JP2004076759A - Magnetic viscosity fluid device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic viscosity fluid damper for giving greater constraining force to a piston 3 to be moved by using an electromagnet 9 for applying magnetic force to a magnetic viscosity fluid 2 in a fluid passage 8 communicating a first fluid chamber 4 and a second fluid chamber 5 partitioned with the piston 3 with each other when the piston 3 is moved to a rod protruding direction while giving smaller constraining force to the piston 3 to be moved by stopping the magnetic force when the piston 3 is moved to a rod set-in direction, allowing sufficient constraint of the piston 3 to be moved even when the piston is moved to the rod set-in direction at a very low speed. <P>SOLUTION: The electromagnet 9 is provided extending along a cylinder body 1, and an extending portion 10 thereof applies the magnetic force to the magnetic viscosity fluid 2 in the first fluid chamber 4 located on the front side of the piston 3 in its moving direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetorheological fluid device such as a fluid damper that restricts the movement of a piston by utilizing the magnetorheological characteristics of a magnetorheological fluid, and more particularly to a measure for increasing the constraint force on the movement of a piston.
[0002]
[Prior art]
Generally, in a hydraulic damper using oil as a working fluid, a good damping force is applied to an object to be applied by the structure and the viscosity of the oil.
[0003]
By the way, in the case of the above-mentioned hydraulic damper, it is difficult to obtain good damping characteristics over a wide range because the operation on the damping target is a passive mechanism and the damping characteristics are constant.
[0004]
On the other hand, as shown in FIG. 3, the applicant of the present application in the earlier application (Japanese Patent Application No. 2001-222097) applied a certain pressure to the belt in the belt-type accessory drive device of the automobile engine by a spring a. While applying pressure, the movement of the piston b in the direction opposite to the belt pressing direction (movement to the left in the drawing) when the belt tension is increased is changed by the fluid passage g communicating the two fluid chambers d and e. The oil is replaced by a magnetic viscous fluid (MRF) for the hydraulic belt tensioner which is configured to attenuate the tension vibration of the belt by constraining by the flow path resistance of the belt. By applying a magnetic force to the magnetorheological fluid in the passage g, an active damping mechanism is provided to increase the viscosity and increase the flow path resistance of the fluid passage g, thereby providing good damping. It has proposed a technique to be able to widen the range capable of obtaining sex.
[0005]
Here, the vibration model of the hydraulic belt tensioner is as shown in FIG. 4, and the equation of motion is such that the mass of the movable part including the piston b is m, the displacement of the movable part from the balanced position is x, and Assuming that the viscous damping constant is c, the spring constant of the spring a is k, and the belt tension is F (t), the following equation 1 is obtained. In this equation, c (dx / dt) is a dashpot element, and kx is a spring element.
[0006]
m (dx / dt) ² + c (dx / dt) + kx = F (t). . . . [1]
However, even in the above proposed example, when the moving speed of the piston b is very slow, there is a disadvantage that a sufficient restraining force cannot be exerted. Furthermore, since it is difficult to hold the piston b at a fixed moving position, there is a problem that the piston b cannot be used for applications such as a brake device and a lock device.
[0007]
[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 change the viscosity by applying a magnetic force to a magnetorheological fluid in a fluid passage communicating with two fluid chambers by a magnetic force applying means. In a magnetorheological fluid device such as a magnetorheological fluid damper that changes the restraining force against the movement of the piston, if the movement speed of the piston is extremely slow or if the piston is held at a fixed movement position, sufficient An object of the present invention is to make it possible to exert a damping force and a holding force and to be used for applications such as a brake device and a lock device.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a magnetic force is applied to a plurality of magnetorheological fluids in a body, so that a restraining force against movement of a piston can be increased.
[0009]
Specifically, according to the first aspect of the present invention, a hollow body, and a piston movably disposed in the body and defining two fluid chambers each filled with a magnetorheological fluid, When the piston moves in at least one direction, the viscosity of the magnetorheological fluid in the fluid passage increases, and the restraining force against the movement of the piston is increased when the piston moves in at least one direction. A magnetic viscous fluid device including a magnetic force applying means for applying a magnetic force so as to increase the size is assumed.
[0010]
The magnetic force applying means is a first magnetic force applying means, and when a magnetic force is applied to the magnetorheological fluid in the fluid passage by the first magnetic force applying means, the fluid chamber located on the front side in the movement direction of the piston. Second magnetic force applying means for applying a magnetic force to the magnetorheological fluid to increase the viscosity and generate a restraining force against the movement of the piston.
