JP2020002980A - Cylinder device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder device capable of suppressing the accumulation of particles in an electrorheological fluid around an application portion to which a voltage is applied. A shock absorber 1 includes an inner cylinder 2 in which an electrorheological fluid 20 whose properties change with an electric field is enclosed, an outer cylinder 3 provided on the outside of the inner cylinder 2, and an inner cylinder 2 and an outer cylinder 3. It is an electrode provided between the two, and has an intermediate cylinder 17 that forms a passage 18 through which the electrorheological fluid 20 flows between the inner cylinder 2 and the inner cylinder 2. The intrinsic resistance value is larger than that of the electrorheological fluid 20 and the dielectric constant is larger than that of the electrorheological fluid 20 on the outer periphery of the contact member 22C and the pin 22D which are arranged from the outer cylinder 3 to the intermediate cylinder 17 and apply the voltage from the battery 21 to the intermediate cylinder 17. Is provided with a covering member 22F made of a material smaller than the electrorheological fluid 20. [Selection diagram] Fig. 2

Description

  The present invention relates to a cylinder device that is suitably used for, for example, buffering vibration of an automobile, a railway vehicle, and the like.

  2. Description of the Related Art Generally, a vehicle such as an automobile is provided with a cylinder device typified by a hydraulic shock absorber between a vehicle body (above the spring) and each wheel (below the spring). As this type of cylinder device, there is known a device in which an electro-rheological fluid is sealed in a cylinder and a generated damping force is variably controlled by applying an electric field by high voltage (for example, see Patent Reference 1).

German Patent Application Publication No. 10201301488

  By the way, in Patent Literature 1, an application portion (high voltage pin) for applying a high voltage in a reservoir chamber of a cylinder device (buffer) is brought into contact with an electrode serving as an intermediate cylinder. In this case, since the electric field is strong around the application portion, particles in the electrorheological fluid may accumulate between the application portion and the outer cylinder (base shell) serving as ground, and a tracking discharge may occur.

  It is an object of the present invention to provide a cylinder device that suppresses particles in an electrorheological fluid from accumulating around a voltage application unit.

  In order to solve the above-described problem, a cylinder device of the present invention defines an inner cylinder in which an electrorheological fluid whose properties change due to an electric field is sealed, and slides the inner cylinder into two chambers. A piston, one end of which protrudes outside the inner cylinder, the other end of which is connected to the piston, an outer cylinder provided outside the inner cylinder, and an electrode provided between the inner cylinder and the outer cylinder An intermediate cylinder that forms a passage through which the electrorheological fluid flows between the inner cylinder and the intermediate cylinder and the outer cylinder, wherein the electrorheological fluid and working gas are sealed. A reservoir guide, a rod guide provided to close one end of the inner cylinder and the outer cylinder, and supporting a rod; and a rod guide arranged from the outer cylinder to the intermediate cylinder, and provided from a voltage supply unit. An application part for applying a voltage to the intermediate cylinder. An apparatus, on the outer circumference of the applying portion, the coating member is provided greater than the resistivity of the electro-rheological fluid, and the dielectric constant is formed by a small material than the electrorheological fluid.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the particle in an electrorheological fluid accumulates between an application part and an outer cylinder which apply a voltage.

It is a longitudinal section showing a shock absorber as a cylinder device by an embodiment. It is principal part sectional drawing which expands and shows the electric field provision body in FIG.

  Hereinafter, an example in which the cylinder device according to the embodiment of the present invention is applied to a shock absorber provided in a vehicle such as a four-wheel vehicle will be described with reference to the accompanying drawings.

  In FIG. 1, a shock absorber 1 as a cylinder device is configured as a damping force-adjustable hydraulic shock absorber (semi-active damper) using an electrorheological fluid 20 enclosed therein. The shock absorber 1 constitutes a suspension device for a vehicle together with a suspension spring (not shown) formed of, for example, a coil spring. In the following description, one end in the axial direction of the shock absorber 1 is referred to as an “upper end” side, and the other end in the axial direction is referred to as a “lower end” side.

  The shock absorber 1 includes an inner cylinder 2, an outer cylinder 3, a piston 5, a piston rod 8, an intermediate cylinder 17, and the like. The inner cylinder 2 is formed as a cylindrical cylinder extending in the axial direction, and contains therein an electrorheological fluid 20 whose properties change according to an electric field. A piston rod 8 described later is inserted into the inner cylinder 2, and an outer cylinder 3 is provided radially outside the inner cylinder 2 so as to be coaxial.

