JP5851159B2 - Shock absorber - Google Patents

Description

  The present invention relates to a shock absorber.

  Among the shock absorbers, there is a shock absorber whose damping force characteristics are variable according to the vibration state (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 7-19642

  Incidentally, it is required to control the damping force characteristic in more detail.

  Therefore, an object of the present invention is to provide a shock absorber capable of controlling damping force characteristics in more detail.

To achieve the above object, the present invention provides a piston that divides a cylinder into a rod side chamber and a bottom side chamber, a piston rod having one end connected to the piston and the other end extending outside the cylinder. A housing provided on one end side of the piston rod, a free piston slidably inserted into the housing, a pressure chamber defined by the rod side chamber and the free piston in the housing. a rod passage communicating, at damper comprising a damping valve provided in the passage communicating with the rod side chamber and bottom side chamber, said housing and said free piston, said free piston rod side chamber side in the housing when moved to the inhibit transfer inhibiting the movement of the free piston by utilizing the flowability of the working fluid Configuration is provided, between the free piston and the housing, when the free piston is moved to the bottom chamber side within the housing, and an elastic member for restricting the movement of the free piston is provided, The movement suppression mechanism is formed in the housing and is provided only in the orifice communicating with the pressure chamber side opening of the rod passage and the rod side chamber side of the free piston, and when the free piston moves to the rod side chamber side A shutter part that enters the orifice, and is provided with at least one of a free piston contact surface that the elastic body of the free piston contacts and a housing contact surface that the elastic body of the housing contacts. The surface has a surface inclined with respect to the moving direction of the free piston .
A piston that divides the inside of the cylinder into a rod-side chamber and a bottom-side chamber; a piston rod having one end connected to the piston and extending the other end to the outside of the cylinder; and one end of the piston rod. A housing, a free piston slidably inserted in the housing, a rod passage communicating the rod side chamber and a pressure chamber defined by the free piston in the housing, and the rod side chamber In the shock absorber composed of a damping valve provided in a passage communicating with the bottom side chamber, the housing and the free piston are provided with the free piston when the free piston moves toward the rod side chamber in the housing. A movement restraining mechanism for restraining movement using the fluidity of the working fluid is provided. An elastic body is provided between the housing and the housing to restrict the movement of the free piston when the free piston moves toward the bottom side chamber in the housing. A taper surface provided on the inner periphery of the free piston, and an outer peripheral surface of the inner cylinder portion of the lid provided on the housing so as to be accessible from the rod side chamber side. At least one of the free piston contact surface that contacts the body and the housing contact surface that contacts the elastic body of the housing has a surface that is inclined with respect to the moving direction of the free piston. The configuration .

  According to the present invention, the damping force characteristic can be controlled in more detail.

It is sectional drawing which shows the buffer of 1st Embodiment which concerns on this invention. It is sectional drawing which shows the principal part of the buffer of 1st Embodiment which concerns on this invention. It is a characteristic diagram which shows the relationship between the position with respect to the housing of the free piston of the buffer of 1st Embodiment which concerns on this invention, and the passage area of an orifice. It is sectional drawing which shows the principal part of the buffer of 2nd Embodiment which concerns on this invention. It is sectional drawing which shows the principal part of the buffer of 3rd Embodiment which concerns on this invention. It is sectional drawing which shows the principal part of the buffer of 4th Embodiment which concerns on this invention. It is sectional drawing which shows the principal part of the buffer of 5th Embodiment which concerns on this invention.

The embodiment described below solves various problems and has an effect without stopping at the contents described in the column of problems to be solved by the above-described invention and the column of effects of the invention. The main problems to be solved by the following embodiments are listed below, including the contents described in the above-mentioned column.
(Characteristic improvement)
When changing the damping force characteristic (damping force with respect to the piston speed) according to the vibration state, characteristic setting such as a smoother change is required. This is because if the characteristics that generate a small damping force and the characteristics that generate a large damping force occur suddenly, the actual damping force also switches suddenly, which deteriorates the ride comfort of the vehicle and further reduces the damping force. This is because the behavior of the vehicle becomes unstable and the driver may feel uncomfortable with respect to the steering when the changeover occurs during the steering of the vehicle. For this reason, characteristic setting that is more smoothly changed as shown in Patent Document 1 described above has been studied, but further characteristic improvement is desired.
[Suppression of enlargement]
As shown in Patent Document 1 described above, in addition to a piston having a mechanism for generating two damping chambers and generating a damping force, a free piston that moves up and down in the housing is provided on one end side of the piston. Various cylinder devices that have been improved so as to obtain damping force characteristics corresponding to a wide range of vibration frequencies have been developed. A problem common to these cylinder devices is that an area in which the free piston moves up and down is necessary, and therefore, it becomes longer in the axial direction. When the size of the cylinder device is increased, the degree of freedom of attachment to the vehicle body is reduced, and thus an increase in the axial length of the cylinder device is a big problem. In addition, if a region in which the free piston moves up and down is secured and the axial length of the cylinder device is maintained as before, the stroke range of the piston is shortened, and there is a problem in that the ride comfort and steering stability are affected. Further, if a mechanism for adjusting the damping force is attached from the outside, it is not possible to increase the size accordingly, so there is a strong demand for downsizing the frequency sensitive portion.
[Reduction of the number of parts]
As shown in Patent Document 1 described above, since components such as a housing and a free piston are provided in addition to the piston, the number of components increases. As the number of parts increases, productivity, durability, reliability, etc. will be affected, so the desired characteristics, that is, the damping force characteristics corresponding to a wide range of vibration frequencies can be obtained, and the number of parts Reduction is desired.
Hereinafter, each embodiment according to the present invention will be described with reference to the drawings.

“First Embodiment”
1st Embodiment which concerns on this invention is described based on FIGS. 1-3. In the following description, in order to help understanding, the lower side of the figure is defined as one side, and conversely, the upper side of the figure is defined as the other side.

  As shown in FIG. 1, the shock absorber of the first embodiment is a so-called double cylinder type hydraulic shock absorber, and is concentrically covered with a cylindrical cylinder 1 and a cylinder 1 having a larger diameter than the cylinder 1. An outer cylinder 2 is provided, and a reservoir chamber 3 is formed between the cylinder 1 and the outer cylinder 2.

  A piston 5 is slidably fitted in the cylinder 1. The piston 5 divides the inside of the cylinder 1 into an upper chamber (rod side chamber) 6 and a lower chamber (bottom side chamber) 7. In the upper chamber 6 and the lower chamber 7 in the cylinder 1, an oil liquid as a working fluid is sealed, and in the reservoir chamber 3 between the cylinder 1 and the outer cylinder 2, an oil liquid as a working fluid, High pressure (about 20 to 30 atmospheres) gas is enclosed.

  The other end of the piston rod 10 whose one end extends to the outside of the cylinder 1 is inserted into the cylinder 1, and the piston 5 is connected to the other end of the piston rod 10 in the cylinder 1. . The piston rod 10 is inserted through a rod guide 11, a cup seal 12, an oil seal 13, and the like attached to one end opening of the cylinder 1 and extends to the outside of the cylinder 1. The rod guide 11 has a stepped shape in which the outer peripheral part has a larger diameter at the upper part than the lower part. The rod guide 11 is fitted to the inner peripheral part at the upper end of the cylinder 1 at the lower part and the inner peripheral part at the upper end of the outer cylinder 2 at the upper part. To fit. Thereby, the upper part of the cylinder 1 is positioned with respect to the outer cylinder 2. The upper end portion of the outer cylinder 2 is crimped inward and sandwiches the oil seal 13 and the rod guide 11 with the cylinder 1.

  The piston rod 10 is formed with an attachment shaft portion 15 for attaching the piston 5 on the distal end side of insertion into the cylinder 1, and the other portion is a main shaft portion 16 having a larger diameter than the attachment shaft portion 15. Yes. A retainer 23 that extends radially outward is fixed to the main shaft portion 16.

  An annular spring receiver 25 is arranged opposite to the piston 5 of the retainer 23, and a rebound spring 26 made of a coil spring is arranged opposite to the retainer 23 of the spring receiver 25. Further, an annular spring receiver 27 is disposed opposite to the spring receiver 25 of the rebound spring 26, and a buffer 28 made of an annular elastic material is provided opposite to the rebound spring 26 of the spring receiver 27. It has been.

