JPH07102305A - Method for sizing powder compact and device therefor - Google Patents

Abstract

PURPOSE:To size a sintered machine part having an undercut into a desired size by compression. CONSTITUTION:An upper punch 15 and a lower punch 13 are provided and vertically brought close to or separated from each other. A sintered work W is placed on the lower punch 13 and clamped between the upper and lower punches 13 and 15, and a supporting punch 17 is then inserted into the undercut of the work W. An upper die 23 and a lower die 21 are brought close to each other until they are in contact with each other on the abutting surfaces, and the work W is positioned inside the dies 21 and 23. A groove forming the passage corresponding to the supporting punch 17 is provided respectively on the abutting surfaces, and the supporting punch 17 is inserted into the undercut of the work W to bring both dies 21 and 23 into contact with each other. Accordingly, the work is sized while the undercut is supported.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to recompressing (sizing) a molded product which has been compression molded by a powder molding press and sintered.
On how to do.

[0002]

2. Description of the Related Art So-called sinter machine parts are manufactured by compressing a powder material by a compressing means such as a powder molding press machine to sinter a compression-molded article by a heating means such as a heating furnace. When the molded product (hereinafter, sintered product) W after sintering is further molded into a desired dimension, usually, after the sintering process is completed, the sintered product is as follows. The sizing process is underway. That is, as shown in FIGS. 11 (a) and 11 (b), the formed sintered product W is formed into the die 10
After being inserted into the die 1, the sintered product W in the die 101 is compressed by the upper punch 103 and the lower punch 105. In this way, the sintered machine component is manufactured by forming the sintered product W into a desired size.

[0003]

However, when the shape of the sintered product W has an undercut portion U as in the double chain type sprocket 1 shown in FIG.
Problems occur when sizing is performed by the conventional sizing method. That is, as shown in FIG. 12, since there is no member that supports the undercut portion U of the sintered product W, the upper and lower punches 1
When a compressive force from 03, 105 is applied, an excessive force is applied to the sintered product W, and the parts may be damaged.

On the other hand, if the undercut portion U is not supported, the surface facing the undercut portion U will not receive a compressive force for correcting the dimensions. In such cases,
Even if sizing is performed on this portion, the dimensional accuracy is not improved. Therefore, in order to obtain the dimensional accuracy required for the sintered product W, machining is required.

The present invention made in view of the above problems has an object to provide a sizing method capable of molding a sintered machine part having a shape having an undercut portion into a desired size.

[0006]

A method for sizing a powder molded article according to the present invention for achieving the above object comprises a first punch and a second punch for compressing the powder molded article in a compression direction. A step of holding by a punch, and an undercut support punch having a shape part corresponding to the shape of the undercut part in the undercut part of the powder molded product held by the first punch and the second punch. A step of inserting and a first step for surrounding the periphery of the powder molded article 1
Moving the die and the second die relatively close to each other in the compression direction and bringing them into contact with each other to surround the periphery of the powder molded article; the first punch and the second punch; and an undercut support punch, And a step of compression-molding the powder molded article by cooperation with the first die and the second die. Further, the sizing device of the powder molded product of the present invention to achieve the above object, a die that surrounds the powder molded product over the entire circumference thereof, and the relative closeness and separation in the compression direction of the powder molded product and A sizing apparatus for a powder molded product, comprising: a pair of first and second punches for compressing the powder molded product carried into a die in the compression direction, wherein the die is
The first die and the second die which move relatively toward and away from each other in the compression direction.
An undercut support punch that is formed from a die and that is inserted into and withdrawn from the undercut portion of the powder molded product is provided.

[0007]

In the present invention having such characteristics, the powder molded product is first held by the first punch and the second punch, and the undercut of the undercut support punch is held in the undercut portion of the powder molded product. The shape part corresponding to the shape of the part is inserted. Next, the first die and the second die are brought into contact with each other to surround the periphery of the powder molded product. And
1st punch, 2nd punch, undercut support punch,
The powder molded product is compression molded by the cooperation of the first die and the second die.

Further, according to the present invention, the die is composed of a first die and a second die which move toward and away from each other in the compression direction. And, it has an undercut support punch to be inserted into the undercut portion of the powder molded product. Then, with the undercut portion of the powder molded product being supported by the undercut support punch, the first die and the second die are brought into contact with each other for sizing.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. In this embodiment, an example of sizing the double row cam sprocket 1 having the shape shown in FIG. 8 will be described. FIG. 1 is a side sectional view showing a main part of the sizing apparatus of this embodiment, and FIG. 2 is a partial side sectional view showing a state in which a sintered product is sized by the sizing apparatus. As shown in FIG. 1, this sizing device has a lower punch (second punch) 13 supported by a lower base plate 11, and an upper side of this lower punch 13 has
An upper punch (first punch) 15 that is moved toward and away from the lower punch 13 by a driving unit (not shown) is attached. Therefore, by relatively moving the upper and lower punches 13 and 15 relatively close to each other, the sintered product W placed on the lower punch 13 can be compressed from the vertical direction as shown in FIG.

