JP2006169961A - Method of manufacturing cam for camshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high dimensional accuracy, while dispensing with the final finishing processing (machining), by continuously performing a plurality of cold forging processes. <P>SOLUTION: The final product of a cam for a camshaft having high dimensional accuracy, is provided while dispensing with the final finishing processing (machining) of a cam (profile) surface, by continuously applying the plurality of cold forging processes composed of contour preliminary upsetting, contour drawing, simultaneous punching of an inner diameter surface and an outer diameter surface, pressure molding for forming a surplus part on the inner diameter surface as a burr, inner diameter surface punching for punching the burr of the inner diameter surface, and simultaneous ironing of the inner diameter surface and the outer diameter surface, to a billet having the volume larger by a predetermined quantity than the final product. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a camshaft cam manufacturing method for opening and closing a valve of an internal combustion engine.

  In an internal combustion engine such as a gasoline engine, an assembly type camshaft that rotates in conjunction with a crankshaft and controls opening and closing timings of intake and exhaust valves is known.

  In this assembled camshaft, for example, the shaft body is made of a metal pipe, and the pipe is fixed to the shaft insertion hole of the cam piece by a method such as press fitting.

  As a method for manufacturing a camshaft according to this type of prior art, for example, in Patent Document 1, a round bar-shaped stretched steel material having a volume corresponding to a cam as a product is heated to 1250 to 1280 ° C., and then heated by stamping. It is disclosed to perform inter-forging.

  Patent Documents 2 and 3 disclose a technical idea that achieves both molding accuracy and manufacturing cost by suppressing the drooping using a so-called fine blanking (precision punching) method.

JP-A-8-90139 JP 2001-355709 A JP 2002-147572 A

  However, when the hot forging method disclosed in Patent Document 1 is used, an oxide layer is formed on the surface layer portion of the forged product, and burrs and entanglement scratches are generated by stamping forging. As a finishing process, machining is required.

  Furthermore, when the fine blanking method disclosed in Patent Documents 2 and 3 is used, the fine blanking method is a shearing process. However, if a fracture surface or a sag occurs on the surface of the cam, which is a processed product, there is a problem that the surface pressure increases locally when the valve is pressed on the cam surface.

  The present invention has been made in consideration of the above points, and by performing a plurality of cold forging processes continuously, the final finishing process (machining) is not required and high dimensional accuracy is obtained. An object of the present invention is to provide a camshaft cam manufacturing method that can be used.

  In order to achieve the above-described object, according to the present invention, first, a contour pre-upsetting is performed on a forging material having a volume larger than a final product by a predetermined amount, and a primary cooling comprising a rough shape is performed. A forged compact is obtained.

  Subsequently, contour drawing is performed on the primary cold forging formed body to obtain a secondary cold forging formed body in which surplus meat that has flowed along the contour shape is formed as burrs on the outer diameter surface. .

  Next, the second cold forging formed body is subjected to simultaneous punching of the inner diameter surface and the outer diameter surface to remove burrs formed on the outer diameter surface, and to release a smaller diameter than the shaft insertion hole. A third cold forging formed body having holes formed in the inner diameter is obtained.

  Further, a fourth cold forging formed body in which the third cold forging formed body is pressed to form a predetermined thickness and a surplus meat is formed as a burr on the inner diameter surface. obtain.

  Furthermore, the fifth cold forging molded body is subjected to inner surface punching to remove burrs formed on the inner surface and a fifth portion formed with a hole corresponding to the shaft insertion hole. A cold forging compact is obtained.

  Finally, the inner surface and the outer surface are simultaneously ironed and formed on the fifth cold forging formed body, for example, finishing processing such as cutting and polishing is performed on the cam (profile) surface. Thus, a final product in which dimensional accuracy and predetermined surface roughness are ensured can be obtained.

  In addition, when contour pre-upsetting is performed on the forging material, a chamfered portion is formed at the peripheral edge of the primary cold forged molded body, and the burr formed on the outer diameter surface by contour drawing is formed. By setting the area of the first chamfered portion formed at the peripheral portion of one surface adjacent to the one surface to be larger than the area of the second chamfered portion formed at the peripheral portion of the other surface opposite to the one surface The contour drawing is smoothly performed.

