JP6554361B2 - Magnetorheological fluid damper - Google Patents

Description

  The present invention relates to a damper using a magnetorheological fluid.

  For example, in the magnetorheological fluid damper disclosed in Patent Document 1, an orifice is formed in a piston, and magnetic field applying means (coil) is embedded around the orifice. By applying a current to the magnetic field applying means, a magnetic field is applied to the magnetorheological fluid flowing through the orifice. By changing the strength of the magnetic field, a desired damping force can be obtained. There is.

JP 2007-187176 A

  Since the above-mentioned magnetorheological fluid damper controls the damping force of the damper by adjusting the viscosity of the magnetorheological fluid passing through the orifice, the ON / OFF ratio of damping force (damping constant) (maximum damping constant and It is difficult to increase the ratio to the minimum damping constant). In particular, since the orifice always restricts the flow of the working fluid (magnetic viscous fluid) due to its structure, a certain amount of damping force is generated even when no magnetic field is applied to the magnetic viscous fluid. From this, it is difficult to meet the demand that the damper be operated in a near unloaded condition under predetermined conditions.

  The present invention was devised in view of such a problem, and provides a magnetorheological fluid damper capable of reducing the minimum damping constant and thereby increasing the ON / OFF ratio of the damping force. The purpose is to

  The magnetorheological fluid damper of the present invention is a magnetorheological fluid damper in which a piston made of a magnetic material is accommodated in a cylinder body made of a non-magnetic material so that the piston can move directly, and a magnetorheological fluid is used as a working fluid. The minute gap formed at two positions between the cylinder body and the piston, and the minute gap formed between the two minute gaps between the cylinder body and the piston. It is characterized by comprising a larger gap (hereinafter also referred to as “large gap”) and a magnetic pole portion respectively disposed on the back surface of the portion of the cylinder body where the two minute gaps are formed.

  According to the magnetorheological fluid damper having such a configuration, the minimum damping constant of the magnetorheological fluid damper is set to a very low value by setting the dimension of the “large gap” through which the magnetorheological fluid passes when the piston moves. can do. In addition, since the magnetic path formed between the magnetic pole portions passes through the “small gap” and does not pass through the “large gap”, the maximum attenuation coefficient does not decrease even if the size of the “large gap” is increased. .

  The magnetorheological fluid damper has rods connected to the front and rear portions of the piston in the linear motion direction, and the piston is supported by the cylinder body through these rods so as to be linearly movable. It is desirable to do.

  According to the magnetorheological fluid damper having such a configuration, the dimension of the “fine gap” and the dimension of the “large gap” are reliably maintained, and desired damping performance can be stably obtained.

  According to the magnetorheological fluid damper according to the present invention, it is possible to easily set the minimum damping constant to a low value, so that the ON / OFF ratio of the damping constant can be increased.

FIG. 3 is a cross-sectional view of the magnetorheological fluid damper according to the embodiment of the present invention cut along a plane including the axis of the rod. However, the magnetic field forming portion, the rod, the piston and the like are not sectioned. It is AA sectional drawing of FIG. However, the rods, pistons, etc. are not cross-sectioned. It is the B section enlarged view of FIG. It is CC sectional drawing of FIG. However, hatching of the cross section of the magnetic field forming portion is omitted. It is a figure corresponding to the B section enlarged view of FIG. 1, Comprising: It is a figure which shows the state which does not have a piston between magnetic pole parts. FIG. 7 is a cross-sectional view of the magnetorheological fluid damper according to another embodiment of the present invention cut along a plane including the axis of the rod. However, the yoke, the rod, the piston, etc. are not sectioned.

  Hereinafter, a magnetorheological fluid damper according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 4, the magnetorheological fluid damper 1 according to this embodiment includes a cylinder body 2, a piston 3, rods 4 and 5, a magnetic field forming unit 6, a magnetorheological fluid 7, and the like.

