JP2002235727A - Hollow pipe with serration formed therein, and method and device for forming the serration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a reduced diameter part and a serration in a single process and easily and accurately form the serration in a hollow pipe having the serration in the inner surface of the reduced diameter part. SOLUTION: A die 7 for reducing the diameter of the end part of a pipe material 12 is disposed on the outside of the pipe material 12. A core metal 8a formed in an irregular shape for serration formation is disposed in the end part of the pipe material 12 on the side where the die 7 is disposed. A load is applied to the other end part of the pipe material 12 to push the pipe material 12 into the die 7 so as to move the core metal 8a in the same direction of the pressing direction for the pipe material 12. Thus the reduced diameter part and the serration can be formed at the end part of the pipe material 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow tube having a serration on an inner surface thereof, such as a steering shaft for an automobile, a serration forming method and a serration forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in a shock absorbing mechanism of an automobile steering shaft, a male serration is formed on an outer peripheral surface of an inner shaft constituting a steering shaft, and a female serration is formed on an inner peripheral surface of an outer shaft. When these serrations are meshed with each other to transmit a rotational torque at the serrations and receive an impact, they are relatively moved in the axial direction to absorb the impact.

[0003] As a method of forming the serrations on the inner surface side of the outer shaft as described above, before performing the serration forming, a tube material is previously reduced so that the diameter of the inner peripheral surface is smaller than the diameter of the serration pitch circle. Japanese Patent Application Laid-Open No. H11-247835 discloses a method of forming a serration by performing diameter processing, and then press-fitting a core metal having an uneven shape for serration forming from an end portion on a reduced diameter side.

[0004]

In the conventional serration forming method, it is necessary to reduce the diameter of the tube material before the serration is formed, and as a measure against buckling deformation of the tube material at the time of the serration forming. The core metal needs an introduction part for insertion into the tube material, a land part for stabilizing the shape and dimensions, and a relief part for reducing the molding load, and the core metal has a very complicated shape. Is required.

Accordingly, an object of the present invention is to provide a hollow tube having a serration on the inner surface, a method of forming the serration, and a device for forming the serration, which can solve the above-mentioned problems.

[0006]

According to a first aspect of the present invention, in order to solve the above-mentioned problem, a die for reducing the diameter of the tube material is disposed outside the tube material, and a die is provided inside the tube material. A core metal having an uneven shape for serration molding is arranged, an axial load is applied to the tube material to push the tube material into the die, and accordingly, the core metal is driven in the same direction as the pushing direction of the tube material. A hollow tube having serrations on an inner surface, wherein serrations are formed on an inner surface of a tube material by a molding method.

According to a second aspect of the present invention, a die for reducing the diameter of an end of the tube material is arranged outside the tube material, and a serration molding is provided in an end of the tube material on the side where the die is arranged. Arrange a metal core having an irregular shape, press the tube material into the die by applying a load to the other end of the tube material,
Accordingly, a hollow tube having serrations on the inner surface is characterized in that serrations are formed on the inner surface of the end portion of the tube material by a molding method in which the core metal is driven in the same direction as the pushing direction of the tube material.

A third invention according to claim 3 is the invention of the method for forming a serration of a hollow tube according to the first invention, wherein a die for reducing the diameter of the tube material is arranged outside the tube material. A core metal having an uneven shape for serration molding is arranged in a tube material, and an axial load is applied to the tube material to push the tube material into the die, and accordingly, the core is moved in the same direction as the pushing direction of the tube material. This is a method of forming serrations on the inner surface of a hollow tube, characterized in that gold is driven to form serrations on the inner surface of a tube material.

According to a fourth aspect of the present invention, there is provided a method of forming a serration of a hollow tube according to the second aspect of the present invention, wherein a die for reducing the diameter of an end of the tube material is provided outside the tube material. Arranged, a core metal having an uneven shape for serration molding is arranged in the end of the tube material on the side where the dice is arranged, and a tube material is pushed into the die by applying a load to the other end of the tube material, Along with this, a method for forming serrations on the inner surface of a hollow tube is characterized in that the core metal follows in the same direction as the pushing direction of the tube material to form serrations on the inner surface of the tube material.

A fifth aspect of the present invention relates to an apparatus for forming a serration according to the first and third aspects, wherein a die for reducing the diameter of the tube material and an axial load applied to the tube material are provided. In addition, it has a pushing means for pushing the tube material into the die, a core placed in the tube material, and a mechanism for taking out the product after the formation of the serration, and the core has an uneven surface for serration molding on its outer peripheral surface. An inner surface of the hollow tube, wherein the inner surface of the hollow tube has a shape, is supported by the die in a floating manner, and moves in the same direction as the tube material is pushed in as the tube material is pushed into the die. This is a device for forming serrations.