  According to the present invention, the following effects can be obtained.

  That is, contour pre-upsetting, contour drawing, simultaneous punching of the inner and outer diameter surfaces, press forming to form the surplus as burrs on the inner surface, inner surface punching to punch out burrs on the inner surface, inner surface and The final product has high dimensional accuracy by eliminating the need for final finishing (machining) of the cam (profile) surface by continuously performing multiple cold forging processes consisting of simultaneous iron forming of the outer diameter surface. Can be obtained.

  As a result, in the present invention, the outer surface of the final product does not have a fracture surface or a sag, and a predetermined surface roughness is ensured as the cam surface, and the shaft insertion hole into which the shaft is press-fitted A final product having a predetermined fitting dimension can be obtained.

  A preferred embodiment of a method for manufacturing a cam for a camshaft according to the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of an engine 12 in which an assembling camshaft 10 manufactured by the camshaft cam manufacturing method according to the present embodiment is used. The camshaft 10 is used in, for example, a single cylinder engine 12 and operates the rocker arm 18 to open and close the valve 20 by pushing up the push rod 16 in synchronization with the rotation of the crankshaft 14. Can do.

  In practice, there are two valves 20 for supply and exhaust, and an individual rocker arm 18 and push rod 16 are provided. The camshaft 10 is provided with two cams 22 and 24 having different phases in order to push up the two push rods 16 individually.

  As shown in FIG. 2, the camshaft 10 includes a shaft 26 formed by cold forging, a cam 22 and a cam 24 press-fitted into the shaft 26, and a drive gear 14a of the crankshaft 14 (see FIG. 1). And a gear 28 made of synthetic resin (for example, nylon) that rotates the shaft 26 by meshing with the gear. A metal bush 28 a (for example, carbon steel such as S35C) is provided at the shaft center portion of the gear 28, and the metal bush 28 a is press-fitted into the shaft 26.

  The gear 28 is formed by injection molding a synthetic resin, and at this time, a metal bush 28a may be inserted in advance. Since the gear 28 is provided with the metal bush 28a, the shaft 26 can be reliably press-fitted and fastened. For example, by using a synthetic resin for the gear 28, a production method with high production efficiency such as injection molding can be used, and the weight can be reduced as compared with a metal gear.

  The gear 28 may be a press-worked product, a machined product, a sintered molded product, or the like using a metal according to the specifications of the engine 12 or the like.

  The cam 22 (24) has a cam surface (sliding surface) 30 that contacts the lower end surface of the push rod 16 and presses the push rod 16 upward, and a penetrating shaft insertion into which the shaft 26 is inserted. A hole 32 is provided (see FIG. 2).

  Next, the manufacturing process of the cam 22 (24) will be described with reference to the flowchart shown in FIG.

  First, in step S1, a cylindrical billet 34 is obtained as a forging material by cutting a rod-shaped material (not shown) into a predetermined length (see FIGS. 4A to 4C). The billet 34 does not correspond to the volume of the cam 22 (24) which is the final product, and is composed of a volume obtained by adding the volume of the cam 22 (24) which is the final product and the volume removed as burrs. The billet 34 may be obtained by shearing a coil material (not shown).

  In step S2, the billet 34 obtained in step S1 is loaded into the cavity 38 of the first cold forging die 36 shown in FIG. Intrusion molding.

  In this contour pre-upsetting, the billet 34 is pressed from above through the punch 40, so that it is thicker than the thickness of the final product, and the contour size (width dimension) of the outer periphery is set larger. A primary cold forging formed body 42 having a shape is formed (see FIGS. 5A to 5C).

  In the primary cold forging formed body 42, the plastic deformation by the punch 40 does not sufficiently flow with respect to the direction of the tip portion 44 that forms the cam surface. It is thinner than the part (see FIG. 5C).

