Clutch plate, friction clutch, and coupling device

Abstract

A friction clutch has a plurality of iron inner clutch plates and a plurality of iron outer clutch plates. Both the clutch plates have sliding surfaces which are friction-engaged each other. A thin carbon film in a diamond form, which functions as a solid lubricant, is formed on each of the sliding surfaces of the outer clutch plates by a known method such as the Chemical Vapor Deposition method. A known nitride treatment or quenching and tempering treatment is applied to the sliding surfaces of the inner clutch plates. A coupling device has a pilot clutch mechanism with the friction clutch and an electromagnetic actuator. As a result, the friction clutch is resistant to wear and the coupling device is excellent in durability.

1 . An iron clutch plate having a sliding surface that contacts another clutch plate, wherein a thin carbon film in a diamond form is formed on the sliding surface.  
   
   
       2 . The clutch plate according to  claim 1 , wherein the thin carbon film is formed by diamond-like carbon.  
   
   
       3 . A friction clutch comprising: 
 a first clutch plate having a first sliding surface; and    a second clutch plate having a second sliding surface that contacts the first sliding surface, wherein the clutch plates friction-engage with each other to transmit torque, and wherein a thin carbon film in a diamond form is formed on at least one of the first and second sliding surfaces.    
   
   
       4 . The friction clutch according to  claim 3 , wherein the thin carbon film is formed by diamond-like carbon.  
   
   
       5 . The friction clutch according to  claim 3 , wherein the thin carbon film is formed on the first sliding surface, and wherein nitride treatment or quenching and tempering treatment is applied to the second sliding surface.  
   
   
       6 . The friction clutch according to  claim 3 , wherein the thin carbon film is formed on the first and second sliding surfaces.  
   
   
       7 . The friction clutch according to  claim 3 , wherein at least one of the first and second sliding surfaces includes a plurality of grooves that extend about the rotation axis of the associated clutch plate.  
   
   
       8 . The friction clutch according to  claim 3 , wherein at least one of the first and second sliding surfaces includes grooves in a substantially net form.  
   
   
       9 - 17 . (canceled)  
   
   
       18 . A coupling device comprising: 
 a first rotary member;    a second rotary member, which is rotatable relative to the first rotary member;    a housing chamber defined between the first rotary member and the second rotary member, wherein the housing chamber is charged with lubricant oil; and    a plurality of clutches located in the housing chamber, wherein the clutches cooperate to transmit torque between the first rotary member and the second rotary member,    wherein at least one of the clutches is a friction clutch having a first iron clutch plate and a second clutch plate, wherein the clutch plates friction-engage with each other, wherein the first clutch plate has a first sliding surface that contacts the second clutch plate, wherein the second clutch plate has a second sliding surface that contacts the first clutch plate, and wherein a thin carbon film in a diamond form is formed on at least one of the first and second sliding surfaces.    
   
   
       19 . The coupling device according to  claim 18 , wherein the plurality of clutches include a first clutch and a second clutch, at least one of which being the friction clutch, wherein the second clutch is located between the rotary members, torque being transmitted between the rotary members through the second clutch, wherein the coupling device further comprises an electromagnetic actuator for actuating the first clutch, wherein, when the electromagnetic actuator actuates the first clutch, the second clutch is actuated to transmit torque between the rotary members in accordance with motion of the first clutch.  
   
   
       20 . The coupling device according to  claim 18 , further comprising an electromagnetic actuator, which actuates the friction clutch such that the clutch plates friction-engage with each other, wherein the friction clutch and the electromagnetic actuator form a pilot clutch mechanism, wherein the clutches include a main clutch located between the rotary members, torque being transmitted between the rotary members through the main clutch, wherein a cam mechanism is located between the pilot clutch mechanism and the main clutch, and wherein the cam mechanism actuates the main clutch in response to motion of the pilot clutch mechanism.  
   
   
       21 . The coupling device according to  claim 19 , wherein the electromagnetic actuator includes an armature and an electromagnet for actuating the armature.  
   
   
       22 . The coupling device according to  claim 18 , wherein the thin carbon film is formed on the first sliding surface, and wherein nitride treatment or quenching and tempering treatment is applied to the second sliding surface.  
   
   
       23 . The coupling device according to  claim 18 , wherein the thin carbon film is formed on the first and second sliding surfaces.  
   
   
       24 . The coupling device according to  claim 18 , wherein at least one of the first and second sliding surfaces includes a plurality of grooves that extend about the rotation axis of the associated clutch plate.  
   
   
       25 . The coupling device according to  claim 18 , wherein at least one of the first and second sliding surfaces includes grooves in a substantially net form.