Linear motion damper

Abstract

Provided is a linear motion damper that enables performance improvement with respect to speed dependency. The linear motion damper is provided with a cylinder 3 for forming a pressure chamber 11, a piston 5 that is mounted inside the cylinder 3 so as to define the pressure chamber 11, and can move forward and backward between the defined pressure chamber 11 and a non-pressure chamber 13, a piston rod 7 that is provided coaxially with the piston 5, protrudes to the outside of the cylinder 3, and moves in conjunction with the forward and backward movement, a seal member 9 that performs sealing between the cylinder 3 and the piston 5, a circumferential seal mounting portion 23 that supports the seal member 9 so as to move in conjunction with the forward and backward movement of the piston 5, a circumferential flow passage portion 9a that is provided on the outer periphery of the seal member 9 and faces an inner peripheral surface 3a of the cylinder 3, or that is provided between the seal member 9 and the seal mounting portion 23, and an orifice 9b penetrating through the flow passage portion 9a to the pressure chamber 11 and the non-pressure chamber 13.

Description

Linear damper

[0001] The present invention relates to a velocity dependent linear damper.

[0002] A conventional linear damper is disclosed in Patent Document 1. In this damper, a seal ring is housed in a seal housing formed in a piston. The seal housing is formed by a second restricting portion on the first chamber side and a first restricting portion on the second chamber side, and the second restricting portion has a notch.

[0003] When the opening and closing body pulls the transmission part, the piston moves, maintaining the seal ring in its normal state in contact with the second restrictor. At this time, the first chamber's volume increases, creating a negative pressure, generating resistance. This causes the opening and closing body to open slowly. The negative pressure in the first chamber is released by the orifice formed in the cap.

[0004] On the other hand, if the opening and closing body is suddenly opened and the negative pressure in the first chamber becomes too high, the force pulling the piston back becomes large, and the opening and closing body that was suddenly opened is returned in the closing direction.

[0005] At this time, part of the seal ring enters the notch in the second restricting portion, allowing air from the second chamber to enter the first chamber through the gap between the second restricting portion and the seal ring, thereby eliminating the negative pressure in the first chamber and stopping the piston from retracting.

[0006] However, with this structure, it is not possible to generate appropriate drag when the piston moves fast and when it moves slowly, and there is a limit to the improvement in performance with respect to speed dependency.

[0007] Japanese Patent Application Laid-Open No. 2022-69167

[0008] The problem to be solved is that there is a limit to the performance improvement in relation to speed dependency.

[0009] The linear damper of the present invention comprises a cylinder for forming a pressure chamber, a piston that is housed within the cylinder and partitions the pressure chamber while being movable back and forth between the partitioned pressure chamber and a non-pressurized chamber, a piston rod that is coaxially attached to the piston and protrudes outside the cylinder and is linked to the forward and backward movement, a seal member that provides a seal between the cylinder and the piston, a circular seal mounting portion that supports the seal member and is linked to the forward and backward movement of the piston, a circumferential flow path portion that is attached to the outer periphery of the seal member and extends relative to the inner surface of the cylinder or between the seal member and the seal mounting portion, and an orifice that passes through the flow path portion between the pressure chamber and the non-pressurized chamber.

[0010] The linear damper of the present invention can improve performance against velocity dependency.

