WO2016088629A1

WO2016088629A1 - Damper

Info

Publication number: WO2016088629A1
Application number: PCT/JP2015/083142
Authority: WO
Inventors: 和隆稲満; 崇志寺岡
Original assignee: Ｋｙｂ株式会社
Priority date: 2014-12-01
Filing date: 2015-11-26
Publication date: 2016-06-09
Also published as: JP2016104997A; JP6462341B2

Abstract

This damper D is provided with: a piston 2 that divides the inside of a cylinder 1 into an expansion-side chamber L1 and a pressure-side chamber L2; a reservoir T that is formed in a tank 10 that is attached to the outside of the cylinder 1; a base member 3 that divides the reservoir T and the pressure-side chamber L2; a first main channel R1 that connects the expansion-side chamber L1 and the pressure-side chamber L2; a second main channel R2 that connects the pressure-side chamber L2 and the reservoir T; a free piston 4 that divides a pressure chamber L4 formed in the tank 10 into an expansion-side pressure chamber L40 and a pressure-side pressure chamber L41; a spring element S that suppresses displacement of the free piston 4; an expansion-side channel R3 that connects the expansion-side pressure chamber L40 and the reservoir T; and a pressure-side channel R4 that connects the pressure-side pressure chamber L41 and the pressure-side chamber L2.

Description

Shock absorber

This invention relates to a shock absorber.

The shock absorber is interposed between the vehicle body and the axle of the vehicle and is used to suppress vehicle body vibration. The shock absorber is slidably inserted into the cylinder and includes a piston that divides the cylinder into a rod-side extension side chamber and a piston-side pressure side chamber, and is provided in the piston so that the extension-side chamber and the pressure-side chamber communicate with each other. A first passage that opens to the tip of the rod and a second passage that opens to the side of the rod and communicates the extension side chamber and the pressure side chamber, and a pressure chamber attached to the tip of the rod and connected to the second passage Includes a housing formed therein, a free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, and a coil spring that urges the free piston. That is, the expansion side pressure chamber communicates with the expansion side chamber through the second passage, and the compression side pressure chamber communicates with the compression side chamber through the second passage.

In the shock absorber configured as described above, since the pressure chamber is partitioned into the expansion side pressure chamber and the compression side pressure chamber by the free piston, the expansion side chamber and the compression side chamber are not directly communicated with each other through the second passage. However, when the free piston moves, the volume ratio between the expansion side pressure chamber and the compression side pressure chamber changes, and the liquid in the pressure chamber enters and exits the expansion side chamber and the compression side chamber according to the amount of movement of the free piston. For this reason, the shock absorber operates as if the extension side chamber and the pressure side chamber communicate with each other through the second passage.

Here, on the basis of the pressure in the compression side chamber, P is the differential pressure between the expansion side chamber and the compression side chamber during the expansion operation of the shock absorber, Q is the flow rate of the liquid flowing out from the expansion side chamber, and the differential pressure P and the first passage The coefficient which is the relationship with the flow rate Q1 of the liquid passing through the cylinder is C1, the differential pressure between the extension side chamber and the extension side pressure chamber is P1, and the differential pressure P1 and the flow rate Q2 of the liquid flowing from the extension side chamber into the extension side pressure chamber The coefficient that is the relationship between the pressure side chamber and the pressure side pressure chamber is P2, and the coefficient that is the relationship between the differential pressure P2 and the flow rate Q2 of the liquid flowing out from the pressure side pressure chamber to the pressure side chamber is C3. When the cross-sectional area, which is the pressure receiving area of the piston, is A, the displacement of the free piston with respect to the pressure chamber is X, and the spring constant of the coil spring is K, the transfer function of the differential pressure P with respect to the flow rate Q is obtained. can get. In equation (1), s represents a Laplace operator.

Further, substituting jω for the Laplace operator s in the transfer function shown in the above equation (1) to obtain the absolute value of the frequency transfer function G (jω) yields the following equation (2).

As can be understood from the above equations, the frequency characteristics of the transfer function of the differential pressure P with respect to the flow rate Q of the buffer are Fa = K / {2 · π · A ² · (C1 + C2 + C3)} and Fb = K / {2 · It has two breakpoint frequencies of π · A ² · (C2 + C3)}. In the region of F <Fa, the transmission gain is substantially C1, and in the region of Fa ≦ F ≦ Fb, the transmission gain is changed so as to gradually decrease from C1 to C1 · (C2 + C3) / (C1 + C2 + C3), and F> Fb. It is constant in the area. That is, in the frequency characteristic of the transfer function of the differential pressure P with respect to the flow rate Q, the transfer gain increases in the low frequency range, and the transfer gain decreases in the high frequency range.

Therefore, with this shock absorber, a large damping force can be generated for low frequency vibration input, while a small damping force can be generated for high frequency vibration input. For this reason, a high damping force can be reliably generated in a scene where the input vibration frequency is low, such as when the vehicle is turning, and a low damping force is used in a scene where the input vibration frequency is high such that the vehicle passes through the unevenness of the road surface. It can be reliably generated and the riding comfort in the vehicle can be improved (for example, refer to JP2006-336816A, JP2008-21559A).

