JP3697473B2 - Manufacturing method and manufacturing apparatus for long shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method and a manufacturing apparatus for a long shaft having a molded part such as a gear or a serration at one end, such as used for a shaft of a starter motor of an internal combustion engine.
[0002]
[Prior art]
For example, a starter motor for starting an automobile engine is provided with a long shaft having a driving gear coaxially and integrally formed at the tip.
This type of long shaft is preferably manufactured by cold forging because it is excellent in dimensional accuracy and strength. Generally, a long rod-like shape is formed in a material charging hole formed in a die of a manufacturing apparatus. The material was put in and molded by pushing it forward with a punch.
[0003]
In this cold forging, in order to avoid the seizure due to the friction force generated between the outer wall surface of the material and the inner wall surface of the material charging hole, the material is charged into the material charging hole at a high speed and injected therefrom. It was necessary to reduce the frictional force as much as possible.
In addition, when injecting the molded material from the material insertion hole, the molding part such as the gear formed on the front end side of the material is pushed out toward the rear end side by the knockout pin of the manufacturing apparatus, so that the frictional force If this is large, a large compressive force is applied to the molded part and it is deformed. Therefore, it is necessary to reduce the frictional force.
[0004]
The problem based on this frictional force becomes a problem when using an elongated material. In particular, the ratio of the total length of the material divided by its diameter (the total length is L, the diameter is d, hereinafter this ratio is referred to as L / d ratio). However, in a long shaft of 10 or more, the frictional force is increased and the yield is deteriorated. This is a factor that limits the length dimension that can be manufactured.
However, nowadays, there is a high demand for an elongated long shaft having an L / d ratio of 10 or more, and it has been strongly desired to realize a manufacturing method and a manufacturing apparatus that can prevent high yield and perform high-precision processing.
[0005]
Under such circumstances, for example, a manufacturing method and a manufacturing apparatus shown in FIGS. 8 and 9 are conceivable as a means for avoiding the problem of the frictional force generated between the material and the material insertion hole.
In the manufacturing apparatus 1 shown in FIG. 8, reference numeral 2 denotes a die provided in the manufacturing apparatus 1, and a material charging hole 3 is formed in the die 2. The material insertion hole 3 is generally composed of a first straight hole 5, a second straight hole 6, and a molding hole 7 having a common axis 4. The forming hole 7 is, for example, a hole in which gear teeth are formed, the second straight hole 6 is a cylindrical hole continuous to the forming hole 7, and the first straight hole 5 is formed in the second straight hole 6. It is a cylindrical hole that is continuous and thicker than the second straight hole 6 by a radius t with a distance t.
[0006]
Production of the long shaft 8 by the production apparatus 1 described above is performed as follows. First, a long bar-shaped material 9 covered with a lubricating film is charged into the material charging hole 3. Subsequently, the rear end side of the material 9 is pressed forward by the punch 11 provided in the manufacturing apparatus 1 and pushed out into the forming hole 7.
Due to this compressive force, the distal end side of the material 9 is plastically deformed to match the gear shape of the molding hole 7 to form a gear-shaped molding portion 8a, and the portion located in the second straight hole 6 is thick. The inner wall surface 6a of the second straight hole 6 is pressed.
[0007]
At this time, the frictional force caused by the outer wall surface 8 b of the long shaft 8 compressing the inner wall surface 6 a and the inner wall surface 7 a of the molding hole 7 between the long shaft 8 and the material insertion hole 3. The first straight hole 5 reduces the frictional force in the first straight hole 5 due to the lubricating film interposed in the clearance t between the long shaft 8 and the material insertion hole 3. It has come to be.
[0008]
That is, the frictional force in the direction of the axis 4 is limited to the portion of the second straight hole 6 and the forming hole 7 and is reduced. Thus, when the long shaft 8 is pushed out by the knockout pin 12 after molding, the force applied to the molding portion 8a can be reduced, so that the gear of the molding portion 8a is not easily deformed.
[0009]
[Problems to be solved by the invention]
Thus, by providing the first straight hole 5, the frictional force between the material insertion hole 3 and the long shaft 8 is reduced. On the other hand, as shown in FIG. This portion of the shank shaft 8 is thicker than the second straight hole 6 by a clearance of 2t in diameter, and thicker than the shaft diameter originally required.
