Abstract:
An anti-reverse input clutch is provided which includes an output member including an output shaft held so as to be rotatable about the axis of an input member, and a cam member which is a separate member from the output shaft and on which cam surfaces are formed. The cam member is rotationally fixed to the output shaft. Thus, each of the output shaft and the cam shaft can be easily formed, so that it is possible to significantly reduce the time and cost for manufacturing the output member and improve the freedom of design thereof.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to an anti-reverse input clutch which transmits torque only from an input member to an output member and not from the output member to the input member.  
         [0002]     Such an anti-reverse input clutch transmits torque applied to the input member in either direction to the output member but does not transmit reverse input torque applied to the output member to the input member.  FIGS. 8A and 8B  show a clutch having such a reverse input blocking function disclosed in Japanese patent publication 2-271116A. This clutch includes an input member  51  and an output member  52 . A pin  53  secured to the input member  51  is inserted in a pin hole  54  formed in the output member with a slight clearance defined therebetween in the rotational direction. The clutch further includes a stationary outer ring  55  having a cylindrical inner surface radially opposed to the outer periphery of the output member  52 , defining wedge-shaped spaces  56  therebetween which gradually narrow from the central portion thereof toward both circumferential ends. A pair of rolling elements  57  and an elastic member  58  are received in each wedge-shaped space  56  with the elastic member  58  disposed between the rolling elements  57 . The clutch further includes a retainer  59  coupled to the input member  51  through the pin  53  and having legs  59   a  each inserted between a pair of adjacent wedge-shaped spaces  56 . Driving and driven shafts (not shown) are inserted into the input member  51  and the output member  52 , respectively, and coupled thereto through serrations.  
         [0003]     Because the rolling elements  57  are biased toward the narrow portions of the respective wedge-shaped spaces by the elastic members  58 , even if reverse input torque is applied to the output member  52 , the rear one of each pair of the rolling elements  57  with respect to the rotational direction of the output member  52  engages the inner periphery of the outer ring  55  and the outer periphery of the output member  52 , thus locking the output member  52 , so that such reverse input torque is not transmitted to the input member  51 .  
         [0004]     When input torque is applied to the input member  51 , the legs  59   a  of the retainer  59 , which is rotationally fixed to the input member  51 , push the rear one of each pair of rolling elements  57  with respect to the rotational direction of the input member  51  against the force of the elastic member  58 , so that the rear one of each pair of rolling elements  57  disengages from the inner periphery of the outer ring  55  and the outer periphery of the output member  52 . Thus, the rotation of the input member  51  is transmitted to the output member  52  with a slight angular delay.  
         [0005]     In this anti-reverse input clutch, on the outer periphery of a large-diameter portion  60  at the axially central portion of the output member  52 , cam surfaces  60   a  are formed which define the wedge-shaped spaces  56  in cooperation with the inner cylindrical surface of the outer ring  55 . Thus, the output member  52  is complicated in structure and only limited options are available as methods for forming such an output member  52 . It is therefore troublesome and thus costly to form such an output member, which will push up the manufacturing cost of the entire clutch.  
         [0006]     An object of the present invention is to provide an anti-reverse input clutch of which the output member can be formed easily at a low cost.  
       SUMMARY OF THE INVENTION  
       [0007]     According to the present invention, the output member comprises an output shaft which is held so as to be rotatable about the axis of the input member, and a cam member which is a separate member from the output shaft and on which the cam surfaces are formed, the cam member being rotationally fixed to the output shaft. Since the output member comprise the output shaft and the cam member which are separate members from each other, each of the output shaft and the cam shaft can be easily formed, so that it is possible to significantly reduce the time and cost for manufacturing the output member and improve the freedom of design thereof.  
         [0008]     Preferably, a plurality of adjacent ones of the rolling elements are disposed between each of the legs of the retainer and the elastic member while in contact with each other. With this arrangement, it is possible to reduce the size of the entire clutch without reducing the maximum reverse input torque that can be blocked, and thus to further reduce the cost.  
         [0009]     Preferably, the output shaft includes a flange, and the stationary member includes flange restricting portions which sandwich the flange from both axial sides thereof. With this arrangement, even if radial loads and/or axial loads act on the output shaft, the output shaft and the cam member, which is coupled to the output shaft, will not significantly incline or move axially relative to the stationary member. The clutch thus operates stably.  
