JP2003286505A - Method for manufacturing sintered member with bore superior in coaxiality accuracy of inside and outside perimeters - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a sintered member with a bore superior in coaxiality accuracy. <P>SOLUTION: When manufacturing the sintered member by performing a primary compression molding and a secondary compression molding, with the use of a compacting mold consisting of a die, a core rod inserted into the central part inside a die hole of the die, an upper punch, and a lower punch, this manufacturing method employs the mold having a salient at least on one part of the surfaces of an inner circumferential part, a thick-wall central part, and an outer circumferential part of the upper and/or lower punches, wherein the salient of the upper punch or the lower punch used for the secondary compression molding is equal to or larger than that used for the primary compression molding. Thereby, the outer and inner circumferential coaxiality accuracies are improved. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sintered member having an inner hole, the method including a plurality of compression molding steps,
Particularly, it relates to improvement of accuracy of coaxiality of the inner and outer circumferences of the sintered cam piece.

[0002]

2. Description of the Related Art Powder metallurgical products can be processed into shapes close to those of parts, and cutting costs can be reduced. In recent years, many have been used as parts for internal combustion engines from the viewpoint of reducing the manufacturing cost of internal combustion engines. Has been done. Since a considerable load is applied to parts for internal combustion engines, materials having high strength and excellent slidability are required. As a method for obtaining a material having high strength, that is, high density, a warm forming method, a two-time compression / two-time sintering method (2P2S method), a sintering forging method, or the like is generally known. However, for example, in a powder metallurgical product manufactured by using the 2P2S method, the dimensional accuracy is insufficient to completely omit the cutting process, and the sizing treatment is added to improve the dimensional accuracy. However, the amount of deformation due to the sizing process is naturally limited, and the dimensional accuracy of the product may be insufficient depending on the dimensional accuracy before the sizing process.

In recent years, an assembly type camshaft has been manufactured in which a shaft (shaft) and a cam piece are manufactured separately and a plurality of cam pieces are assembled on the same shaft (shaft). In particular, since the cam pieces are made of different materials depending on the application, a plurality of cam peas made of different materials may be assembled on the same shaft. In the manufacture of prefabricated camshafts in which multiple cam pieces are assembled on the same shaft, in addition to the dimensional accuracy of the inner diameter of the cam pieces, the axial center based on the outer diameter of the outer circumference of the cam pieces (outer circumference of the base circle) It is required to improve the accuracy of coaxiality with the shaft center based on the inner diameter of the inner peripheral portion.

In response to such a demand, for example, Japanese Patent Laid-Open No. 2001-2001
-293531 discloses a work (sintered body) having an inner peripheral portion and an outer peripheral portion that define a hole, and a die having a die hole and a core rod arranged in the die hole is used. The inner periphery of the work is squeezed by the outer periphery of the core rod while the outer periphery of the work is constrained by the inner periphery of the die hole. There has been proposed a method for improving the inner diameter accuracy of a work, which includes an ironing step for increasing the coaxiality with the axis center based on the outer diameter of the workpiece.

Further, in Japanese Patent Laid-Open No. 2001-198645, a material having a thickness larger than that of a cam lobe to be manufactured, a small outer shape, and an axial hole slightly larger than the shape of the axial hole is manufactured. An outer mold having a wall surface complementary to the contour shape of the cam lobe to be formed, a middle mold having a wall surface complementary to the shape of the axial hole of the cam lobe, and a lower mold having a receiving hole for engaging the bottom surface and the middle mold. There has been proposed a method of manufacturing a cam lobe for an assembly type cam shaft, which is placed in a mold and cold pressed in the thickness direction with a pressing die having the same cross-sectional shape as the cam lobe.

[0006]

[Problems to be Solved by the Invention]
In the technology described in 01-198645, the manufactured cam lobe (sintered body) lacks the coaxiality accuracy and often requires finishing, which complicates the process and raises the manufacturing cost. There was a problem. In addition, Japanese Patent Laid-Open No. 2001-29353
The technique described in Publication No. 1 requires ironing of the inner peripheral surface of the sintered body, and may not always achieve the desired coaxiality accuracy, often requiring finishing. There is a problem that the process becomes complicated and the manufacturing cost rises.

