JP4610405B2 - Hydroform method and apparatus - Google Patents

Description

The present invention relates to hydroforming method and apparatus for producing such A box Le housing.

  In general, as shown in FIG. 10, an axle housing 101 of a vehicle includes a banjo portion 102 that extends in the width direction of the vehicle and accommodates a differential at a central portion in the longitudinal direction. The shape of the banjo portion 102 is determined in order to secure a differential storage space, and the conventional product has a curved shape. Further, the banjo part 102 is not symmetrical with respect to the axle because of the cover part 103 projecting toward the vehicle rear side.

  Conventionally, in such an axle housing 101, as shown in FIG. 11, a plate material or the like is pressed to form a halved housing member 104, a hemispherical cover member 105, and a plurality of triangular plates 106, which are welded together. (See, for example, Patent Document 1).

  For this reason, there is a problem that the number of parts increases and the welding assembly cost increases. In addition, the plate thickness of each member is difficult to ensure the penetration rate of the weld at 100%, so it is assumed that the penetration rate is about 70% to 80%, and the strength is ensured by the penetration rate. It was set to be possible. Therefore, the axle housing 102 has a plate thickness that is excessive than the plate thickness that should be originally required.

  Therefore, for example, Patent Document 2 proposes that an axle housing is manufactured by expanding the pipe material with hydroform in order to reduce the number of welds.

  According to this, as shown in FIG. 12, the axle housing 107 is divided into left and right shaft pipe portions 108 and 109 and a banjo portion 110, and the axle housing 107 is divided into left and right shaft pipe portions. After 108 and 109 and the banjo part 110 are each formed by hydroforming, they are manufactured by welding them. Thereby, compared with the axle housing 101 of FIG. 10, the number of parts reduces and a welding location can be reduced.

Japanese Patent Laid-Open No. 9-300904 JP 2004-291926 A

  By the way, in general, the circumference of the banjo part is longer than the circumference of the shaft tube part. For example, in the axle housing for a drive shaft of a small truck, the circumference is about 2.5 times the circumference of the shaft tube part. Have For this reason, if the entire axle housing is to be molded integrally with hydroform, the banjo portion is molded with a large tube expansion ratio, and there is a risk of rupture. If the axial push amount is increased in order to prevent the burst, buckling may occur due to the non-axisymmetric shape.

  In order to prevent rupture, for example, it is conceivable to mold while holding the banjo part with a counter punch. However, as described above, the conventional axle housing has a curved banjo part, so the counter punches interfere with each other. It was difficult to install without it.

  In patent document 2, the banjo part 110 is shape | molded from a pipe material with a diameter larger than the axial pipe parts 108 and 109, the pipe expansion rate is reduced and the burst is prevented. Therefore, it becomes a three-part welded assembly structure, and the disadvantages of welding cannot be completely eliminated.

  Thus, since the conventional axle housing requires joining by welding, it has been difficult to reduce the manufacturing cost and reduce the weight.

An object of the present invention, the above problem was solved is to provide a reduction in manufacturing cost, the Ruha Hydro foam method and apparatus can be achieved and weight.

In order to achieve the above object, the present invention accommodates a cylindrical tube material in a mold, applies fluid pressure to the tube material to form shaft portions at both ends, and places the tube material between the shaft portions. This is a hydroforming method of expanding a tube to form a tube expansion portion comprising a central tube portion having a polygonal cross section at the center portion and different diameter tube portions formed by connecting both sides of the center tube portion and the shaft portion. Then, a groove part for forming the shaft part in the mold and a recess part for forming the tube expansion part at the center part of the groove part are formed, and on the other hand, one surface of the center cylinder part is moved in the radial direction. A free-form center forming plate and a pair of tiltable tilts that are supported by a long hole provided on both sides of the center-forming plate so as to be rotatable and movable along the longitudinal direction and form one surface of the different-diameter pipe portion. The center forming plate moves radially outward by the tilting of the inclined forming plate. The formed link member is formed, and the formed link member is provided in the recess along the axial direction of the tube material at a plurality of intervals in the circumferential direction in the recess, and the formed link member is inclinedly formed in the recess. When a plate is opened to a tube expansion molding position where it abuts against the inner surface of the recess, a fixed molding surface is formed to mold the axial surface of the tube expansion portion between the molding link members, and fluid pressure is applied to the tube material. When the forming link member opens to the tube expansion forming position, the tube expanding portion is formed by the forming link member and the fixed forming surface .