[0010]
When considering such a surface finish on the long shaft 8, as shown in FIG. 9, after forming the centering hole 10a and the hole 10b at the front end 8b and the rear end 8c of the long shaft 8, respectively. It is necessary to perform surface finishing of the side surface with an abrasive (not shown) while being sandwiched between jigs 11a and 11b of a machine tool for surface finishing and fixed so as to be free from tilting the axis 4.
However, in this surface finishing method, an extra step of forming the holes 10a and 10b for centering takes place, which causes a problem that the manufacturing cost increases.
[0011]
Therefore, as a method of performing surface finishing without the step of forming such holes 10a and 10b, centerless polishing in which the long shaft 8 is sandwiched and polished by a plurality of polishing rolls (not shown) can be considered.
However, even in this centerless polishing, there is a disadvantage that the long shaft 8 is not evenly polished due to the slanting of the long shaft 8 with respect to the polishing roll because of the step formed on the side surface of the long shaft 8. An extra process for dealing with the shank shaft 8 so as not to tilt is necessary, which also causes a problem that the manufacturing cost increases.
[0012]
As described above, in the conventional manufacturing method and manufacturing apparatus, when the long shaft 8 having an L / d ratio of 10 or more is manufactured, the first straight hole 5 is formed in the die 2 in order to reduce the frictional force. Although it is conceivable to provide this, since the long shaft 8 is partially thickened, a process for removing the long shaft 8 is required, which causes a new problem that the man-hour for that is excessive and the cost is increased. It was.
[0013]
The present invention has been made in view of the above circumstances and intends to achieve the following object.
That is, it aims at provision of the manufacturing method and manufacturing apparatus of a long shaft which can be manufactured cheaply and with high precision.
[0014]
[Means for Solving the Problems]
The long shaft manufacturing method and manufacturing apparatus of the present invention employ the following means in order to solve the above problems.
That is, in the method for manufacturing a long shaft according to claim 1, a long rod-shaped material coated with a lubricating film is coaxially charged into a material charging hole formed in a die, and the rear end of the material is punched. Press forward, push the material out into the molding hole formed in front of the material insertion hole Has a molded part In the method for producing a long shaft for obtaining a molded product, during the extrusion, the lubricating film is The forming hole side of the material injection hole And is released through an oil escape groove having an oil escape hole communicating with the gap between the outer wall surface of the material and the inner wall surface of the material input hole, and after the extrusion, the rear end of the long shaft and the oil An inflating portion is formed at a portion where the escape hole is located.
[0015]
According to the method for manufacturing a long shaft according to claim 1, the extruded material tends to swell by causing plastic deformation in its radial direction, except for the portion where the oil relief hole is located in the axial direction. Then, since the lubricating film covering the outer wall surface of the material fills the gap between the inner wall surface of the material charging hole and the outer wall surface of the material, the swelling is suppressed. On the other hand, in the part where the oil escape hole is located, the lubricating film is pushed out by the outer wall surface of the material through the oil escape groove, so in this part of the material, the material is charged while being kept coaxial with the axis of the material input hole. An inflatable portion is formed by expanding in the diameter direction so as to match the inner wall surface of the hole. Further, due to the pressure of the punch at the time of extrusion, an inflating portion that is coaxial with the axis of the material charging hole and swells in the diameter direction so as to match the inner wall surface of the material charging hole is formed at the rear end portion of the material. These expanded portions are removed by surface finishing in centerless processing.
[0016]
The method for producing a long shaft according to claim 2 is the method for producing a long shaft according to claim 1, wherein the extrusion molding is performed in a plurality of steps, and each of the steps is performed according to the progress of these steps. It is characterized in that the diameters of the material input holes are sequentially increased.
[0017]
According to the method for manufacturing a long shaft according to the second aspect, in each step, each expanded portion is formed in the material by extrusion, but the diameter of the material input hole in the next step is made larger than that in the previous step. Therefore, when the material is put inside, it is easy to put each expansion part without being caught.
[0018]
According to a third aspect of the present invention, there is provided a long shaft manufacturing apparatus in which a long rod-shaped material coated with a lubricating film is introduced coaxially and at the leading end of the raw material in the charging direction. Form the molded part In the manufacturing apparatus of a long shaft provided with a die in which a material charging hole having a forming hole is formed, a hole diameter of the material charging hole is larger than an outer diameter of the material, The forming hole side of the material injection hole And an oil escape groove having an oil escape hole communicating with the gap is formed.
