JP5193650B2 - Core bar set and hollow rack bar - Google Patents

Description

  The present invention relates to a core set including a plurality of core bars used for manufacturing a hollow part such as a hollow rack bar used in an automobile power staying device or the like, and a hollow having a tooth portion meshed with a pinion gear. The present invention relates to rack bars, particularly those that can reduce equipment costs.

  Conventionally, as a method of manufacturing a hollow rack bar (hollow part) used in a power steering device of an automobile, there are many methods by cutting from a round bar. However, in order to cope with a complicated shape and weight reduction, what is manufactured from a pipe material by transfer forging is known (for example, refer to Patent Document 1). Specifically, first, the pipe material is pressurized with a cold forging die to form a flat upper surface as the first step of the tooth forming step, and the core metal is press-fitted into the cavity of the pipe material in the next step. The metal core has a taper-shaped protrusion, and the protrusion engages with the flat part of the pipe material on the inner peripheral side, so that the meat of the flat part flows plastically toward the teeth of the mold. By doing so, a linear tooth row having a shape corresponding to the tooth row of the mold is applied to the outer peripheral flat portion of the pipe material by the transfer method, and a hollow rack bar can be obtained.

As shown in FIG. 12, the cored bar 400 used for such transfer forging has a bar 401 and a protrusion 402 protruding from the bar 401. The cored bar 400 is formed of a plurality of sets in which the protruding amount of the protruding portion 402 is gradually increased as shown by a two-dot chain line in FIG. The optimum combination was used depending on the shape and the like.
Japanese Examined Patent Publication No. 3-5892

  The above-described cored bar set has the following problems. That is, the maximum width W of the bar 401 of the core metal 400 is set to be the same regardless of the protrusion amount of the protrusion 402. For this reason, when the protrusion amount of the protrusion 402 increases, as shown in FIG. 13, the pipe material P is pressed or slid against the predetermined width S1 of the inner wall surface in the lateral direction, and the molding load is increased. There is a tendency to increase. In addition, when the width of the bar varies due to an error in the manufacturing process, the forming load varies.

  For this reason, finally, an apparatus for generating a large molding load is required in consideration of variations in the molding load, which may increase the equipment cost.

  On the other hand, as shown in FIG. 14, the hollow portion of the pipe material P that becomes the hollow rack bar is located on the opposite side of the flat portion Pa where the tooth portion is formed when the inner peripheral surface thereof has a cross section orthogonal to the axial direction. The shape is a combination of the semicircular part Q and the linear part T provided on the tooth part side.

  For this reason, when the height of the tooth part is large, the width between the outer peripheral surface on the flat part Pa side where the tooth part is formed and the inner peripheral surface of the hollow part is narrow, and the load during the tooth part molding cannot be endured. was there.

  Then, it aims at providing the metal core set which can suppress the fluctuation | variation of the molding load required at the time of press fit, and can reduce installation cost.

  In order to solve the above problems and achieve the object, the metal core set and the hollow rack bar of the present invention are configured as follows.

A core metal used in a method of manufacturing a hollow rack bar by press-fitting a hollow material held in a mold into an internal cavity of the hollow material and projecting the hollow material from the inner diameter side toward the mold. In the M metal core set having 1 to M, the metal core is provided with a bar having a maximum cross-sectional area smaller than the minimum cross-sectional area of the hollow portion of the hollow material, and protruding from the bar. The maximum protrusion amount gradually increases from No. to M, and the protrusion has a maximum width set constant, and the bar has the protrusion as a maximum width on the side opposite to the mold. gradually towards, wherein the constant taper angle is set such that the width is narrowed.

Comprising a hollow cylindrical portion having a tooth portion which is engaged in pin Niongia, the cross-sectional shape of the hollow portion of the cylindrical portion includes a first hollow portion located on the back side of the teeth, to the first hollow portion A second hollow portion located on the opposite side of the tooth portion with respect to the center of the cylindrical portion and having a maximum inner diameter width larger than a maximum inner diameter width of the first hollow portion; the first hollow portion; the second hollow portion; Provided at a boundary portion with the hollow portion and projecting toward the inner diameter side, the inner peripheral surface of the first hollow portion includes a straight portion, and one end thereof is connected to the projecting portion. , The other end is formed in combination with a pair of first curved portions connected to both ends of the linear portion, and the straight line extending both ends of the first curved portion is closed rather than parallel, and the second hollow portion Is provided on the opposite side of the linear portion with respect to the center of the cylindrical portion. Characterized in that it comprises a second curved portion having at least semicircular portion.

  According to the present invention, it is possible to prevent breakage without extremely increasing the load required for press-fitting.

