wheel

Abstract

A wheel (100) comprises a boss part (10), a rim part (20), and a plate part (30). The boss part (10) includes a contour line (14) extending from the plate part (30) to an end face (12) in the axial direction of the boss part (10) when viewed in a longitudinal cross-section of the wheel (100). The contour line (14) includes curves (141, 142). The first curve (141) is continuous with the plate part (30). The first curve (141) has a first curvature radius (R1). The second curve (142) is positioned on the side of the end face (12) in the axial direction of the boss part (10) with respect to the first curve (141). The second curve (142) has a second curvature radius (R2). The second curvature radius (R2) is larger than the first curvature radius (R1). The length of the second curve (142) is longer than that of the first curve (141).

Description

[Technical Field]

[0001] The present disclosure relates to wheels for rail vehicles. [Background technology]

[0002] A railway vehicle wheel comprises a boss portion, a rim portion, and a plate portion. An axle is inserted into the boss portion. The rim portion is disposed on the outer periphery of the boss portion. The rim portion includes a tread surface and a flange. The tread surface is the surface that contacts the top surface of the rail. The flange is provided contiguous with one end of the tread surface and protrudes toward the outer periphery of the wheel relative to the tread surface. The plate portion connects the rim portion and the boss portion.

[0003] Wheels of various shapes have been proposed in the past. For example, Patent Documents 1 and 2 disclose wheels having a curved plate portion. In Patent Document 1, the plate portion has a substantially S-shape in a longitudinal cross section of the wheel. In Patent Document 2, the plate portion has a curved shape that is convex on one side in the axle direction in a longitudinal cross section of the wheel.

[0004] The wheels of Patent Documents 3 and 4 have a substantially straight plate portion. In the wheels of Patent Documents 3 and 4, the plate portion is inclined with respect to the radial direction of the wheel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-29401 [Patent Document 2] Special Publication No. 2009-545484 [Patent Document 3] International Publication No. 2020 / 241401 [Patent Document 4] International Publication No. 2022 / 091764 Summary of the Invention [Problem to be solved by the invention]

[0006] Strength is a fundamental requirement for railway vehicle wheels. Furthermore, railway vehicle wheels are also required to be lightweight from the viewpoints of energy conservation and reducing track aggression. In other words, it is preferable for railway vehicle wheels to have the required strength while being as lightweight as possible.

[0007] An object of the present disclosure is to provide a wheel for a railway vehicle that can achieve weight reduction while ensuring strength. [Means for solving the problem]

[0008] A railway vehicle wheel according to the present disclosure comprises a boss portion, a rim portion, and a plate portion. The boss portion has a cylindrical shape. The rim portion is disposed on the outer periphery of the boss portion. The plate portion connects the boss portion and the rim portion. When viewed in a longitudinal cross section of the wheel, the boss portion includes a contour line extending from the plate portion to an axial end face of the boss portion. The contour line includes a first curve and a second curve. The first curve is continuous with the plate portion. The first curve is curved concavely inward of the boss portion and has a first radius of curvature. The second curve is disposed on the axial end face side of the boss portion relative to the first curve. The second curve is curved concavely inward of the boss portion and has a second radius of curvature. The second radius of curvature is greater than the first radius of curvature. The line length of the second curve is greater than the line length of the first curve. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to reduce the weight of a wheel for a railway vehicle while ensuring the strength of the wheel. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a longitudinal sectional view of a wheel for a railway vehicle according to an embodiment. [Figure 2] FIG. 2 is a longitudinal sectional view of a railway vehicle wheel according to a modified example of the above embodiment. [Figure 3] FIG. 3 is a longitudinal sectional view of a railway vehicle wheel according to another modified example of the above embodiment. [Figure 4]FIG. 4 is a diagram showing the outer edge of a longitudinal section of a wheel used in the second embodiment. [Figure 5] FIG. 5 is a diagram showing the outer edge of a longitudinal section of a wheel used in the third embodiment. [Figure 6] FIG. 6 is a diagram showing the outer edge of a longitudinal section of a wheel used in the fourth embodiment. [Figure 7] FIG. 7 is a diagram showing the 1 / 3 octave band frequency characteristics of equivalent radiated power (ERP). DETAILED DESCRIPTION OF THE INVENTION

[0011] A railway vehicle wheel according to an embodiment includes a boss portion, a rim portion, and a plate portion. The boss portion has a cylindrical shape. The rim portion is disposed on the outer periphery of the boss portion. The plate portion connects the boss portion and the rim portion. When viewed in a longitudinal cross section of the wheel, the boss portion includes a contour line extending from the plate portion to an axial end face of the boss portion. The contour line includes a first curve and a second curve. The first curve is continuous with the plate portion. The first curve is curved concavely inward of the boss portion and has a first radius of curvature. The second curve is disposed closer to the axial end face of the boss portion than the first curve. The second curve is curved concavely inward of the boss portion and has a second radius of curvature. The second radius of curvature is greater than the first radius of curvature. The line length of the second curve is greater than the line length of the first curve (first configuration).

