JPH0596567U - Viscous coupling - Google Patents

Abstract

(57) [Abstract] [Purpose] The plates are designed to prevent the plates from biting into or being damaged by the engaging members for non-rotatably engaging the plate sets and the transmitting members, and to provide a one-way clutch function. Provide a compact viscous coupling with. [Structure] Each of the spline teeth 56 formed on the outer periphery of each outer plate 55 has an engaging surface 55a and an engaging surface 55b having different inclination angles α and β with respect to a center line R extending in the plate radial direction. have. The outer plate 55 imparts a plate locking force acting in the circumferential direction of rotation to the housing 33, and the inclination angle α of one engagement surface 55a.
Is smaller than the inclination angle β of the other engagement surface 55b. In order to non-rotatably engage the outer plate 55 with the housing 33, an elastic spline portion 63, which is made of an elastic material such as rubber having appropriate rigidity and is elastically deformable outward in the radial direction, is provided inside the housing 33. It is arranged on the peripheral surface.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a viscous coupling that transmits torque via a viscous fluid.

[0002]

[Prior Art]

 Generally, a viscous coupling used as a differential device in a power transmission system of a vehicle includes a first and a second transmission member that are relatively rotatably arranged, two plate sets, and an operation in which a viscous fluid is sealed. A second plate assembly, the first plate assembly being slidable in the rotation axis direction of the first transmission member and rotatably arranged together with the first transmission member. Is slidable in the direction of the rotation axis of the second transmission member and is rotatably arranged together with the second transmission member, and each plate of the first and second plate sets is provided in the working chamber. Are arranged alternately.

Further, in such a viscous coupling, a spacer ring is arranged between the plates of one plate set so that the plates of the first and second plate sets have a gap therebetween. Is configured. Therefore, each plate of the plate group having no spacer ring is movable in the direction of the rotation axis by the gap.

Therefore, when the first and second transmission members rotate relative to each other and a differential torque is generated between the first and second plate sets, each plate of the plate set in which the spacer ring is not arranged is arranged. Moves in the direction of the rotation axis due to the pressure difference generated between the plate sets. In particular, if the viscous coupling operates for a long time with relative rotation exceeding a certain level, the internal temperature rises, the silicone oil expands, and the air enclosed with the silicone oil is compressed. It becomes impossible to absorb the pressure difference generated on both sides of the plate, and there is a so-called "hump phenomenon" in which the plate of one plate group that can move in the axial direction starts to move and comes into direct contact with the plate of the other plate group. Occurs. At this time, the torque transmission due to the viscosity of the silicone oil between the plate sets is switched to the torque transmission due to the frictional contact of the plates between the plate sets, so that the transmitted torque rapidly increases.

Therefore, such a viscous coupling is used as a power transmission device in a power transmission system between front and rear axles of a four-wheel drive vehicle (4WD vehicle) or in a power transmission system between left and right wheels of a rear wheel drive vehicle. When used as a differential limiting device, by effectively utilizing the hump state, even if one wheel runs idle, the driving force can be transmitted to the other wheel with high efficiency. It is possible to improve running performance on rough roads.

Further, in such a viscous coupling, a transmission torque is generated due to a difference in the number of rotations due to the relative movement of the first and second plate sets regardless of the rotation direction. Here, for example, when the vehicle is braked and the front wheels are locked, the rear wheels rotate at a higher speed than the front wheels, and in this state, a rotational speed difference occurs due to relative movement between the first and second plate sets. Therefore, the viscous coupling causes a driving torque to rotate the front wheel and the rear wheel at the same rotation speed, which hinders the operation of the anti-skid brake system (ABS) and induces the lock of the rear wheel. As a result, the stability of the vehicle is impaired.

Therefore, conventionally, in order to prevent such a problem, for example, each plate of the first and second plate sets is associated with the rotation speed difference and the rotation direction of the first and second transmission members. The torque transmission characteristics can be changed by varying the interval and the pressure of the viscous fluid in the working chamber, and the tightening force of the switching clutch such as the multi-plate clutch arranged in series with the viscous coupling can be adjusted to make It is structured so that it can be changed.

