JP2023054956A - Buffer, rod-shaped member and manufacturing method of rod-shaped member - Google Patents

Abstract

To provide a buffer which can suppress a manufacturing cost, a rod-shaped member and a manufacturing method of the rod-shaped member.SOLUTION: A buffer comprises: a cylinder 2; a bulkhead member 18 inserted into the cylinder 2, and defining the inside of the cylinder 2; a rod-shaped insertion part 28 inserted into the bulkhead member 18; a screw part 31 arranged at the insertion part 28; a rod-shaped member 21 arranged at least at a part of the insertion part 28 at the outside in a radial direction, and having a groove part 30 in which an axial end part extends up to an incomplete screw part 201 of the screw part 31; and a nut 195 screwed to the screw part 31, and suppressing the movement of the bulkhead member 18 to the rod-shaped member 21 in an axial direction.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a shock absorber, a rod-shaped member, and a method for manufacturing the rod-shaped member.

There is a shock absorber in which a high-performance device such as a frequency sensitive part that changes the damping force in response to the piston frequency is attached to the piston rod. In such shock absorbers, grooves serving as passages for working fluid may be formed on the radially outer side of the piston rod (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-16288

It is desired to suppress the cost when manufacturing a rod-shaped member such as a piston rod.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a shock absorber, a rod-shaped member, and a method for manufacturing the rod-shaped member, which can reduce manufacturing costs.

In order to achieve the above object, a first aspect of the present invention includes a cylinder, a partition member inserted into the cylinder to partition the interior of the cylinder, a rod-shaped insertion portion inserted into the partition member, a threaded portion provided in the insertion portion; a rod-shaped member provided in at least a portion of a radially outer side of the insertion portion and having an axial end extending to an incompletely threaded portion of the threaded portion; a nut that is screwed into the partition member and restrains axial movement of the partition member with respect to the rod member.

A second aspect of the present invention is the rod-shaped member in the shock absorber comprising a partition member and a rod-shaped member, wherein the rod-shaped member is a rod-shaped insert inserted into the partition member defining the interior of the shock absorber. a threaded portion provided in the insertion portion; and a groove portion provided in at least a portion of the radially outer side of the insertion portion and having an axial end portion extending to an incompletely threaded portion of the threaded portion.

A third aspect of the present invention is a method for manufacturing a rod-shaped member in a shock absorber comprising a partition member and a rod-shaped member, wherein a rod-shaped insertion portion to be inserted into the partition member defining the interior of the shock absorber is provided. forming a threaded portion provided in the insertion portion; and a groove portion provided in at least a portion of a radially outer side of the insertion portion, the axial end portion of which extends to an incompletely threaded portion of the threaded portion. and forming a.

According to the present invention, manufacturing costs can be suppressed.

It is a sectional view showing a shock absorber of an embodiment concerning the present invention. 3 is a cross-sectional view showing a piston, a first damping force generating mechanism, a second damping force generating mechanism, a variable frequency mechanism, etc. of the shock absorber according to the embodiment of the present invention; FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, showing the principal part of the piston rod of the shock absorber of the embodiment according to the present invention; FIG. 4 is a cross-sectional view taken along IV-IV of FIG. 3 showing the piston rod of the shock absorber of the embodiment according to the present invention; It is a front view which shows the state before a thread-rolling process after the lathe-turning process of the principal part of the piston rod of the shock absorber of embodiment which concerns on this invention.

A shock absorber, a rod-shaped member, and a method for manufacturing the rod-shaped member according to the embodiment will be described below with reference to the drawings. In the following, for convenience of explanation, the upper side in FIGS. 1 to 3 and 5 will be referred to as "upper", and the lower side in FIGS. 1 to 3 and 5 will be referred to as "lower".

As shown in FIG. 1, the damper 1 of the embodiment is a double-tube hydraulic damper. The shock absorber 1 is used for a suspension system of a vehicle, specifically an automobile. The shock absorber 1 has a cylinder 2 in which an oil liquid L as working fluid is sealed. The cylinder 2 has an inner cylinder 3 and an outer cylinder 4 . The inner cylinder 3 is cylindrical. The outer cylinder 4 is cylindrical with a bottom. The inner diameter of the outer cylinder 4 is larger than the outer diameter of the inner cylinder 3 . The inner cylinder 3 is arranged radially inside the outer cylinder 4 . The central axis of the inner cylinder 3 and the central axis of the outer cylinder 4 coincide. A reservoir chamber 6 is provided between the inner cylinder 3 and the outer cylinder 4 .

The outer cylinder 4 has a body member 11 and a bottom member 12 . The trunk member 11 is cylindrical. The bottom member 12 is cylindrical with a bottom. The bottom member 12 is fitted on the lower side of the body member 11 and fixed by welding. The bottom member 12 closes the lower portion of the body member 11 . A mounting eye 13 is fixed to the bottom member 12 on the outer side opposite to the body member 11 in the axial direction.

The damper 1 has a piston 18 (partition member). The piston 18 is inserted inside the inner cylinder 3 of the cylinder 2 . The piston 18 is slidably fitted inside the inner cylinder 3 of the cylinder 2 . The piston 18 is a partition wall member that partitions the interior of the inner cylinder 3 into two chambers, an upper chamber 19 and a lower chamber 20 . The upper chamber 19 is located on the opposite side of the bottom member 12 from the piston 18 in the axial direction of the cylinder 2 . The lower chamber 20 is closer to the bottom member 12 than the piston 18 in the axial direction of the cylinder 2 . An upper chamber 19 and a lower chamber 20 in the inner cylinder 3 are filled with oil L as a working fluid. A reservoir chamber 6 between the inner cylinder 3 and the outer cylinder 4 is filled with an oil liquid L and a gas G as working fluids.

The shock absorber 1 has a piston rod 21 (bar-shaped member). The piston rod 21 is a rod-shaped member, and one axial end side of the piston rod 21 is disposed inside the inner cylinder 3 of the cylinder 2 . One end of the piston rod 21 is connected to the piston 18 . The piston rod 21 extends from the cylinder 2 to the outside of the cylinder 2 at the other end side opposite to the one end portion in the axial direction. Piston 18 is fixed to piston rod 21 . Therefore, the piston 18 and the piston rod 21 move together. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction to increase the amount of projection from the cylinder 2 is the extension stroke in which the entire length is extended. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction to reduce the amount of projection from the cylinder 2 is the contraction stroke in which the overall length is reduced. In the shock absorber 1, the piston 18 moves toward the upper chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves toward the lower chamber 20 during the compression stroke.

A rod guide 22 is fitted to the upper opening side of the inner cylinder 3 and the upper opening side of the outer cylinder 4 . A seal member 23 is fitted to the outer cylinder 4 above the rod guide 22 . Both the rod guide 22 and the seal member 23 are annular. The piston rod 21 slides along the axial directions of the rod guide 22 and the seal member 23, respectively. The piston rod 21 extends from the inside of the cylinder 2 to the outside of the cylinder 2 beyond the seal member 23 .

The rod guide 22 restricts the radial movement of the piston rod 21 with respect to the inner cylinder 3 and the outer cylinder 4 of the cylinder 2 . The piston rod 21 is fitted in the rod guide 22 and the piston 18 is fitted in the inner cylinder 3 . As a result, the central axis of the piston rod 21 and the central axis of the cylinder 2 are aligned. The rod guide 22 supports the piston rod 21 movably in the axial direction of the piston rod 21 . The seal member 23 is in close contact with the outer cylinder 4 at its outer peripheral portion. The seal member 23 has its inner peripheral portion in close contact with the outer peripheral portion of the piston rod 21 . The piston rod 21 moves in the axial direction of the sealing member 23 with respect to the sealing member 23 . The seal member 23 prevents the oil L in the inner cylinder 3 and the high-pressure gas G and oil L in the reservoir chamber 6 from leaking to the outside.

The outer peripheral portion of the rod guide 22 has a larger diameter at the upper portion than at the lower portion. The rod guide 22 is fitted to the inner peripheral portion of the upper end of the inner cylinder 3 at the smaller diameter lower portion. The rod guide 22 is fitted to the inner peripheral portion of the upper portion of the outer cylinder 4 at the large-diameter upper portion. A base valve 25 is installed on the bottom member 12 of the outer cylinder 4 . The base valve 25 is radially positioned with respect to the outer cylinder 4 . The inner peripheral portion of the lower end of the inner cylinder 3 is fitted to the base valve 25 . The base valve 25 is a partition wall member that partitions the lower chamber 20 and the reservoir chamber 6 .
The upper end portion of the outer cylinder 4 is crimped inward in the radial direction of the outer cylinder 4 . The sealing member 23 is fixed to the cylinder 2 by being sandwiched between the crimped portion and the rod guide 22 .

