Wheel for railway vehicle

Abstract

A wheel (100) comprises a boss part (10), a rim part (20), and a plate part (30). The rim part (20) includes a tread surface (21) and a flange (22). A center (Cb) of the boss part (10) in the axial direction of the wheel (100) is disposed closer to the flange (22) than is a center (Cr) of the rim part (20) in the axial direction. The plate part (30) has a linear plate-thickness center line (A) in a vertical cross-sectional view of the wheel (100). The wheel (100) satisfies L≥0.053α-3.8626 where α is an angle between the plate-thickness center line (A) and the axial direction, Pw is a distance in the axial direction between a side surface (24) of the rim part (20) and an outer end (Aa) of the plate-thickness center line (A), Wr is the length of the rim part (20) in the axial direction, and L is a value obtained by dividing Pw by Wr. The angle α is 90° or less.

Description

Technical Field

[0001] The present disclosure relates to wheels used for railway vehicles.

Background Art

[0002] As a type of braking method for railway vehicles, tread braking is known. Tread braking is a braking method in which a brake shoe is pressed against the tread of the wheel of a railway vehicle to generate a frictional force between the tread and the brake shoe, and the railway vehicle is braked by that frictional force.

[0003] When braking a railway vehicle using tread braking, frictional heat is generated between the tread and the brake shoe, so the temperature of the wheel, particularly the rim portion that constitutes the outer peripheral portion of the wheel, rises. As a result, thermal expansion of the rim portion occurs, and thermal stress is generated in the rim portion. In order to reduce this thermal stress, various wheel shapes have been proposed conventionally.

[0004] For example, in Patent Document 1, a wheel is proposed that includes a rim portion that constitutes the outer peripheral portion of the wheel, a boss portion that constitutes the inner peripheral portion of the wheel, and a plate portion having a substantially S-shaped cross section. In the wheel of Patent Document 1, for the purpose of reducing the thermal stress of the plate portion and the rim portion, the displacement amount of the rim portion with respect to the boss portion and the displacement amount of the rim portion side of the plate portion are each set to a predetermined value or more. The displacement amount of the rim portion with respect to the boss portion is the distance between a perpendicular line dropped from the end portion on the rim portion side of the curved plate thickness center line of the plate portion to the axis of the wheel and a perpendicular line dropped from the end portion on the boss portion side of the plate thickness center line to the axis of the wheel. The displacement amount of the rim portion side of the plate portion is the distance between a perpendicular line dropped from the end portion on the rim portion side of the plate thickness center line to the axis of the wheel and a perpendicular line dropped from the center of the rim portion in the axial direction of the wheel to the axis of the wheel.

[0005] For example, Patent Document 2 proposes a wheel having a curved cross-sectional shape in the plate portion for the purpose of reducing the thermal stress in the rim portion. In the wheel of Patent Document 2, the plate portion has a cross-sectional shape called a bell shape. Both ends of the curved plate thickness center line of this plate portion are arranged on the same side with respect to the central plane of the wheel (a plane perpendicular to the axis of the wheel). On the other hand, the midpoint of the plate thickness center line is arranged on the opposite side of both ends of the plate thickness center line with respect to the central plane of the wheel.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, in the rim portion of the wheel used for railway vehicles, compressive residual stress is usually applied by performing heat treatment or the like during manufacturing. However, when the railway vehicle is braked by the tread brake, if high thermal stress is generated in the rim portion and plastic deformation occurs, the compressive residual stress in the rim portion may be reversed to tensile residual stress. That is, during braking of the railway vehicle, due to the friction between the tread and the brake wheel, the temperature rises in the rim portion and the rim portion tries to thermally expand. On the other hand, since the temperature rise is small on the inner peripheral side of the wheel, the thermal expansion of the rim portion is inhibited, and compressive stress particularly in the circumferential direction of the wheel is generated in the rim portion. When this compressive stress exceeds the yield point, plastic deformation occurs in the rim portion. After the rim portion is cooled, the compressive stress is reversed to tensile stress and acts as residual stress on the rim portion. When a crack occurs on the tread in a state where tensile residual stress is generated in the rim portion, it is conceivable that the generated crack may progress to the inside of the wheel. Therefore, when using the tread brake for braking the railway vehicle, it is necessary to reduce the thermal stress generated in the rim portion due to the tread brake and suppress the generation of tensile residual stress in the rim portion.

