TW201600360A - Aluminum wheel for motorcycle - Google Patents

Abstract

To provide an aluminum wheel for a motorcycle in which productivity can be improved while ensuring sufficient strength, lightweight properties, and toughness. The rim diameter is 14-17 inches. Ten spokes (151) are provided. When the smallest of the cross-section areas of cross-sections orthogonal to a direction (D1) of extension of a spoke (151) (e.g., line A-A cross-section) is deemed to be a minimum spoke cross-section area, the total sum of the minimum spoke cross-section areas of the ten spokes (151) is 8 cm2 to 15 cm2. Heat processing is performed after casting by die casting.

Description

Aluminum rim for locomotive

The present invention relates to an aluminum rim for a locomotive.

For aluminum rims for locomotives, strength and toughness are required to be ensured and lightweight. In the production of aluminum rims, in order to secure these three characteristics, the gravity casting product is subjected to T6 heat treatment (for example, Patent Document 1). The casting speed of gravity casting is relatively slow, and the air is not easily mixed, so the internal quality of the manufactured casting is good. Therefore, rims manufactured by gravity casting generally ensure high toughness. Further, according to the T6 heat treatment, the ductility is lowered as compared with the case where the heat treatment is not performed, but the strength is improved. As a result, the entire rim is made lighter by reducing the sectional area of the spokes and the sectional area of the rim within the range of ensuring strength and toughness.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-103577

However, gravity casting ensures strength, lightness, and toughness of the rim, but casting takes time, so there is a problem of low productivity. Therefore, in order to improve productivity, it is considered to use die casting.

However, when die casting is applied to casting a mold, air is easily mixed into the melt as compared with gravity casting. Therefore, compared with gravity casting, die casting is the internal product of castings. The quality is easy to get worse.

Further, when the T6 heat treatment is performed after die casting, as in the case of gravity casting, there is a so-called foaming caused by expansion of the air mixed into the melt, and the toughness of the rim is further lowered. Therefore, it is difficult for die casting to increase the strength by heat treatment. Therefore, in order to secure strength and toughness, it is necessary to make the sectional area of the spokes and the sectional area of the rims to a certain extent, and thus the weight is increased.

According to the above, it is considered that it is difficult to improve the productivity while ensuring strength, lightness, and toughness in the casting of the aluminum rim for a locomotive.

An object of the present invention is to provide an aluminum rim for a locomotive that can improve productivity while ensuring strength, lightness, and toughness.

The aluminum rim for a locomotive of the present invention has an axle insertion portion formed with an axle insertion hole into which the axle is inserted, and a spoke portion including a plurality of spokes respectively inserted from the axle insertion portion along the axle insertion hole a central axis extending radially and spaced apart from each other in a circumferential direction of the central axis; and a rim portion extending in a circumferential direction of the central axis and formed in an annular shape and connected to the plurality of spokes The spoke portion is 5 or more and 10 or less, and the minimum spoke area of the cross section orthogonal to the direction in which the spokes extend is the minimum cross-sectional area of the spoke, the spokes The sum of the minimum sectional areas is 8 cm ² or more and 15 cm ² or less, and the diameter of the rim is 14 inches or more and 17 inches or less, and heat treatment is performed after die casting.

According to the present invention, there are five or more spokes, which are relatively large. When the number of spokes is increased, the molten metal flows continuously through the spokes, so that the path for the molten metal to flow becomes short during casting. Thereby, the filling time of the melt is easily shortened. If the filling time is short, the melt containing air can be brought to the overflow portion of the mold by keeping the molten state flowing. Therefore, air does not easily remain on the rim. Thereby, heat treatment can be performed while suppressing the decrease in toughness. Further, the difference in flow length caused by the portion of the rim becomes small, and the rim strength is uniformized. Since the reduction in toughness can be suppressed and the rim strength is uniformized, the sectional area of the rim can be made small. Further, since the heat treatment can be performed, the sum of the minimum sectional areas of the spokes can be made 15 cm ² or less and relatively small.

According to the above, productivity can be improved by die casting while ensuring strength, lightness, and toughness.

In the present invention, preferably, in each of the spokes, the spoke has a minimum sectional area of 3 cm ² or less.

According to this configuration, the shape of the rim corresponds to various cross-sectional shapes in which the cross-sectional area of the rim portion or the spoke is suppressed to reduce the weight.