[0008]

[Problems to be solved by the device]

 However, as means for engaging each plate set and each transmission member in the conventional viscous coupling as described above, a spline groove formed on the peripheral surface of each transmission member and a peripheral edge of each plate are formed. Spline engagement with spline teeth is used.If excessive transmission torque is generated between each plate group due to the above hump, excessive stress acts on each spline engagement part. May bite into or damage the spline groove of the transmission member.

Further, as described above, in order to achieve the matching with the ABS, the torque transmission characteristics may be changed by changing the plate spacing of the first and second plate sets in the viscous coupling and the pressure of the viscous fluid in the working chamber. However, the effect was small and the response was not good. Further, when the torque transmission characteristics are changed by the switching clutch as described above, the switching clutch, which is a supplementary component, must be separately provided, so that the entire apparatus is large and heavy, and the structure becomes complicated.

Therefore, an object of the present invention is to solve the above problem, and the plate bites into the transmission member at the engaging portion for non-rotatably engaging each plate set and each transmission member. It also provides a compact viscous coupling with a one-way clutch function while preventing damage.

[0011]

[Means for Solving the Problems]

 The first object of the present invention is to rotatably engage the first and second transmission members, the working chamber in which the viscous fluid is sealed, and the first transmission member non-rotatably engaged. A viscous coupling having a first plate set and a second plate set alternating with the first plate set in the working chamber and non-rotatably engaged with a second transmission member. The engaging portion of at least one of the first and second transmission members supports the plate locking force acting in the circumferential direction to non-rotatably lock the plate set to the transmission member. It has an engaging member which is elastically deformable in the radial direction by the component force of the plate locking force in the radial direction, and when a transmission torque more than a predetermined value acts between the first and second plate groups, The engaging member is elastically deformed in the radial direction and is not rotated through the engaging member. It is achieved by the viscous coupling, characterized in that manner are configured to release the plate pairs in the circumferential direction of the engagement being engaged.

A second object of the present invention is to provide the engaging members so as to face each other in the forward and reverse rotation directions in order to receive a component force in the radial direction of the plate locking force acting in the rotation circumferential direction. This is achieved by the above-mentioned viscous coupling formed so that each engagement surface formed has different inclination angles with respect to the center line extending in the radial direction.

[0013]

[Action]

 With the above structure, when an excessive circumferential plate locking force acts on the engaging member, the engaging member elastically deforms in the radial direction due to the radial component force of the plate locking force. Since the circumferential engagement of the plate set that is non-rotatably engaged with the transmission member via the coupling member is released, excessive stress is applied to the engaging portion between the transmission member and the plate set. Can be prevented. Further, by changing the inclination angle of each engaging surface formed on the engaging member for each of the opposite rotating directions, the circumference required for elastically deforming the engaging member in the radial direction by the forward and reverse rotating directions. The magnitude of the plate locking force in the direction can be changed.

[0014]

【Example】

 Hereinafter, a first embodiment of the present invention will be described in detail with reference to the attached FIGS. 1 to 3 and 8. First, the configuration of the power system of the 4WD vehicle using the first embodiment of the present invention will be described with reference to FIG. This power system includes an engine 1, a transmission 3, a front differential 5 (a front wheel differential device), left and right front wheels 7, 9, a transfer 11, a viscous coupling 13 of this embodiment, a propeller shaft 15, a rear differential 17 (rear differential). (Wheel side differential device), left and right rear wheels 19, 21 and the like.

Next, the configuration of the viscous coupling 13 will be described with reference to FIG. The housing 33 (second transmission member) and the hub 35 (first transmission member) are arranged so as to be rotatable relative to each other. The hub 35 is connected to the output shaft of the transfer 11 by an integral spline 37, and is rotationally driven by the driving force from the engine 1. The housing 33 is flange-connected to the connecting shaft 27 on the propeller shaft 15 side by a bolt screwed into the bolt hole 39, and a bearing 29 is arranged between the housing 33 and the output shaft of the transfer 11. It

A working chamber 45 is formed between the housing 33 and the hub 35, and the working chamber 45 is filled with high-viscosity silicone oil (viscous fluid). Further, a bearing 41 is arranged between the housing 33 and the hub 35, and X-rings 47 and 49 (seal having an X-shaped cross section) and backup rings 51 and 53 are arranged to keep the working chamber 45. It is kept liquid tight.