  The outer cylinder 3 forms an outer shell of the shock absorber 1 and is formed as a cylindrical body. The outer cylinder 3 is provided outside the inner cylinder 2, and a lower end thereof is a closed end closed by a bottom cap 4 using welding means or the like. The bottom cap 4 constitutes a base member together with a valve body 13 of a bottom valve 12 described later. An upper end side of the outer cylinder 3 is an open end, and a caulking portion 3A is formed on the open end side so as to be bent radially inward. The caulking portion 3A holds the outer peripheral side of the annular plate body 11A of the seal member 11 in a state where it cannot be removed. Further, the outer cylinder 3 is formed with a mounting hole 3B for mounting an electric field imparting body 22 described later as a horizontal hole (through hole) in the radial direction.

  On the other hand, the inner cylinder 2 is provided in the outer cylinder 3 coaxially with the outer cylinder 3. The lower end of the inner cylinder 2 is fitted and attached to the valve body 13 of the bottom valve 12, and the upper end is fitted and attached to the rod guide 9. The inner cylinder 2 is formed with a plurality of (for example, 4 to 8) oil holes 2A that are always in communication with a passage 18 described later and are spaced apart in the circumferential direction as horizontal holes in the radial direction. The rod-side oil chamber B in the inner cylinder 2 communicates with the passage 18 through an oil hole 2A.

  The inner cylinder 2 constitutes a cylinder together with the outer cylinder 3, and in this cylinder, an electrorheological fluid (ERF) 20 made of a liquid is filled (filled). In each figure, the enclosed electrorheological fluid 20 is colorless and transparent.

  The electrorheological fluid 20 is a kind of a functional fluid whose properties change according to an external stimulus, and is a fluid whose viscosity (properties) changes according to increase / decrease of a voltage (strength and strength of an electric field). That is, the flow resistance (damping force) of the electrorheological fluid 20 changes according to the applied voltage (electric field strength). The electrorheological fluid 20 is composed of, for example, a base oil (base oil) made of silicon oil or the like, and particles (urethane particles) mixed (dispersed) in the base oil to change the viscosity according to a change in an electric field. ing. The shock absorber 1 is configured to control (adjust) the generated damping force by generating a potential difference in a passage 18 described later and variably controlling the viscosity of the electrorheological fluid 20 passing through the passage 18. .

  An annular reservoir chamber A is formed between the inner cylinder 2 (an intermediate cylinder 17 described later) and the outer cylinder 3. In the reservoir chamber A, a gas serving as a working gas together with the liquid electrorheological fluid 20 is sealed. This gas may be air at atmospheric pressure, or a gas such as compressed nitrogen gas may be used. The gas in the reservoir chamber A is compressed when the piston rod 8 is contracted (contraction stroke) to compensate for the volume of the piston rod 8 that has entered.

  The piston 5 is slidably inserted into the inner cylinder 2. The piston 5 defines the inside of the inner cylinder 2 into two chambers, a rod-side oil chamber B and a bottom-side oil chamber C. The piston 5 is formed with a plurality of oil passages 5A and 5B, respectively, which allow the rod-side oil chamber B and the bottom-side oil chamber C to communicate with each other, and are spaced apart in the circumferential direction. Here, the shock absorber 1 according to the embodiment has a uniflow structure. For this reason, the electrorheological fluid 20 in the inner cylinder 2 flows from the rod-side oil chamber B (that is, the oil hole 2A of the inner cylinder 2) to the passage 18 in both the contraction stroke and the extension stroke of the piston rod 8. 1 always flows in one direction (that is, the direction of arrow F indicated by the two-dot chain line in FIG. 1).

  In order to realize such a uniflow structure, the valve is opened at the upper end surface of the piston 5 when the piston 5 is slid downwardly in the inner cylinder 2 during the reduction stroke (shrinkage stroke) of the piston rod 8. In other cases, a contraction-side check valve 6 that closes the valve is provided. The contraction-side check valve 6 allows the liquid (the electrorheological fluid 20) in the bottom-side oil chamber C to flow through the oil passages 5A toward the rod-side oil chamber B, and the liquid in the opposite direction. To stop the flow.