An object of the present invention is to solve the above-mentioned problems of the prior art advantageously, and to propose a method for manufacturing a sintered member with an inner hole, particularly a sintered cam piece, which is excellent in coaxial precision of the inner and outer circumferences. . The term "excellent in coaxiality accuracy" as used in the present invention refers to the shaft center based on the outer diameter of the outer peripheral portion (base circle) of the sintered member (sintered cam piece) and the inner diameter of the inner peripheral portion. The deviation (difference) from the axis is within 0.04 mm.

[0008]

In order to achieve the above-mentioned object, the present inventor further diligently studied the factors affecting the accuracy of coaxiality between the base circle and the inner circumference of the sintered cam piece. As a result, in the method for manufacturing a sintered cam piece including the recompression step, a clearance is required between the die and the pre-sintered body (workpiece) at the time of recompression, so that the pre-sintering is performed within the clearance. There is a degree of freedom in the loading position of the body (workpiece), which causes a deviation (difference) between the axis centering on the base circle (outer diameter) and the axis centering on the inner diameter, and the accuracy of coaxiality Was found to decrease.

Particularly, since there is a clearance (degree of freedom) between the work and the die, as shown in FIG. 3, the nose portion of the pre-sintered body (cam piece) may be displaced to the left and right. As a result, the density distribution of the product (sintered cam piece) becomes non-uniform, and the amount of springback varies, and the axial center and inner diameter of the sintered cam piece based on the base circle (outer diameter) are used as references. A deviation (difference) occurs between the shaft center and the accuracy of coaxiality is lowered.

