Title of Invention

A SPRAG TYPE ONE WAY CLUTCH

Abstract

A spring type oneway clutch comprises an outer race having an inner peripheral raceway surface and an inner race disposed within the outer race and having an annular outer peripheral raceway surfae the outer race and the inner race being redially spaced apart from each other and conocontrically disposedfor relative rotation a plurality of sprage disposed between the oute race and inner race for transmitting a torque between the outer peripheral raceway surface and inner peripheral raceway surface and annula retainer retaining the sprage and a sporing member holding the sprage between itself and the retainer and biasing the sprage in a maching direction and its characterised in that the retainer is provided with a cylinder portion having a radially exteneding window portion the sprage are fitted in the window portion for pivotal movement and the spring member is guided in a substantially circular form the outer peripheral surface of the cylinder portion.

Full Text

SPRAG TYPE ONE-WAY CLUTCH BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a one-way clutch used as a part, for torque transmission or back stop, for example, in the drive device of an automobile, a two-wheeled vehicle, an industrial machine or the like, and more particularly to a sprag type one-way clutch having a reduced number of parts. Related Background Art Generally, a sprag type one-way clutch provided with a sprag functioning as a cam, as shown in Figures 5 and 6 of the accompanying drawings, comprises an annular wire cage 60, a plurality of sprags 20 held by the wire cage, an annular spring 30 engaged with grooved formed in the sprags 20 and holding the sprags 20 between itself and the wire cage 30, and two side plates 40 and 50 holding the sprags 20 between the axial opposite ends thereof. An inner race is fitted to the inside of the wire cage 60, and the outer peripheral surface of the inner race is in contact with the inner sides of the sprags 20. Also, an outer race is fitted to the outside of j the wire cage so as■to contact with the outer sides of the sprags 20. As a result, the transmission of a torque is effected between the inner and outer races through the sprags 20. In Figures 5 and 6, the inner race and the outer rfece are not shown. In such a sprag type one-way clutch according to the prior art, however, the number of parts is great and recent severe requirements in terms of manufacture and cost could not i be coped with. If in order to meet such requirements, for example, the number of sprags is decreased, the guiding property of the spring will become bad because the grooves in the sprags provide a guide for the spring, and it will become difficult to keep the entire spring in a circular state and as a result, there will be the possibility that a sufficient biasing force in a meshing direction which acts on the sprags are not obtained. In this case, there arises the problem that the meshing engagement between the outer peripheral surface of the inner race and the sprags and between the inner peripheral surface of the outer race and the sprags becomes bad and also the durability of the spring is spoiled. SUMMARY OF THE INVENTION Accordingly, it is the object of the present invention to provide a sprag type one-way clutch in i which the number of parts can be decreased as compared with the prior art and the guiding property of a spring holding sprags between it and a retainer can be improved and the meshing engagement between the outer peripheral surface of an inner race and the sprag and between the inner peripheral surface of an outer race and sprags becomes reliable and also the durability of the spring is not spoiled. To achieve the above object, the sprag type one¬ way clutch of the present invention is a sprag type one-way clutch comprising an outer race having an inner peripheral raceway surface and an inner race disposed within the outer race and having an annular outer peripheral raceway surface, the outer race and the inner race being radially spaced apart from each other and concentrically disposed for relative rotation, a plurality of sprags disposed between the outer race and the inner race for transmitting a torque between the outer peripheral raceway surface and the inner peripheral raceway surface, an annular retainer retaining the sprags, and a spring member holding the sprags between itself and the retainer and biasing the i sprags in a meshing direction, characterized in that the retainer is provided with a cylinder portion having a radially extending window portion, the sprags are fitted in the window portion, and the spring member is guided in a substantially circular form by the outer peripheral surface of the cylinder portion. According to the present invention, the retainer functions as side plates and a wire cage at a time and therefore, the number of parts can be decreased and also, the spring can be guided by the cylinder portion of the retainer and therefore, the circularity of the spring is improved and any reduction in the basing force thereof does not result and thus, the meshing engagement of the sprags becomes reliable and the durability of the spring is also improved. