JP2001038444A - Method and device to manufacture shaft with steps - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a processing having no flashes or an underfill without damaging a die by restraining a solid column, which is a processing material, with a fixed die, a knockout pin, an outer punch and a center punch, and making the outer punch face pressure larger than that of the center punch for performing a pressurization. SOLUTION: A processing material 1 is inserted into a hole die being constituted with a fixed die 2 and a knockout pin 4 and, mounted on the knockout pin 4. Then, an outer punch 5 and a center punch 6 are lowered so as to restrain the processing material 1. Thereafter, the processing material 1 is pressurized with the outer punch 5 and the center punch 6. In this case, a face pressure of the outer punch 5 is made larger than that of the center punch 6. When a swaging part of the processing material 1 is completely formed, an excessive volume or a short volume of the processing material 1 is absorbed by a backward or a forward movement of the center punch 6. In a case where ratio between a length and a diameter of the processing material 1 exceeds 2.25, it is preferable that a portion equivalent to the swaging part is preliminary formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a stepped shaft having an upset portion from a solid cylinder having a diameter larger than the diameter of the cylinder, and an apparatus for manufacturing the stepped shaft. More specifically, a solid cylinder is a material (workpiece)
The present invention relates to a method and an apparatus for manufacturing the stepped shaft without generating burrs or underfill.

[0002]

2. Description of the Related 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,
For example, it has been manufactured by forging using a mechanical press or closed forging using a hydraulic press.

Among the above, forging using a mechanical press includes, for example, a punch (upper die) 8, a lower fixed die (lower die) 9, and a knockout pin 4 as schematically shown in FIG. A mechanical press is used. In this case, as shown in FIG. 4, burrs and underfills (unfilled material) usually occur in the forged workpiece 1 as shown in FIG. 4. Therefore, it is necessary to perform a cutting process in order to obtain a desired stepped shaft shape, and further, the yield of the material is lowered.

[0004] In addition, closed forging using a hydraulic press,
For example, as shown in FIG. 5, a hydraulic press having an upper center punch 10, a lower center punch 11, an upper mold 12, and a lower mold 13 is used, and the upper mold 12 and the lower mold 13 are brought into close contact by hydraulic pressure. Then, the workpiece 1 is pressed by the upper center punch 10 and the lower center punch 11 so that the upper mold 1
2. It is formed into a target shape in a closed mold formed by the lower die 13, the upper center punch 10 and the lower center punch 11. In this closed forging, the volume of the closed mold has a constant value. Therefore, the workpiece 1
If the volume of the forged product is smaller than the volume of the closed mold, the underfill is generated at the corner of the forged product (workpiece 1). Conversely, if the volume of the workpiece 1 is larger than the volume of the closed mold, the upper mold 12
Burrs (insert burrs) are generated on the mating surface between the mold and the lower mold 13, and in some cases, the mold may be damaged.
For this reason, in the case of closed forging, it is necessary to make the volume variation of the workpiece 1 extremely small, and it takes a lot of time and cost to produce a processing material.

On the other hand, in plasticity and processing (Vol. 27, No. 300 (1986), pp. 121-131),
The "principle of discarded shaft" proposed as "development of precision cold forging method by split flow method" is said to be a technology that allows the die to be filled with the work material with a low forging load. In order to obtain the desired stepped shaft, it is not possible to control the dimensions and end face shape of the
After forging by adjusting the "disposable shaft portion" to be longer than a predetermined value, it is necessary to cut the portion to a desired length, and the yield of the material is reduced.
In addition, the material supplied for filling the meat is difficult to control because it becomes a natural flow of forging, and therefore, the dimensions of the forged product,
It is difficult to manage the shape. Further, specific troubles such as mold breakage may occur.

Also, Sumitomo Metal (vol. 50, No. 3)
(1998), pages 16 to 24, propose a technique of "forming a helical gear for an automobile using a five-cylinder hydraulic double-acting press". However, even in the case of this technique, as described on page 24, depending on the balance between the amounts of the boss portion and the gear body portion, the tool surface pressure increases as compared with the disposal shaft method. There are inherent problems such as the occurrence of fogging flaws in the part.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to use a solid cylinder manufactured by a conventional technique having a volume variation of, for example, about ± 3%. Since the upsetting process does not generate burrs or underfill in the upset portion, the material yield is large, and there is no breakage of the mold. Suitable stepped material such as gear with shaft and piston with shaft An object of the present invention is to provide a shaft manufacturing method and a stepped shaft manufacturing apparatus.