[0012] When a railway vehicle wheel is viewed in longitudinal section, the boss portion includes a pair of contour lines that form its outer circumferential surface. One contour line continues to the plate portion on the flange side and extends to one axial end face of the cylindrical boss portion. The other contour line continues to the plate portion on the opposite side of the flange and extends to the other axial end face of the boss portion. Each contour line typically consists of a curved line that forms a fillet portion connecting the boss portion to the plate portion and a straight line that extends from the curved line to the end face of the boss portion. For example, if the proportion of straight lines in the contour line is relatively large, the thickness of the boss portion tends to be large. Increasing the thickness of the boss portion increases the weight of the wheel.

[0013] One possible way to reduce the wheel weight is to make the entire boss contour a single curve with a constant radius of curvature. However, if the boss contour is made of a single curve with a constant radius of curvature, it becomes difficult to balance weight reduction and strength. For example, to smoothly connect the boss to the plate, the slope of the tangent to the plate-side end of the single curve constituting the boss contour must match the slope of the plate contour. However, if the boss contour extends from the plate to the end face of the boss with a constant and relatively large radius of curvature, the thickness of the boss is expected to be very thin near the end face of the boss. This reduces the boss's grip on the axle, which could result in insufficient wheel strength. On the other hand, while a small radius of curvature can be used to ensure a sufficient boss thickness, an excessively small radius of curvature results in the boss contour flaring outward in the radial direction near the end face of the boss (a flared shape). This not only increases the wheel weight but also increases the likelihood of stress concentration at the boundary between the boss and the plate. Therefore, if the contour line of the boss portion is formed by a single curve with a constant radius of curvature, it is difficult to reduce the weight of the wheel while ensuring the strength of the wheel, and the degree of freedom in wheel design is reduced.

[0014] In contrast, in a wheel according to a first configuration, a first curve and a second curve are provided on the contour line of the boss portion. The second curve is located closer to the end face of the boss portion than the first curve. This second curve allows the outer peripheral surface of the boss portion to be hollowed out in a concave shape. Therefore, the thickness of the boss portion can be reduced compared to when the portion of the contour line of the boss portion closer to the end face of the boss portion is configured as a straight line. This allows the weight of the boss portion and the wheel to be reduced. Meanwhile, the first curve is a fillet portion connecting the boss portion to the plate portion, and has a smaller radius of curvature than the second curve on the end face side of the boss portion. Because the first curve is provided as a fillet portion separately from the second curve on the end face side of the boss portion, the contour line of the boss portion can be smoothly connected to the plate portion without having to be flared. This prevents stress concentration at the boundary between the boss portion and the plate portion, ensuring the strength of the wheel.

[0015] In this way, according to the first configuration, it is possible to ensure the strength of the wheel for a railway vehicle while realizing a reduction in the weight of the wheel.

[0016] In addition to being lightweight, railway vehicle wheels are required to be quiet from an environmental perspective. However, improving wheel quietness is in a trade-off relationship with reducing the wheel's weight. In other words, improving the quietness of wheels while a railway vehicle is running usually results in an increase in the wheel's weight.

[0017] The inventors used general-purpose structural analysis software to perform a frequency response analysis using the finite element method in order to identify the parts of a railway vehicle wheel that affect quietness. In this analysis, a force simulating rail reaction force was applied to the tread of a 360° wheel model, and the response to vibration at that time was evaluated. The evaluation index used was equivalent radiated power (ERP), which is calculated using the following formula:

[0018]

number

[0019] In the above formula, ΔS i is the element area of ​​the wheel surface, and V ni is the vibration velocity in the normal direction of the surface. c is a coefficient determined by atmospheric conditions, etc. The larger the ERP, the higher the ability to radiate sound. The wheel material was carbon steel with a carbon content of 0.7%.

[0020] Figure 7 is a graph obtained by performing a frequency response analysis, showing the 1 / 3 octave band frequency characteristics of ERP. OA in Figure 7 is the sum of the energy amounts of all frequencies (overall ERP level). As shown in Figure 7, the ERP levels at frequencies A, B, and C are higher than the ERP levels in other frequency bands, confirming that frequencies A, B, and C contribute significantly to OA. We then investigated the wheel deformation modes for each of frequencies A, B, and C, and found that the amount of displacement in the boss was very small compared to the rim and plate. This suggests that the shape of the boss has only a minor effect on ERP, or in other words, on wheel quietness.

