JPH074638B2 - 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 technology and its problems]

Generally, a die for plastic working such as a die for cold forging has an allowable internal pressure (the maximum pressure that can be received inside the die during forming such as forging so that the die does not break at the time of forming, because it is processed at a considerably high pressure. That is, it is required that the allowable internal pressure at the time of molding is high. In particular, if they have the same allowable internal pressure,
From the viewpoints of economy and workability, it is desirable that the amount of material used is smaller and the outer diameter size is smaller, and conventionally, a multiple interference fit mold as shown in FIG. 7 has been frequently 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. Therefore, it is possible to prevent the stress in the circumferential direction of the die hole 5 from being on the tension side due to the high pressure applied in the die hole 5 during processing, and to prevent the stress of the insert 4 from exceeding the yield stress, thereby breaking the die. It is possible to increase the allowable internal pressure in the die hole 5 as compared with the case of a single die by preventing these problems. More specifically, tensile stress acts on the inner peripheral surface of the insert (4) in the circumferential direction due to the press working. To alleviate this, the insert (4) is tightened (preloaded) with a tightening ring in advance, and a compressive stress is applied in the circumferential direction of the circumferential surface. Obviously, it is advantageous to make this compressive stress as large as possible without exceeding the compressive yield stress of the material constituting the insert. Therefore, it is desired to increase the tightening force of the tightening ring, but if one tightening ring is used to achieve this purpose, the inner peripheral surface of the tightening ring will yield. Therefore, measures are taken to increase the thickness of the tightening ring or to increase the number of tightening rings. There is a problem that the mold becomes large by any of these means.

Many studies have been published on the design of such multiple interference fit molds (for example, plasticity and machining vol.10 no.101 (1969) issued by the Japan Society for Plasticity Processing).
-6) from page 460 to page 471, hereinafter referred to as Matsubara's method), if the number of combinations of the tightening cylinders, or the mechanical properties of each cylinder, inner diameter, outer diameter, etc. are determined It is possible to know in advance the allowable internal pressure when it is configured based on the optimum conditions. On the contrary, the permissible internal pressure can be further increased by appropriately selecting these elements. However, when a high performance material is used to improve the mechanical properties, the material is expensive and the economy is reduced. 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 fitted inside these are provided, and At least one of the tightening cylinders other than the outermost one is provided with a tightening force attenuation preventing means consisting of an axial cut.

In the multiple interference fit mold configured in this way,
The tightening force attenuation preventing means provided in the tubular body relieves the stress in the circumferential direction generated in the tubular body and repels the tightening force from the tubular body circumscribing the tubular body to generate in the tubular body. The generation of circumferential stress is suppressed, and the tightening force 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 tightening force attenuation preventing means such as a break, when receiving the tightening force from the outer cylindrical body, a circumferential stress is generated against the inward deformation, Circumferential stress attenuates the tightening force from the outside and cannot be sufficiently transmitted to the insert inside.

However, in the present invention, since the tubular body is divided in the circumferential direction (completely or partially) by providing the fastening force damping preventing means such as a break, the above-mentioned circumferential stress does not occur, It is possible to directly transmit the tightening force from the inside to the insert or the like without being attenuated.

Further, the compression ratio per unit area when the tightening force is transmitted is increased by the ratio of the inner diameter to the outer diameter of the tubular body, and the preload of the central tubular body is increased to improve the allowable internal pressure.

With these, the insert is strongly tightened by effectively utilizing the tightening force of multiple tightening cylinders, and the insert is preloaded from the outside, and even if the insert receives a large internal pressure during molding, a strong preload from the outside is applied. 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 can be improved.

The present invention thus achieves the above object and solves the above problems.

〔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 includes tightening rings 1, 2 and 3 which are tightening cylinders and insert 4 which is a center cylinder.
It has and. A die hole 5 is provided at the center of the insert 4. The tightening ring 3 is provided with a large number of cuts 6 in the axial direction as a means for preventing the damping of the tightening force, and the cuts 6 divide the tightening ring 3 completely. The tightening ring 1 is fitted with a tightening ring 2, and the tightening ring 2 is fitted with a tightening ring 3. Further, an insert 4 is tightly fitted inside the tightening ring 3.

In addition, each of the interference fits is a normal optimum fitting diameter, an optimum fitting margin calculation method (for example, a general "Matsubara method",
The tightening rings 1 to 3 are set so that the breakage of the insert 4 and the breakage of the tightening rings 1 to 3 occur at substantially the same time.
Of the insert 4 to maximize the allowable internal pressure of the insert 4), and when the tightening ring 3 is fitted into the tightening ring 2, a spacer or the like is formed on the cut 6. The gaps between the cuts 6 are made even by sandwiching the gaps, and a part of the gaps is fitted, and then the gaps are completely pressed in except for the spacers.