In the present invention, it is preferable that at least one of a cross section orthogonal to a direction in which the rim portion extends and a cross section orthogonal to a direction in which the spoke is extended has a normal direction of the outer surface The wall thickness is 4 mm or less.

According to this configuration, the shape of the rim corresponds to various cross-sectional shapes in which the rim portion or the spoke is made thin. The shape of the spokes can be selected in a variety of shapes depending on the desired appearance and strength. When the wall thickness is 4 mm or less as described above, the effect of quenching the melt upon solidification occurs, and the strength is further improved.

Further, in the present invention, the heat treatment is preferably performed by cooling the semi-finished product after die casting by using water or an aqueous solution, and then performing aging treatment.

Further, in the invention, it is preferable that at least one of the axle insertion portion, the spoke portion, and the rim portion has a 0.2% proof force of 150 MPa or more.

According to this configuration, the strength of the rim is secured. This strength can be ensured, for example, by performing water quenching at the time of casting.

In the T6 heat treatment of the rim for gravity casting, a high-temperature solution treatment is performed before the aging treatment. According to the above configuration of the present invention, since the solution treatment at a high temperature is not performed, foaming does not occur. As a result, the toughness is not lowered, which contributes to the improvement of toughness.

Further, in the invention, it is preferable that the crystal constituting the material of the axle insertion portion is The average of the particle sizes is larger than the average of the grain sizes in the materials constituting the rim portion.

This characteristic is ensured by setting the injection port of the melt at the axle insertion portion during casting.

Further, in the invention, it is preferable that the injection port of the molten metal at the time of casting is set in the axle insertion portion.

According to this configuration, at the time of casting, the casting path from the axle insertion portion to the rim portion through the spoke portion is used. Therefore, the casting path can be shortened by increasing the number of spokes, so that the effect of easily discharging air from the rim can be ensured.

1‧‧‧ locomotive

2‧‧‧front wheel

2a‧‧‧ tires

3‧‧‧ Rear wheel

4‧‧‧ body frame

7‧‧‧ Front fork

9‧‧‧Hand unit

9L‧‧‧ grip

10‧‧‧Clutch rod

11‧‧‧ Riding seat

12‧‧‧ swing arm

13‧‧‧ Engine

14‧‧‧ fuel tank

15‧‧‧ front cover

16‧‧‧ meter unit

17‧‧‧ axle

23‧‧‧foot table

26‧‧‧Chapter

100‧‧‧ rims

110‧‧‧Axle Insertion

110a‧‧‧Protruding

111‧‧·Wheel hub

111a‧‧‧Axle insertion hole

112‧‧‧Bolt holes

140‧‧‧Ran

141‧‧‧flat

142‧‧‧ recess

143‧‧‧ Both ends

143a‧‧ base

150‧‧‧ spokes

151‧‧‧ spokes

151a‧‧‧Edge

151b‧‧‧Edge

151c‧‧‧ ribs

200‧‧‧ mould

200a‧‧‧Area

200b‧‧‧Area

200c‧‧‧ area

201‧‧‧Mold

202‧‧‧Injection path

203‧‧‧Overflow

204‧‧‧Drainage path

205‧‧‧Piston

300‧‧ rims

310‧‧‧Axle Insertion

311a‧‧‧Axle insertion hole

312‧‧‧Bolt holes

340‧‧ rim

350‧‧‧ spokes

351‧‧‧ spokes

B‧‧‧ arrow

D1‧‧‧ double arrow

F‧‧‧ arrow

L‧‧‧ arrow

P‧‧‧ Straight line

Q‧‧‧Area

R‧‧‧ arrow

T1‧‧‧minimum wall thickness

T2‧‧‧ wall thickness

Fig. 1 is a side view of a locomotive according to an embodiment of the present invention.

Figure 2 is a left side view of the rim for the locomotive of Figure 1.

Fig. 3(a) is a cross-sectional view taken along line A-A of Fig. 2, and is associated with a section perpendicular to the direction in which the spoke extends. Fig. 3(b) is a cross-sectional view taken along line B-B of Fig. 2, and is related to a cross section orthogonal to the direction in which the rim portion extends. Fig. 3(c) is a cross-sectional view taken along line C-C of Fig. 2, and is related to a cross section orthogonal to the direction in which the rim portion extends.

Fig. 4 is a flow chart showing the manufacturing steps of the rim of the embodiment.

Figure 5 is a front elevational view of the mold used in the die casting step of Figure 4. The broken line indicates the structure formed inside the mold.

