an impact even when a sudden load is applied, and durability is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a power transmission device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a cam portion of the device, and FIG.
FIG. 4 is a front view of a first cam member of the device, FIG. 4 is a partial plan development view of a cam portion of the device, and FIG. 5 is a schematic configuration diagram of a vehicle equipped with the device. DESCRIPTION OF SYMBOLS 10 ... Power transmission device, 10a ... Friction clutch, 10b ... Viscous resistance generating means, 10c ... Thrust converting means, 11 ... Outer case, 12 ... Inner case, 14 ... First cam Member, 15 ... Second cam member, 14b ... Cam body member, 14c ... Cam forming member, 14d ... Recess, 14f ... Communication hole, 16 ... Roller, 25, 26 ... Propeller shaft.

Claims (1)

(57) [Claims] 1. A frictional engagement force which is disposed between both inner and outer rotating members coaxially and relatively rotatably arranged and which is actuated by relative rotation of these both rotating members to couple the both rotating members so that torque can be transmitted. And a friction clutch for increasing / decreasing the friction engagement force according to the applied thrust force, a viscous resistance generating means for generating a viscous resistance force according to the relative rotation of the rotating members, the viscous resistance generating means and the friction clutch. A pair of cam members, which are disposed between the cam members and rotate relative to each other in response to the viscous resistance force generated by the viscous resistance force generating means, and are interposed between a plurality of cam surfaces of the both cam members, and separate the cam members from each other. A plurality of cam followers that act accordingly, one of the cam members on the side of the viscous resistance generating means is formed with a plurality of cams having a cam surface. And a cam body member having a plurality of recesses into which the cam forming member is fitted, and the recesses communicate with the viscous fluid chamber forming the viscous resistance force generating means at the bottom thereof, A power transmission device characterized in that a forming member is supported by being fitted in a recess of the cam body member in a liquid-tight manner and capable of advancing and retracting with respect to the other cam member.