JP6855327B2 - Rack bar manufacturing method and manufacturing equipment - Google Patents

Description

The present invention relates to a method and a manufacturing apparatus for a rack bar used in a rack and pinion type steering apparatus or the like of a vehicle.

As a rack bar used in a rack and pinion type steering device or the like, for example, a rack bar in which a plurality of teeth are formed by cutting on a solid shaft material is known, but it is lightweight due to the use of a hollow shaft material. A so-called hollow rack bar is also known.

The hollow rack bar is roughly manufactured as follows. First, a flat tooth-forming surface formed by crushing a part of the hollow shaft material is provided on the outer surface of the shaft material, and the tooth mold is pressed against the tooth-forming surface. Then, the core metal is inserted into the shaft material in a state where the tooth mold is pressed against the tooth forming surface. When the core metal is inserted into the shaft material, the material of the tooth-forming surface of the shaft material is squeezed by the core metal and bites into the tooth mold. Then, by repeating the insertion of the core metal with the core metal gradually becoming larger, a plurality of teeth formed by transferring the shape of the tooth mold are formed on the shaft material.

In the hollow rack bar manufactured as described above, the tooth width of the teeth formed at both ends of the tooth forming surface may be smaller than the tooth width of the teeth formed at the center of the tooth forming surface. Measures to suppress the decrease in the width of the teeth formed at both ends are also known. For example, in the method for manufacturing a hollow steering rack shaft described in Patent Document 1, flat portions arranged at the height of the tooth bottom are provided at both ends of the tooth forming surface, and the hollow rack bar described in Patent Document 2 is manufactured. In the method, the central portion in the axial direction of the portion of the shaft material where the tooth forming surface is provided is high-frequency induction heated, and the tooth forming surface is provided after heating.

Japanese Unexamined Patent Publication No. 2005-28924 Japanese Unexamined Patent Publication No. 2014-69220

In the method for manufacturing a hollow steering rack shaft described in Patent Document 1, teeth are not formed at both ends of the tooth forming surface, the effective length of the rack is shortened, and the entire length of the tooth forming surface is effectively used. There was room for improvement from the perspective of Further, the method for manufacturing a hollow rack bar described in Patent Document 2 requires a separate heating device for high-frequency induction heating of the outer surface of the shaft material, and there is room for improvement from the viewpoint of simplifying the manufacturing equipment.

The present invention has been made in view of the above circumstances, and is a method for manufacturing a rack bar made of a hollow shaft member, which can form teeth having a uniform tooth width over the entire length of the tooth forming surface. The purpose is to provide a manufacturing apparatus.

In the method for manufacturing a hollow rack bar according to one aspect of the present invention, the tooth mold is pressed against the flat tooth forming surface provided so as to extend in the axial direction on the outer surface of the hollow shaft material, and the tooth mold is pressed against the shaft material. A tooth forming step in which the material of the tooth forming surface is plastically flowed toward the tooth mold by reciprocating the inserted core metal over the entire length of the tooth forming surface, and after the tooth forming step, the above-mentioned With the tooth mold pressed against the tooth forming surface, the core metal inserted into the shaft material through the first opening end of the shaft material located on the first end side of the tooth forming surface is inserted into the first end. After the first tooth correction step of plastically flowing the material of the first end portion toward the tooth mold and the tooth formation step by reciprocating at the portion, the tooth mold is placed on the tooth formation surface. By reciprocating the core metal inserted into the shaft member through the second opening end of the shaft member located on the second end side of the tooth forming surface in the pressed state at the second end portion. A second tooth correction step is provided in which the material at the second end is plastically flowed toward the tooth mold.

Further, the apparatus for manufacturing a hollow rack bar according to one aspect of the present invention includes a tooth mold that is pressed against a flat tooth forming surface extending in the axial direction on the outer surface of the hollow shaft material, and the shaft material. A mold that holds the tooth, a core metal that is inserted into and removed from the shaft material, and a push rod that is separate from the core metal, and the shaft material that is located on the first end side in the axial direction of the tooth forming surface. It is inserted and removed from the shaft material through the first push rod inserted and removed from the shaft material through the first opening end of the tooth forming surface and the second opening end of the shaft material located on the second end side in the axial direction of the tooth forming surface. A second push rod, a first drive unit for driving the first push rod, and a second drive unit for driving the second push rod are provided, and the first drive unit and the second drive unit are the first. The push rod and the second push rod are alternately driven, the core metal inserted in the shaft member is reciprocated over the entire length of the tooth forming surface, and the push rod is inserted into the shaft member through the first opening end. The core metal is reciprocated at the first end portion, and the core metal inserted into the shaft member through the second opening end is reciprocated at the second end portion.

