JPWO2007077880A1 - Manufacturing method of shaft member to which sintered parts are joined, and camshaft for internal combustion engine - Google Patents

Abstract

To provide a method for manufacturing a shaft member to which sintered parts are joined, which is simple, has a good yield, and has good positional accuracy and angular accuracy. When a green compact is formed by compression molding metal or alloy powder, and the green compact is assembled to the shaft member, the convex portion formed on the outer peripheral surface of the shaft member is used, and the green compact is pressed by the convex portion. The convex part and the shaft member are assembled by causing the convex part to bite into the green compact while scraping a part of the powder, and then sintering.

Description

  The present invention relates to a method for manufacturing a shaft member to which sintered parts are joined. Specifically, for example, the present invention relates to a manufacturing method applicable when manufacturing a so-called assembly camshaft.

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

  In manufacturing such a so-called assembly camshaft, it is necessary to perform sintering while fixing a cam lobe as a sintered part to a predetermined position of a shaft as a shaft member at a predetermined angle. Various fixing methods have been developed.

  For example, Patent Literature 1 and Patent Literature 2 disclose that a concave portion (groove) is provided on the outer peripheral surface of a shaft as a shaft member, and a convex portion corresponding to the concave portion is provided on the cam lobe side. .

  Patent Document 3 discloses that a concave portion is provided on both the outer peripheral surface of the shaft and the cam lobe, and both are fixed by inserting a pin into a gap formed by the two concave portions.

Further, Patent Document 4 discloses that a protrusion is formed by pressing a punch on the outer peripheral surface of the shaft, and the cam lobe and the shaft are temporarily fixed using the protrusion.
Japanese Patent Laid-Open No. 54-041266 Japanese Patent Laid-Open No. 60-033302 Japanese Patent Laid-Open No. 08-210110 Japanese Patent Laid-Open No. 03-168305

  However, in the methods disclosed in Patent Document 1 and Patent Document 2, it is necessary to form concave portions and convex portions that are not necessary for the original function of the camshaft, and the degree of design freedom may be reduced. there were. In particular, when a concave portion (that is, a groove) continuous in the axial direction is formed on the outer peripheral surface of the shaft, a gap is often generated between the portion where the concave portion is formed and the cam lobe, which may cause a problem in strength. there were.

  Further, even in the method disclosed in Patent Document 3, as in Patent Document 1, it is necessary to form a recess, which causes a problem that the degree of freedom in design is reduced and the strength is reduced. In addition, since a pin member is necessary in addition to the cam lobe and the shaft, the manufacturing process becomes complicated, the yield decreases, and the production cost increases.

  Furthermore, in the method disclosed in Patent Document 4, the joining method of the cam lobe and the shaft is welding joining, and it is an invention that does not take into account joining by sintered diffusion joining as in the present invention. Here, when the contents of Patent Document 4 are examined, it is described that the protrusion formed by the punch is crushed by the cam lobe and deformed in composition when the cam lobe is inserted. Judging from this description, it is clear that the cam lobe is not a green compact obtained by compression molding a metal or alloy powder as in the present invention. Considering the hardness of the cam lobe and the shaft, the cam lobe is harder. it is obvious. Furthermore, according to the description of Patent Document 4, since the protrusion is already crushed and lost at the stage where the cam lobe is inserted into the camshaft, the cam lobe is no longer fixed to the shaft at this stage, or Even if it is fixed, it is weak. In this situation, when the sintering process is performed as in the present invention, the cam lobe rotates, and it is considered impossible to fix the cam lobe accurately at a desired angle.

  The present invention has been made to solve such problems, and is a method for manufacturing a shaft member joined with sintered parts, which is simple, has a good yield, and has good positional accuracy and angular accuracy. It is a main object to provide a camshaft for an internal combustion engine manufactured by a manufacturing method.

