Damping force generation device, and suspension device

Abstract

To provide a technique that can increase a damping force when a piston speed is in a high-speed region while restraining an influence on damping force characteristics when it is in a low-speed range or a medium-speed range.SOLUTION: A piston part 30 comprises: a piston 100 that is held by a rod 20, and in which a first hole 101 extending in the axial direction of the rod 20 so as to serve as a flow passage for oil is formed; an annular first valve group 31 for opening and closing the first hole 101; and a change member 150 arranged in the first hole 101, and capable of changing the area of the flow passage by moving in the axial direction in association with movement of the first valve group 31.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a damping force generating device and a suspension system. [Background technology]

[0002] Conventionally, devices have been proposed that provide an appropriate damping force over the entire range of piston speeds, from low to high. For example, the piston structure described in Patent Document 1 includes a piston body, a valve arranged on a first direction side thereof, and a valve arranged on a second direction side thereof. The piston body is provided with seats on the end face on the first direction side and the end face on the second direction side, respectively, on which the valves sit. The piston body is provided with a plurality of flow paths that communicate the first chamber and the second chamber. The valves seated on the seats are pushed open to allow fluid to flow, generating a damping force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-139605 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to increase the damping force when the piston speed is high. In particular, in recent years, the spring constant of coil springs has increased due to an increase in vehicle weight, etc., which has resulted in a tendency for the piston speed on the extension side to be high and the impact to be large when going over a bump, etc., and therefore it is desirable to increase the damping force in order to reduce the kinetic energy at the point of full extension. On the other hand, if the plate thickness or number of layers of the valve (the valve in Patent Document 1) is increased in order to increase the damping force when the piston speed is high, this will also affect the damping force characteristics when the piston speed is in the low or medium speed range. The present invention aims to provide a damping force generating device, etc. that can increase the damping force when the piston speed is in the high speed range while suppressing the effect on the damping force characteristics when the piston speed is in the low speed or medium speed range. [Means for solving the problem]

[0005] The present invention, which was completed with this objective in mind, is a damping force generating device that includes a piston held by a rod and having a hole extending in the axial direction of the rod to serve as a fluid flow path, a circular valve that opens and closes the hole, and a modifying member that is positioned within the hole and moves in the axial direction in conjunction with movement of the valve, thereby changing the area of ​​the flow path. Effect of the Invention

[0006] According to the present invention, it is possible to increase the damping force in the high speed range while suppressing the influence on the damping force characteristics when the piston speed is in the low speed range or the medium speed range. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing an example of a schematic configuration of a suspension device according to a first embodiment. [Diagram 2] FIG. 4 is an example of a perspective view of the piston according to the first embodiment, as viewed from a second side. [Diagram 3] 2 is an example of a perspective view of a piston according to the first embodiment, as viewed from a first side. FIG. [Figure 4] 4 is a diagram showing an example of a cross section of the piston portion according to the first embodiment taken along line IV-IV in FIG. 2. FIG. [Diagram 5] 4 is an example of a perspective view of a change member according to the first embodiment as viewed from a second side. FIG. [Figure 6] FIG. 11 is an example of a cross-sectional view showing the flow of oil during extension when the amount of protrusion of the rod from the cylinder portion increases, and shows the flow of oil when the piston speed is in the low speed range. [Figure 7]FIG. 11 is an example of a cross-sectional view showing the flow of oil during extension when the amount of protrusion of the rod from the cylinder portion increases, and shows the flow of oil when the piston speed is in the medium speed range. [Figure 8] FIG. 11 is an example of a cross-sectional view showing the flow of oil during extension when the amount of protrusion of the rod from the cylinder portion increases, and shows the flow of oil when the piston speed is in the high speed range. [Figure 9] FIG. 11 is a diagram showing a change in flow path area of ​​an extension-side flow path. [Figure 10] FIG. 11 is a diagram illustrating an example of a correlation between a piston speed and a damping force. [Figure 11] 13 is an example of a view of the piston according to the second embodiment as viewed from a second side. FIG. [Figure 12] 12 is a diagram showing an example of a cross section of a piston portion according to a second embodiment taken along line XII-XII in FIG. 11. FIG. [Figure 13] FIG. 11 is an example of a perspective view of a change member according to a second embodiment. [Figure 14] FIG. 13 is an example of a cross-sectional view showing the flow of oil during extension when the amount of protrusion of the rod from the cylinder portion increases, and shows the flow of oil when the piston speed is in the low to medium speed range. [Figure 15] FIG. 11 is an example of a cross-sectional view showing the flow of oil during extension when the amount of protrusion of the rod from the cylinder portion increases, and shows the flow of oil when the piston speed is in the high speed range. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. First Embodiment FIG. 1 is a diagram showing an example of a schematic configuration of a suspension device 1 according to the first embodiment. The suspension 1 is a suspension used in a four-wheeled vehicle such as a passenger car, and includes a hydraulic shock absorber 2 and a coil spring 3 arranged on the outside of the shock absorber 2, as shown in FIG. 1. Hereinafter, the center line direction of an outer cylinder 12 of the shock absorber 2, which will be described later, may be simply referred to as the "center line direction". Also, the first side in the center line direction (lower side in FIG. 1) and the second side in the center line direction (upper side in FIG. 1) may be simply referred to as the "first side" and the "second side", respectively. Also, a direction intersecting the center line direction (for example, a perpendicular direction) is referred to as the "radial direction". In the radial direction, the center line side of the outer cylinder 12 may be simply referred to as the "inner side", and the side away from the center line may be simply referred to as the "outer side".

