JP2519718Y2 - Power transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a power transmission device, and in particular, it is disposed between both inner and outer rotating members that are coaxially and relatively rotatable, and torque transmission between these both rotating members. The present invention relates to a power transmission device.

(Prior Art) As a power transmission device of this type, a special table Sho 61-501583
There is a power transmission device including a viscous fluid coupling (viscus coupling) disclosed in Japanese Patent Laid-Open No. 63-287631, a viscous coupling disclosed in Japanese Patent Laid-Open No. 63-287631, a friction clutch, and a cam means for connecting the two. . 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. They are roughly classified into those used as a limited differential mechanism. 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, in order to generate a large viscous friction torque, the shearing force that constitutes the viscous coupling becomes extremely large, the amount of heat generation increases, and the viscosity of the viscous fluid becomes high, resulting in a significant decrease in its viscosity. 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 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 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 both inner and outer rotating members that are coaxially and relatively rotatably positioned, and is operated by relative rotation of the both rotating members to generate viscous resistance force generating means, and A friction clutch that generates a frictional engagement force that connects both rotating members so that torque can be transmitted, and that increases or decreases the frictional engagement force according to the applied thrust, and the viscous resistance force generated by the viscous resistance force generation means A thrust converting means for converting the thrust to the clutch; the thrust converting means includes a pair of cam members that rotate relative to each other in accordance with the viscous resistance force generated by the viscous resistance generating means; and cam surfaces of both cam members. A viscous resistance force generation means, comprising a cam follower interposed between the cam members and acting to separate the cam members from each other.
A viscous fluid chamber defined by one cam member of the thrust converting means in the outer rotating member, and a large number of fin portions that are integrally provided on the cam member and project into the fluid chamber are concentrically provided. A first fin and a large number of fin portions that are integrally rotatably provided in one of the rotating members in the fluid chamber, project into the fluid chamber, and are concentrically and alternately fitted with the fin portions of the first fin. And a second fin having

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, the shear rate increases and the viscosity of the viscous fluid decreases as the differential rotation speed increases, so the increase rate of the transmission torque decreases as the differential rotation speed increases.
FIG. 13 shows the relationship between the transmission torque and the differential rotation speed. Graph (I) shows the transmission torque of the power transmission device, and graph (II) shows the transmission torque of the known latter power transmission device. Relationships are shown. Since the power transmission device does not use the viscous coupling, the influence of the decrease in the viscosity of the viscous fluid is small. Therefore, although the transmission torque increases from the coupling, the increase rate tends to gradually decrease. For this reason, the torque transmission characteristic gradually deviates from the lower limit of the tight corner braking phenomenon occurrence region (III), which is disadvantageous in the running performance of the vehicle.

Therefore, in the power transmission device according to the above-mentioned prior application, the object of the present invention is to further increase the transmission torque in accordance with the differential rotation so that the torque transmission characteristic is set to the lower limit of the tight corner braking phenomenon generation region. Is to improve the running performance of.

(Means for Solving the Problems) A power transmission device according to the present invention is disposed between inner and outer rotating members that are coaxially and relatively rotatably positioned, and operates by the relative rotation of both of these rotating members to generate a viscous resistance force. A viscous resistance force generating means, a friction clutch that generates a frictional engagement force that connects the rotating members so that torque can be transmitted, and a frictional clutch force that increases or decreases the frictional engagement force according to the applied thrust, and the viscous resistance force generation unit. Means for converting the viscous resistance force generated by the means into thrust force for the friction clutch, the thrust force conversion means having a pair of relative rotations according to the viscous resistance force generated by the viscous resistance force generation means. A power transmission device comprising a cam member and a cam follower interposed between the cam surfaces of the cam members and acting to separate the cam members from each other. A plurality of the viscous resistance generating means are provided in the outer rotating member by the one cam member of the thrust converting means and a viscous fluid chamber that is integrally provided in the cam member and projects into the fluid chamber. First fins having concentric fin portions and one of the rotating members provided in the fluid chamber so as to be integrally rotatable, projecting into the fluid chamber and concentrically alternating with the fin portions of the first fin. And a second fin having a large number of fins that fit into each other, the one cam member is slidably assembled, and a predetermined amount of viscous fluid and gas are sealed in the fluid chamber, The one cam member is configured to slide toward the fluid chamber side by relative rotation with the other cam member to increase the overlapping length of the fin portions of the both fins.

In the power transmission device, one cam member forming the thrust converting means may be configured to be spring-biased in a direction in which the fins are separated from each other.

(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 transmission proportional to the differential rotation speed is performed between the both rotary members. 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 limiting mechanism between the members and between the driven side rotating members.

