KR101002987B1 - A method of producing hollow rack member - Google Patents

Abstract

The present invention relates to a method and apparatus for forging a rack bar used in a steering mechanism of a vehicle in a pipe, and aims to reduce costs by increasing the precision of the product and extending the life of the tool.

In order to preliminarily adjust the cross-sectional shape of the steel pipe, the steel pipe is passed through a die to reduce the diameter by swaging, and then the core bar is drawn from the center while the steel pipe is supported by a clamp mold having a predetermined cross-sectional shape on the outer periphery. Ironing. Accordingly, the cross section of the clamp die is set so that predetermined release of thick flesh is made at the ends of the axial length direction and the tooth width direction. After preliminary adjustment of the cross-sectional shape of the steel pipe, the teeth of the rack molding are formed on the outer peripheral side thereof. By supporting the core bar and pressing the core bar into the steel pipe to form a hollow rack member having a tooth shape on the outer circumference of the steel pipe by forging.

Description

A manufacturing method of hollow rack member {A METHOD OF PRODUCING HOLLOW RACK MEMBER}             

1 is a view showing a cross-sectional area management process of steel pipe by swaging and ironing.

FIG. 2 is a view showing the cross-sectional shape of the steel pipe after mold release, (A) is a cross-sectional view taken along the line A-A of FIG. 1, (B) is a cross-sectional view taken along the line B-B of FIG.

3 is a cross-sectional view of the rack bar forging device by a steel pipe.

4 is a bottom view of the mold in the rack bar forging apparatus of FIG.

FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 3, (a) when flattened, and (b) when a press-fit process of the core bar is shown.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 3, (a) when flattened, and (b) when the core bar is press-fitted.

Fig. 7 is a plan view of a rack bar obtained by forging, wherein (a) shows the present invention and (b) shows that they are obtained by conventional techniques.

8 shows another embodiment of a core bar.

FIG. 9 is a sectional view when forging in a mold by the core bar of FIG.

Fig. 10 shows another embodiment of the core bar.

FIG. 11 is a cross-sectional view when forging in a mold by the core bar of FIG.

Explanation of symbols on the main parts of the drawings

10: steel pipe made of steel

12: Swaging die

14 core bar 16 clamp mold

18: rack-shaped mold

20: upper mold 22: lower mold

24: support member 26: holder

28: tooth 30: lock member

32, 33: rack protrusion pin

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming a rack bar for use in a steering mechanism of a vehicle by forging by using a pipe as a material. .

The rack bar, which is a part of the steering system of a vehicle, is usually cut by a broach from a bar material filled with a center portion. However, in the variable gear ratio (so-called VGR) in which the inclined angle of the tooth is heavy because the center portion is filled and used for power steering, the width of the groove ( VIII) changes, so no machining is done in broach cutting. In addition, the invention regarding the forging of a hollow rack bar from a pipe material in order to enable weight reduction and the formation of a variable tooth is disclosed in Japanese Laid-Open Patent Publication. Japanese Patent Laid-Open No. Hei 5-89181, Japanese Laid-Open Patent Publication No. Hei 6-246379, and the like. However, the forging of the rack bars disclosed in these conventional techniques has various problems, and the present inventors have already proposed the improvement in Japanese Patent Application No. 2001-15439.

