Sintered body and method for manufacturing a sintered body

Abstract

The sintered body comprises: a cylindrical base portion having a side portion and, with respect to the side portion, a base portion end surface that is continuous through a first arc-shaped portion or a first inclined portion forming an obtuse angle; an insertion hole into which the rod of the buffer is inserted at the center; a boss portion protruding axially from the base portion end surface and provided around the insertion through hole; a plurality of first through holes and a plurality of second through holes located on the outer side of the boss portion and arranged intersectingly along the circumferential direction; and a round portion protruding axially from the base portion end surface and provided in plurality, forming a seal surrounding the first through hole, on which the valve body of the piston is seated or spaced apart. The round portion is provided along the outer circumference of the base portion end surface and has an outer edge portion that is continuous with respect to the side portion through a second arc-shaped portion or a second inclined portion forming an obtuse angle, and a set of arm portions extending from both ends of the outer edge portion toward the boss portion.

Description

Technology Field

[0001] The present invention relates to a sintered body and a method for manufacturing a sintered body.

[0002] The present application claims priority based on Patent Application No. 2024-025202 filed in Japan on February 22, 2024, and incorporates the contents thereof herein. Background Technology

[0003] The damper generates a damping force by moving a piston installed on a piston rod within a cylinder (e.g., see Patent Document 1). Prior art literature

[0004] Patent Document 1: Japanese Patent Publication No. 2021-063557 The problem to be solved

[0005] However, in this type of buffer, a sintered body constituting the piston is used, but there is a desire to suppress the increase in costs regarding such sintered bodies.

[0006] The objective of the present invention is to provide a sintered body and a method for manufacturing a sintered body, which makes it possible to suppress cost increase. means of solving the problem

[0007] The present invention has adopted the following embodiments to solve the above problem and achieve the corresponding objective.

[0008] That is, one aspect of the present invention is,

[0009] As a sintered body constituting a piston used in a buffer,

[0010] A cylindrical base portion formed having a side portion, and a base portion end surface that is continuous with respect to the side portion through a first arc-shaped portion or a first inclined portion forming an obtuse angle;

[0011] An insertion through hole in the center through which the rod of the above buffer is inserted and penetrates;

[0012] A boss portion protruding axially from the end surface of the base portion and provided around the insertion through hole;

[0013] A plurality of first through holes and a plurality of second through holes located on the outer side of the above boss portion and alternately arranged along the circumferential direction;

[0014] A plurality of round portions are provided protruding axially from the end surface of the base portion, surrounding the first through hole to form a seal, and on which the valve body of the piston is seated or spaced apart.

[0015] Equipped with,

[0016] The above round part,

[0017] An outer edge portion formed along the outer circumference of the end surface of the base portion and continuous with respect to the side portion through a second arc-shaped portion or a second inclined portion forming an obtuse angle, and

[0018] A pair of arm portions extending from both ends of the outer periphery toward the boss portion

[0019] has

[0020] In addition, another aspect of the present invention is,

[0021] A method for manufacturing a sintered body constituting a piston used in a buffer,

[0022] A compression process for forming a molded article having a base portion and a round portion by compressing powdered metal with a mold, and

[0023] A sintering process for heating the above-mentioned molded product to process it into a sintered body, and

[0024] Removal process for removing a portion of the above sintered body

[0025] having,

[0026] The above base part,

[0027] A cylindrical main body, and

[0028] A first inclined portion that extends annularly outward in the diameter direction from the main body portion and gradually decreases in the axial size of the base portion, and

[0029] A flat portion extending outward in the diameter direction from the first inclined portion above

[0030] Having,

[0031] The round portion on which the valve body of the above piston is seated or separated,

[0032] It has an outer edge portion adjacent to a second inclined portion on the first inclined portion, and a set of arm portions extending from both ends of the outer edge portion toward the center of the base portion, and also,

[0033] A plurality of components are provided protruding axially from one end surface of the main body, and

[0034] In the above removal process,

[0035] By deleting the portion extending outward in the diameter direction from the predetermined position of the first inclined portion,

[0036] In addition to forming a side portion which is a perimeter plane of the base portion,

[0037] On the end surface of the base portion, an arc-shaped portion that is continuous with respect to the side portion, which is the remaining portion of the first inclined portion, or an inclined portion that forms an obtuse angle continuously with respect to the side portion is formed. Effects of the invention

[0038] According to each of the above embodiments of the present invention, it is possible to suppress the increase in costs. Brief explanation of the drawing

[0039] FIG. 1 is a cross-sectional view showing a buffer comprising a sintered body according to one embodiment of the present invention. The symbol CL indicates a central axis shared by the buffer and the sintered body. FIG. 2 is a partial enlarged side view showing the main part of the piston rod of a buffer containing a copper sintered body. Here, (a) is a view of the copper main part from one direction, and (b) is a view of (a) from the arrow O. FIG. 3 is a drawing showing the first piston and the second piston of a buffer including a copper sintered body, and is a partial enlarged cross-sectional view showing part P of FIG. 1. FIG. 4 is a drawing showing the second piston of a buffer including a copper sintered body, and is a partial enlarged cross-sectional view showing part Q of FIG. 3. FIG. 5 is a plan view showing the second piston body, which is a copper sintered body. FIG. 6 is a lower view showing the second piston body, which is a copper sintered body. FIG. 7 is a partial enlarged cross-sectional view showing the second piston body, which is a copper sintered body. FIG. 8 is a partial enlarged cross-sectional view showing the second piston body, which is a copper sintered body. FIG. 9 is a partial enlarged plan view showing the second piston body, which is a copper sintered body. FIG. 10 is a partially enlarged perspective view showing a part of the second piston body, which is a copper sintered body. Figure 11 is a partial enlarged view showing the second piston body, which is a copper sintered body. FIG. 12 is a partial enlarged cross-sectional view showing a molded product of a second piston body that is a copper sintered body. FIG. 13 is a partial enlarged cross-sectional view showing a molded product of the second piston body, which is a copper sintered body. FIG. 14 is a partial enlarged cross-sectional view showing the molded product and mold of the second piston body, which is a copper sintered body. FIG. 15 is a partial enlarged cross-sectional view showing the molded product and the mold. FIG. 16 is a partially enlarged cross-sectional view showing a modified example of the second piston body, which is the sintered body. FIG. 17 is a partially enlarged cross-sectional view showing a modified example of the second piston body, which is a copper sintered body. Specific details for implementing the invention

[0040] An embodiment of the sintered body and the method for manufacturing the same according to the present invention will be described based on the drawings. In addition, the symbol CL in each drawing indicates a central axis shared by the buffer and the sintered body.

[0041] The shock absorber (1) comprising the sintered body of the present embodiment is used in the suspension system of a railway vehicle or a two-wheeled or four-wheeled vehicle. Specifically, the shock absorber (1) is used in the suspension system of a four-wheeled vehicle. As shown in FIG. 1, the shock absorber (1) is a double-tube type shock absorber having a cylinder (4) having an inner tube (2) and an outer tube (3). The inner tube (2) is cylindrical. The outer tube (3) is tubular with a bottom having a larger diameter than the inner tube (2). The outer tube (3) is provided coaxially with the inner tube (2) on the outer side in the diameter direction of the inner tube (2). The space between the outer tube (3) and the inner tube (2) is a reservoir chamber (5).

[0042] The outer tube (3) has a tube portion (8) and a bottom portion (9). The tube portion (8) is cylindrical. The bottom portion (9) closes one end of the tube portion (8) in the axial direction. The side of the tube portion (8) opposite to the bottom portion (9) is an opening. An attachment eye (10) is fixed to the side of the bottom portion (9) opposite to the tube portion (8) in the axial direction.

[0043] The buffer (1) is equipped with a valve body (12) and a rod guide (13). The valve body (12) is annular and is provided on the axial bottom portion (9) side of the inner tube (2) and outer tube (3). The rod guide (13) is annular and is provided on the opposite side from the axial bottom portion (9) of the inner tube (2) and outer tube (3). The valve body (12) constitutes a base valve (15). The valve body (12) has a stepped outer circumference and is positioned on the bottom portion (9) in a radial direction relative to the tube portion (8) at its large diameter portion. The rod guide (13) also has a stepped outer circumference and is positioned in a radial direction relative to the tube portion (8) at its large diameter portion.

[0044] One end of the inner tube (2) in the axial direction is fitted to the small diameter portion of the outer circumference of the valve body (12). One end of the inner tube (2) in the axial direction is connected to the bottom portion (9) of the outer tube (3) through the valve body (12). Additionally, the other end of the inner tube (2) in the axial direction is fitted to the small diameter portion of the outer circumference of the rod guide (13). The other end of the inner tube (2) in the axial direction is connected to the tube portion (8) of the outer tube (3) through the rod guide (13). In this state, the inner tube (2) is positioned in the radial direction relative to the outer tube (3). Here, the valve body (12) and the bottom portion (9) are connected to the inner tube (2) and the outer tube (3). Accordingly, the space between the valve body (12) and the bottom part (9) forms a reservoir chamber (5), just like the space between the inner tube (2) and the outer tube (3).

[0045] The buffer (1) is equipped with a seal member (18). The seal member (18) is provided on the side opposite to the bottom portion (9) of the rod guide (13). This seal member (18) is also fitted to the inner circumference of the tube portion (8), just like the rod guide (13). A catch portion (19) is formed at the end opposite to the bottom portion (9) of the tube portion (8). The catch portion (19) is formed by plastically deforming the tube portion (8) inwardly in the radial direction through a caulking process such as curl processing. The seal member (18) is clamped between this catch portion (19) and the rod guide (13). The seal member (18) is used to close the opening of the outer tube (3), and specifically, it is an oil seal.

[0046] The buffer (1) is equipped with a first piston body (21). The first piston body (21) is slidably installed within the cylinder (4). The first piston body (21) is slidably installed in the inner tube (2) of the cylinder (4). The first piston body (21) divides the inner tube (2) into two chambers: a first chamber (22) (upstream area) and a second chamber (23). The first chamber (22) is provided between the first piston body (21) and the rod guide (13) within the inner tube (2). The second chamber (23) is provided between the first piston body (21) and the valve body (12) within the inner tube (2). The second chamber (23) is divided into a reservoir chamber (5) by the valve body (12). An oil liquid (L), which is a fluid, is sealed in the first chamber (22) and the second chamber (23) within the cylinder (4). Inside the cylinder (4), gas (G) and oil (L), which are fluids, are sealed in the reservoir chamber (5). Therefore, the buffer (1) is a hydraulic buffer using the oil (L), which is a fluid.

[0047] The buffer (1) is equipped with a rod (31), which is a rod-shaped axial member. One end of the rod (31) in the axial direction is positioned inside the cylinder (4) and is connected to and fixed to the first piston body (21). The other end of the rod (31) in the axial direction extends outside the cylinder (4). The rod (31) is made of metal and penetrates the first chamber (22). The rod (31) does not penetrate the second chamber (23). Therefore, the first chamber (22) is the rod-side chamber through which the rod (31) penetrates. The second chamber (23) is the bottom-side chamber on the bottom part (9) side of the cylinder (4).

[0048] The first piston body (21) and the rod (31) move as a single unit. During the extension stroke of the buffer (1) in which the rod (31) increases the amount of protrusion from the cylinder (4), the first piston body (21) moves toward the first chamber (22). During the contraction stroke of the buffer (1) in which the rod (31) reduces the amount of protrusion from the cylinder (4), the first piston body (21) moves toward the second chamber (23).

[0049] The rod guide (13) and the seal member (18) are both toroidal. The rod (31) is slidably inserted and penetrates into each of the rod guide (13) and the seal member (18) and extends from the inside to the outside of the cylinder (4). One end portion of the rod (31) in the axial direction is fixed to the first piston body (21) inside the cylinder (4). The other end portion of the rod (31) in the axial direction extends to the outside of the cylinder (4) through the rod guide (13) and the seal member (18).

[0050] The rod guide (13) supports the rod (31) relative to the cylinder (4) so ​​that it can move in the axial direction while restricting its movement in the diameter direction. The rod guide (13) guides the axial movement of the rod (31). The outer circumference of the seal member (18) is in close contact with the outer casing (3) of the cylinder (4). The inner circumference of the seal member (18) slides in contact with the outer circumference of the rod (31) that moves in the axial direction. By doing so, the seal member (18) prevents the oil liquid (L) or gas (G) inside the cylinder (4) from leaking out.

[0051] The rod (31) has a main shaft portion (32) and an attachment shaft portion (33). The attachment shaft portion (33) has a smaller diameter than the main shaft portion (32). The main shaft portion (32) of the rod (31) is slidably fitted to the rod guide (13) and the seal member (18). The attachment shaft portion (33) of the rod (31) is positioned within the cylinder (4) and connected to the first piston body (21), etc. The end of the main shaft portion (32) on the side of the attachment shaft portion (33) is widened in the direction perpendicular to the axis.

[0052] As shown in FIG. 2, the attachment shaft (33) has a base-side cylindrical part (41), an intermediate shaft part (42), a tip-side cylindrical part (43), and a screw shaft part (44). In the attachment shaft (33), the base-side cylindrical part (41), the intermediate shaft part (42), the tip-side cylindrical part (43), and the screw shaft part (44) are arranged in this order from the axial main shaft part (32).

[0053] The base-side cylindrical portion (41) is a cylindrical portion and is provided on the side of the main shaft portion (32) in the axial direction of the attachment shaft portion (33), that is, on the base side. The outer surface (41a) of the base-side cylindrical portion (41) in the diameter direction is formed as a cylindrical surface that is continuous along the entire circumference in the circumferential direction of the base-side cylindrical portion (41).

[0054] The tip-side cylindrical portion (43) is a cylindrical portion and is provided on the side opposite to the main shaft portion (32), i.e., the tip-side, compared to the base-side cylindrical portion (41) in the axial direction of the attachment shaft portion (33). The outer surface (43a) of the tip-side cylindrical portion (43) in the diameter direction is formed as a cylindrical surface that is continuous along the entire circumference in the circumferential direction of the tip-side cylindrical portion (43). The outer surface (43a) of the tip-side cylindrical portion (43) is coaxial with the outer surface (41a) of the base-side cylindrical portion (41). In this embodiment, the outer surface (43a) of the tip-side cylindrical portion (43) has the same diameter as the outer surface (41a) of the base-side cylindrical portion (41), but it may not have the same diameter.

[0055] The intermediate shaft portion (42) is provided at an intermediate position in the axial direction of the attachment shaft portion (33). The intermediate shaft portion (42) has a pair of outer cross-sectional surfaces (42a), a base-side circumferential groove (51), a pair of axial grooves (52), and a tip-side circumferential groove (53) on the outer side in the radial direction.

[0056] A pair of outer end surfaces (42a) both form the shape of a part of a cylindrical surface that is coaxial and identical in diameter with the outer surface (41a) of the base-side cylinder (41) and the outer surface (43a) of the tip-side cylinder (43). In other words, a pair of outer end surfaces (42a) are arranged on the same cylindrical surface as the outer surface (41a) of the base-side cylinder (41) and the outer surface (43a) of the tip-side cylinder (43). A pair of outer end surfaces (42a) are positioned 180 degrees apart in the circumferential direction of the intermediate shaft (42). However, in this embodiment, the outer end surfaces (42a) are a pair of two locations with a 180-degree phase difference, but are not limited to this. For example, the outer cross-section (42a) may be formed at one location in the circumferential direction of the intermediate shaft, or at three or more locations. In addition, when multiple are installed, the phases may be symmetrical as in the present embodiment, or asymmetrical.

[0057] The base-side circumferential groove (51) is provided at the end of the base-side cylinder portion (41) in the axial direction of the intermediate shaft portion (42). The base-side circumferential groove (51) is recessed inward in the radial direction of the base-side circumferential groove (51) and the intermediate shaft portion (42) from the outer surface (41a) of the base-side cylinder portion (41) and a pair of outer end surfaces (42a) of the intermediate shaft portion (42). The base-side circumferential groove (51) is an annular shape that is continuous along the entire circumference in the periphery direction of the intermediate shaft portion (42).

