Title of Invention

''CAM BLOCK AND ITS MANUFACTURING METHOD''

Abstract

A cam block made of metal having an arc-cam shape which is used for on/off control of a valve of an internal combustion engine. A thick plate-shaped metal material B to be worked is pressed by a punch 10 and a plate pressing member 11, received by a die 12 and a backward pressing member 13, and pressed, thereby shearing its outline into an arc-cam shape. Upon shearing, when the material (blank) B is pressed by the punch 10 and backward pressing member 13, a cylindrical convex portion 16a is formed on one plate surface of an extending portion 16 in accordance with a concave 10a of the punch 10, the other plate surface is punched by a projection 13b of the backward pressing member 13 to thereby form a shaft through-hole 17, and a concave portion 16b is also formed in a half-punching state on the back side of the material B corresponding to the convex portion 16a by a projection 13a. Unevenness of the thickness in the direction of an edge position 16c of the extending portion 16 is prevented. The occurrence of cut break surfaces on a punched cut surface is suppressed.

Full Text

The present invention relates to a cam block. The invention relates to a technique regarding a cam block made of metal and, more particularly, to a cam block which has an extending portion extending outwardly in one direction from a shaft through-hole for a cam shaft, is punched into an arc cam shape, and is suitable for use in on/off control or the like of, for example, an exhaust valve or an intake valve of an internal combustion engine and to a manufacturing method of such a cam block. Background Art Hitherto, a cam block which is used in, for example, an internal combustion engine of a motorcycle is generally constructed in a manner such that, for example, as shown in Fig. 5, a plate thickness is relatively thick, an outline having an extending portion 2 which extends outwardly in one direction from a shaft through-hole 1 has an arc cam shape, and the cam block is rotatably supported by inserting a cam shaft (not shown) into the shaft through—hole 1 by pressure. In the case of manufacturing such a thick cam block, usually that is called a fine blanking method is used. A material to be worked which has a thick plate shape and is made of metal is pressed by a punching operation and an outer peripheral plate pressing operation from one side and is also pressed by a die and an inner peripheral back pressing operation f 2:0m the opposite side, thereby punching the material into an arc cam shape provided with the shaft through-hole 1 and working the cam block. However, because of a specificity of the shape of the cam block such that the cam block is thick- and has the extending portion 2 which extends outwardly in one direction from a shaft through-hole 1, when pressure is applied, unevenness of the thickness in the direction of an edge position 2a shown by an arrow in Fig. 5 is caused in the extending portion 2. If the plate is cut in such an uneven state, in a shear cut surface, a defective shape (flatness, parallel degree) or a cut break surface is caused in each of a cam surface portion (a) near the edge position 2a of the extending portion 2 and an inner surface portion (b) near a hole edge position 2b of the shaft through-hole 1. There is consequently a problem such that in the shaft through-hole 1, a bore precision for cam shaft pressure insertion deteriorates and, in the cam surface portion, the position of contact with the follower such as a valve or the like is deviated and an operational precision deteriorates. It is, therefore, an object of the invention to solve the conventional problem, suppress the occurrence of a cut break surface on a punched cut surface at the time of a punching work of a cam block, prevent a deterioration of a bore precision of a shaft through—hole, and eliminate a deviation of a position of contact with a follower, thereby improving operational precision. Disclosure of Invention Accordingly the present invention relates to a cam block having an arc-cam-shaped outline, comprising: a shaft through-hole into which a cam shaft is inserted by pressure; and an extending portion which extends outwardly in one direction from said shaft through-hole, wherein two of said cam blocks made of metal each having a single thickness are positioned while shifting their phases by a predetermined angle and assembled to said cam shaft , thereby forming a cam assembly C, a convex portion is formed in one position in the vicinity of a top part of one plate surface of said extending portion , a concave portion is formed in one position in the vicinity of a too part of the other plate surface corresponding to the back side of said extending portion, and said two cam blocks are integratedly assembled. With the above construction, according to the invention, upon punching of the cam block, when the material to be worked is pressurized by the punch and the backward pressing member, unevenness of the thickness in the edge position direction of the extending portion is prevented by the concave and convex portions in the plate thickness direction. Thus, most of the punched cut surface becomes the shear cut surface. The occurrence of the cut break surfaces in the cam surface portion near the edge portion of the extending portion and the inner surface portion near An object of the invention to suppress the occurrence of a cut break surface on a punched cut surface