JP3772090B2 - Manufacturing method of tubular member with rack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a tubular member with a rack, that is, a member having a rack portion in a part of the length of a tube material. Such a device is used, for example, as a part of a steering device of an automobile and is generally called a rack bar. Therefore, in the following description, the name of the rack bar is used in principle. The present invention provides a method capable of efficiently producing a hollow rack bar using a steel pipe as a raw material by plastic working.
[0002]
[Prior art]
Conventionally, a rack bar of a steering device of an automobile has been used as a solid bar, but the manufacture of a hollow bar for the purpose of weight reduction is directed. FIG. 6 is a perspective view showing such a rack bar 1, and reference numeral 2 in FIG. 6 denotes rack teeth. In this way, it is a general manufacturing method that the hollow part is drilled after cutting the rack part in the bar, but on the other hand, there is a method of forming the rack part by plastic working using a steel pipe as the material. This is shown in Japanese Patent Publication No. 3-5892.
[0003]
This method consists of a two-step process in which a portion of a steel pipe rack to be formed is first crushed to a flat surface and then a rack is formed in this portion. For this purpose, first, a split mold for primary forming that can be opened to the left and right is provided to accommodate the portion of the steel pipe to be processed, but this die penetrates the portion where the upper rack is to be formed in the combined state. A hole is provided. Then, a press die having a flat tip is inserted into the through hole from above, and the portion of the steel pipe is processed into a flat surface, which is used as a primary molded body. Next, the said primary molded object is accommodated in the split mold for secondary shaping | molding which inner surface shape corresponds with the external shape of the finished product of a rack bar, and can open to right and left. That is, the secondary molding split mold is configured such that when the left and right molds are combined, a female mold of rack teeth is formed at the top. Then, the mandrel is inserted into the steel pipe, and the previously flattened portion is ironed from the inside. As a result, the material swells outside the primary molded body, and the rack is molded according to the shape of the secondary molding split mold.
[0004]
The present inventors previously presented a method for producing a hollow rack bar which has been further improved as Japanese Patent Application No. 11-370086. In this method, first, as shown in the longitudinal sectional view of FIG. 7 and the transverse sectional view of FIG. 8, the part to be processed of the length of the steel pipe 3 and the parts on both sides of the part are surrounded by the split mold surrounding the entire circumference of the steel pipe. 5 and 6. This split mold is formed with a vertical hole 8 penetrating at a position corresponding to a portion to be processed of the steel pipe in the combined state. In this state, the punch 9 is inserted into the vertical hole 8 and the steel pipe 3 in this portion is pressed to make a flat surface. Next, as shown in the longitudinal sectional view of FIG. 9 and the transverse sectional view of FIG. 10, instead of the punch 9, the rack forming die 11 is inserted into the longitudinal hole 8 and held in contact with the flattened portion of the steel pipe 3. The mandrel 12 is pushed into the steel pipe, and the inner surface of the flattened portion is squeezed to form a rack according to the rack forming mold 11.
[0005]
Since both methods of the above Japanese Patent Publication No. 3-5892 and Japanese Patent Application No. 11-370086 are all based on plastic working, there is no waste of materials unlike cutting, and there is also an effect of material strengthening by processing. Can also be excellent. In the method of Japanese Patent Publication No. 3-5892, two types of split molds are used. However, in the method of Japanese Patent Application No. 11-370086, only one type of split mold is required to accommodate the entire steel pipe. Although it has been found that the female part of the rack is heavily worn, in this method, it is only necessary to replace the rack-forming mold without changing the split mold itself, thereby reducing the cost of the mold. In mass production, a split mold combining punches or a split mold combining rack-forming molds is dedicated, and the material can be moved between them for processing. In this case, for the split mold combined with the rack forming mold, the rack forming mold may be fixed to one mold such as the upper mold. Even in this case, there is no change in the advantage that such replacement can be performed when the life of the rack forming type comes.
