JP7472332B1 - Method for manufacturing hot rotary forged wheel rims for vehicles made of light metal - Google Patents

Abstract

[Problem] Using a thick, hollow, tubular material made of light metal, a roll die is controlled by hot roll forging to form a disc mounting flange portion for mounting a wheel disc on the inner peripheral side of a wheel rim, and the wheel disc is mounted to the inner peripheral side of the wheel rim without welding.
[Solution] A tubular material W made of a light metal having a thickness greater than the combined thickness of the plate thickness of the side surface of the wheel rim 2 after molding and the protruding amount of the disc mounting flange portion 21 is used, and the disc mounting flange portion 21 for attaching the wheel disc 3 is protrudingly molded on the inner side surface of the tubular material W. A mandrel 52 having a recess 52a for molding the disc mounting flange portion formed on its side surface is used, and the tubular material W is heated to a high temperature within the recrystallization temperature range and the mandrel 52 is inserted inside it, and the thickness is reduced between the main roll 51 and the mandrel 52 while the disc mounting flange portion 21 is protrudingly molded on the inner side surface of the wheel rim 2.
[Selection diagram] Figure 8

Description

The present invention relates to a method for manufacturing a vehicle wheel rim, on the outer periphery of which a tire necessary for the vehicle to run is fitted, and more particularly to a method for manufacturing a hot rotary forged wheel rim for vehicles made of light metal, in which a seamless, thick-walled, hollow, tubular material made of light metal is formed into a wheel rim by controlling roll dies in a hot roll forging process .

A vehicle wheel, on which tires necessary for a vehicle to run are fitted, is composed of a roughly cylindrical wheel rim on whose outer periphery the tire is attached, and a roughly circular wheel disc fitted to the inner periphery of the wheel rim.
Known methods for manufacturing vehicle wheels include a casting type and a plastic working type.
The casting type is a manufacturing method suitable for mass production in which the material for the vehicle wheel is melted and poured into a mold to finish the wheel rim and wheel disc to the shape and dimensions. This casting type includes the so-called one-piece type in which the wheel rim and wheel disc of the vehicle wheel are integrated.
In contrast, the plastic processing type is a manufacturing method in which a rectangular thin flat plate is bent into a cylinder, and then the short sides are lightly butted together and flash pad welded to produce an approximately cylindrical thin plate wheel rim material, and this approximately cylindrical thin plate is then subjected to cold rolling spinning to finish it into the shape and dimensions of the wheel rim.
Then, a roughly circular wheel disc is inserted into the wheel rim, which is made of a roughly cylindrical thin plate, and the two are joined together, for example by MIG welding or TIG welding, to produce a so-called two-piece type, and this two-piece type is the mainstream type of wheel for vehicles.
Furthermore, because of the demand for lighter vehicles such as automobiles, it is becoming mainstream to use light metals such as aluminum as the material for both the wheel rim and the wheel disc.

Patent No. 4543218 Patent No. 5967920

However, the above-mentioned cast-type vehicle wheels have a coarse texture and fine bubbles remain because the metal structure is not rolled, making them weak. For this reason, the wheel rim must be made thick to maintain strength, but the weight of the wheel rim must be increased, which is a factor in reducing driving performance and fuel efficiency.
Furthermore, in the case of cast vehicle wheels manufactured as described above, the wheel disc and the wheel rim are integrated, so it is naturally not possible to perform maintenance on them separately.
In addition, the set position of the wheel disc is fixed at zero in/out when it is cast, so it cannot be adapted to changes in vehicle model, etc.
Furthermore, the cast type has low durability because the material is weak against impact loads, and its lifespan as a vehicle wheel is shorter than that of the processed type.