[0008] The wheels of Patent Documents 1 and 2 both have a curved plate portion. As a result, the restraint of the plate portion against the thermal expansion of the rim portion is relaxed. Therefore, in the wheels of Patent Documents 1 and 2, it is considered that the thermal stress generated in the rim portion during braking of the railway vehicle is reduced, and tensile residual stress is less likely to occur in the rim portion. However, when the plate portion is curved, there is a problem that the weight of the wheel increases.

[0009] An object of the present disclosure is to provide a wheel capable of achieving both weight reduction and suppression of the generation of tensile residual stress in the rim portion.

Means for Solving the Problems

[0010] The wheel according to the present disclosure is used for a railway vehicle. The wheel includes a boss portion, a rim portion, and a plate portion. The boss portion constitutes the inner peripheral portion of the wheel. An axle of the railway vehicle is inserted into the boss portion. The rim portion constitutes the outer peripheral portion of the wheel. The rim portion includes a tread surface and a flange. The tread surface contacts the top surface of the rail on which the railway vehicle travels. The flange protrudes outward from the tread surface in the radial direction of the wheel. The annular plate portion connects the boss portion and the rim portion. The center of the boss portion in the axial direction is arranged closer to the flange in the axial direction than the center of the rim portion in the axial direction. The axial direction is the direction in which the central axis of the wheel extends. The plate portion has a straight plate thickness center line in a longitudinal sectional view of the wheel. Let the angle formed by the plate thickness center line and the axial direction be α, the axial distance from the side surface of the rim portion on the opposite side of the flange to the outer end in the radial direction of the plate thickness center line be Pw, the length of the rim portion in the axial direction be Wr, and L = Pw / Wr. The wheel according to the present disclosure satisfies the following formula (1). L≧0.053α - 3.8626···(1) However, the angle α is 90° or less. The angle α is 90° when the plate thickness center line is parallel to the radial direction, and is defined as less than 90° when the plate thickness center line is inclined with respect to the radial direction by rotating from the 90° position around the inner end in the radial direction to the opposite side of the flange.

Effects of the Invention

[0011] According to the present disclosure, it is possible to achieve both weight reduction of the wheel and suppression of the generation of tensile residual stress in the rim portion.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0013] The wheel according to the embodiment (the first configuration) is used for a railway vehicle. The wheel includes a boss portion, a rim portion, and a plate portion. The boss portion constitutes the inner peripheral portion of the wheel. An axle of the railway vehicle is inserted into the boss portion. The rim portion constitutes the outer peripheral portion of the wheel. The rim portion includes a tread surface and a flange. The tread surface contacts the top surface of the rail on which the railway vehicle travels. The flange protrudes outward from the tread surface in the radial direction of the wheel. The annular plate portion connects the boss portion and the rim portion. The center of the boss portion in the axial direction is arranged closer to the flange in the axial direction than the center of the rim portion in the axial direction. The axial direction is the direction in which the central axis of the wheel extends. The plate portion has a straight plate thickness center line in the longitudinal sectional view of the wheel. Let the angle formed by the plate thickness center line and the axial direction be α, the axial distance from the side surface opposite to the flange among the two side surfaces in the axial direction of the rim portion to the outer end in the radial direction of the plate thickness center line be Pw, the length of the rim portion in the axial direction be Wr, and L be Pw / Wr. The wheel according to the first configuration satisfies the following formula (1). L≧0.053α-3.8626···(1) However, the angle α is 90° or less. The angle α is defined as 90° when the plate thickness center line is parallel to the radial direction, and less than 90° when the plate thickness center line is inclined with respect to the radial direction by rotating from the 90° position around the inner end in the radial direction to the side opposite to the flange.

[0014] In the wheel according to the first configuration, the plate thickness center line of the plate portion is straight and has no inflection point in the longitudinal sectional view of the wheel. That is, the plate portion connects the boss portion and the rim portion without substantially bending. Therefore, compared with the case where the plate portion is curved, the weight of the plate portion can be reduced. Thus, the weight of the wheel can be reduced.