Fig. 6 is a view showing a rim of a variation of the front view from a slightly oblique lower side.

Hereinafter, an embodiment of the present invention will be described using the locomotive 1 as an example. The locomotive 1 is provided with a rim 100 using an aluminum rim for a locomotive of the present invention.

In the following description, the front-rear direction refers to the vehicle front-rear direction observed from the rider R riding on the following riding seat portion 11 of the locomotive 1. The left-right direction refers to the left-right direction (vehicle width direction) of the vehicle when viewed from the rider R riding on the riding seat portion 11. The arrow F direction and the arrow B direction in the figure indicate the front and the rear. The arrow L direction and the arrow R direction in the figure indicate the right side and the left side. After Figure 2, the front, back, left, and right sides The orientation corresponds to the direction in which the rim 100 is placed in the state of the locomotive 1.

As shown in FIG. 1, the locomotive 1 includes a front wheel 2, a rear wheel 3, a vehicle body frame 4, and a riding seat portion 11. A handle unit 9 is provided in a portion of the body frame 4 that is forward from the riding seat portion 11. A grip 9R is provided at the right end of the handle unit 9, and a grip 9L is provided at the left end. Further, only the grip 9L is illustrated in FIG. The grip 9R is disposed on the opposite side of the grip 9L in the left-right direction. Grip 9R is the accelerator grip. A brake lever is mounted near the grip 9R. A clutch lever 10 is attached to the vicinity of the grip 9L. The upper end portion of the front fork 7 is fixed to the handle unit 9. At the lower end of the front fork 7, an axle 17 extending in the left-right direction is fixed. The front wheel 2 is supported on the axle 17 . The front wheel 2 has a rim 100 and a tire 2a attached to the outer circumference of the rim 100.

The front end of the swing arm 12 is supported at the lower portion of the body frame 4 so as to be swingable. The rear end of the swing arm 12 supports the rear wheel 3. The portion of the swing arm 12 that is different from the swing center is connected to the body frame 4 by absorbing the impact in the up and down direction and then suspension.

The body frame 4 supports the water-cooled engine 13. Furthermore, the engine 13 can also be air cooled. The body frame 4 can directly support the engine 13 or indirectly support the engine 13 via other components. A fuel tank 14 is disposed above the engine 13.

A gearbox having a plurality of shifting gears is disposed behind the engine 13. The driving force of the engine 13 is transmitted to the rear wheel 3 via the gearbox and the chain 26. A shift pedal 24 for switching the gear of the transmission is provided on the left side of the transmission. A footrest 23 is provided on both sides of the body frame 4 and slightly in front of the rear wheel 3. The rider R rests his feet on the footrest 23 during the ride.

A front cover 15 is disposed above the front wheel 2 and before the grips 9R and 9L. The meter unit 16 is disposed between the front cover 15 and the grips 9R and 9L in the front-rear direction. The meter unit 16 is disposed to be inclined with respect to the front-rear direction and the vertical direction so that the display surface faces rearward and upward. The speed of the vehicle or the number of engine revolutions, the state of the vehicle, the distance traveled, the clock, the measurement time, etc. are displayed on the display surface.

Hereinafter, the rim 100 using the aluminum rim of the present invention will be described in more detail with reference to Figs. 2 to 4 . The rim 100 is formed of an aluminum alloy and integrally cast by a die casting method. Further, after the die casting, the rim 100 is subjected to a T5 heat treatment. Details regarding die casting and T5 heat treatment are described below.

As shown in FIGS. 2 to 4, the rim 100 has an axle insertion portion 110 formed with an axle insertion hole 111a into which the axle 17 is inserted, and a spoke portion 150 having the axle insertion portion 110 along the axle insertion hole 111a. A plurality of spokes 151 extending in the radial direction of the central axis (hereinafter, simply referred to as "radial direction"); and a rim portion 140 connected to the spokes 151. In addition, the "radial extension" in the present specification is not limited to the case of extending in a strict radial direction (for example, the radial direction shown in FIG. 2) passing through the central axis of the axle insertion hole 111a. The case of extending from the axle insertion portion 110 toward the rim portion 140 in a direction oblique to a strict radial direction is also included in the "radial extension". That is, the case where the straight line that does not pass through the central axis of the axle insertion hole 111a extends from the axle insertion portion 110 toward the rim portion 140 is also included in the "radial extension."

