JP2003014000A - Coupling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coupling capable of securing lubrication for a sliding part of a pilot clutch and magnetic force for fastening. SOLUTION: The coupling is comprised of a case-shaped torque transmitting member 3 and shaft-shaped torque transmitting member 9, a main clutch 11 arranged between both torque transmitting members, a pilot clutch 19, an electromagnet 51 and armature 53 fastening the pilot clutch 19, a rotary member 31 formed by a magnetic body integrally rotating with the case-shaped torque transmitting member 3 and forming a part of a magnetic circuit, and a cam mechanism 13 operating by receiving transmitting torque of the torque transmitting members 3 and 9 by means of fastening the pilot clutch 19 and fastening a main clutch 11 via a pressing member 15. The pilot clutch 19 is comprised of a multi-plate clutch laid between the rotary member 31 and armature 53 and relatively sliding each other. At least, either a clutch plate 91 facing a rotating body in the multi-plate clutch or a clutch plate 97 facing an armature is arranged so as to rotate integrally with the neighbouring rotating body 31 or armature 53 respectively, and a lubricating groove is formed only in the sliding surface of the multi-plate clutch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coupling for engaging a main clutch by connecting a pilot clutch with an electromagnet.

[0002]

2. Description of the Related Art FIG.
Such a driving force transmission device 301 is described.

The driving force transmission device 301 includes a rotating case 30.
3, inner shaft 305, main clutch 307,
It is composed of a ball cam 309, a pressure plate 311, a cam ring 313, a pilot clutch 315, an armature 317, an electromagnet 319 and the like.

The driving force transmission device 301 is arranged so as to divide the propeller shaft on the rear wheel side, which is cut off during two-wheel drive traveling in a four-wheel drive vehicle, and the rotating case 303 is connected to the propeller shaft on the front side to form an inner shaft. Three
Reference numeral 05 is connected to the rear propeller shaft.

The rotating case 303 has a main clutch 307.
, And a rotor 323. The rotor 323 constitutes a part of the magnetic path of the electromagnet 319, and the cylindrical member 321 is made of stainless steel to prevent leakage of magnetic flux from the magnetic path. Made of steel.

The main clutch 307 has a cylindrical member 321.
Is a multi-disc clutch disposed between the inner shaft 3 and the inner shaft 305.
Pressure plate 31 movably connected to 05
1 and the cam ring 313.

The pilot clutch 315 comprises a multi-plate clutch and is sandwiched between the armature 317 and the rotor 323.

In this driving force transmission device 301, the rotor 3
23, pilot clutch 315, and armature 317
Etc., the magnetic path of the electromagnet 319 is formed like a magnetic force line 325. When the electromagnet 319 is excited, the magnetic force line 3
Since the armature 317 is sucked by 25, the pilot clutch 315 is pressed and fastened.

When the pilot clutch 315 is engaged, a pilot torque is generated to apply the driving force of the engine to the ball cam 309, and the generated cam thrust force presses the main clutch 307, so that the driving force transmission device 3
01 is connected, the driving force is transmitted to the rear wheel side, and the vehicle is
Wheel drive state.

When the excitation of the electromagnet 319 is stopped,
The pilot clutch 315 is released and the ball cam 30 is released.
The cam thrust force of No. 9 disappears, the main clutch 307 is opened, the connection of the driving force transmission device 301 is released, the rear wheel side is disconnected, and the vehicle enters the two-wheel drive state.

The pilot clutch 315, which is a multi-plate clutch, is constructed by alternately stacking a plurality of outer plates and inner plates.

The outer plate engages with the cylindrical member 321, and engaging projections for that are formed on the outer peripheral side at regular intervals. Inner plate is cam ring 313
The engaging projections for that are formed on the inner peripheral side at regular intervals. Pilot clutch 315 in which a plurality of outer plates and inner plates are laminated
In, the outer plate is positioned outside the stack so as to contact the armature 317 and the rotor 323, respectively.

Since the outer plate and the inner plate slide on each other when the multi-plate clutch 315 is not fastened, conventionally, in order to improve durability, both sides of all the inner plates and both sides of the outer plate are conventionally used. On the other hand, a lubricating groove for oil lubrication is formed, nitriding treatment such as gas nitriding or salt bath nitriding, and surface treatment such as tempering (quenching and tempering) are performed.