In order to achieve the above object, the present invention accommodates a cylindrical tube material in a mold, applies fluid pressure to the tube material to form shaft portions at both ends, and places the tube material between the shaft portions. and tube expansion, a central cylindrical portion of the polygonal section in the center, met hydroforming apparatus for forming a tube expansion portion made of a different diameter pipe portion formed by connecting the both sides and the shaft portion of the central cylindrical portion Then, a groove part for forming the shaft part in the mold and a recess part for forming the tube expansion part at the center part of the groove part are formed, and on the other hand, one surface of the center cylinder part is moved in the radial direction. A pair of freely adjustable central molding plates and a pair of tiltable moldings that form one surface of the above-mentioned different-diameter pipe portion that is supported by the elongated holes provided on both sides of the central molding plate so as to be rotatable and movable along the longitudinal direction . Ri Do and a tilt forming plate, move the central molding plate radially outwards tilting of the tilt forming plate Together they constitute a form link member, provided at a plurality intervals in the circumferential direction of the recess and the molded link member along the axial direction of the pipe member within the recess, in the recess, tilt forming of the molded link member plate forms a fixed molding surface for molding the axial direction of the surface of the expanded portion between the molded link member when opened to bulge forming position abutting the inner surface of the recess, as well as imparting fluid pressure to the tubing in When the forming link member opens to the tube expansion forming position, the tube expanding portion is formed by the forming link member and the fixed forming surface .

  According to the present invention, the excellent effect of reducing the manufacturing cost of the axle housing and reducing the weight can be achieved.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  First, the structure of the axle housing of this embodiment will be described based on FIG.

  The axle housing 1 of the present embodiment is used, for example, for storing a drive shaft of a small truck, and is arranged extending in the vehicle width direction. The axle housing 1 has a banjo part 2 formed at the center in the longitudinal direction and enlarged in the vertical direction and the rearward direction of the vehicle, and an axial tube formed by extending from the banjo part 2 to both sides in the vehicle width direction. Part 4.

  The banjo part 2 of the present embodiment includes a central cylinder part 5 formed in a polygonal shape (specifically, a hexagon formed by dividing an octagon into two parts), and the longitudinal length of the central cylinder part 5. It consists of different-diameter pipe parts 6 and 6 formed by connecting both ends in the direction and the shaft pipe part 4 (tube material), and has a hexahedral shape as a whole.

  The shaft tube portion 4 includes a shaft portion 8 having a substantially rectangular cross section, a cylindrical end portion 9, and a tapered portion 10 formed by connecting the shaft portion 8 and the end portion 9.

  In the present embodiment, the above axle housing 1 is obtained by integrally forming a pipe material by hydroforming, and the banjo part 2 is formed from the pipe expansion part of the pipe material.

  Next, a schematic structure of a hydroform apparatus for manufacturing the axle housing 1 of the present embodiment will be described.

  As shown in FIG. 2, the hydroform apparatus 20 includes a mold 22 for housing a pipe material (element tube) 21, a plurality of forming link members 24 provided in the mold 22, and a fluid pressure in the pipe material 21. Fluid pressure applying means, and a shaft pressing device that presses the tube material 21 in the axial direction (left-right direction in FIG. 2) inward (that is, axially presses).

  The fluid pressure applying means applies fluid pressure to the tube material 21 by injecting a fluid (preferably liquid, specifically water) into the tube material 21, and the pump, the pump and the tube material 21 (Not shown).