[0019]
According to the apparatus for manufacturing a long shaft according to claim 3, the material being extruded into the material charging hole tends to swell by causing plastic deformation in its radial direction, but its axial direction. In a portion other than the portion where the oil escape hole is located, the lubricating film covering the outer wall surface of the material fills the gap between the inner wall surface of the material charging hole and the outer wall surface of the material, so that the swelling is suppressed. On the other hand, in the part where the oil escape hole is located, the lubricant film is pushed out by the expansion of the material through the oil escape groove, so in this part of the material, the material input hole is kept coaxial with the axis of the material input hole. Swell in the diametrical direction so as to conform to Further, due to the pressure at the time of extrusion, an inflating portion that swells in the diametrical direction so as to be coaxial with the axis of the material charging hole and coincide with the material charging hole is formed at the rear end portion of the material. These expanded portions are removed by surface finishing in centerless processing.
[0020]
The method for manufacturing a long shaft according to claim 4 is characterized in that, in the method for manufacturing a long shaft according to claim 1 or 2, the expanded portion after extrusion is used as a guide surface for surface finishing by centerless processing. To do.
[0021]
According to the long shaft manufacturing method of the fourth aspect, the expanded portion becomes a guide surface in the centerless processing, and is removed by the surface finishing of the centerless processing.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an apparatus for producing a long shaft according to the present invention will be described with reference to the drawings.
In the long shaft manufacturing apparatus 15 shown in FIG. 1, a long bar-shaped material 16 coated with a lubricating film is introduced coaxially, and a molding hole 17 is provided to give a predetermined shape to the leading end of the raw material 16 in the charging direction. A die 19 having a material insertion hole 18 is provided.
[0023]
As shown in the figure, the material input hole 18 is generally composed of a straight hole 21 having a common axis 20 and a molding hole 17. Reference numeral 30 denotes an extruding punch, reference numeral 22 denotes a long shaft after forming by extrusion, and reference numeral 23 denotes a knockout pin for injecting the long shaft 22 after forming. The shaft 20 is an axis of the material insertion hole 18 and an axis of the long shaft 22.
[0024]
As shown in FIGS. 1, 3, and 4, the straight hole 21 is a cylindrical hole that is continuous with the molding hole 17. The hole diameter of the material insertion hole 18, that is, the hole diameter d1 of the straight hole 21 is larger than the outer diameter d2 of the material 16 (d1> d2), and a gap t ′ is formed between them with a radius. Yes. The gap t ′ is preferably about 0.01 mm to 0.03 mm (0.02 mm to 0.06 mm in diameter), for example. In each figure, the gap t ′ is drawn wider for the sake of explanation.
[0025]
As shown in FIGS. 1 and 2, the die 19 has an oil relief groove 26 that is located on the tip side from about half of the entire length of the material 16 in the direction of the axis 20 and has an oil relief hole 24 that communicates with the gap t ′. Are formed at two locations in the direction of the axis 20.
As shown in FIG. 3, three oil relief grooves 26 at each location are arranged at equiangular intervals of about 120 degrees around the shaft 20 in a cross section perpendicular to the shaft 20. It has an elongated hole shape that is about 10% or less of the inner diameter of 18.
[0026]
As shown in FIG. 5, the molding hole 17 is a hole in which gear teeth are formed. By pressing the tip of the material 16 there, the tip of the material 16 is plastically deformed to form gear teeth. It is like that.
[0027]
The manufacturing method by the manufacturing apparatus of the long shaft of this embodiment which has the said structure is demonstrated below.
First, the long bar-shaped material 16 covered with the lubricating film 27 is coaxially charged into the material charging hole 18, and then the rear end of the material 16 is pressed by the punch 30 to form the material charging hole 18. The material 16 is extruded into the molding hole 17.
[0028]
Due to the compression force at this time, the distal end side of the material 16 is plastically deformed so as to match the gear shape of the molding hole 17 to form a gear-shaped molding portion 22a, and the portion where the oil escape hole 24 is located is Buckling deformation (plastic deformation) is caused to increase the thickness, and the inner wall surface 21a of the straight hole 21 is pressed. The lubricating film 27 being extruded escapes through a plurality of oil relief grooves 26 that are located in front of about half of the entire length of the material 16 in the direction of the axis 20 and have oil relief holes 24 that communicate with the gap t ′.
