Axle spring

Abstract

To provide an axle spring which can improve durability by preventing the occurrence of a crack and the exfoliation of an upper part of an elastic body at the innermost layer.SOLUTION: An axle spring comprises: a spindle 2 arranged in a vertical direction; a tapered cylindrical outer cylinder 3 coaxially arranged at the outside of the spindle 2 in a radial direction with respect to an axial core P of the spindle 2; and an elastic part 4 interposed between the spindle 2 and the outer cylinder 3. The elastic part 4 has a lamination structure in which coaxially-arranged tapered cylindrical elastic bodies 5 to 9 and intermediate hard cylinders 11 to 14 are alternately laminated on each other in the radial direction, and a magnitude relation of W1>W3>W2 is established between and among a thickness W1 of an upper part of the elastic body 5 at the innermost layer which firmly adheres to an external peripheral face of the spindle 2, a thickness W2 of an intermediate part and a thickness W3 of a lower part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an axle spring suitable for use in vehicles, particularly railway vehicles. [Background technology]

[0002] For example, in railway vehicles, axle springs are interposed between the wheels that run on the rails and the bogie. The bogie is elastically suspended by the axle springs, thereby absorbing and mitigating the impacts that the bogie receives.

[0003] Various proposals have been made regarding axle springs (see, for example, Patent Documents 1 and 2), and these have already been put to practical use. An example of a conventional axle spring is shown in FIG.

[0004] 9 is a vertical cross-sectional view showing an example of a conventional axle spring, and the illustrated axle spring 101 is configured to include a main shaft 102 disposed in the up-down direction, a tapered cylindrical (tapered cylindrical) outer cylinder 103 disposed radially outward of the main shaft 102 and concentrically with the axis P of the main shaft 102, and an elastic portion 104 interposed between the main shaft 102 and the outer cylinder 103. The elastic portion 104 is configured as a laminated structure in which a plurality (five in the illustrated example) of tapered cylindrical elastic bodies 105, 106, 107, 108, 109 and a plurality (four in the illustrated example) of tapered cylindrical intermediate hard cylinders 111, 112, 113, 114, which are concentrically disposed, are alternately laminated in the radial direction.

[0005] In the axle spring 101, the main shaft 102, the outer cylinder 103, and the intermediate hard cylinders 111-114 are made of metal. The elastic bodies 105-109 are made of rubber. The outer cylinder 103, the elastic bodies 105-109, and the intermediate hard cylinders 111-114 are configured as tapered cylinders (frustum cone cylinders) inclined inward (diametrically inward) by a predetermined angle with respect to the axis P of the main shaft 102 so as to reduce in diameter toward the top. In the inclined (cone-shaped) axle spring 101 having the inclined outer cylinder 103, the elastic bodies 105-109, and the intermediate hard cylinders 111-114, the upper end of the outer cylinder 103 is attached to the bogie side via a mounting plate (not shown), and the lower end of the main shaft 102 is attached to an axle box (not shown). Although not shown, the axle box rotatably supports the wheels and axles, and an axle spring 101 is interposed between the axle box and the bogie. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6789094 [Patent Document 2] JP 2020-063761 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional axle spring 101 shown in FIG. 9, the elastic bodies 105-109 made of rubber are fixed between the main shaft 102 and the intermediate hard tube 111, between adjacent intermediate hard tubes 111 and 112, between 112 and 113, and between 113 and 114, and between the outer tube 103 and the intermediate hard tube 114 by vulcanization adhesion or the like. The axle spring 101 is subjected to dynamic loads in each of the up-down, left-right, and front-rear directions when a static load is applied in the up-down direction. In this case, in the inclined axial spring 101 in which the elastic bodies 105-109 and the intermediate hard cylinders 111-114 are inclined, when a load is applied in the vertical direction, a shear force and a compressive force act on each of the elastic bodies 105-109, but a large shear force acts on the upper surface side of each of the elastic bodies 105-109, and in this state, when each of the elastic bodies 105-109 receives a load in the front-rear and left-right directions, these elastic bodies 105-109 are subjected to tensile and compressive loads.

[0008] As described above, when tensile and compressive loads are applied to each of the elastic bodies 105-109, large stress and strain are generated in the upper parts of these elastic bodies 105-109, particularly in the upper part of the innermost elastic body 105 (part Y in Figure 9), causing cracks and peeling in this part, resulting in a problem of reduced durability of the axial spring 101.