  The shaft pushing device is fitted into a groove portion 71 of the lower mold 41 to be described later, and has a pair of shaft pushing tools 25 having a substantially rectangular parallelepiped outer shape, and the tube material 21 is compressed in the axial direction via the pair of shaft pushing tools 25. And a shaft pushing cylinder (not shown). Each axial pushing tool 25 has a cylindrical shape whose outer side in the axial direction is closed, and its inner peripheral surface 26 has the same shape as the outer shape of the end portion 9 and the tapered portion 10 (see FIG. 1) of the axle housing 1. It is formed. Each axial push tool 25 is provided with a convex portion 28 protruding inward in the axial direction, and a through hole (not shown) for communicating the inside of the tube material 21 with the fluid pressure applying means. A fluid is injected into the tube material 21 through the through-hole, and both ends of the tube material 21 are sealed by the axial push tool 25.

  The mold 22 has a substantially rectangular outer shape, and accommodates the tube material 21 with the axial direction of the tube material 21 aligned with its longitudinal direction (left-right direction in FIG. 2). In the present embodiment, the mold 22 is divided into an upper part and a lower part and includes an upper mold 31 and a lower mold 41.

  First, the upper mold 31 will be described with reference to FIGS. 6 is a view taken in the direction of the arrow A in FIG. 2, and the support shaft 68 and the shaft 70 show only the shaft core.

As shown in FIG. 2, a concave portion 32 is formed on the lower surface of the upper mold 31 so as to extend upward from the center in the longitudinal direction (left-right direction in FIG. 2) and the width direction (front-back direction in FIG. 2). The The recess 32 defines a funnel-shaped space S that is upside down. More specifically, the concave portion 32 is formed in the central portion and has a substantially rectangular cross-sectional guide groove 33 passing through the upper die 31 in the vertical direction, and the longitudinal direction from the lower end portion of the guide groove 33 to the lower surface of the upper die 31. (The left and right directions in FIGS. 2 and 3) Two substantially rectangular first inner surfaces 34 (see FIGS. 2 and 3) that respectively incline and extend outward, and the lower surface of the upper die 31 from the lower end of the guide groove 33. Two substantially rectangular second inner surfaces 35 (see FIG. 4 and FIG. 5) each extending obliquely outward in the width direction (left and right direction in FIGS. 4 and 5), and the first inner surfaces 34, 34 and the first It has four substantially triangular third inner surfaces (not shown) formed between the two inner surfaces 35, 35. A step portion is provided between the first inner surface 34 and the third inner surface, and the first inner surface 34 is obliquely above the second inner surface 35 and the third inner surface by the thickness of an inclined molding plate 37 described later. Located in. Further, the end portion on the lower surface side of the upper die 31 in the first inner surface 34 is formed to be curved inward in the longitudinal direction, and comes into contact with the bearing portion 69 of the inclined molding plate 37.

  As shown in FIG. 2, in the concave portion 32 of the upper mold 31 described above, a portion projecting rearward in the vehicle traveling direction in the banjo portion 2 (the side surface shown by reference numerals 5a and 6a in FIG. One forming link member 24 for forming a portion corresponding to the portion 105 is provided.

  The forming link member 24 of the upper die 31 is disposed in the guide groove 33 and is movable in the vertical direction. The inclined forming plate 37 is rotatably provided on both sides in the longitudinal direction of the central forming plate 36. , 37.

  The central molding plate 36 has a substantially rectangular parallelepiped outer shape, and a lower surface thereof forms a molding surface 38. Above the central molding plate 36, a cylinder device 39 is provided that serves as a link driving means for moving the central molding plate 36 in the vertical direction. The cylinder device 39 is arranged such that the advancing / retreating direction of the piston 40 coincides with the vertical direction, and the tip of the piston 40 is fixed to the upper surface of the central molding plate 36.