[0006]
[Problems to be solved by the invention]
By the way, in the manufacturing method of the hollow rack bar of Japanese Patent Application No. 11-370086, the female teeth of the rack teeth in the rack forming mold 11 shown in FIGS. 9 and 10 are approximately the width of the flat portion of the steel pipe 3. It is common to use a tooth with a matching width. The rack forming mold shown in FIGS. 9 and 10 has an advantage that the rack forming mold can be easily manufactured if the tooth shape is uniform and penetrates in the width direction. When such a rack forming mold is used, the shape of the finally formed rack is not governed by the rack forming mold with respect to the width dimension, but the ironing of the inner surface of the steel pipe is made to an appropriate rack width. It is adjusted by stopping at the number of times.
[0007]
That is, since ironing is generally a cold working, it requires a considerable amount of processing force. For this reason, for example, a plurality of mandrels having one or more ironing portions whose dimensions are gradually changed so as to be processed in 20 steps are used. . For example, if the mandrel has two ironing points, use ten. As a result, the inner surface of the flattened portion of the steel pipe is sequentially ironed, but the process ends when the rack width reaches a predetermined dimension. FIG. 11 is a cross-sectional view showing the state of ironing in the method of Japanese Patent Application No. 11-370086, and has a relationship of a partially enlarged view in which the split molds 5 and 6 in FIG. 10 are omitted. In the mandrel 41, the position of the surface facing the inner surface of the flattened portion of the steel pipe is 42A at the beginning, 42B is in the middle, and 42C indicates when the machining is completed (the cross section hatching of the mandrel 41 corresponds to the position of 42C. is doing). Ironing is performed using a plurality of mandrels whose positions are sequentially changed between 42A and 42C, for example, in 20 steps. The mandrel shown here conforms to a mandrel having a cross-section in FIG. 10 as a basic form, but part of both side surfaces are flat. That is, 43A is the first position, 43B is the middle, and 43C is the position of the side surface when the machining is completed.
[0008]
On the other hand, in the steel pipe 3 of FIG. 11, 44A has shown the state initially processed, ie, the part which made a part of outer surface periphery flat. In addition, 44B indicates a position on the way, and 44C indicates the position of the tooth tip surface that has been processed (hatching of the cross section of the steel pipe 3 corresponds to the position of 44C). As shown here, at the beginning of the ironing process by mandrel insertion, as shown by reference numeral 44B, the central portion of the tooth width first bulges, and the raised metal collides with the tooth bottom 13 of the rack forming die 11. Later, that is, after the top of the teeth of the rack is formed at the central portion of the tooth width, a phenomenon is observed in which the raised portions are sequentially expanded in the width direction. Then, the processing is completed with the number of ironing operations so that the necessary tooth width is obtained at the top of the rack teeth, but the rack teeth 44C at this time leave a space 45 between the rack forming mold 11 in the width direction. .
[0009]
By the way, the shape of the rack in the width direction of the rack is not controlled by the mold as described above, but as a result of the shape formed naturally, an inclined portion is formed from the top to the root of the rack teeth as shown in FIG. Is a comparatively gentle shape with a skirt. Therefore, if the necessary tooth width is secured at the top of the tooth, the end of the tooth width protrudes from the initial plane position at the root, and a part of the end protrudes from the range of the surface extending the outer periphery of the steel pipe. This protruding portion is removed by grinding at the finishing stage of the manufacturing process of the rack bar as the flash 46, but the process is increased and labor is increased accordingly. It is an object of the present invention to provide a method that can prevent the occurrence of the above-described flash and that can manufacture a rack bar more efficiently than a conventional method.
[0010]
[Means for Solving the Problems]
The present invention solves the above-mentioned problem, and presses a part of the length of the steel pipe of the raw material to make a part of the outer circumferential surface planar, and a rack forming mold is brought into contact with the planarized part. In this state, one or more mandrels having at least one ironing portion in the entire length are pushed into the steel pipe, and the inner surface of the flat portion is sequentially ironed by a plurality of ironing portions. In the method of manufacturing a tubular member with a rack that forms a rack according to the rack forming mold, the flattened portion has a flat portion having a width of 20 to 80% of the entire width at the center in the width direction, and end portions on both sides thereof. It is a manufacturing method of the tubular member with a rack characterized by having the shape which has the inclination part which becomes low in a direction. Here, the difference in height between the flat part and the end of the inclined part is 0.2 to 4.0 mm, the width of the flat part in the flattened part, and the flat part and the inclined part in the inclined part It is also characterized in that at least one of the height differences from the end portions is changed in the length direction of the tubular member with a rack.