[0015] When the braking wheel of the tread brake is pressed against the tread of the rim portion of the wheel and frictional heat is generated, the rim portion thermally expands. By the plate portion restraining this thermal expansion of the rim portion, thermal stress is generated in the rim portion. If the thermal stress in the rim portion becomes excessive, the rim portion may plastically deform during braking of the railway vehicle, and tensile residual stress may occur in the circumferential direction of the wheel after the rim portion is cooled. On the other hand, the wheel according to the first configuration is formed in a shape that relaxes the restraint of the rim portion by the plate portion. More specifically, in the wheel according to the first configuration, assuming that the center of the boss portion is located closer to the flange than the center of the rim portion, the dimensions of each part are set so as to satisfy Expression (1) considering both the angle of the center line of the plate thickness of the plate portion with respect to the axial direction of the wheel and the position of the center line of the plate thickness with respect to the rim portion. Thereby, the restraint of the rim portion by the plate portion can be effectively relaxed, and the thermal expansion of the rim portion during braking can be tolerated. Therefore, the thermal stress of the rim portion can be reduced, and the plastic deformation of the rim portion can be suppressed. Therefore, when the rim portion is cooled after braking of the railway vehicle, it is possible to suppress the reversal of the residual stress of the rim portion to tension.

[0016] Thus, according to the wheel according to the first configuration, it is possible to achieve both weight reduction of the wheel and suppression of the generation of tensile residual stress in the rim portion.

[0017] As described above, in the wheel according to the first configuration, the center line of the plate thickness of the plate portion is linear in a longitudinal sectional view of the wheel and has no inflection point. In this case, stress concentration is less likely to occur in the plate portion. Therefore, the thermal stress of the plate portion generated during braking of the railway vehicle can be reduced.

[0018] According to the first configuration, the angle of the center line of the plate thickness of the plate portion with respect to the axial direction of the wheel is 90° or less. Therefore, as the plate portion moves toward the outer side in the radial direction, it does not tilt inward of the track. Thus, it is possible to ensure the rigidity of the plate portion against the load that the wheel receives from the rail in its axial direction when passing through a curve, in other words, the load (lateral pressure) that the wheel receives from the inner side of the track. Therefore, the stress generated in the plate portion can be reduced.

[0019] The angle α formed by the plate thickness center line and the axial direction is preferably less than 90° (second configuration).

[0020] According to the second configuration, the angle of the plate thickness center line of the plate portion with respect to the axial direction of the wheel is less than 90°. In this case, as the plate portion moves toward the outer side in the radial direction, it will tilt toward the outer side of the track. Therefore, the rigidity of the plate portion against lateral pressure can be improved, and the stress generated in the plate portion can be further reduced. In addition, since the necessity of increasing the plate thickness of the plate portion to ensure the rigidity of the plate portion against lateral pressure is reduced, the plate portion and the wheel can be made lighter.

[0021] The plate portion may become smaller as it goes toward the outer side in the radial direction and have a minimum plate thickness in front of the outer end of the plate thickness center line (third configuration).

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For the same or corresponding configurations in each figure, the same reference numerals are given, and the same description will not be repeated.

[0023] FIG. 1 is a longitudinal sectional view of a wheel 100 according to this embodiment. The longitudinal section refers to a section obtained by cutting the wheel 100 with a plane including the central axis X. Since the longitudinal section of the wheel 100 is symmetric with respect to the central axis X, only one side of the wheel 100 on the side of the central axis X is shown in FIG. 1. Hereinafter, the direction in which the central axis X of the wheel 100 extends is referred to as the axial direction, and the radial direction and the circumferential direction of the wheel 100 are simply referred to as the radial direction and the circumferential direction, respectively.

[0024] Referring to FIG. 1, the wheel 100 is used for a railway vehicle. The wheel 100 includes a boss portion 10, a rim portion 20, and a plate portion 30.

[0025] The boss portion 10 constitutes the inner peripheral portion of the wheel 100. The boss portion 10 has a substantially cylindrical shape with the central axis X as the axis. An axle (not shown) of a railway vehicle is inserted into the boss portion 10.

[0026] The rim portion 20 constitutes the outer peripheral portion of the wheel 100. The rim portion 20 is arranged outside the boss portion 10 in the radial direction. The rim portion 20 includes a tread surface 21 and a flange 22. The tread surface 21 and the flange 22 are provided on the outer peripheral surface of the rim portion 20.

[0027] The tread surface 21 is a radially outward-facing surface. The tread surface 21 contacts the top surface of the rail on which the railway vehicle travels. The diameter of the tread surface 21 typically gradually increases toward the flange 22 side. The tread surface 21 may be, for example, a conical tread surface or an arc tread surface.

[0028] The flange 22 is provided at one axial end portion of the rim portion 20. The flange 22 protrudes outward from the tread surface 21 in the radial direction. The flange 22 is positioned inside the left and right rails when the railway vehicle travels on the rails. Hereinafter, in the axial direction of the wheel 100, the side on which the flange 22 is arranged is referred to as the flange direction, and the opposite side is referred to as the anti-flange direction.