[0011] FIG. 1 is a cross-sectional view of a portion of a linear damper during compression according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is an enlarged cross-sectional view of part III in FIG. 1. FIG. 4 is a cross-sectional view of the linear damper of FIG. 1 during expansion. FIG. 5 is a schematic diagram showing an image of air flow. FIG. 6 is a graph showing the relationship between piston speed and pressure change. FIG. 7 is a graph showing the relationship between piston speed, pressure change, and resistance change for the example and the comparative example. FIG. 8 is a graph showing the relationship between the piston displacement of a linear damper and resistance change for a comparative example, where (A) is a graph showing the relationship between the displacement of the piston of a linear damper and resistance change, and (B) is a graph converted into velocity and resistance. FIG. 9 is a graph showing the relationship between the piston displacement of a linear damper and resistance change for a comparative example, where (A) is a graph showing the relationship between the displacement of the piston of a linear damper and resistance change, and (B) is a graph converted into velocity and resistance. FIG. 10 relates to Example 5, and (A) is a graph showing the relationship between the displacement of the piston of the linear damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 11 relates to a modified example of Example 1, and (A) is a graph showing the relationship between the displacement of the piston of the linear damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 12 relates to Example 1, and (A) is a graph showing the relationship between the displacement of the piston of the linear damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 13 relates to a modified example of Example 1 and is a cross-sectional view showing a portion of the linear damper during compression. FIG. 14 is a cross-sectional view taken along the arrow XIV-XIV in FIG. 13. FIG. 15 is an enlarged cross-sectional view of portion XV in FIG. 13. FIG. 16 relates to Example 2 and is a cross-sectional view showing a portion of the linear damper during compression. FIG. 17 is a cross-sectional view taken along the arrows XVII-XVII in FIG. 16. FIG. 18 is an enlarged cross-sectional view of a portion XIIX in FIG. 16. FIG. 19 is a cross-sectional view of a portion of a linear damper during a compression operation according to a third embodiment. FIG. 20 is a cross-sectional view taken along the arrows XX-XX in FIG. 19. FIG. 21 is an enlarged cross-sectional view of a portion XXI in FIG. 19. FIG. 22 is a cross-sectional view of a portion of a linear damper during a compression operation according to a fourth embodiment. FIG. 23 is a cross-sectional view of a portion of a linear damper during an extension operation according to a fifth embodiment. FIG. 24 is an enlarged cross-sectional view of a portion of the orifice of the linear damper in FIG. 23 corresponding to FIG. 2. FIG. 25 is a cross-sectional view of a portion of a linear damper during an extension operation according to a first modified example of the fifth embodiment.FIG. 26 is an enlarged cross-sectional view of a portion of the orifice of the linear damper of FIG. 25 corresponding to the cross-sectional view of FIG. 2. FIG. 27 is a cross-sectional view showing a portion of a linear damper during a pushing operation according to a second modification of the fifth embodiment. FIG. 28 is a cross-sectional view showing a portion of a linear damper during an extending operation according to a third modification of the fifth embodiment. FIG. 29 is an enlarged cross-sectional view of a portion of the orifice of the linear damper of FIG. 28 corresponding to the cross-sectional view of FIG. 2. FIG. 30 is a cross-sectional view showing a portion of a linear damper during an extending operation according to a fourth modification of the fifth embodiment. FIG. 31 is a cross-sectional view showing a portion of a linear damper during a pushing operation according to a fifth modification of the fifth embodiment. FIG. 32 is a cross-sectional view showing a portion of a linear damper during a compression operation according to a sixth embodiment. FIG. 33 is a cross-sectional view showing a portion of a linear damper during a compression operation according to a sixth modification of the sixth embodiment.

[0012] The present invention achieves the object of enabling performance improvement with respect to speed dependency as follows.

[0013] The piston rod is provided coaxially with the piston and protrudes outside the cylinder so as to move in conjunction with the forward and backward movement; a circumferential flow path portion provided between the pressure chamber and the non-pressure chamber or between the pressure chamber and the outside of the cylinder; and an orifice that connects the flow path portion to the pressure chamber and the non-pressure chamber or to the pressure chamber and the outside of the cylinder.

[0014] The seal mounting portion can be provided on the piston, between the piston and the piston rod, or on the piston rod. The seal member is a seal ring, but the shape and structure can be freely set even if it is not ring-shaped as long as it has a similar effect.

[0015] The flow path portion is provided in a sealing member that seals between the cylinder and the piston or in a circular seal mounting portion that supports the sealing member and links it to the back and forth movement of the piston, and the orifice penetrates in the direction of the back and forth movement.

[0016] The flow path portion was provided in a plurality of rows adjacent to each other in the axial direction, and the orifices were arranged with their phases shifted.

[0017] The phase can be selected from various options, such as 180 degrees.

[0018] The circular shape of the flow path portion can be selected in various ways, such as by passing through the entire circumference of the sealing member, or by setting it within a range of less than 360 degrees.

[0019] The sealing member comprises a sealing member disc and a spacer, the sealing member disc is arranged on the seal mounting portion, the spacer positions the sealing member disc in the advancing / retreating direction relative to the seal mounting portion, and the flow path portion is provided radially between the spacer and the inner surface of the cylinder.

[0020] The cylinder is provided with a closing member that closes the pressure chamber, and the flow path and the orifice are provided in the closing member or the cylinder.

[0021] The cylinder includes a guide through which the piston rod tightly passes to form a pressure chamber between the piston and the guide, a return spring is interposed between the piston and the guide, and the flow path and orifice are provided in the guide.

[0022] The device comprises a piston that is housed within the cylinder and partitions the pressure chamber while being movable back and forth between the partitioned pressure chamber and a non-pressure chamber; a piston rod that is coaxially attached to the piston and protrudes outside the cylinder and moves in conjunction with the forward and backward movement; a seal member that seals between the cylinder and the piston; a circular seal mounting portion that supports the seal member and moves in conjunction with the forward and backward movement of the piston; and a flow path portion that is spirally attached to the outer periphery of the seal member and communicates with the pressure chamber and the non-pressure chamber.

[0023] [Linear-acting damper] Fig. 1 is a cross-sectional view of a linear-acting damper during a compression operation according to a first embodiment. Fig. 2 is a cross-sectional view taken along the line II-II in Fig. 1. Fig. 3 is an enlarged cross-sectional view of part III in Fig. 1. Fig. 4 is a cross-sectional view of the linear-acting damper of Fig. 1 during an extension operation.

[0024] 1 and 2, the linear damper 1 of the first embodiment is configured as an air damper. However, the linear damper 1 may also be configured as an oil damper or the like.