[0008]

The gist of the present invention resides in a method for manufacturing a stepped shaft shown in the following (1) and (2) and an apparatus for manufacturing a stepped shaft shown in (3).

(1) The shape of the stepped shaft corresponding to the product is formed by a closed die composed of a fixed die, a floating die, a knockout pin, an outer punch and a center punch, and the diameter of the column is changed from a solid column to a column. A method of manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a workpiece, wherein a solid cylinder as a workpiece is restrained 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. A stepped shaft which is larger than the surface pressure of the center punch.

(2) The shape of the stepped shaft corresponding to the product is formed by a closed die composed of a fixed die, a floating die, a knockout pin, an outer punch and a center punch, and the diameter of the column is from a solid cylinder. A method of manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a workpiece, wherein a portion corresponding to the upset portion of a solid cylinder as a workpiece is preformed, and then the preformed workpiece At least with a fixed die, a knockout pin, an outer punch, and a center punch, and then increasing the surface pressure of the outer punch to be greater than the surface pressure of the center punch.

(3) An apparatus for manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder from a solid cylinder, comprising: a fixed die, a knockout pin, and independent control of rolling force and position. An outer punch and a center punch capable of being provided with a floating die linked to the operation of the outer punch, the fixed die, a knockout pin,
A stepped shaft manufacturing apparatus capable of forming a closed mold having a stepped shaft shape corresponding to a product by an outer punch, a center punch, and a floating die.

FIG. 1 to be described later is a schematic cross-sectional view showing a situation in which a stepped shaft is manufactured (however, only one vertical cross section is shown). The fixed die 2, floating die 3, and knockout pin 4 are described above. , Outer punch 5 and center punch 6
Are in the positional relationship shown in FIG. 1, and when the respective positions are in the relationship shown in FIG. 1D, for example, a "sealed mold having a stepped shaft shape corresponding to the product" is formed. You. 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, At the stage until the upset portion 1 is completely formed, at least the floating die 3 does not completely contact the workpiece 1 and the space S is formed.

The outer punch 5 is an outer die for applying a forging force to the workpiece 1, and the center punch 6 is an inner die for applying a forging force to 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. The floating die 3 is capable of being extended and contracted by a member 7 (for example, a spring, an air cylinder, rubber, urethane, ) Is supported at the rear. The fixed die 2 is a fixed mold on the side receiving the forging force, and the knockout pin 4 is a mold on the side receiving the forging force. It also has the function of discharging the material 1).

FIG. 2 shows a "stepped shaft having an upset portion whose diameter is larger than the diameter of a solid cylinder (material)."
(A), (b), and (c). In the case of a stepped shaft as shown in FIGS. 2 (a) and 2 (b), the end face of the upsetting portion is formed by the center punch 6 shown in FIG.
It is forged on the side.

Hereinafter, the inventions described in the above (1) to (3) are referred to as the inventions (1) to (3), respectively.

The present inventors have conducted various studies on forging techniques for solving the above-mentioned problems. As a result, the following findings were obtained.

(A) A fixed die, a floating die, a knockout pin, an outer punch, and a center punch are each used to form a hermetically sealed mold having a stepped shaft shape corresponding to a product. If the surplus volume after the filling portion fills the closed mold is absorbed by the retraction of the center punch, the product does not have burrs or underfill, and the mold does not crack.

(B) To achieve the above (a), a double-acting press capable of independently controlling the rolling force and position of an outer punch and a center punch, which are dies for pressing a forging force on a workpiece. Forging (upsetting) so that the work material has a desired shape of the upsetting portion mainly by the outer punch, and further, assisting the work material by the center punch so as to have the desired shape of the upsetting portion. What is necessary is just to perform the forging and control the material flow of the workpiece.

(C) In order to control the material flow of the workpiece by the center punch, the surface pressure of the outer punch is set to be larger than the surface pressure of the center punch, and the floating is performed by a telescopic member such as a spring. The die may be linked to the operation of the outer punch.

The present invention has been completed based on the above findings.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and apparatus of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the method of the invention of (1) and FIG.
2 is a schematic longitudinal sectional view showing an example of a one-sided situation in which a stepped shaft having the shape shown in FIG.