As mentioned above, in the plastic processing type, a rectangular thin flat plate is bent into a cylinder and then the short sides are welded together to produce a cylindrical thin plate wheel rim material. This not only takes time to manufacture, but the ironing process places stress on localized areas, which can lead to wrinkles, sink marks, and buckling.
As mentioned above, wheel rim material is made by bending a thin, rectangular plate into a cylinder and welding the short sides together, so there is always a risk of poor welding on the wheel rim. In addition, because the wheel rim is subjected to repeated impacts while in motion, there is always a risk that the welded parts will be easily damaged by those impacts.
Because the cylindrical thin plate material is cold-rolled, it is possible to form flange portions on both ends of the approximately cylindrical wheel rim, but it is not possible to form a mounting flange portion for the wheel disc on the inner side surface near the middle of the approximately cylindrical inside of the wheel rim. As a result, the only way to fasten the wheel rim and wheel disc is by welding, which means that there is always a risk of poor welding on the wheel.
In addition, because the wheel rim and wheel disc are fixed together by welding, there are structural problems such as the inability to remove and replace the wheel rim and wheel disc components separately for repairs, or to perform individual maintenance.
Furthermore, because the wheel rim and wheel disc need to be fixed together by welding, the fact that the wheel rim must be made of a material that is suitable for welding posed a major bottleneck in terms of manufacturing.

The present invention has been made in view of and to solve the above-mentioned problems, and has as its object to provide a method of manufacturing a hot rotary forged wheel rim for a vehicle made of light metal, which uses a seamless, thick-walled, hollow, tubular material made of light metal, and controls the roll dies in a hot roll forging process to form a disc mounting flange portion for mounting a wheel disc on the inner circumferential side near the middle of the approximately cylindrical inside of the wheel rim, thereby enabling the wheel disc to be mounted on the inner circumferential side of the wheel rim without the use of welding .

In order to achieve the above object, a method for manufacturing a hot rotary forged wheel rim for a vehicle made of light metal according to the present invention comprises the steps of: manufacturing a hot rotary forged wheel rim for a vehicle made of light metal using a driven main roll for forming an outer periphery of a hollow cylindrical material and a rotatable driven mandrel inserted inside the cylindrical material for forming an inner periphery;
A seamless hollow cylindrical material made of light metal having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used as the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
The mandrel is inserted inside the tubular material which has been softened by heating it to a high temperature within the range of the recrystallization temperature of the tubular material, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim thickness of the tubular material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner peripheral side of the tubular material towards the main roll, and in the process, the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel protrudes and forms a disc mounting flange portion which has a texture density and is circumferentially dense for rolling a metal texture for mounting a wheel disc, asymmetrically in cross section on the inner peripheral side of the wheel rim of the tubular material, to give a predetermined wheel rim shape and dimensions.

The method for manufacturing a hot rotary forged wheel rim for a vehicle made of light metal according to the present invention comprises the steps of: manufacturing a hot rotary forged wheel rim for a vehicle made of light metal using a driven main roll for forming an outer periphery of a hollow cylindrical material; and a rotatable driven mandrel inserted inside the cylindrical material for forming an inner periphery thereof,
A seamless hollow cylindrical material made of a light metal aluminum alloy having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used for the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
The aluminum alloy cylindrical material is heated to a high temperature of 300°C to 480°C within the recrystallization temperature range of the cylindrical material to make it soft, and the mandrel is inserted inside the softened material, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim thickness of the cylindrical material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner peripheral side surface of the cylindrical material towards the main roll. In the process, the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel protrudes and forms a disc mounting flange portion which has a texture density and is circumferentially dense for rolling a metal texture for mounting a wheel disc, asymmetrically in cross section on the inner peripheral side surface of the wheel rim of the cylindrical material, to give a predetermined wheel rim shape and dimensions.

The method for manufacturing a hot rotary forged wheel rim for a vehicle made of light metal according to the present invention comprises the steps of: manufacturing a hot rotary forged wheel rim for a vehicle made of light metal using a driven main roll for forming an outer periphery of a hollow cylindrical material; and a rotatable driven mandrel inserted inside the cylindrical material for forming an inner periphery thereof,
A seamless hollow cylindrical material made of a light metal magnesium alloy having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used for the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
The magnesium alloy cylindrical material is heated to a high temperature of 200°C to 400°C within the recrystallization temperature range of the cylindrical material to make it soft, and the mandrel is inserted inside the softened material, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim thickness of the cylindrical material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner peripheral side of the cylindrical material towards the main roll, and in the process, the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel protrudes and forms a disc mounting flange portion which has a texture density and is formed circumferentially with dense grain flows for rolling a metal texture for mounting a wheel disc, asymmetrically in cross section on the inner peripheral side of the wheel rim of the cylindrical material, to give a predetermined wheel rim shape and dimensions.