[0058] The tip-side circumferential groove (53) is provided at the end of the tip-side cylinder portion (43) in the axial direction of the intermediate shaft portion (42). The tip-side circumferential groove (53) is recessed inward in the radial direction of the tip-side cylinder portion (43) and the intermediate shaft portion (42) from the outer surface (43a) of the tip-side cylinder portion (43) and a pair of outer end surfaces (42a) of the intermediate shaft portion (42). The tip-side circumferential groove (53) is an annular shape that is continuous along the entire circumference in the circumferential direction of the intermediate shaft portion (42).

[0059] A pair of axial grooves (52) are recessed inwardly in the radial direction of the intermediate shaft (42) from a pair of outer end surfaces (42a). A pair of axial grooves (52) have the same shape, and the bottom surface of the inner side in the radial direction of the intermediate shaft (42) is a plane that widens perpendicularly to the radial direction of the intermediate shaft (42). A pair of axial grooves (52) extend in the axial direction of the rod (31). A pair of axial grooves (52) are provided with a 180-degree phase difference in the circumferential direction of the intermediate shaft (42) and widen parallel to each other. In the intermediate shaft (42), the outer end surfaces (42a) and the axial grooves (52) are alternately arranged in the circumferential direction of the intermediate shaft (42). A pair of axial grooves (52) have one end in the axial direction of the intermediate shaft (42) opened in the base-side circumferential groove (51), and the other end in the axial direction of the intermediate shaft (42) opened in the tip-side circumferential groove (53).

[0060] As shown in FIG. 3, the passage within the base side circumferential groove (51), the passage within a pair of axial grooves (52), and the passage within the tip side circumferential groove (53) form an axial passage (54) that extends in the axial direction of the rod (31).

[0061] The screw shaft portion (44) is provided at the end of the shaft portion (44), which is opposite to the main shaft portion (32) in the axial direction of the attachment shaft portion (33), that is, at the tip end. The screw shaft portion (44) is cylindrical in shape, and a male screw (57) is formed on the outer side in the diameter direction.

[0062] The shock absorber (1) is supported by the vehicle body, for example, by having the protruding part shown in FIG. 1 from the cylinder (4) of the rod (31) positioned in the upper vertical direction. At that time, the shock absorber (1) is connected to the wheel side by having the attachment eye (10), which is fixed to the bottom part (9) of the cylinder (4), positioned in the lower vertical direction. If the shock absorber (1) is a single-tube type, it is also possible to configure it so that, conversely, the cylinder (4) side is supported by the vehicle body and the rod (31) is connected to the wheel side.

[0063] As shown in FIG. 3, the first piston body (21) is composed of a metal body member (61) supported by a rod (31) and an annular friction member (62) integrally mounted on the outer surface of the body member (61) and sliding inside the inner tube (2).

[0064] In the main body member (61), a plurality of passage holes (71) (in FIG. 3, only one is shown due to the cross-sectional view) and an annular passage groove (72) that connects the ends opposite to the first chamber (22) of these passage holes (71) are formed. Additionally, in the main body member (61), a plurality of passage holes (75) (in FIG. 3, only one is shown due to the cross-sectional view) and an annular passage groove (76) that connects the ends of the first chamber (22) of these passage holes (75) are formed. The plurality of passage holes (71) are formed in the circumferential direction of the main body member (61), with one passage hole (75) between them.

[0065] A passage within a plurality of passage holes (71) and a passage within a passage groove (72) form a piston passage (81) that penetrates the first piston body (21) in the axial direction of the first piston body (21) and is capable of communicating the first chamber (22) and the second chamber (23). A passage within a plurality of passage holes (75) and a passage within a passage groove (76) form a piston passage (82) that penetrates the first piston body (21) in the axial direction of the first piston body (21) and is capable of communicating the first chamber (22) and the second chamber (23).

[0066] A valve mechanism (85), which is a valve that opens and closes the piston passage (81) to generate damping force, is provided in the piston passage (81). The valve mechanism (85) is positioned on the side of the second chamber (23), which is one end of the axial direction of the first piston body (21), and is attached to the rod (31). By positioning the valve mechanism (85) on the side of the second chamber (23), the oil liquid (L) flowing out from the first chamber (22) flows toward the second chamber (23) during the movement of the first piston body (21) toward the first chamber (22), that is, the extension stroke. The valve mechanism (85) provided for the piston passage (81) is an extension-side valve mechanism that generates damping force by suppressing the flow of oil liquid (L) from the extension-side piston passage (81) to the second chamber (23).

[0067] In the piston passage (82), a valve mechanism (86) is provided, which is a valve that opens and closes the piston passage (82) to generate damping force. The valve mechanism (86) is positioned on the side of the first chamber (22), which is the other end in the axial direction of the first piston body (21), and is attached to the rod (31). By positioning the valve mechanism (86) on the side of the first chamber (22), the piston passage (82) allows the oil liquid (L) flowing out from the second chamber (23) to flow toward the first chamber (22) during the movement of the first piston body (21) toward the second chamber (23), that is, the contraction stroke. The valve mechanism (86) provided for the piston passage (82) is configured as a contraction-side valve mechanism that generates damping force by suppressing the flow of oil liquid (L) from the contraction-side piston passage (82) to the first chamber (22).

[0068] By the above, the piston passage (81) and the piston passage (82) are connected so that the fluid oil (L) flows between the first chamber (22) and the second chamber (23) by the movement of the first piston body (21), and the oil (L) passes through the piston passage (81) when the rod (31) and the first piston body (21) move toward the extension side, and the oil (L) passes through the piston passage (82) when the rod (31) and the first piston body (21) move toward the contraction side.

[0069] The main body member (61) comprises two members: a first component (91) and a second component (92). The first component (91) forms the portion on the second seal (23) side in the axial direction of the main body member (61), and the second component (92) forms the portion on the first seal (22) side in the axial direction of the main body member (61).

[0070] The first component (91) has a roughly disc shape. In the center of the diameter direction of the first component (91), a circular fixing hole (101) is formed penetrating the first component (91) in the axial direction of the first component (91). The fixing hole (101) is a portion of the first component (91) for fitting the attachment shaft portion (33) of the rod (31).

[0071] On the end surface of the second component (92) side in the axial direction of the first component (91), a passage groove (102) extending in the radial direction of the first component (91) is formed. The passage within the passage groove (102) is a piston internal passage (103) communicating with the piston passage (81).

[0072] The above-mentioned passage groove (72) is formed at the end of the second chamber (23) side in the axial direction of the first component (91). At the end of the second chamber (23) side in the axial direction of the first component (91), an annular valve seat portion (105) constituting part of the valve mechanism (85) is formed radially outward from the opening of the second chamber (23) side of the passage groove (72). Additionally, at the end of the second chamber (23) side in the axial direction of the main body member (61), a boss portion (106) is formed radially inward from the opening of the second chamber (23) side of the passage groove (72).

[0073] In the first component (91), a connecting convex portion (108) is formed that protrudes outward along the axial direction of the first component (91) from the end surface on the side of the second component (92) in the axial direction of the first component (91). The connecting convex portion (108) is partially provided in the circumferential direction of the first component (91).

[0074] The second component (92) has a roughly disc shape. In the center of the second component (92) in the diameter direction, a circular fixing hole (111) is formed penetrating the second component (92) in the axial direction of the second component (92). The fixing hole (111) is a portion of the second component (92) for fitting the attachment shaft portion (33) of the rod (31).

[0075] The above-mentioned passage groove (76) is formed at the end of the first chamber (22) side in the axial direction of the second component (92). At the end of the first chamber (22) side in the axial direction of the second component (92), an annular valve seat portion (115) constituting part of the valve mechanism (86) is formed radially outward from the opening of the first chamber (22) side of the passage groove (76). Additionally, at the end of the first chamber (22) side in the axial direction of the main body member (61), a boss portion (116) is formed radially inward from the opening of the first chamber (22) side of the passage groove (76).

[0076] In the second component (92), a coupling recess (118) is formed that is recessed inwardly along the axial direction of the second component (92) from the end surface on the side of the first component (91) in the axial direction of the second component (92). The coupling recess (118) is partially provided in the circumferential direction of the second component (92).

[0077] The first component (91) and the second component (92) are connected by connecting the connecting convex portion (108) of the first component (91) to the connecting concave portion (118) of the second component (92). By doing so, the first component (91) and the second component (92) are connected in a circumferentially positioned state to form a piston passage (81) and a piston passage (82). In this state, a friction member (62) is placed on the radially outer side of the first component (91) and the second component (92). By doing so, the first component (91) and the second component (92) are integrated to become a main body member (61), and the first component (91), the second component (92), and the friction member (62) are integrated to become a first piston main body (21).

[0078] In the first configuration (91), an opening on the second chamber (23) side of the piston passage (82) on the contracting side is arranged on the outer side in the radial direction of the valve seat portion (105). Additionally, in the second configuration (92), an opening on the first chamber (22) side of the piston passage (81) on the extending side is arranged on the outer side in the radial direction of the valve seat portion (115).

[0079] The first piston body (21) has a fixing hole (111) fitted to the outer surface (41a) shown in FIG. 2 of the base-side cylindrical portion (41) of the rod (31), and a fixing hole (101) shown in FIG. 3 fitted to a pair of outer surface surfaces (42a) shown in FIG. 2 of the intermediate shaft portion (42) of the rod (31). In other words, the rod (31) has a base-side cylindrical portion (41) which is a cylindrical part that is inserted and penetrated into the fixing hole (111) shown in FIG. 3. In the first piston body (21), the piston internal passage (103) is arranged so as to overlap with the base-side circumferential groove (51) of the rod (31) in the axial direction of the rod (31). By doing so, even without circumferential phase alignment with respect to the rod (31) of the first piston body (21), the internal path (103) of the piston can be connected to the axial path (54) of the rod (31).

[0080] The valve mechanism (86) on the reduction side includes the valve seat portion (115) of the first piston body (21). The valve mechanism (86) has one disc (121) and a plurality of discs (122) in order from the axial direction of the first piston body (21). On the side opposite to the disc (121) in the axial direction of the plurality of discs (122), one disc (123), one disc (124), and one annular member (125) are provided in order from the side of the plurality of discs (122). The discs (121 to 124) and the annular member (125) are all circular flat plates having holes, and all of them are fitted with the outer surface (41a) shown in FIG. 2 of the base side cylinder portion (41) of the attachment shaft portion (33) on the inside.

[0081] As shown in FIG. 3, the disc (121) has an outer diameter that is larger than the outer diameter of the boss portion (116) of the first piston body (21) and smaller than the inner diameter of the valve seat portion (115). The disc (121) is in constant contact with the boss portion (116).

[0082] Among the multiple discs (122), the disc (122) located closest to the disc (121) in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion (115) of the first piston body (21). Among the multiple discs (122), the disc (122) located closest to the disc (121) in the axial direction is configured to be seated on the valve seat portion (115).

[0083] The disc (123) has an outer diameter smaller than the outer diameter of the multiple discs (122) and an outer diameter slightly smaller than the outer diameter of the boss portion (116) of the first piston body (21).

[0084] The disk (124) has an outer diameter larger than the outer diameter of the disk (123).

[0085] The annular member (125) has a smaller diameter than the outer diameter of the disk (124) and a larger diameter than the outer diameter of the end on the side of the attachment shaft (33) in the axial direction of the main shaft (32) of the rod (31). The annular member (125) is thicker and has higher rigidity than the disks (121-124) and contacts the end on the side of the attachment shaft (33) in the axial direction of the main shaft (32).

[0086] A plurality of discs (122) form a valve member (131) on the reducing side that can be seated on or separated from the valve seat portion (115). The valve member (131) has flexibility and, by separating from the valve seat portion (115), connects the piston passage (82) to the first chamber (22). At that time, the valve member (131) generates a damping force by suppressing the flow of oil (L) between the valve seat portion (115) and the valve member (131). The valve member (131) blocks the connection between the piston passage (82) and the first chamber (22) by seating on the valve seat portion (115). The annular member (125), by means of the disc (124), suppresses deformation exceeding the specified limit in the opening direction of the valve member (131) by contacting the valve member (131).

[0087] The passage between the piston passage (82), the valve member (131) and the valve seat portion (115) that appear when the valve is opened constitutes the first passage (132). The first passage (132) is provided in the first piston body (21). The first passage (132) is a constricted passage through which oil liquid (L) flows from the second chamber (23), which is the upstream area within the cylinder (4), to the first chamber (22), which is the downstream area, by moving the first piston body (21) toward the second chamber (23). The constricted valve mechanism (86) that generates damping force includes the valve member (131) and the valve seat portion (115). The valve mechanism (86) is provided in the first passage (132). The first Euro (132) is provided in the first piston body (21) including the valve seat portion (115), and the oil liquid (L) passes through when the rod (31) and the first piston body (21) move toward the contraction side.

[0088] Here, in the valve mechanism (86) on the reducing side, there is no fixed orifice provided in either the valve seat portion (115) or the valve member (131) in contact therewith to connect the first chamber (22) and the second chamber (23) even when the valve seat portion (115) and the valve member (131) are in contact. Therefore, the first passage (132) is not a passage that constantly connects the first chamber (22) and the second chamber (23).

[0089] The valve mechanism (85) on the extension side includes the valve seat portion (105) of the first piston body (21). The valve mechanism (85) has one disc (141) and multiple discs (142) in order from the axial direction of the first piston body (21). On the side opposite to the disc (141) in the axial direction of the multiple discs (142), one disc (143) and multiple discs (144) are provided in order from the side of the multiple discs (142). The discs (141 to 144) are all circular flat plates having holes, and all of them have a pair of outer cross-sections (42a) shown in FIG. 2 of the intermediate shaft portion (42) of the attachment shaft portion (33) fitted to their inner sides.

[0090] The disc (141) has an outer diameter larger than the outer diameter of the boss portion (106) of the first piston body (21) and an outer diameter smaller than the inner diameter of the valve seat portion (105). The disc (141) is in constant contact with the boss portion (106).

[0091] Among the multiple discs (142), the disc (142) located closest to the disc (141) in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion (105) of the first piston body (21). Among the multiple discs (142), the disc (142) located closest to the disc (141) in the axial direction is configured to be seated on the valve seat portion (105).

[0092] The disc (143) has a smaller outer diameter than any of the multiple discs (142) and an outer diameter equal to the outer diameter of the boss portion (106) of the first piston body (21).

[0093] Multiple discs (144) have an outer diameter larger than the outer diameter of the disc (143).

[0094] Multiple discs (142) form an extendable valve member (151) that can be seated on or separated from the valve seat portion (105). The valve member (151) is flexible and, by separating from the valve seat portion (105), connects the piston passage (81) to the second chamber (23). At that time, the valve member (151) generates a damping force by suppressing the flow of oil (L) between it and the valve seat portion (105). The valve member (151) blocks the connection between the piston passage (81) and the second chamber (23) by seating on the valve seat portion (105).

[0095] The passage between the piston passage (81), the valve member (151) and the valve seat portion (105) that appear when the valve is opened constitutes the first passage (152). The first passage (152) is formed in the first piston body (21). The first passage (152) is an extensional passage in which oil liquid (L) flows from the first chamber (22), which is the upstream area within the cylinder (4), to the second chamber (23), which is the downstream area, by moving the first piston body (21) toward the first chamber (22). The extensional valve mechanism (85) that generates damping force includes the valve member (151) and the valve seat portion (105). The valve mechanism (85) is provided in this first passage (152). The first Euro (152) is provided in the first piston body (21) including the valve seat portion (105), and the oil liquid (L) passes through when the rod (31) and the first piston body (21) move toward the extension side.

[0096] In the valve mechanism (85) on the extension side, a fixed orifice is not formed anywhere on the valve seat portion (105) and the valve member (151) in contact therewith to connect the first chamber (22) and the second chamber (23) even when the valve seat portion (105) and the valve member (151) are in contact. Therefore, the first passage (152) is not a passage that constantly connects the first chamber (22) and the second chamber (23).

[0097] The piston internal passage (103) provided in the first piston body (21) communicates with the first chamber (22) through a portion of the first chamber (22) side of the piston internal passage (103) of the piston passage (81). The piston internal passage (103) and the portion of the first chamber (22) side of the piston internal passage (103) of the piston passage (81) provided in the first piston body (21) form the first chamber-side passage (156). In the first chamber-side passage (156), at least a portion of the piston internal passage (103) is provided parallel to the first passage (152).

