JP4835097B2 - Steering device rack and manufacturing method thereof - Google Patents

Description

  The present invention relates to a steering device rack and a manufacturing method thereof, and more particularly to a steering device rack formed by a processing method using a mold and a manufacturing method thereof.

  In recent years, many variable racks (variable speed steering racks) having a complicated shape have been used as racks for steering devices. Such a variable rack has a complicated rack tooth shape and is difficult to process by cutting, and is often formed by plastic processing using a mold. As a method for manufacturing a rack by plastic working using a mold, there are manufacturing methods shown in Patent Documents 1 to 8.

  The rack manufacturing methods of Patent Document 1 and Patent Document 2 use a solid round bar rack material, and the excess wall removed at the time of rack tooth molding protrudes as a burr on the rack side, and this protruding burr is pressed or It is a rack manufacturing method that is deleted by machining. In the manufacturing methods of Patent Document 1 and Patent Document 2, an extra process for removing burrs is required, which increases the processing cost, and in order to discharge surplus as burrs to the side, As the pressure load increases, the material escapes to the burr side, so that the rack teeth are not sufficiently filled with the material.

  In the rack manufacturing method of Patent Document 3, a rack-shaped molded portion is previously processed into a thin shape by turning to a solid round bar rack material, and an escape absorbing portion that accommodates the surplus portion removed at the time of rack-tooth molding is provided. This is a rack manufacturing method in which burrs are not produced by forming in a multi-stage on the mold on the back side of the rack teeth. In the manufacturing method of Patent Document 3, since the shape of the mold is complicated and becomes a closed mold, the stress applied to the mold is increased, and the life of the mold is shortened. Rises. In addition, since the shape of the back side of the rack teeth becomes complicated in multiple stages, the shape of the rack guide (part 21 shown in FIG. 12 of Patent Document 4) for guiding the back side of the rack teeth becomes complicated. There was a problem that the steering device was expensive.

  Moreover, since the rack manufacturing method of the said patent document 1-patent document 3 uses a solid round bar rack raw material, in order to make it lightweight, especially parts other than a rack tooth molding part are solid and heavy. In addition, it becomes necessary to perform drilling with a drill or the like, and the processing cost for drilling increases. In addition, since the rack material needs to be heated in order to sufficiently fill the rack teeth with the material, there is a problem that the accuracy of forming the rack teeth decreases.

  Furthermore, the rack manufacturing methods of Patent Document 5 to Patent Document 8 are rack manufacturing methods in which a mandrel is press-fitted into an inner diameter hole of a hollow tubular rack material to form a rack tooth profile. In the manufacturing methods of Patent Document 5 to Patent Document 8, since a large processing force is required for ironing by a mandrel, it is necessary to perform processing while exchanging a plurality of mandrels whose dimensions are changed little by little, and the processing time is long. In addition, since a dedicated processing machine is required, the manufacturing cost increases. Moreover, since the thickness of the bottom of the rack tooth is thin, there is a problem that the strength of the rack tooth is lowered.

JP-A-10-58081 Japanese Patent Laid-Open No. 2001-79639 Japanese Patent No. 3442298 JP 2004-34829 A Japanese Examined Patent Publication No. 3-5892 Japanese Patent No. 2928427 US Pat. No. 6,575,009 JP 2002-178095 A

  The present invention provides a rack for a steering device and a manufacturing method thereof, in which the rack is lightweight, the mold shape is simple, the life is long, the filling degree of the material into the tooth profile is improved, and the rigidity of the entire rack tooth is improved. The task is to do.

