JP3674399B2 - Stepped shaft manufacturing method and stepped shaft manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a stepped shaft having a solid cylinder and an upset portion whose diameter is larger than the diameter of the column, and an apparatus for manufacturing the stepped shaft. More specifically, the present invention relates to a method and an apparatus for manufacturing the stepped shaft using a solid cylinder as a raw material (workpiece) without generating burrs and undercut portions.
[0002]
[Prior art]
A stepped shaft used for various applications such as a gear with a shaft, a piston with a shaft, and a spool with a shaft has been manufactured by, for example, forging using a mechanical press or closed forging using a hydraulic press.
[0003]
Among the above, forging using a mechanical press is, for example, a mechanical press including a punch (upper die) 8, a lower fixed die (lower die) 9, and a knockout pin 4 as schematically shown in FIG. Is used. In this case, normally, as shown in FIG. 4, burrs and underfilling (unfilled material) occur in the work material 1 after forging. Therefore, in order to obtain a desired stepped shaft shape, it is necessary to perform a cutting process, and the material yield is also lowered.
[0004]
The closed forging process using a hydraulic press uses, for example, a hydraulic press provided with an upper center punch 10, a lower center punch 11, an upper mold 12, and a lower mold 13 as shown in FIG. The upper mold 12 and the lower mold 13 are brought into close contact with each other, and the workpiece 1 is pressed with the upper center punch 10 and the lower center punch 11 to thereby form the upper mold 12, the lower mold 13, the upper center punch 10, and the lower center. This is formed into a target shape in a sealed mold formed by the punch 11. In this closed forging process, the volume of the sealed mold is a constant value. Therefore, when the volume of the workpiece 1 is smaller than the volume of the sealed mold, a lack of thickness occurs at the corner of the forged product (workpiece 1). Conversely, if the volume of the workpiece 1 is larger than the volume of the sealed mold, burrs (inserted burrs) occur on the mating surfaces of the upper mold 12 and the lower mold 13, and the mold may be damaged in some cases. May occur. For this reason, in the case of closed forging, it is necessary to make the volume variation of the workpiece 1 extremely small, and much time and cost are required to manufacture the processed material.
[0005]
On the other hand, in the plasticity and processing (Vol. 27, No. 300 (1986), pages 121-131), the “principle of the discarded shaft” proposed as “development of the precision cold forging method by the diversion method” is low forging. Although it is a technique that can fill the mold with the work material with a load, the dimension and end face shape of the `` discard shaft '' cannot be controlled, so in order to obtain the desired stepped shaft, After adjusting and forging so that the “discarded shaft portion” is longer than a predetermined value, it is necessary to cut the portion to a desired length, which lowers the yield of the material. In addition, the material supplied for fullness of the meat is difficult to control because it becomes a natural flow of forging. Therefore, it is difficult to manage the size and shape of the forged product. Furthermore, peculiar troubles such as mold breakage may occur.
[0006]
Further, Sumitomo Metals (vol. 50, No. 3 (1998), pages 16 to 24, proposes a technique of “forming a helical gear for automobiles by a 5-cylinder hydraulic double-acting press”. In this case, as described on page 24, (1) the tool surface pressure rises compared to the (1) scrap shaft method. (2) Depending on the balance between the amount of the boss and gear body, There are inherent problems such as fogging on the teeth.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described present situation, and the purpose thereof is, for example, upsetting by using a solid cylinder manufactured by a normal technique having a volume fluctuation of about ± 3% as a material. A method for manufacturing a stepped shaft suitable for a material such as a gear with a shaft or a piston with a shaft, and a stepped shaft, which does not cause burrs or undercutting and has a high material yield and does not cause damage to the mold. It is to provide a manufacturing apparatus.
[0008]
[Means for Solving the Problems]
The gist of the present invention resides in a stepped shaft manufacturing method shown in the following (1) and (2) and a stepped shaft manufacturing apparatus shown in (3).