The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28 (insertion portion). Both the main shaft portion 27 and the mounting shaft portion 28 are rod-shaped.
The mounting shaft portion 28 has an outer diameter smaller than that of the main shaft portion 27 . The mounting shaft portion 28 is arranged inside the cylinder 2 . A piston 18 is attached to the attachment shaft portion 28 . The main shaft portion 27 has a shaft stepped portion 29 . The shaft stepped portion 29 is provided at an axial end portion of the main shaft portion 27 on the mounting shaft portion 28 side. The axial step portion 29 widens in a direction orthogonal to the central axis of the piston rod 21 .
A groove portion 30 is formed in the outer peripheral portion of the mounting shaft portion 28 of the piston rod 21 . The groove portion 30 extends in the axial direction of the mounting shaft portion 28 . A plurality of groove portions 30 are formed at intervals in the circumferential direction of the mounting shaft portion 28 . A threaded portion 31 is formed on the outer peripheral portion of the mounting shaft portion 28 at the end opposite to the main shaft portion 27 with respect to the groove portion 30 in the axial direction of the mounting shaft portion 28 .

The piston rod 21 is provided with an annular stopper member 32 and an annular buffer 33 . Both the stopper member 32 and the buffer 33 are provided in a portion of the main shaft portion 27 between the piston 18 and the rod guide 22 . The piston rod 21 is inserted into the inner peripheral side of the stopper member 32 and the buffer 33 . The stopper member 32 is crimped and fixed to the main shaft portion 27 . The buffer 33 is arranged between the stopper member 32 and the rod guide 22 .

The shock absorber 1 is connected to the vehicle body of the vehicle, for example, with the portion of the piston rod 21 protruding from the cylinder 2 arranged at the top. At that time, the shock absorber 1 is connected to the wheel side of the vehicle with the mounting eye 13 provided on the cylinder 2 side arranged at the bottom. Conversely, the shock absorber 1 may be connected to the vehicle body on the cylinder 2 side. In this case, the shock absorber 1 has the piston rod 21 connected to the wheel side.

As shown in FIG. 2, the piston 18 has a piston body 35 and a sliding member 36. As shown in FIG. The piston body 35 is made of metal and has an annular shape. A piston body 35 of the piston 18 is fitted to the piston rod 21 . The sliding member 36 is made of synthetic resin and has an annular shape. The sliding member 36 is integrally attached to the outer peripheral surface of the piston body 35 . The piston 18 slides on the inner cylinder 3 while the sliding member 36 is in contact with the inner cylinder 3 .

A passage hole 37 , a passage groove 38 , a passage hole 39 , and a passage groove 40 are provided in the piston body 35 . The passage hole 37 extends in the axial direction of the piston body 35 . A plurality of passage holes 37 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35 (only one passage hole is shown in FIG. 2 because it is a cross section). The passage hole 39 extends in the axial direction of the piston body 35 . A plurality of passage holes 39 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35 (only one passage hole is shown in FIG. 2 because it is a cross section). In the piston body 35, passage holes 37 and passage holes 39 are alternately formed at regular intervals in the circumferential direction of the piston body 35. As shown in FIG.

The passage groove 38 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35 . The passage groove 38 is formed at one end of the piston body 35 in the axial direction. All the passage holes 37 are open to the passage groove 38 at one end side in the axial direction of the piston body 35 . The passage groove 40 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35 . The passage groove 40 is formed at the other end of the piston body 35 on the opposite side to the passage groove 38 in the axial direction. All the passage holes 39 are open to the passage groove 40 at the ends opposite to the passage groove 38 in the axial direction of the piston body 35 . In the piston 18 , the inner side of the plurality of passage holes 37 and the inner side of the passage groove 38 form a first passage portion 43 . The first passage portion 43 passes through the piston 18 in the axial direction of the piston 18 . In the piston 18 , the inner side of the plurality of passage holes 39 and the inner side of the passage groove 40 form a first passage portion 44 . The first passage portion 44 penetrates the piston 18 in the axial direction of the piston 18 .

A first damping force generating mechanism 41 is provided in the first passage portion 43 . The first damping force generating mechanism 41 opens and closes the first passage portion 43 to generate a damping force. The first damping force generating mechanism 41 is arranged on the lower chamber 20 side, which is one end side of the piston 18 in the axial direction, and attached to the piston rod 21 . As a result, the first passage portion 43 becomes a passage through which oil liquid L as a working fluid flows from the upper chamber 19 toward the lower chamber 20 as the piston 18 moves toward the upper chamber 19 side. That is, the first passage portion 43 is a passage through which the oil L flows from the upper chamber 19 toward the lower chamber 20 during the extension stroke. The first damping force generating mechanism 41 is an elongation-side damping force generating mechanism that suppresses the flow of the oil L from the first passage portion 43 to the lower chamber 20 during the elongation stroke to generate a damping force.

A first damping force generating mechanism 42 is provided in the first passage portion 44 . The first damping force generating mechanism 42 opens and closes the first passage portion 44 to generate a damping force. The first damping force generating mechanism 42 is arranged on the upper chamber 19 side, which is the other end side of the piston 18 in the axial direction, and attached to the piston rod 21 . As a result, the first passage portion 44 becomes a passage through which the oil L flows from the lower chamber 20 toward the upper chamber 19 as the piston 18 moves toward the lower chamber 20 side. That is, the first passage portion 44 is a passage through which the oil L flows from the lower chamber 20 toward the upper chamber 19 during the contraction stroke. The first damping force generation mechanism 42 is a compression-side damping force generation mechanism that suppresses the flow of the oil L from the first passage portion 44 to the upper chamber 19 during the compression stroke to generate a damping force.

The piston body 35 has an insertion hole 45 formed in the center in the radial direction so as to penetrate the piston body 35 in the axial direction. The insertion hole 45 allows the mounting shaft portion 28 of the piston rod 21 to pass therethrough. The insertion hole 45 has a smaller diameter on the upper chamber 19 side than on the lower chamber 20 side in the axial direction, and the mounting shaft portion 28 of the piston rod 21 is fitted into this small diameter portion.

A valve seat portion 48 is formed at the axial end of the piston body 35 on the side of the lower chamber 20 . The valve seat portion 48 is annular. The valve seat portion 48 is arranged radially outward of the piston body 35 from the opening of the passage groove 38 on the lower chamber 20 side. The valve seat portion 48 forms part of the first damping force generating mechanism 41 .
A valve seat portion 49 is formed at the axial end of the piston body 35 on the side of the upper chamber 19 . The valve seat portion 49 has an annular shape. The valve seat portion 49 is arranged radially outward of the piston body 35 from the opening of the passage groove 40 on the upper chamber 19 side. The valve seat portion 49 forms part of the first damping force generating mechanism 42 .
The openings of all the passage holes 39 on the lower chamber 20 side are arranged in the piston body 35 on the opposite side of the passage groove 38 of the valve seat portion 48 in the radial direction of the piston body 35 . The upper chamber 19 side openings of all the passage holes 37 are arranged in the piston body 35 on the opposite side of the passage groove 40 of the valve seat portion 49 in the radial direction of the piston body 35 .

On the side of the valve seat portion 48 in the axial direction of the piston 18, in order from the piston 18 side in the axial direction of the piston 18, a plurality of (specifically two) discs 50 and a plurality of (specifically four) discs 50 are provided. ), one pilot disk 52, a plurality of (specifically two) disks 53, one pilot case 55, one disk 56, and a plurality of (specifically 6 discs 57, one disc 58 and one disc 59 are provided. Disks 50, 51, 53, 56-59 and pilot case 55 are all made of metal. Each of the disks 50, 51, 53, 56-59 is a perforated circular flat plate having a constant thickness. Each of the discs 50, 51, 53, 56-59 has the mounting shaft portion 28 of the piston rod 21 fitted therein. Both the pilot disk 52 and the pilot case 55 are annular. Both the pilot disc 52 and the pilot case 55 have the mounting shaft portion 28 of the piston rod 21 fitted therein.

The pilot case 55 is cylindrical with a bottom. A through hole 70 is formed in the center of the pilot case 55 in the radial direction. The through hole 70 passes through the pilot case 55 in its axial direction. The pilot case 55 has a bottom portion 71 , an inner cylindrical portion 72 , an outer cylindrical portion 73 , an inner seat portion 74 and a valve seat portion 75 .

The through hole 70 has a smaller diameter on the piston 18 side than the opposite side to the piston 18 in the axial direction, and the mounting shaft portion 28 of the piston rod 21 is fitted into this small diameter portion.
The bottom portion 71 is in the shape of a perforated disc. A passage hole 78 is formed in the bottom portion 71 radially outwardly of the through hole 70 so as to pass through the bottom portion 71 in the axial direction thereof.
The inner cylindrical portion 72 has a cylindrical shape and protrudes from the inner peripheral edge portion of the bottom portion 71 toward the piston 18 along the axial direction of the bottom portion 71 .
The outer cylindrical portion 73 has a cylindrical shape and protrudes from the outer peripheral edge of the bottom portion 71 to the same side as the inner cylindrical portion 72 along the axial direction of the bottom portion 71 .
The passage hole 78 is arranged between the inner cylindrical portion 72 and the outer cylindrical portion 73 in the radial direction of the bottom portion 71 .