at the time of a punching work of a cam block, prevent a deterioration of a bore precision of a shaft through-hole, and eliminate a deviation of a position of contact with a follower, thereby improving operational precision. Disclosure of Invention The invention is constructed as follows in order to accomplish the above object, the cam block according to the invention is constructed as follows. That is, the invention is characterized by a cam block having an arc-cam-shaped outline, comprising: a shaft through-hole into which a cam shaft is inserted by pressure; and an extending portion which extends outwardly in one direction from said shaft through-hole, wherein cwo of the cam blocks made of metal each having a single thickness are positioned while shifting their phases by a predetermined angle and assembled to the cam shaft, thereby forming a cam assembly, a convex portion is formed on one plate surface of said extending portion, a concave portion is formed on the other plate surface corresponding to the back side of the extending portion, xn the case where the concave and convex portions are seen in the cam axial direction, the concave and convex portions are arranged on a center line connecting a center of the shaft through-hole and an edge position of the extending portion existing at the farthest position from the center, that is, the concave and convex portions are formed in one intermediate position between the edge position and a hole edge position of the shaft through-hole that is nearest to the edge position, and said two cam blocks are integratedly assembled. With the above construction, according to the invention, upon punching of the cam block, when the material to be worked is pressurized by the punch and the backward pressing member, unevenness of the thickness in the edge position direction of the extending portion is prevented by the concave and convex portions in the plate thickness direction. Thus, most of the punched cut surface becomes the shear cut surface. The occurrence of the cut break surfaces in the cam surface portion near the edge portion of the extending portion and the inner surface portion near the hole edge position of the shaft through-hole is suppressed. Consequently, the deterioration of the bore precision of the shaft through-hole can be prevented, the deviation of the position of contact with the follower can be eliminated, and the operational precision can be improved. Moreover, since the concave and convex portions of the cam block are formed in the positions where the best balance can be obtained on the extending portion as mentioned above, the unevenness of the thickness in the edge position direction of the extending portion can be effectively prevented, the number of cut break surfaces occurring in the punched cut surface can be further reduced, and the bore can be finished at high precision. The invention is also characterized by a cam block having an arc-cam-shaped outline, comprising: a shaft through-hole into which a cam shaft is inserted by pressure; and an extending portion which extends outwardly in one direction from the shaft through-hole, wherein two of the cam blocks made of metal each having a single thickness are positioned while shifting their phases by a predetermined angle and assembled'to the cam shaft, thereby forming a cam assembly, a convex portion is formed in one position on one plate surface of the extending portion, a concave portion is formed in one position on the other plate surface corresponding to the back side of the extending portion, the forming positions on the extending portion where the concave and convex portions are formed are made different every different arc-cam shape, thereby enabling them to be discriminated, and the two cam blocks are integratedly assembled. Thus, in addition, the difference of the types of the cam blocks can be easily distinguished by the eyes at the time of the assembling work of the cam blocks, and the occurrence of the erroneous assembly can be easily and certainly prevented. Further, the cam block according to the invention is characterized in that in the case where the concave and convex portions are seen in the cam axial direction and a center line connecting a center of the shaft through-hole and an edge position of the extending portion existing at the farthest position from the center is used as a reference, the concave and convex portions are formed in positions within an angle range of about 10° to the right and left. Therefore, by forming the concave and convex portions at the positions where unevenness of the thickness mainly occurs upon punching work as mentioned above, unevenness of the thickness in the edge position direction of the extending portion can be effectively prevented. The number of cut break surfaces occurring on the punched cut surface can be further reduced. Subsequently, according to the invention, the above object can be accomplished with the following construction. That is the invention is characterized by a cam block manufacturing method whereby a thick plate-shaped material which is made of metal and should be worked is pressed by a punch and its outer peripheral plate pressing member, and the material is received by a die and its inner peripheral backward pressing member from an opposite side and pressed, thereby forming a shaft through-hole into which a cam shaft is inserted, said material is sheared into an arc-cam shape having an extending portion which extends