[0029]
That is, the material 16 being extruded tends to bulge due to buckling deformation (plastic deformation) in its radial direction, but covers the material 16 except for the portion where the oil escape hole 24 is located in the direction of the axis 20. The lubricating film 27 is confined between the gap t ′ between the inner wall surface 18a of the material charging hole 18 and the outer wall surface 16a of the material 16, and the swelling thereof is suppressed.
[0030]
On the other hand, in the portion where each oil relief hole 24 is positioned in the direction of the axis 20, the lubricant film 27 is pushed out through the oil relief groove 26 by the outer wall surface 16 a of the material 16, so 2 inflated portions 28 that swell in the diametrical direction so as to match the inner wall surface 21a. At the same time, due to the pressure from the punch 30 at the time of extrusion, an expanding portion 28 that swells in the diametrical direction so as to be coaxial with the material charging hole 18 and match the inner wall surface 21a is formed at the rear end portion of the material 16.
[0031]
The extruded long shaft 22 is injected from the material charging hole 18 by the pressing force of the knockout pin 23. FIG. 6 shows the long shaft 22 after injection. Thereafter, the long shaft 22 is sandwiched between a plurality of polishing rolls (not shown), and guides the three inflatable portions 28 formed at the rear end and the portion where the oil escape hole 24 is located. As shown in FIG. 7, the surface finish is performed by centerless processing. Note that the roundness deviation of the expanding portion 28 is made slightly (4 μm to 6 μm) by the precision machining of the die 19, and each expanding portion 28 can be made to have substantially the same diameter. By setting as described above, it is possible to directly function as a guide surface of the polishing roll.
[0032]
In the above-described embodiment, an example in which molding is completed in one process by one manufacturing apparatus 15 is shown. However, the present invention is not limited to this, and the diameter of each material input hole varies with the progress of the process. It is also possible to use a plurality of manufacturing apparatuses (not shown) each having a die that becomes larger in order and form by extrusion divided into a plurality of processes.
[0033]
According to this manufacturing method, in each process, each expanded portion is formed in the material by extrusion, but since the diameter of the material input hole in the next process is larger than that in the previous process, the material is put inside. At this time, the respective inflatable portions are easily caught without being caught, and the material can be smoothly transferred between the respective steps.
[0034]
According to the long shaft manufacturing method of the present invention, the oil relief groove 26 is provided, so that the expanded portion 28 having a uniform radius around the shaft 20 is formed in the shaft 20 direction on the long shaft 22 after molding. Multiple locations are formed. Thereby, the portion where the long shaft 22 is in contact with the material charging hole 18 when injected from the material charging hole 18 is limited to the molding portion 22a and the expanding portion 28, and in other places, the lubricating film is interposed between the two. 27 is interposed and the frictional force between them is reduced, so that the long shaft 22 after molding can be injected from the material charging hole 18 with a small force, and the compression force applied to the molding portion 22a by the knockout pin 23 is small. It becomes difficult to deform this.
[0035]
Furthermore, each expansion portion 28 is kept coaxial with the material charging hole 18 and is regulated by the inner wall surface 21a so that each diameter is substantially equal to the diameter d1 of the material charging hole 18, so that the core has already been cored. Since it is in the centered state and is placed between the polishing rolls in order to perform centerless processing, it is supported at a plurality of locations by the centered expansion portion 28, so that the shaft 20 Does not tilt.
Therefore, since the centerless processing can be applied, the step of providing the centering hole 10a and the hole 10b shown in FIG. 9 of the prior art is unnecessary.
Furthermore, by setting the gap t ′ to a minimum required width of 0.01 mm to 0.03 mm, it is possible to reduce the level difference and easily remove it during surface finishing.
As described above, it is possible to provide a method for manufacturing a long shaft that can be manufactured inexpensively and with high accuracy.
[0036]
In addition, in the above manufacturing method, when it is necessary to perform molding by extrusion multiple times, the material diameter in the next process is increased by sequentially increasing the diameter of each material input hole as each process proceeds. Since the hole diameter of the hole is larger than that of the previous process, it becomes easy to insert each expanded part without being caught when putting the material in, and the material can be smoothly transferred between the processes. .
As described above, the expanded portion 28 having an optimal shape can be formed for each process, and a manufacturing method that can be applied even when it is necessary to perform molding by extrusion multiple times.