[0014]

However, according to the above-mentioned conventional structure, in order to improve the durability of the pilot clutch 315, conventionally, both sides of all inner plates and both sides of the outer plate are lubricated for oil lubrication. Lubrication groove was formed, or surface treatment such as nitriding treatment such as gas nitriding or salt bath nitriding was performed. Since the surface treatment layer (nitride film or the like) is formed, the magnetic force of the electromagnet 319 is blocked by these, and the resistance of the magnetic circuit increases,
There was a risk that the armature suction power would decrease.

In particular, conventionally, since the lubricating groove and the surface treatment are formed on both sides of the inner plate and the outer plate, the outer plate and the armature 317 and the outer plate which are arranged so as to rotate integrally and do not slide. Even between the plate and the rotor 323 (rotating body), the magnetic force loss as described above may reduce the armature attraction force.

Therefore, an object of the present invention is to provide a coupling capable of improving durability of the multi-plate clutch and reducing the resistance of the magnetic circuit of the electromagnet to prevent the armature attraction force from decreasing. And

[0017]

According to a first aspect of the present invention, there is provided a coupling comprising a case-shaped torque transmitting member and a shaft-shaped torque transmitting member, a main clutch arranged between them, a pilot clutch, and a pilot clutch. An electromagnet and an armature to be fastened, a rotary member made of a magnetic body that rotates integrally with the case-shaped torque transmitting member and forms a part of a magnetic circuit, and a pilot clutch are fastened to transfer torques of both torque transmitting members. A coupling having a cam mechanism that receives and operates to fasten a main clutch through a pressing member, wherein the pilot clutch is a multi-plate clutch that is sandwiched between a rotating body and an armature and slides with each other. , At least one of a clutch plate facing the rotating body and a clutch plate facing the armature in the multi-plate clutch Adjacent as well as arranged to rotate integrally with these rotary member or armature, is characterized by the formation of the lubrication groove only on the sliding surface of the multi-plate clutch.

When the electromagnet is excited in this coupling, the armature is attracted by the electromagnetic induction action, and the pilot clutch is pressed and engaged. When the pilot clutch is engaged and the pilot torque is generated, the case-shaped torque transmitting member is formed. The torque between the shaft-shaped torque transmitting member and the shaft-shaped torque transmitting member acts on the cam mechanism, and the thrust force of the cam mechanism presses and engages the main clutch.

According to the present invention, at least one of the clutch plate facing the rotating body and the clutch plate facing the armature in the pilot clutch is arranged so as to rotate integrally with the adjacent rotating body or armature, and sliding in the pilot clutch is performed. The lubrication groove is formed only on the surface.

That is, no lubricating groove is formed on at least one of the surface of the pilot clutch facing the rotating body and the surface facing the armature. Since the clutch plate having these facing surfaces rotates together with the rotating body or the armature, there is no need for lubrication with oil, and the clutch plate can smoothly rotate even without a lubricating groove.

As described above, even if a lubricating groove is not formed in a part of the clutch plates, the lubricating grooves are formed in the other clutch plates, so that the clutch plates can be lubricated to improve the durability. . Therefore, it is possible to keep the lubrication groove within the necessary minimum range, increase the mutual contact area of the clutch plates, and improve the magnetic permeability.

Further, since the magnetic permeability is increased, the engaging force of the pilot clutch based on the attractive force of the electromagnet is increased, so that the engaging force of the main clutch via the cam mechanism is increased and the power transmission is stabilized. .

According to another aspect of the present invention, there is provided a coupling including a case-shaped torque transmitting member and a shaft-shaped torque transmitting member, a main clutch arranged between them, a pilot clutch, an electromagnet and an armature for engaging the pilot clutch. A pressing member that operates by receiving the transmission torque of both torque transmitting members by engaging a pilot clutch with a rotating member made of a magnetic material that rotates integrally with the case-shaped torque transmitting member and forms a part of a magnetic circuit. And a cam mechanism for engaging the main clutch via the pilot clutch, the pilot clutch being a multi-disc clutch sandwiched between a rotating body and an armature and sliding relative to each other. Adjacent at least one of the clutch plate facing the rotating body and the clutch plate facing the armature. As well as arranged to the rolling bodies or rotate integrally with the armature, and wherein the surface-treated only on the sliding surface of the multi-plate clutch.

In the surface treatment, gas nitriding, salt bath nitriding or the like is performed to harden the surface of the clutch plate to enhance friction efficiency. By increasing the friction efficiency, it is possible to smoothly slide the adjacent clutch plates.