[0009] The suspension device 1 also includes a lower spring seat 4 that supports a first end of the spring 3, and an upper spring seat 5 that supports a second end of the spring 3. The suspension device 1 also includes a vehicle body side bracket 6 that is attached to the second end for mounting the suspension device 1 to a vehicle, and a wheel side bracket 7 that is fixed to a first end of a cylinder section 10 (described later) for mounting the suspension device 1 to a wheel. The suspension device 1 also includes a dust cover 8 that covers the cylinder section 10 and at least a part of a rod 20 (described later). The vehicle body side bracket 6 is attached to the second end of the rod 20.

[0010] The shock absorber 2 will be described in detail below. The shock absorber 2 includes a cylinder portion 10 that contains oil, and a rod 20 whose second end protrudes from the cylinder portion 10 and whose first end is slidably inserted into the cylinder portion 10. The shock absorber 2 also includes a piston portion 30 provided at the first end of the rod 20, and a bottom portion 40 provided at the first end of the cylinder portion 10.

[0011] [Cylinder section 10] The cylinder portion 10 includes a cylinder 11 filled with oil, a cylindrical outer tube 12 provided on the outside of the cylinder 11, and a bottom cover 13 that closes a first end of the outer tube 12. The outer peripheral surface of the cylinder 11 and the inner peripheral surface of the outer tube 12 form a reservoir chamber R. The cylinder portion 10 also includes a rod guide portion 14 that movably supports the rod 20, a bump stopper cap 15, and an oil seal 16 that prevents oil from leaking from within the cylinder 11 and prevents foreign matter from entering the cylinder 11.

[0012] [Rod 20] The rod 20 is a solid or hollow rod-shaped member, and has a columnar or cylindrical rod portion 21. The rod 20 also has a lower attachment portion 22 for attaching the piston portion 30 to its lower end, and an upper attachment portion 23 for attaching the vehicle body side bracket 6 to its upper end. Male threads are formed at the ends of the lower attachment portion 22 and the upper attachment portion 23. The piston portion 30 is fixed to the rod 20 by tightening a nut 24 onto the male thread formed on the lower attachment portion 22. The rod 20 moves in the center line direction while holding the piston portion 30. The axial direction of the rod 20 is the same as the center line direction.

[0013] [Bottom part 40] The bottom portion 40 includes a valve body 41 having a plurality of oil passages penetrating in the center line direction, a first valve 42 provided on a first side of the valve body 41, and a second valve 43 provided on a second side of the valve body 41. The valve body 41 of the bottom portion 40 separates a first chamber Y1 and a reservoir chamber R, which will be described later.

[0014] [Piston portion 30] FIG. 2 is an example of a perspective view of the piston 100 according to the first embodiment, as viewed from the second side. FIG. 3 is an example of a perspective view of the piston 100 according to the first embodiment as viewed from the first side. FIG. 4 is a diagram showing an example of a cross section of the piston portion 30 according to the first embodiment taken along line IV-IV in FIG. FIG. 5 is an example of a perspective view of the change member 150 according to the first embodiment as viewed from the second side.

[0015] The piston section 30 includes a piston 100, a first valve group 31 that blocks first ends of some of the oil passages formed in the piston 100, and a second valve group 32 that blocks second ends of some of the oil passages formed in the piston 100. The piston section 30 also includes a first annular washer 33 that is disposed between the first valve group 31 and a nut 24 that fixes the piston section 30 to the rod 20, and a second annular washer 34 that is disposed between the second valve group 32 and the rod 20. The first valve group 31 and the second valve group 32 can be exemplified as valve groups in which a plurality of thin annular members are stacked. However, instead of the first valve group 31 and the second valve group 32, one thin annular valve may be disposed. In addition, the piston portion 30 is disposed within a first hole 101, which will be described later, that functions as a flow path for oil, and has a change member 150 that can change the area of ​​the flow path by moving in the center line direction in conjunction with the movement of the first valve group 31.

[0016] (Piston 100) The piston 100 is provided on its outer peripheral surface and contacts the inner peripheral surface of the cylinder 11 via a sealing member 109 that seals the gap between the outer peripheral surface of the piston 100 and the inner peripheral surface of the cylinder 11, dividing the space filled with oil within the cylinder 11 into a first chamber Y1 on the first side of the piston 100 and a second chamber Y2 on the second side of the piston 100. The piston 100 is a cylindrical member having a central hole 105 formed in its radially inner portion, through which the rod 20 passes, and is formed by, for example, sintering.