         [0010]     The cam member of the output member is preferably coupled to the output shaft so as to be movable to an eccentric position relative to the output shaft. With this arrangement, even if the inner ring and the outer ring are not exactly coaxial with each other when the clutch is assembled, because the rollers are wedged into the narrow portions of the respective wedge-shaped spaces by the springs during use, the inner ring will automatically move to a position where it is coaxial with the outer ring. Thus, there should be no run-out of the inner ring relative to the outer ring. The clutch thus operates stably.  
         [0011]     At least one of the output shaft and the cam member of the output shaft is preferably made of one of sintered metals, forged metals and plastics.  
         [0012]     Since the output member comprises the output shaft and the cam member which are separate members from each other, each of the output shaft and the cam shaft can be easily formed, so that it is possible to significantly reduce the time and cost for manufacturing the output member and improve the freedom of design thereof and thus to reduce the manufacturing cost of the entire clutch. Such clutches can therefore be stably mass-produced. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:  
         [0014]      FIG. 1  is an exploded perspective view a clutch according to a first embodiment of the present invention;  
         [0015]      FIG. 2  is a vertical sectional front view of the clutch of  FIG. 1 ;  
         [0016]      FIG. 3  is a sectional view taken along line III-III of  FIG. 2 ;  
         [0017]      FIG. 4  is a vertical sectional front view of a clutch having a different coupling structure through which an output shaft is coupled to an inner ring;  
         [0018]      FIG. 5  is a sectional view taken along line V-V of  FIG. 4 ;  
         [0019]      FIG. 6  is a vertical sectional front view of a clutch according to a second embodiment of the present invention;  
         [0020]      FIG. 7  is an exploded perspective view of an output shaft of the clutch of  FIG. 6 ;  
         [0021]      FIG. 8A  is a vertical sectional front view of a conventional clutch; and  
         [0022]      FIG. 8B  is a sectional view taken along line VIII-VIII of  FIG. 8A . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Now referring to FIGS.  1  to  7 , the embodiments according to the present invention are described. First, FIGS.  1  to  3  show the first embodiment. As shown in  FIGS. 1 and 2 , the anti-reverse input clutch of this embodiment includes an input shaft (input member)  1 , an output member  4  comprising an output shaft  2  and an inner ring (cam member)  3  defining a plurality of cam surfaces  3   a  on the outer periphery thereof, a stationary member  8  comprising a housing  5 , an outer ring  6  and a presser lid  7 , and a retainer  9  having two legs  9   a  inserted between the inner ring  3  and the outer ring  6 . Cylindrical rollers (rolling elements)  10  and springs (elastic members)  11  are disposed between the two legs  9   a  of the retainer. The output shaft  2  and the inner ring  3 , which constitute the output member  4 , are preferably made of sintered metal, forged metal or plastic.  
         [0024]     The input shaft  1  has a front end portion formed with two parallel flat surfaces  1   a  on its outer periphery and extending through a disk portion  9   b  of the retainer  9  and inserted in a bore  3   b  formed in the inner ring  3 . A small-diameter cylindrical protrusion  1   b  is provided on the end surface of the front end portion of the input shaft  1  and is fitted in a hole  2   a  formed centrally in an end surface of the output shaft  2 . The input shaft  1  is thus rotatable with its axis in alignment with the axis of the output shaft  2 .  
         [0025]     The output shaft  2  has a flange  2   b  at its end facing the inner ring  3 . The flange  2   b  has four protrusions  2   c  formed on the inner edge thereof and engaged in recesses  3   c  formed in the end surface of the inner ring  3  facing the output shaft  2 , thereby rotationally coupling the output shaft  2  to the inner ring  3 . But the output shaft  2  and the inner ring  3  may be rotationally coupled together by means other than the means comprising the protrusions  2   c  and the recesses  3   c.    