The above problem is solved by the following means. That is, the first invention is a hollow cylindrical first rack material having an inner diameter hole, and the first rack material inserted into the inner diameter hole of the first rack material and forming the rack teeth. A rack of the first rack material is used by using a solid second rack material having a cross-sectional shape capable of forming a gap between the rack tooth forming side of the inner diameter hole and the side orthogonal to the rack tooth forming side. The outer periphery excluding the tooth forming part is constrained by a die, a punch having a rack tooth profile is pressed against the rack tooth forming part on the outer periphery of the first rack material, and the inner diameter hole of the first rack material is changed to the first hole The rack material is made to abut against the outer periphery of the second rack material on the side facing the rack tooth forming side of the rack material, and the punch is pushed in, and the material material excluded during the rack tooth forming by the punch is used as the first rack material. Outside of the inner hole and the second rack material A first rack material by accommodating to flow into the space between the performed intermediate forming step of forming the rack teeth of the schematic with to integrate second rack materials, during the intermediate molding step is completed, the There are still gaps between the side of the inner diameter hole of the first rack material orthogonal to the rack tooth forming shape side and the outer periphery of the second rack material, and both sides of the outer peripheral surface of the side orthogonal to the rack tooth forming shape side. The width between them is formed narrower than the width between both sides of the outer surface of the desired rack tooth profile, and then the die having the desired rack tooth profile and the die having the desired outer peripheral shape on the side facing the rack tooth molding side. Sizing the desired rack teeth while widening the width of the outer circumference on the side perpendicular to the rack tooth forming shape side by sandwiching and pressing the first rack material after the intermediate forming step between the child that is responsible for the molding process It is a manufacturing method of a rack for a steering apparatus according to claim.

A second invention is a method for manufacturing a steering device rack according to the first invention, wherein the second rack material is cylindrical.

Third invention is a method of manufacturing a steering apparatus for a rack according to the first aspect of the invention, the axial length of the second rack material, at least the rack teeth forming the length and the same length of the first rack Material Or a method of manufacturing a steering device rack characterized in that the rack is slightly longer.

Fourth invention is a method of manufacturing a steering apparatus for a rack according to the first aspect of the invention, the above second rack material, the outer periphery of the side facing the rack teeth forming side of the first rack material, The manufacturing method of the rack for a steering device is characterized in that the same number of concaves and convexes as the rack tooth profile are formed.

Fifth invention is a method of manufacturing a steering apparatus for a rack according to the third aspect of the invention, the above second rack material, the outer periphery of the side facing the rack teeth forming side of the first rack material, The manufacturing method of the rack for a steering device is characterized in that the same number of concaves and convexes as the rack tooth profile are formed.

A sixth invention is a steering device rack manufactured by the method for manufacturing a steering device rack according to any one of the first to fifth inventions.

In the steering device rack manufacturing method and the steering device rack manufactured by the manufacturing method of the present invention, a tubular first rack material having an inner diameter hole and an inner diameter hole of the first rack material are inserted, At the time of rack tooth molding, a second rack material having a cross-sectional shape capable of forming a gap between the inner diameter hole of the first rack material and the side orthogonal to the rack tooth molding side is used.

  Therefore, the material material excluded at the time of forming the rack teeth flows and is accommodated in the space between the inner diameter hole of the first rack material and the outer periphery of the second rack material, and a gap remains in the inner diameter hole. The mold does not become hermetically sealed, and the molding load is small, so that the mold life is extended. Further, since the molding load is small, it is possible to perform the molding in the cold, and the molding accuracy of the rack teeth is improved.

  In addition, since the inner diameter hole of the first rack material abuts on the second rack material, and the reaction material is effectively used for forming the rack teeth of the first rack material, The filling degree is improved. Furthermore, since the second rack material bites into the inner diameter hole of the first rack material and the first rack material and the second rack material are integrated, the rigidity of the entire formed rack tooth is improved.

  Further, since the material material excluded at the time of forming the rack teeth flows and is accommodated in the inner diameter hole of the rack material, burrs are not generated in the formed rack, and the number of processing steps for removing the burrs is reduced. In addition, since the shape of the mold is simple and molding can be performed with a general-purpose press, the mold production cost and molding equipment cost are reduced, and a mandrel is not used, so that the processing time is short.

In the steering device rack manufacturing method and the steering device rack manufactured by the manufacturing method according to the present invention, the axial length of the second rack material is the same as the rack tooth forming length of the first rack material. Length. Therefore, parts other than the rack tooth molding part are reduced in weight, and the hole processing for making it lightweight becomes unnecessary.

