JP2004270719A - Adjustable damping force type damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand an adjustable range of damping force without enlarging an apparatus by increasing the number of electromagnets in a cylinder type adjustable damping force damper which can increase the resistance against the linear movement of a piston in a cylinder body by increasing the shearing stress of magnetorheological fluid contained in a fluid passage by the magnetic force generated in a magnetic circuit formed using electromagnets. <P>SOLUTION: Two magnetic circuits 21, 22 are formed such that shearing stress S<SB>1</SB>, S<SB>2</SB>of magnetorheological fluid 2 contained in two fluid passages 7, 8 are increased respectively using one electromagnet 9 in common. In this case, the sum of the shearing stresses S1, S2 is set to be larger than the shearing stress S of the magnetorheological fluid 2 caused by one magnetic circuit formed using the electromagnet 9 as written by the following equation, (S<SB>1</SB>+S<SB>2</SB>>S). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a damping force variable damper that changes a damping force in accordance with a magnetic force applied to a magnetic viscous fluid by a magnetic circuit formed by using an electromagnet, and in particular, enlarges a device by adding an electromagnet. The present invention relates to a measure for expanding a variable range of a damping force by energizing an electromagnet while avoiding the problem.
[0002]
[Prior art]
As this type of damper, a damper described in Patent Document 1 is known. For example, in the case of a rotary damping force variable damper, as shown in FIG. As the volumes of the two fluid chambers c and d change in opposite directions when the body b rotates, the magnetorheological fluid e will pass through the fluid passage f which is an annular gap in the central flow control mechanism. In this case, the shearing stress of the magnetorheological fluid e in the fluid passage f is changed in accordance with the turning on and off of the power supply to the electromagnet g, thereby changing the passage resistance of the magnetorheological fluid e in the fluid passage f. Thus, the damping force against the rotation of the cylindrical body b is changed.
[0003]
Specifically, when the power is turned on, a magnetic circuit is formed for each of a plurality of electromagnets g arranged via spacers along the fluid passage f, and a magnetic force is applied to the magnetorheological fluid e in the fluid passage f. As a result, a large shear stress is generated in the magnetorheological fluid e, so that the damping force with respect to the rotation of the cylindrical body b increases. On the other hand, when the power is turned off, the shear stress decreases and the magnetorheological fluid e flows through the fluid passage f. Since it is possible to pass through quickly, the damping force with respect to the rotation of the cylinder b is reduced.
[0004]
[Patent Document 1]
JP-A-7-332427 (pages 4 and 5, FIGS. 14 and 15)
However, in the above-mentioned conventional damping force variable damper, if the minimum value of the damping force is reduced or the maximum value is increased to expand the variable range, the electromagnets g of a corresponding number are set along the flow path f. And the number of components such as the electromagnet g (specifically, a core and an electromagnetic coil) and spacers increases, and the installation space for the electromagnet g is required, thus increasing the size of the device. There is a problem of doing.
[0005]
That is, in order to reduce the minimum value of the damping force, it is necessary to increase the flow path area by that much. However, by itself, the maximum value of the damping force is also reduced, and therefore, as much as the flow path area is increased, It is necessary to increase the number of electromagnets. On the other hand, to increase the maximum value of the damping force, the number of electromagnets must be increased accordingly.
[0006]
The “magnetic viscous fluid” refers to a magnetic particle having a particle diameter of 0.5 to 100 μm dispersed and contained in a medium such as a hydrocarbon-based or silicone-based medium. The method of dispersing and the damping characteristics are greatly different from those of the "magnetic fluid" in which extremely small magnetic particles are dispersed and contained in a medium, and the application fields are also greatly different.
[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 apply a magnetic force to a magnetorheological fluid by a magnetic circuit formed by using an electromagnet to change the damping force. It is an object of the present invention to provide a variable damper capable of securing or widening a variable range of the damping force without increasing the number of electromagnets and enlarging the device.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a plurality of magnetic circuits are formed using one electromagnet, whereby a variable range of damping force is secured or widened without increasing the number of electromagnets. I was able to do it.