  FIG. 1 is a side view showing one cored bar 10 of the cored bar set according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a main part showing a hollow rack bar manufacturing apparatus 100 in which the cored bar 10 is used. is there. In FIG. 2, P indicates an iron pipe (hollow material).

  The cored bar 10 includes a semicircular bar 11. The bar 11 includes a distal end portion 12 positioned on the distal end side in the press-fitting direction that is first inserted into the pipe P, and a proximal end portion 13 connected to the drive device.

  The upper surface of the bar 11 is flat as a whole, but three protrusions 21, 22, and 23 are integrally provided along the axial direction of the bar 11. The bar 11 is in close contact with the inner peripheral surface of the pipe P on the bottom surface side, and linear movement in the axial direction of the pipe P is possible while maintaining close contact with the inner peripheral surface of the vip P during the forging process. Further, the bar 11 has a maximum cross-sectional area smaller than the minimum cross-sectional area of the hollow portion of the pipe P. That is, as will be described later, the pipe P is formed in such a size that it can smoothly move under the flat portion Pa even after the pipe P is flattened. Further, as shown in FIG. 3, the bar 11 gradually decreases in width toward the lower side, that is, the side opposite to the tooth mold 130 described later, with the upper surface of the protrusions 21 to 23 having a certain maximum width G. Is set to a taper angle θ.

  The taper angle θ is set to about 3 °, for example, but is not limited thereto. The taper angle θ is appropriately determined depending on the inner diameter, thickness, etc. of the pipe P.

  Each of the protrusions 21 to 23 is formed with a gently tapered guide surface so that a smooth movement of the cored bar 10 can be obtained regardless of the flow resistance at the time of molding. The maximum protrusion amount of the protrusions 21 to 23 is set to gradually increase from No. 1 to No. M.

  Next, the structure of the hollow rack bar manufacturing apparatus 100 using this mandrel 10 will be described. The hollow rack bar manufacturing apparatus 100 includes a lower mold 110 and an upper mold 120 that hold an iron pipe P. The hollow rack bar manufacturing apparatus 100 presses the core metal 10 into the internal cavities of the pipes P held by the lower mold 110 and the upper mold 120 so that the meat of the pipe P is stretched from the inner diameter side toward the tooth mold 130 described later. It is an apparatus which manufactures a hollow rack bar by making it take out.

  The lower mold 110 includes a semicircular inner peripheral surface 111 in a cross section, and the pipe P is placed on the semicircular inner peripheral surface 111. The upper die 120 is detachably provided with a tooth die 130 whose upper inner surface is spaced in the longitudinal direction over a predetermined length, and the tooth die is placed at a predetermined length on the upper surface of the pipe P by transfer forging. A rack can be formed according to the unevenness of the (mold) 130.

  The pipe P is forged using the hollow rack bar manufacturing apparatus 100 and the core bars 10 and 10A thus configured.

  In advance, the center portion of the pipe P is flattened into a concave shape by using another mold to form a flat portion Pa having a semi-circular shape with a concave shape. The pipe P is held between the upper mold 120 and the lower mold 110 and positioned so that the flat portion Pa of the pipe P contacts the tooth mold 130.

  In this state, press-fitting of the cored bar 10 into the pipe P is started. The cored bar 10 is introduced into the hollow portion of the pipe P from the tip 12 thereof. Then, the first projecting portion 21 acts on the inner surface of the flat portion Pa of the pipe P through the tapered guide surface, and the meat of the pipe P is projected toward the tooth profile of the tooth mold 130. Then, by continuing the press-fitting of the core bar 10, the overhang of the meat by the protrusions 22 and 23 is sequentially received, and the press-forging is performed. Next, while pressing the cored bar 10 in the backward direction and press-fitting the cored bar 10A, the press forging is alternately performed.

  In this way, the cores 10 and 10A are press-fitted and retracted, and press-fitting forging is performed. Next, the core metal 10, 10A of the next count is pressed and retracted. Thereafter, the final processing is completed by repeating a predetermined process while increasing the count of the cored bar 10 one by one in the same manner. Finally, the height of the metal core 10 completes the transfer forging of the rack in which the meat of the pipe P is sufficiently stretched corresponding to the unevenness of the tooth mold 130 by the metal core press-fitting.

  As described above, the width of the upper surface of the metal core 10 is constant from No. 1 to M, and the width gradually decreases downward, so that the portion where the metal core 10 contacts the inner diameter of the pipe P is a protrusion. Since it is limited to 21-23 and slight width S2 of the upper part of the bar 11, there are few unnecessary contacts. In addition, regarding the variation in width when the bar 11 is formed, since there is little contact with the pipe P, it is not necessary to consider the fluctuation of the required forming load, and the necessary equipment can be made as small as possible. This can reduce the equipment cost.

