Sealing device for hydraulic equipment

Abstract

This absorber seal (1) comprises: a support ring (10) which is an annular member, i.e., a member having a ring shape around an axis (x); and an elastic body part (20) which is an elastic body having a ring shape attached to the inner circumferential side of the support ring (10). The elastic body part (20) has a main lip (30) which is a portion having a ring shape in contact with a piston rod of a shock absorber. The main lip (30) has a thickness T corresponding to desired durability performance.

Description

Sealing device for hydraulic equipment

[0001] The present invention relates to a sealing device for hydraulic equipment.

[0002] Conventionally, in hydraulic equipment using hydraulic pressure, a sealing device has been used to seal oil. For example, in a shock absorber used in a vehicle such as an automobile, the sealing device seals the gap between the piston rod and the cylinder in order to seal the oil in the cylinder (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2001-173797

[0004] In a shock absorber, the main lip of the sealing device receives force from the sliding piston rod and also receives force from the compressed oil. Therefore, in addition to the durability against the force received from the moving piston rod, the durability against the force received from the compressed oil is also required for the main lip. The design of the main lip is made so as to satisfy this required durability performance.

[0005] Conventionally, the design of the sealing device has been made so as to have the desired durability performance based on the evaluation by an actual shock absorber. The number of evaluations by an actual machine that can be carried out during the design of the sealing device is limited. Therefore, the conventional sealing device is designed based on limited evaluation results, and the durability performance of the conventional sealing device may deviate from the desired durability performance. For this reason, a configuration has been demanded for the conventional sealing device to have the desired durability performance.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a sealing device for hydraulic equipment that can bring the durability performance it has closer to the desired durability performance.

[0007] To achieve the above objective, the sealing device for hydraulic equipment according to the present invention is a sealing device for hydraulic equipment used in hydraulic equipment having a cylindrical body and a shaft, comprising an annular member which is an annular member around the axis and an elastic body portion which is an annular elastic body attached to the inner circumference side of the annular member, wherein the elastic body portion has a main lip which is an annular portion that contacts the shaft, and the main lip has a thickness corresponding to the desired durability performance.

[0008] In a sealing device for hydraulic equipment according to one aspect of the present invention, the durability performance is a durability performance relating to the number of reciprocating motions of the shaft, and the thickness of the main lip is set to a value based on the number of reciprocating motions of the shaft.

[0009] In a sealing device for hydraulic equipment according to one aspect of the present invention, the thickness of the main lip is set to a value such that the main lip is not damaged even if the shaft reciprocates a certain number of times.

[0010] In a sealing device for hydraulic equipment according to one aspect of the present invention, the number of reciprocating motions of the shaft is 30,000 or more, and the thickness of the main lip is 2 mm or more.

[0011] In a sealing device for hydraulic equipment according to one aspect of the present invention, the elastic body portion has a base portion which is attached to the inner circumference end of the ring member, the main lip extends from the base portion along the axis to one side in the axial direction and has a lip waist portion which is connected to the base portion and a lip tip portion which is in contact with the axis, and the thickness of the main lip is the thickness at the lip waist portion.

[0012] The sealing device for hydraulic equipment according to the present invention can bring its durability closer to the desired durability performance.

[0013] This is a cross-sectional view showing a plane containing the axis of an absorber seal as a sealing device for hydraulic equipment according to an embodiment of the present invention. This is a partial cross-sectional view showing the vicinity of the main lip in the absorber seal shown in Figure 1. This is a partial cross-sectional view showing the vicinity of the absorber seal in a cross-section along the axis of the shock absorber, to show the state of use when the absorber seal is attached to the shock absorber. This is a schematic diagram showing an example of a durability evaluation test machine that can create a simulated usage state. This is a graph showing the relationship between the stroke amount of the simulated piston rod and the oil pressure in the durability evaluation test machine. This is a diagram showing the evaluation results of a durability evaluation test.