  An extension-side disc valve 7 is provided on the lower end surface of the piston 5. When the piston 5 is slid upward in the inner cylinder 2 during the extension stroke (extension stroke) of the piston rod 8, the pressure in the rod-side oil chamber B exceeds the relief set pressure. , And the pressure at this time is relieved to the bottom side oil chamber C via each oil passage 5B.

  The piston rod 8 as a rod extends in the inner cylinder 2 in the axial direction (in the same direction as the central axis of the inner cylinder 2 and the outer cylinder 3 and in the upward and downward directions in FIG. 1). That is, the piston rod 8 protrudes outside the inner cylinder 2 and the outer cylinder 3 whose upper ends (one end) are cylinders, and the lower end (the other end) is connected (fixed) to the piston 5 inside the inner cylinder 2. ing. In this case, the piston 5 is fixed (fixed) to the lower end side of the piston rod 8 using a nut 8A or the like. On the other hand, the upper end side of the piston rod 8 projects outside via the rod guide 9. In addition, the lower end of the piston rod 8 may be further extended so as to protrude outward from the bottom portion (for example, the bottom cap 4) side.

  A stepped cylindrical rod guide 9 is fitted on the upper end (one end) of the inner cylinder 2 and the outer cylinder 3 so as to close the upper ends of the inner cylinder 2 and the outer cylinder 3. I have. The rod guide 9 supports the piston rod 8, and is formed as a cylindrical body having a predetermined shape by subjecting a metal material, a hard resin material, or the like to molding, cutting, or the like. The rod guide 9 positions the upper part of the inner cylinder 2 and the upper part of the later-described intermediate cylinder 17 at the center of the outer cylinder 3. At the same time, the rod guide 9 guides (guides) the piston rod 8 slidably in the axial direction on the inner peripheral side.

  Here, the rod guide 9 has an annular large-diameter portion 9 </ b> A positioned above and inserted into the inner peripheral side of the outer cylinder 3, and an inner large-diameter portion 9 </ b> It is formed in a stepped cylindrical shape by a short cylindrical small-diameter portion 9B inserted and fitted on the circumferential side. On the inner peripheral side of the small diameter portion 9B of the rod guide 9, a guide portion 9C for guiding the piston rod 8 slidably in the axial direction is provided. The guide portion 9C is formed by, for example, applying an ethylene tetrafluoride coating to the inner peripheral surface of the metal cylinder.

  On the other hand, between the large diameter portion 9A and the small diameter portion 9B on the outer peripheral side of the rod guide 9, an annular holding member 10 is fitted and attached. The holding member 10 holds the upper end side of an intermediate cylinder 17 described later in a state of being positioned in the axial direction. The holding member 10 is formed of, for example, an electrically insulating material, and keeps the inner cylinder 2 and the rod guide 9 and the intermediate cylinder 17 in an electrically insulated state.

  An annular seal member 11 is provided between the large diameter portion 9A of the rod guide 9 and the caulked portion 3A of the outer cylinder 3. The seal member 11 is made of a metallic annular plate 11A having a hole in the center of which the piston rod 8 is inserted, and an elastic material such as rubber fixed to the annular plate 11A by means such as printing. The elastic body 11B is included. The seal member 11 liquid-tightly and air-tightly seals with the piston rod 8 by the inner periphery of the elastic body 11B slidingly contacting the outer periphery of the piston rod 8.

  At the lower end (the other end) of the inner cylinder 2, a bottom valve 12 is provided between the inner cylinder 2 and the bottom cap 4. The bottom valve 12 includes a valve body 13, an extension check valve 15, and a disc valve 16. The valve body 13 defines a reservoir chamber A and a bottom oil chamber C between the bottom cap 4 and the inner cylinder 2. In the valve body 13, oil passages 13A and 13B that allow the reservoir chamber A and the bottom oil chamber C to communicate with each other are formed at intervals in the circumferential direction.

  A step portion 13C is formed on the outer peripheral side of the valve body 13, and the lower end inner peripheral side of the inner cylinder 2 is fitted and fixed to the step portion 13C. Further, an annular holding member 14 is fitted to the outer peripheral side of the inner cylinder 2 and attached to the step portion 13C. The holding member 14 holds the lower end side of the later-described intermediate cylinder 17 in a state of being positioned in the axial direction. The holding member 14 is formed of, for example, an electrically insulating material, and keeps the inner cylinder 2 and the valve body 13 and the intermediate cylinder 17 electrically insulated. Further, the holding member 14 is formed with a plurality of oil passages 14 </ b> A that communicate a passage 18 described below with the reservoir chamber A.