According to a sixth aspect of the present invention, there is provided an apparatus for forming serrations according to the second and fourth aspects, wherein a die for reducing the diameter of the tube material and a load applied to the other end of the tube material. A pushing means for pushing the tube material into the die by adding the core material, a core metal arranged in the end of the tube material on the side where the dice is arranged, and a knockout mechanism for pushing out a product after the formation of the serrations. Has an uneven surface for serration molding on its outer peripheral surface, is supported by the die in a floating manner, and moves in the same direction as the pushing direction of the tube material as the tube material is pushed into the die. An apparatus for forming serrations on the inner surface of a hollow tube.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described based on an embodiment shown in the drawings.

FIGS. 1 to 4 show a first embodiment.

An abutment 2 is erected on a base 1, and a cavity 3 is formed in the abutment 2.

A base plate 5 having a through hole 4 formed in the center is fixed on the support 2, and an annular die holder 6 is fixed on the base plate 5. A reduced-diameter die 7 is fixed to the die holder 6 and arranged in the die holder 6.

As shown in the enlarged view of FIG. 3, the reduced diameter die 7 is formed with a throttle hole 7a penetrating in the insertion direction of the tube material to be machined. The upper part on the insertion side is the enlarged diameter part 7b, and the lower part is the reduced diameter part 7c.
Is formed.

A shaft 8 is arranged on the axis of the throttle hole 7a of the reduced diameter die 7 so as to be able to move up and down. On the upper part of the shaft 8, a core formed with irregularities 8b necessary for serration forming on the outer periphery. Gold 8a is formed, and the lower portion is a columnar portion 8c without the above-mentioned uneven portion. The irregularities 8b
Has a concave-convex cross section in the circumferential direction of the shaft 8, and its concave and convex portions are parallel to the axial direction, and are formed over the entire axial direction of the cored bar 8a. Further, the lower end of the shaft 8 is provided with a shaft holder 9 provided in the support 2 so as to be movable up and down.
The shaft 8, that is, the core bar 8 a, moves up and down together with the shaft holder 9.

A receiving member 10 is provided on the shaft holder 9, and between the lower end surface of the receiving member 10 and the base 1.
An urging means 11 for urging the shaft holder 9 in the ascending direction is provided, and the shaft 8, that is, the core metal 8a is supported by floating. The urging means 11 uses a coil spring in the illustrated embodiment, but is not limited to this coil spring, and urges the shaft holder 9 upward such as a hydraulic cylinder or an elastic body such as urethane rubber. Anything should do.

A core bar 8a formed on the shaft 8
Moves in the axial direction into the drawing hole 7a of the diameter reducing die 7.
And the axial length of the metal core 8a.
L ₁Forms serrations on the tube material 12 to be processed
Length L_Two(See FIG. 4), and
The raised position of the cored bar 8a, that is, the shaft holder
9 in a state where the upper end of the base 9 is in contact with the stopper 13 of the base plate 5.
The position of the core metal 8a to be cut is within the reduced diameter die 7 and the reduced diameter die.
The end of the tube material 12 at the insertion side
(The upper end of chair 7)
Is set.

The inner diameter of the reduced diameter portion 7c of the reduced diameter die 7 is:
After serration molding, the inner surface of the pipe is set to have an appropriate area reduction ratio (cross-sectional area of pipe material−cross-sectional area of serration forming portion / cross-sectional area of pipe material).

Further, the urging means 11 controls the weight of the shaft 8 having the metal core
When the coil spring is used as in the embodiment, the initial length and the compression load are selected. The compression load is preferably set to the minimum necessary.

A thin cylindrical knockout pin 14, which is a mechanism for taking out a product (pipe) after molding, is fitted on the outer peripheral portion of the shaft 8 so as to be slidable in the axial direction. The lower part of the tube 12 (product) formed by the diameter die 7 is slidably penetrated through the shaft holder 9 and the receiving member 10 and partially protrudes below the shaft holder 9. The base 1 is provided with an elevating member 15 for pushing the lower end 14b of the knockout pin 14 upward. The knockout pin 14 and the elevating member 15 constitute a knockout mechanism. The component having the reduced diameter die 7 as described above is referred to as a reduced diameter die-side mold A.

A push pin 16 is arranged above the reduced-diameter die side mold A concentrically with the reduced-diameter die 7 so as to be able to move up and down. It has become. The pushing means 16 is constituted by the pushing pin 16 and its driving means.

Next, a method of forming serrations on the inner surface of the hollow tube according to the first embodiment will be described.