The inner seat portion 74 has an annular shape and slightly protrudes from the inner peripheral edge portion of the bottom portion 71 in the axial direction opposite to the inner cylindrical portion 72 . A passage groove 79 is formed in the inner seat portion 74 so as to penetrate the inner seat portion 74 in its radial direction.
The valve seat portion 75 has an annular shape with a larger diameter than the inner seat portion 74 . The valve seat portion 75 protrudes from the bottom portion 71 to the same side as the inner seat portion 74 along the axial direction of the bottom portion 71 at a radially outer side of the inner seat portion 74 relative to the inner seat portion 74 .
The passage hole 78 is arranged between the inner seat portion 74 and the valve seat portion 75 in the radial direction of the bottom portion 71 . The passage in the passage groove 79 of the inner seat portion 74 always communicates with the passage in the groove portion 30 of the piston rod 21 and the passage in the passage hole 78 .

Among the plurality of discs 50 , the disc 50 on the side of the piston 18 in the axial direction is in contact with a portion radially inside the passage groove 38 of the piston 18 . A notch 81 is formed in the disc 50 . The passage in the notch 81 always communicates with the first passage portion 43 of the piston 18 and the passage in the groove portion 30 of the piston rod 21 .
Among the plurality of discs 51 , the disc 51 closest to the piston 18 in the axial direction is in contact with the valve seat portion 48 of the piston 18 . The plurality of discs 51 opens and closes the opening of the first passage portion 43 formed in the piston 18 by separating from and coming into contact with the valve seat portion 48 .

The pilot disk 52 consists of a disk 85 and a seal member 86. As shown in FIG.
The disk 85 is made of metal and has a perforated circular flat plate shape. The mounting shaft portion 28 of the piston rod 21 is fitted inside the disk 85 . Of the plurality of discs 51 , the disc 51 on the opposite side of the piston 18 in the axial direction is in contact with the disc 85 of the pilot disc 52 .
The seal member 86 is made of rubber and adhered to the opposite side of the disk 85 from the piston 18 in the axial direction. The seal member 86 is fixed to the outer peripheral side of the disk 85 and has an annular shape. The seal member 86 is liquid-tightly fitted over the entire circumference of the inner peripheral portion of the outer cylindrical portion 73 of the pilot case 55 . The seal member 86 is axially slidable relative to the inner peripheral portion of the outer cylindrical portion 73 . The seal member 86 always seals the gap between the pilot disk 52 and the outer cylindrical portion 73 .

A plurality of discs 51 and pilot discs 52 constitute a damping valve 91 . When the damping valve 91 is separated from the valve seat portion 48 of the piston 18 and opened, the oil L from the first passage portion 43 is directed downward through the space between the piston 18 and the outer cylindrical portion 73 of the pilot case 55 . Flow to chamber 20. At that time, the damping valve 91 suppresses the flow of the oil L between the valve seat portion 48 and the valve seat portion 48 . The damping valve 91 constitutes the extension-side first damping force generating mechanism 41 . In the damping valve 91 , fixed orifices 92 are formed in the plurality of discs 51 to allow the first passage portion 43 to communicate with the lower chamber 20 even when the valve seat portion 48 is in contact with the discs 51 . This fixed orifice 92 also constitutes the first damping force generating mechanism 41 .

Among the plurality of discs 53 , the disc 53 on the opposite side of the pilot case 55 in the axial direction is in contact with the disc 85 of the pilot disc 52 . Among the plurality of discs 53 , the disc 53 on the side of the pilot case 55 in the axial direction is in contact with the inner cylindrical portion 72 of the pilot case 55 .
The disc 56 is in contact with the inner seat portion 74 of the pilot case 55 .
Among the plurality of discs 57 , the disc 57 on the side of the disc 56 in the axial direction can be seated on the valve seat portion 75 . A plurality of discs 57 constitute a disc valve 99 . The disk valve 99 can be seated and removed from the valve seat portion 75 .
The disk 58 has an outer diameter smaller than that of the disk valve 99 .
The disc 59 has an outer diameter larger than that of the disc 58 .

Between the bottom portion 71 of the pilot case 55, the inner cylindrical portion 72 and the outer cylindrical portion 73, the pilot disk 52 and the disk 53, the bottom portion 71 of the pilot case 55, the inner seat portion 74 and the valve seat portion 75, and the disk 56 and the disk valve 99 and inside the passage hole 78 of the pilot case 55 constitute a back pressure chamber 100 . The back pressure chamber 100 applies pressure to the plurality of discs 51 through the pilot disc 52 in the direction of the piston 18 . In other words, the back pressure chamber 100 applies internal pressure to the damping valve 91 in the valve closing direction in which the damping valve 91 is seated on the valve seat portion 48 . These multiple discs 51 , pilot discs 52 and back pressure chamber 100 constitute a part of the first damping force generating mechanism 41 . The back pressure chamber 100 always communicates with the passage in the groove portion 30 of the piston rod 21 via the passage in the passage groove 79 of the pilot case 55 .

The passage in the notch 81 of the disk 50, the passage in the groove 30 of the piston rod 21, and the passage in the passage groove 79 of the pilot case 55 always connect the first passage 43 of the piston 18 and the back pressure chamber 100. A second passage portion 102 communicates with the first passage portion 43 to introduce the oil L into the back pressure chamber 100 . The first damping force generating mechanism 41 on the extension side introduces part of the flow of the oil L into the back pressure chamber 100 via the second passage portion 102, and the pressure in the back pressure chamber 100 causes the damping valve 91 to open. to control.

The disc valve 99 allows the back pressure chamber 100 and the lower chamber 20 to communicate with each other by being separated from the valve seat portion 75 . At that time, the disc valve 99 suppresses the flow of the oil L between the valve seat portion 75 and the disc valve 99 . The disc 59 abuts against the disc valve 99 when the disc valve 99 is deformed in the opening direction, thereby suppressing the disc valve 99 from being deformed more than specified.
The disc valve 99 and the valve seat portion 75 constitute a second damping force generating mechanism 110 . The second damping force generating mechanism 110 allows the back pressure chamber 100 and the lower chamber 20 to communicate with each other when the disc valve 99 is released from the valve seat portion 75 . At that time, the second damping force generating mechanism 110 suppresses the flow of the oil L between the back pressure chamber 100 and the lower chamber 20 to generate a damping force. The second damping force generating mechanism 110 is provided between the back pressure chamber 100 and the lower chamber 20 and generates a damping force by the flow of the oil L. The second damping force generating mechanism 110 causes oil L to flow from the upper chamber 19 to the lower chamber 20 via the first passage portion 43 , the second passage portion 102 and the back pressure chamber 100 in the extension stroke. The second damping force generating mechanism 110 is an elongation-side damping force generating mechanism that suppresses the flow of the oil L from the back pressure chamber 100 to the lower chamber 20 during the elongation stroke to generate a damping force.

On the side of the valve seat portion 49 in the axial direction of the piston 18, in order from the piston 18 side in the axial direction of the piston 18, one disc 111, a plurality of (specifically, seven) discs 112, and one disk 113, one disk 114, and one annular member 115 are provided. Disks 111-114 and annular member 115 are all made of metal. Each of the disks 111 to 114 and the annular member 115 is a perforated circular flat plate of constant thickness. The discs 111 to 114 and the annular member 115 have the mounting shaft portion 28 of the piston rod 21 fitted therein.

The disk 111 abuts on a portion of the piston 18 radially inner than the passage groove 40 .
Among the plurality of discs 112 , the disc 112 closest to the piston 18 in the axial direction is in contact with the valve seat portion 49 of the piston 18 . The plurality of discs 112 opens and closes the opening of the first passage portion 44 formed in the piston 18 by separating from and contacting the valve seat portion 49 .
A plurality of discs 112 constitute a disc valve 122 . The disk valve 122 can be seated and removed from the valve seat portion 49 . The disc valve 122 can open the first passage portion 44 to the upper chamber 19 by separating from the valve seat portion 49 . When the disc valve 122 is separated from the valve seat portion 49 of the piston 18 and opened, the oil L from the first passage portion 44 flows into the upper chamber 19 . At that time, the disc valve 122 suppresses the flow of the oil L between the valve seat portion 49 and the disc valve 122 . Therefore, the disc valve 122 suppresses the flow of the oil L from the lower chamber 20 to the upper chamber 19 via the first passage portion 44 . The disc valve 122 and the valve seat portion 49 constitute the first damping force generating mechanism 42 on the compression side. The disc 112 is formed with a fixed orifice 123 that allows the first passage portion 44 to communicate with the upper chamber 19 even when it is in contact with the valve seat portion 49 . The fixed orifice 123 also constitutes the first damping force generating mechanism 42 .

The disk 113 has an outer diameter smaller than that of the disk valve 122 .
The disk 114 and the annular member 115 abut against the disk valve 122 when the disk valve 122 is deformed in the opening direction, thereby suppressing the deformation of the disk valve 122 in the opening direction beyond a prescribed limit. The annular member 115 is in contact with the axial stepped portion 29 of the piston rod 21 .