  The extension side check valve 15 is provided, for example, on the upper surface side of the valve body 13. The extension-side check valve 15 opens when the piston 5 slides upward during the extension stroke of the piston rod 8, and closes at other times. The extension side check valve 15 allows the electrorheological fluid 20 in the reservoir chamber A to flow through each oil passage 13A toward the bottom side oil chamber C, and prevents the liquid from flowing in the opposite direction. I do.

  The reduction side disk valve 16 is provided on the lower surface side of the valve body 13. The disc valve 16 on the reduction side opens when the pressure in the bottom side oil chamber C exceeds the relief set pressure when the piston 5 slides downward during the reduction stroke of the piston rod 8, and the pressure at this time is reduced. To the reservoir chamber A side via each oil passage 13B.

  Between the inner cylinder 2 and the outer cylinder 3, there is provided an intermediate cylinder 17 composed of a pressure pipe extending in the axial direction. The intermediate cylinder 17 is formed using a conductive material, and forms a cylindrical electrode to which a high voltage (electric field) is applied from an electric field applying body 22 described later. The intermediate cylinder 17 forms a passage 18 with the inner cylinder 2 through which the electrorheological fluid 20 flows as the piston rod 8 moves forward and backward from the upper end to the lower end in the axial direction.

  That is, the intermediate cylinder 17 is attached to the outer peripheral side of the inner cylinder 2 via the holding members 10 and 14. The holding members 10 and 14 are provided on the outer peripheral side of the inner cylinder 2 so as to be separated in the axial direction (vertical direction). In this case, the upper end side of the intermediate cylinder 17 cannot rotate relative to the outer cylinder 3 via the holding member 10 and the rod guide 9. The lower end of the intermediate cylinder 17 cannot rotate relative to the outer cylinder 3 via the holding member 14, the valve body 13, and the bottom cap 4. The intermediate cylinder 17 surrounds the outer circumference of the inner cylinder 2 over the entire circumference, so that an annular flow path, that is, the electrorheological fluid 20 flows between the inner circumference of the intermediate cylinder 17 and the outer circumference of the inner cylinder 2. A passage 18 is formed. An electrode spring 22C2 of the electric field applying body 22 described later is mounted on the outer diameter side of the intermediate cylinder 17 at a position radially facing the mounting hole 3B of the outer cylinder 3.

  The passage 18 is always in communication with the rod-side oil chamber B through an oil hole 2A formed in the inner cylinder 2 as a radial horizontal hole. In the shock absorber 1, the electrorheological fluid 20 flows into the passage 18 from the rod-side oil chamber B through the oil hole 2A in both the contraction stroke and the extension stroke of the piston 5. The electrorheological fluid 20 that has flowed into the passage 18 causes the axially upper end of the passage 18 to move by the advance and retreat when the piston rod 8 advances and retreats in the inner cylinder 2 (that is, while the contraction stroke and the extension stroke are repeated). It flows from the side toward the lower end. That is, the electrorheological fluid 20 flows in the direction indicated by the arrow F in FIG.

  The electrorheological fluid 20 that has flowed into the passage 18 flows out of the lower end of the intermediate cylinder 17 to the reservoir chamber A via the oil passage 14A of the holding member 14. At this time, the pressure of the electrorheological fluid 20 is highest on the upstream side of the passage 18 (that is, on the side of the oil hole 2A), and gradually decreases due to flow path (passage) resistance while flowing through the passage 18. Therefore, the electrorheological fluid 20 in the passage 18 has the lowest pressure when flowing through the downstream side of the passage 18 (that is, the oil passage 14A of the holding member 14).

  Between the outer periphery of the inner cylinder 2 and the inner periphery of the intermediate cylinder 17, there is provided a partition member 19 that partitions the passage 18 through which the electrorheological fluid 20 flows (guides the flow of the electrorheological fluid 20). The partition member 19 is attached to the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the intermediate cylinder 17 so as not to rotate relatively. The partition member 19 is a flow path forming member that guides the electrorheological fluid 20 between the inner cylinder 2 and the intermediate cylinder 17 not only in the axial direction but also in the circumferential direction. Thus, the passage 18 through which the electrorheological fluid 20 flows can be one or a plurality of spiral or meandering passages (flow passages) having a portion extending in the circumferential direction. In this case, the entire length of the passage 18 (the length of the passage from the oil hole 2A to the oil passage 14A) can be made longer than that of the passage extending linearly in the axial direction.