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an axial front view of a sprag type one-way clutch according to an embodiment of the present invention. Figure 2 is a radial cross-sectional view of the sprag type one-way clutch of Figure 1 with an outer race and an inner race omitted. Figure 3 is a cross-sectional view showing a first example of the shape of the window portion of a retainer applicable to the embodiment of Figure 1. Figure 4 is a cross-sectional view showing a second example of the shape of the window portion of the retainer applicable to the embodiment of Figure 1. Figure 5 is an axial front view showing an example of the sprag type one-way clutch according to the prior art. Figure 6 is a radial cross-sectional view of the sprag type one-way clutch of Figure 5. Figure 7 is a qross-sectional view showing a third example of the shape of the window portion of the retainer applicable to the embodiment of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will hereinafter be described in detail with reference to the drawings. Of course, an embodiment which will hereinafter be described is illustrative of the present invention and does not restrict the present invention. Throughout the drawings, like portions are designated by like reference-characters. Figure 1 is a front view of a sprag type one-way clutch 10 according to an embodiment of the present invention as it is steen from the axial direction thereof. The sprag type one-way clutch 10 is provided with an outer race 4 indicated by a phantom line, and an i inner race 5 disposed concentrically with the outer race 4, and comprises a plurality of sprags 2 disposed between the outer peripheral raceway surface of the inner race 5 and the inner peripheral raceway surface of the outer race 4, an annular retainer 1 holding the sprags 2 equidistantly in the circumference thereof, and a spring 3 holding the sprags 2 between itself and the retainer 1. •> As is apparent from Figure 2, the retainer 1 is provided with a cylinder portion 1c, and an annular flange portion la integrally and radially outwardly extending from an axial end of the cylinder portion lc. The cylinder portion lc is provided with a window portion Id radially extending therethrough at predetermined positions equidistant in the circumferential direction thereof, and the sprags 2 are fitted in this window portion Id. The flange portion la of the retainer 1 is formed two cut-aways lb cut in from the radial edge portion thereof to the cylinder portion lc. The cut-aways lb are offset outwardly from the outer periphery of the flange portion la and therefore, a portion lb' sandwiched between the cut-aways lb of the flange portion la is in contact with the outer race 4 to thereby prevent the rotation of the retainer 1 relative to the outer race 4. As shown in Figure 2, each sprag 2 is formed with a groove 2a formed therethrough in the circumferential direction on the cam surface 2b (see Figures 3 and 4) side thereof, and the spring 3 is guided and mounted in these grooves 2a. The spring 3 is of a continuous annular close contact coil type, and at the other locations than the grooves 2a of the sprags 2, it holds the sprags 2 between itself and the retainer 1 while being guided and held by the outer peripheral surface of the cylinder portion lc of the retainer 1. l' As described above the spring 3 holding the sprags 2 is guided also by the outer peripheral surtace 01 uie cylinder portion 1c of the retainer 1 and therefore, the circularity of the spring 3 can be improved, and the guiding property of the spring 3 is improved. That is, the cylinder portion lc of the retainer 1 and the grooves 2a of the sprags 2 guide the spring 3 and therefore, even when the number of the sprags 2 is increased or decreased to set a necessary torque capacity arbitrarily, the spring 3 is always in a circular state and the one-way clutch 10 can secure reliable meshing performance. It is also possible to use any other spring than a coil spring as the spring 3. Description will now be made of the sprags 2 which are torque transmitting members in the sprag type one¬way clutch 10. Each sprag 2, as shown in Figures 1 to 4 and 7, is of a cylindrical shape having a portion thereof having a predetermined thickness in the axial direction thereof cut away. As shown in Figures 3 and 4, the sprag 2 is provided with a cam portion 2b comprised of an irregular curve having a portion of the circumference thereof broken away when it is seen from the front thereof, and the cam portion 2b is designed to be opposed to and contact with the inner peripheral surface of the outer race 4. The portion opposed to the cam portion 2b of the sprag is a substantially circular portion 2c, which is designed to be opposed to and contact with the outer peripheral raceway surface of the inner race 5. The circular portion 2c of the sprag 2, as shown in Figures 3 and 4, is fitted in the window portion id of the retainer 1 for pivotal movement in the circumferential direction thereof. When the sprag 2 pivotally moves in the window portion Id of the retainer 1, the circular portion 2c of the sprag 2 slidably contacts with the opposed two circumferential edge portions le of the window portion Id. As can be seen from a first example shown in Figure 3, the circular portion 2c of the sprag 2 is in slidable contact with the circumferential edge portions le with a length corresponding substantially to the thickness of the circumferential edge portions le of the window portion Id. Design is made such that the curvature of the circular portion 2c and the curvature of the circumferential edge portions le are substantially egual to each other. Also, the end portions of the opposed two circumferential edge portions le of the window" portion Id of the