A frequency sensitive mechanism 130 is provided on the axial side of the disk 59 opposite to the disk 58 . The frequency sensitive mechanism 130 varies the damping force according to the frequency of axial movement of the piston 18 (hereinafter referred to as piston frequency).
The frequency sensitive mechanism 130 has one housing body 131 on the disk 59 side in the axial direction. The frequency sensitive mechanism 130 has a plurality of (specifically, two) discs 132 and one partition disc 135 on the side opposite to the disc 59 in the axial direction of the housing body 131 . The frequency sensitive mechanism 130 has a plurality of (specifically five) discs 136 on the opposite side of the disc 132 and the partition disc 135 from the disc 59 in the axial direction. The frequency sensitive mechanism 130 has a plurality of (specifically, two) discs 137 on the opposite side of the disc 59 in the axial direction of the disc 136 . An annular member 138 is provided on the opposite side of the disc 137 from the disc 136 in the axial direction.

The housing body 131, the discs 132, 136, 137 and the annular member 138 are all made of metal. Each of the disks 132, 136, 137 and the annular member 138 is a perforated circular flat plate of constant thickness. The discs 132, 136, 137, the housing body 131 and the annular member 138 all have the mounting shaft portion 28 of the piston rod 21 fitted therein. The partition disk 135 allows the mounting shaft portion 28 of the piston rod 21 to pass through the inner peripheral side with a radial gap. Disks 132 , 136 , 137 and housing body 131 constitute housing 145 of frequency sensitive mechanism 130 .

The housing body 131 is cylindrical with a bottom.
The housing main body 131 has a through hole 155 formed in the radial center thereof, the through hole 155 passing through the housing main body 131 in its axial direction. The through hole 155 has a smaller diameter on the piston 18 side than the opposite side to the piston 18 in the axial direction, and the mounting shaft portion 28 of the piston rod 21 is fitted in this small diameter portion.

The housing body 131 has a bottom portion 150 , a projecting portion 151 , a cylindrical portion 153 and a seat portion 154 .
The bottom portion 150 is in the shape of a perforated disc.
The projecting portion 151 has an annular shape. The protruding portion 151 protrudes from the inner peripheral edge portion of the bottom portion 150 along the axial direction of the bottom portion 150 toward the side opposite to the disk 59 . A passage groove 161 is formed in the projecting portion 151 so as to penetrate the projecting portion 151 in its radial direction. A passage in the passage groove 161 communicates with a passage in the groove portion 30 of the piston rod 21 .
The tubular portion 153 is cylindrical. The cylindrical portion 153 extends from the outer peripheral edge of the bottom portion 150 to the same side as the projecting portion 151 along the axial direction of the bottom portion 150 .
The seat portion 154 has an annular shape. The seat portion 154 protrudes from a position between the projecting portion 151 and the cylindrical portion 153 in the radial direction of the bottom portion 150 to the same side as the projecting portion 151 and the cylindrical portion 153 along the axial direction of the bottom portion 150 . The sheet portion 154 is intermittently notched in the circumferential direction at the tip portion on the projecting side.

Compartment disk 135 consists of valve disk 171 and elastic sealing member 172 . The partition disk 135 is arranged radially between the tubular portion 153 of the housing body 131 and the disk 132 .
The valve disc 171 is made of metal. The valve disc 171 is a perforated circular flat plate of constant thickness. The mounting shaft portion 28 of the piston rod 21 is inserted through the inner peripheral side of the valve disc 171 . The valve disc 171 is elastically deformable or bendable. The valve disc 171 has an inner diameter that allows a plurality of discs 132 to be arranged inside with a gap in the radial direction. The valve disc 171 is thinner than the total thickness of the plurality of discs 132 .

The elastic sealing member 172 is made of rubber and has an annular shape. The elastic sealing member 172 is adhered to the outer peripheral side of the valve disc 171 . The elastic seal member 172 is baked on the valve disc 171 and provided integrally with the valve disc 171 . The elastic seal member 172 has a seal portion 175 and a contact portion 176 . The seal portion 175 has an annular shape and is fixed to the outer peripheral side of the valve disc 171 over the entire circumference. The seal portion 175 protrudes from the valve disc 171 toward the bottom portion 150 of the housing body 131 in the axial direction of the partition disc 135 . The contact portion 176 protrudes from the valve disc 171 to the opposite side of the bottom portion 150 in the axial direction of the partition disc 135 . The contact portion 176 is fixed to the outer peripheral side of the valve disc 171 . The contact portion 176 is intermittently notched in the circumferential direction at the tip portion on the protruding side. The seal portion 175 and the contact portion 176 are connected to each other on the outer peripheral side of the valve disc 171 .

The seal portion 175 of the elastic seal member 172 is liquid-tightly fitted over the entire circumference of the cylindrical portion 153 of the housing body 131 . The seal portion 175 is slidable in the axial direction of the tubular portion 153 with respect to the tubular portion 153 . The seal portion 175 of the elastic seal member 172 always seals the gap between the partition disk 135 and the cylindrical portion 153 . The seal portion 175 is radially outward of the seat portion 154 . A valve disc 171 of the partition disc 135 can be seated on the seat portion 154 of the housing body 131 .

Among the plurality of discs 136 , the disc 136 closest to the disc 132 in the axial direction has an outer diameter larger than the inner diameter of the valve disc 171 . This disk 136 abuts on the inner peripheral side of the valve disk 171 over the entire circumference. This closes the gap between the disc 136 and the valve disc 171 . The partition disk 135 has an inner peripheral side of the valve disk 171 arranged between the projection 151 and the disk 136 in the axial direction, and is supported in contact with the disk 136 . The partition disk 135 is movable on the inner peripheral side of the valve disk 171 between the projecting portion 151 and the disk 136 within the axial length range of the plurality of disks 132 . Compartment disk 135 is centered with respect to housing 145 by sealing portion 175 contacting tubular portion 153 over the entire circumference. The partition disk 135 is supported by the disk 136 only on one side without being clamped from both sides on the inner peripheral side of the valve disk 171 . The partition disc 135 is supported by the seat portion 154 only on one side without being clamped from both sides at the portion of the valve disc 171 which is radially outside the disc 136 . Therefore, the partition disk 135 has a simple support structure in which one surface side of the valve disk 171 is supported by the disk 136 and the other surface side of the valve disk 171 is supported by the seat portion 154 . Compartment disk 135 is generally toroidal and elastically deformable or deflectable.

The disk 137 contacts the disk 136 on the inner peripheral side and contacts the contact portion 176 of the partitioning disk 135 on the outer peripheral side.
The plurality of discs 137 have an outer diameter larger than the outer diameter of the disc 136 and smaller than the inner diameter of the cylindrical portion 153 . A plurality of discs 137 restricts movement of the partition disc 135 in the axial direction of the housing body 131 opposite to the seat portion 154 .

The seat portion 154 of the housing body 131 supports the valve disc 171 of the partition disc 135 from one side in the axial direction. The plurality of discs 136 support the inner peripheral side of the valve disc 171 from the seat portion 154 from the other side in the axial direction. The shortest axial distance between the seat portion 154 and the disc 136 is smaller than the axial thickness of the valve disc 171 . Therefore, the valve disk 171 is pressed against the seat portion 154 and the disk 136 by its own elastic force in a slightly elastically deformed state.

The partition disk 135 partitions the inside of the housing 145 into a variable chamber 181 and a variable chamber 182 . The variable chamber 181 is axially between the bottom 150 of the housing body 131 and the partition disk 135 . The variable chamber 182 is located between the partition disc 135 and the disc 137 in the axial direction of the housing body 131 . Both the variable chamber 181 and the variable chamber 182 have variable capacities, and the capacities change according to the deformation of the partition disc 135 . The variable chamber 181 always communicates with the passage in the groove portion 30 of the piston rod 21 via the passage in the passage groove 161 of the housing body 131 . The variable chamber 181 always communicates with the upper chamber 19 via the passage in the passage groove 161 , the passage in the groove portion 30 , the passage in the notch 81 and the first passage portion 43 . Also, the variable chamber 181 always communicates with the back pressure chamber 100 via the passage in the passage groove 161 , the passage in the groove portion 30 , and the passage in the passage groove 79 . The variable chamber 182 always communicates with the lower chamber 20 through a passage between the disk 137 and the tubular portion 153 of the housing body 131 .

In the extension stroke, the oil L from the upper chamber 19 flows through the first passage portion 43, the passage in the notch 81 of the disk 50, the passage in the groove portion 30 of the piston rod 21, and the passage groove 161 in the housing body 131. It is introduced into the variable chamber 181 through the passage. Then, the valve disc 171 of the partition disc 135 deforms into a tapered shape so that the outer peripheral side moves away from the seat portion 154 in the axial direction of the seat portion 154 with the point of contact with the abutting disc 136 as a fulcrum. At this time, the valve disk 171 compresses and deforms the contact portion 176 of the elastic seal member 172 that contacts the disk 137 . This deformation of the valve disc 171 causes the volume of the variable chamber 181 to increase. Here, during this deformation of the valve disc 171, the volume of the variable chamber 182 will decrease. At this time, the oil L in the variable chamber 182 flows into the lower chamber 20 through the passage between the disc 137 and the tubular portion 153 of the housing body 131 .