In forging molding of a hollow rack bar, the pipe material is supported by a metal mold having a tooth shape, and a core bar is pressed into a steel pipe supported by the metal mold to form a tooth shape. The rack teeth are formed by causing radial projection of the material to be directed (plastic flow of material metal). Therefore, it is important to manage the cross-sectional area of the material in order to mold the rack bar with the desired precision. However, in the supply phase from the maker, the inner and outer diameters and the thickness of the flesh are controlled only by predetermined tolerances such as JIS, which is a Japanese industrial standard. Insufficient precision, which causes a large fluctuation in metal flow and excessive forming force during the forging, as it is, which causes a decrease in product precision and tools. It was a heavy burden on the industrial equipment and shortened the life span. Also, in the quenching of post-processing, even if the hollow product is quenched by indenting the outer part into a divided mold, the movement due to heat torsion to the inner diameter is not possible. Since it cannot be restricted at all, it cannot prevent movement by insertion of a core bar as long as the inner diameter of a steel pipe is a tolerance of a commercial item. Therefore, quenching of the hollow rack bar requires a special construction method, which is a cause of an increase in cost because it requires more work process and time. In addition, forging causes the flow of metal in a direction in which the moving distance is short and easy to move. For this reason, in core rods having a uniform load-load shape in a simple and uniform cross-sectional area depending on the shape, it is easy to cause excessive shortage in metal flow and high performance cannot be obtained. In addition, a method of imparting non-uniform flow to the metal by manufacturing the shape of the plurality of core bars in an uneven shape has been proposed, but this method is very disadvantageous in terms of cost and effective in adjusting the axial metal flow. none.

The present invention has been made in view of the above problems, and relates to forging a rack bar from a steel pipe. The object of the present invention is to improve the precision of the product and to extend the life of the tool, thereby realizing cost reduction.

According to the invention described in claim 1, the steel pipe is supported by a rack molding tooth on its outer circumferential side, and a core bar is press-fitted into the steel pipe. In the method for manufacturing a hollow rack member by forging a hollow rack member according to the tooth shape on the outer circumference of the steel pipe, the cross section of the steel pipe by plastic working prior to forging A manufacturing method of a hollow rack member is provided, including a step of adjusting a shape.

Referring to the action and effect of the invention of claim 1, in the present invention, the hollow rack bar is formed by inserting a core bar into a steel pipe supported by a tooth. The material flows plastically toward the tooth by the insertion of the core bar. And the adjustment of the cross-sectional shape of the steel pipe by plastic processing prior to the forging process ensures the proper metal flow to the teeth, so that the cutting process is performed to obtain high precision of the final product in the tolerance of several tens of micro units. In addition, it is possible to realize an appropriate load on the teeth and to extend the service life thereof. In addition, the precise control of the inner diameter of the member in a few microns by adjustment enables press-in hardening with inserting the right core bar when quenching in post-processing, and minimizes hardening distortion. Therefore, the shape, the dimension tolerance, the material of the insert core bar used in the quenching treatment, the shape of the high frequency coil, the frequency, the magnetic density, the swirl current, etc. By the suitable choice, an ideal quenching product can be obtained at low cost.

According to the invention of claim 2, in the invention of claim 1, the step of adjusting the cross-sectional shape of the steel pipe by plastic working comprises a step of forming the cross-sectional shape of the steel pipe into a predetermined shape. Provided is a method for preparing.

Referring to the action and effect of the invention of claim 2, the material flows into the tooth by the press-in of the core bar, but the molding is performed, but the inner diameter side of the end of the axial movement is farther than the monotonous flow into the tooth. Since a part flows to the release part of the axial direction or the tooth width direction which is short and easy to move, the tooth-forging amount of this part becomes insufficient. This causes a lack of rack accuracy. In the present invention, the cross-sectional shape of the steel pipe is formed into a predetermined shape such as a circular shape or a mold release shape before the press fitting step, and the thickness of the flesh of the cross-section is increased in the part where the flow becomes insufficient in that state. By doing so, the flow shortage can be corrected and a desired forging process can be performed. In addition, in tooth forging, it is not necessary to protrude uniformly over the entire tooth width, but may have an occlusal width with a pinion sufficient for force transmission. Therefore, both sides of the forged tooth width are usually open. However, in that state, there is a possibility that the amount of movement of the flesh in the tooth width direction increases, resulting in a lack of occlusion. In the invention of claim 2, it is desired to make the cross-sectional shape of the steel pipe uneven by managing the cross-sectional shape by ironing before forging molding, that is, by increasing the flesh thickness of the steel pipe at the ends in the longitudinal direction and the width direction. You can get the flow of flesh. In other words, the management of the non-uniform cross-sectional shape is based on the expansion of the groove width and the movement of the core bar by the change of the pitch and inclination angle due to the miter gear and VGR. To cope with the shortage of both ends of the open teeth in the axial direction of the teeth forming portion, the shortage of both ends of the left and right ends of the width of the forged teeth. As a result, the moving distance of the metal is made uniform, so that it is possible to suppress molding force, prolong tool life, improve accuracy, and increase occlusion rate by releasing only a single clamp mold without performing uneven shaping of a plurality of core bars. This can be

