JP2008215406A - Magnetic fluid damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely restrain an attack of a magnetic substance particle on a seal part in a rod guide without having adverse influence on initial responsiveness. <P>SOLUTION: This magnetic fluid damper of a twin tube type structure compensates for a magnetic fluid equivalent to intrusion and leaving of a piston rod 4 by a reservoir chamber 11, by forming a part between a cylinder 1 and an outer tube 2 as the reservoir chamber 11. A first filter 14 and a second filter 15 checking the passing of the magnetic substance particle in the magnetic fluid and allowing the passing of the oil content, are installed on the rod guide 6 for inserting the piston rod 4 and a body valve 12 controlling going in and out of the fluid to the reservoir chamber 11. Infiltration of the magnetic substance particle into the seal part in the rod guide 6 is restrained by the first filter 14, and an oil seal 8 held by the rod guide 6 is prevented from being damaged by receiving the attack of the magnetic substance particle. Infiltration of the magnetic substance particle into the reservoir chamber 11 is restrained by the second filer 15, and the magnetic substance particle is prevented from precipitating in the reservoir chamber 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic fluid damper that generates a damping force by the flow resistance of a magnetic fluid imparted with electromagnetic action.

  This type of magnetic fluid damper is similar to a general-purpose oil damper except that an electromagnet that imparts an electromagnetic action to the magnetic fluid is incorporated. The other end of the piston rod whose one end is connected to the piston is inserted through a rod guide attached to the opening end of the cylinder and extends outside the cylinder, and a seal member is provided between the rod guide and the piston rod. It has a sealed structure.

  By the way, in a fluid damper, in order to ensure smooth sliding of a piston rod, some fluid permeates into the seal part in a rod guide. However, the magnetic fluid contains magnetic particles (iron powder) having a considerably large particle diameter (5 to 10 μm), and when such a magnetic fluid enters the seal portion, the seal member and the piston rod become magnetic materials. Under the attack of particles, the sealing performance deteriorates early.

  Therefore, for example, in the shock absorber (magnetic fluid damper) described in Patent Document 1, an annular groove is provided on the end surface of the rod guide, a permanent magnet is disposed in the groove, and the groove is formed by a diaphragm. Covering and taking measures to adsorb the magnetic particles in the magnetic fluid to the permanent magnet by bending the diaphragm to the permanent magnet side as the rod side chamber in the cylinder becomes high pressure.

JP 2003-278821 A

  However, according to the countermeasure described in Patent Document 1, since the permanent magnet is disposed in the annular portion away from the piston rod, the magnetic particles entering the sliding portion between the piston rod and the seal member are sufficiently captured. There was a problem that it was not possible to do so and it did not lead to fundamental measures. Further, since the rod side chamber is substantially enlarged due to the deflection of the diaphragm in the initial stage of operation, there is a possibility that the generation of damping force may be delayed.

  On the other hand, the magnetic particles in the magnetic fluid have a property of being easily settled. When there is almost no expansion / contraction movement of the piston rod, that is, when there is almost no movement of the magnetic fluid, the precipitation of the magnetic particles proceeds. The magnetic particles once settled easily disperse in the magnetic fluid in accordance with the stirring of the magnetic fluid accompanying the expansion and contraction of the piston rod. However, the magnetic fluid that enters and exits the piston rod is stored in the reservoir around the cylinder. In the so-called twin tube type magnetic fluid damper that compensates in the chamber, since the magnetic fluid is not stirred much in the reservoir chamber, it is difficult to disperse the magnetic particles that have settled in the reservoir chamber. As the sedimentation of the magnetic particles progresses, the dispersion concentration of the magnetic particles in the magnetic fluid decreases, making it difficult to stably maintain the desired damping performance. However, conventionally, no special measures have been taken to suppress the sedimentation of the magnetic particles in the reservoir chamber, including the invention described in Patent Document 1, and there is a problem that the reliability is inferior. there were.

  Further, as the magnetic fluid damper, there is a so-called monotube type gas-filled structure in which the magnetic fluid of the piston rod entering and leaving is compensated by a reservoir chamber defined by a free piston on the bottom side of the cylinder. However, in this case, there is a problem that the seal member that seals between the free piston and the cylinder is quickly worn out by the attack of the magnetic particles, similarly to the seal member on the rod guide side. However, conventionally, no special measures have been taken to suppress the sedimentation of the magnetic particles in the reservoir chamber, including the invention described in Patent Document 1, and there is a problem that the reliability is inferior. there were.

