Abstract:
The present invention provides a one-way clutch in which spring force of tongue pieces of a spring will not be decreased, even in case where a larger tightening margin is provided between a cage and an outer race, but proper spring force can be maintained thereby to attain reliable synchronization between the outer race and the cage, and a rise of cost will not be incurred. The one-way clutch includes a cage, a spring arranged along an inner diameter side of the cage, and a sprag assembly. Each of sprag is inserted into pockets of the spring and cage, respectively. One end of the spring is overlapped with the other end at a position where the largest repulsive force is exerted from the cage. Thereby, rigidity of the spring is increased in a part of the spring corresponding to the position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a one-way clutch provided with a spring along an inner circumference of a cage, and more particularly, to the one-way clutch in which sprags can be properly urged without damaging the spring, even though an irregular repulsive force is applied to the sprags when the cage is press fitted into an outer race.  
           [0003]    2. Description of the Related Art  
           [0004]    Generally, in order to repeatedly conduct transmission and interruption of an engine power between an inner race and an outer race, a one-way clutch is provided between these inner race and outer race.  
           [0005]    [0005]FIG. 6 shows a conventional one-way clutch including a cage  23  having a flange portion  23   f , a spring  24 , and a plurality of sprags  25 . In the one-way clutch of this type, the cage  23  is often provided with a tightening margin when it is press fitted into an outer race (not shown), for the purpose of synchronously rotating the cage  23  and the outer race. For this reason, the one-way clutch is designed in such a manner that an outer diameter of the cage  23  (an outer diameter of the flange portion  23   f ) may be somewhat larger than an inner diameter of a track face of the outer race so as to give retaining force, when the cage is press fitted to the outer race. However, there has been a problem that the cage  23  may become off-center with s respect to the outer race due to a pressure when it is press fitted to the inner peripheral face of the outer race, and clearances between the sprags  25  and respective pockets of the cage  23  may become narrow. Under the circumstances, in order to avoid such phenomenon, it has been proposed that the flange portion  23   f  of the cage  23  is cut at an equal interval in a circumferential direction to form cut-outs  23   c  (Japanese Utility Model Registration No. 2598500). Alternatively, there has been disclosed a structure in which a cage having a somewhat elliptical shape is press fitted into an outer race so that the outer race and the cage may be integrally rotated (Japanese Utility Model Publication No. JP-B-6-10233U).  
           [0006]    Further, it often happens in the one-way clutch that a distance of a space between the outer race and the inner race may vary in size, due to misalignment. Specifically, in case where there is a large distance between an inner peripheral face of the outer race and an outer peripheral face of the inner race, recovering force from tongue pieces of the spring will be decreased, and in case where there is a small distance between the inner peripheral face of the outer race and the outer peripheral face of the inner race, the recovering force from the tongue pieces of the spring will be increased. Such variation of the recovering force may lead to difficulty in synchronous operation of the sprags on occasion of torque transmission, and in order to overcome this difficulty, an example of the one-way clutch as shown in FIG. 7 has been proposed. Specifically, this one-way clutch includes a cage  13 , a spring  14  (usually, a ribbon spring is employed) and a plurality of sprags  15 , and disposed in an annular space  20  between an outer race  11  and an inner race  12  When the one-way clutch is rotated in one direction along with relative rotation of the outer race  11  and the inner race  12  on occasion of power transmission, the sprags  15  function as wedges allowing the outer race  11  and the inner race  12  to rotate integrally (locked). On the other hand, when the one-way clutch is rotated in the revers direction, the wedge function will be released to put the one-way clutch into an idle rotation, and transmission of the power will be interrupted (unlocked). This one-way clutch is characterized in that a value of a length L of an arm after variation which is represented by a distance between a function line of a recovering force F acting at a tongue piece  14   t  and a perpendicular line from an edge  14   a  of a pocket  14   p  abutted against the sprag  15  as a pivotal center is set so as to be in a reciprocal proportion to a value of the recovering force F after variation caused by misalignment in a locked or a free state of the sprag  15  (Japanese Patent No. 2653040).  