Further, the apparatus for manufacturing a hollow rack bar according to one aspect of the present invention includes a tooth mold that is pressed against a flat tooth forming surface extending in the axial direction on the outer surface of the hollow shaft material, and the shaft material. A mold for holding the tooth, a core metal to be inserted into and removed from the shaft material, and a first open end of the shaft material located on the first end side in the axial direction of the tooth forming surface. Through the first driving portion that drives the pushing rod portion of the core metal that is inserted into and removed from the shaft material, and the second opening end of the shaft material that is located on the second end side in the axial direction of the tooth forming surface. A second drive unit for driving the push rod portion of the core metal inserted into and removed from the shaft material is provided, and at least one of the first drive unit and the second drive unit is the core inserted into the shaft material. The core metal of gold is reciprocated over the entire length of the tooth forming surface, the first drive unit reciprocates the core metal at the first end portion, and the second drive unit reciprocates. The core metal is reciprocated at the second end portion.

According to the present invention, in a rack bar made of a hollow shaft member, teeth having a uniform tooth width over the entire length of the tooth forming surface can be formed.

It is a top view of an example of a rack bar for demonstrating the embodiment of this invention. It is sectional drawing of the rack bar of FIG. It is a schematic diagram of an example of the rack bar manufacturing apparatus used for manufacturing the rack bar shown in FIG. It is a schematic diagram of the main part of the rack bar manufacturing apparatus shown in FIG. It is a schematic diagram which shows an example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram which shows an example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram which shows an example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram which shows an example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram which shows an example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram of an example of the structure for preventing the rotation of a core metal. It is a schematic diagram of another example of the structure for preventing the rotation of a core metal. It is a schematic diagram which shows another example of the manufacturing method of the rack bar shown in FIG. It is a schematic diagram which shows the evaluation method of the tooth width of a rack tooth. It is a schematic diagram which shows the evaluation method of the tooth width of a rack tooth. It is a graph which shows the evaluation result of the tooth width of an experimental example. It is a graph which shows the evaluation result of the tooth width of an experimental example.

1 and 2 show an example of a rack bar for explaining an embodiment of the present invention.

The rack bar 10 is made of a metal material such as steel, and a flat tooth forming surface F extending in the axial direction is provided on a part of the outer surface of a cylindrical hollow shaft member 11 having both ends open, and the tooth forming is provided. A plurality of rack teeth 12 arranged in the axial direction are formed on the surface F.

The tooth forming surface F of the rack bar 10 is provided unevenly on one open end side of the shaft member 11. In the following, the opening end on the side where the distance to the tooth forming surface F is short is referred to as the first opening end 11A, the opening end on the side where the distance to the tooth forming surface F is long is referred to as the second opening end 11B, and the teeth are also referred to. The end of the forming surface F near the first opening end 11A is referred to as the first end, and the end close to the second opening end 11B is referred to as the second end.

In the illustrated example, the tooth width direction of the rack teeth 12 is orthogonal to the axial direction of the shaft member 11, and the pitch of the rack teeth 12 is constant, but the tooth width direction of the rack teeth 12 is the shaft member. It may be slanted with respect to the axial direction of 11, and the pitch of the rack teeth 12 is relatively narrow at the central portion of the tooth forming surface F, for example, and relatively wide at both ends of the tooth forming surface F. It may have changed to.

3 and 4 show an example of a rack bar manufacturing apparatus used for manufacturing the rack bar 10.

The rack bar manufacturing apparatus 20 includes a plurality of cores housed in the base 21, the mold 22, the first core metal holder 23a, the second core metal holder 23b, the first core metal holder 23a, and the second core metal holder 23b. 24, a first push rod 25a, a second push rod 25b, a first drive unit 26a, and a second drive unit 26b are provided. The first core metal holder 23a, the first push rod 25a, and the first drive unit 26a, and the second core metal holder 23b, the second push rod 25b, and the second drive unit 26b are arranged on opposite sides of the mold 22. Has been done.