According to the invention as set forth in claim 3, in the invention as set forth in claim 1, the step of adjusting the cross-sectional shape of the steel pipe by plastic working is a diameter reduction step by swaging and ironing subsequent thereto. Provided is a method for producing a hollow rack member, comprising a complex step of applying a predetermined cross-sectional shape imparting step by ironing.

Referring to the action and effect of the invention of claim 3, a desired cross section including a diameter of the steel pipe by swaging and then an uneven flesh with a desired thickness of flesh at a desired outer diameter by ironing. Prior to forging the shape, it can be given to steel pipes, which contributes to improved product accuracy and longer tool life.

According to the invention according to claim 4, in the manufacturing method of the hollow rack member, as a preliminary molding step, in a state in which a clamp die is arranged to reduce the diameter by swaging and then impart a predetermined shape to the outer circumference. By pulling out the core bar, ironing is performed on the inner diameter side of the steel pipe, thereby providing a cross section of a predetermined shape in the axial direction and the radial direction with respect to the steel pipe. As a forming process, the steel teeth are supported on the outer surface of the steel pipe by press-fitting the core bar for rack molding into the inner diameter cavity while supporting the steel pipe from the outer circumference with a mold for rack tooth shaping. A method for producing a hollow rack member is provided, which is forged and molded.

Referring to the action and effect of the invention of claim 4, the outer diameter and the cross-sectional shape of the core bar can be adjusted as desired by drawing the core bar in a state in which the diameter of the core is reduced by swaging and the clamp mold is placed on the outer circumference. Since it is controlling, the precision of the product by the rack shaping | molding by the support of the metal mold | die afterwards and the insertion of the forging core bar can be improved, and the lifetime of a tool, such as a tooth, can be extended.

According to the invention as set forth in claim 5, the hollow rack member according to the teeth is formed on the outer circumference of the steel pipe by supporting the steel pipe by a clamp mold having a rack forming tooth on the inner circumference thereof and pressing the core bar into the steel pipe. In the method of manufacturing a hollow rack member formed by forging, the hollow rack member is characterized in that when the core bar is press-fitted, the core bar is projected and forged while simultaneously projecting the core bar in a different direction from the axial direction of the teeth. Provided is a method for preparing.

Referring to the action and effect of the invention of claim 5, the core bar is formed of a mountain or curved portion having different teeth by forming a plurality of head portions in the core bar, or by forming an inclined groove in the head portion. As forging proceeds while simultaneously protruding and polymerization, the load becomes more uniform, the core bar is press-fitted, and the load applied to the tooth is reduced, and the life of the die can be extended.

According to the invention as set forth in claim 6, the steel pipe is supported on its outer circumference and has a mold for rack forming on its inner circumference, and is pressed into the steel pipe supported by the mold to protrude the steel pipe toward the tooth so as to protrude to the outer surface of the steel pipe. In the forging molding apparatus of a hollow rack member having a core bar having a widening portion forming a rack tooth, the core bar simultaneously protrudes at a portion different from the axial direction of the tooth. A forging molding apparatus for a hollow rack member is provided, which includes a forging action means configured to forge.

Referring to the action and effect of the invention of claim 6, since the forging proceeds while the tooth is polymerically protruding from the other acid or curved portion, the core bar is press-fitted in the core bar while the load becomes more uniform as in the invention of claim 5 As a result, the load on the teeth is reduced, and the life thereof can be extended.

