JP4332844B2 - Manufacturing method for vehicle wheel - Google Patents

Description

  The present invention relates to a method of manufacturing a vehicle wheel that is formed entirely of a light alloy such as an aluminum alloy, for example, by a low pressure casting apparatus having a side gate.

As a vehicle wheel mounted on an automobile, for example, a passenger car, in order to reduce the weight of the vehicle body, an aluminum wheel formed entirely by a light alloy typified by an aluminum alloy, for example, a low pressure casting method is used. Has been. The aluminum wheel is composed of a rim portion on which a tire is mounted, a disk portion mounted on an axle, and a spoke portion that couples both. As a method for casting the aluminum wheel, various methods have been put into practical use. Recently, for example, a casting method for pouring from a multi-gate including a side gate described in Patent Literature 1 and Patent Literature 2 is practical. It has become. In Patent Document 1, two gates are provided between the both ends of the cavity forming the rim portion and near the lower end and symmetrically between the gates formed in the center of the cavity forming the disk portion, It is described that pouring from each gate. Patent Document 2 describes that after pouring into the spoke part forming space and the disk part forming space, the rim part forming space is poured. According to this casting method, since the disk portion is thinned and directional solidification is performed from the rim portion toward the disk portion, there is an advantage that a light weight wheel can be obtained. A wheel material having a rim portion and a disk portion is cast by pouring from each gate, and a non-product portion including a side gate portion is removed from the material and then processed into a predetermined dimension, thereby obtaining a final product. As a method for removing the side gate from the wheel material, for example, the side gate is cut from the rim, and then heat treatment is performed to remove distortion generated in the rim at the time of cutting. Further, in order to easily remove the non-product part from the cast material, it has been proposed to reduce the cross-sectional area of the gate (weir). For example, Patent Document 3 describes that a connecting portion between a cavity and a feeder formed in a mold is formed of a porous refractory and the area of the connecting port is reduced. In Patent Document 4, a hammer attached to the tip of a piston rod of an air cylinder is caused to collide with a part of a product design part such as a casting gate, a runway, a feeder, a weir, and the product design part is blocked by the impact force. A dam folding device that breaks from the portion and separates from the product is described, and it is described that a cut is provided in the dam portion for easy separation.
JP 2000-254766 (page 3-5, FIG. 1) JP 2001-287014 (page 2-3, FIG. 1) JP-A-4-41043 (2nd page, FIG. 1) Japanese Utility Model Publication No. 5-5263 (2nd page, Fig. 1)

  In the casting mold structure described in Patent Literature 1 and Patent Literature 2, there is a problem that it takes time to remove the side gate and productivity is lowered. Therefore, it is conceivable to form the connecting portion between the side gate and the rim as described in Patent Document 3 and Patent Document 4, but only by reducing the area of the connecting portion (weir) or by providing a notch. There is a problem that traces of the weir remain and need to be deleted.

  Accordingly, an object of the present invention is to provide a method of manufacturing a vehicle wheel that can easily be lathe processed by removing a side gate from a cast wheel material.

In order to achieve the above object, in the present invention, a light alloy wheel material having a rim part and a disk part is cast by pouring into the molding cavity from a side gate provided adjacent to the rim part molding cavity. In the method for manufacturing a vehicle wheel for removing a non-product part including a side gate part from the material, the side gate part is formed by a horizontal draft that is inclined in a range of 15 to 35 degrees with respect to a movable direction. The notch part for breaking the side gate part with a small load is connected to the rim part at a place where the thickness is formed, and within 10 mm from the rim part surface of the light alloy wheel material of the side gate part. The technical means of forming at a position and along the width direction of the rim portion and then lathe-working the rim portion was adopted. Moreover, in this invention, it is preferable that the said notch part is formed in linear form. Further, it is preferable that the notch portions are formed on both surfaces of the side gate portion, and the distance Y between the notch portions is set to a distance of 10 mm or more and 20 mm or less.