  As shown in FIG. 6, comb teeth 61 are formed at both ends in the longitudinal direction (left and right direction in FIG. 6) of the central molding plate 36, respectively, into which comb teeth 65 of each inclined molding plate 37 described later can be fitted. Is done. The interval between the comb teeth of the comb tooth portion 61 is such that the comb teeth of the inclined molding plate 37 can be inserted between them, and the tube material 21 to which the internal pressure is applied does not enter between the comb teeth. Appropriately set in consideration of the wall thickness. Each comb tooth portion 61 is formed with two elongated holes 64 that extend in the longitudinal direction and support a support shaft 68 of an inclined molded plate 37 described later so as to be movable in the longitudinal direction, spaced apart in the longitudinal direction. . By the comb-tooth portion 61, the inclined molding plate 37 is rotatably supported by the central molding plate 36 without interference.

Returning to FIG. 2, each inclined molding plate 37 has a substantially rectangular plate shape, and its lower surface forms a molding surface 42. The inclined molded plate 37 is supported at its one end portion so as to be rotatable and movable in the longitudinal direction through the elongated hole 64, and at its other end portion through the shaft 70. Supported by Specifically, as shown in FIG. 6, at one end, a comb tooth portion 65 that can be fitted to the comb tooth portion 61 of the central molding plate 36, and the comb tooth portion 65 are arranged in the width direction (up and down in FIG. 6). And a support shaft 68 penetrating in the direction). The support shaft 68 is supported in the elongated hole 64 of the central molding plate 36 so as to be movable in the longitudinal direction. Further, as shown in FIG. 2, the other end portion, is formed a bearing portion 69 that mates with the shaft 70 extending in the upper die 3 1 width direction is provided in the recess 32, tilt forming plate 37 is rotatably Supported by As described above, the inclined molded plate 37 is supported so as to be tiltable in the vertical direction (in the radial direction of the tube material 21) as the central molded plate 36 moves.

In the formed link member 24 configured as described above, when the piston 40 of the cylinder device 39 is retracted upward, the central formed plate 36 moves upward, and each inclined formed plate 37 has the other end (the shaft 70). It pivots upward toward the center and one end moves outward in the longitudinal direction. That is, the forming link member 24 is opened upward. Further, when the forming link member 24 is opened until the back surface (upper surface) of the inclined forming plate 37 comes into contact with the first inner surface 34 of the recessed portion 32 (see FIG. 3), the forming surface 42 of the inclined formed plate 37 becomes the recessed portion 32. In contact with the second inner surface 35 and the third inner surface. In this embodiment, at this time, the forming link member 24 is positioned at the tube expansion portion forming position. In addition, the second inner surface 35 and the third inner surface of the recess 32 of the upper die 31 are fixed so as to form a circumferential surface between the forming link members 24 when the forming link member 24 is opened to the tube expansion portion forming position. Make the molding surface.

  Next, the lower mold | type 41 is demonstrated based on FIG. 7 and FIG. 7 and 8 are plan sectional views of the hydroform apparatus 20, and only the lower mold 41 is shown.

  As shown in FIG. 7, a groove portion 71 is formed on the upper surface of the lower die 41 so as to extend in the longitudinal direction (the left-right direction in FIG. 7) over the entire length of the lower die 41 and store the tube material 21. The groove portion 71 has a substantially rectangular cross-sectional shape with an open top, and is formed such that the peripheral length of the four sides of the rectangular cross-section is substantially the same as the peripheral length of the tube material 21 before forming.

In addition, the lower mold 41 is formed with recesses 72, 72 extending from the center in the longitudinal direction of the groove 71 to both sides in the width direction (vertical direction in FIG. 7). Each recess 72 extends outward in the width direction and penetrates the lower mold 41, and has a substantially rectangular cross section, and is inclined outward in the longitudinal direction from the inner end of the guide groove 74 in the width direction to the side surface of the groove 71. And two first inner surfaces 75 having a substantially rectangular shape. The end of each first inner surface 75 on the groove 71 side is curved inward in the longitudinal direction, like the first inner surface 34 of the upper die 31 .