Further, the second rack material has the same number of concavities and convexities as the rack tooth profile on the outer periphery of the first rack material on the side facing the rack tooth forming side. Therefore, since a gap remains between the concave and convex portions of the second rack material and the inner diameter hole of the first rack material, the molding load can be further reduced.

  In addition, since the concave and convex portions of the second rack material serve to cause the material material to flow toward the rack tooth forming side of the first rack material, the material material flows to the rack teeth more effectively. The filling degree of the tooth profile is improved.

  In the steering device rack manufacturing method and the steering device rack manufactured by the manufacturing method according to the present invention, the width between the outer peripheral sides on the side orthogonal to the rack tooth forming side is set to a desired rack tooth shape in the intermediate forming step. It is formed narrower than the width between the outer peripheral sides, and is formed into a predetermined width in the sizing molding process.

  Therefore, it is easy to put the rack material into the sizing molding process, and even if the die used in the sizing molding process is a pair of upper and lower simple dies, burrs protrude from the outer periphery of the rack material. Therefore, the number of processing steps for removing burrs is reduced.

  Hereinafter, the first embodiment, the second embodiment, and another embodiment of the second rack material according to the present invention will be described with reference to the drawings.

  1 (1A) and (1B) are explanatory views showing a tubular first rack material according to the first embodiment of the present invention, and FIG. 1 (1A) is a cross-sectional view taken along line AA in FIG. 1 (1B). FIG. 1 (1B) is a longitudinal sectional view cut along the axis of the first rack material. FIGS. 1 (2A) and (2B) show the state in which a solid second rack material is inserted into the inner diameter hole of the first rack material shown in FIGS. 1 (1A) and (1B). FIG. 1 (2A) is a cross-sectional view taken along the line BB of FIG. 1 (2B).

  FIG. 2 is a process diagram showing a method of manufacturing a rack according to the first embodiment of the present invention, and FIGS. 2 (1A) and 2 (1B) show a first rack as a mold in an intermediate molding process for forming a rough rack tooth. It is explanatory drawing which shows the state which attached the raw material, Comprising: FIG. 2 (1A) is CC sectional drawing of FIG. 2 (1B). 2 (2A) and (2B) are explanatory views showing a state in the middle of the intermediate forming step, and FIG. 2 (2A) is a cross-sectional view taken along the line DD in FIG. 2 (2B).

  3 (1A) and (1B) are explanatory views showing a state at the end of molding in the intermediate molding step, and FIG. 3 (1A) is a cross-sectional view taken along line EE of FIG. 3 (1B). 3 (2A) and (2B) are process diagrams showing a post-process of FIGS. 3 (1A) and (1B), and are explanatory views showing a sizing molding process for molding a desired rack tooth. (2A) is an FF cross-sectional view of FIG. 3 (2B).

  As shown in FIGS. 1 (1A) and (1B), the tubular first rack material 1 of Example 1 is formed in a hollow cylindrical shape in which the outer periphery 11 and the inner diameter hole 12 have a circular cross section. As the shape of the first rack material 1, in the first embodiment, both the outer periphery 11 and the inner diameter hole 12 are circular. However, the shape of the first rack material 1 is not limited to a circular shape and may be a tube having an arbitrary cross-sectional shape such as a rectangle or a polygon. That's fine.

  As shown in FIGS. 1 (2A) and (2B), a material obtained by inserting a solid second rack material 2 into an inner diameter hole 12 of a tubular first rack material 1 is used as a rack forming material. use. In the first embodiment, the second rack material 2 is formed in a solid cylindrical shape.

* Intermediate forming step As shown in FIGS. 2 (1A) and (1B), a material for rack molding in which the second rack material 2 is inserted into the first rack material 1 is used as shown in FIGS. It is sandwiched between the die 32. The lower die 31 is formed with a pressing surface (constraint surface) 311 having a polygonal cross-sectional shape that is slightly narrower than the outer periphery 11 of the first rack material 1.

  A guide hole 321 for guiding the punch 41 in the vertical direction is formed in the upper die 32, and a rough rack tooth profile 42 is formed on the lower surface of the punch 41 over substantially the entire length in the left-right direction in FIG. Is formed. In this intermediate forming step, the rack tooth profile 42 is pressed against the rack tooth forming portion of the outer periphery 11 of the first rack material 1 to form an approximate rack tooth (roughly processed rack tooth).