[0009]
(1) The shape of the stepped shaft corresponding to the product is formed by a closed mold composed of a fixed die, floating die, knockout pin, outer punch and center punch, and the diameter from the solid cylinder is larger than the diameter of the cylinder A method of manufacturing a stepped shaft having a large upsetting portion, in which a solid cylinder, which is a workpiece, is constrained by a fixed die, a knockout pin, an outer punch and a center punch, and then the surface pressure of the outer punch is controlled by the center punch. A method for producing a stepped shaft, wherein the pressure is made larger than the surface pressure.
[0010]
(2) The shape of the stepped shaft corresponding to the product is formed by a closed mold composed of a fixed die, floating die, knockout pin, outer punch and center punch, and the diameter from the solid cylinder is larger than the diameter of the cylinder A method of manufacturing a stepped shaft having a large upsetting portion, wherein a portion corresponding to the upsetting portion of a solid cylinder which is a workpiece is preformed, and then the preformed workpiece is at least fixed A method for manufacturing a stepped shaft, comprising: constraining with a die, a knockout pin, an outer punch, and a center punch, and then pressing the outer punch with a surface pressure greater than that of the center punch.
[0011]
(3) A device for manufacturing a stepped shaft having a mounting portion having a diameter larger than the diameter of the solid cylinder from a solid cylinder, and the control of the rolling force and the position can be independently performed on the fixed die and the knockout pin. A sealed die having a shape of a stepped shaft corresponding to a product by the outer die, the center punch, and a floating die interlocking with the operation of the outer punch, and corresponding to the product by the fixed die, the knockout pin, the outer punch, the center punch and the floating die. Equipment for stepped shafts that can be formed.
[0012]
FIG. 1 to be described later is a schematic cross-sectional view (however, only a vertical cross section on one side is shown) showing a state of manufacturing a stepped shaft, but the above-mentioned fixed die 2, floating die 3, knockout pin 4, outer punch 5 and the center punch 6 are in the positional relationship shown in FIG. 1, and when the respective positions are in the relationship shown in FIG. 1 (d), for example, “sealing metal having the shape of a stepped shaft corresponding to the product” A mold is formed. The stage until the fixed die 2, the floating die 3, the knockout pin 4, the outer punch 5 and the center punch 6 form a “sealed mold having a stepped shaft shape corresponding to the product”, that is, the workpiece In the stage until one upsetting portion is completely formed, at least the floating die 3 does not completely contact the workpiece 1 and a space S is formed.
[0013]
The outer punch 5 is an outer die for pressing the forging force on the workpiece 1, and the center punch 6 is an inner die for pressing the forging force on the workpiece 1. The floating die 3 is a mold that operates in the same direction in conjunction with the operation of the outer punch 5, and is a member 7 (for example, a spring, an air cylinder, rubber, urethane, etc.) that can be expanded and contracted with respect to the base B of the double-action press. Etc.) is supported behind it. The fixed die 2 is a fixed mold on the side that receives the forging force, and the knockout pin 4 is the mold on the side that receives the forging force. This is a product (work to be processed) at the end of forging by a press discharge mechanism (not shown). It also has the effect of discharging the material 1).
[0014]
“A stepped shaft having an upsetting portion whose diameter is larger than the diameter of a solid cylinder (which is a material)” refers to a shaft as shown in FIGS. 2 (a), 2 (b), and 2 (c). In the case of a stepped shaft as shown in FIGS. 2 (a) and 2 (b), the end surface of the upsetting portion is forged with the center punch 6 side in FIG.
[0015]
Hereinafter, those described in (1) to (3) above are referred to as inventions (1) to (3), respectively.
[0016]
The present inventors have made various studies on forging techniques for solving the above-described problems. As a result, the following knowledge was obtained.
[0017]
(A) A fixed die, a floating die, a knockout pin, an outer punch, and a center punch are used to form a sealed die having a stepped shaft shape corresponding to the product, and the work material upsetting portion is If the surplus volume after filling the hermetic mold is absorbed by the retraction of the center punch, the product will not be burred or missing, and the mold will not crack.