JP 2006-336816A and JP 2008-215459A disclose a shock absorber in which a frequency sensitive part is attached to the tip of a rod in order to obtain the above-described attenuation characteristics. The frequency sensitive unit includes a free piston, a pressure chamber, a second passage, and a coil spring. The frequency sensitive portion is disposed so as to protrude in the axial direction from the piston toward the pressure side chamber. Therefore, when trying to secure the stroke length of the shock absorber, the length from the vehicle body side attachment portion for attaching the shock absorber to the vehicle body to the axle side attachment portion for attaching the shock absorber to the axle (hereinafter referred to as the basic length). ) Becomes longer, and the mountability on the vehicle may be deteriorated.

Therefore, an object of the present invention is to provide a shock absorber capable of improving the mountability to a vehicle by shortening the basic length while ensuring the stroke length.

According to an aspect of the present invention, a cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, one end connected to the piston and the other end A rod that extends outside the cylinder, a tank that is attached to the outside of the cylinder, a reservoir that is formed in the tank and compensates for the change in the cylinder volume corresponding to the volume of the rod, and the reservoir and the pressure side chamber A first main passage communicating the extension side chamber and the pressure side chamber, a second main passage communicating the pressure side chamber and the reservoir, and a pressure chamber formed in the tank A free piston that is movably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, and a displacement of the free piston with respect to the pressure chamber. A shock absorber is provided that includes a spring element that generates a biasing force to be controlled, an extension side passage that communicates the extension side pressure chamber and the reservoir, and a pressure side passage that communicates the pressure side pressure chamber and the pressure side chamber. Is done.

FIG. 1 is a front view of a shock absorber according to an embodiment of the present invention, partially cut away. FIG. 2 is an enlarged view of the main part of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals used throughout the several drawings indicate the same parts.

As shown in FIGS. 1 and 2, a shock absorber D according to an embodiment of the present invention includes a cylinder 1 and a cylinder 1 that is slidably inserted into the cylinder 1 into an extension side chamber L1 and a pressure side chamber L2. The partitioning piston 2, one end connected to the piston 2 and the other end extending to the outside of the cylinder 1, the tank 10 attached to the outside of the cylinder 1, and the inside of the tank 10 formed for the rod protruding and retracting volume A reservoir T that compensates for changes in the volume in the cylinder, a base member 3 that partitions the reservoir T and the compression side chamber L2, a first main passage R1 that is formed in the piston 2 and communicates with the expansion side chamber L1 and the compression side chamber L2, and a base A second main passage R2 formed in the member 3 for communicating the pressure side chamber L2 and the reservoir T, a pressure chamber L4 formed in the tank 10, and a pressure chamber L4 is movably inserted to extend the pressure chamber L4. Side pressure chamber 40 and the pressure-side pressure chamber L41, the spring element S that generates a biasing force that suppresses the displacement of the free piston 4 with respect to the pressure chamber L4, and the extension side pressure chamber L40 and the reservoir T that communicate with each other. A side passage R3, and a pressure side passage R4 that communicates the pressure side pressure chamber L41 and the pressure side chamber L2.

The shock absorber D is interposed between the vehicle body and the axle of the vehicle and is used to suppress vehicle body vibration. The shock absorber D is interposed between a vehicle body side attachment portion (not shown) connected to the vehicle body side, an axle side attachment portion J connected to the axle side, and the vehicle body side attachment portion and the axle side attachment portion J. A shock absorber body D1.

The shock absorber main body D1 has a cylindrical cylinder 1 arranged vertically, a piston 2 slidably inserted into the cylinder 1, and a lower end in FIG. The rod 6 whose upper end extends outside the cylinder 1, the annular head member 11 that closes the upper opening of the cylinder 1 in FIG. 1 and supports the rod 6 slidably, and the bottom of the cylinder 1 in FIG. 1. A bottomed cylindrical bottom member 12 that closes the side opening, a tank 10 provided outside the cylinder 1, one end connected to the bottom member 12, and the other end connected to the tank 10 to connect the inside of the cylinder 1 and the tank 10. The joint pipe 13 communicating with the inside, the sliding partition wall 14 slidably inserted into the tank 10, and the base member 3 and the housing provided on the joint pipe 13 side of the sliding partition wall 14 in the tank 10. It comprises a ring 5, and the fixed rod 8 connecting the base member 3 and the housing 5, a.

A vehicle body side mounting portion (not shown) is fixed to an upper end portion in FIG. 1 of the rod 6 extending outside the cylinder 1, and an axle side mounting portion J is fixed to the bottom portion of the bottom member 12. For this reason, when vibration is input, the piston 2 moves together with the rod 6 in the cylinder 1 in the axial direction, and the shock absorber D expands and contracts. The shock absorber D is not limited to the upright type, and is an inverted type in which the cylinder 1 is connected to the vehicle body side via the vehicle body side mounting member and the rod 6 is connected to the axle side via the axle side mounting member J. It may be a mold.

In the cylinder 1, an extension side chamber L1 on the rod 6 side defined by the piston 2 and a pressure side chamber L2 on the piston 2 side are formed. The extension side chamber L1 and the compression side chamber L2 are filled with a liquid such as hydraulic oil. In addition, a reservoir T that is separated from the pressure side chamber L2 by the base member 3 is formed in the tank 10. The reservoir T is partitioned by a sliding partition wall 14 into an in-tank working chamber L3 on the joint pipe 13 side and an air chamber G on the opposite side. The in-tank working chamber L3 is filled with the same liquid as the liquid filling the expansion side chamber L1 and the compression side chamber L2, while the gas chamber G is filled with compressed gas.

