Brake discs for railway vehicles

Abstract

To facilitate cooling of an outer peripheral part of a disc body which is disadvantageous in cooling of a disc body, especially thermally, at the time of braking of a brake disc for railway vehicle.SOLUTION: A brake disc (100) includes an annular disc body (10), and a fin (20). A thickness of the disc body (10) becomes smaller toward the inside in the radial direction. The fin (20) is arranged radially on a rear surface (12) of the disc body (10). At least part of the fin (20) has a bolt hole (22) at a central part in the radial direction. The disc body (10) includes a protrusion (13). The protrusion (13) is formed at a portion positioned outside with respect to the bolt hole (22) out of the rear surface (12) in the radial direction. Each fin (20) includes a top surface (21), and a protrusion part (25). The protrusion part (25) protrudes inside with respect to a virtual plane (S1) in the radial direction. The virtual plane (S1) passes an end part (212) of the top surface (21) and an inner peripheral edge (122) of the rear surface (12).SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Disc brakes are widely used as braking devices for railway vehicles. Disc brakes include an annular brake disc and a brake lining. The brake disc is fastened to, for example, a wheel and rotates together with the wheel. The brake lining is pressed against the brake disc. The brake disc and the wheel are braked by friction between the brake lining and the brake disc.

[0003] For example, brake discs used in railway vehicles that travel at high speeds, such as the Shinkansen, are required to have sufficient cooling performance (heat dissipation performance) during braking in order to ensure their durability. In particular, when a high-speed railway vehicle is traveling on a downhill section, braking by the brake disc is performed intermittently. If the cooling performance of the brake disc is insufficient at this time, the brake disc will become hot, resulting in a loss of durability of the brake disc. Furthermore, the high temperature causes the brake disc to thermally expand, which increases the load on the bolts that fasten the brake disc to the wheel.

[0004] Patent Document 1 discloses a brake disc for railway vehicles that improves cooling performance during braking. In this brake disc, a plurality of fins are radially arranged on the back surface of the disc body. Each fin comes into contact with the wheel and forms an air passage between the disc body and the wheel. When the brake disc rotates together with the wheel, the air passage allows air to pass from the inner periphery side to the outer periphery side of the brake disc. This air cools the brake disc.

[0005] In Patent Document 1, some of the fins have bolt holes. The bolt holes are formed in the center of the fin in the radial direction of the brake disc. In each fin, grooves are formed on the outer and inner peripheral sides of the bolt holes along the circumferential direction of the brake disc. These grooves cause a pressure loss in the air flowing through the air passage between the disc body and the wheel, and reduce the amount of air flow, thereby reducing aerodynamic noise.

[0006] Patent Document 2 discloses a brake disc intended for application to an automobile disc brake. This brake disc has a pair of disc bodies (sliding plates) attached to an axle, and a plurality of fins arranged radially between the disc bodies. Each fin extends in the radial direction of the brake disc, and defines an air passage together with the adjacent fin and the pair of disc bodies. Of the pair of disc bodies, the disc body arranged on the inside in the axle direction has a tapered portion. The tapered portion is formed so that the distance between the disc bodies becomes wider as it moves inward in the radial direction of the brake disc. According to Patent Document 2, this tapered portion increases the opening area of ​​the air passage on the inner circumferential side of the brake disc, and reduces the inflow resistance of air to the air passage, thereby increasing the air volume in the air passage and improving the cooling performance of the brake disc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 038621 [Patent Document 2] Patent No. 3521266 Summary of the Invention [Problem to be solved by the invention]

[0008] In the brake disc of Patent Document 2, a tapered portion is provided on the disc body, thereby increasing the amount of airflow in the air passage compared to when the disc body is a normal flat ring-shaped disc, thereby improving heat dissipation performance. However, railway vehicles have a greater vehicle weight and travel speed than automobiles, and require a greater braking force. Therefore, the thermal load on the brake discs used in railway vehicles is relatively excessive compared to brake discs used in automobiles as in Patent Document 2.

[0009] In addition, fins are arranged radially on the disk body of the brake disk. The interval between adjacent fins increases from the inner circumference toward the outer circumference. This causes a lack of heat capacity at the outer circumference of the disk body. Furthermore, since the peripheral speed of the disk body is faster at the outer circumference than at the inner circumference, the amount of heat input due to friction between the disk body and the brake lining is greater at the outer circumference of the disk body. This puts the outer circumference of the disk body at a thermal disadvantage.

[0010] Therefore, in order to promote cooling of the disc body, particularly the cooling of the outer periphery of the disc body, in brake discs for railway vehicles, the technology of Patent Document 2, which is intended for application to automobiles, is insufficient by itself.