In the present invention, at least one of the clutch plate facing the rotating body and the clutch plate facing the armature in the pilot clutch is arranged so as to rotate integrally with the adjacent rotating body or armature, and sliding in the pilot clutch is performed. Since only the surface is surface-treated, at least one of the surface of the pilot clutch facing the rotating body and the surface facing the armature is not surface-treated.

Treatment layer (nitride film etc.) by this surface treatment
Because it acts to block the magnetic flux of the electromagnet, the surface of at least one of the surface facing the rotating body and the surface facing the armature in the pilot clutch is not subjected to the surface treatment. The magnetic permeability of the clutch can be improved, and the engaging force of the pilot clutch based on the attractive force of the electromagnet can be increased. Therefore, the engagement force of the main clutch is increased, and the power transmission is stable.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 shows a coupling according to a first embodiment of the present invention. In the four-wheel drive vehicle, the coupling 1 of this embodiment is arranged between the rear differential, which is on the separated side, and the engine (transfer) side. The left side of FIG. 1 corresponds to the front side (engine side) of this vehicle.

The entire coupling 1 is housed in a casing (not shown) fixed to the vehicle body side. The coupling 1 has a clutch housing 3 as a case-shaped torque transmission member and a clutch hub 9 as a shaft-shaped torque transmission member. The main clutch 1 is provided between the clutch housing 3 and the clutch hub 9.
1, ball cam 13, pressing member 15, cam ring 17,
A pilot clutch 19 and the like are arranged.

The clutch housing 3 is made of magnetic steel, and has a cylindrical shape. The front side of the clutch housing 3 is connected to the power transmission shaft 5. An opening 21 is provided at the rear of the clutch housing 3.

The power transmission shaft 5 is made of a shaft steel material (magnetic material), and a serration 7 for connecting a companion flange (not shown) to the serration is formed on the outer surface of the shaft portion 5a. There is. The companion flange is connected to the engine (transfer) side by being connected to the flange on the propeller shaft side.

The opening 21 at the rear of the clutch housing 3
A ring-shaped rotor 31 (rotating member) made of a magnetic material that rotates integrally with the clutch housing 3 is attached to the. As described above, the power transmission shaft 5, the clutch housing 3, and the rotor 31 are integrated. Further, these are a bearing (not shown) on the power transmission shaft 5 and the rotor 31.
The upper bearing (not shown) supports the casing on the vehicle body side.

The clutch hub 9 is the clutch housing 3
Is located inside the ball bearing and the front end is the ball bearing 4.
3 is supported on the clutch housing 3, and the rear end is supported on the rotor 31 by a needle bearing 45. The clutch hub 9 is connected to the drive pinion shaft on the rear differential side.

The main clutch 11 is a multi-plate clutch and is arranged between the clutch housing 3 and the clutch hub 9. The ball cam 13 is arranged between the pressing member 15 and the cam ring 17, and the ball cam 13 and the cam ring 17 form a cam mechanism.

The pressing member 15 is spline-connected to the clutch hub 9 so as to be movable in the axial direction.
The main clutch 11 is pressed and engaged by the thrust force of.

The cam ring 17 is arranged on the outer circumference of the clutch hub 9, and a thrust bearing 47 for receiving the cam reaction force of the ball cam 13 is arranged between the cam ring 17 and the rotor 31.

The pilot clutch 19 is the multiple disc clutch 4
9 and is arranged between the clutch housing 3 and the cam ring 17. The armature 53 is arranged adjacent to the front side of the multi-plate clutch 49 so as to rotate integrally with the clutch housing 3, and sandwiches the multi-plate clutch 49 with the rotor 31.

An electromagnet 51 corresponds to the rotor 31, and a yoke 55 of the electromagnet 51 is inserted in a recess 57 of the rotor 31 with a proper gap. The rotor 31 is supported on the yoke 55 by a seal bearing 59.

The electromagnet 51 is fixed to the vehicle body side casing. The electromagnet 51 is connected to the battery via the lead wire 29, and the operation of exciting and stopping the excitation is performed by the controller.

Magnetic lines 61 of the electromagnet 51 are formed by the rotor 31, the multi-plate clutch 49, the armature 53 and the like.

A non-magnetic stainless steel ring 63 is arranged on the rotor 31 to prevent short circuit of the magnetic force of the magnetic force lines 61. Further, the multi-plate clutch 49 is provided with a notch 65 at a position corresponding to the ring 63 to prevent the magnetic force lines 61 from short-circuiting and leaking.