  In order to solve the above problems, the present invention uses a jig to form a green compact by forming a green compact by compressing a metal or alloy powder, and a desired position on the outer peripheral surface of the shaft member The convex portion formed on the outer peripheral surface of the shaft member, and the outer peripheral surface of the shaft member is deformed by pressing to form a convex portion having a height of 0.03 to 0.25 mm at the position. The assembling step of assembling the green compact and the shaft member by causing the convex portion to bite into the green compact while scraping a part of the green compact with the convex, and the green compact. A method for producing a shaft member to which sintered parts are joined, comprising a sintering step in which the green compact and the shaft member are integrated by sintering diffusion bonding by sintering.

  Moreover, in the said invention, after the said assembly | attachment process is complete | finished, you may perform the temporary fix | stop process which temporarily fixes the said green compact and a shaft member with an adhesive agent before performing the said sintering process.

  Further, in the invention, the sintered part may be a cam lobe or a cam lobe and a journal, and the shaft member may be a shaft.

  Furthermore, the present invention for solving the above problems is a camshaft for an internal combustion engine formed by a method for manufacturing a shaft member.

  According to the present invention, a compact formed by using a metal or alloy powder is placed on a shaft member, and is sintered and integrated by sintering diffusion bonding. In the method for producing a member, before the green compact is placed on the shaft member, a fine convex portion is formed on the surface of the shaft member, and the green compact and the shaft member are assembled and fixed using this. Therefore, as in Patent Documents 1 and 2, there is no need to process both the green compact (cam lobe in Patent Documents 1 and 2) and the shaft member (shaft in Patent Documents 1 and 2). Since it is sufficient to process only the shaft member, the yield can be improved, and the degree of freedom in design can be improved. Further, the processing for the shaft member performed in the manufacturing method of the present invention is only to form a fine convex portion by pressing a jig on the surface, and finally the convex portion is formed of a green compact. Since it is hidden behind the joint, there is no possibility that the strength is reduced by the processing as in Patent Documents 1 and 2.

  Moreover, in such a manufacturing method of the present invention, a separate member typified by a pin as described in Patent Document 3 is unnecessary, so that the cost can be reduced.

  Furthermore, in the manufacturing method of the present invention, since the shaft member and the green compact are assembled and fixed by causing the fine projections formed on the outer peripheral surface of the shaft member to bite into the green compact, the patent As described in Document 4, there is no fear that the green compact is displaced in the axial direction or rotated in the circumferential direction after assembly, and as a result, the positional accuracy and the angular accuracy can be improved.

  In addition, in the conventional method, when a groove is formed on the shaft and a protrusion is formed on the cam lobe for fitting and sintering, only the cam lobe contracts during sintering, so the clearance increases and the angle is large. On the other hand, in the present invention, since the convex portion is formed on the shaft side, the cam lobe embraces the convex portion due to the shrinkage of the cam lobe (green compact) during sintering, so that the angular accuracy is improved.

It is a flowchart which shows the process of the manufacturing method of this invention. It is explanatory drawing for demonstrating the convex part formation process in the manufacturing method of this invention, (a) is a schematic sectional drawing which shows the procedure of the said process, FIG.2 (b) is the shaft in which the convex part was formed. It is an expanded sectional view of the outer peripheral surface. It is explanatory drawing for demonstrating the assembly | attachment process in the manufacturing method of this invention.

Explanation of symbols

20 ... Shaft 21 ... Jig 22 ... Projection

  Below, the manufacturing method of this invention is concretely demonstrated using drawing.

  FIG. 1 is a flowchart showing the steps of the production method of the present invention.

  The present invention is not limited to the method of manufacturing the camshaft, and can be applied when manufacturing general articles formed by integrating sintered parts and shaft members by sintering diffusion bonding. In order to explain specifically, a case where a so-called assembly cam shaft is manufactured by assembling a sintered part such as a cam lob and a journal separately manufactured on the shaft is described as an example. The member will be described as a shaft.

  As shown in FIG. 1, in the manufacturing method of the present invention, a green compact forming step S1 for forming a green compact by compressing a metal or alloy powder, and a desired position on the outer peripheral surface of the shaft member, Deformation of the outer peripheral surface of the shaft member by pressing using a jig, and forming a convex portion forming step S2 for forming a fine convex portion at the position; an assembly step S3 for assembling the green compact and the shaft member; Temporary fixing step S4 for temporarily fixing the green compact and the shaft member with an adhesive, and sintering for integrating the green compact and the shaft member by sintering diffusion bonding by sintering the green compact. Step S5.