  The axial length L1 of the second rack material 2 is formed slightly longer than the axial length L2 of the rack tooth profile 42 of the punch 41 (that is, the rack tooth forming length formed on the first rack material 1) L2. Has been. The length L1 in the axial direction of the second rack material 2 is desirably at least the same as the length L2 in the axial direction of the rack tooth profile 42 of the punch 41. And the 2nd rack raw material 2 is arrange | positioned in the internal diameter hole 12 of the 1st rack raw material 1 so that the rack tooth shaping | molding range shape | molded in the 1st rack raw material 1 may be covered.

  On the upper die 32, a semicircular pressing surface (restraining surface) 322 having the same cross-sectional shape as the outer periphery 11 of the first rack material 1 is formed in a portion other than the guide hole 321. Four knockouts 33 are fitted in the lower die 31 so as to be slidable in the vertical direction, and an upward biasing force is always applied by a spring (not shown).

  The knockout 33 supports the first rack material 1 from below by the upward biasing force when the punch 41 is pressed against the first rack material 1 to form the approximate rack teeth into the first rack material 1. To do. Further, when the intermediate forming process is completed and the punch 41 is raised, the knockout 33 pushes the first rack material 1 upward by the biasing force of a spring (not shown), and the rack tooth forming portion of the first rack material 1 is pushed. It is forcibly separated from the lower die 31.

  As shown in FIGS. 2 (2 A) and (2 B), when the punch 41 is pushed downward along the guide hole 321, the outer periphery 11 of the first rack material 1 is pushed downward by the rack tooth profile 42 of the punch 41. By this pushing, the rack teeth 13 start to be formed on the punch 41 side of the outer periphery 11 of the first rack material 1, and the inner diameter hole 12 of the first rack material 1 becomes the upper surface (first surface) of the second rack material 2. The surface of the rack material 1 facing the rack tooth forming side).

  In the state in the middle of the intermediate forming step in FIGS. 2 (2A) and (2B), since the thin portion of the hollow first rack material 1 is only plastically deformed, the molding load is small unlike the solid material. That's it. In addition, since gaps 51 and 51 exist between the side perpendicular to the rack tooth forming side of the inner diameter hole 12 of the first rack material 1 and the outer periphery 22 of the second rack material 2, the mold is Accordingly, the mold is not sealed, and therefore the molding load is small, and the life of the mold is prolonged.

  As shown in FIGS. 3 (1 A) and (1 B), when the punch 41 is pushed further down along the guide hole 321, the inner diameter hole 12 of the first rack material 1 becomes the upper surface 21 of the second rack material 2. The plastic material is bitten into the upper surface 21 while being plastically deformed, and the material material flows upward due to the reaction force and is effectively used for forming the rack teeth 13 of the first rack material 1. improves.

  Further, as shown in FIGS. 3 (1A) and (1B), even at the end of the rack tooth forming in the intermediate forming step, the side orthogonal to the rack tooth forming side of the inner diameter hole 12 of the first rack material 1, Since the gaps 52 and 52 remain between the outer circumferences 22 of the two rack materials 2, the mold is not hermetically sealed. Therefore, the molding load is small, and the life of the mold is extended.

  Further, since the molding load is small, it is possible to perform the molding in the cold, and the molding accuracy of the rack teeth is improved. Further, since the upper surface 21 of the second rack material 2 bites into the inner diameter hole 12 of the first rack material 1 and the first rack material 1 and the second rack material 2 are integrated, the formed rack teeth Overall rigidity is improved.

  That is, the raw material (excess) that has been removed when the rack teeth 13 are formed flows and is accommodated in the space between the inner diameter hole 12 of the first rack raw material 1 and the outer periphery 22 of the second rack raw material 2. Is done. 3 (1A) and (1B), the clearance between the inner diameter hole 12 of the first rack material 1 and the upper surface 21 of the second rack material 2 is B, and the rack tooth profile 42 of the punch 41 is used. When the indentation dimension of the tooth bottom with respect to the first rack material 1 is A, the dimension relationship is B ≧ 0.7A.