The piston 2 that partitions the extension side chamber L1 and the compression side chamber L2 is formed in an annular shape, and is held by a nut 7 on the outer periphery of the lower end portion of the rod 6 inserted into the cylinder 1 in FIG. The piston 2 is provided with a first main passage R1 that communicates the extension side chamber L1 and the pressure side chamber L2. The first main passage R1 includes an extension side piston passage 2a and a pressure side piston passage 2b. The lower end of the extension side piston passage 2a in FIG. 1 is an extension consisting of a leaf valve stacked below the piston 2 in FIG. 1 is opened and closed by the side valve V1, and the upper end of the pressure side piston passage 2b in FIG. 1 is opened and closed by a pressure side valve V2 comprising a leaf valve stacked above the piston 2 in FIG. The extension side valve V1 and the pressure side valve V2 are both formed in an annular shape. The lower end in FIG. 1 of the rod 6 is inserted into the inner peripheral side of the extension side valve V1 and the pressure side valve V2. The expansion side valve V1 and the pressure side valve V2 are laminated on the piston 2 in a state where the inner peripheral side is fixed to the rod 6 and the outer peripheral side deflection is allowed.

The expansion side valve V1 stacked on the piston 2 is bent and opened by the differential pressure between the expansion side chamber L1 and the compression side chamber L2 when the shock absorber D is extended, opens the expansion side piston passage 2a, and is compressed from the expansion side chamber L1. Resistance is given to the flow of the liquid moving to the chamber L2. During the contraction operation of the shock absorber D, the expansion side valve V1 closes the expansion side piston passage 2a. Thus, the extension side piston passage 2a is a one-way passage. The pressure side valve V2 stacked on the piston 2 is opposite to the expansion side valve V1, and the flow of the liquid that moves from the pressure side chamber L2 to the expansion side chamber L1 by opening the pressure side piston passage 2b when the shock absorber D is contracted. Give resistance. During the extension operation of the shock absorber D, the pressure side valve V2 closes the pressure side piston passage 2b. Thus, the pressure side piston passage 2b is a one-way passage.

Furthermore, the expansion side valve V1 and the pressure side valve V2 have different pressure flow characteristics (pressure characteristics with respect to the flow rate). Specifically, when the piston speed when the shock absorber D is expanded and contracted is the same, the resistance imparted to the fluid by the expansion side valve V1 is set to be larger than the resistance imparted to the fluid by the compression side valve V2. The side damping force is larger than the compression side damping force. The basic damping force of the shock absorber D is generated by the expansion side valve V1 and the compression side valve V2.

The number of stacked leaf valves and the thickness of the leaf valves constituting the extension side valve V1 and the pressure side valve V2 can be arbitrarily changed according to the required damping characteristics. By adopting a leaf valve that is a thin annular plate as the extension side valve V1 and the pressure side valve V2, the axial length when the extension side valve V1 and the pressure side valve V2 are stacked on the piston 2 is shortened. It becomes easy to ensure the stroke length of the device D. The extension side valve V1 and the pressure side valve V2 may be valves other than the leaf valve.

The base member 3 that partitions the in-tank working chamber L3 of the reservoir T and the compression side chamber L2 in the cylinder 1 is formed in an annular shape. Is retained. Specifically, as shown in FIG. 2, the fixed rod 8 is connected to the shaft main body 8a to which the base member 3 is attached to the outer periphery and the lower end of the shaft main body 8a in FIG. A flange portion 8b that protrudes to the side, and a screw portion 8c that is connected to the upper end portion in FIG. 2 of the shaft main body 8a and has a screw groove formed on the outer periphery. The shaft body 8a is inserted into the inner peripheral side of the base member 3 from the screw portion 8c side, and the hooked nut 9 is screwed onto the outer periphery of the screw portion 8c protruding from the base member 3, so that the hook portion 8b and The base member 3 is sandwiched and fixed between the attached nuts 9. The fixed rod 8 is formed with a pressure side passage R4 penetrating the fixed rod 8 in the axial direction. The pressure side passage R4 communicates a pressure side chamber L41 and a pressure side chamber L2, which will be described later, formed in the housing 5 through the inside of the joint pipe 13 and the bottom member 12. In addition, the pressure side passage R4 shown in FIG. 2 does not show a valve element serving as a resistance. A damping force generating element such as a throttle may be provided in the pressure side passage R4.

The base member 3 is provided with a second main passage R2 that connects the in-tank working chamber L3 and the pressure side chamber L2 through the inside of the joint pipe 13 and the bottom member 12. The second main passage R2 includes an extension-side base passage 3a and a pressure-side base passage 3b. The lower end of the extension-side base passage 3a in FIG. 2 is an extension consisting of a leaf valve stacked below the base member 3 in FIG. 2 is closed by the side valve V3, and the upper end of the pressure side base passage 3b in FIG. 2 is opened and closed by a pressure side valve V4 formed of a leaf valve stacked above the base member 3 in FIG. Both the expansion side valve V3 and the compression side valve V4 are formed in an annular shape. The shaft body 8a of the fixed rod 8 is inserted into the inner peripheral side of the extension side valve V3 and the pressure side valve V4. The expansion side valve V3 and the pressure side valve V4 are stacked on the base member 3 in a state where the inner peripheral side is fixed to the fixed rod 8 and the outer peripheral side is allowed to bend.

