Vibration-damping bushing for axle box support device

Abstract

To provide an anti-vibration bushing for an axle box support device with excellent durability.SOLUTION: A anti-vibration bushing 10 for an axle box support device comprises: a central axis 12 that has an axis center intersecting with a front-back direction of a vehicle; an elastic part 13 provided on the central axis 12; a pair of outside parts provided on the elastic part 13 with a gap between them; and a stopper part 15 provided on the elastic part 13 between the pair of outside parts. The central axis 12 has a recessed part 33 at a position facing the stopper part 15 via the elastic part 13.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a vibration isolation bush for an axle box support device that is preferably used for railway vehicles.

Background Art

[0002] Conventionally, in railway vehicles, an axle extends from an axle box portion that holds the axle in the vehicle longitudinal direction, and an axle box support device is provided at a connection portion between the tip of the axle and the bogie frame. The axle box support device has a vibration isolation bush (also referred to as a rubber bush) fitted in a housing portion provided at the tip of the axle. The vibration isolation bush has a central axis arranged so as to intersect the vehicle longitudinal direction, an elastic portion provided on the central axis, and an outer portion provided on the elastic portion. The elastic portion of the vibration isolation bush absorbs vibrations and impacts at the connection portion between the axle and the bogie frame while allowing rotational movement around the central axis of the axle.

[0003] Due to a large load in the vehicle longitudinal direction acting during acceleration and deceleration of the railway vehicle, the central axis and the outer portion are relatively displaced, and the elastic portion between the central axis and the outer portion is compressed. In particular, a large load is likely to act during deceleration by braking. The vibration isolation bush may have cracks in the elastic portion due to repeated action of a large load. Therefore, a stopper portion may be provided to suppress the relative displacement between the central axis and the outer portion (for example, see Patent Document 1).

[0004] Patent Document 1 discloses a vibration isolation bush having a stopper portion formed to project in the vehicle longitudinal direction from the central axis and bite into the elastic portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the vibration-damping bush disclosed in Patent Document 1 has a reduced thickness of the elastic part due to a stopper portion protruding from the central axis, making it difficult to reduce the stress and strain acting on the elastic part and thus difficult to improve durability.

[0007] Therefore, the present invention aims to provide a vibration-damping bush for axle box support device that offers excellent durability. [Means for solving the problem]

[0008] The vibration-damping bush for axle box support device according to the present invention comprises a central shaft having an axis intersecting the longitudinal direction of the vehicle, an elastic portion provided on the central shaft, a pair of outer portions provided on the elastic portion at intervals from each other, and a stopper portion provided on the elastic portion between the pair of outer portions, wherein the central shaft has a recessed portion at a position facing the stopper portion via the elastic portion. [Effects of the Invention]

[0009] According to the present invention, a recess is provided in the central shaft at a position opposite the stopper portion, and the thickness of the elastic portion in the recess is increased, thereby reducing the stress and strain acting on the elastic portion. The vibration-damping bush for shaft box support devices according to the present invention can suppress the occurrence of cracks in the elastic portion, and therefore has excellent durability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view showing a portion of the axle box support device to which the vibration-damping bushing according to this embodiment is applied, with a cutaway section. [Figure 2] This is a perspective view of a vibration-damping bushing. [Figure 3] This is a perspective view of the vibration-damping bushing from a different angle. [Figure 4] This is a front view showing a portion of the vibration-damping bush cut out. [Figure 5] This is a cross-sectional view taken along the VV line in Figure 4. [Figure 6] This is an explanatory diagram illustrating the method for assembling vibration-damping bushings to the shaft beams. [Figure 7] This is a cross-sectional view of the vibration-damping bush in its assembled state. [Figure 8] This is a cross-sectional view taken along the line VIII-VIII in Figure 4. [Figure 9] This graph shows the load on the deflection in the front-to-back direction for vibration-damping bushings with and without recesses. [Modes for carrying out the invention]

[0011] 1. Embodiment Embodiments of the present invention will be described in detail below with reference to the drawings.