As shown in FIG. 1, the core 8a is
In a state where it is raised by the urging force of 1 and is located in the reduced diameter die 7 and its upper part protrudes above the reduced diameter die 7, the hollow tube material 12 made of metal is removed from the reduced diameter die 7 and the core metal. Insert and set between 8a. The pipe material 12
Has an upper side projecting upward from the upper end of the cored bar 8a.

Next, the push-down pin 16 is lowered to bring its lower end into contact with the upper end of the tube blank 12, and the push-down pin 16 is further lowered to apply an axial load (compressive force) to the tube blank 12. As shown in FIG. 2, the lower portion of the tube blank 12 is pushed between the reduced diameter portion 7c of the reduced diameter die 7 and the cored bar 8a. When the tube material 12 is pushed in this way, the outer shape of the tube material 12 is reduced in diameter by the diameter reducing die 7, and at the same time, the material inside the tube material 12 is moved in the direction of the central axis of the tube material 12, that is, the core metal 8a. It flows toward the unevenness 8b side, the unevenness surface of the core metal 8a is transferred to the inner surface of the tube material 12, and serration is formed.

At this time, the elongating direction (downward in FIG. 1) of the tube blank 12 due to the diameter reduction is opposite to the forming direction (upward in FIG. 1). The flow is promoted and serration can be formed with high accuracy.

Following the downward movement of the tube blank 12 while the serrations are being formed, the core bar 8a also moves in the same direction (downward) against the urging means 11, ie, the coil spring 11 is compressed. And move. Here, “following” means that the core metal 8 a is also moving in the reduced diameter die 7 when the tube material 12 is moving in the reduced diameter die 7.

As described above, since the core bar 8a moves following the tube blank 12, the frictional force generated between the inner peripheral surface of the tube blank 12 and the core bar 8a is reduced, and the shape of the core bar is simplified. , The life of the core metal can be improved, and the serration molding load can be reduced.

Further, since the axial forming length of the serration is determined by the moving amount (falling amount) of the tube blank 12, after the tube blank 12 is lowered by a predetermined amount by the pushing pin 16, the pushing pin 16 is stopped. Then, a reduced diameter portion having a predetermined length and serrations are formed on one end side of the tube blank 12 as shown in FIG.

At the time of forming the above-mentioned serration,
Due to the load applied to the upper end of the tube material 12, the shaft 8
The coil spring 11 serving as the urging means is compressed by the downward load acting on the shaft member and the elongation load of the material of the tube blank 12 generated by the diameter reduction and the serration forming, and as shown in FIG. Core 8a
Is lowered, the shaft holder 9 and the knockout pin 14 are also lowered by their own weight.

After the diameter reduction and the serration forming of the tube blank 12 are completed as described above, the push-in pin 16 is raised and retracted. Then, the lifting member 15 is moved upward to push the knockout pin 14 upward, and the upper end 14a of the knockout pin 14 pushes the product formed from the tube blank 12 upward from between the reduced diameter die 7 and the cored bar 8a. Take out. Thus, the shaft 8 having the core bar 8a, the receiving member 10, and the shaft holder 9 are raised and returned by the restoring force of the coil spring 11, which is the urging means. FIG. 4 shows the shape of the product 12A taken out as described above.
Shown in In this product 12A, 12a indicates a tube-shaped portion, 12b indicates a reduced diameter portion, and 12c indicates serrations.

In the first embodiment, the diameter reducing die 7 is used.
Although the mold A on the side is fixed and the push pin 16 is moved, the mold A on the reduced-diameter die side may be moved while the push pin 16 is fixed.

FIGS. 5 to 7 show a second embodiment.

In the second embodiment, as shown in FIG. 7, a reduced diameter portion 12b and a serration 12c similar to those of the first embodiment are formed at one end of a hollow tube product 12B, and at the other end. This is an example of forming the reduced diameter portion 12d or the enlarged diameter portion.

The structure of the second embodiment is different from that of the first embodiment in that the pressing pin 16 of the pressing means C provided above the diameter reducing die 7 is replaced with a contracting die 21 as shown in FIG.
And a knockout pin 22 are provided, and the other structure is the same as that of the first embodiment.

At the center of the reduced-diameter die 21, a diameter-reducing hole 21a having a lower end opening is formed concentrically with the reduced-diameter die 7. The inner diameter of the diameter reducing hole 21a is smaller than the outer diameter of the tube blank 12 by the diameter reduced, and
The lower end of “a” is open in a trumpet shape with a larger diameter than the tube material 12.

A knockout pin 22 is fixed in the diameter reducing hole 21a, and a tip 22a of the knockout pin 22 is reduced by an axial length of a reduced diameter portion 12d formed in the tube blank 12. It is located behind the diameter hole 21a.