[0017] The piston 100 is formed with a first hole 101 penetrating in the center line direction, which constitutes a part of the extension side flow passage Rt through which the oil flows from the second chamber Y2 to the first chamber Y1 during extension when the amount of protrusion of the rod 20 from the cylinder part 10 increases. The piston 100 is also formed with a second hole 102 extending in the center line direction, which constitutes a part of the compression side flow passage Rc through which the oil flows from the first chamber Y1 to the second chamber Y2 during compression when the amount of protrusion of the rod 20 from the cylinder part 10 decreases. The first hole 101 and the second hole 102 are each formed in a plurality (four in FIG. 2) around the central hole 105. The plurality of first holes 101 and second holes 102 are formed alternately in the circumferential direction. The first hole 101 is cylindrical, and the second hole 102 is rectangular prism-shaped.

[0018] The piston 100 is also formed with a first recess 111 recessed from a first end face 110, which is an end face on the first side, to the second side. The first recess 111 is formed in an annular shape around the central hole 105. The cross-sectional shape of the first recess 111 cut along a plane passing through the center line is a trapezoid, and the radial size gradually decreases from the opening on the first end face 110 side to the second side. The opening on the first side of the first hole 101 is formed at the bottom of the first recess 111.

[0019] The first end surface 110 has an inner end surface 115 provided on the inner side and an outer end surface 116 provided on the outer side by forming the first recess 111. The first valve group 31 is fixed between the first washer 33 and the inner end surface 115. As a result, the inner part of the first valve group 31 functions as a fixed end, and the outer part functions as a working end. When the outer part of the first valve group 31 comes into contact with the outer end surface 116, the extension-side flow passage Rt is closed, and when the outer part of the first valve group 31 moves away from the outer end surface 116, the extension-side flow passage Rt is opened.

[0020] The piston 100 also has a second end surface 120 which is an end surface on the second side. The second end surface 120 has a central surface 121 provided around the central hole 105, a pair of radial surfaces 122 extending radially from the central surface 121, and a circumferential surface 123 extending circumferentially so as to connect the radially outer ends of the pair of radial surfaces 122. The pair of radial surfaces 122 and the circumferential surface 123 are provided to surround the periphery of the second hole 102 together with the outer periphery of the central surface 121, and the number of pairs of the radial surfaces 122 and the circumferential surfaces 123 is the same as the number of the second holes 102 (four in FIG. 2). The second valve group 32 is fixed between the central surface 121 of the second end surface 120 and the second washer 34. As a result, the inner part of the second valve group 32 functions as a fixed end, and the outer part functions as an operating end. When the second valve group 32 comes into contact with the pair of radial surfaces 122 and the circumferential surface 123, the compression side flow passage Rc is closed, and when the second valve group 32 moves away from the circumferential surface 123, the compression side flow passage Rc is opened.

[0021] In addition, the piston 100 is formed with an expansion-side recess 127 recessed from the second end face 120 around the first hole 101. The expansion-side recess 127 is formed at a portion outside the central face 121 and located in the second chamber Y2. The cross-sectional shape of the expansion-side recess 127 cut along a plane passing through the center line is a trapezoid, and the radial size gradually decreases from the opening on the second end face 120 side toward the first side. An opening on the second side of the first hole 101 is formed at the bottom of the expansion-side recess 127.

[0022] The piston 100 is also formed with a groove 130 recessed inward from the outer circumferential surface all around. A radial through hole 131 communicating with the second hole 102 is formed in an inner portion of the groove 130. The through holes 131 are formed in the circumferential direction in the same number as the number of the second holes 102 (four in FIG. 2). The diameter of the outer circumferential surface of the piston 100 at a portion on the first side of the groove 130 is smaller than the diameter of the outer circumferential surface of a portion on the second side of the groove 130, and the groove 130 constitutes a part of the compression side flow path Rc.

[0023] (Modified part 150) The change member 150 has a cylindrical portion 160, a first protruding portion 170 that protrudes cylindrically from a first end of the cylindrical portion 160 to the first side, and a second protruding portion 180 that protrudes cylindrically from a second end of the cylindrical portion 160 to the second side. The diameters of the outer circumferential surfaces of the cylindrical portion 160, the first protruding portion 170, and the second protruding portion 180 are the same as or slightly smaller than the diameter of the first hole 101 of the piston 100. The change member 150 is disposed in the first hole 101 of the piston 100 and moves in the center line direction within the first hole 101. The size of the change member 150 in the center line direction is the same as the size of the center line direction between the first end face 110 and the second end face 120 of the piston 100. The movement of the change member 150 toward the first side is restricted by the first valve group 31, and the movement of the change member 150 toward the second side is restricted by the second valve group 32. Note that the change member 150 can be, for example, molded from resin. However, the change member 150 may also be molded from metal.