According to the invention according to claim 7, in the invention according to claim 6, the forging action means is a forging molding apparatus of a hollow rack member, characterized in that it consists of a plurality of enlarged head portion that the working diameter is sequentially expanded Is provided.

Referring to the action and effect of the invention of claim 7, the forging proceeds while the tooth is protruded synchronously and polymerization reliably with the other series by the formation of a series of enlarged portions having an enlarged working diameter sequentially. The load applied to the rod can be further dispersed, and the tooth life can be reliably extended.

According to the invention according to claim 8, in the invention according to claim 6, the forging action means is formed so as to be inclined in the inverse direction to the inclination direction of the tooth shape and in the axial direction, and is formed at intervals in the axial direction. Provided is a forging molding apparatus for a hollow rack member, comprising a plurality of oil grooves.

Referring to the operation and effect of the invention of claim 8, by forming a plurality of oil grooves inclined in the inverted direction of the tooth shape in the broadened portion, the polymerizable protrusion action similar to the invention of claim 7 can be performed. The structure of the bar becomes simpler, so that the cost is reduced, and the formation of the oil grooves enables smooth protrusion.

According to the invention according to claim 9, there is provided a hollow rack member comprising a mold supporting a steel pipe, a holder for inserting a tooth, and a core bar press-fitted into the steel pipe supported by the mold to forge the rack teeth according to the tooth shape of the steel pipe. In the forging molding apparatus, the forging molding apparatus of the hollow rack member, characterized in that the tooth insertion opening portion is formed through the holder, the tooth is supported by the tooth insertion opening portion. Is provided.

Referring to the action and effect of the invention of claim 9, by making the tooth insertion opening in the holder a through hole, the precision of machining increases, and as a result, the load applied to the tooth is homogenized, and the life of the forged molding tooth is improved along with the life extension. We can plan.

According to invention of Claim 10, in the invention of Claim 9, the forging molding apparatus of a hollow rack member is provided in which the tooth insertion opening part forms large R part in the both ends.                     

Referring to the operation and effect of the invention of claim 10, the tooth insertion opening can form large R portions at both ends thereof, thereby preventing concentration of stress and contributing to extending the life of the tooth holder.

According to the invention of claim 11, in the invention of claim 9, there is provided a forging molding apparatus for a hollow rack member, comprising a built-in cylinder for mounting the holder to a mold.

The built-in cylinder simplifies the structure and contributes to cost reduction. In addition, if the built-in cylinder is made sealless, the working oil may leak, but it can be soaked by proper surface roughness treatment, and since the holder is immersed in lubricating oil from the beginning, It is practically harmless to seep the hydraulic oil from the lease.

(Example)

Hereinafter, a series of steps for forming a rack bar according to the present invention will be described in order. Before the forging, the cross-sectional shape is first adjusted as a preparation step. In other words, as a pipe material, which is a raw material, it is supplied by a steel pipe maker, but has an error corresponding to the tolerance of JIS, which is a Japanese industrial standard. This is not the case, and this causes a decrease in accuracy and shorten the life of tools such as teeth when forging a tooth by press-fitting a core bar. In the present invention, the desired cross-sectional shape can be obtained by plastic working (swaging and ironing). In Fig. 1, 10 is a steel pipe made of steel, and 12 is a die for swaging. In step (a), the steel pipe 10 is supported by a suitable means, and then the die 12 is moved in the direction of the arrow a, and step (b) shows the state in which the die 12 is moved, and the steel pipe 10 is the outer diameter thereof. This die 12 is reduced to the inner diameter. The dice 12 are then moved in the opposite direction to return as indicated by arrow a 'and removed from the steel pipe 10 after the diameter is reduced. In this way, the diameter reduction of the steel pipe 10 by plastic working is completed by swaging.