[0009]
More specifically, according to the first aspect of the present invention, a housing member for housing a magneto-rheological fluid that changes shear stress in accordance with an applied magnetic force, and two fluid chambers are formed in the housing member, and the two fluid chambers are formed. A partition member displaceable with respect to the housing member so as to change the volumes of the two fluid chambers in directions opposite to each other, a fluid passage provided to communicate the two fluid chambers, and a magnetorheological fluid in the fluid passage. It is premised on a damping force variable damper including an electromagnet for forming a magnetic circuit for applying a magnetic force to a fluid.
[0010]
A plurality of magnetic circuits are formed for each electromagnet, and a plurality of fluid passages are formed accordingly.
[0011]
In the above configuration, in the variable damping force damper, for example, when the power is ON, a plurality of magnetic circuits are formed on the electromagnet, and the plurality of magnetic circuits apply a magnetic force to the magnetorheological fluid in the plurality of fluid passages. This increases the shear stress of the magnetorheological fluid and increases the shearing resistance of the magnetorheological fluid in the fluid passage, so that the passage of the magnetorheological fluid in the fluid passage due to the displacement of the partition member with respect to the housing member. Thus, the damping force against the displacement of the partition member is increased.
[0012]
On the other hand, when the power supply to the electromagnet is turned off, for example, the magnetic circuit disappears, the application of magnetic force to the magnetorheological fluid in the fluid passage stops, and the shearing resistance due to the magnetorheological fluid decreases. Becomes smaller.
[0013]
At this time, when the power to the electromagnet is turned on, a plurality of magnetic circuits are formed for each electromagnet, so that the number of magnetic circuits can be increased without increasing the number of electromagnets. Unlike the case where one magnetic circuit is formed, the variable range of the damping force can be widened without increasing the number of electromagnets and enlarging the device. In other words, this means that the number of electromagnets can be reduced and the device can be miniaturized without narrowing the variable range of the damping force.
[0014]
According to the second aspect of the present invention, in the first aspect of the present invention, the total value of the shear stress of the magnetic viscous fluid by the plurality of magnetic circuits formed for each electromagnet is determined when one magnetic circuit is formed for each electromagnet. It is assumed that the magnetic circuit is configured to be larger than the value of the shear stress of the magnetic viscous fluid by the one magnetic circuit.
[0015]
The shear stress of the magnetic viscous fluid by the magnetic circuit formed using the electromagnet changes according to the magnetic flux density of the magnetic circuit. On the other hand, the magnetic flux density of the magnetic circuit is divided according to the number of magnetic circuits sharing the electromagnet, and the magnetic flux density of the magnetic circuit when one magnetic circuit is formed for each electromagnet and a plurality of magnetic circuits for each electromagnet Is formed, the sum of the magnetic flux densities of the magnetic circuits is equal, so that if the relationship between the shear stress and the magnetic flux density is linear, even if a plurality of magnetic circuits are formed for each electromagnet, the shear stress Are the same.
[0016]
However, it is known that the relationship between the shear stress and the magnetic flux density is non-linear, and by utilizing this, the shearing of the magnetorheological fluid in a plurality of fluid passages by a plurality of magnetic circuits formed for each electromagnet is utilized. The total value of the stresses can be greater than the value of the shear stress of the magneto-rheological fluid by one magnetic circuit when one magnetic circuit is formed for each electromagnet, so that the electromagnet It is possible to increase the maximum value of the damping force and widen the variable range while avoiding an increase in the number of devices and an increase in the size of the device.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
1 and 2 schematically show the overall configuration of a cylinder-type (also referred to as a telescopic type) variable damping force damper according to an embodiment of the present invention.