[0011] An object of the present disclosure is to promote cooling of the disc body, particularly the outer periphery of the disc body which is thermally disadvantageous, during braking of a brake disc for a railway vehicle. [Means for solving the problem]

[0012] A brake disc for a railway vehicle according to the present disclosure includes an annular disc body and a plurality of fins. The disc body has a front surface and a back surface. The thickness of the disc body decreases radially inward. The plurality of fins are radially arranged on the back surface. At least some of the plurality of fins have bolt holes in the radial center of the disc body. The disc body includes a plurality of protrusions. The plurality of protrusions are formed on a portion of the back surface that is located radially outward from the bolt holes. Each of the fins includes a top surface and a convex portion. The top surface extends in the radial direction. The convex portion protrudes radially inward beyond an imaginary plane when viewed in a cross section of the brake disc cut along the radial direction. When viewed in the cross section, the imaginary plane passes through an end portion located on the inside of both ends of the top surface in the radial direction and an inner peripheral edge of the back surface. Effect of the Invention

[0013] According to the present disclosure, when braking a railway vehicle brake disc, it is possible to promote cooling of the disc body, in particular the cooling of the outer periphery of the disc body which is thermally disadvantageous. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a back view of a railway vehicle brake disc according to an embodiment. [Diagram 2] FIG. 2 is a partial perspective view of a ⅛ circle of the brake disc shown in FIG. [Diagram 3] FIG. 3 is a radial cross-sectional view of the brake disc shown in FIG. [Figure 4] FIG. 4 is a diagram illustrating an example of the temperature distribution in a typical brake disc during braking. [Diagram 5] FIG. 5 is a diagram showing another brake disc to be compared with the railway vehicle brake disc according to the embodiment. [Figure 6] FIG. 6 is a diagram showing another brake disc to be compared with the railway vehicle brake disc according to the embodiment, which is different from the brake disc shown in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the radial cross section of each model used in the thermal fluid analysis. [Figure 8] FIG. 8 is a graph showing the relationship between the ventilation amount and the heat dissipation index obtained by thermal fluid analysis for each model. [Figure 9] FIG. 9 is a graph showing the relationship between the radial coordinate of the rear surface of the disk body and the heat dissipation index for each model. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A brake disc for a railway vehicle according to an embodiment includes an annular disc body and a plurality of fins. The disc body has a front surface and a back surface. The thickness of the disc body decreases radially inward. The plurality of fins are arranged radially on the back surface. At least some of the plurality of fins have bolt holes in the radial center of the disc body. The disc body includes a plurality of protrusions. The plurality of protrusions are formed on a portion of the back surface that is located radially outward from the bolt holes. Each of the fins includes a top surface and a convex portion. The top surface extends in the radial direction. The convex portion protrudes radially inward beyond an imaginary plane when viewed in a cross section of the brake disc cut along the radial direction. When viewed in the cross section, the imaginary plane passes through an inner end of both ends of the top surface in the radial direction and an inner peripheral edge of the back surface (first configuration).

[0016] The brake disc for a railway vehicle is fastened to a disc-shaped rotating member (e.g., a wheel) fixed to an axle during use. The brake disc is attached to the rotating member such that the top surface of each fin contacts the side surface of the rotating member. The fins, together with the disc body and the rotating member, define a plurality of ventilation passages extending in the radial direction of the brake disc. In the first configuration, since the thickness of the disc body decreases toward the inner side in the radial direction, each ventilation passage opens widely on the inner peripheral side of the disc body. Therefore, during braking, a large amount of air can flow into the ventilation passage from this opening, and the ventilation volume in the ventilation passage can be increased. When the ventilation volume in the ventilation passage increases, the air flow velocity on the outer peripheral side of the disc body also increases. Therefore, during braking, cooling of the disc body, particularly cooling of the outer peripheral portion of the disc body, which is thermally disadvantageous, can be promoted.

[0017] According to the first configuration, a plurality of protrusions are formed on the back surface of the disc body at a portion radially outside the bolt holes of the fins. These protrusions expand the surface area of the outer peripheral portion of the disc body. Also, according to the first configuration, during braking, since the ventilation volume in the ventilation passage increases and the air flow velocity increases on the outer peripheral side of the disc body, the temperature boundary layer formed on the surface of each protrusion becomes thinner. Therefore, the heat transfer coefficient of the outer peripheral portion of the disc body can be increased. As a result, during braking, cooling of the disc body, particularly cooling of the outer peripheral portion of the disc body, which is thermally disadvantageous, can be further promoted.

[0018] If the heat dissipation performance of the brake disc for railway vehicles is insufficient, the temperature reached during heating of the brake disc will be high, and the degree of deformation of the brake disc or the load stress on the bolts will be large. As a result, the brake disc may have strength problems (durability problems). In addition, if the heat dissipation performance of the brake disc is low, the brake disc will cool down slowly after heating, and the time required to cool the brake disc will be long. This may cause a problem that it becomes difficult to slow down the railway vehicle by repeatedly applying the brakes intermittently. In contrast, the brake disc in the first configuration promotes cooling of the disc body, particularly the outer periphery of the disc body, which is thermally disadvantageous, and therefore the heat dissipation performance required for a brake disc for railway vehicles can be ensured. Therefore, the occurrence of the above problems caused by insufficient heat dissipation performance can be suppressed.