[0018]
(B) In order to achieve the above (a), a double-acting press capable of independently controlling the rolling force and position of the outer punch and the center punch, which are dies for pressurizing the forging force on the workpiece, Mainly forged so that the workpiece has an upset portion of a desired shape mainly by an outer punch, and further forged so that the workpiece has an upset portion of a desired shape by a center punch. And the material flow of the workpiece may be controlled.
[0019]
(C) In order to control the material flow of the workpiece by the center punch, the outer die is pressed by making the surface pressure of the outer punch larger than the surface pressure of the center punch, and the floating die is moved by the elastic member such as a spring. What is necessary is just to make it interlock | cooperate with the action | operation of a punch.
[0020]
The present invention has been completed based on the above findings.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The method and apparatus of the present invention will be described in detail below with reference to the drawings.
[0022]
FIG. 1 is a schematic longitudinal sectional view showing an example of a one-side situation in which a stepped shaft having the shape shown in FIG. 2C is manufactured by the method of the invention of (1).
[0023]
First, a workpiece (solid cylinder) 1 lubricated by a normal method is inserted into a hole mold formed by a fixed die 2 and a knockout pin 4 and placed on the knockout pin 4. Next, as shown in FIG. 1A, the outer punch 5 and the center punch 6 are lowered, and the workpiece 1 is restrained by these punches, the fixed die 2 and the knockout pin 4. Thereafter, pressure is applied with both punches as shown in FIGS. At this time, the surface pressure of the outer punch 5 is set to be larger than the surface pressure of the center punch 6. The surface pressure of the outer punch 5 is set to be greater than the surface pressure of the center punch 6 not immediately after the restraint of the workpiece 1 as shown in FIG. It may be carried out after the axial distance between the end surfaces of the punch 5 and the center punch 6 on the pressing side reaches the final product dimension H ₁ shown in FIG.
[0024]
When the pressure is applied as described above, as shown in FIG. 1 (d), the excess volume of the workpiece 1 after the upsetting portion of the workpiece 1 is completely formed is set as the backward movement of the center punch 6 or Since it can be absorbed in advance, the final product will not be burred or missing, and the mold will not crack.
[0025]
The reduction speed of the outer punch 5 and the center punch 6 in the invention of (1) may be a normal forging reduction speed.
[0026]
In addition, the pressurization at this time is a force that uses a double pressure press to make the surface pressure of the outer punch 5 to be “2 ± 0.2” times the deformation resistance of the work material 1. It is preferable to carry out with a force that makes the surface pressure of the center punch 6 “1.7 ± 0.2” times the resistance, and it is even better if the reduction by both punches is synchronized.
[0027]
For example, as shown in FIG. 3, the deformation resistance of the workpiece 1 varies depending on the strain, the stress state, the friction state between the tool (die) and the workpiece 1, and the like. As long as the deformation resistance is obtained, it can be easily reflected in the pressurization of both the punches.
[0028]
When the value of (L / d), which is the ratio of the length L corresponding to the upset portion of the solid cylinder (workpiece 1) of diameter d shown in FIG. In order to prevent the occurrence of buckling, the method according to the invention of (2), that is, after the portion corresponding to the upsetting portion is preformed, the outer punch 5 and the center punch 6 may be pressurized. preferable.
[0029]
That is, first, a portion corresponding to the upset portion of the workpiece (solid cylinder) 1 lubricated by a normal method is preformed by a normal method. For example, as shown in FIG. 7, this preforming includes the length f of the preformed portion, the average diameter g of the maximum diameter e and the minimum diameter d of the preformed portion (that is, the diameter d of the solid cylinder 1), (F / g), which is the ratio of the above, may be performed so as to be 2.25 or less. The maximum diameter e of the preformed portion is a value equal to or smaller than the diameter of the upset portion of the stepped shaft.