  Thereby, a sufficient space between the inner diameter hole 12 of the first rack material 1 and the outer periphery 22 of the second rack material 2 can be secured, and the rack teeth 13 can be molded with a small molding load. Yes.

* Sizing Molding Process The first rack material 1 after the intermediate molding process is carried into a sizing molding mold shown in FIGS. 3 (2A) and (2B) and formed on the lower surface of the upper die 61. The outer circumference of the first rack material 1 is pressed between a semicircular pressing surface (restraining surface) 611 and a pressing surface 621 having a desired rack tooth shape formed on the upper surface of the lower die 62. Thus, desired rack teeth (finished rack teeth) are formed while increasing the width of the outer periphery of the first rack material 1 on the side orthogonal to the rack tooth forming side.

  By the intermediate forming step, the width on the outer peripheral side on the side orthogonal to the rack tooth forming side is made narrower than the width between the outer peripheral both sides of the desired rack tooth profile. Therefore, it is easy to put the first rack material 1 into the sizing molding process. Further, even if the upper die 61 and the lower die 62 used in the sizing molding process are a pair of simple upper and lower dies, burrs do not protrude from the outer periphery of the first rack material 1. The processing man-hours for removing burrs are reduced.

  In the first embodiment, the raw material (remaining wall) removed during the formation of the rack teeth 13 is all in the space between the inner diameter hole 12 of the first rack material 1 and the outer periphery 22 of the second rack material 2. Since it is accommodated, burrs are not generated in the molded rack, and the number of processing steps for removing burrs is reduced. Moreover, since a tubular rack material is used, parts other than the rack tooth molding part are also reduced in weight. Furthermore, since the shape on the back side of the rack teeth is a simple shape, the shape of the rack guide for guiding the back side of the rack teeth is simplified.

  In addition, since the shape of the mold is simple and molding can be performed with a general-purpose press, the mold production cost and molding equipment cost are reduced, and a mandrel is not used, so that the processing time is short. Moreover, since no mandrel is used, the thickness of the bottom of the rack tooth is sufficiently secured, and the strength of the rack tooth is improved.

  Next, a second embodiment of the present invention will be described. 4 (1A) and (1B) are explanatory views showing a tubular first rack material according to the second embodiment of the present invention, and FIG. 4 (1A) is a sectional view taken along the line GG of FIG. 4 (1B). is there. 4 (2A) and (2B), a solid second rack material having irregularities is inserted into the inner diameter hole of the tubular first rack material shown in FIGS. 4 (1A) and (1B). It is explanatory drawing of Example 2 of this invention which shows a state, FIG. 4 (2A) is HH sectional drawing of FIG. 4 (2B).

  FIG. 5 is a process diagram showing a method of manufacturing a rack according to the second embodiment of the present invention. FIGS. 5 (1A) and 5 (1B) show a tubular first mold in an intermediate molding process for forming an approximate rack tooth. It is explanatory drawing which shows the state which attached the rack raw material, Comprising: FIG. 5 (1A) is JJ sectional drawing of FIG. 5 (1B). FIGS. 5 (2A) and (2B) are explanatory views showing a state in the middle of the intermediate forming step, and FIG. 5 (2A) is a sectional view taken along the line KK of FIG. 5 (2B).

  6 (1A) and (1B) are explanatory views showing a state at the end of molding in the intermediate molding step, and FIG. 6 (1A) is an LL cross-sectional view of FIG. 6 (1B). FIGS. 6 (2A) and (2B) are process diagrams showing a post-process of FIGS. 6 (1A) and (1B), and are explanatory diagrams showing a sizing forming process for forming a desired rack tooth. 2A) is a cross-sectional view taken along line MM in FIG. 6 (2B). In the following description, only structural parts different from the above-described embodiment will be described, and redundant description will be omitted.

  In the second embodiment, by forming irregularities on the upper surface 21 of the second rack material 2, a gap is formed between the inner diameter hole 12 of the first rack material 1 and the upper surface 21 of the second rack material 2 at the time of molding. As a result, the forming load is further reduced, and the convex shape of the upper surface 21 allows the material material to be used more efficiently for forming the rack teeth 13 of the first rack material 1. This is an example in which the filling degree of the raw material is improved.