[0014] Embodiments of the present invention will be described below with reference to the drawings. In the drawings, not all of the components are assigned reference numerals, and some of the reference numerals for components may be omitted.

[0015] The sealing device for hydraulic equipment according to the present invention is a sealing device used in hydraulic equipment having a cylindrical body and a shaft. The cylindrical body is, for example, a housing, and the shaft is supported so that a part of it is inside the cylindrical body and can move relative to the housing. The sealing device for hydraulic equipment is used to seal the annular gap between the cylindrical body and the shaft and to seal the oil inside the cylindrical body. The hydraulic equipment to which the sealing device for hydraulic equipment according to the present invention is applied is, for example, a shock absorber used in the suspension of a vehicle such as an automobile. Hereinafter, the sealing device for hydraulic equipment according to the present invention will be described with a shock absorber as the target application. However, the hydraulic equipment to which the sealing device for hydraulic equipment according to the present invention is applied is not limited to shock absorbers, and various types of hydraulic equipment are included as targets for the sealing device for hydraulic equipment according to the present invention.

[0016] Figure 1 is a cross-sectional view showing a plane containing the axis x of an absorber seal 1 as a sealing device for hydraulic equipment according to an embodiment of the present invention. As shown in Figure 1, the absorber seal 1 comprises a support ring 10, which is an annular member around the axis x, and an elastic body portion 20, which is an annular elastic body attached to the inner circumference of the support ring 10. The elastic body portion 20 has a main lip 30, which is an annular portion that contacts the piston rod of the shock absorber. The main lip 30 has a thickness T corresponding to the desired durability performance. The configuration of the absorber seal 1 will be described in detail below.

[0017] Figure 2 is a partial cross-sectional view showing the vicinity of the main lip 1 in the absorber seal 1 shown in Figure 1. As shown in Figures 1 and 2, the support ring 10 is, for example, an annular plate-shaped member about an axis x, and has an outer surface 11 and an inner surface 12 which are a pair of annular surfaces facing each other. The outer surface 11 is the surface facing one side (outside) in the direction of the axis x, and the inner surface 12 is the surface facing the other side (inside) in the direction of the axis x. The outer surface 11 extends, for example, parallel or substantially parallel to a plane perpendicular to the axis x, and similarly, the inner surface 12 extends, for example, parallel or substantially parallel to a plane perpendicular to the axis x. The support ring 10 also has an inner circumferential end surface 13 and an outer circumferential end surface 14 which are a pair of annular surfaces facing each other in the radial direction. The radial direction is the direction perpendicular to the axis x. The inner circumferential end surface 13 is an annular surface facing the inner circumference and extends between the outer surface 11 and the inner surface 12 at the end on the inner circumference side. The inner circumferential end surface 13 is, for example, a cylindrical surface or a substantially cylindrical surface with axis x as its central axis or substantially central axis. The outer circumferential end surface 14 is an annular surface facing the outer circumference and extends between the inner surface 11 and the outer surface 12 at the end on the outer circumference side. The outer circumferential end surface 14 is, for example, a cylindrical surface or a substantially cylindrical surface with axis x as its central axis or substantially central axis.

[0018] The support ring 10 is formed from, for example, a metallic material. Examples of metallic materials for the support ring 10 include hot-rolled steel such as SAPH440 and cold-rolled steel such as SPCC. However, the material of the support ring 10 is not limited to metallic materials.

[0019] As shown in Figures 1 and 2, the elastic body portion 20 has a base portion 21 in addition to the main lip 30, which is, for example, attached to the inner circumferential end portion 10a, which is the inner end of the support ring 10. The base portion 21 is an annular portion around axis x and is attached to the outer surface 11, inner surface 12, and inner circumferential end surface 13 at the inner circumferential end portion 10a of the support ring 10. The main lip 30 extends inward from the base portion 21 along axis x and has a lip waist portion 31, which is the portion connected to the base portion 21, and a lip tip portion 32. The lip tip portion 32 is the portion that contacts the piston rod of the shock absorber when the absorber seal 1 incorporated into the shock absorber, which will be described later, is in use. The lip waist portion 31 and the lip tip portion 32 extend annularly around axis x.