  According to the present invention, since the notch portion extending in the width direction of the rim is formed in the vicinity of the rim of the side gate, the boundary portion between the side gate and the rim portion can be obtained only by applying a small load. A large plastic strain is generated in the portion, and the side gate portion can be removed from the wheel material without leaving a trace and without causing a large deformation of the product portion. Since the straight notch is formed at the part where the thick rim part is formed by the draft provided in the horizontal mold, there is no problem such as chipping of the cutting tool even if the rim part is turned. . Accordingly, it is possible to improve the production efficiency of a lightweight and high-strength vehicle wheel.

  Details of the present invention will be described below with reference to the accompanying drawings. 1 is a cross-sectional view of a mold apparatus used in the present invention, FIG. 2 is an external perspective view of a wheel material, FIG. 3 is an enlarged view of the main part of FIG. 2, and FIG. FIG.

  In FIG. 1, reference numeral 1 denotes a low pressure casting mold, which includes a lower mold 11 and an upper mold 12 having surface shapes corresponding to wheel designs, horizontal molds 13 a and 13 b that are fitted to form a molding cavity 14, and a lower mold 13 A base 15a for fixing the mold 11 and a base 15b for supporting the upper mold 12 are provided. The cavity 14 includes a disk part cavity 14a and a rim part cavity 14b, and each cavity communicates with a molten metal supply part via a gate (pouring gate). That is, the rim cavities 14a and 14b communicate with the stalks 17b and 17c connected to the molten metal holding furnace (not shown) via the side gates 16a and 16b. The side gates 16a and 16b are arranged so as to exist at symmetrical positions across the axis of the wheel. The horizontal type is provided with projections 18a and 18b for forming side gate notches of the wheel. Further, the upper mold is provided with a feeder 19 for pushing the molten metal in the disk portion cavity 14a.

  According to the mold apparatus 1, low pressure casting is performed as follows. When the molten metal in the holding furnace is pressurized and the stalks 17a and 17b are raised, the molten metal is injected into the molding cavity 14 from the side gates 16a and 16b, filled into the rim cavity 14b, and finally filled into the disk cavity 14a. The After the predetermined time has elapsed, the molten metal remaining in the stalks 17a and 17b is returned to the holding furnace by releasing the pressurization. The molten metal injected into the cavity 14 is subjected to directional solidification from the inner flange side (upper end portion of the rim portion cavity 14b) toward the rim center and from the spoke portion toward the disk portion center side. A disk portion 21 is formed. After completion of solidification in such a process, the mold is opened, and the cast product (wheel material) shown in FIG. 2 is taken out.