[0098] A first piston body (21), a disc (121), a valve member (131), a disc (141), and a valve member (151) constitute a first piston (155) that divides the inner tube (2) of a cylinder (4) into a first chamber (22) and a second chamber (23). The first piston (155) divides the inner tube (2) of the cylinder (4) into a first chamber (22) which is an upstream region during the extension stroke and a second chamber (23) which is a downstream region during the extension stroke. The first piston (155) has a circular fixed hole (101, 111) penetrating in the axial direction, a first passage (152) capable of communicating with a first chamber (22) which is an upstream region and a second chamber (23) which is a downstream region during an extension stroke, a valve member (151) which is flexible and capable of closing the first passage (152), and a first chamber-side passage (156) in which at least a portion of the piston internal passage (103) is provided parallel to the first passage (152).

[0099] As shown in FIG. 4, on the side opposite to the disk (143) in the axial direction of the disk (144), in order from the disk (144) side, one disk (160), one spring member (161), multiple disks (162), one valve member (163) (valve body), and one second piston body (166) (sintered body) having one O-ring (165) on the outer circumference are provided. Additionally, on the side opposite to the valve member (163) in the axial direction of the second piston body (166), in order from the second piston body (166) side, one valve member (167) (valve body), multiple disks (168), one spring member (169), and one disk (170) are provided. Additionally, on the side opposite to the spring member (169) in the axial direction of the disk (170), one disk (172), one disk (173), and one disk (174) are provided in order from the disk (170) side. Also, on the side opposite to the disk (173) in the axial direction of the disk (174), one disk (176), one disc spring (177), one case member (178) (partition member), one disk (181), and one annular member (182) are provided in order from the disk (174) side.

[0100] The discs (160, 162, 168, 170, 172, 173, 174, 176, 181), spring members (161, 169), valve members (163, 167), second piston body (166), disc spring (177), case member (178), and annular member (182) each fit the attachment shaft portion (33) of the rod (31) to their respective inner sides. At that time, the disc (160), spring members (161), discs (162), valve members (163), and second piston body (166) each fit the pair of outer cross-sections (42a) shown in FIG. 2 of the intermediate shaft portion (42) of the attachment shaft portion (33) to their respective inner sides. Additionally, as shown in FIG. 4, the second piston body (166), valve member (167), disk (168), spring member (169), disk (170), disk (172), disk (173), disk (174), disk (176), disc spring (177), case member (178), disk (181) and annular member (182) each fit the outer surface (43a) shown in FIG. 2 of the front end cylindrical part (43) of the attachment shaft part (33) to the respective inner side.

[0101] As shown in FIG. 3, the attachment shaft portion (33) of the rod (31) has a screw shaft portion (44) disposed on a portion protruding from the annular member (182). A retainer (185) is screw-coupled to a male screw (57) on the outer circumference of this screw shaft portion (44). The retainer (185) is in contact with the annular member (182).

[0102] As shown in FIG. 4, the disc (160, 162, 168, 170, 172, 173, 174, 176, 181), spring member (161, 169), valve member (163, 167), second piston body (166), disc spring (177), case member (178) and annular member (182) are each axially clamped by the main shaft portion (32) and retainer (185) shown in FIG. 3 of the rod (31), at least on the inner circumference in the radial direction.

[0103] The disks (160, 162, 168, 170, 172, 173, 176, 181), valve members (163, 167), and annular members (182) shown in FIG. 4 are all circular flat plates with holes.

[0104] The case member (178) is a tubular, integrally molded product with a bottom. The case member (178) has a bottom portion (191), an intermediate tapered portion (192), and a tubular portion (193). As shown in FIG. 3, the outer diameter of the case member (178) is smaller than the outer diameter of the first piston body (21).

[0105] As shown in FIG. 4, the bottom portion (191) is a flat plate with holes.

[0106] The intermediate tapered portion (192) extends from the outer edge portion of the bottom portion (191) toward one side of the bottom portion (191) in the axial direction, expanding in diameter. The intermediate tapered portion (192) is annular.

[0107] The tubular portion (193) extends in the opposite direction to the bottom portion (191) from the end edge portion opposite to the bottom portion (191) of the intermediate tapered portion (192) in the axial direction of the intermediate tapered portion (192). The tubular portion (193) is cylindrical. Additionally, the case member (178) may not provide an intermediate tapered portion (192) and may have the tubular portion (193) directly continuous from the bottom portion (191).

[0108] In the case member (178), the tip-side cylindrical portion (43) of the attachment shaft portion (33) of the rod (31) fits into the inner circumference of the bottom portion (191) on the outer surface (43a) shown in FIG. 2. As shown in FIG. 4, a plurality of passage holes (195) are formed in the bottom portion (191). The plurality of passage holes (195) penetrate the bottom portion (191) in the axial direction of the bottom portion (191). The plurality of passage holes (195) are arranged at equal intervals in the circumferential direction of the bottom portion (191) at positions equidistant from the center of the bottom portion (191). In the case member (178), the bottom portion (191) is positioned in a direction opposite to the disk (144) in its axial direction compared to the tubular portion (193). The bottom portion (191) of the case member (178) contacts the disk (181). The outer diameter of the disk (181) is sized so as not to block the passage hole (195) of the case member (178).

[0109] A second piston body (166), a valve member (163, 167), a disc (168, 170, 172, 173, 174, 176), a spring member (169), and a disc spring (177) are arranged on the inner side in the diametrical direction of the case member (178).

[0110] The disc spring (177) is flexible. The disc spring (177) has an inner toroidal portion (201) and an outer tapered portion (202).

[0111] The inner annular portion (201) is a circular flat plate with a hole. A passage hole (205) is formed in the inner annular portion (201) that penetrates the inner annular portion (201) in the axial direction of the inner annular portion (201). The passage hole (205) forms an arc shape that extends in the circumferential direction of the inner annular portion (201).

[0112] The outer tapered portion (202) is a conical tube shape that widens outward in the radial direction and in one axial direction from the outer edge portion of the inner annular portion (201).

[0113] The disc spring (177) contacts the bottom portion (191) of the case member (178) in the inner annular portion (201), and the outer tapered portion (202) moves further away from the bottom portion (191) in the axial direction of the bottom portion (191) as it extends outward in the radial direction. When the inner annular portion (201) contacts the bottom portion (191) of the case member (178), the disc spring (177) connects the passage hole (205) of the inner annular portion (201) to the passage hole (195) of the case member (178).

[0114] The disc (176) has an outer diameter that is smaller than the outer diameter of the inner toroidal portion (201) of the disc spring (177).

[0115] The disc (174) is flexible. The outer diameter of the disc (174) is larger than the outer diameter of the disc spring (177), that is, the outer diameter of the outer tapered portion (202). The disc spring (177) presses the circular outer edge portion of the outer tapered portion (202) in the diameter direction outward to the outer edge portion of the disc (174) over the entire circumference.

[0116] A communication hole (211) is formed in the disk (174) that penetrates the disk (174) in the axial direction of the disk (174). In the disk (174), the communication hole (211) is formed at a position that is not blocked by the disk (176).

[0117] The disc (173) is flexible. The outer diameter of the disc (173) is smaller than the outer diameter of the disc (174). The outer diameter of the disc (173) is sized to be able to block the communication hole (211) of the disc (174). The disc (173) contacts the disc (174) over its entire circumference. Then, the disc (173) blocks the communication hole (211) of the disc (174). The disc (173) opens the communication hole (211) of the disc (174) when the disc (174) elastically deforms the outer tapered portion (202) of the disc spring (177) and elastically deforms toward the bottom portion (191) of the case member (178).

[0118] The outer diameter of the disk (172) is smaller than the outer diameter of the disk (173) and smaller than the outer diameter of the disk (176).

[0119] The disc (170) is flexible. The outer diameter of the disc (170) is larger than the outer diameter of the disc (173) and slightly smaller than the outer diameter of the disc (174).

[0120] The spring member (169) has flexibility. The spring member (169) has a substrate portion (221) and a plurality of spring plate portions (222).

[0121] The substrate portion (221) is a circular flat plate with a hole. The substrate portion (221) fits the attachment shaft portion (33) into its inner circumference.

[0122] A plurality of spring plate portions (222) extend radially from the outer edge portion of the substrate portion (221). The further the plurality of spring plate portions (222) are from the substrate portion (221) in the axial direction of the substrate portion (221), the further they are from the substrate portion (221) in the radial direction of the substrate portion (221).

[0123] The spring member (169) contacts the disk (170) in the substrate portion (221). The plurality of spring plate portions (222) are further from the disk (170) in the axial direction of the substrate portion (221) as they are further outward in the radial direction of the substrate portion (221).

[0124] The outer diameter of the disk (168) is smaller than the outer diameter of the substrate portion (221) of the spring member (169) and larger than the outer diameter of the disk (172). The disk (168) contacts the substrate portion (221) of the spring member (169).

[0125] The valve member (167) is flexible. The outer diameter of the valve member (167) is larger than the maximum outer diameter of the spring member (169).

[0126] The second piston body (166) is a sintered metal body formed integrally without seams and is a disc-shaped body with a hole, as shown in FIGS. 5 and 6. The second piston body (166) has an insertion through hole (231) formed in its diameter direction center, which penetrates the second piston body (166) in the axial direction, as shown in FIG. 4. In other words, the insertion through hole (231) extends in the axial direction of the second piston body (166) and penetrates the second piston body (166) in the axial direction. The attachment shaft portion (33) of the rod (31) is inserted through the center of the insertion through hole (231).

[0127] As shown in FIGS. 5 and 6, the insertion through hole (231) has a first inner wall (232) and a second inner wall (233).

[0128] The first inner wall (232) has an inner surface that is cylindrical. As shown in FIG. 4, the first inner wall (232) penetrates the second piston body (166) in the axial direction.

[0129] As illustrated in FIGS. 5 and 6, the second inner wall (233) is recessed radially outward from the inner surface of the first inner wall (232). The inner surface of the second inner wall (233) is semi-cylindrical. As illustrated in FIG. 4, the second inner wall (233) extends in a straight line along the axial direction of the second piston body (166) and penetrates the second piston body (166) axially. The insertion through hole (231) has one or more second inner walls (233). Here, as illustrated in FIGS. 5 and 6, the insertion through hole (231) has a plurality of second inner walls (233) at equal intervals along the circumference of the first inner wall (232).

[0130] The insertion through hole (231) has an insertion through hole body (234) in which the inner side of the first inner wall (232) is inserted through by the attachment shaft portion (33) of the rod (31) as shown in FIG. 4, and an extension portion (235) in which the inner side of the second inner wall (233) extends radially outward from the insertion through hole body (234). The second piston body (166) has an insertion through hole body (234) and one or more extension portions (235) extending in the radial direction from the insertion through hole body (234). Here, as shown in FIG. 5 and FIG. 6, the second piston body (166) has a plurality of extension portions (235) at equal intervals in the circumferential direction of the insertion through hole body (234). As shown in FIG. 4, the insertion through hole body (234) and the extension (235) both extend from one end surface in the axial direction of the second piston body (166) to the other end surface and penetrate the second piston body (166).

[0131] In the insertion through hole (231), the attachment shaft portion (33) of the rod (31) fits into the first inner wall (232) at the outer surface (43a) of the intermediate shaft portion (42) and the pair of outer cross-sectional surfaces (42a) shown in FIG. 2 and the tip-side cylindrical portion (43). In this way, as shown in FIG. 4, the second inner wall (233) is spaced apart in the radial direction from the attachment shaft portion (33) of the rod (31). The extension portion (235) is formed from the side opposite to the side facing the first piston (155) shown in FIG. 3 of the second piston body (166) to a position communicating with the axial passage (54). The insertion through hole (231) is positioned in the axial direction of the rod (31) with the tip-side circumferential groove (53) of the rod (31). Accordingly, the insertion through hole (231) is directly or indirectly connected to the circumferential groove (53) on the tip side of the rod (31), in this case, directly connected. An intermediate chamber (237) is formed between the second inner wall (233) of the second piston body (166) and the attachment shaft portion (33) of the rod (31). By means of the circumferential groove (53) on the tip side of the rod (31), the intermediate chamber (237) can be connected to the axial passage (54) without circumferential phase alignment with respect to the rod (31) of the second piston body (166).

[0132] As shown in FIG. 4, the second piston body (166) has a base portion (240) formed in a cylindrical shape with a hole in the middle of the axial direction. The base portion (240) has a cylindrical side portion (401) extending over the entire circumference on the outer side in the radial direction, a flat base portion end surface (402) on one side in the axial direction, and a flat base portion end surface (403) on the other side in the axial direction. The base portion end surface (402) and the base portion end surface (403) are widened perpendicularly with respect to the side portion (401).

[0133] The second piston body (166) has a boss portion (241) and a valve seat portion (242) at one end in the axial direction. The boss portion (241) and the valve seat portion (242) protrude axially from the base portion end surface (402) of the base portion (240). As shown in FIG. 5, the boss portion (241) forms an annular shape surrounding the insertion through hole (231). In other words, the boss portion (241) is formed around the insertion through hole (231). The valve seat portion (242) widens outward from the boss portion (241) in the diameter direction of the boss portion (241).

[0134] As illustrated in FIG. 4, the second piston body (166) has a boss portion (244) and a valve seat portion (245) at the other end of the axial direction opposite to the boss portion (241) and the valve seat portion (242). The boss portion (244) and the valve seat portion (245) protrude axially from the base portion end surface (403) of the base portion (240). As illustrated in FIG. 6, the boss portion (244) forms an annular shape surrounding the insertion through hole (231). In other words, the boss portion (244) is formed around the insertion through hole (231). The valve seat portion (245) widens outward from the boss portion (244) in the diameter direction of the boss portion (244).

[0135] As illustrated in FIG. 4, the second piston body (166) has a base portion (240) between the axial boss portion (241) and valve seat portion (242), and the boss portion (244) and valve seat portion (245). The base portion (240) is a disc-shaped plate with a hole. An insertion through hole (231) penetrates the base portion (240), the boss portion (241), and the boss portion (244).

[0136] The boss portion (241) protrudes to one side along the axial direction of the base portion (240) from the inner circumferential edge portion of the base portion end surface (402) on one side in the axial direction of the base portion (240). The valve seat portion (242) protrudes eastward from the boss portion (241) from the base portion end surface (402) of the base portion (240) along the axial direction of the base portion (240) on the outer side in the diameter direction of the boss portion (241).

[0137] The boss portion (241) has a flat surface on the protruding side end surface (411) shown in FIG. 5, that is, the front surface (411) opposite to the base portion (240). The valve seat portion (242) has a flat surface on the protruding side end surface (412), that is, the front surface (412) opposite to the base portion (240). The front surface (411) of the boss portion (241) and the front surface (412) of the valve seat portion (242) are arranged on the same plane, widened in the direction perpendicular to the axis of the second piston body (166).

[0138] As shown in FIG. 4, the boss portion (244) protrudes along the axial direction of the base portion (240) toward the side opposite to the boss portion (241) from the inner circumferential edge portion opposite to the boss portion (241) in the axial direction of the base portion (240). The valve seat portion (245) protrudes from the base portion (240) toward the side opposite to the boss portion (244) along the axial direction of the base portion (240) from the outer side in the diametric direction of the boss portion (244).

[0139] The boss portion (244) has a flat surface on the protruding side end surface (421) shown in FIG. 6, that is, the front surface (421) opposite to the base portion (240). The valve seat portion (245) has a flat surface on the protruding side end surface (422), that is, the front surface (422) opposite to the base portion (240). The front surface (421) of the boss portion (244) and the front surface (422) of the valve seat portion (245) are widened in the direction perpendicular to the axis of the second piston body (166) and arranged on the same plane.

[0140] As shown in FIG. 5, the boss portion (241) has an annular portion (251) and a plurality of protruding portions (252).

[0141] The annular portion (251) is circular and is formed to surround the insertion through hole (231).

[0142] The protruding portion (252) extends outward in the radial direction from the outer edge portion of the annular portion (251). A plurality of protruding portions (252) are arranged at intervals along the circumference of the annular portion (251).

[0143] The boss portion (241) has a diameter-direction communication groove (253) that penetrates the annular portion (251) in the diameter direction of the annular portion (251). Multiple diameter-direction communication grooves (253) are formed at equal intervals along the circumference of the annular portion (251). The diameter-direction communication groove (253) is formed by being recessed along the axial direction of the second piston body (166) from the front end surface (411) on the side opposite to the base portion (240) of the boss portion (241).

