JP2005188654A - Method of manufacturing cam lobe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a cam lobe at a low cost by further reducing the weight of the cam lobe while dispensing with conventionally required broaching of the inner peripheral surface of a shaft hole of the cam lobe in assembling the cam lobe to a camshaft of an automobile or the like, thereby dissolving a crack initiated when assembling the cam lobe to the inner peripheral surface of the shaft hole. <P>SOLUTION: The hole shape 5 of the shaft hole 2 for fitting and locking the cam lobe 1 to the outer periphery of the camshaft to stop whirling in assembling the cam lobe 1 to the camshaft is formed in elliptic shape, and thin-walled parts 7 formed of recesses whose depth from a plate face 4 of a cam lobe tip part 3 is 20-25% of plate thickness 4 of the cam lobe 1, are formed on both sides of the plate face 4 of the cam lobe tip part 3. Further, a cam lobe outer peripheral surface 16 on one side of the plate face 4 of a shaft hole peripheral edge part 6 on the opposite side to the cam lobe tip part 3 with respect to the shaft hole 2 is thinned to form a thin-walled part 7 with a width reaching 48-52% of the width from the cam lobe outer peripheral surface 16 to a shaft hole inner peripheral surface 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a material for a lightened cam lobe, which is an automotive part, and more particularly to a cam lobe used for an assembly camshaft.

  In a camshaft in which a cam lobe assembled and used for an engine of an automobile is fitted and locked, a material for the cam lobe is manufactured by hot forging. By the way, when manufacturing this cam lobe, the inner surface shape of the shaft hole for fitting and locking the cam shaft of the cam lobe is formed into a circular shape by forging, and then broaching is performed on the inner peripheral portion of this circular shaft hole, This broached cam lobe was inserted into the camshaft and pressed to assemble. By the way, when the cam lobe and the camshaft are assembled, there is a problem that cracks frequently occur in the inner surface shape portion of the shaft hole in which the cam lobe is broached.

  On the other hand, for example, a plurality of concave portions are formed on the inner peripheral surface of the shaft hole of the cam lobe into which the cam shaft is inserted, and after the cam lobe is fitted on the cam shaft made of a hollow tube, the hollow tube is expanded. By assembling to the inner peripheral surface of the shaft hole of the cam lobe, an assembled cam shaft was obtained (for example, see Patent Document 1). By the way, this mechanism has a plurality of concave portions on the inner peripheral surface of the shaft hole into which the camshaft is inserted by broaching, and is not in pressure contact like the above-described conventional one. However, a plurality of convex portions that can be fitted into a plurality of concave portions provided in the shaft hole of the cam lobe need to be formed on the outer periphery of the cam shaft in advance instead of being pressed. Further, as described above, after the cam lobe is fitted on the camshaft of the hollow tube, the hollow tube of the camshaft is expanded by the tube expansion punch, and the convex portion is not fitted to the concave portion of the shaft hole. There has been a problem that the number of processes is complicated.

JP 2000-326028 A

  The problem to be solved by the present invention is that a cam lobe used for a camshaft of an automobile or the like is manufactured by hot forging. It is an object of the present invention to provide a method for eliminating the need for broaching, eliminating the occurrence of cracks due to the broached portion that occurs when the cam lobe is assembled to the camshaft, and reducing the weight of the cam lobe at a low cost.

  According to a first aspect of the present invention, there is provided a shaft for externally fitting and locking the cam lobe 1 to the cam shaft for the purpose of preventing rotation when the cam lobe 1 is assembled to the cam shaft. The hole shape 5 of the hole 2 is an elliptical shape, and the plate surface 4 of the cam lobe tip 3 and the plate surface 4 of the shaft hole peripheral portion 6 opposite to the cam lobe tip 3 are formed in the thin portion 7. It is the manufacturing method of the cam lobe 1 characterized by performing a thinning process.

  In the invention of claim 2, the thinning process for forming the plate surface 4 of the cam lobe tip 3 on the thin portion 7 is performed by setting the depth of the cam lobe tip 3 from the plate surface 4 to 20 to 25% of the plate thickness 4 of the cam lobe 1. The method of manufacturing the cam lobe according to claim 1, wherein the thin-walled portion 7 made of a depression is formed on both sides of the plate surface 4.

  In the invention of claim 3, the thinning process for forming the plate surface 4 of the shaft hole peripheral portion 6 of the cam lobe 1 into the thin portion 7 is performed on the plate surface 4 of the shaft hole peripheral portion 6 of the cam lobe 1 from the cam lobe outer peripheral surface 16 to the shaft hole. 3. The cam lobe 1 according to claim 1 or 2, wherein the thin portion 7 having a width of 48 to 52% of the width to the inner peripheral surface 15 is formed on the outer peripheral surface 16 of the cam lobe on one side of the plate surface 4. Is the method.

  According to the present invention, the hole shape of the inner peripheral surface of the shaft hole, which is the outer fitting portion of the cam lobe that is externally fitted and locked to the camshaft, is made elliptical, so that the broaching of the inner peripheral surface of the shaft hole required in the conventional cam lobe is performed. This eliminates the need for cracks on the inner surface of the cam lobe shaft, which was frequently encountered when assembling broached products to the camshaft, and simplifies the shape of the cam lobe. The present invention has excellent effects, such as being able to manufacture at a low cost with a horizontal hot high-speed forging machine that can be manufactured with increased productivity and a lighter cam lobe.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a cam lobe according to the present invention. FIG. 2 is a side view of the cam lobe cut along AA in FIG.