[0037]
According to the long shaft manufacturing apparatus of the present invention, by providing the oil relief groove 26, the expanded portion 28 having a uniform radius around the axis 20 is formed in the direction of the axis 20 on the long shaft 22 after molding. Multiple locations are formed. Thereby, the portion where the long shaft 22 is in contact with the material charging hole 18 when injected from the material charging hole 18 is limited to the molding portion 22a and the expanding portion 28, and in other places, the lubricating film is interposed between the two. 27 is interposed and the frictional force between them is reduced, so that the long shaft 22 after molding can be injected from the material charging hole 18 with a small force, and the compression force applied to the molding portion 22a by the knockout pin 23 is small. It becomes difficult to deform this.
[0038]
Furthermore, each inflating portion 28 is kept coaxial with the material charging hole 18 and is regulated by the inner wall surface 21a so that each diameter is substantially equal to the diameter d1 of the material charging hole. In order to perform centerless processing, when this is placed between the polishing rolls, the shaft 20 is supported at a plurality of locations by the centered expansion portion 28. It will not be tilted. Therefore, since the centerless processing can be applied, the step of providing the centering hole 10a and the hole 10b shown in FIG. 9 of the prior art is unnecessary.
Furthermore, by setting the gap t ′ to a minimum required width of 0.01 mm to 0.03 mm, it is possible to reduce the level difference and easily remove it during surface finishing.
As described above, it is possible to provide a long shaft manufacturing apparatus that can be manufactured inexpensively and with high accuracy.
[0039]
In the above embodiment, the gap t ′ is set to 4 μm to 6 μm. However, the present invention is not limited to this, and an optimal dimension may be appropriately adopted according to the outer diameter d2 of the material 16 to be molded and other processing conditions. .
Moreover, in the said embodiment, although the number of installation of the oil escape hole 24 and the oil escape groove 26 was 2 places in the direction of the axis | shaft 20, it is not restricted to this, At least 1 place ahead of about half of the full length of the raw material 16 What is necessary is just to have the above, and it is good also as a structure provided in one place or three places or more. In addition, as the installation location in the direction of the axis 20, the distance from the expansion portion 28 formed at the rear end can be increased by providing the material 16 on the front end side, that is, on the side closer to the molding portion 22a. It is preferable to be made more accurately.
[0040]
Moreover, in the said embodiment, although the structure which provided the oil escape hole 24 and the oil escape groove 26 in three places in the cross section perpendicular | vertical to the axis | shaft 20 was employ | adopted, it is not restricted to this, The outer diameter d2 of the raw material 16 to shape | mold Alternatively, a configuration provided at one or two places, or four or more places may be employed depending on other processing conditions. At this time, when provided at a plurality of locations, it is preferable that they are arranged at equiangular intervals because the lubricating film 27 can easily escape in the circumferential direction.
In the above embodiment, the case where gear teeth are formed on the forming portion 22a of the material 16 has been described as an example. However, the present invention is not limited to this, and other shapes such as serration may be formed. .
[0041]
In the above embodiment, the hole diameter of the oil relief groove 26 is set to about 10% or less of the inner diameter of the material charging hole 18, but not limited to this, depending on the outer diameter d2 of the material 16 to be molded and other processing conditions. Thus, an optimum hole diameter may be adopted as appropriate. Furthermore, the shape of the oil relief groove 26 may be other shapes such as a polygonal cross section instead of a hole.
[0042]
【The invention's effect】
According to the long shaft manufacturing method of the present invention, by providing the oil relief groove, a plurality of inflatable portions having a uniform radius around the axis are formed in the axial direction in the long shaft after molding. As a result, the portion of the long shaft that comes into contact with the material input hole when injected from the material input hole is limited to the molded part and the expanded part, and in other parts, a lubricating film is interposed between them. Therefore, the long shaft after molding can be injected from the material injection hole with a small force, and the compressive force applied to the molding part becomes small and it is difficult to deform it.
[0043]
Furthermore, each inflatable part is kept coaxial with the material input hole and is regulated by the inner wall surface of the material input hole so that each diameter is substantially equal to the diameter of the material input hole. When this is placed to perform centerless processing, it is supported at a plurality of locations by the centered expansion portion, so that the shaft does not tilt. Therefore, since centerless processing can be applied, a step of providing a centering hole or the like is not necessary.
As described above, it is possible to provide a method for manufacturing a long shaft that can be manufactured inexpensively and with high accuracy.
[0044]
In addition, in the above manufacturing method, when it is necessary to perform molding by extrusion multiple times, the material diameter in the next process is increased by sequentially increasing the diameter of each material input hole as each process proceeds. Since the hole diameter of the hole is larger than that of the previous process, it becomes easy to insert each expanded part without being caught when putting the material in, and the material can be smoothly transferred between the processes. .