  Each step will be specifically described below.

(1) Green compact forming step The green compact forming step S1 in the production method of the present invention is intended to form a green compact by compressing and molding a metal or alloy powder. The shape of the green compact is not particularly limited, and may be appropriately designed in consideration of the shape of the final molded product. For example, when manufacturing a camshaft, the green compact is a cam lobe. The shape will be exhibited.

  The metal or alloy powder used in the step S1 is not particularly limited, and any conventionally known metal or alloy powder can be used, but the shrinkage ratio ((( It is preferable to use, for example, a stainless alloy powder such that the green compact size−sintered body size) / green compact size × 100) is 4 to 7%.

  The green compact formed in the step S1 is bitten by the convex portions formed on the shaft member (for example, the shaft) in an assembly step S3 described later, that is, a certain amount of load is applied. It is necessary to have a hardness that can withstand the load received in the assembly step S3. Specifically, the green compact is preferably formed by applying a pressure of about 440 to 690 MPa, and the relative density of the green compact is preferably 70% or more.

(2) Convex part formation process Convex part formation process S2 in the manufacturing method of the present invention deforms the outer peripheral surface of the shaft member by pressing a desired position of the outer peripheral surface of the shaft member using a jig, It aims at forming a fine convex part in the said position.

  FIG. 2 is an explanatory view for explaining the convex portion forming step S2, (a) is a schematic sectional view showing the procedure of the step, and FIG. 2 (b) is a diagram of the shaft on which the convex portion is formed. It is an expanded sectional view of an outer peripheral surface.

  As shown to Fig.2 (a), in the said process, pressing the desired position of the outer peripheral surface of the shaft 20 as a shaft member using the jig | tool 21 is performed. Then, after the end of the process, as shown in FIG. 2B, the outer peripheral surface of the shaft 20 is deformed, and a fine convex portion 22 is formed at the position.

  The fine protrusions 22 are used in assembling the cam lobe-shaped green compact and the shaft 20 in an assembling step S3 described later.

  The height h of the fine convex portion 22 may be such that the convex portion 22 can fix the green compact by biting into the above-described green compact in the assembly step S3 described later, and can achieve this purpose. The height can be set as appropriate. However, making it higher than necessary may cause an obstacle when assembling the green compact, and at the same time, causes excessive pressure on the green compact and causes the green compact to be crushed. Since it may become, it is not preferable. Increasing the height of the projection more than necessary increases the load, resulting in a decrease in the life of the jig, an increase in the load for forming the projection, and an increase in equipment load due to an increase in the press-fit load during assembly. Is undesirable. Specifically, the height of the convex portion is preferably about 0.03 to 0.25 mm. Particularly preferable is about 0.03 to 0.2 mm when three convex portions are formed, and about 0.05 to 0.2 mm when two convex portions are formed. When forming five places, it is about 0.03-0.1 mm.

  On the other hand, the concave portion 23 inevitably formed to form the fine convex portion 22 is not used in the manufacturing method of the present invention, and therefore its shape (depth and size) is particularly limited. Not. However, it is preferable that the concave portion 23 is as small as possible. Therefore, it is preferable to devise the tip shape of the jig 21 and the like.

  The jig 21 used in the method of the present invention is not particularly limited as long as the fine protrusions 22 described above can be efficiently formed, and can be appropriately selected. Specifically, for example, the tip is preferably conical, and the angle is preferably about 40 to 80 °. The R (curvature radius) of the cone tip is preferably 1 mm or less, and particularly preferably about 0.05 to 0.5 mm. If the cone angle is less than 40 °, the life of the jig 21 may be shortened. On the other hand, if the cone angle is more than 80 °, it may be difficult to obtain an appropriate convex portion 22. Further, if the tip R is larger than 1 mm, it is difficult to form an appropriate convex portion 22 and the pressure for pressing the jig 21 becomes large.

