JPH0683878B2 - Multiple interference fit mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multiple interference fit mold used under high pressure, and can be used as a die for cold forging used for plastic working and the like.

[Background Art and its problems] Generally, a die for plastic working such as a die for cold forging is processed at a considerably high pressure, so that an allowable internal pressure (within a range where the die is not destroyed during forming such as forging) is used. The maximum pressure that can be received inside, that is, the internal pressure that can be tolerated at the time of molding is required to be high.In particular, as long as the internal pressure is the same, the amount of material used is economical and workable. Is smaller, and it is desirable that the outer diameter is smaller.
For example, a multiple interference fit mold as shown in FIG. 8 is often used.

This multiple interference fit mold includes a plurality of tightening rings 1, which are tightening cylinders fitted by tight fit.
2, 3 and an insert 4 which is a central cylinder fitted into the innermost of these tightening cylinders by an interference fit,
A die hole 5 is provided at the center of this insert 4. In the multiple interference fit mold thus configured, the insert 4 is preloaded from the outside by the tightening force of the tightening rings 1, 2, and 3 so that the circumferential stress on the surface of the die hole 5 is compressed. In order to prevent the stress in the circumferential direction of the die hole 5 from becoming excessive on the tensile side due to the high pressure applied in the die hole 5 during processing, the stress of the insert 4 should not exceed the yield stress. It was possible to prevent the breakage of the mold and the like, and thereby increase the allowable internal pressure in the die hole 5 as compared with the case of a single mold.

Regarding the design of such multiple interference fit molds, many studies have been published so far, and the number of combinations of the tightening cylinders or the mechanical properties of each cylinder, the inner diameter, the outer diameter, etc. If is determined, it is possible to know in advance the allowable internal pressure when the configuration is performed based on the optimum conditions. vice versa,
By appropriately selecting these elements, the allowable internal pressure can be further increased. However, when high performance materials are used to improve mechanical properties, the material costs
It leads to a decrease in economic efficiency. Further, there is a limit to increasing the number of combinations of the tightening cylinders with the same outer diameter, and further, there is a problem that increasing the outer diameter leads to a decrease in workability.

[Object of the Invention]

It is an object of the present invention to provide a multiple interference fit cylinder having a higher allowable internal pressure than that of the conventional one.

[Means and Actions for Solving Problems]

In the present invention, two or more tightening cylinders that are combined as a multiple interference fit mold and a central cylinder that is fitted inside these are provided, and a cylinder excluding the outermost one of the tightening cylinders. At least one of the bodies is provided with a circumferential stress relieving means composed of an axial cut, and the axial length of the surfaces where this tubular body and the inner tubular body are in pressure contact with each other is the outer side of this tubular body. It is configured to be shorter than the length in the axial direction of the surfaces in pressure contact with the cylindrical body.

In the multiple interference fit mold configured in this way,
By the circumferential stress relieving means provided in the tubular body, it is possible to suppress the occurrence of the circumferential stress generated in the tubular body in response to the fastening force from the tubular body circumscribing the tubular body, and to reduce the fastening force. It is efficiently transmitted to the tubular body inscribed in the tubular body without being attenuated.

That is, in a cylindrical body that is continuous in the circumferential direction without a circumferential stress relaxation means such as a break, when receiving a tightening force from the outer cylindrical body, a circumferential stress is generated against the inward deformation, This circumferential stress attenuates the tightening force from the outside and cannot be sufficiently transmitted to the insert or the like on the inside.

However, in the present invention, since the cylindrical body is divided in the circumferential direction (completely or partially) by providing the circumferential stress relaxation means such as a break, the aforementioned circumferential stress does not occur, It is possible to directly transmit the tightening force from the outside to the insert or the like inside without being attenuated.

Further, in the cylindrical body provided with the circumferential stress relieving means, the peripheral surface area becomes smaller on the inner side than on the outer side in accordance with the difference in the diameter of the inner and outer peripheral surfaces, and the tightening force from the outer side is reduced to a smaller area. By concentrating, the tightening force can be increased.