[0021] Based on the new finding that the shape of the boss has only a minor effect on the quietness of the wheel, the first configuration reduces the weight of the boss by devising a new shape. More specifically, by positioning the second curve, which has a relatively large radius of curvature, on the contour line of the boss, closer to the end face of the boss than the first curve, which acts as a fillet, the thickness of the boss is reduced while maintaining the rigidity of the plate, which contributes greatly to quietness. This makes it possible to reduce the weight of the wheel while maintaining the quietness of the wheel when the railway vehicle is running.

[0022] The second radius of curvature is preferably equal to or greater than 108 mm and less than 700 mm (second configuration).

[0023] In the second configuration, the radius of curvature of the second curve on the end face side of the boss portion of the contour line extending from the plate portion is 108 mm or more and less than 700 mm. In this case, the wheel weight can be reduced while improving the quietness of the wheel when the railway vehicle is running.

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0025] [Wheel configuration] FIG. 1 is a longitudinal cross-sectional view of a wheel 100 for a railway vehicle according to this embodiment. The longitudinal cross-section of the wheel 100 refers to a cross-section of the wheel 100 that includes a central axis X. Because the longitudinal cross-section of the wheel 100 is symmetrical with respect to the central axis X, FIG. 1 shows only one side of the wheel 100 about the central axis X. In this embodiment, the direction in which the central axis X of the wheel 100 extends is referred to as the axial direction. Also, in this embodiment, the radial direction of the wheel 100 may be simply referred to as the radial direction.

[0026] Referring to FIG. 1, a wheel 100 includes a boss portion 10, a rim portion 20, and a plate portion 30.

[0027] The boss portion 10 forms the inner periphery of the wheel 100. The boss portion 10 has a cylindrical shape. An axle (not shown) of a railway vehicle is inserted into the boss portion 10.

[0028] The rim portion 20 is disposed on the outer peripheral side of the boss portion 10. The rim portion 20 forms the outer peripheral portion of the wheel 100. The rim portion 20 includes a tread surface 21 and a flange 22.

[0029] The tread surface 21 is provided on the outer peripheral surface of the rim portion 20. The tread surface 21 is a surface facing outward in the radial direction of the wheel 100. The tread surface 21 comes into contact with the top surface of the rail on which the railway vehicle runs.

[0030] The flange 22 is provided contiguous with one end of the tread 21 in the axial direction of the wheel 100. The flange 22 protrudes radially outward from the tread 21. When the railway vehicle runs on the rail, the flange 22 is positioned on the inside of the rail in the track width direction. Hereinafter, the side closer to the flange 22 in the axial direction will be referred to as the flange side, and the side farther from the flange 22 in the axial direction will be referred to as the anti-flange side.

[0031] In this embodiment, the rim portion 20 is positioned inward in the track width direction relative to the boss portion 10. More specifically, the rim width center Cr is located closer to the flange than the boss width center Cb. The rim width center Cr is the center of the rim portion 20 in the axial direction of the wheel 100. The boss width center Cb is the center of the boss portion 10 in the axial direction of the wheel 100.

[0032] The plate portion 30 is annular and connects the boss portion 10 and the rim portion 20. The plate portion 30 is formed integrally with the boss portion 10 and the rim portion 20. In the example of this embodiment, the plate portion 30 has a substantially straight shape when viewed in vertical cross section of the wheel 100. The plate portion 30 may be inclined with respect to the radial direction of the wheel 100. In the example of FIG. 1, the plate portion 30 is inclined with respect to the radial direction so that the outer periphery of the plate portion 30 is positioned on the anti-flange side compared to the inner periphery.

[0033] Still referring to FIG. 1, the configuration of the boss portion 10 will be described in more detail.

[0034] As shown in FIG. 1, the boss portion 10 includes an inner peripheral surface 11, end surfaces 12 and 13, a contour line 14, and corner portions 15.

[0035] When viewing the wheel 100 in vertical cross section, the inner circumferential surface 11 of the boss portion 10 extends in the axial direction of the wheel 100. When viewing the wheel 100 in vertical cross section, the end faces 12, 13 of the boss portion 10 are continuous with both ends of the inner circumferential surface 11 and extend radially outward from the inner circumferential surface 11. One end face 12 is located on the opposite flange side from the other end face 13.

[0036] When viewed in a longitudinal cross section of the wheel 100, the contour line 14 of the boss portion 10 is disposed radially outward relative to the inner circumferential surface 11. When viewed in a longitudinal cross section of the wheel 100, the contour line 14 extends from the plate portion 30 to an end face 12 on the anti-flange side of the boss portion 10. When viewed in a longitudinal cross section of the wheel 100, the contour line 14 is provided continuous with the contour line 31 on the anti-flange side of the plate portion 30. Furthermore, the contour line 14 is connected to the end face 12 on the anti-flange side of the boss portion 10 via a substantially arc-shaped corner portion 15. The contour line 14 includes a first curve 141 and a second curve 142.