  As described above, according to the cored bar set according to the present embodiment, it is possible to reduce the variation in the molding load required at the time of press-fitting, reduce unnecessary sliding, and reduce the capacity of the driving device, Equipment costs can be reduced. At the same time, the press machine for applying a load to the lower mold 110 and the upper mold 120 is not required to be enlarged, and the apparatus cost and production cost can be reduced.

  FIG. 5 is a side view showing a short-type core bar 10B which is one of the core bar sets according to the second embodiment of the present invention, and FIGS. 6 to 8 are hollow rack bar manufacturing apparatuses using the same core bar set. FIG. 6 shows a state where the core metal is clamped around the mold and the core metal holder, FIG. 7 shows a state where the core metal is delivered around the mold and the core metal holder, and FIG. 8 shows press-fitting of the core metal around the mold and the core metal holder. Is shown in a completed state. 5, the same functional parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The length of the bar 11 of the core metal 10B is as short as half or less of the length of the tooth portion of the tooth mold 213 described later.

  The hollow rack bar manufacturing apparatus 200 includes a metal mold 210, a metal core holder 220 that stores a set of a plurality of metal cores 10B, a first metal core push bar 230, a second metal core push bar 240, a metal core guide 250, and the like. It has.

  The mold 210 includes a lower mold 211 and an upper mold 212 that hold the iron pipe material P. The lower mold 211 includes a semicircular inner peripheral surface 211a in the cross section, and the pipe material P is placed on the semicircular inner peripheral surface 211a. The upper die 212 is detachably provided with a tooth die 213 whose inner surface on the upper side is spaced in the length direction over a predetermined length, and a tooth is placed on a portion of the predetermined length on the upper surface of the pipe material P by transfer forging. A rack can be formed according to the unevenness of the mold 213.

  The core metal holder 220 is disposed only on one side of the mold 210, for example, on the right side of the mold 210 in FIGS. As shown in FIGS. 6 to 8, the cored bar holder 220 has a plurality of holding holes 221. These holding holes 221 penetrate the cored bar holder 220 in the direction in which the pipe material P extends, and the cored bar 10B is individually accommodated therein. The housed core 10B is held in a proper posture with respect to the mold 210 and by a leaf spring or the like (not shown) so as not to fall off carelessly. Each cored bar 10B supported by the cored bar holder 220 is positioned on the side where the first cored bar pusher 230 is inserted into and removed from the mold 210.

  The cored bar holder 220 is moved by a holder driving unit (not shown). Each time this driving is performed, one of the plurality of holding holes 221 is sequentially selected and opposed to one end of the pipe material P that is joined together. Therefore, the cored bar 10B supported by the cored bar holder 220 can be sequentially put in and out of the pipe material P. For this purpose, the metal core holder 220 is moved by a fixed pitch in the vertical direction (vertical direction) in FIGS. However, instead of this, it may be moved in the lateral direction (the front and back direction of the paper on which FIGS. 6 to 8 are drawn). Alternatively, the core metal holder 220 can be rotatably provided and rotated by a predetermined angle by the holder driving unit.

  The leading end side of the first cored bar 230 is formed to be detachable with respect to the pipe material P held by the mold 210. In that case, it inserts in the pipe material P hold | maintained at the metal mold | die 210 with the core metal 10B. In addition, the code | symbol 260 in FIGS. 6-8 has shown the tubular push rod guide.

  The distal end side of the second cored bar 240 is formed to be detachable with respect to the pipe material P held by the mold 210.

  As shown in FIGS. 6 to 8, the metal core guide 250 is disposed between the metal mold 210 and the metal core holder 220 and close to the metal mold 210. The cored bar guide 250 is made of metal or the like and has a through hole 251 penetrating in the thickness direction. The through hole 251 communicates with the hollow portion of the pipe material P held by the mold 210.

  Next, a procedure for manufacturing a hollow rack bar using the hollow rack bar manufacturing apparatus 200 having the above configuration will be described. The set pipe material P is disposed in the mold 210, and the other end side of the pipe material P protrudes from the mold 210. Further, the mold is clamped between the lower mold 211 and the upper mold 212 and the tooth mold 213 is brought into contact with the flat portion Pa.

  Before or after the setting operation, the cored bar holder 220 is operated to hold one of the plurality of cored bars 10B accommodated in the state facing the through hole 251 of the cored bar guide 250. At the same time, the tip end of the first metal core push rod 230 is engaged with the right end of the metal core 10B facing the through hole 251.

