JP5448019B2 - Vehicle wheel - Google Patents

Description

  The present invention relates to a vehicle wheel made of a light alloy, and more particularly, a vehicle wheel cast from a light alloy material using a mold having a cavity for forming a disk portion and a cavity for forming a rim portion provided with a pouring port for molten metal. About.

  There are various materials and structures for automobile road wheels. For the purpose of reducing the weight and improving the appearance and design of automobiles, the ratio of mounting light alloy wheels such as aluminum wheels has increased. Yes. This light alloy wheel is often manufactured by a low pressure casting method. That is, in the low pressure casting method, the molten metal is filled into the mold cavity at a low speed, so that gas entrainment and oxide generation are suppressed as much as possible as compared with other casting methods.

  Generally, a light alloy wheel 30 includes a thick hub fixing portion 25 attached to an axle by bolts and nuts as shown in FIG. 1, a disk portion having a spoke portion, and a window portion 27, and a thin wall to which a tire is attached. It consists of the rim part. In FIG. 3, the upper side is the inner side and the lower side is the outer side of the disk surface, and the cylindrical rim portion 24 and the disk portion intersect at a cross portion 26. From the viewpoint of improving the fuel efficiency of vehicles, weight reduction by changing the shape of the wheel has been studied. In this case, the hub fixing part and rim part cannot be changed significantly in terms of handling with the vehicle body and tires, so the shape of the design part can be changed (for example, the area of the design hole can be increased or the spoke part can be made thinner). However, it is extremely difficult to reduce the weight significantly.

When the wheel is manufactured by low-pressure casting, there is a method (center gate method) in which a gate is provided in the hub fixing portion 25, molten metal is injected therefrom, and molten metal is injected from the design portion toward the rim portion 24. Further, a method (side gate method) in which a plurality of (usually two) gates are provided in the rim portion 24 and molten metal is injected therefrom is also employed.
In the center gate method, the directional solidification is performed in the order of the rim portion, the design portion, and the hub fixing portion in order to sufficiently exhibit the effect of the gate hot water as a solidification form after filling the molten metal. However, in this casting method, the design part has a complicated shape in which a thick part and a thin part are mixed, so that it is difficult to achieve directional solidification from the rim part to the disk part.
On the other hand, in the side gate method, the design part itself functions as a molten metal replenishment passage to the hub fixing part, which is easy to solidify, so that the design part becomes thick in order to ensure a good hot water flow in the design part. Even with the casting method, it is difficult to significantly reduce the weight of the entire wheel.

  In order to eliminate the disadvantages of the above-mentioned methods, as described in Patent Document 1 to Patent Document 3, gates for pouring molten metal are provided at the disc center portion (hub fixing portion) and the rim portion, respectively. A method of pouring hot water into the mold from the gate (multi-gate method) has been proposed. According to this casting method, since the directional solidification from the rim portion toward the disk portion can be achieved even if the thickness of the design portion is reduced, the weight of the wheel can be significantly reduced.

JP-A-5-269563 JP-A-6-269923 Japanese Patent No. 3573338

However, when this multi-gate method is used, as described in Patent Document 3, the molten metal poured from the gate provided at the center of the disk (hub fixing portion) and the molten metal poured from the gate provided at the rim portion. The molten metal joins somewhere on the disk surface. That is, this multi-gate method has a problem that a hot water boundary is likely to occur on the disk surface where design is most important, and the vehicle wheel is likely to have a poor appearance.
In Patent Document 3, in order to solve this problem, a gate (hereinafter referred to as a side gate) provided in the rim portion is provided at a position higher than a gate (hereinafter referred to as a center gate) provided in the disc center portion (hub fixing portion). The timing at which the molten metal is poured from each gate is changed. By disposing each gate as described above, after the molten metal poured from the center gate fills the disk portion, the molten metal poured from the side gate is poured. For this reason, the hot water boundary is less likely to occur on the disk surface.
However, as a result of further investigation, the plan with a difference in height between the center gate and the side gate is that the melt flowing from the side gate merges with the melt filled in the disk surface while entraining the gas. There are problems that gas is easier to entrain than the side gate method and casting defects are likely to occur.