The first passage portion 43, the passage in the notch 81, the passage in the groove portion 30 of the piston rod 21, the passage in the passage groove 161, the variable types 181 and 182, the disk 137, and the cylindrical portion of the housing body 131. 153 constitutes a passage 191 . The passage 191 can communicate between the upper chamber 19 and the lower chamber 20 . In the passage 191 , the first passage portion 43 , the passage in the notch 81 , the passage in the groove portion 30 , the passage in the passage groove 161 , and the variable chamber 181 always communicate with the upper chamber 19 . In the passage 191 , the variable chamber 182 and the passage between the disk 137 and the tubular portion 153 of the housing body 131 are always in communication with the lower chamber 20 .

The partition disk 135 is axially movable between the housing body 131 and the disk 136 at the inner peripheral side of the valve disk 171 . The partition disk 135 blocks the flow of the oil L between the variable chambers 181 and 182 when the inner peripheral side of the valve disk 171 is in contact with the disk 136 over the entire circumference. Further, the partition disc 135 allows the oil L to flow between the variable chambers 182 and 181 when the inner peripheral side of the valve disc 171 is separated from the disc 136 . The inner peripheral side of the valve disc 171 and the disc 136 constitute a check valve 193 . A check valve 193 is provided in the passage 191 . The check valve 193 allows the oil L to flow from the variable chamber 182 to the variable chamber 181 while regulating the flow of the oil L from the variable chamber 181 to the variable chamber 182 . The check valve 193 blocks communication between the upper chamber 19 and the lower chamber 20 via the passage 191 during the extension stroke when the pressure in the upper chamber 19 becomes higher than the pressure in the lower chamber 20 . The check valve 193 communicates the lower chamber 20 and the upper chamber 19 via the passage 191 in the contraction stroke in which the pressure of the lower chamber 20 becomes higher than the pressure of the upper chamber 19 .

The piston rod 21 has an annular member 115, a disc 114, a disc 113, a plurality of discs 112, a disc 111, a piston 18, a plurality of discs 50, a plurality of A plurality of discs 51, a pilot disc 52, a plurality of discs 53, a pilot case 55, a disc 56, a plurality of discs 57, a disc 58, a disc 59, a housing body 131 and a plurality of discs 132 are arranged in this order on the shaft stage. Part 29 is superimposed. At this time, the pilot case 55 fits the seal member 86 of the pilot disk 52 to the outer cylindrical portion 73 .

Also, the partition disk 135 is superimposed on the seat portion 154 of the housing main body 131 in a state in which the mounting shaft portion 28 and the plurality of disks 132 are inserted inside. At this time, the elastic seal member 172 of the partition disk 135 is fitted into the cylindrical portion 153 of the housing main body 131 .
Furthermore, in a state in which the mounting shaft portion 28 is inserted inside each of them, a plurality of discs 136, a plurality of discs 137 and an annular member 138 are stacked in this order on the disc 132 and the valve disc 171 of the partition disc 135. be done.

With the parts from the annular member 115 to the annular member 138 thus arranged on the piston rod 21 , the nut 195 is screwed onto the threaded portion 31 of the mounting shaft portion 28 projecting beyond the annular member 138 . As a result, the inner peripheral sides or all of the parts from the annular member 115 to the annular member 138 are sandwiched between the axial step portion 29 of the piston rod 21 and the nut 195 and clamped in the axial direction. At that time, the partition disk 135 is not axially clamped on the inner peripheral side. In this state, the partition disc 135 abuts the valve disc 171 against the seat portion 154 of the housing body 131 and the disc 136 . Nut 195 restrains axial movement of piston 18 relative to piston rod 21 .

Here, the rod-shaped mounting shaft portion 28 of the piston rod 21 is inserted into the parts from the annular member 115 including the piston 18 to the annular member 138 as described above. The mounting shaft portion 28 is provided with the threaded portion 31 on the outer peripheral portion of the end portion on the side opposite to the shaft stepped portion 29 in the axial direction.
The mounting shaft portion 28 has a mounting shaft body portion 200 between the shaft stepped portion 29 and the screw portion 31 in the axial direction.

The screw portion 31 is a male screw. The screw portion 31 has an incomplete screw portion 201 , a complete screw portion 202 and an incomplete screw portion 203 . The incomplete threaded portion 201, the complete threaded portion 202, and the incompletely threaded portion 203 are continuous.
The fully threaded portion 202 is provided at an intermediate portion of the threaded portion 31 in the axial direction of the mounting shaft portion 28 . The fully threaded portion 202 has a constant outer diameter at the crest portion of the thread.

The incomplete threaded portion 201 is provided adjacent to and between the fully threaded portion 202 and the attachment shaft body portion 200 in the axial direction of the attachment shaft portion 28 . The incomplete threaded portion 201 has a smaller outer diameter at the crest portion than the fully threaded portion 202 . The outer diameter of the crest of the incomplete threaded portion 201 becomes smaller as the distance from the completely threaded portion 202 in the axial direction of the mounting shaft portion 28 increases. The incomplete threaded portion 201 overlaps the annular member 138 in the axial direction of the mounting shaft portion 28 .
The incomplete threaded portion 203 is provided on the opposite side of the fully threaded portion 202 from the mounting shaft body portion 200 in the axial direction of the mounting shaft portion 28 . The incomplete threaded portion 203 is provided at the end portion of the mounting shaft portion 28 on the side opposite to the shaft stepped portion 29 in the axial direction. The incomplete threaded portion 203 has a smaller outer diameter at the crest portion than the fully threaded portion 202 . The outer diameter of the crest portion of the incomplete threaded portion 203 becomes smaller as the distance from the completely threaded portion 202 in the axial direction of the mounting shaft portion 28 increases.

The mounting shaft body portion 200 has a neck portion 205 and a main portion 206 .
The neck portion 205 is provided at the end portion of the mounting shaft body portion 200 on the shaft step portion 29 side in the axial direction of the mounting shaft portion 28 . The neck portion 205 is also provided at the axial end portion of the mounting shaft portion 28 on the shaft step portion 29 side.
The main body portion 206 is provided adjacently on the opposite side of the shaft stepped portion 29 of the neck portion 205 in the axial direction of the mounting shaft portion 28 . The screw portion 31 described above is provided adjacently on the opposite side of the neck portion 205 of the main body portion 206 in the axial direction of the mounting shaft portion 28 .
The mounting shaft portion 28 is provided with an annular groove 208 and an annular groove 209 on its radially outer side. The annular groove 208 is provided at a boundary position between the neck portion 205 and the main portion 206 in the axial direction of the mounting shaft portion 28 . The annular groove 209 is provided at a boundary position between the main body portion 206 and the screw portion 31 in the axial direction of the mounting shaft portion 28 .

The neck portion 205 has an outer peripheral surface portion 211 which is a cylindrical surface continuous over the entire circumference.
The annular groove 208 is recessed radially inward of the mounting shaft portion 28 from the outer peripheral surface portion 211 of the neck portion 205 . Annular groove 208 is annular. The annular groove 208 has an annular shape centered on the central axis of the attachment shaft portion 28 . As shown in FIG. 3, annular groove 208 has tapered surface 212 and tapered surface 213 .

The tapered surface 212 is provided adjacent to the axial stepped portion 29 of the outer peripheral surface portion 211 of the neck portion 205 in the axial direction of the mounting shaft portion 28 . The tapered surface 212 is tapered around the central axis of the mounting shaft portion 28 . The tapered surface 212 has a smaller diameter as it moves away from the outer peripheral surface portion 211 in the axial direction of the mounting shaft portion 28 . The tapered surface 212 is arranged on the neck portion 205 .

The tapered surface 213 is provided adjacent to the tapered surface 212 on the side opposite to the outer peripheral surface portion 211 in the axial direction of the mounting shaft portion 28 . The tapered surface 213 is tapered around the central axis of the mounting shaft portion 28 . The tapered surface 213 has a diameter that increases with increasing distance from the tapered surface 212 in the axial direction of the mounting shaft portion 28 . The tapered surface 213 is arranged on the main body portion 206 .
The annular groove 208 having the tapered surface 212 and the tapered surface 213 is a V-shaped groove that is recessed inward in the radial direction of the mounting shaft portion 28 from the outer peripheral surface portion 211 .

The annular groove 209 is recessed inward in the radial direction of the mounting shaft portion 28 from the top portion of the thread of the fully threaded portion 202 of the threaded portion 31 . Annular groove 209 is annular. The annular groove 209 has an annular shape centered on the central axis of the mounting shaft portion 28 . The annular groove 209 is formed by the curved surface 215 and the crest portion of the incomplete thread portion 201 of the thread portion 31 described above. In other words, the annular groove 209 is partially formed by the crest portion of the thread of the incomplete thread portion 201 .
The curved surface 215 is provided adjacent to the main portion 206 side of the incomplete threaded portion 201 in the axial direction of the attachment shaft portion 28 . The curved surface 215 has a diameter that increases with increasing distance from the incomplete threaded portion 201 in the axial direction of the mounting shaft portion 28 . The curved surface 215 has an arcuate cross-section on a plane including the central axis of the mounting shaft portion 28 and has a center radially outward of the mounting shaft portion 28 relative to the mounting shaft portion 28 . Curved surface 215 is located on main body 206 .