In the power transmission device, however, one cam member gradually slides toward the fluid chamber due to the action of the cam follower in response to an increase in the differential rotation speed between the two rotary members, and the fin portions of both fins overlap. The length is increased and the filling rate of the viscous fluid in the fluid chamber is increased. For this reason,
The transmission torque increases due to the increase of both of them, and supplements the decrease of the transmission torque due to the decrease of the viscosity of the viscous fluid or exceeds the decrease of the transmission torque. As a result, in the power transmission device, the torque transmission characteristic can be brought close to the lower limit of the region where the tight corner braking phenomenon occurs, and the running performance of the vehicle can be improved.

Further, in the power transmission device, if one cam member is configured to be spring-biased in a direction in which the fins are separated from each other, sliding of the cam member toward the fluid chamber is suppressed by the biasing force. As shown in the solid line graph in FIG. 1, the overlapping length of each fin portion and the filling rate of the viscous fluid with respect to the differential rotation speed are compared with those in the case where the spring is not biased as shown in the one-dot chain line graph. Increase linearly. Therefore, the desired load (spring biasing force) on the cam member
By properly setting, as shown in the graph (V) of FIG. 13, the torque transmission characteristic is compared with the case where the spring is not biased as shown in the graph (IV), and the area where the tight corner braking phenomenon occurs (III ) Can be further approximated to the lower limit, and the running performance of the vehicle can be improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a power transmission device 10 according to an embodiment of the present invention. As shown in FIG. 10, the power transmission device 10 is arranged in a rear-wheel power transmission system path 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 includes a friction clutch 10a, a viscous resistance generating means 10b, and a thrust converting means 10c 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 constituting a thrust converting means 10c described later, a first fin 14a provided in the first cam member 14, and an outer circumference of the inner case 12 in the fluid chamber R. The second fin 15 is mounted so as to be integrally rotatable with its axial movement restricted. The first fin 14a is in the body 14b of the first cam member 14 be integrally formed, and a plurality of fin portions 14a ₁ formed concentrically projecting into the fluid chamber R. Further, the second fin 15 is provided with a large number of concentric fin portions 15a protruding toward the first cam member 14 side. 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 located between each fin portion 15a of the second fin 15. Are fitted to each other with a predetermined minute gap and are superposed on each other for a predetermined length. The fluid chamber R is filled with a predetermined amount of highly viscous fluid such as silicon oil and air.

The thrust converting means 10c is composed of a first cam member 14, a second cam member 16 and a plurality of rollers 17 which are cam followers. In the first cam member 14, three cam grooves 14c are formed at a portion of the body 14b opposite to the first fins 14a at equal intervals in the circumferential direction, as shown in FIG. Second cam member 16 is the first cam member
The outer case 11 is integrally rotatably mounted between the friction clutch 10a and the leftmost clutch plate 13a of the friction clutch 10a. In this second cam member 16,
The third portion is provided at a portion of the first cam member 14 facing the cam groove 14c.
As shown in the figure, a cam groove 16a having the same shape as the cam groove 14c is integrally formed. As shown in FIGS. 4 (a) to 4 (c), each of the cam grooves 14c and 16a has a valley portion having a cam top angle of θ, and rollers 17 are interposed between the valley portions facing each other. .

As shown in FIG. 5, the needle bearing 18 is provided between the bottom portion 11b of the outer case 11 and the first cam member 14.
a, a bearing ring 18b, and a wave washer spring 18c shown in FIG. 6 are interposed. As a result, the first cam member 14 is biased toward the second cam member 16 side by the spring 18c, and the set initial load is applied.

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 second cam member, which are integral with the first propeller shaft 25, are formed.
16 and the first cam member 14, and the second propeller shaft
Relative rotation occurs between the inner case 12 and the first fin 15 that are integral with the 26, and a viscous shear torque T represented by the following equation is generated between the fins 15 and 14a.

K: constant, μ: viscosity of viscous fluid, N: differential rotation speed, l: overlapping length of each fin, 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 17 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.
16 and roller 17 are shown in FIGS. 4 (a) to (b) and (c).
The thrust S is S when the cam apex angle is θ.
= Ftan θ / 2. 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.