[0011]
In the above configuration, when the piston moves in one direction, the first magnetic force applying means applies a magnetic force to the magnetorheological fluid in the fluid passage, and the viscosity of the magnetorheological fluid increases. The passage resistance of the passage increases. Therefore, a restricting force due to an increase in the flow path resistance of the fluid passage is applied to the movement of the piston.
[0012]
At this time, the magnetic force is applied by the second magnetic force applying means to the magnetorheological fluid in the fluid chamber located on the front side in the movement direction of the piston, so that the viscosity of the magnetorheological fluid in this fluid chamber also increases, and the piston becomes plastic. You will receive the same restraining force as moving inside. Therefore, in addition to the flow path resistance of the fluid passage, a restraining force due to the increase in viscosity of the magnetic viscous fluid in the fluid chamber on the front side in the movement direction is applied, so that the restraining force against the movement of the piston, that is, the damping force is increased accordingly.
[0013]
According to a second aspect of the present invention, in the first aspect of the present invention, when the first magnetic force applying means is arranged on the body side of the body and the piston, the first magnetic force applying means has at least one piston. The piston extends along the body so that a magnetic force can also be applied to the magnetorheological fluid in the fluid chamber located on the front side in the moving direction of the piston when moving in the moving direction. The second magnetic force applying means is constituted by an extension of the first magnetic force applying means.
[0014]
In the above configuration, since the second magnetic force applying means is constituted by an extended portion of the first magnetic force applying means, the second magnetic force applying means is different from the case where the dedicated second magnetic force applying means is provided separately from the first magnetic force applying means. The structure of the magnetorheological fluid device is simplified.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 shows an overall configuration of a magnetorheological fluid damper according to an embodiment of the present invention. The magnetorheological fluid damper applies a predetermined tension to a belt in a belt-type accessory drive device of an automobile engine. In order to constitute the tensioner as described above, the tension pulley is used in combination with a belt pressing portion which holds the tension pulley so as to be swingable in the belt pressing direction and the opposite direction.
[0017]
Although not shown, the belt pressing portion holds a fixing member fixed to a cylinder block of an automobile engine and the tension pulley so as to be rotatable around its axis, and extends in parallel with the axis. A rotation member rotatably supported by the fixed member about an extending axis.
[0018]
The magneto-rheological 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, so that the volume of the cylinder body 1 changes in accordance with the movement of the piston 3. First and second two fluid chambers 4 and 5 are defined.
[0019]
A rod 6 that penetrates in the moving direction of the piston 3 and moves integrally with the piston 3 is disposed on an end wall of the cylinder body 1 on the second fluid chamber 5 side (the right side in FIG. 1). . The end of a rod 6 located inside the cylinder body 1 is connected to the piston 3. Between the cylinder body 1 and the piston 3 in the first fluid chamber, a compression coil spring 7 arranged along the moving direction of the piston 3 is contracted, whereby the piston 3 Are always urged in a direction (right direction in the figure) to project from the cylinder body 1.
[0020]
This magnetorheological fluid damper is arranged such that the projecting direction of the rod 6 substantially coincides with the belt pressing direction of the belt pressing portion. The end of the rod 6 located outside the cylinder body 1 is connected to the belt pressing portion. Is connected to the turning member. As a result, the rotating member of the belt pressing portion is constantly urged in the belt pressing direction, and when the belt tension decreases, the piston 3 moves in the direction in which the rod 6 protrudes from the cylinder body 1, while the belt 3 When the tension increases and the rotating member rotates in the anti-belt pressing direction, the rod 6 is retracted into the cylinder body 1 against the urging force of the compression coil spring 7 (to the left in FIG. 1). The piston 3 moves.
[0021]
In addition, when the belt tension decreases, the volume of the first fluid chamber 4 increases and the volume of the second fluid chamber 5 decreases with the movement of the piston 3, and when the belt tension increases, the volume of the piston 3 moves with the movement of the piston 3. The capacity of the first fluid chamber 4 is reduced and the capacity of the second fluid chamber 5 is increased.
[0022]
A fluid passage 8 is provided between the first fluid chamber 4 and the second fluid chamber 5 to communicate the fluid chambers 4 and 5 with each other. The movement of the magnetorheological fluid 2 between the two fluid chambers 4 and 5 due to the volume change of the 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 8 allows the fluid passage 8 to be moved by the cylinder. It is formed in an annular shape between the body 1 and the piston 3.
