JP2004019741A - Shock absorber using magnetic viscous fluid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid early deterioration due to wear on a body wall surface in respective fluid chambers 4, 5 by magnetic particles in magnetic viscous fluid 2, and to maintain magnetic viscosity characteristics in a fluid passage 7 with the magnetic particles for a long term in a cylinder body 1 by the magnetic force of an electromagnet 8, in a cylinder type magnetic viscous fluid damper where damping force to kinetic energy added to the piston 3 via a rod 6 is changed by changing viscosity in the magnetic viscous fluid 2 within the fluid passage 7 for communicating with the first and second fluid chambers 4, 5 divided and formed by a piston 3. <P>SOLUTION: Permanent magnets 11 whose magnetic force is smaller than that of the electromagnet 8 are arranged at both end face sections of the piston 3 so that the magnetic particles in the magnetic viscous fluid 2 within the fluid chambers 4, 5 are unevenly distributed near both the edges of the fluid passage 7, and the magnetic particles are allowed to flow in the fluid passage 7, when the electromagnet 8 generates the magnetic force. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shock absorber such as a damper using a magnetorheological fluid in which magnetic particles are dispersed in a medium and made into a colloid, and in particular, to avoid early deterioration due to the magnetic particles abrading the inner wall surface of the body, and to reduce magnetic particles. To reduce costs by reducing the content of
[0002]
[Prior art]
For example, in a cylinder type magnetorheological fluid damper, as schematically shown in FIG. 3, as the piston b moves in the cylinder body c by the kinetic energy imparted to the piston b via the rod a, A fluid f containing magnetic particles moves between the two fluid chambers d and e via a fluid passage g. At this time, when a magnetic force is applied to the magnetorheological fluid f in the fluid passage g by the magnet h, as shown schematically in FIG. , The movement of the piston b is restricted, and as a result, the kinetic energy can be attenuated.
[0003]
By the way, in the conventional damper using the fluid containing magnetic particles, the magnetic particles in the fluid f containing the magnetic particles easily wear the inner wall surface of the cylinder body c in each of the fluid chambers d and e, and lack durability. .
[0004]
On the other hand, in the fluid f containing the magnetic particles, the magnetic particles tend to settle, and the amount of the magnetic particles in the fluid passage g gradually decreases, whereby the magnetorheological properties of the magnetorheological fluid f in the fluid passage g decrease. Therefore, it is difficult to maintain a necessary damping force for a long period of time.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and a main object of the present invention is to provide a magnetic force applied to a magnetorheological fluid in a fluid passage communicating two fluid chambers defined by pistons in a cylinder body. By utilizing the magnetic properties of magnetic particles in a buffer device such as a fluid damper that changes its viscosity to change the restraining force against the movement of the piston, the area where magnetic viscous properties are unnecessary An object of the present invention is to prevent abrasion of a wall surface and to maintain the magnetorheological properties for a long period of time in a region on the fluid passage side where the magnetorheological properties are required.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, the magnetic particles in the magnetorheological fluid in each fluid chamber are unevenly distributed in the region on the fluid passage side. While the content of the magnetic particles in the viscous fluid is reduced, the content of the magnetic particles in the magnetic viscous fluid is ensured to be large in a region where the magnetic viscous characteristics are required.
[0007]
Specifically, according to the first aspect of the present invention, a first member having a hollow portion and a first member are disposed in the hollow portion of the first member so as to be relatively movable with respect to the first member. A second member that defines two fluid chambers filled with the contained magnetic viscous fluid, and a second member that is provided so as to communicate with the two fluid chambers, with the relative movement of the second member. A fluid passage through which the magnetorheological fluid moves between the two fluid chambers, and magnetic force applying means for applying a magnetic force so that the viscosity of the magnetorheological fluid in the fluid passage is increased and the relative movement of the second member is restricted. It is premised on a shock absorber using a magnetorheological fluid provided with.
[0008]
In addition, it is assumed that a magnetic particle in the magnetic viscous fluid in the two fluid chambers is attracted by magnetic force to be unevenly distributed in a region on the fluid passage side.