Further, the thrust bearing 47 and the rotor 3
A spacer 73 including a washer and the like is disposed between the spacer 73 and the spacer 1. The spacer 73 is made of a non-magnetic material such as aluminum or stainless steel, and prevents the magnetic force lines 61 of the electromagnet 51 from leaking to the cam ring 17 side.

2 and 3 show a multi-plate clutch 49 constituting the pilot clutch 19 in the lower half of FIG. 1, and FIG. 4 shows a disassembled state of the multi-plate clutch 49.

As shown in FIGS. 2 and 3, a plurality of (4
The outer plates 91, 93, 95, 97 of one sheet and the inner plates 77, 77, 77 of a plurality of sheets (three sheets) are alternately laminated. In the stacking, outer plates 91, 97 are arranged at both end portions, and all the inner plates 77 have outer plates 91, 97.
It is sandwiched between 93, 95 and 97.

Outer plates 91, 93, 95, 97
Are spline-connected to the clutch housing 3, and each inner plate 77 is spline-connected to the cam plate 17.

As a result, the rotor 31 and the rotor 3 are
The outer plate 91 and the armature 53 adjacent to 1 and the outer plate 91 adjacent to the armature 53 rotate together.

In order to connect these splines, arc-shaped engagement projections 79 are formed on the outer plates 91, 93, 95, 97 at the outer peripheral side at regular intervals.
On the inner plate 77, arcuate engagement projections 81 are formed on the inner peripheral side at regular intervals. In addition, in each outer plate 91, 93, 95, 97 and inner plate 77,
Arc-shaped oil holes 76 and 78 for oil lubrication penetrate through a plurality of locations.

Outer plates 91, 93, 9 in a laminated state
Adjacent plates of 5, 97 and the inner plate 77 slide on each other, so that a lubricating groove 85 for lubricating oil is formed.

The sliding groove 85 is composed of a thin cross-shaped groove, and as shown in FIG. 3, both sides of all the inner plates 77, both sides of the outer plates 93, 95 in the middle portion and the outer plates 91, 91 in both side portions. One side surface 91a of 97,
It is formed in 97a. These surfaces serve as sliding surfaces that slide with adjacent plates, and by forming the lubrication groove 85, lubrication is performed with oil,
It can rotate smoothly.

On the other hand, the outer plates 9 on both sides
Lubricating grooves are not formed on the surfaces 91b and 97b on the other side of the parts 1, 97. The other surface 9 of the outer plate 91
Reference numeral 1b is a surface facing the rotor 31, and the outer plate 97
The surface 97b on the other side is a surface facing the armature 53.

These outer plates 91, 97 are clutch plates that rotate together with the armature 53 and the rotor 31, as described above, and the surfaces 91b, 97b are the rotor 31,
Since it does not slide on the armature 53, it is not necessary to provide a lubricating groove for oil lubrication.

In this way, the surface 9 of the outer plates 91, 97 facing the rotor 31 side and the armature 53 side.
When the lubrication groove is not formed in 1b and 97b, the gap caused by the lubrication groove disappears, and the outer plates 91 and 9
The contact area between the rotor 7, the rotor 31, and the armature 53 can be increased. This improves the magnetic permeability,
The attraction force of the electromagnet 51 is increased, and the engagement force of the pilot clutch 19 can be increased.

In the above structure, when the electromagnet 51 is excited, the armature 53 is attracted by the magnetic force lines 61, and the pilot clutch 19 is pressed and fastened to generate the pilot torque. When pilot torque is generated in the pilot clutch 19, the clutch housing 3
The driving force of the engine is applied to the ball cam 13 from the pilot clutch 19 and the cam ring 17 by the thrust force of the engine, and the thrust force of the engine causes the main clutch 1 to pass through the pressing member 15.
1 is pressed and fastened, and the coupling 1 is connected.

When the coupling 1 is connected, the rear differential is connected to the engine side, and the vehicle is in a four-wheel drive state.
At this time, if the strength of the magnetic force of the electromagnet 51 is controlled by the controller, the pilot clutch 19 is slipped.
Since the pilot torque of No. 1 changes and the thrust force of the ball cam 13 changes, the connecting force between the main clutch 11 and the coupling 1 can be adjusted.

By adjusting the coupling force of the coupling 1 in this way, the torque distribution ratio between the front wheels and the rear wheels of the vehicle can be adjusted arbitrarily.

