JP2007303581A - Magnetic viscous fluid shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic viscous fluid shock absorber of a simple structure. <P>SOLUTION: This magnetic viscous fluid shock absorber has a cylinder 1 sealed with a magnetic viscous fluid of changing viscosity by the action of a magnetic field, a piston 2 movably arranged at a predetermined interval with the inner periphery of the cylinder 1 in the cylinder 1 and defining the inside of the cylinder 1 into two fluid chambers 3 and 4, a flow passage 6 passing the magnetic viscous fluid by the movement of the piston 2 in the cylinder 1, a coil 9 making the magnetic field act on the flow passage 6, and a rod 5 fixing the piston 2 to one end. The flow passage 6 is formed between the inner periphery of the cylinder 1 and the outer periphery of the piston 2. The coil 9 is stored in a case 7 joined to the outer periphery of the cylinder 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetorheological fluid shock absorber using a magnetorheological fluid whose apparent viscosity changes due to the action of a magnetic field.

  Some shock absorbers mounted on vehicles such as automobiles generate a damping force by applying a magnetic field to a flow path through which the magnetorheological fluid passes to change the apparent viscosity of the magnetorheological fluid.

  In this type of shock absorber, a coil that generates a magnetic field is generally disposed in a piston assembly that slides in a cylinder (for example, Patent Document 1).

On the other hand, Patent Document 2 discloses a structure in which a coil is provided outside a cylinder filled with a magnetorheological fluid. The shock absorber described in Patent Document 2 is provided with a tube on the outer periphery of a cylinder, connecting a coil and a piston rod via the tube, and generating a damping force by moving the cylinder.
JP 2006-029421 A US Pat. No. 6,382,369

  The shock absorber described in Patent Document 2 requires a tube for providing a coil outside the cylinder, a member for moving the cylinder, and the like, and thus has a large number of parts and a complicated structure. For this reason, the assembly of the shock absorber requires a lot of labor and cannot be produced efficiently.

  The present invention has been made in view of the above problems, and an object thereof is to provide a magnetorheological fluid shock absorber having a simple structure.

  The present invention includes a cylinder in which a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is sealed, and is disposed in the cylinder so as to be movable at a predetermined interval from the inner circumference of the cylinder. A magnet comprising: a defining piston; a flow path through which the magnetorheological fluid passes by movement of the piston in the cylinder; a coil for applying a magnetic field to the flow path; and a rod to which the piston is fixed at one end. In the viscous fluid buffer, the flow path is formed between an inner periphery of the cylinder and an outer periphery of the piston, and the coil is housed in a case coupled to the outer periphery of the cylinder.

  According to the present invention, since the structure for providing the coil outside the cylinder is only the case coupled to the outer periphery of the cylinder, the structure of the magnetorheological fluid shock absorber can be simplified with a small number of parts. .

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

  A magnetorheological fluid shock absorber 100 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a magnetorheological fluid shock absorber 100.

  The magnetorheological fluid shock absorber 100 is interposed between a vehicle body and an axle of a vehicle such as an automobile, and functions as a shock absorber that suppresses changes in the vehicle body posture.

  The magnetorheological fluid shock absorber 100 includes a cylindrical cylinder 1 and a piston 2 that is movably disposed in the cylinder 1 and that defines the cylinder 1 in two fluid chambers 3 and 4. The cylinder 1 and the piston 2 are made of a magnetic material.

  The piston 2 is fixed to one end of the rod 5. The other end of the rod 5 extends to the outside of the cylinder 1.

  A magnetorheological fluid is sealed in the cylinder 1. This magnetorheological fluid changes its apparent viscosity by the action of a magnetic field, and is a liquid in which fine particles having ferromagnetism are dispersed in a liquid such as oil. The viscosity of the magnetorheological fluid can be adjusted by changing the strength of the applied magnetic field and is restored to its original state by removing the magnetic field.

  A gas chamber (not shown) is provided in the cylinder 1 to compensate for volume changes in the cylinder 1 due to the entry and withdrawal of the rod 5.

  The piston 2 has a cylindrical shape, and the rod 5 passes through the through hole, and the outer periphery of the rod 5 is closely fitted to the inner periphery.