The present inventor remarkably improves the coaxiality accuracy of the product (sintered cam piece) by adjusting the die shape so that the temporary sintered body (workpiece) is loaded at a fixed position during recompression. The present invention has been completed based on the idea of improvement. That is, the gist of the present invention is as follows. (1) A step including at least primary compression molding and secondary compression molding using a molding die including a die, a core rod inserted into the center of the die hole of the die, an upper punch, and a lower punch. In the method for producing a sintered member with an inner hole, the molding die comprises an upper punch and / or a lower punch, at least one of an inner peripheral side surface, a center wall surface and an outer peripheral side surface. A mold having a convex portion at a place and the convex portion of the upper or lower punch used for the secondary compression molding is equal to or larger than the convex portion of the upper or lower punch used for the primary compression molding. A method for manufacturing a sintered member having an inner hole, which is excellent in accuracy of coaxiality of inner and outer circumferences. (2) A die, a core rod inserted into the center of a die hole of the die, a primary molding die including an upper punch and a lower punch are used, and the die of the primary molding die and the core rod are used. After filling the raw material powder in the die hole between and the primary compression molding of the raw material powder by the upper punch and the lower punch, and then subjected to temporary sintering to form a temporary sintered body having an inner hole A forming step, the die, the core rod inserted into the center of the die hole of the die, the upper punch,
It is inserted into a die hole of a secondary molding die including a lower punch, and secondary sintering is performed on the temporary sintered body by the upper punch and the lower punch, followed by main sintering, and a central portion. In the method for producing a sintered member with an inner hole, which comprises a secondary forming step of forming a sintered body having an inner hole in the inner die, an upper punch and / or a lower punch of the primary forming die, and the secondary forming die. The upper punch and / or the lower punch has a convex portion on at least one of the inner peripheral side surface, the wall thickness central surface and the outer peripheral side surface, and is used for the secondary compression molding. A method for producing a sintered member with an inner hole having excellent coaxiality accuracy of inner and outer circumferences, wherein a die having a convex portion of the punch equal to or larger than the convex portion of the upper or lower punch used for the primary compression molding is used. (3) A step including at least primary compression molding and secondary compression molding using a molding die including a die, a core rod inserted into the center of the die hole of the die, an upper punch, and a lower punch. In the method of manufacturing a sintered cam piece consisting of,
In the molding die, the upper punch and / or the lower punch are provided with an inner peripheral side surface corresponding to the cam piece nose position, a central wall surface corresponding to the cam piece nose position, and an outer peripheral side corresponding to the cam piece nose position. At least one of the surfaces
It is characterized in that it has a convex portion at a portion, and the convex portion of the upper or lower punch used for the secondary compression molding is equal to or larger than the convex portion of the upper or lower punch used for the primary compression molding. A method for manufacturing a sintered cam piece with excellent coaxial precision on the inner and outer circumferences. (4) A die, a core rod inserted into the center of the die hole of the die, a primary molding die including an upper punch and a lower punch are used, and the die of the primary molding die and the core rod are used. Filling the raw material powder into the die hole between and the primary compression molding of the raw material powder by the upper punch and the lower punch, and then performing preliminary sintering to form a cam piece-shaped temporary sintered body. Steps, and inserting the pre-sintered body into a die hole of a secondary molding die including a die, a core rod inserted in the center of the die hole of the die, an upper punch, and a lower punch. Then, a sinter cam piece comprising a secondary molding step of forming the cam piece-shaped sintered body by subjecting the temporary sintered body to secondary compression molding by the upper punch and the lower punch and then performing main sintering. In the method, the upper punch and / or the primary molding die The lower punch, and the upper punch and / or the lower punch of the secondary molding die are the inner peripheral side surface corresponding to the cam piece nose position, the center wall surface corresponding to the cam piece nose position, and the cam piece nose position. At least one of the outer peripheral side surface has a convex portion,
Moreover, the convexity of the upper or lower punch used for the secondary compression molding is the same as or larger than the convexity of the upper or lower punch used for the primary compression molding. For manufacturing sintered cam pieces.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a molding die composed of a die, a core rod inserted into the center of the die hole of the die, an upper punch and a lower punch, and uses at least raw material powder as a raw material powder. A method of manufacturing a sintered member with an inner hole, comprising: a primary molding step of performing primary compression molding; and a secondary molding step of performing secondary compression molding (recompression molding) on the primary molded body that has undergone the primary molding step. Is. In the present invention, the primary molding step includes a step of performing primary compression molding to form a primary molded body and then performing preliminary sintering to form a temporary sintered body, and in the secondary molding step, in the primary molding step, It is preferable to use a so-called 2P2S method, which comprises a step of subjecting the obtained temporary sintered body to recompression molding (secondary compression molding) and further main sintering to obtain a sintered body. Hereinafter, description will be made based on the case where the 2P2S method is used, but it goes without saying that the present invention is not limited to this.

An example of the sintered member with an inner hole is a sintered cam piece. Hereinafter, a sintered cam piece will be described as an example, but it goes without saying that the present invention is not limited to this. First, in the present invention, a die 11 and a core rod 14 inserted into the center of the die hole of the die 11 as shown in FIG. A molding die including an upper punch 12 and a lower punch 13 is used. Raw material powder 1 and core rod 14
Is filled in the die hole around and is compression-molded by the upper punch 12 and the lower punch 13 to obtain a primary molded body. Note that the upper punch
12 or the lower punch 13 has holes 122 and 132 in the central portion so that the core rod 14 can slide. The upper punch 12 and the lower punch 13 have an inner peripheral portion that defines a hole and an outer peripheral portion that defines an outer peripheral surface that slides with the inner peripheral surface of the die. Further, the raw material powder to be used is not particularly limited, and it is preferable to appropriately select it according to the application of the sintered cam piece which is a product. For example, in the case of an iron-based sintered member (sintered cam piece), it is preferable to use, as the raw material powder, a mixed powder obtained by mixing iron-based powder such as iron powder with graphite powder, alloy powder, lubricant and the like.