The wheel material 20 includes a disc-shaped disk portion 21 attached to an axle (not shown), a rim portion 22 on which a tire (not shown) is mounted, and an inner flange portion 23 formed on the upper end surface of the rim portion 22. The outer flange portion 24 formed on the lower end surface of the rim portion 22 and the side gate portions 26a and 26b formed on the outer peripheral surface of the rim portion 22, and after removing the side gate portions 25a and 25b from the rim portion 22, The design surface 25 is processed, airtightness-inspected, and surface-treated (painted) to finish the product. If the entire end portion of the side gate portion 26a extends to the outer periphery of the rim portion 22 as indicated by a broken line in FIG. 3, chipping remains when the side gate portion 26a is removed from the end portions 28 and 28, and a tool is used during machining. Therefore, the side gate portion has a shape indicated by a solid line in FIG. The wheel blank 20 is provided with notches 27a and 27b having a height h along the width direction of the rim 22 on the side gates 26a and 26b (FIGS. 3 and 4 show one of the cuts). Only the notch 27a is shown). The cutout 27a is preferably formed in a straight line from the upper end to the lower end of the side gate 26a. This is because when the cutout portion 27a is formed in a non-linear shape (for example, a shape bent in the middle) as shown by a one-dot chain line in FIG. This is because an unremoved portion 29 surrounded by a broken line is likely to occur, and problems such as chipping of a cutting tool occur during lathe processing. The cutout portion 27a is a biting portion having a wedge-shaped cross-sectional shape, and is formed in the vicinity of the rim portion, for example, at a position where the distance X from the outer peripheral surface of the rim portion is 10 mm or less so as to be broken by a small load. It is preferable that The cutout portion 27a may be formed on one side of the side gate portion 26a as viewed from above, but is preferably formed on both sides of the side gate portion 26a so as to be broken by a small load. In the case where notches are formed on both sides, the gap Y between the notches 27a is set to 20 mm or less because the load necessary for breaking increases when the notches 27a are too wide and large distortion occurs in the product part. Is preferred. However, if the interval (Y) is too narrow, the pouring speed becomes low, so it is desirable to set it to 10 mm or more. Although the rim of the side gate part 26a is narrower, the length L ₃ of the portions is shorter and the solidification rate becomes slower, casting defects in the side gate 26a is there is a risk that fall within the rim, long and The range of 10 to 20 mm is good because the hot water effect is insufficient and breaks. Further, according to the above-described side gate, the horizontal type is provided with a draft gradient over the range of lengths L ₁ and L ₂ as shown in FIG. 4 to prevent mold galling when releasing the horizontal type and the side gate. Even if the shrinkage nest enters the rim, it can be stopped at the part where the draft is provided. Since the portion provided with the draft is finally cut by a lathe process, it does not become a defect of the rim portion 22, and the soundness of the product portion is maintained. From these, the side gate portions 26a and 26b can be quickly removed from the rim portion 22 only by applying a slight hit to the side gate portions 26a and 26b with a tool (for example, a hammer). Furthermore, when the shape of the notch is made straight, a part of the side gate protrudes and remains in the center of the rim, and there is a problem that the cutting tool jumps during lathe processing. It eliminates sudden stress changes and eliminates problems in turning. The angle of the draft is preferably 15 to 35 degrees with respect to the horizontal movable direction. As a result, the side gate portions 26a and 26b are easily removed from the rim portion 22 with a slight force, and the rim portion 22 is hardly distorted. High-quality wheels can be manufactured. In particular, the present invention is effective because distortion tends to occur in a large diameter wheel of 17 inches or more.

Assuming the case where the wheel material 20 is cast with an Al—Si—Mg based alloy {however, the notch depth = 2 mm, X = 1.5 mm, L ₃ = 15 mm, h = 138 mm set}, The plastic strain generated in the wheel was calculated using the analysis model shown in FIG. That is, as shown in FIG. 5, the boundary condition is set such that the wheel material 20 is placed on the surface plate 30, the outer flange 24 is constrained to the surface plate 30, and a load is applied to the side gate portion 26a from the illustrated arrow S direction. And the result of having calculated the distortion which generate | occur | produces in the wheel raw material 20 is shown in FIG. For comparison, FIG. 7 shows the result of calculating the strain generated in the wheel material 20 under the same conditions as above except that the notch 27a is not provided in the wheel material 20. In these simulations, when the plastic strain generated in the wheel material 20 reaches 15%, the side gate portion 26a is broken and can be removed from the rim portion 22, and the limit plastic strain is set to 15%. In FIG. 6, the region S ₀ between the outermost equal strain line and the inner equal strain line shows a plastic strain of 3 to 4.5%, and the innermost equal strain line inside the inner strain line. The region S _i shows a plastic strain of 13.5 to 15%. FIG. 8 shows changes in the diameter D of the inner flange 25 when the load is changed.