[0009] Therefore, a first object of the present invention is to provide an axle spring capable of preventing cracks and peeling off of the upper part of the elastic body of the innermost layer and improving durability.

[0010] One possible solution to the above problem is to increase the thickness of the innermost layer of elastic body 105 to reduce the strain rate (displacement of elastic body / thickness). However, increasing the thickness of elastic body 105 reduces the spring constant of elastic body 105, making it impossible to ensure the spring characteristics required of axial spring 101.

[0011] Another possible method is to adjust the spring constant of the axle spring 101 by increasing the hardness of the rubber elastic bodies 105-109. However, this method would reduce the spring constant of the innermost elastic body 105 alone, which would increase the displacement of the innermost elastic body 105 due to the load, resulting in the strain rate remaining the same or even increasing, and as a result, the durability of the axle spring 101 would decrease.

[0012] Therefore, a second object of the present invention is to provide an axle spring that can improve durability while maintaining required spring characteristics. [Means for solving the problem]

[0013] In order to achieve the above object, an axle spring according to the present invention includes a main shaft disposed in a vertical direction, a tapered cylindrical outer cylinder disposed radially outward of the main shaft and concentric with an axial center of the main shaft, and an elastic portion interposed between the main shaft and the outer cylinder, the elastic portion having a layered structure in which a tapered cylindrical elastic body and an intermediate hard cylinder disposed concentrically are alternately layered in the radial direction, and a thickness W1 of an upper portion of the elastic body of an innermost layer fixed to an outer circumferential surface of the main shaft, a thickness W2 of an intermediate portion, and a thickness W3 of a lower portion of the elastic body are provided between the upper portion and the outer cylinder. W1>W3>W2 The magnitude relationship between these two is established.

[0014] In addition, the axle spring of the present invention has the same spring characteristics as other axle springs in which the vertical length and longitudinal cross-sectional area of ​​the innermost layer elastic body are the same and the thickness of the innermost layer elastic body is constant, and has higher durability than the other axle springs. Effect of the Invention

[0015] According to the present invention, the thickness W1 of the upper part of the innermost elastic body fixed to the outer circumferential surface of the spindle is made the thickest, so that the stress and strain generated in this part can be kept small. As a result, the occurrence of cracks and peeling in the upper part of the innermost elastic body where the greatest stress and strain are generated is prevented, and the durability of the axle spring is improved.

[0016] In addition, by making the longitudinal cross-sectional area of ​​the innermost elastic layer the same as that of the innermost elastic layer of another axle spring, whose thickness is constant in the vertical direction, it is possible to satisfy the spring characteristics (such as the spring constant in the vertical and horizontal directions) required of the axle spring, thereby increasing the durability of the axle spring while ensuring the spring characteristics required of the axle spring. [Brief description of the drawings]

[0017] [Figure 1] 1 is a side view of a main part of a railway vehicle, illustrating an example of use of an axle spring according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a vertical sectional view of an axle spring according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a plan view of the axle spring according to the first embodiment of the present invention. [Figure 4] 4 is a diagram showing a change in thickness along the vertical direction of the elastic body of the innermost layer of the axle spring according to the first embodiment of the present invention in comparison with a comparative example. FIG. [Diagram 5] FIG. 1 shows the results of stress analysis of an elastic body using the finite element method (FEM), where (a) is a cross-sectional oblique view of a key part of the elastic part of an axle spring according to embodiment 1 of the present invention, and (b) is a cross-sectional oblique view of a key part of the elastic part of an axle spring of a comparative example. [Figure 6] FIG. 2(a) is a diagram showing the relationship between the load and the vertical displacement of the axial spring in accordance with the first embodiment of the present invention, and FIG. 2(b) is a diagram showing the relationship between the load and the horizontal displacement of the same axial spring. [Figure 7] FIG. 11 is a vertical sectional view of an axle spring according to a second embodiment of the present invention. [Figure 8] 10 is a diagram showing a change in thickness of an elastic body in the innermost layer of an axle spring according to embodiment 2 of the present invention in the vertical direction in comparison with a comparative example. FIG. [Figure 9] FIG. 11 is a vertical cross-sectional view showing an example of a conventional axle spring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] <Embodiment 1> FIG. 1 is a side view of a main part of a railway vehicle showing an example of the use of an axle spring according to this embodiment. As shown in FIG. 1, a wheel 50 and an axle 51 are rotatably supported by an axle box 60 via a bearing 52. An axle spring 1 according to this embodiment is interposed between the front and rear (left and right in FIG. 1) of the axle 51 of the axle box 60 and a bogie frame 70A of the bogie 70, sandwiching the axle 51. Therefore, a part of the load of the bogie 70 is supported by the two axle springs 1 at the front and rear, and the bogie 70 is suspended so as to be displaceable in the up-down, left-right, and front-rear directions with respect to the wheel 50 and the axle 51. Note that FIG. 1 shows only a support structure on one side in the width direction (perpendicular to the paper surface of FIG. 1), but in reality, the wheel 50, the axle box 60, and a pair of axle springs 1 at the front and rear are provided on both sides in the width direction, and the bogie 70 is elastically supported by a total of eight axle springs 1.