[0019]
This damper has a cylinder body 1 as a housing member having a cylindrical shape and closed at both ends. A magnetic viscous fluid 2 in which magnetic particles are dispersed and contained in a medium is sealed in the cylinder body 1. In addition, a piston 3 as a partition member is fitted in the cylinder body 1 so as to be movable in the left-right direction in FIG. 1, whereby the piston 3 moves in the cylinder body 1 in accordance with the movement of the piston 3. Two fluid chambers 4, 5 whose volumes change in opposite directions are defined.
[0020]
On the fluid chamber 5 side (the right side in FIG. 1) of the cylinder body 1, a rod 6 provided so as to move integrally with the piston 3 is disposed so as to extend longitudinally through the fluid chamber 5. Note that a portion of the end wall of the cylinder body 1 where the rod 6 penetrates is sealed by a sealing mechanism (not shown) so that the magnetorheological fluid 2 in the cylinder body 1 does not leak outside.
[0021]
Between the fluid chamber 4 and the fluid chamber 5, there are provided two outer and inner fluid passages 7 and 8, which communicate the fluid chambers 4 and 5, respectively. By moving, the magnetorheological fluid 2 relatively moves through the fluid passages 7 and 8. An outer magnetic circuit 21 and an inner magnetic circuit 22 to be described later are formed in each of the fluid passages 7 and 8, respectively. When these magnetic circuits 21 and 22 are not formed, the piston 3 When the magnetic circuits 21 and 22 are formed, the magnetic viscous fluid 2 exhibits a relatively small flow resistance with the change in the volume of the fluid chambers 4 and 5. The magnetic particles in the magnetorheological fluid 2 form a cluster, and the viscous resistance (shear stress) to the movement of the piston 3 increases.
[0022]
Specifically, the outer fluid passage 7 is formed by an annular gap between the cylinder body 1 and the piston 3. Further, a gap is formed in the piston 3 so as to penetrate the piston 3 in the axial direction, and to form a circular cross section at both ends in the axial direction and an annular shape at the center in the axial direction. The inner fluid passage 8 is formed. The gap in the radial direction at both axial ends of the fluid passages 7 and 8 is usually about 0.7 to 0.8 mm, and is set according to the variable damping force range.
[0023]
An outer peripheral portion 3a, which is a portion of the piston 3 closer to the outer periphery than the inner fluid passage 8, is made of a ferromagnetic material. The outer peripheral portion 3a has a large diameter with the same diameter at both axial ends, and a small diameter at the axial central portion, and is a core of the electromagnet 9 for forming the magnetic circuits 21 and 22. Is configured. The electromagnetic coil 10 of the electromagnet 9 is accommodated in a concave groove 3b formed in the central portion in the axial direction of the outer peripheral surface so as to extend in the circumferential direction because the central portion in the axial direction has a small diameter.
[0024]
The cylinder body 1 is made of a ferromagnetic material. When power is supplied to the electromagnetic coil 10, the cylinder body 1 moves from one axial end of the outer peripheral portion 3 a of the piston 3 to the shaft of the outer fluid passage 7. An outer magnetic circuit 21 is formed to reach one end in the axial direction, the other end in the axial direction of the cylinder body 1 and the outer fluid passage 7 to the other end in the axial direction of the outer peripheral portion 3a of the piston 3.
[0025]
On the other hand, the inner peripheral portion 3c, which is a portion of the piston 3 closer to the inner fluid side than the inner fluid passage 8, is also made of a ferromagnetic material, and both ends in the axial direction are formed to have the same large diameter. The central portion in the axial direction is formed to have a small diameter, so that when power is supplied to the electromagnetic coil 10, one end in the axial direction of the outer peripheral portion 3 a of the piston 3 is moved to one end in the axial direction of the inner fluid passage 8. The inner magnetic circuit 22 is formed to reach the other axial end of the outer peripheral portion 3a of the piston 3 via the inner peripheral portion 3c of the piston 3 and the other axial end of the inner fluid passage 8. I have.