[0009]
In the above configuration, in each of the fluid chambers, the magnetic particles in the magnetorheological fluid are attracted to the uneven distribution means and gather in a region on the fluid passage side. As a result, in other regions in each fluid chamber, the content of magnetic particles in the magnetorheological fluid is reduced. Therefore, the situation where the inner wall surface of the first member in each fluid chamber is worn by the magnetic particles is reduced as compared with the conventional case where the magnetic particles are substantially uniformly diffused in the magnetic viscous fluid. On the other hand, in the region on the fluid passage side, since the magnetic particles are unevenly distributed, the content of the magnetic particles in the magnetic viscous fluid is maintained despite the fact that the magnetic particles are likely to settle, and therefore, The magnetorheological properties are retained.
[0010]
Also, even when the absolute amount of magnetic particles as a whole is small, magnetic particles are secured in the region on the side of the fluid passage. A working fluid containing no particles can be used, which can contribute to cost reduction.
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, when the magnetic force applying means is an electromagnet that generates a magnetic force when supplied with electric power, the uneven distribution means is disposed near both ends of the fluid passage, When the magnetic force applying means is not generating a magnetic force, the magnetic particles in the magnetorheological fluid in each fluid chamber are respectively unevenly distributed in the region near the end of the fluid passage, while when the magnetic force applying means is generating the magnetic force, Each of the fluid chambers is configured to allow the magnetic particles in the magnetorheological fluid to move into the fluid passage.
[0012]
In the above configuration, when the electromagnet as the magnetic force applying means does not generate a magnetic force, in each fluid chamber, the magnetic particles in the magnetorheological fluid are attracted to the uneven distribution means and are located in a region near the end of the fluid passage. get together. As a result, in other areas in each fluid chamber, the content of magnetic particles in the magnetic viscous fluid is reduced. Therefore, the situation where the wall surface of the first member in each fluid chamber is worn by the magnetic particles is reduced as compared with the conventional case where the magnetic particles are substantially uniformly diffused in the magnetic viscous fluid.
[0013]
On the other hand, when the electromagnet is generating a magnetic force, in each fluid chamber, the magnetic particles unevenly distributed in the region near the end of the fluid passage are allowed to move to the fluid passage, so that the , A magnetorheological fluid having a high content of magnetic particles flows in. As a result, in each fluid chamber, a magnetorheological fluid having a large content of magnetic particles flows into the fluid passage despite the fact that the content of the magnetic particles in the magnetorheological fluid is small.
[0014]
According to a third aspect of the present invention, in the second aspect of the present invention, the uneven distribution means is a permanent magnet which constantly generates a magnetic force smaller than the magnetic force applying means.
[0015]
In the above configuration, when the magnetic force applying unit does not generate a magnetic force, in each fluid chamber, the magnetic particles in the magnetorheological fluid are attracted to the permanent magnet and gather in a region near the end of the fluid passage. On the other hand, when the upper magnetic force applying means is generating a magnetic force, in each fluid chamber, the magnetic particles unevenly distributed in the region near the end of the fluid passage are such that the magnetic force of the permanent magnet is smaller than the magnetic force of the electromagnet, Movement to the fluid passage is allowed. Therefore, the function of the uneven distribution means in the second aspect of the invention is specifically performed.
[0016]
According to a fourth aspect of the present invention, in the second aspect of the invention, the uneven distribution means is an electromagnet that generates a magnetic force smaller than at least the magnetic force applying means when the magnetic force applying means is generating a magnetic force.
[0017]
In the above configuration, when the magnetic force applying unit does not generate a magnetic force, in each fluid chamber, the magnetic particles in the magnetorheological fluid are attracted to the uneven distribution unit and gather in a region near the end of the fluid passage. At this time, since the magnetic force of the uneven distribution means is variable, by increasing the magnetic force, the uneven distribution of the magnetic particles becomes higher than in the case of the third aspect of the present invention. On the other hand, when the upper magnetic force applying means is generating a magnetic force, in each fluid chamber, the magnetic particles unevenly distributed in the region near the end of the fluid passage have a magnetic force of the electromagnet smaller than that of the magnetic force applying means, or Since the generation of the magnetic force itself stops, the movement to the fluid passage is permitted as in the case of the third aspect of the present invention. Therefore, the uneven distribution function of the uneven distribution means in the second aspect of the invention is more strongly performed than in the case of the third aspect of the invention.
