JP2006220265A - Magnetorheological fluids device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contribute to improvement of durability of a magnetorheological fluids device by reducing an amount of ferromagnetic particles reaching a sealing material 20 without biasing distribution of the ferromagnetic particles in magnetorheological fluids, improving classification accuracy of the ferromagnetic particles, and carrying out a special machining process to a surface of a second member 31, and extending a sealing service life without causing extensive cost increase, and impairing magnetorheological characteristics and lubricity to the second member in the magnetorheological fluids device sealing a gap between through holes 12a and 15a of a first member 10, and the second member 31 to prevent leaking of the magnetorheological fluids. <P>SOLUTION: One or more engagement member 40 having a sliding contact face 40a slidably contacting a surface of the second member 31 in an inner space side of the sealing material 20 in the through holes 12a and 12b is provided for holding magnetic particles in the sliding contact face 40a with respect to the ferromagnetic particles in the magnetorheological fluids on the surface of the second member 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magneto-rheological fluid device such as a damping device using a magneto-rheological fluid (MRF) whose shear stress changes according to an applied magnetic field, and more particularly to an improvement in a sealing structure in a gap between relatively moving members. .

  In general, a magnetorheological fluid is obtained by uniformly dispersing carbonyl iron powder (particle diameter of about 5 μm) as a ferromagnetic particle in a hydraulic fluid such as silicone as a dispersion medium at a ratio of several tens volume%. There is a damper as an apparatus using this.

This type of damper has, for example, a cylinder tube and an electromagnet, a piston provided in the cylinder tube so as to be relatively movable in the axial direction, and the piston so as to move integrally with the piston. and linked piston rod, the piston rod have a through hole penetrating relatively movable, and a cover enclosing the opening of the cylinder tube. Then, by supplying an electric current to the electromagnet, a magnetic circuit is formed across the annular orifice that connects the two fluid chambers in the cylinder body defined by the piston to each other, and the apparent viscosity of the magnetorheological fluid at the orifice ( By changing the yield shear stress, the relative movement of the piston with respect to the cylinder body is damped, and it is beginning to be applied to a semi-active suspension for automobiles and the like.

  By the way, in general, in a damper using a magnetorheological fluid, a sealing material such as a U-packing having a lip portion is interposed between the through hole of the cylinder body and the piston rod. There is a concern that wear is promoted by iron powder in the magnetorheological fluid. In other words, iron powder enters the minute recesses on the piston rod surface, and the lip of the sealing material is attacked by iron powder every time the piston rod expands and contracts, resulting in a shock that the piston moves relatively frequently. In applications such as an absorber, since the sealing material is easily worn, it is expected that the magnetorheological fluid leaks early. Therefore, from the viewpoint of contamination in the hydraulic fluid, the magnetorheological fluid different from the hydraulic fluid used in a general hydraulic damper is sealed by the same sealing structure as that of the hydraulic damper. Obviously, the seal life is shortened.

In contrast, Patent Document 1 describes that the relationship between the surface roughness Rz (0.3 to 0.5 μm) of the piston rod and the nominal particle size (1 to 6 μm) of the iron powder is specified. Yes. This is a technique for reducing the aggressiveness to the sealing material by reducing the size of the concave portion on the surface of the piston rod as much as possible so that iron powder does not enter the concave portion.
JP 2000-514161 A (4th page)

  However, in the above conventional case, in order to obtain the expected effect, it is necessary to classify the particle size of the iron powder with extremely high accuracy and to reduce the particle size distribution width. The cost increases, and the surface processing cost of the piston rod also increases.

  Moreover, it is not preferable to reduce the concave portion on the surface of the piston rod in terms of maintaining lubricity.

  Incidentally, in an apparatus using a so-called magnetic fluid (MF), as described in, for example, Japanese Patent Application Laid-Open No. 2003-278821, a sealing material is obtained by attracting iron powder in the magnetic fluid in the vicinity of the sealing material with a permanent magnet or an electromagnet. Technology is known to reduce the aggressiveness of the iron powder to the sealing material by reducing the amount of iron powder reaching the point, but according to this, the distribution of iron powder in the fluid is biased Therefore, in the case of a magnetorheological fluid whose viscosity is changed by forming a cluster in the orifice, the magnetorheological property may be adversely affected, and therefore cannot be adopted.

