JP2911229B2 - Method for manufacturing hollow sintered body cam piece - Google Patents

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 hollow sintered body, and more particularly to a method for manufacturing a high density hollow sintered body cam piece by powder metallurgy.

[0002]

2. Description of the Related Art A camshaft of an internal combustion engine is used for a mechanism for opening and closing an intake valve and an exhaust valve via a tappet and a rocker arm, or through a rocker arm. Since it slides with the partner component, wear resistance is required.

Conventionally, cast iron has been frequently used as a material for these components. Taking a camshaft as an example, the surface of the cam piece is rapidly solidified using a chill during casting,
A so-called chill camshaft in which a hard white cast iron structure surface layer is formed on the surface of a cam piece to impart wear resistance is often used.

[0004] However, the chill camshaft uses a diesel engine or a leaded gasoline in which lubricating oil is contaminated with carbon sludge as a fuel. There is a tendency for the wear of the cam piece to increase.

[0005] Sintered alloys manufactured by powder metallurgy have a uniform structure because there is no solidification segregation unlike alloys manufactured by the melting method, and a unique structure that cannot be obtained by the usual melting method. Since it can be obtained relatively easily, the degree of freedom in the design of the structure is high, and the dimensional accuracy of the sintered body is high.

As a method of imparting wear resistance to a camshaft, it has been considered to use a cam piece or journal made of a sintered alloy having excellent wear resistance and to form a camshaft by a so-called insert molding method. Such a cam piece and a journal portion need to be formed into a hollow cylindrical body so that molten metal is supplied to the inside during casting to be integrated. When the cam piece and the journal are made of a sintered alloy, it is necessary to increase the density from the viewpoint of wear resistance and mechanical strength. However, it is necessary to adopt a sintering method in which the porosity is reduced as much as possible to increase the density.

In general, a high-density sintered alloy is a so-called liquid phase sintering in which the sintering temperature is raised and a phase having a relatively low melting point out of the phases constituting the structure of the raw material powder particles is converted into a liquid phase. Can be manufactured. However, these methods are not economical because the equipment cost increases. Therefore, the high-density sintered body
The height is limited to a relatively small one, and it is difficult to apply to a cam piece or a journal.

[0008] Accordingly, the applicant has determined that regardless of the density,
For the purpose of providing a method for manufacturing a hollow sintered body having high dimensional accuracy, Japanese Patent Application Laid-Open No.
No. 4678), (1) a step of preparing a compact having substantially the same outer dimensions as the inner method (uchiri) of the hollow sintered body to be produced; and (2) forming a raw material powder, (3) inserting the compact into a hollow portion of the hollow green compact and performing liquid phase sintering to form the hollow green compact; And (4) a step of removing the compact from the sintered body.

That is, this method has a point in that densification by liquid phase sintering and densification by straightening are simultaneously performed.
Specifically, during liquid phase sintering, in which a metal hollow compact formed uniaxially by a metal mold is greatly shrunk, a compact that is not welded even at the sintering temperature is formed inside the hollow compact. It is characterized by suppressing the variation in the amount of shrinkage in the direction perpendicular to the pressing direction while correcting the deformation by placing it inside the body and making the hollow green compact conform to the shape of the molded body at the time of sintering shrinkage This is a sintering method.

A specific example of a method for manufacturing a camshaft by using a hollow sintered body obtained by the liquid phase sintering of the above method as a cam piece will be described.

FIG. 7 is a front view of a camshaft material manufactured using the cylindrical cam piece sintered body 1 of FIG. The camshaft 9 is manufactured by an insert molding method (also called an insert molding method). That is, the cylindrical cam piece sintered body 1 and the cylindrical journal part sintered body 7 are set at predetermined positions in the mold cavity, and molten metal is poured into the mold to form an integral camshaft. ,
Perform grinding, etc.

The journal sintered body 7 is manufactured by the same method as the cylindrical cam piece sintered body 1. In FIG. 6, 1a
Is a mark for determining a phase to be described later. In FIG.
Reference numeral 8 denotes a poured shaft portion, the material of which is spheroidal graphite cast iron FCD
60.

The camshaft is manufactured by casting as described above, and a steel pipe is inserted into a cylindrical cam piece sintered body and a cylindrical journal part sintered body. It can be manufactured by fixing the sintered body and the journal part sintered body. The diameter of the steel pipe is increased by providing a taper at the tip, slightly smaller than the inner diameter of the steel pipe (0.5 to 1.0 m).
m) This is performed by press-fitting and inserting a pipe expanding tool having a pipe expanding portion having a large diameter at the tip into a steel pipe. By making the camshaft hollow in this way, weight reduction can be achieved. In this case, as shown in FIG. 8, a cylindrical cam piece sintered body (the same applies to a journal portion sintered body) 1
It is preferable to form a concave-convex engaging portion 1b on the inner peripheral surface. When the tubular cam piece sintered body 1 is fixed to the steel pipe by expanding the steel pipe, the engaging portion 1b bites into the outer peripheral surface of the steel pipe, and the two mesh with each other, so that the fixing of both is ensured.