  Here, in the extension stroke in which the piston rod 10 moves in the direction protruding from the cylinder 1, the spring receiver 25, the rebound spring 26, the spring receiver 27, and the shock absorber 28 are connected to the rod guide 11 side together with the retainer 23 fixed to the piston rod 10. The buffer body 28 comes into contact with the rod guide 11 at a predetermined position. When the piston rod 10 further moves in the protruding direction, the buffer 28 and the spring receiver 27 are stopped with respect to the rod guide 11 and the cylinder 1, and as a result, the moving retainer 23 and spring receiver 25, Is close. Thereby, the spring receiver 25 and the spring receiver 27 contract the rebound spring 26 between them. In this way, the rebound spring 26 provided in the cylinder 1 acts elastically on the piston rod 10 and suppresses the piston rod 10 from being fully extended. In this way, the rebound spring 26 becomes the resistance of the piston rod 10 to fully extend, so that the lifting of the inner peripheral wheel during turning of the vehicle is suppressed and the roll amount of the vehicle body is suppressed.

  The piston 5 communicates with the upper chamber 6 and the lower chamber 7, and a plurality of oil liquids flow from the upper chamber 6 toward the lower chamber 7 during the movement of the piston 5 toward the upper chamber 6, that is, the extension stroke (FIG. 1). In FIG. 1, only a single passage is shown in relation to the cross section, and a plurality of oil liquids flow out from the lower chamber 7 toward the upper chamber 6 in the movement toward the lower chamber 7 side of the piston 5, that is, in the contraction stroke (in FIG. 1). There is provided a passage 40b (shown only in one place due to the cross-sectional relationship).

  Half of these passages 40a are formed at an equal pitch in the circumferential direction with one passage 40b interposed therebetween, and one side of the piston 5 in the axial direction (the upper side in FIG. 1) has a diameter. On the outer side in the direction, the other side in the axial direction (the lower side in FIG. 1) opens radially inward. A damping valve 41a that generates a damping force is provided in the half of the passages 40a. The damping valve 41 a is disposed on the lower chamber 7 side in the axial direction of the piston 5. The passage 40a constitutes an extension-side passage through which oil liquid passes when the piston 5 moves to the extension side where the piston rod 10 extends out of the cylinder 1, and a damping valve 41a provided for these passages The extension side damping valve generates a damping force by regulating the flow of the oil liquid in the extension side passage 40a.

  The other half of the passages 40b are formed at an equal pitch in the circumferential direction with one passage 40a interposed therebetween, and the other side in the axial direction of the piston 5 (lower side in FIG. 1). Is opened radially outward, and one axial side (upper side in FIG. 1) is opened radially inward. A damping valve 41b that generates a damping force is provided in the remaining half of the passages 40b. The damping valve 41 b is disposed on the upper chamber 6 side in the axial direction of the piston 5. The passage 40b constitutes a contraction-side passage through which oil liquid passes when the piston 5 moves to the contraction side where the piston rod 10 enters the cylinder 1, and a damping valve 41b provided for these passages includes: This is a contraction-side damping valve that restricts the flow of the oil liquid in the contraction-side passage 40b and generates a damping force.

  A damping force variable mechanism 45 is attached to the piston rod 10 further on the end side than the piston 5 of the attachment shaft portion 15 on one end side in the cylinder 1.

  The outer cylinder 2 includes a cylindrical cylindrical member 47 and a bottom lid member 48 that is fitted to the lower end of the cylindrical member 47 and closes the opening at the lower end. The bottom cover member 48 is fitted to the inner peripheral portion of the cylindrical member 47 at the outer peripheral portion, and in this state, has a stepped shape so as to be positioned on the lower side toward the center side. The bottom cover member 48 is fixed to the cylindrical member 47 so as to be sealed by welding. An attachment member 49 is fixed to the outside of the bottom lid member 48 by welding.

  A bottom valve 53 that defines the lower chamber 7 in the cylinder 1 and the above-described reservoir chamber 3 is provided at the lower end of the cylinder 1. The bottom valve 53 includes a suction valve 51a that allows oil to flow from the reservoir chamber 3 to the lower chamber 7 in the expansion stroke without substantially generating a damping force, and from the lower chamber 7 to the reservoir chamber 3 side in the contraction stroke. And a damping valve 51b for flowing the oil while generating a damping force.

  The bottom valve 53 has a substantially disc-shaped bottom valve member 55 that is fitted into the cylinder 1 and partitions the inside of the cylinder 1 into two chambers, a lower chamber 7 and a reservoir chamber 3. The bottom valve member 55 has a stepped shape in which the upper part has a smaller diameter than the lower part. The bottom valve member 55 is fitted to the inner peripheral part of the lower end of the cylinder 1 at the upper part and is in contact with the outer cylinder 2 at the lower part. Position with respect to the outer cylinder 2.

  In the bottom valve member 55, a plurality of flow paths 57a penetrating in the axial direction on the outer side in the radial direction are formed at intervals in the circumferential direction. A plurality of flow paths 57b penetrating in the axial direction on the inner side in the radial direction are formed at intervals in the circumferential direction. The fluid can flow between the lower chamber 7 and the reservoir chamber 3 by these flow paths 57a and 57b.

  The bottom valve 53 is provided with the above-described suction valve 51 a on the lower chamber 7 side in the axial direction of the bottom valve member 55 so that the outer flow path 57 a can be opened and closed. On the side opposite to the lower chamber 7, the above-described attenuation valve 51b is provided so that the inner flow path 57b can be opened and closed.

  The suction valve 51a on the lower chamber 7 side is separated from the bottom valve member 55 when the piston rod 10 moves to the extension side, the piston 5 moves to the upper chamber 6 side, and the pressure in the lower chamber 7 decreases, and the flow path 57a. open. That is, the oil liquid flows from the reservoir chamber 3 toward the lower chamber 7 in the flow path 57a when the piston rod 10 moves to the extension side. Note that the suction valve 51a is located below the reservoir chamber 3 mainly to compensate for the shortage of oil due to the protrusion of the piston rod 10 from the cylinder 1 due to the relationship with the expansion-side damping valve 41a provided on the piston 5. The oil liquid is allowed to flow through the chamber 7 substantially without resistance (to the extent that no damping force is generated).

  The damping valve 51b on the opposite side of the lower chamber 7 is separated from the bottom valve member 55 when the piston rod 10 moves to the contraction side and the piston 5 moves to the lower chamber 7 side and the pressure in the lower chamber 7 increases. Then, the inner flow path 57b is opened. That is, when the piston rod 10 moves to the contraction side, the oil liquid flows through the flow path 57b from the lower chamber 7 to the reservoir chamber 3, and the damping valve 51b opens and closes the flow path 57b to attenuate. It is a compression-side damping valve that generates force. It should be noted that the damping valve 51b is connected to the reservoir from the lower chamber 7 so as to discharge the excess liquid mainly caused by the piston rod 10 entering the cylinder 1 due to the relationship with the compression-side damping valve 41b provided in the piston 5. It fulfills the function of flowing liquid into the chamber 3.

  For example, one side of the shock absorber described above is supported by the vehicle body, and the wheel side is fixed to the other side of the shock absorber. Specifically, it is connected to the vehicle body side by the piston rod 10 and is connected to the wheel side by an attachment member 49 attached to the bottom of the cylinder 1 opposite to the protruding side of the piston rod 10. Contrary to the above, the other side of the shock absorber may be supported by the vehicle body and the wheel side may be fixed to one side of the shock absorber.

  When the wheels vibrate as the vehicle travels, the positions of the cylinder 1 and the piston rod 10 change relatively with the vibrations, but the change is suppressed by the fluid resistance of the flow path formed in the piston 5. As will be described in detail below, the fluid resistance of the flow path formed in the piston 5 is made different depending on the speed and amplitude of vibration, and the ride comfort is improved by suppressing the vibration. Between the cylinder 1 and the piston rod 10, in addition to vibration generated by the wheels, inertial force and centrifugal force generated in the vehicle body as the vehicle travels also act. For example, a centrifugal force is generated in the vehicle body when the traveling direction is changed by a steering operation, and a force based on the centrifugal force acts between the cylinder 1 and the piston rod 10. As will be described below, the shock absorber according to the present embodiment has good characteristics with respect to vibration based on the force generated in the vehicle body as the vehicle travels, and high stability in vehicle travel is obtained.