[0020] Next, the axle spring 1 according to this embodiment will be described below with reference to Figures 2 to 6. Note that since the pair of front and rear axle springs 1 have the same configuration, only one of the axle springs 1 will be described below.

[0021] As shown in Figures 2 and 3, the axle spring 1 in this embodiment is of an inclined type (cone type) and includes a main shaft 2 arranged in the vertical direction, a tapered cylindrical (tapered tubular) outer tube 3 arranged radially outward of the main shaft 2 and concentrically with the axis P of the main shaft 2, and an elastic portion 4 interposed between the main shaft 2 and the outer tube 3.

[0022] The main shaft 2 is made of metal and is generally cylindrical, with a hollow portion 2a and a screw hole 2b formed in the upper and lower parts of the shaft center. A flange portion 2A is formed on the outer periphery of the lower end of the main shaft 2. The lower end of the main shaft 2 is attached to an axle box 60 shown in FIG. 1 by a bolt (not shown) that is screwed into the screw hole 2b.

[0023] The outer cylinder 3 is formed into a tapered cylindrical shape from the same metal as the main shaft 2. In detail, the outer cylinder 3 is formed into a tapered cylindrical shape whose diameter decreases toward the top, and is inclined inward (radially inward) by a predetermined angle with respect to the axis P of the main shaft 2. A fitting step 3a is formed on the inner periphery of the upper end of the outer cylinder 3, and a disk-shaped mounting plate 71 for mounting the outer cylinder 3 to a bogie frame 70A (see FIG. 1) is fitted into the fitting step 3a.

[0024] The elastic part 4 is configured as a laminated structure (five-layer structure) in which a plurality (five in the illustrated example) of tapered cylindrical (tapered tube-shaped) elastic bodies 5, 6, 7, 8, 9 and a plurality (four in the illustrated example) of tapered cylindrical (tapered tube-shaped) intermediate hard tubes 11, 12, 13, 14 are alternately laminated in the radial direction, which are arranged concentrically. Here, each of the elastic bodies 5-9 is made of rubber. Each of the intermediate hard tubes 11-14 is made of the same metal as the main shaft 2 and the outer tube 3. The elastic bodies 5-9 and the intermediate hard tubes 11-14 are formed in a tapered cylindrical shape that decreases in diameter toward the top. In detail, each of the elastic bodies 5-9 and the intermediate hard tubes 11-14 is inclined inward (diametrically inward) by a predetermined angle (the same angle as the inclination angle of the outer tube 3) with respect to the axis P of the main shaft 2. The rubber constituting each of the elastic bodies 5 to 9 may be natural rubber, chloroprene rubber, nitrile rubber, butyl rubber, or the like.