Next, a molding process to a predetermined shape such as mold release of the cross-sectional shape of the steel pipe 10 will be described. In this embodiment, rack forging in the present process described later will be described. ), Cross-sectional mold release is performed to secure the width of the teeth at both ends of the rack. In the case of rack forging, the head of the forging core bar is pushed into the steel pipe to protrude radial flesh, and the teeth of the forging core bar are formed in the steel pipe. The movement of the flesh in the axial direction is large, the movement of the flesh in the width direction is insufficient, and the width of the teeth becomes short, so that the rack teeth tend to become flat in a planar view when viewed from above. To eliminate the tendency of the tooth width at both ends of the rack to be insufficient, and to secure the required tooth width at both ends of the rack, a steel pipe shape of a cross section can be obtained so that the thickness of the flesh at both ends of the steel pipe can be thickened. In other words, in (c), the cross-section forming means of the steel pipe is composed of a core bar 14 and a clamp die 16 for imparting a predetermined shape. The clamp metal mold | die 16 which gives a predetermined shape is comprised from the upper and lower halves 16-1 and 16-2. In step (c), the core bar 14 shows the state inserted into the steel pipe 10. The core bar 14 is provided with the enlarged head 14-1 for ironing at the front-end | tip. On the other hand, the upper and lower halves 16-1 and 16-2 are in an open state. In this state, the upper and lower halves 16-1 and 16-2 are opposed to each other as shown by the arrows, or either one of the halves 16-1 and 16-2 is moved to (d). As shown, the upper and lower halves 16-1 and 16-2 are coalesced to reduce the outer diameter of the steel pipe 10 in contact with the upper and lower halves 16-1 and 16-2. FIG. 2 (A) shows cross-sectional shapes of the upper and lower halves 16-1 and 16-2 cut along the AA line in FIG. 1 (D), and the inner peripheral surface of the upper and lower divided molds. Both 16-1a and 16-2a form a semicircle shape. 2 (B) shows the cross-sectional shapes of the upper and lower halves 16-1 and 16-2 of the both ends of the metal mold cut along the BB line of FIG. 1 (D). -2b has a semi-circular shape, but the upper portion of the divided mold 16-1 has a deformed shape in which both ends protrude. Of course, it can also be easily non-uniformized into the shape of the BB line portion, that is, the cross-sectional shape of Fig. 2B over the entire length of the ironing process including the AA line portion.

The cross-section mold release process of the steel pipe is performed by swaging by pulling out the core bar 14 in the direction of the arrow b in the state shown in Fig. 1 (d). In the drawing of the core bar 14, the head 14-1 is slightly larger than the inner diameter of the steel pipe 10 of the portion supported by the clamp mold 16, which gives a predetermined shape, and is formed at both ends of the clamp mold 16, which gives a predetermined shape. The protruding portion 16-1b of Fig. 1 exists. Therefore, the flow of the flesh by swaging also occurs in the protruding portion 16-1b, and as shown in Fig. 2B, the portion of the steel pipe 10 at both ends of the mold has a thick thickness of the flesh on both shoulder portions 100 of the upper surface. It shows the release cross section which becomes. Fig. 1 (e) shows the state after removing the core bar 14, and also shows a portion 100 of the steel pipe which becomes both ends of the rack teeth whose thickness is thickened by cross-sectional release. The mold width | variety which thickens the site | part of the steel pipe 10 in such both ends of a metal mold | die can ensure | secure the tooth width | variety in the rack both ends in rack forging.

In the description of the above embodiments, the mold release is to secure the tooth width at both ends of the mold 16 by thickening the steel pipe 10 at both ends of the mold, but the mold release event in the present invention is in the tooth width direction. It can also be usefully used as a solution to measures for the flow of flesh at both ends. That is, even in the center part of a metal mold | die, a flow of flesh may generate | occur | produce in the both ends of a tooth width direction, and this causes a lack of the height of the teeth in both ends of a tooth width direction. As a countermeasure against this, both ends of the teeth can be demolded according to Fig. 1 (e) even at the center of the mold, so that the thickness of the flesh can be thickened. Since there is room in the amount of flesh, the lack of height of the teeth at both ends of the tooth width can be avoided.