[0011]
Further, the present invention is a method in which a part of the length of the steel pipe of the material is pressed to make a part of the outer circumference flat, and the rack forming die is brought into contact with and held by the flattened part. One or more mandrels having at least one ironing portion are pushed into the steel pipe, the inner surface of the flattened portion is sequentially ironed by a plurality of ironing locations, and the rack is formed according to the rack forming mold. In the manufacturing method of the tubular member with a rack to be formed, the tooth forming tip of the rack forming die is further advanced by 0.1 to 2.5 mm from the contact position with the flattened portion, and then rubbed by a mandrel It is a manufacturing method of the tubular member with a rack characterized by starting processing. Further, in this method, in the method of manufacturing a tubular member with a rack in which the flattened portion has a shape having a flat portion and an inclined portion, the rack-shaped tooth tip end portion is in contact with the flat portion. Then, it is applied by starting ironing with a mandrel after further 0.1 to 2.5 mm .
[0012]
Further, in each of the methods for manufacturing a tubular member with a rack, both side surfaces in the ironing portion of the mandrel are perpendicular to a surface facing the inner surface of the flattened portion of the steel pipe, and both sides in the ironing portion. It is also characterized in that the distance between the surfaces is the same in all the mandrels used. Still further, for at least one or more of the plurality of mandrels to be used, a recess having a width of 20 to 70% of the full width at the center in the width direction of the surface facing the inner surface of the flattened portion of the steel pipe at the ironing site. It is characterized by having. Moreover, the depth in the width direction center part of the said hollow is 0.2 mm or more, It is characterized by the above-mentioned.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view of a method of manufacturing a tubular member with a rack according to the present invention in a state in which a part of the length of a steel pipe 3 as a raw material is pressed to make a part of the outer circumference circumferential. That is, when the outer surface of the steel pipe is a flat surface, no method other than making a literally virtually flat surface has been conventionally performed. However, in the present invention, this is a special shape. In the present invention, the expression “planar” means not only a complete plane but also a shape close to a plane. And the outer surface when a part of length of the steel pipe 3 of the raw material in this invention is pressed planarly has the shape which has the flat part 31 in the center part of the width direction, and the inclination part 32 which becomes low in the edge part direction at the both sides. It has become. In the length direction of the rack bar, it is generally sufficient that such a shape continues uniformly. However, as will be described later, the shape can be changed in the length direction of the rack bar.
[0014]
FIG. 2 is a cross-sectional view of a state in which the steel pipe is pressed into a shape as shown in FIG. 1 to start ironing with a mandrel, and the split molds 5 and 6 are omitted. FIG. 3 is a cross-sectional view of the state where the processing is completed in this way. The mandrels 21A and 21B have a cross-sectional shape different from that shown in FIG. 11, which is shown in a particularly preferred form in the present invention and will be described later. In FIG. 2, the tooth tip 14 of the rack forming die 11 bites into the steel pipe 3, which will be described later.
[0015]
The outer surface when a part of the length of the steel pipe of the material is pressed flat is shaped as described above, so that the rack width end portion of the rack in the rack bar after completion of ironing as shown in FIG. It is possible to prevent the flash 46 as shown in FIG. Furthermore, the shape of the rack teeth in the width direction also changes, and the inclined portion 33 near the root portion of the rack teeth becomes steeper than when pressed against a conventional simple flat surface. Therefore, it is possible to ensure a larger rack width than in the conventional method. Such an effect can be obtained when the steel pipe is pressed into the shape of the present invention, and in the inclined portion that becomes lower in the end direction, there is no material bulge at the beginning of the ironing process, and the ironing process proceeds. Since the material of the inclined portion rises after the material starts moving in the tooth width direction, it is considered that the occurrence of flash can be prevented and the inclination of the tooth width end portion becomes steep.