[0037] The first curve 141 is continuous with the plate portion 30. In a vertical cross-sectional view of the wheel 100, the first curve 141 is disposed adjacent to the contour line 31 on the anti-flange side of the plate portion 30. The first curve 141 is smoothly connected to the contour line 31 of the plate portion 30. In a vertical cross-sectional view of the wheel 100, the first curve 141 is curved concavely toward the inside of the boss portion 10. The first curve 141 is a fillet portion that connects the boss portion 10 to the plate portion 30.

[0038] The second curved line 142 is disposed closer to the end face 12 of the boss portion 10 than the first curved line 141. In this embodiment, the second curved line 142 is provided continuous with the first curved line 141. The second curved line 142 extends from the first curved line 141 to the corner portion 15. The second curved line 142 is curved concavely toward the inside of the boss portion 10.

[0039] The first curve 141 has a radius of curvature R1. The second curve 142 has a radius of curvature R2. The radius of curvature R2 of the second curve 142 is larger than the radius of curvature R1 of the first curve 141, which is a fillet portion. The radius of curvature R2 of the second curve 142 is, for example, 2.0 times or more, and preferably 2.5 times or more, the radius of curvature R1 of the first curve 141. The radius of curvature R2 of the second curve 142 is preferably 108 mm or more and less than 700 mm. The radius of curvature R2 of the second curve 142 is more preferably 108 mm or more and 200 mm or less, and even more preferably 110 mm or more and 200 mm or less. The radius of curvature R1 of the first curve 141 is, for example, 50 mm or less. The radius of curvature R1 of the first curve 141 may be 30 mm or more.

[0040] When viewed in a vertical cross section of the wheel 100, the line length of the second curve 142 is greater than the line length of the first curve 141. In other words, the proportion of the contour 14 of the boss portion 10 that is occupied by the second curve 142 is greater than the proportion that is occupied by the first curve 141. The line length of the second curve 142 is, for example, 1 / 3 or more of the line length of the entire contour 14. The line length of the second curve 142 is preferably 2 / 5 or more, and more preferably 2 / 3 or more, of the line length of the entire contour 14. The line length of the entire contour 14 is the length along the outer shape of the wheel 100 from the boundary between the contour 31 of the plate portion 30 and the first curve 141 to the end of the R on the side opposite the end face 12 of the corner portion 15.

[0041] The first curve 141 is a single curve with a substantially constant radius of curvature in a vertical cross-sectional view of the wheel 100. The second curve 142 may be any line that can be recognized as a single continuous curve in a vertical cross-sectional view of the wheel 100. For example, if a pseudo-curve is formed by connecting multiple straight lines of short length, this pseudo-curve can be regarded as a single continuous curve. Also, for example, if a pseudo-curve is formed by a mixture of straight lines and curves of short length, this pseudo-curve can be regarded as a single continuous curve. In this embodiment, a curve is defined as a line that extends with a radius of curvature of less than 1000 mm.

[0042] The first curve 141 and the second curve 142 can be specified as follows.

[0043] In a longitudinal cross-sectional view of the wheel 100, there is usually a point where the curvature changes at the boundary between the contour line 31 of the plate portion 30 and the contour line 14 of the boss portion 10. A single curve that extends from this curvature change point radially inward and toward the end face 12 of the boss portion 10 with a constant radius of curvature can be identified as the first curve 141.

[0044] The second curve 142 exists in a region of the contour 14 of the boss portion 10 that is radially inward of the first curve 141. In this region, a line that can be recognized as a single, seemingly continuous curve can be identified as the second curve 142. For example, an obvious straight line with a line length of more than 90 mm or a broken line that forms a distinctive shape such as an uneven shape is not included in the line that can be recognized as a single curve. The radius of curvature R2 of the second curve 142 can be the radius of curvature when a line that can be recognized as a single curve is approximated as an arc. If there are multiple lines that can be recognized as a single, seemingly continuous curve in a region of the contour 14 of the boss portion 10 that is radially inward of the first curve 141, the line that has the largest length and a radius of curvature when approximated as an arc that is greater than the radius of curvature R1 of the first curve 141 is the second curve 142.

[0045] When the axial distance between both end faces 12, 13 of boss portion 10 is defined as the overall width W0 of boss portion 10, and the axial distance from end face 12 on the contour line 14 side to the apex of curvature of first curve 141 is defined as the width W1 of contour line 14, it is preferable that the width W1 of contour line 14 account for a large proportion of the overall width W0 of boss portion 10. The overall width W0 of boss portion 10 and the width W1 of contour line 14 preferably satisfy W1 / W0≧0.5, and more preferably W1 / W0≧0.6. There is no particular upper limit to W1 / W0, but it may be, for example, W1 / W0≦0.8.