[0030]
Then, after the preformed workpiece 1 is inserted into the hole mold formed by the fixed die 2 and the knockout pin 4 and placed on the knockout pin 4, as shown in FIG. The outer punch 5 and the center punch 6 are lowered, and the workpiece 1 is restrained by these punches, the fixed die 2 and the knockout pin 4. When the maximum diameter e of the preformed portion of the preformed workpiece 1 is equal to the value of the diameter of the upset portion of the stepped shaft, the restraint of the workpiece 1 is the two punches, that is, The outer punch 5 and the center punch 6, the fixed die 2, the knockout pin 4, and the floating die 3 are used. Thereafter, pressure is applied with both punches as shown in FIG. At this time, the surface pressure of the outer punch 5 is set to be larger than the surface pressure of the center punch 6.
[0031]
The surface pressure of the outer punch 5 is set to be larger than the surface pressure of the center punch 6, and the outer punch 5 and the center punch 6, the fixed die 2 and the knockout pin as shown in FIG. The axial distance between the end surfaces of the outer punch 5 and the center punch 6 on the pressing side is not the state immediately after the restraint of the workpiece 1 by 4 is started, but the final product dimension H ₁ shown in FIG. You may decide to do it.
[0032]
When the pressure is applied as described above, as shown in FIG. 1 (d), the excess volume of the workpiece 1 after the upsetting portion of the workpiece 1 is completely formed is set as the backward movement of the center punch 6 or Since it can be absorbed in advance, the final product will not be burred or missing, and the mold will not crack.
[0033]
Also in the case of the method of the invention of (2), the reduction speed of the outer punch 5 and the center punch 6 may be a normal forging reduction speed.
[0034]
In addition, the pressurization at this time is a force that uses a double pressure press to make the surface pressure of the outer punch 5 to be “2 ± 0.2” times the deformation resistance of the work material 1. It is preferable to carry out with a force that makes the surface pressure of the center punch 6 “1.7 ± 0.2” times the resistance, and it is even better if the reduction by both punches is synchronized.
[0035]
For example, as shown in FIG. 3, the deformation resistance of the workpiece 1 varies depending on the strain, the stress state, the friction state between the tool (die) and the workpiece 1, and the like. As long as the deformation resistance is obtained, it can be easily reflected in the pressurization of both the punches.
[0036]
The method of the invention of (1) and the method of the invention of (2) include not only so-called “metal materials” such as steel materials, aluminum and alloys thereof, copper and alloys thereof, titanium and alloys thereof, but also ceramics. It can be applied to general plastically deformable materials.
[0037]
Further, the production of the stepped shaft by the above method is not limited to so-called “cold” but may be performed in a state where the temperature of “warm” or “hot” is increased.
[0038]
The mold of the stepped shaft manufacturing apparatus according to the invention of (3) is, for example, a fixed die 2 and a knockout pin 4 as shown in FIG. 1, and an outer punch 5 capable of independently controlling the rolling force and position. And the center punch 6 and the floating die 3 interlocked with the operation of the outer punch 5.
[0039]
The floating die 3 is structured to operate in conjunction with the operation of the outer punch 5, and can be expanded and contracted with respect to the double-acting press base B (for example, a spring, an air cylinder, rubber, urethane, etc.). The latter is supported. Although not shown behind the knockout pin 4, a discharge mechanism for discharging the molded product (workpiece 1) is provided.
[0040]
Out of the above-mentioned molds constituting the closed mold, the outer punch 5 and the center punch 6 are individually connected to the piston rod (not shown) of each cylinder of the double-action press. Further, a load cell (not shown) for detecting the forging force and a linear scale (not shown) for detecting the position are attached to both the punches, and the reduction force and the position can be controlled independently. It is possible.
[0041]
Hereinafter, the present invention will be described more specifically with reference to examples.
[0042]
【Example】
(Example 1)
While preparing the various molds according to the method of the present invention shown in FIG. 1 and the mold according to the method using the conventional mechanical press shown in FIG. 4, the S10C steel specified in JIS G 4051 is used as a normal method. The solid cylinder was melted, hot-rolled and drawn, and cut to prepare a solid cylinder with a nominal diameter of 19.95 mm and a length of 61.6 mm.
