JPH06145707A - Die for compacting - Google Patents

Abstract

PURPOSE:To prevent the deformation, wear and breakage at the lower edge part on the outer circumferential side of an upper punch in a die for compacting a spherical bearing. CONSTITUTION:The outer circumferencial part of the lower edge side of an upper punch 21 is constituted of a recessed spherical part 23. A tapered chamfer 25 is formed at the lower edge part of the spherical part 23. The lower edge of the chamfer 25 is positioned higher than the crossed line between the extended face of the outer circumferential face 22 of the upper punch 21 and the extended face of the spherical part 23 by 0.02 to 0.3mm. The angle formed by the chamfer 25 and the outer circumferential face 22 is regulated to 35 to 50 deg.. In this way, the service life of the die for compacting is prolonged. The generation of burrs on the outer circumferential face of a green compact can also be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding die for molding a spherical bearing or the like.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a sintered oil-impregnated bearing 1 manufactured by powder metallurgy. This bearing 1 is a spherical bearing having a substantially cylindrical seat surface, but the seating surface is spherical. The intermediate portion of the outer peripheral surface is a cylindrical surface portion 2, while the outer peripheral surface ends are respectively It has convex spherical surfaces 3 and 4. Further, the bearing 1 has a point-symmetrical shape, and both the spherical surface portions 3 and 4 are centered on the point of symmetry O. By the way, when manufacturing the bearing 1, first, the raw material powder is compressed by a powder molding press to mold a green compact 1a as shown by a chain line. The green compact 1a also has an outer peripheral surface including a cylindrical surface portion 2a and spherical surface portions 3a and 4a. Next, the green compact 1a is heated and sintered in a sintering furnace. Then, the sintered body 1a is recompressed and straightened by a straightening press to finish it into a predetermined size and shape shown by a solid line. further,
The straightened sintered body 1 is impregnated with oil.

Next, an example of the powder molding die of the powder molding press will be described with reference to FIG. 11 is a die, and this die 11 is fixed to a die plate 12. The die 11 forms the cylindrical surface portion 2a of the outer peripheral surface of the green compact 1a, and has a cylindrical shape, and the inner peripheral surface is a vertical cylindrical surface. Further, in the die 11, a core rod 13 forming an inner peripheral surface of the green compact 1a is coaxially and fixedly provided. 14 is a substantially cylindrical lower punch, and the lower punch 14 includes the die 11 and the core rod 13
It is fitted slidably from below between and. Further, 15 is a substantially cylindrical upper punch, and this upper punch 15 is the die
It is fitted between the core 11 and the core rod 13 so as to be slidable and insertable and removable from above. Both punches 14 and 15 are die 11
The outer peripheral surface fitted to the inner peripheral surface of and the inner peripheral surface fitted to the outer peripheral surface of the core rod 13 are vertical cylindrical surfaces. And
The lower punch 14 forms the lower end surface of the green compact 1a and the lower spherical portion 3a of the outer peripheral surface, and in order to form this spherical portion 3a, the outer peripheral portion of the upper end surface is more than the upper end surface. Also has a concave spherical surface portion 16 having its center above and on the vertical center line of the lower punch 14. Further, the upper punch 15 forms the upper end surface of the green compact 1a and the upper spherical surface portion 4a of the outer peripheral surface. In order to form the spherical surface portion 4a, the outer peripheral portion of the lower end surface has the lower end surface. It is a concave spherical surface portion 17 having its center below and above the vertical center line of the upper punch 15. And, in the conventional upper punch 15, FIG.
As shown in, the spherical surface 17 remains the same spherical surface
As a result, the intersection between the outer peripheral surface 18 and the spherical surface portion 17 was very sharp. The same applies to the lower punch 14.

When powder molding, the upper punch from the die 11
The raw material powder is filled into the die 11 from a feeder (not shown) in a state where 15 is pulled out upward. Next, the descending upper punch 15 is fitted into the die 11, and the raw material powder is pressed and compressed by the punches 14 and 15 in the die 11 to form the green compact 1a.