  The present invention has been made in view of the above-described conventional problems. The first problem is that the magnetic particles attack the seal portion in the rod guide without adversely affecting the initial response. An object of the present invention is to provide a magnetic fluid damper capable of reliably suppressing the above-described problem. In addition to the first problem described above, the second problem is to provide a twin-tube magnetic fluid damper that suppresses the sedimentation of magnetic particles in the reservoir chamber. Furthermore, in addition to the first problem, a third problem is to provide a monotube gas-filled magnetic fluid damper that can reliably suppress the attack of magnetic particles on the seal portion of the free piston. is there.

  According to a first aspect of the present invention for solving the first problem, a piston is disposed in a cylinder filled with a magnetic fluid, and the other end of a piston rod having one end connected to the piston is connected to the cylinder. A rod guide attached to the opening end is inserted to extend outside the cylinder, and a seal member seals between the rod guide and the piston rod, which is attenuated by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod. In the magnetic fluid damper that generates force, a filter that prevents passage of the magnetic particles contained in the magnetic fluid to the rod guide side but allows passage of oil is provided in the rod side chamber in the cylinder. It is characterized by that.

  In the first aspect of the invention, the magnetic particles are prevented from flowing toward the rod guide by the filter, so that the attack of the magnetic particles on the seal portion in the rod guide can be suppressed. In addition, since the rod side chamber does not inadvertently expand in the initial stage of operation, there is no delay in the generation of the damping force. Moreover, since the oil in the magnetic fluid passes through the filter and reaches the seal part, the seal part does not cause an oil film breakage, and the deterioration of the sliding characteristics and durability due to the oil film breakage is obviated. Can be prevented.

  A second invention for solving the second problem is a rod in which the other end of a piston rod whose one end is connected to a piston in a cylinder filled with a magnetic fluid is attached to the open end of the cylinder. A guide is inserted to extend outside the cylinder, a seal member seals between the rod guide and the piston rod, and a damping force is generated by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod. In the ferrofluid damper having a twin tube structure in which the ferrofluid of the rod entering and exiting is compensated in the reservoir chamber around the cylinder, the magnetic particles contained in the ferrofluid are contained in the anti-rod side chamber in the cylinder. A filter is provided which prevents passage of oil to the reservoir chamber side but allows passage of oil.

  In the second aspect of the invention, the sedimentation of the magnetic particles in the reservoir chamber is eliminated by the filter.

  A third invention for solving the third problem is a rod in which the other end of a piston rod whose one end is connected to a piston in a cylinder in which a magnetic fluid is sealed is attached to the open end of the cylinder. A guide is inserted to extend outside the cylinder, a seal member seals between the rod guide and the piston rod, and a damping force is generated by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod. In the magnetic fluid damper of the monotube type gas-filled structure in which the magnetic fluid for the intrusion and withdrawal of the rod is compensated by a reservoir chamber defined via a free piston on the bottom side of the cylinder, the magnetic fluid enters the anti-rod side chamber in the cylinder. In addition, a filter that prevents the passage of the magnetic particles contained in the magnetic fluid to the free piston side but allows the passage of oil is provided. Characterized in that it was.

  In this 3rd invention, the attack of the magnetic body particle | grains of the magnetic body particle | grains with respect to the seal part by the side of a free piston is suppressed by the filter.

  According to the magnetic fluid damper as the first invention, since the attack of the magnetic particles to the seal portion in the rod guide can be surely suppressed without adversely affecting the initial response, the durability reliability is greatly increased. improves.

  According to the magnetic fluid damper as the second invention, since the sedimentation of the magnetic particles in the reservoir chamber is eliminated, the durability reliability in the case of the twin tube structure is greatly improved.

  According to the magnetic fluid damper as the third invention, since the attack of the magnetic particles of the magnetic particles against the seal portion on the free piston side is suppressed, the durability reliability in the case of the monotube gas-filled structure is greatly increased. improves.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1-3 show a first embodiment of a magnetic fluid damper according to the present invention. This magnetic fluid damper has a twin-tube structure, and includes a cylinder 1 in which a magnetic fluid is sealed and a bottomed outer tube 2 that houses the cylinder 1. A piston 3 containing an electromagnet (not shown) is disposed in the cylinder 1, and one end of a piston rod 4 is connected to the piston 3. The other end side of the piston rod 4 is extended outside the cylinder by inserting a rod guide 6 mounted in common by a caulking member 5 (FIG. 4) into the upper end openings of the cylinder 1 and the outer tube 2. The guide 6 holds a bush 7 that slidably guides the piston rod 4 and an oil seal (seal member) 8 that seals between the piston rod 4 so as to be separated from each other in the cylinder axial direction.