[0019] In general, if a brake disc for a railway vehicle becomes excessively hot during use, the degree of deformation of the brake disc or the load stress on the bolts increases, which may cause problems with the durability of the brake disc. On the other hand, if the braking force is reduced to avoid excessive heating of the brake disc, the braking distance of the railway vehicle will be extended. Therefore, it is necessary to ensure an appropriate heat capacity in a brake disc for a railway vehicle. Here, if the disc body is simply thinned radially inward, the mass of the inner periphery of the brake disc decreases and the heat capacity decreases. As a result, localized high temperature may occur on the inner periphery of the brake disc during braking. However, in the first configuration, the heat capacity of the inner periphery of the brake disc is compensated for by increasing the mass of each fin by the convex portion protruding radially inward. Therefore, localized high temperature on the inner periphery of the brake disc can be avoided. That is, by providing the convex portion protruding radially inward on the fin, an appropriate heat capacity can be ensured in the brake disc, and the high temperature of the brake disc can be suppressed without unnecessarily reducing the braking force. Therefore, the durability required for a brake disc for a railway vehicle can be ensured. In addition, the surface area of ​​the fins can be increased by the convex portions protruding radially inward, which is expected to have the effect of improving the cooling performance of the brake disc.

[0020] The protrusion may be formed over the entire back surface of the disc body (second configuration).

[0021] According to the second configuration, the protrusions are scattered over the entire back surface of the disk body. This increases the overall surface area of ​​the back surface of the disk body, thereby increasing the heat transfer coefficient of the entire disk body. This further improves the cooling performance of the brake disk.

[0022] Each of the fins having bolt holes may include a first groove extending therethrough, the first groove being disposed radially outboard of the bolt holes (third configuration).

[0023] According to the third configuration, the first grooves arranged on the outer side of the bolt holes in the radial direction of the disc body increase the surface area of ​​the fins on the outer periphery of the brake disc. Also, separation of the air flow occurs at the edge of the first grooves, making the temperature boundary layer thinner, improving the heat transfer coefficient on the outer periphery of the brake disc. This can further promote cooling of the outer periphery of the disc body during braking.

[0024] Generally, when the amount of air flow in the air passage increases, the amount of aerodynamic noise generated when the railway vehicle is traveling increases. In contrast, in the third configuration, a first groove is formed in a fin having a bolt hole. The edge and wall surface of the first groove promote cooling of the outer periphery of the disc body, while causing a slight pressure loss in the air flowing through the air passage, reducing the amount of air flow. Therefore, it is possible to suppress the generation of aerodynamic noise during traveling while improving the cooling performance of the brake disc.

[0025] Each of the fins having bolt holes may further include a second groove extending therethrough, the second groove being disposed radially inward of the bolt holes (fourth configuration).

[0026] According to the fourth configuration, the second grooves arranged inside the bolt holes in the radial direction of the disc body increase the surface area of ​​the fins even on the inner circumferential side of the brake disc, and the thermal boundary layer becomes thinner, improving the heat transfer coefficient. This makes it possible to improve the overall cooling performance of the brake disc. In addition, both the first and second grooves can cause a pressure loss in the air flowing through the ventilation passage, reducing the amount of airflow, thereby further improving the cooling performance of the brake disc and more reliably suppressing the generation of aerodynamic noise.

[0027] It is preferable that the rear surface of the disc body is inclined with respect to the front surface so as to approach the front surface toward the inner peripheral edge when viewed in a cross section of the brake disc cut along the radial direction (fifth configuration).

[0028] According to the fifth configuration, the rear surface of the disc body is an inclined surface. As a result, the cross-sectional area of ​​the ventilation passage formed between the disc body and the rotating member is gradually reduced from the inner periphery side to the outer periphery side of the brake disc without a sudden change. This makes it possible to prevent a large pressure loss from occurring in the air flowing through the ventilation passage. As a result, it is possible to ensure a sufficient amount of ventilation in the ventilation passage, and to further improve the cooling performance of the brake disc.

[0029] According to the fifth configuration, the rear surface of the disc body approaches the front surface as it approaches the inner peripheral edge, so that the height of the fins provided on the rear surface increases toward the inner peripheral side of the brake disc. In other words, the surface area of ​​the fins is enlarged on the inner peripheral side of the brake disc. This can promote cooling on the inner peripheral side of the brake disc.