  The present invention has been made in view of such various points, and its main purpose is to seal a gap between a through hole of a first member such as a cylinder body and a second member such as a piston rod with a sealing material. In the magnetorheological fluid device in which the magnetorheological fluid is prevented from leaking out, the distribution of the ferromagnetic particles in the magnetorheological fluid is not biased, and the classification accuracy of the ferromagnetic particles is increased, or the second member It is possible to reduce the amount of ferromagnetic particles reaching the sealing material without performing special processing on the surface of the material, thereby not only causing a significant increase in cost but also the magnetic viscosity characteristics and the second member. An object of the present invention is to extend the seal life and contribute to the improvement of the durability of the magnetorheological fluid device without impairing the lubricity.

  In order to achieve the above object, the present invention does not collect particles in the fluid in the vicinity of the sealing material as in the case of the magnetic fluid device, but instead of collecting the liquid that moves to the sealing material with the relative movement of the second member. On the other hand, the particles are held so as not to move by being engaged with the particles in the liquid, thereby biasing the distribution of the particles in the fluid, The amount of particles reaching the sealing material can be reduced without special processing on the surface.

  Specifically, in the present invention, the first member having an internal space and having a through hole that communicates the internal space with the external space, and the first member are disposed so as to pass through the through hole, A second member that can move relative to the first member in the penetration direction and a through-hole of the first member that seals the internal space of the first member while allowing relative movement of the second member It is premised on a magnetorheological fluid device comprising a sealing material for sealing, and a magnetorheological fluid that is filled in the internal space of the first member and contains ferromagnetic particles (hereinafter referred to as iron powder).

  And it has a sliding contact surface which contacts the surface of the said 2nd member in the internal space side of the sealing material in said through-hole, and with respect to the iron powder in the magnetorheological fluid on the surface of this 2nd member One or more engaging members are provided to engage the iron powder so as to be held in the sliding contact surface.

  In the above configuration, the engaging member is a fiber assembly provided so as to keep the fiber in a predetermined shape by an elastic material and to expose a part of the fiber on the sliding contact surface. It is possible to keep the iron powder in the sliding contact surface by entanglement of the fibers with the iron powder. In this case, the dimension of the sliding contact surface of the fiber assembly in the relative movement direction of the second member is preferably 0.5 mm or more. Further, the fiber assembly has a ring shape having an insertion hole formed so that the second member is inserted and the inner wall surface forms the sliding contact surface, and the inner wall surface is formed on the surface of the second member. In the case of being provided so as to be in pressure contact, it is preferable that the spread allowance of the fiber assembly in the direction orthogonal to the relative movement direction of the second member is 0.1 to 1.0 mm. Furthermore, a plurality of fiber assemblies can be provided, and the plurality of fiber assemblies can be arranged in the relative movement direction of the second member.

  In the above configuration, the engaging member is a resin body made of a flexible resin material (for example, PTFE) and provided so that the sliding contact surface is in pressure contact with the surface of the second member. The iron powder can also be held in the sliding contact surface by burying the iron powder in the sliding contact surface. In this case, if the resin body has a ring shape with an insertion hole formed so that the second member is inserted and the inner wall surface forms the sliding contact surface, the outer periphery of the resin body In addition, a fastening member (for example, an O-ring) for fastening the resin body in a direction in which the sliding contact surface is pressed against the surface of the 21st member may be fitted. Further, a plurality of resin bodies may be provided, and the plurality of resin bodies may be arranged so as to be aligned in the relative movement direction of the second member.

  Furthermore, it is also possible to use one or more of the fiber assemblies and one or more of the resin bodies together and arrange them in the relative movement direction of the second member. In this case, it is preferable to arrange one of the one or more fiber aggregates at a position farthest from the sealing material.

  In addition, when the above magnetorheological fluid device is applied to a damping device, a piston that divides the internal space into two fluid chambers divided in the relative movement direction of the second member is disposed in the internal space of the first member. The piston is provided so as to be movable relative to the first member in the relative movement direction, and a communication passage is provided for communicating the two fluid chambers with each other, and the magnetorheological fluid is provided in the two fluid chambers and the communication passage. Further, it is sufficient to provide a magnetic field applying means for applying a magnetic field to the magnetorheological fluid in the communication path. In this case, the second member is a piston rod that is integrally connected to the piston.