retainer according to a second example shown in Figure 4 are bent radially inwardly to form bent portions If, whereby there can be formed circumferential edge portions lg longer than the circumferential edge portions le shown in Figure 3. Design is made such that the curvature of the circular portion 2c and the curvature of the circumferential edge portions lg are substantially equal to each other. As is apparent from the foregoing description, the sprags 2 are contained in the window portion Id of the retainer 1 and are designed such that they can pivotally move in the circumferential direction, but hardly pivotally move in the axial direction. The circumferential edge portions le and lg described above, as compared with the relation between the sprags 20 and the wire cage 60 in Figure 5 showing the one-way clutch according to the prior art, have the following effect. In Figure 5, the circular portions of the sprags 20 bear against the wire cage only on a line. In contrast, in Figures 3 and 4 which shows the embodiment of the present invention, the sprags 2 contact with the circumferential edge portions le and lg of the window portion Id of the retainer 1 not on a line, but on a plane and therefore, the sprags 2 can smoothly and reliably pivotally move relative to the window portion Id of the retainer 1. Particularly when design is made as shown in Figure 4, the slidable contact surface between the circular portions 2c of the sprags 2 and the circumferential edge portions le and lg of the retainer 1 can be secured longer and therefore, the sprags 2 can more smoothly and reliably pivotally move relative to the witidow portion Id of the retainer 1. In the embodiment shown in Figures 3 and 4, the circular portion 2c of the sprag 2 and the circumferential edge portions le and lg of the window portion of the retainer are of shapes complementary to each other. Of course, the circular portion 2c of the sprag 2 need not always be circular, but may by of any other shape which has a smooth curve. Also, of course, in the present embodiment, the object of the present invention is achieved even by a shape in which the window portion Id of the retainer 1 remains radially punched by press as in a third example shown in Figure 7. According to the sprag type one-way clutch of the present invention described above, there are obtained the following effects. The window portion of the retainer performs the functions of the side plates and the wire cage in the prior art at a time and therefore, the number of parts decreases as compared with the prior art. The retainer is provided with the cylinder portion i > having a radially extending window portion and the sprags are fitted in the window portion, and the spring is guided by the outer peripheral surface of the cylinder portion and.therefore, the circularity of the spring can be improved and the spring can be guided well by the sprags and the cylinder portion of the retainer to thereby make the biasing force contact. Further, the spring is not deformed and therefore, the durability of the spring is improved and the operation including the meshing operation of the one-way clutch becomes stable. Also, according to the embodiment, the circumferential portions of the window portion of the retainer are made into a predetermined construction and therefore, the pivotal movement of the sprags takes place smoothly and accurately. WE CLAIM: 1. A sprag type one-way clutch comprising an outer race having an inner peripheral raceway surface and an inner race disposed within said outer race and having an annular outer peripheral raceway surface, said outer race and said inner race being radially spaced apart from each other and concentrically disposed for relative rotation, a plurality of sprags disposed between said outer race and said inner race for transmitting a torque between said outer peripheral raceway surface and said inner peripheral raceway surface, an annular retainer retaining said sprags, and a spring member holding said sprags between itself and said retainer and biasing said sprags in a meshing direction, characterized in that said retainer is provided with a cylinder portion having a radially extending window portion, said sprags are fitted in said window portion for pivotal movement, and said spring member is guided in a substantially circular form by the outer peripheral surface of said cylinder portion. 2. The sprag type one-way clutch according to claim 1, wherein circumferentially extending grooves are formed in the outer peripheral surfaces of said sprags, and said spring is fitted in said grooves. 3. The sprag type one-way clutch according to claim 1, wherein said retainer is provided with an annular flange portion extending radially outwardly from one end of said cylinder portion, and said flange portion is formed with a cut-away. 4. The sprag type one-way ciutch according to claim 1, wherein two edge portions opposed to each other in the circumferential direction of said window portion of said retainer has a shape complementary to the configuration of said sprags. 5. A sprag type one-way ciutch, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

2288-mas-1996 abstract.jpg

2288-mas-1996 abstract.pdf

2288-mas-1996 claims.pdf

2288-mas-1996 correspondence others.pdf

2288-mas-1996 correspondence po.pdf

2288-mas-1996 description (complete).pdf

2288-mas-1996 drawings.pdf

2288-mas-1996 form-26.pdf

2288-mas-1996 form-4.pdf

2288-mas-1996 form-9.pdf

2288-mas-1996 petition.pdf