  One end of the piston 2 is locked to a step portion 5 a formed on the rod 5, and the other end is pressed by a tightening force of a nut 8 that is screwed to the tip of the rod 5. Thus, the piston 2 is clamped by the step 5 a of the rod 5 and the nut 8 and fixed to the rod 5.

  Since the piston 2 is positioned coaxially with the piston 1 by the rod 5 in the cylinder 1, the piston 2 is arranged at a predetermined minute interval from the inner periphery of the cylinder 1. As described above, an equal annular flow path 6 through which the magnetorheological fluid passes is formed between the outer periphery of the piston 2 and the inner periphery of the cylinder 1. Passes through the flow path 6.

  A cylindrical case 7 is disposed on the outer periphery of the cylinder 1, and the inner periphery of the case 7 is coupled to the outer periphery of the cylinder 1. Case 7 is made of a magnetic material.

  An annular recess 7a is formed on the inner periphery of the case 7, and the coil 9 wound in an annular shape is accommodated in the recess 7a. In this way, the coil 9 is arranged opposite to the outer periphery of the cylinder 1 by the case 7.

  By causing a current to flow through the coil 9, the coil 9 generates a magnetic force, and the magnetic force acts on the magnetorheological fluid flowing in the flow path 6 through the magnetic path formed by the case 7, the cylinder 1, and the piston 2. become.

  The lead wire 10 of the coil 9 is inserted through a passage 7b formed in the case 7 and connected to a controller (not shown) mounted on the vehicle. A drive current from the controller is input to the coil 9 through the lead wire 10.

  As a method of accommodating the coil 9 in the recess 7a of the case 7, first, the coil 9 wound in an annular shape is formed, and the case 7 is divided into a semicylindrical shape. And the coil 9 is accommodated in the recessed part 7a of one semi-cylindrical case, and the other semi-cylindrical case 7 is match | combined with one semi-cylindrical case after that. In this way, the coil 9 is accommodated in the recess 7 a of the case 7.

  As shown in FIG. 1, a plurality of coils 9 (9, 9a, 9b) are preferably arranged in the axial direction of the cylinder 1 so as to correspond to the stroke range of the piston 2. Since the coil 9 is fixed to the outer periphery of the cylinder 1, the relative position with the piston 2 changes. Therefore, when one coil 9 is provided, depending on the stroke amount of the piston 2, the piston 2 may be separated from the coil 9, and it may be difficult for the magnetic force to act on the magnetorheological fluid flowing through the flow path 6. . Therefore, if a plurality of coils 9 are arranged, an appropriate magnetic force can be applied to the magnetorheological fluid within the stroke range of the piston 2.

  The operation of the magnetorheological fluid shock absorber 100 configured as described above will be described.

  When the piston 2 moves in the cylinder 1, the magnetorheological fluid in the fluid chambers 3 and 4 on both sides of the piston 2 moves through the flow path 6. At this time, when a current is passed through the coil 9, a magnetic force acts on the magnetorheological fluid, and the viscosity of the magnetorheological fluid changes. Thereby, the magnetorheological fluid shock absorber 100 generates a damping force corresponding to the magnitude of the viscosity resistance of the magnetorheological fluid flowing through the flow path 6.

  As the current of the coil 9 increases, the viscosity of the magnetorheological fluid increases and the damping force generated by the magnetorheological fluid shock absorber 100 also increases. As described above, the damping force generated by the magnetorheological fluid shock absorber 100 is adjusted by changing the current flowing through the coil 9 and changing the strength of the magnetic field acting on the flow path 6.

  When a plurality of coils 9 are arranged in the axial direction of the cylinder 1, the generated damping force can be changed depending on the stroke position of the piston 2 by making the currents flowing through the coils 9 different. For example, if the current flowing through the coils 9a and 9b arranged on both ends of the cylinder 1 is increased and the magnetic force generated by the coils 9a and 9b is set to be high, the piston 2 is highly damped at the stroke end. A stroke position-dependent shock absorber that generates force can be configured.