outwardly in one direction from said shaft through-Mole, the cam block is punched, subsequently, two of the cam blocks each having a single thickness are positioned and supported while shifting their phases by a predetermined angle, and the cam shaft is inserted into the shaft through-hole by pressure, thereby forming a cam assembly, wherein when the material to be worked is pressed by the punch and the backward pressing member, a convex portion is formed in on Therefore, upon punching as mentioned above, when the material to be worked is pressed by the punch and backward pressing member, a convex portion is formed on one plate surface of the extending portion and a concave portion is formed on the other plate surface corresponding to the back side of the extending portion. Therefore, unevenness of the thickness in the edge position direction of the extending portion is prevented by the concave and convex portions in the plate thickness direction. Thus, most of the punched cut surface becomes the shear cut-surface. The occurrence of the cut break surfaces in the cam surface portion near the edge portion of the extending portion and the inner surface portion near the hole edge position of the shaft through-hole is suppressed. Thus, the deterioration of the bore precision of the shaft through-hole can be prevented, the deviation of the position of contact with the follower can be eliminated, and the operational precision can be improved. Further, a manufacturing method of a cam block according to the invention is characterized in that in the case where the concave and convex portions are seen in the cam axial direction and a center line connecting a center of the shaft through-hole and an edge position of the extending portion existing at the farthest position from the center is used as a reference, the concave and convex portions are formed in positions within an angle range of about 10° to the right and left. Therefore, by-forming the concave and convex portions at the positions where unevenness of the thickness mainly occurs upon punching work as mentioned above, unevenness of the thickness in the edge position direction of the extending portion can be effectively prevented. The number of cut break surfaces occurring on the punched cut surface can be further reduced. In addition, a manufacturing method of a cam block according to the invention is characterized in that in the case where the concave and convex portions are seen in the cam axial direction, the concave and convex portions are arranged on a center line connecting a center of the shaft through-hole and an edge position qf the extending portion existing at the farthest position from the center through-hole that is nearest to the edge position. Therefore, since the concave and convex portions of the cam block are formed in the positions where the best balance can be obtained on the extending portion as mentioned above, the unevenness of the thickness in the edge position direction of the extending portion can be effectively prevented, the number of cut break surfaces occurring in the punched cut surface can be further reduced, and the bore can be finished at high precision. A manufacturing method of a cam block according to the invention is characterized in that the forming positions on the extending portion where the concave and convex portions are formed are made different every different arc-cam shape, thereby enabling them to be discriminated. Therefore, the difference of the types of the cam blocks can be easily distinguished by the eyes at the time of the assembling work of the cam blocks, and the occurrence of the erroneous assembly can be easily and certainly prevented. Brief Description of Drawings Fig. 1 is an explanatory diagram showing a construction of a die for punching a cam block by a cam block manufacturing method of the invention. Fig. 2(A) is a front view of the cam block obtained after the punching work and Fig. 2(B) is a side sectional view. Fig. 3 is a perspective view of a cam block assembly which is obtained by assembling cams and used in an internal combustion engine. Fig. 4 is a front view showing a modification of a cam block. Fig. 5 is a perspective view showing a conventional cam block. Best Mode for Carrying Out the Invention An embodiment of the invention will be described hereinbelow further in detail with reference to the drawings. Fig. 1 shows an example of a die which is used in the case of punching a cam block by using a manufacturing method according to the invention. Figs. 2A and 2B show the cam block obtained by being punched by the manufacturing method of the invention. As such a cam block, for example, a cam block which is used for an opening/closing control of an exhaust valve or an intake valve of an internal combustion engine for a motorcycle will be explained. In Fig. 2, reference numeral 15 denotes a cam block made of metal and having an arc-cam-shaped outline. The cam block 15 has: a shaft through-hole 17 into which a cam shaft 20 (which will be explained hereinlater) made of metal is inserted by pressure; and an extending portion 16 which extends outwardly in one direction from the shaft through-hole 17. Particularly, a convex portion 16a is formed on one plate surface of the extending portion 16 of the cam block 15 and a concave portion 16b is formed on the other plate surface corresponding to the back side of the extending portion 16. As shown in Fig. 1, the die for punching the cam block 15 is fundamentally