[0018]
According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, the first member is a cylinder body, and the second member reciprocates in the cylinder body by kinetic energy imparted to the second member. A magnetic force applying unit applies a magnetic force to the magnetorheological fluid in the fluid passage, thereby restricting the movement of the piston due to the kinetic energy to attenuate the kinetic energy. It is assumed that
[0019]
According to the above configuration, it is possible to obtain a magnetorheological fluid damper that does not cause deterioration due to the magnetic particles and does not cause early deterioration due to the magnetorheological characteristics of the magnetorheological fluid and that can be reduced in cost.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
1 and 2 show the overall configuration of a cylinder-type magnetorheological fluid damper according to an embodiment of the present invention. This magnetorheological fluid damper is used, for example, in a belt-type accessory drive device for an automobile engine. It is used to attenuate the operation of the tensioner which tries to keep the tension constant according to the operation direction.
[0022]
This magnetorheological fluid damper includes a cylinder body 1 having a cylindrical shape and closed at both ends. A magnetic viscous fluid 2 containing magnetic particles is sealed in the cylinder body 1. Further, the piston 3 is inserted into the cylinder body 1 so as to be movable in the left-right direction in the figure, whereby the volume of the cylinder body 1 is reversed in accordance with the movement of the piston 3. First and second two fluid chambers 4 and 5 that change in direction are defined.
[0023]
A rod 6 extending through the end wall of the cylinder body 1 in the moving direction of the piston 3 is disposed on the second fluid chamber 5 side (the right side in FIGS. 1 and 2) of the cylinder body 1. The penetrating portion of the rod 6 in the end wall is sealed by a sealing mechanism (not shown) so that the magnetorheological fluid 2 in the cylinder body 1 does not leak outside. The end of the rod 6 located outside the cylinder body 1 is pressed by a tensioner which is always biased by a biasing member in a direction in which a tension pulley pivotally supported by the pressing member presses the belt. When the pressing member is displaced in the belt pressing direction due to a decrease in belt tension, the rod 6 moves in a direction protruding from the cylinder body 1 as shown by an arrow in FIG. When the belt tension increases and the pressing member is displaced in a direction opposite to the belt pressing direction, the pressing member moves in a direction of retracting into the cylinder body 1 as indicated by an arrow in FIG. .
[0024]
An end of the rod 6 located inside the cylinder body 1 is connected to the piston 3 so as to move integrally therewith. When the belt tension decreases, the rod 6 pulls the piston 3 in a direction in which the volume of the first fluid chamber 4 increases and the volume of the second fluid chamber 5 decreases (the direction of the arrow in FIG. 1). When increasing, the piston 3 is pressed in a direction in which the volume of the first fluid chamber 4 decreases and the volume of the second fluid chamber 5 increases (the direction of the arrow in FIG. 2).
[0025]
Between the first fluid chamber 4 and the second fluid chamber 5, there is provided a fluid passage 7 communicating the fluid chambers 4 and 5 with each other, and the magnetorheological fluid 2 passes through the fluid passage 7. Thus, the movement of the magnetorheological fluid 2 between the two fluid chambers 4 and 5 due to the volume change of the two fluid chambers 4 and 5 is allowed while receiving a relatively small flow resistance. Specifically, a certain clearance is secured between the inner wall surface of the side peripheral portion of the cylinder body 1 and the outer wall surface of the side peripheral portion of the piston 3, and the fluid passage 7 allows the cylinder It is formed in an annular shape between the body 1 and the piston 3.
[0026]
A plurality of electromagnets 8, 8, ... are arranged and buried in the side peripheral portion of the piston 3 so as to be arranged in a circumferential direction. Each electromagnet 8 is configured such that an electric wire is wound around an iron core, and the electric power is supplied to the electric wire by a power supply control unit 10 via a wiring 9 arranged in a rod 6. At this time, in the present embodiment, when the belt tension decreases, the power supply is stopped, and power is supplied only when the belt tension increases.