[0005]

However, in the above-mentioned conventional powder molding die, in the upper punch 15, the spherical surface portion 17 intersects with the vertical outer peripheral surface 18 while keeping the same spherical surface, and as a result, the outer peripheral surface 18 Since the intersection between the and the spherical portion 17 was very sharp, the following problems were caused. That is, the upper punch 15 that is inserted into and removed from the die 11 may have a slight axial misalignment between the upper punch 15 and the die 11 due to, for example, an error in the assembly of the mold. The lower edge of the outer peripheral side, which is extremely sharp and weak, is likely to be deformed, damaged, or worn. More specifically, as shown by the chain line in FIG. 6, when the upper punch 15 is fitted into the die 11, the upper punch 15 is eccentric to the upper punch 15 from the upper side of the die 11.
A force is applied to the inner side of the upper punch 15 in the radial direction to easily deform the lower end portion of the upper punch 15 on the outer peripheral side inward, or the outer peripheral surface 18 of the upper punch 15 is worn away.
The outer peripheral side lower end portion is damaged. In the conventional mold, such a defect was generated by repeating molding on average about 10,000 times. When the outer peripheral lower end of the upper punch 15 is deformed, worn or damaged as described above, a burr 5a is formed between the cylindrical surface portion 2a and the spherical surface portion 4a of the green compact 1a as shown in FIG. Stand up. The burr 5a remains after being straightened, although it falls down. As shown in FIG. 8, a burr mark 5 such as a scratch is formed on the bearing 1 after straightening. This burr mark 5 is the bearing 1
When the bearing 1 is assembled into the housing, the spherical portion 3 of the above-mentioned spherical surface 3 interferes with the spring for self-alignment provided in the housing, which impairs the self-aligning property.

The present invention is intended to solve such a problem, and in a powder molding die in which the outer peripheral portion of the lower punch has a concave spherical surface, the outer punch of the upper punch has a lower peripheral portion. The purpose of the present invention is to prevent deformation, wear, and damage, to prevent burrs from being generated on the outer peripheral surface of the green compact, and to prolong the life of the upper punch.

[0007]

In order to achieve the above object, a powder molding die of the present invention comprises a die, a lower punch which is slidably fitted into the die from below, and the inside of the die. Is equipped with an upper punch that is slidably fitted from above and can be inserted and removed. The upper punch has a vertical cylindrical surface on the inner peripheral surface of the die and a lower end surface. Has a concave spherical surface centered below the lower end surface and on the center line of the upper punch, and the lower end extends to the lower end portion connected to the outer peripheral surface of the spherical portion. 0.02 to 0 from the line of intersection between the surface and the extended surface of the spherical surface.
It is located 3 mm higher and the angle between it and the outer peripheral surface is 35-50.
The chamfered part is formed.

[0008]

In the powder molding die of the present invention, at the time of molding, after the raw material powder is filled in the die, the upper punch is lowered and fitted into the die, and the raw material powder is fed by the lower punch and the upper punch in the die. Compress to form a green compact. On the upper end side of the outer peripheral surface of the green compact, a convex spherical surface portion is formed by the concave spherical surface portion of the outer peripheral portion of the lower end surface of the upper punch. By the way, since the chamfered portion is formed at the lower end of the spherical portion of the upper punch and the lower end on the outer peripheral side of the upper punch is relatively dull, the die and the upper punch that is inserted into and removed from the die are separated. Deformation of the lower end on the outer peripheral side of the upper punch against the misalignment of the axis,
Wear or damage is prevented, and burrs are also prevented from occurring on the outer peripheral surface of the green compact due to the deformation or wear. The height from the intersection of the extension surface of the outer peripheral surface of the upper punch and the extension surface of the spherical surface to the lower end of the chamfer should be changed depending on the size of the green compact, but is 0.02 mm or less. If so, the effect of preventing the deformation and damage becomes insufficient, while if it is 0.3 mm or more, when correcting the sintered body formed by sintering the green compact, the spherical portion of this sintered body The amount of compression at the lower end becomes too large, making correction difficult. Further, regarding the angle formed by the chamfered portion with the outer peripheral surface of the die, if the angle is 35 ° or less, the effect of preventing the deformation and damage becomes insufficient, while if it is 50 ° or more, the correction becomes difficult. Therefore, the height is 0.02-0.3mm and the angle is 35mm.
It is preferably ˜50 °.