[0025] The linear damper 1 includes a cylinder 3, a piston 5, a piston rod 7, and a seal ring 9 as a seal member.

[0026] The cylinder 3 defines a pressure chamber 11 from a non-pressure chamber 13 by means of the piston 5, and one end of the cylinder 3 on the pressure chamber 11 side is fitted with, for example, a cap to seal the end.

[0027] The piston 5 is installed inside the cylinder 3 together with a seal ring 9, and defines a pressure chamber 11 relative to the inner circumferential surface 3a, while being movable back and forth between the defined pressure chamber 11 and a non-pressure chamber 13. The piston 5 is comprised of a head portion 15 and a spring seal receiving portion 17. The head portion 15 is formed with a smaller diameter than the spring seal receiving portion 17, and the outer periphery of the spring seal receiving portion 17 is formed with a slightly smaller diameter than the inner circumferential surface 3a of the cylinder 3. A return spring 19 is interposed between a cap portion (not shown) and the spring seal receiving portion 17.

[0028] A first receiving surface 17a is formed on the spring seal receiving portion 17. A radial groove 17ab is formed on the first receiving surface 17a. The radial direction means the radial direction of the cylinder 3.

[0029] The piston rod 7 is provided coaxially with the piston 5, passes through a rod guide (not shown) on the non-pressure chamber 13 side, and protrudes outside the cylinder 3, and is configured to move in conjunction with the forward and backward movement of the piston 5.

[0030] A flange 21 is formed integrally with the piston rod 7. The flange 21 is disposed opposite the spring seal receiving portion 17 of the piston 5. The outer periphery of the flange 21 is formed to have a diameter slightly smaller than the inner circumferential surface 3a of the cylinder 3. The flange 21 is formed with a second receiving surface 21a that faces the seal ring 9. The flange 21 is formed with a contact surface 21b, and a radial groove 21ba is formed in the contact surface 21b.

[0031] Between the spring seal receiving portion 17 and the flange 21 of the piston 5, a circumferential seal mounting portion 23 is formed on the outer periphery of the piston rod 7. A seal ring 9 is fitted and supported by the seal mounting portion 23. This support allows the seal ring 9 to move in conjunction with the forward and backward movement of the piston 5. The seal ring 9 provides a seal between the cylinder 3 and the piston 5.

[0032] The seal ring 9 is made of rubber or the like and includes a flow path portion 9 a and an orifice 9 b. The flow path portion 9 a is provided between the pressure chamber 11 and the non-pressure chamber 13. The orifice 9 b is configured to allow the flow path portion 9 a to pass through between the pressure chamber 11 and the non-pressure chamber 13.

[0033] The flow path portion 9a also functions as an expansion chamber that expands the airflow passing through the orifice 9b as described below, and is provided on the outer periphery of the seal ring 9 so as to have a substantially U-shaped cross section. Multiple flow path portions 9a are provided adjacent to each other in the axial direction between the ridge portions 9c. Specifically, multiple flow path portions 9a (for example, three) are formed circumferentially around the inner circumferential surface 3a of the cylinder 3 and are provided adjacent to each other at regular intervals in the axial direction. The axial direction refers to the direction in which the piston 5 advances and retreats, and is the direction along the axis of the cylinder 3.

[0034] The seal ring 9 has four ridges 9c arranged on the outer periphery thereof so as to sandwich each flow passage 9a, and is provided with a crushing margin so as to slide on the inner circumferential surface 3a of the cylinder 3. In the drawing, the crushing margin of the ridges 9c is shown overlapping the inner circumferential surface 3a.

[0035] The seal ring 9 is loosely fitted onto the outer periphery of the piston rod 7 at the seal mounting portion 23 .

[0036] The orifice 9 b is configured to allow the flow passage portion 9 a to pass through the pressure chamber 11 and the non-pressure chamber 13 .

[0037] 1 to 3, one orifice 9b is provided for each ridge 9c, and is set so as to cut out the top of the ridge 9c. This orifice 9b penetrates between the inner circumferential surface 3a of the cylinder 3 in the axial direction, which is the direction of the back and forth movement of the piston 5. The orifices 9b for each ridge 9c are arranged so as to be 180 degrees out of phase with each other.

[0038] The gap between the piston 5 and the flange 21 is formed to be larger than the axial width of the seal ring 9. Therefore, the seal ring 9 is configured to be movable relative to the seal mounting portion 23 in the direction of the back and forth movement of the piston 5.

[0039] A D-shaped cut portion 7a is formed in the piston rod 7 between the piston 5 and the flange 21. The D-shaped cut portion 7a forms a passage between the inner periphery of the seal ring 9 and the piston rod 7. This passage connects the pressure chamber 11 to the non-pressure chamber 13.

[0040] Therefore, as shown in Figure 4, when the piston 5 moves back relative to the pressure chamber 11, the seal ring 9 is in a position where it abuts against the first receiving surface 17a of the piston 5, and the pressure chamber 11 and the non-pressure chamber 13 are connected via the passage in the D-cut portion 7a and the groove 17ab on the piston 5 side.