[0024] The cylindrical portion 160 has an outer peripheral recess 161 recessed inward from the outer peripheral surface formed in a part of the circumferential direction. A plurality of (for example, two) outer peripheral recesses 161 are formed in the circumferential direction. The outer peripheral recess 161 has a rectangular shape when viewed radially from the outside, with the center line direction being the longitudinal direction and the circumferential direction being the short side direction. The size of the outer peripheral recess 161 in the center line direction is larger than the size of the first hole 101 of the piston 100 in the center line direction. Therefore, when the opening degree of the first valve group 31 and the second valve group 32 is zero, the first side end of the outer peripheral recess 161 is located on the first side of the opening of the first hole 101 on the first side and is located in the first recess 111 of the piston 100. Also, when the opening degree of the first valve group 31 and the second valve group 32 is zero, the second side end of the outer peripheral recess 161 is located on the second side of the opening of the second hole 101 on the second side and is located in the extension-side recess 127 of the piston 100.

[0025] A first cutout 171 that connects the inside and the outside is formed in a part of the circumferential direction of the first protruding portion 170. A plurality of (for example, two) first cutouts 171 are formed in the circumferential direction, and the position of the first cutout 171 in the circumferential direction is within the region where the outer circumferential recess 161 is formed. The second protruding portion 180 has a second notch 181 formed in a part of the circumferential direction, which connects the inside and the outside. A plurality of second notches 181 (two in FIG. 5) are formed in the circumferential direction. The circumferential position of the second notch 181 is within the region where the outer circumferential recess 161 is formed. In addition, the circumferential position of the second notch 181 is the same as the circumferential position of the first notch 171.

[0026] Because the modification member 150 has the above-described configuration, oil can flow between the first recess 111 of the piston 100 and the extension side recess 127 of the piston 100 (in other words, the second chamber Y2) via the first notch 171 of the first protruding portion 170, the inside of the cylindrical portion 160, and the second notch 181 of the second protruding portion 180, regardless of the opening degree of the first valve group 31 and the second valve group 32. The thickness of the first protruding portion 170 and the second protruding portion 180 is smaller than the thickness of the cylindrical portion 160. Therefore, the first end face and the second end face of the cylindrical portion 160 are subjected to the pressure of the oil.

[0027] [Function of piston portion 30] Next, the operation of the piston portion 30 according to the first embodiment will be specifically described. Figures 6, 7, and 8 are examples of cross-sectional views showing the flow of oil during extension, when the amount of protrusion of the rod 20 from the cylinder portion 10 increases. Figures 6, 7, and 8 show the oil flow when the piston speed is in the low, medium, and high speed ranges, respectively.

[0028] When the piston speed is in the low speed range and the pressure in the second chamber Y2 is higher than the pressure in the first chamber Y1 but not high enough to open the first valve group 31, as shown in FIG. 4, the second side end of the outer peripheral recess 161 of the change member 150 is located in the extension side recess 127 of the piston 100. Also, the first side end of the outer peripheral recess 161 of the change member 150 is located on the first side of the opening on the first side of the first hole 101 and is located in the first recess 111 of the piston 100. Therefore, the oil can flow between the first recess 111 of the piston 100 and the second chamber Y2 through the outer peripheral recess 161 of the change member 150. Also, the oil can flow between the first recess 111 of the piston 100 and the second chamber Y2 through the inside of the cylindrical portion 160 of the change member 150, the first notch 171 of the first protruding portion 170 (see FIG. 5), and the second notch 181 of the second protruding portion 180 (see FIG. 5).

[0029] When the piston speed increases and the pressure in the second chamber Y2 becomes higher than the pressure in the first chamber Y1 to the extent that the first valve group 31 is opened, the change member 150 moves toward the first side in response to the deflection of the first valve group 31. Then, as the change member 150 moves toward the first side, the area of ​​the flow path Rt1 through which the oil in the second chamber Y2 can flow to the first recess 111 of the piston 100 via the outer circumferential recess 161 of the change member 150 gradually decreases (see FIGS. 6 and 7).

[0030] 8, when the second end of the outer circumferential recess 161 of the change member 150 moves toward the first side until it is positioned at the bottom of the extension-side recess 127 of the piston 100, in other words, until the second end of the outer circumferential recess 161 is positioned at the second-side opening of the first hole 101, the oil in the second chamber Y2 stops flowing into the outer circumferential recess 161. As a result, the only flow path through which the oil in the second chamber Y2 can flow to the first recess 111 of the piston 100 is the flow path Rt2 passing through the inside of the cylindrical portion 160 of the change member 150.

[0031] FIG. 9 is a diagram showing a change in the flow channel area of ​​the expansion-side flow channel Rt. In Fig. 9, the horizontal axis indicates the piston speed, and the vertical axis indicates the flow path area of ​​the extension-side flow path Rt. Point A in Fig. 9 indicates the first speed, which is the first piston speed at which the first valve group 31 begins to open. Point B in Fig. 9 indicates the second speed, which is the piston speed at which the oil in the second chamber Y2 stops flowing into the outer circumferential recess 161.