As shown in FIG. 2, a hub portion 111 having an axle insertion hole 111a formed therein is provided at the center of the axle insertion portion 110. The hub portion 111 has a cylindrical shape in the axial direction along the left-right direction. Further, in the axle insertion portion 110, four bolt holes 112 for fixing the brake disc are formed around the hub portion 111. Furthermore, the bolt holes may be three to six.

The axle insertion portion 110 has a substantially pentagonal plate shape including five projecting portions 110a that protrude in the radial direction toward the rim portion 140. The five projections 110a are connected to the spokes 151. The two spokes 151 extend radially from the respective projections 110a toward the rim portion 140. The region including the protruding portion 110a and the two spokes 151 connected thereto (the region surrounded by the two-point chain line Q of Fig. 2) has the same shape and the same size. Hereinafter, each of these regions is referred to as a region Q. These regions Q are arranged at equal intervals in the circumferential direction and are disposed at the same position in the radial direction. The region Q is substantially symmetrical with respect to the straight line P along the radial direction shown in FIG. In the region Q, an edge portion 151a defining a substantially triangular space in Fig. 2 is formed between the two spokes 151. Between the spokes 151 of the adjacent two regions Q, a substantially trapezoidal space defined in FIG. 2 is formed. The edge portion 151b. In this manner, the ten spokes 151 are integrally arranged at intervals in the circumferential direction of the central axis of the axle insertion hole 111a (hereinafter, simply referred to as "circumferential direction").

Each of the spokes 151 has a smaller cross-sectional area of the spokes 151 orthogonal to the direction in which the spokes 151 extend (for example, in the direction of the double arrow D1 of FIG. 2) as the self-axle insertion portion 110 faces the rim portion 140. The way is formed. Therefore, with respect to each of the spokes 151, the area in the cross section orthogonal to the direction in which the spokes 151 are orthogonal to each other is the section close to the position of the rim portion 140 (the line AA in Fig. 2). Hereinafter, the minimum sectional area is referred to as "the minimum sectional area of the spokes". The radial position of the section taking the smallest sectional area of the spoke is identical to each other between the spokes 151. The total of the ten spokes 151 is formed so that the total sum of the smallest cross-sectional areas of the spokes is 8 cm ² or more and 15 cm ² or less. Further, the spokes of each of the spokes 151 have a minimum sectional area of 1.5 cm ² or less.

Further, each of the spokes 151 has a cross section orthogonal to the direction D1 and has an H-shaped shape including two ribs 151c as shown in Fig. 3(a). In the cross-sectional shape, each of the ribs 151c is formed to be tapered toward the front end of each of the left and right sides. Further, both the left end and the right end of the rib 151c are formed in an R shape. In the present embodiment, the wall thickness of the spokes 151 is set to the size of the wall associated with the normal direction of the outer surface. Further, the wall thickness is defined in a region other than the region in which the rib 151c is formed in an R shape such as the left end or the right end. At this time, in the cross-sectional shape of Fig. 3(a), the portion of the rib 151c other than the R-shaped portion closest to the front end is the portion having the smallest wall thickness. In the present embodiment, the minimum wall thickness is 4 mm or less. Specifically, in the cross section of Fig. 3(a) showing a cross section taken along line A-A of Fig. 2, the minimum wall thickness in the portion of the rib 151c other than the R-shaped portion closest to the front end is t1. Further, the minimum wall thickness t1 is set to 4 mm or less. Furthermore, the minimum wall thickness t1 may also be in the range of 2 mm to 2.5 mm. Under certain casting conditions, the lower limit of the minimum wall thickness t1 is 1.8 mm.

The rim portion 140 extends in the circumferential direction and is formed in a ring shape. The rim portion 140 has a diameter of 14 to 17 inches and is set to be suitable for the size of a locomotive. Each spoke 151 is connected to the surface of the rim portion 140 facing the axle insertion hole 111a. In the rim portion 140, radially away from A tire 2a is attached to the surface of the axle insertion portion 110. As shown in FIGS. 3( a ) and 3 ( b ), the mounting surface of the tire 2 a includes a flat portion 141 and a concave portion 142 that is recessed from the flat portion 141 toward the axle insertion portion 110 in the radial direction. The recess 142 is formed over the entire circumference of the rim portion 140. The concave portion 142 is formed in such a manner that the region in which the spokes 151 are formed is deeper than the region where the spokes 151 are not formed in the circumferential direction. Both end portions 143 of the rim portion 140 in the left-right direction protrude in a direction opposite to the direction toward the axle insertion portion 110. The front ends of the both end portions 143 are formed in an R shape.