  Next, the second metal core push rod 240 is inserted into the pipe material P, and the tip of the second metal core push rod 240 is inserted through the pipe material P and the through hole 251 of the metal core guide 250, and this through hole 251. It comes in contact with the left end of the core bar 10B in the core bar holder 220 facing the. Accordingly, the cored bar 10B in the through hole 251 is sandwiched between the first cored bar push bar 230 and the second cored bar pusher 240 that are in contact with both ends from both ends in the axial direction.

  Thereafter, the first cored bar 230 passes through the holding hole 221 of the cored bar holder 220 and the through-hole 251 of the cored bar guide 250, and inside the pipe material P held by the mold 210 as shown in FIG. Inserted into.

  At this time, the metal core 10B is pressed by the first metal core push bar 230 and press-fitted into the pipe material P while being held between the first metal core push bar 230 and the second metal core push bar 240. Is done. By this press-fitting, the overhang of meat is received by the protruding portions 21 to 23 of the cored bar 10B, and press-forging is performed. The press-fitting of the cored bar 10B is completed in a state where the cored bar 10B cannot be completely removed from the flat portion Pa as shown in FIG.

  Next, the first cored bar 230 is pulled back. At this time, the second cored bar push rod 240 is moved toward the cored bar holder 220. Thus, the core metal 10B is pressed by the second core metal push bar 240 while being held between the first core metal push bar 230 and the second core metal push bar 240 in contact with both ends of the core metal 10B. Then, it is pushed back into the metal core holder 220 through the pipe material P and the through hole 251 of the metal core guide 250. Also in this case, press forging is performed in response to the overhanging of the meat by the protruding portions 21 to 23 of the core metal 10B.

  Thereafter, the metal core holder 220 is moved so that the metal core 10B having the next largest protrusion amount and the holding hole 221 in which the metal core 10B is accommodated are opposed to the opening of the pipe material P through the through hole 251 of the metal core guide 250. .

  After the core bar 10B to be used next is clamped, the core bar 10B is similarly held between the first core bar push bar 230 and the second core bar push bar 240. Then, it is pressed by the first cored bar 230 and press-fitted into the pipe material P, and is reciprocated once. By sequentially repeating these procedures, a hollow rack bar having a rack corresponding to the tooth mold 213 of the mold 210 on the pipe material P is manufactured.

  Finally, after the last used cored bar 10B is returned to the cored bar holder 220, the second cored bar 240 is pulled out from the pipe material P, and then the mold 210 is opened.

  Even when the short-type cored bar set according to the second embodiment is used, the same effect as that obtained when the above-described cored bar set according to the first embodiment is used can be obtained. .

  FIG. 9 is a cross-sectional view of a main part showing a hollow rack bar 300 according to the third embodiment of the present invention. A hollow cylindrical portion 301 having a tooth portion 302 meshed with a pinion gear is provided, and the cross-sectional shape of the hollow portion 303 of the cylindrical portion 301 includes a first hollow portion 303a located on the back side of the tooth portion 302, and the first hollow portion 303a. A second hollow portion 303b located on the opposite side of the tooth portion 302 with respect to the center C of the cylindrical portion 301 with respect to the first hollow portion 303a and having a maximum inner diameter width H2 larger than the maximum inner diameter width H1 of the first hollow portion 303a; And an overhanging portion 303c that is provided at a boundary portion between the first hollow portion 303a and the second hollow portion 303b and projects to the inner diameter side.

  The inner peripheral surface of the first hollow portion 303a includes a straight portion 310 having a length W1, one end of which is connected to the overhang portion 303c, and the other end is connected to both ends of the straight portion 310, respectively. It is formed in combination with one curved portion 311. The distance W1 between both ends of the first curved portion 311 is formed smaller than the width W0 (see FIG. 14) of the straight portion T when the protruding portion 303c is not provided. Moreover, the straight line which extended the both ends of this 1st curve part 311 is parallel.

  The second hollow portion 303 b includes a second curved portion 312 having at least a semicircular portion provided on the opposite side of the straight portion 310 with respect to the center C of the cylindrical portion 301.

  If formed in this way, the thickness of the material between the outer peripheral surface and the inner peripheral surface on the tooth portion 302 side can be sufficiently taken by the overhang portion 303c, which is sufficient for the molding load when the tooth portion 302 is formed. It becomes possible to endure. In addition, this makes it possible to reduce the load resistance of the cored bar, so that the cored bar can be manufactured at low cost.