[0030] Hereinafter, a brake disc for a railway vehicle according to an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are given the same reference numerals, and the same description will not be repeated. Each drawing is a schematic diagram for explaining the main components of the brake disc according to the embodiment. Therefore, the detailed shape or dimensional ratio of the brake disc shown in each drawing may differ from those of an actual brake disc.

[0031] [Brake disc configuration] Fig. 1 is a back view of a railway vehicle brake disc 100 according to an embodiment. Fig. 2 is a perspective view of a 1 / 8 circle portion of the brake disc 100 shown in Fig. 1. The brake disc 100 is fastened to a rotating member (not shown) of the railway vehicle. The rotating member is an annular disk that is fixed to an axle and rotates together with the axle. The rotating member is, for example, a wheel.

[0032] With reference to FIGS. 1 and 2, a brake disc 100 includes a disc body 10 and a plurality of fins 20.

[0033] The disc body 10 is an annular disk. The disc body 10 has a front surface 11 and a back surface 12. The front surface 11 is a sliding surface against which a brake lining (not shown) is pressed. The back surface 12 is the surface facing opposite to the front surface 11. When the brake disc 100 is fastened to a rotating member, the back surface 12 faces a side surface of the rotating member. Hereinafter, for convenience of explanation, the radial direction and circumferential direction of the disc body 10 will be simply referred to as the radial direction and the circumferential direction, and the direction perpendicular to both the radial direction and the circumferential direction will be referred to as the thickness direction.

[0034] The disk body 10 includes a plurality of protrusions 13. These protrusions 13 are formed on the rear surface 12. Each protrusion 13 has, for example, a hemispherical or semi-spheroidal shape. Each protrusion 13 may have the same shape as the other protrusions 13, or may have a different shape from the other protrusions 13.

[0035] The multiple fins 20 are radially arranged on the back surface 12 of the disc body 10. The fins 20 extend from the inner periphery side to the outer periphery side of the disc body 10. Each of the fins 20 includes a top surface 21 extending in the radial direction. When the brake disc 100 is fastened to a rotating member, the top surface 21 comes into contact with a side surface of the rotating member. This forms a space between the rotating member, the fins 20 adjacent in the circumferential direction, and the disc body 10. The space serves as an air passage through which air passes when the brake disc 100 rotates together with the rotating member.

[0036] At least some of the fins 20 have bolt holes 22 in the radial center. In this embodiment, the bolt holes 22 are provided in only some of the fins 20 among the multiple fins 20 arranged on the back surface 12 of the disc body 10. The bolt holes 22 penetrate the fins 20 and the disc body 10 in the thickness direction. A bolt (not shown) is inserted into the bolt hole 22 when fastening the brake disc 100 to a rotating member.

[0037] Each of the fins 20 having the bolt holes 22 has grooves 23, 24. The grooves 23, 24 are concave from the top surface 21 toward the disk body 10. The grooves 23, 24 extend generally in the circumferential direction and traverse the fin 20.

[0038] The grooves 23, 24 are disposed on both sides of the bolt hole 22 in the radial direction. The groove 23 is provided on the outer side of the bolt hole 22 in the radial direction. The groove 24 is provided on the inner side of the bolt hole 22 in the radial direction. The shapes of the grooves 23, 24 are not particularly limited. The wall surfaces and bottom surfaces of the grooves 23, 24 can be configured as flat surfaces, convex curved surfaces, concave curved surfaces, or combinations thereof. In this embodiment, the fins 20 that do not have the bolt holes 22 also have the grooves 23, 24.

[0039] The configurations of the disc body 10 and the fins 20 will be described in more detail with reference to Fig. 3. Fig. 3 is a cross-sectional view of the brake disc 100 shown in Fig. 1 taken along line III-III, that is, a cross-sectional view of the brake disc 100 cut along the radial direction. Hereinafter, a cross-section of the brake disc 100 along the radial direction will be referred to as a radial cross-section.

[0040] In a radial cross-sectional view of the brake disc 100, the back surface 12 of the disc body 10 is inclined with respect to the front surface 11. The back surface 12 is inclined so as to approach the front surface 11 from its outer peripheral edge 121 toward its inner peripheral edge 122. In a radial cross-sectional view of the brake disc 100, the angle α that the back surface 12 forms with the front surface 11 is preferably 8° or less, and more preferably 6° or less. The angle α is preferably 2° or more.

[0041] Because the back surface 12 is inclined with respect to the front surface 11, the thickness of the disk body 10 decreases radially inward. That is, the disk body 10 as a whole is gradually thinned from the outer side to the inner side in the radial direction. The disk body 10 has a maximum thickness t1 at the position of the outer circumferential edge 121 of the back surface 12. The disk body 10 has a minimum thickness t2 at the position of the inner circumferential edge 122 of the back surface 12.