In the present embodiment, the thickness of the rim portion 140 is set to the size of the wall associated with the normal direction of the outer surface. Further, the wall thickness is defined in a region other than the region in which the R portion is formed at both end portions 143 except for the tip end. At this time, in the cross-sectional shape of FIG. 3(b) or FIG. 3(c), the portion having the smallest wall thickness is the base portion 143a of the both end portions 143. The base portion 143a is a portion where the edge (bead) of the tire 2a is contacted when the tire is mounted. In the present embodiment, the thickness of the portion is t2 in any of the cross sections orthogonal to the direction in which the rim portion 140 extends. Further, t2 is set to be 4 mm or less.

Hereinafter, a manufacturing procedure of the rim 100 of the present embodiment will be described with reference to Figs. 4 and 5 . First, die casting is performed using the mold 200 shown in Fig. 5 (step S1 of Fig. 4). The mold 200 is formed inside the mold 201 to have a shape corresponding to the shape of the rim 100. An injection path 202 for injecting a molten aluminum alloy into the region 200a corresponding to the axle insertion portion 110 in the mold 200 is connected. In other words, the rim 100 of the present embodiment is provided with an injection port for the melt in the axle insertion portion 110. A piston 205, a rod, and a cylinder that apply pressure to the melt are connected to the injection path 202 via a sleeve. Around the mold 200, an overflow portion 203 that discharges a portion of the molten metal that has flowed into the molten metal of the mold 200 is discharged. The overflow portion 203 is connected to a region 200c corresponding to the rim portion 140 in the mold 200. The overflow portion 203 is disposed in a direction corresponding to the circumferential direction of the rim 100, and is disposed between the regions 200b corresponding to the spokes 151 in the mold 200. The overflow unit 203 is further connected to the discharge path 204. The discharge path 204 is for discharging the air in the mold and the molten metal having poor internal quality to the flow path outside the mold 201.

After the injection of the melt into the piston 205, a higher pressure of 30 to 60 MPa (mega Pascal) is applied to the melt by the piston 205. Thereby, the melt is injected into the mold 200 from the piston 205 via the injection path 202. The melt is discharged into the overflow portion 203 in the mold 200 at a speed faster than other casting methods (0.04 to 0.16 seconds in a desired time) through the region 200a, the region 200b, and the region 200c. Thereby, the air or the like existing in the mold 200 is discharged together with the molten metal. The thick black arrow in Fig. 5 indicates an example of the flow of the melt. The melt flows into the region 200c from each of the regions 200b corresponding to the ten spokes 151, and is divided into two in the circumferential direction. The melt which is divided into two paths flows into the overflow portion 203 which exists in the circumferential direction between the regions 200b. When the molten metal flows into the region 200c from the region 200b, the molten metal flows into the overflow portion 203 which is present in the middle of the route to the adjacent region 200b. On the other hand, the distance to the adjacent region 200b is shorter as the number of spokes 151 is larger. Therefore, the more the spokes 151 are, the more easily the path from the flow of the molten metal to the region 200c until reaching the overflow portion 203 becomes shorter. Therefore, in the case where the spokes 151 are provided with a relatively large number of spokes as in the present embodiment, the path of the melt flow is relatively short.

The following differences occur in the composition of the material in the region 200a, the region 200b, and the region 200c after the die casting. First, the region 200a adjacent to the injection path 202 is cooled and solidified by a higher temperature injection to form relatively large grains. On the other hand, in the region 200b and the region 200c far from the injection path 202, the temperature of the liquid injection at the time of arrival becomes low. Therefore, in these regions, relatively small crystal grains are formed due to the cold-solidification of the injecting liquid having a lower temperature than the region 200a. The farther away from the position of the injection path 202, the lower the temperature of the liquid injection at the time of arrival, so there is a tendency to form crystal grains less. For example, the average of the grain sizes in region 200a is greater than the average of the grain sizes in region 200b or region 200c.

After the die casting (step S1 of Fig. 4), the T5 heat treatment was carried out as follows. After the end of step S1, the semi-finished product is taken out from the mold 200 (step S2 of Fig. 4). Then, quenching is performed by immersing the taken-out semi-finished product in water (step S3). Thereby, quenching is performed at a specific temperature after casting. Furthermore, as a refrigerant during quenching, water can be used in addition to water. liquid. After quenching, the aging treatment is carried out by maintaining the semi-finished product at a specific temperature for a specific period of time (step S4). By quenching, the 0.2% endurance of the cast material reaches 150 to 200 MPa. On the other hand, if it is not quenched, the tensile strength of the material after casting is less than 150 MPa.