  As shown in FIG. 2, the piston 5 includes a substantially disc-shaped piston main body 61 and a sliding contact member 62 that is mounted on the outer peripheral surface of the piston main body 61 and that slides in the cylinder 1. The piston main body 61 is formed with an insertion hole 63 through which the attachment shaft portion 15 of the piston rod 10 is inserted in the center in the radial direction. Further, the passages 40 a and 40 b described above are formed in the piston main body 61.

  At the end of the piston body 61 on the lower chamber 7 side in the axial direction, a seat portion 71a constituting the damping valve 41a is formed in an annular shape at one end opening position of the extending side passage 40a. At the end of the piston body 61 on the upper chamber 6 side in the axial direction, a seat portion 71b constituting the damping valve 41b is formed in an annular shape at the opening position of one end of the passage 40b on the contraction side.

  In the piston main body 61, the side opposite to the insertion hole 63 of the seat portion 71a is an annular stepped portion 72b whose axial direction height is lower than that of the seat portion 71a, and a path on the contraction side at the position of the stepped portion 72b. The other end of 40b is open. Similarly, in the piston main body 61, the side opposite to the insertion hole 63 of the seat portion 71b is an annular stepped portion 72a having an axial height lower than that of the seat portion 71b, and the position of the stepped portion 72a. The other end of the extended passage 40a is open.

  The damping valve 41a is composed of the above-described seat portion 71a and an annular disc 75a that can be simultaneously seated on the entire seat portion 71a, and is a disc valve. The disk 75a is configured by stacking a plurality of annular single disks. An annular valve restricting member 77a having a smaller diameter than the disk 75a is disposed on the opposite side of the disk 75a from the piston body 61.

  The damping valve 41a is provided with a fixed orifice 78a between the seat portion 71a and the disc 75a so that the passage 40a communicates with the lower chamber 7 even when they are in contact with each other. It is formed by the opening formed in 75a. The disc 75a is separated from the seat portion 71a to open the passage 40a. At that time, the valve regulating member 77a regulates deformation beyond the regulation in the opening direction of the disc 75a. The damping valve 41a is provided in the passage 40a and generates a damping force by suppressing the flow of the oil liquid generated in the passage 40a due to the sliding of the piston 5 toward the upper chamber 6 side.

  Similarly, the damping valve 41b includes the above-described seat portion 71b and an annular disc 75b that can be simultaneously seated on the entire seat portion 71b, and is a disc valve. The disk 75b is also configured by stacking a plurality of annular single disks. On the opposite side of the disk 75b from the piston body 61, an annular valve restricting member 77b having a smaller diameter than the disk 75b is disposed. The valve regulating member 77 b is in contact with the end surface of the main shaft portion 16 of the piston rod 10 on the mounting shaft portion 15 side.

  The damping valve 41b is provided with a fixed orifice 78b between the seat portion 71b and the disk 75b, which allows the passage 40b to communicate with the upper chamber 6 even when they are in contact with each other. It is formed by the opening formed in 75b. The disc 75b is separated from the seat portion 71b to open the passage 40b. At that time, the valve regulating member 77b regulates deformation beyond the regulation in the opening direction of the disc 75b. The damping valve 41b is provided in the passage 40b, and generates a damping force by suppressing the flow of oil liquid generated in the passage 40b due to the sliding of the piston 5 toward the lower chamber 7 side.

  In the first embodiment, an example in which the damping valves 41a and 41b are disc valves with inner circumference clamps is shown. However, the present invention is not limited to this, and any mechanism that generates damping force may be used. For example, the disc valve is attached with a coil spring. It may be a lift type valve, or may be a poppet valve.

  A male screw 80 is formed at the tip of the mounting shaft portion 15 of the piston rod 10, and this male screw 80 is a frequency sensitive portion that makes the damping force variable without being controlled from the outside by the frequency (vibration state). A damping force variable mechanism 45 is screwed.

  The damping force varying mechanism 45 includes a lid member 82 formed with a female screw 81 that is screwed into the male screw 80 of the piston rod 10, and a substantially cylindrical housing attached to the lid member 82 so that one end opening side thereof is closed. A housing 85 including a main body 83, a free piston 87 slidably inserted into the housing 85, and a free piston 87 interposed between the free piston 87 and the housing main body 83 of the housing 85. On the other hand, it is composed of an O-ring 89 that is an elastic body that compressively deforms when moved to the opposite side of the lid member 82. In FIG. 2 (the same applies to FIGS. 4 to 7 described later), an O-ring 89 in a natural state is shown for convenience. Since this O-ring 89 also functions as a seal, it is desirable that the O-ring 89 be arranged so that it is always deformed (non-circular in cross section) when attached. The O-ring 89 is a resistance element that compresses and deforms to generate a resistance force against the displacement of the free piston 87 when the free piston 87 moves in the other direction.

  The lid member 82 is formed mainly by cutting, and has a substantially cylindrical inner cylinder part 91 and a disk-like shape that extends radially outward from the axial end of the inner lid part 91. A lid substrate portion 92, a substantially cylindrical lid outer cylinder portion 93 extending in the same direction as the lid inner cylinder portion 91 from a radial intermediate position of the lid substrate portion 92, and a lid substrate portion of the lid inner cylinder portion 91. The lid 94 covers the opposite side of the nozzle 92 and has an orifice 94 formed at the center in the radial direction. A male screw 98 is formed on the outer peripheral surface of the lid outer cylinder portion 93. A chamfer 99 is formed outside the boundary position between the lid inner cylinder portion 91 and the lid tip plate portion 95.

  The orifice 94 is on the side opposite to the lid substrate portion 92 in the axial direction and is continuous with the tapered hole 94A having a smaller diameter toward the lid substrate portion 92 side, and the lid substrate portion 92 side of the tapered hole 94A. It has a tapered hole 94B having a larger diameter. Between the taper hole 94 </ b> A and the taper hole 94 </ b> B is a minimum diameter portion 94 </ b> C that is the minimum diameter in the orifice 94. The taper of the taper hole 94A is equal to the taper of the taper hole 94B, and the axial length of the taper hole 94A is longer than the axial length of the taper hole 94B.

  The housing main body 83 is formed mainly by cutting, and has a substantially cylindrical shape in which an inner annular protrusion 100 protruding radially inward is formed on one side in the axial direction. A small-diameter cylindrical surface portion 101, a curved surface portion 102, a large-diameter cylindrical surface portion 103, and a female screw 104 are formed on the inner peripheral surface of the housing main body 83 in order from one side in the axial direction. The small-diameter cylindrical surface portion 101 has a constant diameter, and the curved surface portion 102 connected to the small-diameter cylindrical surface portion 101 has an annular shape with a larger diameter as the distance from the small-diameter cylindrical surface portion 101 increases, and the large-diameter cylindrical surface portion 103 connected to the curved surface portion 102. Has a constant diameter larger than that of the small-diameter cylindrical surface portion 101. The curved surface portion 102 has an arc-shaped cross section including the central axis of the housing body 83, and the small-diameter cylindrical surface portion 101 and the curved surface portion 102 are formed on the inner annular protrusion 100. Although the housing main body 83 is described as being cylindrical, the inner peripheral surface is preferably circular in cross section, but the outer peripheral surface may be polygonal and non-circular in cross section.

  The male screw 98 of the lid member 82 is screwed onto the female screw 104 of the housing body 83, so that they are integrated into a housing 85.

  The free piston 87 is an integrally formed product mainly formed by forging and cutting, and includes a substantially cylindrical piston cylinder portion 106 and a piston closing plate portion 107 that closes one end side of the piston cylinder portion 106 in the axial direction. have. An annular outer annular protrusion 108 that protrudes radially outward is formed on the piston cylinder portion 106 on the side opposite to the piston closing plate portion 107 in the axial direction. In addition, a shutter portion 109 that protrudes in the axial direction on the same side as the piston cylinder portion 106 is formed at the radial center of the piston closing plate portion 107. Here, the shutter portion 109 is formed so as to protrude from the piston closed plate portion 107 by forging, and a concave portion 110 generated during forging is formed opposite to the shutter portion 109 of the piston closed plate portion 107.