           [0007]    Generally, in the one-way clutch, a spring  34  is provided on an inner diameter side of a cage  33  which holds sprags  35 , and the sprags  35  are always urged into a locked state by means of tongue pieces  34   t  of the spring  34 , as shown in FIG. 8 and FIG. 9 which is a view as seen in a direction of arrows A-A in FIG. 8. However, when the cage  33  whose one part (around an upper part in FIG. 6) is formed in a somewhat elliptical shape in order to rotate the cage  33  synchronously with the outer race is press fitted to an inner peripheral face (a track face)  1   a  of the outer race  1 , the spring  34  will be locally deformed toward a center in a radial direction to a large extent, especially due to a repulsive force when the elliptical part is press fitted. Consequently, as shown in FIG. 10 which is a view as seen in a direction of arrows B-B in FIG. 9, urging force of the tongue pieces  34   t  of the spring  34  exerted on the sprags  35  which have been preloaded by the tongue pieces  34   t  of the spring  34  will be decreased, and at a position where the spring has been largely deformed, an inclined posture of the sprags  35  will be promoted to come into an idle rotation. As the results, there has been such a problem that on occasion of shifting from the idle rotation to an engaged position, an count of deformation of the tongue pieces  34   t  of the spring may be increased, and the tongue pieces  34   t  will be liable to be damaged, thus causing a defective engagement of the one-way clutch.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention has been made in order to solve the above described problem, and an object of the invention is to provide a one-way clutch in which spring force of tongue pieces of a spring will not be decreased, even in case where a larger tightening margin is provided between a cage and an outer race, but proper spring force can be maintained to attain reliable synchronization between the outer race and the cage, and a rise of cost will not be incurred.  
           [0009]    The invention has been made in order to solve the above described problems, and the invention as claimed in claim  1  is a one-way clutch comprising a cage, a spring arranged along an inner diameter side of the cage, and a plurality of sprags inserted into respective pockets in the aforesaid cage and the aforesaid spring, the aforesaid cage being press fitted to an inner peripheral face of an outer race,  
           [0010]    characterized in that corrugated parts are formed in annular portions of the aforesaid spring, and rigidity of the spring is increased in a part of the spring at a position where the largest repulsive force is exerted from the aforesaid cage, by partly overlapping one end portion of the spring on the other end portion, and that positioning of the overlapped portion of the spring is conducted by means of the corrugated part formed in the annular portion of the spring and an edge of the other end portion.  
           [0011]    The invention as claimed in claim  2  is characterized in that positioning of the overlapped portion of the aforesaid spring is conducted by means of the corrugated part formed in the annular portion of the spring and a bent portion formed at the edge of the other end portion so as to be curved along a Round portion from a foot to a crest of the corrugated part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is an enlarged side view of a part of a one-way clutch according to the invention;  
         [0013]    [0013]FIG. 2A is an enlarged plan view of a part of a spring constituting the invention, and FIG. 2B is a side view of the part of the spring;  
         [0014]    [0014]FIG. 3 is a perspective view of an entire structure of the spring which is employed in the invention;  
         [0015]    [0015]FIG. 4A is a side view of a part of the spring employed in the one-way clutch of the invention for explaining a position of an overlapped portion of the spring, and FIG. 4B is an enlarged view of an encircled part Q in FIG. 4A;  
         [0016]    [0016]FIGS. 5A and 5B are views showing a modified embodiment of the overlapped portion of the spring employed in the one-way clutch of the invention;  
         [0017]    [0017]FIG. 6 is a view showing a structure of a conventional one-way clutch including sprags, a cage and a ribbon spring;  
         [0018]    [0018]FIG. 7 is a side view showing another example of the conventional one-way clutch;  
         [0019]    [0019]FIG. 8 is a side view showing a further example of the conventional one-way clutch;  
         [0020]    [0020]FIG. 9 is a sectional view as seen in a direction of arrows A-A in FIG. 8; and  
         [0021]    [0021]FIG. 10 is a sectional view as seen in a direction of arrows B-B in FIG. 8.  