[0025] In the elastic portion 4 configured as described above, the multiple rubber elastic bodies 5-9 have their inner and outer peripheral surfaces fixed by vulcanization adhesion to the outer peripheral surface of the main shaft 2 or the inner peripheral surface of the outer cylinder 3, or the inner and outer peripheral surfaces of the adjacent intermediate hard cylinders 11-14. Specifically, the inner peripheral surface of the elastic body 5 of the innermost layer is fixed to the outer peripheral surface of the main shaft 2, and its outer peripheral surface is fixed to the inner peripheral surface of the intermediate hard cylinder 11. The other elastic bodies 6-8 constituting the intermediate layer are fixed to the inner and outer peripheral surfaces of the two adjacent intermediate hard cylinders 11 and 12, 12 and 13, and 13 and 14, respectively. The elastic body 9 of the outermost layer is fixed to the outer peripheral surface of the intermediate hard cylinder 14 and the inner peripheral surface of the outer cylinder 3. The upper and lower end surfaces of each of the elastic bodies 5-9 are concavely curved to avoid stress concentration.

[0026] The axle spring 1 constructed as above elastically supports the carriage 70 on the wheels 50 and the axles 51, as shown in FIG. 1, and the load from the carriage 70 is input from the outer tube 3, and this load is received by the multiple elastic bodies 5-9 of the elastic part 4 constituting the laminated structure. Here, in the axle spring 1, the outer tube 3 and the multiple elastic bodies 5-9 and the intermediate hard tube 11-14 constituting the elastic part 4 are inclined at a predetermined angle with respect to the axis P of the main shaft 2 as described above, so that each of the elastic bodies 5-9 receives dynamic loads in each of the vertical, left-right, and front-rear directions when a static load is applied to each of the elastic bodies 5-9 in the vertical direction. In this case, shear force and compression force act on each of the elastic bodies 5-9, but a large shear force acts on the upper surface side of each of the elastic bodies 5-9, and when each of the elastic bodies 5-9 receives a load in the front-rear and left-right directions in this state, these elastic bodies 5-9 are subjected to tensile and compressive loads.

[0027] As described above, when tensile and compressive loads are applied to each of the elastic bodies 5 to 9, large stress and strain are generated in the upper part of each of the elastic bodies 5 to 9, particularly in the upper part of the innermost elastic body 5 (part Y in Figure 2), causing cracks and peeling in this part, resulting in a problem of reduced durability of the axle spring 1.

[0028] In this embodiment, as shown in Fig. 2, a part of the outer circumferential surface of spindle 2 to which innermost elastic body 5 is fixed is made part of spherical surface 2c (shown as a part of a circular arc in the longitudinal cross section of Fig. 2), and the thickness W of innermost elastic body 5 gradually decreases from the upper part to the middle part (middle height position) and gradually increases from the middle part to the lower part. When the thickness W of elastic body 5 is W1 at the upper part, W2 at the middle part, and W3 at the lower part, the magnitude relationship shown in the following formula (1) is established. W1>W3>W2…(1) The thickness W of the elastic body 5 represents the thickness of the elastic body 5 in the direction perpendicular to the tapered cylindrical surface of the intermediate hard cylinder 11. The thickness W1 of the upper part is the thickness of the part of the elastic body 5 where the thickness W is the largest at the upper part. The thickness W2 of the middle part is the thickness of the part of the elastic body 5 between the upper and lower parts where the thickness W is the smallest. The thickness W3 of the lower part is the thickness of the part of the elastic body 5 where the thickness W is the largest at the lower part.

[0029] The following shows the results of evaluating the characteristics of an axle spring of an example, which is the axle spring 1 according to the present embodiment, and an axle spring of a comparative example. The axle spring of the comparative example is a conventional axle spring 101 shown in FIG. 9, which has the thickness of the elastic body of the innermost layer shown in FIG. 4, which will be described later.

[0030] FIG. 4 shows the change in thickness W of the innermost elastic body in the vertical direction of the axle spring 1 of the embodiment and the axle spring 101 of the comparative example. The thickness W of the elastic body 5 of the axle spring 1 of the embodiment shows a maximum value W1 at the upper part, gradually decreases from the upper part to the middle part, and shows a minimum value W2 at the middle part. Then, it gradually increases from the minimum value W2 at the middle part to W3 at the lower part. W1, W2, and W3 satisfy the magnitude relationship shown in the above formula (1). The thickness W0 of the innermost elastic body 105 of the axle spring 101 of the comparative example is constant as shown by the dashed line in FIG. 4. This thickness W0 is set to be smaller than the thickness W1 of the upper end and the thickness W3 of the lower end of the innermost elastic body 5 of the axle spring 1 of the embodiment, and larger than the thickness W2 of the middle part, and the magnitude relationship shown in the following formula (2) is established between these thicknesses W0, W1, W2, and W3. W1>W3>W0>W2…(2)