In the above-mentioned cross-sectional release process, the steel tube 10 is strongly clamped by the clamp mold 16 which gives a predetermined shape, and the thickness of the wall thickness is strongly compressed by the core bar 14, and the flesh is reduced (ironing). The surface roughness of the inner and outer diameters of the inner and outer diameters is obtained by transferring the surface roughness of the clamp mold 16 and the core bar 14, which give a predetermined shape, to the surface roughness of several microns, such as the surface roughness of 1 to 2 µm. Machining of the outer diameter tolerance can be facilitated.

3-7 show the metal mold | die 18 for shape | molding the inclined tooth-shaped rack member from the steel pipe preformed as mentioned above. The rack molding mold 18 has an upper mold 20 and a lower mold 22. The upper die 20 is composed of a support member 24, a holder 26, a tooth 28, a lock member 30, and rack protrusion pins 32 and 33. The tooth 28 has a concave-convex portion 28-1 on its lower surface, and the concave-convex portion 28-1 has a shape corresponding to the teeth of the rack member to be forged formed. Fig. 7A is a plan view of the forged rack member 34. In this embodiment, the rack member 34 to be formed by forging is intended to have an inclined tooth 34-1. The rack serrated uneven portion 28-1 of the teeth 28 is also inclined according to the teeth of the rack member. Holder 26 is fixed to support member 24 by suitable means. The holder 26 forms a penetrating, elongated tooth insertion opening 26A for accommodating the teeth 28. The teeth 28 are mounted on the tooth insertion openings 26A with the liner 33 fitted to the protruding surface with the support member 24. As shown in Fig. 3, in the state where the teeth 28 are attached to the opening 26A, the uneven portions 28-1 of the lower surface of the teeth 28 slightly protrude from the teeth holder 26. The lock member 30 is driven between the opposing wall surface of the opening 26A while the teeth 28 are mounted, and since the lock member 30 has a tapered shape, the teeth 28 are inserted into the holder 26 by inserting the lock member 30. It is firmly fixed. The holder 26 is provided with the cylinder part 26-1, and the rack protruding pins 32 and 33 slide in this cylinder part 26-1. The rack protruding pins 32 and 33 are pushed out by the switching in the inflow direction of the hydraulic pressure to the cylinder portion 26-1, and the protruding operation allows the rack member to protrude after the forging. Done. The rack protruding pins 32 and 33 can omit the seal parts which are needed more in a normal hydraulic cylinder if the hydraulic release operation can be performed, and the structure can be simplified as much. In addition, although the hydraulic piping and the switching valve of the outgoing movement of the rack protrusion pins 32 and 33 are required, it is abbreviate | omitted in the figure for simplicity.                     

Prior to the forging of the rack teeth, the upper mold 20 and the lower mold 22 are moved together to face each other with the steel pipe 10 interposed therebetween, and the state of the coalescence is shown in FIG. At this time, as shown in Figs. 5A and 6A, the uneven portion 28-1 of the tooth 28 is in contact with the upper surface of the steel pipe 10, and the upper surface of the steel pipe 10 is in contact with the uneven portion 28-1 of the tooth 28. The in-rack forming surface 10A becomes a substantially flat shape by pressure. In the preliminary molding step shown in Fig. 6A, the part 100 where the thickness of the flesh became thick due to the swaging in the preforming step is thus formed at both ends of the rack forming surface 10A having a substantially flat shape by pressure. Located in