[0041] [Function and Effect] As shown in FIG. 1 , during the contraction operation in which the piston rod 7 strokes from the extension state to the contraction state, the spring seal receiving portion 17 bends the return spring 19, and the piston 5 and the seal ring 9 compress the pressure chamber 11, and a resistance force acts on the piston rod 7.

[0042] During this stroke, the seal ring 9 moves while being pressed by the flange portion 21 .

[0043] At this time, air moving from the outer periphery of the spring seal receiving portion 17 of the piston 5 toward the seal mounting portion 23 passes through the orifice 9b of the first ridge 9c on the seal receiving portion 17 side of the seal ring 9 and enters the adjacent first flow path portion 9a. In the first flow path portion 9a, the axial air flow from the orifice 9b is diverted to both circumferential sides and spreads throughout almost the entire circumferential direction of the flow path portion 9a. At this time, the flow path portion 9a functions as an expansion chamber, causing the incoming high-speed air flow to expand and decelerate.

[0044] Since the orifice 9b of the next ridge 9c is located 180 degrees circumferentially from the first orifice 9b, the air that has traveled 180 degrees through the flow path 9a passes through the orifice 9b of the next ridge 9c and enters the next flow path 9a. This increases the volume of the flow path 9a, and the amount of expansion of the air that flows in increases.

[0045] This air movement occurs sequentially through the orifices 9b of all the peaks 9c and all the flow passages 9a, and then from the last orifice 9b, the air passes around the outer periphery of the flange 21 and reaches the non-pressure chamber 13. Therefore, the high-speed air flowing from each orifice 9b into each flow passage 9a expands and decelerates repeatedly, and the energy of the air flow from the pressure chamber 11 decreases. This energy decrease ΔP increases rapidly as the movement speed of the piston 5 increases. Therefore, when the movement speed of the piston 5 increases, the pressure difference between the pressure chamber 11 side and the non-pressure chamber 13 side increases rapidly in response to the movement speed of the piston 5.

[0046] As shown in FIG. 4 , during the extension operation in which the piston rod 7 strokes from the contracted state to the extended state, the spring seal receiving portion 17 receives the elastic force of the return spring 19, and the piston 5 and the seal ring 9 move back from the pressure chamber 11.

[0047] During this stroke, air moves from the non-pressure chamber 13 to the pressure chamber 11 side through the passage of the D-cut portion 7a and the groove 17ab.

[0048] FIG. 5 is a schematic diagram showing an image of the air flow.

[0049] During the contraction operation shown in FIG. 1, the air flowing from the pressure chamber 11 to the non-compression chamber 13 moves as shown in FIG.

[0050] That is, the flow velocity of the air from the compression chamber 11 is increased at each orifice 9b, and the flow velocity is relatively slowed at each flow path portion 9a, and the air passes through a long flow path.

[0051] In this case, the change in pressure of the air from the pressure chamber 11 to the non-pressure chamber 13 is approximately as shown in FIG.

[0052] Assuming that each flow path section 9a is a straight pipe, and the friction coefficient and air density are the same, the pressure loss is proportional to the square of the flow velocity and the length of the straight pipe, and inversely proportional to the diameter of the straight pipe, and therefore varies depending on the setting of the orifice 9b, the setting of the flow path area and length of each flow path section 9a, and the air flow velocity.

[0053] Therefore, depending on the piston speed, line segment A in Figure 6 represents the high-speed characteristics, line segment B represents the medium-speed characteristics, and line segment C represents the low-speed characteristics, with Aa, Ba, and Ca representing the pressure losses in each orifice 9b, and Ab, Bb, and Cb representing the pressure losses in each flow path portion 9a.

[0054] The speed dependency characteristics are shown in FIG. 7 in relation to the comparative example.

[0055] Line A represents the characteristics of Example 1, line B represents the characteristics of a modified example in which the orifices 9b are arranged in series in the axial direction without any phase shift, line C represents the characteristics of Example 5 (described below) in which the flow path portions 9a are arranged in a spiral, line D represents the characteristics of a general pneumatic U-packing as a comparative example, and line E represents the characteristics of a comparative example in which one orifice is set in the outer diameter lip portion of the general pneumatic U-packing as a comparative example.

[0056] The characteristics of Example 1 of line segment A show that when the operating speed is slow, the pressure difference between the pressure chamber 11 and the non-pressure chamber 13 and the maximum resistance are low, and as the operating speed increases, the pressure difference and the maximum resistance rise significantly.

[0057] The characteristic of the modified example of line segment B, although not as great as line segment A, showed a relatively large gradient of the rise in pressure difference and maximum drag as the operating speed increased compared to the comparative example.

[0058] As will be described later, the characteristics of Example 5 of line segment C show that as the operating speed increases, the gradient of the rise in pressure difference and maximum drag force becomes relatively larger than that of the comparative example.