First, a work material (solid cylinder) 1 lubricated by an ordinary method is fixed to a fixed die 2 and a knockout pin 4.
And is mounted 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 pins 4. Thereafter, as shown in FIGS. 1B and 1C, pressure is applied by both punches. 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 to apply the pressure. It should be noted that the reason why the surface pressure of the outer punch 5 is set to be larger than the surface pressure of the center punch 6 to apply pressure is as shown in FIG.
A not immediately after the restraint of the workpiece 1 as shown was started, the axial distance of the end face of the pressure-side of the outer punch 5 and the center punch 6 is the final product dimensions H ₁ shown in FIG. 1 (d) Status It may be performed after it becomes.

When pressure is applied as described above, FIG.
As shown in FIG. 5, since the surplus volume of the workpiece 1 after the swaged portion of the workpiece 1 is completely formed can be absorbed by retreating or advancing the center punch 6, burrs or burrs are generated on the final product. There is no underfill and no cracks in the mold.

The rolling speed of the outer punch 5 and the center punch 6 in the invention (1) may be a normal forging rolling speed.

The pressurizing at this time is performed by a double-acting press by a force that makes the surface pressure of the outer punch 5 "2 ± 0.2" times the deformation resistance of the workpiece 1. It is preferable to use a force of "1.7 ± 0.2" times the deformation resistance of 1 as the surface pressure of the center punch 6, and it is even better if the reduction by both punches is synchronized.

The deformation resistance of the workpiece 1 varies depending on, for example, a strain or stress state or a friction state between a tool (die) and the workpiece 1 as shown in FIG. As long as the deformation resistance is determined by experimenting under the conditions, it can be easily reflected on the pressing of the two punches.

The value of (L / d), which is the ratio of the length L corresponding to the upsetting portion of the solid cylinder (workpiece 1) of diameter d shown in FIG. If it exceeds, use the method according to the invention of (2) to prevent the occurrence of buckling.
In other words, it is preferable to press the outer punch 5 and the center punch 6 after preforming the portion corresponding to the upsetting portion.

That is, first, a portion corresponding to the upsetting portion of the workpiece (solid cylinder) 1 which has been lubricated by a normal method is preformed by a normal method. This preforming includes, for example, as shown in FIG. 7, 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) is 2.
What is necessary is just to make it 25 or less. The maximum diameter e of the preformed portion is equal to or smaller than the diameter of the upset portion of the stepped shaft.

Next, the preformed workpiece 1
Is inserted into a hole formed by the fixed die 2 and the knockout pin 4 and is placed on the knockout pin 4.
As shown in (b), the outer punch 5 and the center punch 6 are lowered, and these punches and the fixed die 2 are moved downward.
The workpiece 1 is restrained by the knockout pin 4. The maximum diameter e of the preformed part of the preformed workpiece 1
Is equal to the value of the diameter of the upsetting portion of the stepped shaft, the work piece 1 is restrained by the two punches, namely, the outer punch 5 and the center punch 6, the fixed die 2, the knockout pin 4, This is performed with the floating die 3. Thereafter, as shown in FIG. 1C, pressure is applied by both punches. 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 to apply the pressure.

The reason why the surface pressure of the outer punch 5 is made larger than the surface pressure of the center punch 6 and pressurized is as shown in FIG.
As shown in (b), not immediately after the restraint of the workpiece 1 by the outer punch 5 and the center punch 6, the fixed die 2 and the knockout pin 4 is started, but on the pressing side of the outer punch 5 and the center punch 6. the axial distance of the end surface may be decided to do from a situation of the final product dimensions H ₁ shown in FIG. 1 (d).

When pressure is applied as described above, FIG.
As shown in FIG. 5, since the surplus volume of the workpiece 1 after the swaged portion of the workpiece 1 is completely formed can be absorbed by retreating or advancing the center punch 6, burrs or burrs are generated on the final product. There is no underfill and no cracks in the mold.

Also in the case of the method (2) of the invention, the reduction speed of the outer punch 5 and the center punch 6 may be a normal forging reduction speed.

The pressurizing at this time is performed by a double-acting press by a force that sets the surface pressure of the outer punch 5 to “2 ± 0.2” times the deformation resistance of the workpiece 1. It is preferable to use a force of "1.7 ± 0.2" times the deformation resistance of 1 as the surface pressure of the center punch 6, and it is even better if the reduction by both punches is synchronized.

The deformation resistance of the workpiece 1 varies depending on, for example, a strain or stress state or a friction state between a tool (die) and the workpiece 1 as shown in FIG. As long as the deformation resistance is determined by experimenting under the conditions, it can be easily reflected on the pressing of the two punches.