  According to the present invention, in the magnetorheological fluid device in which the gap between the through hole of the first member and the second member is sealed with the sealing material so that the magnetorheological fluid does not leak, the relative movement of the second member is performed. Accordingly, the ferromagnetic particles in the magnetorheological fluid that moves to the sealing material can be held in the sliding surface of the engaging member, so that the distribution of the ferromagnetic particles in the magnetorheological fluid is biased. Without increasing the accuracy of classification of the ferromagnetic particles, or without performing special processing on the surface of the second member, the amount of ferromagnetic particles reaching the sealing material can be reduced, Not only does it cause a significant increase in cost, but it also contributes to improving the durability of the magnetorheological fluid device by extending the seal life without compromising both the magnetorheological properties and the lubricity of the second member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 schematically shows the overall configuration of the MRF damper according to the embodiment of the present invention, and this MRF damper is for damping the linear motion of another member connected in series or in parallel to the MRF damper, for example. Used for.

  The present MRF damper includes a cylinder body 10 as a first member having an internal space. The cylinder body 10 is an iron cylinder tube having a bottomed cylindrical shape with one end side in the axial direction (left end side in FIG. 2) closed and the other end side in the axial direction (right end side in the figure) opened. 11.

  On the outer surface of the bottom of the cylinder tube 11, a mounting piece 11a for mounting the MRF damper is provided. On the other hand, a cover 12 is fitted into the opening of the cylinder tube 11. A through hole 12 a having a circular cross section that penetrates the cover 12 in the axial direction is formed in the axial center portion of the cover 12. Further, on the cylinder tube 11 side (the left side in FIG. 2) of the cover 12, an insertion wall 12 b that fits into the opening of the cylinder tube 11 is formed in an annular shape along the peripheral edge. A circumferential groove 12c is provided on the outer periphery of the fitting wall 12b, and an O-ring 13 that elastically contacts the inner circumferential surface of the cylinder tube 11 is fitted in the circumferential groove 12c. A presser ring 14 having an L-shaped cross section is fitted on the outer periphery of the opening end of the cylinder tube 11. The presser ring 14 presses and fixes the peripheral portion of the cover 12 to the cylinder tube 11 side. On the other hand, on the side opposite to the cylinder tube 11 of the cover 12 (the right side in the figure), a convex portion 12d that protrudes toward the opposite side is formed. On the opposite side of the cover 12 from the cylinder tube 11, a cap 15 fitted to the convex portion 12 d of the cover 12 is disposed. A through-hole 15 a having a circular cross section that passes through the cap 15 in the axial direction is formed in the axial center portion of the cap 15. Further, the through hole 12a of the cover 12 and the through hole 15a of the cap 15 cooperate with each other to form a through hole in the present invention. A portion on the outer space side in the through hole 15a of the cap 15 has a larger diameter than a portion on the inner space side, and a substantially cylindrical rod guide 16 is disposed in the enlarged diameter portion. Further, the opening edge of the cap 15 on the cover 12 side is cut out in a substantially rectangular shape, and the cutout portion and the cover 12 form a concave portion 17 having a concave cross section that is opened inward in the radial direction. Yes. A U-shaped packing 20 (hereinafter referred to as “U packing”) having a lip portion 20 a on the inner peripheral side is mounted in the recess 17.

  A piston 30 having a substantially cylindrical shape is disposed in the cylinder body 10. The piston 30 is provided in the cylinder body 10 so as to be movable in the axial direction. In addition, two spaces divided in the axial direction are defined in the cylinder body 10 by the piston 30. A piston rod 31 as a second member extending in the axial direction is connected to the other end side in the axial direction of the piston 30 (on the right side in FIG. 2) in an integral manner. The piston rod 31 passes through the through hole 12a of the cover 12 and the through hole 15a of the cap 15 in the axial direction, and the lip portion 20a of the U-packing 20 and the rod guide 16 are formed on the surface of the piston rod 31. Are in sliding contact with each other. Furthermore, the other axial end portion of the piston rod 31 is located in the external space, and an attachment piece 31a for attaching the MRF damper is provided at the other axial end portion.