used in the case of finely shearing it by, for example, a fine blanking method. An upper die of the die has a punch 10 and a plate pressing member 11 arranged at an outer peripheral position thereof, and a lower die has a die 12, a backward pressing member 13 arranged at an inner peripheral position of a hole of the die 12, and the like. The plate pressing member 11 has an annular projection 11a on a pressurizing surface on the lower side. With respect to this die, particularly, the punch 10 has a shape such that a cylindrical concave 10a adapted to form the convex portion 16a is formed on the lower pressurizing surface corresponding to an outline curve of the cam block 15. The backward pressing member 13 which faces the punch 10 is formed in a shape such that a cylindrical projection 13a adapted to form the concave portion 16b is provided at the position corresponding to the concave 10a of the punch 10 and a cylindrical projection 13b adapted to punch the shaft through-hole 17 is provided. In the case of manufacturing the cam block 15 by using the die by the cam block manufacturing method of the invention, the punch 10 is moved downward together with the plate pressing member 11 by a pressing apparatus (not shown) and the annular projection 11a is thrust into the surface of a thick-plate-like material (blank) B which is made of metal and should be worked at a position around a shearing outline, thereby pressing the material B. On the other hand, the material B is received by the die 12 and backward pressing member 13 and pressed, thereby shearing the outline into an arc-cam shape also as shown in Fig. 2 and working the cam block 15. At the time of the shearing work, when the material B is pressurized by the punch 10 and backward pressing member 13, the cylindrical convex portion 16a is formed on one plate surface of the extending portion 16 in accordance with the concave 10a of the punch 10, the shaft through-hole 17 is formed by punching the other plate surface by the projection 13b of the backward pressing member 13, and at the same time, the concave portion 16b is formed on the back side of the convex portion 16a by half-punching the material B by the projection 13a. Upon shearing, since the concave and convex portions 16b and 16a are formed in the plate thickness direction of the extending portion 16, unevenness of the thickness in the direction of an edge position 16c of the extending portion 16 is prevented. Thus, most of the punching cut surface becomes a shear cut surface and the occurrence of cut break surfaces in both of a cam surface portion near the edge position 16c of the extending portion 16 and an inner surface portion near a hole edge position 17a of the shaft through-hole 17 is suppressed. Subsequently, after the punching step, the cam block 15 is positioned and supported by using a positioning tool (not shown) and the cam shaft 20 is inserted and penetrated by pressure into the shaft through-hole 17 as shown in Fig. 3. In the example shown in the diagram, two cam blocks 15 are positioned by deviating phases by a predetermined angle and assembled to the cam shaft 20 and a gear 21 is similarly assembled thereto, thereby forming a cam assembly C. When the cam assembly C is used in the internal combustion engine, a timing gear (not shown) attached onto a crank shaft which is rotated synchronously with an engine cycle is come into engagement with the gear 21, thereby rotating the cam shaft 20. The cam blocks 15 are rotated in accordance with the rotation of the cam shaft 20, thereby performing an opening/closing control of an exhaust valve or an intake valve. The concave and convex portions 16b and 16a of the cam block 15 are formed on the extending portion 16 as mentioned above. In this case, as shown in Figs. 2A and 2B, it is preferable that they are arranged on a center line S connecting a center 0 of the shaft through-hole 17 and an edge position 16c of the extending portion 16 existing at the farthest position from the center 0, that is, they are formed in intermediate positions on a line segment connecting the edge position 16c and the hole edge position 17a of the shaft through-hole 17 that is nearest to the edge position 16c. In the case where the concave and convex portions 16b and 16a are formed on the extending portion.16, for example, as shown in Fig. 4, it is preferable that the center line S is used as a reference and they are formed in positions within an angle range of, for example, about 10° to the right and left. Although each of the concave and convex portions 16b and 16a has the cylindrical shape, it can also have another proper shape like a prism or the like. Although not shown, according to the invention, it is also possible to discriminate the concave and convex portions 16b and 16a on the extending portion 16 by making the forming positions different every different arc-cam shape of the cam block. Thus, the user can easily distinguish a difference of the types of the cam blocks by the eyes at the time of the assembling work of the cam blocks, and the occurrence of an erroneous assembly can be prevented. Although the invention has been described with respect to the example of the cam blocks which are used in the internal combustion engine for a motorcycle and the manufacturing method of such cam blocks, the invention can be also widely applied to a case of a cam having an arc-cam shape which is used in any apparatus other than the internal combustion engine and a