  A small-diameter cylindrical surface portion 111, a curved surface portion 112, and a large-diameter cylindrical surface portion 113 are formed on the outer peripheral surface of the piston cylinder portion 106 in order from the piston closing plate portion 107 side in the axial direction. The curved surface portion 112 and the large-diameter cylindrical surface portion 113 are formed on the outer annular protrusion 108. A cylindrical surface portion 115 and a tapered surface portion 116 are formed on the inner peripheral surface of the piston cylinder portion 106 in order from the piston closing plate portion 107 side.

  The small-diameter cylindrical surface portion 111 has a constant diameter, and the curved surface portion 112 connected to the small-diameter cylindrical surface portion 111 has an annular shape with a larger diameter as the distance from the small-diameter cylindrical surface portion 111 increases. The large diameter cylindrical surface portion 113 connected to the curved surface portion 112 has a constant diameter larger than that of the small diameter cylindrical surface portion 111. The curved surface portion 112 has an arc shape in cross section including the central axis of the free piston main body 106. The cylindrical surface portion 115 has a constant diameter, and the tapered surface portion 116 connected to the cylindrical surface portion 115 has a tapered shape with a larger diameter as the distance from the cylindrical surface portion 115 increases.

  The shutter portion 109 has a rod shape, and the tapered surface portion 117 that becomes smaller in diameter in the axial direction from the piston closing plate portion 107 and the piston closing plate portion 107 that is continuous with the opposite side of the taper surface portion 117 from the piston closing plate portion 107. The taper surface portion 118 having a smaller diameter as it moves away from the axis direction, the cylindrical surface portion 119 having a constant diameter that is continuous to the opposite side of the taper surface portion 117 of the taper surface portion 118, and the taper surface portion 118 of the cylindrical surface portion 119 being continuous to the opposite side of the taper surface portion 118. In addition, a tapered tip tapered surface portion 120 having a smaller diameter as it moves away from the cylindrical surface portion 119 in the axial direction is provided. The taper of the tip tapered surface portion 120 is larger than the taper of the tapered surface portion 117 and smaller than the taper of the tapered surface portion 118.

  The free piston 87 is disposed in the housing 85 in such a direction that the shutter portion 109 can enter the orifice 94 of the housing 85. In this state, the large-diameter cylinder of the housing main body 83 is formed in the large-diameter cylindrical surface portion 113. The small diameter cylindrical surface portion 111 is slidably inserted into the small diameter cylindrical surface portion 101 of the housing main body 83. Thus, in a state where the free piston 87 is disposed in the housing 85, the curved surface portion 112 of the free piston 87 and the curved surface portion 102 of the housing main body 83 overlap each other in the radial direction. Therefore, the curved surface portion 102 of the housing body 83 and the curved surface portion 112 of the free piston 87 face each other in the moving direction of the free piston 87.

  And between the small diameter cylindrical surface portion 111 and the curved surface portion 112 of the free piston 87 and the curved surface portion 102 and the large diameter cylindrical surface portion 103 of the housing main body 83, in other words, the outer annular projection 108 of the free piston 87 and the inside of the housing 85. An O-ring 89 (the natural state is shown in FIG. 2) is disposed between the annular protrusion 100. When the O-ring 89 is in a natural state, the cross section including the central axis is circular, the inner diameter is smaller than the small-diameter cylindrical surface portion 111 of the free piston 87, and the outer diameter is the large-diameter cylindrical surface portion 103 of the housing body 83. The diameter is larger than. That is, the O-ring 89 is fitted to both the free piston 87 and the housing 85 with tightening margins in these radial directions.

  The O-ring 89 allows the free piston 87 to move in both directions in the axial direction with respect to the housing 85, and compresses and deforms when the free piston 87 moves to the opposite side of the lid member 82 to generate a resistance force. Restricts the movement of the free piston 87.

  In the free piston 87, the O-ring 89 comes into contact with the small-diameter cylindrical surface portion 111 and the curved surface portion 112, and the curved surface portion 112 is inclined with respect to the moving direction of the free piston 87. Further, in the housing 85, the O-ring 89 comes into contact with the large-diameter cylindrical surface portion 103 and the curved surface portion 102, and the curved surface portion 102 is inclined with respect to the moving direction of the free piston 87.

  In other words, the outer annular protrusion 108 is provided on the outer peripheral portion of the free piston 87, and one surface in the axial direction of the outer annular protrusion 108 forms a curved surface portion 112, which is on one side of the outer annular protrusion 108 on the inner periphery of the housing 85. An inner annular protrusion 100 having a curved surface portion 102 is provided at a position, and an O-ring 89 is provided between the outer annular protrusion 108 and the inner annular protrusion 100.

  In the small-diameter cylindrical surface portion 111 and the curved surface portion 112 of the free piston 87, the free piston contact surface that is in contact with the O-ring 89, and in the large-diameter cylindrical surface portion 103 and the curved surface portion 102 of the housing 85, The shortest distance that passes through the center of the O-ring 89 of the portion that is in contact with the O-ring 89 is changed by the movement of the free piston 87, and the portion that is in contact with the housing is contacted with the housing contact surface. The direction of the line changes. In other words, the small-diameter cylindrical surface portion so that the direction of the line segment that connects the shortest distance between the free piston contact surface of the free piston 87 and the housing contact surface of the housing 85 and the portion where the O-ring 89 contacts is changed. The shapes of 111 and the curved surface portion 112, the large diameter cylindrical surface portion 103 and the curved surface portion 102 are set. Specifically, when the free piston 87 is positioned on the upper chamber 6 side (upper side in FIG. 2) in the axial direction with respect to the housing 85, the O-ring 89 contacts the free piston contact surface and the housing contact surface. The shortest distance between the large diameter cylindrical surface portion 103 and the small diameter cylindrical surface portion 111 is the radius difference between the outer diameter and the inner diameter of the O-ring 89 rather than the radial difference between the large diameter cylindrical surface portion 103 and the small diameter cylindrical surface portion 111. Since the difference is larger, the O-ring 89 collapses the difference, and that portion, that is, the line segment of the shortest distance has an inclination angle of 0). On the other hand, when the free piston 87 moves toward the lower chamber 7 in the axial direction with respect to the housing 85 (lower side in FIG. 2), the contact portion with the O-ring 89 becomes the curved surface portion 112 and the curved surface portion 102, and the O-ring 89 is the most. The crushing position, that is, the inclination angle of the shortest distance line segment becomes oblique.

  The damping force variable mechanism 45 includes, for example, an O-ring 89 inserted into the housing main body 83 up to the position of the curved surface portion 102, and a free piston 87 is fitted inside the housing main body 83 and the O-ring 89 so as to cover the lid member. Assembling is performed by screwing 82 to the housing body 83. The damping force variable mechanism 45 assembled in advance in this way is attached by screwing the female screw 81 into the male screw 80 of the mounting shaft portion 15 of the piston rod 10, and at that time, the lid substrate portion of the housing 85 92 comes into contact with the valve regulating member 77a. The outer diameter of the damping force variable mechanism 45, that is, the outer diameter of the housing 85 is set to be smaller than the inner diameter of the cylinder 1 so as not to cause flow path resistance.

  A passage hole 125 extending in the radial direction is formed in the piston rod 10 at a position in the vicinity of the piston 5 of the main shaft portion 16, and a passage that communicates with the passage hole 125 and opens at the distal end portion on the mounting shaft portion 15 side. A passage hole 126 having a diameter larger than that of the hole 125 is formed along the axial direction. The passage holes 125 and 126 constitute a rod passage 127 provided in the piston rod 10. The rod passage 127 has a pressure chamber 130 in which the upper chamber 6 is formed in the housing 85 through a chamber 128 surrounded by the piston rod 10, the lid inner cylinder portion 91 and the lid tip plate portion 95, and an orifice 94. Communicate with. The orifice 94 formed in the housing 85 communicates with the pressure chamber side opening 129 of the rod passage 127 via the chamber 128, and the passage area defined by the minimum diameter portion 94 </ b> C is equal to the rod passage 127 and the chamber. It is narrower than the passage area at any of 128 positions. The pressure chamber 130 is defined by a housing 85, an O-ring 89, and a free piston 87.