[0027]
In the present embodiment, permanent magnets 11, 11 serving as uneven distribution means that constantly generate a magnetic force smaller than the magnetic force generated by the electromagnet 8 are arranged near both ends of the fluid passage 7. .
[0028]
Specifically, each of the permanent magnets 11 has a ring shape whose outer diameter is equal to or slightly smaller than the outer diameter of the piston 3, and is disposed at both end portions of the piston 3. .
[0029]
Here, the operation of the cylinder type magnetorheological fluid damper configured as described above will be described.
[0030]
When the belt tension in the belt-type auxiliary device driving device of the automobile engine is reduced, the tensioner operates to push the pressing member in the belt pressing direction by the urging force of the urging member, and the operation of the pressing member is performed via the rod 6. And transmitted to the piston 3. Accordingly, the piston 3 moves in a direction in which the volume of the first fluid chamber 4 is large and the volume of the second fluid chamber 5 is small (rightward in FIG. 1). With this movement, the magnetorheological fluid 2 in the second fluid chamber 5 passes through the fluid passage 7 and moves to the first fluid chamber 4.
[0031]
At the same time, power supply to each electromagnet 8 is stopped, and no magnetic force is generated by each electromagnet 8, so that the flow resistance of the magnetorheological fluid 2 in the fluid passage 7 is relatively small. Accordingly, the piston 3 easily moves in the above-described direction, so that when the belt tension is reduced, the restraining force against the movement of the piston 3 is small, and the damping force against the operation of the tensioner in the belt pressing direction is small. Therefore, the belt tension increases quickly.
[0032]
When the belt tension is reduced, the magnetic particles in the magnetorheological fluid 2 are attracted to the permanent magnet 11 in the first and second fluid chambers 4 and 5 of the magnetorheological fluid damper, and the magnetic particles in the vicinity of both ends of the fluid passage 7 are respectively provided. In other regions in each of the fluid chambers 4 and 5, the magnetic viscous fluid 2 has a small magnetic particle content. Therefore, the situation where the inner wall surface of the cylinder body 1 in the fluid chambers 4 and 5 is worn by the magnetic particles is less than that in the conventional case where the magnetic particles are substantially uniformly diffused in the magnetic viscous fluid.
[0033]
On the other hand, when the belt tension increases, the tensioner operates such that the pressing member is displaced in the direction opposite to the belt pressing direction by the belt tension, and the operation of the pressing member is transmitted to the piston 3 via the rod 6. . Accordingly, the piston 3 moves in a direction (leftward in FIG. 2) in which the volume of the first fluid chamber 4 is small and the volume of the second fluid chamber 5 is large, contrary to the above case. With this movement, the magnetorheological fluid 2 in the first fluid chamber 4 moves to the second fluid chamber 5 through the fluid passage 7. At the same time, power is supplied to each electromagnet 8 and a magnetic force is generated by each electromagnet 8, so that the flow resistance of the magnetorheological fluid 2 in the fluid passage 7 increases. Thus, the change in the volume of the first and second fluid chambers 4 and 5 is greatly suppressed, and the restraining force against the movement of the piston 3 in the above-described direction increases. In other words, when the belt tension is increased, the damping force for the operation in the direction opposite to the belt pressing direction of the tensioner is large. Therefore, immediately after that, the amount of operation of the tensioner in the belt pressing direction when the belt tension sharply decreases is small. As a result, the fluttering of the belt due to the fluctuation of the tension is properly suppressed.
[0034]
When the belt tension increases, in the first fluid chamber 4 in which the magnetorheological fluid 2 flows into the fluid passage 7 in the magnetorheological fluid damper, since the magnetic force of the permanent magnet 11 is smaller than the magnetic force of the electromagnet 8, the permanent magnet 11 The movement of the magnetic particles that have been drawn to the fluid passage 7 is allowed. As a result, the magnetorheological fluid 2 having a high magnetic particle content flows into the fluid passage 7.