  As shown in FIGS. 4 (1A) and (1B), the tubular first rack material 1 of the second embodiment is a hollow cylindrical shape having a circular cross section of the outer periphery 11 and the inner diameter hole 12, and the first rack material 1 of the first embodiment. The same shape as the rack material 1 of FIG.

  As shown in FIGS. 4 (2A) and (2B), the second rack material 2 inserted into the inner diameter hole 12 of the tubular first rack material 1 has a solid cylindrical shape. Further, the rack teeth 13 (rack tooth profile of the punch 41) formed on the first rack material 1 are formed on the upper surface 21 of the second rack material 2 (the surface facing the rack tooth forming side of the first rack material 1) 21. 42) The same number of projections and depressions 23 are formed as the pitch.

* Intermediate forming step As shown in FIGS. 5 (1A) and (1B), the shapes of the lower die 31, the upper die 32, the punch 41, and the knockout 33 used in the intermediate forming step are the same as those in the first embodiment. It is. The axial length L1 of the second rack material 2 is formed slightly longer than the axial length L2 of the rack tooth profile 42 of the punch 41 (that is, the rack tooth forming length formed on the first rack material 1) L2. Has been.

  And the 2nd rack raw material 2 is arrange | positioned in the internal diameter hole 12 of the 1st rack raw material 1 so that the rack tooth shaping | molding range shape | molded in the 1st rack raw material 1 may be covered. In addition, the inner diameter hole of the first rack material 1 so that the position of the concave portion of the concave and convex portions 23 on the upper surface 21 of the second rack material 2 coincides with the position of the convex portion of the tooth profile of the rack tooth profile 42 of the punch 41. The second rack material 2 is arranged in the 12.

  In this state, as shown in FIGS. 5 (2A) and (2B), when the punch 41 is pushed downward along the guide hole 321, the outer periphery 11 of the first rack material 1 is lowered by the rack tooth profile 42 of the punch 41. Is pushed into. By this pushing, rack teeth 13 start to be formed on the punch 41 side of the outer periphery 11 of the first rack material 1, and the inner diameter holes 12 of the first rack material 1 are formed on the upper surface (first surface) of the second rack material 2. The surface of the rack material 1 facing the rack tooth forming side) 21.

  5 (2A) and (2B), in the middle of the molding process, only the thin portion of the hollow first rack material 1 is plastically deformed. Therefore, unlike the solid material, the molding load is small. That's it. In addition, since gaps 51 and 51 exist between the side perpendicular to the rack tooth forming side of the inner diameter hole 12 of the first rack material 1 and the outer periphery 22 of the second rack material 2, the mold is Accordingly, the mold is not sealed, and therefore the molding load is small, and the life of the mold is prolonged.

  Furthermore, in the second embodiment, since a gap 24 exists between the concave portion of the unevenness 23 on the upper surface 21 of the second rack material 2 and the inner diameter hole 12 of the first rack material 1, the second rack material 2 is further more than in the first embodiment. Small molding load is sufficient.

  As shown in FIGS. 6 (1 A) and (1 B), when the punch 41 is pushed further down along the guide hole 321, the inner periphery 12 of the first rack material 1 becomes the upper surface 21 of the second rack material 2. Therefore, the degree of filling of the tooth profile is further improved as compared with the first embodiment.

  As shown in FIGS. 6 (1A) and 6 (1B), as in Example 1, the rack tooth forming side of the inner diameter hole 12 of the first rack material 1 is also at the end of rack tooth forming in the intermediate forming step. Since the gaps 52 and 52 remain between the side orthogonal to the outer periphery 22 of the second rack material 2, the mold is not sealed, and therefore the molding load can be reduced. Mold life is extended.

  Further, since the inner diameter hole 12 of the first rack material 1 bites into the irregularities 23 on the upper surface 21 of the second rack material 2 and the first rack material 1 and the second rack material 2 are integrated, molding is performed. The rigidity of the entire rack tooth is improved.