[0042] The maximum thickness t1 is the length in the thickness direction from the outer peripheral edge 121 of the back surface 12 to the front surface 11. The maximum thickness t1 can be, for example, 17 mm to 25 mm.

[0043] The minimum thickness t2 is the length in the thickness direction from the inner peripheral edge 122 of the back surface 12 to the front surface 11. In this embodiment, a notch 111 is provided on the inner peripheral edge of the front surface 11, but the minimum thickness t2 is a thickness that does not take into consideration this notch 111. The minimum thickness t2 can be set to, for example, 3 mm to 12 mm.

[0044] A plurality of the above-mentioned protrusions 13 are provided between adjacent fins 20 in the circumferential direction on the back surface 12 of the disk body 10. For example, at least five protrusions 13 are arranged between adjacent fins 20 on the back surface 12.

[0045] The multiple protrusions 13 are formed on at least a portion of the back surface 12 that is located radially outward from the bolt holes 22. In this embodiment, the protrusions 13 are formed over the entire back surface 12. That is, when the back surface 12 is divided into an outer circumferential side and an inner circumferential side with the center X of the bolt holes 22 as the boundary, the multiple protrusions 13 are provided from the outer circumferential side region to the inner circumferential side region.

[0046] In this embodiment, all of the protrusions 13 are semispherical. However, in consideration of moldability, it is preferable that the protrusions 13 located radially outward from the bolt holes 22 are semispheroidal.

[0047] The height of the fin 20 gradually increases from the outer side toward the inner side in the radial direction. The height of the fin 20 here refers to the distance in the thickness direction from the back surface 12 of the disc body 10 to the top surface 21 of the fin 20. In this embodiment, the top surface 21 is substantially parallel to the front surface 11 of the disc body 10, while the back surface 12 is inclined relative to the front surface 11 so as to approach the front surface 11 toward the inner side in the radial direction. Therefore, the top surface 21 of the fin 20 is farther away from the back surface 12 of the disc body 10 toward the inner side of the brake disc 100, and the height of the fin 20 increases.

[0048] Each fin 20 includes a protruding portion 25. The protruding portion 25 is a portion of the fin 20 that protrudes radially inward from an imaginary plane S1. In a radial cross-sectional view of the brake disc 100, the protruding portion 25 is provided between the imaginary plane S1 and an imaginary plane S2. The imaginary plane S1 is an imaginary plane that passes through an end 212 located on the inner side of both ends 211, 212 of the top surface 21 in the radial direction and an inner peripheral edge 122 of the back surface 12 of the disc body 10. The imaginary plane S2 is an imaginary plane that passes through the inner peripheral edge 122 of the back surface 12 and extends in the thickness direction.

[0049] The protrusion 25 has a surface 251 facing inward in the radial direction. In this embodiment, the surface 251 is configured as a smooth curved surface. However, the surface 251 may be configured as a flat surface. In a radial cross-sectional view of the brake disc 100, the surface 251 can be configured by combining multiple types of curves and / or straight lines.

[0050] [Effects of the embodiment] In the brake disc 100 according to this embodiment, the thickness of the disc body 10 decreases radially inward. This increases the cross-sectional area of ​​the air passage formed by the rotating member of the railway vehicle, the fins 20 adjacent in the circumferential direction, and the disc body 10 on the inner circumferential side of the brake disc 100. This makes it possible to increase the amount of air (airflow rate) flowing into the air passage from the inner circumferential side of the brake disc 100 when braking the rotating member.

[0051] Fig. 4 is a diagram illustrating the temperature distribution during braking of a typical brake disc. Referring to Fig. 4, during braking of a rotating member, the temperature of the disc body 10 tends to be particularly high in the portion radially outward of the bolt holes 22 (outer periphery). This is because the cross-sectional area of ​​the air passage expands in the circumferential direction toward the outer periphery of the disc body 10 due to the fins 20 arranged radially on the back surface 12, and the air flow rate decreases at the outer periphery of the disc body 10, resulting in a decrease in the heat transfer coefficient. In addition, the peripheral speed of the outer periphery of the disc body 10 is higher than that of the inner periphery, so that the amount of heat input due to friction with the brake lining is also larger, and the temperature is likely to rise.

[0052] In contrast, in the brake disc 100 according to this embodiment, a plurality of protrusions 13 are formed on the back surface 12 of the disc body 10 at least in a portion (outer periphery) radially outward from the bolt holes 22. These protrusions 13 can increase the surface area of ​​the outer periphery of the back surface 12. Furthermore, in this embodiment, the disc body 10 is made thinner toward the radially inward direction, thereby increasing the amount of air passing through the air passage. Therefore, the air flow rate increases at the outer periphery of the back surface 12, and the temperature boundary layer formed on the surface of each protrusion 13 becomes thinner. Therefore, the heat transfer coefficient of the outer periphery of the back surface 12 can be increased. Therefore, the cooling of the disc body 10, particularly the cooling of the outer periphery of the disc body 10 which is thermally disadvantageous, can be promoted.