[0035]
Therefore, according to the present embodiment, in the cylinder type magnetorheological fluid damper, the magnetic force in the fluid passage 7 communicating the first and second fluid chambers 4, 5 defined by the piston 3 in the cylinder body 1 to each other. When the electromagnets 8, 8,... Do not generate a magnetic force with respect to the viscous fluid 2, the permanent magnets 11, 11 separate the magnetic particles in the magnetic viscous fluid 2 in each of the fluid chambers 4, 5 into both ends of the fluid passage 7. When the electromagnets 8, 8,... Generate magnetic force and the magnetorheological fluid 2 in the first fluid chamber 4 flows into the fluid passage 7, the magnetic force of the permanent magnets 11, 11 is reduced. Since the magnetic particles are smaller than the electromagnets 8, 8,..., The movement of the magnetic particles unevenly distributed in the vicinity of the end of the fluid passage 7 near the first fluid chamber 4 to the fluid passage 7 can be allowed. Two fluid chamber 4, In the body wall, while it is possible to avoid premature degradation by the magnetic particles, within the fluid passage 7, it can be secured over a long period of time magneto-rheological properties of magnetorheological fluid 2 by the magnetic particles. Further, in the region other than the region of the fluid passage 7 and the region near the both ends, the working fluid may be the magnetic viscous fluid 2 having a low magnetic particle content or the oil not containing the magnetic particles. It can also contribute to cost reduction of the type magnetorheological fluid damper.
[0036]
In the above embodiment, the permanent magnets 11 are used as the uneven distribution means. However, an electromagnet may be used instead of the permanent magnet 11. In that case, when the electromagnet 8 is not generating a magnetic force, a magnetic force is generated, while when the electromagnet 8 is generating a magnetic force, a magnetic force smaller than the magnetic force is generated, or the magnetic force is generated. It is good to stop itself.
[0037]
Further, in the above embodiment, the fluid passage 7 is formed by the gap between the inner peripheral surface of the cylinder body 1 and the outer peripheral surface of the piston 3, but the piston 3 penetrates the piston 3 in the axial direction. An orifice may be provided and constituted by the orifice.
[0038]
Further, in the above embodiment, the electromagnet 8 is used as the magnetic force applying means. For example, the required damping characteristics do not have directivity, and the magnitude of the damping force in each direction is the same. In some cases, a permanent magnet may be used.
[0039]
Further, in the above embodiment, the case of the cylinder type magnetorheological fluid damper is described, but the present invention is applied to various shock absorbers using magnetorheological fluid including other types of magnetorheological fluid dampers. can do.
[0040]
【The invention's effect】
As described above, according to the first aspect of the present invention, the magnetic force applying means applies the magnetic viscous fluid to the magnetorheological fluid in the fluid passage communicating the two fluid chambers defined by the second member in the hollow portion of the first member. In the shock absorber configured to restrict the relative movement of the second member by applying a magnetic force, the magnetic particles in the magnetorheological fluid can be unevenly distributed in the region on the fluid passage side by the uneven distribution means, In the region, the viscosity characteristics of the magnetorheological fluid by the magnetic particles can be ensured for a long period of time, while in the other regions, the magnetic particles wear out the inner wall surface of the first member in each of the fluid chambers. Deterioration can be avoided. In the other regions, a magnetic viscous fluid containing a small amount of magnetic particles or a working fluid containing no magnetic particles can be used, which can contribute to cost reduction.
[0041]
According to the second aspect of the present invention, when the magnetic force applying means is an electromagnet, when the magnetic force is applied by the magnetic force applying means, the magnetic viscous force in the fluid chamber is increased with respect to the uneven distribution means arranged near both ends of the fluid passage. Since the movement of the magnetic particles in the fluid into the fluid passage can be allowed, the effect according to the first aspect of the present invention can be obtained without impairing the magnetorheological characteristics of the magnetic particles in the fluid passage.
[0042]
According to the third aspect of the present invention, since the magnetic particles can be unevenly distributed with a smaller magnetic force than the magnetic force applying means by the permanent magnet as the uneven distribution means, the fluid passage is provided when the magnetic force is applied by the magnetic force applying means. The movement of the magnetic particles unevenly distributed in the vicinity of the both ends into the fluid passage can be permitted, and the effect of the second aspect of the invention can be specifically obtained.