The expansion side valve V3 stacked on the base member 3 is bent and opened by the differential pressure between the compression side chamber L2 and the in-tank working chamber L3 when the shock absorber D is extended, and the expansion side base passage 3a is opened to open the inside of the tank. Resistance is given to the flow of the liquid moving from the working chamber L3 to the pressure side chamber L2. During the contraction operation of the shock absorber D, the expansion side valve V3 closes the expansion side base passage 3a. Thus, the extension side base passage 3a is a one-way passage. Also, the pressure side valve V4 stacked on the base member 3 moves from the pressure side chamber L2 to the in-tank working chamber L3 by opening the pressure side base passage 3b when the shock absorber D is contracted, contrary to the expansion side valve V3. Provides resistance to liquid flow. During the extension operation of the shock absorber D, the pressure side valve V4 closes the pressure side base passage 3b. Thus, the pressure side base passage 3b is a one-way passage.

The extension side valve V3 and the pressure side valve V4 laminated on the base member 3 have the same pressure flow characteristics. Specifically, when the piston speed when the shock absorber D is expanded and contracted is the same, the resistance applied to the fluid by the expansion side valve V3 and the resistance applied to the fluid by the compression side valve V4 are set to be the same. Is done. The expansion side valve V3 and the compression side valve V4 generate additional damping force when the shock absorber D is expanded or contracted.

The number of laminated leaf valves and the thickness of the leaf valves constituting the extension side valve V3 and the pressure side valve V4 can be arbitrarily changed according to the required damping characteristics. By adopting a leaf valve that is a thin annular plate as the expansion side valve V3 and the pressure side valve V4, the axial length when the expansion side valve V3 and the pressure side valve V4 are laminated on the base member 3 is shortened. The axial length of the tank 10 can be shortened. The extension side valve V3 and the pressure side valve V4 may be valves other than the leaf valve.

The opening 5a of the cylindrical housing 5 is fixed to the flange portion 9a of the flanged nut 9 screwed to the screw portion 8c of the fixed rod 8 by caulking from the opposite side of the base member 3. A pressure chamber L4 is defined by the housing 5 in the tank working chamber L3. A free piston 4 is slidably inserted in the pressure chamber L4 and a spring element S is provided. The pressure chamber L4 is divided by the free piston 4 into an upper extension pressure chamber L40 in FIG. 2 and a lower pressure side pressure chamber L41 in FIG. The spring element S includes coil springs S1 and S2 disposed above and below the free piston 4 in FIG. The spring element S causes the urging force that suppresses the displacement in proportion to the amount of displacement of the free piston 4 with respect to the pressure chamber L4 to act on the free piston 4.

The housing 5 that divides the pressure chamber L4 on the inside includes an opening 5a that is fixed to the flange portion 9a of the flanged nut 9, a cylindrical large inner diameter portion 5b that extends upward from the opening 5a in FIG. A cylindrical small inner diameter portion 5c having an inner diameter smaller than the inner diameter portion 5b and extending upward from the large inner diameter portion 5b in FIG. 2 and a top portion 5d for closing the upper opening in FIG. 2 of the small inner diameter portion 5c. . Thus, the housing 5 is comprised from one component. The housing 5 is not limited to the above configuration, and may be formed by combining a plurality of components. The housing 5 may be attached to the joint pipe 13 side of the base member 3.

The central portion of the top portion 5 d of the housing 5 protrudes toward the inside of the housing 5. A fixed orifice 5e that communicates between the tank internal working chamber L3 and the expansion side pressure chamber L40 is provided at the central portion. Further, the large inner diameter portion 5 b is provided with a variable orifice 5 f that communicates with the in-tank working chamber L 3 and the expansion side pressure chamber L 40 and is opened and closed by the free piston 4. That is, the expansion side passage R3 that connects the in-tank working chamber L3 and the expansion side pressure chamber L40 of the reservoir T is constituted by the fixed orifice 5e and the variable orifice 5f. Further, as described above, the pressure side passage R4 formed in the fixed rod 8 communicates the pressure side pressure chamber L41 and the pressure side chamber L2 through the inside of the joint pipe 13 and the bottom member 12.

In this way, the in-tank working chamber L3 and the expansion side pressure chamber L40 are communicated by the expansion side passage R3, and the pressure side chamber L2 and the pressure side pressure chamber L41 are communicated by the pressure side passage R4. Here, the volume of the expansion side pressure chamber L40 and the volume of the compression side pressure chamber L41 change as the free piston 4 is displaced in the housing 5. Therefore, in the shock absorber D, the flow path composed of the expansion side passage R3, the expansion side pressure chamber L40, the pressure side pressure chamber L41, and the pressure side passage R4 apparently connects the in-tank working chamber L3 and the pressure side chamber L2. Yes. That is, the in-tank working chamber L3 and the pressure side chamber L2 are communicated not only by the second main passage R2 including the extension side base passage 3a and the pressure side base passage 3b but also by this apparent flow passage.

The free piston 4 that divides the expansion side pressure chamber L40 and the compression side pressure chamber L41 is formed in a top cylinder shape including a top portion 4a and a cylinder portion 4b extending downward from the outer periphery of the top portion 4a in FIG. The The free piston 4 is slidably inserted into the large inner diameter portion 5 b of the housing 5. Since the housing 5 is disposed so that the axis of the large inner diameter portion 5b into which the free piston 4 is inserted and the axis of the cylinder 1 are parallel, the width of the shock absorber D in the left-right direction in FIG. Can be reduced. In addition, in order to avoid that the free piston 4 vibrates in the vertical direction with respect to the housing 5 when the entire shock absorber D vibrates in the vertical direction in FIG. You may arrange | position the housing 5 so that the axial center line of the part 5b may cross | intersect.