In FIG. 3, the forging core bar 40 is disposed to face the opening of the steel pipe 10. In the figure, only one side of the forging core bar 40 is shown in the drawings, but as disclosed in the applicant's application, the forging core bar 40 is installed on both sides to influence the indentation of the core bar 40 into the steel pipe 10. By repeating with each other in the forging of the rack member is made. The core bar 40 is located behind the guide portion 40-1 at the distal end and the plurality of enlarged portions 40-2, 40-3 and the enlarged portions 40-2, 40-3 whose working diameters are gradually expanded. (Iii) oil grooves 40-4, 40-5 are provided, and the widened portions 40-2, 40-3 act on the portion of the steel pipe flattened by the teeth 28 in the radial direction, that is, the uneven portion 28-1. The plastic flow of the raw material to the concave portion in the steel sheet is caused, and the rack teeth according to the shape of the uneven portion 28-1 can be forged into the steel pipe. 5 and 6, (b) shows a state in which the core bar 40 is press-fitted into the steel pipe 10. The insertion of the core bar 40 protrudes radially outwardly of the flat portion 10A of the steel pipe to 10 " The portion of the flesh shown flows into the concave portion in the uneven portion 28-1 of the tooth 28, so that the rack teeth 34-1 in Fig. 7 are formed, and in the tooth center portion in Fig. 5, the entire tooth width direction is shown. The flow of the flesh is relatively smooth, so that the desired tooth width can be obtained, but both ends of the tooth (both ends of the rack forming surface 10A) tend to flow in the axial direction or the tooth width after forging in the state tends to be insufficient. As shown in Fig. 7 (b), the width of the tooth is large at the center and small at both ends. However, in the present invention, both ends of the portion of the steel pipe in contact with the uneven portion 28-1 of the tooth 28 are mold-released so that both sides thereof become thick portions 100 as shown in FIG. Therefore, as shown in Fig. 6B, when the core bar 40 is press-fitted, it has room to flow to both ends of the tooth width, so as shown in Fig. 7A, both ends from the center It is possible to set it as the rack member 34 provided with the tooth | gear part 34-1 by which the width | variety is provided until it reaches.

As described above, that is, when forging by forging from the inner diameter side by the core bar, the front and rear ends of the tooth forgings in the axial length direction become open portions where metal flow is likely to occur. In order to suppress the decrease of the flesh, as shown in Fig. 2 (B), the mold release processing is performed so that the thickness is t2 with respect to the flesh thickness t1 at the center of the tooth width of the tooth forging site, and thus Securing a predetermined tooth width at an open portion where movement is likely to occur can be realized with only one type. In addition, although the left and right ends in the axial length direction of the tooth forging part are open parts where metal flow is likely to occur, the same mold release can also be performed in this part. By increasing the thickness of the flesh of the open portion where such metal flow is likely to occur, a desired tooth width can be secured. Conventionally, although coping was carried out by using a plurality of mold release core bars, it was not possible to cope with the movement of an axis length direction also by this. The present invention is excellent in that both mold movements in the tooth width direction and the axial direction can be coped with simultaneously by releasing only one mold.

8 and 9 show another embodiment of the forging molding core bar according to the present invention. In this embodiment, the core bars 140 are inclined with respect to the center portions 143 of the widened portions 140-1 and 140-2. The inclination angles of the widespreads 140-1 and 140-2 are represented by θ, and the inclined angles are simultaneously projected to a plurality of adjacent tooth grooves of the teeth 128 by one wider 140-1 or 140-2. (The flow of the flesh of the material to the teeth 128). For example, in Fig. 9, the first enlarged portion 140-1 protrudes from the adjacent grooves 128-1 and 128-2 of the teeth 128, and the second enlarged portion 140-2 protrudes from the adjacent grooves 128-3 of the teeth 128. , Protruding from 128-4. These teeth 128 are protruded from the core bar 140 to the teeth 128 by the simultaneous protruding action of one tip 140-1 or 140-2 to the adjacent grooves 128-1, 128-2 or 128-3, 128-4. The load applied can be dispersed, and the life of the core bar or the tooth can be extended.

10 and 11 show a core bar 240 of another embodiment, wherein the core bar 240 is sloped and has a gently inclined broadening portion, and an oil groove 240- inclined in a mountain shape on the broadening portion. 1 is formed in parallel a plurality at intervals. Therefore, continuous engagement of four to six stages or more can be achieved to obtain smoother movement of the load. In other words, in this embodiment, it can be achieved by one slope surface which continues the equivalent amount of protrusion by the widened portion corresponding to 4 to 6 steps. In addition, since a plurality of oil grooves can be easily formed in post-processing while inclining the oil groove, the processing cost of the core bar required before and after ten can be greatly reduced. As a modified embodiment, instead of the mountain groove 240-1, a plurality of simple side-by-side inclined grooves may be used.