According to the embodiment described above, since die casting is used, the time from filling to solidification is short, and productivity is higher than gravity casting or the like. Further, gravity casting is applied to the surface of the mold during casting, so that the surface of the product becomes unsmooth. On the other hand, in the case of die casting, a smooth appearance can be obtained. Specifically, in gravity casting, the ten-point average roughness of the surface of the casting is about 100 μm. In contrast, in the die casting, the ten-point average roughness of the surface of the casting is about 20 μm. Further, in gravity casting, the minimum wall thickness of the casting is about 3 mm (the limit is 2.5 mm), whereas in the die casting, the minimum thickness of the casting can be about 2 mm (the limit is 1.8 mm).

On the other hand, in the casting of aluminum rims for locomotives, it is difficult to improve the productivity while ensuring strength, lightness, and toughness due to the following reasons. Die casting is the process of casting a mold, and air is easily mixed into the melt compared to gravity casting. Therefore, die casting is less likely to be tougher than gravity casting. Further, a method of reducing the amount of air to be mixed by vacuuming the inside of the mold has been studied. However, this method is generally not widely used for die casting because the size of the mold or equipment has become large. Further, when the T6 heat treatment which is a heat treatment used in gravity casting or the like is performed, so-called foaming due to expansion of the air mixed into the melt occurs, and the toughness of the rim is further lowered. Therefore, it is difficult for die casting to increase the strength by heat treatment. Therefore, in order to secure strength and toughness, it is necessary to make the sectional area of the spokes and the sectional area of the rims to a certain extent, so that the weight is increased.

Therefore, the inventors of the present invention can perform heat treatment while suppressing the decrease in toughness by relatively increasing the number of spokes. In particular, in the present embodiment, ten spokes 151 are provided. If the spokes are increased in this manner, as described above, the path through which the melt flows during casting is shortened. With this, The filling time of the melt is easily shortened. When the filling time is short, the melt containing air can be brought to the overflow portion 203 of the mold 200 while keeping the molten state flowing. Therefore, the melt containing the poor internal quality of the air is less likely to remain in the region 200c of the mold 200 corresponding to the rim portion 140. Therefore, the toughness is not easily lowered. Further, the strength of the rim portion 140 is uniformized.

As described above, the reduction in the toughness can be suppressed, and the strength of the rim portion 140 can be made uniform, so that the cross-sectional area of the rim portion 140 can be made small. Further, since the heat treatment by T5 is used in the heat treatment and the solid solution is not performed at a high temperature, the total sectional area of the spokes can be made 15 cm ² or less and relatively small. Therefore, the weight of the rim 100 as a whole can be reduced. In this way, an aluminum rim that can improve productivity by die casting while achieving strength, lightness, and toughness is realized.

Further, if the minimum sectional area of the spokes is less than 8 cm ² , the flow of the molten metal passing through the portion at the time of casting is hindered, so that it is difficult to keep the molten metal in the flow state and the molten liquid containing the air reaches the overflow portion of the mold. Moreover, even if this does not occur, there is a possibility that the flow rate is too large and the burning occurs. Therefore, in order to avoid such problems, the minimum sectional area of the spokes is set to 8 cm ² or more. Further, if the number of spokes exceeds 10, the stress applied to each of the spokes is reduced, so that the profile coefficient of the spokes can be made small. However, if the wall thickness of the spokes is not ensured to be at least about 2 mm in order to ensure the fluidity of the melt in the die casting, casting is difficult. Therefore, an arbitrary increase in the number of spokes results in an increase in the overall weight of the rim. As a result, the significance of weight reduction by performing heat treatment is lowered. Therefore, in order to ensure the lightweight, the upper limit of the number of spokes is 10.

Further, in the present embodiment, in the cross section of the spoke 151 shown in Fig. 3(a), the minimum wall thickness t1 is 4 mm or less. Further, in the cross section of the rim portion 140 shown in Fig. 3 (b) or Fig. 3 (c), the minimum wall thickness t2 is set to 4 mm or less. Thereby, the shape of the rim 100 corresponds to various cross-sectional shapes obtained by thinning the rim portion 140 or the spokes 151. Further, if the minimum wall thickness t1 or t2 is less than about 2 mm, the melt does not easily flow during casting. Therefore, in order to facilitate the flow of the melt, it is preferable that the minimum wall thicknesses t1 and t2 are both 2 mm or more.

