JP2009068572A - Magnetic viscous fluid shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic viscous fluid shock absorber for reducing the quantity of magnetic viscous fluid used. <P>SOLUTION: This invention is the magnetic viscous fluid shock absorber having a second shaft member 20 freely supported in the axial direction by a first shaft member 10, a conversion means 30 converting displacement in the axial direction of the second shaft member into rotational displacement, a rotor 41 connected to the conversion means and rotating by the rotational displacement, a cell 49 rotatably arranging the rotor inside and sealing the magnetic viscous fluid 1, and a coil 42 arranged on the outer peripheral side of the rotor and making a magnetic field act on the magnetic viscous fluid 1. The rotor is provided with an annular groove part on an outer peripheral surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  As a shock absorber mounted on a vehicle such as an automobile, a magnetorheological fluid whose viscosity is changed by the action of a magnetic field is used. Instead of a damping force adjusting valve, a coil is arranged in the piston portion, and an electric current is applied to the coil. Various damping force adjustment type shock absorbers that adjust the damping force by changing the viscosity of the magnetorheological fluid flowing through the control unit have been proposed (see, for example, Patent Document 1).

In the shock absorber of Patent Document 1, when the control current to the coil is reduced, the magnetic field acting on the path of the magnetorheological fluid is weakened, the viscosity of the magnetorheological fluid is lowered and the damping force is reduced, and the control current is increased. The magnetic field acting on the passage becomes stronger, the viscosity of the magnetorheological fluid becomes higher, and the damping force becomes larger.
US Pat. No. 6,260,675

  However, the shock absorber disclosed in Patent Document 1 has a problem that a large amount of expensive magnetorheological fluid is required and the weight of the shock absorber increases because the magnetorheological fluid is filled in the shock absorber cylinder.

  The present invention has been made in view of the above problems, and provides a magnetorheological fluid shock absorber that reduces the amount of magnetorheological fluid while reducing the damping force characteristic, thereby reducing the weight and cost. The purpose is to do.

  The present invention converts a first shaft member, a second shaft member freely supported in the axial direction with respect to the first shaft member, and an axial displacement of the second shaft member into a rotational displacement. Conversion means, a rotor connected to the conversion means and rotated by the rotational displacement, a compartment in which the rotor is rotatably arranged and a magnetorheological fluid is sealed, and an outer peripheral side of the rotor. A coil for applying a magnetic field to the magnetorheological fluid, and the rotor is provided with an annular groove portion on an outer peripheral surface thereof, and the magnetorheological viscosity serving as a rotational resistance of the rotor according to an electric current applied to the coil. A magnetoviscous fluid shock absorber characterized in that the damping force is changed by changing the viscosity of the fluid.

  According to the present invention, the amount of the magnetorheological fluid is provided by providing the compartment for sealing the magnetorheological fluid around the rotor rotating with the relative displacement between the first shaft member and the second shaft member. Can be significantly reduced. As a result, the weight of the shock absorber can be reduced and the cost can be reduced. Further, since the groove portion is provided on the outer peripheral surface of the rotor, the contact area between the rotor and the magnetorheological fluid is increased, the resistance is increased, and as a result, the damping force can be increased.

  A magnetorheological fluid shock absorber 100 according to an embodiment of the present invention will be described with reference to FIG.

  The magnetorheological fluid shock absorber 100 of the present invention includes a rod (second shaft member) including an outer cylinder (first shaft member) 10 connected to a suspension device for suspending an axle and a rod member 22 connected to the vehicle body. 20, a conversion means 30 that converts a linear displacement in the vertical (axial) direction between the outer cylinder 10 and the rod 20 into a rotational displacement around the center line of the rod 20, and the viscosity of the magnetorheological fluid 1 by the action of a magnetic field. And a damping force generator 40 that generates a damping force by changing characteristics.

  The outer cylinder 10 has an annular cylindrical member 11, a lid member 19 that closes the bottom opening end thereof, and an annular shape that is fixed to the lid member 19 with a center line disposed perpendicular to the center line of the cylindrical member 11. Bracket 12, a rubber bush 13 that is press-fitted into the bracket 12, and a bearing 14 that is installed near the opening end of the first cylindrical member 11 and supports the rod 20 slidably in the axial direction. .