[0016]
The width of the flat portion 31 at the center in the width direction as described above and the inclination of the inclined portions 32 on both sides thereof may be determined optimally in consideration of the tooth width necessary for actual processing, The width F of the flat portion in FIG. 1 is preferably in the range of 20 to 80% of the total width W of the planar portion. If the width F of the flat part is larger than 80%, the effect will be inadequate, approaching the situation when the whole is flat, and if it is smaller than 20% of the total width W, an excessive burden will be applied to the central part of the rack-forming tooth width. Life is shortened. The height difference H between the flat portion and the end of the inclined portion is preferably in the range of 0.2 to 4.0 mm. Also, if the difference in height H between the flat part and the end of the inclined part is smaller than 0.2 mm, the effect of the approach to the situation when the whole is a flat surface becomes insufficient, but this point is particularly preferably 0.3 mm or more. is there. On the other hand, if it is larger than 4.0 mm, the shape of the teeth of the formed rack becomes poor, but in this respect, it is particularly preferably 3.0 mm or less.
[0017]
In the present invention, when a part of the length of the steel pipe of the material is pressed with a punch to have a shape having the flat portion 31 and the inclined portion 32, the tip portion is formed at once by a punch having a female shape with the above shape. Good. For example, it is particularly necessary to work twice, such as forming a flat surface in the first step and forming an inclined portion in the second step, or forming a mountain-shaped surface shape in the first step and flattening the central portion in the width direction in the second step. However, this method is not excluded in the present invention.
[0018]
Further, in the present invention, when the rack forming die is brought into contact with and held in the flat portion as described above, the tooth die tip portion 14 of the rack forming die 11 is flattened as shown in FIG. It is preferable to start the ironing process after biting in from the contact position with the applied portion. This is because in the ironing process of the inner surface of a steel pipe by a mandrel, the stress to move the material is not only upward, which raises the rack teeth, but also the stress to move in the axial direction of the steel pipe. However, this is to limit the movement of the material in this axial direction.
[0019]
That is, FIG. 4 is a cross-sectional view showing the positional relationship between the rack forming die 11 and the steel pipe 3 that is a material in the initial stage of ironing by a mandrel, and the material moves upward while sliding in the axial direction 15. The movement of the material in the axial direction of the steel pipe during ironing as described above delays the formation of the rack tooth portion, and the number of unnecessary ironing operations increases. This axial slip is significant until the tooth tip 14 of the rack forming mold 11 bites into the material, and once it bites in, the movement in the axial direction 15 is constrained and reduced. In the present invention, the state in which the tooth tip portion 14 of the rack forming die 11 bites into the material is expressed before the ironing process by the mandrel is started.
[0020]
For this purpose, the tip of the tooth of the rack forming die is further advanced from the contact position with the flattened portion of the steel pipe, and then the ironing process by the mandrel is started. In the case where the planar portion as shown in FIG. 1 is configured by the flat portion 31 and the inclined portion 32, it is flat that the rack-shaped tooth tip portion first comes into contact with the planar portion. It is a part, and the width of the bite in the inclined part is widened as the bite becomes deeper. In this case, as shown in FIG. 2, it does not bite to the depth of the end of the inclined portion, that is, the biting width may not be up to the full width of the planar portion.
[0021]
This method of biting the rack forming mold prior to the ironing process with the mandrel is somewhat effective regardless of the shape of the flat surface when the steel pipe is made flat. In this case, it is not excluded to carry out a method of biting the rack forming mold. However, in the case of the shape having the flat portion 31 and the inclined portion 32 of the present invention described above, the rack is preferentially placed in the central portion in the width direction of the flat portion where the material first protrudes in the ironing process, that is, the flat portion. Since the forming mold 11 is bitten, the effect is great. Furthermore, the central portion in the width direction of the flattened portion is easy to dent because the inside is hollow, but in the case of the shape of the present invention, since this portion is preliminarily raised as a flat portion, the rack forming mold is effectively bitten. Can be made.