         [0026]     With the outer ring  6  fitted in a cylindrical portion  5   a  of the housing  5 , the presser lid  7  is fitted in the cylindrical portion  5   a  of the housing  5 . The cylindrical portion  5   a  of the housing  5  has four axial ribs  5   b  formed on the inner periphery thereof and engaged in axial grooves  6   a  formed in the outer periphery of the outer ring  6 , thereby rotationally coupling the outer ring  6  to the housing  5 . The cylindrical portion  5   a  of the housing  5  is also formed with an annular groove  5   c  in the inner periphery thereof. The presser lid  7  is formed with a corresponding annular rib  7   a  on the outer periphery thereof that is engaged in the annular groove  5   c  to prevent separation of the presser lid  7  from the housing  5 . A shoulder  5   d  is formed on the inner periphery of the cylindrical portion  5   d  of the housing  5  near its end remote from the presser lid  7 . The shoulder  5   d  and the end of the outer ring  6  facing the shoulder  5   d  serves as a flange restrictor by loosely sandwiching the flange  2   b  of the output shaft  2  therebetween. The flange restrictor prevents the output shaft  2  and the inner ring  3 , which is coupled to the output shaft  2 , from markedly inclining or axially moving relative to the stationary member  8  even under radial and/or axial loads.  
         [0027]     The legs  9   a  of the retainer  9  are provided on diametrically opposite points along the outer edge of the disk portion  9   b . The disk portion  9   b  is centrally formed with a hole  9   c  into which the front end portion of the input shaft  1  is tightly fitted. The retainer  9  is thus rotationally coupled to the input shaft  1 .  
         [0028]     The bore  3   b  formed in the inner ring  3  has a cross-section that is substantially identical to that of the front end portion of the input shaft  1 , but is shaped such that a slight circumferential clearance is present between the bore  3   b  and the front end portion of the input shaft  1 . Thus, the rotation of the input shaft  1  is transmitted to the output shaft  2  with a slight angular delay. Means for transmitting the rotation of the input shaft to the inner ring with a slight angular delay is not limited to the one shown. For example, the input shaft and the inner ring may be coupled together through e.g. serrations arranged with a circumferential play therebetween.  
         [0029]     As shown in  FIG. 3 , the cam surfaces  3   a  of the inner ring  3  are circumferentially inclined, thereby defining a wedge-shaped space  12  that gradually narrows from one circumferential end thereof toward the other between each cam surface  3   a  and the inner cylindrical surface of the outer ring  6 . One of the cylindrical rollers  10  is received in each wedge-shaped space  12 . The wedge-shaped spaces  12  comprise four groups of wedge-shaped spaces, each group comprising three circumferentially adjacent wedge-shaped spaces defined by three circumferentially adjacent cam surfaces that are inclined in the same direction. The cam surfaces defining the wedge-shaped spaces of any adjacent groups are circumferentially inclined in opposite directions to each other. In each of two spaces between adjacent pairs of groups which are circumferentially adjacent the wider circumferential ends of the wedge-shaped spaces, one of the springs  11  is mounted to bias the three rollers on each side toward the narrow circumferential ends of the respective wedge-shaped spaces while keeping the three rollers in contact with each other. In each of two spaces between adjacent pairs of groups which are circumferentially adjacent the narrower circumferential ends of the wedge-shaped spaces, one of the legs  9   a  of the retainer  9  is inserted while keeping a slight distance from the adjacent roller on each side thereof.  
         [0030]     With this arrangement, if reverse input torque is applied to the output shaft  2 , the three rollers  10  in the rear of each spring  11  with respect to the rotational direction of the output shaft  2  are pushed into the narrow portions of the respective wedge-shaped spaces  12  by the spring  11 , thereby locking the inner ring  3  by the engagement between the inner periphery of the outer ring  6  and the outer periphery of the inner ring  3 . Thus, torque applied to the output shaft  2  is not transmitted to the input shaft  1 .  
         [0031]     Conversely, when input torque is applied to the input shaft  1 , because the retainer  9  is rotationally coupled to the input shaft  1 , the three rollers  10  in the rear of each spring  11  with respect to the rotational direction of the input shaft  1  is pushed by the leg  9   a  toward the wider ends of the respective wedge-shaped spaces  12  against the force of the spring  11 , thereby disengaging the outer periphery of the inner ring  3  from the inner periphery of the outer ring  6 . When the input shaft  1  further rotates and the flat surfaces  1   a  engages the flat surfaces of the bore  3   b  of the inner ring  3 , rotation of the input shaft  1  is transmitted to the output shaft  2  through the inner ring  3 .  