As shown in FIG. 4, the main body portion 206 has an outer peripheral end surface portion 216 and the pair of groove portions 30 described above.
As shown in FIG. 3, the outer peripheral end surface portion 216 is provided between the tapered surface 213 and the curved surface 215 in the axial direction of the mounting shaft portion 28 and adjacent thereto. The outer peripheral end surface portion 216 has the shape of a portion of a cylindrical surface. The outer peripheral end surface portion 216 is arranged on the same cylindrical surface as the outer peripheral surface portion 211 of the neck portion 205 . The annular groove 208 is recessed inward in the radial direction of the attachment shaft portion 28 from the outer peripheral surface portion 211 of the neck portion 205 and the outer peripheral end surface portion 216 of the main body portion 206 . The annular groove 209 is recessed inward in the radial direction of the mounting shaft portion 28 from the top portion of the screw thread of the fully threaded portion 202 of the threaded portion 31 and the outer peripheral end face portion 216 of the main portion 206 . An annular groove 209 having a curved surface 215 and a crest portion of the thread of the incompletely threaded portion 201 extends radially inwardly of the mounting shaft portion 28 from the crest portion of the thread of the outer peripheral end face portion 216 and the fully threaded portion 202 . It is recessed in a substantially V shape.

As shown in FIG. 4 , the pair of grooves 30 are provided on at least part of the radially outer side of the mounting shaft 28 . As shown in FIG. 2 , the pair of grooves 30 are provided in a portion of the radially outer side of the main body portion 206 of the mounting shaft portion 28 . The pair of grooves 30 are recessed radially inward from the crests of the outer peripheral surface portion 211 and the fully threaded portion 202 in the radial direction of the mounting shaft portion 28 . As shown in FIG. 4 , the pair of grooves 30 are recessed radially inward from the annular groove 208 in the radial direction of the mounting shaft 28 . As shown in FIG. 2 , the pair of grooves 30 are deeply recessed radially inward from the annular groove 209 in the radial direction of the mounting shaft portion 28 .
As shown in FIG. 4 , the pair of grooves 30 are arranged on both sides of the mounting shaft 28 in the radial direction. Each of the pair of grooves 30 has a plane portion 218, a wall surface portion 219, and a wall surface portion 220, as shown in FIG. Accordingly, the mounting shaft portion 28 is provided with a pair of flat surface portions 218 , a pair of wall surface portions 219 and a pair of wall surface portions 220 .

The pair of planar portions 218 are planar. The pair of plane portions 218 are parallel to the central axis of the mounting shaft portion 28 and, as shown in FIG. 4, parallel to each other. The pair of plane portions 218 are equidistant from the central axis of the mounting shaft portion 28 . The pair of planar portions 218 are shorter in distance from the center axis of the mounting shaft portion 28 than the distance of the outer peripheral end face portion 216 from the center axis of the mounting shaft portion 28 . Therefore, the pair of grooves 30 has a shorter distance from the central axis of the attachment shaft 28 than the distance of the outer peripheral end face 216 from the central axis of the attachment shaft 28 . Both of the pair of flat portions 218 are rectangular. The pair of plane portions 218 are symmetrical with respect to the central axis of the mounting shaft portion 28 .

The pair of planar portions 218 cross the tapered surface 213, the outer peripheral end surface portion 216, and the curved surface 215 of the main body portion 206 shown in FIG. As shown in FIG. 4 , each of the pair of planar portions 218 extends to the outer peripheral end face portion 216 at both end edges in the circumferential direction of the mounting shaft portion 28 . As shown in FIG. 2, each flat portion 218 of the pair of grooves 30 extends to the tapered surface 212 of the neck portion 205 at one end in the axial direction of the mounting shaft portion 28, and the threaded portion 31 at the other end. extends to the incomplete threaded portion 201 of the . The planar portion 218 of each of the pair of groove portions 30 extends to the annular groove 208 at the end opposite to the screw portion 31 in the axial direction of the mounting shaft portion 28, and extends to the annular groove 208 at the end on the screw portion 31 side. Extends to 209. In other words, in the axial direction of the mounting shaft portion 28 , the ends of the pair of grooves 30 on the side opposite to the threaded portion 31 extend to the annular groove 208 , and the ends on the side of the threaded portion 31 extend to the annular groove 209 . ing.

The pair of wall surface portions 219 are planar. One wall surface portion 219 of the pair of wall surface portions 219 extends from the end edge of one of the pair of flat surface portions 218 on the side of the shaft step portion 29 in the axial direction of the mounting shaft portion 28 to the mounting shaft. It spreads outward in the radial direction of the portion 28 . The other wall surface portion 219 of the pair of wall surface portions 219 extends from the end edge of the other flat surface portion 218 of the pair of flat surface portions 218 on the side of the shaft step portion 29 in the axial direction of the mounting shaft portion 28 to the mounting shaft. It spreads outward in the radial direction of the portion 28 . The pair of wall surface portions 219 are arranged on the same plane extending orthogonally to the central axis of the mounting shaft portion 28 . The tapered surface 212 spreads from the radially outer edge of the mounting shaft portion 28 of the pair of wall surface portions 219 .
The pair of wall surfaces 220 are planar. One wall surface portion 220 of the pair of wall surface portions 220 is an end edge portion of one of the pair of flat surface portions 218 opposite to the shaft stepped portion 29 in the axial direction of the mounting shaft portion 28 . , extending outward in the radial direction of the mounting shaft portion 28 . The other wall surface portion 220 of the pair of wall surface portions 220 is the edge portion of the other flat surface portion 218 of the pair of flat surface portions 218 on the side opposite to the shaft stepped portion 29 in the axial direction of the mounting shaft portion 28 . , extending outward in the radial direction of the mounting shaft portion 28 . The incomplete threaded portion 201 extends from the radially outer edge portion of the mounting shaft portion 28 of the pair of wall portions 220 to the opposite side of the shaft stepped portion 29 in the axial direction of the mounting shaft portion 28 .

A manufacturing method for manufacturing the piston rod 21 described above will be described.
The base material of the piston rod 21 is machined through a turning process, a thread rolling process and a milling process.

A turning process is performed on the piston rod 21 including the mounting shaft portion 28 . In this turning process, the base material is machined as shown in FIG. That is, the main shaft portion 27, the mounting shaft portion 28, and the like are formed in the base material. Regarding the mounting shaft portion 28, the neck portion 205 is formed, and the main body portion 206 and the screw portion 31 are partially extended. Form. That is, the threaded portion 31 is in a state before the incompletely threaded portions 201 and 203 and the completely threaded portion 202 are formed. Also, the main body portion 206 is in a state before the pair of groove portions 30 are formed. By this turning process, the tapered surfaces 212 and 213 of the annular groove 208 are formed in an annular shape continuously over the entire circumference of the mounting shaft portion 28 . That is, the annular groove 208 is a V-groove that is continuously formed over the entire circumference of the mounting shaft portion 28 . In addition, by this turning process, the annular groove 209 is formed in an annular shape so that the curved surface 215 and the portion that will later become the incomplete threaded portion 201 are continuous over the entire circumference of the mounting shaft portion 28 .

Next, a thread rolling process is performed. In this thread rolling step, incomplete threaded portions 201 and 203 and a complete threaded portion 202 are formed in the threaded portion 31 by thread rolling.

A milling step is then performed. In this milling process, a pair of plane portions 218 are formed on the main body portion 206 by milling. At this time, the tapered surface 213 of the annular groove 208, the outer peripheral end surface portion 216, and the curved surface 215 of the annular groove 209 of the main body portion 206 are milled in the axial direction of the mounting shaft portion . At that time, the main body portion 206 is milled to a position deeper than the groove bottoms of the annular grooves 208 and 209 in the radial direction of the mounting shaft portion 28 . As a result, a pair of flat surface portions 218 are formed at positions deeper than the groove bottoms of the annular grooves 208 and 209, and a pair of wall surface portions 219 and a pair of wall surface portions 220 are formed. As a result, a pair of grooves 30 are formed as shown in FIGS. As a result, in the axial direction of the mounting shaft portion 28 , a pair of groove portions 30 extending to the tapered surface 212 of the neck portion 205 at one end and to the incomplete thread portion 201 of the thread portion 31 at the other end are formed in the mounting shaft portion 28 . It is formed. Note that the milling process may be performed before the thread rolling process.

The manufacturing method for manufacturing the piston rod 21 in this manner includes the steps of forming the rod-shaped mounting shaft portion 28 to be inserted into the piston 18 defining the interior of the shock absorber 1, and the step of forming the threaded portion 31 provided on the mounting shaft portion 28 At least a portion of the radially outer side of the mounting shaft portion 28 is provided with one axial end extending to the incompletely threaded portion 201 of the threaded portion 31, and the other axial end is the neck portion. and forming a groove 30 extending to the tapered surface 212 of 205 .

As shown in FIG. 1, the above-described base valve 25 is provided between the bottom member 12 of the outer cylinder 4 and the inner cylinder 3 . This base valve 25 has a base valve member 221 , a disc valve 222 , a disc valve 223 and a mounting pin 224 . The base valve 25 is mounted on the bottom member 12 at the base valve member 221 and is fitted to the inner cylinder 3 at the base valve member 221 . A base valve member 221 separates the lower chamber 20 and the reservoir chamber 6 . The disc valve 222 is provided below the base valve member 221, that is, on the reservoir chamber 6 side. The disk valve 223 is provided above the base valve member 221, that is, on the lower chamber 20 side. Mounting pins 224 attach disc valve 222 and disc valve 223 to base valve member 221 .