[0022]
The biting amount B shown in FIG. 2 is effective if it is 0.1 mm or more from the contact position between the tooth mold tip 14 of the rack forming die 11 and the flattened portion, that is, the contact position with the flat portion 31 in this case. Although it is obtained, it is particularly preferably 0.2 mm or more. On the other hand, even if it exceeds 2.5 mm, the effect is saturated and the dent in the central portion in the width direction becomes large. This biting amount B is defined as the distance from the contact position between the tooth tip 14 of the rack forming die 11 and the flat portion 31 as described above, and the steel pipe is removed after the rack forming die is bitten. The indentation depth does not usually match. That is, as described above, the central portion in the width direction of the flattened portion of the steel pipe is hollow and easily recessed, and the indentation is shallower than the rack-forming movement distance from the contact position with the flat portion of the steel pipe. Because it becomes.
[0023]
The effect of restricting the movement of the material in the rack length direction by biting into the flattened portion of the rack-forming steel pipe as described above is effective in the teeth at both ends where there is no tooth type to bite next to one side. Will be less. For this reason, regardless of whether or not the method of the present invention in which the rack forming mold is bitten prior to ironing is adopted, the teeth at the both ends of the rack are delayed in the formation of teeth by ironing, and the tooth width is different from that of the other. It is usually much smaller than the teeth. This influence also extends to adjacent teeth, and in some teeth at both ends in the longitudinal direction of the rack, the tooth width tends to gradually decrease toward the ends. In the method of the present invention, in which the steel pipe is flattened, the flat portion at the center in the width direction and the inclined portions that are lowered in the end direction on both sides thereof are formed. By changing at least one of the height differences from the end of the inclined portion in the length direction of the rack bar, it is possible to prevent such a variation in the tooth width to some extent. Further, when it is desired to sequentially change the tooth width of a plurality of teeth for a special purpose, the difference between the width of the flat portion and the height of the flat portion and the inclined portion at the inclined portion is determined by the length of the rack bar. It is also possible to adjust by changing in direction.
[0024]
Further, the mandrels 21A and 21B shown in FIG. 2 and FIG. 3 show particularly preferable forms in the manufacturing method of the present invention. That is, this mandrel is characterized in that both side surfaces 23 in the ironing portion are perpendicular to the surfaces 22A and 22B facing the inner surface of the flattened portion of the steel pipe. Further, the distance between both the side surfaces 23 is the same at all the mandrel ironing portions to be used.
[0025]
That is, in the mandrel having a cross section as shown in FIG. 11, the surfaces 42A to 42C facing the inner surface of the flattened portion of the steel pipe and the surfaces 43A to 43C on both sides adjacent thereto are not perpendicular but obtuse. Yes. For this reason, when ironing is performed sequentially, the surfaces on both sides proceed sequentially as shown in 43A, 43B and 43C and bite into the inner surface of the steel pipe 3, so that a large working force is exerted on the side portion. Occurs, and the amount of machining per process cannot be increased. On the other hand, in the mandrel shown in FIGS. 2 and 3, both side surfaces 23 are perpendicular to the surfaces 22A and 22B facing the inner surface of the flattened portion of the steel pipe. Since the intervals of 23 are the same, no processing force is consumed in this portion. For this reason, the amount of processing at one time can be increased, and the number of ironing operations by the mandrel can be reduced.
[0026]
Furthermore, in the present invention, it is preferable that the mandrel shown in the cross-sectional view of the ironing portion in FIG. 5 is used in combination with the mandrel for at least one of a plurality of mandrels used in ironing. That is, the conventional mandrel is a simple flat surface facing the inner surface of the flattened portion of the steel pipe at the ironing site, but as described above with reference to FIG. In the first stage, first, the central portion of the tooth width is raised, and after the raised metal collides with the bottom portion of the rack forming mold, the raised portion gradually spreads in the width direction. In the present invention, paying attention to this phenomenon, particularly after the raised metal collides with the bottom portion of the rack forming mold, the material actively flows toward both ends in the width direction of the rack. is there.