         [0022]    In the figures, a reference numeral  1  refers to an outer race;  2  to an inner race;  3  to a cage;  3   p  to a pocket of cage;  4  to a spring;  4   p  to a pocket of spring;  5  to a sprag; and  6  to an overlapped portion of spring. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Now, a specified embodiment of the invention will be described referring to the drawings.  
         [0024]    [0024]FIG. 1 is an enlarged side view showing a part of a one-way clutch according to the invention, FIG. 2A is an enlarged plan view of a part of a spring constituting the one-way clutch of the invention, and FIG. 2B is a side view of the part of the spring. It is to be noted that FIG. 2A is shown in a developed state in a longitudinal direction for facility of understanding, and that FIG. 2B is shown in a state where one of overlapped portions is detached from the other. FIG. 3 is a perspective view showing an entire structure of the spring which is employed in the invention.  
         [0025]    This one-way clutch includes a cage  3 , a spring (a ribbon spring)  4  disposed along an inner diameter side of the cage  3 , and a plurality of sprags  5 ,  5  . . . inserted into pockets  3   p ,  3   p , . . . of the aforesaid cage  3 . The one-way clutch is disposed in an annular space  10  between an outer race  1  and an inner race  2  (See FIG. 9). The aforesaid cage  3  is provided with a flange portion  3   f  at its one side. The flange portion  3   f  of the aforesaid cage  3  whose outer peripheral face  3   e  is press fitted to an inner peripheral face (a track face)  1   a  of the outer race  1  is partially formed in an elliptical shape (See an encircled part P in FIG. 8) so as to be reliably press fitted and secured. Although the following description will be made referring to a case in which a single cage  3  is employed, the invention can be also applied to the one-way clutch in which two cages, namely an outer cage and an inner cage are employed, as often used generally. Moreover, the aforesaid cage  3  may be provided with two flange portions at both sides thereof, but, in this case, an outer diameter of one of the flange portions should be smaller than an inner diameter of the outer race  1 .  
         [0026]    The aforesaid spring  4  has substantially the same shape as the cage  3  as shown in FIG. 3, and includes an annular portions  4   a ,  4   a  at both sides, pillar portions  4   b  interconnecting these annular portions ( 4   a ,  4   a ) at a constant interval in a circumferential direction, pockets  4   p ,  4   p  defined by these annular portions ( 4   a ,  4   a ) and the pillar portions  4   b  for positioning the sprags  5  therein, and tongue pieces  4   t  projected from the pillar portions  4   b  into the pockets  4   p  for urging the sprags  5 . The spring  4  is made of a thin metal plate by stamping to form the annular portions  4   a  having a ring-like shape, and corrugated parts  4   w ,  4   w , . . . are respectively formed in these annular portions  4   a . And, smooth parts are also formed between the corrugated parts. In addition, as described below, a part of one end portion  4   c  of this spring  4  is overlapped on a part of the other end portion  4   d  to form an overlapped portion  6  so as to give an increased rigidity. The overlapped portion  6  reinforces the spring  4  against the largest repulsive force exerted from the cage  3 .  
         [0027]    As has been described also in “Description of the Related Art”, when the flange portion  3   f  of the cage  3  is press fitted to the track face  1   a  of the outer race  1 , the elliptical part of the flange portion  3   f  of the cage  3  has the largest tightening margin, and an amount of deformation of the cage  3  becomes larger locally in this area. Usually, in such a case, an amount of deformation of the spring  4  which is disposed along the inner diameter side of the cage  3  will be decreased. Accordingly, an amount of deformation of the tongue pieces  4   t  of the spring  4  which press the sprags  5  in a locking direction will be also decreased, and thus, pre-load applied to the sprags  5  by the tongue pieces  4   t  will be decreased. In order to avoid such phenomenon, one end portion  4   c  of the spring  4  is overlapped on the other end portion  4   d  to form the partly overlapped portion  6  as shown in FIGS. 1 and 2, thereby increasing the rigidity (spring force) of the spring  4  (In FIG. 2, the one end portion and the other end portion are shown in a detached state for convenience of explanation). When the rigidity (spring force) of the overlapped portion  6  has increased in this manner, it will be possible to ensure an amount of the pre-load acting on the sprags  5  to such an extent that the sprags  5  may not be inclined more than required, even though the amount of deformation in the elliptical part (the upper part in FIG. 8) of the cage  3  has increased and the amount of deformation of the tongue pieces  4   t  of the spring  4  has decreased. As the results, the sprags  5  will not be largely deformed in a direction of idle rotation, so that all the sprags  5  can be operated synchronously as usual, even when they are shifted from the position of idle rotation to the engaged position.  