In the outer periphery of the free piston 4, an annular groove 4c is formed along the circumferential direction, and a hole 4d penetrating in the axial direction from the top 4a of the free piston 4 to the annular groove 4c is formed. Coil springs S1 and S2 are interposed between the top 4a of the free piston 4 and the top 5d of the housing 5, and between the top 4a of the free piston 4 and the flange 9a of the flanged nut 9. The The free piston 4 is positioned at a predetermined neutral position in the pressure chamber L4 and elastically supported by the spring element S including the coil springs S1 and S2.

The upper end portion of the coil spring S1 in FIG. 2 is inserted into the small inner diameter portion 5c of the housing 5, and the lower end portion of the coil spring S1 in FIG. 2 is formed inside the hole 4d of the top portion 4a of the free piston 4. Inserted into the annular recess 4e. The upper end portion of the coil spring S2 in FIG. 2 is inserted into the cylindrical portion 4b of the free piston 4, and the lower end portion of the coil spring S2 in FIG. 2 is an annular shape formed on the flange portion 9a of the hooked nut 9. It is inserted into the recess 9b. Thus, since the upper end part and lower end part of each coil spring S1, S2 are the inserted states, the remarkable position shift of coil spring S1, S2 can be prevented. For this reason, it becomes possible to make an urging | biasing force act on the free piston 4 stably by each coil spring S1, S2. In addition, it is possible to prevent the sliding resistance from increasing due to shaft displacement or the like of the free piston 4 with respect to the housing 5. The free piston 4 is in sliding contact with the inner peripheral surface of the large inner diameter portion 5b via the cylindrical portion 4b of the upper and lower portions of the annular groove 4c in FIG. The axial displacement of the free piston 4 can also be suppressed by ensuring a sufficient axial length of the sliding portion.

Here, when the free piston 4 is in the neutral position, the annular groove 4c of the free piston 4 and the variable orifice 5f face each other, and the in-tank working chamber L3 and the expansion side pressure chamber L40 include the variable orifice 5f, the annular groove 4c, and It communicates through the hole 4d. However, when the free piston 4 is displaced to the stepped surface 5g formed at the boundary portion between the large inner diameter portion 5b and the small inner diameter portion 5c in the housing 5 or the stroke end contacting the flange portion 9a of the flanged nut 9, the variable orifice 5 f is completely covered by the sliding portion of the free piston 4. As a result, the communication between the in-tank working chamber L3 and the expansion side pressure chamber L40 is blocked.

That is, in the process in which the free piston 4 is gradually displaced from the neutral position and all the openings of the variable orifice 5f are shifted from the state facing the annular groove 4c to the state facing the sliding portion, the flow area of the variable orifice 5f is It gradually decreases as the displacement of the free piston 4 increases. For this reason, according to the amount of displacement from the neutral position of the free piston 4, the resistance when the liquid passes through the extension side passage R3 gradually increases. Before the free piston 4 reaches the stroke end, the variable orifice 5f is completely closed by the opposed sliding portion, and the tank working chamber L3 communicates with the expansion side pressure chamber L40 only by the fixed orifice 5e. At this time, the resistance when the liquid passes through the extension side passage R3 becomes maximum.

Hereinafter, the operation of the shock absorber D will be described.

During the extension operation of the shock absorber D in which the rod 6 is withdrawn from the cylinder 1, the extension side chamber L1 is compressed by the piston 2 and the compression side chamber L2 is expanded, so that the liquid for the rod withdrawal volume is insufficient in the cylinder 1. For this reason, the pressure in the expansion chamber L1 increases and the pressure in the compression chamber L2 decreases, and the differential pressure between the expansion chamber L1 and the compression chamber L2 and between the compression chamber L2 and the in-tank working chamber L3. Occurs. The liquid in the expansion side chamber L1 opens the expansion side valve V1 stacked on the piston 2, passes through the expansion side piston passage 2a, and moves to the compression side chamber L2. Furthermore, the expansion side valve V3 in which the liquid in the tank working chamber L3 is stacked on the base member 3 is opened, passes through the expansion side base passage 3a, and moves to the compression side chamber L2. In addition to this, the liquid in the tank working chamber L3 moves to the pressure side chamber L2 through an apparent flow path including the extension side passage R3, the extension side pressure chamber L40, the pressure side pressure chamber L41, and the pressure side passage R4. At this time, since the liquid of the rod withdrawal volume flows out from the in-tank working chamber L3, the sliding partition wall 14 is pushed downward in FIG. As described above, the expansion of the air chamber G compensates for the change in the cylinder internal volume corresponding to the rod withdrawal volume.