  The passage 18 provides resistance to the electrorheological fluid 20 flowing through the outer cylinder 3 and the inner cylinder 2 by sliding the piston 5. For this reason, the intermediate cylinder 17 is connected to the positive electrode of a battery 21 serving as a power supply via, for example, a high-voltage driver (not shown) that generates a high voltage and an electric field applying body 22 described later. The battery 21 forms a voltage supply unit (electric field supply unit) together with the high-voltage driver, and the intermediate cylinder 17 serves as an electrode (electrode) for applying an electric field to the electrorheological fluid 20 flowing in the passage 18. Here, both ends of the intermediate cylinder 17 are electrically insulated from the rod guide 9 and the valve body 13 (the bottom cap 4) via the holding members 10 and 14. On the other hand, the inner cylinder 2 is connected to a negative electrode (ground) via a rod guide 9, a bottom valve 12 (valve body 13), a bottom cap 4, an outer cylinder 3, a high-voltage driver, and the like.

  The high-voltage driver boosts the DC voltage output from the battery 21 based on a command signal (high-voltage command) output from a controller (not shown) for variably adjusting the damping force of the shock absorber 1. Then, it is supplied (output) to the intermediate cylinder 17. As a result, a potential difference corresponding to the high voltage applied to the intermediate cylinder 17 is generated between the inner cylinder 2 and the intermediate cylinder 17, in other words, in the passage 18, and the viscosity of the electrorheological fluid 20 changes. . In this case, the shock absorber 1 changes the characteristic of the generated damping force (damping force characteristic) in accordance with the high voltage applied to the intermediate cylinder 17 into a hard characteristic (hard characteristic) and a soft characteristic (soft characteristic). (Soft characteristics). Note that the damper 1 may be capable of adjusting the damping force characteristics in two or more stages without being continuous. In the present embodiment, the voltage boosted by the high-voltage driver is a DC voltage, but may be an AC voltage.

  The electric field applying body 22 is arranged from the outer cylinder 3 to the intermediate cylinder 17, and applies a voltage from the battery 21 to the intermediate cylinder 17. As shown in FIG. 2, the electric field applying body 22 includes a casing 22A, a lock nut 22B, a contact member 22C, a pin 22D, a spacer 22E, and a covering member 22F.

  The casing 22A is formed, for example, of a conductive metal material into a cylindrical shape, and is fixed to the outer peripheral side of the outer cylinder 3 at a position corresponding to the mounting hole 3B of the outer cylinder 3. The casing 22A is attached by welding over the entire circumference in a state where the distal end side is in contact with the outer peripheral side of the attachment hole 3B of the outer cylinder 3. On the other hand, a male screw portion 22A1 is formed on the outer periphery on the base end side of the casing 22A.

  The lock nut 22B is formed in a cylindrical shape with a bottom from a conductive metal material, and is attached to the base end side of the casing 22A. A female screw portion 22B1 that is screwed to the male screw portion 22A1 of the casing 22A is formed on the inner periphery on the distal end side of the lock nut 22B. The lock nut 22B holds the pin 22D, the spacer 22E, and the covering member 22F in the casing 22A by sealing the base end side opening of the casing 22A.

  The contact member 22C is attached to the outer peripheral side of the intermediate cylinder 17 at a position corresponding to the attachment hole 3B of the outer cylinder 3. The contact member 22C includes a band 22C1 attached to the outer peripheral side of the intermediate cylinder 17, and an electrode spring 22C2 attached to the band 22C1 and extending toward the pin 22D. The band 22 </ b> C <b> 1 and the electrode spring 22 </ b> C <b> 2 are formed of a conductive metal material, and serve as an application unit that applies a voltage from the high-voltage driver and the battery 21 to the intermediate cylinder 17.

  The pin 22D is formed in a stepped columnar shape from a conductive metal material, and is disposed on the tip side in the casing 22A. A seal member 23 is provided on the outer peripheral side of the pin 22D to prevent the electrorheological fluid 20 from flowing out to the outside between the cover member 22F. The connector 22D1 connected to the positive electrode side of the battery 21 via the high voltage driver is formed on the base end side of the pin 22D, and the electrode spring 22C2 of the contact member 22C is in elastic contact with the distal end side. Thereby, the voltage from the battery 21 is applied to the intermediate cylinder 17 from the pin 22D via the contact member 22C. The pin 22D, together with the contact member 22C, serves as an application section that applies the voltage from the high-voltage driver and the battery 21 to the intermediate cylinder 17.