Further, in the present embodiment, the T5 heat treatment is employed and the T6 heat treatment is not employed. That is, after the semi-finished product is cooled by water or an aqueous solution after die casting (step S2 of FIG. 4), aging treatment is performed (step S4). In the T6 heat treatment, a solid solution treatment at a high temperature is performed before the aging treatment. On the other hand, in the case of the heat treatment of T5 in the present embodiment, since the solution treatment at a high temperature is not performed, foaming does not occur. As a result, ductility is not easily reduced, and thus, the toughness is improved. Moreover, in the case of heat treatment of T5, the solution treatment is not performed. Therefore, it is not necessary to heat the semi-finished product again, so the productivity is high.

Further, in the present embodiment, the injection port of the molten metal at the time of casting is set in the region 200a corresponding to the mold 200 of the axle insertion portion 110. Therefore, at the time of casting, the molten metal flows from the region 200a corresponding to the axle insertion portion 110 to the region 200c corresponding to the rim portion 140 through the region 200b corresponding to the spoke 151. Thereby, the casting path can be shortened by increasing the number of spokes 151. Therefore, it is possible to ensure the effect of easily discharging the molten metal having poor internal quality from the rim portion 140.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the claims. Modifications in the present specification can be carried out in appropriate combination. In addition, in the present specification, the term "better" is non-exclusive and means "preferably, but not limited to".

For example, in the above embodiment, ten spokes 151 are provided. However, the number of spokes is not limited to this. For example, five spokes 351 may be provided as in the rim 300 shown in FIG. The rim 300 is formed of an aluminum alloy, and is cast by die casting in the same manner as in the above embodiment, and subjected to T5 heat treatment after casting. The rim 300 has an axle insertion portion 310 formed with an axle insertion hole 311a, a spoke portion 350 including five spokes 351, and a rim portion 340 which is annular in the circumferential direction of the central axis of the axle insertion hole 311a. Extend the ground. In the following description of the rim 300, the "circumferential direction" and the "radial direction" are directions related to the central axis of the axle insertion hole 311a.

The axle insertion portion 310 has a disk shape, and four or three to six bolt holes 312 for fixing the brake disk are formed around the axle insertion hole 311a. The spokes 351 have the same size and the same shape as each other. Further, the spokes 351 are arranged at equal intervals in the circumferential direction and are disposed at the same position in the radial direction. The spoke 351 extends radially from the axle insertion portion 310 toward the rim portion 340. Both ends of the radial direction of the spoke 351 are formed to be thicker than the central portion in the radial direction. The DD line profile of Fig. 6 is the smallest in the section of the spoke 351 in the direction of extension. In the other spokes 351, the area of the section corresponding to the DD line profile is also the smallest. Therefore, the area of the sections is the minimum cross-sectional area of the spokes. The sum of the minimum cross-sectional areas of the spokes is set to be 8 cm ² or more and 15 cm ² or less in the same manner as in the above embodiment. The spokes in each of the spokes 351 have a minimum sectional area of 3 cm ² or less. Further, the rim portion 340 has a diameter of 14 to 17 inches and is set to be suitable for the size of a locomotive.

If there are five spokes as in the rim 300, a relatively large number of spokes can be provided. Therefore, similarly to the above embodiment, the path through which the molten metal flows during casting becomes relatively short. Therefore, the toughness is not easily lowered. Further, the strength of the rim portion 340 is uniformized. However, if the number of spokes is less than five, the path through which the melt flows becomes long, and the filling time of the melt becomes long. Therefore, air is likely to remain in the rim portion after casting. Therefore, even if heat treatment is performed, the toughness is not easily lowered, so the lower limit of the number of spokes is five.

According to the rim 300, similarly to the above-described embodiment, heat treatment can be performed while suppressing reduction in toughness, and the strength of the rim portion 140 can be made uniform, so that the cross-sectional area of the rim portion 140 can be reduced. Further, since the heat treatment can be performed, the sum of the minimum sectional areas of the spokes can be made 15 cm ² or less and relatively small. Therefore, the weight of the rim 300 as a whole can be reduced. In this way, in the rim 300, the strength, the lightness, and the toughness can be ensured, and the productivity can be improved by die casting.