  First, the steel bar used as a raw material is heated, then cut and upset, and hot forged to obtain the cam lobe 1 in which the elliptical shaft hole 2 and the thin portion 7 are formed. This hot forging is performed by a horizontal high-speed forging device.

  The manufacturing method of the cam lobe 1 of the present invention using the horizontal high-speed forging device will be described in more detail. In the invention according to claim 1, the cam lobe 1 is formed with a shaft hole 2 for externally locking the cam lobe 1 to the cam shaft for the purpose of preventing rotation when assembled to the cam shaft (not shown). To do. In this case, the shaft hole 2 is formed in an elliptical shape that is difficult to crack. For example, as shown in FIGS. 1 and 2, the shaft hole 2 has a cam lobe length 12 of 41.81 mm and a plate thickness 10 of 11.0 mm which are the maximum length in the direction of the cam lobe tip 3 of the cam lobe 1. The major axis 8 is 25.2 mm and the minor axis 9 is an elliptical shape having a size of 23.4 mm. Thus, by making the shaft hole 2 into an elliptical shape, broaching which has been performed on the shaft hole 2 of the conventional cam lobe 1 is further unnecessary. Further, in order to reduce the weight of the cam lobe 1, the cam lobe tip 3 is subjected to a thinning process to form a recess having the plate surface 4 as the thin portion 7. In this case, in the cam lobe 1 of the above size, the depth of the recess is 2.5 mm. Further, the shaft hole peripheral portion 6, which is an elliptical peripheral portion facing the cam lobe tip 3 and the shaft hole 2 on the opposite side, is subjected to a thinning process so that the plate surface 4 is moved from the cam lobe outer peripheral surface 16 side to the shaft hole inner peripheral surface 15. It is set as the thin part 7 in the direction. In this case, in the size of the cam lobe 1 in the above example, the size from the cam lobe outer peripheral surface 16 side to the shaft hole inner peripheral surface 15 of the shaft hole peripheral portion 6 is 3.9 mm. The width from the cam lobe outer peripheral surface 16 side of the thin wall portion 7 formed by the thinning process is 2.0 mm. Further, in the center of the shaft hole 2, the range on both sides of the cam lobe tip 3 at an angle of 30 ° is rounded off and the corner is rounded.

  In the invention according to claim 2, in the above processing method, each of the both sides of the plate surface 4 is further formed as a recess whose depth is 20 to 25% of the plate thickness of the cam lobe 1 from the plate surface 4 of the cam lobe tip 3. The thin-walled portions 7 are formed by thinning. In the above example, the depth of the dent is 2.5 mm, which is 23%. In the above, when the depth of the recess exceeds 25% of the upper plate thickness, the mold life is shortened and the strength of the cam lobe 1 is lowered. For example, if 3 mm exceeds 25% and 27%, the mold life is reduced by about 70%. Moreover, if it is less than 20%, for example, 2.2 mm, the material cost reduction merit cannot be obtained and the weight cannot be reduced, so 20% that does not affect the mold life is secured.

  Furthermore, in the invention according to claim 3, in the above processing method, the plate surface 4 of the cam lobe outer peripheral surface 16 of the shaft hole peripheral portion 6 facing the shaft hole 2 on the opposite side of the cam lobe tip portion 3 is processed. By forming, the thin portion 7 is formed. In this case, the thinning process to be formed on the plate surface 4 of the shaft hole peripheral portion 6 of the cam lobe 1 takes into consideration the weight reduction and strength on only one side of the plate surface 4 and then the cam hole outer peripheral surface 16 to the shaft hole inner peripheral surface. The thin portion 7 having a width reaching 43 to 57% (preferably 48 to 52%) of the width up to 15 is formed from the cam lobe outer peripheral surface 16. The width of the thin portion 7 from the cam lobe outer peripheral surface 16 is 51% at 2 mm in the above example. For example, if the thickness is 1 mm 26%, the weight increases 5% relative to 2 mm 51%, and if it is 3 mm 77%, the strength decreases 60% relative to 2 mm 51%.

It is a top view of the cam lobe of this invention. It is a side view cut | disconnected and shown by AA of FIG. 1 of the cam lobe of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cam lobe 2 Shaft hole 3 Cam lobe tip part 4 Plate | surface 5 Hole shape 6 Shaft hole peripheral part 7 Thin part 8 Long diameter 9 Short diameter 10 Plate thickness 11 Plate thickness 11 Thin part edge part thickness 12 Cam lobe length 13 Shaft hole peripheral part width 14 Thin part width 15 Shaft hole inner peripheral surface 16 Cam lobe outer peripheral surface

Claims (3)

  For the purpose of preventing rotation when the cam lobe is assembled to the camshaft, the hole shape of the shaft hole that fits and locks the cam lobe on the camshaft is elliptical, and the cam lobe tip is against the plate surface and shaft hole of the cam lobe tip. The cam lobe manufacturing method characterized by performing the thinning process which forms the plate | board surface of the shaft hole peripheral part on the opposite side to a part in a thin part.   The thinning process that forms the plate surface of the cam lobe tip into a thin portion forms thin portions on both sides of the plate with a depth from the plate surface of the cam lobe tip of 20 to 25% of the plate thickness of the cam lobe. The cam lobe manufacturing method according to claim 1, wherein the cam lobe is processed.   The thinning process in which the plate surface of the cam lobe shaft hole peripheral portion is formed into a thin wall portion has a width reaching 48 to 52% of the width from the cam lobe outer peripheral surface to the shaft hole inner peripheral surface on the plate surface of the cam lobe shaft hole peripheral portion. 3. The method of manufacturing a cam lobe according to claim 1, wherein the thin portion is formed on the outer peripheral surface of the cam lobe on one side of the plate surface.

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