[0026]
Incidentally, examples of the ferromagnetic material include soft iron, Fe-Si alloy, Fe-Al alloy, permalloy, and mu metal. Further, a circular end plate made of a non-magnetic material (for example, brass or the like) for suppressing magnetic fluxes of the outer and inner magnetic circuits 21 and 22 from leaking into the fluid chambers 4 and 5 is provided at both axial ends of the piston 3. 11 and 11 are attached integrally with the movable body.
[0027]
That is, in the present embodiment, in a damping force variable damper having two fluid passages 7 and 8, two electromagnets are arranged in parallel (one for each fluid passage) in the conventional case. One electromagnet 9 is arranged.
[0028]
Here, the reason why a large damping force can be obtained in the damper in which one electromagnet 9 forms two outer and inner magnetic circuits 21 and 22 as described above will be described.
[0029]
In the magnetorheological fluid 2, the magnetic particles are arranged in a direction substantially perpendicular to the flow paths 7, 8 according to the strength of the applied magnetic field (magnetic flux density), and the viscous resistance (shear stress to the movement of the piston 3) is reduced. To increase. The applied magnetic flux density and the shear stress generated in the magneto-rheological fluid 2 show an S-shaped nonlinear relationship as shown in FIG. 3, and the S-shaped nonlinear relationship with a straight line regarded as linear (broken line in FIG. 3). In addition to the area A where the curve is lower and the change in the shear stress is smaller than the change in the magnetic flux density, the effect area where the S-type nonlinear curve is higher and the change in the shear stress is larger than the change in the magnetic flux density It is known that there exists a saturation region C in which the shear stress does not change even when the magnetic flux density is increased.
[0030]
In the present embodiment, utilizing the relationship between the magnetic flux density and the shear stress, the magnetic flux densities X ₁ and X ₂ of the _two magnetic circuits 21 and 22 formed in parallel by one electromagnet 9 are used to determine the effect area. By setting B, a shear stress (S ₁ + S ₂ > S) larger than a shear stress S of one electromagnet having a magnetic flux density X (= X ₁ + X ₂ ) obtained by combining the two is obtained. I have. If each of the magnetic flux densities X ₁ and X _{2 is set} to the saturation region C, the shearing stress (2S) equivalent to the shearing stress (2S) by two magnetic circuits formed by two electromagnets arranged in series along the cylinder body 1. Stress can be obtained with one electromagnet. In the magnetic circuit shown in FIG. 4A, generally, there is a relation of Φ = F / R between the magnetomotive force F, the magnetic flux Φ, and the magnetic resistance R. the, X = Φ / α: there is a relation of (alpha unit area), for example, a magnetic flux density X ₁ of the outer magnetic circuit 21, to make equal to the flux density X ₂ of the inner magnetic circuit 22, the in a magnetic circuit shown in FIG. (b), a magnetic resistance R ₁ of the outer magnetic circuit 21 may be such that the magnetic resistance R ₂ of the inner magnetic circuit 22 become equal.
[0031]
That is, if two fluid passages 7 and 8 are provided for one electromagnet 9 and a shear stress is generated in each of the effect areas B, two electromagnets forming one magnetic circuit are connected in series. Compared to the conventional case in which a shear stress is generated by arranging, only one electromagnet 9 suffices, so that the space for arranging the electromagnet can be reduced and the device can be downsized, and the length of the fluid passage can be reduced. As a result, the damping force at the time of power-off is reduced, and at the time of power-on, a shearing stress (damping force) equal to or close to that of the conventional case is obtained. Become.
[0032]
Therefore, according to the present embodiment, in a cylinder type variable damping force type damper having two fluid passages 7 and 8, in the conventional case, it is necessary to arrange two electromagnets in series via a spacer. One electromagnet 9 is sufficient as compared with the case, and accordingly, the number of parts constituting the electromagnet can be reduced and the size can be reduced.