According to the method for manufacturing a hot rotary forged wheel rim for a vehicle made of light metal, according to the present invention, the following effects can be obtained.
1) Unlike conventional plastic processing types using thin plate material, a seamless hollow cylindrical material made of light metal having a wall thickness greater than the combined thickness of the plate thickness of the side peripheral surface of the formed wheel rim and the protruding amount of a disk mounting flange portion for mounting a wheel disc can be formed on the inner peripheral side surface near the middle of the approximately cylindrical inside of the wheel rim by controlling the roll die in a hot roll forging process. This makes it possible to easily fit and mount an approximately disk-shaped wheel disc on the inner peripheral side of the wheel rim using bolts and nuts without welding.
2) The wheel disc is not fixed to the inner circumference of the wheel rim by welding, but is attached with removable bolts and nuts. Therefore, the wheel rim and wheel disc can be replaced separately. From the standpoint of design, there are many variations and the wheel rim structure offers a high degree of freedom in design, which also improves maintainability.
3) Even for the same model of vehicle wheel, the set position of the wheel disc differs depending on the vehicle model, and even if the wheel disc has an installation position such as zero set, inset, or outset, the wheel rim and wheel disc are not fixed by welding, so the wheel disc corresponding to each case can be freely changed and adapted, which is practical.
4) The wheel rim of the present invention, unlike conventional plastic processing types, has no welded parts, so there is no risk of poor welding or the risk of the welded parts being easily damaged by impact.
5) The wheel rim according to the present invention is manufactured by hot forging, and therefore the metal structure is rolled, which allows for the formation of dense circumferential grain flows with a high structural density, making it possible to produce a lightweight wheel rim with excellent mechanical properties.
6) The wheel rim of the present invention is manufactured by hot forging, unlike conventional cold-worked plastic processing types that use thin plate material. Therefore, it is possible to perform rolling processing using seamless thick-walled hollow tubular material, and it is possible to manufacture hot-forged wheel rims that are suitable for mass production and are low cost.
7) The wheel rim of the present invention has no welded parts, and therefore the wheel rim is not limited to materials suitable for welding. Unlike conventional plastic processing types, the wheel rim material does not become a major bottleneck in manufacturing.

1 is a cross-sectional view of a wheel rim showing an embodiment of the present invention; 1 is a cross-sectional view of a wheel rim when a wheel disc is inset, showing an embodiment of the present invention. 1 is a cross-sectional view of a wheel rim when the wheel disc is zero-set, showing an embodiment of the present invention. 1 is a cross-sectional view of a wheel rim when the wheel disc is outset, showing an embodiment of the present invention. 1A is a schematic perspective view of an initial manufacturing process of a wheel rim by a wheel rim hot rotary forging apparatus showing an embodiment of the present invention, and FIG. 1B is a schematic side sectional view of FIG. 1A is a schematic perspective view of a wheel rim hot rotary forging apparatus showing an embodiment of the present invention, illustrating a manufacturing process of the wheel rim at the beginning of the middle stage, and FIG. 1A is a schematic perspective view of a middle stage of a wheel rim manufacturing process using a wheel rim hot rotary forging device showing an embodiment of the present invention, and FIG. 1B is a schematic side sectional view of FIG. 1A is a schematic perspective view of a final manufacturing process of a wheel rim by a wheel rim hot rotary forging apparatus showing an embodiment of the present invention, and FIG.

The present invention will now be described in more detail based on the embodiments shown in the drawings.