[0009]

EXAMPLE An example of the powder molding die of the present invention will be described below with reference to FIGS. The powder molding die of this example has the same structure as the above-described die shown in FIG. 5 except for the outer peripheral side lower end portion of the upper punch. Attach
The description is omitted. The upper punch 21 of the present embodiment includes the die 11
The outer peripheral surface 22 fitted to the inner peripheral surface of is a vertical cylindrical surface, and the outer peripheral portion of the lower end surface is below the lower end surface and the center O is located on the vertical center line a of the upper punch 21. It has a concave spherical surface portion 23. The radius R of the spherical portion 23 is about 18.6 mm. Further, the height B from the center O to the horizontal plane portion 24 of the upper punch 21 forming the upper end surface of the green compact 1a is about 6.7 mm. Further, the outer diameter of the horizontal surface portion 24, that is, the inner diameter r of the spherical surface portion 23 is about 12.9 mm. Further, a tapered chamfered portion 25 is formed over the entire circumference at the lower end portion of the spherical surface portion 23 connected to the outer peripheral surface 22. An angle θ formed by the chamfered portion 25 and the vertical outer peripheral surface 22 of the upper punch 21 is 45 °. The height H from the line of intersection b between the extended surface of the outer peripheral surface 22 and the extended surface of the spherical portion 23 to the lower end of the chamfered portion 25 is 0.15 mm.

The height H should be changed depending on the size of the green compact 1a and the like. For example, θ = 45 °
As a result, it may be determined as shown in FIG. 3 according to the height A from the intersection line b to the horizontal plane portion 24. In the upper punch 21 of the above embodiment, A is about 3.2 mm. Further, the height C from the upper end of the chamfered portion 25 to the horizontal surface portion 24 is about 3.0 mm.

Next, the operation of the above configuration will be described. The upper punch 21 from the die 11
In the state where the powder is pulled out upward, the raw material powder is filled in the die 11 from a feeder (not shown). Next, the descending upper punch 21 is fitted into the die 11, and the raw material powder is pressed and compressed by the lower punch 14 and the upper punch 21 in the die 11 to form the green compact 1a. This molding is repeated. Green compact 1a
On the outer peripheral surface of, by the spherical surface portions 16 and 23 of both punches 14 and 21,
Convex spherical surfaces 3a and 4a are formed on the lower end side and the upper end side, respectively. The molded green compact 1a is then heated and sintered in a sintering furnace to form a sintered body 1a. Next, the sintered body 1a is recompressed and straightened by a straightening press having a straightening die having a structure similar to that of the powder molding die, and finished into a predetermined size and shape.

According to the configuration of the above embodiment, the chamfered portion 25 is formed at the lower end of the spherical portion 23 of the upper punch 21, and the lower end of the upper punch 21 on the outer peripheral side is relatively dull. It is possible to prevent the lower end portion of the upper punch 21 on the outer peripheral side from being deformed, worn or damaged against the misalignment of the axial center between the upper punch 21 and the upper punch 21 which is inserted into and removed from the die 11. That is, since the strength of the lower end portion on the outer peripheral side of the upper punch 21 is increased, it is difficult for the upper punch 21 to be deformed.
22 is also less likely to wear. Therefore, the lower end portion on the outer peripheral side of the upper punch 21 is less likely to be damaged. Further, even if a defect occurs in the outer peripheral side lower end portion of the upper punch 21 due to the progress of wear, since the outer peripheral side lower end portion becomes thicker as it goes upward, the defect is very small. It will be small. It should be noted that the chamfered portion 25 of the upper punch 21 is likely to be worn near the angular upper end of the chamfered portion 25 due to sliding of the raw material powder. The strength of the lower end portion of the outer peripheral side of 21 is hardly reduced, and rather the deformation of the green compact 1a during correction is made smooth. In this way, the life of the powder molding die including the upper punch 21 is significantly extended. In fact, the mold of the above embodiment,
It lasted between 400,000 and 500,000 times. Therefore, it is not necessary to frequently replace the mold, which leads to cost reduction. Further, since it is possible to prevent deformation and damage of the outer peripheral side lower end of the upper punch 21, due to this deformation and damage, there is a burr between the cylindrical surface portion 2a and the spherical surface portion 4a on the outer peripheral surface of the green compact 1a. Can also be prevented. Therefore, no burrs are left on the corrected bearing 1, and there is no inconvenience such as hindering the operation of the self-aligning spring provided in the housing.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, H = 0.15 mm and θ = 45 ° are set, but the present invention is not limited to this. However, if H <0.02 mm, the effect of preventing deformation and damage of the outer peripheral side lower end of the lower punch 21 becomes insufficient, while if H> 0.3 mm, the green compact 1a is sintered. When the sintered body 1a consisting of
The amount of compression at the lower end of the spherical portion 4a of 1a becomes too large, and correction becomes difficult. Further, when θ <35 °, the effect of preventing the deformation and damage becomes insufficient, while when θ> 50 °, at the time of straightening, at the lower end of the spherical portion 4a of the sintered body 1a. The amount of compression becomes too large, making it difficult to correct. Therefore, it is preferable that 0.02 mm ≦ H ≦ 0.3 mm and 35 ° ≦ θ ≦ 50 °.