Further, outer plates 55 and inner plates 57 are alternately arranged in the working chamber 45. The outer plate 55 (second plate) is spline-coupled to the elastic spline portion 63, which is an engaging member provided on the inner periphery of the housing 33, so as to be axially movable. The inner plate 57 (first plate) is spline-coupled to a spline 62 formed on the outer periphery of the hub 35 so as to be movable in the axial direction, and a spacer ring 61 is arranged between the inner plates 57. Has been done.

As shown in FIGS. 2 and 3, the outer plate 55 has saw tooth-shaped spline teeth 56 formed on the outer periphery thereof, and each spline tooth 56 has a center line R extending in the plate radial direction. On the other hand, it has an engagement surface 55a and an engagement surface 55b which are formed so as to have different inclination angles α and β. Then, when the outer plate 55 rotates in the direction of arrow X in the figure, the inclination angle α of the one engagement surface 55a that applies the plate locking force acting in the circumferential direction of rotation to the housing 33 is It is configured to be smaller than the inclination angle β of the other engagement surface 55b.

Further, the elastic spline portion 63 is made of an elastic body such as rubber having appropriate rigidity, and has an engaging surface 63 a and an engaging surface 63 b corresponding to the shape of the spline teeth 56 of the outer plate 55. Is formed on the inner peripheral surface of the housing 33 for non-rotatably engaging the outer plate 55 with the housing 33.

Therefore, the rotation of the hub 35, which is rotationally driven by the driving force from the engine 1, is transmitted from the inner plate 57 to the outer plate 55 by the shear resistance of the silicone oil, and the outer plate 55 is shown with respect to the housing 33. When the vehicle relatively rotates in the direction of the arrow X, the driving force is transmitted to the rear wheels 19 and 21. At this time, the transmission torque of the viscous coupling 13 is based on the torque transmission characteristics of the viscous coupling, the transmission torque is larger as the differential rotation speed difference between the inner plate 57 and the outer plate 55 is larger, and the differential rotation speed is larger. The smaller the number difference, the smaller the transmitted torque.

When the viscous coupling 13 is operated for a long time with a relative rotation of a certain amount or more, the outer plate 55 moves in the rotation axis direction due to the pressure difference between the outer plate 55 and the inner plate 57, and the inner plate 57 moves. Since a hump phenomenon of directly contacting with each other occurs, the torque transmission between the inner plate 57 and the outer plate 55 is switched from the torque transmission due to the viscosity of the silicon oil to the torque transmission due to the frictional contact of each plate, and the transmission torque rapidly increases.

By the way, since the engaging surface 55a has a tilt angle α with respect to the center line R extending in the plate radial direction, the engaging surface 55a is radially outward with respect to the engaging surface 63a. Gives the component force of. Then, when the transmission torque increases, the plate locking force that the engagement surface 55a of the outer plate 55 acts on the engagement surface 63a of the elastic spline portion 63 in the rotation circumferential direction also increases, and the radius is increased. Since the component force outward in the direction becomes large, the spline teeth 56 pass over so as to crush the spline teeth 64 of the elastic spline portion 63 that is elastically deformable, and the outer plate 55 rotates relative to the housing 33. ..

Therefore, when a predetermined or more transmitted torque is generated between the inner plate 57 and the outer plate 55, the spline engagement of the outer plate 55 with respect to the housing 33 in the circumferential direction is released. It is possible to prevent excessive stress from acting on 56 and 64, and the spline teeth 56 of the outer plate 55 do not bite into or damage the spline teeth 64 of the housing 33.

When the outer plate 55 rotates relative to the housing 33 in a direction opposite to the arrow X direction in the figure, the engaging surface 63 b of the elastic spline portion 63 and the engaging surface 55 b of the outer plate 55 are A plate locking force that acts in the circumferential direction of rotation acts between them, but the engagement surface 55b has an inclination angle β larger than the inclination angle α with respect to the center line R extending in the plate radial direction. Therefore, the radial outward component force applied by the engagement surface 55b to the engagement surface 63b is applied to the engagement surface 63a by the engagement surface 55a at the same relative rotational speed difference. Is larger than the component force in the radial direction.

Therefore, when the outer plate 55 relatively rotates with respect to the housing 33 in the direction opposite to the arrow X direction in the drawing, the spline teeth 56 are elastically deformable. The differential rotation speed at which the outer plate 55 starts to rotate relative to the housing 33 becomes low as the tooth 64 is crushed over.