[0059] In contrast, in the comparative examples of lines D and E, even when the operating speed increased, the gradient of the rise in the pressure difference and maximum drag was gentle, and the speed dependency characteristics were virtually nonexistent.

[0060] FIG. 8 relates to a comparative example, where (A) is a graph showing the relationship between the displacement of the piston of a linear-acting damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 9 relates to a comparative example, where (A) is a graph showing the relationship between the displacement of the piston of a linear-acting damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 10 relates to Example 5, where (A) is a graph showing the relationship between the displacement of the piston of a linear-acting damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 11 relates to a modified example of Example 1, where (A) is a graph showing the relationship between the displacement of the piston of a linear-acting damper and the change in resistance, and (B) is a graph converted into velocity and resistance. FIG. 12 relates to Example 1, where (A) is a graph showing the relationship between the displacement of the piston of a linear-acting damper and the change in resistance, and (B) is a graph converted into velocity and resistance.

[0061] Fig. 8 shows the characteristics of a typical pneumatic U-packing as a comparative example, Fig. 9 shows the characteristics of a comparative example in which a single orifice is provided on the outer diameter lip of a typical pneumatic U-packing as a comparative example, Fig. 10 shows the characteristics of Example 5 described below in which the flow passages 9a are arranged in a spiral, Fig. 11 shows the characteristics of a modified example in which the orifices 9b are arranged in series in the axial direction, and Fig. 12 shows the characteristics of Example 1.

[0062] In the comparative examples of Figures 8 and 9, there was not much difference in the degree of change in resistance even when the piston pushing speed was changed to 10 mm / s, 50 mm / s, 100 mm / s, and 200 mm / s.

[0063] In contrast to this, in Example 5 (described later) in which the flow path portion 9a in FIG. 10 is arranged in a spiral, the modified example in which the orifices 9b in FIG. 11 are arranged in series in the axial direction, and Example 1 in FIG. 12, the degree of change in the resistance force with respect to the change in the piston pushing amount speed all increased.

[0064] As described above, a linear damper with velocity-dependent characteristics can be obtained by using multiple flow path sections 9a circumferentially arranged on the outer periphery of the seal ring 9 and orifices 9b that penetrate between the pressure chamber 11 and the first flow path section 9a, between the first flow path section 9a and the next flow path section 9a, and between this flow path section 9a and the non-pressure chamber 13.

[0065] In particular, when the flow path portion 9a is provided in multiple rows between the ridge portions 9c adjacent to each other in the axial direction of the seal ring 9, and the orifice 9b is arranged out of phase with the ridge portions 9c, a linear damper with significantly speed-dependent characteristics can be obtained.

[0066] [Modification] Fig. 13 is a cross-sectional view of a part of a linear damper during compression operation according to a modification of the first embodiment. Fig. 14 is a cross-sectional view taken along the arrows XIV-XIV in Fig. 13. Fig. 15 is an enlarged cross-sectional view of part XV in Fig. 13. The basic configuration is the same as in the first embodiment, and the same or corresponding components are designated by the same reference numerals, and redundant explanations will be omitted.

[0067] 13 to 15, in the linear damper 1 of the modified example, the axial dimension of the seal mounting portion 23 is set to be approximately equal to the axial width of the seal ring 9. The groove 17ab of the spring seal receiving portion 17 and the D-cut portion 7a of the piston rod 7 are eliminated.

[0068] The seal ring 9 is supported at a substantially fixed position between the piston 5 and the flange 21, and the seal ring 9 does not move relative to the seal mounting portion 23 in the direction of the piston 5's forward and backward movement.

[0069] Therefore, the flow passage portion 9a and the orifice 9b function during both the contraction and extension of the piston 5, thereby improving the speed-dependent characteristics.

[0070] Fig. 16 is a cross-sectional view showing a part of a linear damper during compression operation according to Example 2. Fig. 17 is a cross-sectional view taken along the arrows XVII-XVII in Fig. 16. Fig. 18 is an enlarged cross-sectional view of part XIIX in Fig. 16. The basic configuration is the same as in Example 1, and the same or corresponding components are designated by the same reference numerals, and redundant explanations will be omitted.

[0071] As shown in FIGS. 16 to 18, in the linear damper 1 of the second embodiment, the flow path portion 9 a and the orifice 9 b are set on the inner periphery of the seal ring 9 .

[0072] In this second embodiment, the D-cut portion 7a of the piston rod 7 is eliminated from the seal mounting portion 23, and a groove 17ab is provided on the first receiving surface 17a of the spring seal receiving portion 17, and a groove 21ab is provided on the second receiving surface 21a of the flange portion 21.

[0073] Therefore, in both the contraction and extension motions of the piston 5, the flow passage portion 9a and the orifice 9b function via the grooves 17ab and 21ab, thereby improving the speed-dependent characteristics.

[0074] In addition, the second embodiment can also achieve the same effects as the first embodiment.