On the other hand, during the contraction operation of the shock absorber D in which the rod 6 enters the cylinder 1, the compression side chamber L <b> 2 is compressed by the piston 2 and the expansion side chamber L <b> 1 expands, and the liquid corresponding to the rod entry volume becomes redundant in the cylinder 1. For this reason, the pressure in the expansion side chamber L1 increases at the same time as the pressure in the compression side chamber L2, and the pressure difference between the expansion side chamber L1 and the compression side chamber L2 and between the compression side chamber L2 and the in-tank working chamber L3. Occurs. The liquid in the pressure side chamber L2 opens the pressure side valve V2 stacked on the piston 2, passes through the pressure side piston passage 2b, and moves to the expansion side chamber L1. Further, the pressure side valve V4 in which the liquid in the pressure side chamber L2 is stacked on the base member 3 is opened, passes through the pressure side base passage 3b, and moves to the in-tank working chamber L3. In addition, the liquid in the pressure side chamber L2 moves to the in-tank working chamber L3 through an apparent flow path including the expansion side passage R3, the expansion side pressure chamber L40, the pressure side pressure chamber L41, and the pressure side passage R4. At this time, since the liquid corresponding to the rod entry volume flows into the in-tank working chamber L3, the sliding partition wall 14 is pushed upward in FIG. 1, and the air chamber G is compressed. In this way, by compressing the air chamber G, a change in the cylinder internal volume corresponding to the rod entry volume is compensated.

At the time of expansion / contraction operation, the shock absorber D has an extension side piston passage 2a and a pressure side piston passage 2b that constitute a first main passage R1, and an extension side base passage 3a and a pressure side base passage 3b that constitute a second main passage R2. Generates damping force due to resistance when passing. That is, the expansion side valves V1 and V3 stacked on the piston 2 and the base member 3 are damping force generating elements that generate the expansion side damping force during the expansion operation of the shock absorber D, and the compression side valves V2 and V4 are buffering. It is a damping force generating element that generates a compression side damping force when the container D is contracted. In addition to the second main passage R2, the pressure side chamber L2 and the in-tank working chamber L3 pass through an apparent flow path including an extension side passage R3, an extension side pressure chamber L40, a pressure side pressure chamber L41, and a pressure side passage R4. The total flow rate of the liquid flowing through the apparent flow path and the second main passage R2 corresponds to the rod retracting volume. For this reason, when the flow rate of the liquid passing through the apparent flow path changes, the flow rate of the liquid passing through the second main passage R2 changes. That is, the damping force of the shock absorber D changes by changing the flow rate of the liquid passing through the apparent flow path.

More specifically, when the piston speed during the expansion / contraction operation of the shock absorber D is the same, the amplitude of the shock absorber D at the time of low frequency vibration input is larger than the amplitude of the shock absorber D at the time of high frequency vibration input. Thus, when the frequency of the vibration input to the shock absorber D is low, the amplitude is large, so that the flow rate of the liquid flowing between the compression side chamber L2 and the tank internal chamber L3 increases in one expansion / contraction cycle. The displacement amount of the free piston 4 increases substantially in proportion to this flow rate. Here, since the free piston 4 is biased by the spring element S, when the displacement amount of the free piston 4 increases, the biasing force from the spring element S received by the free piston 4 also increases. As the biasing force received by the free piston 4 from the spring element S increases, a pressure difference occurs between the pressure in the expansion side pressure chamber L40 and the pressure in the pressure side pressure chamber L41, and the tank internal working chamber L3 and the expansion side pressure chamber L40 The differential pressure and the pressure difference between the pressure side chamber L2 and the pressure side pressure chamber L41 are reduced, and the flow rate passing through the apparent flow path is reduced. The flow rate of the liquid passing through the second main passage R2 is increased by the small flow rate that passes through the apparent flow path, and the pressure in the pressure side chamber L2 is kept low during the expansion operation of the shock absorber D, and during the compression operation. The pressure in the pressure side chamber L2 is kept high. Therefore, the damping force generated by the shock absorber D is maintained in a large state.

On the other hand, when the high frequency vibration is input to the shock absorber D, the amplitude is smaller than that when the low frequency vibration is input. The amount of displacement becomes smaller. When the displacement of the free piston 4 is small, the pressure in the expansion side pressure chamber L40 and the pressure in the pressure side pressure chamber L41 become substantially the same pressure, and the differential pressure between the in-tank working chamber L3 and the expansion side pressure chamber L40 and the pressure side chamber L2 The pressure difference in the pressure side pressure chamber L41 becomes larger than that at the time of low frequency vibration input, and the flow rate of the liquid passing through the apparent flow path increases compared to that at the time of low frequency vibration input. Since the flow rate of the fluid passing through the second main passage R2 is decreased by the increase in the flow rate passing through the apparent flow path, when the buffer D is extended, compared to when the low frequency vibration is input. In, the degree of decrease in pressure in the pressure side chamber L2 becomes small, and the degree of increase in pressure in the pressure side chamber L2 becomes small during the compression operation. For this reason, the damping force generated by the shock absorber D is smaller than the damping force when the low frequency vibration is input.