Further, the cylindrical cam piece sintered body and the cylindrical journal part sintered body can be connected to the shaft by a resin.

[0015]

The mark 1a (FIG. 6) for determining the phase in the camshaft manufacturing process described above.
Reference) is required.

That is, when the cylindrical cam piece sintered body 1 is arranged at a predetermined offset angle around the cam shaft in the cast-in process, the mark 1a is used to set the cylindrical cam piece sintered body 5 in a mold. It is used as an alignment mark with the mold or a phase determination mark.

In expanding the pipe, the steel pipe is press-fitted after the mark previously written on the steel pipe and the mark 1a of the cylindrical cam piece sintered body 1 are aligned.

Similarly, in the case of resin bonding, it is necessary to match the phase of the cylindrical cam piece sintered body and the shaft with the mark 1a.

Further, when cutting or grinding the camshaft assembled as shown in FIG. 7, it is necessary to determine the phase for the purpose of minimizing the cutting or grinding allowance.
For this purpose, one cylindrical cam piece sintered body 1 is provided with a mark 1a.

As described above, it is necessary to make a concave or convex mark in the sintering process due to the necessity of processing work in the post-sintering process. For this purpose, a mark is formed on the hollow green compact by die molding. Since the hollow green compact is easily deformed, machining of the mark is easy, and the reproducibility of the size and position of the mark is high.

However, during the liquid phase sintering, the hollow green compact with the mark and the straightening body may be topologically shifted from a desired position.

FIG. 9A shows a case where the hollow green compact 10 and the correction body 20 are arranged in an ideal phase, and the hollow green compact 10 uniformly shrinks around the correction body 20. Therefore, a cylindrical cam piece sintered body 1 having an ideal shape as shown in FIG. 9C is obtained. FIG. 9B shows a case where the correction body 20 is rotated clockwise from the ideal phase. Since the contraction of the hollow green compact 10 becomes non-uniform, the mark for determining the phase as shown in FIG. It deviates from the position, resulting in processing defects such as unbalance in the allowance for cutting and grinding.

Therefore, the present invention prevents the phase determination mark attached to the hollow green compact, which is the starting material of the cam piece, using a mold from shifting during liquid phase sintering, and prevents processing defects in the processing step after sintering. It is an object of the present invention to reduce a decrease in yield due to mechanical cutting or the like.

[0024]

SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a cam piece of a camshaft by arranging a straightening body inside a hollow compact and subjecting the hollow compact to liquid phase sintering. At least two places on the end face of the powder, the first mark having a convex or concave shape extending substantially in the direction of the center of the hollow green compact and having a convex or concave cross section formed therein, and the hollow green compact having the straightening body disposed on the inner face thereof is provided. A second mark to be fitted with the first mark is provided on a base plate supported by the above, and a hollow compact is mounted on the base plate so that each mark is fitted to perform correction and liquid phase sintering. The present invention relates to a method of manufacturing a hollow sintered body cam piece. Also,
A convex or concave third extending in the same direction as the first mark;
Marking may be formed on the end face of the straightening body and straightening and liquid phase sintering may be performed such that the second mark is fitted with the first mark and the third mark.

In the present invention, as shown in FIGS. 1 (a) and 1 (b), a hollow green compact 10 in which a straightening body 20 is disposed inside.
Is used for sintering. The base plate 12 is provided with a second mark 22 having a convex shape, and the hollow green compact 10 is provided with a first mark 23 having a concave shape to be fitted with the second mark 22 as shown in FIG. The hollow green compact 10 shrinks toward the center.
Does not hinder this shrinkage, and constrains the movement of the hollow green compact that causes a phase shift indicated by the arrow in FIG. For this purpose, the marks 22 and 23 are formed along the above-mentioned contraction direction. In addition, when the first mark 23 is provided only at one position, the turning motion about the mark as the central axis is not suppressed,
Since the effect of preventing the phase shift is not sufficient, it is necessary to form at least two places. In addition, as shown in FIG.
When the first mark and the second mark 22 are formed at several places, the effect of preventing the phase shift becomes larger.