[0031] Furthermore, the area of ​​the elastic body 5 in the longitudinal cross section of the axle spring 1 of the embodiment is set equal to the area of ​​the elastic body 105 in the longitudinal cross section of the axle spring 101 of the comparative example. In detail, in Fig. 4, the value ΣW obtained by integrating the thickness W of the elastic body 5 of the innermost layer of the axle spring 1 of the embodiment in the vertical direction (the horizontal direction in Fig. 4) is 1 / 2 (=S / 2) of the longitudinal cross-sectional area S of the elastic body 5, and is represented by the area of ​​the portion hatched with a solid line in Fig. 4. In the axle spring 101 of the comparative example, the thickness W0 of the elastic body 105 of the innermost layer is constant, so that 1 / 2 (=S0 / 2) of the longitudinal cross-sectional area S0 of the elastic body 105 is represented by the area of ​​the portion hatched with a dashed line (rectangular portion) in Fig. 4. The longitudinal cross-sectional area S of the elastic body 5 is set equal to the longitudinal cross-sectional area S0 of the elastic body 105 (S=S0). Here, the vertical lengths of both elastic bodies 5 and 105 are equal, and both elastic bodies 5 and 105 are made of the same rubber material.

[0032] Table 1 shows the strain rates of the innermost elastic bodies 5 and 105 when a load causing the same displacement of 2 mm was applied to the axle spring 1 of the embodiment and the axle spring 101 of the comparative example.

[0033] [Table 1] As shown in Table 1, the thickness W0 of the innermost elastic body 105 of the axle spring 101 of the comparative example is 17.9 mm at both the upper and middle parts, while the thicknesses W1, W2 of the upper and middle parts of the innermost elastic body 5 of the axle spring 1 of the embodiment are 24.2 mm and 13.6 mm, respectively. The strain rates of the upper and middle parts of the innermost elastic body 105,5 of the two axle springs 101,1 were calculated, and the strain rates of the upper and middle parts of the innermost elastic body 105 of the axle spring 101 of the comparative example were both 11%.

[0034] In contrast, the strain rates of the upper and middle parts of the innermost elastic body 5 in the axle spring 1 of the embodiment were 8% and 15%, respectively, and it was confirmed that the strain rate (tensile stress and strain) of the upper part, where cracks and peeling of the elastic body 5 are likely to occur, can be kept low, thereby improving the durability of the axle spring 1.

[0035] Here, the ratio of the thickness W2 of the innermost elastic body 5 of the axle spring 1 of the embodiment to the thickness W0 of the innermost elastic body 105 of the axle spring 101 of the comparative example is as follows: W2 / W0=13.6 / 17.9=0.76 In the axle spring 1 according to this embodiment, the ratio of the thickness W2 of the middle part of the innermost elastic body 5 to the thickness of the innermost elastic body of another axle spring in which the vertical length and longitudinal cross-sectional area of ​​the innermost elastic body are the same and the thickness of the innermost elastic body is constant, i.e., the ratio W2 / W0, is preferably 70% or more, and more preferably in the range of 70% to 80%.

[0036] Next, the results of stress analysis using the finite element method (FEM) when loads are applied simultaneously from two directions, vertical and horizontal, to the axle spring 1 of the embodiment and the axle spring 101 of the comparative example are shown in Figures 5(a) and (b), respectively.

[0037] In FIG. 5, the darker the hatching, the greater the stress. As shown in FIG. 5(b), in the comparative axle spring 101, the highest stress is concentrated at the upper end portion near the region fixed to the main shaft of the innermost elastic body 105 (black hatched portion), and a high stress of 1.27 MPa is generated. In contrast, in the axle spring 1) of the embodiment shown in FIG. 5(a), a stress concentration region is observed at the upper end portion near the region fixed to the main shaft of the innermost elastic body 5, as in the comparative axle spring 101, but the maximum stress is suppressed to a low level of 0.72 MPa. As is clear from this analysis result, the axle spring 1 according to the present embodiment can increase durability by suppressing the stress and strain at the upper portion of the innermost elastic body 5, where cracks and peeling are likely to occur, to a low level.