In Figures 1 to 4, a vehicle wheel 1 made of light metal is composed of a roughly cylindrical wheel rim 2 made of light metal, on whose outer periphery a tire is mounted, and a roughly disk-shaped wheel disc 3 that fits onto the inner periphery of the wheel rim 2 and is attached to the axle of the vehicle.

The vehicle wheel 1 made of light metal is a so-called two-piece type in which the wheel rim 2 and wheel disc 3 are not integrated. The wheel disc 3, which is fitted to the inner periphery of the wheel rim 2, is attached to the inner periphery of the wheel rim 2 by bolts and nuts 4, not by welding or the like. For this reason, a circular disc mounting flange portion 21 is formed to protrude from the inner periphery side of the wheel rim 2.

The wheel rim 2 is made of light metal, such as an aluminum alloy or magnesium alloy, and is manufactured by hot rotary forging. The wheel rim 2 made of light metal is manufactured by hot rotary forging, so the metal structure is rolled, which creates a dense circumferential grain flow, resulting in a lightweight wheel rim with high mechanical properties.

The wheel disc 3 is attached by bolts and nuts 4 through a circular disc mounting flange 21 formed on the inner peripheral side of the wheel rim 2. Therefore, if the wheel disc 3 is damaged, the bolts and nuts 4 can be removed and the damaged wheel disc 3 can be easily replaced with a new wheel disc 3.

A circular disk mounting flange 21 for mounting the wheel disk 3 with bolts and nuts 4 is formed on the inner peripheral side of the substantially cylindrical wheel rim 2, protruding all the way around in the circumferential direction toward the center of the inside of the wheel rim 2. A plurality of bolt holes 21a are drilled in the circumferential direction of the circular disk mounting flange 21. Each of the bolt holes 21a is formed parallel to the inner central axis CL of the wheel rim 2 (the horizontal axis in Figures 1 to 4).

The disk mounting flange portion 21 formed on the inner peripheral side surface of the approximately cylindrical wheel rim 2 has multiple bolt holes 21a drilled in its circumferential direction as described above. Therefore, the amount of protrusion S of the annular disk mounting flange portion 21 from the inner peripheral side surface of the wheel rim 2 is sufficiently larger than the diameter of the bolt holes 21a.

As described above, this annular disk mounting flange 21 is manufactured integrally with the wheel rim 2 by hot rotary forging, so the metal structure is rolled, resulting in a high density of structure and dense grain flows formed around the circumference, resulting in high mechanical properties. For this reason, the strength around the bolt holes 21a formed in the disk mounting flange 21 is also sufficiently high.

Each bolt hole 21a formed in the disk mounting flange portion 21 is formed so as to be parallel to the inner central axis CL (horizontal axis in Figs. 1 to 4) of the substantially cylindrical wheel rim 2. A bolt nut 4 that connects the wheel disk 3 to the disk mounting flange portion 21 of the wheel rim 2 is inserted into each bolt hole 21a.

The bolts and nuts 4 are inserted through bolt holes (not shown) formed on the periphery of the wheel disc 3 and bolt holes 21a formed in the disc mounting flange portion 21, and the wheel disc 3 is fitted to the inner periphery of the wheel rim 2 and tightened to attach the wheel disc 3 to the wheel rim 2, connecting the wheel disc 3 and the wheel rim 2.

The protruding positions of the disk mounting flange portion 21 formed on the inner peripheral side surface of the approximately cylindrical wheel rim 2 are different for the inset 31, zero set 32, and outset 33 (see Figures 2 to 4) of the wheel disk 3, based on the vertical center line VCL perpendicular to the inner peripheral side surface facing horizontally of the approximately cylindrical wheel rim 2. This vertical center line VCL is located in the center of both open ends of the approximately cylindrical wheel rim 2.

In the offset 31 shown in FIG. 2, the disk mounting flange 21 is formed to protrude between the outer opening end 2a of the substantially cylindrical wheel rim 2 and the outer side of the vertical center line VCL. At this time, the offset amount p between the vertical center line VCL of the substantially cylindrical wheel rim 2 and the mounting surface 31a of the wheel disk 3 attached to the disk mounting flange 21 is as shown in FIG. 2.