The mold 22 includes an upper mold 27 and a lower mold 28. The upper mold 27 is molded and opened from above with respect to the lower mold 28 by a mold clamping mechanism (not shown), and the shaft member 11 is sandwiched by the upper mold 27 and the lower mold 28 from above and below. A tooth mold 29 is removably attached to the upper mold 27, and the tooth mold 29 has a molded surface formed in a tooth shape corresponding to a plurality of rack teeth 12 formed on the shaft member 11.

The first core metal holder 23a has a plurality of holding holes 30 penetrating the first core metal holder 23a in parallel with the axial direction of the shaft member 11 held by the mold 22, and each holding hole 30 has a core metal. 24 is housed. The sizes (outer diameters) of the plurality of cores 24 held in the first core holder 23a are different from each other. The first core metal holder 23a is rotationally driven by a holder drive unit (not shown). Each time the first core metal holder 23a is rotationally driven, one of the plurality of holding holes 30 is arranged on the axis of the shaft member 11 held by the mold 22.

The first push rod 25a is arranged on the axis of the shaft member 11 which sandwiches the first core metal holder 23a with the mold 22 and is held by the mold 22. When the first push rod 25a is driven by the first drive unit 26a, one of the plurality of holding holes 30 of the first push rod 25a and the first core metal holder 23a is arranged on the axis of the shaft member 11. The core metal 24 housed in the 30 is inserted into the shaft member 11 through the first opening end 11A of the shaft member 11.

Similarly, the second core metal holder 23b has a plurality of holding holes 30 penetrating the second core metal holder 23b in parallel with the axial direction of the shaft member 11 held by the mold 22, and each holding hole 30 has a plurality of holding holes 30. The core metal 24 is housed. The plurality of cores 24 held in the second core holder 23b are different in size (outer diameter) from each other. The second core metal holder 23b is rotationally driven by a holder drive unit (not shown), and one of the plurality of holding holes 30 is arranged on the axis of the shaft member 11 each time the second core metal holder 23b is rotationally driven. Will be done.

The second push rod 25b is arranged on the axis of the shaft member 11 held by the mold 22 with the second core metal holder 23b sandwiched between the second push rod 25b and the mold 22. When the second push rod 25b is driven by the second drive unit 26b, one of the plurality of holding holes 30 of the second push rod 25b and the second core metal holder 23b is arranged on the axis of the shaft member 11. The core metal 24 housed in the 30 is inserted into the shaft member 11 through the second opening end 11B of the shaft member 11.

A method of manufacturing the rack bar 10 using the rack bar manufacturing apparatus 20 configured as described above will be described below.

First, as shown in FIG. 5A, a part of the outer surface of the cylindrical hollow shaft member 11 is crushed inward by press working to be flattened, and flat teeth extending in the axial direction of the shaft member 11 The forming surface F is formed in advance on a part of the outer surface of the shaft member 11.

<Tooth formation step>
Next, as shown in FIG. 5B, the shaft member 11 is set in the mold 22 so that the tooth forming surface F is arranged so as to face the molding surface of the tooth mold 29 attached to the upper mold 27, and the shaft member 11 is set in the mold 22. 11 is sandwiched between the upper mold 27 and the lower mold 28 of the mold 22.

Then, the first push rod 25a is driven by the first drive unit 26a, and one of the plurality of core metal 24 housed in the first core metal holder 23a passes through the first opening end 11A of the shaft member 11 to form the shaft member 11. It is inserted inside. In the tooth forming step, the core metal 24 is transferred from the first end portion of the tooth forming surface F (the end portion of the shaft member 11 close to the first opening end 11A) to the second end portion of the tooth forming surface F (the second end portion of the shaft member 11). 2 It is inserted over the entire length of the tooth forming surface F over the opening end 11B).

Subsequently, as shown in FIG. 5C, the second push rod 25b is driven by the second drive unit 26b and is inserted into the shaft member 11 through the second opening end 11B of the shaft member 11. At this time, the second core metal holder 23b is arranged out of the orbit of the second push rod 25b, and the second push rod 25b is independently inserted into the shaft member 11.

The core metal 24 inserted to the second end of the tooth forming surface F is pushed back by the second push rod 25b, discharged from the shaft material 11 through the first opening end 11A of the shaft material 11, and is discharged from the shaft material 11 of the first core metal holder 23a. It is housed again in the holding hole 30. In the process in which the core metal 24 is reciprocated over the entire length of the tooth forming surface F in this way, the material of the tooth forming surface F of the shaft member 11 pressed against the forming surface of the tooth mold 29 is made of the core metal 24. It is squeezed and plastically flows toward the tooth mold 29.