[0046] As shown in FIG. 1, the boss portion 10 has a boss thickness T. The boss thickness T is the radial length from the inner peripheral surface 11 of the boss portion 10 to the boundary between the contour line 14 and the corner portion 15 (where the R of the corner portion 15 ends). From the viewpoint of ensuring the force with which the boss portion 10 grips the axle, the boss thickness T is preferably 10 mm or more. The boss thickness T may be 20 mm or more. The boss thickness T is, for example, 60 mm or less. The boss thickness T is preferably 45 mm or less.

[0047] Although not particularly limited, such a wheel 100 can be manufactured by, for example, forging, casting, or machining (cutting) a forged or cast product, etc. The material of the wheel 100 is preferably carbon steel.

[0048] [effect] In the wheel 100 according to this embodiment, the contour line 14 of the boss portion 10 has a first curve 141. The first curve 141 is adjacent to the contour line 31 of the plate portion 30 and has a relatively small radius of curvature R1. This first curve 141 smoothly connects the contour line 14 of the boss portion 10 to the contour line 31 of the plate portion 30. Furthermore, because the first curve 141 does not extend to the vicinity of the end face 12 of the boss portion 10, it is possible to prevent the contour line 14 from becoming flared toward the end face 12. This makes it difficult for stress to concentrate at the boundary between the contour line 14 of the boss portion 10 and the contour line 31 of the plate portion 30. This ensures the strength of the wheel 100.

[0049] In the wheel 100 according to this embodiment, the contour line 14 of the boss portion 10 is further provided with a second curve 142. The second curve 142 is positioned closer to the end face 12 of the boss portion 10 than the first curve 141. The second curve 142 extends toward the end face 12 of the boss portion 10, carving out a concave shape in the outer circumferential surface of the boss portion 10 with a relatively large radius of curvature R2. This makes it possible to reduce the boss thickness T on the end face 12 side. This makes it possible to reduce the weight of the boss portion 10 and the wheel 100 including the boss portion 10.

[0050] As described above, according to this embodiment, the required strength of the wheel 100 for railway use can be ensured, and the weight of the wheel 100 can be reduced.

[0051] When the wheel 100 is running, the boss portion 10 is less likely to deform than the rim portion 20 and the plate portion 30, and the shape of the boss portion 10 has little effect on the quietness of the wheel 100. For this reason, in this embodiment, in addition to the first curve 141 serving as a fillet portion, a second curve 142 having a relatively large radius of curvature R2 is provided on the end face 12 side of the boss portion 10 in the contour line 14 of the boss portion 10, thereby reducing the thickness of the boss portion 10. In this case, the weight of the boss portion 10 and the wheel 100 including the boss portion 10 can be reduced without substantially reducing the quietness of the wheel 100.

[0052] In this embodiment, the radius of curvature R2 of the second curve 142 is preferably 108 mm or more and less than 700 mm. This makes it possible to improve the quietness of the wheel 100 when the railway vehicle is running while reducing the weight of the wheel 100. From the viewpoint of further reducing the weight of the wheel 100, the radius of curvature R2 of the second curve 142 is more preferably 108 mm or more and 200 mm or less, and even more preferably 110 mm or more and 200 mm or less.

[0053] In the wheel 100 according to this embodiment, it is preferable that the ratio of the width W1 of the contour line 14 to the overall width W0 of the boss portion 10 is large. The overall width W0 of the boss portion 10 and the width W1 of the contour line 14 preferably satisfy, for example, W1 / W0≧0.5, and more preferably W1 / W0≧0.6. When W1 / W0 is large, the length of the second curve 142 included in the contour line 14 is more likely to be ensured. In other words, the area of ​​the boss portion 10 that is hollowed out concavely by the second curve 142 is more likely to be large. Therefore, when W1 / W0 is large, a greater weight reduction in the wheel 10 can be achieved than when W1 / W0 is small, even if the radius of curvature R2 of the second curve 142 is the same.

[0054] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0055] In the wheel 100 according to the above embodiment, the rim width center Cr is located closer to the flange than the boss width center Cb. In addition, in the above embodiment, the plate portion 30 is substantially straight in a vertical cross-sectional view of the wheel 100. Furthermore, in the above embodiment, the contour line 14 of the boss portion 10, including the curves 141 and 142, is provided continuous with the contour line 31 on the anti-flange side of the plate portion 30. However, the shape of the wheel 100 and the location where the contour line 14 is provided are not limited to the example of the above embodiment.