         [0032]     In this embodiment, the cam surfaces  3   a  of the inner ring  3  are convex curved surfaces as shown in  FIG. 3 . Thus, even if any of the rollers  10  is skewed, it will come into line contact with the cam surface  3   a , and will never wedge into the cam surface  3   a  at its end. The rollers  10  can therefore always smoothly disengage.  
         [0033]     Since the output member  4  comprises the output shaft  2  and the inner ring  3 , which is a separate member from the output shaft  2 , each of the output shaft  2  and the inner ring  3  can be easily formed. Thus, the output member  4  according to the present invention can be formed far more easily at a far lower cost with a greater freedom of design than integral output members.  
         [0034]      FIGS. 4 and 5  show a modified arrangement for coupling the output shaft  2  to the inner ring  3 . In this arrangement, the flange  2   b  of the output shaft  2  has a larger inner diameter than the outer diameter of the inner ring  3 , and the protrusions  2   c  on the inner edge of the flange  2   b  have a width smaller than the width of the recesses  3   c  formed in the end surface of the inner ring  3  so that the inner ring  3  can move radially by a distance equal to the gap therebetween. The inner ring  3  can therefore rotate with its axis offset from the axis of the output shaft  2 .  
         [0035]     With this arrangement, even if the inner ring  3  and the outer ring  6  are not exactly coaxial with each other when the clutch is assembled, because the rollers  10  are wedged into the narrow portions of the respective wedge-shaped spaces  12  by the springs  11  during use, the inner ring  3  will automatically move to a position where it is coaxial with the outer ring  6 . Thus, there should be no run-out of the inner ring  3  relative to the outer ring  6 . By positively preventing run-out of the inner ring  3 , it is possible to retain the rollers at positions exactly as designed, thereby making it possible to simultaneously unlock the rollers  10  (and disengage the inner periphery of the outer ring  6  and the outer periphery of the inner ring  3  from each other). This stabilizes the torque necessary to unlock the rollers, and prevents excessive loads from being applied to the rollers when unlocking the rollers, which in turn minimizes the possibility of damage to the cam surfaces  3   a , thus prolonging the life of the inner ring  3 .  
         [0036]      FIGS. 6 and 7  show the second embodiment, which includes a stationary member  13  comprising an outer ring  14  and a housing  15  which are integral with each other. The outer ring  14  has a flange at one end thereof to which a presser lid  16  is mounted. The clutch of this embodiment further includes an output member  17  comprising an output shaft  18  and an inner ring  19  which are separate members from each other. The output shaft  18  has a flange  18   a  inserted in a thin-walled portion  19   a  of the inner ring  19  with protrusions  19   b  formed on the thin-walled portion  19   a  engaged in recesses  18   b  formed in the flange  18   a , so that the output shaft  18  is rotationally coupled to the inner ring  19 . The flange  18   a  of the output shaft  18  has an outer diameter greater than the inner diameter of the thin-walled portion  19   a  of the inner ring  19 , and the recesses  18   b  of the output shaft  18  have a larger width than the protrusions  19   b  of the inner ring  19 . Thus, the inner ring  19  can rotate with its axis offset from the output shaft  18 . Circumferentially arranged cam surfaces  19   c  are formed on the outer periphery of the inner ring  19 . Any circumferentially adjacent cam surfaces  19   c  are circumferentially inclined in opposite directions to each other. One roller  20  is disposed between each leg  21   a  of the retainer  21  and each spring (not shown). Otherwise, this embodiment is identical in structure to the first embodiment. Functionally, too, rotation of the input shaft  22  is transmitted to the output shaft  18 , while reverse input from the output shaft  18  is blocked, in the same manner as in the first embodiment.  
         [0037]     Thus, as with the first embodiment, the output shaft  18  and the inner ring  19  of this embodiment can also be formed easily at a low cost. Since the output shaft  18  and the inner ring  19  are coupled together so as to be rotatable with their axes offset from each other, runout of the inner ring is effectively prevented, so that the life of the inner ring is long.