[0053] According to this embodiment, cooling of the outer periphery of the disc body 10, which is particularly susceptible to high temperatures, is promoted, thereby improving the cooling performance and durability of the brake disc 100. Such a brake disc 100 can be used in high-speed railway vehicles.

[0054] In the brake disc 100 according to this embodiment, the thickness of the disc body 10 is gradually reduced radially inward, which allows the brake disc 100 to be made lighter, thereby enabling energy savings during the running of the railway vehicle.

[0055] In this embodiment, the protrusions 25 increase the amount of fins 20 on the inner circumferential side of the brake disc 100. Therefore, even though the entire disc body 10 is thinner going radially inward, it is possible to ensure heat capacity on the inner circumferential side of the brake disc 100. This makes it possible to prevent the inner circumferential side of the brake disc 100 from becoming locally hot during braking. As a result, it is possible to ensure the durability required of a brake disc for a railway vehicle in the brake disc 100.

[0056] When increasing the heat capacity on the inner periphery side of the brake disc 100, it is also possible to make a part of the fin 20 protrude in the circumferential direction on the inner periphery side of the brake disc 100. For example, as shown in FIG. 5, if the heat capacity on the inner periphery side of the brake disc 100 is simply to be increased, it is also possible to provide a protrusion 26 on both sides of the fin 20 on the inner periphery side of the brake disc 100. However, in this case, the cross-sectional area of ​​the air passage on the inner periphery side of the brake disc 100 is reduced, particularly in the circumferential direction, so that the amount of air passing through the air passage is reduced. That is, as shown by hatching in the upper diagram of FIG. 5, the air inflow surface in the air passage is reduced by the protrusion 26, and the air permeability between the brake disc 100 and the rotating member is reduced. Therefore, the cooling performance of the brake disc 100 is reduced. Furthermore, when the fin 20 is partially protruded in the circumferential direction, a part where the cross-sectional area suddenly expands is formed in the air passage extending in the radial direction. As a result, the pressure loss of the air flowing inside the air passage increases, reducing the amount of air flow and decreasing the air flow velocity and heat transfer coefficient.

[0057] Alternatively, if the heat capacity of the inner periphery of the brake disc 100 is simply to be increased, it is possible to provide a protrusion 14 on the back surface 12 of the disc body 10 on the inner periphery of the brake disc 100, for example, as shown in Fig. 6. However, in this case, the cross-sectional area of ​​the air passage on the inner periphery of the brake disc 100 is reduced, particularly in the thickness direction, and the amount of air passing through the air passage is reduced. That is, as shown by hatching in the upper diagram of Fig. 6, the air inflow surface in the air passage is reduced by the protrusion 14, and the air permeability between the brake disc 100 and the rotating member is reduced. Therefore, the cooling performance of the brake disc 100 is reduced.

[0058] In contrast, in this embodiment, the fins 20 are protruded radially inward on the inner circumferential side of the brake disc 100 to form the protrusions 25. The protrusions 25 do not protrude into the air passage, so the cross-sectional area of ​​the air passage is not substantially reduced on the inner circumferential side of the brake disc 100. That is, the air inflow surface in the air passage is not reduced by the protrusions 25, and good ventilation between the brake disc 100 and the rotating member can be ensured. Therefore, the heat capacity can be increased while maintaining excellent cooling performance in the brake disc 100. In addition, the surface area of ​​the fins 20 can be increased by the protrusions 25, so that the cooling performance on the inner circumferential side of the brake disc 100 can be further improved.

[0059] In this embodiment, the protrusions 13 are formed over the entire back surface 12 of the disc body 10. Therefore, the surface area of ​​the back surface 12 can be expanded overall, and the heat transfer coefficient of the entire back surface 12 can be increased. Thus, the cooling performance of the brake disc 100 can be further improved.

[0060] In this embodiment, each fin 20 has grooves 23, 24 formed therein, which cross the fin. The edges and walls of the grooves 23, 24 cause pressure loss in the air flowing through the air passage, slightly reducing the amount of air passing through the air passage. This makes it possible to suppress the generation of aerodynamic noise during braking. On the other hand, the grooves 23, 24 can increase the surface area of ​​the fin 20, and can also cause separation of the air flow at the edges, thinning the temperature boundary layer. This promotes cooling of the brake disc 100 during braking. That is, the grooves 23, 24 can also contribute to improving the cooling performance of the brake disc 100.

[0061] In this embodiment, all of the fins 20 have the grooves 23, 24. However, the grooves 23, 24 are not essential components for each fin 20, and some or all of the fins 20 may not have the grooves 23, 24. For example, the grooves 23, 24 may be formed on both sides of the bolt hole 22 only in the fin 20 in which the bolt hole 22 is provided. The fin 20 in which the bolt hole 22 is provided may have the groove 23 on the radially outer side, but may not have the groove 24 on the radially inner side.