[0043]
According to the fourth aspect of the present invention, when the magnetic force applying means does not generate a magnetic force, the magnetic particles are strongly unevenly distributed by the electromagnet as the uneven distribution means, while the magnetic force applying means generates the magnetic force. Since the movement of the magnetic particles into the fluid passage can be permitted with a magnetic force smaller than at least the magnetic force applying means, the magnetic particles can be distributed more efficiently than in the case of the third aspect of the present invention. .
[0044]
According to the fifth aspect of the present invention, when the piston as the second member inserted into the cylinder body as the first member moves by the kinetic energy imparted to the piston, the magnetic force applying means is provided in the fluid passage. By applying a magnetic force to the magnetorheological fluid inside the magnetron damper, the movement of the piston is restrained to attenuate the kinetic energy, thereby avoiding early deterioration due to magnetic particles without reducing the damping characteristics. And cost reduction can be achieved.
[Brief description of the drawings]
FIG. 1 is a vertical cross-sectional view schematically showing an overall configuration of a cylinder type magnetorheological fluid damper according to an embodiment of the present invention when a damping force is small.
FIG. 2 is a diagram corresponding to FIG. 1, schematically showing the entire configuration when the damping force of a cylinder type magnetic viscous fluid damper is large.
FIG. 3 is a diagram corresponding to FIG. 1, schematically showing the entire configuration of a conventional cylinder type magnetorheological fluid damper when the damping force is small.
FIG. 4 is a diagram corresponding to FIG. 2, schematically showing an overall configuration when a damping force of a conventional cylinder type magnetorheological fluid damper is large.
[Explanation of symbols]
1 cylinder body (first member)
2 Magnetic viscous fluid 3 Piston (second member)
4 First fluid chamber (fluid chamber)
5 Second fluid chamber (fluid chamber)
7 fluid passage 8 electromagnet (magnetic force applying means)
11 Permanent magnets (localized means)

Claims (5)

A first member having a hollow portion,
A second member which is disposed in the hollow portion of the first member so as to be relatively movable with respect to the first member, and defines two fluid chambers each filled with a magnetorheological fluid containing magnetic particles; ,
A fluid passage that is provided so as to communicate the two fluid chambers with each other, and that moves the magnetorheological fluid between the two fluid chambers with the relative movement of the second member;
A damping device using a magnetorheological fluid comprising: a magnetorheological fluid in the fluid passage, the magnetorheological fluid having a viscosity increasing, and a magnetic force applying means for applying a magnetic force so that the relative movement of the second member is restricted.
A buffer device using a magnetorheological fluid, comprising: an uneven distribution means for attracting magnetic particles in each of the magnetorheological fluids in the two fluid chambers by magnetic force and unevenly distributing the magnetic particles to a region on the fluid passage side. A shock absorber using the magnetorheological fluid according to claim 1,
The magnetic force applying means is an electromagnet that is supplied with power and generates a magnetic force,
The uneven distribution means are disposed near both ends of the fluid passage, and when the magnetic force applying means does not generate a magnetic force, the magnetic particles in the magnetorheological fluid in each fluid chamber are respectively moved to the end of the fluid passage. While the magnetic force applying means is generating a magnetic force, the magnetic particles are allowed to move into the fluid passage in the magnetic viscous fluid in each fluid chamber, respectively. A shock absorber using a magnetorheological fluid. A shock absorber using the magnetorheological fluid according to claim 2,
The uneven distribution means is a permanent magnet that constantly generates a magnetic force smaller than the magnetic force applying means, wherein the shock absorber uses a magnetorheological fluid. A shock absorber using the magnetorheological fluid according to claim 2,
The uneven distribution unit is an electromagnet that generates a magnetic force at least smaller than the magnetic force application unit when the magnetic force application unit is generating a magnetic force, wherein the buffer device is a magnetorheological fluid. A shock absorber using the magnetorheological fluid according to claim 1, 2, 3, or 4,
The first member is a cylinder body,
The second member is a piston provided to reciprocate in the cylinder body by kinetic energy imparted to the second member,
A magnetic viscous fluid characterized in that the magnetic force applying means applies a magnetic force to the magnetic viscous fluid in the fluid passage, thereby restricting the movement of the piston due to the kinetic energy and attenuating the kinetic energy. Shock absorber using.

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