  Further, in the primary cold forging formed body 42, a first chamfered portion 46a made of an annular inclined surface is formed on the peripheral portion of the upper surface (one surface), and on the peripheral portion of the lower surface (the other surface) on the opposite side. A second chamfered portion 46b made of an annular inclined surface is formed. In this case, the area of the first chamfered portion 46a formed on the upper surface is set to be larger than the area of the second chamfered portion 46b formed on the lower surface (see FIG. 7). In this case, the punch side is the upward direction and the die side is the downward direction.

  By forming the first and second chamfered portions 46a and 46b on the upper and lower surfaces of the primary cold forged formed body 42, respectively, when the outer surface burr 56 is cut in step S4, the cut surface is cut. Against the occurrence of burrs. Therefore, the work process can be simplified without providing a work for removing the burr specially in the subsequent process of step S4.

  Next, in step S3, the first cold forging formed body 42 obtained in step S2 is loaded into the cavity 50 of the second cold forging die 48 shown in FIG. Contour drawing is performed by pressurizing the primary cold forging compact 42.

  The width direction dimension A of the cavity 50 formed by the lower die 48a of the second cold forging die 48 is defined as the width direction of the cavity 38 formed by the lower die 36a of the first cold forging die 36. By setting it smaller than the dimension B, contour drawing can be performed smoothly (see FIG. 6 and FIG. 9 for comparison).

  In this contour drawing, the first cold forging formed body 42 is pressed from above via the punch 52, and the plastically deformed meat flows along the contour shape of the outer peripheral surface corresponding to the shape of the final product. Then, the secondary cold forging formed body 54 in which the front end portion 44a that has been insufficient in the contour preliminary upsetting process is sufficiently filled with plastic meat is formed (see FIGS. 8A to 8C).

  In addition, on the outer peripheral surface in the vicinity of the upper surface portion of the secondary cold forging formed body 54, an extra flesh volume that flows along the contour shape of the outer peripheral surface is formed as an annular burr 56 (FIG. 8B). reference). The contour drawing is performed along the contour of the outer peripheral surface without affecting the first and second chamfered portions 46a and 46b formed in the previous step.

  In step S4, the second cold forging formed body 54 obtained in step S3 is loaded into the third cold forging die 58 shown in FIG. 11 and inserted into the hole 62 of the die 60. By pressing the second cold forging formed body 54 from above with a hollow punch 64, the burrs 56 protruding from the outer peripheral surface are punched out, and the surplus of fluidized meat in the subsequent steps and beyond is inserted at the insertion position of the shaft 26. In order to make the fluid flow, the inner diameter surface and the outer diameter surface obtained by punching the escape hole 66 having a diameter smaller than the inner diameter of the shaft insertion hole 32 of the final product by the fixed punch 68 fixed to the lower mold 58a are simultaneously punched.

  In the simultaneous punching molding of the inner and outer diameter surfaces, when the burr 56 protruding from the outer peripheral surface is punched, the outer peripheral surface has a fractured surface with improved surface accuracy without causing burrs to be generated. Then, a third cold forging formed body 70 having a relief hole 66 having a smaller diameter than the shaft insertion hole 32 is formed on the inner diameter surface (see FIGS. 10A to 10C).

  The relief holes 66 are formed in order to flow the surplus portion of the fluidized meat only to the inner diameter side in a state where the outer peripheral surface is constrained in the subsequent steps.

  In step 5, the third cold forging molded body 70 obtained in step S4 is loaded into the cavity of the fourth cold forging die 72 shown in FIG. In a state where the outer peripheral surface of 70 is constrained by the mold surface, the third cold forging formed body 70 is pressed by a punch 76 having an annular stepped portion 74 protruding by a predetermined length toward the lower mold 72a side. In this way, press forming is performed to form a predetermined thickness, and to form surplus fluid meat as burrs 78 on the inner diameter surface.

  In the press molding, guide holes 80 are provided at the portions of the relief holes 66 close to the upper surface and the lower surface as preliminary molding for punching the inner diameter surface in the next step, and the thickness is substantially the same as that of the final product. A fourth cold forging formed body 82 set to the dimensions is formed (see FIGS. 12A to 12C).