[0027]
As a means for this purpose, as shown in FIG. 5, a hollow 36 is provided at the center in the width direction of the surface 35 facing the inner surface of the flattened portion of the steel pipe at the ironing site. A mandrel 34 having both ends in the width direction that are desired to flow is used. Such a mandrel allows the material to flow directly toward both ends of the rack in the width direction to promote the formation of the rack in the width direction of the rack, and also reduces the burden on the bottom portion of the rack forming mold. Can extend the lifespan. Such an effect is the above-described present invention, the outer surface when a part of the length of the steel pipe is pressed flat, the flat portion at the center in the width direction, and the inclined portions that are lowered in the end direction on both sides thereof. This is particularly noticeable when combined with a method of forming a shape having a.
[0028]
In the mandrel in which the central portion in the width direction of the surface facing the inner surface of the flattened portion of the steel pipe in the ironing portion as described above is depressed, at least one or more of the plurality of mandrels used are such. It only has to be. That is, as described above, it may be used for all ironing processes after the stage in which the raised metal collides with the bottom part of the rack forming mold, or in the stage after using this mandrel. It does not prevent the surface facing the inner surface of the flattened portion from switching again to a flat normal mandrel. Furthermore, a mandrel having such a depression may be used at an earlier stage of ironing.
[0029]
The mandrel 34 shown in FIG. 5 is similar to the mandrels 21A and 21B shown in FIGS. 2 and 3, and a surface 35 opposite to the inner surface of the portion where both side surfaces 37 of the ironing portion are made flat. It also has a right-angled feature. Naturally, the distance between the two side surfaces 37 is the same in all the mandrel ironing portions to be used. However, providing the depression in the center in the width direction of the surface facing the inner surface of the planarized portion of the steel pipe is also applicable to a mandrel whose both side surfaces are not parallel as shown in FIG.
[0030]
The width G of the recess 36 at the center in the width direction on the surface 35 facing the inner surface of the planarized portion of the steel pipe of the mandrel as shown in FIG. 5 may be in the range of 20 to 70% of the total width T. If it is less than 20%, there is little effect of promoting the material flow in the width direction of the rack, and if it exceeds 70%, the material flow may concentrate in a narrow range at both ends of the width. Moreover, the depth D in the center part of the width direction of the said hollow 36 should just be 0.2 mm or more. If it is less than 0.2 mm, the effect is small, and 0.4 mm or more is particularly preferable. On the other hand, the upper limit of the depth is not particularly limited because a process of processing only the material at both ends of the width may be sandwiched at a certain stage of ironing by a mandrel. Therefore, in the extreme case, there may be a mandrel with a cross section close to a U-shape, but in reality, if the depth D at the center in the width direction exceeds 5.0 mm, the material is only a ladder at both ends in the width direction. It comes to be.
[0031]
【The invention's effect】
As described above, according to the present invention, when the steel pipe is flattened in the manufacturing process of the rack bar, the flat portion is provided in the central portion in the width direction and the inclined portions that are lowered in the end portion direction are provided on both sides thereof. In the rack bar after completion, it is possible to prevent burrs from appearing at the root portion of the rack width end portion of the rack, and to secure a larger rack width than in the conventional method. In addition, when starting ironing, the rack-forming tooth tip is further digged in from the contact position with the flattened portion of the steel pipe, limiting the stress that tends to move the material in the axial direction of the steel pipe. Thus, the rack teeth can be raised. In addition, by using a mandrel in which both side surfaces in the ironing part are perpendicular to the surface facing the inner surface of the flattened portion of the steel pipe, the processing force is prevented from being consumed on both sides, The number of ironing operations by mandrels can be reduced. In addition, by using a mandrel having a depression in the center in the width direction of the surface facing the inner surface of the planarized portion of the steel pipe, the formation of the rack teeth in the tooth width direction is promoted, and the rack forming type The burden on the bottom portion can be reduced and the life of the rack forming mold can be extended. In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible within the scope of the invention. Modifications from the embodiments shown in the drawings are within the scope of the present invention without departing from the spirit of the present invention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a state in which a part of a steel pipe of a material is flattened in the present invention. 