  FIG. 10 is a cross-sectional view of a main part showing a hollow rack bar 300A according to the fourth embodiment of the present invention. 10, the same functional parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the hollow rack bar 300A in the present embodiment, the overhang amount of the overhang portion 303c is slightly smaller than that of the hollow rack bar 300, and the distance W2 between both ends of the first curved portion 311 is the above-described distance W1. It is formed larger than Moreover, the straight line which extended the both ends of this 1st curve part 311 is about 0 degree-10 degrees with respect to parallel.

  Also in the hollow rack bar 300A in the present embodiment, the same effect as that of the hollow rack bar 300 described above can be obtained.

  FIG. 11 is a cross-sectional view of a main part showing a hollow rack bar 300B according to the fifth embodiment of the present invention. 10, the same functional parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the hollow rack bar 300B in the present embodiment, the overhang amount of the overhang portion 303c is slightly larger than that of the hollow rack bar 300, and the distance W3 between both ends of the first curved portion 311 is the above-described distance W1. It is formed larger than Further, the straight line extending from both ends of the first curved portion 311 is about 0 ° to −3 ° with respect to the parallel.

  Also in the hollow rack bar 300B in the present embodiment, the same effect as that of the hollow rack bar 300 described above can be obtained.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

The side view which shows the principal part of the metal core which is one of the metal core sets which concern on one embodiment of this invention. Sectional drawing which shows the hollow rack bar manufacturing apparatus with which a concentric metal bar set is applied. The principal part sectional drawing which shows a concentric bar. The principal part sectional drawing which shows the state which inserted the concentric metal bar into the pipe. The side view which shows the principal part of the metal core which concerns on the 2nd Embodiment of this invention. It is a figure which shows the hollow rack bar manufacturing apparatus using the same metal core, Comprising: Sectional drawing which shows a metal mold | die and the metal core holder periphery in the state by which the metal core was clamped. Sectional drawing which shows the metal mold | die of the said hollow rack bar manufacturing apparatus, and a metal core holder periphery in a metal core delivery state. Sectional drawing which shows the metal mold | die of the same hollow rack bar manufacturing apparatus, and the core metal holder periphery in the state which press-fit of the metal core was completed. The principal part sectional view which shows the hollow rack bar which concerns on the 3rd Embodiment of this invention. The principal part sectional drawing which shows the hollow rack bar which concerns on the 4th Embodiment of this invention. The principal part sectional drawing which shows the hollow rack bar which concerns on the 4th Embodiment of this invention. The principal part sectional drawing which shows an example of the conventional metal core. The principal part sectional drawing which shows the state which inserted the concentric metal bar into the pipe. Sectional drawing which shows the principal part which shows the conventional hollow rack bar.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,10A ... Core metal, 11 ... Bar, 21, 22, 23 ... Projection part, 100, 200 ... Hollow rack bar manufacturing apparatus, 110, 211 ... Lower mold, 120, 212 ... Upper mold, 130, 213 ... Teeth Mold, 220 ... cored bar holder, 230 ... first cored bar, 240 ... second cored bar, 250 ... cored bar guide, 300, 300A, 300B ... hollow rack bar, P ... pipe (hollow material), Pa: Flat part.

Claims (2)

A core metal used in a method of manufacturing a hollow rack bar by press-fitting a hollow material held in a mold into an internal cavity of the hollow material and projecting the hollow material from the inner diameter side toward the mold. In the 1 to M number cored bar set,
The core bar is a bar having a maximum cross-sectional area smaller than the minimum cross-sectional area of the hollow portion of the hollow material,
Protruding to this bar, the maximum protrusion amount gradually increases from No. 1 to M No., and provided with a protrusion whose maximum width is set constant,
The cored bar set, wherein the bar has a fixed taper angle so that the width gradually decreases toward the side opposite to the mold, with the protrusion being the maximum width. A hollow cylindrical portion having a tooth portion meshed with the pinion gear;
The cross-sectional shape of the hollow portion of the cylindrical portion is a first hollow portion located on the back side of the tooth portion,
A second hollow portion located on the opposite side of the tooth portion with respect to the center of the cylindrical portion with respect to the first hollow portion, and having a maximum inner diameter width larger than a maximum inner diameter width of the first hollow portion;
Provided at a boundary portion between the first hollow portion and the second hollow portion, and a projecting portion projecting to the inner diameter side,
The inner peripheral surface of the first hollow portion includes a straight portion, and one end is connected to the projecting portion, and the other end is combined with a pair of first curved portions each connected to both ends of the straight portion. And the straight line extending at both ends of the first curved portion is closed rather than parallel,
The hollow rack bar, wherein the second hollow portion includes a second curved portion having at least a semicircular portion provided on the opposite side of the linear portion with respect to the center of the cylindrical portion. .

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