  In the first embodiment, the shutter unit 109 at the center of the free piston 87 is aligned with the central axis of the orifice 94 at the center of the housing 85 and can enter the orifice 94. As shown in FIG. 2, when the free piston 87 is located at the movement center position that is the center of the movement range with respect to the housing 85, the shutter portion 109 has an end portion on the tip tapered surface portion 120 side of the cylindrical surface portion 119 and the end of the orifice 94. The axial position with the small diameter portion 94C is matched.

  When the free piston 87 slides in the housing 85 and moves to the lid member 82 side, the shutter portion 109 of the free piston 87 enters the orifice 94. In the state where the shutter portion 109 matches the axial position of the cylindrical surface portion 119 with the minimum diameter portion 94C of the orifice 94, the rod passage 127 is narrowed to a certain minimum passage area. In addition, when the free piston 87 moves to the opposite side from the lid member 82 from this state, the axial position of the boundary between the cylindrical surface portion 119 and the tip tapered surface portion 120 is matched with the minimum diameter portion 94C of the orifice 94, and then the free piston 87 The piston 87 moves while expanding the passage area of the orifice 94 by separating the tapered end surface 120 of the shutter 109 from the inner peripheral surface of the tapered hole 94A of the orifice 94 according to the moving distance. When the shutter portion 109 is separated from the orifice 94 by a predetermined distance or more, the shutter 94 opens the orifice 94 with a certain maximum passage area by the minimum diameter portion 94C. Thus, the shutter 109 adjusts the passage area of the orifice 94 according to the position of the free piston 87 relative to the housing 85.

  Therefore, the shutter portion 109 and the orifice 94 are moved in the state where the free piston 87 moves to the lid member 82 side which is one side in the axial direction in the housing 85 and the shutter portion 109 enters the orifice 94. The passage area of the communication through the rod passage 127 of the chamber 6 is narrowed. In this state, the flow of the oil liquid between the pressure chamber 130 and the upper chamber 6 is restricted, and the movement of the free piston 87 with respect to the housing 85 is suppressed. That is, the movement of the free piston 87 is suppressed when the orifice 94 of the housing 85 and the shutter portion 109 of the free piston 87 move to the lid member 82 side which is one side in the axial direction in the housing 85. The movement restraining mechanism 135 is configured. The movement suppressing mechanism 135 adjusts the passage area of the orifice 94 according to the position of the free piston 87 with respect to the housing 85 as described above, and may be a variable orifice that makes the passage area of the orifice 94 communicating with the rod passage 127 variable. Function.

  Here, the passage area of the orifice 94 has the characteristics shown in FIG. 3, where the position of the free piston 87 relative to the housing 85 is on the horizontal axis and the passage area is on the vertical axis. That is, in the movable range A of the free piston 87 with respect to the housing 85, in the one end regions a1 to a2 where the free piston 87 is separated from the piston rod 10 by a predetermined distance or more and the shutter portion 109 is separated from the orifice 94 by a predetermined distance or more, The area is the maximum constant value defined by the fully-open minimum diameter portion 94C. In the intermediate areas a2 to a4 including the moving center position a3, the passage area of the orifice 94 is proportionally reduced as the free piston 87 approaches the piston rod 10 and the shutter 109 approaches the orifice 94. To change. Further, in the other end regions a4 to a5 in which the free piston 87 is brought close to the piston rod 10 to a predetermined distance or less and the shutter portion 109 is inserted into the orifice 94 until the cylindrical surface portion 119 overlaps the minimum diameter portion 94C in the axial direction, The passage area of 94 is a minimum constant value defined by the diameter difference between the cylindrical surface portion 119 and the minimum diameter portion 94C. The movement restraining mechanism 135 shown in FIG. 2 reverses from the contraction stroke to the expansion stroke at which the passage area of the orifice 94 is minimized when low frequency vibration is input to the shock absorber, in which the displacement of the free piston 87 with respect to the housing 85 increases. The movement of the free piston 87 relative to the housing 85 is restrained in the front-rear direction.

  In other words, the free piston 87 is provided with the shutter portion 109 that adjusts the opening area of the orifice 94 communicating with the rod passage 127 according to the movement of the free piston 87. The shutter 109 protrudes from the free piston 87 and has a shape that can enter the orifice 94.

  The above-described rod passage 127 is communicated with the upper chamber 6 which is one of the upper chamber 6 and the lower chamber 7, and the oil liquid is drawn from the upper chamber 6 in the cylinder 1 by moving the piston 5 toward the upper chamber 6. , Flow into the pressure chamber 130 through the chamber 128 and the orifice 94. The movement suppression mechanism 135 is provided in series with the pressure chamber 130. The O-ring 89 provided between the free piston 87 and the housing 85 generates a resistance force against the displacement of the free piston 87 at this time. That is, the O-ring 89 generates an elastic force when the free piston 87 moves to the extending side that expands the pressure chamber 130 with respect to the housing 85.

  Here, in the extension stroke in which the piston rod 10 moves to the extension side, the oil liquid flows from the upper chamber 6 to the lower chamber 7 via the passage 40a. However, when the piston speed is in a very low speed range, The oil liquid introduced into the passage 40a from 6 basically flows into the lower chamber 7 through a fixed orifice 78a that is always open formed between the seat portion 71a and the disk 75a that contacts the seat portion 71a. At that time, a damping force having an orifice characteristic (a damping force is approximately proportional to the square of the piston speed) is generated. When the piston speed increases and reaches a low speed region, the oil introduced into the passage 40a from the upper chamber 6 basically passes between the disk 75a and the seat portion 71a while opening the disk 75a. 7 will flow. For this reason, a damping force having a valve characteristic (a damping force is substantially proportional to the piston speed) is generated.

  In the contraction stroke in which the piston rod 10 moves to the contraction side, the oil liquid flows from the lower chamber 7 to the upper chamber 6 via the passage 40b. However, when the piston speed is in a very low speed region, the passage from the lower chamber 7 The oil liquid introduced into 40b basically flows into the upper chamber 6 via a fixed orifice 78b that is always open and formed between the seat portion 71b and the disk 75b that contacts the seat portion 71b. A damping force having a characteristic (a damping force is approximately proportional to the square of the piston speed) is generated. Further, when the piston speed increases and reaches a low speed region, the oil introduced into the passage 40b from the lower chamber 7 basically passes between the disk 75b and the seat portion 71b while opening the disk 75b. 6 will flow. For this reason, a damping force having a valve characteristic (a damping force is substantially proportional to the piston speed) is generated.

  Here, when the piston speed is low, that is, the region where the frequency in the very low speed region (for example, 0.05 m / s) is relatively high (for example, 7 Hz or more) is, for example, vibration caused by unevenness on the fine surface of the road surface. In such a situation, it is preferable to reduce the damping force. Similarly, even when the piston speed is low, the region where the frequency is relatively low (for example, 2 Hz or less) is vibration such as wobbling caused by the roll of the vehicle body. In such a situation, the damping force Is preferable.

  Correspondingly, the damping force variable mechanism 45 described above makes the damping force variable according to the frequency even when the piston speed is low as well. That is, when the piston speed is low and the frequency of the reciprocating motion of the piston 5 is increased, the pressure in the upper chamber 6 is increased in the extension stroke, and the damping force varying mechanism 45 of the piston rod 10 is connected via the rod passage 127. While the oil liquid is introduced from the upper chamber 6 into the pressure chamber 130, the free piston 87 resists the biasing force of the O-ring 89 on the lower chamber 7 side in the axial direction, and the lower chamber 7 side in the axial direction with respect to the housing 85. Move to. As the free piston 87 moves to the lower chamber 7 side in the axial direction in this way, the oil liquid is introduced from the upper chamber 6 into the pressure chamber 130 according to the passage area of the orifice 94, and the passage from the upper chamber 6. The flow rate of the oil introduced into 40a and passing through the damping valve 41a and flowing into the lower chamber 7 is reduced. Thereby, a damping force falls. Thus, the free piston 87 makes the volume of the pressure chamber 130 variable by the movement of the piston 5.