[0032] As described above, when the piston speed is equal to or lower than the second speed due to the movement of the change member 150 to the first side in response to the piston speed, the flow path area of ​​the extension-side flow path Rt through which oil can flow becomes the total area of ​​the flow path Rt2 passing through the inside of the cylindrical portion 160 of the change member 150 and the flow path Rt1 passing through the outer circumferential recess 161, as shown in Fig. 9. When the piston speed exceeds the second speed, the flow path area of ​​the extension-side flow path Rt through which oil can flow becomes the area of ​​the flow path Rt2 passing through the inside of the cylindrical portion 160 of the change member 150, as shown in Fig. 9.

[0033] The area of ​​the flow path Rt1 through which the oil passes through the outer peripheral recess 161 is maximum when the opening degree of the first valve group 31 is zero, and decreases as the opening degree of the first valve group 31 increases and the change member 150 moves to the first side. Therefore, as shown in Fig. 9, the flow path area of ​​the extension-side flow path Rt through which the oil can flow gradually decreases as the piston speed increases in the range of the first speed or more and the second speed or less. For example, the flow path area (area of ​​the flow path Rt2) of the extension-side flow path Rt through which the oil can flow when the piston speed exceeds the second speed can be 1 / 3 of the flow path area (area of ​​the flow path Rt1 + area of ​​the flow path Rt2) when the piston speed is less than the first speed.

[0034] FIG. 10 is a diagram showing an example of the correlation between the piston speed and the damping force. 10, the solid line indicates the change in damping force of the piston portion 30 according to this embodiment. Also, the dashed line indicates the change in damping force of a piston portion having a configuration that does not include the modification member 150 compared to the piston portion 30 according to this embodiment (hereinafter, may be referred to as the "damping force according to a comparative example"). However, it is assumed that the flow path area is the same when the piston speed is less than the first speed.

[0035] As shown by the solid line in Fig. 10, the damping force of the piston section 30 according to this embodiment gradually becomes larger than that of the comparative example as the flow passage area through which oil can flow gradually becomes smaller when the piston speed is in the range of from the first speed to the second speed. When the piston speed exceeds the second speed, the flow passage area through which oil can flow becomes smaller (e.g., 1 / 3) than the flow passage area when the piston speed is less than the first speed, so that the damping force of the piston section 30 becomes significantly larger than that of the comparative example. As a result, when the piston speed increases during the extension stroke, such as when the wheel goes over a step, the kinetic energy at the time of full extension, for example, becomes smaller.

[0036] In Fig. 10, the two-dot chain line indicates the change in damping force when the damping force at high piston speeds is increased by increasing the plate thickness or number of layers of the valves constituting the first valve group 31, compared to the configuration of the damping force generating device that generates the damping force according to the comparative example. If the plate thickness or number of layers of the valves is increased, the damping force at low and medium piston speeds also increases, as shown by the two-dot chain line. Therefore, by providing the modification member 150 rather than increasing the plate thickness or number of layers of the valves, it is possible to increase the damping force at high piston speeds while suppressing the effect on the damping force characteristics at low and medium piston speeds.

[0037] As described above, the piston portion 30 is an example of a damping force generating device. The piston portion 30 includes the piston 100 that is held by the rod 20 and has a first hole 101 (an example of a hole) that extends in the center line direction (an example of the axial direction of the rod 20) to serve as an extension-side flow path Rt (an example of a flow path) for oil (an example of a fluid), and an annular first valve group 31 (an example of a valve) that opens and closes the first hole 101. The piston portion 30 also includes a change member 150 that is disposed in the first hole 101 and moves in the center line direction in accordance with the movement of the first valve group 31 to change the area of ​​the extension-side flow path Rt.

[0038] According to the piston section 30 configured as above, it is possible to suppress the influence on the damping force characteristics when the piston speed is in the low speed range or the medium speed range, while increasing the damping force when the piston speed is in the high speed range. In addition, since the area of ​​the extension side flow passage Rt can be changed steplessly by the change member 150, the fluctuation of the damping force becomes gentle, and it is possible to reduce the impact and abnormal noise generated in the suspension device 1 due to the damping force fluctuation. And, since the change member 150 is configured to be disposed in the first hole 101 of the piston 100, it is not necessary to form a bypass flow passage by, for example, cutting the rod 20. As a result, the above function can be realized at low cost.

[0039] Here, the change member 150 is a member extending in the center line direction, and forms a flow path Rt2 (an example of an internal flow path) configured by the inside of a cylindrical portion 160 as an example of a through hole penetrating the interior, and a flow path Rt1 (an example of an external flow path) configured by an outer peripheral recess 161 as an example of a recess recessed inward from the outer surface. This makes it possible to change the area of ​​the extension-side flow path Rt with a simple configuration by moving in the center line direction in conjunction with the movement of the first valve group 31.

[0040] The second-side end of the outer circumferential recess 161, which is located in the center line direction of the start point of the flow path Rt1 in the modification member 150, is closer to the first valve group 31 than the second-side opening of the cylindrical portion 160, which is located in the center line direction of the start point of the flow path Rt2 in the modification member 150. Therefore, when the pressure in the second chamber Y2 is higher than the pressure in the first chamber Y1, the second-side end face of the cylindrical portion 160 receives the pressure of the second chamber Y2 and is more likely to move toward the first side in conjunction with the movement of the first valve group 31.