In addition to this, in the present invention, the axial length of the surface of the cylinder body and the inner cylinder body in pressure contact with each other is made shorter than the length of the surface of the cylinder body and outer cylinder body in pressure contact with each other. The inner surface area of the contact surface of the contact cylinder is smaller than that of the outer contact surface, and the unit area is applied when the tightening force applied to the outer contact surface is transmitted to the inner contact surface. The compression force per area is increased on the inside and the outside depending on the area ratio.

With these, the insert is strongly tightened by effectively using the tightening force of multiple tightening cylinders, and the insert is preloaded from the outside. As a result, a large amount of stress that would lead to breakage is suppressed, and breakage is suppressed. That is, the allowable internal pressure is improved.

The present invention is intended to improve the allowable internal pressure in the die hole by increasing the preload that can be applied to the central cylindrical body as described above.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. For simplification, the same names are used for the same parts as the above-mentioned conventional example.

The multiple interference fit mold shown in FIG. 1 and FIG. 2 is configured by including tightening rings 1, 2, 3 which are tightening cylinders and an insert 4 which is a center cylinder in order from the outside. The fastening ring 2 is tightly fitted with the fastening ring 2, and the fastening ring 3 is tightly fitted with the fastening ring 2. Further, the insert 4 is provided inside the tightening ring 3.
The insert 4 has a die hole 5 that penetrates vertically in the center of the insert 4.

The conical surface shape 3A is provided on each of the upper end surface and the lower end surface of the tightening ring 3 just outside the insert 4, and the tightening ring 3 itself has an axial length of the inner surface.
Hi is formed to be shorter than the axial length Ho of the outer surface. In addition, tightening rings 1 and 2 have an axial length of H
The insert 4 has an axial length equal to Hi, and the tightening ring 3 has an axial length Hi of the surface contacting the insert 4 in the tightening ring 2.
It is configured to be shorter than the axial length Ho of the surface that comes into pressure contact with.

Further, the tightening ring 3 is provided with a large number of axial cuts 6 as a circumferential stress relaxation means, and the tightening ring 3 is completely divided by the cuts 6. In each of the interference fits, a normal optimum fit diameter and a method for calculating an optimum fit allowance (for example, a general "Matsubara's method") causes the fracture of the insert 4 and the fracture of each of the tightening rings 1 to 3 to occur at substantially the same time. As the setting, etc., the strength of each of the tightening rings 1 to 3 is used to the maximum, and the dimension for maximizing the allowable internal pressure of the insert 4 is set). One end is fitted into the tightening ring 2 by sandwiching them and the like, and then it is completely press-fitted except for the spacers so that the gaps between the cuts 6 are made uniform.

In the present embodiment configured as described above, the tightening force from the tightening rings 1 and 2 is transmitted to the insert 4 via the tightening ring 3 and preloads the insert 4. That is, since the tightening ring 3 is completely divided by the cut line 6 and does not tighten the insert 4 by itself, the generation of the circumferential stress repulsing from the tightening rings 1 and 2 is relieved. The tightening force from the tightening rings 1 and 2 is not attenuated by the stress generated in the tightening ring 3, and is efficiently transmitted to the insert 4.

That is, the tightening ring 3 is divided in the circumferential direction and is not a continuous elastic body. As such, it does not create circumferential stresses against the compressive stresses from the outer clamping rings 1, 2. Therefore, the tightening force from the outside is not attenuated, and the tightening force can be directly transmitted to the insert 4.

On the other hand, when the conventional non-divided tightening ring 3 is used, since this ring 3 becomes an elastic body continuous in the circumferential direction, a part of the pressure stress from the outer tightening rings 1 and 2 is elastically deformed. Is used as its circumferential stress, and only the remaining compressive stress is transmitted to the insert 4. Therefore, the compressive stress transmitted to the insert 4 is reduced by the ring 3.