         [0028]    On occasion of providing the partly overlapped portion  6  by overlapping the one end portion  4   c  of the spring  4  on the other end portion  4   d , in a state where an edge  4   f  of the other end portion  4   d  is locked to a halfway of the end portion  4   c  of the one annular portion  4   a  as shown in an encircled part Q of FIG. 4A, the end portion  4   c  and the end portion  4   d  are always somewhat moved by spring action as shown in FIG. 4E, because the spring  4  is liable to be elastically deformed by nature. Consequently, the edge  4   f  of the other end portion  4   d  can not be secured, but will become easy to move in an unstable state. When the end portion  4   c  and the end portion  4   d  have moved in this manner, positioning of the sprag  5  will be made at the overlapped edges  4   e  of the pocket  4   p  and the pocket  4   p  which are respectively formed in the end portion  4   c  and the end portion  4   d  located in the back of the sprag  5  (see the encircled part Q in FIG. 4A). Thus, the sprag  5  located on the overlapped portion  6  of the spring  4  will receive the spring force from the overlapped edges  4   e  of the pockets  4   p  of the spring  4  which has been wrapped, and cannot move in harmonization with the other sprags. Then, as compared with those sprags located in the other pockets of the spring, a compelling force will be exerted on this sprag, and engaging ability of this sprag will be deteriorated.  
         [0029]    Under the circumstances, according to the invention, positioning of the overlapped portion  6  is conducted by abutting the edge  4   f  of the end portion  4   d  of the other annular portion  4   a  against a foot of the corrugated part  4   w  which is formed in the annular portion  4   a  of the one end portion  4   c  of the spring  4 , as shown in FIGS. 1 and 2. By thus conducting the positioning of the overlapped portion  6  of the spring  4  by abutment between the wave-form part  4   w  formed in the annular portion  4   a  of the end portion  4   c  and the edge  4   f  of the end portion  4   d  of the other annular portion  4   a , the sprag  5  located on the overlapped portion  6  of the spring will not receive a compelling force from the edges  4   e  of the pockets  4   p . Therefore, this sprag  5  can achieve a favorable state of engagement in the same manner as those sprags  5  on the other positions of the spring  4 .  
         [0030]    [0030]FIGS. 5A and 53 are views showing a modified embodiment for positioning the overlapped portion  6  of the spring  4 . Specifically, the overlapped portion  6  of the spring  4  is stabilized by abutting the edge  4   f  of the end portion  4   d  of the other annular portion  4   a  against the foot of the corrugated part  4   w  which is formed in the annular portion  4   a  of the one end portion  4   c  of the spring  4 , as described above. However, in this embodiment, the edge  4   f  of the other end portion  4   d  is further curved along a Round portion at the foot of the corrugated part  4   w  of the one end portion  4   c  of the annular portion  4   a  of the spring  4  up to a halfway thereof. By thus forming a bent portion in the edge  4   f  of the other end portion  4   d  so as to be curved along a crest of the corrugated part  4   w  of the one end portion  4   c  up to a halfway of the Round portion at the foot thereof, the overlapped portion  6  will be stabilized, and the back face of the sprag  5  will be free from the compelling force which is exerted from the edges  4   e  of the pockets  4   p  due to the overlapping of the spring  4 . Accordingly, it will be possible to ensure a favorable state of engagement of the sprag  5 .  
         [0031]    As described in detail herein above, according to is the one-way clutch of this invention, it is possible to reinforce the spring force of the tongue piece of the ribbon spring which is located at the position where the largest tightening margin is provided between the cage and the outer race. Moreover, because the sprag located on the overlapped portion of the spring will not be affected by the compelling force from the pockets, the sprag can be positioned in a stabilized state, and a favorable state of engagement can be always maintained.