  The inside of the cylinder 1 is divided into a piston upper chamber (rod side chamber) 9A and a piston lower chamber (anti-rod side chamber) 9B. The upper and lower chambers 9A and 9B are the inner surface of the piston 3 and the inner surface of the cylinder 1. It is formed between the peripheral surface and communicated by an annular resistance passage 10. On the other hand, an annular reservoir chamber 11 is formed between the cylinder 1 and the base shell 2, and the reservoir chamber 11 and the piston lower chamber 9 </ b> B are connected to a resistance passage of a body valve 12 attached to the bottom of the cylinder 1. 13 to communicate with each other. The magnetic fluid has magnetic particles (iron powder) dispersed in the hydraulic oil, and its current changes by supplying current to the electromagnet built in the piston 3. As the viscosity of the magnetic fluid changes, the flow resistance of the magnetic fluid passing through the resistance passage 10 around the piston 3 increases, and the motion applied to the piston rod 4 is attenuated. Note that air is sealed in the upper side of the reservoir chamber 11.

  In the first embodiment, the rod guide 6 is provided with a first filter 14 that prevents the passage of the magnetic particles in the magnetic fluid but allows the passage of oil, and is also attached to the body valve 12. A second filter 15 having the same function as described above is attached. The first and second filters 14 and 15 may be of any type as long as they have appropriate rigidity, and may be a porous sintered material or a porous mesh material.

  As shown in FIG. 2, the mounting structure of the first filter 14 to the rod guide 6 is such that the first filter 14 is in a stepped recess 6a formed at the end of the rod guide 6 facing the piston upper chamber 9A. The fitting is fixed. A seal member (O-ring) 16 that seals between the first filter 14 and the piston rod 4 is attached to the inner periphery of the first filter 14, whereby the piston upper chamber 9 A and the inside of the rod guide 6, that is, the bush 7 and Infiltration of magnetic particles into the oil seal 8 side is prevented. On the other hand, the mounting structure of the second filter 15 to the body valve 12 is such that the second filter 15 is attached to one end of the body valve 12 facing the piston lower chamber 9B by a spacer 17 and a caulking pin 18 as shown in FIG. It is fixed. The second filter 15 has a sufficient size so that the outer peripheral surface thereof is in close contact with the inner peripheral surface of the cylinder 1, whereby magnetic particles from the piston lower chamber 9 </ b> B to the reservoir chamber 11 side. Intrusion is prevented. When the first filter 14 is attached to the rod guide 6 and the second filter 15 is attached to the body valve 12 in this way, the filter can be easily supported by slight changes in the shape of the rod guide 6 and body valve 12. Can do.

Hereinafter, the operation of the magnetic fluid damper having the above-described configuration will be described.
When the magnetic fluid damper is used as a shock absorber for a suspension of an automobile, a mounting eye 19 attached to the bottom of the outer tube 2 and a bolt part (not shown) integrally formed on the upper end of the piston rod 4 are provided. Utilized, it is interposed between the axle and the vehicle body. During the extension stroke in which the piston rod 4 extends, the magnetic fluid in the piston upper chamber 9A flows into the piston lower chamber 9B through the resistance passage 10 around the piston 3, and a damping force is generated during this time. At the same time, the fluid of the piston rod 4 withdrawing from the cylinder 1 is replenished from the reservoir chamber 11 through the resistance passage 13 in the body valve 12 to the piston lower chamber 9B, and a damping force is also generated in this portion. To do. On the other hand, during the contraction stroke in which the piston rod 4 is shortened, the magnetic fluid in the piston lower chamber 9B passes through the resistance passage 10 around the piston 3 and passes through the upper piston chamber 9A and the resistance passage 13 in the body valve 12 to the reservoir chamber 11. During this time, a damping force is generated. At the same time, the fluid corresponding to the intrusion of the piston rod 4 into the cylinder 1 flows into the reservoir chamber 10 through the resistance passage 13 in the body valve 12, and a damping force is also generated in this portion.

