JP2530706Y2 - Power transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power transmission device, and more particularly to a power transmission device, which is disposed between an input member and an output member that are coaxially and relatively rotatably positioned, and that transmits torque between these two members. To a power transmission device that performs

(Prior art) As a power transmission device of this type, Japanese Patent Publication No. 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. . Such a 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 two members are relatively rotated to drive the driven-side rotating member. The one used as a mechanism and the one provided between the driving side and the driven side rotating members, between the two driving side rotating members or between both the driven side rotating members, and the difference in rotation between these two members when the two members rotate relative to each other. It is roughly classified into a mechanism used as a differential 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) In the viscous coupling, which is the former viscous fluid coupling, the viscous fluid caused by the shear force of the viscous fluid existing between the inner and outer plates during relative rotation between the inner and outer plates. The friction torque enables the transmission of torque between the two plates, but the viscous friction torque is not so large and the rise 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 characteristics between the two plates become unstable. In particular, when the rotation difference between the two plates gradually increases and then gradually decreases, hysteresis occurs in the torque transmission characteristics. Therefore, when such a viscous coupling is used as a coupling mechanism of one power transmission path in a four-wheel drive vehicle, a differential limiting mechanism of each differential, etc., the transmission torque of one power transmission path, the differential limiting torque. Becomes unstable, affecting 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 covers the above-described problem of the viscous coupling.

On the other hand, in a vehicle, a driving force Tf in the traveling direction due to the engine driving force and a side force Sf acting on the centrifugal force of the vehicle are generated on the tires at the time of cornering, and these Tf
And the resultant force Ff of Sf works on the tire and the road surface. In a four-wheel drive vehicle, since the driving force Tf is distributed to four wheels, the driving force Tf of the front wheels is smaller than in a two-wheel drive vehicle, and the maximum side force Sf at the tire grip limit can be increased. For this reason, the four-wheel drive vehicle has a margin for the side force at the time of cornering, and can run stably. However, the running stability is very good even with disturbance such as when a side wind is applied by the side force. Therefore, it is preferable that the vehicle be driven by four wheels even when the vehicle is running straight at high speed. However, none of the power transmission devices described above can be brought into the four-wheel drive state unless differential rotation occurs. Japanese Patent Application Laid-Open No. 61-270526 discloses a power transmission device for increasing the transmission torque between both rotating members by utilizing centrifugal force.
There is a device disclosed in Japanese Patent Application Laid-Open Publication No. H11-157, but the power transmission device also employs a viscous coupling and cannot be put into a four-wheel drive state unless differential rotation occurs.

Therefore, the purpose of the present invention is to address these problems.

(Means for Solving the Problems) A power transmission device according to the present invention is disposed between an input member and an output member that are coaxially and relatively rotatably positioned and transmits power between these two members. A viscous resistance generating means for generating a viscous resistance in the viscous fluid chamber by operating by a relative rotation of a pair of rotary members respectively connected to the respective members, and connecting the two rotary members so as to be capable of transmitting torque. A friction clutch for generating a frictional engagement force and increasing or decreasing the frictional engagement force in accordance with the applied thrust, and a piston for partitioning a viscous fluid chamber of the viscous resistance force generating means. Pressure-intensifying means that operates by centrifugal force acting on the input member to increase the pressure in the viscous fluid chamber as the rotation of the input member increases,
A viscous resistance force generated in the viscous fluid chamber, comprising a pair of cam members disposed movably in the axial direction between the viscous resistance force generating means and the friction clutch; A thrust converting means for converting the applied pressure into a thrust for the friction clutch is provided.