Therefore, a so-called one-way clutch is formed between the elastic spline portion 63 and the outer plate 55 by appropriately setting the inclination angle α of the engaging surface 55 a and the inclination angle β of the engaging surface 55 b. It Next, the function of the viscous coupling 13 will be described according to the power performance of the vehicle shown in FIG. The viscous coupling 13 is arranged so that the hub 35 rotates in the direction of the arrow X in the drawing when the vehicle travels forward and the driving force can be transmitted.

The rotation of the engine 1 is transmitted to the front differential 5 via the transmission 3 and is split and output to the left and right front wheels 7 and 9, and is also transmitted to the rear differential 17 via the transfer 11, the viscous coupling 13, and the propeller shaft 15. And output to the left and right rear wheels 19 and 21 separately. When the rotational speed difference due to the relative movement between the front and rear axles is small, such as when driving on a good road, the rotational speed difference is absorbed by the viscous coupling 13 and almost no driving force is transmitted to the rear wheels 19, 21. .. Therefore, the vehicle is in the front-wheel drive 2WD state, the fuel efficiency is improved, and the tit corner braking phenomenon does not occur even when the vehicle turns into a garage or makes a slow turn such as a U-turn.

When the front wheels 7 and 9 run idle on a bad road or the like and a rotation speed difference occurs between the front and rear axles, and the rotation speed difference between the rotation of the housing 33 and the rotation of the hub 35 is large, Due to the torque transmission characteristics of the viscous coupling 13, the driving force is split and output from the transfer 11, the viscous coupling 13, and the propeller shaft 15 to the left and right rear wheels 19 and 21 via the rear differential 17, and the vehicle enters the 4WD state. Therefore, high running performance is obtained.

Further, when the front wheels 7 and 9 are stuck in mud or the like and the vehicle is stacked, the rotation speed difference between the front and rear axles increases and the relative rotation continuously occurs for a long time. The viscous coupling 13 causes a hump state. For this reason, the transmission torque by the viscous coupling 13 increases rapidly, and the transmission efficiency of the driving force to the rear wheels 19, 21 increases, so that a high driving force is generated in the rear wheels 19, 21 and the driving force from the stack is increased. You can escape. At this time, according to the present invention, when a transmission torque greater than a predetermined value is generated between the inner plate 57 and the outer plate 55, the circumferential spline engagement of the outer plate 55 with the housing 33 is released. The torque limit is prevented from damaging the engaging portion between the outer plate 55 and the housing 33, and the durability of the viscous coupling 13 is not reduced.

Further, in the viscous coupling 13 of the above embodiment, the outer plate 55 is engaged with the housing 33 with a one-way clutch function. Therefore, a rotation speed difference occurs between the rotation of the housing 33 and the rotation of the hub 35 in a direction in which the front wheels are locked and the rear wheels rotate at a higher speed than the front wheels, for example, during braking during high-speed traveling. In this case, since the outer plate 55 rotates relative to the housing 33 in the direction opposite to the arrow X direction in the figure, the driving force transmission between the front wheel side and the rear wheel side is irrelevant regardless of the rotational speed difference. It is automatically shut off and the rear wheel side remains disconnected. Therefore, the interference of the braking force between the front and rear wheels during braking is prevented, the front wheel lock does not induce the rear wheel lock, and the normal function of the anti-skid brake system (ABS) is protected.

Next, the structure of the viscous coupling 71 according to the second embodiment of the present invention will be described with reference to FIGS. 4 to 7. The viscous coupling 71 of the second embodiment is arranged at the same position as the viscous coupling 13 of the first embodiment in the vehicle shown in FIG. 8, for example. It is the same. A working chamber 45 is formed between the housing 73 and the hub 75 which are arranged so as to be rotatable relative to each other, and the working chamber 45 is filled with high-viscosity silicone oil (viscous fluid). An elastic engaging member 76, which is an engaging member having a uniform thickness, is provided on the inner circumference of the housing 73. The elastic engaging member 76 is made of rubber or the like having an appropriate rigidity. It consists of an elastic body.

Further, in the working chamber 45, the outer plates 78 and the inner plates 79 are alternately arranged, and the spacing plates 82 are arranged outside the inner plates 79 located at both ends in the rotation axis direction. Has been done. The inner plate 79 is spline-coupled with the outer periphery of the hub 75 by a spline engaging means 83 so as to be axially movable, and a spacer ring 81 is arranged between the inner plates 79.