The core metal 24 selected from the plurality of core metal 24 housed in the first core metal holder 23a and inserted into the shaft member 11 is sequentially replaced with a larger one, and the core metal over the entire length of the tooth forming surface F. By repeating the reciprocating movement of 24, the material of the tooth forming surface F of the shaft member 11 that plastically flows toward the tooth mold 29 gradually bites into the molding surface of the tooth mold 29, and the tooth shape formed on the molding surface is formed. It is transferred and a plurality of rack teeth 12 are formed on the tooth forming surface F.

In the plurality of rack teeth 12 formed on the tooth forming surface F of the shaft member 11 by the above tooth forming step, the tooth width of the rack teeth 12 formed on the first end portion and the second end portion of the tooth forming surface F is , It is smaller than the tooth width of the rack teeth 12 formed in the central portion excluding both ends of the tooth forming surface F, and the rack teeth formed on both ends of the tooth forming surface F by the tooth correction step described below. 12 is widened.

<First tooth correction step>
In the first tooth correction step, the rack teeth 12 formed at the first end of the tooth forming surface F of the shaft member 11 are widened.

As shown in FIG. 5D, the first push rod 25a is driven by the first drive unit 26a, and one of the plurality of core metal 24 housed in the first core metal holder 23a is the first opening end 11A of the shaft member 11. It is inserted into the shaft member 11 through the shaft member 11. At this time, the core metal 24 inserted into the shaft member 11 is larger than the core metal 24 used last in the tooth forming step. Then, in the first tooth correction step, the insertion of the core metal 24 is stopped at the first end portion of the tooth forming surface F.

Subsequently, the second push rod 25b is driven by the second drive unit 26b and is inserted into the shaft member 11 through the second opening end 11B of the shaft member 11. At this time, the second core metal holder 23b is arranged out of the orbit of the second push rod 25b, and the second push rod 25b is independently inserted into the shaft member 11.

The core metal 24 inserted into the first end portion of the tooth forming surface F is pushed back by the second push rod 25b, discharged from the shaft member 11 through the first opening end 11A of the shaft member 11, and is discharged from the shaft member 11 of the first core metal holder 23a. It is housed again in the holding hole 30. In the process of reciprocating the core metal 24 at the first end portion of the tooth forming surface F in this way, the first end portion of the tooth forming surface F of the shaft member 11 pressed against the forming surface of the tooth mold 29. The material is squeezed by the core metal 24 and plastically flows toward the tooth mold 29.

The core metal 24 selected from the plurality of core metal 24 housed in the first core metal holder 23a and inserted into the shaft member 11 is sequentially replaced with a larger one, and at the first end portion of the tooth forming surface F. By repeating the reciprocating movement of the core metal 24, the material at the first end of the tooth forming surface F of the shaft member 11 that plastically flows toward the tooth mold 29 further bites into the molding surface of the tooth mold 29 to form teeth. The rack teeth 12 formed at the first end of the surface F are widened.

<Second tooth correction step>
In the second tooth correction step, the rack teeth 12 formed on the second end portion of the tooth forming surface F of the shaft member 11 are widened.

As shown in FIG. 5E, the second push rod 25b is driven by the second drive unit 26b, and one of the plurality of core metal 24 housed in the second core metal holder 23b is the second opening end 11B of the shaft member 11. It is inserted into the shaft member 11 through the shaft member 11. At this time, the core metal 24 inserted into the shaft member 11 is larger than the core metal 24 used last in the tooth forming step. Then, in the second tooth correction step, the insertion of the core metal 24 is stopped at the second end portion of the tooth forming surface F.

Subsequently, the first push rod 25a is driven by the first drive unit 26a and is inserted into the shaft member 11 through the first opening end 11A of the shaft member 11. At this time, the first core metal holder 23a is arranged out of the orbit of the first push rod 25a, and the first push rod 25a is independently inserted into the shaft member 11.

The core metal 24 inserted into the second end of the tooth forming surface F is pushed back by the first push rod 25a, discharged from the shaft material 11 through the second opening end 11B of the shaft material 11, and is discharged from the shaft material 11 of the second core metal holder 23b. It is housed again in the holding hole 30. In the process of reciprocating the core metal 24 at the second end portion of the tooth forming surface F in this way, the second end portion of the tooth forming surface F of the shaft member 11 pressed against the forming surface of the tooth mold 29. The material is squeezed by the core metal 24 and plastically flows toward the tooth mold 29.