The method of the invention (1) and the method of the invention (2) are not limited to so-called “metal materials” such as steel materials, aluminum and its alloys, copper and its alloys, titanium and its alloys, but also ceramics and the like. The present invention can be applied to general plastic deformable materials.

The production of the stepped shaft by the above method is not limited to the so-called "cold", but may be performed in a state where the temperature of "warm" or "hot" is raised.

The mold of the apparatus for manufacturing a stepped shaft according to the invention (3) includes, for example, a fixed die 2 as shown in FIG.
It comprises a knockout pin 4, an outer punch 5 and a center punch 6, each of which can independently control a rolling force and a position, and a floating die 3 linked to the operation of the outer punch 5.

The floating die 3 operates in conjunction with the operation of the outer punch 5. The floating die 3 is provided with an extensible member 7 (for example, a spring, an air cylinder, rubber or urethane) with respect to a base B of a double-acting press. ) Is supported at the rear. Although not shown, a discharge mechanism for discharging the formed product (workpiece 1) is provided behind the knockout pin 4.

Of the above molds constituting the closed mold,
The outer punch 5 and the center punch 6 are individually connected to a piston rod (not shown) of each cylinder of the double-acting press. Further, a load cell (not shown) for detecting a forging force and a linear scale (not shown) for detecting a position are attached to both the punches, so that the rolling force and the position can be controlled independently. It is possible.

Hereinafter, the present invention will be described more specifically with reference to examples.

[0042]

Embodiment 1 Various dies according to the method of the present invention shown in FIG. 1 and dies according to a method using a conventional mechanical press shown in FIG. The specified S10C steel is melted, hot-rolled and drawn by a usual method, and cut to form a nominal diameter of 19.95 m.
A solid cylinder having a length of 61.6 mm and a length of 61.6 mm was prepared.

Next, the surface of the solid cylinder was subjected to a zinc phosphate coating treatment by a usual method, and the stepped shaft shown in FIG. Manufactured individually.

Specifically, in the method according to the present invention using the apparatus shown in FIG. 1, a workpiece (solid cylinder) 1 which has been subjected to a zinc phosphate coating treatment is formed by a fixed die 2 and a knockout pin 4. Then, the outer punch 5 and the center punch 6 are lowered at 35 mm / sec and 35 mm / sec, respectively, and these punches, the fixed die 2 and the knockout pin 4 are lowered. 4
The work piece 1 was restrained. Thereafter, the surface pressure of the outer punch 5 is reduced to 145 k based on the deformation resistance obtained in advance.
gf / mm ² , the surface pressure of the center punch 6 is 122 kgf
/ Mm ² . The fixed die 2 and the knockout pin 4 formed a portion having a length of 20 mm.

When the pressure is applied as described above in the method of the present invention, as shown in FIG. 1D, the surplus volume of the workpiece 1 after the upset portion of the workpiece 1 is completely formed. Was absorbed by the retraction of the center punch 6, so that no burrs or underfill occurred in the final product. Further, no crack was generated in the mold.

On the other hand, in the method using a conventional mechanical press shown in FIG. 4, a workpiece (solid cylinder) 1 which has been subjected to a zinc phosphate coating treatment is fixed to a lower fixing die 9 and a knockout pin 4.
And placed on the knockout pin 4 and lowered the punch 8 at 35 mm / sec.
Was subjected to upsetting with a surface pressure of 149.7 kgf / mm ² . When the upsetting is performed by the conventional method, burrs and underfill are generated, and therefore, the productivity for obtaining a desired stepped shaft is extremely poor.

Embodiment 2 Various dies according to the method of the present invention shown in FIG. 1 and dies according to a method using a conventional mechanical press shown in FIG. 4 are prepared, and are stipulated in JIS G 4052. The resulting SCr420H steel was melted, hot-rolled, spheroidized annealing, and wire-drawn in a usual manner, and cut to prepare a solid cylinder having a nominal diameter of 19.95 mm and a length of 90 mm.

Next, the surface of the solid cylinder was coated with zinc phosphate by a usual method, and the stepped shaft shown in FIG. 9 was heated at room temperature for 10 times by the method of the present invention and a method using a conventional mechanical press. Manufactured individually.