[0041] In addition, the outer peripheral shape of the modification member 150 is preferably the same as the inner peripheral shape of the first hole 101. This makes it possible to reduce the gap between the outer peripheral surface of the modification member 150 and the inner peripheral surface of the first hole 101, and it is possible to highly reliably make the expansion-side flow passage Rt only the flow passage Rt2 when the piston speed is in the high-speed range. As a result, it is possible to highly reliably increase the damping force when the piston speed is in the high-speed range.

[0042] In addition, although the outer peripheral recess 161 of the modification member 150 is formed in the circumferential direction, the size of each of the outer peripheral recess 161 may be different. For example, by varying the circumferential size of each of the outer peripheral recess 161 while keeping the position of the outer peripheral recess 161 in the center line direction unchanged, the flow path area of ​​each of the multiple flow paths Rt1 can be made different. In addition, by varying the position of the outer peripheral recess 161 in the center line direction while keeping the circumferential size of the outer peripheral recess 161 unchanged, it is possible to provide variation in the change in the flow path area of ​​the flow path Rt1 in response to the movement of the first valve group 31. Therefore, by varying the size of the outer peripheral recess 161, it is possible to finely set the change in the damping force relative to the piston speed.

[0043] Moreover, the modifying members 150 may be disposed around the central hole 105, in other words, all of the multiple first holes 101 formed around the rod 20, or the modifying members 150 may be disposed in some of the multiple first holes 101. By changing the number of modifying members 150, it is possible to change the change in damping force relative to the piston speed.

[0044] In addition, in the above-described embodiment, the flow path area of ​​the expansion side flow path Rt is changed by disposing the change member 150 in the first hole 101, but the second hole 102 may be provided with a change member that moves in the center line direction in conjunction with the movement of the second valve group 32 and can change the flow path area of ​​the compression side flow path Rc.

[0045] <Second embodiment> FIG. 11 is an example of a view of the piston 200 according to the second embodiment as viewed from the second side. FIG. 12 is a diagram showing an example of a cross section of the piston portion 230 according to the second embodiment taken along line XII-XII in FIG. FIG. 13 is an example of a perspective view of a change member 250 according to the second embodiment. The piston section 230 according to the second embodiment differs from the piston section 30 according to the first embodiment in that it has a piston 200 corresponding to the piston 100 and a modified member 250 corresponding to the modified member 150. The following describes the differences from the first embodiment. The same reference numerals are used for the same parts in the first and second embodiments, and detailed descriptions thereof will be omitted.

[0046] The piston 200 is formed with a first hole 201 corresponding to the first hole 101 and an expansion-side recess 227 corresponding to the expansion-side recess 127. The first hole 201 has an arc shape with a certain width in the circumferential and radial directions when viewed in the center line direction, and a plurality of first holes 201 (three in FIG. 11 ) are formed around the central hole 105. The expansion-side recess 227 is composed of an inner inclined surface 228 formed inside the first hole 201 and an outer inclined surface 229 formed at a portion outside the first hole 201. The inner inclined surface 228 is a surface inclined from the second end surface 120 outward and toward the first side with respect to the center line direction. The outer inclined surface 229 is a surface inclined from the outer periphery of the piston 200 inward and toward the first side with respect to the center line direction.

[0047] (Modified part 250) The change member 250 is disposed in the first hole 201 and moves in the center line direction within the first hole 201. Therefore, like the first hole 201, the change member 250 has an arc shape with a constant width in the circumferential and radial directions when viewed in the center line direction, and the size of the change member 250 in the center line direction is the same as the size of the gap between the first end face 110 and the second end face 120 of the piston 200 in the center line direction. The modification member 250 has an arc-shaped portion 260, a first protrusion 270 protruding to the first side from the first end of the arc-shaped portion 260, and a second protrusion 280 protruding to the second side from the second end of the arc-shaped portion 260.

[0048] A central hole 261, which is a through hole in the center line direction, is formed in the center of the arc-shaped portion 260. The central hole 261 is formed in an arc shape when viewed in the center line direction. However, the radial size of the central hole 261 differs between a first central hole 262 formed on the first side and a second central hole 263 formed on the second side, with the first central hole 262 being larger than the second central hole 263.

[0049] Additionally, an inner through hole 264 is formed in the inner side wall of the arc-shaped portion 260 to allow oil to circulate between the outside and the first central hole 262. The inner through hole 264 is a rectangular hole when viewed radially from the inside. Additionally, an outer through hole 265 is formed in the outer side wall of the arc-shaped portion 260 to allow oil to circulate between the outside and the first central hole 262. The outer through hole 265 is a rectangular hole when viewed radially from the outside.

[0050] The first protruding portion 270 protrudes to the first side from a portion of the arc-shaped portion 260 that is outer than the first central hole 262. The first protruding portion 270 is provided over the entire circumferential area of ​​the arc-shaped portion 260. A first side through hole 271 is formed in the first protruding portion 270 to allow oil to flow between the outer side and the inner side of the first protruding portion 270. The first side through hole 271 is a rectangular hole when viewed radially from the outer side.