The core metal 24 selected from the plurality of core metal 24 housed in the second core metal holder 23b and inserted into the shaft member 11 is sequentially replaced with a larger one, and at the second end portion of the tooth forming surface F. By repeating the reciprocating movement of the core metal 24, the material at the second end of the tooth forming surface F of the shaft member 11 that plastically flows toward the tooth mold 29 further bites into the forming surface of the tooth mold 29 to form teeth. The rack teeth 12 formed at the second end of the surface F are widened.

Since the first tooth correction step and the second tooth correction step are carried out, the tooth width of the rack teeth 12 formed on the first end portion and the second end portion of the tooth forming surface F becomes the tooth forming surface F. It is equal to the tooth width of the rack teeth 12 formed in the central portion excluding both end portions of the above. The first tooth correction step and the second tooth correction step are carried out in order, but the first tooth correction step may be carried out first, or the second tooth correction step may be carried out first. May be good.

According to the above method for manufacturing a rack bar, in a rack bar 10 made of a hollow shaft member 11, rack teeth 12 having a uniform tooth width over the entire length of the tooth forming surface F can be formed.

Here, in the second tooth correction step described above, the core metal 24 is pushed into the shaft member 11 through the second opening end 11B by being pushed by the second push rod 25b. Since the tooth forming surface F is provided unevenly on the side of the first opening end 11A of the shaft member 11, the distance from the second opening end 11B to the tooth forming surface F is relatively long, and the core metal 24 is the second. It may rotate around the longitudinal axis of the core metal 24 from the opening end 11B to the tooth forming surface F. When the core metal 24 rotates, the contact between the material at the second end of the tooth forming surface F of the shaft member 11 and the core metal 24 may be biased.

In order to suppress the rotation of the core metal 24, preferably, as shown in FIG. 6, when the core metal 24 is inserted into the shaft member 11 in the second tooth correction step, the shaft is passed through the first opening end 11A. The first push rod 25a is inserted into the material 11, and the core metal 24 is sandwiched between the first push rod 25a and the second push rod 25b. As a result, it is possible to prevent the core metal 24 from rotating around the longitudinal axis, and it is possible to more reliably widen the rack teeth 12 formed at the second end portion of the tooth forming surface F.

Further, as shown in FIG. 7, the contact surfaces of the second push rod 25b and the core metal 24 are formed as uneven surfaces that can be fitted to each other, and the contact surfaces of the second push rod 25b and the core metal 24 are fitted to each other. By doing so, the rotation of the core metal 24 around the longitudinal axis may be prevented.

The rotation of the core metal 24 around the longitudinal axis may be blocked not only in the second tooth correction step but also in the first tooth correction step. That is, the core metal 24 inserted into the shaft member 11 through the first opening end 11A is sandwiched between the first push rod 25a and the second push rod 25b, and the contact surfaces of the first push rod 25a and the core metal 24, respectively. May be uneven surfaces that can be fitted to each other.

Up to this point, an example in which the rack teeth 12 are formed on the tooth forming surface F of the shaft member 11 by the core metal 24 formed separately from the first push rod 25a and the second push rod 25b has been described, but is shown in FIG. As described above, the rack teeth 12 may be formed on the tooth forming surface F of the shaft member 11 by the core metal 34 integrally provided with the push rod portion 35.

According to the core metal 34 integrally provided with the push rod portion 35, the core metal 34 inserted and removed through the first opening end 11A of the shaft member 11 can be reciprocated by the first drive portion 26a alone, and the shaft member 11 can be reciprocated. The core metal 34 inserted and removed through the second opening end 11B of the second drive unit 26b can be reciprocated by itself.

Therefore, in the first tooth correction step described above, the core metal 34 can be reciprocated at the first end portion of the tooth forming surface F by the first drive unit 26a alone, and in the second tooth correction step, the second drive The core metal 34 can be reciprocated at the second end portion of the tooth forming surface F by the portion 26b alone. As a result, the first tooth correction step and the second tooth correction step can be performed at the same time. Further, in the tooth forming step described above, the core metal 34 inserted to the second end portion of the tooth forming surface F through the first opening end 11A of the shaft member 11 is pulled out from the shaft member 11 by the first driving portion 26a, and the core metal 34 is pulled out from the shaft member 11. At the same time, the core metal 34 can be inserted by the second driving portion 26b through the second opening end 11B of the shaft member 11 to the first end portion of the tooth forming surface F, and similarly, the tooth can be inserted through the second opening end 11B of the shaft member 11. The core metal 34 inserted up to the first end of the forming surface F is pulled out from the shaft member 11 by the second driving portion 26b, and at the same time, the second opening end 11A of the shaft member 11 is passed through the second opening end 11A of the forming surface F. The core metal 34 can be inserted up to the end by the first drive unit 26a. As a result, the time required for manufacturing the rack bar 10 can be shortened.