[0038] Next, the spring characteristics in the vertical direction measured for the axle spring 1 of the embodiment and the axle spring 101 of the comparative example are shown in FIG. 6(a), and the spring characteristics in the horizontal direction are shown in FIG. 6(b).

[0039] The horizontal axis of Figures 6(a) and (b) represents the displacement x, and the vertical axis represents the load F. In Figure 6(a), the solid curves A and B respectively represent the characteristics of the axle spring 1 of the embodiment when a load is applied and when it is unloaded, and the dashed curves A' and B' represent the characteristics of the axle spring 101 of the comparative example when a load is applied and when it is unloaded. As shown in Figure 6(a), the relationship between the load F and the displacement x in the vertical direction of the axle spring 1 of the embodiment and the axle spring 101 of the comparative example almost overlap, and it can be seen that the spring characteristics in the vertical direction are almost the same.

[0040] In Fig. 6(b), solid curves C and D respectively show the characteristics of the axle spring 1 of the embodiment when a load is applied and when it is unloaded, and dashed curves C' and D' respectively show the characteristics of the axle spring 101 of the comparative example when a load is applied and when it is unloaded. As shown in Fig. 6(b), the relationship between the horizontal load F and the displacement x of the axle spring 1 of the embodiment and the axle spring 101 of the comparative example almost overlap, and it can be seen that the spring characteristics in the horizontal direction are almost the same.

[0041] The amount of displacement of the axial spring with respect to the load, i.e., the spring characteristics, is considered to be determined by the average thickness along the vertical direction of each layer of the elastic body and the vertical length (height). Since the vertical lengths of the elastic bodies 5 and 105 of the axial spring 1 of the embodiment and the axial spring 101 of the comparative example are equal, and the vertical cross-sectional areas S of the elastic bodies 5 and S0 of the elastic bodies 105 are equal, it is considered that the two have equivalent spring characteristics.

[0042] Therefore, the axle spring 1 of this embodiment, in which the thickness W of the innermost layer elastic body 5 is set so that the thickness W1 of the upper portion, the thickness W2 of the middle portion, and the thickness W3 of the lower portion satisfy the magnitude relationship shown in equation (1), has the same spring characteristics as other axle springs in which the vertical length and longitudinal cross-sectional area of ​​the innermost layer elastic body are the same and the thickness of the innermost layer elastic body is constant, and can keep the stress and strain generated in the upper part of the innermost layer elastic body 5 low compared to other axle springs in which the vertical length and longitudinal cross-sectional area of ​​the innermost layer elastic body are the same and the thickness of the innermost layer elastic body is constant.

[0043] As described above, the axle spring 1 of this embodiment has the same spring characteristics as other axle springs in which the vertical length and cross-sectional area of ​​the innermost layer elastic body are the same and the thickness of the innermost layer elastic body is constant, and also has higher durability than the other axle springs.

[0044] In other words, by setting the vertical cross-sectional area S of the innermost elastic body 5 to be the same as the vertical cross-sectional area S0 of the innermost elastic body 105 of the conventional axle spring 101, whose thickness is constant in the vertical direction (S=S0), it is possible to satisfy the spring characteristics (spring constants in the vertical and horizontal directions, etc.) required of the axle spring 1. Therefore, it is possible to obtain the effect of increasing the durability of the axle spring 1 while ensuring the spring characteristics required of the axle spring 1.

[0045] In addition, the longitudinal cross-sectional area S of the innermost elastic body 5 of the axle spring 1 in this embodiment and the longitudinal cross-sectional area S0 of the innermost elastic body 105 of the axle spring 101 in the comparative example being the same (S=S0) does not mean that they are completely identical, but also includes cases where there is a slight error (approximately ±5%) between the two longitudinal cross-sectional areas S and S0.

[0046] In axle spring 1 according to the present embodiment, the center of the sphere constituting part of spherical surface 2c formed on the outer peripheral surface of main shaft 2 does not need to be on axis P of main shaft 2. At least the portion of the outer peripheral surface of this main shaft 2 to which elastic body 5 of the innermost layer is fixed may be a convex curved surface, and may be, for example, an elliptical curved surface.

