JP3440540B2 - Mold - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die used for forging and the like. 2. Description of the Related Art It is known that forging of a bevel gear shown as an example in FIG. 3 is performed by a closed forging method using a mold having a pair of opposed upper and lower die blocks as shown in FIG. It is generally performed by a forging press in which the upper die block 20 is moved up and down and the lower die block 10 is fixed. FIG. 4 shows that the upper die block 20 is lowered to the lowermost position with respect to the lower die block 10 supported in a fixed state by a forging press (not shown).
1, counter punch 8, knockout 9 and upper die 2
1. A situation where a bevel gear 6 is forged into a desired shape from a heated cylindrical material blank in a cavity formed by a punch 7 is shown. The lower die 11 is press-fitted into a lower tightening ring 13, and the lower die plate 12 is similarly mounted by press-fitting on the lower tightening ring 13, and these are integrated to form a lower die block 10. Counter punch 8 and knockout 9 are lower die 11 and lower die plate 1
2 is slidably fitted in the center hole. The forging operation starts from the initial state of the forging press in which the upper die block 20 is raised by the forging press and the counter punch 8 and the knockout 9 in the lower die block 10 are in the lowered state. [0004] A heated material blank is inserted into the center hole of the lower die 11 and the upper die block 20 and the punch 7 are lowered by operating a forging press (not shown). The punch 8 and the knockout 9 are both raised to predetermined positions to press the heated material blank, and the state shown in FIG. 4 is completed, forging is completed, and the material blank is shaped into a predetermined bevel gear. Next, the forging press machine raises the upper die block 20 and also raises the knockout 9 in the lower die block 10, so that the forged working mass adhered to the lower die 11 and the counter punch 8 by the forging working pressure. The gear 6 is pushed up from them and peeled off, and after taking out the bevel gear 6 which facilitates this removal, the gear 6 is lowered again to a predetermined position together with the counter punch 8 to return to the initial state. FIG. 5 is a sectional view showing the lower die block 10. The lower die 11 is pressed into the lower tightening ring 13,
Similarly, a lower die plate 12 for supporting a downward force at the time of forging the lower die 11 is firmly attached to the lower tightening ring 13 by press-fitting. The lower die 11 receives the forging press force of the upper die 21 and the punch 7 as a strong internal pressure via the material to be processed during forging. The lower die 1
Numeral 1 is press-fitted into the lower tightening ring 13 to apply a pre-compression force from the outer periphery toward the center. On the other hand, lower die plate 1
The lower die 2 is also firmly attached to the lower tightening ring 13 by press-fitting to support the lower surface of the lower die 11, and these three parts are integrated to form the lower die block 10, which is manufactured, managed, prepared, and actually used as one unit. Is to be performed. When the stress between the three components in the lower die block 10 is analyzed, since the lower die 11 is firmly pressed into the lower tightening ring 13, a compressive stress toward the center is applied to the outer periphery of the lower die 11. In the inside, a compressive force in the center direction and a circumferential direction is generated, and an outward reaction force acts on the inner circumferential surface of the lower tightening ring 13, which is compressed in the radial direction and is reduced in the circumferential direction. It becomes tensile stress. The lower die plate 12 also has a lower tightening ring 13.
And receives a stress toward the center on the outer periphery thereof, and as a reaction force, generates an outward stress on the inner peripheral surface of the lower tightening ring 13. The stress is applied to the lower die 11 by the lower tightening ring 13. The required tightening force will be reduced,
As a result, the function of compressing the lower die 11 by the lower tightening ring 13 is reduced, the resistance to the stress generated in the lower die 11 during forging is reduced, and the life of the lower die 11 is shortened. Further, on the manufacturing side of the lower die block 10, the lower die plate 1 is further inserted into the lower tightening ring 13 into which the lower die 11 is firmly pressed.
There is also a manufacturing difficulty of press-fitting 2 over its entire length. Japanese Patent Application Laid-Open No. 1-254340 discloses that in a mold for closed forging, a plurality of annular grooves are provided in a molding portion as a measure for preventing burrs during forging, which suppresses the flow of material in the direction in which the burrs extend. A grooved forging die is described, in which a lower die and a lower die plate are attached to a lower tightening ring by press-fitting, and a lower die block is formed by these. [0009] The prior art in forging dies is to press-fit a lower clamping ring over the entire length of a lower die plate into a lower die that is press-fit adjacent thereto. Lowering the tightening force of the lower tightening ring, lowering the strength of the lower die against the internal pressure generated during forging, shortening the mold life, and pressing the lower die plate into the lower tightening ring over the entire length. Difficulties also arise.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem of shortening the mold life and making it difficult to manufacture. [0010] The present invention is a molding die having a pair of upper and lower dies opposed to each other, wherein the lower die is mounted by press-fitting an outer periphery of a die into a tightening ring, and mounted below the die. in those with integrally die block outer periphery of the die plate fitted to the inner periphery of said clamping ring, said clamping Li
Between the inner circumference of the ring and the outer circle of the die plate
The shorter part farther from the die than the part closer to the die.
The press-fitting portion of the die plate and the tightening ring is formed only in a short portion farther from the die, and the other portions are loosely fitted. In the fitting portion between the outer periphery of the lower die plate and the inner periphery of the lower tightening ring in the lower die block, tightening is performed.
Inner and outer diameters of the fitting area between the inner circumference of the ring and the outer circumference of the die plate
The shorter part farther from the die than the part closer to the die.