  As described above, the present embodiment has a structure in which the coil 9 is provided outside the cylinder 1. In the case of a general magnetorheological fluid shock absorber in which a coil is housed in a piston assembly disposed in a magnetorheological fluid and a lead wire is guided to the outside through a passage formed in a rod, the magnetorheological fluid is externally provided. In order to prevent leakage, it is necessary to seal the passage through which the lead wire is guided with an adhesive or resin. However, according to the present embodiment, since the coil 9 is disposed outside the cylinder 1, that is, at a location where no magnetorheological fluid exists, it is not necessary to seal the passage 7b through which the lead wire 10 is inserted.

  Further, since there is no need to provide a passage in the rod 5, the structure of the rod 5 can be a solid rod, and the rod processing cost can be reduced. Thus, by providing the coil 9 outside the cylinder 1, a very excellent effect can be obtained.

  The structure for providing the coil 9 outside the cylinder 1 is only the case 7 coupled to the outer periphery of the cylinder 1 in the present embodiment. As described above, according to the present embodiment, the coil 9 can be disposed outside the cylinder 1 only by applying the case 7 to the single cylinder type shock absorber. The structure can be simplified with a small number of parts.

  Hereinafter, another aspect of the present embodiment will be described with reference to FIG.

  When the accuracy of the coaxiality of the cylinder 1, the piston 2, and the rod 5 is poor, the flow of the magnetorheological fluid flowing through the flow path 6 may be disturbed. In that case, the damping force of the magnetorheological fluid shock absorber 100 varies, which adversely affects the controllability of the damping force.

  In order to prevent such an adverse effect on the controllability of the damping force, as shown in FIG. 2, a guide member that slides on the inner periphery of the cylinder 1 on a part of the outer periphery of the piston 2 when the piston 2 moves. 11 is desirable. In order to stably guide the piston 2 along the inner periphery of the cylinder 1, it is desirable to provide at least two guide members 11 on the outer periphery of the piston 2. In that case, the region between the guide members 11 becomes the flow path 6.

  By providing the guide member 11, the accuracy of the coaxiality between the cylinder 1 and the piston 2 is improved, so that the disturbance of the flow of the magnetorheological fluid can be prevented, and the variation in the damping force of the magnetorheological fluid buffer 100 can be reduced. It becomes possible to prevent.

  Moreover, as shown in FIG. 2, it is desirable to lock the piston 2 to the step portion 5b of the rod 5 via an annular washer 12 which is an elastic body. Even if the nut 8 is loosened and the piston 2 moves in the axial direction by interposing the washer 12 between the piston 2 and the rod 5, the urging force of the washer 12 causes the piston 2 to move against the nut 8. Therefore, relative movement of the piston 2 with respect to the rod 5 can be reliably prevented.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be applied to a shock absorber mounted on a vehicle.

It is sectional drawing which shows the magnetorheological fluid shock absorber 100 in embodiment of this invention. It is sectional drawing which similarly shows the other aspect of the magnetorheological fluid shock absorber 100. FIG.

Explanation of symbols

100 Magnetorheological fluid shock absorber 1 Cylinder 2 Pistons 3 and 4 Fluid chamber 5 Rod 6 Flow path 7 Case 8 Nut 9 Coil 10 Lead wire 11 Guide member 12 Washer

Claims (3)

A cylinder filled with a magnetorheological fluid whose viscosity is changed by the action of a magnetic field;
A piston that is movably disposed within the cylinder at a predetermined interval from the inner circumference of the cylinder, and that defines two fluid chambers within the cylinder;
A flow path through which the magnetorheological fluid passes by movement of the piston in the cylinder;
A coil for applying a magnetic field to the flow path;
A magnetorheological fluid damper comprising: a rod to which the piston is fixed at one end;
The flow path is formed in an annular shape between the cylinder inner periphery and the piston outer periphery,
The magnetorheological fluid shock absorber is characterized in that the coil is accommodated in a case coupled to the outer periphery of the cylinder.   2. The magnetorheological fluid shock absorber according to claim 1, wherein a plurality of the coils are arranged in the axial direction of the cylinder so as to correspond to a stroke range of the piston.   The magnetorheological fluid shock absorber according to claim 1 or 2, wherein a guide member that slides with the inner periphery of the cylinder when the piston moves is provided on a part of the outer periphery of the piston. .