JP2015010561A - Assembly camshaft and manufacturing method of cam lobe used in assembly camshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assembly camshaft that can securely reduce its weight and improve its strength with a simple method and prevents deformation after sintered, and a manufacturing method of a cam lobe used in the assembly camshaft.SOLUTION: An assembly camshaft integrally assembles a cam lobe to a shaft with sintered diffusion junction. The cam lobe has a through hole into which the shaft is inserted, and on the inner peripheral surface of the through hole, a recess part, which does not contact with a part of the outer peripheral surface of the shaft, is formed.

Description

  The present invention relates to an assembly camshaft and a method of manufacturing a cam lobe used for the assembly camshaft.

  For example, a camshaft used in an internal combustion engine such as an automobile engine is formed by compression molding a metal or alloy powder into a cam lobe shape, assembling the powder into a cam lobe, and then sintering it to sinter diffusion bonding the cam lobe and shaft It is manufactured by integrating.

  Since such a camshaft rotates at a high speed as a part of an internal combustion engine component, it is desired to reduce the weight in accordance with recent demands for improving fuel consumption while maintaining the necessary rigidity. The method is known.

  For example, Patent Document 1 discloses that a plurality of through holes are formed in the nose portion of the cam lobe to reduce the weight.

  Further, Patent Document 2 discloses that as shown in FIG. 3, notches 121 and 122 are formed on both side surfaces of the nose portion 120b and the base circle portion 120a of the cam lobe 120 to reduce the weight.

Japanese Utility Model Publication No. 60-56855 JP 60-33303 A

  However, in the method disclosed in Patent Document 1, in order to form a through hole in the nose portion, the through hole is formed when a cam lobe is manufactured by compression molding powder with a pair of punches. It is necessary to insert a plurality of pins into a pair of punches, and there is a problem that if the compression molding is repeated a plurality of times, the pins are broken or worn and the replacement frequency becomes high. Moreover, since a plurality of through-holes are formed thin, there is a problem that the strength is reduced between the through-holes.

  In the cam lobe manufacturing method disclosed in Patent Document 2, as shown in FIG. 4, the die 131 is filled with powder while the rod 132 is inserted into the die 131, and the upper punch 134 and the lower Steps 134a and 135a corresponding to the notches 121 and 122 are formed on the press surface of the punch 135, and the stepped portions 134a and 135a are forcibly compacted and manufactured. In this case, a difference occurs in the green body density between the notches 121 and 122 and a portion that does not have the notches 121 and 122, and deformation occurs due to the difference in the green body density during sintering. was there. Furthermore, in this manufacturing method, the cutout portions 121 and 122 have a problem that it is difficult to achieve a large weight reduction because the powder is forcibly compressed. Furthermore, since the notches 121 and 122 are formed thinner than other portions, there is a problem that the strength of the notches 121 and 122 is reduced.

  The present invention has been made to solve such problems. An assembly camshaft that can reliably reduce the weight and improve the strength by a simpler method and does not cause deformation after sintering. It is a main object to provide a manufacturing method of a cam lobe used for this assembly cam shaft.

  An assembly camshaft according to the present invention for solving the above-described problems is an assembly camshaft in which a cam lobe is integrally assembled to the shaft by sintered diffusion bonding, and the cam lobe has a through hole into which the shaft is inserted. The inner peripheral surface of the through hole is formed with a recess that does not contact a part of the outer peripheral surface of the shaft.

  In the above invention, the concave portion may be formed on any of the inner peripheral surfaces of the through holes, but is preferably formed in the nose portion of the cam lobe.

  Moreover, although the said recessed part is formed in at least one place in the internal peripheral surface of the said through-hole, you may form in multiple numbers. Further, the shape of the concave portion may be any of an arc shape such as a semicircle or an ellipse or a polygonal shape such as a rectangle.

  Furthermore, a cam lobe manufacturing method according to the present invention for solving the above-mentioned problems is a cam lobe manufacturing method used for an assembled cam shaft in which a cam lobe is integrally assembled to a shaft by sintered diffusion bonding, and the cam lobe outer shape (cam A die having an outer shape forming a shape), a rod having at least one convex portion projecting in a radial direction and forming a through hole into which the shaft of the cam lobe is inserted, and an upper punch and a lower punch are prepared, The powder is filled with the rod and the lower punch inserted in the outer shape hole, and the powder is compression-molded by the upper punch and the lower punch inserted from one end of the outer shape hole.