In the zero set 32 shown in FIG. 3, the disk mounting flange portion 21 is formed to protrude slightly outward from the vertical center line VCL of the approximately cylindrical wheel rim 2. At this time, the vertical center line VCL of the approximately cylindrical wheel rim 2 and the mounting surface 32a of the wheel disk 3 attached to the disk mounting flange portion 21 are in the same position as shown in FIG. 3, so the inset amount is zero.

In the outset 33 shown in Fig. 4, the disc mounting flange 21 is formed to protrude between the inner opening end 2b of the substantially cylindrical wheel rim 2 and the inner side of the vertical center line VCL. In this case, the outset amount q between the vertical center line VCL of the substantially cylindrical wheel rim 2 and the mounting surface 33a of the wheel disc 3 attached to the disc mounting flange 21 is as shown in Fig. 4.

The wheel rim hot rotary forging device 5 shown in Figures 5 to 8 is a device that manufactures wheel rims 2 by hot rotary forging using a lightweight hollow cylindrical tubular material W, such as an aluminum alloy or magnesium alloy.

The thickness T of the hollow tubular material W is greater than the sum of the protrusion amount S of the disk mounting flange portion 21 for mounting the wheel disk 3 and the plate thickness t of the inner peripheral side surface of the wheel rim 2 at the location where the disk mounting flange portion 21 is formed (t+S). The hollow tubular material W is heated to a high temperature within the recrystallization temperature range (e.g., 300°C to 480°C for aluminum alloys, 200°C to 400°C for magnesium alloys) to soften it, and then formed by hot forging.

This wheel rim hot rotary forging device 5 is mainly composed of a main roll 51 that rotates a hollow tubular material W of, for example, an aluminum alloy, a mandrel 52 that faces the main roll 51 and pressurizes the tubular material W between the main roll 51 and rolls it radially outward, left and right centering rolls 53 that maintain the circularity of the tubular material W while preventing it from moving horizontally, and upper and lower axial rolls 54 that hold the tubular material W from above and below, adjusting the height (width) of the tubular material W.

The main roll 51 rotatably contacts and presses the outer peripheral side surface of the hollow tubular material W. A drive device such as a motor is connected to the main roll 51 so that it can rotate. When the main roll 51 rotates, the hollow tubular material W in contact with the main roll 51 rotates. The entire circumference of the outer peripheral side surface of the main roll 51 that contacts the outer peripheral side surface of the tubular material W is an annular metal mold having the same cross-sectional shape.

The surface of the annular die on the outer periphery of the main roll 51 that comes into contact with the outer periphery of the tubular material W is shaped to engage with the outer periphery of the wheel rim 2 after molding. In other words, the wheel rim 2 after molding that comes into contact with the convex portion of the annular die of the main roll 51 becomes a concave portion, and conversely, the wheel rim 2 after molding that comes into contact with the concave portion of the annular die of the main roll 51 becomes a convex portion.

The annular die on the outer peripheral side of the main roll 51 usually has a different shape, for example, above the center and below the center with respect to the vertical axis of the main roll 51. In other words, the annular die on the outer peripheral side of the main roll 51 has a vertically asymmetric cross-sectional shape. As a result, a vertically asymmetric uneven shape is formed on the outer peripheral surface of the wheel rim 2 formed from the cylindrical material W.

The mandrel 52 has a cylindrical shape with a smaller diameter than the main roll 51, and is rotatably installed in a position facing the main roll 51 with the thickness of the hollow tubular material W sandwiched between them (on the inner peripheral surface side of the hollow tubular material W). The mandrel 52 can move horizontally (radially), contacts the inner peripheral side of the tubular material W, and presses the inner peripheral side of the tubular material W toward the main roll 51, which is located on the opposite side with the inner peripheral side of the tubular material W in between.