[0029] The rim portion 20 further includes both axial side surfaces 23 and 24. The side surface 23 is the side surface on the flange 22 side, and the side surface 24 is the side surface on the side opposite to the flange 22. That is, the side surface 23 is arranged in the flange direction with respect to the side surface 24. The side surface 24 sandwiches the tread surface 21 and the flange 22 and is arranged in the anti-flange direction with respect to the side surface 23.

[0030] The rim portion 20 is arranged in the anti-flange direction with respect to the boss portion 10. In other words, in the axial direction, the center Cb of the boss portion 10 is arranged closer to the flange 22 than the center Cr of the rim portion 20. When the railway vehicle travels, the center Cr of the rim portion 20 is positioned outside in the track width direction with respect to the center Cb of the boss portion 10.

[0031] The plate portion 30 is annular. The plate portion 30 connects the boss portion 10 and the rim portion 20. The plate thickness of the plate portion 30 is smaller than each of the boss width Wb and the rim width Wr as a whole. The plate thickness of the plate portion 30 is larger on the boss portion 10 side and smaller on the rim portion 20 side. The boss width Wb refers to the length of the boss portion 10 in the axial direction. The rim width Wr is the length of the rim portion 20 in the axial direction and is the maximum distance in the axial direction from the side surface 23 to the side surface 24 of the rim portion 20.

[0032] The plate portion 30 includes both side surfaces 31 and 32 in the axial direction. The side surface 31 is the side surface on the flange 22 side, and the side surface 32 is the side surface on the side opposite to the flange 22. That is, the side surface 31 is arranged in the flange direction with respect to the side surface 32. The side surface 32 is arranged in the anti-flange direction with respect to the side surface 31. In the longitudinal sectional view of the wheel 100, it is preferable that the side surfaces 31 and 32 are inclined with respect to the radial direction. The side surfaces 31 and 32 are respectively connected to the rim portion 20 via the connection portions 41 and 42. The side surfaces 31 and 32 are respectively connected to the boss portion 10 via the connection portions 43 and 44. Each of the connection portions 41, 42, 43, and 44 is substantially arc-shaped in the longitudinal sectional view of the wheel 100, for example.

[0033] In the present embodiment, among the ends (R stops) 411 on the plate portion 30 side of the connection portion 41 and the ends (R stops) 421 on the plate portion 30 side of the connection portion 42, the one located more inward in the radial direction is defined as the outer peripheral end of the plate portion 30. Also, among the ends (R stops) 431 on the plate portion 30 side of the connection portion 43 and the ends (R stops) 441 on the plate portion 30 side of the connection portion 44, the one located more outward in the radial direction is defined as the inner peripheral end of the plate portion 30. The outer peripheral end of the plate portion 30 can also be said to be the base of the plate portion 30 with respect to the rim portion 20. The inner peripheral end of the plate portion 30 can also be said to be the base of the plate portion 30 with respect to the boss portion 10. In the present embodiment, the end 411 of the connection portion 41 and the end 441 of the connection portion 44 are respectively the outer peripheral end and the inner peripheral end of the plate portion 30.

[0034] The plate thickness of the plate portion 30 decreases toward the outer side in the radial direction and becomes minimum in front of the outer peripheral end 411. The plate portion 30 has the minimum plate thickness inside the outer peripheral end 411 in the radial direction and in the vicinity of the outer peripheral end 411. The position where the plate thickness of the plate portion 30 becomes minimum substantially coincides with the position where the bending stress generated in the plate portion 30 by the bending load received by the wheel 100 from the rail when the railway vehicle passes through a curve is minimum. For example, the plate thickness of the plate portion 30 can be minimized at a position 5 mm to 30 mm radially inward from the outer peripheral end 411.

[0035] The plate portion 30 has a plate thickness center line A. The plate thickness center line A is a line formed by connecting the center of the plate thickness of the plate portion 30 extending from the boss portion 10 to the rim portion 20 in the longitudinal sectional view of the wheel 100. The plate thickness center line A extends from the boss portion 10 side to the rim portion 20 side through the middle of the side surfaces 31, 32. The plate thickness center line A is linear in the longitudinal sectional view of the wheel 100. The linear shape here is not just a perfect straight line, but a concept including, for example, a very gentle arc with a radius of curvature of 1000 mm or more and a broken line. That is, the plate thickness center line A may be recognized as substantially linear in the longitudinal sectional view of the wheel 100. Since the plate thickness center line A is linear in the longitudinal sectional view of the wheel 100, the plate portion 30 has a substantially flat plate shape and does not substantially curve in the axial direction.