As described above, since an expanded portion having an optimal shape can be formed for each process, it is possible to provide an applicable manufacturing method even if it is necessary to perform molding by extrusion a plurality of times.
[0045]
Moreover, in the said manufacturing method, since an expansion part can be used as a guide surface in the case of surface finishing, centering becomes unnecessary and it becomes possible to apply centerless processing.
[0046]
According to the long shaft manufacturing apparatus of the present invention, by providing the oil relief groove, a plurality of inflatable portions having a uniform radius around the axis are formed in the axial direction in the long shaft after molding. As a result, the portion of the long shaft that comes into contact with the material input hole when injected from the material input hole is limited to the molded part and the expanded part, and in other parts, a lubricating film is interposed between them. Therefore, the long shaft after molding can be injected from the material injection hole with a small force, and the compressive force applied to the molding part becomes small and it is difficult to deform it.
Furthermore, each inflatable part is kept coaxial with the material input hole and is regulated by the inner wall surface of the material input hole so that each diameter is substantially equal to the diameter of the material input hole. When this is placed to perform centerless processing, it is supported at a plurality of locations by the centered expansion portion, so that the shaft does not tilt. Therefore, since centerless processing can be applied, a step of providing a centering hole or the like is not necessary.
As described above, it is possible to provide a long shaft manufacturing apparatus that can be manufactured inexpensively and with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a long shaft manufacturing apparatus according to the present invention, and is a cross-sectional view of a main part.
FIG. 2 is a view showing a main part of the same long shaft manufacturing apparatus, and is an enlarged view of a part A in FIG. 1;
FIG. 3 is a view showing a main part of the same long shaft manufacturing apparatus, and is a cross-sectional view taken along line BB of FIG. 1;
4 is a view showing a main part of the same long shaft manufacturing apparatus, and is a cross-sectional view taken along line CC of FIG. 1; FIG.
5 is a view showing a main part of the same long shaft manufacturing apparatus, and is a cross-sectional view taken along the line DD of FIG. 1. FIG.
FIG. 6 is a perspective view showing a long shaft formed by the long shaft manufacturing apparatus.
FIG. 7 is a perspective view showing a long shaft after a surface finishing process is performed.
FIG. 8 is a sectional view showing a main part of a conventional long shaft manufacturing apparatus.
FIG. 9 is a cross-sectional view showing a surface finishing process of a long shaft formed by the long shaft manufacturing apparatus.
[Explanation of symbols]
16 ... Material
16a ... Outer wall surface
17 ... Molding hole
18 ... Material input hole
19 ... Die
20 ... axis
21a ... inner wall surface
22 ... Long shaft (molded product)
24 ... Oil escape hole
26 ... Oil escape groove
27 ... Lubrication film
28 ... Expansion part
30 ... Punch
t ′ ・ ・ ・ Gap

Claims (4)

A long rod-shaped material coated with a lubricating film is coaxially charged into the material charging hole formed in the die, the rear end of the material is pressed forward by a punch, and formed in front of the material charging hole. In the manufacturing method of a long shaft that obtains a molded product having a molded part by extruding the material into a molding hole,
An oil escape groove having an oil escape hole located in the molding hole side of the material input hole and communicating with a gap between the outer wall surface of the material and the inner wall surface of the material input hole during the extrusion. Escape through
After the extrusion, a method of manufacturing a long shaft, wherein an inflating portion is formed at a rear end of the long shaft and a portion where the oil escape hole is located. In the manufacturing method of the elongate shaft of Claim 1,
The molding by the extrusion is performed in a plurality of processes,
With the progress of these steps, the diameter of each material charging hole is sequentially increased, and the method for manufacturing a long shaft is characterized in that A long shaft having a die in which a long rod-shaped material coated with a lubricating film is coaxially charged and a material charging hole having a molding hole for forming a molding portion at the tip of the material in the charging direction is formed. In manufacturing equipment,
The hole diameter of the material injection hole is larger than the outer diameter of the material,
An apparatus for producing a long shaft, wherein the die is formed with an oil escape groove that is located on the molding hole side of the material input hole and has an oil escape hole communicating with the gap. In the manufacturing method of the elongate shaft of Claim 1 or 2,
A method of manufacturing a long shaft, wherein the expanded portion after extrusion is used as a guide surface to perform surface finishing by centerless processing.

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