Here, on the basis of the pressure in the pressure side chamber L2, the differential pressure between the tank working chamber L3 and the pressure side chamber L2 during the expansion operation of the shock absorber D is P, and the flow rate of the liquid flowing out from the tank working chamber L3 is Q. The coefficient which is the relationship between the differential pressure P and the flow rate Q1 of the liquid passing through the second main passage R2 is C1, the differential pressure between the tank working chamber L3 and the expansion side pressure chamber L40 is P1, and the differential pressure P1 and the tank The coefficient which is the relationship with the flow rate Q2 of the liquid flowing from the internal working chamber L3 into the expansion side pressure chamber L40 is C2, the differential pressure between the pressure side chamber L2 and the pressure side pressure chamber L41 is P2, and the differential pressure P2 and the pressure side pressure chamber L41. C3 is a coefficient which is a relationship with the flow rate Q2 of the liquid flowing out from the pressure side chamber L2, and A is a cross-sectional area which is a pressure receiving area of the free piston 4, and X is a displacement of the free piston 4 with respect to the pressure chamber R4. If the spring constant of S is K, Gain characteristic with respect to frequency of the frequency transfer function of the differential pressure P relative to the flow rate Q are characteristics indicated in the conventional example also by the formula (2). As described above, the shock absorber D can generate a large damping force with respect to vibrations in the low frequency range, and can reduce the damping force with respect to vibrations in the high frequency range. The change can be made dependent on the input vibration frequency. Even during the compression operation of the shock absorber D, a large damping force is generated for vibrations in the low frequency range and the damping force is reduced for vibrations in the high frequency range, as in the above-described expansion operation. The change of the damping force of the shock absorber D can be made to depend on the input vibration frequency. Further, the damping characteristics of the shock absorber D are set by appropriately changing the coefficients C1, C2, C3, the spring constant K of the spring element S, and the pressure receiving area A of the free piston 4 as in the conventional shock absorber. The restriction (fixed orifice 5e or variable orifice 5f) provided in the extension side passage R3 or the pressure side passage R4 may not be provided depending on the settings of the coefficients C1, C2, C3, the spring constant K, and the pressure receiving area A of the free piston 4. Also good.

That is, the shock absorber D includes a frequency sensitive portion F1 including the free piston 4, the pressure chamber L4, the extension side passage R3, the pressure side passage R4, and the spring element S, so that the change in damping force depends on the input vibration frequency. Can be made. And the frequency sensitive part F1 is arrange | positioned in the tank 10 attached to the outer side of the cylinder 1. As shown in FIG. For this reason, the basic length (the length from the vehicle body side mounting portion to the axle side mounting portion when in the stroke reference position) M of the shock absorber D including the frequency sensitive portion F1 is shortened, and the stroke length can be secured. At the same time, the mountability on the vehicle can be improved.

Further, the sliding partition wall 14 that divides the in-tank working chamber L3 and the air chamber G has a recess 14a on the in-tank working chamber L3 side. When the shock absorber D is fully extended and the sliding partition wall 14 is displaced downward in FIG. 1, the upper end of the housing 5 in FIG. 1 enters the recess 14a. Thus, the axial direction length of the tank 10 can be shortened by providing the recessed part 14a in the sliding partition 14. FIG.

In the shock absorber D, the pressure flow characteristics of the expansion side valve V1 and the pressure side valve V2 stacked on the piston 2 are changed, and the pressure flow characteristics of the expansion side valve V3 and the pressure side valve V4 stacked on the base member 3 are made the same. The extension side damping force is made larger than the compression side damping force. This improves the ride comfort of the vehicle.

Here, for example, as disclosed in JP2006-336816A and JP2008-215459A, in a shock absorber in which a pressure chamber constituting a frequency sensitive portion is communicated with an extension side chamber and a pressure side chamber, an extension side valve provided on a piston is provided. If the expansion side damping force is made larger than the compression side damping force by changing the pressure flow characteristics of the compression side valve, the damping force reducing effect by the frequency sensitive part may not be sufficiently exhibited. More specifically, when the shock absorber repeatedly expands and contracts at a high frequency, the pressure in the extension side chamber tends to be higher than the pressure in the compression side chamber. For this reason, the pressure in the expansion side pressure chamber through which the pressure in the expansion side chamber propagates is higher than the pressure in the pressure side pressure chamber through which the pressure in the compression side chamber propagates, and the free piston is displaced toward the pressure side pressure chamber side. It becomes a state. When the free piston is biased and displaced in this way, the amount of displacement of the free piston toward the pressure side pressure chamber becomes small. As a result, there is a possibility that the damping force reduction effect by the frequency sensitive part cannot be sufficiently exhibited.

However, in the shock absorber D configured as described above, even if there is a difference between the extension side damping force and the compression side damping force, the pressure flow characteristics of the extension side valve V3 and the compression side valve V4 stacked on the base member 3 are the same. Thus, it is possible to suppress the displacement of the free piston 4 from being biased to one of the expansion side pressure chamber L40 side and the pressure side pressure chamber L41 side. For this reason, even when the extension side damping force is set larger than the compression side damping force and the high frequency vibration is continuously inputted, the displacement amount of the free piston 4 can be secured, and the damping force as described above is obtained. A reduction effect can be exhibited.

Furthermore, in the upright shock absorber D, the rod 6 is connected to the vehicle body side, the cylinder 1 is connected to the axle side, and the frequency sensitive portion F1 is disposed under the spring of the vehicle. For this reason, compared with a shock absorber in which the frequency sensitive part is coupled to the rod, the hitting sound when the free piston 4 reaches the stroke end is less likely to be propagated to the vehicle body side via the rod 6, and the rider makes a hitting sound. It becomes difficult to perceive.

Hereinafter, the function and effect of the shock absorber D according to the above embodiment will be described.