Or a larger form, the press-fit portions of both and only a short portion of the side away from the lower die, fitted loose fitting of the other sites
And fit because, by and shall not perform a press-fit,
Prevents a decrease in the tightening force of the lower tightening ring on the lower die,
The life of the lower die is prevented from being shortened due to a decrease in the proof stress of the lower die against the internal pressure during molding. Also, when the lower die, the lower die plate, and the lower tightening ring are integrally formed into a block, the portion for press-fitting the lower die plate into the lower tightening ring is shortened, and the manufacturing difficulty during press-fitting is reduced. it can. An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross section of a lower die block in which a lower die 1, a lower die plate 2, and a lower tightening ring 3 are integrally formed in a forging die. The lower die 1 is firmly pressed into the lower tightening ring 3, As shown in FIG. 1, only the short portion 4 opposite to the lower die 1 is press-fitted into the fitting portion between the outer periphery of the lower die plate 2 and the inner periphery of the lower clamping ring 3, and the portion 5 close to the lower die 1 There is a loose fit. The inner and outer diameters of the press fit 4 are slightly larger than those of the loose fitting portion 5. In addition, lower die 1
The lower die plate 2 and the upper surface of the lower die plate 2 are in close contact with each other, so that the lower die plate 2 supports the forging press reduction force received by the lower die 1 during forging. The lower surface is flush. [0013] With the above structure, the fitting of the lower die plate 2 to the lower die ring 2 is loose in most of the inner diameter of the lower tightening ring 3, so that the lower die plate 3 is not pressed into the lower tightening ring 3 over its entire length. The lowering of the tightening force of the lower tightening ring 3 to the lower die 1 is reduced, the resistance of the lower die 1 to internal pressure during forging is reduced, and the life of the mold is not shortened. Also, the lower die plate 2 is fixed to the lower
Also, the manufacturing difficulty of press-fitting over the entire length is reduced. FIG. 2 illustrates the state of the stress generated inside the lower die 1 and the lower clamping ring 3. The lower die block is shown in the lower part of FIG. 2, and the state of the stress generated inside the lower die 1 and the lower clamping ring 3 is shown in a diagram above the lower die block in relation to the radial position of the mold. This diagram shows all the stresses generated in the circumferential direction inside the lower die block. The state of the internal stress of the lower die 1 at the time of non-forging is shown by a curve a ′ and a curve b ′. The state of the internal stress is shown by a curve c ′ and a curve d ′. Curves a 'and c' shown by solid lines show the stress state at the time of non-forging of the present embodiment, and are not affected by press-fitting over the entire length of the lower die plate 2, and the tightening force of the lower tightening ring 3 is large. The compressive stress applied to the lower die 1 increases as shown by the curve a '. The stress state at the time of non-forging in the case of the conventional lower die block shown in FIG. 5 is shown by broken line curves b ′ and d ′. A dashed curve b 'shows a situation where the tightening force of the lower tightening ring is reduced due to the influence of press-fitting over the entire length of the lower die plate, and the compressive stress applied to the lower die is reduced. On the other hand, the situation of the internal stress when forging is actually performed is shown by curves a, b, c and d on the right side of FIG. A curve f indicates a circumference generated by an applied pressure during forging when there is no internal stress generated in the lower die 1 and the lower tightening ring 3, for example, when it is assumed that the lower die and the lower tightening ring are integrated. It shows the tensile stress in the direction. Actually, the lower die 1 and the lower tightening ring 3 are configured separately,
The stresses indicated by the curves a ′, b ′, c ′, and d ′ are generated therein, and the stresses generated therein are indicated by the curves a, b, c, and d, which are the sums with the curve f. It becomes stress. Here, the curve a shown by a solid line indicates the stress generated inside the lower die 1 in the present embodiment, and is lower than the curve b showing the stress generated inside the lower die 1 according to the prior art. The peak value decreases from B to A, and this difference prevents the expensive lower die 1 from being damaged and extends the mold life. Lower fastening ring 3
Is generated at the inner circumference of the lower tightening ring 3 during the non-forging operation, which is also lower than the curve d generated by the prior art in the present embodiment. Is lower than the stress curve d 'caused by press-fitting the lower die 1 and the lower die plate 2 over the entire length thereof as shown by the curve c'. In this regard, this embodiment is superior. As described above, the lower die plate is press-fitted into the lower tightening ring only at the short side opposite to the lower die, and the other fitting portion is loosely fitted to form the lower die block of the mold. As a result, the occurrence of die cracks due to the stress generated during forging is reduced, and a favorable result of lowering the press-fit of the lower die plate when forming the lower die block is obtained. In the above embodiment, the forging die has been described. However, the present invention can also be applied to an injection molding die to which a high internal pressure is applied during molding. According to the present invention, in a mold used in a molding method, a circumferential stress generated in a lower die, which is subjected to a high internal pressure during molding, is reduced to reduce the occurrence of die cracks, and to produce a mold. In this case, the press-fitting operation can be facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of stress generated inside a mold of the present invention. FIG. 3 is a sectional view of a part forged by a die. FIG. 4 is a sectional view of a conventional forging die. FIG. 5 is a sectional view of a conventional lower die block. [Description of Signs] 1 Lower die 2 Lower die plate 3 Lower tightening ring 10 Lower die block

Claims (1)

(57) [Claim 1] A molding die having a pair of opposing upper and lower dies, wherein the lower die is mounted by press-fitting an outer periphery of a die into a tightening ring, and a die plate is provided below the lower die. die plate in which the integrally die blocks the outer periphery of the fitted on the inner periphery of the clamping ring, the inner periphery of the clamping ring the
The inner and outer diameters of the fitting part on the outer circumference of the
The part is formed slightly larger than the part close to the die, the press-fitting part of the die plate and the tightening ring is made only a short part on the side far from the die, and the other parts are loosely fitted. Molding die.