[0043]
Next, a zinc phosphate coating treatment is applied to the surface of the solid cylinder by an ordinary method, and 10 stepped shafts shown in FIG. 8 are produced at room temperature by the method of the present invention and the method using a conventional mechanical press. did.
[0044]
Specifically, in the method according to the present invention using the apparatus shown in FIG. 1, a hole type in which a workpiece (solid cylinder) 1 subjected to a zinc phosphate coating treatment is formed by a fixed die 2 and a knockout pin 4. The outer punch 5 and the center punch 6 are lowered at 35 mm / second and 35 mm / second, respectively, and these punches, the fixed die 2 and the knockout pin 4 are covered. Work material 1 was restrained. Thereafter, the surface pressure of the outer punch 5 was increased to 145 kgf / mm ² and the surface pressure of the center punch 6 was increased to 122 kgf / mm ² based on the deformation resistance obtained in advance. A portion having a length of 20 mm was formed by the fixed die 2 and the knockout pin 4.
[0045]
When the pressure is applied as described above by the method of the present invention, as shown in FIG. 1 (d), the surplus volume of the workpiece 1 after the upsetting portion of the workpiece 1 is completely formed becomes the center punch. Since it was absorbed at a retreat of 6, the final product was free of burrs and cutouts. Furthermore, the mold did not crack.
[0046]
On the other hand, in the method using the conventional mechanical press shown in FIG. 4, the workpiece (solid cylinder) 1 having been subjected to the zinc phosphate coating treatment is inserted into the hole mold formed by the lower fixing die 9 and the knockout pin 4. The punch 8 was lowered at a rate of 35 mm / second and the surface pressure of the punch 8 was set at 149.7 kgf / mm ² . In the case of upsetting by this conventional method, burrs and undercutting occur, and therefore the productivity for obtaining a desired stepped shaft was extremely inferior.
[0047]
(Example 2)
While preparing the various molds according to the method of the present invention shown in FIG. 1 and the mold according to the method using the conventional mechanical press shown in FIG. 4, the SCr420H steel defined in JIS G 4052 is used as a normal method. Were melted, hot-rolled, spheroidized and drawn, and cut to prepare a solid cylinder having a nominal diameter of 19.95 mm and a length of 90 mm.
[0048]
Next, the surface of the solid cylinder is subjected to a zinc phosphate coating treatment by an ordinary method, and 10 stepped shafts shown in FIG. 9 are produced at room temperature by the method of the present invention and the method using a conventional mechanical press. did.
[0049]
Specifically, in the method according to the present invention using the apparatus shown in FIG. 1, a portion corresponding to the upsetting portion of the workpiece (solid cylinder) 1 that has been subjected to the zinc phosphate coating treatment is illustrated by a normal method. Pre-molded as shown in FIG. Next, the preformed workpiece 1 was inserted into a hole mold formed by the fixed die 2 and the knockout pin 4 and placed on the knockout pin 4. Next, the outer punch 5 and the center punch 6 were lowered at 35 mm / second and 35 mm / second, respectively, and the workpiece 1 was restrained by these punches, the fixed die 2 and the knockout pin 4. Thereafter, the surface pressure of the outer punch 5 was increased to 185 kgf / mm ² and the surface pressure of the center punch 6 was increased to 158 kgf / mm ² based on the deformation resistance obtained in advance. A portion having a length of 20 mm was formed by the fixed die 2 and the knockout pin 4.
[0050]
When the pressure is applied as described above by the method of the present invention, as shown in FIG. 1 (d), the surplus volume of the workpiece 1 after the upsetting portion of the workpiece 1 is completely formed becomes the center punch. Since it was absorbed at a retreat of 6, the final product was free of burrs and cutouts. Furthermore, the mold did not crack.
[0051]
On the other hand, in the method using the conventional mechanical press shown in FIG. 4, the workpiece (solid cylinder) 1 subjected to the zinc phosphate coating treatment is directly formed by the lower fixing die 9 and the knockout pin 4 without preforming. The punch 8 was inserted into the hole mold and placed on the knockout pin 4, the punch 8 was lowered at 35 mm / sec, and the surface pressure of the punch 8 was set to 176.6 kgf / mm ² . When the workpiece which has not been preformed as shown in FIG. 10 is processed by this conventional method, buckling occurs and a final product having a desired shape cannot be obtained.