  An object of the present invention is to solve the above-described problems and to provide a vehicle wheel having a shape in which the gas is less involved in the molten metal.

The vehicle wheel according to the present invention is a vehicle wheel 30 that is cast from a light alloy material having a rim portion and a disk portion in which a spoke portion is formed, and the spoke portion is provided with an intermediate rib 21 on the back side. The middle rib 21 extends from the rim 24 side of the spoke portion, and is formed so as to disappear in the middle portion of the spoke portion.

  These vehicle wheels are preferably applied to those cast by a mold in which a gate is provided in a cavity forming a disk portion and a cavity forming a rim portion. Further, as a casting method, a method using a mold in which the gate of the rim part is formed at a position above the gate of the disk part is preferable.

  In the vehicle wheel of the present invention, since the intermediate rib is formed as described above, there are few portions where the gas stays even if the molten metal is poured from the center gate, and the gas entrained in the spoke portion moves toward the rim portion. It becomes easy to escape and the occurrence of casting defects can be reduced. In particular, the multi-gate method with side gates and center gates in the rim and disk portions, and even when using a die with a side gate higher than the center gate in the multi-gate method, the design surface is A sound, high-strength and lightweight vehicle wheel can be obtained.

As shown in FIG. 3, the conventional middle rib 21 is formed at the same height as the outer rib. The middle rib 21 has a substantially uniform height from the rim portion 24 side to the hub fixing portion 25 side. Although the height of the middle rib is different from the height of the outer rib, a shape in which the height of the middle rib is different between the inner diameter side and the outer diameter side has not been studied.
In the method of pouring the molten metal from the center gate with the disk surface down, the molten metal flows only under the cavity (the surface side of the disk surface) immediately after pouring. Therefore, although the molten metal is filled in the cast-out part 23, the cavity on the upper side (inner side) of the middle rib 21 is a mere gap without flowing the molten metal. The gap is gradually filled as the molten metal accumulates on the disk surface. However, since the middle rib 21 has a lower ceiling portion at the center than the inner diameter side, the molten metal is first filled at the central portion. The gas accumulated on the inner diameter side of 21 is blocked from the escape path to the rim portion 24 side.
In the present invention, the height of the inner diameter side and the outer diameter side of the intermediate rib 21 is changed, and the height is increased from the inner diameter side toward the outer diameter side. It was possible to carry out mass production while suppressing the above.

  Specific shapes are as follows: 1. Inclined so that the height on the outer diameter side of the middle rib 21 is higher than the height on the inner diameter side. 2. When the axial cross section at the position of the middle rib is viewed, the contour on the back side 42 is formed so that the outer diameter side is inclined toward the inner side than the contour on the front side 41 of the spoke portion. The middle rib 21 extends from the rim 24 side of the spoke portion, and is formed so as to disappear from the middle portion of the spoke portion.

In addition, the use of a multi-gate low-pressure casting method can achieve the effect of thinning the design portion and making the structure fine. Since the center gate for pouring the molten metal is located at a position lower than the lower end of the cavity opening of the side gate, the molten metal injected from the center gate and the molten metal injected from the side gate do not merge on the design surface. A sound design can be obtained. Of course, as described above, the hot water boundary is most conspicuous on the design surface, and therefore, the position of the side gate is preferably higher than the rim end and the design surface. In FIG. 2, the design surface is the surface position of the wheel on the lower side of the design portion. Furthermore, it is preferable that the side gate is higher than the entire spoke portion.
However, when the side gate is raised in this way, the molten metal is poured so that the molten metal flowing from the rim side falls toward the disk surface. When the gas flows into the molten metal accumulated on the disk surface, the gas merges while being entrained, so that the gas is likely to be entrained at the end of the spoke portion or at the cross portion at the boundary between the rim portion and the spoke portion. Therefore, casting defects are more likely to occur in the multigate method than in the center gate method.
In the present invention, since the intermediate rib has the shape as described above, the cross-sectional area of the spoke portion decreases toward the inner diameter side, and the molten metal flowing from the side gate side to the disk surface does not easily enter the inner diameter side of the spoke portion. . For this reason, the entrainment of gas in the spoke portion can be reduced. Moreover, even if gas enters the spoke portion, the gas is easily drawn out to the rim side, and the occurrence of casting defects can be suppressed.