[0144] Each of the radial communication grooves (253) is aligned with one of the corresponding second inner walls (233) among the plurality of second inner walls (233) of the insertion through hole (231) in the circumferential direction of the annular portion (251), and is connected within the corresponding second inner wall (233). Each of the plurality of radial communication grooves (253) is provided between adjacent protruding portions (252) in the circumferential direction of the annular portion (251).

[0145] The valve seat portion (242) is a non-circular, petal-shaped irregular seat. The valve seat portion (242) has a plurality of round portions (255). These round portions (255) have the same shape and are arranged at equal intervals in the circumferential direction of the second piston body (166). Additionally, these round portions (255) do not need to have the same shape, and may have two or more types of shapes or be different from each other. They may also be arranged at unequal intervals in the circumferential direction of the second piston body (166). By configuring it in this way, the valve opening pressure applied to the valve member (163) described later is made uneven in the circumferential direction, thereby allowing the valve opening timing to be different and the damping force characteristics to be changed smoothly.

[0146] The round portion (255) has a pair of arm portions (256) and an outer portion (257).

[0147] A pair of arm portions (256) are all extended outward in the radial direction of the annular portion (251) from the outer edge portion of the annular portion (251) of the boss portion (241). A pair of arm portions (256) are spaced apart in the circumferential direction of the annular portion (251). Each of the pair of arm portions (256) has an inclined portion (431) that extends from the front end surface (412) of the valve seat portion (242) toward the outside of the round portion (255) and is continuous with the base portion end surface (402). The inclined portion (431) intersects at an obtuse angle with respect to the front end surface (412) and intersects at an obtuse angle with respect to the base portion end surface (402).

[0148] The outer edge (257) connects the outer ends of the annular portion (251) of a pair of arm portions (256) in the radial direction. The outer edge (257) extends in the circumferential direction of the annular portion (251). The outer edge (257) forms an arc shape centered on the central axis of the second piston body (166). As shown in FIG. 7, the outer edge (257) has an inclined portion (432) (second inclined portion) that extends from the front end surface (412) of the valve seat portion (242) toward the outside of the round portion (255) and is continuous with the side portion (401). The inclined portion (432) forms an arc shape when viewed in the axial direction of the second piston body (166). The inclined portion (432) is a tapered shape that forms a straight line when the second piston body (166) is cross-sectionally formed in a plane including the center axis of the second piston body (166). The inclined portion (432) intersects at an obtuse angle with respect to the front end surface (412) and intersects at an obtuse angle A with respect to the side portion (401). The outer edge portion (257) of the round portion (255) starts from the outer circumference of the base portion (240) and, as it moves toward the center of the base portion (240), the amount of protrusion from the base portion (240) increases. The inclined portion (432) is continuous with each of the inclined portions (431) of the pair of arm portions (256).

[0149] In other words, as illustrated in FIG. 5, the round portion (255) is provided in multiple portions protruding axially from the base portion end surface (402), and has an outer edge portion (257) that is provided along the outer circumference of the base portion end surface (402) and is continuous through an inclined portion (432) that forms an obtuse angle A with the side portion (401), and a set of arm portions (256) that extend from both ends of the outer edge portion (257) toward the boss portion (241).

[0150] Here, a pair of protruding parts (252) adjacent to the boss part (241) in the circumferential direction are arranged on the inner side of the second piston body (166) of the round part (255), and a diameter-direction connecting groove (253) is arranged between these pair of protruding parts (252). Accordingly, a pair of protruding parts (252) and a diameter-direction connecting groove (253) are arranged on the inner side of the second piston body (166) of each of the plurality of round parts (255) in the circumferential direction.

[0151] As shown in FIG. 8, the base portion (240) has an inclined portion (435) (first inclined portion) formed therein that is continuous with the base portion end surface (402) and the side portion (401). Accordingly, the base portion end surface (402) is continuous with respect to the side portion (401) through the inclined portion (435). The inclined portion (435) forms an arc shape when viewed in the axial direction of the second piston body (166). The inclined portion (435) is a tapered shape that forms a straight line when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The inclined portion (435) intersects the base portion end surface (402) at an obtuse angle and intersects the side portion (401) at an obtuse angle. The diameter of the inclined portion (435) decreases as it approaches the base portion end surface (402) in the axial direction of the second piston body (166). The obtuse angle B formed by the inclined portion (435) with respect to the side portion (401) is smaller than the obtuse angle A formed by the inclined portion (432) with respect to the side portion (401) as shown in FIG. 7.

[0152] As illustrated in FIG. 9, the inclined portion (435) is positioned between adjacent portions in the circumferential direction of the second piston body (166) of the plurality of round portions (255), and is adjacent to the inclined portion (432) in the circumferential direction of the second piston body (166). As illustrated in FIG. 10, the distance L1 between the inclined portion (435) of the base portion (240) and the axial center C of the side portion (401) is smaller than the distance L2 between the inclined portion (432) of the outer edge portion (257) and the axial center C of the side portion (401). That is, the inclined portion (435) of the base portion (240) is located closer to the axial center C of the side portion (401) than to the inclined portion (432) of the outer edge portion (257). In the base portion (240), as shown in FIG. 5, an inclined portion (435) is formed at a position between all combinations of adjacent round portions (255) in the circumferential direction of the second piston body (166).

[0153] In each of the multiple round portions (255), a recess (258) (recess) is formed between the boss portion (241) and the inner side. The recess (258) is formed by being surrounded by a part of the boss portion (241) and the round portion (255). The recess (258) is recessed in the axial direction of the second piston body (166) from the front end surface (411) of the protruding side of the boss portion (241) and the front end surface (412) of the protruding side of the valve seat portion (242). A recess (258) is formed in the inner side of all round portions (255).

[0154] A through hole (259) (connecting hole) is formed at the central position of the concave chamber (258) in the circumferential direction of the second piston body (166). In other words, the round portion (255) surrounds the through hole (259) to form the concave chamber (258). In other words, the through hole (259) is a hole formed in the area surrounded by the outer edge portion (257) and a pair of arm portions (256). The through hole (259) is formed in the base portion (240). The through hole (259) is positioned between a pair of protruding portions (262) in the circumferential direction of the second piston body (166) within the concave chamber (258) where it is formed. As shown in FIG. 4, the through hole (259) penetrates the base portion (240) in the axial direction and penetrates the second piston body (166) in the axial direction. The through hole (259) is a straight hole parallel to the center axis of the second piston body (166). As shown in FIG. 5, the through hole (259) is formed on the bottom surface of all the concave chambers (258).

[0155] As shown in FIG. 6, the boss portion (244) has an annular portion (261) and a plurality of protruding portions (262).

[0156] The annular portion (261) is circular and is formed to surround the insertion through hole (231).

[0157] The protruding portion (262) extends outward in the radial direction from the outer edge portion of the annular portion (261). A plurality of protruding portions (262) are arranged at intervals along the circumference of the annular portion (261).

[0158] In the boss portion (244), a plurality of communication grooves (263) are formed at equal intervals along the circumference of the annular portion (261), traversing the annular portion (261) in the diameter direction of the annular portion (261). The communication grooves (263) are formed by being recessed in the axial direction of the second piston body (166) from the front end surface (421) on the side opposite to the base portion (240) of the boss portion (244).

[0159] Each of the plurality of communication grooves (263) is aligned with one of the corresponding second inner walls (233) among the plurality of second inner walls (233) of the insertion through hole (231) in the circumferential direction of the annular portion (261), and is connected within the corresponding second inner wall (233). Each of the plurality of communication grooves (263) is provided between adjacent protruding portions (262) in the circumferential direction of the annular portion (251).

[0160] The valve seat portion (245) is a non-circular, petal-shaped irregular seat. The valve seat portion (245) has a plurality of round portions (265). These round portions (265) have the same shape and are arranged at equal intervals in the circumferential direction of the second piston body (166). Additionally, these valve seat portions (245) do not need to have the same shape, and may have two or more types of shapes or different shapes. They may also be arranged at unequal intervals in the circumferential direction of the second piston body (166). By configuring it in this way, the valve opening pressure applied to the valve member (167) described later is made uneven in the circumferential direction, thereby allowing the valve opening timing to be different and the damping force characteristics to be changed smoothly.

[0161] In the annular portion (261) of the boss portion (244), a communication groove (263) is disposed between the round portion (265) adjacent to the second piston body (166) in the circumferential direction. Accordingly, the communication groove (263) is formed in the portion disposed on the outer side of the valve seat portion (245) in the boss portion (244).

[0162] The round portion (265) has a pair of arm portions (266) and an outer portion (267).

[0163] A pair of arm portions (266) are all extended outward in the radial direction of the annular portion (261) from the outer edge portion of the annular portion (261) of the boss portion (244). A pair of arm portions (266) are spaced apart in the circumferential direction of the annular portion (261). Each of the pair of arm portions (266) has an inclined portion (441) that extends from the front end surface (422) of the valve seat portion (245) toward the outside of the round portion (265) and is continuous with the base portion end surface (403). The inclined portion (441) intersects at an obtuse angle with respect to the front end surface (422) and intersects at an obtuse angle with respect to the base portion end surface (403).

[0164] The outer edge (267) connects the outer ends of the annular portion (261) of a pair of arm portions (266) in the radial direction. The outer edge (267) extends in the circumferential direction of the annular portion (261). The outer edge (267) forms an arc shape centered on the central axis of the second piston body (166). As shown in FIG. 8, the outer edge (267) has an inclined portion (442) (second inclined portion) that extends from the front end surface (422) of the valve seat portion (245) toward the outside of the round portion (265) and is continuous with the side portion (401). The inclined portion (442) forms an arc shape when viewed in the axial direction of the second piston body (166). The inclined portion (442) is a tapered shape that forms a straight line when the second piston body (166) is cross-sectionally formed in a plane including the center axis of the second piston body (166). The inclined portion (442) intersects at an obtuse angle with respect to the front end surface (422) and intersects at an obtuse angle A with respect to the side portion (401). The outer edge portion (267) of the round portion (265) starts from the outer circumference of the base portion (240) and, as it moves toward the center of the base portion (240), the amount of protrusion from the base portion (240) increases. The inclined portion (442) is continuous with each of the inclined portions (441) of the pair of arm portions (266).

[0165] In other words, the round portion (265) is provided in multiple portions that protrude axially from the base portion end surface (403) as shown in FIG. 6, and has an outer edge portion (267) that is provided along the outer circumference of the base portion end surface (403) and is continuous through an inclined portion (442) that forms an obtuse angle A with the side portion (401), and a set of arm portions (266) that extend from both ends of the outer edge portion (267) toward the boss portion (244).

[0166] Here, a pair of protruding parts (262) adjacent to the circumferential direction of the boss part (244) are arranged on the inner side in the circumferential direction of the second piston body (166) of the round part (265). Accordingly, a pair of protruding parts (262) are arranged on the inner side in the circumferential direction of each of the second piston bodies (166) of the plurality of round parts (265).

[0167] As shown in FIG. 7, the base portion (240) has an inclined portion (445) (first inclined portion) formed therein that is continuous with the base portion end surface (403) and the side portion (401). Accordingly, the base portion end surface (403) is continuous with respect to the side portion (401) through the inclined portion (445). The inclined portion (445) forms an arc shape when viewed in the axial direction of the second piston body (166). The inclined portion (445) is a tapered shape that forms a straight line when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The inclined portion (445) intersects the base portion end surface (403) at an obtuse angle and intersects the side portion (401) at an obtuse angle (B). The diameter of the inclined portion (445) decreases as it approaches the end surface (403) of the base portion in the axial direction of the second piston body (166). The obtuse angle B formed by the inclined portion (445) with respect to the side portion (401) is smaller than the obtuse angle A formed by the inclined portion (442) shown in FIG. 8 with respect to the side portion (401). Additionally, the distance between the inclined portion (445) of the base portion (240) shown in FIG. 7 and the center of the side portion (401) in the axial direction is smaller than the distance between the inclined portion (442) of the outer edge portion (267) shown in FIG. 8 and the center of the side portion (401) in the axial direction. That is, the inclined portion (445) of the base portion (240) shown in FIG. 7 is located at a position closer to the center C of the side portion (401) in the axial direction than the inclined portion (442) of the outer edge portion (267) shown in FIG. 8.

[0168] As illustrated in FIG. 11, the inclined portion (445) is provided at a position between adjacent round portions (265) in the circumferential direction of the second piston body (166) and is adjacent to the inclined portion (442) in the circumferential direction of the second piston body (166). In the base portion (240), as illustrated in FIG. 6, the inclined portion (445) is formed at a position between all combinations of adjacent round portions (265) in the circumferential direction of the second piston body (166).

[0169] In each of the multiple round portions (265), a concave chamber (268) (chamber) is formed between the boss portion (244) and the inner side. The concave chamber (268) is formed by being surrounded by a part of the boss portion (244) and the round portion (265).

[0170] The concave chamber (268) is recessed in the axial direction of the second piston body (166) from the front end surface (421) of the protruding side of the boss portion (244) and the front end surface (422) of the protruding side of the valve seat portion (245). The concave chamber (268) is formed on the inner side of all round portions (265).

[0171] A through hole (269) (connecting hole) is formed at the central position of the concave chamber (268) in the circumferential direction of the second piston body (166). In other words, the round portion (265) surrounds the through hole (269) to form the concave chamber (268). In other words, the through hole (269) is a hole formed in the area surrounded by the outer edge portion (267) and a pair of arm portions (266). The through hole (269) is formed in the base portion (240). The through hole (269) is positioned between a pair of protruding portions (262) in the circumferential direction of the second piston body (166) within the concave chamber (268) where it is formed. As shown in FIG. 4, the through hole (269) penetrates the base portion (240) in the axial direction and penetrates the second piston body (166) in the axial direction. The through hole (269) is a straight hole parallel to the center axis of the second piston body (166). As shown in FIG. 6, the through hole (269) is formed on the bottom surface of all the concave chambers (268). In the second piston body (166), a plurality of through holes (259) and a plurality of through holes (269) are provided alternately one by one in the circumferential direction of the second piston body (166), on the outer side of the boss portion (241) shown in FIG. 5 and the boss portion (244) shown in FIG. 6.

[0172] Here, the arrangement pitch of the plurality of round sections (255) shown in FIG. 5 in the circumferential direction of the second piston body (166) and the arrangement pitch of the plurality of round sections (265) shown in FIG. 6 in the circumferential direction of the second piston body (166) are the same. In addition, the round sections (255) and the round sections (265) are out of phase with each other by half the arrangement pitch in the circumferential direction of the second piston body (166). In other words, the plurality of round sections (255) on the end surface (402) of the base section (240) on one side shown in FIG. 5 and the plurality of round sections (265) on the end surface (403) of the base section (240) on the other side shown in FIG. 6 are arranged with a phase out of phase. In other words, the plurality of round portions (255) and the plurality of round portions (265) are arranged with phases offset on both sides of the base portion end surface (402) and the base portion end surface (403) of the base portion (240).

[0173] And, as shown in FIG. 5, the through hole (269) is positioned between adjacent round portions (255) and round portions (255) in the circumferential direction of the second piston body (166). Thus, the through hole (269) is positioned outside the range of the valve seat portion (242). The through hole (269) is formed between the arm portions (256) of two adjacent round portions (255) on the base portion (240). Thus, the through hole (269) is provided in an area surrounded by the outer edge portion (267) of the round portion (265) and a pair of arm portions (266) on one axial side as shown in FIG. 6, and on the other axial side between the arm portions (256) of two adjacent round portions (255) on the base portion (240) as shown in FIG. 5.

[0174] Additionally, as shown in FIG. 6, the through hole (259) is positioned between adjacent round portions (265) and round portions (265) in the circumferential direction of the second piston body (166). Thus, the through hole (259) is positioned outside the range of the valve seat portion (245). The through hole (259) is formed between the arm portions (266) of two adjacent round portions (265) on the base portion (240). Thus, the through hole (259) is provided in the area surrounded by the outer edge portion (257) of the round portion (255) and a pair of arm portions (256) as shown in FIG. 5 on the other axial side, and is provided between the arm portions (266) of two adjacent round portions (265) on the base portion (240) as shown in FIG. 6 on the one axial side.