Thus, in the power transmission device 10, the fluid chamber R
A predetermined amount of viscous fluid and air are enclosed therein, and the first cam member 14 is assembled so as to be slidable in the axial direction.
Therefore, during differential rotation of both cases 11 and 12, the first cam member 14 is gradually pushed toward the fluid chamber R side, compresses the air in the fluid chamber R to increase the filling rate of the viscous fluid, and 15, 14
The polymerization length of each fin portion 15a, 14a ₁ of a is increased. Thus, FIG. 11 shows the amount of increase in the overlapping length of each fin and the filling rate of the viscous fluid with respect to the differential rotation speed.
The value of this example is shown by the solid line graph. The viscous shear torque T generated by the viscous resistance force generating means 10b is proportional to the overlapping length of each fin portion as is clear from the above equation, and the filling rate of viscous fluid is proportional to the filling rate of viscous fluid as is clear from the graph of FIG. Since it is proportional, the decrease in the viscous shear torque due to the decrease in the viscosity of the viscous fluid is sufficiently compensated. In this case, in this embodiment, the first cam member 14 slides toward the fluid chamber R side against the spring 18c, so that the sliding is suppressed as compared with the case where the spring 18c is not interposed. The superposition length of each of the fin portions 14a ₁ and 15a and the filling rate of the viscous fluid are linear with respect to the differential rotation speed as shown in the solid line graph of FIG. The dashed-dotted line graph in the figure shows values when the spring 18c is not interposed.
Therefore, by appropriately setting the initial load on the first cam member 14, the torque transmission characteristic is brought closer to the lower limit of the tight corner braking phenomenon occurrence region (III) as shown in the graph (V) of FIG. Therefore, the running performance of the vehicle can be improved.

7 to 9 show three modified examples of the spring biasing means for the first cam member 14. In the first modification shown in FIG. 7, a plurality of compression coil springs 18d are used as spring members, and a bearing ring 18f having a plurality of columnar protrusions 18e is employed as a bearing ring. The protrusions 18e of the bearing ring 18f correspond to the cylindrical portions 14d of the first cam member 14, respectively.
The first cam member 1 fits loosely inside and is located on the outer periphery of each cylindrical portion 14d.
Each spring 18d is interposed between the bearing 4 and the bearing ring 18f.
The second modification shown in FIG. 8 is the needle bearing 18.
This is an example in which a and a spring 18c are arranged on the opposite side to the above-mentioned embodiment, and the third modified example shown in FIG. 9 has the needle bearing 18a, the spring 18d and the bearing ring 18f on the opposite side to the first modified example. This is an example of arrangement.

[Brief description of drawings]

1 is a sectional view of a power transmission device according to an embodiment of the present invention, FIG. 2 is a front view of a first cam member, and FIG.
A front view of the cam member, FIGS. 4 (a) and 4 (b) are partially developed views of the cam portion in the same apparatus, and FIG. 4 (c) is the same figure (b).
FIG. 5 is an enlarged cross-sectional view of a main part of the apparatus, FIG. 6 is a perspective view of a wave washer spring as an example of a spring member, and FIGS. 7 to 9 are urging means. Sectional view corresponding to FIG. 5 showing three modified examples,
FIG. 10 is a schematic configuration diagram of a vehicle equipped with the same device, and FIG. 11 is a graph showing the relationship between the overlapping length of the fin portion and the increasing amount of the viscous fluid filling rate with respect to the differential rotation speed, and FIG. FIG. 13 is a graph showing the relationship between the filling factor and the torque multiplication factor, and FIG. 13 is a graph showing the relationship between the transmission torque and the differential rotation speed. 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, 14a …… First fin, 15 …… Second fin, 16 …… Second cam member, 17 …… Roller, 18a …… Needle bearing, 18b, 18f …… Race ring, 18c, 18d …… Spring,
25, 26 …… Propeller shaft.

Claims (2)

(57) [Scope of utility model registration request] 1. A viscous drag force generating means which is disposed between inner and outer rotary members coaxially and relatively rotatably positioned to operate by relative rotation of these rotary members to generate a viscous drag force; 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, and a viscous resistance force generated by the viscous resistance force generation means to the friction clutch. A thrust converting means for converting into a thrust, the thrust converting means is provided between a pair of cam members that relatively rotate in accordance with the viscous resistance force generated by the viscous resistance generating means, and between the cam surfaces of these cam members. A viscous resistance force generating means, comprising a cam follower that is interposed and acts to separate both cam members from each other.
A viscous fluid chamber defined by one cam member of the thrust converting means in the outer rotating member, and a large number of fin portions that are integrally provided on the cam member and project into the fluid chamber are concentrically provided. A first fin and a large number of fin portions that are integrally rotatably provided in one of the rotating members in the fluid chamber, project into the fluid chamber, and are concentrically and alternately fitted with the fin portions of the first fin. And a second fin having a second fin, the one cam member is slidably assembled, and a predetermined amount of viscous fluid and gas are sealed in the fluid chamber, and the one cam member is A power transmission device configured to slide toward the fluid chamber by relative rotation with a cam member to increase a superposed length of fin portions of the both fins. 2. The power transmission according to claim 1, wherein one cam member constituting the thrust converting means is spring-biased in a direction in which the fins are separated from each other. apparatus.