By providing the side gate above the cross portion, the side gate can be easily broken in structure. Since the influence of the stress on the vehicle wheel during folding is reduced, it is possible to cast a high roundness aluminum wheel. The cross portion refers to a portion where the rim portion and the disc portion intersect. If the side gate is formed in an L shape on the two sides of the rim wall and the cross wall, a large structural mechanical force is required to buckle and remove the side gate. A great amount of bending stress and shear force are applied. When this wheel is heat-treated, the roundness of the wheel may deteriorate due to the influence of the bending stress or the like. Therefore, it is preferable to form the side gate only on the vertical wall of the rim portion.
Further, the molten metal does not flow from the side gate through the lateral wall of the cross portion directly toward the disk portion, and there is no merge of molten metal that entrains gas into the molten metal filled on the disk surface.

  In the present invention, casting is performed using an aluminum alloy material corresponding to AC4C or AC4CH material defined in JIS. For example, Cu 0.20 mass% or less, Si 6.5-7.5 mass% or less, Mg 0.25-0.45 mass% or less, Zn, Fe, Mn, Ni, Ti, Pb, Sn, Cr are impurities and the total amount Is preferably an aluminum alloy material having a composition of 0.8 mass% or less and the balance being Al.

Hereinafter, the details of the present invention will be described with reference to the drawings.
FIG. 4 is a sectional view showing a main part of a casting apparatus for carrying out the present invention.
In FIG. 4, reference numeral 1 denotes a mold, and a lower mold 2 having various surface shapes corresponding to a wheel design, an upper mold 3 positioned above the lower mold 2, and a lower mold 2 and an upper mold 3 are fitted into the cavity. The horizontal molds 4 and 5 are slidable to the left and right so as to form 6. The lower mold 2 is installed on a lower mold base 8 fixed to the lower mold platen 7. The upper die 3 is fixed to the upper die base 9 with bolts 10. The cavity 6 includes a disk part cavity 60 and a rim part cavity 61. The disk part cavity 60 includes a hub fixing part cavity 62 and a design part cavity 63. The rim part cavity 61 includes a cross part cavity 64 and a central part cavity 65. Become. A center gate 11a is formed in the hub fixing portion cavity 62, and side gates 11b and 11c are formed in the cross portion cavities 64 and 64, respectively. The gates are connected to the stalks 13a, 13b and 13c via the runners 12a, 12b and 12c. Communicating with The gates 11b and 11c are arranged symmetrically on both sides of the center gate 11a, that is, the centers of the gates are located on the same straight line. The lower end portions of these stalks are inserted into a sealed container (not shown) in which the molten metal is accommodated. The lower mold 2 is provided with a lower mold cooling passage 14 at a position corresponding to the design portion cavity 63. Reference numeral 15 denotes a mold breaking surface.

The operation of the above configuration will be described. First, by pressurizing the molten metal in the sealed container, the molten metal is filled into the cavity 6 from the gates 11a, 11b and 11c through the runners 12a, 12b and 12c from the stalks 13a, 13b and 13c.
Here, since there is a height difference between the center gate 11a and the side gates 11b and 11c, the molten metal passing through the center gate 11a fills the design portion cavity 63, and the molten metal passing through the side gates 11b and 11c is rim. The partial cavity 61 is filled. That is, the molten metal joins at the rim cavity 61. When the pressurization is released after the lapse of a predetermined time, the molten metal in each stalk returns to the sealed container, and the molten metal in the cavity 6 is solidified to obtain a vehicle wheel.