[0056] For example, as in the wheel 100 shown in Figure 2, the rim width center Cr may be located on the anti-flange side of the boss width center Cb. Also, as shown in Figure 2, the plate portion 30 may be curved in a vertical cross-sectional view of the wheel 100. In the example of Figure 2, the contour line 14 of the boss portion 10 is continuous with the contour line 31 on the anti-flange side of the plate portion 30, as in the above embodiment. However, the contour line 14 including the curves 141 and 142 may also be continuous with the contour line 32 on the flange side of the plate portion 30.

[0057] For example, even when the rim width center Cr is located on the flange side of the boss width center Cb, as in the wheel 100 shown in Figure 3, the contour line 14 of the boss portion 10 can be provided continuous with the flange-side contour line 32 of the plate portion 30. In this case, when viewed in vertical cross section of the wheel 100, the contour line 14 extends from the flange-side contour line 32 of the plate portion 30 and is connected to the flange-side end face 13 of the boss portion 10 via a corner portion 15.

[0058] In this way, the contour line 14 of the boss portion 10 described in the above embodiment can be applied to any basic shape of a railway vehicle wheel. The contour line 14 including the curves 141 and 142 only needs to be located adjacent to at least one of the contour line 31 on the anti-flange side of the plate portion 30 and the contour line 32 on the flange side.

[0059] In the above embodiment, the contour line 14 of the boss portion 10 is composed of two curves 141, 142. However, the contour line 14 may include three or more curves with different radii of curvature. When the contour line 14 includes three or more curves, the curve that is located closest to the plate portion 30 among these curves is the first curve 141, and the curve that has the longest line length and a larger radius of curvature than the radius of curvature R1 of the first curve 141 among the remaining curves is the second curve 142. From the perspective of ensuring a sufficient line length for the second curve 142 and effectively reducing the weight of the boss portion 10, it is preferable that the number of curves included in the contour line 14, i.e., the number of lines that are considered to be one continuous curve, be four or less.

[0060] The contour line 14 of the boss portion 10 may include one or more straight lines in addition to multiple curves. A straight line here refers to a region of the contour line 14 that has a line length of more than 90 mm and a radius of curvature of 1000 mm or more, for example. When the contour line 14 includes one or more straight lines, the line length of the straight lines is significantly shorter than the line length of the second curve 142. [Example]

[0061] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to the following examples.

[0062] [First Example] To confirm the effects of the present disclosure, a finite element analysis was performed on the shape of the wheel 100 shown in Figure 1 using general-purpose structural analysis software. In this analysis, a force simulating a rail reaction force was applied to the tread of a 360° wheel model, and the response to vibration at that time was evaluated as the quietness of the wheel. The above-mentioned equivalent radiated power (overall ERP level) was used to evaluate the quietness. The conditions and results of this analysis are shown in Table 1.

[0063] [Table 1]

[0064] The "Weight" column in Table 1 shows the value obtained by subtracting the wheel weight of each example from the wheel weight of Comparative Example 1 (the difference between each example and Comparative Example 1). The "Quietness Index" column in Table 1 shows the value obtained by subtracting the overall ERP level of each example from the overall ERP level of Comparative Example 1 (the difference between each example and Comparative Example 1). A positive weight value in Table 1 indicates that the wheel is lighter than Comparative Example 1. A positive quietness index value in Table 1 indicates that the quietness of the wheel is improved compared to Comparative Example 1. Comparative Example 1 has a straight line instead of the second curve 142 on the outer circumferential side of the boss portion 10. Therefore, in Table 1, the radius of curvature R2 of the second curve 142 of Comparative Example 1 is shown as ∞. The radius of curvature R1 of the first curve 141 is the same in Examples 1 to 6 and Comparative Example 1, and is smaller than the radius of curvature R2 of the second curve 142 in Examples 1 to 6.

[0065] As shown in Table 1, for all of Examples 1 to 6, the difference in weight from Comparative Example 1 is a positive value, and the wheels are lighter than Comparative Example 1. Such a reduction in wheel weight has a significant impact on the weight reduction of the entire railway vehicle in which the wheels are used, and the entire train. That is, a railway vehicle has two bogies, one at the front and one at the back, and four wheels are attached to each bogie, resulting in eight wheels per vehicle. Therefore, if the weight of the wheels is reduced, the weight of the entire railway vehicle is reduced by eight times the weight reduction per wheel. In a train consisting of multiple railway vehicles, the weight reduction is eight times the weight reduction per wheel multiplied by the number of cars.

[0066] Furthermore, as shown in Table 1, in all of Examples 1 to 6, the quietness index is equal to or higher than that of Comparative Example 1, and quietness equal to or higher than that of Comparative Example 1 is ensured.