[0062] In this embodiment, the rear surface 12 of the disk body 10 is inclined with respect to the front surface 11 in a radial cross-sectional view of the brake disk 100. The rear surface 12 is configured to gradually approach the front surface 11 toward the inner peripheral edge 122. As a result, the cross-sectional area of ​​the air passage formed between the disk body 10 and the rotating member is gradually reduced from the radial inner side to the radial outer side without a sudden change. Therefore, it is possible to ensure a sufficient amount of air flow in the air passage without causing a large pressure loss in the air in the air passage. Therefore, the cooling performance of the brake disk 100 can be further improved.

[0063] By inclining the rear surface 12 of the disc body 10 so as to approach the front surface 11 toward the inner peripheral edge 122, the height of the fins 20 becomes larger on the inner peripheral side of the brake disc 100. In other words, the surface area of ​​the fins 20 increases on the inner peripheral side of the brake disc 100. Therefore, cooling on the inner peripheral side of the brake disc 100 can be promoted.

[0064] However, the rear surface 12 of the disk body 10 does not have to be a single inclined surface in its entirety. The rear surface 12 may be composed of, for example, an inclined surface and a convex curved surface, or may be composed of a concave curved surface and a convex curved surface. As long as the disk body 10 as a whole is substantially thinner toward the inside in the radial direction, the shape of the rear surface 12 is not particularly limited.

[0065] 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. EXAMPLES

[0066] 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.

[0067] In order to verify the effect of the railway vehicle brake disc according to the present disclosure, a three-dimensional thermal fluid analysis was performed using general-purpose thermal fluid analysis software (product name: ANSYS Fluent, manufactured by ANSYS, Inc.) assuming a railway vehicle running steadily at 360 km / h. The basic specifications of the brake disc used in the thermal fluid analysis are as follows: <Basic specifications> Forged steel brake discs for bullet trains -Inner diameter of disc body: 466mm Outer diameter of disc body: 722mm Radial length of fin: 128mm Bolt holes: Centered on a circle with a diameter of 585 mm

[0068] The heat dissipation index was used as an evaluation index for the cooling performance of brake discs. The heat dissipation index is the product of the average heat transfer coefficient of the disc surface and the disc surface area (per brake disc at a steady driving speed of 360km / h). The higher this heat dissipation index, the better the cooling performance of the brake disc.

[0069] Additionally, the airflow volume was used as an evaluation index showing the level of aerodynamic noise. The airflow volume is the amount of air passing between the brake disc and the wheel (rotating member) during steady driving at 360 km / h. As described in International Publication No. 2010 / 071169, there is a strong correlation between the amount of air passing between the brake disc and the wheel and the level of aerodynamic noise. For this reason, the airflow volume (per unit time) obtained by thermal fluid analysis was used as an index for evaluating the level of aerodynamic noise. It can be said that the greater the airflow volume, the greater the level of aerodynamic noise.

[0070] FIG. 7 is a schematic diagram showing a radial cross section of each model used in the thermal fluid analysis. In the models of Examples 1 to 4, similarly to the brake disc 100 according to the above embodiment, the entire disc body 10 is thinned toward the radially inward direction, and the fins 20 are provided with protrusions 25. In the model of Example 1, the protrusions 13 are provided over the entire back surface 12 of the disc body 10. In the model of Example 2, the protrusions 13 are provided only in the region of the back surface 12 that is radially outer than the bolt holes 22. In the model of Example 3, the protrusions 13 are provided over the entire back surface 12, and the fins 20 are provided with grooves 23 and 24 on both sides of the bolt holes 22. In the model of Example 4, the protrusions 13 are provided over the entire back surface 12, and only the radially outer grooves 23 are provided in the fins 20.

[0071] In the models of each comparative example, the fin 20 is provided with a protrusion 25, as in each example. However, in the models of comparative examples 1, 3, and 4, the disk body 10 has a substantially constant thickness throughout. In the model of comparative example 3, the protrusion 13 is provided on the back surface 12 of the disk body 10, but the grooves 23, 24 are not provided on the fin 20. In the model of comparative example 4, the grooves 23, 24 are provided on the fin 20, but the protrusion 13 is not provided on the back surface 12. In the model of comparative example 2, the entire disk body 10 is thinned radially inward, but the protrusion 13 is not formed on the back surface 12.

[0072] In Examples 1 to 4 and Comparative Example 2, the angle α (FIG. 3) of the back surface 12 of the disc body 10 was set to 5°. In each Example and Comparative Example, the thickness t1 (FIG. 3) of the disc body 10 at the outer circumferential edge 121 was the same.