  The spacer 22E is formed of a cylindrical body having an insulating property, and is disposed between the pin 22D and the lock nut 22B. The spacer 22E electrically insulates between the pin 22D and the lock nut 22B. When the lock nut 22B is screwed into the casing 22A, the spacer 22E presses the pin 22D toward the distal end of the casing 22A to dispose the pin 22D on the distal end of the casing 22A.

  Next, a description will be given of the covering member 22F for relaxing the electric field around the contact member 22C and the pin 22D.

  The covering member 22F is formed as a stepped cylindrical cover having an insulating property, and is provided in the casing 22A. The covering member 22F is provided between the casing 22A, the pin 22D, and the spacer 22E. That is, the pins 22D and the spacers 22E are arranged side by side in the covering member 22F. The covering member 22F electrically insulates between the casing 22A and the pin 22D. The covering member 22F includes a large-diameter portion 22F1 located in the casing 22A, a small-diameter portion 22F2 protruding from the tip of the large-diameter portion 22F1 toward the outside of the casing 22A, and a radial direction from the casing 22A side of the small-diameter portion 22F2. It comprises a step 22F3 projecting outward toward the inner peripheral surface of the casing 22A and connecting the large diameter portion 22F1 and the small diameter portion 22F2.

  The large-diameter portion 22F1 of the covering member 22F is provided inside the casing 22A, and a seal member 24 is provided on the outer peripheral side to prevent the electrorheological fluid 20 from flowing out of the casing 22A. On the other hand, the small-diameter portion 22F2 of the covering member 22F protrudes from the casing 22A and is inserted into the mounting hole 3B of the outer cylinder 3. That is, the small-diameter portion 22F2 projects from the mounting hole 3B of the outer cylinder 3 toward the intermediate cylinder 17, so that the distal end side is located in the reservoir chamber A. Thus, the small diameter portion 22F2 is configured to be located between the outer cylinder 3 and the pin 22D and between the outer cylinder 3 and the contact member 22C.

The coating member 22F is formed of a material having a specific resistance greater than that of the electrorheological fluid 20 and a dielectric constant smaller than that of the electrorheological fluid 20. Specifically, the covering member 22F is formed of, for example, a thermoplastic resin such as polyacetal having high abrasion resistance and high electrical insulation. As an example, the covering member 22F has a withstand voltage of, for example, a voltage (for example, 5 kV) or more applied to the intermediate cylinder 17, and has a relative dielectric constant / thickness of 2 [mm ^-1 ] or less. And the like.

  The small-diameter portion 22F2 of the covering member 22F is located between the contact member 22C and the outer cylinder 3 and between the pin 22D and the outer cylinder 3. Thereby, the electric field between the contact member 22C and the pin 22D and the outer cylinder 3 can be reduced, so that the particles in the electrorheological fluid 20 are prevented from being deposited around the contact member 22C and the pin 22D. Can be. As a result, occurrence of tracking discharge between the contact member 22C and the pin 22D and the outer cylinder 3 can be suppressed.

  In addition, by covering the intermediate cylinder 17 around the band 22C1 of the contact member 22C with a covering member having a specific resistance value higher than that of the electrorheological fluid 20 and a dielectric constant smaller than that of the electrorheological fluid 20, Accumulation of particles in the electrorheological fluid 20 around it can be further suppressed.

  The shock absorber 1 according to the present embodiment has the above-described configuration, and its operation will be described next.

  When mounting the shock absorber 1 on a vehicle such as an automobile, for example, the upper end side of the piston rod 8 is attached to the vehicle body side, and the lower end side (bottom cap 4 side) of the outer cylinder 3 is attached to the wheel side (axle side). . When the vehicle travels, when upward and downward vibrations are generated due to unevenness of the road surface or the like, the piston rod 8 is displaced so as to extend and contract from the outer cylinder 3. At this time, a potential difference is generated between the inner cylinder 2 and the intermediate cylinder 17 based on the damping force command from the controller, and an electric field is applied to the passage 18 so that the viscosity of the electrorheological fluid 20 passing through the passage 18 is increased. , The generated damping force of the shock absorber 1 is variably adjusted.