[0067] In Example 5, in which the radius of curvature R2 of the second curve 142 was 700 mm, the quietness of the wheel was the same as in Comparative Example 1. In Example 6, in which the radius of curvature R2 of the second curve 142 was 107 mm, the weight of the wheel was significantly reduced compared to Comparative Example 1, but the quietness of the wheel was slightly lower than in the comparative examples. On the other hand, in Examples 1 to 4, in which the radius of curvature R2 of the second curve 142 was in the range of 108 mm or more and less than 700 mm, the quietness of the wheel was improved compared to Comparative Example 1.

[0068] In Examples 1 to 4, the radius of curvature R2 of the second curve 142 was 200 mm or less. In Examples 1 to 4, the degree of reduction in the weight of the wheel compared to Comparative Example 1 was relatively large.

[0069] This analysis confirmed that providing the second curve 142 on the contour line 14 of the boss portion 10 makes it possible to reduce the weight of the wheel while maintaining the quietness of the wheel when the railway vehicle is running. In particular, it was found that quietness is improved when the radius of curvature R2 of the second curve 142 is 108 mm or more and less than 700 mm. It was also confirmed that the weight of the wheel is more likely to be reduced when the radius of curvature R2 of the second curve 142 is 200 mm or less.

[0070] [Second Example] For a wheel having a different shape from that of Example 1, the same analysis and evaluation as in Example 1 were carried out. The outer edge of the longitudinal cross section of the wheel used in this analysis is shown in Figure 4.

[0071] In the first embodiment, the contour line 14 including the first curve 141 and the second curve 142 was provided on the anti-flange side of the boss portion 10 (Fig. 1), whereas in the second embodiment, the contour line 14 including the first curve 141 and the second curve 142 is provided on the flange side, as shown in Fig. 4. Also, in the first embodiment, the plate portion 30 was inclined relative to the radial direction so that the outer periphery was located on the anti-flange side relative to the inner periphery, whereas in the second embodiment, the plate portion 30 is inclined relative to the radial direction so that the outer periphery is located on the flange side relative to the inner periphery, which is the opposite of the first embodiment. Furthermore, in the first embodiment, the rim width center Cr was located on the flange side relative to the boss width center Cb, whereas in the second embodiment, the rim width center Cr is located on the anti-flange side relative to the boss width center Cb.

[0072] The conditions and results of this analysis are shown in Table 2.

[0073] [Table 2]

[0074] The "Weight" column in Table 2 shows the value obtained by subtracting the wheel weight of each example from the wheel weight of Comparative Example 2 (the difference between each example and Comparative Example 2). The "Quietness Index" column in Table 2 shows the value obtained by subtracting the overall ERP level of each example from the overall ERP level of Comparative Example 2 (the difference between each example and Comparative Example 2). A positive weight value in Table 2 indicates that the wheel is lighter than Comparative Example 2. A positive quietness index value in Table 2 indicates that the quietness of the wheel is improved compared to Comparative Example 2. Comparative Example 2 has a straight line instead of the second curve 142 in the contour line 14 of the wheel-shaped boss portion 10 shown in FIG. 4. Therefore, in Table 2, the radius of curvature R2 of the second curve 142 of Comparative Example 2 is shown as ∞. The radius of curvature R1 of the first curve 141 is the same in Examples 7 to 9 and Comparative Example 2, and is smaller than the radius of curvature R2 of the second curve 142 in Examples 7 to 9.

[0075] As shown in Table 2, for all of Examples 7 to 9, the difference in weight from Comparative Example 2 was a positive value, meaning that the wheels were lighter than Comparative Example 2. Furthermore, for all of Examples 7 to 9, the quietness index was a positive value, meaning that quietness was improved compared to Comparative Example 2.

[0076] This analysis confirmed that even for wheel shapes different from those in the first embodiment, by providing the second curve 142 on the contour line 14 of the boss portion 10, it is possible to reduce the weight of the wheel while ensuring the quietness of the wheel when the railway vehicle is running.

[0077] [Third Example] The same analysis and evaluation as above was carried out for a wheel having a different shape from that of Examples 1 and 2. The outer edge of the longitudinal cross section of the wheel used in this analysis is shown in Figure 5.

[0078] 5, in the third embodiment, unlike the first and second embodiments, the plate portion 30 is curved. In the third embodiment, a wheel shape is used in which the rim width center Cr is located on the opposite flange side from the boss width center Cb.

[0079] The conditions and results of this analysis are shown in Table 3.