  Further, in the cylinder main body 10, of the two spaces partitioned by the piston 30, the space opposite to the piston rod 31 (the left side in FIG. 2) is partitioned into two spaces divided in the axial direction. A free piston 32 is arranged. The free piston 32 is provided so as to be movable in the axial direction within the cylinder body 10. Of the two spaces defined by the free piston 32, the space opposite to the piston rod 31 is an accumulator chamber Ac, and this accumulator chamber Ac is filled with, for example, high-pressure nitrogen gas. On the other hand, the space on the piston rod 31 side (the right side in the figure), that is, the space formed between the free piston 32 and the piston 30 is defined as a first fluid chamber C1. Of the two spaces partitioned by the piston 30, the space on the piston rod 31 side is a second fluid chamber C2.

  An annular gap is formed between the side circumferential surface of the piston 30 and the inner circumferential surface of the cylinder tube 11, and this gap allows the first fluid chamber C1 and the second fluid chamber C2 to mutually communicate. The communication path 34 communicates. The first fluid chamber C1, the second fluid chamber C2, and the communication path 34 are filled with a magnetorheological fluid containing ferromagnetic particles (hereinafter referred to as iron powder). As a result, as the piston 30 moves relative to the cylinder body 10, the magnetorheological fluid in the fluid chamber C1 (or C2) that changes in the direction in which the volume decreases becomes the fluid chamber in the side in which the volume increases in the direction that increases in volume. It moves to C2 (or C1) via the communication path 34.

  Furthermore, the piston 30 is made of iron. A concave groove 30a having a substantially concave shape in cross section is provided around the side periphery of the piston 30, and a coil portion 35a formed by winding a conductive wire around the axis is embedded in the concave groove 30a. Has been. The lead wire of the coil portion 35 a extends through the piston 30 and the piston rod 31 to the outside of the cylinder body 10. Since the coil part 35a is disposed in the concave groove 30a of the piston 30, an electromagnet 35 having the piston 30 as an iron core is formed and connected to a power supply part (not shown). When a current is supplied to the electromagnet 35 by the power supply unit, the electromagnet 35 generates a magnetic force, and by this magnetic force, each fluid chamber C1 in the axial center portion of the piston 30, the cylinder tube 11, and the communication passage 34 is generated. , The magnetic circuit M passing through the end on the C2 side is formed.

  In this embodiment, as shown in FIG. 1 (a), the surface of the piston rod 31 is slidably brought into contact with the inner space side (the left side in the figure) of the U packing 20 in the through holes 12a and 15a. And a fiber assembly 40 as an engaging member that engages so as to hold the iron powder in the magnetorheological fluid interposed in the gap between the piston rod 31 and the piston rod 31.

  Specifically, the fiber assembly 40 is a fiber in which a fiber is hardened in a disc shape with rubber as an elastic material. As shown schematically in FIGS. A circular insertion hole through which the piston rod 31 is inserted is formed. The inner wall surface of the insertion hole is a slidable contact surface 40a that is slidably contacted with the surface of the piston rod 31, and a part of the fiber is exposed to protrude slightly from the rubber surface. . The fiber assembly 40 is interposed in the concave groove 15b of the cap 15 between the concave groove 15b and the piston rod 31 in a radially compressed state. As a specific example, when the diameter φ of the piston rod 31 is φ = 12 mm, the crushing margin (diameter dimension) on the outer peripheral side with respect to the groove bottom of the concave groove 15b is 0.2 to 2.0 mm. In addition, the expansion margin (diameter dimension) on the inner peripheral side with respect to the piston rod 31 is 0.1 to 1.0 mm. The thickness dimension (axial dimension) is 0.5 mm or more. Examples of such a fiber assembly 40 include “soft wiper (trade name)” (manufactured by Sakagami Seisakusho Co., Ltd.).

  Here, the effect | action of the fiber assembly 40 in the MRF damper comprised as mentioned above is demonstrated.

  First, in the MRF damper, when a current is supplied from the power supply unit to the electromagnet 35, the electromagnet 35 generates a magnetic force, thereby forming a magnetic circuit M between the piston 30 and the side peripheral wall of the cylinder tube 11. The Then, a magnetic field is applied to the magnetorheological fluid in the communication path 34 by the magnetic circuit M, and as a result, the apparent viscosity of the magnetorheological fluid in the communication path 34 increases. Thereby, since the passage resistance of the magnetorheological fluid in the communication path 34 increases, the movement of the magnetorheological fluid via the communication path 34 between the first fluid chamber C1 and the second fluid chamber C2 is suppressed. . Therefore, when the movement to move the piston rod 31 in the axial direction is transmitted to the piston rod 31 and the piston 30 moves in the axial direction, the piston 30 moves to the fluid chamber C1 (or the front side in the movement direction). The movement is suppressed by receiving the pressure of the magnetorheological fluid of C2). Thereby, the motion applied to the piston rod 31 is attenuated.