[0023]
A plurality of electromagnets 9, 9,... Are arranged on the side peripheral portion of the cylinder body 1 so as to be arranged in a circumferential direction. Each electromagnet 9 does not generate a magnetic force when the belt tension is reduced, but generates a magnetic force when the belt tension is increased and applies the magnetic force to the magnetorheological fluid 2 in the fluid passage 8.
[0024]
In the present embodiment, each of the electromagnets 9 extends along the cylinder body 1 so that a magnetic force can also be applied to the magnetorheological fluid 2 in the first and second fluid chambers 4 and 5. Each extended portion 10 constitutes a second magnetic force applying unit in the present invention.
[0025]
Here, the operation of the magnetorheological fluid damper configured as described above will be described.
[0026]
In the belt-type auxiliary device driving device for an automobile engine, when the belt tension is reduced, the piston 3 is biased by the compression coil spring 7 so that the volume of the first fluid chamber 4 is large and the volume of the second fluid chamber 5 is small ( (To the right in FIG. 1). At this time, since the power supply to each electromagnet 9 is stopped and no magnetic force is generated by each electromagnet 9, the viscosity of the magnetorheological fluid 2 in the fluid passage 8 is determined when the magnetism is not applied to the magnetorheological fluid 2. Level has dropped. Accordingly, the volume change of the first and second fluid chambers 4 and 5 due to the movement of the magnetorheological fluid 2 in the second fluid chamber 5 to the first fluid chamber 4 via the fluid passage 8 is relatively small. Since it is permitted while receiving the road resistance, the restraining force against the movement of the piston 3 in the belt pressing direction is relatively small.
[0027]
On the other hand, when the belt tension increases, the piston 3 acts against the urging force of the compression coil spring 7 in a direction in which the volume of the first fluid chamber 4 is small and the volume of the second fluid chamber 5 is large (left in FIG. 1). Direction). At this time, since a magnetic force is generated by each electromagnet 9, the flow path resistance in the fluid passage 8 increases.
[0028]
Further, the magnetic force generated by the two extending portions 10 of each electromagnet 9 is applied to the magnetorheological fluid 2 in the first and second fluid chambers 4 and 5, respectively. As a result, the viscosity of the magnetorheological fluid 2 in the first fluid chamber 4 increases, so that the magnetorheological fluid 2 becomes plastic, so that the movement of the piston 3 is restrained. That is, with respect to the movement of the piston 3 in the direction opposite to the belt pressing direction, the urging force of the compression coil spring 7, the increase in the flow path resistance of the fluid passage 8, and the magnetic viscosity in the first fluid chamber 4 are increased. A large restraining force due to the plasticization of the fluid 2 is applied.
[0029]
FIG. 2 is a vibration model when the movable part including the piston 3 vibrates due to the fluctuation of the belt tension. In the figure, m is the mass of the movable part, x is the displacement of the movable part from the balanced position, c Is a viscous damping constant in the fluid passage 8, f is a slider force by the high-viscosity magnetorheological fluid 2 in the first fluid chamber 4, and F (t) is a belt tension.
[0030]
The equation of motion of this vibration model is as shown in the following equation 2. In this equation, c (dx / dt) is a dashpot element, kx is a spring element, and f is a slider element. Here, the “slider element” is an element named from the point of exhibiting a characteristic similar to static friction that the object starts moving when the force applied to the object at rest reaches a certain value.
[0031]
m (dx / dt) ² + c (dx / dt) + kx + f = F (t). . . . [2]
From FIGS. 2 and 2, it can be seen that in the present embodiment, the restraining force against the movement of the piston 3 by the amount of the slider element f, compared to the case of the previously proposed example (see FIGS. 3 and 4). Is large.
[0032]
Therefore, according to the present embodiment, in the magnetorheological fluid bumper used for the tensioner in the belt-type accessory drive device of the automobile engine, the electromagnets 9, 9,. In addition to increasing the viscosity by applying a magnetic force to the magnetorheological fluid 2 in the fluid passage 8 and increasing the viscosity by applying a magnetism to the magnetorheological fluid 2 in the first fluid chamber 4, when the belt tension increases, Even when the moving speed of the piston 3 is very slow, the movement of the piston 3 can be sufficiently restrained. Further, when the belt tension is increased, a brake function or a lock function of restraining the piston 3 from moving from a certain moving position until the belt tension reaches a predetermined value can be exhibited.