Thus, even if the same tightening force is applied from the outside, the divided ring 3 can increase the tightening force that can be transmitted to the insert 4 as compared with the case where it is not divided, and the allowable internal pressure of the insert 4 is improved. Further, as shown in FIG. 3, the tightening ring 3 has an axial length of Ho on the outer peripheral side and Hi on the inner peripheral side, with a diameter of Do on the outer peripheral side and Di on the inner peripheral side.
, The outer surface area So and the inner surface area Si
Is It is represented by. Therefore, if there is no damping of the tightening force in the tightening ring 3, the tightening rings 1, 2
When the compression force Po is applied to the outer peripheral side by the tightening force from And Do> Di and Ho> Hi, so Pi> Po.
In this way, when the tightening ring 3 is tightened to the tightening rings 1 and 2, the compressing force is increased according to the area ratio of the inner and outer circumferences of the tightening ring 3, and the insert 4 is tightened more strongly and preloaded.

According to this embodiment as described above, a large preload can be applied to the insert 4 without changing the outer diameter dimension, the material, the number of combinations, etc., as compared with the conventional multiple interference fit mold. Therefore, there is an effect that the allowable internal pressure of the mold can be further increased.

Also, if the allowable internal pressure is the same, the size and weight can be reduced, workability and economy can be improved, and the die hole 5
Can be increased, and the range of products that can be processed with a mold having the same diameter can be expanded.

Furthermore, since the multiple interference fit mold of this embodiment can be easily implemented by replacing it with the conventional multiple interference fit mold, the working range of forged products and the like that can be manufactured using the same press machine, etc. There is also the effect that it can be expanded.

In the first embodiment, the tightening ring 3 is provided with the cut 6 as the circumferential direction stress relieving means, and the tightening ring 3 is completely divided. However, in the second embodiment shown in FIG. Slits 7 are provided in the tightening ring 3 having upper and lower end surfaces each having a conical surface shape 3A, and the tightening ring 3 is not completely divided.

In FIG. 4, the tightening ring 3 is provided with a slit 7 as a circumferential stress relieving means, and the tightening ring 3 is axially cut by the slit 7 except for a part thereof. It is continuous and is not completely divided. The rest of the configuration is the same as that of the first embodiment, so the description is omitted. According to this embodiment as described above, the tightening ring 3 is divided in the axial direction to relieve the stress generation in the circumferential direction, and the same effect as that of the first embodiment is obtained, and the tightening ring 3 is also provided. Since it is not completely divided, there is an effect that the work at the time of interference fitting becomes remarkably easy.

Furthermore, in the third embodiment shown in FIG. 5, the fastening ring 3 having the conical surface shape 3A at the upper and lower end surfaces is provided with a cut 6 for completely cutting the fastening ring 3 in the axial direction.
Only the book is provided to alleviate the stress in the circumferential direction without completely dividing the tightening ring 3, and the same effect as the second embodiment can be obtained. However, in terms of stress relaxation in the circumferential direction, the first embodiment in which the tightening ring 3 is completely divided is more effective than the second and third embodiments.

As described above, the number and width of the cuts 6 or the slits 7 are not particularly limited, and in short, the intervals can be maintained even in the state of being clamped from the outer circumference, and the occurrence of the circumferential stress of the tubular body can be relaxed. This means that such a cut 6 or slit 7 is provided.

On the other hand, in each of the above-described embodiments, the conical surface shape 34 is provided on each of the upper end surface and the lower end surface of the tightening ring 3, but it may be provided only on the upper end surface or the lower end surface. The same effect can be obtained by forming so that the axial length thereof is shorter than the axial length on the outer peripheral side.