Further, if necessary, a chamfered portion similar to the chamfered portion 25 at the lower end portion of the spherical portion 23 of the upper punch 21 in the above embodiment may be formed on the upper end portion of the spherical portion of the lower punch. However, the lower punch that is always fitted to the die requires less chamfer than the upper punch that is inserted into and removed from the die. It should be noted that it is possible to use a stepped die as the die and to form the spherical portion on the lower side of the outer peripheral surface of the green compact by the die, but in this case, not only the sharp portion on the outer peripheral portion of the upper end surface of the lower punch is used. Does not happen. Further, the powder molding die of the above-mentioned embodiment had one lower punch, but the lower punch is
It may be divided into a lower first punch that forms a spherical portion on the lower side of the outer peripheral surface of the green compact and a lower second punch that forms the horizontal lower end surface of the green compact.

[0015]

According to the present invention, in the upper punch that is inserted into and removed from the die, the outer peripheral surface fitted in the die is a vertical cylindrical surface, and the outer peripheral portion of the lower end surface is more than this. In a powder molding die having a concave spherical portion having a center on the center line of the lower punch below, in a lower end portion of the spherical portion connected to the outer peripheral surface, a lower end is an extended surface of the outer peripheral surface and the spherical surface. Since the chamfered portion is located 0.02 to 0.3 mm higher than the line of intersection with the extension surface of the section and forms an angle of 35 to 50 ° with the outer peripheral surface, the molded green compact is sintered. It is possible to prevent deformation, wear or damage of the lower end of the upper punch on the outer peripheral side without making it difficult to correct the sintered body.
The life of the powder molding die including the upper punch can be significantly extended, and the cost can be reduced. Further, since it is possible to prevent the lower end portion on the outer peripheral side of the upper punch from being deformed, worn or damaged, it is possible to prevent burrs from being generated on the outer peripheral surface of the green compact.

[Brief description of drawings]

FIG. 1 is a sectional view of a part of an upper punch and a die showing an embodiment of a powder molding die of the present invention.

FIG. 2 is an enlarged view of the vicinity of a chamfered portion of the above punch.

FIG. 3 is a graph for determining a dimension of the chamfered portion.

FIG. 4 is a sectional view of a bearing.

FIG. 5 is a cross-sectional view showing an example of a conventional powder molding die.

6A and 6B are views showing the same problem, where FIG. 6A is a sectional view of a lower end portion on the outer peripheral side of the upper punch, and FIG. 6B is a side view thereof.

FIG. 7 is a sectional view showing a state at the time of powder molding.

FIG. 8 shows a bearing after straightening with burr marks as above.
(A) is a partial sectional view and (b) is an overall perspective view.

[Explanation of symbols]

 11 Die 14 Lower punch 21 Upper punch 22 Outer peripheral surface 23 Spherical surface 25 Chamfer O Center a Center line b Intersection line

Claims (1)

[Claims] 1. A die, a lower punch slidably fitted into the die from below, and an upper punch slidably and slidably fitted into the die from above. The upper punch has a vertical cylindrical surface on the outer peripheral surface that fits on the inner peripheral surface of the die, and the outer peripheral portion of the lower end surface is a concave shape whose center is located below the lower end surface and on the center line of the upper punch. The lower end portion of the spherical portion connected to the outer peripheral surface is located 0.02 to 0.3 mm higher than the intersection line between the extended surface of the outer peripheral surface and the extended surface of the spherical surface.
A metal mold for powder molding, characterized in that a chamfered portion having an angle of 35 to 50 ° with the outer peripheral surface is formed.