(Operation / Effect of the Invention) In the power transmission device having such a configuration, when the relative rotation occurs between the input member and the output member, the viscous drag force corresponding to the differential rotation speed is generated in the viscous fluid chamber of the viscous drag force generating means. The generated viscous resistance force is converted into thrust for the friction clutch by the thrust conversion means. Further, the pressure in the viscous fluid chamber of the viscous resistance generating means is increased in proportion to the number of revolutions of the input member, and the pressure is converted into thrust for the friction clutch by the thrust converting means similarly to the viscous resistance. Therefore, the friction clutch is pressed by these two types of thrusts, and between the two rotating members, torque transmission proportional to the differential rotation speed and torque transmission proportional to the rotation speed of the input member are performed. Therefore, the power transmission device is particularly adopted as a power transmission device between an input member and an output member in one power transmission path of a four-wheel drive vehicle, and the driving force of the engine is distributed to both front and rear wheels even during straight traveling. Since the vehicle is driven by four wheels, the maximum side force at the tire grip limit is large, and the running stability is very good even with disturbance such as when a cross wind is applied.

Further, in the power transmission device, the torque transmission between the two rotating members is performed by the friction torque of the friction clutch, and the above-described torque transmission is not directly performed by the viscous resistance force generating means. Further, in the viscous fluid chamber forming the viscous drag force generating means, a viscous drag force is generated according to the differential rotation speed of the input member and the output member, and the pressure in the viscous fluid chamber is proportional to the rotation speed of the input member. Then, the pressure may be increased. Therefore,
Such a viscous resistance generating means does not need to generate a large viscous resistance, and therefore generates a small amount of heat. The power transmission device is less affected by a viscosity change caused by a temperature change of the viscous fluid, and the torque transmission characteristic is poor. It will not be stable.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 show a power transmission device 10 according to a first embodiment of the present invention. As shown in FIG. 4, the power transmission device 10 is provided on a rear-wheel-side power transmission system of a four-wheel drive vehicle of a rial type.

In this vehicle, a front wheel side is constantly driven and a rear wheel side is driven when necessary. A transaxle 22 mounted on one side of an engine 21 includes a transmission and a transfer, and a driving force from the engine 21 is transmitted by an 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, and when both the shafts 25, 26 can transmit power, the driving force is output to the axle shaft 28 via the rear differential 27. Then, the rear wheel 29 is driven.

The power transmission device 10 includes a friction clutch 10a, a viscous resistance generating means 10b, a thrust converting means 10c, and a pressure increasing means 10d in an annular working chamber including 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 includes a number of clutch plates 13a and clutch discs 13b. Each clutch plate 13a has its outer spline portion fitted to the inner spline portion 11a of the outer case 11 and integrated with the same case 11. Each clutch disc 13b is rotatably and axially movable, and each clutch disc 13b has its inner spline part fitted to the outer spline part 12a of the inner case
Are mounted so as to be integrally rotatable and movable in the axial direction.

The viscous resistance generating means 10b is integrally formed on a viscous fluid chamber R formed by a first cam member 14 constituting a thrust converting means 10c described later and a first piston 15 constituting a pressure increasing means 10d, and an outer periphery of the inner case 12. First fin rotatably mounted
16 and a second fin 14a provided on the first cam member 14.
It consists of. The first fin 16 includes a large number of concentric fin portions 16a, and each fin portion 16a protrudes coaxially toward the second fin 14a by a predetermined length. The second fins 14a are integrally formed on the body 14b of the first cam member 14, a number of fins 14a ₁ is formed concentrically and coaxially projecting a predetermined length into the fluid chamber R. 1st cam member
14 is mounted to both cases 11 and 12 so as to be rotatable in a liquid-tight manner and slidable in the axial direction, and each fin portion 14a ₁ has a predetermined minute distance between each fin portion 16a of the first fin 16. They are fitted with a gap and overlap each other for a predetermined length. In addition,
The fluid chamber R is filled with a predetermined amount of highly viscous fluid such as silicone oil and air.

The thrust converting means 10c includes a first cam member 14, a second cam member 17, and a plurality of rollers 18a serving as cam followers. In the first cam member 14, a cam groove 14c is formed in a portion of the body 14b opposite to the second fin 14a as shown in FIG. The second cam member 17 is provided between the first cam member 14 and the leftmost clutch plate 13a of the friction clutch 10a.
Is mounted so as to be integrally rotatable on the inner periphery of the. The second
In the cam member 17, a cam groove 17a having the same shape as the cam groove 14c is formed integrally with the cam groove 14c of the first cam member 14. Each of the cam grooves 14c and 17a has a valley having a cam apex angle θ as shown in FIGS. 3 (a) to 3 (c), and a roller 18a is interposed between the valleys facing each other.