[0047] Furthermore, the axial spring 1 in this embodiment has an elastic portion 4 with a five-layer structure in which five elastic bodies 5-9 and four intermediate hard tubes 11-14 are alternately stacked in the radial direction, but the layer structure of the elastic portion 4 is arbitrary and may be a layer structure of less than five layers or six or more layers.

[0048] <Embodiment 2> Next, a second embodiment of the present invention will be described below with reference to FIGS.

[0049] Fig. 7 is a vertical cross-sectional view of an axle spring according to embodiment 2 of the present invention. In Fig. 7, the same elements as those shown in Fig. 2 are denoted by the same reference numerals, and repeated explanations of those elements will be omitted below.

[0050] In the axle spring 1A according to this embodiment, as shown in FIG. 7, a part of the outer circumferential surface of the main shaft 2 to which the elastic body 5 of the innermost layer is fixed is made into a plurality of tapered surfaces 2d, 2e, and 2f (three in the illustrated example) with different inclination angles, and the thickness W of the elastic body 5 of the innermost layer is gradually decreased from the upper part to the middle part and gradually increased from the middle part to the lower part. The thickness W of the elastic body 5 shows a maximum value W1 at the upper part, gradually decreases from the upper part to the middle part, and shows a minimum value W2 at the middle part. The thickness W of this elastic body 5 gradually increases from the minimum value W2 at the middle part to W3 at the lower part. The thickness W1 of the upper part and the thickness W3 of the lower part are larger than the thickness W2 of the middle part, and the thickness W1 of the upper part is larger than the thickness W3 of the lower part. As with the axle spring 1 according to the first embodiment, the magnitude relationship of formula (1) is satisfied.

[0051] Of the three tapered surfaces 2d, 2e, and 2f, the upper tapered surface 2d and the lower tapered surface 2f have inclination angles in opposite directions, and the tapered surface 2d is inclined inward so as to decrease in diameter upward, while the tapered surface 2f is inclined outward so as to increase in diameter upward. For example, the inclination angle α of the upper tapered surface 2d with respect to the axis P of the main shaft 2 is set to be larger than the inclination angle β of the lower tapered surface 2f with respect to the axis P of the main shaft 2 (α>β). The tapered surface 2e in the middle portion is inclined inward (diametrically inward) at the same angle as the intermediate rigid cylinder 11 so as to decrease in diameter upward, and the distance between this tapered surface 2e and the intermediate rigid cylinder 11 (thickness W2 of the middle portion of the elastic body 5) is kept constant.

[0052] 8 shows the change in thickness W of the innermost elastic body 5 in the up-down direction in comparison with the comparative example. The thickness W of the elastic body 5 of the axle spring 1A according to the embodiment shows a maximum value W1 at the upper part, gradually decreases from the upper part to the middle part, shows a minimum value W2 at the middle part, and gradually increases from the minimum value W2 at the middle part to W3 at the lower part. In this case, the thickness W1 of the upper part and the thickness W3 of the lower part are greater than the thickness W2 of the middle part, and the thickness W1 of the upper part is greater than the thickness W3 of the lower part.

[0053] In addition, the thickness W0 of the innermost elastic body 105 of the comparative example axle spring 101 is constant as shown by the dashed line in Figure 8, and this thickness W0 is set to be smaller than the thickness W1 of the upper part and the thickness W3 of the lower part of the innermost elastic body 5 of the axle spring 1A of this embodiment, and larger than the thickness W2 of the middle part.

[0054] In this embodiment as well, the vertical cross-sectional area of ​​the innermost elastic body 5 can be set equal to the vertical cross-sectional area of ​​the innermost elastic body 105 of the axle spring 101 of the comparative example.

[0055] In Fig. 8, the value ΣW obtained by integrating the thickness W of the innermost elastic body 5 in the up-down direction (left-right direction in Fig. 8) is 1 / 2 (=S / 2) of the vertical cross-sectional area S of the elastic body 5, and is represented by the area of ​​the portion hatched with solid lines in Fig. 8. In contrast, in the axle spring 101 of the comparative example, the thickness W0 of the innermost elastic body 105 is constant, so 1 / 2 (=S0 / 2) of the vertical cross-sectional area S0 of the elastic body 105 is represented by the area of ​​the portion hatched with dashed lines (rectangular portion) in Fig. 8.