[0175] In the second piston body (166), as shown in FIG. 4, a seal groove (271) is formed at the central position in the axial direction of the outer circumference of the base portion (240). The seal groove (271) is annular and is recessed inward in the radial direction of the side portion (401) from the middle position in the axial direction of the side portion (401) of the base portion (240). An O-ring (165) is disposed within this seal groove (271).

[0176] Here, when manufacturing the second piston body (166), a molded article (166A) shown in FIGS. 12 and FIGS. 13 is formed by a compression process in which powder metal is compressed into a mold. The molded article (166A) has a base part (240A) which later becomes a base part (240), a round part (255A) which later becomes a round part (255), and a round part (265A) which later becomes a round part (265).

[0177] As shown in FIG. 13, the base portion (240A) includes a cylindrical main body portion (501) which later becomes the base portion (240), a groove (502) formed on the base portion end surface (402) on one side of the axial direction of the main body portion (501) and including an inclined portion (435A) (first inclined portion) which extends annularly from one end of the axial direction of the main body portion (501) toward the outer side in the radial direction and reduces the axial size of the base portion (240A) and later becomes the inclined portion (435), and a flat portion (503) which extends outward in the radial direction beyond the groove (502) including the inclined portion (435A). The base portion end surface (402) and the flat portion (503) are arranged on the same plane. The groove (502) is arc-shaped when viewed in the axial direction of the molded article (166A), is formed between adjacent rounded portions (255A) in the circumferential direction of the molded article (166A), and between the base end surface (402) and the flat portion (503) in the diameter direction of the molded article (166A). The bottom surface of the groove (502) is a plane parallel to the flat portion (503).

[0178] As shown in FIG. 12, the base portion (240A) includes a groove (512) formed in the cross-section (403) of the base portion on the axial side of the main body portion (501), which includes an inclined portion (445A) (first inclined portion) that extends outward in the radial direction from the axial end of the main body portion (501) and reduces the axial size of the base portion (240A) and later becomes an inclined portion (445), and a flat portion (513) that extends outward in the radial direction beyond the groove (512) including the inclined portion (445A). The base portion end surface (403) and the flat portion (513) are arranged on the same plane. The groove (512) is arc-shaped when viewed in the axial direction of the molded article (166A), is formed between adjacent rounded portions (265A) in the circumferential direction of the molded article (166A), and between the base end surface (403) and the flat portion (513) in the diameter direction of the molded article (166A). The bottom surface of the groove (512) is a plane parallel to the flat portion (513).

[0179] A number of round portions (255A) are provided, protruding axially from the base portion end surface (402) and the flat portion (503) on one side of the axial direction of the main body portion (501). The round portion (255A) has an outer edge portion (257A) adjacent in the circumferential direction to the inclined portion (435A) shown in FIG. 13, and the inclined portion (432A) (second inclined portion) shown in FIG. 12, which later becomes the inclined portion (432), and a set of arm portions (256) extending toward the center of the base portion (240A) from both ends in the circumferential direction of the molded product (166A) of the outer edge portion (257A). The inclined portion (432A) is continuous with respect to the flat portion (503) at an obtuse angle.

[0180] The round portion (265A) shown in FIG. 13 is provided in multiple portions that protrude axially from the base portion end surface (403) and the flat portion (513) on one side of the axial direction of the main body portion (501). The round portion (265A) has an outer edge portion (267A) that is adjacent in the circumferential direction to the inclined portion (445A) shown in FIG. 12, and the inclined portion (442A) (second inclined portion) shown in FIG. 13, which later becomes the inclined portion (442), and a set of arm portions (266) that extend toward the center of the base portion (240A) from both ends in the circumferential direction of the molded product (166A) of the outer edge portion (257A). The inclined portion (442A) is continuous with respect to the flat portion (513) at an obtuse angle.

[0181] A molded article (166A) formed in the above shape by a compression process is heated in a sintering process and processed into a sintered body (166A).

[0182] Then, in the removal process, a portion of the outer side of the sintered body (166A) is removed. The removal process involves removing a portion of the sintered body (166A) that is radially outward from a predetermined position of the inclined portion (432A) and inclined portion (445A) shown in FIG. 12, as well as a portion of the sintered body (166A) that is radially outward from a predetermined position of the inclined portion (435A) and inclined portion (4442A) shown in FIG. 13, as shown by the two-dot dashed line in FIG. 12 and FIG. 13, and forming a seal groove (271). By doing so, a side portion (401) that is a circumferential surface of the base portion (240) is formed, and an inclined portion (442) and an inclined portion (445) that form an obtuse angle continuously with respect to the side portion (401) are formed on the base portion end surface (403) of the base portion (240). Along with that, on the base end surface (402) of the base part (240), an inclined portion (432) and an inclined portion (435) are formed that form an obtuse angle continuously with respect to the side portion (401).

[0183] The sintered body (166A) has a base portion (240A) having a groove (502) formed on the end surface (402) of the base portion, and the portion extending outward in the diameter direction from the groove (502) is a flat portion (503). Furthermore, the groove (502) is formed such that a portion of the groove (502) remaining after the removal process, which is on the side of the main body portion (501) rather than the bottom portion, becomes an inclined portion (435) that continuously forms an obtuse angle B with respect to the side portion (401).

[0184] Additionally, the sintered body (166A) has a base portion (240A) having a groove (512) formed on the end surface (403) of the base portion, and the portion extending outward in the diameter direction from the groove (512) is a flat portion (513). Furthermore, the groove (512) is formed such that a portion of the groove (512) remaining after the removal process, which is on the side of the main body portion (501) rather than the bottom portion, becomes an inclined portion (445) that continuously forms an obtuse angle B with respect to the side portion (401).

[0185] As the removal process is performed, the sintered body (166A) becomes the second piston body (166).

[0186] As illustrated in FIG. 4, a passage within a through hole (259) and a recess (258) into which the through hole (259) opens constitute a passage section (281) provided in the second piston body (166). In the second piston body (166), a plurality of passage sections (281) are provided at equal intervals in the circumferential direction of the second piston body (166). The passage section (281) communicates with a passage within a radial communication groove (253) and a passage within a communication groove (263).

[0187] A through hole (269) and a recess (268) into which the through hole (269) opens constitute a passage section (282) provided in the second piston body (166). In the second piston body (166), a plurality of passage sections (282) are provided at equal intervals in the circumferential direction of the second piston body (166).

[0188] The second piston body (166) is fitted to the tubular portion (193) of the case member (178) on its outer circumference, with the boss portion (241) and the valve seat portion (242) facing opposite to the bottom portion (191) of the case member (178). In this state, the O-ring (165) seals the gap between the tubular portion (193) of the case member (178) and the second piston body (166).

[0189] The case member (178), O-ring (165), and second piston body (166) form a case chamber (285) inside the case member (178). The case chamber (285) is provided between the bottom portion (191) of the case member (178) and the second piston body (166). The valve member (167), discs (168, 170, 172, 173, 174, 176), spring member (169), and disc spring (177) are provided within this case chamber (285). The second piston body (166) has a valve seat portion (245) positioned on the case chamber (285) side.

[0190] A first chamber communication chamber (286) for storing oil liquid (L) is formed within the case chamber (285). The first chamber communication chamber (286) is formed by being surrounded by a case member (178), a disc spring (177), a disc (174), a disc (173), a disc (172), a disc (170), a spring member (169), a disc (168), a valve member (167), and a second piston body (166).

[0191] A second chamber communication chamber (287) for storing oil liquid (L) is formed within the case chamber (285). The second chamber communication chamber (287) is formed by being surrounded by a disk (173), a disk (174), a disc spring (177), and a disk (176). The first chamber communication chamber (286) is the part of the case chamber (285) excluding the second chamber communication chamber (287). The second chamber communication chamber (287) communicates with the passage within the passage hole (205) of the disc spring (177), and the passage within the passage hole (205) communicates with the passage within the plurality of passage holes (195) of the bottom portion (191) of the case member (178).

[0192] The first room communication room (286) and the second room communication room (287) are blocked from communicating by a disc spring (177), a disc (174) that contacts the outer edge of the disc spring (177), and a disc (173) that contacts the disc (174).

[0193] As illustrated in FIG. 3, an annular second piston body (166) and a cylindrical case member (178) with a bottom are positioned in the second chamber (23), which is one of the first chamber (22) and the second chamber (23). At that time, the valve seat portion (242) of the second piston body (166) is positioned on the side of the second chamber (23). As illustrated in FIG. 4, the passage within the passage hole (195) of the case member (178) is always in communication with the second chamber (23). Thus, the second chamber communication chamber (287) is in communication with the second chamber (23).

[0194] The first chamber communication chamber (286) is in constant communication with the first chamber (22) through the passage (288) in the communication groove (263) of the second piston body (166) and the intermediate chamber (237) in the second inner wall (233), the axial passage (54) of the rod (31), and the piston inner passage (103) and piston passage (81) provided in the first piston body (21) shown in FIG. 3.

[0195] As the disk (174) shown in FIG. 4 bends in the axial direction, the volumes of the first chamber communication room (286) and the second chamber communication room (287) change. The second chamber communication room (287) decreases in volume to absorb the increase in volume of the first chamber communication room (286) and discharges oil liquid (L) to the second chamber (23). The second chamber communication room (287) increases in volume to absorb the decrease in volume of the first chamber communication room (286) and draws in oil liquid (L) from the second chamber (23). Conversely, the first chamber communication room (286) decreases in volume to absorb the increase in volume of the second chamber communication room (287) and discharges oil liquid (L) toward the first chamber (22) shown in FIG. 3. The first chamber communication chamber (286) increases in volume to absorb the reduction in volume of the second chamber communication chamber (287) and introduces oil liquid (L) from the first chamber (22) side. In this way, the deformation of the disk (174) is prevented from being inhibited by the oil liquid (L) of the first chamber communication chamber (286) and the second chamber communication chamber (287).

[0196] As shown in FIG. 3, a plurality of passage sections (282) of the second piston body (166) are provided facing the second chamber (23) and are in constant communication with the second chamber (23).

[0197] The valve member (167) illustrated in FIG. 4 is flexible. The valve member (167) has an outer diameter equal to the outer diameter of the valve seat portion (245) of the second piston body (166). The valve member (167) is in constant contact with the boss portion (244) and is capable of being seated or separated from the valve seat portion (245), that is, the plurality of round portions (265). By seating the entire valve seat portion (245), the valve member (167) blocks all passage portions (282). Additionally, by separating from any one of the round portions (265) of the valve seat portion (245), the valve member (167) opens the passage portion (282) inside the separated round portion (265).

[0198] The spring member (169) presses the valve member (167) to contact the valve seat portion (245) of the second piston body (166). The valve member (167) sits on the valve seat portion (245) by the pressing force of the spring member (169) and closes the passage portion (282). The valve member (167) is deformed against the pressing force of the spring member (169) and opens the passage portion (282) by separating from the valve seat portion (245).

[0199] When the valve member (167) is separated from the valve seat portion (245), it communicates with a plurality of passage portions (282) and a first chamber communication chamber (286). As a result, the second chamber (23) communicates with the plurality of passage portions (282), the first chamber communication chamber (286), the passage (288) within the communication groove (263) of the second piston body (166), the intermediate chamber (237) within the second inner wall (233), the axial passage (54) of the rod (31), and the piston internal passage (103) and piston passage (81) provided in the first piston body (21) shown in FIG. 3. At this time, the valve member (167) shown in FIG. 4 generates a damping force by suppressing the flow of oil (L) between it and the valve seat portion (245).

[0200] The valve member (167) is an inlet valve that opens when oil liquid (L) is introduced from the second chamber (23) to the first chamber communication chamber (286) through a plurality of passage sections (282). The valve member (167) is a check valve that regulates the outflow of oil liquid (L) through the passage sections (282) from the first chamber communication chamber (286) to the second chamber (23). Here, the passage section (281) is opened outside the range of the valve seat section (245) in the second piston body (166). Because of this, the passage section (281) is always in communication with the first chamber communication chamber (286) regardless of the valve member (167) seated on the valve seat section (245).

[0201] A plurality of passage sections (282), a passage between a valve member (167) and a valve seat section (245) that appears when the valve is opened, a first chamber communication chamber (286), a passage (288) within a communication groove (263), an intermediate chamber (237), an axial passage (54), a passage (103) inside the piston shown in FIG. 3, and a piston passage (81) constitute the second passage (291). The second passage (291) is opened and closed by the valve member (167) shown in FIG. 4. In the second passage (291), oil liquid (L) flows from the second chamber (23), which is the upstream side within the cylinder (4), to the first chamber (22), which is the downstream side, by moving the first piston body (21) toward the second chamber (23). The second passage (291) is a passage on the reduction side through which oil liquid (L) flows from the second chamber (23), which is the upstream side, toward the first chamber (22), which is the downstream side, during the movement of the first piston body (21) toward the second chamber (23), that is, the reduction stroke. At least part of the second passage (291) on the reduction side, in this case the whole, is provided in parallel with the first passage (132) on the reduction side shown in FIG. 2. The second passage (291) includes the first chamber side passage (156).

[0202] As illustrated in FIG. 4, the passage within the passage hole (195), the passage within the passage hole (205), and the second chamber communication chamber (287) form a second chamber communication passage (292). The second chamber communication passage (292) is a reduced-side passage that is always in communication with the second chamber (23). The reduced-side second chamber communication passage (292) is provided separately from the likewise reduced-side second passage (291). The second chamber communication passage (292) is provided in parallel with the second passage (291).

[0203] A valve mechanism (301) is formed by a second piston body (166) including a valve member (167) and a valve seat portion (245), a disc (168), and a spring member (169). The valve mechanism (301) is provided in a second fluid passage (291) on the reduction side. The valve mechanism (301) opens and closes this second fluid passage (291) and generates a damping force by suppressing the flow of oil liquid (L) from this second fluid passage (291) to the first seal (22). The valve mechanism (301) is a valve mechanism on the reduction side.

[0204] The valve mechanism (301) comprises a valve seat portion (245) which is a valve seat and a valve member (167) which is a flexible valve chain, and is a check valve mechanism that allows flow in the direction from the second chamber (23), which is the upstream area, to the first chamber (22), which is the downstream area, during the contraction stroke of the second path (291), while restricting flow in the direction from the first chamber (22), which is the upstream area, to the second chamber (23), which is the downstream area, during the extension stroke. In other words, the valve mechanism (301) allows only flow in the direction from the second chamber (23), which is the upstream area, to the first chamber (22), which is the downstream area, during the contraction stroke of the second path (291).

[0205] The valve mechanism (301) has its valve seat portion (245) provided in the second piston body (166). The valve mechanism (301) is arranged separately from the valve mechanism (86) that generates damping force during the same reduction stroke. The valve member (167) constituting the reduction-side valve mechanism (301) is a reduction-side sub-valve.

[0206] In the valve mechanism (301) on the reducing side, a fixed orifice is not formed anywhere in the valve seat portion (245) and the valve member (167) in contact therewith to communicate the first chamber (22) and the second chamber (23) even when the valve seat portion (245) and the valve member (167) are in contact. In other words, the second passage (291) is not provided with a fixed orifice to constantly communicate the first chamber (22) and the second chamber (23). The second passage (291) is not a passage that constantly communicates the first chamber (22) and the second chamber (23).

[0207] The second flow path (291) on the reduced side, which is capable of connecting the first chamber (22) and the second chamber (23), is parallel to the first flow path (132), which is a passage on the reduced side, which is also capable of connecting the first chamber (22) and the second chamber (23). A valve mechanism (86) is provided in the first flow path (132). A valve mechanism (301) is provided in the second flow path (291). Accordingly, the valve mechanism (86) and the valve mechanism (301), both of which are on the reduced side, are arranged in parallel.

[0208] The valve member (163) is flexible. The valve member (163) has an outer diameter equal to the outer diameter of the valve seat portion (242) of the second piston body (166). The valve member (163) is in constant contact with the boss portion (241) and is capable of being seated or separated from the valve seat portion (242), that is, the plurality of round portions (255). When the valve member (163) is seated on the entire valve seat portion (242), it blocks all passage portions (281). Additionally, when the valve member (163) is separated from any one of the round portions (255) of the valve seat portion (242), it opens the passage portion (281) inside the separated round portion (255).

[0209] The outer diameter of the disc (162) is smaller than the outer diameter of the valve member (163) and smaller than the outer diameter of the boss part (241).