[0012] As shown in Figure 1, the axle box support device used in railway vehicles has a structure in which an axle box section 2 that rotatably holds the axle 1 supports the bogie frame 4 in the vertical direction via an axle spring 3, and also supports the bogie frame 4 in the longitudinal direction of the vehicle via an axle beam 5 that extends from the axle box section 2 in the longitudinal direction of the vehicle. A vibration-damping bush 10 for the axle box support device is fitted into a housing section 6 provided at the longitudinal end of the axle beam 5. For simplicity, the vibration-damping bush for the axle box support device is simply referred to as a vibration-damping bush. The vibration-damping bush 10 is non-rotatably supported by a bracket 7 provided on the bogie frame 4. In the drawings, the X-axis direction is defined as the longitudinal direction (vehicle longitudinal direction), the Y-axis direction as the vertical direction, and the Z-axis direction as the left-right direction.

[0013] Figure 2 is a perspective view of the vibration-damping bush 10 from the front side in the longitudinal direction of the vehicle (see Figure 1). Figure 3 is a perspective view of the vibration-damping bush 10 from the rear side in the longitudinal direction of the vehicle. Figure 4 is a front view showing a portion of the vibration-damping bush 10 cut out.

[0014] In FIG. 4, the vibration isolator bush 10 includes a central axis 12 having an axis P that intersects the vehicle longitudinal direction (X-axis direction), an elastic portion 13 provided on the central axis 12, a pair of outer portions 14 provided on the elastic portion 13 with a space therebetween, and a stopper portion 15 provided on the elastic portion 13 between the pair of outer portions 14. In FIG. 4, the lower half with reference to the axis P of the central axis 12 is shown as a front view, and the upper half is shown as a partial cross-sectional view.

[0015] The central axis 12 is made of, for example, metal. The axis P of the central axis 12 is parallel to the Z-axis direction. When assembling the vibration isolator bush 10 onto the shaft 5, the central axis 12 is arranged such that its axis P intersects the vehicle longitudinal direction.

[0016] The central axis 12 has a mandrel portion 12A, a pair of inner flange portions 12B provided at both ends of the mandrel portion 12A in the direction of the axis P, and a pair of attachment portions 12C protruding from each inner flange portion 12B toward both sides in the direction of the axis P. The mandrel portion 12A is formed in a cylindrical shape. The inner flange portion 12B is formed in a flange shape that spreads outward in the radial direction of the central axis 12 and becomes thinner toward the outer side in the radial direction. The inner flange portion 12B has an outer surface 17 provided at a right angle to the axis P and an inner surface 18 provided inclined with respect to the axis P. The attachment portion 12C is formed in a polygonal prism shape (see FIGS. 2 and 3). The attachment portion 12C has a through-hole 19 extending in the Y-axis direction, and for example, by inserting a bolt into the through-hole 19, it is attached to the bracket 7 of the carriage frame 4. In this example, the mandrel portion 12A, the inner flange portion 12B, and the attachment portion 12C are integrally formed.

[0017] The elastic part 13 is formed of a cylindrical rubber. The elastic part 13 is disposed between the central axis 12 and the outer part 14 and vulcanization-bonded to the central axis 12 and the outer part 14. The elastic part 13 has a cylindrical part 13a provided on the outer peripheral surface 21 of the mandrel part 12A and a pair of rubber flange parts 13b provided on the inner side surface 18 of the pair of inner flange parts 12B. The rubber flange part 13b has an outer side surface 22 and an inner side surface 23 provided inclined with respect to the axis P. In this example, the cylindrical part 13a and the pair of rubber flange parts 13b are integrally formed.

[0018] FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 4. As shown in FIG. 5, the cylindrical part 13a of the elastic part 13 has a pair of large-diameter parts 25 formed symmetrically above and below about the axis P, a medium-diameter part 26 formed on one side between the pair of large-diameter parts 25, and a small-diameter part 27 formed on the other side between the pair of large-diameter parts 25. In a state where the vibration isolator bush 10 is not assembled to the shaft 5, the outer diameters are set to decrease in the order of the large-diameter part 25, the medium-diameter part 26, and the small-diameter part 27.