manufacturing method of such a cam block. Industrial Applicability As mentioned above, the invention is useful as a cam block made of metal which is used in various internal combustion engines for a motorcycle and the like and also suitable for manufacturing such a kind of cam block. Further, it is also useful as a cam block having an arc-cam shape which is used in any apparatus other than the internal combustion engine and suitable for manufacturing such a kind of cam block. We Claim: 1. A cam block (15) characterized by an arc-cam-shaped outline, comprising: a shaft through-hole (17) into which a cam shaft 20 is inserted by pressure; and an extending portion 16 which extends outwardly in one direction from said shaft through-hole (17), wherein two of said cam blocks (15-15) made of metal each having a single thickness are positioned while shifting their phases by a predetermined angle and assembled to said cam shaft (20), thereby forming a cam assembly C, a convex portion (16a) is formed in one position in the vicinity of a top part of one plate surface of said extending portion (16), a concave portion (16b) is formed in one position in the vicinity of a too part of the other plate surface corresponding to the back side of said extending portion (16), and said two cam blocks (15-15) are integratedly assembled. 2. A cam block (15) as claimed in claim 1, wherein the forming positions on said extending portion (16) where said concave and convex portions (16b 16a) are formed are made different every different are-cam shape, thereby enabling them to be discriminated, and said two cam blocks (15-15) are integratedly assembled. 3. A cam block as claimed in claim 1, wherein said concave and convex portions are seen in the cam axial direction and a centre line connecting a center of said shaft through-hole and an edge position of said extending portion existing at the farthest position from said center is used as a reference, said concave and convex portions are formed in positions within an angle range of 10° to the right and left. 4. A cam block (15) manufacturing method wherein a thick plate- shaped material B which is made of metal and should be worked is pressed by a punch (10) and its outer peripheral plate pressing member (11), and said material B is received by a die (12) and its inner peripheral backward pressing member (13) from an opposite side and pressed, thereby forming a shaft through-hole (17) into which. A cam shaft (20) is inserted, said material B is sheared into an arc-cam shape having an extending portion (16) which extends outwardly in one direction from said shaft through-hole (17), said cam block (15) is punched, subsequently, two of said cam blocks (15-15) each having a single thickness are positioned and supported while shifting their phases by a predetermined angle, and said cam shaft (20) is inserted into said shaft through-hole (17) by pressure, thereby forming a cam assembly C, characterized in that when the material B to be worked is pressed by said punch (10) and said backward pressing member (13), a convex portion (16a) is formed in one position in the vicinity of a top part of one plate surface on the punch side of said extending portion (16) and a concave portion (16b) formed in one position in the vicinity of a top part of said other plate surface corresponding to the back side of said extending portion (16), respectively. 5. A cam block manufacturing method as claimed in claim 5, wherein said concave and convex portions are seen in the cam axial direction and a center line connecting a center of said shaft through-hole and an edge position of said extending portion existing at the farthest position from said center is used as a reference, the concave and convex portions are formed in positions within an angle range of about 10° to the right and left. 6. A cam block manufacturing method as claimed in claim 5, wherein said concave and convex portions are seen in the cam axial direction, the concave and convex portions are arranged on a center line connecting a center of said shaft through-hole and an edge position of said extending portion existing at the farthest position from said center is used as a reference, that is, the concave and convex portions are formed in intermediate positions between said edge positions and a hole edge position of said shaft through-hole that is meant to said edge position. 7. A cam block manufacturing method as claimed in claim 5, wherein the forming positions on said extending portion where said concave and convex portions are formed are made different every different arc-cam shape, thereby enabling them to be discriminated. 8. A cam block substantially of the kind as herein described before with reference accompanying drawings. 9. A cam block manufacturing method substantially of the kind as herein before described before with reference to accompanying drawings.

Documents:

651-delnp-2003-abstract.pdf

651-delnp-2003-assignment.pdf

651-delnp-2003-claims.pdf

651-delnp-2003-complete specification (granted).pdf

651-DELNP-2003-Correspondence-Others.pdf

651-delnp-2003-correspondence-po.pdf

651-delnp-2003-description (complete).pdf

651-delnp-2003-drawings.pdf

651-delnp-2003-form-1.pdf

651-delnp-2003-form-19.pdf

651-delnp-2003-form-2.pdf

651-delnp-2003-form-3.pdf

651-delnp-2003-form-5.pdf

651-delnp-2003-form-6.pdf

651-delnp-2003-gpa.pdf

651-delnp-2003-pct-101.pdf

651-delnp-2003-pct-210.pdf

651-delnp-2003-pct-301.pdf

651-delnp-2003-pct-304.pdf