  The rod 20 includes a lid-shaped cylindrical second cylindrical member 21 having an open end on the lower side, and a rod-shaped rod member 22 fixed to the lid portion of the second cylindrical member 21 and connected to the vehicle body. It is arranged on the center line of the cylindrical member 11.

  The conversion means 30 includes a so-called ball screw mechanism 30a, and a ball screw nut 31 is fitted and fixed to the inner peripheral surface of the rod 20 near the opening end of the second cylindrical member 21. The ball screw shaft 32 that is screwed with the ball screw nut 31 is disposed in the axial direction, and one end extends into the second cylindrical member 21. A male screw (not shown) is formed at the tip of the ball screw shaft 32, and a stopper nut 33 for restricting the amount of movement of the ball screw nut 31 on the extending side is screwed into the male screw portion. The stopper nut 33 includes a cushioning material 34 for reducing an impact when the stopper nut 33 and the ball screw nut 31 are in contact with each other. The buffer material 34 is made of, for example, a urethane material or a rubber material. On the other hand, the other end of the ball screw shaft 32 is rotatably supported around the center line by a bearing 15 disposed on the bottom surface 16 (see FIG. 2) of the first cylindrical member 11.

  With such a configuration, when the outer cylinder 10 is axially displaced with respect to the rod 20 as the axle is relatively displaced in the vertical direction with respect to the vehicle body, the axial displacement is about the center line due to the action of the ball screw mechanism 30a. The ball screw shaft 32, which is converted into rotational displacement and screwed into the ball screw nut 31, rotates about the center line.

  FIG. 2 is a diagram illustrating a detailed configuration of the damping force generation unit 40. A partition member 43 is installed in the first cylindrical member 11 at a predetermined distance in the axial direction from the bottom surface 16, and a partition 49 is partitioned and formed in the first cylindrical member 11 by the partition member 43. 49 is filled with the magnetorheological fluid 1. In addition, a rotor 41 that rotates integrally with the ball screw shaft 32 is disposed in the compartment 49, and the viscosity of the magnetorheological fluid 1 becomes a resistance force of the rotation of the rotor 41, and this resistance force becomes a damping force of the shock absorber. Further, in order to change the damping force depending on the operating state, a magnetic field is applied to the magnetorheological fluid 1 so that the viscosity can be changed. For this purpose, an annular coil 42 is provided on the outer periphery of the rotor 41 with a predetermined gap and to which a current is applied from an external power source through the wiring 48.

  Further, in order to prevent the magnetorheological fluid 1 from leaking to the outside, an O-ring 46 that prevents the magnetorheological fluid 1 from leaking from between the partition member 43 and the inner peripheral surface of the lid member 19, and a ball screw shaft The magnetorheological fluid 1 between the O-ring 47 that prevents leakage of the magnetorheological fluid 1 from the gap between the outer peripheral surface of the rotor 32 and the rotor 41 and the rotor 41 provided on the partition member 43. A seal 45 is provided to prevent leakage.

  The rotor 41 includes a cylindrical main body 51 fitted on the outer peripheral surface of the end of the ball screw shaft 32 and an inner peripheral surface of the ball screw shaft 32, and a plurality of disc-shaped flanges extending from the main body 51 in the outer diameter direction. The coil 42 is arranged on the outer peripheral side of the flange portion 52 so as to surround the flange portion 52 with a predetermined distance.

  Here, the rotor 41, the partition member 43, and the lid member 19 are preferably made of a magnetic material in order to increase the rotational resistance when a current is applied to the coil.

  The flange portions 52 are arranged at predetermined intervals in the axial direction, and a plurality of annular groove portions 53 are formed between the adjacent flange portions 52, and the cross-sectional shape of the outer peripheral surface of the rotor 41 of the flange portions 52 and the groove portions 53 is the same. It is configured to be a comb shape. In order to facilitate the manufacturing method, the rotor 41 may be formed by alternately laminating two types of thin disks having different outer diameters in the axial direction.

  The coil 42 is disposed in contact with the inner peripheral bottom surface 16 of the first cylindrical member 11, and a compartment 49 in which the partition member 43 is inserted from the axial direction and the magnetorheological fluid 1 is filled is defined on the top surface of the coil 42. The The rotor 41 is rotatably disposed in the compartment 49.