  According to the present invention, since the concave portion that does not contact a part of the outer peripheral surface of the shaft is formed on the inner peripheral surface of the through hole of the cam lobe, the shape of the rod that forms the through hole can be formed without using a plurality of pins. The cam lobe can be easily reduced in weight simply by deformation. Moreover, since a thin part is not formed in a cam lobe, strength can be maintained.

  Further, in the present invention, when the concave portion is formed in the nose portion of the cam lobe, the configuration of the mold is simplified, and the cost of the mold and the powder molding machine can be simplified, so that the cost can be reduced. Furthermore, the radial thickness of the base circle portion and the nose portion approaches more uniformly, and the run-out characteristics during rotation of the assembly camshaft are improved.

  In the present invention, if a plurality of recesses are formed, the weight can be further reduced.

  Further, in the present invention, since the convex portion protruding in the radial direction is formed on the rod forming the through hole, the convex portion improves the strength of the rod. The frequency of maintenance such as replacement is reduced, and the manufacturing cost can be suppressed.

The perspective view of the assembly cam shaft which concerns on this embodiment. (A) is a top view of a cam lobe used for the assembly camshaft according to the present embodiment, and (b) is a diagram for explaining a manufacturing method of the cam lobe used for the assembly camshaft according to the present embodiment. Sectional drawing which shows the AA cross section view of a cam lobe. The perspective view of the conventional assembly cam shaft. (A) is a top view of a cam lobe used for a conventional assembly camshaft, and (b) is a BB cross section of the cam lobe in (a) for explaining a manufacturing method of the cam lobe used for the conventional assembly camshaft. Sectional drawing which shows a view.

  Hereinafter, an assembly camshaft according to an embodiment of the present invention and a method for manufacturing a cam lobe used in the assembly camshaft will be specifically described with reference to the drawings.

  FIG. 1 is a perspective view of an assembly camshaft according to the present embodiment, FIG. 2A is a top view of a cam lobe used for the assembly camshaft according to the present embodiment, and FIG. It is sectional drawing which shows the AA cross section view of the cam lobe in (a) for demonstrating the manufacturing method of the cam lobe used for the assembly cam shaft which concerns on a form.

  As shown in FIG. 1, the assembled camshaft 1 according to the present embodiment has a cam lobe 20 integrally assembled to a shaft 10 extending in the longitudinal direction by sintered diffusion bonding.

  As the shaft 10, various types of conventionally used shafts can be appropriately selected and used. In recent years, since the weight reduction of the camshaft itself is required, it is preferable to use a hollow shaft as the shaft 10.

  The cam lobe 20 includes a base circle portion 20a in which a through hole 21 into which the shaft 10 is inserted is formed, and a nose portion 20b protruding in the radial direction from the base circle portion 20a.

  Concave portions 22 and 23 are formed on the inner peripheral surface of the through hole 21 so as to avoid contact with part of the outer peripheral surface of the shaft 10. Since the recesses 22 and 23 penetrate along the thickness direction of the cam lobe 20, the cam lobe 20 has a uniform thickness in a cross section parallel to the axial direction of the shaft 10.

  The concave portions 22 and 23 are formed in the nose portion 20b and the base circle portion 20a, respectively, and the concave portion 22 formed in the nose portion 20b is larger than the concave portion 23 formed in the base circle portion 20a. Yes.

  Thus, since the nose portion 20b is formed thicker in the radial direction than the base circle portion 20a, the recess 22 formed toward the nose portion 20b can be formed in a large opening. Further weight reduction can be achieved. Moreover, if the recessed part 22 is formed in the nose part 20b, since the weight of the nose part 20b can be achieved, the entire camshaft can be reduced in weight, which contributes to an improvement in fuel consumption.

  Next, a method for manufacturing the cam lobe 20 will be described with reference to FIG.