  Here, during the above-described extension stroke, the magnetic fluid in the piston upper chamber 9A tends to enter the rod guide 6. However, since the first filter 14 is disposed on the front surface of the rod guide 6 facing the piston upper chamber 9A, the passage of the magnetic particles in the magnetic fluid is blocked by the first filter 14. Accordingly, the magnetic particles are prevented from entering the seal portions of the bush 7 and the oil seal 8 that are in sliding contact with the piston rod 4, thereby preventing damage to the bush 7, the oil seal 8, and the piston rod 4. Sex is maintained stably over the long term. Further, since the first filter 14 allows the passage of oil, the oil sufficiently permeates the seal portions of the bush 7 and the oil seal 8 described above, thereby preventing the seal portion from causing an oil film breakage. Smooth sliding characteristics of the rod 4 are ensured. In addition, since the first filter 14 is a rigid body, the piston upper chamber 9A does not inadvertently expand in the initial stage of operation, and the generation of damping force is not delayed.

  On the other hand, during the above-described contraction stroke, the magnetic fluid in the piston lower chamber 9 </ b> B tends to flow to the reservoir chamber 11 through the resistance passage 13 in the body valve 12. However, since the second filter 15 is disposed on the front surface of the body valve 12 facing the piston lower chamber 9B, the passage of the magnetic particles in the magnetic fluid is blocked by the second filter 15. That is, the infiltration of the magnetic particles into the reservoir chamber 11 side is suppressed, and therefore the sedimentation of the magnetic particles in the reservoir 11 is performed even when there is almost no expansion / contraction movement of the piston rod 4, that is, when there is almost no movement of the magnetic fluid. Is prevented. As a result, the dispersion concentration of the magnetic particles in the magnetic fluid is not lowered, and the desired attenuation performance is stably maintained. The magnetic particles settled on the second filter 15 are easily dispersed in the magnetic fluid in accordance with the stirring of the magnetic fluid accompanying the expansion and contraction of the piston rod 4.

  Here, in the first embodiment, the seal member 16 that seals the space between the piston rod 4 and the piston rod 4 is disposed on the inner periphery of the first filter 14 on the rod guide 6 side. Instead of the sealing member 16, an annular permanent magnet 20 may be provided as shown in FIG. In this case, the magnetic particles that are about to move to the rod guide 6 side through the gap between the piston rod 4 and the first filter 14 are attracted to the permanent magnet 20, so that the bush 7 slidably contacting the piston rod 4 Infiltration of the magnetic particles into the seal portion of the oil seal 8 is more reliably prevented, and the stability of the sealing performance is more reliably ensured.

  In the first embodiment, the first filter 14 is attached to the rod guide 6 and the second filter 15 is attached to the body valve 12. However, the first and second filters 14 and 15 are attached. May be separated from the rod guide 6 and the body valve 12 and fixed to the cylinder 1. In this case, the fixing method with respect to the cylinder 1 is arbitrary, and for example, a fixing method by caulking can be used.

  In the first embodiment, an example in which the magnetic fluid damper is configured as a twin tube type is shown. However, as the twin tube type, a so-called twin tube type gas-filled structure in which high pressure gas is sealed in the reservoir 11 is used. The present invention can also be configured as such a twin tube gas-filled structure. In this case, since the body valve 12 may be omitted from the bottom of the cylinder 1, in this case, the second filter 15 is fixed to the cylinder 1 by a method such as caulking.

  FIG. 5 shows a second embodiment of the magnetic fluid damper according to the present invention. The magnetic fluid damper has a monotube type gas-filled structure, and a reservoir chamber 22 is defined via a free piston 21 on the bottom side of the cylinder 1 filled with the magnetic fluid. A space between the free piston 21 and the cylinder 1 is sealed by a seal member (O-ring) 23, and the reservoir chamber 22 is filled with high-pressure gas. In the second embodiment, the second filter 24 that prevents the passage of the magnetic particles in the magnetic fluid but allows the passage of the oil at the portion of the bottom of the cylinder 1 that does not interfere with the free piston 21 is provided. It is arranged. Here, the second filter 24 is caulked and fixed by pushing the cylinder 1 locally from the outside of the radius, but the fixing method is arbitrary. The upper structure of the magnetic fluid damper is substantially the same as that of the first embodiment except that the outer tube 2 is not included. Therefore, the illustration is omitted here and the same components are denoted by the same reference numerals. Will be attached.