The pressure increasing means 10d functions to increase the pressure in the viscous fluid chamber R, and the first piston 1
5, a plurality of balls 18b, which are weights, and a second piston 19
It consists of. The first piston 15 has an annular shape and is attached to both cases 11 and 12 so as to be liquid-tight and movably in the axial direction. The first piston 15 is integrally rotatable with the outer case 11 via a ball 18d and is connected to the inner case 12. Is rotatable. A plurality of tapered first recesses 15a are formed in the first piston 15 on the side opposite to the fluid chamber R,
A plurality of second recesses 15b are formed in the base of the piston 15 and open to the inner peripheral side of the first recess 15a. Ball 1
8b is accommodated in the space formed by the first recess 15a and the outer case 11, abuts on the tapered surface 15c of the first recess 15a, and fits into the guide groove 11b provided on the bottom of the outer case 11. doing. Thus, the ball 18b connects the outer case 11 and the first piston 15 so as to be integrally rotatable. Second
The piston 19 is fitted in the second recess 15b of the first piston 15 in a liquid-tight and slidable manner in the radial direction.
It faces 15a and is in contact with ball 18b.

In the power transmission device 10 having such a configuration, when the first propeller shaft 25 rotates, torque is transmitted between the two shafts 25 and 26 regardless of the presence or absence of relative rotation between the shafts 25 and 26. That is, when relative rotation occurs between these two shafts 25, 26, the outer case 11 and both cam members 17, 14 integral with the first propeller shaft 25, the inner case 12 integral with the second propeller shaft 26, and the first fin 16
Relative rotation occurs between the first fin 16 and the second fin 14.
A viscous shear torque T expressed by the following equation is generated during a.

K: constant, μ: viscosity of viscous fluid, N: differential rotation speed, l: length of each fin facing each other, h: gap between facing surfaces of each fin, r
i: Each radius of the viscous shearing force generating portion This viscous shearing torque T acts as a resistance for restricting the differential rotation of the first cam member 14, and this resistance F is
If the arrangement radius of 18a 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.
17 and rollers 18a are shown in FIGS. 3 (a) to 3 (b),
The operation is performed as shown in (c), and the thrust S is given by S = Ftan θ / 2, where θ is the cam apex angle. As a result, the friction clutch 10
In a, the clutch plate 13a and the clutch disc 13
b and friction engagement according to the differential rotation speed.
Torque transmission between the two shafts 25, 26 is performed.

On the other hand, regardless of the relative rotation between the two shafts 25 and 26, when the first propeller shaft 25 rotates,
Outer case 11, 1st piston 15, ball 18 with 25
b and the second piston 19 rotate, and at this time, a centrifugal force acts on the ball 18b and the second piston 19. Therefore, the ball 18b moves radially outward to slide the first piston 15 toward the fluid chamber R, and the second piston 19 moves radially outward to move radially outward of the ball 18b. Assist in moving to. As a result, the pressure in the fluid chamber R is increased in proportion to the rotation speed of the first propeller shaft 25, and the cam members 14, 17 are pressed by the pressure, and the friction clutch 10a is pressed. Therefore, a torque transmission proportional to the rotation speed of the first propeller shaft 25, that is, the vehicle speed is added between the two shafts 25 and 26. The sliding of the first piston 15 toward the fluid chamber R compresses the air in the fluid chamber R and increases the filling rate of the viscous fluid. Therefore, the viscous shear torque T generated in the fluid chamber R when the shafts 25 and 26 rotate relative to each other increases in proportion to the filling rate as shown in the graph of FIG. Increase torque transmission at the time.

FIG. 6 shows the torque transmission characteristics depending on the presence or absence of the pressure increasing means 10d. Graph (I) shows the case where the pressure increasing means 10d is provided, and graph (II) shows the case where the pressure increasing means 10d is not provided. It is. When the pressure increasing means 10d is provided, even if the differential rotation speed is zero, torque transmission of ΔT is performed, and the rate of increase of the transmission torque with respect to the differential rotation speed is large. Also,
The transmission torque ΔT increases and decreases in proportion to the vehicle speed. In the power transmission device 10, heat generation of the viscous fluid of the viscous resistance force generating means 10b is small, and a change in viscosity of the viscous fluid is small, so that torque transmission characteristics do not become unstable.

