Method for manufacturing a one-way clutch cage

Abstract: A method for manufacturing a one-way clutch cage allows slits of the cage to be punched out with a short punching distance wherein the slits are narrow in width and less prone to deformation. In this method for manufacturing a one-way clutch cage, after slits 8, 10, 11, 12 have been punched out, windows 17 are punched out and then an outer annular part 18 is cut. Therefore, since slits can be formed in a cylindrical member 2 that has not yet been subjected to the window punch-out process or the outer annular part cut-out process and that is in a sufficient strength state, a diagonal punching that a boundary portion between a cylindrical portion 3 and an outer flange 5 is punched out from radial diagonal inside toward radial diagonal outside can be used to form the slits. Thus, the punching distance can be shortened, the punching die can be thinned in thickness and the slit width can be reduced, as compared with the horizontal punching.

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a one-way clutch cage to be used in, for example, transmissions of automobiles or the like. Conventionally, there has been a method for manufacturing a one-way clutch cage as shown in Figs. 4A to 4F. In this manufacturing method, first, as shown in Fig. 4A, a disc 101 is punched out from a metal plate. Next, as shown in Fig. 4B, central part of the disc 101 is drawn by drawing process and a bottom thereof is punched out, by which a circular-cylindrical member 102 is formed. This cylindrical member 102 is composed of a cylindrical portion 103 and an outer flange 105 located at an axial end of the cylindrical portion 103. Next, as shown in Fig. 4C, a plurality of windows 107, 107, ... are punched out in the cylindrical portion 103 of the cylindrical member 102 so as to be circumferentially spaced from one another with specified intervals. Subsequently, as shown in Fig. 4D, an outer annular part 106 ranging from the radially outermost rim to a radially inward place by a specified length is punched out of the outer flange 105 of the cylindrical member 102. Next, as shown in Figs. 4E and 5C, circumferential four places of the cylindrical member 102 are punched out from inside to outside, so that slits 108 ranging across the outer flange 105 to the windows 107 are formed. One window 107 is sandwiched by one pair of adjacent slits 108, 108, while another window 107 opposite to the one window 107 is sandwiched by the other pair of adjacent slits 108, 108. Next, as shown in Fig. 4F, pillars 110, 110 beside the window 107 sandwiched by aforementioned one pair of slits 108, 108 are tilted radially outward so that a rim portion 111 sandwiched by the pair of slits 108, 108 is protruded radially outward. This rim portion 111 protruded radially outward, when the one-way clutch is assembled to an outer ring (not shown), presses the inner circumferential surface of the outer ring so that a cage 112 is frictionally coupled to the outer ring. The above-described method for manufacturing a one-way clutch cage, unfortunately, has the following problems (1), (2) and (3): (1) In the slit punch-out process of Fig. 4E, because a punch 200 is thrust out from radial inside to radial outside to form the slits 108 as shown in Figs. 5B and 5C, it is necessary to add, as the punching distance, a disc thickness t to a radial distance D of the outer flange 105 resulting after the cutout of the outer annular part 106. A long punching distance causes a need of increasing the punching width in terms of the punching die life, which in turn makes the slit width wider so that another cage is more likely to catch in this slit, resulting in a disadvantage of difficulty in handling. Also, a wide slit width causes a lower strength so that the cage becomes prone to deformation as another disadvantage; (2) As shown in Fig. 5A, in the slit punch-out process, there is a tendency toward occurrence of burrs in the windows 107 as a disadvantage; and (3) In the slit punch-out process, because of a large slit width as described in paragraph (1), the windows 107 are prone to deformation so that when the cage is assembled to a one-way clutch, the sprag deteriorates in operation and the one-way clutch deteriorates in performance as a disadvantage. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a one-way clutch cage which method allows cage slits to be punched out with a short punching distance and in which method the slits are narrow in width and less prone to deformation. Another object of the present invention is to provide a method for manufacturing a one-way clutch cage in which method the slit punch-out process does not cause occurence of burrs at the windows. The method of the invention is defined by claim 1. According to the invention, there is provided a method for manufacturing a one-way clutch cage, comprising: a slit forming step for punching out slits in a cylindrical member having a cylindrical portion and an outer flange at an axial end of the cylindrical portion so that the slits are formed by punching out a boundary portion between the cylindrical portion and the outer flange from radial diagonal inside toward radial diagonal outside, namely radially inward from a place which is inner than an outer edge of the outer flange by a specified distance and axially from the axial end of the cylindrical portion to a specified distance; and an outer flange cutting step for, after the slit