  In this case, during the extension stroke of the piston rod 8, the movement of the piston 5 in the inner cylinder 2 closes the contraction-side check valve 6 of the piston 5. Before the disc valve 7 of the piston 5 is opened, the electrorheological fluid 20 in the rod-side oil chamber B is pressurized and flows into the passage 18 through the oil hole 2A of the inner cylinder 2. At this time, the electrorheological fluid 20 corresponding to the movement of the piston 5 flows from the reservoir chamber A into the bottom oil chamber C by opening the extension check valve 15 of the bottom valve 12.

  On the other hand, during the compression stroke of the piston rod 8, the movement of the piston 5 in the inner cylinder 2 opens the compression-side check valve 6 of the piston 5 and closes the extension-side check valve 15 of the bottom valve 12. Before the bottom valve 12 (disk valve 16) is opened, the liquid in the bottom oil chamber C flows into the rod oil chamber B. At the same time, the liquid corresponding to the amount of the piston rod 8 entering the inner cylinder 2 flows from the rod-side oil chamber B into the passage 18 through the oil hole 2A of the inner cylinder 2.

  In any case (in both the extension stroke and the contraction stroke), the electrorheological fluid 20 that has flowed into the passage 18 has a viscosity corresponding to the electric field strength of the passage 18 (the potential difference between the inner cylinder 2 and the intermediate cylinder 17). The fluid flows through the inside 18 toward the outlet side (lower side), and flows from the passage 18 to the reservoir chamber A via the oil passage 14A of the holding member 14. At this time, the damper 1 generates a damping force according to the viscosity of the electrorheological fluid 20 passing through the passage 18 and can buffer (attenuate) the vertical vibration of the vehicle.

  By the way, in the above-described conventional technology, the particles in the electrorheological fluid 20 accumulate on the application portion because the electric field is strong around the application portion (high-voltage pin) for applying a voltage to the intermediate cylinder (electrode). There is a possibility that tracking discharge may occur due to particles accumulated between the portion and the outer cylinder. Further, when particles accumulate around the application section, the concentration of the particles in the electrorheological fluid 20 varies, so that the damping characteristics of the shock absorber 1 may become unstable.

  Therefore, in the present embodiment, the covering member 22F is provided on the outer periphery of the contact member 22C and the pin 22D, which are application portions for applying a voltage to the intermediate cylinder 17. That is, as shown in FIG. 2, the small diameter portion 22F2 of the covering member 22F protrudes into the reservoir chamber A from the mounting hole 3B of the outer cylinder 3. Thereby, the small diameter portion 22F2 of the covering member 22F is provided between the contact member 22C (electrode spring 22C2) and the outer cylinder 3 and between the pin 22D and the outer cylinder 3.

  The covering member 22F is formed of a material having a specific resistance greater than that of the electrorheological fluid 20 and a dielectric constant smaller than that of the electrorheological fluid 20. Accordingly, the electric field between the contact member 22C and the pin 22D and the outer cylinder 3 can be reduced, so that the particles in the electrorheological fluid 20 can be interposed between the contact member 22C and the pin 22D and the outer cylinder 3 serving as the ground. Can be suppressed from being deposited. As a result, it is possible to suppress the occurrence of tracking discharge due to particles between the outer cylinder 3 and the contact member 22C and the pin 22D. Further, since the uneven distribution of particles in the electrorheological fluid 20 can be reduced, the damping force characteristics of the shock absorber 1 can be stabilized.

  In the above-described embodiment, the covering member 22F eliminates the gap between the large-diameter portion 22F1, the small-diameter portion 22F2, and the step portion 22F3, and prevents tracking discharge from the gap and the intrusion of foreign matter (dust and the like) during assembly. In order to suppress the possibility, the large-diameter portion 22F1, the small-diameter portion 22F2, and the step portion 22F3 were integrally formed. Therefore, the case where the cover member covers the outer peripheral side of the contact member 22C and the pin 22D has been described as an example. However, the present invention is not limited to this. For example, the covering member may be formed of a heat-shrinkable tube made of polypropylene that covers the contact member 22C and the pin 22D. Further, the coating member may apply a paint such as an epoxy resin to the contact member 22C and the pin 22D. In this case, the covering member 22F can be formed in a small space, or the number of assembled parts can be reduced.