  A through-hole 84 that penetrates along the thickness direction is formed between the pair of guide holes 80 so that the material can easily flow when the inner surface burr 78 is removed in the next step. Has been.

  In step S6, the fourth cold forging formed body 82 obtained in step S5 is loaded into the cavity of the fifth cold forging die 86 shown in FIG. Formed on the inner diameter surface of the fourth cold forged molded body 82 by pressing the upper surface of the fourth cold forged molded body 82 with a hollow punch 88 in a state where the outer diameter surface of the 82 is constrained. The formed burr 78 is punched out by a fixed punch 90 fixed to the lower die 86a.

  In this inner surface punching, a fifth cold forging formed body 92 having a shaft insertion hole 32 having a predetermined inner diameter is formed by punching a burr 78 formed on the inner surface of the fourth cold forging formed body 82. Is formed (see FIGS. 14A to 14C).

  In step S7, the fifth cold forging formed body 92 obtained in step S6 is loaded into the cavity of the sixth cold forging die 94 shown in FIG. The fifth cold forging formed body 92 of the fifth cold forging formed body 92 is so arranged that the fixed punch 96 fixed to the lower mold 94a is inserted along the shaft insertion hole 32 in a state where the outer diameter surface of the 92 is constrained by the mold surface. The upper surface is pressed by the hollow punch 98 and the inner diameter surface and the outer diameter surface are simultaneously ironed.

  By performing simultaneous ironing of the inner diameter surface and the outer diameter surface, a final product (see FIGS. 16A to 16C) in which a predetermined surface roughness is secured on the inner diameter surface and the outer diameter surface can be obtained (step S8). ). Note that the steps from Step S2 to Step S8 may be continuously formed by a header or a forging press.

  In the present embodiment, first to sixth cold forging dies 36, 48, 58, 72, 86, 94 are used, and contour pre-upsetting, contour drawing, simultaneous punching of the inner surface and outer surface. A plurality of cold forging forming steps including forming, pressing forming to form the surplus as a burr 78 on the inner surface, inner surface punching to punch out the inner surface burr 78, and simultaneous ironing of the inner surface and the outer surface are continuously performed. As a result, the final finishing process (machining) of the cam (profile) surface is unnecessary, and a final product having high dimensional accuracy can be obtained.

  Therefore, in the present embodiment, the fracture surface or mold sagging does not occur on the outer peripheral surface of the final product, a predetermined surface roughness is ensured as the cam surface, and the shaft insertion hole into which the shaft is press-fitted A final product having a predetermined fitting dimension can be obtained.

  Further, in the present embodiment, the billet 34 having a volume larger than that of the final product is used, the extra burr 56 is formed on the outer diameter surface by contour drawing, and the extra burr 78 is formed on the inner diameter surface by press molding. The outer surface burr 56 and the inner surface burr 78 are removed by punching.

  In this case, compared with the case where a forged product is formed by a plurality of forgings using a billet having a volume corresponding to the final product, in this embodiment, the flow direction of the meat in the contour drawing is the outer diameter surface. The outer diameter surface is constrained in the press molding, and the flow direction of the meat is the single direction on the inner diameter surface side. Therefore, the final finishing process is not necessary by, for example, cutting and polishing, and a final product having high surface roughness and dimensional accuracy can be obtained.