[0075] Fig. 19 is a cross-sectional view of a part of a linear damper during compression operation according to Example 3. Fig. 20 is a cross-sectional view taken along the arrows XX-XX in Fig. 19. Fig. 21 is an enlarged cross-sectional view of part XXI in Fig. 19. The basic configuration is the same as in Example 1, and the same or corresponding components are designated by the same reference numerals, and redundant explanations will be omitted.

[0076] 19 to 21, the linear damper 1 of Example 3 has a flow path 7a and an orifice 7b arranged around the outer circumferential surface of the piston rod 7 within the seal mounting portion 23. The flow path 7a is designated by the same reference numeral as the D-cut portion, and corresponds to the flow path 9a, orifice 9b, and ridge portion 9c, respectively.

[0077] The inner periphery of the seal ring 9 is in close contact with the ridge portion 9c. The first receiving surface 17a of the spring seal receiving portion 17 is provided with a groove 17ab, and the second receiving surface 21a of the flange portion 21 is provided with a groove 21ab.

[0078] Therefore, in both the contraction and extension motions of the piston 5, the flow passage portion 7a and the orifice 7b function via the grooves 17ab and 21ab, and the speed-dependent characteristics can be improved.

[0079] In addition, the third embodiment can also achieve the same effects as the first embodiment.

[0080] 22 is a cross-sectional view showing a part of a linear damper during compression operation according to Example 4. The basic configuration is the same as that of Example 1, and the same or corresponding components are designated by the same reference numerals, and redundant explanations will be omitted.

[0081] 22 , in the linear damper 1 of Example 4, a plurality of, for example, four donut-shaped seal ring disks 9d made of rubber or the like are arranged on the seal mounting portion 23, and the seal ring 9 is configured with spacers 9e, 9f made of metal or resin that position the seal rings in the forward and backward directions relative to the seal mounting portion 23. Each flow path 9a is provided radially between the spacer 9e and the inner circumferential surface 3a of the cylinder 3, and the orifices 9b are provided in each seal ring disk 9d with a phase shift.

[0082] Therefore, the flow passage portion 9a and the orifice 9b function during both the contraction and extension of the piston 5, thereby improving the speed-dependent characteristics.

[0083] In addition, the fourth embodiment can also achieve the same effects as the first embodiment.

[0084] FIG. 23 is a cross-sectional view of a portion of a linear-acting damper according to a fifth embodiment, during an extension operation. FIG. 24 is an enlarged cross-sectional view of a portion of the orifice of the linear-acting damper of FIG. 23, corresponding to FIG. 2. FIG. 25 is a cross-sectional view of a portion of a linear-acting damper according to a first modification of the fifth embodiment, during an extension operation. FIG. 26 is an enlarged cross-sectional view of a portion of the orifice of the linear-acting damper of FIG. 25, corresponding to the cross-sectional view of FIG. 2. FIG. 27 is a cross-sectional view of a portion of a linear-acting damper according to a second modification of the fifth embodiment, during a pushing operation. FIG. 28 is a cross-sectional view of a portion of a linear-acting damper according to a third modification of the fifth embodiment, during an extension operation. FIG. 29 is an enlarged cross-sectional view of a portion of the orifice of the linear-acting damper of FIG. 28, corresponding to the cross-sectional view of FIG. 2. FIG. 30 is a cross-sectional view of a portion of a linear-acting damper according to a fourth modification of the fifth embodiment, during an extension operation. FIG. 31 is a cross-sectional view of a portion of a linear-acting damper according to a fifth modification of the fifth embodiment, during a pushing operation. The basic configuration is the same as in the first embodiment, and the same or corresponding components are denoted by the same reference numerals, and redundant explanations will be omitted.

[0085] The linear damper 1 of the fifth embodiment shown in FIG. 23 includes a flow path portion 25 a between the pressure chamber 11 and the outside of the cylinder 3 .

[0086] The cylinder 3 is provided with a closing member 25 that closes the pressure chamber 11. The closing member 25 is provided with a flow path portion 25a and an orifice 25b.

[0087] The closing member 25 is integrally provided with a fitting portion 27 and a flange 29, and has a hat-shaped cross section. The fitting portion 27 of the closing member 25 is press-fitted into the end of the cylinder 3, and the flange 29 is abutted against the end face of the cylinder 3 and bonded or welded to it.

[0088] The flow path portion 25a is composed of a circumferential groove provided on the outer peripheral surface of the closing member 25, and the circumferential groove is closed by the inner peripheral surface of the cylinder 3, so that the flow path portion 25a is provided between the closing member 25 and the cylinder 3.

[0089] The closing member 25 has a passage 26 formed in a flange 29 at its outer end. The passage 26 is connected to a flow path portion 25a near the flange 29. The flow path portion 25a is open to the outside of the cylinder 3 via the passage 26.

[0090] 23 and 24, the configuration of the orifices 25b is the same as in Example 1, and they are formed on the outer periphery of each ridge 25c and are mutually shifted in phase by 180°. The orifices 25b communicate between the flow path portions 25a in the axial direction, and also communicate the flow path portions 25a with the pressure chamber 11 on one side and with the passage 26 on the other side.