  Further, the hardness of the jig 21 is preferably equal to or higher than the hardness of the shaft as the shaft member in order to carry out the method of the present invention. Steel) or the like may be used.

  On the other hand, for example, the hardness of a shaft member typified by a shaft can be appropriately set according to the use and required performance of the final product manufactured by the manufacturing method of the present invention. It is necessary to have a certain degree of hardness because it is necessary to form the fine convex portion 22 and use the formed convex portion 22 to bite into the green compact. Specifically, for example, in the case of a shaft for a camshaft, the surface hardness is preferably about HRB 75 to 105. If the surface hardness is less than HRB 75, it may be difficult to form the convex portion 22 having the desired height h even if the jig 21 is pressed. This is because the service life is reduced. Examples of the material having such hardness include S45C, STKM13, and SUJ2 material.

  In the step S2, the pressure when the jig 21 is pressed against the surface of the shaft 20 is set to the desired height h described above in consideration of the balance of the hardness of the jig 21 and the hardness of the shaft 20. What is necessary is just to set to the grade which can form the convex part 22 which has, and it does not specifically limit. For example, it is preferable that it is about 490-2450N. If the pressure is smaller than 490N, the height h of the convex portion may not be set to a desired value. On the other hand, if it exceeds 2450N, the depth of the unnecessary concave portion 23 becomes deeper, and the thickness of the shaft 20 depends on the thickness. This is because the entire shaft may be deformed depending on the case.

  In the step S2, it is only necessary to form at least one convex portion 22 for one green compact, and the number to be formed is not particularly limited. Depending on the case, about five may be formed. . For example, when the method of the present invention is applied to the manufacture of an assembled camshaft and one convex portion 22 is formed for one cam lobe, the convex portion 22 is a nose portion in the cam lobe. It is preferably provided at a position corresponding to (the thickest part) (an angle with respect to the circumferential direction of the shaft). On the other hand, in the case where two convex portions 22 are formed for one cam lobe, the convex portion 22 has a position of 0 to + 35 ° and 0 to −35 from the position corresponding to the nose portion in the cam lobe. It is preferably provided at a position of 25 °, more preferably at a position of 25 ± 10 ° and −25 ± 10 °, and particularly preferably at a position of 25 ± 7 ° and −25 ± 7 °. In the case of forming three convex portions, from the position corresponding to the nose portion in the cam lobe, it is provided at a position of 0 to + 35 °, a position of 0 °, and a position of 0 to −35 °, or It is preferable to provide at a position of 0 to + 35 °, a position of + 180 °, and a position of 0 to −35 ° from the position corresponding to the nose portion. Further, in the case of forming four convex portions, from the position corresponding to the nose portion in the cam lobe, the position of 0 to + 35 °, the position of 0 °, the position of 0 to −35 °, and + 180 ° It is preferable to provide at the position. Further, in the case of forming five convex portions, from the position corresponding to the nose portion in the cam lobe, the position of 0 to + 35 °, the position of 0 °, the position of 0 to −35 °, and + 150 ° Or at a position of −150 °, or at a position of 0 to + 35 °, a position of 180 °, a position of 0 to −35 °, a position of + 150 °, and a position of −150 °. Is preferred.

  In addition, about the position angle which forms said convex part, a high precision is not required. When the method of the present invention is applied to the manufacture of the assembly camshaft, the number and position of the projections formed on the shaft member are preferably the combination of the number and position described above. When integrally manufacturing by sintering diffusion bonding, it may be provided in consideration of the shape and strength of the green compact, and is not particularly limited.

(3) Assembling step The assembling step S3 in the manufacturing method of the present invention uses the convex portion formed on the outer peripheral surface of the shaft member, and presses the convex portion while scraping a part of the green compact with the convex portion. The object is to assemble the green compact and the shaft member by biting into the powder.

  FIG. 3 is an explanatory diagram for explaining the assembly step S3.