The reduced diameter mold 21 and knockout pin 2
The reference numeral 2 is adapted to be moved up and down by a lifting drive means (not shown).

Since the other structure, that is, the structure of the die A on the reduced diameter side is the same as that of the first embodiment, the same parts as those described above are denoted by the same reference numerals and the description of the structure is omitted. I do.

The molding method according to the second embodiment will be described.

As shown in FIG. 5, the die A on the side of the reduced-diameter die 7
Contraction mold 21 and knockout pin 2
In the state where the tubes 2 are opposed to each other, the tube material 12 is inserted and set between the reduced diameter die 7 and the cored bar 8a as in the first embodiment.

Next, when the reduced-diameter pipe mold 21 is moved downward together with the knockout pin 22, the reduced-diameter hole 21 of the reduced-diameter mold 21 is formed on the upper side (the other side) of the pipe blank 12 as shown in FIG.
a, the reduced diameter portion 12d is formed, and then the tube material 12 is pushed downward by the knockout pin 22,
A reduced diameter portion 12b and a serration 12c similar to those in the first embodiment are formed on the lower side (one side) of the tube material 12 by the reduced diameter die 7 and the core bar 8a.

The above is the case where the molding load on the reduced diameter die 21 side is smaller than that of the reduced diameter die side mold A, and in the opposite case, the knockout of the reduced diameter die side mold A is performed. The pin 14 is configured so that the tube material 12 can be positioned in the axial direction.

After the diameter reduction and the serration forming of the tube blank 12 are completed as described above, the contraction die 21 is retracted upward, and the lifting member 15 is moved upward to push the knockout pin 14 upward. The product is taken out in the same manner as in the first embodiment. FIG. 7 shows the shape of the product 12B taken out. In this product 12B, 12a is a tube-shaped portion, 12b is a reduced diameter portion, 12c is a serration,
12d denotes a reduced diameter portion on the other side.

In the second embodiment, the other side of the tube blank 12 is reduced in diameter by the contraction mold 21. However, the other side of the tube blank 12 is replaced by the contraction mold 21. The diameter of the other side of the tube blank 12 may be expanded by using a diameter expanding die for expanding the diameter.

Further, in the second embodiment, the reduced-diameter die A is fixed and the reduced-diameter die 21 is moved. However, the reduced-diameter die 21 is fixed and the reduced-diameter die is moved. The side mold A may be moved.

FIGS. 8 to 10 show a third embodiment.

In the third embodiment, as shown in FIG. 10, a hollow tube having a reduced diameter portion 12b and a serration 12c similar to that of the first embodiment is formed on both sides of a tube material.

As shown in FIG. 8, the configuration of the third embodiment is such that two dies A having the same reduced diameter as described above are used, and the side where the tube material is inserted is spaced apart and opposed to be coaxial. A driving means (not shown) for disposing and driving the two reduced-diameter die-side dies A in the axial direction is provided.
A clamp 31 of the tube blank 12 is disposed in the middle of A. In the third embodiment, the knockout pin 14 and the lifting member 15 of the above embodiment are not provided.

The dies A, A on both sides of the reduced diameter die of the third embodiment.
Is the same as that of the first embodiment except for the knockout pin 14 and the elevating member 15 as described above. Therefore, the same parts as those described above are denoted by the same reference numerals and the description thereof is omitted.

Next, a molding method according to the third embodiment will be described.

First, the two dies A, shown in FIG.
A is separated at an interval longer than the axial length of the tube material 12 to be formed, and the intermediate portion of the tube material 12 is clamped in this state.
1 and hold the tube blank 12 in both reduced-diameter die-side dies A, A
Is arranged coaxially with the reduced diameter die 7.

Next, the two dies A, A on both sides of the reduced-diameter die are shown in FIG.
As shown in (2), these opposing intervals are moved in a direction in which they decrease. As a result, the same reduced diameter portions 12b and serrations 12c as described above are simultaneously formed on both sides of the tube blank 12 by the reduced diameter dies 7 and the cores 8a provided on both the reduced diameter die side dies A, A. This molding method is effective when the molding loads on both sides are equal.

Next, after the above-mentioned molding is completed, the two dies A, A with reduced diameters are moved and returned so that the distance between the opposite dies is longer than the axial length of the molded product. Then, the clamp 31 is released and the product is taken out. The shape of the product 12C taken out is shown in FIG. This product 1
In 2C, 12a is a tube-shaped portion, 12b is a reduced diameter portion,
12c shows serration.