[0056] In this embodiment, as in the first embodiment, the longitudinal cross-sectional area S of the innermost elastic body 5 of the axle spring 1 is set equal to the longitudinal cross-sectional area S0 of the innermost elastic body 105 of the axle spring 101 of the comparative example (S=S0). In this case, the vertical lengths of both elastic bodies 5, 105 are set equal. In addition, both elastic bodies 5, 105 are formed of the same rubber material.

[0057] Therefore, even if the thickness W of the innermost elastic body 5 is changed in the height direction as shown in Figure 8, as in the case of the axle spring 1A of this embodiment, by setting the longitudinal cross-sectional area S of the elastic body 5 to be the same as the longitudinal cross-sectional area S0 of the innermost elastic body 105 of the conventional axle spring 101, whose thickness is constant in the vertical direction (S = S0), it is possible to satisfy the spring characteristics required of the axle spring 1A of this embodiment (such as spring constants in the vertical and horizontal directions), while keeping the stress and strain generated in the upper part of the innermost elastic body 5 of the axle spring 1A low, thereby increasing the durability of the axle spring 1A.

[0058] In the axle spring 1A according to this embodiment, three tapered surfaces 2d, 2e, and 2f having different inclination angles are formed on the outer peripheral surface of the main shaft 2 to which at least the innermost layer of elastic body 5 is fixed, but the number of tapered surfaces is arbitrary.

[0059] Furthermore, the present invention is not limited to the application of the above-described embodiment, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0060] 1,1A Axle spring 2 main shaft 2c Spherical surface (convex curved surface) 2d~2f Tapered surface 3. Outer cylinder 4 Elastic part 5~9 Elastic body 11~14 Intermediate hard cylinder W0 Comparative Example: Thickness of the middle part of the innermost elastic layer of the axle spring W1: Thickness of the top of the innermost elastic layer W2: Thickness of the middle part of the innermost elastic layer W3: Thickness of the bottom of the innermost elastic layer S: longitudinal cross-sectional area of ​​the innermost elastic layer S0 Comparative Example Axle Spring Elastic Body Cross-Sectional Area α,β Inclination angle of tapered surface

Claims

1. A main shaft arranged in the vertical direction; a tapered outer cylinder arranged radially outward of the spindle and concentrically with respect to an axis of the spindle; an elastic portion interposed between the main shaft and the outer cylinder, the elastic portion has a laminated structure in which a tapered cylindrical elastic body and an intermediate hard cylinder, which are concentrically arranged, are alternately laminated in the radial direction, and the elastic body and the intermediate hard cylinder are tapered cylindrically shaped with a diameter decreasing upward and upper and lower ends being open, The thickness W of the upper part of the innermost layer of the elastic body of the tapered cylindrical shape with the upper and lower ends open, which is fixed to the outer circumferential surface of the main shaft １ and the thickness of the middle part W ２ and the thickness of the lower part W ３ Between W １ >W ３ >W ２ The magnitude relationship between An axle spring, in which at least a portion of the outer circumferential surface of the main shaft, to which the elastic body of the innermost layer is fixed, is a part of a spherical surface.

2. A main shaft arranged in the vertical direction, a tapered outer cylinder arranged radially outward of the spindle and concentrically with respect to an axis of the spindle; an elastic portion interposed between the main shaft and the outer cylinder, the elastic portion has a laminated structure in which a tapered cylindrical elastic body and an intermediate hard cylinder, which are concentrically arranged, are alternately laminated in the radial direction, and the elastic body and the intermediate hard cylinder are tapered cylindrically shaped with a diameter decreasing upward and upper and lower ends being open, The elastic body of the innermost layer, which is a tapered cylinder with open upper and lower ends and is fixed to the outer circumferential surface of the main shaft, has a thickness W1 at the top, a thickness W2 at the middle, and a thickness W3 at the bottom, W1>W3>W2 The magnitude relationship between An axle spring in which at least a portion of the outer circumferential surface of the main shaft to which the elastic body of the innermost layer is fixed is a plurality of tapered surfaces with different inclination angles, the upper tapered surface and the lower tapered surface have inclination angles in opposite directions, the upper tapered surface inclined inwardly so as to reduce in diameter toward the top, and the lower tapered surface inclined outwardly so as to increase in diameter toward the top.

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