  In the subsequent contraction stroke, the pressure in the lower chamber 7 increases, so that the oil liquid is discharged from the pressure chamber 130 to the upper chamber 6 through the rod passage 127 according to the passage area of the orifice 94, and until then the axial direction of The free piston 87 that has moved to the lower chamber 7 side moves to the upper chamber 6 side in the axial direction with respect to the housing 85. As the free piston 87 moves to the upper chamber 6 side in the axial direction in this way, the volume of the lower chamber 7 is expanded, and the upper chamber is introduced from the lower chamber 7 into the passage 40b and passes through the damping valve 41b. The flow rate of the oil liquid flowing to 6 is reduced. Thereby, a damping force falls.

  In the region where the frequency of the piston 5 is high, the frequency of the movement of the free piston 87 also increases, and as a result, the oil liquid flows from the upper chamber 6 to the pressure chamber 130 each time the above-described expansion stroke occurs, and every time the compression stroke occurs. The volume of the lower chamber 7 is increased by the amount of movement of the free piston 87, so that the damping force is maintained in a reduced state as described above.

  On the other hand, when the piston speed is low and the frequency of the piston 5 is low, the frequency of movement of the free piston 87 is also low, so that the oil liquid flows from the upper chamber 6 to the pressure chamber 130 at the beginning of the extension stroke. However, after that, the free piston 87 compresses the O-ring 89 and stops on the lower chamber 7 side in the axial direction with respect to the housing 85, and the oil does not flow from the upper chamber 6 to the pressure chamber 130. The flow rate of the oil liquid introduced into the passage 40a and passing through the damping valve 41a and flowing into the lower chamber 7 is not reduced, and the damping force is increased.

  Even in the subsequent contraction stroke, the volume of the lower chamber 7 is initially increased by the movement of the free piston 87 with respect to the housing 85, but thereafter, the free piston 87 is moved in the axial upper chamber 6 side with respect to the housing 85. Since it stops and does not affect the volume of the lower chamber 7, the flow rate of the oil liquid introduced into the passage 40b from the lower chamber 7 through the damping valve 41b and flowing into the upper chamber 6 is not reduced, and the damping force is increased. .

  In the present embodiment, as described above, the O-ring 89 made of a rubber material is used as a component that applies a biasing force to the free piston 87, and when the free piston 87 is in the movement center position with respect to the housing 85, the O The ring 89 is located between the large diameter cylindrical surface portion 103 of the housing main body 83 and the small diameter cylindrical surface portion 111 of the free piston 87.

  In the extension stroke, for example, from the center position of the movement, an oil liquid flows from the upper chamber 6 to the pressure chamber 130 via the rod passage 127 due to the pressure increase in the upper chamber 6, and the free piston 87 is axially lower with respect to the housing 85. Move to the 7th side. Then, the large-diameter cylindrical surface portion 103 of the housing 85 and the small-diameter cylindrical surface portion 111 of the free piston 87 rotate the O-ring 89 so that the inner diameter side and the outer diameter side move in opposite directions. The housing 85 is moved toward the lower chamber 7 in the axial direction, and thereafter, the upper chamber 6 side in the axial direction of the curved surface portion 102 of the housing 85 and the lower chamber in the axial direction of the curved surface portion 112 of the free piston 87. 7 side compresses in the axial direction and the radial direction of the free piston 87 while rolling the O-ring 89, and then the axial lower chamber 7 side of the curved surface portion 102 of the housing 85 and the curved surface portion of the free piston 87. 112 and the upper chamber 6 side in the axial direction compress the O-ring 89 in the axial direction and the radial direction of the free piston 87. The free piston 87 is restrained from moving relative to the housing 85 by the elastic force of the O-ring 89. That is, when the free piston 87 moves to the lower chamber 7 side, which is the other side in the axial direction, in the housing 85, the O-ring 89 between the free piston 87 and the housing 85 suppresses the movement of the free piston 87, Then regulate.

  At this time, a region where the O-ring 89 rolls between the large-diameter cylindrical surface portion 103 of the housing 85 and the small-diameter cylindrical surface portion 111 of the free piston 87, and the curved surface portion 102 of the housing 85 and the curved surface portion 112 of the free piston 87 The region where the O-ring 89 rolls is the rolling region where the O-ring 89 rolls at a position away from the downstream end in the moving region of the free piston 87, and is separated from the downstream end. In this position, the O-ring 89 is a moving region in which the O-ring 89 moves in the moving direction of the free piston 87 while being in contact with both the housing 85 and the free piston 87. This movement means that at least the downstream end position (the lower end position in FIG. 2) of the O-ring 89 in the free piston movement direction moves.

  Further, the region where the O-ring 89 is compressed between the curved surface portion 102 of the housing 85 and the curved surface portion 112 of the free piston 87 is the downstream end portion side of the moving region of the free piston 87. This is a moving direction deformation region that is elastically deformed in the moving direction 87. The elastic deformation in the movement direction deformation region is a deformation in which the upstream end position (the upper end position in FIG. 2) of the free piston movement direction of the O-ring 89 moves and the downstream end position does not move. Here, the rolling region and the moving region overlap with a part of the moving direction deformation region. As described above, the O-ring 89 is crushed in the movement direction in the movement direction deformation region.

  In the subsequent contraction stroke, when the pressure of the lower chamber 7 increases, the oil liquid flows from the pressure chamber 130 to the upper chamber 6 via the rod passage 127, and the free piston 87 moves toward the upper chamber 6 in the axial direction with respect to the housing 85. The axial lower chamber 7 side of the curved surface portion 102 of the housing 85 and the axial upper chamber 6 of the curved surface portion 112 of the free piston 87 release the compression of the O-ring 89, and then the curved surface of the housing 85. The upper chamber 6 side in the axial direction of the portion 102 and the lower chamber 7 side in the axial direction of the curved surface portion 112 of the free piston 87 further release the compression while rolling the O-ring 89, The large-diameter cylindrical surface portion 103 of the housing 85 and the small-diameter cylindrical surface portion 111 of the free piston 87 move the O-ring 89 toward the upper chamber 6 in the axial direction with respect to the housing 85 while rolling between them.

  From the middle stage to the latter stage of the movement of the free piston 87 in the axial direction toward the upper chamber 6 side, the shutter portion 109 gradually narrows the orifice 94, and finally the orifice 94 is narrowed to the minimum area. The flow of the oil liquid from the pressure chamber 130 to the upper chamber 6 through the passage 127 is suppressed, and as a result, the movement of the free piston 87 relative to the housing 85 is suppressed.

  In the extension stroke that follows, the oil liquid flows from the upper chamber 6 to the pressure chamber 130 via the rod passage 127 due to the pressure increase in the upper chamber 6, and the free piston 87 moves toward the lower chamber 7 in the axial direction with respect to the housing 85. Moving. In the initial stage of this movement, until the free piston 87 moves to a predetermined position with respect to the housing 85, the shutter 109 maintains the state where the orifice 94 is narrowed to the minimum area, and the movement suppressing mechanism 135 is The movement with respect to the housing 85 is suppressed. Thereafter, the shutter portion 109 gradually widens the orifice 94 and widens from the predetermined position to the maximum area, and the movement restraint mechanism 135 releases the restraint on the movement of the free piston 87 relative to the housing 85. Therefore, in the initial stage of the extension stroke after the stroke reversal, the state where the movement of the free piston 87 with respect to the housing 85 is suppressed by the movement suppression mechanism 135 is maintained. In this extension stroke, the O-ring 89 is caused to roll between the large-diameter cylindrical surface portion 103 of the housing 85 and the small-diameter cylindrical surface portion 111 of the free piston 87 so that the O-ring 89 is in the axial lower chamber 7 side with respect to the housing 85. Will be moved to.

  Here, the characteristic of the load with respect to the displacement of the free piston 87 by the O-ring 89 made of a rubber material is a non-linear characteristic. In other words, in a predetermined range before and after the moving central position of the free piston 87, the characteristics are close to linear, and when this range is exceeded, the rate of increase in load increases smoothly with respect to displacement. As described above, in the region where the operating frequency of the piston 5 is high, since the amplitude of the piston 5 is small, the displacement of the free piston 87 is also small, and the operation is performed in a linear characteristic range before and after the movement center position. Thereby, the free piston 87 becomes easy to move and vibrates following the vibration of the piston 5 to contribute to the reduction of the damping force generated by the damping valves 41a and 41b.