* Sizing molding process The first rack material 1 after the intermediate molding process is carried into a sizing molding mold shown in FIGS. 6 (2A) and 6 (2B) and formed on the lower surface of the upper die 61. The outer circumference of the first rack material 1 is pressed between a semicircular pressing surface (restraining surface) 611 and a pressing surface 621 having a desired rack tooth shape formed on the upper surface of the lower die 62. Thus, desired rack teeth (finished rack teeth) are formed while increasing the width of the outer periphery of the first rack material 1 on the side orthogonal to the rack tooth forming side.

  Next, a third embodiment of the present invention will be described. 7 (2A) and (2B) are explanatory views of the third embodiment showing a modification of the second rack material 2 inserted into the inner diameter hole 12 of the tubular first rack material 1. FIG. In the following description, only structural parts different from those of the second embodiment will be described, and redundant description will be omitted.

  In the second embodiment, the shape of the second rack material 2 is a solid cylindrical shape as shown in FIGS. 7A and 7B, and the first rack material 2 has the first rack material 2 on the upper surface 21. Although the same number of unevennesses 23 of the same pitch as the rack teeth 13 formed on the rack material 1 are formed, the shape of the second rack material 2 is not limited to a cylindrical shape.

  That is, in Example 3 shown in FIGS. 7 (2A) and (2B), the second rack material 2 is flattened over the entire length on both sides of the outer periphery of the first rack material 1 on the side orthogonal to the rack tooth forming side. Surfaces 25 and 25 are formed, and on the upper surface 21 of the second rack material 2, the same number of asperities 23 with the same number of rack teeth 13 formed on the first rack material 1 are formed. The unevenness 23 may not be present.

  Moreover, in Example 4 shown in FIGS. 7 (3A) and (3B), the second rack material 2 is flattened over the entire length on both sides of the outer periphery of the first rack material 1 on the side orthogonal to the rack tooth forming side. The surfaces 25 and 25 are formed, and the upper surface 21 of the second rack material 2 is also formed as a flat surface. Further, the same number of unevennesses 23 of the same pitch as the rack teeth 13 formed on the first rack material 1 are formed on the upper surface 21 formed flat. The unevenness 23 may not be present.

  In the first to fourth embodiments, the material of the second rack material 2 may be the same as or different from the material of the first rack material 1. Furthermore, in the said Example 1-Example 4, although the 2nd rack raw material 2 is solid, you may make it hollow.

(1A), (1B) is explanatory drawing which shows the tubular 1st rack raw material of Example 1 of this invention, (1A) is AA sectional drawing of (1B). (2A), (2B) is a first embodiment of the present invention showing a state where a solid second rack material is inserted into the inner diameter hole of the first rack material shown in (1A), (1B). (2A) is BB sectional drawing of (2B). It is process drawing which shows the manufacturing method of the rack of Example 1 of this invention, (1A) and (1B) attached the tubular 1st rack raw material to the metal mold | die of the intermediate forming process which shape | molds a rough rack tooth. It is explanatory drawing which shows a state, Comprising: (1A) is CC sectional drawing of (1B). (2A), (2B) is explanatory drawing which shows the state in the middle of the shaping | molding of an intermediate shaping | molding process, (2A) is DD sectional drawing of (2B). (1A), (1B) is explanatory drawing which shows the state at the time of completion | finish of shaping | molding of an intermediate shaping | molding process, (1A) is EE sectional drawing of (1B). (2A) and (2B) are process diagrams showing a subsequent process of (1A) and (1B), and are explanatory diagrams showing a sizing molding process for molding a desired rack tooth, and (2A) is (2B) It is FF sectional drawing of. (1A), (1B) is explanatory drawing which shows the tubular 1st rack raw material of Example 2 of this invention, (1A) is GG sectional drawing of (1B). (2A) and (2B) are books showing a state in which a solid second rack material having irregularities is inserted into the inner diameter hole of the tubular first rack material shown in (1A) and (1B). It is explanatory drawing of Example 2 of invention, (2A) is HH sectional drawing of (2B). It is process drawing which shows the manufacturing method of the rack of Example 2 of this invention, (1A) and (1B) attached the tubular 1st rack raw material to the metal mold | die of the intermediate forming process which shape | molds a rough rack tooth. It is explanatory drawing which shows a state, Comprising: (1A) is JJ sectional drawing of (1B). (2A), (2B) is explanatory drawing which shows the state in the middle of the shaping | molding of an intermediate shaping | molding process, (2A) is KK sectional drawing of (2B). (1A), (1B) is explanatory drawing which shows the state at the time of completion | finish of shaping | molding of an intermediate shaping | molding process, (1A) is LL sectional drawing of (1B). (2A) and (2B) are process diagrams showing a subsequent process of (1A) and (1B), and are explanatory diagrams showing a sizing molding process for molding a desired rack tooth, and (2A) is (2B) It is MM sectional drawing of. It is explanatory drawing of Example 3 which shows the modification of the 2nd rack raw material inserted in the internal-diameter hole of a tubular 1st rack raw material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st rack raw material 11 Outer periphery 12 Inner diameter hole 13 Rack tooth 2 2nd rack raw material 21 Upper surface 22 Outer periphery 23 Concavity and convexity 24 Crevice 25 Flat surface 31 Lower die 311 Press surface (restraint surface)
32 Upper die 321 Guide hole 322 Press surface (restraint surface)
33 Knockout 41 Punch 42 Rack tooth profile 51 Gap 52 Gap 61 Upper die 611 Press surface (restraint surface)
62 Lower die 621 Press surface (restraint surface)