[0019] The pair of outer parts 14 are, for example, made of metal. The outer part 14 has a cylindrical plate part 14a provided on the outer peripheral surface 31 of the cylindrical part 13a of the elastic part 13 and a pair of flange plate parts 14b provided on the inner side surface 23 of the pair of rubber flange parts 13b. Specifically, the cylindrical plate part 14a is provided on the large-diameter part 25 of the cylindrical part 13a. The pair of flange plate parts 14b are provided so as to be connected to the cylindrical plate part 14a. The cylindrical plate part 14a and the pair of flange plate parts 14b are integrally formed.

[0020] The stopper portion 15 is made of metal, for example. The stopper portion 15 is provided on the outer circumferential surface 31 of the cylindrical portion 13a of the elastic portion 13. More specifically, the stopper portion 15 is provided on the small diameter portion 27 of the cylindrical portion 13a. The stopper portion 15 is vulcanized and bonded to the small diameter portion 27. The stopper portion 15 is formed in a rectangular shape with long sides and short sides when viewed from the front, and has four corners 30 (see Figures 2 and 4). Of the outer circumference of the stopper portion 15, the opposing long sides extend along the axis P direction of the core portion 12A, and the opposing short sides extend along the circumferential direction of the core portion 12A. Here, the rectangular shape is not limited to cases where the corners are right angles, but also includes cases where the corners are R-shaped (rounded). The stopper portion 15 is a plate-like member formed in an arc shape when viewed from the side.

[0021] As shown in Figure 6, the vibration-damping bush 10 is fitted into the fitting hole 32 of the housing portion 6 and assembled to the axial beam 5. The housing portion 6 is made of metal, for example. The housing portion 6 has a configuration that is divided into two parts in the vehicle's longitudinal direction (X-axis direction). The housing portion 6 has a base-side half-part 6A that is fixed to the tip of the axial beam 5 and a tip-side half-part 6B that is fixed to the base-side half-part 6A. The base-side half-part 6A and the tip-side half-part 6B are connected using fastening members such as bolts (not shown). The fitting hole 32 is formed by the inner surfaces of the base-side half-part 6A and the tip-side half-part 6B. The housing portion 6 is assembled into a cylindrical shape by connecting the base-side half-part 6A and the tip-side half-part 6B so as to sandwich a pair of outer parts 14 of the vibration-damping bush 10. The housing portion 6 applies a tightening force to the vibration-damping bush 10 and applies pre-compression to the elastic portion 13.

[0022] The vibration-damping bush 10 is assembled to the axial beam 5 by positioning the vibration-damping bush 10 between the base half-body 6A and the tip half-body 6B, with the pair of large-diameter portions 25 facing up and down, the medium-diameter portion 26 facing the base half-body 6A, and the small-diameter portion 27 facing the tip half-body 6B. Then, the base half-body 6A and the tip half-body 6B are brought closer together in the X-axis direction and connected by a fastening member (not shown). As a result, the vibration-damping bush 10 is fitted into the fitting hole 32 of the housing portion 6 with the large-diameter portion 25 of the elastic portion 13 compressed. The vibration-damping bush 10 fitted into the fitting hole 32 is supported by the bracket 7 so as not to rotate by a pair of mounting portions 12C provided on both sides in the direction of the axis P of the central axis 12. This structure allows the axle beam 5 to swing and move around the axis P of the central axis 12, and also absorbs vibrations and shocks at the connection point between the axle beam 5 and the trolley frame 4.

[0023] Figure 7 is a cross-sectional view of the vibration-damping bush 10 in its assembled state. As shown in Figure 7, the outer diameter of the stopper portion 15 in the assembled state is smaller than the outer diameter of the outer portion 14. The outer diameter of the outer portion 14 is equal to the inner diameter of the fitting hole 32. For this reason, a gap D is provided between the stopper portion 15 and the housing portion 6 (the inner surface of the fitting hole 32). The distance of this gap D, that is, the difference in diameter between the outer diameter of the stopper portion 15 and the inner diameter of the fitting hole 32, is set to 3 mm in this example, but is not particularly limited. In this embodiment, the outer diameter of the stopper portion 15 in the assembled state is configured to be equal to the outer diameter of the medium diameter portion 26 of the elastic portion 13. For this reason, a gap D of 3 mm is also provided between the medium diameter portion 26 and the inner surface of the fitting hole 32.