[0036] The plate thickness center line A has an outer end Aa in the radial direction and an inner end Ab in the radial direction. The outer end Aa is the point where the plate thickness center line A is connected to the straight line extending axially through the outer peripheral end 411 of the plate portion 30. The inner end Ab of the plate thickness center line A is the point where the plate thickness center line A is connected to the straight line extending axially through the inner peripheral end 441 of the plate portion 30.

[0037] The position of the plate portion 30 relative to the rim portion 20 is determined by the axial position of the outer end Aa of the plate thickness center line A. In the present embodiment, among the both side surfaces 23 and 24 of the rim portion 20, the distance in the axial direction from the side surface 24 in the anti-flange direction to the outer end Aa of the plate thickness center line A is defined as the plate portion position Pw. The smaller the ratio L = Pw / Wr of the plate portion position Pw to the rim width Wr, the farther the outer peripheral end 411 of the plate portion 30 is from the flange 22, and the larger the ratio L, the closer the outer peripheral end 411 of the plate portion 30 approaches the flange 22.

[0038] The ratio L = Pw / Wr of the plate portion position Pw to the rim width Wr is determined by the relationship with the angle α of the plate thickness center line A. The ratio L of the plate portion position Pw to the rim width Wr and the angle α of the plate thickness center line A are defined so as to satisfy the following formula (1). L≧0.053α - 3.8626···(1)

[0039] The angle α of the plate thickness center line A is the angle formed by the plate thickness center line A with respect to the axial direction in the longitudinal sectional view of the wheel 100. When the plate thickness center line A is a very gentle curve, the angle α is the angle formed by the tangent line at the center of the plate thickness center line A (the midpoint between the outer end Aa and the inner end Ab) with respect to the axial direction. When the plate thickness center line A is a broken line, the angle α is the angle formed by the longest line segment among the line segments constituting the plate thickness center line A with respect to the axial direction. Regarding the angle α, it is defined as 90° when the plate thickness center line A is parallel to the radial direction. Also, when the plate thickness center line A rotates to the opposite side of the flange 22 around the inner end Ab from the 90° position, and the plate thickness center line A is inclined with respect to the radial direction, the angle α is defined as less than 90°. That is, with the position where the angle α is 90° as a reference, when the outer end Aa of the plate thickness center line A is arranged in the anti-flange direction, the angle α is less than 90°.

[0040] The angle α of the plate thickness center line A is set to 90° or less. Although it also depends on the specifications of the tread brake used for the wheel 100, the angle α is preferably less than 90°. As the angle α becomes smaller and the plate portion 30 inclines in the anti-flange direction, the restraint of the rim portion 20 by the plate portion 30 is relaxed, and the deformation of the rim portion 20 during braking of the railway vehicle is more likely to be permitted. From the viewpoint of the manufacturability of the wheel 100, etc., the angle α is preferably 70° or more.

[0041] On the other hand, as the ratio L of the plate portion position Pw to the rim width Wr increases and the base of the plate portion 30 with respect to the rim portion 20 approaches the flange 22, the restraint of the rim portion 20 by the plate portion 30 is relaxed, and the deformation of the rim portion 20 during braking of the railway vehicle is more likely to be permitted. The ratio L is preferably set in the range of 0.26 or more and 0.72 or less from the viewpoint of the manufacturability of the wheel 100, etc.

[0042] [Effect] In the wheel 100 according to the present embodiment, both the angle α of the plate thickness center line A and the ratio L of the plate portion position Pw to the rim width Wr are appropriately set so that the restraint of the rim portion 20 by the plate portion 30 is relaxed. Specifically, in the present embodiment, assuming that the center Cb of the boss portion 10 is located closer to the flange 22 compared to the center Cr of the rim portion 20, and the plate portion 30 and its plate thickness center line A are linear in the longitudinal sectional view of the wheel 100, the angle α of the plate thickness center line A and the ratio L of the plate portion position Pw to the rim width Wr are set so as to satisfy the relationship of the above formula (1). Thereby, in the wheel 100 in which the center Cb of the boss portion 10 is located closer to the flange 22 compared to the center Cr of the rim portion 20, and the plate portion 30 and its plate thickness center line A are linear, the degree of restraint of the rim portion 20 by the plate portion 30 can be effectively reduced. Therefore, when the braking wheel of the tread brake is pressed against the tread 21 of the rim portion 20 and frictional heat is generated, the thermal expansion of the rim portion 20 is less likely to be inhibited. Thus, when using the tread brake for braking the railway vehicle, the thermal stress of the rim portion 20 generated due to this tread brake can be reduced, and the plastic deformation of the rim portion 20 can be suppressed. As a result, after the rim portion 20 is cooled, it is possible to suppress the reversal of the residual stress of the rim portion 20 to tension.