When the excitation of the electromagnet 51 is stopped, the pilot torque of the pilot clutch 19 disappears, the main clutch 11 is released, and the coupling 1 is disconnected. When the coupling 1 is released, the rear differential is disconnected, and the vehicle enters the front-wheel drive two-wheel drive state.

Oil is injected into the power transmission shaft 5, the clutch housing 3, and the rotor 31 through an oil hole 67 provided in the clutch housing 3. After the oil is injected, the oil hole 67 is sealed by the ball 68.

An X ring 37 is arranged between the clutch housing 3 and the clutch hub, an O ring 39 is arranged between the clutch housing 3 and the rotor 31, and an O ring 39 is arranged between the rotor 31 and the clutch hub 9. X-rings 41 are arranged to prevent oil leakage to the outside.

The oil thus sealed is held in the oil sump 33 provided on the clutch hub 9. Further, the clutch hub 9 is provided with a radial oil passage 69 communicating with the oil reservoir 33. Therefore, when the clutch hub 9 rotates, the oil passes from the oil sump 33 through the oil flow path 69 to the main clutch 11 and the ball bearing 43 to lubricate them, and further, the ball cam 1
3. Lubricate the thrust bearing 47, the multi-plate clutch 49, the X rings 37 and 41, and the like.

According to the structure of the above embodiment, the rotor 31, the outer plate 91 adjacent to the rotor 31, the armature 53, and the outer plate 91 adjacent to the armature 53 are arranged so as to rotate integrally. The lubricating groove 85 is formed only on both surfaces of the inner plate 77 that slides adjacently in the pilot clutch 19, both surfaces of the outer plates 93 and 95, and the surfaces 91a and 97a on one side of the outer plates 91 and 97. , 97
Since no lubrication groove is formed on the surfaces 91b and 97b, it is possible to keep the lubrication groove 85 to a necessary minimum and reduce the occurrence of a gap due to the lubrication groove 85.

In addition to this, the outer plates 91, 97
The contact areas between the surfaces 91b and 97b of the above and the rotor 31 and the armature 53 corresponding to these surfaces 91b and 97b can be increased, the magnetic permeability is improved, and the attractive force of the electromagnet 51 is increased. The engagement force of the pilot clutch 19 can be increased, and as a result, the engagement force of the main clutch 11 can be increased and the power transmission can be stabilized.

Further, the loss of exciting power to the electromagnet 51 is greatly reduced and the load on the battery is reduced. Further, the electromagnet 51 can be downsized, and the coupling 1
The whole can be made lightweight and compact.

Further, since the surface 91b of the outer plate 91 that contacts the rotor 31 is not provided with the lubricating groove, when the rotor 31 is screwed into the clutch housing 3, the rotor 31 does not rub against the outer plate 91 and the rotor 31 does not rub. It is possible to prevent the surface of 31 from being damaged.

In this embodiment, the rotor 3
1 and the outer plate 91 adjacent to the rotor 31 and the armature 53 and the outer plate 91 adjacent to the armature 53 are integrally rotated so that the two outer plates 91 located at both ends of the pilot clutch 19 , 97 of the outer plates 91, 97 have no lubricating grooves formed on the surfaces 91b, 97b.
The case where the lubricating groove is not formed in 1b and 97b may be used. Also in this case, the magnetic permeability is improved and the engagement force of the pilot clutch 19 can be increased.

[Second Embodiment] This embodiment will be described with reference to FIG. 3 in the first embodiment. In this embodiment, the sliding surface of the pilot clutch 19 is surface-treated. The surface treatment is carried out by subjecting the clutch plate to gas nitriding treatment or salt bath nitriding treatment, and by this surface treatment, the surface of the clutch plate becomes hard, friction efficiency is improved, and slidability of the sliding surface of the clutch plate is improved. At the same time, the durability can be improved.

Also in this second embodiment, the rotor 31, the outer plate 91 adjacent to the rotor 31, the armature 53, and the outer plate 91 adjacent to the armature 53 rotate together.

Then, the surface treatment is applied to both surfaces of all the inner plates 77, both surfaces of the outer plates 93 and 95 in the middle portion, and the surfaces 91a and 97a on one side of the outer plates 91 and 97 in both side portions, and also to the both side portions. No surface treatment is applied to the other side surfaces 91b and 97b of the outer plates 91 and 97.