[0024] Here, the vibration-damping bush is required to have different spring characteristics (spring constants) in three directions: vertical, longitudinal, and lateral. In particular, the spring characteristics in the longitudinal direction of the vehicle require a nonlinear spring characteristic in which the spring constant is small (soft spring characteristics) when the load on the vibration-damping bush is small, such as during normal driving, and a large spring constant (stiff spring characteristics) when the load on the vibration-damping bush is large, such as during sudden braking. The vibration-damping bush 10 is designed so that a gap D is provided between the stopper portion 15 and the inner surface of the fitting hole 32, resulting in a small spring constant when the load is small before the stopper portion 15 contacts the inner surface of the fitting hole 32, and a large spring constant when the load is large after the stopper portion 15 contacts the inner surface of the fitting hole 32. If a gap D is not provided between the stopper portion 15 and the inner surface of the fitting hole 32, the required nonlinear spring characteristics cannot be obtained.

[0025] Furthermore, vibration-damping bushings are subjected to large loads in the longitudinal direction of the vehicle during acceleration and deceleration, especially during braking. Repeated application of these large loads compresses the elastic portion between the central shaft and the stopper, leading to problems such as cracks forming in the elastic portion. Stress is particularly high near the corners of the stopper, making cracks more likely to occur in the elastic portion near these corners. To prevent crack formation, methods such as hardening the elastic portion or increasing the thickness of the central shaft to reduce the relative displacement between the central shaft and the housing are considered effective. However, with such methods, the spring constant becomes large whether a large load is applied, such as during braking, or a small load is applied, such as during normal driving, thus compromising ride comfort. Increasing the thickness of the stopper (length in the longitudinal direction of the vehicle) can suppress the effects of small loads while also suppressing displacement under large loads, but since the thickness of the elastic portion decreases by the amount the stopper thickness increases, the stress and strain acting on the elastic portion cannot be reduced. In contrast, the vibration-damping bush 10 has a configuration that reduces the stress and strain acting on the elastic part 13, thereby suppressing the occurrence of cracks in the elastic part 13. The configuration that reduces stress and strain will be described in detail below.

[0026] Figure 8 is a cross-sectional view taken along the line VIII-VIII in Figure 4. As shown in Figure 8, the central axis 12 of the vibration-damping bush 10 has a recessed portion 33 at a position facing the stopper portion 15 via the elastic portion 13. Specifically, the recessed portion 33 is provided at a position facing the corner portion 30 of the stopper portion 15, which is formed in a rectangular shape when viewed from the front. The recessed portion 33 is formed by gouging (shaving off) the outer circumferential surface 21 of the spindle portion 12A to a predetermined depth. The diameter of the spindle portion 12A of the central axis 12 is larger in the portion other than the recessed portion 33 than in the portion with the recessed portion 33. The diameter of the portion of the central axis 12 other than the recessed portion 33 is designed to be equivalent to the diameter of the central axis of a conventional vibration-damping bush without a recessed portion.

[0027] The recessed portion 33 is provided in the shape of a continuous groove along the outer circumference of the stopper portion 15. In this embodiment, the recessed portion 33 is provided in the shape of a groove along the short sides of the outer circumference of the stopper portion 15 that are opposite to each other. More specifically, the recessed portion 33 is configured as an annular groove that goes around the circumferential direction of the spindle portion 12A. The vibration-damping bush 10 has a pair of recessed portions 33 provided at two locations in the axial direction P of the spindle portion 12A, but Figure 8 shows only one of the pair of recessed portions 33. The depth of the recessed portion 33 (the dimension from the outer circumferential surface 21 of the spindle portion 12A to the bottom surface of the recessed portion 33) is set to about 4 mm in this example, but is not limited to this.

[0028] The cylindrical portion 13a of the elastic portion 13 has a thick-walled portion 34 provided in the recessed portion 33 of the core portion 12A, and a thin-walled portion 35 provided in the portion of the core portion 12A other than the recessed portion 33, and having a thickness less than the thick-walled portion 34. In Figure 8, the thickness of the thick-walled portion 34 is shown as T1 and the thickness of the thin-walled portion 35 is shown as T2. The thick-walled portion 34 is provided between the corner portion 30 of the stopper portion 15 and the recessed portion 33 of the core portion 12A. Thus, the elastic portion 13 has a configuration in which the thickness is partially increased near the corner portion 30 of the stopper portion 15.