[0043] In the wheel 100 according to this embodiment, the plate thickness center line A of the plate portion 30 is linear in the longitudinal sectional view of the wheel 100 and has no inflection point. That is, the plate portion 30 connects the boss portion 10 and the rim portion 20 without substantially curving. Therefore, the weight of the plate portion 30 can be reduced as compared with the case where the plate portion 30 is curved. Thus, the weight reduction of the wheel 100 can be realized.

[0044] Further, since the plate thickness center line A is linear and the plate portion 30 does not substantially curve, stress concentration in the plate portion 30 can be alleviated during braking of a railway vehicle by a tread brake. Thus, the thermal stress of the plate portion 30 generated during braking of the railway vehicle can also be reduced.

[0045] For example, when the plate portion 30 inclines in the flange direction (inner side of the track) as it goes radially outward, the rigidity of the plate portion 30 with respect to the load that the wheel 100 receives from the rail in its axial direction when passing through a curve, that is, the load (lateral pressure) that the wheel 100 is pushed in the flange direction by the rail, becomes low. On the other hand, in this embodiment, since the angle α of the plate thickness center line A is set to 90° or less, substantially, the plate portion 30 does not incline in the flange direction as it goes radially outward. Thus, the rigidity of the plate portion 30 with respect to the lateral pressure can be ensured. Therefore, the stress generated in the plate portion 30 can be reduced.

[0046] In the wheel 100 according to this embodiment, the angle α of the plate thickness center line A is preferably less than 90°. In this case, the plate portion 30 will incline in the anti-flange direction (outer side of the track) as it goes radially outward. Thereby, the rigidity of the plate portion 30 with respect to the lateral pressure can be improved, and the stress generated in the plate portion 30 can be further reduced.

[0047] In a longitudinal sectional view of the wheel 100, when the side surfaces 31 and 32 of the plate portion 30 are parallel to the radial direction of the wheel 100 (when perpendicular to the central axis X of the wheel 100), the rim portion 20 is more likely to be restrained by the plate portion 30. Therefore, it is preferable that the side surfaces 31 and 32 of the plate portion 30 are inclined with respect to the radial direction of the wheel 100. Each of the side surfaces 31 and 32 may be inclined with respect to the radial direction so as to face the anti-flange direction (outer side of the track) as it approaches the rim portion 20, for example. By inclining the side surfaces 31 and 32 with respect to the radial direction, the restraint of the rim portion 20 by the plate portion 30 can be further relaxed.

[0048] In the present embodiment, the plate thickness of the plate portion 30 decreases toward the outer side in the radial direction and is minimized in front of the outer end Aa of the plate thickness center line A. More specifically, in the plate portion 30, the position where the bending stress generated by the bending load received from the rail during the passage of the curve is minimized is approximately made to coincide with the position where the plate thickness is minimized. By doing so, fatigue failure of the plate portion 30 can be prevented and the durability of the wheel 100 can be improved.

[0049] As described above, the embodiments according to the present disclosure have been described. However, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof.

Examples

[0050] Hereinafter, the present disclosure will be described in more detail by way of examples. However, the present disclosure is not limited to the following examples.

[0051] In order to study a wheel shape capable of suppressing the generation of tensile residual stress in the rim portion, numerical analysis (FEM analysis) by the finite element method was performed. In the FEM analysis, an analysis model having the same shape as the wheel 100 (FIG. 1) according to the above embodiment was created, and the angle (plate angle) α of the straight plate thickness center line A and the ratio of the plate portion position Pw to the rim width Wr: L = Pw / Wr were changed to evaluate the residual stress in the rim portion. In addition, the residual stress in the rim portion was also evaluated for an analysis model of a wheel having a plate portion with an S-shaped cross section. FIG. 2 is a diagram schematically showing a wheel having a plate portion with an S-shaped cross section.