The outer plates 91 and 97 are clutch plates that rotate together with the armature 53 and the rotor 31, as described above, and the surfaces 91b and 97b of these clutch plates 91 and 97 slide on the rotor 31 and the armature 53. Never. Therefore, it is not necessary to improve the friction efficiency, and the surface treatment for that purpose is not performed.

When the surfaces 91b and 97b of the outer plates 91 and 97 are not surface-treated in this way,
The magnetic flux is not dispersed or blocked by the treatment layer, and the magnetic permeability can be improved accordingly. Then, since the magnetic permeability is increased, the attraction force of the electromagnet 51 is increased, so that the engagement force of the pilot clutch 19 is increased, and as a result, the engagement force of the main clutch is increased, and stable power transmission can be performed. It will be possible.

In this embodiment as well, one of the outer plates 91, 97 is the outer plate 9
The surface treatment may not be performed on the surfaces 91b and 97b of 1,97. Also in this case, the magnetic permeability is improved and the engagement force of the pilot clutch 19 can be increased.

[0070]

According to the invention of claim 1, at least one of the clutch plate adjacent to the rotating body or the clutch plate adjacent to the armature is arranged so as to rotate integrally with the adjacent rotating body or armature. Since the lubrication groove is formed only on the sliding surface of the pilot clutch, the part that forms the lubrication groove can be limited to the minimum necessary range, the magnetic permeability is improved, and the pilot based on the attractive force of the electromagnet is used. The clutch engagement force increases.
Therefore, the engagement force of the main clutch is increased, and the power transmission is stable.

According to the invention of claim 2, at least one of the clutch plate adjacent to the rotating body and the clutch plate adjacent to the armature is arranged so as to rotate integrally with the adjacent rotating body or armature, and the pilot is provided. Since only the sliding surface of the clutch is surface-treated, it is possible to keep the surface-treated part within the minimum necessary range, improve the magnetic permeability, and engage the pilot clutch based on the attractive force of the electromagnet. Power can be increased. Therefore, the engagement force of the main clutch increases,
Power transmission is stable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a multi-plate clutch.

FIG. 3 is an exploded cross-sectional view of a multi-plate clutch.

FIG. 4 is an exploded perspective view of a multi-plate clutch.

FIG. 5 is a cross-sectional view of a conventional example.

[Explanation of symbols]

1 Coupling 3 Clutch Housing 9 Clutch Hub 11 Main Clutch 13 Ball Cam 15 Pressing Member 17 Cam Ring 19 Pilot Clutch 31 Rotor 49 Multi-plate Clutch 51 Electromagnet 53 Armature 91, 93, 95, 97 Outer Plate (Clutch Plate) 77 Inner Plate (Clutch) Plate) 85 lubrication groove

Claims (2)

[Claims] 1. A case-shaped torque transmission member and a shaft-shaped torque transmission member, a main clutch arranged between them, a pilot clutch, an electromagnet and an armature for engaging the pilot clutch, and the case-shaped torque transmission member. When a pilot clutch is engaged with a rotating member made of a magnetic material that rotates integrally and forms a part of a magnetic circuit, it operates by receiving the transmission torque of both torque transmission members and engages the main clutch via a pressing member. A coupling having a cam mechanism, wherein a pilot clutch is a multi-disc clutch sandwiched between a rotating body and an armature and sliding with each other, and a clutch plate facing the rotating body in the multi-disc clutch or At least one of the clutch plates facing the armature is integrated with the adjacent rotating body or armature. Together arranged to rolling, coupling, characterized in that the formation of the lubrication groove only on the sliding surface of the multi-plate clutch. 2. A case-shaped torque transmission member and a shaft-shaped torque transmission member, a main clutch arranged between them, a pilot clutch, an electromagnet and an armature for engaging the pilot clutch, and the case-shaped torque transmission member. When a pilot clutch is engaged with a rotating member made of a magnetic material that rotates integrally and forms a part of a magnetic circuit, it operates by receiving the transmission torque of both torque transmission members and engages the main clutch via a pressing member. A coupling having a cam mechanism, wherein a pilot clutch is a multi-disc clutch sandwiched between a rotating body and an armature and sliding with each other, and a clutch plate facing the rotating body in the multi-disc clutch or At least one of the clutch plates facing the armature is integrated with the adjacent rotating body or armature. Together arranged to rolling, the coupling being characterized in that the surface treatment only on the sliding surface of the multi-plate clutch.