[0051] The second protruding portions 280 protrude toward the second side from both circumferential ends of the arc-shaped portion 260. Therefore, oil can pass between the two second protruding portions 280 and reach the second central hole 263 of the arc-shaped portion 260.

[0052] The distance from the tip of the first protruding portion 270 to the tip of the second protruding portion 280, which is the size in the center line direction of the change member 250 configured as described above, is the same as the size in the center line direction between the first end face 110 and the second end face 120 of the piston 200. When the opening degrees of the first valve group 31 and the second valve group 32 are zero, the first protruding portion 270 of the change member 250 comes into contact with the first valve group 31 and the second protruding portion 280 comes into contact with the second valve group 32, and the movement of the change member 250 to the first side is restricted by the first valve group 31 and the movement of the change member 250 to the second side is restricted by the second valve group 32.

[0053] Regardless of the opening degree of the first valve group 31 and the second valve group 32, oil can flow between the first recess 111 of the piston 200 and the extension side recess 227 of the piston 200 (in other words, the second chamber Y2) through the first side through hole 271 of the first protrusion 270, the central hole 261 of the arc-shaped portion 260, and between the two second protrusions 280.

[0054] [Function of the piston portion 230] Next, the operation of the piston portion 230 according to the second embodiment will be specifically described. Figures 14 and 15 are examples of cross-sectional views showing the flow of oil during extension, when the amount of protrusion of the rod 20 from the cylinder portion 10 increases. Figures 14 and 15 show the oil flow when the piston speed is in the low / medium speed range and the high speed range, respectively.

[0055] When the piston speed is in the low speed range and the pressure in the second chamber Y2 is higher than the pressure in the first chamber Y1 but not high enough to open the first valve group 31, as shown in FIG. 12, the second side end of the outer through hole 265 of the arc-shaped portion 260 of the change member 250 is located on the second side of the first side end of the outer inclined surface 229 of the piston 200. Therefore, oil can flow between the first recess 111 of the piston 200 and the second chamber Y2 through the outer through hole 265 of the change member 250. In addition, oil can flow between the second chamber Y2 and the first recess 111 of the piston 200 through the two second protruding portions 280 of the change member 250, the central hole 261 of the arc-shaped portion 260, and the first side through hole 271 of the first protruding portion 270.

[0056] When the piston speed increases and the pressure in the second chamber Y2 becomes higher than the pressure in the first chamber Y1 to open the first valve group 31, the change member 250 moves toward the first side in response to the deflection of the first valve group 31. Then, as the change member 250 moves toward the first side, the area of ​​the flow path Rt1 through which the oil in the second chamber Y2 can flow to the first recess 111 of the piston 200 via the outer through-hole 265 of the change member 250 gradually decreases (see FIG. 14).

[0057] 15 , when the second side end of the outer through hole 265 of the change member 250 moves toward the first side until it is positioned at the first side end of the outer inclined surface 229 of the piston 200, the oil in the second chamber Y2 stops flowing into the central hole 261 through the outer through hole 265. As a result, the only flow path through which the oil in the second chamber Y2 can flow to the first recess 111 of the piston 200 is the flow path Rt2 through the inside of the central hole 261 of the change member 250.

[0058] Therefore, in the piston portion 230 according to the second embodiment, the flow path area of ​​the extension-side flow path Rt through which oil can flow during extension also changes as shown in FIG. As a result, the correlation between the piston speed and the damping force is as shown by the solid line in FIG. Therefore, rather than increasing the plate thickness or number of layers of the valve, by providing the modification member 250, it is possible to increase the damping force in the high speed range while suppressing the effect on the damping force characteristics when the piston speed is in the low speed or medium speed range.

[0059] As described above, the piston portion 230 is an example of a damping force generating device. The piston portion 230 includes the piston 200 that is held by the rod 20 and has the first hole 201 (an example of a hole) that extends in the center line direction (an example of the axial direction of the rod 20) to become an extension-side flow path Rt (an example of a flow path) for oil (an example of a fluid), and the annular first valve group 31 (an example of a valve) that opens and closes the first hole 201. The piston portion 230 also includes a change member 250 that is disposed in the first hole 201 and moves in the center line direction in accordance with the movement of the first valve group 31 to change the area of ​​the extension-side flow path Rt.

[0060] The piston section 230 configured as above can increase the damping force when the piston speed is in the high speed range while suppressing the influence on the damping force characteristics when the piston speed is in the low speed range or the medium speed range. In addition, since the area of ​​the extension-side flow passage Rt can be steplessly switched by the change member 250, the fluctuation of the damping force becomes gentle, and it is possible to reduce the impact and abnormal noise generated in the suspension device 1 due to the damping force fluctuation. And, since the change member 250 is configured to be disposed in the first hole 201 of the piston 200, the above function can be realized at low cost.