[0052] The FEM analysis was performed using general-purpose software (ABAQUS Ver.6.14, manufactured by Dassault Systèmes). In the analysis, in order to simulate the braking of a railway vehicle by a tread brake, a heat flux was applied to the area of the wheel tread that contacts the braking wheel of the tread brake for 1200 seconds and then cooled for 10000 seconds. The inner peripheral portion of the wheel was completely constrained and insulated.

[0053] Table 1 shows the conditions of the parameters α and L and the residual stress in the rim portion obtained by the FEM analysis.

[0054]

Table 1

[0055] In Table 1, the rim portion residual stress indicates the maximum circumferential stress in the rim portion after braking and cooling. If the rim portion residual stress is a negative value, it means that the residual stress in the rim portion is still compressive after braking, and if the rim portion residual stress is a positive value, it means that the residual stress in the rim portion has turned to tension after braking.

[0056] As shown in Table 1, in Examples 1 to 6, the residual stress in the rim portion became a negative value. That is, in Examples 1 to 6, since the thermal stress in the rim portion during braking simulating the tread brake was reduced, the residual stress in the rim portion could remain compressed even after braking. On the other hand, in Comparative Examples 2 to 4, the residual stress in the rim portion became a positive value. That is, in Comparative Examples 2 to 4, the residual stress in the rim portion turned to tension after braking. In Comparative Example 1, although the residual stress in the rim portion became a negative value, since the plate portion was curved, the weight of the wheel increased as compared with Examples 1 to 6 and Comparative Examples 2 to 4 in which the plate portion was not curved. Thus, in Examples 1 to 6, it was possible to suppress the generation of tensile residual stress in the rim portion without increasing the weight of the wheel.

[0057] Hereinafter, the influence of the ratio L of the plate portion position Pw to the plate angle α and the rim width Wr on the residual stress in the rim portion will be examined.

[0058] FIG. 3 is a graph showing the relationship between the plate angle α and the residual stress in the rim portion for Examples 1 to 3 and Comparative Examples 2 to 4 in which the values of the ratio L of the plate portion position Pw to the rim width Wr are equal. From FIG. 3, it can be seen that when the plate angle α is 90° or less, the value of the residual stress in the rim portion increases as the plate angle α increases. Therefore, it can be said that if the plate angle α is small, the possibility that the residual stress in the rim portion turns to tension after braking of the railway vehicle is low.

[0059] FIG. 4 is a graph showing the relationship between the ratio L of the plate portion position Pw to the rim width Wr and the residual stress in the rim portion for Examples 4 to 6 in which the plate angle α is equal. From FIG. 4, it can be seen that even when the plate angle α is the same, the value of the residual stress in the rim portion decreases as the ratio L of the plate portion position Pw to the rim width Wr increases. Therefore, it can be said that if the ratio L increases, the possibility that the residual stress in the rim portion turns to tension after braking of the railway vehicle is low.

[0060] As described above, in the above analysis, it was confirmed that the smaller the plate angle α, the lower the residual stress in the rim portion, and the larger the ratio L of the plate portion position Pw to the rim width Wr, the lower the residual stress in the rim portion. The reason for this will be described with reference to FIGS. 5 and 6. FIGS. 5 and 6 are diagrams exaggerating the deformation occurring in the wheel during braking in Example 2 and Comparative Example 3, respectively.

[0061] In Example 2, the plate angle α is 75°, and the ratio L of the plate portion position Pw to the rim width Wr is 0.48. In Example 2, as shown in FIG. 5, when a heat flux was applied to the tread 21, the rim portion 20 moved greatly in the flange direction. That is, in Example 2, the restraint of the plate portion 30 against the movement of the rim portion 20 in the flange direction was small, and the thermal expansion of the rim portion 20 could be tolerated. In Example 2, the thermal stress generated in the rim portion 20 during braking was reduced, and the residual stress in the rim portion 20 remained compressive even after braking.

[0062] In Comparative Example 3, the ratio L of the plate portion position Pw to the rim width Wr is the same as that in Example 2, but the plate angle α is 90°, which is larger than that in Example 2. In this Comparative Example 3, as shown in FIG. 6, almost no movement of the rim portion 20 occurred. In Comparative Example 3, the restraint of the plate portion 30 against the movement of the rim portion 20 was large, and when a heat flux was applied to the tread 21, the thermal expansion of the rim portion 20 was inhibited. In Comparative Example 3, the thermal stress generated in the rim portion 20 during braking became large, and the residual stress in the rim portion 20 reversed to tension after braking.