[0020] As shown in Figures 1 and 2, the lip tip portion 32 is connected to the lip waist portion 31 from the inside and has an annular lip tip surface 33 on its inner circumference. The lip tip surface 33 forms a wedge-shaped or substantially wedge-shaped cross-section that is convex toward the axis x on the lip tip portion 32. The lip tip surface 33 has an inner diameter such that its tip 33a contacts the inserted piston rod with a predetermined amount of interference when in use, as will be described later. Furthermore, an annular groove 34 is formed on the outer circumference of the lip tip portion 32 at a position opposite to the lip tip surface 33, and a garter spring 24 is fitted into this groove 34. The garter spring 24 presses the lip tip portion 32 radially inward, providing a predetermined amount of tension to the lip tip portion 32 against the piston rod when in use. Furthermore, an annular support projection 31c is formed at the end of the lip waist portion 31 that is close to the lip tip surface 33, projecting inward around an axis x.

[0021] Furthermore, the elastic body portion 20 has, for example, an annular dust lip 22 around the axis x, as shown in Figure 1. The dust lip 22 extends from the base body 21 to the side opposite the main lip 30, that is, outward, and in the usage state described later, its tip portion 22a comes into contact with the piston rod.

[0022] Furthermore, the elastic body portion 20 has, for example, an annular gasket portion 23 around the axis x, as shown in Figure 1. The gasket portion 23 is, for example, the portion attached to the outer peripheral end 10b, which is the outer peripheral end of the support ring 10. Specifically, for example, as shown in Figure 1, the gasket portion 23 is attached to the inner surface 12 of the support ring 10 at the outer peripheral end 10b of the support ring 10. The gasket portion 23 is configured to contact the cylinder and rod guide of the shock absorber in the operating state described later.

[0023] As described above, the elastic body portion 20 has a base portion 21, a main lip 30, a dust lip 22, and a gasket portion 23, and is formed integrally from the same elastic material to form the elastic body. In other words, the base portion 21, the main lip 30, the dust lip 22, and the gasket portion 23 are connected as a single unit. The elastic material of the elastic body portion 20 can be, for example, various types of rubber. Examples of various types of rubber are synthetic rubbers such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), and fluororubber (FKM). The elastic body portion 20 is fixed to the support ring 10 by adhesive, for example, vulcanization bonding.

[0024] Figure 3 is a partial cross-sectional view showing the vicinity of the absorber seal 1 along the axis x of the shock absorber 100, illustrating the state in which the absorber seal 1 described above is attached to the shock absorber 100. In Figure 3, only one side of the axis x is shown.

[0025] As shown in Figure 3, the absorber seal 1 is fitted and fixed to the cylinder 101, which is the cylindrical body of the shock absorber 100, in the operating state, and seals the annular gap between the cylinder 101 and the piston rod 102, which is the shaft. In the shock absorber 100, the piston rod 102 is inserted through an opening 103 formed at one end of the cylinder 101 and is supported by a rod guide 104 so as to be able to reciprocate along the axis x. The rod guide 104 is an annular member, and a bearing (not shown) is disposed at its inner circumference end, supporting the piston rod 102 so as to be able to slide in the direction of the axis x. The rod guide 104 is also fitted and fixed to the inner circumference surface of the cylinder 101. A flange 101a defining the opening 103 is formed at one end of the cylinder 101. The absorber seal 1 is held between the flange 101a of the cylinder 101 and the rod guide 104, with the inner surface 12 of the support ring 10 being pressed outward via the elastic body portion 20 by the rod guide 104, and the outer surface 11 of the support ring 10 being pressed against the flange 101a. Furthermore, the outer peripheral end surface 14 of the support ring 10 is in contact with the inner peripheral surface of the cylinder 101 via the gasket portion 23 of the elastic body portion 20, thereby positioning the absorber seal 1 radially within the cylinder 101. The configuration of the shock absorber 100 may be a conventionally known configuration, and further detailed explanation is omitted.