3 is a cross-sectional view in a state where the machining is completed as shown in FIG. 2. FIG. 4 is a cross-sectional view showing the positional relationship between the rack forming die and the steel pipe in the initial stage of ironing. FIG. 5 is an example of the mandrel of the present invention. FIG. 6 is a perspective view showing a hollow rack bar. FIG. 7 is a longitudinal sectional view showing a method for manufacturing the hollow rack bar. FIG. 8 is a cross section showing a method for manufacturing the hollow rack bar. FIG. 9 is a longitudinal sectional view showing a method for manufacturing a hollow rack bar. FIG. 10 is a transverse sectional view showing a method for manufacturing a hollow rack bar. FIG. 11 is a sectional view showing a state of ironing in the method of the previous invention. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rack bar 2 Rack tooth 3 Steel pipe 5, 60 Split type 8 Vertical hole 9 Punch 11 Rack forming type 12 Mandrel 13 Tooth shape bottom part 14 Tooth type tip part 15 Axial direction 21A, 21B Mandrel 22A, 22B The flat part of the steel pipe Surface 23 facing the inner surface of the steel plate Side surface 31 Flat portion 32 Inclined portion 33 Inclined portion 34 Mandrel 35 Surface 36 facing the inner surface of the flattened portion of the steel pipe Depression 37 Side surface mandrel 41
42A, 42B, 42C Surfaces 43A, 43B, 43C opposite to the inner surface of the flattened portion of the steel pipe Side surface 44A Initial position 44B, 44C Position of the tooth tip on the steel pipe 45 Space 46 Beam

Claims (8)

  A part of the length of the steel pipe of the material is pressed to make a part of the outer circumference flat, and the rack forming mold is held in contact with the flat part and is squeezed to at least one part of the entire length. One or more mandrels having processing points are pushed into a steel pipe, and the inner surface of the flattened portion is sequentially ironed by a plurality of ironing points to form a rack according to the rack forming mold. In the method for producing a member, the planar portion has a shape having a flat portion having a width of 20 to 80% of the full width at a central portion in the width direction and inclined portions that are lowered in the end direction on both sides thereof. A method for manufacturing a tubular member with a rack, which is characterized in that:   The method for manufacturing a tubular member with a rack according to claim 1, wherein a difference in height between the flat portion and the end of the inclined portion is 0.2 to 4.0 mm.   At least one of a width difference of the flat portion in the flattened portion and a height difference between the flat portion and the inclined portion end portion in the inclined portion is changed in the length direction of the tubular member with a rack. The manufacturing method of the tubular member with a rack of Claim 1 or 2. A part of the length of the steel pipe of the material is pressed to make a part of the outer circumference flat, and the rack forming mold is held in contact with the flat part and is squeezed to at least one part of the entire length. One or more mandrels having processing points are pushed into a steel pipe, and the inner surface of the flattened portion is sequentially ironed by a plurality of ironing points to form a rack according to the rack forming mold. In the method of manufacturing a member, starting the ironing process with a mandrel after the rack-shaped tooth tip is further advanced by 0.1 to 2.5 mm from the contact position with the flattened portion. A method for producing a tubular member with a rack, characterized in that: The rack-forming type tooth mold tip portion is further advanced by 0.1 to 2.5 mm from the contact position with the flat portion in the flattened portion, and then ironing by a mandrel is started. The manufacturing method of the tubular member with a rack in any one of Claim 1 thru | or 3. Both side surfaces of the mandrel ironing portion are perpendicular to the surface facing the inner surface of the flattened portion of the steel pipe, and the distance between both side surfaces of the ironing portion is the same in all of the mandrels used. The method for manufacturing a tubular member with a rack according to any one of claims 1 to 5 , wherein: At least one or more of the plurality of mandrels to be used has a recess having a width of 20 to 70% of the full width at the center in the width direction of the surface facing the inner surface of the flattened portion of the steel pipe at the ironing site. A method for manufacturing a tubular member with a rack according to any one of claims 1 to 6 . The method for manufacturing a tubular member with a rack according to claim 7 , wherein a depth at a central portion in the width direction of the recess is 0.2 mm or more.

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