Further, according to the core metal 34 integrally provided with the push rod portion 35, it is possible to prevent the core metal 34 from rotating around the longitudinal axis inside the shaft member 11.

An experimental example will be described below.

In the rack bar of Experimental Example 1, the tooth forming step is performed using 12 core metal 24, and the reciprocating movement of the core metal 24 over the entire length of the tooth forming surface F of the shaft member 11 is repeated to reach the tooth forming surface F. A plurality of rack teeth 12 were formed. With respect to the obtained rack bar, the tooth width of each rack tooth 12 was evaluated in two ways, the tooth tip tooth width and the pin contact length.

As shown in FIG. 9, the evaluation based on the tooth tip width measures the plane length L1 of the tip portion of the rack tooth 12. In the evaluation based on the pin contact length, as shown in FIG. 10, a pin gauge 40 is inserted between two adjacent rack teeth 12 and the length L2 of the contact portion between the rack teeth 12 and the pin gauge 40 is measured. is there. The evaluation based on the pin contact length measures the tooth width of the portion of the rack tooth 12 that is closer to the portion that meshes with the pinion, and can be said to be an evaluation based on the actual situation.

The evaluation results of the rack bar of Experimental Example 1 are shown in FIGS. 11 and 12. FIG. 11 shows the evaluation result based on the tooth tip tooth width, and FIG. 12 shows the evaluation result based on the pin contact length. From these evaluation results, the tooth width of the plurality of rack teeth 12 formed on the first end portion of the tooth forming surface F is smaller than the tooth width of the rack teeth 12 formed on the central portion of the tooth forming surface F. Similarly, it can be seen that the tooth width of the rack teeth 12 formed at the second end portion of the tooth forming surface F is also smaller than the tooth width of the rack teeth 12 formed at the central portion. For example, according to the evaluation result of the pin contact length shown in FIG. 12, the rack tooth 12 located on the protruding end side of the first end portion of the tooth forming surface F has a tooth No. As No. 1, the tooth No. 1 formed at the first end of the tooth forming surface F. 1-tooth No. The tooth width of the rack tooth 12 of 5 is the tooth No. It is smaller than the tooth width of the rack teeth 12 formed in the central portion of the tooth forming surface F after 6.

In the rack bar of Experimental Example 2, the tooth forming step is first performed on the same shaft member 11 as the rack bar of Experimental Example 1 using 12 core metal pieces 24, and the total length of the tooth forming surface F of the shaft member 11 is obtained. The reciprocating movement of the core metal 24 was repeated to form a plurality of rack teeth 12 on the tooth forming surface F. Next, the first tooth correction step is performed using seven cores larger than the core 24 used last in the tooth formation step, and the tooth No. 1 at the first end of the tooth formation surface F is subjected to the first tooth correction step. 1-tooth No. The reciprocating movement of the core metal 24 was repeated within the range of 5. With respect to the obtained rack bar, the tooth width of each rack tooth 12 was evaluated in two ways, the tooth tip tooth width and the pin contact length.

The evaluation results of the rack bar of Experimental Example 2 are shown together with FIGS. 11 and 12. From these evaluation results, the tooth No. 1-tooth No. The tooth width of the rack tooth 12 of 5 is widened, and the tooth No. It can be seen that the width is equivalent to the tooth width of the rack teeth 12 formed in the central portion of the tooth forming surface F after 6. By carrying out the first tooth correction step in this way, the tooth width of the rack teeth 12 formed on the first end portion of the tooth forming surface F is changed to the rack formed on the central portion of the tooth forming surface F. It can be equal to the tooth width of the tooth 12. Similarly, by carrying out the second tooth correction step, the tooth width of the rack tooth 12 formed on the second end portion of the tooth forming surface F is changed to the rack tooth formed on the central portion of the tooth forming surface F. It can be equal to 12 tooth widths.