  In the above-described embodiment, the case where the contact member 22C is attached to the intermediate cylinder 17 by the band 22C1 has been described as an example. However, the present invention is not limited to this. For example, the contact member 22C (electrode spring 22C2) may be attached to the pin 22D to elastically contact the intermediate cylinder 17.

  Further, in the above-described embodiment, the case where the shock absorber 1 as the cylinder device is used for a four-wheel vehicle has been described as an example. However, the present invention is not limited to this. For example, shock absorbers used for motorcycles, shock absorbers used for railway vehicles, shock absorbers used for various mechanical devices including general industrial equipment, shock absorbers used for buildings, etc. It can be widely used as various types of shock absorbers (cylinder devices) for damping objects to be processed.

  As the cylinder device based on the embodiment described above, for example, the following configuration can be considered.

  As a first aspect of the cylinder device, an inner cylinder in which an electrorheological fluid whose fluid property is changed by an electric field is sealed, a piston which defines two chambers in the inner cylinder and slides, A rod protruding outside the inner cylinder, the other end of which is connected to the piston, an outer cylinder provided outside the inner cylinder, and an electrode provided between the inner cylinder and the outer cylinder; An intermediate cylinder that forms a passage through which the viscous fluid flows between the inner cylinder, a reservoir chamber that is formed between the intermediate cylinder and the outer cylinder, and that contains the electrorheological fluid and working gas; A rod guide that is provided to close one end of the inner cylinder and the outer cylinder, supports the rod, and is disposed from the outer cylinder to the intermediate cylinder, and applies a voltage from a voltage supply unit to the intermediate cylinder. And a applying unit for applying, wherein the cylinder device has The outer periphery of the given section, the covering member is provided greater than the resistivity of the electro-rheological fluid, and the dielectric constant is formed by a small material than the electrorheological fluid. Thereby, the damping force characteristics can be stabilized.

  As a second aspect, in the first aspect, the application section is configured by a pin connected to the voltage supply section, and a contact member attached to the intermediate cylinder and elastically contacting the pin. The covering member is provided between the pin and the contact member and the outer cylinder. Thereby, the accumulation of particles in the electrorheological fluid 20 around the electric field applying body 22 can be further suppressed.

  As a third aspect, in the second aspect, the covering member comprises a cover member projecting from the outer cylinder into the reservoir chamber and covering the outer periphery of the pin and the contact member. Thereby, the covering member can be formed in a small space, or the number of assembled parts can be reduced.

1 shock absorber (cylinder device)
2 inner cylinder 3 outer cylinder 5 piston 8 piston rod (rod)
9 Rod guide 17 Intermediate cylinder 18 Passage 20 Electrorheological fluid 21 Battery (voltage supply unit)
22 electric field applying body 22C contact member (applying part)
22D pin (application part)
22F Covering member A Reservoir chamber B Rod side oil chamber C Bottom side oil chamber

Claims (3)

An inner cylinder in which an electrorheological fluid whose properties change due to an electric field is sealed,
A piston that defines and slides in the inner cylinder into two chambers,
A rod having one end protruding outside the inner cylinder and the other end being connected to the piston;
An outer cylinder provided outside the inner cylinder,
An electrode provided between the inner cylinder and the outer cylinder, an intermediate cylinder that forms a passage through which the electrorheological fluid flows between the inner cylinder,
A reservoir chamber formed between the intermediate cylinder and the outer cylinder and in which the electrorheological fluid and working gas are sealed;
A rod guide provided to close one end of the inner cylinder and the outer cylinder, and supporting the rod,
An application unit disposed from the outer cylinder to the intermediate cylinder, and an application unit that applies a voltage from a voltage supply unit to the intermediate cylinder,
A cylinder device is provided on the outer periphery of the applying portion, the covering member being formed of a material having a specific resistance greater than that of the electrorheological fluid and a dielectric constant smaller than that of the electrorheological fluid. . The applying section is configured by a pin connected to the voltage supply section, and a contact member attached to the intermediate cylinder and elastically contacting the pin.
The cylinder device according to claim 1, wherein the covering member is provided between the pin and the contact member and the outer cylinder.   The cylinder device according to claim 2, wherein the covering member comprises a cover member protruding from the outer cylinder into the reservoir chamber and covering an outer periphery of the pin and the contact member.

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