As shown in FIGS. 5 and 6, a cutout portion 84 having an inclined surface 88 whose distance from the inner peripheral edge decreases along the circumferential direction is continuously formed on the outer periphery of each outer plate 78. ing. A roller 77, which is a meshing element penetrating the notch 84 of each outer plate 78 in the axial direction, is arranged in the opening formed by the notch 84 and the inner peripheral surface of the elastic engaging member 76. In addition, holding portions 85, which are notches for holding the rollers 77 at equal intervals, are formed on the outer periphery of the spacing holding plate 82, and a so-called one-way clutch 80 is configured. The roller 77 has a diameter larger than the gap between the outermost peripheral edge of the outer plate 78 and the inner peripheral surface of the elastic engaging member 76.

That is, as shown in FIG. 5, when the housing 73 and the outer plate 78 are relatively rotated in the directions of the arrow Y and the arrow X, respectively, the roller 77 rolls and meshes with the narrow portion 86 of the cutout portion 84. The housing 73 and the outer plate 78 are moved together. Further, as shown in FIG. 6, when the housing 73 and the outer plate 78 respectively rotate relative to each other in the directions of the arrow X and the arrow Y, the roller 77 rolls to a wide portion 87 of the cutout portion 84 and meshes with each other. The housing 73 and the outer plate 78 are disengaged and released.

At this time, since the rollers 77 are always kept at equal intervals by the spacing plate 82, all the rollers 77 roll in the same direction at the same time. Therefore, for each outer plate 78, the surface pressure acting on the inclined surface 88 of each notch 84 becomes uniform, and only the surface pressure of the inclined surface 88 of each notch 84 does not increase. .. Therefore, although the outer plate 78 is formed of a very thin metal plate, the inclined surface 88 of the cutout portion 84 can transmit torque without being deformed or damaged.

Therefore, the rotation of the hub 75, which is rotationally driven by the driving force from the engine 1, is transmitted from the inner plate 79 to the outer plate 78 by the shear resistance of the silicone oil, and the outer plate 78 is one-way with respect to the housing 73. When the clutch 80 relatively rotates in the torque transmission direction, the driving force is transmitted to the rear wheels 19 and 21. When the housing 73 rotates relative to the outer plate 78 in the direction opposite to the torque transmission direction of the one-way clutch 80, the driving force is cut off and the torque is not transmitted to the rear wheel side.

When the driving torque is transmitted to the rear wheel side, it is accompanied by relative movement between the outer plate 78 and the inner plate 79 (between the front and rear axles) based on the torque transmission characteristic of the viscous coupling. The larger the rotational speed difference, the larger the transmitted torque, and the smaller the rotational speed difference, the smaller the transmitted torque. Further, when the viscous coupling 71 is operated for a long time with a relative rotation of a certain amount or more, the outer plate 78 moves in the rotation axis direction due to the pressure difference between the outer plate 78 and the inner plate 79 and directly contacts the inner plate 79. Since a phenomenon occurs, the torque transmission between the inner plate 79 and the outer plate 78 is switched from the torque transmission due to the viscosity of the silicon oil to the torque transmission due to the frictional contact of each plate, and the transmission torque rapidly increases.

By the way, the roller 77, which is caught between the inner peripheral surface of the elastic engagement member 76 and the inclined surface 88 of the cutout portion 84, exerts a component force outward in the radial direction by the inclined surface 88. Has been granted. Then, when the transmission torque increases, the biting force between the elastic engagement member 76 and the cutout portion 84 via the roller 77 also increases, and the component force outward in the radial direction increases, so that FIG. 7 shows. In this way, the roller 77 is retracted radially outward while recessing the elastically deformable elastic engaging member 76, and the outer plate 78 rotates relative to the housing 73.

Therefore, when a torque greater than a predetermined value is transmitted between the inner plate 79 and the outer plate 78, the outer plate 78 is disengaged from the housing 73 in the circumferential direction, so that the roller 77 tilts. It does not bite into the surface 88 to perform a normal function or damage the notch 84. Further, the function of the viscous coupling 71 itself and the function according to the power performance of the vehicle are almost the same as those of the viscous coupling 13 of the first embodiment.