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. Here, the tightening ring 3 is completely divided by the cut line 6, and does not tighten the insert 4 by itself, but the generation of the circumferential stress that repels the tightening from the tightening rings 1 and 2 is mitigated. . For this reason,
The tightening force from the tightening rings 1 and 2 can be efficiently transmitted to the insert 4 without being attenuated.

That is, the tightening ring 3 is divided in the circumferential direction and is not a continuous elastic body. Therefore, it does not itself generate a circumferential stress that opposes the compressive stress 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, part of the compressive 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.

Therefore, 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, the tightening ring 3 transmits the tightening force from the outside to the insert 4 on the inner side.
The tightening force is increased in accordance with the area ratio between the inside and the outside, that is, the inside-outside diameter ratio. That is, the tightening ring 3
The inward tightening force received by the surface having a large outer peripheral area is transmitted to the insert 4 by the surface having a small inner peripheral area to concentrate the pressure. As a result, the tightening pressure is increased and the insert 4 is tightened with a stronger force to be 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 a means for preventing the tightening force, and the tightening ring 3 is completely divided.
In this embodiment, the tightening ring 3 is provided with the slit 7 and the tightening ring 3 is not completely divided.

In FIG. 2, the tightening ring 3 is provided with a slit 7 as a means for preventing damping of the tightening force, and the tightening ring 3 is axially cut by the slit 7 except for a part thereof. It is continuous and 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.

Further, as in the third embodiment shown in FIG. 3, the fastening ring 3 is provided with only one cut 6 for completely cutting the fastening ring 3 in the axial direction, and the fastening ring 3 is completely divided. Instead, the stress in the circumferential direction is relaxed, and the same effect as the second embodiment is 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.

In each of the above-described embodiments, the number and width of the cuts 6 or slits 7 are not particularly limited, and in short, the intervals are maintained even in the state of being tightened from the outer circumference, and the stress in the circumferential direction of the cylindrical body is kept. That is, the slits 6 or the slits 7 are provided so as to alleviate the occurrence.

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 embodiments, the innermost tightening ring 3 of the tightening cylinder is provided with the slit 6 or the slit 7 as a means for preventing damping of the tightening force. It is to be provided in one of the tubular bodies excluding the outermost tubular body. However, when the cut 6 or the slit 7 as the tightening force attenuation preventing means is provided in the cylindrical body closer to the insert 4 on the inner side, it is more effective in alleviating the stress in the circumferential direction that attenuates the tightening force, There is an effect that the internal pressure can be improved.

Here, an experimental example according to the embodiment of the present invention will be described using specific numerical values.

The following Tables 1 and 2 show the conditions for the experiment, and the experimental results are shown in FIGS. 4 to 6.

As shown in FIG. 1, the first experimental example is configured based on the first embodiment, and the number of combinations is 4 in which the tightening ring 3 is provided with a cut 6 as a tightening force attenuation preventing means.
This is a multiple interference fit mold. In the second experimental example, which is almost the same as the first experimental example, the outer diameter of the insert 4 is reduced, the thickness of the tightening ring 3 is increased, and the inner / outer diameter ratio is increased. Further, as a comparative example, as shown in FIG. 7, an experiment using a conventional multiple interference fit mold without a tightening force attenuation preventing means was also conducted.

In each experiment, based on the above-mentioned Matsubara method and the theory of maximum shear stress, the materials shown in Table 1 were used for the material of each part, and the dimensions are shown in Table 2 by ordinary optimum calculation. I was supposed to. Therefore, in Table 1,
Yield with shear as a yield condition means that the yield occurs when the shear force reaches half of the tensile yield stress peculiar to each member.

The stress distribution according to the distance from the center of the circumferential stress and the radial stress under the above conditions
Shown in Figures, 5 and 6. The stress shown in each of the above figures is a calculated value, but it is roughly in agreement with the experimental result.

4 (A) to 6 (A) show no load, and FIGS. 4 (B) to 6 (B) show that the internal pressure in the die hole 5 is the allowable internal pressure P ₀ . Indicates the status. The concentric circles in the figure indicate the die hole 5, the insert 4, and the tightening rings 3, 2, 1 from the inside. Further, in the polygonal curve in the figure, the stress from the center to the left is the circumferential stress, the right is the radial stress, and the tensile stress is upward and the compression stress is downward.