  FIG. 6 shows that the wheel blank 20 of the present invention reaches a limit plastic strain of 15% at a load of 80 KN, and the plastic strain is concentrated only in the notch 26a. From FIG. 7, the wheel blank 20 without the notch 26a reaches a limit plastic strain of 15% at a load of 130 KN, and a wide range of plastic strain extending not only to the side gate portion 25a but also to the rim portion 22 is generated. I understand that. From FIG. 8, the wheel material 20 of the present invention has a change amount of the diameter D of the inner flange 25 of 0.36 mm when the side gate portion 25a is broken by a load of 80 KN, and has no notch portion 26a. It can be seen that the amount of change of the diameter D of the 20 inner flanges 25 can be reduced by as much as 30% compared to the amount of change 0.51 mm. That is, the wheel material 20 of the present invention reaches the limit plastic strain with a load reduced by 40% or more compared to the wheel material 20 without the notch 26a, and the plastic strain is concentrated only in the notch. Since the deformation of the inner flange portion 23 can be reduced, it is possible to produce a product without performing post-processing such as conventional strain relief heat treatment.

A molten metal (about 450 ° C.) of an Al—Si—Mg alloy (JIS AC4CH material) is poured into a mold (about 450 ° C.) shown in FIG. 1 and cast at a predetermined pressure (0.049 to 0.063 MPa). Thus, the wheel material 20 shown in FIG. 4 was produced. In this case, the distance X from the protrusion to the outer peripheral surface of the rim was changed in the range of 0 to 15 mm and the width Y in the range of 0 to 20 mm. Moreover, the draft was set to 25 degrees, a narrower portion _{L 3} of the rim of the side gate part 26a was 15 mm.

  As a result of removing the side gate from each wheel material by applying a load to the wheel material from the same direction as the load S shown in FIG. 5, the side gate is removed when the distance X is 0 to 15 mm and the width Y is 10 to 15 mm. It was confirmed that the surface condition was normal without significantly reducing the man-hours and producing no casting defects (appearance nests). On the other hand, when X is longer than 10 mm and width Y exceeds 15 mm, a large distortion occurs on the outer peripheral surface of the rim, and a large distortion occurs on the outer peripheral surface of the rim even when notch portions are not provided. Confirmed to do.

It is sectional drawing which shows an example of the die apparatus for casting used by this invention. It is an external appearance perspective view of a wheel material. FIG. 3 is an enlarged view of a main part of FIG. 2. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is a perspective view which shows the analysis model for calculating the plastic strain distribution of the wheel raw material of FIG. It is a figure which shows the plastic strain distribution of the wheel raw material which has a notch part. It is a figure which shows the plastic strain distribution of the wheel raw material which does not have a notch part. It is a figure which shows the diameter change of the inner flange of a wheel raw material.

Explanation of symbols

1: Low pressure casting mold, 11: Lower mold, 12: Upper mold, 13a, 13b: Horizontal mold,
14: cavity, 14a: disk part cavity,
14b, 14c: rim cavity, 15a, 15b: base,
16a, 16b: Side gates, 17a, 17b: Stoke, 18a, 18b: Protruding part, 19: Pusher part, 20: Wheel material, 21: Disc part 21, 22: Rim part,
23: inner flange, 24: outer flange, 25: design surface,
26a, 26b: side gate portion, 27a, 27b: notch portion, 28: end portion,
29: Unremoved part, 30: Surface plate, 31: Symmetrical boundary surface

Claims (3)

A non-product part including a side gate part is cast from the material by casting a light alloy wheel material having a rim part and a disk part by pouring into the molding cavity from a side gate provided at least adjacent to the rim part forming cavity. In the vehicle wheel manufacturing method for removing
The side gate portion is connected to the rim portion at a place where the side gate portion is thickly formed by a horizontal escape gradient that is inclined in a range of 15 to 35 degrees with respect to the movable direction ,
A notch for breaking the side gate portion with a small load is formed at a position within 10 mm from the rim surface of the light alloy wheel material of the side gate portion and along the width direction of the rim portion, Thereafter, the rim portion is lathe processed, and the vehicle wheel manufacturing method is characterized.   The method for manufacturing a vehicle wheel according to claim 1, wherein the notch is formed in a straight line. Together with the cutout portion is formed on both surfaces of the side gate part, the distance Y between the cutout portion according to claim 1 or 2, characterized in that it is set to a distance of 10mm or more 20mm or less Method for manufacturing a vehicle wheel.

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