  When the piston rod 31 moves in the extending direction (right direction in FIG. 2), the magnetorheological fluid adhering to the surface of the piston rod 31 passes through the through holes 12a and 15a together with the piston rod 31. Trying to leak into the external space. At this time, since the lip portion 20a of the U-packing 20 is in sliding contact with the surface of the piston rod 31, the magnetic viscous fluid adhering to the surface is prevented from leaking to the external space. However, since the magnetorheological fluid contains iron powder, and the piston rod 31 repeats expansion and contraction, wear of the lip portion 20a may be accelerated by the iron powder.

  At this time, the magnetorheological fluid on the piston rod 31 passes along the sliding contact surface 40 a of the fiber assembly 40 in front of the U packing 20. The iron powder in the magnetorheological fluid is entangled with the fibers on the sliding contact surface 40a of the fiber assembly 40 and is held in the sliding contact surface 40a. Movement to is restricted. Moreover, since the iron powder entangled with the fiber plays a role of entwining the subsequent iron powder, the above-described action of restricting the movement of the iron powder is exhibited over a long period of time. Therefore, as schematically shown in FIG. 1B, the amount of iron powder (iron powder concentration) reaching the lip portion 20a of the U packing 20 is reduced, and accordingly, the amount of the U packing 20 in the MRF damper is reduced. Life expectancy will be extended.

  In addition, since only the magnetorheological fluid passing through the through holes 12a and 15a holds the iron powder in the magnetorheological fluid in the sliding contact surface 40a of the fiber assembly 40, the distribution of iron powder in the magnetorheological fluid is reduced. Therefore, there is no possibility that the attenuation characteristic as the magnetic viscosity characteristic is lowered due to such uneven distribution of the iron powder.

  Furthermore, since it is not necessary to classify the particle size of the iron powder with higher accuracy than in the conventional case (see Patent Document 1), the material cost of the magnetorheological fluid is not increased, and the piston rod Since it is not necessary to make the value of the surface roughness of 31 smaller than the current value, not only does the processing cost of the piston rod 31 increase, but the current level of lubricity is maintained.

  Therefore, according to this embodiment, in the MRF damper in which the gap between the through hole 12a15a of the cylinder body 10 and the piston rod 31 is sealed with the U packing 20 so that the magnetorheological fluid does not leak out, the piston rod 31 The iron powder in the magnetorheological fluid that moves to the lip portion 20a of the U-packing 20 with the relative movement of the magnet can be held in the sliding contact surface 40a of the fiber assembly 40, so that the iron powder in the magnetorheological fluid The amount of iron powder that reaches the lip portion 20a of the U-packing 20 is reduced without biasing the distribution of the powder, without increasing the accuracy of classification of the iron powder, or without performing special processing on the surface of the piston rod 31. Thus, not only does not cause a significant increase in cost, but also the magnetic viscosity characteristics and the lubricity with respect to the piston rod 31 are not impaired. It can contribute to the improvement of the durability of the MRF damper to extend the Le life.

  In the above-described embodiment, one fiber assembly 40 is used. However, a plurality of (two in the illustrated example) fibers are used as in Modification 1 schematically shown in FIG. The aggregates 40 may be arranged side by side in the axial direction. Thereby, the quantity (iron powder density | concentration) of the iron powder which reaches | attains the lip | rip part 20a of the U packing 20 will further reduce, as typically shown to the same figure (b).

  In the above embodiment, the engagement member of the present invention is the fiber assembly 40. However, the engagement member is not limited to the fiber assembly 40. For example, the piston rod 31 is used. Resin ring 50 such as PTFE (polytetrafluoroethylene) having a low sliding resistance and a hardness durometer D (ASTM D 2240) of about 60 degrees (the modification shown in FIGS. 5A and 5B) 2). At that time, if the resin ring 50 alone cannot provide a sufficient pressure contact force of the sliding contact surface 50a against the surface of the piston rod 31, as shown in the enlarged view of FIG. A fastening member such as 51 is preferably fitted. Further, one or a plurality of such resin rings 50 may be used. Further, such one or more resin rings 50 may be used in combination with one or more of the fiber assemblies 40. In that case, it is preferable to arrange the fiber assembly 40 at a position farthest from the U-packing 20.