In the primary molding die used for the primary compression molding of the present invention, one or both of the upper punch 11 and the lower punch 12 is provided with an inner peripheral side surface, a central wall surface and an outer peripheral portion. The protrusion 131 is fixed to at least one of the surfaces. The convex 131 is preferably in the shape of a triangular pyramid, but is not limited to this. When the sintered member is a sintered cam piece, the convex portion 131 is formed on the inner peripheral side surface of the cam piece nose-corresponding position 133, the center wall surface of the cam piece nose-corresponding position 133, and the cam piece nose-corresponding position 133. At least one of the outer peripheral side surfaces of 133 is preferable.

FIG. 2 shows an example of a fixed position of the convex portion 131 in the case of the sintered cam piece. FIG. 2A shows a projection 13 on the inner peripheral side surface of the lower punch corresponding to the nose 133 of the cam piece.
1a and FIG. 2 (b) are positions 133 corresponding to the nose of the cam piece.
An example in which a convex portion 131a is provided on the surface of the center portion of the thickness of is schematically shown. The example shown in FIG. 2 shows a case where all the convex portions are triangular pyramids, but the present invention is not limited to this.

For example, when the raw material powder 1 is compression-molded into a primary compact using a primary-molding die having a lower punch as shown in FIG. As shown in Fig. 6, a recess 131b is formed on the inner peripheral side (inner hole side) of the nose of the temporary sintered body (cam piece) on the side that contacts the lower punch. Becomes In the present invention, the pre-sintering conditions are not particularly limited. It is preferable to carry out under the conditions determined according to the raw material powder used.

As described above, the inner peripheral side surface of the temporary sintered body,
By forming a recess in at least one of the surface of the central portion and the outer peripheral side surface and using it together with the protrusion formed in the secondary molding die described below, the secondary molding in the subsequent secondary molding is performed. The charging position of the work (temporary sintered body) in the molding die can be fixed. In addition,
When the pre-sintered body has a cam piece shape, it is preferable that the recess be provided at a position corresponding to the nose of the cam piece.

As described above, in the primary molding step, the inner peripheral side portion of the temporary sintered body (the position corresponding to the nose in the case of the cam piece)
The pre-sintered body 2 having recesses formed on the surface (inner hole side), the surface of the central portion of the wall thickness or the surface of the outer peripheral side is then placed in a secondary molding die and subjected to secondary compression molding. Then, a secondary forming step is performed in which the main sintering is performed to obtain a sintered body.
In the secondary compression molding, as in the primary compression molding, the die
The lower punch 23 is inserted into the die hole of 21, the core rod 24 is inserted into the center of the die hole, and the core rod 24 is inserted into the inner hole 232 of the lower punch 23. The lower punch 23 descends with the die 21 fixed, and the inner peripheral surface of the die 21 and the core rod
A pre-sintered body (cam piece: work) 2 is loaded into the portion (die hole) surrounded by the outer peripheral surface of 24 and the lower punch 23.

As the secondary molding die used in the secondary compression molding, one or both of the upper punch 22 and the lower punch 23 is used as in the primary molding die, and in the case of the cam piece, the cam piece is used. Nose-equivalent position 133 inner peripheral side surface, cam piece nose-equivalent position 133 central wall surface and cam piece nose-equivalent position 133 outer-peripheral side surface are fixedly provided with at least one convex portion 231. .
The protrusion 231 is preferably in the shape of a triangular pyramid, but is not limited to this. Further, the convex portions 221, 231 of the upper or lower punch used for the secondary compression molding are convex portions having a size equal to or larger than that of the convex portions 121, 131 of the upper or lower punch used for the primary compression molding.