[0091] The flow path portion 25a, the orifice 25b, and the ridge portion 25c correspond to the flow path portion 9a, the orifice 9b, and the ridge portion 9c of the first embodiment.

[0092] A return spring 19 is interposed between the closing member 25 and the piston 5 .

[0093] The flow path portion 25a and the orifice 25b function in the same manner as in Example 1 through the passage 26 between the pressure chamber 11 and the outside of the cylinder 3, and can achieve the same effects, thereby obtaining a linear damper with velocity-dependent characteristics.

[0094] 25 , the linear damper 1 of the first modification has a configuration in which the closing member 25 is fitted onto the outer surface of the end of the cylinder 3. The closing member 25 is provided with a flow path portion 25a and an orifice 25b.

[0095] The flow path 25a is configured as a circumferential groove provided on the inner circumferential surface of the closing member 25. The circumferential groove is closed by the outer circumferential surface of the cylinder 3, and the flow path 25a is provided between the closing member 25 and the cylinder 3.

[0096] As shown in Figures 25 and 26, the configuration of the orifices 25b is basically the same as that of the examples in Figures 23 and 24, and they are formed on the inner periphery of each ridge 25c and are shifted in phase by 180 degrees from each other.

[0097] The closing member 25 has an end wall 29A that abuts against the end face of the cylinder 3 instead of the flange 29, and the passage 26 is formed by a groove formed in the end face of the cylinder 3.

[0098] Therefore, in the first modification, the flow path portion 25a and the orifice 25b function and can provide the same effects, thereby providing a linear damper with velocity-dependent characteristics.

[0099] [Modification 2] As shown in FIG. 27, the linear damper 1 of modification 2 is applied to a so-called pull damper.

[0100] The linear damper 1 includes a guide 31 in the cylinder 3. The guide 31 includes a flow path 31a and an orifice 31b.

[0101] The piston rod 7 tightly passes through the guide 31 to form a pressure chamber 11 between the guide 31 and the piston 5. The guide 31 is provided with a seal 35 that tightly contacts the piston rod 7. A return spring 33 is interposed between the piston 5 and the guide 31.

[0102] The flow path portion 31a is composed of a circumferential groove provided on the outer periphery of the guide 31, and the circumferential groove is closed by the inner periphery of the cylinder 3, and the flow path portion 31a is provided between the guide 31 and the cylinder 3.

[0103] As shown in Figure 27, the configuration of the orifices 31b is basically the same as in Figures 23 and 24, and they are formed on the outer periphery of each ridge 31c and are mutually shifted in phase by 180°. The orifices 31b on the one hand connect the flow path portion 31a to the pressure chamber 11, and on the other hand connect the flow path portion 31a from between the piston rod 7 and the cylinder 3 to the outside, instead of the passage 26.

[0104] The flow path portion 31a, the orifice 31b, and the ridge portion 31c correspond to the flow path portion 9a, the orifice 9b, and the ridge portion 9c of the first embodiment.

[0105] In variant 2, when the piston rod 7 is pulled out and pushed in, the flow path portion 31a and the orifice 31b function, and the same effect as described above can be achieved, thereby obtaining a linear damper with velocity-dependent characteristics in a so-called pull damper.

[0106] [Modification 3] As shown in Figs. 28 and 29, the linear damper 1 of modification 3 has a configuration in which the flow path portion 3a is provided between the closing member 25 and the cylinder 3, similar to the example of Fig. 23 .

[0107] On the other hand, in the examples of Figures 28 and 29, the flow path portion 3a is configured as a circumferential groove provided on the inner surface of the cylinder 3, and the circumferential groove is closed by the outer surface of the closing member 25.

[0108] The passage 26 is formed by a groove formed in the end face of the cylinder 3 .

[0109] The flow path portion 3a, the orifice 3b, and the ridge portion 3c correspond to the flow path portion 9a, the orifice 9b, and the ridge portion 9c of the first embodiment.

[0110] Therefore, in the third modification, the flow path 3a and the orifice 3b function to provide the same effects, and a linear damper having velocity-dependent characteristics can be obtained.

[0111] 30 , the linear damper 1 of the fourth modification has a configuration in which the closing member 25 is fitted onto the outer surface of the end of the cylinder 3, similar to the example of FIG. 25 . The flow path 3 a and the orifice 3 b are provided in the closing member 25.

[0112] The flow path portion 3a is configured as a circumferential groove provided on the outer periphery of the cylinder 3. The circumferential groove is closed by the inner circumferential surface of the closing member 25, and the flow path portion 3a is provided between the closing member 25 and the cylinder 3.

[0113] Therefore, in the fourth modification, the flow path portion 3a and the orifice 3b function, and the same effects as those described above can be achieved, making it possible to obtain a linear damper with velocity-dependent characteristics.

[0114] 31, the linear damper 1 of the fifth modification is applied to a so-called pull damper, similar to the second modification of FIG. 27. The flow path 3a and the orifice 3b are provided in the cylinder 3.