  The magnetic fluid damper as the second embodiment is similar to the first embodiment in that the piston upper chamber 9A passes through the resistance passage 10 (FIG. 1) around the piston 3 according to the expansion and contraction of the piston rod 4. The magnetic fluid flows between the piston lower chamber 9B and a damping force is generated. However, the volume of the reservoir chamber 22 changes through the free piston 21 for the magnetic fluid that enters and exits the piston rod 4. To compensate.

  Thus, while the piston rod 4 is in operation, the magnetic fluid in the cylinder 1 tries to enter the seal portion by the seal member 23, but the second filter 24 is disposed on the bottom side of the cylinder 1. The passage of magnetic particles in the magnetic fluid is blocked by the second filter 24. Therefore, infiltration of the magnetic particles into the seal portion around the free piston 21 is suppressed, and as a result, damage to the seal member 23 is suppressed, and the sealing performance is stably maintained for a long time. On the other hand, since the second filter 24 allows oil to pass therethrough, the oil sufficiently penetrates into the above-described seal portion, whereby the seal portion does not cause an oil film breakage, and the free piston 21 smoothly slides. Characteristics are secured. Since the first filter 14 prevents the magnetic particles from entering the seal portion (bush 9, oil seal 8) on the rod guide 6 side, it is the same as the first embodiment. Then, description of the effect by this is abbreviate | omitted.

1 shows a first embodiment of a magnetic fluid damper according to the present invention, and is a cross-sectional view showing the entire structure of a magnetic fluid damper configured as a twin-tube structure. FIG. 1 is an enlarged sectional view showing an upper structure of a magnetic fluid damper in FIG. FIG. 1 is an enlarged sectional view showing a lower structure of a magnetic fluid damper in FIG. FIG. 5 is a cross-sectional view showing a modification of the first embodiment and enlarging an upper structure of a magnetic fluid damper. FIG. 7 is a cross-sectional view showing a lower structure of a magnetic fluid damper configured as a monotube type gas-filled structure, showing a second embodiment of the magnetic fluid damper according to the present invention.

Explanation of symbols

1 Cylinder, 2 Outer tube 3 Piston, 4 Piston rod 6 Rod guide, 8 Oil seal (seal member)
9A Piston upper chamber (rod side chamber)
9A Piston lower chamber (anti-rod side chamber)
DESCRIPTION OF SYMBOLS 10 Resistance passage, 11 Reservoir chamber 12 Body valve, 13 Resistance passage 14 1st filter, 15 2nd filter 16 Seal member, 20 Permanent magnet 21 Free piston, 22 Reservoir chamber 23 Seal member, 24 2nd filter

Claims (5)

  A piston is arranged in a cylinder filled with a magnetic fluid, and the other end of a piston rod having one end connected to the piston is inserted through a rod guide attached to the opening end of the cylinder and extends out of the cylinder. In addition, in the magnetic fluid damper that seals between the rod guide and the piston rod by a seal member and generates a damping force by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod, the rod side chamber in the cylinder A magnetic fluid damper is provided, wherein a filter that prevents passage of magnetic particles contained in the magnetic fluid to the rod guide side but permits passage of oil is provided.   The magnetic fluid damper according to claim 1, wherein a permanent magnet is disposed at a sliding contact portion of the filter with the piston rod.   3. The magnetic fluid damper according to claim 1, wherein the filter is supported by a rod guide.   The other end of the piston rod whose one end is connected to the piston in the cylinder in which the magnetic fluid is sealed is inserted through a rod guide attached to the opening end of the cylinder and extends out of the cylinder. A gap between the piston rod and the piston rod is sealed by a seal member, and a damping force is generated by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod. In the magnetic fluid damper having a twin tube structure that compensates in the reservoir chamber, the passage of oil is prevented while the magnetic particles contained in the magnetic fluid are prevented from passing to the reservoir chamber side in the anti-rod side chamber in the cylinder. A magnetic fluid damper having an allowable filter.   The other end of the piston rod whose one end is connected to the piston in the cylinder in which the magnetic fluid is sealed is inserted through a rod guide attached to the opening end of the cylinder and extends out of the cylinder. A gap between the piston rod and the piston rod is sealed by a sealing member, and a damping force is generated by the flow resistance of the magnetic fluid accompanying the expansion and contraction of the piston rod. In a magnetic fluid damper having a monotube type gas-filled structure that compensates in a reservoir chamber defined through a free piston, a magnetic particle contained in the magnetic fluid is contained in the anti-rod side chamber in the cylinder on the free piston side. A magnetic fluid damper is provided, which is provided with a filter that prevents passage of oil but permits passage of oil.

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