The temporary sintered body (workpiece) 2 charged in the inner peripheral surface of the die 21, the outer peripheral surface of the core rod 24 and the portion (die hole) surrounded by the lower punch 23 is formed into a temporary sintered body. By the concave portion and the convex portion of the upper or lower punch, the charging position of the work (temporary sintered body) 2 at the time of the secondary compression molding can be set to a constant position without variation, and the inner circumference of the die 21 and the calcination are performed. The clearance between the united body 2 and the clearance between the core rod 21 and the work 2 are uniform over the entire circumference. As a result, after recompression molding-main sintering, it is possible to remarkably improve the difference between the axial center based on the outer diameter of the outer circumference and the axial center based on the inner diameter of the inner circumference, and the concentricity accuracy.

The sintered member to be molded is a sintered cam piece,
An example of the secondary molding die in which the convex portion 231a is provided on the inner peripheral side surface of the nose-corresponding position 133 of the cam piece on the lower punch is shown in the state immediately before the secondary compression molding (recompression molding) as shown in FIG. Shown in. Further, in FIG. 6, similarly, the sintered member to be molded is a sintered cam piece, and the lower punch is provided with a convex portion 231a on the inner peripheral side surface of the nose-corresponding position 133 of the cam piece.
An example of a secondary molding die in which the upper punch is provided with a convex portion 221a on the inner peripheral side surface of the nose-corresponding position 133 of the cam piece is shown in a state immediately before secondary compression molding (recompression molding).

The temporary sintered body (workpiece) 2 fixed at a fixed position in the die hole is compressed by the lowered upper punch 22,
It is a secondary compact (recompression compact). After that, the upper punch 22 and the lower punch 23 ascend to move the secondary molded body to the die 21.
Take out from. The secondary compact taken out from the die is further subjected to main sintering to form a sintered cam piece (sintered body). The present sintering conditions are not particularly limited in the present invention.
It is preferable to carry out under the conditions determined according to the raw material powder used.

[0022]

[Example] After sintering graphite powder and copper powder to iron powder, C: 0.8 quality
%, Cu: 1.5% by mass, and further lubricated
Zinc stearate as an agent is the sum of iron powder, graphite powder and copper powder.
1 part by weight is mixed with 100 parts by weight and mixed to form a mixed powder.
did. Using this mixed powder as the raw material powder, the primary composition shown in FIG.
Filling the die hole of the forming die, surface pressure: 5-7ton / cm ²so
Primary compression molding was performed to obtain a primary molded body. For primary molding
The mold is the inner peripheral side of the lower press cam piece nose position.
Triangular pyramid-shaped convex portion on the surface of the part (bottom surface: triangle with a side of 3 mm, height
Diameter: 2 mm) and has a short diameter as shown in FIG.
D: 40 mm x inner diameter d: 30 mm x thickness 15 mm (major axis L: 52 mm)
The mold was designed to have a cam piece shape.

These primary compacts were placed in a vacuum sintering furnace at 60
A temporary-sintered body was obtained by a primary forming step in which temporary-sintering was performed within a temperature range of 0 to 900 ° C. Then, a surface pressure of 7 to 10 ton / cm ² was applied to these temporary sintered bodies by using a secondary molding die shown in FIG.
After performing secondary compression molding with to make a secondary molded body, 1100 ~
Inventive Example 1 of the present invention was made into a sintered cam piece (product: a sintered member with an inner hole) by a secondary forming process in which main sintering is performed at a temperature of 1200 ° C
And The secondary molding die has a major axis L of 52 mm and a minor axis D of 40 mm after the main sintering as shown in FIG. 5 after the main sintering.
It is a mold designed to be a cam piece with an inner diameter d: 30 mm and a thickness t: 15 mm. The lower inner circumference side of the temporary sintered body is located on the inner circumference side of the lower press cam piece nose position. The metal mold was provided with a triangular pyramid-shaped convex portion having a size larger than the concave portion given to the mold. The clearance between the secondary molding die and the pre-sintered body was set to 0.1 mm (one side).