The base valve member 221 has an annular shape, and a mounting pin 224 is inserted through the center in the radial direction. A plurality of passage holes 225 and a plurality of passage holes 226 are formed in the base valve member 221 . A plurality of passage holes 225 circulate the oil L between the lower chamber 20 and the reservoir chamber 6 . The plurality of passage holes 226 are arranged outside the plurality of passage holes 225 in the radial direction of the base valve member 221 . A plurality of passage holes 226 circulate the oil L between the lower chamber 20 and the reservoir chamber 6 . The disk valve 222 on the reservoir chamber 6 side allows the oil L to flow from the lower chamber 20 to the reservoir chamber 6 via the passage hole 225 . On the other hand, the disc valve 222 suppresses the flow of the oil L from the reservoir chamber 6 to the lower chamber 20 through the passage hole 225 . The disc valve 223 allows the oil L to flow from the reservoir chamber 6 to the lower chamber 20 through the passage hole 226 . On the other hand, the disc valve 223 suppresses the flow of the oil L from the lower chamber 20 to the reservoir chamber 6 through the passage hole 226 .

The disk valve 222 and the base valve member 221 constitute a damping valve mechanism 227 . The damping valve mechanism 227 opens during the contraction stroke of the shock absorber 1 to allow the oil L to flow from the lower chamber 20 to the reservoir chamber 6 and generate a damping force. The disc valve 223 and the base valve member 221 constitute a suction valve mechanism 228 . The suction valve mechanism 228 opens during the extension stroke of the shock absorber 1 to allow the oil liquid L to flow from the reservoir chamber 6 into the lower chamber 20 . In addition, the suction valve mechanism 228 is designed to supply the oil L without substantially generating a damping force from the reservoir chamber 6 to the lower chamber 20 so as to compensate for the lack of liquid caused mainly by the extension of the piston rod 21 from the cylinder 2 . fulfills the function of flowing

Next, main operations of the buffer 1 will be explained.
"In the elongation stroke, assuming that the frequency sensitive mechanism 130 does not act and only the elongation-side first damping force generating mechanism 41 and the second damping force generating mechanism 110 act"
In this case, when the moving speed of the piston 18 (hereinafter referred to as the piston speed) is slower than the first predetermined value, the oil L from the upper chamber 19 flows through the first passage portion 43 and the first attenuation shown in FIG. It flows into the lower chamber 20 through the fixed orifice 92 of the force generating mechanism 41 . Therefore, a damping force having an orifice characteristic (the damping force is approximately proportional to the square of the piston speed) is generated. Therefore, when the piston speed is slower than the first predetermined value, the characteristic of the damping force with respect to the piston speed has a relatively high increase rate of the damping force with respect to the increase in the piston speed.

When the piston speed becomes greater than or equal to the first predetermined value and less than the second predetermined value, the oil L from the upper chamber 19 flows through the first passage portion 43, the passage in the notch 81, the passage in the groove portion 30, and the passage groove 79. While opening the disk valve 99 of the second damping force generating mechanism 110 , it flows between the disk valve 99 and the valve seat portion 75 to the lower chamber 20 through the passage and back pressure chamber 100 . Therefore, a damping force of valve characteristics (the damping force is approximately proportional to the piston speed) is generated. Therefore, the characteristics of the damping force with respect to the piston speed when the piston speed is greater than or equal to the first predetermined value and less than the second predetermined value are such that the rate of increase of the damping force with respect to the increase in piston speed is It will go down over time.

When the piston speed increases to a second predetermined value or more, the relationship between the force (oil pressure) acting on the damping valve 91 of the first damping force generating mechanism 41 is such that the force in the opening direction applied from the first passage portion 43 is applied to the back pressure chamber 100 larger than the force in the closing direction applied from Therefore, in this region, the damping valve 91 opens away from the valve seat portion 48 of the piston 18 as the piston speed increases. Therefore, the oil L from the upper chamber 19 flows through between the disk valve 99 and the valve seat portion 75 to the lower chamber 20 while opening the disk valve 99, and also flows to the lower chamber 20 while opening the damping valve 91. , from the first passage portion 43 to the lower chamber 20 through between the damping valve 91 and the valve seat portion 48 . Therefore, when the piston speed is equal to or higher than the second predetermined value, the increase rate of the damping force with respect to the increase in the piston speed is lower than when the piston speed is equal to or higher than the first predetermined value and is lower than the second predetermined value.

"When assuming that the frequency sensitive mechanism 130 does not act during the compression stroke and only the first damping force generating mechanism 42 on the compression side acts"
In this case, when the piston speed is lower than the third predetermined value, the oil L from the lower chamber 20 passes through the first passage portion 44 and the fixed orifice 123 of the first damping force generating mechanism 42 to the upper chamber 19. flow to As a result, a damping force having an orifice characteristic is generated. Therefore, when the piston speed is lower than the third predetermined value, the characteristic of the damping force with respect to the piston speed has a relatively high increase rate of the damping force with respect to the increase in the piston speed.

When the piston speed increases to a third predetermined value or more, the oil L introduced from the lower chamber 20 into the first passage portion 44 opens the disc valve 122 of the first damping force generating mechanism 42 and causes the disc valve 122 and the valve seat portion to open. 49 to the upper chamber 19. This produces a damping force with valve characteristics. Therefore, when the piston speed is equal to or higher than the third predetermined value, the characteristic of the damping force with respect to the piston speed is such that the increase rate of the damping force with respect to the increase in the piston speed is lower than when the piston speed is less than the third predetermined value. Become.

"When the frequency sensitive mechanism 130 acts in the extension stroke"
In the first embodiment, the frequency sensitive mechanism 130 varies the damping force according to the piston frequency even when the piston speed is the same.

In the extension stroke, the oil L is introduced from the upper chamber 19 into the variable chamber 181 of the frequency sensitive mechanism 130 through the first passage portion 43, the passage in the notch 81, the passage in the groove portion 30, and the passage in the passage groove 161. be done. Therefore, the partition disk 135 that is in contact with the seat portion 154 and the disk 136 is tapered in the direction away from the seat portion 154 with the contact point with the disk 136 as a fulcrum. At that time, the partition disk 135 discharges the oil L from the variable chamber 182 to the lower chamber 20 through the passage between the disk 137 and the cylindrical portion 153 of the housing body 131 .

Here, the stroke of the piston 18 is small in the extension stroke when the piston frequency is high. Therefore, the amount of oil L introduced from the upper chamber 19 into the variable chamber 181 via the first passage portion 43 , the passage in the notch 81 , the passage in the groove portion 30 and the passage in the passage groove 161 is small. Therefore, although the partition disk 135 is deformed as described above, it is not deformed to the limit.

Therefore, in the extension stroke when the piston frequency is high, the dividing disk 135 of the frequency sensitive mechanism 130 is deformed as described above to introduce the oil L from the upper chamber 19 into the variable chamber 181 each time the extension stroke is performed. become. Then, from the upper chamber 19, through the first passage portion 43, the passage in the notch 81, the passage in the groove portion 30, the passage in the passage groove 79, and the back pressure chamber 100, the disc valve 99 of the second damping force generating mechanism 110 is opened, the flow rate of the oil liquid L flowing into the lower chamber 20 is reduced. In addition to this, while opening the damping valve 91 of the first damping force generating mechanism 41 from the first passage portion 43, the flow rate of the oil liquid L flowing into the lower chamber 20 is also reduced. In addition, by introducing the oil L from the upper chamber 19 into the variable chamber 181, the pressure rise in the back pressure chamber 100 is suppressed compared to the case where the variable chamber 181 is not provided, and the damping valve of the first damping force generating mechanism 41 is reduced. 91 becomes easier to open. These soften the damping force on the rebound side.

On the other hand, the stroke of the piston 18 is large in the extension stroke when the piston frequency is low. Therefore, a large amount of oil L is introduced from the upper chamber 19 into the variable chamber 181 via the first passage portion 43 , the passage in the notch 81 , the passage in the groove portion 30 and the passage in the passage groove 161 . Therefore, although the oil L flows from the upper chamber 19 to the variable chamber 181 at the beginning of the stroke of the piston 18, the partition disk 135 is deformed close to its limit after that, and does not deform any more. As a result, the oil L does not flow from the upper chamber 19 to the variable chamber 181 . As a result, from the upper chamber 19, through the first passage portion 43, the passage in the notch 81, the passage in the groove portion 30, the passage in the passage groove 79, and the back pressure chamber 100, the second damping force generating mechanism 110 is opened. , the flow rate of the oil L flowing into the lower chamber 20 does not decrease. In addition to this, while the damping valve 91 of the first damping force generating mechanism 41 is being opened from the first passage portion 43, the flow rate of the oil liquid L flowing into the lower chamber 20 is also not reduced. In addition, since the oil L is not introduced into the variable chamber 181 from the upper chamber 19, the pressure in the back pressure chamber 100 increases, making it difficult for the damping valve 91 of the first damping force generating mechanism 41 to open. As a result, the damping force is harder in the extension stroke when the piston frequency is low than when it is high.