[0063] Thus, even for wheels with the same ratio L of the plate position Pw to the rim width Wr, the generation state of residual stress in the rim portion 20 differs due to the difference in the plate angle α. Similarly, even for wheels with the same plate angle α, the generation state of residual stress in the rim portion 20 differs due to the difference in the ratio L of the plate position Pw to the rim width Wr. That is, both the plate angle α and the ratio L of the plate position Pw to the rim width Wr are related to the tensile reversal of the residual stress in the rim portion generated due to braking by the tread brake. Therefore, the relationship between the plate angle α and the ratio L was obtained such that the residual stress in the rim portion can be prevented from turning to tension when braking a railway vehicle by the tread brake. In the relationship between the plate angle α and the ratio L, the limit line where the residual stress in the rim portion does not reverse to tension is shown in FIG. 7.

[0064] The plotted points in FIG. 7 are the results obtained by performing the same FEM analysis as described above, and represent L = plate position Pw / rim width Wr when the rim portion residual stress becomes 0 at the plate angles α = 75°, 80°, 85°, 90°. The straight line in FIG. 7 is obtained by least-squares approximation of these plotted points and represents L = 0.053α - 3.8626. In the region above this straight line, the rim portion residual stress becomes compressive. Therefore, the case where the residual stress in the rim portion can be substantially prevented from becoming tensile is when the plate angle α and the ratio L satisfy the following equation (1). However, the plate angle α is 90° or less. The following equation (1) can be applied only to wheels in which the center of the boss portion is arranged closer to the flange than the center of the rim portion and the plate portion and its plate thickness center line are linear. L≧0.053α - 3.8626 ···(1)

[0065] For each example and each comparative example, it was confirmed whether the above formula (1) was satisfied. As shown in Table 2, Examples 1 to 6 in which the residual stress in the rim portion was a negative value satisfied the above formula (1). On the other hand, Comparative Examples 2 to 4 in which the residual stress in the rim portion was a positive value did not satisfy the above formula (1). Therefore, in a wheel in which the center of the boss portion is arranged closer to the flange than the center of the rim portion, and the plate portion and its plate thickness center line are linear, when the plate angle α and the ratio L of the plate portion position Pw to the rim width Wr are set to satisfy the above formula (1), it can be said that the generation of tensile residual stress in the rim portion can be suppressed.

[0066]

Table 2

Explanation of symbols

[0067] 100: Wheel 10: Boss portion 20: Rim portion 21: Tread 22: Flange 30: Plate portion A: Plate thickness center line

Claims

1. A wheel used for a railway vehicle, comprising a boss portion that forms the inner peripheral portion of the wheel and is for inserting the axle of the railway vehicle, a rim portion that forms the outer peripheral portion of the wheel and includes a tread surface that contacts the top surface of the rail on which the railway vehicle travels, and a flange that protrudes outward from the tread surface in the radial direction of the wheel, and an annular plate portion that connects the boss portion and the rim portion, wherein the center of the boss portion in the axial direction, which is the direction in which the central axis of the wheel extends, is arranged closer to the flange in the axial direction than the center of the rim portion in the axial direction, of the two side surfaces of the rim portion in the axial direction on the side opposite to the flange, the side surface on the side opposite to the flange is arranged closer to the flange in the axial direction than the side surface on the side opposite to the flange of the two side surfaces of the boss portion in the axial direction, the plate portion has a straight plate thickness center line in a longitudinal sectional view of the wheel, let the angle formed by the plate thickness center line and the axial direction be α. When the plate thickness center line is parallel to the radial direction, it is 90°. When the plate thickness center line is inclined with respect to the radial direction by rotating from the 90° position around the inner end in the radial direction to the side opposite to the flange, it is defined as less than 90°. Let the distance in the axial direction from the side surface on the side opposite to the flange of the two side surfaces of the rim portion in the axial direction to the outer end in the radial direction of the plate thickness center line be Pw, the length of the rim portion in the axial direction be Wr, and when Pw / Wr is L, a wheel that satisfies the following formula (1). L ≥ 0.053α - 3.8626... (1) However, the angle α is 90° or less.

2. The wheel according to claim 1, wherein the angle α is less than 90°.

3. The wheel according to claim 1 or 2, wherein the plate portion has a plate thickness that decreases toward the outer side in the radial direction and is minimum before the outer end of the plate thickness center line.

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