[0029] 2. Action and Effects The vibration-damping bush 10 has a recessed portion 33 on the spindle portion 12A of the central shaft 12, at a position facing the stopper portion 15. The thickness T1 of the thickened portion 34 provided in the recessed portion 33 of the elastic portion 13 is greater than the thickness T2 of the thinned portion 35 provided in the portion other than the recessed portion 33. In this way, the vibration-damping bush 10 can reduce the stress and strain acting on the elastic portion 13 by increasing the thickness of the elastic portion 13 in the recessed portion 33. The vibration-damping bush 10 can suppress the occurrence of cracks in the elastic portion 13, and therefore has excellent durability.

[0030] Since the recessed portion 33 is provided in the shape of a continuous groove along the outer circumference of the stopper portion 15, it reduces the stress and strain acting on the elastic portion 13 near the outer circumference of the stopper portion 15. In particular, since the recessed portion 33 is provided at a position opposite to the corner portion 30 of the stopper portion 15, it can reduce the stress and strain acting on the elastic portion 13 near the corner portion 30. The corner portion 30 of the stopper portion 15 is prone to high stress, but in the vibration-damping bush 10, by increasing the thickness of the elastic portion 13 near the corner portion 30, it is possible to suppress the occurrence of cracks near the corner portion 30 and to suppress the propagation of cracks.

[0031] The vibration-damping bushing 10 is designed such that the diameter of the core portion 12A, excluding the recessed portion 33, is equivalent to the diameter of a conventional central shaft without a recessed portion, thus maintaining the same spring characteristics as conventional bushings. However, if the overall diameter of the core portion of the central shaft is reduced, the spring characteristics will deteriorate.

[0032] 3. Examples Figure 9 is a graph showing the load on deflection in the longitudinal direction of the vehicle for a vibration-damping bush with a recessed portion in the embodiment and a vibration-damping bush without a recessed portion in the comparative example. The vibration-damping bush in the embodiment had the same configuration as the vibration-damping bush 10 in the embodiment. The vibration-damping bush in the comparative example had the same configuration as the vibration-damping bush 10, except that it did not have a recessed portion.

[0033] As shown in Figure 9, both the example and the comparative example have a gap D (3 mm) between the stopper portion 15 and the housing portion 6 (inner surface of the fitting hole 32). Therefore, the load increases relatively slowly until the deflection amount of the elastic portion 13 in the vehicle longitudinal direction reaches 3 mm. When the deflection exceeds 3 mm, the stopper portion 15 contacts the inner surface of the fitting hole 32, and the rate of load increase increases. It was confirmed that the spring constant is small under small loads before the stopper portion 15 contacts the inner surface of the fitting hole 32, and tends to be large under large loads after the stopper portion 15 contacts the inner surface of the fitting hole 32. The difference in spring constant between the example and the comparative example is slight, indicating that the presence or absence of the recess does not have a significant effect on the spring characteristics. Therefore, the vibration-damping bush of the example with the recess 33 has spring characteristics equivalent to those of a conventional vibration-damping bush without a recess.

[0034] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the spirit of the present invention.

[0035] In the above embodiment, a recessed portion 33 is provided at a position opposite the corner portion 30 of the stopper portion 15, increasing the thickness of the elastic portion 13 near the corner portion 30. However, the position of the recessed portion 33 is not limited as long as the thickness of the elastic portion 13 between the central axis 12 and the stopper portion 15 is partially increased. The recessed portion 33 may also be provided at a position opposite a different part (for example, the central part) of the stopper portion 15 via the elastic portion 13. By providing a recessed portion 33 at a position at least opposite the stopper portion 15, the thickness of the elastic portion 13 can be partially increased, and the stress and strain acting on the elastic portion 13 can be relieved. It is preferable that the position of the recessed portion 33 be at a position opposite the corner portion 30 of the stopper portion 15, as in the above embodiment. This is because the stress and strain acting near the corner portion 30, where cracks are likely to occur, can be further relieved, durability can be further improved, and the lifespan can be extended.