  On the other hand, in the region where the operating frequency of the piston 5 is low, the amplitude of the piston 5 increases, so that the displacement of the free piston 87 increases, and the expansion stroke operates in a non-linear characteristic range. As a result, the free piston 87 becomes gradually smooth and difficult to move during the extension stroke, and it is difficult to reduce the damping force generated by the damping valve 41a. In addition, when the displacement of the free piston 87 becomes large in the contraction stroke, the shutter 109 narrows the orifice 94 communicating with the rod passage 127, and the free piston 87 becomes gradually smooth and difficult to move, and the damping valve 41b is generated. It becomes difficult to reduce the damping force.

  In the first embodiment, as described above, in the damping force variable mechanism 45, the displacement of the free piston 87 with respect to the housing 85 increases, and the reversal from the contraction stroke to the expansion stroke at the time of inputting the low frequency vibration to the shock absorber. A movement suppression mechanism 135 including a shutter portion 109 that narrows the passage area of the orifice 94 in the front and rear is provided. For this reason, compared with the case where the shutter part 109 is not provided, the state where damping force is high can be maintained in the initial stage of reversal from the contraction stroke to the expansion stroke.

  That is, the movement suppressing mechanism 135 gradually brings the tip tapered surface portion 120 of the shutter portion 109 close to the inner peripheral surface of the tapered hole 94A of the orifice 94 at the latter stage of the contraction stroke in which the free piston 87 moves to the piston rod 10 side. The rod passage 127 is narrowed and narrowed to a minimum area from a predetermined position. For this reason, in the initial stage of the extension stroke, the shutter portion 109 is in a state in which the orifice 94 communicating with the rod passage 127 is narrowed to the minimum area. Apart from the peripheral surface, the orifice 94 is gradually opened to the maximum passage area. As a result, since the orifice 94 communicating with the rod passage 127 is narrowed in the initial stage of the extension stroke, the flow of the oil liquid from the upper chamber 6 to the pressure chamber 130 is suppressed, The movement of the free piston 87 relative to the housing 85 is suppressed and a delay occurs.

  Therefore, at the initial stage of the extension stroke after the stroke reversal, the flow rate of the oil liquid introduced from the upper chamber 6 into the passage 40a and passing through the damping valve 41a and flowing into the lower chamber 7 is relatively increased. The power goes up. When the extension stroke further proceeds, the shutter 109 is separated and the orifice 94 has the maximum passage area, and the damping force variable mechanism 45 operates in the same manner as in the state where the movement suppressing mechanism 135 is not provided.

  According to the first embodiment described above, the rod passage 127 that connects the upper chamber 6 in the cylinder 1 and the pressure chamber 130 defined by the free piston 87 in the housing 85 is formed. Thus, the damping force is made variable by changing the capacity of the pressure chamber 130, and the opening area of the orifice 94 communicating with the free piston 87 and the rod passage 127 is adjusted according to the movement of the free piston 87. A portion 109 is provided. For this reason, it becomes possible to control the damping force characteristic in more detail. In particular, the housing 85 and the free piston 87 are provided with a movement suppressing mechanism 135 that suppresses the movement of the free piston 87 when the free piston 87 moves to the upper chamber 6 side that is one side in the axial direction within the housing 85. Therefore, the movement restraining mechanism 135 narrows the opening area of the orifice 94 communicating with the rod passage 127 at the time of reversing the stroke from the contraction stroke to the expansion stroke by the shutter portion 109, so that the housing of the free piston 87 after the stroke reversal. By delaying the displacement with respect to 85, the damping force at the initial stage of reversal to the extension stroke can be increased. Therefore, it is possible to prevent the deterioration of handling responsiveness caused by the deterioration of the rising at the initial stage of the reversal of the damping force, which occurs when the shutter unit 109 is not provided, and to increase the responsiveness at the time of the reversal of the stroke from the contraction process to the expansion process. It is possible to improve handling responsiveness and handling stability.

  The housing 85 and the free piston 87 are provided with a movement suppressing mechanism 135 that suppresses the movement of the free piston 87 when the free piston 87 moves to one side in the housing 85. An O-ring 89 that restricts the movement of the free piston 87 when the free piston 87 moves to the lower chamber 7 side, which is the other side in the axial direction, is provided in the housing 85. Therefore, when the damping force is changed in response to the operating frequency of the piston 5, it can be changed smoothly.

  Further, a movement suppression mechanism 135 adjusts the opening area of the orifice 94 formed in the housing 85 and communicating with the pressure chamber side opening 129 of the rod passage 127 and the free piston 87 according to the movement of the free piston 87. And the movement of the free piston 87 with respect to the housing 85 is suppressed by utilizing the fluidity of the fluid that changes depending on the opening area. For this reason, even if an elastic body is not provided, the impact of the contact of the free piston 87 with the lid member 82 when the free piston 87 moves toward the lid member 82 with respect to the housing 85 can be reduced. Therefore, it can suppress that it becomes a transient damping force waveform, and generation | occurrence | production of the abnormal noise resulting from a metal touch collision can be suppressed. As a result, an O-ring that restricts the movement of the free piston 87 when the free piston 87 moves to the lid member 82 side and a structure portion that compresses the O-ring are not required, so the number of parts can be reduced and the axial length can be reduced. It can be shortened.

“Second Embodiment”
Next, the second embodiment will be described mainly based on FIG. 4 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  In the second embodiment, as shown in FIG. 4, a damping force variable mechanism 45 obtained by partially changing the first embodiment is used.

  In the damping force variable mechanism 45 of the second embodiment, first, the lid member 82 of the housing 85 is partially different. That is, in the lid member 82 of the second embodiment, a stepped portion 140 having an outer diameter smaller than that of the lid substrate portion 92 is formed between the lid substrate portion 92 and the lid inner cylinder portion 91. A male screw 98 is formed on the outer peripheral surface of the screw 140 to be screwed into the female screw 104 of the housing main body 83. An annular convex portion 141 is formed on the side of the step portion 140 opposite to the lid substrate portion 92 in the axial direction.

  The damping force variable mechanism 45 of the second embodiment is partially different from the free piston 87. That is, in the free piston 87 of the second embodiment, the tapered surface portion 116 of the first embodiment is not formed on the inner peripheral side of the piston cylinder portion 106, and the cylindrical surface portion 115 is formed over the entire length. An annular recess 142 that allows the projection 141 to enter is formed on the end surface on the outer annular projection 108 side in the axial direction, and an annular holding groove 143 that is further recessed is formed at the bottom of the recess 142. Yes. A square ring-shaped stopper ring 144 is fitted and fixed in the holding groove 143. The stopper ring 144 is an elastic body made of a rubber material and protrudes from the bottom surface of the recess 142. The stopper ring 144 abuts on the convex portion 141 of the free piston 87 and regulates the abutment of the free piston 87 on the lid member 82 by metal touch.

  The suppression of the movement of the free piston 87 toward the lid member 82 by the movement suppression mechanism 135 depends on the moving speed of the free piston 87, and the free piston 87 contacts the lid member 82 in the case of a very low speed and low frequency input. There is a possibility of contact. On the other hand, according to the second embodiment described above, the contact of the free piston 87 with the lid member 82 can be restricted by the stopper ring 144. Therefore, the impact at the time of contact of the free piston 87 with the lid member 82 can be reduced regardless of the moving speed of the free piston 87. Therefore, it can suppress further that it becomes a transient damping force waveform, and can further suppress generation | occurrence | production of the noise resulting from the collision of a metal touch.

“Third Embodiment”
Next, the third embodiment will be described mainly based on FIG. 5 with a focus on the differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  In the third embodiment, as shown in FIG. 5, a damping force variable mechanism 45 obtained by partially changing the first embodiment is used.