[0026] In operation, the lip tip 32 of the main lip 30 of the absorber seal 1 is in contact with the outer circumferential surface 102a of the piston rod 102 with a predetermined overlap. This prevents leakage of the oil 105, which is the working fluid filled in the cylinder 101 of the shock absorber 100, to the outside. Furthermore, outside the main lip 30, the support projection 31c is in contact with the outer circumferential surface 102a of the piston rod 102. This suppresses changes in the posture of the main lip 30 relative to the piston rod 102 when the piston rod 102 is eccentric, and maintains the contact state (contact pressure) of the lip tip 32 with the piston rod 102.

[0027] Furthermore, in use, the gasket portion 23 of the elastic portion 20 is in contact with the inner circumferential surface of the cylinder 101 and the outer circumferential end of the rod guide 104, as shown in Figure 3, thereby preventing the oil 105 filled in the cylinder 101 from leaking to the outside between the cylinder 101 and the absorber seal 1. Also, in use, the dust lip 22 is in contact with the outer circumferential surface 102a of the piston rod 102, as shown in Figure 3. This prevents foreign matter from entering the main lip 30 side from the outside.

[0028] As described above, the main lip 30 has a thickness T corresponding to the desired durability performance. Durability performance is, for example, durability performance related to the number of reciprocating motions of the piston rod. The thickness T of the main lip 30 is set to a value based on, for example, the number of reciprocating motions of the piston rod. More specifically, the thickness T of the main lip 30 is set to a value such that the main lip is not damaged even if the piston rod reciprocates a predetermined number of times.

[0029] As shown in Figure 2, the thickness T of the main lip 30 is, for example, the thickness T of the lip waist portion 31. Specifically, as shown in Figure 2, the thickness T of the main lip 30 is the width between the outer circumferential surface 31a and the inner circumferential surface 31b of the lip waist portion 31. The outer circumferential surface 31a is an annular surface facing the outer circumferential side of the lip waist portion 31, and the inner circumferential surface 31b is an annular surface facing the inner circumferential side of the lip waist portion 31. The outer circumferential surface 31a is the surface that extends between the portion (part 21a) of the base 21 attached to the inner surface 12 of the support ring 10 and the outer end of the groove 34. The inner circumferential surface 31b is the surface that extends between the portion (part 21b) of the base 21 attached to the inner end surface 13 of the support ring 10 and the outer end of the lip tip surface 33. The support projection 31c is formed at the inner end of the inner circumferential surface 31b.

[0030] The thickness T of the main lip 30 is specifically, for example, the distance between the outer circumferential surface 31a and the inner circumferential surface 31b at the center or approximately center (position P1) in the x-direction of the axis of the outer circumferential surface 31a. More specifically, the thickness T is the distance between the outer circumferential surface 31a and the inner circumferential surface 31b in a direction perpendicular to the inner circumferential surface 31b at position P1. In other words, the thickness T is the distance of the line segment between the outer circumferential surface 31a and the inner circumferential surface 31b on a straight line passing through position P1 and perpendicular to the inner circumferential surface 31b. Note that the thickness T may be a value determined by other methods. For example, the thickness T may be the average value of the distance between the outer circumferential surface 31a and the inner circumferential surface 31b, or the distance between the outer circumferential surface 31a and the inner circumferential surface 31b at the edge of the outer circumferential surface 31a or the edge of the inner circumferential surface 31b, etc.