[0033]
In addition, since each of the electromagnets 9 is extended along the cylinder body 1 and a magnetic force is applied to the magneto-rheological fluid 2 in the first fluid chamber 4 by the extended portion 10, the electromagnets 9 are separately provided. The structure of the device can be simplified as compared with a case where an electromagnet dedicated to the first fluid chamber is provided.
[0034]
In the above embodiment, the second magnetic force applying means is constituted by the extended portion 10 of each electromagnet 9 as the first magnetic force applying means. It may be configured. At this time, the configuration and characteristics of each electromagnet can be appropriately designed as needed.
[0035]
Further, in the above embodiment, the magnetic force is applied to the magneto-rheological fluid 2 in both the first and second fluid chambers 4 and 5, but depending on the required damping characteristics, either one of the fluids may be applied. The magnetic force may be applied only to the magnetic viscous fluid in the room.
[0036]
Further, in the above-described embodiment, the first and second magnetic force applying means are each configured by the electromagnet 9 and the extended portion 10 thereof, but may be configured by using a permanent magnet.
[0037]
Further, in the above-described embodiment, the case where the magneto-rheological fluid damper is used as a main component of the belt tensioner in the belt-type accessory drive device of the automobile engine is described. It can also be used for other applications such as a brake device and a lock device.
[0038]
【The invention's effect】
As described above, according to the first aspect of the invention, in the magneto-rheological fluid device, when the first magnetic force applying means applies a magnetic force to the magneto-rheological fluid in the fluid passage to increase the restraining force against the movement of the piston. Since the second magnetic force applying means applies a magnetic force to the magnetorheological fluid in the fluid chamber on the front side in the movement direction of the piston to generate a new constraint force on the movement of the piston, the constraint force on the movement of the piston is further increased. be able to. As a result, when the movement speed of the piston is very slow, particularly when the piston needs to be held at a fixed position, it is possible to exert a sufficient restraining force, so that not only as a damper device but also as a brake device It can also be used as a device or a lock device.
[0039]
According to the second aspect of the present invention, when the first magnetic force applying means is disposed on the body side, the first magnetic force applying means extends along the body to form the second magnetic force applying means. Therefore, the structure of the magneto-rheological fluid device can be simplified as compared with a case where a dedicated second magnetic force applying unit is provided separately from the first magnetic force applying unit.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing an overall configuration of a magneto-rheological fluid damper according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a vibration model of a magnetorheological fluid damper caused by a fluctuation in belt tension.
FIG. 3 is a diagram corresponding to FIG. 1, schematically showing an entire configuration of a magneto-rheological fluid damper of a proposed example.
FIG. 4 is a diagram corresponding to FIG. 2, showing a vibration model of a magneto-rheological fluid damper of a proposed example.
[Explanation of symbols]
1 Cylinder body (body)
2 Magnetic viscous fluid 3 Piston (piston)
4 First fluid chamber (fluid chamber)
5 Second fluid chamber (fluid chamber)
8 fluid passage 9 electromagnet (first magnetic force applying means)
10 Extension part (second magnetic force applying means)

Claims (2)

A hollow body,
A piston movably disposed within the body, each defining two fluid chambers filled with a magnetorheological fluid;
A fluid passage provided to communicate the two fluid chambers with each other;
Magnetic force applying means for applying a magnetic force to the magnetorheological fluid in the fluid passage so that the viscosity of the magnetorheological fluid increases and the constraint force on the movement of the piston increases when the piston moves in at least one direction. A magneto-rheological fluid device comprising:
The magnetic force applying means is a first magnetic force applying means,
When a magnetic force is applied to the magnetorheological fluid in the fluid passage by the first magnetic force applying means, the viscosity of the magnetorheological fluid is higher than the magnetorheological fluid in the fluid chamber located on the front side in the movement direction of the piston. And a second magnetic force applying means for applying a magnetic force so as to generate a restraining force against the movement of the piston. The magneto-rheological fluid device according to claim 1,
The first magnetic force applying means is disposed on the body side of the body and the piston, and also applies a magnetic force to a magnetorheological fluid in a fluid chamber located on the front side in the movement direction of the piston when the piston moves in at least one direction. Is extended along the body so that
The magnetorheological fluid device, wherein the second magnetic force applying means is constituted by an extension of the first magnetic force applying means.

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