[0036] In the above embodiment, the recessed portion 33 is formed in a groove shape along the opposing short sides of the outer circumference of the stopper portion 15, but it is not limited to this, and may also be formed in a groove shape along the opposing long sides of the outer circumference of the stopper portion 15. Furthermore, it is not limited to providing the recessed portion 33 in a continuous groove shape along the outer circumference of the stopper portion 15, but for example, four recessed portions 33 may be provided spaced apart from each other so as to face the four corners 30 of the stopper portion 15.

[0037] In the above embodiment, the stopper portion 15 is positioned on the front side in the vehicle's longitudinal direction, but it is not limited to this, and may be positioned on the rear side in the vehicle's longitudinal direction. Alternatively, a pair of stopper portions 15 may be positioned on both the front and rear sides in the vehicle's longitudinal direction. When a pair of stopper portions 15 are positioned on both the front and rear sides in the vehicle's longitudinal direction, the cylindrical portion 13a of the elastic portion 13 shall have a pair of large-diameter portions 25 formed vertically symmetrically with respect to the axis P, and a pair of small-diameter portions 27 formed horizontally symmetrically with respect to the axis P. A stopper portion 15 is then provided on each of the small-diameter portions 27.

[0038] The elastic portion 13 may use rubber that is harder than the elastic portion used in conventional vibration-damping bushings that do not have a recessed portion. By using rubber that is harder than the conventional elastic portion, the decrease in the spring constant is suppressed, and the same spring characteristics as conventional bushings can be maintained more reliably.

[0039] In the above embodiment, a configuration is adopted in which a tightening force is applied to the vibration-damping bush 10 by the housing portion 6 and pre-compression is applied to the elastic portion 13, but the invention is not limited to this.

[0040] The recessed portion 33 is not limited to being provided on the central axis 12, but may also be provided on the stopper portion 15. The recessed portion 33 can be formed on the stopper portion 15 by gouging (shaving off) the inner surface of the stopper portion 15 (the surface facing the central axis 12 via the elastic portion 13) to a predetermined depth. By increasing the thickness of the elastic portion 13 in the recessed portion 33, the stress and strain acting on the elastic portion 13 can be reduced. As a result, the occurrence of cracks in the elastic portion 13 is suppressed, and durability is improved. It is preferable to provide the recessed portion 33 on the corner portion 30 of the stopper portion 15. This is because increasing the thickness of the elastic portion 13 near the corner portion 30 suppresses the occurrence of cracks near the corner portion 30, where stress tends to be high, and also suppresses the propagation of cracks. [Explanation of Symbols]

[0041] 10 Vibration-damping bushings 12 Center axis 12A Mandrel 12B Inner flange-like part 12C Mounting section 13 Elastic part 13a Cylindrical part 13b Rubber flange portion 14 Outer part 14a Cylinder plate part 14b Flange plate part 25 Large diameter section 26 Medium diameter part 27 Small diameter section 15 Stopper part 30 corners 33. Digging section P axis center

Claims

1. A central axis having an axis that intersects the longitudinal direction of the vehicle, An elastic portion provided on the central axis, A pair of outer parts provided on the elastic part at a distance from each other, Between the pair of outer parts, there is a stopper portion provided on the elastic part, The aforementioned central shaft is a vibration-damping bush for a shaft box support device, having a recessed portion at a position facing the stopper portion via the elastic portion.

2. The vibration-damping bush for a shaft box support device according to claim 1, wherein the recessed portion is provided in the shape of a continuous groove along the outer circumference of the stopper portion.

3. The stopper portion is formed in a rectangular shape when viewed from the front. The vibration-damping bush for a shaft box support device according to claim 1, wherein the recessed portion is provided at a position opposite to the corner of the stopper portion.

4. The central shaft has a core portion, and the recessed portion is provided on the core portion. The elastic portion has a cylindrical portion provided on the core portion, The vibration-damping bush for a shaft box support device according to claim 1, wherein the cylindrical portion has a thick-walled portion provided in the recessed portion of the shaft portion and a thin-walled portion provided in the portion of the shaft portion other than the recessed portion and having a thickness less than the thick-walled portion.

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