FIG. 4 is a stress distribution of the comparative example (case of the conventional example of FIG. 7). In FIG. 4 (A) showing no load, the circumferential stress S ₁ of the tightening ring 3 shows a negative value,
It is considered that the compressive stress due to the tightening from the outside is larger than the tensile force accompanying the tightening of the insert 4 on the inner side. In particular, corresponding to the tightening of the tightening ring 3 from the outside, a larger compressive stress is generated toward the outside. Further, the radial stress S ₂ has a negative value, and since the insert 4 on the inner side is tightened by itself in addition to the tightening from the outer side, a larger compressive stress is generated on the inner side.
It is considered that the cause of the upwardly convex curve is that the tightening force of itself is attenuated by the repulsion of the stress S ₁ . On the other hand, in FIG. 4 (B) showing the time when the allowable internal pressure P ₀ is applied, the circumferential stress S ₃ and the radial stress S ₄ of the tightening ring 3 have different values, but both are the stress S ₁ and the stress S ₁ respectively.
It shows the same properties as S ₂ . The allowable internal pressure at this time is P ₀ = 292 kg / mm ² .

FIG. 5 shows the stress distribution of the first experimental example. In FIG. 4 (A) showing no load, the tightening ring 3 has a circumferential stress S ₁ = 0 due to the provision of the cut 6 as the tightening force attenuation preventing means, and the compressive stress of the comparative example is the same. No occurrence is seen. The radial stress S ₂ is a compressive stress that monotonically increases toward the inside. It is considered that this is because the tightening ring 3 only increases the compressive stress due to the tightening from the outside according to the inner-outer diameter ratio thereof and is not repulsed by the circumferential stress. On the other hand, also in FIG. 5 (B) showing the allowable internal pressure P _0, the circumferential stress S ₃ of the tightening ring 3 is 0, and the radial stress S ₄ monotonically increases toward the inner side, and is The compressive stress is larger than that of the comparative example, and the allowable internal pressure is P ₀ = 305 kg / mm.
Has reached ² . That is, according to this experimental example, it is possible to increase the allowable internal pressure by 13 kg / mm ² with the same material and size as the comparative example.

FIG. 6 shows the stress distribution of the second experimental example. In this experimental example, the circumferential stresses S ₁ and S ₃ are 0 as in the case of the first experimental example, but by increasing the inner / outer diameter ratio of the tightening ring 3, it increases monotonically toward the inside. The rate of change of the radial stresses S ₂ and S ₃ is further increased, and the allowable stress is P ₀ = 335 kg / mm ² . That is, the allowable internal pressure can be further increased as compared with the comparative example and the first experimental example, and the outer diameter of the insert 4 can be reduced to reduce the amount of expensive cemented carbide and reduce the material cost. It is possible.

As described above, in the first and second experimental examples according to the present invention, the allowable internal pressure was higher than that of the conventional multiple interference fit mold shown in the comparative example.

〔The invention's effect〕

As described above, according to the multiple interference fit mold of the present invention, since the tightening force attenuation preventing means is provided, the allowable internal pressure can be further increased as compared with the mold having the same size.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view showing a configuration of a first embodiment of the present invention, FIG. 2 is a perspective view showing an essential part of a second embodiment of the present invention, and FIG. Is a perspective view showing a main part of a third embodiment of the present invention, FIG. 4 is a view showing a stress distribution of a comparative example using a conventional multiple interference fit mold, and FIG. 5 is a first view of the present invention. 6 is a diagram showing the stress distribution of the experimental example of FIG. 6, FIG. 6 is a diagram showing the stress distribution of the second experimental example of the present invention, and FIG. 7 is an exploded perspective view showing the configuration of the conventional example. 1,2,3 ... Tightening ring as a fastening cylinder, 4 ... Insert as a central tubular body, 5 ... Die hole, 6 ... Discontinuity as a means for preventing tightening force attenuation, 7 ... Slit as a means for preventing tightening force attenuation.

Claims (3)

[Claims] 1. A plurality of fastening rings etc. (1, 2, 3) fitted coaxially, and these fastening rings etc.
In a multiple interference fit mold comprising an insert (4) fitted into the inner diameter of a tightening ring group consisting of 2, 3), said tightening ring etc. (1, 2, 3)
Of these, at least one tightening ring or the like (2 or 3) except the outermost tightening ring or the like (1) is provided with a tightening force attenuation preventing means composed of a cut (6 or 7) formed in the axial direction. Multiple interference fit molds characterized by 2. The tightening force attenuation preventing means according to claim 1, characterized in that it comprises a cut (6) that completely divides the tightening ring or the like (2 or 3) in the axial direction. Multiple interference fit molds. 3. In the first aspect of the present invention, the cut formed in the axial direction, which is the tightening force attenuation preventing means, is formed between the one end and the other end of the tightening ring or the like (2 or 3). Multiple interference fit molds characterized by slits (7) that are cut off.