Claims (6)

A hollow cylindrical first rack material having an inner diameter hole, and
Inserted into the inner diameter hole of the first rack material, and when forming rack teeth, a gap can be formed between the rack tooth forming side of the inner diameter hole of the first rack material and the side orthogonal to the rack tooth forming side. Use a solid second rack material with a cross-sectional shape,
Restrain the outer periphery of the first rack material excluding the rack tooth forming part with a die,
A punch having a rack tooth shape is pressed against a rack tooth forming portion on the outer periphery of the first rack material, and an inner diameter hole of the first rack material is formed on a side opposite to the rack tooth forming side of the first rack material. 2 is brought into contact with the outer periphery of the rack material, the punch is further pushed in, and the material material excluded at the time of forming the rack teeth by the punch is changed between the inner diameter hole of the first rack material and the outer periphery of the second rack material. Performing an intermediate forming step of integrating the first rack material and the second rack material by forming a rough rack tooth by flowing and accommodating in the space between ,
At the end of the intermediate forming step, a gap still remains between the side of the inner diameter hole of the first rack material perpendicular to the rack tooth formation shape side and the outer periphery of the second rack material, and the rack tooth formation shape. The width between the outer peripheral surfaces on the side orthogonal to the side is formed narrower than the width between the outer peripheral surfaces of the desired rack tooth shape,
Thereafter, the first rack material after the intermediate forming step is sandwiched and pressed between a die having a desired rack tooth shape and a die having a desired outer peripheral shape on the side facing the rack tooth forming side. Thus, a method of manufacturing a rack for a steering device, wherein a sizing molding step of molding a desired rack tooth is performed while increasing the width of the outer periphery on the side orthogonal to the rack tooth formation side . In the manufacturing method of the steering device rack according to claim 1 ,
A method for manufacturing a steering device rack, wherein the second rack material is cylindrical. In the manufacturing method of the steering device rack according to claim 1,
A method of manufacturing a rack for a steering apparatus, wherein an axial length of the second rack material is at least the same length as or slightly longer than a rack tooth forming length of the first rack material. In the manufacturing method of the steering device rack according to claim 1,
A steering device characterized in that the second rack material is provided with irregularities having the same number and the same pitch as the rack teeth on the outer periphery of the first rack material facing the rack tooth forming side. Rack manufacturing method. In the manufacturing method of the rack for steering devices according to claim 3 ,
A steering device characterized in that the second rack material is provided with irregularities having the same number and the same pitch as the rack teeth on the outer periphery of the first rack material facing the rack tooth forming side. Rack manufacturing method. A steering device rack manufactured by the method for manufacturing a steering device rack according to any one of claims 1 to 5 .

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