[0115] The flow path portion 3a is composed of a circumferential groove provided on the inner surface of the cylinder 3, and the circumferential groove is closed by the outer surface of the guide 31, and the flow path portion 3a is provided between the guide 31 and the cylinder 3.

[0116] The closing member 25 is composed of an end wall 29A and a flange 29.

[0117] In the fifth modification, the flow path 3a and the orifice 3b function to provide the same effects as those described above, and a linear damper having velocity-dependent characteristics can be obtained as a pull damper.

[0118] 32 is a cross-sectional view showing a part of a linear damper during compression operation according to Example 6. The basic configuration is the same as that of Example 1, and the same or corresponding components are denoted by the same reference numerals, and redundant explanations will be omitted.

[0119] As shown in Figure 32, the linear damper 1 of Example 6 has a spiral flow path 9A instead of the flow path 9a and orifice 9b of the seal ring 9 of Example 1. It is also possible to form an orifice at the end of the flow path 9A on the pressure chamber 11 side that passes through the flow path 9A to the pressure chamber 11, and to form an orifice at the end of the flow path 9A on the non-pressure chamber 13 side that passes through the flow path 9A to the non-pressure chamber 13. When an orifice is formed, the flow path 9A also functions as an expansion chamber.

[0120] By setting the flow path area and flow path length of the spiral flow path portion 9A, the pressure loss could be set in the same manner as in Example 1, and the characteristics shown in FIGS. 7 and 10 were obtained.

[0121] [Modification] FIG. 33 is a cross-sectional view showing a part of a linear damper during a compression operation according to a modification of the sixth embodiment.

[0122] 33, in the linear damper 1 of the modified example, the axial dimension of the seal mounting portion 23 is set to be approximately equal to the axial width of the seal ring 9. The groove 17ab of the spring seal receiving portion 17 and the D-cut portion 7a of the piston rod 7 are omitted.

[0123] The seal ring 9 is supported at a substantially fixed position between the piston 5 and the flange 21, and the seal ring 9 does not move relative to the seal mounting portion 23 in the direction of the piston 5's forward and backward movement.

[0124] Therefore, the flow path portion 9A functions during both the contraction and extension of the piston 5, and the speed dependency characteristics can be improved.

[0125] REFERENCE SIGNS LIST 1 Linear damper 3 Cylinder 5 Piston 7 Piston rod 9 Seal ring (seal member) 9A Flow path portion 9a Flow path portion 9b Orifice 9c Ridge portion 9d Seal ring disk 9e, 9f Spacer 11 Pressure chamber 13 Non-pressure chamber 23 Seal mounting portion 25 Closing member 31 Guide

Claims

1. A linear damper comprising: a cylinder for forming a pressure chamber; a piston that is housed within the cylinder and partitions the pressure chamber and is movable back and forth between the partitioned pressure chamber and a non-pressure chamber; a piston rod that is coaxial with the piston and protrudes outside the cylinder and is linked to the forward and backward movement; a circumferential flow path portion that is provided between the pressure chamber and the non-pressure chamber or between the pressure chamber and the outside of the cylinder; and an orifice that connects the flow path portion to the pressure chamber and the non-pressure chamber or to the pressure chamber and the outside of the cylinder.

2. A linear damper according to claim 1, wherein the flow path is provided in a seal member that seals between the cylinder and the piston, or in a circular seal mounting part that supports the seal member and moves it in conjunction with the forward and backward movement of the piston, and the orifice penetrates in the direction of the forward and backward movement.

3. A direct-acting damper according to claim 2, wherein the flow path portion is provided with a plurality of adjacent rows in the axial direction, and the orifices are arranged with a phase shift.

4. A linear damper according to any one of claims 2 to 3, wherein the seal member comprises a seal member disc and a spacer, the seal member disc is disposed on the seal mounting portion, the spacer positions the seal member disc in the advancing / retreating direction relative to the seal mounting portion, and the flow path portion is provided between the spacer and the inner peripheral surface of the cylinder.

5. A linear damper according to claim 1, wherein the cylinder is provided with a closing member that closes the pressure chamber, and the flow path and the orifice are provided in the closing member or the cylinder.

6. A direct-acting damper according to claim 1, comprising a guide within said cylinder through which said piston rod passes tightly to form a pressure chamber between said guide and said piston, a return spring interposed between said piston and said guide, and said flow path and orifice provided in said guide.

7. A linear damper comprising: a cylinder for forming a pressure chamber; a piston that is housed within the cylinder and partitions the pressure chamber and is movable back and forth between the partitioned pressure chamber and a non-pressurized chamber; a piston rod that is coaxial with the piston and protrudes outside the cylinder and moves in conjunction with the forward and backward movement; a seal member that seals between the cylinder and the piston; a circular seal mounting portion that supports the seal member and moves in conjunction with the forward and backward movement of the piston; and a flow path that is spirally provided on the outer periphery of the seal member and communicates with the pressure chamber and the non-pressurized chamber.

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