Patent Publication Number: US-2006011442-A1

Title: Hydraulic clutch

Description:
The present invention claims foreign priority to Japanese patent application No. JP.2003-275076, filed in the Japanese Patent Office on Jul. 16, 2003 the contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a hydraulic clutch that is operated by hydraulic pressure.  
      2. Description of the Related Art  
       FIG. 5  shows a side-cross sectional view of a main structure of a hydraulic clutch  10 . In  FIG. 5 , reference number  20  denotes a clutch case and reference number  30  denotes a piston. In  FIG. 5 , separate plates  41  are spline-engaged with a spline portion  21  of the clutch case, and friction plates  42  that are alternately interposed between the separate plates  41  are spline-engaged with a hub (not shown) to transmit a rotation thereof. Reference numbers  23  and  33  denote O-rings, reference numbers  52  and  53  denote seal members, and a line X-X denotes a rotation axis of the clutch.  
      When the clutch is operated, hydraulic fluid is supplied to a piston operating hydraulic chamber  47  via a hydraulic fluid supply path  51  of the shaft  50  and a hydraulic fluid supply path  24  of the clutch case  20  so as to press the piston  30  (i.e., move the piston  30  rightward in  FIG. 5 ). Accordingly, a tip end portion  31  of the piston  30  pushes the separate plates  41  and the friction plates  42  towards a blocking ring  43 , and then the clutch  10  is in an engaged state.  
       FIG. 4  shows a conventional structure of the O-ring  23  that is set on the clutch case  20  with respect to the piston  30 . In  FIG. 4 , reference number  25  denotes a setting groove and reference number  26  denotes a bottom surface of the setting groove  25 . In the conventional structure, the bottom surface  26  is formed so as to be parallel to a moving direction of the piston in its operation, as shown in  FIG. 4 .  
      When hydraulic pressure loaded on the piston  30  is released for releasing the engaging state of the hydraulic clutch  10 , the piston  30  goes back to left side in  FIG. 5  by a canceller  44  and a return spring  46 , and the pressure loaded on the separate plates  41  and the friction plates  42  (i.e., the friction engaging elements) is released.  
      When the clutch is engaged, the hydraulic fluid enters into the groove  25  and in turn presses the O-ring  23  to right side in  FIG. 5 . When the clutch is released (i.e., disengaged), the pressure loaded on the O-ring  23  is reduced and the O-ring  23  expands. The O-ring  23  then pushes the bottom surface  26  and surrounding walls of the groove  25 . The surrounding walls include the lower surface of the piston  30  and peripheral walls defining the groove  25 . This expansion of the O-ring  23  generates a sliding resistance when the piston  30  starts its retreat (leftwards of  FIG. 4 ), so as to release the engagement (i.e., disengage) of the clutch.  
      For promoting smooth releasing operation, it is necessary to reduce the sliding resistance caused by the expansion of the O-ring  23 , which is in turn caused by the elastic force of the O-ring itself. However, the conventional clutch has a problem in that the sliding resistance is too high, thus resulting in the prevention of a smooth releasing operation.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to solve the above mentioned problem. The object can be achieved by a hydraulic clutch, comprising: 
          an operating hydraulic chamber;     an operational member pressed in an axial direction thereof by hydraulic fluid supplied from the operating hydraulic chamber so as to transmit torque by engaging a frictional engaging elements;     a non-operational member that forms the operating hydraulic chamber with respect to the operational member, the non-operational member having a seal member setting portion thereon; and     a seal member provided in the seal member setting portion of the non-operational member,     wherein a bottom surface of the seal member setting portion is inclined in a direction in which the operational member is pushed.        

      The above-mentioned hydraulic clutch according to the present invention, it is preferable that the bottom surface of the non-operational member is gradually inclined.  
      In addition, the above-mentioned hydraulic clutch according to the present invention, it is more preferable that an inclination angle of the inclined bottom surface of the non-operational member ranges from about 5 to 10 degrees with respect to the axial direction of the operational member.  
      Further, the above-mentioned hydraulic clutch according to the present invention, it is advantageous that the seal member is an O-ring.  
      Moreover, the above-mentioned hydraulic clutch according to the present invention, it is further advantageous that the hydraulic clutch is a wet type multiple disc clutch, the frictional engaging elements include a friction plate and a separate plate, the operational member is a piston of the wet type multiple disc clutch, and the non-operational member is a clutch case of the wet type multiple disc clutch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross sectional view showing a main structure of the hydraulic clutch according to the present invention;  
       FIG. 2  is a cross sectional view showing an O-ring groove provided on the clutch case according to the present invention;  
       FIG. 3  is a cross sectional view showing a situation of the O-ring in operation of the clutch according to the present invention;  
       FIG. 4  is a cross sectional view showing a conventional O-ring groove; and  
       FIG. 5  is a cross sectional view showing a main structure of the conventional hydraulic clutch. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      As an exemplary, non-limiting embodiment of the present invention,  FIG. 1  shows a cross sectional view showing a main structure of a hydraulic clutch, such as a multiple disc clutch of wet type.  FIG. 2  shows a setting state of an O-ring  23  of the clutch case  20  opposing the piston  30 . In  FIG. 2 , the O-ring  23  is set in a setting groove  25  provided on the clutch case  20 . Reference number  26  denotes a bottom surface of a groove  25 . The bottom surface  26  is inclined from a deeper end in the direction opposite the friction plates  42 , and sloping upward gradually in a direction toward the piston  30  (i.e., rightward in  FIG. 2 ), so as to be shallower in the direction of operation of the piston  30  (arrow F) at the engaging portion of the clutch. An inclination angle α of the bottom surface is preferably ranging from about 5 to 10 degrees.  
       FIG. 3  is a drawing illustrating the position of the O-ring  23  in the setting groove  25  when the piston  30  moves forward to an operating direction thereof or when the clutch is engaged. The piston  30  is pushed to right side by hydraulic fluid in a piston operating hydraulic chamber  47  of  FIG. 1 , and the pressed hydraulic fluid enters the groove  25  via a gap between the clutch case  20  and the piston  30 . As the hydraulic pressure indicated as small arrow p loads on the O-ring  23 , the O-ring  23  is pressed into the right wall of the groove  25 . Further, the O-ring  23  is elastically deformed and becomes in a state as emphasized in  FIG. 3 , and the O-ring  23  performs a sealing operation.  
      The hydraulic pressure is reduced when the clutch is released, the piston  30  tends to retreat to left side due to operation of a return spring  46 , and hydraulic pressure p in the inner of groove  25  is reduced. Due to its elasticity, the O-ring  23  is able to return to its natural resting shape when there is no hydraulic pressure thereon. At that time, the O-ring  23  expands, tilting toward the left side in the groove  25  due to the friction between the piston  30  and the O-ring  23 . That is, the O-ring  23  expands toward a deeper side of the groove  25 , thus redeucing the sliding resistance between the piston  30  and the O-ring  23 . Accordingly, the piston is capable of smoothly starting the releasing movement towards to left side in  FIG. 3 .  
      The foregoing description of the present invention is advantageous for at least the following reasons. Because (1) the hydraulic clutch of the present invention has the above-described structure, (2) the seal member setting portion is formed on the non-operational member, and (3) the bottom surface of the non-operational member is gradually shallow in the operational direction of the operational member, when the clutch is released, (1) the operational member retreats to the releasing direction, (2) the seal member expands to the deeper portion of the groove due to its elasticity, (3) the sliding resistance is reduced and (4) the operational member is capable of achieving smooth release operation not present in the conventional art.  
      While the foregoing has been described in connection with the exemplary, non-limiting embodiment of the present invention, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.