In each of the above embodiments, the conical surface shape 3A is provided to change the axial length of the tightening ring 3 linearly and continuously, but it is changed stepwise or curvedly. Alternatively, for example, as a fourth embodiment, as shown in FIG. 6, a substantially spherical shape 3B may be provided on the upper and lower end surfaces of the tightening ring 3 to change the axial length of the inner and outer circumferences of the tightening ring 3. .

Further, in the fifth embodiment shown in FIG. 7, the conical surface shape 3A and the like are omitted and the axial length of the tightening ring 3 itself is inscribed as Ho on both the inner and outer circumferences, and the axial length of the insert 4 is inscribed. If Hi is Hi, the axial length of the surface 3C that is in pressure contact with the insert 4 is Hi, so that the same effect as in each of the above-described embodiments can be obtained.

As described above, the size and shape of the tightening ring 3 are not limited to those in the above-described respective embodiments, and in short, the tightening ring 3 provided with the circumferential stress relieving means is arranged in the axial direction of the surface in pressure contact with the inner cylindrical body. That is, the length is configured to be shorter than the axial length of the surface that comes into pressure contact with the outer cylindrical body.

In each of the above embodiments, the tightening rings 1, 2, 3
However, the present invention is not limited to this, and two or more tightening cylinders are provided.

Further, in each of the above-described embodiments, the axial length of the surface of the innermost tightening ring 3 of the tightening cylinder that is in pressure contact with the inner cylinder is the axial length of the surface that is in contact with the outer cylinder. The tightening ring 3 is made shorter and the cut 6 or slit 7 is provided in the tightening ring 3 as a circumferential stress relieving means. However, the tightening ring 2 may be formed in this manner. That is, one of the cylinders excluding the cylinder is formed into the shape described above. However, when it is applied to the cylindrical body closer to the inner insert 4, it is more effective in alleviating the stress in the circumferential direction that attenuates the tightening force, and has the effect of improving the allowable internal pressure.

〔The invention's effect〕

As described above, according to the multiple interference fit mold of the present invention, the predetermined tightening ring is provided with the circumferential stress relieving means, and the axial length is changed to increase the compressive force. As a result, there is an effect that the allowable internal pressure can be further increased as compared with a mold of the same size.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of a first embodiment of the present invention, FIG. 2 is a sectional view showing the embodiment, FIG. 3 is a perspective view showing an essential part of the embodiment, and FIG. Is a perspective view showing an essential part of the second embodiment of the present invention, FIG. 5 is a perspective view showing an essential part of the third embodiment of the present invention, and FIG. 6 is a fourth embodiment of the present invention. FIG. 7 is a sectional view showing the fifth embodiment of the present invention, and FIG. 8 is an exploded perspective view showing the structure of a conventional example. 1,2,3 …… Tightening ring as a tightening cylinder, 4…
… Insert as central cylinder, 5 …… die hole, 6 ……
A slit as a circumferential stress relaxation means, 7 ... A slit as a circumferential stress relaxation means.

Claims (4)

[Claims] 1. A multiple interference fit mold comprising a plurality of coaxially fitted tightening cylinders and a central cylinder fitted to the innermost side of these cylinders. At least one tubular body except the outer tubular body is provided with a circumferential stress relieving means composed of a slit formed in the axial direction, and a surface on which the tubular body and the inner tubular body are in pressure contact with each other. The axial length of is configured to be shorter than the axial length of the surfaces of the cylindrical body and the outer cylindrical body that are in pressure contact with each other. 2. The multiple interference fit mold according to claim 1, wherein the circumferential stress relieving means comprises a slit that completely divides the tubular body in the axial direction. 3. The multiple interference fit metal according to claim 1, wherein the cylindrical stress relaxation means comprises a slit that is a cut that does not completely divide the cylindrical body in the axial direction. Type. 4. The cylindrical body according to any one of claims 1 to 3, wherein the circumferential stress relieving means is provided, the axial length on the inner peripheral side of the cylindrical body itself. A multiple interference fit mold characterized by being formed shorter than the axial length on the outer peripheral side.