[0080] [Table 3]

[0081] The "Weight" column in Table 3 shows the value obtained by subtracting the wheel weight of each example from the wheel weight of Comparative Example 3 (the difference between each example and Comparative Example 3). The "Quietness Index" column in Table 3 shows the value obtained by subtracting the overall ERP level of each example from the overall ERP level of Comparative Example 3 (the difference between each example and Comparative Example 3). A positive weight value in Table 3 indicates that the wheel is lighter than Comparative Example 3. A positive quietness index value in Table 3 indicates that the quietness of the wheel is improved compared to Comparative Example 3. Comparative Example 3 has a straight line instead of the second curve 142 in the contour line 14 of the wheel-shaped boss portion 10 shown in FIG. 5. Therefore, in Table 3, the radius of curvature R2 of the second curve 142 of Comparative Example 3 is shown as ∞. The radius of curvature R1 of the first curve 141 is the same in Example 10 and Comparative Example 3 and is smaller than the radius of curvature R2 of the second curve 142 in Example 10.

[0082] As shown in Table 3, the difference in weight between Example 10 and Comparative Example 3 is a positive value, and the wheels are lighter than those of Comparative Example 3. Furthermore, the quietness index of Example 10 is a positive value, and quietness is improved compared to Comparative Example 3.

[0083] This analysis confirmed that even for wheel shapes different from those of the first and second embodiments, by providing the second curve 142 on the contour line 14 of the boss portion 10, it is possible to reduce the weight of the wheel while ensuring the quietness of the wheel when the railway vehicle is running.

[0084] [Fourth Example] The same analysis and evaluation as above was carried out for wheels having shapes different from those of Examples 1 to 3. The outer edge of the longitudinal cross section of the wheel used in this analysis is shown in FIG.

[0085] The wheel shape of the fourth embodiment is based on a commonly available wheel shape. As shown in Fig. 6, the fourth embodiment uses a wheel shape in which the plate portion 30 is curved like the third embodiment, but the rim width center Cr is located on the flange side of the boss width center Cb. In addition, while the third embodiment uses a boss portion 10 with a contour line 14 including the first curve 141 and the second curve 142 on the side opposite the flange (Fig. 5), the fourth embodiment uses a contour line 14 including the first curve 141 and the second curve 142 on the flange side, as shown in Fig. 6.

[0086] The conditions and results of this analysis are shown in Table 4.

[0087] [Table 4]

[0088] The "Weight" column in Table 4 shows the value obtained by subtracting the wheel weight of each example from the wheel weight of Comparative Example 4 (the difference between each example and Comparative Example 4). The "Quietness Index" column in Table 4 shows the value obtained by subtracting the overall ERP level of each example from the overall ERP level of Comparative Example 4 (the difference between each example and Comparative Example 4). A positive weight value in Table 4 indicates that the wheel is lighter than Comparative Example 4. A positive quietness index value in Table 4 indicates that the quietness of the wheel is improved compared to Comparative Example 4. Comparative Example 4 has a straight line instead of the second curve 142 in the contour line 14 of the wheel-shaped boss portion 10 shown in FIG. 6. Therefore, in Table 4, the radius of curvature R2 of the second curve 142 of Comparative Example 4 is shown as ∞. The radius of curvature R1 of the first curve 141 is the same in Example 11 and Comparative Example 4, and is smaller than the radius of curvature R2 of the second curve 142 in Example 11.

[0089] As shown in Table 4, in Example 11, the difference in weight from Comparative Example 4 was a positive value, and the wheels were lighter than in Comparative Example 4. In addition, in Example 11, the quietness index was a positive value, and quietness was improved compared to Comparative Example 4.

[0090] This analysis confirmed that even for wheel shapes different from those of the first to third embodiments, by providing the second curve 142 on the contour line 14 of the boss portion 10, it is possible to reduce the weight of the wheel while ensuring the quietness of the wheel when the railway vehicle is running. [Explanation of symbols]

[0091] 100: Wheels 10: Boss Section 12,13: End face 14: Contour 141: 1st curve 142:Second curve 20: Rim 30: Board part R1,R2: radius of curvature

Claims

1. A wheel for a railway vehicle, A cylindrical boss portion; a rim portion disposed on the outer circumferential side of the boss portion; a plate portion connecting the boss portion and the rim portion; Equipped with When viewed in a longitudinal cross section of the wheel, the boss portion includes a contour line extending from the plate portion to an axial end surface of the boss portion, The contour line is a first curved line that is continuous with the plate portion, that is concavely curved toward the inside of the boss portion, and that has a first radius of curvature; a second curved line that is disposed on the end face side of the boss portion with respect to the first curved line, that is concavely curved toward the inside of the boss portion, and that has a second radius of curvature that is larger than the first radius of curvature; Including, A wheel, wherein the line length of the second curve is greater than the line length of the first curve.

2. 2. A wheel according to claim 1, The wheel, wherein the second radius of curvature is equal to or greater than 108 mm and less than 700 mm.

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