10 Rack bar 11 Shaft material 11A 1st open end 11B 2nd open end 12 Rack teeth 20 Rack bar manufacturing equipment 21 Base 22 Mold 23a 1st core metal holder 23b 2nd core metal holder 24 Core metal 25a 1st push rod 25b 2nd push rod 26a 1st drive part 26b 2nd drive part 27 Upper mold 28 Lower mold 29 Tooth mold 30 Holding hole 34 Core metal 35 Push rod part 40 Pin gauge F Tooth forming surface L1 Tooth tip tooth width L2 Pin contact length

Claims (6)

With the tooth mold pressed against the flat tooth-forming surface extending in the axial direction on the outer surface of the hollow shaft material, the core metal inserted into the shaft material extends over the entire length of the tooth-forming surface. A tooth forming step in which the material of the tooth forming surface is plastically flowed toward the tooth mold by reciprocating the tooth forming surface.
After the tooth forming step, the tooth mold is pressed against the tooth forming surface and inserted into the shaft material through the first opening end of the shaft material located on the first end side of the tooth forming surface. A first tooth correction step in which the material of the first end portion is plastically flowed toward the tooth mold by reciprocating the core metal at the first end portion.
After the tooth forming step, the tooth mold is pressed against the tooth forming surface and inserted into the shaft material through the second opening end of the shaft material located on the second end side of the tooth forming surface. A second tooth correction step of plastically flowing the material of the second end portion toward the tooth mold by reciprocating the core metal at the second end portion.
A method of manufacturing a rack bar comprising. The method for manufacturing a rack bar according to claim 1.
The tooth forming surface is provided so as to be biased toward the first opening end side of the shaft member.
The core metal is alternately separated from the core metal by a first push rod that is inserted into and removed from the shaft material through the first opening end and a second push rod that is inserted and removed from the shaft material through the second opening end. It is moved back and forth by being pushed,
A method for manufacturing a rack bar that restrains the core metal and prevents the core metal from rotating around a longitudinal axis when the core metal is pushed by the second push rod at least in the second tooth correction step. The method for manufacturing a rack bar according to claim 2.
A method for manufacturing a rack bar that restrains the core metal by sandwiching the core metal between the first push rod and the second push rod. The method for manufacturing a rack bar according to claim 2 or 3.
A rack bar that restrains the core metal by forming the contact surfaces of the second push rod and the core metal into a concavo-convex surface that fits each other and fitting the contact surfaces of the second push rod and the core metal to each other. Manufacturing method. A mold that includes a tooth mold that is pressed against a flat tooth forming surface that extends in the axial direction on the outer surface of the hollow shaft material and holds the shaft material, and a mold that holds the shaft material.
The core metal to be inserted and removed from the shaft material and
A push rod that is separate from the core metal, and is inserted into and removed from the shaft member through the first opening end of the shaft member located on the first end side in the axial direction of the tooth forming surface, and A second push rod that is inserted into and removed from the shaft member through the second opening end of the shaft member located on the second end side in the axial direction of the tooth forming surface.
A first drive unit that drives the first push rod, a second drive unit that drives the second push rod, and
With
The first drive unit and the second drive unit alternately drive the first push rod and the second push rod, and reciprocate the core metal inserted in the shaft member over the entire length of the tooth forming surface. The core metal inserted into the shaft material through the first opening end is reciprocated at the first end portion, and the core metal inserted into the shaft material through the second opening end is moved to the second end. A rack bar manufacturing device that reciprocates at the end. A mold that includes a tooth mold that is pressed against a flat tooth forming surface that extends in the axial direction on the outer surface of the hollow shaft material and holds the shaft material, and a mold that holds the shaft material.
A core metal that has a push rod portion and is inserted and removed from the shaft material,
The first driving portion for driving the pushing rod portion of the core metal inserted into and removed from the shaft material through the first opening end of the shaft material located on the first end side in the axial direction of the tooth forming surface, and the tooth. A second drive unit that drives the push rod portion of the core metal that is inserted into and removed from the shaft member through the second opening end of the shaft member located on the second end portion side in the axial direction of the forming surface.
With
At least one of the first drive unit and the second drive unit reciprocates the core metal inserted into the shaft member over the entire length of the tooth forming surface, and the first drive unit is the first drive unit. The second drive unit is a rack bar manufacturing apparatus that reciprocates the core metal at the first end portion and reciprocates the core metal at the second end portion.

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