[0210] The spring member (161) has flexibility. The spring member (161) has a substrate portion (311) and a plurality of spring plate portions (312).

[0211] The substrate portion (311) is a circular flat plate with a hole. The substrate portion (311) has an attachment shaft portion (33) fitted to its inner circumference. The outer diameter of the substrate portion (311) is slightly larger than the outer diameter of the disk (162). The substrate portion (311) contacts the disk (162).

[0212] A plurality of spring plate portions (312) extend radially from the outer edge portion of the substrate portion (311). The further the plurality of spring plate portions (312) are from the substrate portion (311) in the axial direction of the substrate portion (311), the further they are from the substrate portion (311) in the radial direction of the substrate portion (311).

[0213] The maximum outer diameter of the spring member (161) is smaller than the outer diameter of the valve member (163). The spring member (161) has a direction in which a plurality of spring plate portions (312) extend from the substrate portion (311) toward the valve member (163) in the axial direction of the substrate portion (311). The spring member (161) presses the leading end of the extension side of the plurality of spring plate portions (312) against the outer circumference side of the valve member (163). By doing so, the spring member (161) presses the plurality of spring plate portions (312) against the outer circumference side of the valve member (163) so that they contact the valve seat portion (242) of the second piston body (166). The valve member (163) sits on the valve seat portion (242) by the pressing force of the spring member (161) and blocks the passage portion (281). The valve member (163) is deformed against the compressive force of the spring member (161) and separates from the valve seat portion (242) to open the passage portion (281).

[0214] The valve member (163) is provided within the second chamber (23). The valve member (163) communicates the first chamber communication chamber (286) and the second chamber (23) through a plurality of passage sections (281) of the second piston body (166) by being spaced apart from the valve seat section (242). At this time, the valve member (163) generates a damping force by suppressing the flow of oil (L) between the valve seat section (242) and the valve member (163). The valve member (163) is a discharge valve that opens when the oil (L) is discharged from the first chamber communication chamber (286) to the second chamber (23) through a plurality of passage sections (281). The valve member (163) is a check valve that regulates the inflow of oil (L) from the second chamber (23) into the first chamber communication chamber (286) through the passage section (281). Here, the passage portion (282) is opened outside the range of the valve seat portion (242) in the second piston body (166). Because of this, the passage portion (282) is always in communication with the second chamber (23) independently of the valve member (163) seated on the valve seat portion (242).

[0215] The radial communication groove (253) formed in the boss portion (241) of the second piston body (166) is a radial flow path (317). The radial flow path (317) is provided at a position opposite to the axial flow path (54) in the radial direction of the second piston body (166) and is connected to the intermediate chamber (237).

[0216] As shown in FIG. 3, the first actual passage (156) including the piston passage (81) and the piston internal passage (103), the axial passage (54) of the rod (31), the intermediate chamber (237) and passage (288) within the second inner wall (233) of the second piston body (166), the first chamber communication chamber (286), the passage section (281), the radial passage (317) shown in FIG. 4, and the passage between the valve member (163) and the valve seat section (242) that appear when the valve is opened constitute the second passage (315).

[0217] The second passage (315) is opened and closed by a valve member (163). The second passage (315) allows oil (L) to flow from the first chamber (22), which is upstream, to the second chamber (23), which is downstream, as the first piston body (21) moves toward the first chamber (22) shown in FIG. 3. The second passage (315) serves as an extension-side passage through which oil (L) flows from the first chamber (22), which is upstream, toward the second chamber (23), which is downstream, during the extension stroke, that is, the movement of the first piston body (21) toward the first chamber (22). The extension-side second passage (315) is provided separately from the extension-side first passage (152). The second passage (315) is provided in parallel with the first passage (152), at least in part, in this case, in part. The second Euro (315) is parallel to the first Euro (152), except for a portion of the first chamber (22) side of the piston internal Euro (103) of the piston passage (81).

[0218] The radial flow path (317) illustrated in FIG. 4 communicates the intermediate chamber (237) and the passage section (281) of the second flow path (315) without passing through the flow path (288) and the first chamber communication chamber (286) within the communication groove (263). The radial flow path (317) communicates from the intermediate chamber (237) to the valve seat section (242). In other words, the radial flow path (317) communicates from the insertion through hole (231) to the valve mechanism (321) including the valve seat section (242).

[0219] As shown in FIG. 3, the rod (31) is formed with an axial channel (54) which is a channel that communicates with the first actual channel (156) and is directed toward the second channel (23) which is the downstream area in the extension stroke, a front-side circumferential groove (53) which is a circumferential groove provided at the end of the axial channel (54) which is the downstream area in the extension stroke of the second channel (23), and a front-side cylindrical part (43) which is a cylindrical part provided toward the second channel (23) rather than the front-side circumferential groove (53).

[0220] As shown in FIG. 4, the disc (160) has an outer diameter equal to the outer diameter of the valve member (163). The disc (160) is flexible.

[0221] A second piston body (166) including a valve member (163) and a valve seat portion (242), a disc (162), and a spring member (161) constitute a valve mechanism (321). The valve mechanism (321) is provided in a second fluid path (315) on the extension side and opens and closes this second fluid path (315). The valve mechanism (321) generates a damping force by suppressing the flow of oil liquid (L) from this second fluid path (315) to the second seal (23). The valve mechanism (321) is a second damping force generating mechanism on the extension side. The valve mechanism (321) is arranged separately from the valve mechanism (85) that generates a damping force during the same extension stroke. The valve member (163) constituting the valve mechanism (321) on the extension side is a sub-valve on the extension side. The valve mechanism (321) includes a radial fluid path (317). In the valve mechanism (321), during the extension stroke, the oil liquid (L) flows from the first actual flow path (156) shown in FIG. 3 to the second chamber (23), which is the downstream area, via the axial flow path (54) including the tip-side circumferential groove (53), the intermediate chamber (237), and the radial flow path (317) shown in FIG. 4. In other words, in the valve mechanism (321), during the extension stroke, the oil liquid (L) flows from the first actual flow path (156) to the second chamber (23), which is the downstream area, via the axial flow path (54) including the tip-side circumferential groove (53), the insertion through hole (231), and the radial flow path (317).

[0222] The valve mechanism (321) includes a valve seat portion (242) which is a valve seat and a valve member (163) which is a flexible valve chain, and is a check valve mechanism that allows flow in the direction from the first chamber (22), which is the upstream area, to the second chamber (23), which is the downstream area, during the extension stroke of the second passage (315) which includes the first actual passage (156), while restricting flow in the direction from the second chamber (23), which is the upstream area, to the first chamber (22), which is the downstream area, during the contraction stroke. In other words, the valve mechanism (321) allows only flow in the direction from the first chamber (22), which is the upstream area, to the second chamber (23), which is the downstream area, during the extension stroke of the second passage (315) which includes the first actual passage (156).

[0223] The second chamber communication chamber (287) and the disk (174), disk (173), disc spring (177), and disk (176) forming it constitute a second chamber volume variable mechanism (325) capable of changing the volume of the second chamber communication chamber (287).

[0224] The second real volume variable mechanism (325) causes the disk (174) and disk (173) to deform and move as a single unit away from the bottom portion (191). Then, the second real volume variable mechanism (325) changes to increase the volume of the second real communication chamber (287). At that time, if the disk (174) is maintained in contact with the disc spring (177) over its entire circumference, the space between it and the outer tapered portion (202) of the disc spring (177) is closed. That is, when the disk (174) is deformed away from the bottom portion (191), if it is maintained in contact with the disc spring (177) over its entire circumference, the blockage between the second real communication chamber (287) and the first real communication chamber (286) is maintained.

[0225] Additionally, the second volume variable mechanism (325) moves the disk (174) and disk (173) as a single unit so that they are close to the bottom portion (191). Then, the second volume variable mechanism (325) changes to reduce the volume of the second chamber communication chamber (287). At that time, the disk (174) is maintained in contact with the disc spring (177) as a whole, and the space between it and the outer tapered portion (202) of the disc spring (177) is closed.

[0226] The first chamber communication chamber (286) communicating with the first chamber (22) forms part of the second chamber (315) on the extension side. The first chamber communication chamber, the second piston body (166) forming it, the valve member (167), the disc (168), the spring member (169), the disc (170), the disc (172), the disc (173), the disc (174), the disc (176), the disc spring (177), and the case member (178) form a first chamber volume variable mechanism (326) capable of changing the volume of the first chamber communication chamber (286).

[0227] The first real volume variable mechanism (326) causes the disk (174) and disk (173) to deform and move as a single unit away from the disk (170). Then, the first real volume variable mechanism (326) changes to increase the volume of the first real communication chamber (286). At that time, if the disk (173) is maintained in contact with the disk (174) as a whole, it blocks the passage within the communication hole (211) of the disk (174). That is, it maintains the blockage state between the second real communication chamber (287) and the first real communication chamber (286).

[0228] Additionally, the first volume variable mechanism (326) moves the disk (174) and disk (173) by deforming them so that they approach the disk (170). Then, the first volume variable mechanism (326) changes the volume of the first communication chamber (286) to reduce it. At that time, the disk (173) remains in contact with the disk (174) as a whole, thereby blocking the passage within the communication hole (211) of the disk (174).

[0229] In the valve mechanism (321) on the extension side, a fixed orifice is not formed anywhere in the valve seat portion (242) and the valve member (163) in contact therewith to connect the first chamber (22) and the second chamber (23) even when the valve seat portion (242) and the valve member (163) are in contact. That is, the valve mechanism (321) on the extension side does not connect the first chamber (22) and the second chamber (23) when the valve seat portion (242) and the valve member (163) are in contact. In other words, the second passage (315) is not provided with a fixed orifice to constantly connect the first chamber (22) and the second chamber (23). The second passage (315) is not a passage that constantly connects the first chamber (22) and the second chamber (23).

[0230] A spring member (161), a disc (162), a valve member (163), an O-ring (165), a second piston body (166), a valve member (167), a disc (168), a spring member (169), a disc (170), a disc (172), a disc (173), a disc (174), a disc (176), a disc spring (177), and a case member (178) constitute the second piston (331). The second piston body (166) is a sintered body that constitutes the second piston (331) used in the shock absorber (1).

[0231] Accordingly, the second piston (331) has a first inner wall (232) that penetrates the center in the axial direction and through which the rod (31) is inserted, and a second inner wall (233) that is spaced radially from the rod (31) more than the first inner wall (232), and has an insertion through hole (231) that communicates directly or indirectly with the tip-side circumferential groove (53) of the rod (31). In addition, the second piston (331) includes a valve seat portion (242) which is a valve seat and a valve member (163) which is a flexible valve chain, and has a valve mechanism (321) that allows only flow in the direction from the first seal (22) to the second seal (23) in the first seal passage (156). In addition, the second piston (331) has a valve mechanism (301) and a valve mechanism (321). Additionally, the second piston (331) has a case member (178) that forms a first chamber communication chamber (286) for storing oil liquid (L) by communicating with an intermediate chamber (237) formed by a second inner wall (233) and a rod (31). Additionally, the second piston (331) has a valve mechanism (321) that allows only the flow of oil liquid (L) in the direction from the first chamber (22) to the second chamber (23), comprising an insertion through hole (231) that penetrates the center in the axial direction and through which the rod (31) is inserted, a valve seat portion (242) which is a valve seat, and a valve member (163) which is a valve chain that is flexible and is placed in the axial passage (54). Additionally, the second piston (331) has a radial passage (317) that is installed at a position opposite to the axial passage (54) and communicates with the valve mechanism (321).Additionally, the second piston (331) further has one or more extensions (235) that extend in the radial direction from the insertion through hole body (234) and are formed from a side opposite to the side facing the first piston (155) to a position communicating with the axial flow path (54), a case member (178) that communicates with the extensions (235) and forms a first seal communication chamber (286) that stores oil liquid (L), and a passage portion (281) that connects the first seal communication chamber (286) and the valve mechanism (321).

[0232] As shown in FIG. 3, the second piston (331) has an outer diameter smaller than the outer diameter of the first piston (155). The second piston (331) has a gap in the diameter direction between it and the inner tube (2). The second piston (331) extends across the tip-side circumferential groove (53) and the tip-side cylindrical portion (43) of the rod (31).

[0233] As described above, the first volume variable mechanism (326) illustrated in FIG. 4 changes the disk (174) to move away from the disk (170) in a deformed manner, thereby increasing the volume of the first chamber communication chamber (286). At that time, when the valve mechanism (321) is in a valve-open state, there may be cases where the pressure difference between the first chamber communication chamber (286) and the second chamber communication chamber (287) exceeds a predetermined value. Then, the first volume variable mechanism (326) causes the disk (174) to elastically deform the outer tapered portion (202) of the disc spring (177) toward the bottom portion (191), and the outer circumference side is deformed toward the bottom portion (191). As a result, the disk (174) moves away from the disk (173) in the axial direction. Then, the disk (174) connects the first room communication room (286) and the second room communication room (287) through the passage within the communication hole (211).

[0234] The disc (174) and the disc (173) constitute the relief mechanism (335). The relief mechanism (335) flows oil (L) from the first chamber communication chamber (286) to the second chamber communication chamber (287) when the valve is opened. In other words, the relief mechanism (335) flows oil (L) from the first chamber (22) to the second chamber (23). The relief mechanism (335) is an extension-side relief mechanism. The relief mechanism (335) is set so that the valve opens after the extension-side valve mechanism (321) is opened.

[0235] The second volume variable mechanism (325) changes the disk (174) so ​​that it moves in a deformed manner to approach the disk (170), thereby increasing the volume of the second chamber communication chamber (287). At that time, when the valve mechanism (301) is in a valve-open state, there may be cases where the pressure difference between the first chamber communication chamber (286) and the second chamber communication chamber (287) exceeds a predetermined value. Then, the amount of deformation on the outer side of the disk (174) increases in the second chamber volume variable mechanism (325). As a result, the disk (174) moves away in the axial direction from the outer edge portion of the disc spring (177). Then, the disk (174) connects the second chamber communication chamber (287) and the first chamber communication chamber (286) through the space between it and the disc spring (177).

[0236] A disc (174) and a disc spring (177) constitute a relief mechanism (336). The relief mechanism (336) flows oil (L) from the second chamber communication chamber (287) to the first chamber communication chamber (286) when the valve is opened. In other words, the relief mechanism (336) flows oil (L) from the second chamber (23) to the first chamber (22). The relief mechanism (336) is a relief mechanism on the reduction side. The relief mechanism (336) is set so that the valve opens after the valve mechanism (301) on the reduction side is opened.

[0237] As illustrated in FIG. 1, the base valve (15) has a valve mechanism (351) on the axial bottom portion (9) side of the valve body (12). Additionally, the base valve (15) has a valve mechanism (352) on the side opposite to the axial bottom portion (9) of the valve body (12).

[0238] When the rod (31) moves toward the reduction side and the first piston body (21) moves in a direction that narrows the second chamber (23), and the pressure in the second chamber (23) becomes higher than the pressure in the reservoir chamber (5) by a predetermined value or more, the base valve (15) has the valve mechanism (351) opened to allow the oil (L) in the second chamber (23) to flow into the reservoir chamber (5). At that time, the valve mechanism (351) generates a damping force.

[0239] When the rod (31) moves toward the extension side and the first piston body (21) moves toward the first chamber (22), and the pressure in the second chamber (23) is lower than the pressure in the reservoir chamber (5), the base valve (15) opens the valve mechanism (352) to allow the oil (L) from the reservoir chamber (5) to flow into the second chamber (23). At that time, the valve mechanism (352) generates a damping force. The valve mechanism (352) may be a suction valve that allows the oil (L) to flow from the reservoir chamber (5) into the second chamber (23) without substantially generating a damping force.

[0240] Next, the operation of the buffer (1) is explained.

[0241] Among the valve mechanism (85) and valve mechanism (321) shown in FIG. 3, which are both extension-side, the valve member (151) of the valve mechanism (85) has higher rigidity and a higher valve opening pressure than the valve member (163) shown in FIG. 4 of the valve mechanism (321). Therefore, during the extension stroke, in the ultra-low speed region where the piston speed is lower than a predetermined value, the valve mechanism (85) shown in FIG. 3 is valve-closed while the valve mechanism (321) is valve-opened. In other words, the valve mechanism (321) is valve-opened at a low piston speed where the piston speed is lower than that of the valve mechanism (85) to generate damping force. Furthermore, in the normal speed region where the piston speed is greater than this predetermined value, the valve mechanism (85) and the valve mechanism (321) are valve-opened together. The valve member (163) shown in FIG. 4 is a micro-low speed valve that is deformed against the compressive force of the spring member (161) in the region where the piston speed is micro-low speed, and the valve opens to generate a damping force.