  In the step S3, as shown in FIGS. 3A and 3B, a cam lobe-shaped green compact is inserted from one end of the shaft 20 on which the fine convex portions are formed by the convex portion forming step S2. Then, assembly is performed by biting the convex portion 22 while scraping the inner surface of the shaft insertion hole formed in the green compact with the fine convex portion. At this time, since the green compact is elastically deformed, there is no deviation in the insertion direction or in the opposite direction after the green compact is inserted.

  In this way, the green compact can be used as a shaft member with higher accuracy than in the past by cutting the convex portion formed on the shaft member (shaft) into the green compact while scraping a part of the green compact (cam lobe). Can be fixed.

  In this case, it is preferable that the convex portion 22 is bitten to about ½ of the thickness W in the width direction (insertion direction) of the green compact. However, when the thickness W in the width direction of the green compact exceeds 20 mm, the amount of insertion is preferably about 10 mm.

  Further, the clearance (gap) between the green compact (cam lobe) and the shaft member (shaft) is appropriately determined depending on the height h of the convex portion 22 formed on the outer peripheral surface of the shaft member in the convex portion forming step S2. For example, the diameter is preferably about 0.05 to 0.2 mm. If the clearance is less than 0.05 mm in diameter, it may be difficult to insert the green compact itself, resulting in problems such as a decrease in yield. This is because the biting of 22 becomes shallower and fixing becomes difficult accordingly. From the same viewpoint, it is preferable to set the clearance so that the convex portion 22 of the shaft member bites into the green compact by 0.01 mm or more.

  FIGS. 3C and 3D show the procedure of the assembling step S3 when a plurality of cam lobes are fixed to the shaft, for example. As shown in the drawing, when a plurality of cam lobes are fixed, it is preferable to repeat the above-described convex portion forming step S2 and the assembling step S3. When the convex portion forming step S2 is continuously performed, when the cam lobe is inserted from one end of the shaft, the cam lobe passes through the convex portion formed on the front side, and at this time, a part of the cam lobe is scraped unnecessarily. This is because there may be a problem in strength.

(4) Temporary fixing step The temporary fixing S4 in the manufacturing method of the present invention aims to temporarily fix the green compact (cam lobe) assembled to the shaft member (shaft) in the assembly step S3 before the sintering step. To do.

  The step S4 is not an essential step in the manufacturing method of the present invention, but is preferably performed for improving accuracy.

  As can be seen from the description of the assembling step S3, in the method of the present invention, since the attaching step is performed while removing a part of the green compact with the convex portion formed on the shaft member, the green compact is inserted. While the displacement in the direction is difficult to occur, the fixing in the direction opposite to the direction in which the green compact is inserted (that is, the direction in which the green compact is returned) may be weaker than that in the insertion direction. However, this is a case where both are compared, and since the convex part bites into the green compact along with the elastic deformation of the green compact, it is fixed even in the direction opposite to the insertion direction. In consideration of such a case, it is preferable to perform the temporary fixing step when higher accuracy is desired.

With respect to the specific means of the step S4, the method of the present invention is not particularly limited, and various means used in a conventional manufacturing method of an assembly camshaft and the like are arbitrarily selected and used. It is possible. For example, an adhesive may be applied to the joint portion between the shaft member and the green compact. Examples of the adhesive used in this case include alpha cyanoacrylate.
(5) Sintering Step The sintering step S5 in the production method of the present invention is performed by sintering the green compact (cam lobe) assembled to the shaft member (shaft) and temporarily fixed as necessary. It aims at integrating powder and a shaft member by sintering diffusion bonding.

  In the said process S5, it is the same as that of a conventionally well-known sintering process, and it does not specifically limit in the manufacturing process of this invention.

  Specifically, for example, it is preferable to sinter at 1100 to 1200 ° C., and the time varies depending on the size of the product to be manufactured and the type of metal or alloy powder used, but is approximately 0.5 to 2 Time is preferred. Sintering at 1200 ° C. or higher is not preferable because the deformation may be too large or minute “blowing” may occur.

  Moreover, it is preferable that the shrinkage ratio of the green compact in the sintering process is about 4 to 7%. If the shrinkage amount is smaller than this, diffusion bonding may be insufficient.