More specifically, in the method according to the present invention using the apparatus shown in FIG. 1, the portion corresponding to the upsetting portion of the workpiece (solid cylinder) 1 which has been subjected to the zinc phosphate coating treatment is formed by a usual method. It was preformed by the method as shown in FIG. Next, the preformed workpiece 1 was inserted into a die 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 / sec and 35 mm / sec, respectively, and the workpiece 1 was restrained by these punches, the fixed die 2 and the knockout pins 4. Thereafter, based on the deformation resistance determined in advance, the outer punch 5 was pressed at a surface pressure of 185 kgf / mm ² and the center punch 6 at a surface pressure of 158 kgf / mm ² . The fixed die 2 and the knockout pin 4 formed a portion having a length of 20 mm.

When the pressure is applied as described above in the method of the present invention, as shown in FIG. 1D, the surplus volume of the workpiece 1 after the upset portion of the workpiece 1 is completely formed. Was absorbed by the retraction of the center punch 6, so that no burrs or underfill occurred in the final product. Further, no crack was generated in the mold.

On the other hand, in the method using a conventional mechanical press shown in FIG. 4, the work piece (solid cylinder) 1 which has been subjected to the zinc phosphate coating treatment is directly formed without lower forming die 9 and knockout pin 1 without preforming. 4 and placed on the knockout pin 4 and the punch 8 is
/ Second to lower the surface pressure of the punch 8 to 176.6 kgf.
/ Mm ² . In the case of processing the work material which has not been preformed as shown in FIG. 10 by this conventional method, buckling occurred and a final product having a desired shape could not be obtained.

[0052]

According to the method of the present invention, the upsetting portion whose diameter is larger than the diameter of the solid cylinder (material) without causing damage to the mold and without generating burrs or underfill. Thus, it is possible to obtain a stepped shaft suitable for a material such as a gear with a shaft or a piston with a shaft.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal section showing an example of a one-sided situation in which a stepped shaft is manufactured by the method of the present invention.

FIG. 2 is a view illustrating a stepped shaft having an upset portion whose diameter is larger than the diameter of a solid cylinder (material).

FIG. 3 is a diagram schematically showing a relationship between strain and deformation resistance of a workpiece.

FIG. 4 is a diagram illustrating the production of a stepped shaft using a mechanical press.

FIG. 5 is a diagram illustrating the production of a stepped shaft by closed forging using a hydraulic press.

FIG. 6 is a diagram illustrating a length L corresponding to an upset portion of a solid cylinder (workpiece 1) having a diameter d.

FIG. 7 is a diagram illustrating the shape of a preformed portion when a portion corresponding to an upset portion of a workpiece is preformed.

FIG. 8 is a view showing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder (made of a material) manufactured in Example 1.

FIG. 9 is a view showing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder (made of a material) manufactured in Example 2.

FIG. 10 is a view showing the shape of a preformed portion when a portion corresponding to an upset 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: elastic member, 8: punch, 9: lower fixed die, 10: Upper center punch, 11: Lower center punch, 12: Upper die, 13: Lower die, B: Double-acting press base, S: Space, d: Diameter of solid cylinder as material, L: Diameter d solid cylinder corresponding to the upsetting of the length of, e: maximum diameter of the preformed part, f: preforming unit length, g: (d + e) / 2, H 1: final product (stepped shaft) Dimensions

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Claims (3)

[Claims] 1. The shape of a stepped shaft corresponding to a product,
A method of manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder formed from a closed cylinder formed of a fixed die, a floating die, a knockout pin, an outer punch, and a center punch. Then, after constraining the solid cylinder, which is the workpiece, with the fixed die, knockout pin, outer punch, and center punch, the outer punch is made to have a greater surface pressure than the center punch and then pressurized. Method of manufacturing a stepped shaft. 2. The shape of a stepped shaft corresponding to a product,
A method of manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder formed from a closed cylinder formed of a fixed die, a floating die, a knockout pin, an outer punch, and a center punch. Then, after preforming the portion corresponding to the upsetting portion of the solid cylinder as the workpiece, and then restraining the preformed workpiece with at least a fixed die, a knockout pin, an outer punch and a center punch, And a step of making the surface pressure of the outer punch greater than the surface pressure of the center punch. 3. An apparatus for manufacturing a stepped shaft having an upset portion having a diameter larger than the diameter of a solid cylinder from a solid cylinder, wherein a fixed die and a knockout pin are independently controlled in rolling force and position. A seal having a possible outer punch and a center punch, a floating die interlocked with the operation of the outer punch, and having a stepped shaft shape corresponding to a product by the fixed die, the knockout pin, the outer punch, the center punch and the floating die. A stepped shaft manufacturing device that can form a mold.