When the mandrel 52 is brought into contact with the inner peripheral surface of the tubular material W, the tubular material W is clamped from the inside and outside by the main roll 51 and the mandrel 52, the tubular material W rotates due to the rotating main roll 51, and the mandrel 52 is rotated by the rotating tubular material W. By moving the contacting mandrel 52 further toward the main roll 51, pressure is applied to the tubular material W, the thickness of the side cross section of the tubular material W decreases, and the outer diameter of the tubular material W increases in inverse proportion to the decrease.

The entire circumference of the outer peripheral side of the mandrel 52, which contacts the inner peripheral side of the cylindrical material W, is an annular metal mold having the same cross-sectional shape. The annular metal mold on the outer peripheral side of the mandrel 52 has a recess 52a for molding the disk mounting flange portion formed on its side surface in order to protrude the disk mounting flange portion 21 for mounting the wheel disk 3.

The annular die for the outer peripheral side of the mandrel 52 is shaped so that the surface that comes into contact with the inner peripheral side of the tubular material W will engage with the inner peripheral side of the wheel rim 2 after molding. In this way, the inner peripheral side of the wheel rim 2 after molding that comes into contact with the convex portion of the annular die for the mandrel 52 will be a concave portion, and conversely, the inner peripheral side of the wheel rim 2 after molding that comes into contact with the concave portion of the annular die for the mandrel 52 will be a convex portion.

In particular, the disk mounting flange portion 21 is formed to protrude from the entire inner peripheral side surface of the wheel rim 2 after molding, which contacts the recessed portion of the disk mounting flange portion molding recess 52a of the annular mold of the mandrel 52. The amount of protrusion S of the disk mounting flange portion 21 from the inner peripheral side surface of the wheel rim 2 is the same as the depth S of the recess in the recessed portion of the disk mounting flange portion molding recess 52a. By adjusting the depth S of this recess, the amount of protrusion S of the disk mounting flange portion 21 from the inner peripheral side surface of the wheel rim 2 can be adjusted.

The position of the disk mounting flange portion 21 formed on the inner peripheral side surface of the wheel rim 2 differs between the inset 31, the zero set 32, and the outset 33. Therefore, the position of the recess 52a for molding the disk mounting flange portion formed in the annular mold of the mandrel 52 also differs between the inset 31, the zero set 32, and the outset 33.

The centering rolls 53 are cylindrical, and are configured as a pair on the left and right sides facing the mandrel 52, and are rotatably fixed to the outer circumferential side of the tubular material W. In other words, the tubular material W passes between the centering rolls 53 on the outer circumferential side and the mandrel 52 on the inner circumferential side, and the roundness of the wheel rim 2 being formed is adjusted by applying pressure to the side of the circumferentially extending tubular material W.

The axial rolls 54 are conical in shape, and are arranged in a pair, upper and lower, at an incline in a position facing the main roll 51. The sides of the pair of upper and lower axial rolls 54 are in contact with each other so as to sandwich the upper and lower end faces of the tubular material W. The contacting axial rolls 54 rotate with the rotation of the tubular material W, and perform pressing down in the vertical height direction. In addition, the vertical movement of the tubular material W is suppressed, and the shape in the vertical direction is maintained.

Next, we will explain the manufacturing method of a hot rotary forged wheel rim (see Figures 5 to 8) in which a hollow light metal tubular material W is rolled by hot rotary forging using the above-mentioned wheel rim hot rotary forging device 5.

The tubular light metal material W used as the raw material has a thickness T of its side cross section that is greater than the sum of the protrusion amount S of the annular disc mounting flange portion 21 for mounting the wheel disc 3 and the plate thickness t of the inner peripheral side surface of the wheel rim 2 after molding at the formation location of the disc mounting flange portion 21, such that (S + t) < T. A seamless cylinder is used for the tubular light metal material W. Because it is seamless, there are no seams between the metals, and the strength of the seams does not decrease or cracks do not occur when it is rolled by hot rotary forging or during use as a wheel rim 2.