Further, as shown in the drawing, the sizing apparatus of this embodiment has a pair of support punches 17 which move back and forth in a direction perpendicular to the moving direction of the upper and lower punches 13, 15. This support punch 17 is shown in FIG.
As shown in (b), the undercut portion U of the sintered product W
(Refer to FIG. 8) It is composed of a distal end portion 17a to be inserted and a proximal end portion 17b on the proximal end side following the distal end portion 17a.
The thickness of the base end portion 17b is smaller than the thickness of the tip end portion 17a, and the width of the base end portion 17b is smaller than the diameter of the die. The support punch 17 is moved back and forth by the hydraulic cylinder 19. Therefore, when the support punch 17 and the undercut portion U have the same height, when the support punch 17 is moved to the forward position, as shown in FIG.
As shown in FIG.
It is inserted into the undercut portion U of. In the present embodiment, the support punch 17 and the hydraulic cylinder 19 for driving the support punch 17 are fixed to, for example, the base plate 11 that supports the lower punch 13.
It may be attached so as to be movable in the up and down direction, which is the moving direction of 3. On the outer periphery of the lower punch 13 described above, a lower die (second die) 21 that moves up and down relative to the lower punch 13 in a sliding state is attached. A groove G corresponding to the base end portion 17b of the is provided (see FIG. 6).

As shown in FIG. 4 or 5, a guide A is formed on the dividing surface S side of the inner peripheral surface I of the molding portion of the lower die 21. The guide A prevents the sintered product W from being scraped or cracked due to the contact between the sintered product W and the corner of the lower die 21, and also smoothly inserts the sintered product W into the forming part. Useful for. The guide A shown in FIG. 4 is formed by chamfering a corner with a bending radius of about 0.3 mm to 1 mm, and the guide A shown in FIG. 5 is a split surface of the molding portion inner peripheral surface I. An inner peripheral surface having a radius larger than the inner peripheral diameter by the distance E is formed on the S side.

On the other hand, on the outer periphery of the upper punch 15, an upper die (first die) 23 which moves up and down relative to the upper punch 15 in a sliding state is attached.
As in No. 1, a groove G corresponding to the support punch 17 is provided. When both dies 21 and 23 as described above are moved relatively close to each other as shown in FIG. 2 and the two divided surfaces S and S are brought into contact with each other, a molding portion in which the sintered product W is housed is formed.

As described above, the width of the base end portion 17b of the support punch 17 is smaller than that of the upper and lower dies 21 and 23, and the thickness of the base end portion 17b depends on the grooves G and G. It is smaller than the thickness of the formed passage Q. Therefore, with the tip portion 17a of the support punch 17 inserted in the undercut portion U of the sintered product W, both dies 21,
It is possible to bring the contact surfaces S, S of the two 23 into contact with each other. Further, since a gap is formed between the passage Q and the support punch 17, even if the relative positions of the dies 21 and 23 and the support punch 17 are deviated during the sizing, a force is applied from one member to the other member. Will not be added. Therefore, the support punch 17 is not deformed or damaged.

Similarly, when the undercut U is a part of the sintered product W, a gap can be formed between the dies 21 and 23 and the support punch.
7 will not be deformed or damaged.

The dies 21 and 23 are moved up and down by driving means (not shown) such as the hydraulic cylinder 19. As these driving means, various driving means such as a pneumatic cylinder and a motor engine can be used in addition to the hydraulic cylinder.

A procedure for sizing the sintered product W having the undercut portion U with such a sizing device will be described with reference to FIG. Note that in FIG. 6, in order to clarify the operation of each member, the movement will be described with reference to the drawing of a sizing device having a simplified structure.

As shown in FIG. 6A, first, the upper die 23 and the lower die 21 are separated from each other, and the height of the compression surface 25 of the lower punch 13 and the height of the dividing surface S of the lower die 21 are matched. The sintered product W on the compression surface 25 of the lower die 21
To place. Next, as shown in FIG. 6B, after the height of the undercut portion U of the sintered product W and the height of the tip portion 17a of the support punch 17 are matched, the support punch 1
The tip portion 17a of No. 7 is inserted into the undercut portion U. Here, the support punch 17 inserted into the undercut portion U
The thickness T of the tip portion 17a of the
It is preferable to make the size smaller than the dimension H of the undercut portion U in the height direction, in consideration of the pressing margin when performing sizing by 5. In this way, the tip portion 1 of the support punch 17 is
7a can be smoothly inserted into the undercut portion U. Since the undercut portion U of the sintered product W is accurately formed as an integrated type, the tip portion 1 of the support punch 17 is always formed.
7a can be smoothly inserted.

Subsequently, as shown in FIG. 6 (b), the upper punch 15 is moved downward in the figure to cooperate with the lower punch 13 to hold the sintered product W sandwiched from above and below.
Alternatively, the front end 17a of the support punch 17 may be inserted into the undercut portion U of the sintered product W after the sintered product W is held by the upper and lower punches 13 and 15.