FIG. 7 shows a power transmission device 30 according to a second embodiment of the present invention.
The power transmission device 30 includes a friction clutch, a viscous resistance generating means 30b, a thrust converting means 30c and a pressure increasing means 30d between an outer case 31 and an inner case 32. Of these, the structure is the same as that of the power transmission device 10 of the first embodiment except for the pressure increasing means 30d.
30d will be described in detail.

As shown in FIGS. 7 and 8, the pressure increasing means 30d includes a plurality of cylinders 31a provided in the outer case 31, a compression spring 39a interposed in the cylinder 31a, and a cylinder
It is constituted by a piston 39b fitted in a liquid-tight and slidable manner in 31a. Each cylinder 31a is formed at equal intervals in the circumferential direction, extends in the radial direction, and opens at the outer periphery. The outer end opening of the cylinder 31a is sealed by a plug 39c, and a variable pressure chamber r communicating with the outer peripheral side of the fluid chamber R is formed between the plug 39c and the piston 39b.

In the pressure increasing means 30d having such a configuration, when the outer case 31 is rotated by the rotation of the first propeller shaft 25, the piston 39b slides outward due to the action of the centrifugal force and the variable pressure chamber r
The pressure in the fluid chamber R is increased. Therefore, the pressure increasing means 30d has the same operation and effect as the pressure increasing means 10d in the first embodiment, has a simple structure, and the pressure in the fluid chamber R and the pressure of the same pressure by the set load of the compression spring 39a. The pressure increase rate can be easily changed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a power transmission device according to a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a main part of the power transmission device, and FIGS.
(B) is a partially developed view of a cam portion in the device, (c) is an enlarged view of a part of FIG. (B), and FIG. 4 is a schematic configuration diagram of a vehicle equipped with the device, and FIG. FIG. 6 is a graph showing the relationship between the viscous shearing torque and the filling rate of the viscous fluid, FIG. 6 is a graph showing the relationship between the transmission torque and the differential rotation speed, and FIG. 7 is a main part of the power transmission device according to the second embodiment. FIG. 8 is an enlarged sectional view taken along the line VIII-VIII of FIG. Explanation of reference numerals 10, 30 ... power transmission device, 10a ... friction clutch, 10b,
30b ... viscous resistance generating means, 10c, 30c ... thrust converting means, 10d, 30d ... pressure increasing means, 11, 31 ... outer case,
12, 32 ... inner case, 14 ... first cam member, 15
... 1st piston, 16 ... 1st fin, 17 ... 2nd cam member, 18a ... roller, 18b ... ball (weight), 19 ...
... second piston, 39a ... compression spring, 39b ... piston, R ... fluid chamber, r ... variable pressure chamber, 25, 26 ... propeller shaft.

Claims (1)

(57) [Scope of request for utility model registration] 1. A power transmission device disposed between an input member and an output member coaxially and relatively rotatable to transmit power between these members, and a pair of power transmission devices connected to the respective members. A viscous resistance generating means that operates by the relative rotation of the rotating members to generate a viscous resistance in the viscous fluid chamber; and a thrust applied while generating a frictional engagement force for connecting the two rotating members so as to transmit torque. A friction clutch for increasing or decreasing the frictional engagement force in response thereto, and a piston for partitioning a viscous fluid chamber of the viscous resistance force generating means, the piston being operated by a centrifugal force acting on the piston when the input member rotates, and A pressure increasing means for increasing the pressure in the viscous fluid chamber as the rotation increases, and a pair of motors movably disposed in the axial direction between the viscous resistance generating means and the friction clutch. A power transmission device comprising a member and a thrust converting means for converting a viscous resistance generated in the viscous fluid chamber and a pressure increased in the viscous fluid chamber into a thrust for the friction clutch. .