[0031] The thickness T of the main lip 30 is specifically set based on the evaluation results of the durability cycles of the absorber seal 1 in a usage state or a simulated usage state that approximates the usage state. The durability cycle is the number of reciprocating motions (strokes) of the piston rod until the main lip 30 of the absorber seal 1 fails. The evaluation results of the durability cycle are, for example, the durability cycle obtained by a durability evaluation test. A durability evaluation test is, for example, a test in which the piston rod is reciprocated under predetermined test conditions to measure the durability cycles of the main lip 30. The predetermined test conditions for the durability evaluation test are, for example, the stroke amount of the piston rod, the period (frequency) of the reciprocating motion of the piston rod, the oil pressure, the oil temperature, etc. The test conditions for the oil pressure are, for example, the range between the oil pressure when the stroke amount is at its maximum in the extension direction and the oil pressure when the stroke amount is at its maximum in the compression direction.

[0032] Durability evaluation tests are conducted using a durability evaluation testing machine that can create simulated usage conditions, such as the one shown in Figure 4. Figure 4 is a schematic diagram showing an example of a durability evaluation testing machine that can create simulated usage conditions.

[0033] As an example of a durability evaluation test, the durability evaluation test machine 50, as shown in Figure 4, has a dummy cylinder 51 which is a cylindrical member and a dummy piston rod 52 which is a cylindrical or substantially cylindrical member. The dummy cylinder 51 is a member for simulating the internal space of a shock absorber cylinder, and the dummy piston rod 52 is a member for simulating the piston rod of a shock absorber. The dummy piston rod 52 passes through the internal space 51a of the dummy cylinder 51 and protrudes from each opening. An absorber seal 1 is fitted into one opening of the dummy cylinder 51, and the annular gap between the dummy cylinder 51 and the dummy piston rod 52 at one opening of the dummy cylinder 51 is sealed by the absorber seal 1. On the other hand, an oil seal 55 is fitted into the other opening of the pseudo-cylinder 51, and the annular gap between the pseudo-cylinder 51 and the pseudo-piston rod 52 at the other opening of the pseudo-cylinder 51 is sealed by the oil seal 55. The oil seal 55 is a known oil seal.

[0034] The durability evaluation test machine 50 has multiple types of simulated piston rods 52 and multiple types of oil seals 55 corresponding to each of the multiple types of simulated piston rods 52. Each of the multiple types of simulated piston rods 52 has a different diameter to correspond to various sizes of absorber seals 1.

[0035] Furthermore, as shown in Figure 4, a drive device 53 is connected to the end of the pseudo-piston rod 52 to cause the pseudo-piston rod 52 to reciprocate in the axial x direction. The durability evaluation test machine 50 also has a hydraulic regulator 54 that can fill the internal space 51a of the pseudo-cylinder 51 with oil 56 and adjust the pressure of the oil 56 in the internal space 51a. The hydraulic regulator 54 is in communication with the internal space 51a, and the hydraulic regulator 54 can supply oil 56 to the internal space 51a and adjust the pressure of the oil 56 in the internal space 51a to any desired value.

[0036] In the durability evaluation test, for example, the drive unit 53 causes the simulated piston rod 52 to reciprocate with a predetermined stroke amount and a predetermined period, and the hydraulic pressure of the oil 56 in the internal space 51a of the simulated cylinder 51 is changed in conjunction with the movement of the simulated piston rod 52 by the hydraulic regulator 54. For example, the hydraulic regulator 54 changes the pressure of the oil 56 in the internal space 51a of the simulated cylinder 51 with the same period as the reciprocating motion of the simulated piston rod 52. Specifically, for example, the pressure of the oil 56 is maximized when the simulated piston rod 52 moves furthest toward the absorber seal 1, and the hydraulic pressure of the oil 56 is reduced to zero when the simulated piston rod 52 moves furthest toward the oil seal 55.