-Experimental example-
Here, the experiment conducted in order to investigate the lifetime of the U packing in the five types of MRF dampers of Examples 1 to 5 will be described.

[Example 1]
The fiber assembly and the resin ring are not attached.

[Example 2]
A fiber assembly (design value of thickness dimension: 1.5 mm) is attached to the inner space side of the U packing in the through hole. In this fiber assembly, neither a spread allowance nor a crush allowance is set, but the crush allowance has a tolerance of −0.2 mm.

[Example 3]
A fiber assembly (thickness dimension: 3.2 mm) having a spread allowance of 0.3 mm and a crush allowance of 0.9 mm is mounted on the inner space side of the U packing in the through hole.

[Example 4]
Instead of the fiber assembly, a resin ring is mounted on the inner space side of the U packing in the through hole. An O-ring is fitted on this resin ring.

[Example 5]
The fiber assembly of Example 3 and the resin ring of Example 4 are mounted on the inner space side of the U packing in the through hole. However, the arrangement is in the order of fiber assembly, resin ring, and U packing from the inner space side.

  In this experiment, each damper was expanded and contracted (frequency: 9 Hz, stroke: 4 mm), and the number of expansions and contractions until the magnetorheological fluid leaked from the U packing was counted. The piston rod had an outer diameter d of φ12f8 (12−0.043 mm ≦ d ≦ 12 + 0 mm). The surface roughness Rz (JIS B 0601-2001 “maximum height” [based on ISO 4287: 1997]) was 3.2 μm (in the case of Example 2, 1.6 μm).

  As a result of the above, in the case of the damper of Example 1, the same number of expansion / contraction times of Example 2 to Example 5 in which the number of expansion / contraction times when the magnetorheological fluid leaks from the U packing is 1, are shown in the following table. Show.

上記の表から判るように、繊維集合体および樹脂リングの何れかを装着した例２〜例５では、Ｕパッキンの寿命が２倍以上になっている。

As can be seen from the above table, in Examples 2 to 5 in which either the fiber assembly or the resin ring is mounted, the life of the U packing is more than doubled.

  In addition, when Example 2 and Example 3 in which both fiber assemblies are mounted are compared, the lifespan is several times longer by setting the spread allowance and crushing allowance while increasing the thickness dimension of the fiber assembly (this test In the case of (4), it can be seen that it extends about 4 times). Moreover, in Example 3, the value of the surface roughness Rz of the piston rod is twice that in Example 2 (= 3.2 / 1.6). Therefore, in Example 3, if the surface roughness Rz of the piston rod is about the same as that in Example 2, it is possible to expect a further increase in life.

  On the other hand, when Example 2 and Example 4 are compared, even if the fiber assembly is replaced with a resin ring, the resin ring is clamped by an O-ring and the sliding contact surface is brought into pressure contact with the surface of the piston rod. Is about doubled.

  Further, comparing Example 3 and Example 5, it can be seen that the life of the damper of Example 3 is further extended by disposing a resin ring between the U packing and the fiber assembly. Incidentally, in the case of this example 5, the life of the U-packing is actually 10 times that in the case of example 1.

It is the longitudinal cross-sectional view (a) which shows typically the principal part of a MRF damper, and the characteristic view (b) which shows typically the change of the iron powder density | concentration in an axial direction position. It is a longitudinal cross-sectional view which shows typically the whole structure of the MRF damper which concerns on embodiment of this invention. It is the top view (a) and longitudinal cross-sectional view (b) which show a fiber assembly typically. It is a FIG. 1 equivalent view which shows typically the change of the iron powder density | concentration in the principal part and axial position of the MRF damper which concerns on the modification 1 of this embodiment, respectively. It is a FIG. 1 equivalent view which shows typically the change of the iron powder density | concentration in the principal part and axial direction position of the MRF damper which concerns on the modification 2 of this embodiment. FIG. 9 is a view corresponding to FIG. 3 schematically showing a resin ring used in an MRF damper according to Modification 2.