  In the damping force variable mechanism 45 of the third embodiment, the lid outer cylinder portion 93 of the lid member 82 and the free piston 87 are fitted so that the stopper ring 150 made of an O-ring is fitted to the large-diameter cylindrical surface portion 103 of the housing body 83. The outer annular protrusion 108 is disposed between the outer annular protrusion 108 and the outer annular protrusion 108. The stopper ring 150 is disposed so as to contact the lid outer cylinder portion 93 of the lid member 82. The axial length of the housing main body 83 is increased by the amount of the stopper ring 150, and the axial length of the lid inner cylindrical portion 91 is also increased in the lid member 82. The stopper ring 150 abuts on the outer annular projection 108 of the free piston 87 and restricts the abutment of the metal touch on the lid member 82 of the free piston 87.

  According to the third embodiment, the stopper ring 150 can restrict the contact of the free piston 87 to the lid member 82 as in the second embodiment. Therefore, the impact at the time of contact of the free piston 87 with the lid member 82 can be reduced regardless of the moving speed of the free piston 87. Therefore, it can suppress further that it becomes a transient damping force waveform, and can further suppress generation | occurrence | production of the noise resulting from the collision of a metal touch.

“Fourth Embodiment”
Next, the fourth embodiment will be described mainly on the basis of FIG. 6 with a focus on differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol.

  In the fourth embodiment, as shown in FIG. 6, a damping force variable mechanism 45 obtained by partially changing the first embodiment is used.

  In the damping force variable mechanism 45 of the fourth embodiment, the cover member 82 does not have the male screw 98 of the first embodiment, and does not have the female screw 104 of the housing body 83. Instead, the housing main body 83 is crimped by fitting the outer portion of the lid substrate portion 92 of the lid member 82 of the housing 85 to the side opposite to the inner annular protrusion 100 of the housing main body 83. Thus, the lid member 82 is fixed to the housing main body 83. For this reason, the axial length of the fixed structure portion is shorter than the screwing, and as a result, the axial lengths of the lid inner cylinder portion 91 and the lid outer cylinder portion 93 of the housing body 83 are short, and the shaft of the shutter portion 109 The direction length is also shortened.

  According to the fourth embodiment, since the lid member 82 is fixed to the housing body 83 by caulking, the axial length of the damping force varying mechanism 45 can be shortened as described above. Further, the cost required for fixing the housing main body 83 and the lid member 82 can be reduced, and the state at the time of fixing can be favorably maintained.

“Fifth Embodiment”
Next, the fifth embodiment will be described mainly on the basis of FIG. 7 with a focus on differences from the fourth embodiment. In addition, about the site | part which is common in 4th Embodiment, it represents with the same name and the same code | symbol.

  In the fifth embodiment, as shown in FIG. 7, a damping force variable mechanism 45 obtained by partially changing the fourth embodiment is used.

  The damping force variable mechanism 45 of the fifth embodiment is connected between the cylindrical surface portion 115 on the inner peripheral side of the free piston 87 and the tapered surface portion 116 on the side opposite to the piston closing plate portion 107 in the axial direction of the cylindrical surface portion 115. The taper surface portion 160 and the taper surface portion 161 connected to the side opposite to the piston closing plate portion 107 in the axial direction of the taper surface portion 160 are provided. The taper of the taper surface portion 160 is smaller than the taper of the taper surface portion 116, and the taper of the taper surface portion 161 is larger than the taper of the taper surface portion 116.

  Further, the chamfer 99 of the fourth embodiment is not formed on the outer side of the lid inner cylinder portion 91 opposite to the lid substrate portion 92. In addition, the orifice 94 has a constant diameter. A movement suppressing mechanism 163 is formed by the cylindrical outer peripheral surface of the lid inner cylindrical portion 91 and the tapered surface portion 160 and the cylindrical surface portion 115 on the inner peripheral side of the free piston 87. When the free piston 87 is separated from the lid member 82 by a predetermined distance or more, the movement suppressing mechanism 163 causes the upper chamber 6 and the pressure chamber 130 to communicate with each other through the passage area of the orifice 94, and the free piston 87 communicates with the lid member 82. When approaching below the distance, the passage area due to the diameter difference between the outer peripheral surface of the lid inner cylinder portion 91 and the tapered surface portion 160 of the free piston 87 is narrowed as the free piston 87 approaches the lid member 82. It operates in the same manner as the movement suppression mechanism 135 of the embodiment.

  According to the fifth embodiment, since it is not necessary to provide the shaft-shaped shutter portion 109 of the fourth embodiment, it is easy to manufacture the free piston 87 and the cost can be reduced.

  Although each said embodiment showed the example which used this invention for the double cylinder type hydraulic shock absorber, it uses not only this but the monotube type hydraulic shock absorber which does not provide an outer cylinder in the outer periphery of a cylinder. It can be used for any shock absorber.

In the above embodiment, the hydraulic shock absorber is shown as an example, but water or air may be used as the fluid.
Further, in each of the above embodiments, one example of the O-ring is shown as the elastic body that is the resistance element. However, if necessary, two or more O-rings may be used with the same technical idea.
In each of the above embodiments, an example in which a rubber (resin) ring is used as an elastic body that is a resistance element has been shown, but a plurality of rubber balls may be provided at intervals in the circumferential direction. The elastic body that can be used in the present invention does not need to be rubber as long as it does not have elasticity in one axial direction but has elasticity in a plurality of axial directions. For example, if a metal spring is used, the durability can be improved.

1 cylinder 5 piston 6 upper chamber (rod side chamber)
7 Lower room (bottom side room)
10 Piston rod 40a, 40b Passage 41a, 41b Damping valve 85 Housing 87 Free piston 89 O-ring (elastic body)
94 Orifice 109 Shutter part 127 Rod passage 129 Pressure chamber side opening 130 Pressure chamber 135,163 Movement suppression mechanism

Claims (2)

A cylinder filled with a working fluid;
A piston that is slidably fitted in the cylinder and divides the cylinder into a rod side chamber and a bottom side chamber;
A piston rod having one end connected to the piston and the other end extending outside the cylinder;
A housing provided at one end of the piston rod;
A free piston slidably inserted into the housing;
A rod passage communicating the rod side chamber and the pressure chamber defined by the free piston in the housing;
In a shock absorber comprising a damping valve provided in a passage communicating the rod side chamber and the bottom side chamber,
The housing and the free piston are provided with a movement suppression mechanism that suppresses the movement of the free piston using the fluidity of the working fluid when the free piston moves toward the rod side chamber in the housing. An elastic body is provided between the free piston and the housing to restrict the movement of the free piston when the free piston moves to the bottom chamber side in the housing .
The movement suppression mechanism is formed in the housing and is provided only on the rod side chamber side of the free piston and the orifice communicating with the pressure chamber of the rod passage, and when the free piston moves to the rod side chamber side, the orifice It consists of a shutter part that goes into
At least one of the free piston contact surface with which the elastic body of the free piston comes into contact and the housing contact surface with which the elastic body of the housing comes into contact is inclined with respect to the moving direction of the free piston. A shock absorber having a surface . A cylinder filled with a working fluid;
A piston that is slidably fitted in the cylinder and divides the cylinder into a rod side chamber and a bottom side chamber;
A piston rod having one end connected to the piston and the other end extending outside the cylinder;
A housing provided at one end of the piston rod;
A free piston slidably inserted into the housing;
A rod passage communicating the rod side chamber and the pressure chamber defined by the free piston in the housing;
In a shock absorber comprising a damping valve provided in a passage communicating the rod side chamber and the bottom side chamber,
The housing and the free piston are provided with a movement suppression mechanism that suppresses the movement of the free piston using the fluidity of the working fluid when the free piston moves toward the rod side chamber in the housing. An elastic body is provided between the free piston and the housing to restrict the movement of the free piston when the free piston moves to the bottom chamber side in the housing.
The movement restraining mechanism,
A tapered surface portion provided on the inner periphery of the front SL free piston,
The taper surface portion is provided so as to be able to enter from the rod side chamber side, and includes an outer peripheral surface of a lid inner cylinder portion formed in the housing,
At least one of the free piston contact surface with which the elastic body of the free piston comes into contact and the housing contact surface with which the elastic body of the housing comes into contact is inclined with respect to the moving direction of the free piston. slow衝器you characterized by having a surface.

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