It is a schematic block diagram of the engine in which the camshaft manufactured by the manufacturing method of the cam for camshafts concerning this Embodiment is used. It is a perspective view of the cam shaft shown in FIG. It is a flowchart which shows the manufacturing process of the cam for camshafts which concerns on this Embodiment. 4A is a plan view of the billet cut to a predetermined length, FIG. 4B is a longitudinal sectional view of the billet, and FIG. 4C is a perspective view of the billet. FIG. 5A is a plan view of a primary cold forging formed body in which contour upsetting is performed on the billet by a first cold forging die, and FIG. 5B is the first cold forging formed body. FIG. 5C is a perspective view of the first cold forging formed body. FIG. 3 is a schematic longitudinal sectional view of the first cold forging die. FIG. 5B is a partially enlarged longitudinal sectional view of the primary cold forging formed body shown in FIG. 5B. FIG. 8A is a plan view of a second cold forging formed body in which contour drawing is applied to the first cold forging formed body by a second cold forging die, and FIG. 8B is the second cold forging formed body. FIG. 8C is a perspective view of the second cold forging formed body, and FIG. 8C is a longitudinal sectional view of the cold forging formed body. It is a schematic longitudinal cross-section figure of the said 2nd die for cold forging. FIG. 10A is a plan view of a third cold forging formed body in which the second cold forged formed body is subjected to simultaneous punching of the inner surface and the outer diameter surface by a third cold forging die, FIG. 10B is a longitudinal cross-sectional view of the third cold forged formed body, and FIG. 10C is a perspective view of the third cold forged formed body. It is a schematic longitudinal cross-section figure of the said 3rd cold forging metal mold | die. FIG. 12A is a plan view of a fourth cold forging formed body that has been subjected to press forming to form the surplus as a burr on the third cold forged formed body using a fourth cold forging die, FIG. 12B is a vertical cross-sectional view of the fourth cold forging formed body, and FIG. 12C is a perspective view of the fourth cold forging formed body. It is a schematic longitudinal cross-section figure of the said 4th cold forging metal mold | die. FIG. 14A is a plan view of a fifth cold forging formed body that has been subjected to inner surface punching to punch out burrs on the inner surface of the fourth cold forged formed body using a fifth cold forging die, FIG. 14B is a longitudinal cross-sectional view of the fifth cold forged formed body, and FIG. 14C is a perspective view of the fifth cold forged formed body. It is a schematic longitudinal cross-section figure of the said 5th cold forging metal mold | die. FIG. 16A is a plan view of a final product in which the inner surface and the outer surface of the fifth cold forged molded body are simultaneously ironed by a sixth cold forging die, and FIG. 16B is the final product. FIG. 16C is a perspective view of the final product. It is a schematic longitudinal cross-section figure of the said 6th die for cold forging.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Cam shaft 22, 24 ... Cam 26 ... Shaft 30 ... Cam surface 32 ... Shaft insertion hole 34 ... Billet 36, 48, 58, 72, 86, 94 ... Cold forging die 42, 54, 70, 82, 92 ... Cold forging formed body 44 ... Tip 46a, 46b ... Chamfer

Claims (3)

In a method for manufacturing a cam for a camshaft constituting an internal combustion engine,
A step of performing contour pre-upsetting on a forging material having a volume larger than the final product by a predetermined amount to obtain a primary cold forging formed body having a rough shape;
A step of performing contour drawing on the primary cold forging formed body to obtain a secondary cold forging formed body in which surplus meat that has flowed along the contour shape is formed as burrs on the outer diameter surface;
The secondary cold forging formed body is subjected to simultaneous punching of the inner diameter surface and the outer diameter surface to remove burrs formed on the outer diameter surface, and an escape hole having a smaller diameter than the shaft insertion hole is provided on the inner diameter surface. A step of obtaining a third cold forging formed body,
A step of performing a press molding for pressing the third cold forged molded body to obtain a fourth cold forged molded body which is formed to have a predetermined thickness and the surplus meat is formed as burrs on the inner diameter surface. When,
Fifth cold forging in which the inner surface is punched into the fourth cold forged molded body to remove burrs formed on the inner surface and a hole corresponding to the shaft insertion hole is formed. Obtaining a molded body; and
A step of simultaneously ironing the inner surface and the outer surface of the fifth cold forged formed body to obtain a final product;
A method of manufacturing a cam for a camshaft, comprising: In the manufacturing method of Claim 1,
A camshaft cam manufacturing method, wherein a chamfered portion is formed at a peripheral edge portion of a primary cold forged molded body when contour preliminary upsetting is performed on a forging material. In the manufacturing method of Claim 2,
The area of the first chamfered portion formed on the peripheral portion of one surface close to the burr formed on the outer diameter surface by contour drawing is formed on the peripheral portion of the other surface opposite to the one surface. The camshaft cam manufacturing method is characterized in that the camshaft cam is set larger than the area of the second chamfered portion.

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