Explanation of symbols

10 Cylinder body (first member)
12a Through hole 15a Through hole 20 U-shaped packing (seal material)
31 Piston rod (second member)
34 communication path 35 electromagnet (magnetic force generating means)
40 Fiber assembly 40a Sliding contact surface 50 Resin ring (resin body)
50a Sliding contact surface 51 O-ring (clamping member)
C1 First fluid chamber (fluid chamber)
C2 Second fluid chamber (fluid chamber)
M Magnetic circuit

Claims (11)

A first member having an internal space and a through-hole communicating the internal space with the external space;
A second member disposed so as to penetrate the through hole of the first member, and movable relative to the first member in the penetration direction;
A sealing material that is provided in the through hole of the first member and seals the internal space of the first member while allowing relative movement of the second member;
A magnetorheological fluid device comprising a magnetorheological fluid filled in the internal space of the first member and containing ferromagnetic particles,
A sliding contact surface in sliding contact with the surface of the second member on the inner space side of the sealing material in the through hole; A magnetorheological fluid device comprising one or more engaging members that engage the magnetic particles so as to be held within the sliding contact surface. The magnetorheological fluid device according to claim 1,
The engaging member is a fiber assembly provided so as to keep the fiber in a predetermined shape by an elastic material and to expose a part of the fiber on the sliding contact surface,
The magneto-rheological fluid device is characterized in that the fiber assembly is configured to hold the ferromagnetic particles in the sliding contact surface by entwining the fibers with the ferromagnetic particles. The magnetorheological fluid device according to claim 2,
A magnetorheological fluid device characterized in that the dimension of the sliding contact surface of the fiber assembly in the relative movement direction of the second member is 0.5 mm or more. The magnetorheological fluid device according to claim 2,
The fiber assembly has a ring shape with an insertion hole formed so that the second member is inserted and the inner wall surface forms a sliding contact surface, and the inner wall surface is in pressure contact with the surface of the second member. Provided in
A magnetorheological fluid device according to claim 1, wherein an expansion margin of the insertion hole of the fiber assembly in the direction orthogonal to the relative movement direction of the second member is 0.1 to 1.0 mm. The magnetorheological fluid device according to claim 2,
There are a plurality of fiber assemblies,
The magnetorheological fluid device, wherein the plurality of fiber assemblies are arranged so as to be aligned in the relative movement direction of the second member. The magnetorheological fluid device according to claim 1,
The engaging member is a resin body made of a flexible resin material and provided so that the sliding contact surface is pressed against the surface of the second member,
2. The magnetorheological fluid device according to claim 1, wherein the resin body is configured to hold the ferromagnetic particles in the sliding surface by burying the ferromagnetic particles in the sliding surface. The magnetorheological fluid device according to claim 6,
The resin body has a ring shape having an insertion hole formed so that the second member is inserted and the inner wall surface forms a sliding contact surface,
A magnetorheological fluid device, wherein a fastening member for fastening the resin body in a direction in which the sliding contact surface is pressed against the surface of the second member is fitted to the outer periphery of the resin body. The magnetorheological fluid device according to claim 6,
There are a plurality of resin bodies,
The plurality of resin bodies are arranged so as to be aligned in the relative movement direction of the second member.   The one or more fiber assemblies in the magnetorheological fluid device according to claim 2 and the one or more resin bodies in the magnetorheological fluid device according to claim 6 are arranged in the relative movement direction of the second member. A magnetorheological fluid device, wherein The magnetorheological fluid device according to claim 9,
One of the one or more fiber assemblies is arranged at a position farthest from the sealing material. A damping device comprising the magnetorheological fluid device according to claim 1,
The first member of the magnetorheological fluid device is disposed so as to divide the internal space of the first member into two fluid chambers divided in the relative movement direction of the second member of the magnetorheological fluid device, A piston provided so as to be relatively movable in the moving direction;
A communication passage communicating the two fluid chambers with each other,
The magnetorheological fluid of the magnetorheological fluid device is filled in the two fluid chambers and the communication path,
Magnetic field applying means for applying a magnetic field to the magnetorheological fluid in the communication path,
The damping device according to claim 1, wherein the second member is a piston rod connected to the piston so as to move and be integrated.

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