It is as follows when the solidification process of the molten metal in said casting process is explained in full detail. The molten metal injected into the cavity 6 from the side gates 11b and 11c is solidified from the upper end of the rim cavity 65 toward the lower end thereof. On the other hand, the molten metal injected from the center gate 11 a into the disk part cavity 60 progresses from the design part cavity 63 toward the hub fixing part cavity 62. Therefore, it is not necessary to provide the design portion cavity 63 with a hot water flow function or a molten metal replenishment function, and the wheel design portion can be made thinner in terms of the casting method. Moreover, since the solidification starts from the design part, the structure of the design part becomes fine and high strength can be maintained.
In addition, in the present invention, since the side gate is provided at a position avoiding the rim end, the structure of the portion requiring high strength such as the front flange or the center of the rim becomes fine, and the thin portion of the design portion is also seen from the viewpoint of strength. Can be realized.

The main part of the vehicle wheel of the present invention is shown in FIG. FIG. 1 shows the spoke part observed from the back side of the disk part. The vehicle wheel of the present invention uses a casting apparatus shown in FIG. 4 to inject a molten metal (about 450 ° C.) of Al—Si—Mg alloy (JIS AC4CH) into a mold (heated to about 480 ° C.). (Pressure 0.5-0.7 kg / cm < ² >) It casted integrally. In FIG. 1, a cast portion connecting the central rim portion and the hub fixing portion 25 is a spoke portion. On the back side of the spoke portion, an outer rib 23 is formed on the window portion 27 side. Further, a cast-out part 23 is formed at the center, and an intermediate rib 21 is formed in the center in the radial direction. As shown in FIG. 2, the middle rib 21 is formed so that its height gradually decreases from the rim portion side toward the hub fixing portion on the center side. Further, the intermediate rib loses its height before reaching the hub fixing portion 25 on the center side, and the cast-out portion 23 is formed in a substantially U shape. The contour 41 on the back side of the middle rib 21 is formed obliquely with respect to the direction perpendicular to the rotation axis so as to go to the inner side as it goes to the beam side.
As a comparison, FIG. 3 shows a conventional medium rib shape. The conventional middle rib 21 is uniformly formed at substantially the same height from the rim portion side to the central hub fixing portion. In FIG. 3, the height of the middle rib 21 is the same as the height of the outer rib. Moreover, it forms so that it may approach an inner side as it goes to an inner diameter side.
Casting was performed by low-pressure casting using the casting mold shown in FIG. The rate of occurrence of casting defects in mass production was about 5% when casting with the shape of FIG. 3, whereas it was 2.3% when casting with the shape of FIG. . Due to this casting defect, a casting defect that looks like a wrinkle on the surface side of the spoke portion occurs. Since correction by reworking is required, the vehicle wheel of the present invention is useful because it can reduce the cost due to a decrease in yield.

It is a figure which shows the principal part of the wheel for vehicles of this invention. It is sectional drawing (AA cross section of FIG. 1) along the middle rib of the vehicle wheel of this invention. It is sectional drawing along the middle rib of the conventional vehicle wheel. It is sectional drawing which shows the principal part of the casting apparatus used by this invention.

Explanation of symbols

  1 Mold, 2 Lower mold, 3 Upper mold, 4,5 Horizontal mold, 6 Cavity, 11a, 11b, 11c Gate, 21 Medium rib, 22 Outer rib, 23 Casting part, 24 Rim part, 25 Hub fixing part, 26 Cross part, 27 Window part, 30 Wheel for vehicle, 41 Outline on the back side of middle rib,

Claims (3)

A vehicle wheel (30) cast from a light alloy material having a disk portion with a spoke portion and a rim portion,
The spoke portion is provided with a middle rib (21) on the back side, and the middle rib (21) is formed so as to extend from the rim (24) side of the spoke portion and disappear from the middle part of the spoke portion. Vehicle wheel. 2. The vehicle wheel according to claim 1 , wherein the vehicle wheel is cast with a mold in which a gate is provided in a cavity forming a disk portion and a cavity forming a rim portion. 3. The vehicle wheel according to claim 2 , wherein the mold is formed such that the gate of the rim portion is located above the gate of the disk portion.

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