[0037] The inventors manufactured two absorber seals: one (Test Example 1) sized to fit a simulated piston rod 52 (piston rod) with a diameter of 22 mm, and another (Test Example 2) sized to fit a simulated piston rod 52 (piston rod) with a diameter of 12.5 mm. Durability evaluation tests were then conducted on each using a durability evaluation tester 50. The diameter of the tip 33a of the lip tip surface 33 of the main lip 30 of the absorber seal 1 in Test Example 1 (hereinafter also referred to as the lip diameter) was set to a value such that it would contact the simulated piston rod 52 with a predetermined tightening allowance in the durability evaluation tester 50, and specifically, it was in the range of 19 mm to 21 mm. Similarly, the diameter of the tip 33a of the lip tip surface 33 of the absorber seal 1 in Test Example 2 was set to a value such that it would contact the simulated piston rod 52 with a predetermined tightening allowance in the durability evaluation tester 50, and specifically, it was in the range of 9.5 mm to 12 mm. The specified tightening tolerance is, for example, a value set similarly to that of a known absorber seal.

[0038] Furthermore, for each of the test examples 1 and 2, absorber seals 1 with different thicknesses T of the main lip 30 were manufactured. Specifically, for the absorber seal 1 of test example 1, absorber seals 1 with a thickness T of T = 1.35 mm (test example 11), absorber seals 1 with a thickness T of T = 1.75 mm (test example 12), absorber seals 1 with a thickness T of T = 1.85 mm (test example 13), absorber seals 1 with a thickness T of T = 2.25 mm (test example 14), and absorber seals 1 with a thickness T of T = 2.3 mm (test example 15) were manufactured. Note that test examples 11 to 15 differ only in thickness T and dimensions related to thickness T, while the dimensions (shape) of other parts are the same. Furthermore, for the absorber seal 1 of Test Example 2, absorber seals 1 with a thickness T of T = 1.3 mm (Test Example 21), absorber seal 1 with a thickness T of T = 1.6 mm (Test Example 22), absorber seal 1 with a thickness T of T = 1.78 mm (Test Example 23), absorber seal 1 with a thickness T of T = 1.8 mm (Test Example 24), and absorber seal 1 with a thickness T of T = 2.2 mm (Test Example 25) were manufactured. Note that Test Examples 21 to 25 differ only in their thickness T and related dimensions; the dimensions (shape) of other parts are the same.

[0039] The durability evaluation test was conducted under the following test conditions. Specifically, the stroke amount of the simulated piston rod 52 was set to ±40 mm, and the period of the simulated piston rod 52 was set to 1 Hz. The maximum pressure of the oil 56 in the internal space 51a of the simulated cylinder 51 was set to 4.9 MPa. The temperature of the oil 56 was set to 100°C. Figure 5 shows a graph illustrating the relationship between the stroke amount of the simulated piston rod 52 and the pressure of the oil 56 in the durability evaluation test machine 50. As shown in Figure 5, in this durability evaluation test, when the simulated piston rod 52 moves from zero to 40 mm, the hydraulic regulator 54 increases the pressure of the oil 56 from zero to 4.9 MPa at a constant or approximately constant rate. When the simulated piston rod 52 moves from 40 mm to below zero to -40 mm, the hydraulic regulator 54 decreases the pressure of the oil 56 from 4.9 MPa to zero at a constant or approximately constant rate. Furthermore, when the pseudo-piston rod 52 moves from a stroke of -40 mm to zero, the hydraulic regulator 54 increases the pressure of the oil 56 from zero to 2.45 MPa at a constant or approximately constant rate.

[0040] Table 1 and Figure 6 show the evaluation results of the durability evaluation tests conducted for each test example 11-15 and 21-25. As mentioned above, the evaluation results of the durability evaluation tests are the measurement results of the number of reciprocating motions (durability cycles) of the simulated piston rod 52 until damage occurs to the main lip 30. Damage to the main lip 30 was determined to have occurred when the pressure of the oil 56 in the internal space 51a of the simulated cylinder 51 no longer reached the maximum value of 4.9 MPa. Specifically, damage to the main lip 30 includes cracks in the lip waist portion 31 and fracture of the lip waist portion 31.