The cylindrical material W is made of light metals such as aluminum alloys and magnesium alloys. These light metal cylindrical materials W are heated to a high temperature within the recrystallization temperature range of the cylindrical material W and then softened before use. For example, a hollow cylindrical material W made of an aluminum alloy is heated in a heating furnace to a predetermined recrystallization temperature range and hot forged at a high temperature of 300°C to 480°C. A hollow cylindrical material W made of a magnesium alloy is heated in a heating furnace to a predetermined recrystallization temperature range and hot forged at a high temperature of 200°C to 400°C.

If the light metal material is not a hollow cylindrical material W but is, for example, a cylindrical material, the cylindrical material is heated to within a predetermined recrystallization temperature range, and the heated cylindrical material is introduced into a press equipped with a pair of dies arranged above and below. The heated cylindrical material is pressed down by the upper die to form a material with a predetermined outer shape. Furthermore, the center of the material is perforated, and it is processed into a hollow cylindrical material W with a predetermined wall thickness.

As described above, a hollow cylindrical tubular material W made of light metal that has been heated in a heating furnace to a high temperature within a predetermined recrystallization temperature range is placed in a wheel rim hot rotary forging device 5. In this wheel rim hot rotary forging device 5, a main roll 51 is brought into contact with the outer peripheral side of the hollow cylindrical tubular material W, and a mandrel 52 is inserted from above into the hollow inside of the tubular material W, and the mandrel 52 is brought into contact with the inner peripheral side of the tubular material W (see Figure 5).

At this time, as described above, the entire circumference of the outer circumferential side of the main roll 51 that contacts the outer circumferential side of the light metal tubular material W is an annular metal mold. In addition, the entire circumference of the outer circumferential side of the mandrel 52 that contacts the inner circumferential side of the tubular material W is also an annular metal mold. In other words, the outer circumferential side of the hollow cylindrical tubular material W contacts the annular metal mold on the outer circumferential side of the main roll 51, and the inner circumferential side of the tubular material W contacts the annular metal mold on the outer circumferential side of the mandrel 52.

As described above, the annular die on the outer peripheral side of the mandrel 52, which contacts the inner peripheral side of the light metal tubular material W, has a recess 52a for forming the disk mounting flange. The recess depth S of the recess 52a for forming the disk mounting flange is the same as the protrusion amount S of the disk mounting flange 21.

The hollow cylindrical material W installed in the wheel rim hot rotary forging device 5 is rotated by the rotation drive of the main roll 51, and the mandrel 52, which is provided opposite the main roll 51 and sandwiches the cylindrical material W, is moved toward the main roll 51 under pressure, so that the cylindrical material W is sandwiched and pressurized between the main roll 51, which is driven to rotate, and the mandrel 52, which is driven to rotate, and the rolling proceeds (see Figure 6).

A cylindrical tubular material W made of light metal, initially with a thick side cross section of thickness T, is clamped and pressurized, reducing its thickness while the outer diameter of the cylindrical tubular material W gradually increases (see Figure 7), and the material W is rolled while rotating until it achieves the rolling precision of the desired shape and dimensions of the wheel rim 2 (see Figure 8). The rolling time for this hot rotary forging is about 1 to 2 minutes per product, as the material is rotary forged after being heated to a high temperature and softened.

As the rolling of the light metal tubular material W by hot rotary forging progresses and the wheel rim diameter is enlarged by hot rolled rotary forging, a circular disk mounting flange portion 21 with a predetermined protrusion amount S is formed on the inner peripheral side of the wheel rim 2 by the recess 52a for forming the disk mounting flange portion of the circular mold on the outer peripheral side of the mandrel 52.

The wheel rim 2 is rolled and formed into a shape and dimensions of a specified height h and outer diameter r by hot rotary forging. After heat treatment, multiple bolt holes 21a are drilled into the annular disc mounting flange portion 21 formed on the inner peripheral side of the wheel rim 2, and after product inspection, it becomes the final vehicle wheel rim product.