Other variations are as follows. In the above embodiment, the positions of the spokes 151 which are the smallest cross-sectional areas of the spokes are the same in the radial direction. However, the radial position of the profile taking the smallest cross-sectional area of the spoke may also vary depending on the spoke.

Moreover, in the present embodiment, each spoke 151 is extended to the spokes 151 thereof. In the cross section orthogonal to the direction, the rib 151c has a minimum wall thickness near the front end. Further, in the cross section of FIG. 3(a) close to the rim portion 140, the minimum wall thickness t1 is set to 4 mm or less. Further, the rim portion 140 is a cross section orthogonal to the direction in which the rim portion 140 extends, and the base portion 143a to which the edge of the tire 2a contacts is the minimum wall thickness. Further, the minimum wall thickness t2 shown in Fig. 3 (b) or Fig. 3 (c) is set to 4 mm or less. However, it is not necessary to set the minimum wall thickness to 4 mm or less. Further, even if it is set as such, the aspect is not limited to the above embodiment. The spoke and the rim portion may be formed so that the minimum thickness of at least one of the entire spoke and the rim portion is 4 mm or less. For example, the minimum wall thickness of the spokes 151 may be set to 4 mm or less in a cross section different from that of FIG. 3(a). Further, in the rim portion 140, a portion other than the base portion 143a may have a minimum wall thickness, and the portion may be set to 4 mm or less. Further, the minimum thickness of the cross section of any of the spoke 151 and the rim portion 140 may be set to 4 mm or less.

Further, in the above-described embodiments and modifications, the case where the number of spokes is 5 and the case where it is 10. However, the number of spokes may also be any of 6 to 9.

Further, in the above embodiments and modifications, the T5 heat treatment was performed after die casting. However, other heat treatments may also be performed after die casting. If the number of spokes is in the range of 5 to 10 in this case, the toughness of the rim is not easily lowered. Moreover, the strength of the rim portion is uniformized. Thereby, strength, lightness, and toughness can be ensured, and productivity can be improved by die casting.

100‧‧‧ rims

110‧‧‧Axle Insertion

110a‧‧‧Protruding

111‧‧·Wheel hub

111a‧‧‧Axle insertion hole

112‧‧‧Bolt holes

140‧‧‧Ran

150‧‧‧ spokes

151‧‧‧ spokes

151a‧‧‧Edge

151b‧‧‧Edge

B‧‧‧ arrow

D1‧‧‧ double arrow

F‧‧‧ arrow

P‧‧‧ Straight line

Q‧‧‧Area

Claims (7)

An aluminum rim for a locomotive, comprising: an axle insertion portion formed with an axle insertion hole for inserting an axle; a spoke portion comprising a plurality of spokes, wherein the spokes are respectively from the axle insertion portion a central axis of the axle insertion hole extending radially and spaced apart from each other in a circumferential direction of the central axis; and a rim portion extending in a circumferential direction of the central axis and formed in a ring shape and connected to the above a plurality of spokes; wherein the spokes are 5 or more and 10 or less, and the smallest cross-sectional area of the cross-section of the cross section orthogonal to the direction in which the spokes extend is set as the minimum cross-sectional area of the spokes The sum of the minimum cross-sectional areas of the spokes is 8 cm ² or more and 15 cm ² or less, and the diameter of the rim is 14 inches or more and 17 inches or less, and heat treatment is performed after die casting. An aluminum rim for a locomotive according to claim 1, wherein in each of the spokes, the spoke has a minimum sectional area of 3 cm ² or less. An aluminum rim for a locomotive according to claim 2, wherein at least one of a cross section orthogonal to a direction in which the rim portion extends and a cross section orthogonal to a direction in which the spoke is extended has an outer surface The wall thickness in the line direction is 4 mm or less. The aluminum rim for a locomotive according to any one of claims 1 to 3, wherein a 0.2% proof endurance of at least one of the axle insertion portion, the spoke portion, and the rim portion is 150 MPa or more. The aluminum rim for a locomotive according to claim 4, wherein the heat treatment is performed by cooling the semi-finished product after the die casting by using water or an aqueous solution, and then performing aging treatment. The aluminum rim for a locomotive according to any one of claims 1 to 3, wherein an average value of a grain size in a material constituting the axle insertion portion is larger than an average value of a grain size in a material constituting the rim portion . The aluminum rim for a locomotive according to any one of claims 1 to 3, wherein the injection opening of the molten metal at the time of casting is set in the axle insertion portion.