[0061] The change member 250 is a member extending in the center line direction, and forms a flow path Rt2 (an example of an internal flow path) configured by a central hole 261 (an example of a through hole) of a circular arc-shaped portion 260 penetrating the inside in the center line direction, and a flow path Rt1 (an example of an external flow path) configured by an outer through hole 265 (an example of an intersecting hole) penetrating from the outer surface in a direction intersecting the center line direction and communicating with the central hole 261. This makes it possible to change the area of ​​the extension-side flow path Rt with a simple configuration by moving in the center line direction in conjunction with the movement of the first valve group 31.

[0062] The second side end of the outer through hole 265, which is located in the center line direction of the start point of the flow path Rt1 in the modification member 250, is closer to the first valve group 31 than the second side opening of the central hole 261, which is located in the center line direction of the start point of the flow path Rt2 in the modification member 250. Therefore, when the pressure in the second chamber Y2 is higher than the pressure in the first chamber Y1, the second side end face of the arc-shaped portion 260 receives the pressure of the second chamber Y2 and becomes more likely to move to the first side in conjunction with the movement of the first valve group 31.

[0063] In addition, the outer peripheral shape of the change member 250 is preferably the same as the inner peripheral shape of the first hole 201. This makes it possible to reduce the gap between the outer peripheral surface of the change member 250 and the inner peripheral surface of the first hole 201, and it is possible to highly reliably make the expansion-side flow passage Rt only the flow passage Rt2 when the piston speed is in the high-speed range. As a result, it is possible to highly reliably increase the damping force when the piston speed is in the high-speed range.

[0064] Note that the outer through-hole 265 of the change member 250 may be formed in a plurality of ways. When the outer through-hole 265 is formed in a plurality of ways, the sizes of the outer through-holes 265 may be different from each other. For example, by varying the circumferential sizes of the outer through-holes 265 while keeping the centerline positions of the outer through-holes 265 the same, the flow path areas of the multiple flow paths Rt1 can be made different from each other. By varying the centerline positions of the outer through-holes 265 while keeping the circumferential sizes of the outer through-holes 265 the same, the flow path area of ​​the flow path Rt1 relative to the movement of the first valve group 31 can be varied. Therefore, by varying the sizes of the outer through-holes 265, the change in the damping force relative to the piston speed can be finely set.

[0065] Moreover, the modifying members 250 may be disposed around the central hole 105, in other words, all of the multiple first holes 201 formed around the rod 20, or the modifying members 250 may be disposed in some of the multiple first holes 201. By changing the number of modifying members 250, it is possible to change the change in damping force relative to the piston speed.

[0066] In addition, in the above-described embodiment, the flow path area of ​​the expansion side flow path Rt is changed by disposing the change member 250 in the first hole 201, but the second hole 102 may be provided with a change member that moves in the center line direction in conjunction with the movement of the second valve group 32 and can change the flow path area of ​​the compression side flow path Rc. [Explanation of symbols]

[0067] 1...suspension device, 2...shock absorber, 3...spring, 10...cylinder portion, 11...cylinder, 12...outer cylinder, 20...rod, 30, 230...piston portion (an example of a damping force generating device), 31...first valve group (an example of a valve), 32...second valve group, 100, 200...piston, 101, 201...first hole (an example of a hole), 150, 250...modifying member, 160...cylindrical portion, 161...peripheral recess (an example of a recess), 260...arc-shaped portion, 261...central hole (an example of a through hole), 265...outer through hole (an example of an intersecting hole), Rt...extension side flow path (an example of a flow path), Rt1...flow path (an example of an external flow path), Rt2...flow path (an example of an internal flow path), Y1...first chamber, Y2...second chamber

Claims

1. a piston held by the rod and having a hole extending in the axial direction of the rod to serve as a fluid passage; an annular valve for opening and closing the hole; a change member that is disposed in the hole and moves in the axial direction in response to movement of the valve to change the area of ​​the flow path; A damping force generating device comprising:

2. The change member is a member extending in the axial direction, and forms an internal flow path formed by a through hole penetrating the interior in the axial direction, and an external flow path formed by a recess recessed inward from an outer surface. The damping force generating device according to claim 1 .

3. a position of the outer flow passage in the modification member in the axial direction is closer to the valve than a position of the inner flow passage in the modification member in the axial direction; The damping force generating device according to claim 2 .

4. The external flow passage is provided in plurality around the internal flow passage, and the flow passage areas of the plurality of internal flow passages are different from each other. The damping force generating device according to claim 2 .

5. The outer circumferential shape of the change member is the same as the inner circumferential shape of the hole. The damping force generating device according to claim 1 .

6. The holes are formed in a plurality of portions around the rod, The change member is disposed in some of the holes. The damping force generating device according to claim 1 .

7. The modification member is a member extending in the axial direction, and forms an internal flow path formed by a through hole penetrating the interior in the axial direction, and an external flow path formed by a cross hole penetrating from an outer surface in a direction intersecting the axial direction and communicating with the through hole. The damping force generating device according to claim 1 .

8. A shock absorber including the damping force generating device according to any one of claims 1 to 7; A spring disposed around the shock absorber; A suspension device comprising:

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