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

Reference Signs List 1 Vehicle wheel made of light metal 2 Wheel rim 2a Outer opening end 2b Inner opening end 21 Disc mounting flange portion 21a Bolt hole 3 Wheel disc 31 Inset 31a Mounting surface 32 Zero set 32a Mounting surface 33 Outset 33a Mounting surface 4 Bolt nut 5 Wheel rim hot rotary forging device 51 Main roll 52 Mandrel 52a Recess for forming disc mounting flange portion 53 Centering roll 54 Axial roll W Cylindrical material CL Center axis VCL Vertical center line T Wall thickness of side cross section of cylindrical material
S: Protrusion amount of the disk mounting flange t: Plate thickness of the inner peripheral side of the wheel rim after forming p: Inset amount q: Outset amount h: Height of the wheel rim r: Outer diameter of the wheel rim

Claims (3)

In manufacturing a hot rotary forging wheel rim for a vehicle using a driven main roll for forming an outer periphery side of a hollow cylindrical material and a rotatable driven mandrel for forming an inner periphery side by being inserted inside the cylindrical material,
A seamless hollow cylindrical material made of light metal having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used as the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
a mandrel is inserted inside the tubular material which has been softened by heating the tubular material to a high temperature within the range of its recrystallization temperature, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim wall thickness of the tubular material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner circumferential surface of the tubular material towards the main roll, and in the process, a disc mounting flange portion is protruded and formed in the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel in a cross-sectionally asymmetric manner on the inner circumferential surface of the wheel rim of the tubular material, the disc mounting flange portion having a texture density and formed with dense circumferential grain flows for rolling a metal texture for mounting a wheel disc, to form a predetermined wheel rim shape and dimensions. In manufacturing a hot rotary forging wheel rim for a vehicle using a driven main roll for forming an outer periphery side of a hollow cylindrical material and a rotatable driven mandrel for forming an inner periphery side by being inserted inside the cylindrical material,
A seamless hollow cylindrical material made of a light metal aluminum alloy having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used for the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
a mandrel is inserted inside a cylindrical material of aluminum alloy which has been heated to a high temperature of 300°C to 480°C within the recrystallization temperature range of the cylindrical material to make it soft, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim thickness of the cylindrical material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner peripheral side of the cylindrical material towards the main roll, and in the process, a disc mounting flange portion is protruded and formed in the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel in a cross-sectionally asymmetric manner on the inner peripheral side of the wheel rim of the cylindrical material, the disc mounting flange portion having a texture density and formed with dense circumferential grain flows for rolling a metal texture for mounting a wheel disc, to form a predetermined wheel rim shape and dimensions. In manufacturing a hot rotary forging wheel rim for a vehicle using a driven main roll for forming an outer periphery side of a hollow cylindrical material and a rotatable driven mandrel for forming an inner periphery side by being inserted inside the cylindrical material,
A seamless hollow cylindrical material made of a light metal magnesium alloy having a wall thickness greater than the sum of the protruding amount of a disk mounting flange portion for mounting a wheel disk and the plate thickness of the inner peripheral side surface of the wheel rim after molding at the forming portion of the disk mounting flange portion is used for the cylindrical material,
A mandrel having a recess for forming a disk mounting flange portion on an outer circumferential side surface is used to protrude a disk mounting flange portion for mounting a wheel disk on an inner circumferential side surface of the cylindrical material,
a mandrel is inserted inside a tubular material of magnesium alloy which is heated to a high temperature of 200°C to 400°C within the recrystallization temperature range of the tubular material to make it soft, and the wheel rim diameter is enlarged by hot rolling rotary forging while the wheel rim thickness of the tubular material is reduced between the driven main roll and the rotatable driven mandrel which presses the inner peripheral side of the tubular material towards the main roll, and in the process, a disc mounting flange portion is protruded and formed in the disc mounting flange portion forming recess formed on the side peripheral surface of the mandrel in a cross-sectionally asymmetric manner on the inner peripheral side of the wheel rim of the tubular material, the disc mounting flange portion having a texture density and formed with dense circumferential grain flows for rolling a metal texture for mounting a wheel disc, to form a predetermined wheel rim shape and dimensions.

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