[0041] As shown in Table 1, in Test Example 11, damage occurred to the main lip 30 after 500 reciprocating motions of the simulated piston rod 52; in Test Example 12, damage occurred to the main lip 30 after 15,330 reciprocating motions of the simulated piston rod 52; in Test Example 13, damage occurred to the main lip 30 after 23,100 reciprocating motions of the simulated piston rod 52; in Test Example 14, damage occurred to the main lip 30 after 37,506 reciprocating motions of the simulated piston rod 52; and in Test Example 15, damage occurred to the main lip 30 after 54,577 reciprocating motions of the simulated piston rod 52. Furthermore, as shown in Table 1, in Test Example 21, damage occurred to the main lip 30 after 5,433 reciprocating motions of the simulated piston rod 52; in Test Example 22, damage occurred to the main lip 30 after 43,311 reciprocating motions of the simulated piston rod 52; in Test Example 23, damage occurred to the main lip 30 after 61,300 reciprocating motions of the simulated piston rod 52; in Test Example 24, damage occurred to the main lip 30 after 98,200 reciprocating motions of the simulated piston rod 52; and in Test Example 25, damage occurred to the main lip 30 after 84,489 reciprocating motions of the simulated piston rod 52.

[0042]

[0043] Figure 6 shows a graph illustrating the evaluation results of the durability evaluation test. From the evaluation results of the durability evaluation test, it can be confirmed that there is a correlation between the thickness T of the main lip 30 and the number of cycles the main lip 30 can withstand in each of the two test examples 1 and 2, where the diameters of the pseudo-piston rods 52 are different. In other words, as shown by the dashed lines in Figure 6, it can be recognized that the relationship between the thickness T of the main lip 30 and the number of cycles the main lip 30 can withstand in each of the two test examples 1 and 2, where the diameters of the pseudo-piston rods 52 are the same, can be approximated by linear functions F1 and F2.

[0044] As shown in Fig. 6, from the evaluation results of the durability evaluation test, a plurality of absorber seals 1 (hereinafter also referred to as an absorber seal group) are manufactured, where the diameters of the applied piston rods are the same and the thicknesses T of the main lips 30 are different. By conducting a durability evaluation test on each absorber seal group with different diameters of the applied piston rods, it can be understood from the evaluation results that for each absorber seal group, a linear function approximating the relationship between the thickness T of the main lip 30 and the number of durable cycles of the main lip 30 can be obtained. Specifically, for example, a plurality of absorber seals 1 (absorber seal group) are manufactured, where the diameters of the applied piston rods are the same and the thickness T of the main lip 30 and the dimensions related to the thickness T are different. By conducting a durability evaluation test on this absorber seal group, a linear function approximating the relationship between the thickness T of the main lip 30 and the number of durable cycles of the main lip 30 can be obtained from the evaluation results for this absorber seal group. By conducting a durability evaluation test on each of a plurality of absorber seal groups with different diameters of the applied piston rods, a linear function approximating the relationship between the thickness T of the main lip 30 and the number of durable cycles of the main lip 30 can be obtained for the plurality of absorber seal groups. Therefore, for the absorber seal group for which the linear function regarding the number of durable cycles has been obtained, based on this linear function regarding the number of durable cycles, the thickness T of the main lip 30 that satisfies the required durability performance can be determined. For example, in the absorber seal group of Test Example 1, when the required durability performance (number of durable cycles) is 30,000 times, based on the linear function F1 obtained from the durability evaluation test, the thickness T of the main lip 30 can be set to 2 mm or more.