Further, since the straightening body is made of ceramic or the like, shrinkage and the accompanying phase shift do not occur. However, when the shrunk hollow green compact is straightened, a phase shift may occur due to the force from the hollow green compact. is there. To prevent this, a convex or concave mark (third mark) 24 is also formed on the correction body 20 as shown in FIGS.
The second mark 22 fitted to the marks 23 and 24
It is desirable to form

[0027]

In particular, in the case of a deformed body for the production of a hollow body for a camshaft, the concave or convex splitting is performed so that the respective phases of the straightened body to be the inner cylinder and the hollow green compact to be sintered coincide with each other. If the mark for fitting is formed with a mold, and the mark to be fitted with the mark is also formed on the base plate on which the correction body and the hollow green compact are mounted, the hollow green compact and the base plate, Since the phase of the hollow green compact, straightening body and base plate match,
As a result, a mark for determining the phase remains at a desired position during sintering.

[0028]

EXAMPLE In a cam-shaped powder molding die having an irregular cross section, a powder (composition, 12) which is liquid phase sintered by an upper punch provided with a convex mark (semicircular cross section, R = 1.1 mm). %
When compression molding of Cr-2% C-0.7% P-1% Mo-Fe), a concave phase determining mark (first mark) 23 having a semicircular cross section (R = 1.1 mm) is formed. Hollow compact 1 formed at two places on the end face (phase shift angle = 180 degrees)
0 (see FIG. 4) is obtained. On the other hand, the correction body 20 has a concave mark (third mark 2) having a semicircular cross section (R = 1 mm) at a position on the line connecting the first marks 23 during sintering.
4) is formed. Further, the alumina base plate on which the hollow green compact 10 and the straightening body 20 are placed also has a semicircular cross section (R
= 1 mm), and an alumina round bar having a radius of 1 mm is fitted into this groove to form a convex linear mark (second mark). The hollow green compact is arranged outside and the straightening body is arranged inside so that the first and third marks are engaged with the alumina round bar. When sintering is performed at 1150 ° C. for 60 minutes in a vacuum atmosphere, the hollow green compact is subjected to liquid phase sintering so as to follow the straightening body, and the phasing mark provided at the time of molding is attached to a predetermined position of the sintered body. ing.

[0029]

According to the present invention, when the sintered body manufactured by the above-described method is compounded or machined based on the mark, a product having an ideal shape can be obtained, and a cutting and grinding allowance in a subsequent process can be minimized. There are advantages that can be set.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view showing an embodiment of a method according to claim 1 of the present invention.

FIG. 2 is a perspective view of the hollow green compact and the straightening body shown in FIG. 1 as viewed from the back side.

FIG. 3 is a perspective view showing an embodiment of the method of claim 1 of the present invention.

FIG. 4 shows an embodiment of the method according to claim 2 of the present invention.
FIG.

FIG. 5 is a sectional view of the hollow green compact and the straightening body of FIG. 4;

FIG. 6 is a plan view and a sectional view of a hollow green compact.

FIG. 7 is a drawing of a camshaft.

FIG. 8 is an explanatory view of a method for expanding a hollow sintered body.

FIG. 9 is an explanatory diagram of a phase shift during sintering.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical cam piece sintered body 7 Journal part sintered body 8 Shaft part 9 Camshaft 10 Hollow green compact 12 Base plate 20 Straightening body 22 Second mark 23 First mark 24 Third mark

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-213402 (JP, A) JP-A-60-100602 (JP, A) JP-A-62-157936 (JP, U) (58) Investigation Field (Int.Cl. ⁶ , DB name) B22F 3/00-7/08 C04B 35/64

Claims (2)

(57) [Claims] 1. A method for producing a cam piece of a camshaft by disposing a straightening body inside a hollow green compact and subjecting the hollow green compact to liquid phase sintering, wherein at least an end face of the hollow green compact is provided. 2
A first mark having a convex or concave shape extending substantially in the center direction of the hollow green compact at a place, and supporting a hollow green compact having a straightening body disposed inside on a base plate at an end face thereof. Providing a second mark to be fitted with the first mark, and performing correction and liquid phase sintering by placing the hollow compact on a base plate so that each mark is fitted; Manufacturing method of united cam piece. 2. A method for producing a cam piece of a camshaft by arranging a straightening body inside a hollow green compact and subjecting the hollow green compact to liquid phase sintering. In some places, a first mark extending substantially in the direction of the center of the hollow green compact and having a convex or concave cross section is formed, and a convex or concave third mark extending in the same direction as the first mark is corrected. A second mark to be fitted with the first mark and the third mark is provided on a base plate formed on the end face of the body and supporting the hollow compact having the correction body disposed therein at the end face, and the first mark is provided. The hollow sintered compact cam characterized in that the hollow compact and the straightening body are placed on a base plate so that the mark and the third mark are fitted to the second mark, and straightening and liquid phase sintering are performed. Method of manufacturing pieces.