Further, the raw material powder having the same composition as that of Inventive Example 1 was used as a primary molding die to form a lower punch having a convex portion on the inner peripheral side of a position corresponding to the cam piece nose, and a lower punch corresponding to the position corresponding to the cam piece nose. A die using an upper punch having a protrusion on the inner peripheral side is used, and as a die for secondary molding, as shown in FIG.
Use a lower punch with a protrusion on the inner side of the cam piece nose and an upper punch with a protrusion on the inner side of the cam piece nose as shown in Except for the above, the primary molding step and the secondary molding step were performed under the same conditions as in Invention Example 1 to obtain a sintered member with an inner hole (sintered cam piece: product), and Invention Example 2 was obtained. In the secondary molding die, the convex part attached to the lower punch and the upper punch is larger than the convex part given to the pre-sintered body by the primary molding die (bottom face: triangle with side 3.2 mm). , Height 2.2 mm
).

Further, Example 1 of the present invention was used except that the die for which the convex portion was not attached to both the lower punch and the upper punch of the primary molding die and the secondary molding die was used. Inventive Example 1 and Inventive Example 2 were prepared using the same raw material powders as in Inventive Example 2.
By the primary molding process and the secondary molding process under the same conditions as above, a sintered cam piece (sintered member with an inner hole) having the same size was obtained, which was used as a comparative example.

In each of Inventive Example 1, Inventive Example 2 and Comparative Example, 60 sintered cam pieces were produced. For these sintered members with inner holes, the amount of deflection was measured along the entire outer circumference with the inner circumference (inner hole) as the reference, and the difference between the axial center based on the outer diameter reference of the outer circumference and the axial center based on the inner diameter reference of the inner circumference (mm ) Was obtained and the coaxiality accuracy was evaluated. The accuracy of the coaxiality is improved as the difference between the axes is smaller. The obtained results are shown in FIG. 7.

From FIG. 7, the coaxiality of each of Inventive Example 1 and Inventive Example 2 is 0.04 mm or less, which is less than that of Comparative Example.
It can be seen that the coaxiality accuracy is significantly improved compared to 05 mm.

[0028]

EFFECTS OF THE INVENTION According to the present invention, a sintered member with an inner hole such as a sintered cam piece, which has excellent dimensional accuracy such as inner diameter and outer diameter, and remarkably excellent coaxiality accuracy, can be manufactured at a low cost by a simple method. In addition, it has a remarkable industrial effect of being able to manufacture stably.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a primary molding die suitable for the present invention.

FIG. 2 is a cross-sectional view schematically showing an example of the structure of a lower punch of a primary molding die suitable for the present invention.

FIG. 3 is an explanatory view schematically showing the variation of the charging position of the pre-sintered body (work piece: cam piece) when a conventional die is used.

FIG. 4 is an explanatory view showing the shape of a temporary sintered body (cam piece) manufactured using the primary molding die of FIG. 2 (a).

FIG. 5 is a cross-sectional view schematically showing an example of the configuration of a secondary molding die suitable for the present invention.

FIG. 6 is a cross-sectional view schematically showing an example of the configuration of a secondary molding die suitable for the present invention.

FIG. 7 is a graph showing a comparison of coaxiality accuracy of the embodiment of the present invention.

[Explanation of symbols]

Raw material powder 11 die (for primary molding) 12 Upper punch (for primary molding) 13 Lower punch (for primary molding) 14 Core rod (for primary molding) 15 Core rod (for primary molding) receiving jig 121 Upper punch protrusion (for primary molding) 122 Upper punch inner hole (for primary molding) 131, 131a Lower punch protrusion (for primary molding) 131b recess 132 Lower punch inner hole (for primary molding) 2 work (temporary sintered body) 21 dies (for secondary molding) 22 Upper punch (for secondary molding) 23 Lower punch (for secondary molding) 24 core rod (for secondary molding) 25 core rod (for secondary molding) receiving jig 221, 221a Upper punch convex part (for secondary molding) 222 Upper punch inner hole (for secondary molding) 231, 231a Lower punch protrusion (for secondary molding) 232 Lower punch inner hole (for secondary molding)

Claims (4)