  Formed link members for forming the portions (the side surfaces indicated by reference numerals 5b and 6b in FIG. 1) of the banjo portion 2 that protrude in the upward and downward directions of the vehicle in the recesses 72 and 72 of the lower die 41 as described above. 24, 24 are provided.

  The forming link member 24 of the lower mold 41 has the same structure as the forming link member 24 of the upper mold 31 and includes a central forming plate 36 and inclined forming plates 37 and 37.

  Further, similarly to the upper mold 31, the lower mold 41 is provided with cylinder devices 39, 39 that form link driving means, corresponding to the respective molding link members 24, 24. Each cylinder device 39 of the lower mold 41 is arranged so that the piston 40 advances and retreats in the vertical direction in FIG. 7 (the width direction of the lower mold 41), and the piston 40 is contracted outward in the width direction, thereby forming the center. As the plate 36 moves outward in the width direction, each of the inclined molded plates 37, 37 pivots outward in the width direction around the other end (shaft 70), and one end moves outward in the longitudinal direction (see FIG. 8). Thereby, each shaping | molding link member 24 and 24 of the lower mold | type 41 opens to the width direction outer side.

  The upper mold 31 and the lower mold 41 are coupled to each other by, for example, a fastening member (not shown) such as a bolt.

  Next, an example of manufacturing the axle housing 1 of the present embodiment by a hydroforming method using the hydroform apparatus 20 of the present embodiment will be described.

  In the present embodiment, as shown in FIG. 9, the tube material 21 (pipe material) in which the both end portions 9 are previously subjected to diameter reduction processing (for example, swaging processing) is hydroformed. This is because, in general, the axle housing for a drive shaft of a small truck has a circumference of the central banjo part that is about 2.5 times the circumference of both ends, and has a large tube expansion ratio exceeding 2 as described above. When hydroforming is performed, bursting and buckling occur. That is, it is very difficult to simply form the straight tubular material by hydroforming. Therefore, in this embodiment, in the manufacturing process of the axle housing 1, the expansion rate in the hydroforming process is reduced to 2 or less by adding a process of contracting both ends of the straight pipe prior to the hydroforming process. Yes.

  In the hydroforming step, first, as shown in FIG. 2, the molding surfaces (molding surfaces of the central molding plate 36 and the inclined molding plates 37) 38 and 42 of the molding link member 24 of the upper die 31 are replaced by the upper die 31. The cylinder device 39 is extended so that the molding link member 24 is moved downward so as to be flush with the lower surface of the cylinder. Similarly, as shown in FIG. 7, the lower mold 41 also has each molded link member such that the molded surfaces 38, 42 of the molded link members 24, 24 are flush with the side surfaces of the groove 71 of the lower mold 41. 24 and 24 are moved inward in the width direction. Furthermore, after the pipe material 21 (material to be molded) having been subjected to contraction processing is installed in the lower mold 41, the lower mold 41 and the upper mold 31 are brought into close contact and assembled (fixed).

  As described above, since the circumferential length of the groove portion 71 of the lower mold 41 is substantially the same as the circumferential length of the installed pipe material 21, the pipe material 21 is sandwiched between the upper mold 31 and the lower mold 41 when the mold is clamped. (See FIG. 4).

  Next, the axial pressing tool 25 is inserted into the groove portion 71 of the lower mold 41 in which the tubular material 21 is accommodated from both sides in the axial direction of the tubular material 21, and the convex portion 28 is inserted into the tubular material 21. Furthermore, the fluid pressure is applied to the tube material 21 by the fluid pressure applying means, and the crushed tube material 21 is expanded. Thereby, the pipe material 21 is expanded to a substantially rectangular cross section.

  Next, in a state where fluid pressure is applied in the tube material 21, both end portions of the tube material 21 are axially pressed by the shaft pressing device, and the molding link members 24 of the upper mold 31 and the lower mold 41 are opened. Specifically, each axial pushing tool 25 is moved toward the inside in the longitudinal direction of the mold 22 to press both end surfaces of the tube material 21, and each of the upper die 31 and the lower die 41 is changed according to the axial pushing amount. Each cylinder device 39 is degenerated.