In this way, the sintered product W is held by the upper and lower punches 13 and 15 and the undercut portion U is formed.
When the tip portion 17a of the support punch 17 is inserted into the
Move the upper punch 15 further downward by a predetermined distance,
The lower side of the sintered product W is inserted into the lower die 21. The lower die 21 may be moved upward in the drawing so that the lower side of the sintered product W is inserted into the lower die 21. Then, when the lower side of the sintered product W is inserted into the lower die 21, the supporting punch 17 moves relatively close to the lower die 21, and as shown in FIG. Part 17b
Is located in the groove G formed on the dividing surface S of the lower die 21. After that, the upper die 23 is moved downward in the figure to abut against the lower die 21, and the periphery of the sintered product W is held by the upper and lower dies 21 and 23.

As shown in FIG. 6D, a groove portion G corresponding to the base end portion 17b of the support punch 17 is formed on the dividing surface S of the upper die 23, similarly to the lower die 21. Therefore, the support punch 1 is attached to the undercut portion U of the sintered product W.
With the tip portion 17a of 7 inserted, the split surfaces S, S of the upper die 23 and the lower die 21 can be brought into contact with each other. Moreover, since there is a gap as shown in FIG. 7 between the die and the support punch, it is possible to allow some deviation in the relative position.

In this way, the upper and lower punches 13, 15
When the sintered product W sandwiched between the two is inserted into the dies 21 and 23, the sintered product W sandwiched by the upper and lower punches 13 and 15 is compressed and sizing is performed. When the sizing process of the sintered product W is completed, the upper die 23 and the lower die 21
After separating each from the other die, the support punch 17 is pulled out from the undercut portion U, the upper punch 15 is moved upward in the drawing, and the finished product on the lower punch 13 is taken out.

When the undercut portion U exists over the entire circumference of the sintered product W, the dividing surfaces S of the dies 21 and 23 and the sintered product W do not come into contact with each other. No burr is generated at the contact portion between the surfaces S, S and the sintered product W. However, for example, when there is an undercut portion U on a part of the outer periphery of the sintered product W, the dies 21 and 23
A so-called burr may occur at the contact position between the divided surface S and the sintered product W. However, even in such a case, in the sizing apparatus of the present embodiment, the position where the burr is generated is the outer peripheral portion of the sintered product W, so the burr can be easily removed compared to other positions. can do.

In the sizing of the double chain type sprocket 1 shown in FIGS. 8 (a) and 8 (b), as shown in FIG. It does not come into contact with the tip portion 17a of the punch 17. There is no problem because the dimension of the flank M can be corrected without supporting it with a die or punch. Further, when the flank M is not formed, the support punch 17 having the shape as shown in FIG. 10 can be formed so that the portion of the tooth tip 31 and the support punch 17 do not come into contact with each other.

[0024]

As described above, according to the present invention, the powder molded product is sized while the undercut portion of the powder molded product is supported by the support punch. Therefore, an unreasonable force is applied to the powder molded product during sizing. It is possible to prevent damage such as damage without being added.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a sizing device according to an embodiment.

FIG. 2 is a partial side cross-sectional view showing a sizing device of this embodiment.

FIG. 3 is a plan view and a side sectional view showing a support punch.

FIG. 4 is a partially enlarged view showing a die guide.

FIG. 5 is a partially enlarged view showing another embodiment of the die guide.

FIG. 6 is a side sectional view for explaining the operation of the sizing device of this embodiment.

FIG. 7 is a side sectional view showing a state in which a support punch is inserted into an undercut portion.

FIG. 8 is a plan view and a side sectional view showing a double chain type sprocket.

FIG. 9 is a side sectional view showing a support punch of another embodiment.

FIG. 10 is a side sectional view showing still another embodiment of the support punch.

FIG. 11 is a side sectional view showing a conventional sizing device.

FIG. 12 is a side sectional view showing a conventional sizing device.

[Explanation of symbols]

13 ... Lower punch, 15 ... Upper punch, 1
7 ... Support punch, 21 ... Lower die, 23 ... Upper die, S ... Contact surface, U ... Undercut portion,
W ... Sintered product.

Claims (2)

[Claims] 1. A step of holding a powder molded product by a first punch and a second punch for compressing the powder molded product in a compression direction, and powder molding held by the first punch and the second punch. A step of inserting an undercut support punch having a shape portion corresponding to the shape of the undercut portion into the undercut portion of the product, and a first die and a second die that surround the periphery of the powder molded product, Enclosing the periphery of the powder molded product by moving it relatively close to and in contact with the compression direction, the first punch and the second punch, the undercut support punch, the first die and the second die And a step of compression-molding the powder molded article in cooperation with the powder molded article. 2. A die which surrounds the powder molded article over the entire circumference thereof, and a die which is relatively movable toward and away from the powder molded article in the compression direction and is carried into the die. A sizing device for a powder molded product, comprising a pair of first and second punches for compressing in a compressing direction, wherein the die is composed of a first die and a second die that move relative to each other in the compressing direction. A sizing apparatus for the powder molded product, comprising an undercut support punch that is inserted into and removed from the undercut portion of the powder molded product.