As described above, in the forging of the hollow rack bar, it is important to manage the cross-sectional area of the pipe material which is a raw material. However, the pipe material supplied from the manufacturer is insufficient in precision for forging molding materials, which causes a drop in product precision and excessive burden on the tool, causing shortening of life. However, according to the forging of the hollow rack bar of the present invention, it is possible to forge the rack bar from the steel pipe to improve the precision of the product, as well as to extend the life of the tool, thereby reducing the cost.

According to the invention of claim 1, by adjusting the cross-sectional shape of the steel pipe by plastic working prior to the forging process, high precision of the final product can be obtained, and the load applied to the teeth can be optimized and its life can be extended.

According to the invention of claim 2, it is possible to obtain a desired flow of flesh by non-uniformizing the cross-sectional shape of the steel pipe by managing the cross-sectional shape by ironing before forging. Accordingly, by releasing only one clamp mold, it contributes to suppressing molding force, extending tool life, improving accuracy, and improving occlusal rate.

According to the invention of claim 3, it is possible to improve the accuracy of the product and to prolong the life of the tool.

According to the invention of claim 4, since the outer diameter and the cross-sectional shape of the core bar are controlled as desired, the accuracy of the product can be increased and the life of the tool such as the tooth can be extended.

According to the invention of claim 5, since the forging proceeds while the core bar protrudes simultaneously and polymerization with other teeth or curves, the load applied to the tooth can be reduced and the life thereof can be extended.

According to the invention of claim 6, since the forging proceeds while the teeth protrude polymerically with other acids or curved portions, the load applied to the teeth can be reduced and the life thereof can be extended.

According to the invention of claim 7, since the forging proceeds while the tooth is protruding synchronously and polymerization with another series of parts reliably, the load applied to the tooth is further dispersed, and the life of the tooth can be reliably extended.

According to the invention of claim 8, the structure of the core bar is simpler, and the cost is reduced, and smooth protrusion can be achieved by the formation of the oil groove.

According to the invention of claim 9, the precision of machining can be increased, and the precision of forged molding teeth can be improved with the extension of its life.

According to the invention of claim 10, the tooth insertion opening can prevent the concentration of stress to extend the life of the tooth holder.

According to the invention of claim 11, by using the built-in cylinder, the structure can be simplified and the cost can be reduced.

Claims (11)

The steel pipe 10 is flattened by pressure on the rack forming surface 10A of the steel pipe by a rack molding die 18 on its outer peripheral side. And the rack forming surface 10A of the rack forming surface 10A of the steel pipe 10, which is supported in the above-described state and flattened by pressure by pressing a core bar 14 into the steel pipe 10. In the manufacturing method of the hollow rack member which is shape | molded by the forging process in a tooth shape according to the metal mold | die 18, Prior to the forging step, wherein the steel pipe 10 is flattened by pressure and subsequently press-molded the core bar 14 to mold the teeth. The outer diameter of the steel pipe 10 whose diameter is enlarged by swaging, and which the diameter is subsequently expanded, corresponds to both ends of the rack forming surface 10A of the steel pipe 10. The inner diameter of the steel pipe 10 is ironed by ironing while being supported by a clamp mold 16 having a protruding portion radially outward from a circular shape at both ends of the inner peripheral portion. Adjusting the inner and outer diameters and forming a cross-sectional shape of the steel pipe 10 into a mold in which both shoulders protrude in a portion corresponding to both ends of the rack forming surface 10A. Adjusting the inner and outer diameters and flattening by pressure against the steel pipe 10 after the release mold, and subsequently adding to the forging process consisting of forming a tooth by press-fitting the core bar 14. Method of manufacturing a hollow rack member as claimed. delete delete delete delete delete delete delete delete delete delete

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