The engaging means having the one-way clutch function as described above may be configured based on another one-way clutch type such as a sprag type or a ratchet type. Further, in each of the above embodiments, the elastically deformable engaging member according to the present invention is provided between the outer plate and the housing, but it may be provided between the inner plate and the hub.

[0041]

[Effect of the device]

 According to the viscous coupling of the present invention, when an excessive plate locking force in the circumferential direction acts on the elastically deformable engaging member, the radial force of the plate locking force causes the engaging member to move radially. Is elastically deformed in the direction, and the circumferential engagement of the plate assembly that is non-rotatably engaged with the transmission member via the engagement member is released. Therefore, the engagement portion between the transmission member and the plate assembly is excessively large. It is possible to prevent the application of various stresses and prevent the plate assembly from biting into or breaking the transmission member.

Further, by changing the inclination angle of each engaging surface formed on the elastically deformable engaging member for each of the opposing rotating directions, the engaging member is elastically deformed in the radial direction by the forward and reverse rotating directions. Since it is possible to change the magnitude of the plate locking force in the circumferential direction that is required to perform the one-way clutch function, the engaging portion between the plate assembly and the transmission member can be configured.

Therefore, an engaging portion for non-rotatably engaging each plate set and each transmission member prevents the plate from biting into the transmission member or being damaged, and has a one-way clutch function. It is possible to provide a compact viscous coupling.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a viscous coupling according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts of the viscous coupling shown in FIG.

FIG. 3 is an enlarged transverse sectional view of a main part of the viscous coupling shown in FIG.

FIG. 4 is an enlarged vertical cross-sectional view of a main part of a viscous coupling according to a second embodiment of the present invention.

5 is a lateral cross-sectional view of a main part for explaining an operating state of the viscous coupling shown in FIG.

6 is a transverse cross-sectional view of a main part for explaining an operating state of the viscous coupling shown in FIG.

FIG. 7 is an enlarged transverse cross-sectional view of a main part for explaining an operating state of the viscous coupling shown in FIG.

FIG. 8 is a skeleton mechanism diagram showing a power system of a vehicle using a viscous coupling according to each embodiment.

[Explanation of symbols]

 1 Engine 3 Transmission 5 Front Diff 7 Front Wheel 9 Front Wheel 11 Transfer 13 Viscous Coupling 15 Propeller Shaft 17 Rear Diff 19 Rear Wheel 21 Rear Wheel 29 Bearing 33 Housing (Second Transmission Member) 35 Hub (First Transmission Member) 37 Spline 39 bolt hole 41 bearing 45 working chamber 47 X ring 49 X ring 51 backup ring 53 backup ring 55 outer plate (second plate) 55a engagement surface 55b engagement surface 57 inner plate (first plate) 58 blade portion 59 Blade portion 61 Spacer ring 62 Spline 63 Elastic spline portion 63a Engaging surface 63b Engaging surface 64 Spline tooth 71 Viscous coupling 73 Housing 75 Hub 76 Elastic engaging portion 77 roller 78 outer plate 79 inner plate 80 one-way clutch 81 spacer ring 82 spacing the holding plate 83 spline-engagement means 84 cutout 85 holding portion 86 narrower portion 87 wider portion 88 inclined surfaces

Claims (2)

[Scope of utility model registration request] 1. A first and a second rotatably arranged relative to each other.
A transmission member, a working chamber in which a viscous fluid is sealed, and a first plate set non-rotatably engaged with the first transmission member,
A viscous coupling having first plate sets and second plate sets alternately arranged in the working chamber and non-rotatably engaged with a second transmission member, the viscous coupling comprising: At least one of the engaging portions of the second transmission member supports the plate locking force that acts in the circumferential direction to non-rotatably lock the plate set to the transmission member, and the radius of the plate locking force. Has an engaging member that is elastically deformable in the radial direction by the component force in the directional direction. When a transmission torque of a predetermined value or more acts between the first and second plate sets, the engaging member is elastic in the radial direction. A viscous coupling that is configured to be deformed to release the circumferential engagement of the plate set that is non-rotatably engaged via the engagement member. 2. The engagement surfaces formed on the engagement member so as to face each other in the forward and reverse rotation directions in order to receive a radial component force of the plate locking force acting in the rotation circumferential direction,
The viscous coupling according to claim 1, wherein the viscous couplings have different inclination angles with respect to a center line extending in the radial direction.