[0242] That is, in the extension stroke, the first piston body (21) shown in FIG. 3 moves toward the first chamber (22), thereby increasing the pressure of the first chamber (22) and decreasing the pressure of the second chamber (23). Here, there is no fixed orifice in either the valve mechanism (85, 86) or the valve mechanism (301, 321) that constantly communicates the first chamber (22) and the second chamber (23). Accordingly, the oil (L) of the first chamber (22) flows into the first chamber communication chamber (286) through the first chamber side passage (156) of the first piston body (21), the axial passage (54) of the rod (31), and the intermediate chamber (237) and passage (288) of the second piston body (166). By doing so, the first chamber communication chamber (286) is pressurized. Because of this, the first volume variable mechanism (326) bends the portion of the disc (174) that is radially inner to the contact position with the outer tapered portion (202) of the disc spring (177) of the disc (174) toward the bottom portion (191) before the valve mechanism (321) opens. Then, the disc (174) increases the capacity of the first chamber communication chamber (286). By this, the first volume variable mechanism (326) suppresses the rise in pressure of the first chamber communication chamber (286). At this time, the disc (173) is deformed along the disc (174) to maintain the closed state of the passage within the communication hole (211). Also, at this time, because the disc (174) moves by bending toward the bottom portion (191), the second volume variable mechanism (325) reduces the volume of the second chamber communication chamber (287).

[0243] Here, during the extension stroke when the buffer (1) receives a low-frequency input (when a large amplitude is applied), the amount of oil (L) flowing from the first chamber (22) to the first chamber communication chamber (286) as described above increases. Because of this, the disk (174) is significantly deformed. As the amount of deformation of the disk (174) increases, the reaction force due to the support rigidity of the clamped inner side increases, thereby limiting the amount of deformation. Consequently, the first chamber communication chamber (286) is pressurized. As a result, the second passage (315) is pressurized until the valve mechanism (321) opens.

[0244] At this time, there is no fixed orifice in either the valve mechanism (85, 86) or the valve mechanism (301, 321) that constantly communicates the first chamber (22) and the second chamber (23). Because of this, the damping force increases rapidly during the extension stroke when the piston speed is below the first predetermined value at which the valve mechanism (321) opens. Additionally, in the region where the piston speed is higher than the first predetermined value and in the ultra-low speed region where it is lower than the second predetermined value which is higher than the first predetermined value, the valve mechanism (321) opens while the valve mechanism (85) is in a closed state.

[0245] That is, the valve member (163) is deformed against the compressive force of the spring member (161) and separated from the valve seat portion (242). Then, the first chamber (22) and the second chamber (23) are connected in the second passage (315) on the extension side. Accordingly, the oil liquid (L) of the first chamber (22) flows into the second chamber (23) through the first chamber side passage (156) of the first piston body (21), the axial passage (54) of the rod (31), the intermediate chamber (237), the passage (288) and passage portion (281) of the second piston body (166), and the passage between the valve member (163) and the valve seat portion (242). Additionally, at that time, the oil (L) of the first chamber (22) flows into the second chamber (23) through the passage between the first chamber measuring path (156), the axial path (54), the intermediate chamber (237) and the radial path (317) of the second piston body (166), the valve member (163), and the valve seat portion (242). By these, a damping force of the valve characteristic (a characteristic in which the damping force is nearly proportional to the piston speed) is obtained even in the ultra-low speed region where the piston speed is lower than the second predetermined value.

[0246] Additionally, in the extension stroke, a relief mechanism (335) is provided that opens after the valve mechanism (321) has opened. Accordingly, when the pressure in the first chamber communication chamber (286) increases in the normal speed range where the piston speed is greater than or equal to a second predetermined value, the relief mechanism (335) opens while the valve mechanism (321) remains in an open state, causing the oil liquid (L) of the first chamber communication chamber (286) to flow into the second chamber (23) through the second chamber communication chamber (287) and the second chamber communication path (292). After that, the valve mechanism (85) opens while the valve mechanism (321) and the relief mechanism (335) remain in an open state. That is, as described above, when the valve member (163) is deformed against the compressive force of the spring member (161) and separated from the valve seat portion (242), oil (L) flows from the first chamber (22) to the second chamber (23) in the second passage (315) on the extension side. After that, with the valve mechanism (321) in the valve open state, the relief mechanism (335) is opened so that oil (L) flows from the first chamber (22) to the second chamber (23) in the second chamber communication chamber (287) and the second chamber communication passage (292). At this time, the flow of oil (L) narrows in the first chamber side passage (156) provided in the second passage (315). As a result, the pressure applied to the valve member (151) increases, the differential pressure increases, and the valve member (151) is separated from the valve seat portion (105), causing oil (L) to flow from the first chamber (22) to the second chamber (23) in the first passage (152) on the extension side. Accordingly, the oil (L) of the first chamber (22) flows into the second chamber (23) through the first passage (152), which includes the piston passage (81) and the passage between the valve member (151) and the valve seat portion (105).

[0247] Accordingly, even in the normal speed region where the piston speed is greater than or equal to a second predetermined value, a damping force with valve characteristics (where the damping force is nearly proportional to the piston speed) is obtained. The rate of increase of the damping force on the extension side with respect to the increase in piston speed in the normal speed region is lower than the rate of increase of the damping force on the extension side with respect to the increase in piston speed in the ultra-low speed region.

[0248] As described above, in the extension stroke, in the normal speed range where the piston speed is greater than or equal to the second predetermined value, the valve member (151) is valve-opened so that the oil liquid (L) can flow through the first flow path (152) in a large volume. As a result, the flow rate through the passage between the valve member (163) and the valve seat portion (242) is reduced. Therefore, for example, the rate of increase of the damping force for the increase of the piston speed in the normal speed range (greater than or equal to the second predetermined value) can be lowered. By doing so, the degree of design freedom can be expanded.

[0249] In the extension stroke when a high frequency input (small amplitude excitation) is input to the buffer (1) at a frequency higher than the low frequency input described above, the amount of oil liquid (L) flowing from the first chamber (22) to the first chamber communication chamber (286) is small. Because of this, the deformation of the disk (174) is small, and the first chamber volume variable mechanism (326) is able to absorb the volume of oil liquid (L) flowing into the first chamber communication chamber (286) by the amount of bending of the disk (174). Therefore, the pressure increase of the first chamber communication chamber (286) is reduced. Because of this, when the ultra-low speed damping force increases, it becomes the same as when there is no disk (174). In other words, when the ultra-low speed damping force increases, it becomes possible to make the first chamber communication chamber (286) constantly communicate with the second chamber (23) in the second chamber communication path (292), that is, to make it the same as a structure without a valve mechanism (321).

[0250] Accordingly, in the extension stroke during high-frequency input, the increase in the ultra-low speed damping force becomes gradual compared to the damping force characteristics during low-frequency input or conventional damping force characteristics. In other words, during the extension stroke, if the frequency of the first piston body (21) exceeds a predetermined frequency, the flow rate of the oil liquid (L) to the valve member (163) of the valve mechanism (321) is limited by the first volume variable mechanism (326) including the disc (174). Additionally, the change in damping force (slope of damping force with respect to piston speed) until the valve opening of the valve mechanism (321) can be adjusted by the difference in the rigidity (plate thickness, etc.) of the disc (174).

[0251] Among the valve mechanism (86) and valve mechanism (301), which are both on the reduction side, the valve member (131) of the valve mechanism (86) has higher rigidity and a higher valve opening pressure than the valve member (167) of the valve mechanism (301). Therefore, during the reduction stroke, in the ultra-low speed region where the piston speed is lower than a predetermined value, the valve mechanism (86) is in a closed state and the valve mechanism (301) is opened. In other words, the valve mechanism (301) is opened to generate damping force when the piston speed is lower than that of the valve mechanism (86). In the normal speed region where the piston speed is greater than this predetermined value, the valve mechanism (86) and the valve mechanism (301) are opened together. The valve member (167) is an ultra-low speed valve that opens to generate damping force in the ultra-low speed region where the piston speed is ultra-low.

[0252] That is, during the reduction stroke, the first piston body (21) moves toward the second chamber (23), thereby increasing the pressure in the second chamber (23) and decreasing the pressure in the first chamber (22). Here, there is no fixed orifice in either the valve mechanism (85, 86) or the valve mechanism (301, 321) that constantly communicates the second chamber (23) and the first chamber (22). Because of this, the oil (L) of the second chamber (23) flows into the second chamber communication chamber (287) through the second chamber communication path (292). As a result, the second chamber communication chamber (287) is pressurized. Because of this, the second chamber volume variable mechanism (325) causes the disc (174) to bend toward the disc (170) before the valve mechanism (301) opens. Accordingly, the disk (174) increases the capacity of the second chamber communication chamber (287). As a result, the second chamber volume variable mechanism (325) suppresses the rise in pressure of the second chamber communication chamber (287). At this time, the disk (173) is deformed along the disk (174) to maintain the closed state of the passage within the communication hole (211). Also, at this time, because the disk (174) moves in a bent direction toward the disk (170), the first chamber volume variable mechanism (326) reduces the volume of the first chamber communication chamber (286).

[0253] Here, during the reduction stroke when the buffer (1) receives a low-frequency input (when a large amplitude is applied), the amount of oil (L) flowing from the second chamber (23) to the second chamber communication chamber (287) increases. Because of this, the disk (174) is significantly deformed. As the amount of deformation of the disk (174) increases, the reaction force due to the support rigidity of the clamped inner side increases, thereby limiting the amount of deformation. Consequently, the second chamber communication chamber (287) is pressurized. As a result, the second passage (291) is pressurized until the valve mechanism (301) opens.

[0254] At this time, there is no fixed orifice in either the valve mechanism (85, 86) or the valve mechanism (301, 321) that constantly communicates the second chamber (23) and the first chamber (22). Because of this, the damping force increases rapidly during the reduction stroke when the piston speed is below the third predetermined value at which the valve mechanism (301) opens. Additionally, in the region where the piston speed is higher than the third predetermined value and in the ultra-low speed region where it is lower than the fourth predetermined value, the valve mechanism (301) opens while the valve mechanism (86) is in a closed state.

[0255] That is, when the valve member (167) is deformed against the compressive force of the spring member (169) and separated from the valve seat portion (245), the second passage (291) on the reduced side connects the second chamber (23) and the first chamber (22). Accordingly, the oil (L) of the second chamber (23) flows to the first chamber (22) through the passage portion (282) within the second piston body (166), the passage between the valve member (167) and the valve seat portion (245), the first chamber connecting chamber (286), the passage (288) and intermediate chamber (237) of the second piston body (166), the axial passage (54) of the rod (31), the first chamber side passage (156) of the first piston body (21), and the piston passage (81) of the first piston body (21). Accordingly, even in the ultra-low speed region where the piston speed is lower than the fourth predetermined value, a damping force of the valve characteristic (a characteristic in which the damping force is nearly proportional to the piston speed) is obtained.

[0256] Additionally, in the reduction stroke, a relief mechanism (336) is provided that opens after the valve mechanism (301) has opened. Therefore, in the normal speed range where the piston speed is greater than or equal to the fourth predetermined value, when the pressure in the second chamber communication chamber (287) increases, the relief mechanism (336) opens while the valve mechanism (301) remains in an open state, causing the oil liquid (L) of the second chamber (23) and the second chamber communication chamber (287) to flow into the first chamber (22) through the first chamber communication chamber (286). After that, the valve mechanism (86) opens while the valve mechanism (301) and the relief mechanism (336) remain in an open state. That is, as described above, when the valve member (167) is separated from the valve seat portion (245), oil (L) flows from the second chamber (23) to the first chamber (22) in the second passage (291) on the reduction side. Then, with the valve mechanism (301) in the valve open state, the relief mechanism (336) is opened to allow oil (L) to flow from the second chamber (23) to the first chamber (22). At this time, the flow of oil (L) narrows in the piston internal passage (103) provided downstream of the valve member (167) and the relief mechanism (336) in the second passage (291). As a result, the pressure applied to the valve member (131) increases, and the differential pressure increases. Then, the valve member (131) is separated from the valve seat portion (115) and the oil liquid (L) flows from the second chamber (23) to the first chamber (22) in the first passage (132) on the reducing side. Accordingly, the oil liquid (L) of the second chamber (23) flows to the first chamber (22) through the piston passage (82) and the passage between the valve member (131) and the valve seat portion (115).

[0257] Accordingly, even in the normal speed region where the piston speed is greater than or equal to the fourth predetermined value, a damping force with valve characteristics (where the damping force is nearly proportional to the piston speed) is obtained. The rate of increase of the damping force on the reduction side with respect to the increase in piston speed in the normal speed region is lower than the rate of increase of the damping force on the reduction side with respect to the increase in piston speed in the ultra-low speed region.

[0258] As described above, in the reduction stroke, in the normal speed range where the piston speed is greater than or equal to the fourth predetermined value, the valve member (131) is valve-opened so that the oil liquid (L) can flow through the first flow path (132) in a large volume. As a result, the flow rate through the passage between the valve member (167) and the valve seat portion (245) is reduced. Therefore, for example, the rate of increase of the damping force for the increase of the piston speed in the normal speed range (greater than or equal to the fourth predetermined value) can be lowered. By doing so, the degree of design freedom can be expanded.

[0259] In the reduction stroke when a high frequency input (small amplitude excitation) is input to the buffer (1) at a frequency higher than the low frequency input mentioned above, the amount of oil liquid (L) flowing from the second chamber (23) to the second chamber communication chamber (287) is small. Because of this, the deformation of the disk (174) is small. As a result, the second chamber volume variable mechanism (325) is able to absorb the volume of oil liquid (L) flowing into the second chamber communication chamber (287) by the amount of bending of the disk (174). Therefore, the pressure increase of the second chamber communication chamber (287) is reduced. Because of this, when the ultra-low speed damping force increases, it becomes the same as when there is no disk (174). In other words, when the ultra-low speed damping force increases, it becomes possible to make the second chamber communication chamber (287) always communicate with the first chamber communication chamber (286), that is, to make it the same as a structure without a valve mechanism (301).

[0260] Accordingly, in the reduction stroke during high-frequency input, the increase in the ultra-low speed damping force becomes gradual compared to the low-frequency input or conventional damping force characteristics. In other words, when the frequency of the first piston body (21) exceeds a predetermined frequency, the flow rate of the oil liquid (L) to the valve member (167) of the valve mechanism (301) is limited by the second volume variable mechanism (325) including the disk (174). Additionally, the change in damping force (slope of damping force with respect to piston speed) until the valve of the valve mechanism (301) opens can be adjusted by the difference in the rigidity (plate thickness, etc.) of the disk (174).

[0261] However, the aforementioned Patent Document 1 discloses generating a damping force by moving a piston installed on a piston rod within a cylinder. This damper has a piston, a valve body, and a piston body that seats or separates the valve body. In this type of damper, the piston body has a plurality of rounded portions spaced apart in the circumferential direction, and the valve body seats or separates the valve body from these rounded portions. When such a piston body is formed as a sintered body made of sintered metal, a burr may form at the boundary between the end surface in the axial direction of the piston body and the side surface in the radial direction of the piston body, in the portion between the rounded portions adjacent to the circumferential direction of the piston body. When such a burr is formed, a removal operation is required, but since a cutting tool must be applied while avoiding the rounded portions, the operation is cumbersome and may lead to increased costs.