forming step, cutting an outer annular part out of the outer flange so that the outer annular part extends from the radially outermost end of the outer flange to a place which is radially inner than a radially outermost end of the slits by such a distance that the slits are opened in radial outside direction. In this invention, slits are punched out before the step of cutting the outer flange. Therefore, the slits can be formed by punching out a boundary portion between the cylindrical portion and the outer flange (i.e., a portion between the later-cut outer annular part and the windows) from radial diagonal inside toward radial diagonal outside. In the case where the slit punch-out is done after the cutting of the outer annular part of the outer flange as in the prior art, the diagonal punch-out of slits is impermissible because of a lack of strength that would lead to deformation. In this invention, since the diagonal punch-out is enabled, the punching distance can be shortened as compared with such horizontal punching as the prior art. This allows the punching die to be thinned in thickness and the slit width to be lessened, making it unlikely that other cages catch in the slits, resulting in an improved handleability. Besides, by virtue of the narrowed slit width, the cage can be improved in strength and prevented from deformation so that the one-way clutch can be improved in performance. One embodiment further comprises a window punch-out step for, after the slit forming step and before the outer flange cutting step, punching out in the cylindrical portion a plurality of windows including windows that are continuous to the slits, so that the windows are circumferentially spaced from one another with specified intervals. In this embodiment, since the windows are formed after the formation of the slits, there occur no burrs at the windows due to the slit formation. In one embodiment, when the slits are formed in the slit forming step, at least one cutout for chucking positioning is formed in the outer flange of the cylindrical member. In this embodiment, in the slit forming step, at least one cutout for chucking positioning is formed. These chucking positioning cutout can be used in later steps of a window punch-out process and an outer-ring cutting step. Therefore, the number of times of positioning can be reduced so that a reduction in manufacturing time as well as a simplification of processes can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: Figs. 1A, 1B, 1C, 1D, 1E and 1F are process diagrams for explaining an embodiment of a method for manufacturing a one-way clutch cage according to the present invention; Fig. 2A is a view showing a state in which slits have been punched out radially in the embodiment, and Fig. 2B is a view showing a state in which slits have been punched out parallel; Fig. 3A is a schematic view showing direction and range for slit punch-out in the embodiment, Fig. 3B is a perspective view of a cylindrical member in which a pair of slits and a pair of chucking cutouts have been formed, and Fig. 3C is a schematic view partly showing a state in which an outer ring of an outer flange is cut out; Figs. 4A, 4B, 4C, 4D, 4E and 4F are process diagrams for explaining a method for manufacturing a one-way clutch cage according to the prior art; and Fig. 5A is a schematic view showing a state, as viewed axially, in which slits are punched out with a punch in the prior art example, Fig. 5B is a sectional schematic view showing a state of the punching, as viewed circumferentially, and Fig. 5C is a view including a view partly showing a cylindrical member in which the slits have been punched out, as viewed axially, and a view showing a state of the cylindrical member as viewed sideways. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinbelow, the present invention is described in detail by an embodiment thereof illustrated in the accompanying drawings. Referring to Figs. 1A, 1B, 1C, 1D, 1E and 1F in order, an embodiment of the method for manufacturing a one-way clutch cage according to the present invention is explained. First, as shown in Fig. 1A, a disc 1 is punched from a specified metal plate. Next, as shown in Fig. 1B, central part of the disc 1 is drawn by drawing process and a bottom thereof is punched out, by which a circular-cylindrical member 2 is formed. This cylindrical member 2 is composed of a cylindrical portion 3 and an outer flange 5 located at an axial end of the cylindrical portion 3. Next, as shown in Fig. 1C, in the outer flange 5 of the cylindrical member 2, two generally semicircular cutouts 6, 7 are formed, and four slits 8, 10, 11, 12 are formed. The cutouts 6 and 7 are cutouts which are used for chucking positioning and shifted from each other by approximately 180° in circumferential position in the outer flange 5. Fig. 3A shows a state in which the slit 8 out of the four slits 8 to 12 is punched out with a punch 15. This punch 15 punches out the slit 8 from radial diagonal inside toward radial diagonal outside. This slit 8 is punched out so as to stretch to the part of a window 17, which will be formed in a later process, and an outer annular part 18, which will be cut out in a later process. Such a diagonal punch-out process allows the punching distance S (see Fig. 3A) to be reduced as compared with the conventional horizontal punch-out process as shown in Fig. 5B. Accordingly, the punching die can be thinned in thickness so that the