  As a result, the center forming plate 36 of the upper mold 31 moves upward (see FIG. 3), and each center forming plate 36 of the lower mold 41 moves outward in the width direction (see FIG. 8). At the same time, each inclined molding plate 37 of the upper mold 31 is tilted upward, and each inclined molding plate 37 of the lower mold 41 is tilted outward in the width direction. Accordingly, the tube material 21 expands while the forming surfaces 38 and 42 of each forming link member 24 abut (contact) with the expanding portion.

  Furthermore, when each forming link member 24 reaches the tube expansion forming position, the back surface of each inclined forming plate 37 and the first inner surfaces 34, 75 of the recesses 32, 72 of the upper mold 31 and the lower mold 41 come into contact with each other, Tilt of the inclined forming plate 37 and movement of each central forming plate 36 are stopped. At this time, the molding surfaces 38 and 42 of the molding link member 24 of the upper mold 31 and the lower mold 41 and the fixed molding surfaces (second inner surface 35 and third inner surface) of the recess 32 are the same as the target banjo part 2. A space having a shape is partitioned between the upper mold 21 and the lower mold 31, and a pipe expansion portion is formed in the pipe material 21. Further, the tube material 21 is substantially the same as the target axle housing 1 except for the curvature of the corner portion (corner portion).

  Next, in the state where the forming link member 24 is positioned at the tube expansion forming position, the internal pressure applied to the tube material 21 is increased to reduce the corner radius.

  As a result, in the central cylinder portion 5 in the axle housing 1 shown in FIG. 1, the side surface 5b in the vehicle vertical direction is molded by the molding surface 38 of each central molding plate 36 of the lower mold 41, and the side surface 5a at the rear in the vehicle traveling direction is formed. The upper mold 31 is molded by the molding surface 38 of the central molding plate 36. Further, the side surface 5 c between the side surfaces 5 a and 5 b is formed by the second inner surface 35 of the recess 32.

  Further, the different-diameter pipe portion 6 of the axle housing 1 has the side surface 6b in the vehicle vertical direction formed by the molding surface 42 of each inclined molding plate 37 of the lower mold 41, and the side surface 6a on the rear side in the vehicle traveling direction of the upper mold 31. The inclined molding plate 37 is molded by the molding surface 42. Further, a side surface 6 c between the side surfaces 6 a and 6 b is formed by the third inner surface of the recess 32.

  Thus, the axle housing 1 of the present embodiment is obtained.

  Thus, in this embodiment, when the banjo part 2 of the axle housing 1 is formed into a polyhedron (16-faced body in the illustrated example) and the forming link member 24 is used, when the banjo part 2 is expanded and formed, It can be molded while holding the expanded portion. As a result, the axle housing 1 can be integrally formed from the pipe material 21 by hydroforming.

  As a result, the number of parts of the axle housing 1 is reduced and welding is not required, and the manufacturing cost can be reduced. Moreover, since there is no welding location, stress concentration at the welded portion is eliminated, the plate thickness of the axle housing 1 can be made thinner than the conventional product, and the axle housing 1 can be reduced in weight.

  Moreover, the hydroform apparatus 20 of this embodiment can prevent the burst (rupture) of the tube material 21 by pressing the expanded portion of the tube material 21 during molding. Further, since no burst occurs, the amount of axial push can be set to an appropriate low value, and the tube material 21 can be prevented from buckling.

  In addition, by making the shaft portion 8 of the axle housing 1 have a rectangular cross section, the section modulus can be increased compared to that of a round cross section, and this also makes the axle housing 1 thinner and lighter. Can do.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications and application examples can be considered.

  For example, it is also conceivable to form a thing other than the axle housing 1 by the hydroforming apparatus 20 of the present embodiment.

  Further, if the shape of the axle housing of the present embodiment is the shape of the first process, the hydroforming process becomes two processes by further hydroforming the axle housing 1 of the present embodiment. In addition, it is possible to manufacture an axle housing having a curved banjo part.