[0033]
In addition, the total value of the shear stresses S ₁ and S ₂ of the magnetic viscous fluid 2 by the two magnetic circuits 21 and 22 forms one magnetic circuit using an electromagnet having the same magnetomotive force F as the electromagnet 9 described above. Is larger than the value of the shear stress S of the magnetic viscous fluid 2 by the one magnetic circuit (S ₁ + S ₂ > S), so that the maximum value of the damping force at power-on is increased to attenuate the damping force. The variable range of force can be widened.
[0034]
In the above-described embodiment, in order to form the magnetic circuits 21 and 22, the entire cylinder body 1 and substantially the entire piston 3 are made of a ferromagnetic material. Only a necessary portion may be made of a ferromagnetic material, or a member made of a ferromagnetic material may be arranged at a necessary position.
[0035]
In the above embodiment, two magnetic circuits 21 and 22 are formed using one electromagnet 9, but three or more magnetic circuits are formed using one electromagnet 9. You may.
[0036]
In the above embodiment, only one electromagnet 9 is used. However, for example, a plurality of electromagnets may be arranged along the fluid passage.
[0037]
Further, in the above embodiment, the case of the cylinder type damping force variable damper has been described. However, the present invention is applicable to various damping force variable dampers such as the rotary type damper described in the section of the related art. Can be.
[0038]
【The invention's effect】
As described above, according to the first aspect of the present invention, since a plurality of magnetic circuits are formed by one electromagnet, the damping force can be varied without increasing the number of electromagnets and enlarging the device. The range can be widened, and the size of the device can be reduced by reducing the number of electromagnets without narrowing the variable range of the damping force.
[0039]
According to the invention of claim 2, the total value of the respective shear stresses of the magneto-rheological fluid by the plurality of magnetic circuits sharing the electromagnet is equal to the shear stress of the magneto-rheological fluid by one magnetic circuit formed by using the electromagnet. Since it is larger than the value, the effect according to the first aspect of the invention can be obtained efficiently.
[Brief description of the drawings]
FIG. 1 is a vertical cross-sectional view schematically showing an overall configuration of a cylinder-type variable damping force damper according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line II-II of FIG.
FIG. 3 is a magnetic circuit diagram showing an outer and inner magnetic circuit (a) formed by using one electromagnet and two magnetic circuits (b) formed by using the same electromagnet.
FIG. 4 is a characteristic diagram showing a relationship between a magnetic flux density and a shear stress in a magnetic viscous fluid.
FIG. 5 is a diagram corresponding to FIG. 1, schematically showing the entire configuration of a conventional rotary damping force variable damper.
[Explanation of symbols]
1 cylinder body (accommodating member)
2 Magnetic viscous fluid 3 Piston (compartment member)
4,5 Fluid chamber 7 Outer fluid passage (fluid passage)
8. Inner fluid passage (fluid passage)
9 Electromagnet 21 Outside magnetic circuit (magnetic circuit)
, 22 Inside magnetic circuit (magnetic circuit)

Claims (2)

An accommodating member for accommodating a magnetic viscous fluid that changes shear stress according to an applied magnetic force,
A partition member that defines two fluid chambers in the housing member and is displaceable relative to the housing member so as to change the volumes of the two fluid chambers in opposite directions;
A fluid passage provided to communicate the two fluid chambers,
An electromagnet for forming a magnetic circuit that applies a magnetic force to the magnetorheological fluid in the fluid passage, and a damping force variable damper including:
A variable damping force damper, wherein a plurality of the magnetic circuits are formed for each of the electromagnets. The damping force variable damper according to claim 1,
The total value of the shear stress of the magneto-rheological fluid by the two magnetic circuits formed for each electromagnet is the value of the shear stress of the magneto-rheological fluid by the one magnetic circuit when one magnetic circuit is formed for each electromagnet A variable damping force type damper characterized by being configured to be larger than the above.

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