The shock absorber D includes a cylinder 1, a piston 2 that is slidably inserted into the cylinder 1, and divides the cylinder 1 into an extension side chamber L 1 and a compression side chamber L 2, and one end connected to the piston 2 and the other end Rod 6 extending outside the cylinder 1, a tank 10 attached to the outside of the cylinder 1, a reservoir T that is formed in the tank 10 to compensate for a change in the cylinder volume corresponding to the rod protruding and retracting volume, and the reservoir T and the pressure side chamber Formed in the tank 10 is a base member 3 that divides L2, a first main passage R1 that communicates the expansion side chamber L1 and the compression side chamber L2, a second main passage R2 that communicates the compression side chamber L2 and the reservoir T, and The pressure chamber L4, the free piston 4 that is movably inserted into the pressure chamber L4 and divides the pressure chamber L4 into the expansion side pressure chamber L40 and the pressure side pressure chamber L41, and the pressure chamber L4 of the free piston 4 A spring element S that generates an urging force that suppresses displacement, an extension side passage R3 that communicates the extension side pressure chamber L40 and the reservoir T, a pressure side passage R4 that communicates the pressure side pressure chamber L41 and the pressure side chamber L2, Is provided.

According to the above configuration, the frequency sensitive portion F1 including the free piston 4, the pressure chamber L4, the extension side passage R3, the pressure side passage R4, and the spring element S is provided in the tank 10 disposed outside the cylinder 1. . For this reason, even if the stroke length of the shock absorber D is ensured, the basic length M of the shock absorber D can be shortened, and the mountability to the vehicle can be improved.

The second main passage R2 includes an extension side base passage 3a and a pressure side base passage 3b communicating the reservoir T and the pressure side chamber L2, and is opened during the extension operation in the middle of the extension side base passage 3a. An expansion valve V3 that allows the flow of fluid from the reservoir T to the pressure side chamber L2 is provided, and the flow of fluid from the pressure side chamber L2 to the reservoir T is opened in the compression side base passage 3b during compression operation. An allowable pressure side valve V4 is provided. The expansion side valve V3 and the pressure side valve V4 have the same pressure flow characteristics.

According to the above configuration, the resistance given to the liquid flow from the reservoir T to the pressure side chamber L2 through the second main passage R2 is the same as the resistance given to the liquid flow from the pressure side chamber L2 to the reservoir T. be able to. For this reason, the bias | inclination of the free piston 4 can be suppressed and the damping force reduction effect can be exhibited.

Further, the shock absorber D includes a sliding partition wall 14 that is slidably inserted into the tank 10 and partitions the reservoir T into an in-tank working chamber L3 and an air chamber G. A second main passage R2 is connected to the in-tank working chamber L3, and a compressed gas is sealed in the air chamber G.

According to the above configuration, since the tank working chamber L3 is pressurized in the air chamber G through the sliding partition wall 14, the liquid traveling from the tank working chamber L3 to the pressure side chamber L2 through the second main passage R2. Even if resistance is given to the flow by the expansion side valve V3, it is possible to suppress the pressure side chamber L2 from becoming negative pressure when the shock absorber D is extended. For this reason, the pressure flow characteristics of the expansion side valve V3 and the pressure side valve V4 laminated on the base member 3 can be made the same.

A first main passage R1 is formed in the piston 2 of the shock absorber D configured as described above, and an extension side valve V1 and a pressure side valve V2 for opening and closing the first main passage R1 are stacked. Instead of this configuration, the first main passage R1 that communicates the expansion side chamber L1 and the pressure side chamber L2 is provided outside the cylinder 1, and the expansion side valve V1 and the pressure side valve V2 that open and close the first main passage R1 are provided in the cylinder 1. It is good also as a structure provided outside. In this case, the basic length M of the shock absorber D can be further shortened.

The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

This application claims priority based on Japanese Patent Application No. 2014-242800 filed with the Japan Patent Office on December 1, 2014, the entire contents of which are incorporated herein by reference.

Claims

A cylinder,
A piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber;
A rod having one end connected to the piston and the other end extending out of the cylinder;
A tank attached to the outside of the cylinder;
A reservoir that is formed in the tank and compensates for the change in volume in the cylinder corresponding to the volume of the rod in and out;
A base member that partitions the reservoir and the pressure side chamber;
A first main passage communicating the extension side chamber and the pressure side chamber;
A second main passage communicating the pressure side chamber and the reservoir;
A pressure chamber formed in the tank;
A free piston that is movably inserted into the pressure chamber and divides the pressure chamber into an extension side pressure chamber and a pressure side pressure chamber;
A spring element that generates a biasing force that suppresses displacement of the free piston with respect to the pressure chamber;
An extension-side passage communicating the extension-side pressure chamber and the reservoir;
A shock absorber comprising: the pressure side pressure chamber and a pressure side passage communicating the pressure side chamber.
The shock absorber according to claim 1,
The second main passage is composed of an extension side base passage and a pressure side base passage communicating the reservoir and the pressure side chamber,
The extension side base passage is provided with an extension side valve that opens during the extension operation and allows the flow of fluid from the reservoir toward the pressure side chamber,
The pressure side base passage is provided with a pressure side valve that opens during compression operation and allows a fluid flow from the pressure side chamber toward the reservoir,
The extension side valve and the pressure side valve are shock absorbers having the same pressure flow characteristics.
The shock absorber according to claim 1,
A sliding partition that is slidably inserted into the tank and divides the reservoir into a tank working chamber and an air chamber;
The second main passage is connected to the working chamber in the tank,
A shock absorber in which compressed gas is enclosed in the air chamber.