[0045] The thickness T of the main lip 30 of the absorber seal 1 is set based on a linear function related to the number of endurance cycles obtained from the endurance evaluation test for the absorber seal group as described above. Therefore, the absorber seal 1 has a main lip 30 having a thickness T that provides a desired endurance performance based on the linear function related to the number of endurance cycles described above. For example, the diameter of the piston rod to which the absorber seal 1 is applied is 22 mm, and the thickness T of the absorber seal 1 is set to a thickness of 2 mm so as to have durability against 30,000 reciprocating motions of the piston rod.

[0046] Thus, the thickness T of the main lip 30 of the absorber seal 1 is specified based on a linear function that approximates the relationship between the thickness T of the main lip 30 and the number of endurance cycles, which is set based on the evaluation result of the endurance evaluation test for the absorber seal group to which it belongs. Therefore, the endurance performance of the thickness T of the main lip 30 is the same as or close to the desired endurance performance.

[0047] As described above, according to the absorber seal 1 according to the embodiment of the present invention, the durability it has can be brought close to the desired endurance performance.

[0048] Although the present invention has been described through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements can also be included in the technical scope of the present invention.

[0049] The embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit its interpretation. Furthermore, the embodiments described above do not limit the scope of application of the present invention, and the present invention may encompass anything as its target application. The components of the above embodiments, as well as their arrangement, materials, conditions, shapes, and sizes, are not limited to those exemplified and can be modified as appropriate. For example, the present invention includes differences that arise in the implementation of manufacturing tolerances, etc. Furthermore, components shown in different embodiments can be partially substituted or combined to the extent that they do not contradict each other in a technical sense. In addition, each configuration can be selectively combined as appropriate to achieve at least some of the problems and effects described above.

[0050] 1 Absorber seal (sealing device for hydraulic equipment), 10 Support ring (ring member), 10a Inner circumference end, 10b Outer circumference end, 11 Outer surface, 12 Inner surface, 13 Inner circumference end surface, 14 Outer circumference end surface, 20 Elastic body part, 21 Base part, 21a, 21b Parts, 22 Dust lip, 22a Tip part, 23 Gasket part, 24 Garter spring, 30 Main lip, 31 Lip waist part, 31a Inner circumference surface, 31b Outer circumference surface, 31c Support projection, 32 Lip tip part, 33 Lip tip surface, 33a Tip, 34 Groove, 50 Durability evaluation test machine, 51 Simulated cylinder, 51a Internal space, 52 Simulated piston rod, 53 Drive device, 54 Hydraulic regulator, 55 Oil seal, 56 Oil, 100 Shock absorber, 101 Cylinder, 101a flange, 102 piston rod, 102a outer surface, 103 opening, 104 rod guide, 105 oil, F1, F2 linear function, T thickness, x axis

Claims

1. A sealing device for hydraulic equipment used in hydraulic equipment having a cylindrical body and a shaft, comprising: an annular member which is an annular member around the axis; and an elastic body portion which is an annular elastic body attached to the inner circumference of the annular member, wherein the elastic body portion has a main lip which is an annular portion that contacts the shaft, and the main lip has a thickness corresponding to a desired durability performance.

2. The sealing device for hydraulic equipment according to claim 1, wherein the durability performance is a durability performance relating to the number of reciprocating motions of the shaft, and the thickness of the main lip is set to a value based on the number of reciprocating motions of the shaft.

3. The sealing device for hydraulic equipment according to claim 2, wherein the thickness of the main lip is set to a value such that the main lip is not damaged even when the shaft reciprocates a number of times.

4. The sealing device for hydraulic equipment according to claim 3, wherein the number of reciprocating motions of the shaft is 30,000 or more, and the thickness of the main lip is 2 mm or more.

5. The elastic body portion has a base portion which is attached to the inner end of the ring member, the main lip extends from the base portion along the axis to one side in the axial direction and has a lip waist portion which is connected to the base portion and a lip tip portion which is in contact with the axis, and the thickness of the main lip is the thickness of the lip waist portion, the sealing device for hydraulic equipment according to claim 1.

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