In the third embodiment, the pipe blank 12
Reduced diameter portion 12b and serration 12 formed on both sides of
The shape of c may be a common shape on both sides, or may be different on both sides.

The present invention can be applied not only to a hollow tube used as an automobile steering shaft but also to a hollow tube other than an automobile steering shaft.

[0058]

As described above, according to the present invention, it is not necessary to perform a diameter reduction step of reducing the diameter of the tube material before forming the serration into the tube material as in the prior art.
In one process, the diameter of the tube material can be reduced and the serration can be formed, so that the forming can be simplified and the forming time can be shortened.

Further, since the elongation direction of the tube material due to the diameter reduction of the tube material is opposite to the forming direction, the flow of the material in the direction of the central axis of the tube material is promoted, and the serration can be formed with high precision. become.

Further, since the core is driven in the same direction as the pushing direction of the tube material, the frictional force generated between the inner peripheral portion of the tube material and the core can be reduced, and the shape of the core can be simplified. , The life of the cored bar can be improved, and the serration molding load can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention and showing a state before molding.

FIG. 2 is a longitudinal sectional view showing a molding state in the embodiment of FIG.

FIG. 3 is an enlarged vertical sectional view showing a reduced diameter die portion in FIG. 1;

FIG. 4 is a longitudinal sectional view showing a product formed according to the embodiment of FIG. 1;

FIG. 5 is a longitudinal sectional view showing a state before molding according to a second embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a molding state in the embodiment of FIG. 5;

FIG. 7 is a longitudinal sectional view showing a product formed according to the embodiment of FIG. 5;

FIG. 8 is a longitudinal sectional view showing a state before molding according to a third embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a molding state in the embodiment of FIG. 8;

FIG. 10 is a longitudinal sectional view showing a product formed according to the embodiment of FIG. 8;

[Explanation of symbols]

 7 Reducing die 8a Core 8b Unevenness 12 Tube material 14 Knockout pin 16 Push-in pin B Knockout mechanism C Push-in means

Claims (6)

[Claims] 1. A die for reducing the diameter of a tube material is disposed outside the tube material, a core metal having an uneven shape for serration molding is disposed in the tube material, and an axial load is applied to the tube material. The tube material is pushed into the die, and the serration is formed on the inner surface of the tube material, wherein the serration is formed on the inner surface of the tube material by a molding method in which the core metal is driven in the same direction as the pushing direction of the tube material. Having a hollow tube. 2. A die for reducing the diameter of an end of the tube material is arranged outside the tube material, and a core metal having an uneven shape for serration molding is arranged in an end of the tube material on a side where the die is arranged. Then, a load is applied to the other end of the tube material to push the tube material into the die, and accordingly, by a molding method in which the core metal is driven in the same direction as the pushing direction of the tube material, the inner surface of the end of the tube material is formed. A hollow tube having serrations on an inner surface, wherein serrations are formed. 3. A die for reducing the diameter of the tube material is arranged outside the tube material, a core metal having an uneven shape for serration molding is arranged in the tube material, and an axial load is applied to the tube material. Forming a serration on the inner surface of the hollow tube, characterized in that the tube material is pushed into the die, and accordingly, the core metal is driven in the same direction as the pushing direction of the tube material to form serrations on the inner surface of the tube material. how to. 4. A dice for reducing the diameter of an end of the tube material is disposed outside the tube material, and a core metal having an uneven shape for serration molding is disposed in an end of the tube material on a side where the die is disposed. Then, a load is applied to the other end of the tube material to push the tube material into the die, and accordingly, the core metal is driven in the same direction as the pushing direction of the tube material to form serrations on the inner surface of the tube material. A method of forming serrations on the inner surface of a hollow tube. 5. A die for reducing the diameter of a tube material, a pressing means for applying an axial load to the tube material to press the tube material into the die, a cored bar arranged in the tube material, and a serration after molding. It has a mechanism to take out the product, the core metal has an irregular shape for serration molding on its outer peripheral surface, is floating supported on the die, and as the tube material is pushed into the die, An apparatus for forming serrations on the inner surface of a hollow tube, wherein the serrations are moved in the same direction as the pushing direction. 6. A die for reducing the diameter of a tube material, pushing means for applying a load to the other end of the tube material to press the tube material into the die, and disposed in an end of the tube material on the side where the die is arranged. And a knockout mechanism for extruding the product after the formation of the serrations, wherein the core has an uneven surface for serration molding on its outer peripheral surface, is flow-supported with respect to the die, and is made of a tube material. An apparatus for forming serrations on the inner surface of a hollow tube, wherein the serrations are moved in the same direction as the direction in which the tube material is pushed in as the tube is pushed into a die.