  In the damping force generator 40 configured in this way, a compartment 49 that fills the magnetorheological fluid 1 around the flange portion 52 of the rotor 41 that rotates together with the ball screw shaft 32 is partitioned in the first cylindrical member 11 to be attenuated. The required amount of the magnetorheological fluid 1 that generates force can be significantly reduced, and the weight can be reduced and the cost can be reduced. Moreover, since the groove part 53 was provided in the outer peripheral surface of the rotor 41, the contact area of the rotor 41 and the magnetic viscous fluid 1 increases, resistance becomes large, and as a result, damping force can be raised.

  Further, when the shock absorber 100 is left for a long period of time and the amount of the magnetorheological fluid 1 is large, ferromagnetic particles such as iron powder in the magnetorheological fluid 1 that is dispersed are precipitated. For this reason, the desired damping characteristic cannot be exhibited until it is sufficiently agitated. However, when the amount of the magnetorheological fluid 1 to be used is small as in the present invention, the agitation time is shortened, and the initial Attenuation characteristics can be obtained.

  When a current is applied to the coil 42, a magnetic field is generated in the axial direction as shown in FIG. 3, in other words, in a direction perpendicular to the magnetorheological fluid 1 between the flanges 52. FIG. 3 shows the state of the magnetic field during current supply. The viscosity of the magnetorheological fluid 1 changes due to the generated magnetic field, and as the current value increases, the magnetic force increases and the viscosity of the magnetorheological fluid 1 increases. As the shock absorber 100 expands and contracts, that is, when the rod 20 expands and contracts with respect to the first cylindrical member 11, the rotor 41 rotates in the magnetorheological fluid 1. At this time, the viscosity of the magnetorheological fluid 1 is rotated by the rotor 41. This resistance acts as a damping force for the expansion / contraction operation of the shock absorber 100 of the present invention. Here, the viscosity of the magnetorheological fluid 1 changes instantaneously according to the current applied to the coil 42, the viscosity increases as the current increases, and a high damping force is generated. Therefore, by controlling the current value, The generated damping force can be variably controlled.

  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 magnetorheological fluid shock absorber mounted on a vehicle.

It is sectional drawing which shows the magnetorheological fluid shock absorber 100 to which this invention is applied. It is a detailed sectional view of a damping force generation part. It is a figure explaining the state of the magnetic field of a damping force generation part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magneto-viscous fluid 10 Outer cylinder 11 1st cylindrical member 20 Rod 21 2nd cylindrical member 22 Rod member 30 Conversion means 31 Ball screw nut 32 Ball screw shaft 34 Buffer material 40 Damping force generating part 41 Rotor 42 Coil 43 Partition member 45 Seal 49 Separation Chamber 51 Body portion 52 Gutter portion 53 Groove portion 100 Magnetorheological fluid shock absorber

Claims (5)

A first shaft member;
A second shaft member that is freely supported in the axial direction with respect to the first shaft member;
Conversion means for converting axial displacement of the second shaft member into rotational displacement;
A rotor connected to the conversion means and rotated by the rotational displacement;
A compartment in which the rotor is rotatably arranged and the magnetorheological fluid is sealed;
A coil that is disposed on the outer peripheral side of the rotor and that acts a magnetic field on the magnetorheological fluid,
The rotor is provided with an annular groove on the outer peripheral surface,
A magnetorheological fluid shock absorber characterized in that the damping force is changed by changing the viscosity of the magnetorheological fluid serving as the rotational resistance of the rotor in accordance with the current applied to the coil.   The magnetorheological fluid shock absorber according to claim 1, wherein the conversion unit includes a ball screw mechanism. The second shaft member includes a cylindrical portion that is slidably supported by the first shaft member,
The ball screw mechanism includes a ball screw nut fitted to the inner peripheral surface of the cylindrical portion, a screw screw engaging with the ball screw nut, one end extending into the cylindrical portion, and the other end extending to the bottom surface of the first shaft member. And a ball screw shaft supported rotatably around a center line of the second shaft member,
The magnetorheological fluid shock absorber according to claim 2, wherein the rotor is fixed to the ball screw shaft. A portion of the first shaft member is partitioned in an axial direction by an defining member to define the compartment;
The magnetorheological fluid shock absorber according to claim 3, wherein the rotor is installed in the compartment.   2. The magnetorheological fluid shock absorber according to claim 1, wherein the rotor is formed by alternately laminating two kinds of discs having different outer diameters in an axial direction to form the groove portion therebetween.

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