[0052]
【The invention's effect】
According to the method of the present invention, a shaft gear having an upsetting portion having a diameter larger than the diameter of a solid cylinder (which is a material) without causing damage to the mold and without generating burrs or thinning. A stepped shaft suitable as a material such as a piston with a shaft can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal section showing an example of a one-side situation in which a stepped shaft is manufactured by the method of the present invention.
FIG. 2 is a view for explaining a stepped shaft having an upsetting portion whose diameter is larger than the diameter of a solid cylinder (which is a raw material).
FIG. 3 is a diagram schematically showing a relationship between distortion of a workpiece and deformation resistance.
FIG. 4 is a diagram illustrating the manufacture of a stepped shaft using a mechanical press.
FIG. 5 is a diagram illustrating the manufacture of a stepped shaft by closed forging using a hydraulic press.
FIG. 6 is a diagram for explaining a length L corresponding to an upset portion of a solid cylinder (workpiece 1) having a diameter d.
FIG. 7 is a diagram for explaining the shape of a preformed portion when a portion corresponding to the upsetting portion of the workpiece is preformed.
FIG. 8 is a view showing a stepped shaft having an upsetting portion in which the diameter manufactured in Example 1 is larger than the diameter of a solid cylinder (which is a raw material).
FIG. 9 is a view showing a stepped shaft having an upset portion having a diameter larger than that of a solid cylinder (which is a material) manufactured in Example 2;
FIG. 10 is a diagram showing a shape of a preformed portion when a portion corresponding to an upsetting portion of a workpiece is preformed in Example 2.
[Explanation of symbols]
1: Work material,
2: Fixed die,
3: Floating die,
4: Knockout pin,
5: Outer punch,
6: Center punch,
7: Stretchable member
8: Punch,
9: Lower fixed die,
10: Upper center punch,
11: Lower center punch,
12: Upper mold,
13: Lower mold,
B: Base of double-acting press,
S: Space,
d: Diameter of the solid cylinder that is the material,
L: length corresponding to the upset portion of a solid cylinder of diameter d,
e: the maximum diameter of the preformed part,
f: length of the preformed part,
g: (d + e) / 2,
H ₁ : Dimensions of the final product (stepped shaft)

Claims (3)

The shape of the stepped shaft corresponding to the product is formed with a closed mold consisting of a fixed die, floating die, knockout pin, outer punch and center punch, and the diameter from the solid cylinder is larger than the diameter of the cylinder A method of manufacturing a stepped shaft having a portion, wherein a solid cylinder as a workpiece is constrained by a fixed die, a knockout pin, an outer punch and a center punch, and then the surface pressure of the outer punch is reduced to the surface pressure of the center punch. A method of manufacturing a stepped shaft, wherein the pressure is increased and pressurized. The shape of the stepped shaft corresponding to the product is formed with a closed mold consisting of a fixed die, floating die, knockout pin, outer punch and center punch, and the diameter from the solid cylinder is larger than the diameter of the cylinder A method of manufacturing a stepped shaft having a portion, wherein a portion corresponding to the upset portion of a solid cylinder that is a workpiece is preformed, and then the preformed workpiece is at least a fixed die and a knockout A method for manufacturing a stepped shaft, comprising: constraining with a pin, an outer punch, and a center punch, and then pressing the outer punch with a surface pressure greater than that of the center punch. An apparatus for manufacturing a stepped shaft having a mounting portion having a diameter larger than the diameter of a solid cylinder from a solid cylinder, a fixed die, a knockout pin, an outer punch capable of independently controlling a reduction force and a position, and A center die and a floating die interlocking with the operation of the outer punch are provided, and the fixed die, the knockout pin, the outer punch, the center punch and the floating die form a sealed mold having a stepped shaft shape corresponding to the product. Possible stepped shaft manufacturing equipment.

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