[0073] Fig. 8 is a graph showing the relationship between the amount of ventilation and the heat dissipation index obtained by thermal fluid analysis for each model. As shown in Fig. 8, the heat dissipation index of the models of Examples 1 to 4 was significantly higher than the heat dissipation index of the models of Comparative Examples 1 to 4. From this result, it can be said that the cooling performance of the brake disc can be improved by thinning the entire disc body 10 radially inward and providing the protrusions 13 at least in the region of the back surface 12 radially outward of the bolt holes 22.

[0074] The heat dissipation index of the model of Example 1 is higher than that of the model of Example 2. That is, by providing the protrusions 13 over the entire back surface 12 of the disc body 10, the cooling performance of the brake disc can be further improved.

[0075] The heat dissipation index of the models of Examples 3 and 4 is higher than that of the model of Example 1. Also, the airflow rate of the models of Examples 3 and 4 is smaller than that of the models of Examples 1 and 2. Therefore, by providing the grooves 23 or the grooves 23, 24 in the fins 20, the cooling performance of the brake disc can be further improved and the aerodynamic noise can be reduced.

[0076] The ventilation amount was the smallest in Example 3 in which grooves 23, 24 were provided on both sides of bolt hole 22. Therefore, it can be said that providing grooves 23, 24 on both the outer circumferential side and the inner circumferential side of bolt hole 22 in fin 20 is particularly effective in reducing aerodynamic noise.

[0077] Fig. 9 is a graph showing the relationship between the dimensionless radial coordinate of the back surface 12 of the disk body 10 and the heat dissipation index for each model of Example 1 and Comparative Examples 1 to 3. In the graph of Fig. 9, the heat dissipation index of the back surface 12 at a plurality of dimensionless radial coordinates is plotted for each model. The dimensionless radial coordinate is non-dimensionalized by dividing the radial distance from the inner peripheral edge 122 of the back surface 12 by the radial length of the back surface 12.

[0078] 9, there is almost no difference in the heat dissipation index of the outer periphery of the back surface 12 between Comparative Example 1 and Comparative Example 2. Therefore, it is found that simply thinning the disk body 10 radially inward does not improve the heat dissipation index on the outer periphery of the disk body 10, and does not promote cooling of the outer periphery of the disk body 10.

[0079] In Comparative Example 3, due to the presence of the protrusions 13 on the back surface 12, the heat dissipation index on the outer periphery of the back surface 12 was slightly higher than in Comparative Examples 1 and 2. However, in Example 1, the heat dissipation index on the outer periphery of the back surface 12 was even higher than in Comparative Example 3. Therefore, it can be said that the cooling of the outer periphery of the back surface 12 is significantly promoted by the synergistic effect of thinning the entire disk body 10 radially inward and providing the protrusions 13 on the back surface 12.

[0080] The heat dissipation index of the inner periphery side of the back surface 12 is lower in Example 1 than in Comparative Examples 1 and 3. However, in Example 1, the height and surface area of ​​the fins 20 are increased on the inner periphery side due to the inclination of the back surface 12. Therefore, the cooling performance on the inner periphery side of the brake disc can be ensured. Therefore, in Example 1, it is not particularly problematic that the heat dissipation index of the inner periphery side of the back surface 12 does not increase. [Explanation of symbols]

[0081] 100: Brake disc 10: Disk body 11: Surface 12: Back side 122: Inner edge 13: Protrusion 20: Finn 21:Top surface 22: Bolt hole 23,24: Groove 25: Convex

Claims

1. A brake disc for a railway vehicle, an annular disk body having a front surface and a back surface, the thickness of which decreases inward in a radial direction; a plurality of fins arranged radially on the back surface, at least some of the fins having a bolt hole at a center in the radial direction; Equipped with The disk body includes: a plurality of protrusions formed on the rear surface at a portion located radially outward from the bolt holes; Including, Each of the fins is the radially extending top surface; a protrusion that protrudes inward in the radial direction from an imaginary plane that passes through an inner peripheral edge of the back surface and an inner end of both ends of the top surface in the radial direction when viewed in a cross section of the brake disc cut along the radial direction; Including brake discs.

2. A brake disc according to claim 1, A brake disc, wherein the protrusion is formed over the entire back surface.

3. A brake disc according to claim 1 or 2, Each of the fins having the bolt holes is a first groove disposed radially outboard of the bolt hole and extending across the fin; Including brake discs.

4. A brake disc according to claim 3, Each of the fins having the bolt holes further comprises: a second groove disposed radially inward of the bolt hole and extending across the fin; Including brake discs.

5. A brake disc according to any one of claims 1 to 4, A brake disc, wherein the back surface is inclined relative to the front surface so as to approach the front surface toward the inner peripheral edge when viewed in the cross section of the brake disc.

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