slit 8 can be reduced in width, thus making it unlikely that another cage catches in the slit, resulting in an improved handleability. Also, by the slit 8 being thinned in width, the cage can be improved in strength and prevented from deformation so that the behavior of sprags to be fitted to the cage can be stabilized and that the performance of the one-way clutch can be improved. In addition, the case with the slit 8 is the same also with the slits 10, 11 and 12. Next, as shown in Fig. 1D, the outer flange 5 is positioned and chucked by making use of the cutouts 6 and 7 serving for chucking positioning, and then a window punch-out process is performed. In this window punch-out process, a plurality of windows 17 are formed in the cylindrical portion 3 of the cylindrical member 2 so as to be spaced circumferentially from one another with specified intervals. Into these windows 17, the sprags of the one-way clutch are fitted, respectively. Since the window punch-out process is done after the formation of the slit 8 as shown above, there occur no burrs at the windows 17 by the slit punch-out process. Therefore, the sprag (not shown) can be smoothly held in the windows 17. Next, the outer annular part 18 of the outer flange 5 is punched out as shown in Figs. 1E and 3C. This outer annular part 18 ranges from the radially outermost end of the outer flange 5 to a place P that is radially inner than the radially outermost end of the slits 8, 10, 11, 12 by a specified extent. By the punch-out of this outer annular part 18, the windows 17 communicating with the slits 8, 10 and 11, 12 are opened through to outside of the outer flange 5. In this embodiment, since the cutouts 6, 7 for chucking positioning formed in the slit punch-out process can be utilized in the window punch-out process and the outer ring cutting process, the number of times of positioning can be reduced so that a reduction of manufacturing time as well as a simplification of processes can be achieved. Next, as shown in Fig. 1F, pillars 21, 22 beside the window 17 located between the slits 8 and 10 are tilted radially outward so that a rim portion 23 sandwiched by the pair of slits 8 and 10 is protruded radially outward. Also, pillars 25, 26 beside another window 17 located between the slits 11 and 12 are tilted radially outward so that a rim portion 27 sandwiched by the pair of slits 11 and 12 is protruded radially outward. The rim portions 23, 27 thus protruded radially outward, when the one-way clutch is assembled to an outer ring, presses the inner circumferential surface of the outer ring so that the cage is frictionally coupled to the outer wheel. In this embodiment, the slits 8, 10, 11, 12 have been punched out radially as shown in Fig. 2A. However, it is also possible to punch out slits 41, 42 and 43, 44 parallel to each other as shown in Fig. 2B.

Claims: A method for manufacturing a one-way clutch cage, comprising: a slit forming step for punching out slits (8, 10, 11, 12, 41, 42, 43, 44) in a cylindrical member (2) having a cylindrical portion (3) and an outer flange (5) at an axial end of the cylindrical portion (3) so that the slits (8, 10, 11, 12, 41, 42, 43, 44) are formed by punching out a boundary portion between the cylindrical portion and the outer flange (5) from radial diagonal inside toward radial diagonal outside namely radially inward from a place which is inner than an outer edge of the outer flange (5) by a specified distance and axially from the axial end of the cylindrical portion (3) to a specified distance; and an outer flange cutting step for, after the slit forming step, cutting an outer annular part (18) out of the outer flange (5) so that the outer annular part (18) extends from the radially outermost end of the outer flange (5) to a place which is radially inner than a radially outermost end of the slits (8, 10, 11, 12, 41, 42, 43, 44) by such a distance that the slits are opened in radial outside direction. The method for manufacturing a one-way clutch cage according to claim 1, further comprising: a window punch-out step for, after the slit forming step and before the outer flange cutting step, punching out in the cylindrical portion (3) a plurality of windows (17) including windows that are continuous to the slits (8, 10, 11, 12, 41, 42, 43, 44), so that the windows are circumferentially spaced from one another with specified intervals. The method for manufacturing a one-way clutch cage according to claim 1, wherein when the slits (8, 10, 11, 12, 41, 42, 43, 44) are formed in the slit forming step, at least one cutout (6, 7) for chucking positioning is formed in the outer flange (5) of the cylindrical member (2). The method for manufacturing a one-way clutch cage according to claim 2, wherein when the slits (8, 10, 11, 12, 41, 42, 43, 44) are formed in the slit forming step, at least one cutout (6, 7) for chucking positioning is formed in the outer flange (5) of the cylindrical member (2).

Inventors: IKEDA TAKAAKI, KAMIJI MICHIYUKI, MAEDA HIROYUKI, NUMATA TETSUAKI, IKEDA, TAKAAKI, KAMIJI,MICHIYUKI, MAEDA, HIROYUKI, NUMATA, TETSUAKI, Ikeda, Takaaki, c/o Koyo Seiko Co.,Ltd., Kamiji,Michiyuki, c/o Nakanishi Metal Works Co.Ltd, Maeda, Hiroyuki, c/o Nakanishi Metal Works Co.Ltd., Numata, Tetsuaki, c/o Koyo Seiko Co.,Ltd.
Applicants: KOYO SEIKO CO, NAKANISHI METAL WORKS CO, KOYO SEIKO CO., LTD., NAKANISHI METAL WORKS CO., LTD.
Application year: 1999
Main classification: B21D53
IPC codes: B21D53, F16D41