[Claims] 1. A molding die comprising a die, a core rod inserted into the center of the die hole of the die, an upper punch and a lower punch, and at least primary compression molding and secondary compression molding are performed. In the method for producing a sintered member with an inner hole, which comprises the step of including, in the molding die, the upper punch and / or the lower punch is one of an inner peripheral side surface, a central wall surface and an outer peripheral side surface. A mold having at least one convex portion, and the convex portion of the upper or lower punch used for the secondary compression molding is equal to or larger than the convex portion of the upper or lower punch used for the primary compression molding. A method for manufacturing a sintered member having an inner hole, which is excellent in coaxiality accuracy of the inner and outer circumferences. 2. A die for primary molding, comprising a die, a core rod inserted into the center of the die hole of the die, an upper punch and a lower punch, and the die of the primary molding die is used. Filling the raw material powder in the die hole between the core rod,
After primary compression molding of the raw material powder by the upper punch and the lower punch, a primary molding step of performing temporary sintering to form a temporary sintered body having an inner hole, the temporary sintered body, a die, The core rod inserted into the center of the die hole of the die, an upper punch, and a lower punch are inserted into the die hole of a secondary molding die, and the temporary punch is performed by the upper punch and the lower punch. In the method for manufacturing a sintered member with an inner hole, which comprises a secondary compression step of subjecting a sintered body to a secondary compression molding and then performing a main sintering to obtain a sintered body having an inner hole in a central portion, The upper punch and / or the lower punch of the die for use in molding, and the upper punch and / or the lower punch of the die for secondary molding are at least one of an inner peripheral side surface, a central surface portion of the wall thickness and an outer peripheral side surface. Upper or lower pan that has a convex part in the place and is used for the secondary compression molding A method for manufacturing a sintered member with an inner hole having excellent coaxiality accuracy of inner and outer circumferences, characterized in that a die having a convex portion of the H is equal to or larger than a convex portion of the upper or lower punch used for the primary compression molding. 3. A molding die comprising a die, a core rod inserted into the center of the die hole of the die, an upper punch and a lower punch, and at least primary compression molding and secondary compression molding are performed. In the method for manufacturing a sintered cam piece, which comprises the steps of: including a molding die, an upper punch and / or a lower punch has an inner peripheral side surface corresponding to a cam piece nose position.
A convex portion is provided on at least one of the surface of the central portion of the wall thickness corresponding to the nose position of the cam piece and the surface of the outer peripheral side portion corresponding to the nose position of the cam piece, and the convex of the upper or lower punch used for the secondary compression molding. A method for manufacturing a sintered cam piece excellent in coaxiality accuracy of inner and outer circumferences, characterized in that a die is the same as or larger than the convex portion of the upper or lower punch used for the primary compression molding. 4. A die for primary molding, comprising a die, a core rod inserted into the center of the die hole of the die, an upper punch, and a lower punch, and the die of the primary molding die is used. Filling the raw material powder in the die hole between the core rod,
After primary compression molding of the raw material powder by the upper punch and the lower punch, a primary molding step of performing temporary sintering to form a cam piece-shaped temporary sintered body, the temporary sintered body, a die, and The core rod inserted into the center of the die hole of the die, an upper punch, and a lower punch are inserted into the die hole of a secondary molding die, and the calcination is performed by the upper punch and the lower punch. In a method for producing a sintered cam piece, which comprises a secondary compression step of subjecting a sintered body to secondary compression molding and then subjecting it to main sintering to obtain a cam piece-shaped sintered body, Alternatively, the lower punch, and the upper punch and / or the lower punch of the secondary molding die may include an inner peripheral side surface corresponding to the cam piece nose position, a wall thickness central portion surface corresponding to the cam piece nose position, and a cam piece nose. Peripheral side corresponding to position A mold having a convex portion on at least one of the surfaces thereof, and the convex portion of the upper or lower punch used for the secondary compression molding is equal to or larger than the convex portion of the upper or lower punch used for the primary compression molding. A method of manufacturing a sintered cam piece having excellent inner and outer circumference coaxiality accuracy.