During the contraction stroke, the pressure in the lower chamber 20 increases, but the valve disc 171 of the partition disc 135 of the frequency sensitive mechanism 130 abuts against the seat portion 154 of the housing body 131 to suppress expansion of the variable chamber 182 . Therefore, the amount of oil L introduced from the lower chamber 20 into the variable chamber 182 through the passage between the disk 137 and the cylindrical portion 153 of the housing main body 131 is suppressed. As a result, the flow rate of the oil L that is introduced from the lower chamber 20 into the first passage portion 44, passes through the first damping force generating mechanism 42, and flows into the upper chamber 19 does not decrease. Therefore, the damping force becomes hard. In the compression stroke, when the piston speed increases and the pressure in the variable chamber 182 becomes higher than the pressure in the variable chamber 181 by a predetermined value or more, the inner peripheral side of the partition disc 135 separates from the disc 136 . In other words, check valve 193 opens. As a result, from the lower chamber 20 , the passage between the cylindrical portion 153 and the disc 137 , the variable chamber 182 , the check valve 193 , the variable chamber 181 , the passage in the passage groove 161 , the passage in the groove portion 30 , the notch 81 The oil L flows into the upper chamber 19 via the passage and the first passage portion 43 . By opening the check valve 193 in this manner, the partition disc 135 suppresses the differential pressure between the variable chamber 182 side and the variable chamber 181 side. Therefore, excessive bending of the partition disk 135 is suppressed.

The above-mentioned Patent Document 1 describes a shock absorber in which a high-performance device such as a frequency sensitive section that changes damping force in response to frequency is attached to the piston rod. In such shock absorbers, grooves forming passages for working fluid may be provided on the radially outer side of the piston rod. A groove formed on the radially outer side of a rod-shaped member such as a piston rod is generally formed by cutting such as milling. When forming the groove portion by cutting, processing burrs may be generated on the radially outer side of the rod-shaped member. If such processing burrs are formed on the rod-shaped member, there is a possibility that the processing burrs interfere with the mounting component when the rod-shaped member is inserted into the mounting component when mounting the mounting component on the rod-shaped member. For this reason, the processing burr removal step for removing such processing burrs is performed as a separate step from the processing step for the groove portion, and the generated processing burrs are removed. However, in order to perform the processing burr removing process, it is necessary to introduce a processing machine for removing processing burrs, which increases the manufacturing cost. Moreover, the cycle time is increased by performing the processing burr removing step. Therefore, the manufacturing cost of the rod-shaped member will increase. On the other hand, it is desired to suppress the cost when manufacturing a rod-shaped member such as a piston rod.

The shock absorber 1 of the embodiment includes a rod-shaped mounting shaft portion 28 whose piston rod 21 is inserted into the piston 18 that defines the interior of the shock absorber 1, a threaded portion 31 provided on the mounting shaft portion 28, and a mounting shaft and a groove portion 30 provided in at least part of the radially outer side of the portion 28 . An end portion of the groove portion 30 in the axial direction of the mounting shaft portion 28 extends to the incomplete thread portion 201 of the thread portion 31 . In other words, the end portion of the groove portion 30 in the axial direction of the mounting shaft portion 28 extends to the annular groove 209 partially constituted by the incomplete thread portion 201 . As a result, even if a processing burr occurs at the end of the groove 30 on the screw portion 31 side in the axial direction of the mounting shaft portion 28 when processing the groove portion 30 , the processing burr is removed from the outer peripheral surface portion 211 of the neck portion 205 . can also occur at the bottom position of the annular groove 209 radially inward. Therefore, it is possible to prevent the processing burr from protruding radially outward from the outer peripheral surface portion 211 of the neck portion 205 . Therefore, it is possible to omit the processing burr removing step for removing processing burrs. As a result, processing machines for removing processing burrs are no longer required, and an increase in cycle time can be suppressed. Moreover, the annular groove 209 required for forming the threaded portion 31 can be used, and the process of forming the V-shaped groove only for suppressing processing burrs is unnecessary. From this point as well, an increase in cycle time can be suppressed. Therefore, the manufacturing cost of the piston rod 21 can be suppressed.

In the shock absorber 1 of the embodiment, the piston rod 21 has an annular annular groove 208 provided radially outside the mounting shaft portion 28 . The groove portion 30 extends to the annular groove 208 at the end portion of the mounting shaft portion 28 opposite to the screw portion 31 in the axial direction. As a result, even if a processing burr occurs at the end of the groove 30 opposite to the screw portion 31 in the axial direction of the mounting shaft portion 28 when processing the groove portion 30, the processing burr is removed from the outer circumference of the neck portion 205. It can occur at a bottom position of the annular groove 208 that is radially inward of the surface portion 211 . Therefore, it is possible to prevent the processing burr from protruding radially outward from the outer peripheral surface portion 211 of the neck portion 205 . Therefore, it is possible to omit the processing burr removing step for removing processing burrs. As a result, processing machines for removing processing burrs are no longer required, and an increase in cycle time can be suppressed. Therefore, the manufacturing cost of the piston rod 21 can be suppressed.

The manufacturing method of the piston rod 21 of the embodiment includes the steps of forming a rod-shaped mounting shaft portion 28 to be inserted into the piston 18, forming a threaded portion 31 provided on the mounting shaft portion 28, and forming the mounting shaft portion 28. and forming a groove portion 30 provided in at least a portion of the radially outer side and having an axial end extending to the incompletely threaded portion 201 of the threaded portion 31 . In other words, the milling range of the milling for forming the groove 30 is extended to the incomplete threaded portion 201 . As a result, even if a processing burr occurs at the end of the groove 30 on the screw portion 31 side in the axial direction of the mounting shaft portion 28 when processing the groove portion 30 , the processing burr is removed from the outer peripheral surface portion 211 of the neck portion 205 . can also occur at the bottom position of the annular groove 209 radially inward. Therefore, it is possible to prevent the processing burr from protruding radially outward from the outer peripheral surface portion 211 of the neck portion 205 . Therefore, it is possible to omit the processing burr removing step for removing processing burrs. As a result, processing machines for removing processing burrs are no longer required, and an increase in cycle time can be suppressed. Moreover, the annular groove 209 required for forming the threaded portion 31 can be used, and the process of forming the V-shaped groove only for suppressing processing burrs is unnecessary. From this point as well, an increase in cycle time can be suppressed. Therefore, the manufacturing cost of the piston rod 21 can be suppressed.

Although the above embodiment shows an example in which the present invention is applied to the piston rod 21 as a rod-shaped member, the present invention can be applied to various rod-shaped members as long as they are rod-shaped members used in shock absorbers. For example, when the base valve is provided with a frequency sensitive mechanism or the like, the present invention can be applied when forming grooves in the rod-shaped member inserted into the base valve member as the partition member of the base valve. Further, when an electromagnetic drive type damping force variable mechanism is provided on the outer peripheral side of the body member 11 of the outer cylinder 4 of the cylinder 2 and the oil passage communicating with the inside of the cylinder 2 is extended to this damping force variable mechanism, this damping force variable mechanism It is possible to apply the present invention when forming grooves in the rod-shaped member of the above. In this case, it becomes a cylinder including the housing of the variable damping force mechanism.
Moreover, although the hydraulic shock absorber is shown as an example in the above embodiment, water or air can also be used as the working fluid.

DESCRIPTION OF SYMBOLS 1... Shock absorber, 2... Cylinder, 18... Piston (partition member), 21... Piston rod (rod-shaped member), 28... Mounting shaft part (insertion part), 30... Groove part, 31... Screw part, 201... Incomplete screw Part, 195... Nut, 208... Annular groove.

Claims (4)

a cylinder;
a partition member that is inserted into the cylinder and partitions the inside of the cylinder;
A rod-shaped insertion portion inserted into the partition member, a threaded portion provided on the insertion portion, and an incompletely threaded portion provided on at least a part of the radially outer side of the insertion portion and having an axial end portion of the threaded portion. A rod-shaped member having a groove extending to
a nut that is screwed onto the threaded portion and suppresses axial movement of the partition member with respect to the rod-shaped member;
Buffer with. A shock absorber according to claim 1,
Having an annular annular groove provided radially outward of the insertion portion,
A shock absorber in which said groove extends to said annular groove at its axial end opposite said threaded portion. The rod-shaped member in a shock absorber comprising a partition member and a rod-shaped member,
The rod-shaped member is
a rod-shaped insertion portion inserted into the partition member defining the interior of the buffer;
a screw portion provided in the insertion portion;
a groove portion provided in at least a portion of the radially outer side of the insertion portion and having an axial end extending to an incompletely threaded portion of the threaded portion;
A rod-shaped member having A method for manufacturing a rod-shaped member in a shock absorber comprising a partition member and a rod-shaped member,
forming a rod-shaped insertion portion to be inserted into the partition member defining the interior of the buffer;
a step of forming a screw portion provided in the insertion portion;
forming a groove provided in at least a portion of the radially outer side of the insertion portion, the axial end of which extends to the incompletely threaded portion of the threaded portion;
A method for manufacturing a rod-shaped member comprising:

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