  The production method of the present invention will be described more specifically with reference to examples.

Example 1
Ten camshafts (one cam lobe per shaft) were manufactured by the manufacturing method of the present invention shown in FIG. Each of them is designated as sample no. 1-10.

  The position and height of each convex portion formed on the shaft of each sample are as shown in Table 1 below. Sample No. 1 to 4 have two protrusions, sample no. Nos. 5 to 7 have three protrusions, sample Nos. 8 to 10 have five convex portions.

  The alloy powder was Fe-8Cr-1.9Ni-2Mo-2.7C, and the shaft was a cold drawn pipe made of STKM13 material.

  The material of the tip portion of the jig was diamond, and the shape of the tip portion was a cone shape with a cone angle = 60 ° and a cone tip R = 0.2 mm.

  In the manufactured camshaft, the position of the cam lobe in the shaft circumferential direction after completion of the temporary fixing process is 0 °, and the position of the cam lobe after completion of the sintering process is from the position (0 °) of the cam lobe after completion of the temporary fixing process. The number of deviations was measured for each sample. The clockwise direction when viewed from the cam lobe insertion direction is positive (+), and the counterclockwise direction is negative (−).

  The results are shown in Table 1 below.

(Comparative Example 1)
Two camshafts were manufactured by the same method as in the above example except that the size of the convex portion was outside the range of the manufacturing method of the present invention. Each of them is sample no. 11-12.

  The measurement results of the sample are shown in Table 1 below as in the above example.

(Conventional example 1)
Three camshafts (one cam lobe per shaft) were manufactured by a conventionally known assembly camshaft manufacturing method. Each of them is designated as sample no. 13-15.

  The conditions for the alloy powder, the shaft, etc. were the same as in the previous examples.

  In addition, in the known method of manufacturing an assembled camshaft, specifically, a groove extending in the axial direction is formed on the outer periphery of the shaft, while a protrusion is formed on the inner peripheral surface of the cam lobe to be joined to the shaft. This is a method in which the cam lobe is joined to the shaft by matching the protrusion and the groove and fitting the cam lobe to the shaft, followed by sintering (see FIGS. 1 to 3 of the aforementioned Patent Document 2).

  The results of the same evaluation as in Example 1 are shown in Table 1 below.

(Contrast of Example 1, Comparative Example 1 and Conventional Example 1)
As is clear from Table 1 above, the method of the present invention has a very high accuracy because the deviation from the cam lobe position (0 °) after completion of the temporary fixing process is small as compared with the comparative example and the conventional example. I understood that.

  In particular, the sample No. of the example in which the height of the convex portion is 0.03. 8 and a comparative sample No. 8 having a height of the convex part of 0.02. When comparing 12, the deviation angle is greatly changed, and it is understood that it is effective to determine the height of the convex portion within the scope of the present invention.

Claims (4)

A green compact forming step of forming a green compact by compression molding metal or alloy powder;
A convex portion that deforms the outer peripheral surface of the shaft member by pressing a desired position of the outer peripheral surface of the shaft member using a jig, and forms a convex portion having a height of 0.03 to 0.25 mm at the position. Forming process;
Utilizing the convex portion formed on the outer peripheral surface of the shaft member, the green compact and the shaft member are formed by biting the convex portion into the green compact while scraping a part of the green compact with the convex portion. Assembly process to assemble,
Sintering the green compact to sinter the green compact and the shaft member by sintering diffusion bonding; and
The manufacturing method of the shaft member to which the sintered component was joined characterized by comprising.   2. The sintered part according to claim 1, wherein a temporary fixing step of temporarily fixing the green compact and the shaft member with an adhesive is performed after the assembly step and before the sintering step. Manufacturing method of joined shaft member.   The method for manufacturing a shaft member to which sintered parts are joined according to claim 1, wherein the sintered component is a cam lobe, and the shaft member is a shaft.   A camshaft for an internal combustion engine, formed by the method for manufacturing a shaft member according to any one of claims 1 to 3.

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