  First, FIG. 2A is a top view of the shape of the cam lobe 20. In order to form the shape shown in this figure, as shown in FIG. 2B, a die 31 in which an outer shape hole 31a that forms the outer shape of the cam lobe 20 is formed, and a rod that forms the through hole 21 in the cam lobe 20. 32 and a pair of punches composed of an upper punch 34 and a lower punch 35 are used to form a green compact.

  The rod 32 is provided with a convex portion 33 extending in the axial direction that forms a concave portion 22 projecting in the radial direction from the inner peripheral surface of the through hole 21 of the cam lobe 20.

  The green compact shown in FIG. 2 (b) is a diagram showing an explanation of forming the AA cross section of FIG. 2 (a). The lower punch 35 and the rod 32 are placed at predetermined positions in the outer shape hole 31a. After inserting and fixing, the powder filling cavity (P) is filled with metal or alloy powder. Next, the upper punch 34 is inserted, and the recess 22 is formed on the inner peripheral surface of the through hole 21 by compressing the powder along the axial direction of the rod 32 by a pair of punches including the upper punch 34 and the lower punch 35. The formed green compact can be formed. The green compact is a cam lobe used for the assembly camshaft according to the present embodiment.

  Moreover, it can also be set as the cam lobe 20 used for the assembly cam shaft which concerns on this embodiment by pre-sintering the compression-molded green compact. Note that the metal or alloy powder is not particularly limited, whether it is a green compact or a pre-sintered body, and a conventionally known powder, for example, a stainless alloy powder may be used. Also, in the preliminary sintering, the same apparatus and method as those used in the conventional preliminary sintering can be used. For example, the green compact is temporarily sintered by sintering at about 900 ° C. for about 45 minutes. can do. By performing pre-sintering, the amount of thermal deformation of the green compact during main sintering can be reduced compared to the case of performing main sintering without pre-sintering. As a result, the accuracy of the final product can be reduced. Can be improved.

  The integration of the shaft 10 and the cam lobe 20 is the same as the conventional integration by sintering, and is not particularly limited. Specifically, after positioning the cam lobe 20 at a predetermined position on the shaft 10, it is preferable to sinter at, for example, 1100 to 1200 ° C. The sintering time depends on the size of the camshaft to be manufactured, the metal to be used, Although it varies depending on the type of alloy powder, it is preferably about 0.5 to 2 hours.

  The assembly camshaft 1 according to the present embodiment described above has been described with respect to the case where the recesses 22 and 23 are formed in each of the nose portion 20b and the base circle portion 20a. However, the present invention is not limited to this, and can be appropriately changed according to the amount and strength of the required weight reduction. For example, the recess 22 may be formed only in the nose portion 20b, or the recess 23 may be formed only in the base circle portion 20a. It doesn't matter. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  1,100 assembly cam shaft, 10, 110 shaft, 20, 120 cam lobe, 20a base circular portion, 20b nose portion, 21 through hole, 22, 23 recess, 31 die, 31a outer hole, 32 rod, 33 convex portion, 34 Upper punch, 35 Lower punch, P powder filling cavity.

Claims (4)

An assembly camshaft in which a cam lobe is integrally assembled to the shaft by sintered diffusion bonding,
The cam lobe has a through hole into which the shaft is inserted,
The assembly camshaft is characterized in that a concave portion that does not contact a part of the outer peripheral surface of the shaft is formed on the inner peripheral surface of the through hole. The assembly camshaft according to claim 1,
The assembly camshaft is characterized in that the recess is formed in a nose portion of the cam lobe. The assembly camshaft according to claim 1 or 2,
The assembly camshaft is characterized in that a plurality of the recesses are formed on the inner peripheral surface of the through hole. A cam lobe manufacturing method used for an assembled camshaft in which a cam lobe is integrally assembled to a shaft by sintered diffusion bonding,
A die having an outer shape hole forming the outer shape of the cam lobe, a rod having a through hole into which the shaft of the cam lobe is inserted and having at least one convex portion projecting in the radial direction, and an upper punch and a lower punch are prepared. And
Filled with powder in a state where the rod and the lower punch are inserted into the outer hole,
A method for producing a cam lobe, wherein the powder is compression-molded by an upper punch and a lower punch inserted from one end of the outer shape hole.

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