[0262] The second piston body (166), which is a sintered body of the embodiment, is formed in a cylindrical shape having a base portion (240) having a side portion (401), a base portion end surface (402) that is continuous with respect to the side portion (401) through an inclined portion (435), and a base portion end surface (403) that is continuous with respect to the side portion (401) through an inclined portion (445). Because of this, the second piston body (166) can suppress the occurrence of burrs between the side portion (401) and the base portion end surface (402) by ensuring that the side portion (401) and the base portion end surface (402) of the base portion (240) are continuous with respect to the side portion (401) and the base portion end surface (402) through an inclined portion (435). Additionally, the second piston body (166) can suppress the occurrence of burrs between the side portion (401) and the base portion end surface (403) by having the side portion (401) of the base portion (240) and the base portion end surface (403) connected through an inclined portion (445). Additionally, the second piston body (166) can suppress the occurrence of burrs between the outer portion (257) and the side portion (401) because the outer portion (257) provided along the outer circumference of the base portion end surface (402) of the round portion (255) is connected to the side portion (401) through an inclined portion (432) that forms an obtuse angle A. Additionally, the second piston body (166) can suppress the occurrence of burrs between the outer edge (267) and the side part (401) because the outer edge (267), which is provided along the outer circumference of the base end surface (403) of the round part (265), is continuous through an inclined part (442) that forms an obtuse angle B with the side part (401). Therefore, the second piston body (166) can suppress the increase in costs because the burr removal operation is unnecessary or can be suppressed.

[0263] The second piston body (166) can form a passage for both the extension stroke and the contraction stroke in the second piston body (166) because it has a through hole (259) formed in the area where the base portion (240) is surrounded by the outer edge portion (257) and a pair of arm portions (256), and a through hole (269) formed between the arm portions (256) of two adjacent round portions (255) on the base portion (240). Additionally, the second piston body (166) has a through hole (269) formed in an area where the base portion (240) is surrounded by the outer edge portion (267) and a pair of arm portions (266), and a through hole (259) formed between the arm portions (266) of two adjacent round portions (265) on the base portion (240), so that a flow path for both the extension stroke and the contraction stroke can be formed in the second piston body (166). Accordingly, the second piston body (166) can suppress cost increase.

[0264] The second piston body (166) has a round portion (255) and a round portion (265) arranged so as to be out of phase on both sides of the base portion end surface (402) on one side of the base portion (240) and the base portion end surface (403) on the other side, and a through hole (259) provided in the area surrounded by the outer edge portion (257) and a pair of arm portions (256) functions as a through hole formed between the arm portions (266) of two adjacent round portions (265) on the base portion end surface (403), and a through hole (269) formed in the area surrounded by the outer edge portion (267) and a pair of arm portions (266) functions as a through hole formed between the arm portions (256) of two adjacent round portions (255) on the base portion end surface (402). It functions as a through hole provided. Because of this, the second piston body (166) can efficiently form a flow path for both the extension stroke and the contraction stroke within the second piston body (166). Accordingly, the second piston body (166) can suppress cost increase.

[0265] In the second piston body (166), the obtuse angle B formed by the inclined portion (435) with respect to the side portion (401) is smaller than the obtuse angle A formed by the inclined portion (432) with respect to the side portion (401), and the obtuse angle B formed by the inclined portion (445) with respect to the side portion (401) is smaller. Therefore, the second piston body (166) has good formability.

[0266] In the second piston body (166), the inclined portion (435) of the base portion (240) is located closer to the center C in the axial direction of the side portion (401) than the inclined portion (432) of the outer edge portion (257), and the inclined portion (445) is located closer to the center C in the axial direction of the side portion (401) than the inclined portion (442) of the outer edge portion (267). Accordingly, the second piston body (166) has good moldability.

[0267] In the method of manufacturing the second piston body (166), a flat portion (503) is provided on the outer side in the radial direction of the inclined portion (432A) of the outer edge (257A) of the round portion (255A) of the molded product (166A) formed in the compression process and the inclined portion (435A) of the base portion (240A). Additionally, a flat portion (513) is provided on the outer side in the radial direction of the inclined portion (442A) of the outer edge (267A) of the round portion (265A) of the molded product (166A) after the compression process and the inclined portion (445A) of the base portion (240A). Then, after the sintering process, the portion on the outer side in the radial direction of the inclined portion (435A, 445A) is removed, and the portion on the outer side in the radial direction of the inclined portion (432A, 442A) is removed from the predetermined position. Accordingly, for example, the part forming the inclined portion (432A) and the flat portion (503) becomes a mold M with the shape as shown in FIG. 14, and the inclined portion forming part (432a) forming the inclined portion (432A) and the flat portion forming part (503a) forming the flat portion (503) form an obtuse angle, thereby eliminating the acute angle portion. Although not illustrated, the mold M is the same for the part forming the inclined portion (435A), the part forming the inclined portion (442A), and the part forming the inclined portion (445A), and the acute angle portion can be eliminated.

[0268] In this regard, if the molded product (166A) does not have, for example, a flat portion (503), the leading edge of the inclined portion forming portion (432a) that forms the inclined portion (432A) of the mold M becomes an acute angle, as shown in FIG. 15. In a mold, the acute angle portion inevitably becomes thinner and is therefore susceptible to wear and tear, which is a factor that worsens the durability of the mold, so it is desirable to avoid it. However, if the acute angle portion is avoided and the round end surface is formed at a right angle as in the prior example, a problem arises in removing the burr as described above.

[0269] Meanwhile, regarding the roundness of the piston, extending it to the entire outer diameter allows for the use of a larger valve body. Since this expands the hydraulic pressure area, it is desirable in terms of valve opening characteristics. More specifically, as the valve body becomes larger, the distance from the clamped center (point) to the outer end increases, and the location (point of effect) where the valve opening pressure acts also moves further away. Consequently, even with the same plate thickness, the required valve opening pressure is lowered, and since valve characteristics occur even in the ultra-low flow velocity region, the valve opening characteristics are improved.

[0270] In addition, if only the valve body is enlarged without increasing the round diameter, equal pressure acts on both sides outside the round, and since no differential pressure is generated in this part, the aforementioned effect does not occur.

[0271] In this embodiment, by providing an inclined portion (432A) and an inclined portion (442A), the generation of burrs is suppressed, and by providing a flat portion (503, 513) with a diameter larger than the intended piston diameter, the acute angle portion of the mold M is eliminated, thereby extending the life of the mold M, and by removing the flat portion (503, 513), it is possible to use a larger valve body (valve member (163, 167)) with superior valve opening characteristics.

[0272] The method of manufacturing the second piston body (166) involves forming a groove (502) on the base end surface (402) of a molded product (166A) formed in a compression process, and a portion of the groove (502) that is on the main body (501) side becomes an inclined portion (435) that forms an obtuse angle continuously with respect to the side portion (401). Additionally, a groove (512) is formed on the base end surface (403) of the molded product (166A), and a portion of the groove (512) that is on the main body (501) side becomes an inclined portion (445) that forms an obtuse angle continuously with respect to the side portion (401). Thus, the inclined portions (435, 445) can be easily formed.

[0273] In addition, the above embodiments may be modified as shown in the following variations.

[0274] <Variation Example>

[0275] Instead of the inclined portion (445) of the second piston body (166), an arc-shaped portion (445D) may be formed as shown in FIG. 16. In this case, an arc-shaped portion (445D) is formed in the base portion (240) that is continuous with the base portion end surface (403) and the side portion (401). Accordingly, the base portion (240) is continuous with respect to the side portion (401) through the arc-shaped portion (445D). The arc-shaped portion (445D) forms a convex arc shape toward the outside of the second piston body (166) when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The base portion end surface (403) and the side portion (401) intersect in the tangential direction of the arc-shaped portion (445D). The diameter of the arc-shaped portion (445D) decreases as it approaches the base portion end surface (403) in the axial direction of the second piston body (166). In this case, the arc-shaped portion (445D) is formed in the base portion (240) at a position between all combinations of adjacent round portions (265) in the circumferential direction of the second piston body (166). In this case as well, the second piston body (166) is connected through the arc-shaped portion (445D) between the side portion (401) of the base portion (240) and the base portion end surface (403), thereby suppressing the occurrence of burrs between the side portion (401) and the base portion end surface (403).

[0276] Instead of the inclined portion (435) of the second piston body (166), an arc-shaped portion (435D) may be formed as shown in FIG. 17. In this case, an arc-shaped portion (435D) is formed in the base portion (240) that is continuous with the base portion end surface (402) and the side portion (401). Accordingly, the base portion (240) is continuous with respect to the side portion (401) through the arc-shaped portion (435D). The arc-shaped portion (435D) forms a convex arc shape toward the outside of the second piston body (166) when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The base portion end surface (402) and the side portion (401) intersect in the tangential direction of the arc-shaped portion (435D). The diameter of the arc-shaped portion (435D) increases as it approaches the side portion (401) in the axial direction of the second piston body (166). In this case, the arc-shaped portion (435D) is formed in the base portion (240) at a position between all combinations of adjacent round portions (255) in the circumferential direction of the second piston body (166). In this case as well, the second piston body (166) is continuous through the arc-shaped portion (345D) between the side portion (401) of the base portion (240) and the base portion end surface (402), thereby suppressing the occurrence of burrs between the side portion (401) and the base portion end surface (402).

[0277] Instead of the inclined portion (432) of the second piston body (166), an arc-shaped portion (432D) may be formed as shown in FIG. 16. In this case, an arc-shaped portion (432D) that is continuous with the front end surface (412) and the side portion (401) is formed on the outer edge portion (257). Thus, the outer edge portion (257) is continuous with respect to the side portion (401) through the arc-shaped portion (432D). The arc-shaped portion (432D) forms a convex arc shape toward the outside of the second piston body (166) when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The front end surface (412) and the side portion (401) intersect at the tangential direction of each of the two ends of the arc-shaped portion (432D). The diameter of the arc-shaped portion (432D) increases as it approaches the side portion (401) in the axial direction of the second piston body (166). In this case as well, the second piston body (166) can suppress the occurrence of burrs between the side portion (401) and the base portion end surface (402) by having the outer edge portion (257) of the second piston body (166) continuous through the arc-shaped portion (342D) between the side portion (401).

[0278] Instead of the inclined portion (442) of the second piston body (166), an arc-shaped portion (442D) may be formed as shown in FIG. 17. In this case, an arc-shaped portion (442D) that is continuous with the front end surface (412) and the side portion (401) is formed on the outer edge portion (267). Thus, the outer edge portion (267) is continuous with respect to the side portion (401) through the arc-shaped portion (442D). The arc-shaped portion (442D) forms a convex arc shape toward the outside of the second piston body (166) when the second piston body (166) is cross-sectionally in a plane including the center axis of the second piston body (166). The front end surface (422) and the side portion (401) intersect at the tangential direction of each of the two ends of the arc-shaped portion (442D). The diameter of the arc-shaped portion (442D) increases as it approaches the side portion (401) in the axial direction of the second piston body (166). In this case as well, the second piston body (166) can suppress the occurrence of burrs between the side portion (401) and the base portion end surface (402) by having the outer edge portion (267) of the second piston body (166) continuous through the arc-shaped portion (442D) between the side portion (401).

[0279] The distance between the arc-shaped portion (435D) of the base portion (240) and the axial center of the side portion (401) is smaller than the distance between the arc-shaped portion (432D) of the outer periphery portion (257) and the axial center C of the side portion (401). That is, the arc-shaped portion (435D) of the base portion (240) is positioned closer to the axial center C of the side portion (401) than the arc-shaped portion (432D) of the outer periphery portion (257). The arc-shaped portion (445D) of the base portion (240) is also positioned closer to the axial center of the side portion (401) than the arc-shaped portion (442D) of the outer periphery portion (267).

[0280] And, the radius of curvature of the arc portion (435D) is made larger than the radius of curvature of the arc portion (432D). Likewise, the radius of curvature of the arc portion (445D) is made larger than the radius of curvature of the arc portion (442D).

[0281] In the above description, an example was given in which an inclined portion (432, 435) or an arc-shaped portion (432D, 435D) is formed on the base end surface (402) side of the second piston body (166) and an inclined portion (442, 445) or an arc-shaped portion (442D, 445D) is formed on the base end surface (403) side of the second piston body (166); however, it is also acceptable to provide only one of the base end surface and the base end surface. That is, an inclined portion (432, 435) or an arc-shaped portion (432D, 435D) is formed on the base end surface (402) side of the second piston body (166), and an inclined portion (442, 445) and an arc-shaped portion (442D, 445D) are not formed on the base end surface (403) side. Conversely, an inclined section (442, 445) or an arc-shaped section (442D, 445D) may be formed on the end surface (403) of the base part, and an inclined section (432, 435) and an arc-shaped section (432D, 435D) may not be formed on the end surface (402) of the base part.

[0282] Industrial applicability

[0283] According to the above-described embodiment of the present invention, it is possible to provide a sintered body and a method for manufacturing a sintered body that can suppress cost increase. Therefore, industrial applicability is high. Explanation of the symbols

[0284] 1: Buffer, 31: Load, 163, 167: Valve member (valve body), 166: Second piston body (sintered body), 231: Insertion through hole, 240: Base part, 241, 244: Boss Division, 255, 265: Round Division, 256, 266: Aambu, 257, 267: Oeyeonbu, 258, 268: Concave thread (thread), 259: Penetrating hole (chimney hole), 269: Penetrating hole (chimney hole), 401: Side section, 402, 403: Base section end surface, 432, 442, 432A, 442A: Inclined section (2nd inclined section), 435, 445, 435A, 445A: Inclined section (1st inclined section).

Claims

Claim 1 A sintered body constituting a piston used in a shock absorber, comprising: a cylindrical base portion formed having a side portion and a base portion end surface that is continuous with respect to the side portion through a first arc-shaped portion or a first inclined portion forming an obtuse angle; an insertion through hole in which the rod of the shock absorber is inserted and penetrated at the center; a boss portion protruding axially from the base portion end surface and provided around the insertion through hole; a plurality of first through holes and a plurality of second through holes located on the outer side of the boss portion and alternately provided along the circumferential direction; and a round portion protruding axially from the base portion end surface and provided in plurality, surrounding the first through hole to form a seal, and having a valve body of the piston seated or spaced apart therefrom, wherein the round portion An outer edge portion formed along the outer circumference of the end surface of the base portion and continuous with respect to the side portion through a second arc-shaped portion or a second inclined portion forming an obtuse angle, and A pair of arm portions extending from both ends of the outer periphery toward the boss portion A sintered body having Claim 2 A sintered body according to claim 1, wherein the base portion is continuous with respect to the side portion through the first inclined portion, the outer edge portion is continuous with respect to the side portion through the second inclined portion, and the obtuse angle formed by the first inclined portion with respect to the side portion is smaller than the obtuse angle formed by the second inclined portion with respect to the side portion. Claim 3 A sintered body according to claim 1, wherein the base portion is continuous with respect to the side portion through the first arc portion, the outer edge portion is continuous with respect to the side portion through the second arc portion, and the first arc portion has a larger radius of curvature than the second arc portion. Claim 4 A sintered body according to claim 1, wherein the first inclined portion or the first arc-shaped portion of the base portion is located closer to the center of the axial direction of the side portion than the second inclined portion or the second arc-shaped portion of the outer edge portion. Claim 5 A method for manufacturing a sintered body constituting a piston used in a buffer, comprising: a compression process for forming a molded article having a base portion and a round portion by compressing powdered metal with a mold; a sintering process for processing the molded article into a sintered body by heating it; and a removal process for processing a part of the sintered body to remove it, wherein the base portion A cylindrical main body, and A first inclined portion that extends annularly outward in the diameter direction from the main body portion and gradually decreases in the axial size of the base portion, and A flat portion extending outward in the diameter direction from the first inclined portion above The round portion having, on which the valve body of the piston is seated or spaced apart, It has an outer edge portion adjacent to a second inclined portion on the first inclined portion, and a set of arm portions extending from both ends of the outer edge portion toward the center of the base portion, and also, A plurality of protruding axially from one end surface of the main body, and in the removal process, By deleting the portion extending outward in the diameter direction from the predetermined position of the first inclined portion, In addition to forming a side portion which is a perimeter plane of the base portion, A method for manufacturing a sintered body, wherein on the end surface of the base portion, an arc-shaped portion that is continuous with respect to the side portion, which is the remaining portion of the first inclined portion, or an inclined portion that forms an obtuse angle that is continuous with respect to the side portion is formed. Claim 6 A method for manufacturing a sintered body according to claim 5, wherein the base portion has a groove formed on the end surface, and the groove is an arc-shaped portion or an obtuse angle-forming portion that is continuous with respect to the side portion, in a part of the main body portion side of the groove than the bottom portion of the groove, and the portion that is radially outward from the groove is the flat portion.

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