It is a perspective view of the axle housing manufactured with the hydrofoam apparatus by one Embodiment concerning this invention. It is a sectional side view of the hydroforming apparatus by one Embodiment concerning the present invention, and shows the state where a forming link member was closed. It is a sectional side view of the hydroforming apparatus of this embodiment, and shows the state where the forming link member opened. It is the IV-IV sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG. It is an A direction arrow directional view of FIG. 2, and shows only a forming link member. It is the VII-VII sectional view taken on the line of FIG. It is the VIII-VIII sectional view taken on the line of FIG. It is a perspective view of the pipe material which the hydroforming apparatus of this embodiment makes object. It is a perspective view of the conventional axle housing. FIG. 11 is an exploded view of FIG. 10. It is an exploded view of the conventional axle housing.

Explanation of symbols

1 Axle housing 2 Banjo part (expanded part)
5 Central cylinder part 6 Different diameter pipe part 21 Tubing material 22 Mold 24 Molding link member 32, 72 Recess 36 Central molding plate 37 Inclined molding plate

Claims (2)

A cylindrical tube material is accommodated in a mold, fluid pressure is applied to the tube material to form shaft portions at both ends, and the tube material is expanded between both shaft portions, and a polygonal cross section is formed at the center portion. A hydroforming method for forming a tube expansion portion composed of a central tube portion, and a different diameter tube portion formed by connecting both sides of the central tube portion and the shaft portion,
Forming a groove for forming the shaft portion in the mold, and a recess for forming the expanded portion at the center of the groove,
On the other hand, a centrally molded plate that is movable in the radial direction for molding one surface of the central cylindrical portion, and supported by a long hole provided on both sides of the central molded plate so as to be rotatable and movable along the longitudinal direction. It is composed of a pair of tiltable molding plates that can be tilted to form one surface of the different-diameter pipe portion, and the center molding plate moves radially outward by the tilting of the tilting molding plate, and its molding Link members are provided in the recess along the axial direction of the pipe material at a plurality of intervals in the circumferential direction in the recess,
A fixed molding surface is formed in the concave portion to mold an axial surface of the expanded portion between the formed link members when the inclined molded plate of the formed link member is opened to a tube expansion forming position where the inclined molded plate contacts the inner surface of the recessed portion. ,
A hydroforming method characterized in that when the fluid pressure is applied in the tube material and the forming link member is opened to the tube expansion forming position, the tube expanding portion is formed by the forming link member and the fixed forming surface . A cylindrical tube material is accommodated in a mold, fluid pressure is applied to the tube material to form shaft portions at both ends, and the tube material is expanded between both shaft portions , and a polygonal cross section is formed at the center portion. A hydroforming device for forming a tube expansion portion composed of a central tube portion, and a different diameter tube portion formed by connecting both sides of the central tube portion and the shaft portion ,
Forming a groove for forming the shaft portion in the mold, and a recess for forming the expanded portion at the center of the groove ,
On the other hand, it is supported by a centrally molded plate that is movable in the radial direction for molding one surface of the central cylindrical portion, and a long hole provided on both sides of the central molded plate so as to be rotatable and movable along the longitudinal direction. Ri Do and a tiltable pair of inclined shaping plate for shaping the one surface of the different-diameter pipe portion, with the tilting of the tilt forming plate with constituting the molded link member you move the central molding plate radially outward , provided at a plurality intervals in the circumferential direction of the recess and the molded link member along the axial direction of the pipe material in the recess,
A fixed molding surface is formed in the concave portion to mold an axial surface of the expanded portion between the formed link members when the inclined molded plate of the formed link member is opened to a tube expansion forming position where the inclined molded plate contacts the inner surface of the recessed portion. ,
A hydroforming apparatus characterized in that when the fluid pressure is applied in the pipe material and the forming link member is opened to the tube expansion forming position, the tube expanding portion is formed by the forming link member and the fixed forming surface .

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