  A piston 3 is accommodated in the cylinder body 2 so as to be capable of direct movement. Between the cylinder body 2 and the piston 3, a minute gap is formed at two places, and a gap larger than the minute gap is formed between the circumferential directions of the two minute gaps. For example, as shown in FIG. 4, each of the cylinder body 2 and the piston 3 has a rectangular cross section in which the direction sandwiched between the magnetic pole portions 6N and 6S is the short direction and the direction orthogonal to the long direction is the longitudinal direction. It is supposed to be. The surfaces 2a and 3a formed along the longitudinal direction are opposed to each other through a minute gap, and the surfaces 2b and 3b formed along the shorter direction are disposed through a gap larger than the minute gap. Are facing each other. Hereinafter, the surfaces 2a and 3a facing each other through the minute gap are referred to as proximity facing surfaces 2a and 3a, and the surfaces 2b and 3b facing through the gap larger than the minute gap are also referred to as remote facing surfaces 2b and 3b. The cylinder body 2 is made of a non-magnetic material, and the piston 3 is made of a magnetic material so that the magnetic path formed between the magnetic pole portions 6N and 6S passes through the minute gap.

  As shown in FIG. 1, rods 4 and 5 made of nonmagnetic material are connected to front and rear portions in the linear motion direction of the piston 3 respectively. One rod 4 is supported so as to be linearly movable in a first guide cylinder 10 connected to one of the cylinder bodies 2. The other rod 5 is supported for direct movement in a second guide cylinder 11 connected to the other of the cylinder body 2. By these guide cylinders 10 and 11, the size of the minute gap between the adjacent facing surfaces 2a and 3a and the size of the gap between the remote facing surfaces 2b and 3b are securely held. As shown in FIG. 3, the gap at the connection portion between the cylinder body 2 and the first guide cylinder 10 and the gap at the connection portion between the cylinder body 2 and the second guide cylinder 11 are sealed with a sealing material 13. ing. In addition, an O-ring 16, a bush 17, and the like are fitted in the gaps between the shaft holes of the guide cylinders 10 and 11 and the rods 4 and 5.

  As shown in FIG. 1, the magnetic field forming unit 6 is composed of two permanent magnets 8 and a yoke 9 connected between them, and the magnetic pole portions 6N and 6S face each other with the cylinder body 2 therebetween. It has become. As shown in FIG. 3, each magnetic pole portion 6N, 6S is installed at a specific position (stroke position where a damping force is desired to be applied) in the piston linear movement direction on the back surface of the proximity facing surface 2a of the cylinder body 2. . The width dimensions (vertical dimensions in FIG. 4) of the magnetic pole portions 6N and 6S are substantially the same as the longitudinal dimension of the cross section of the piston 3. In addition, the magnetic field formation part 6 can be installed in arbitrary positions with respect to the cylinder body 2, and the said specific position of the magnetic pole parts 6N and 6S can also be set in arbitrary positions along a piston linear motion direction.

  The magnetorheological fluid 7 is filled in the cylinder body 2 in the two liquid chambers 14 and 15 defined by the piston 3 and in the gap between the piston 3 and the cylinder body 2. The magnetorheological fluid 7 is a liquid in which magnetic particles are dispersed in a dispersion medium, and in particular, a liquid in which the magnetic particles are composed of nano-sized metal particles (metal nanoparticles) can be used. The magnetic particles are made of a magnetizable metal material, and the metal material is not particularly limited, but a soft magnetic material is preferable. Examples of the soft magnetic material include alloys such as iron, cobalt, nickel and permalloy. The dispersion medium is not particularly limited, but can be, for example, a hydrophobic silicone oil. The compounding amount of the magnetic particles in the magnetorheological fluid may be, for example, 3 to 40 vol%. It is also possible to add various additives to the magnetorheological fluid to obtain various desired properties.

In the magnetorheological fluid damper 1 having the above-described configuration, as shown by the solid line in FIG. 5, when the piston 3 is at the position X1 completely separated from between the magnetic pole portions 6N and 6S, between the magnetic pole portions 6N and 6S A magnetic path is not formed because only the cylinder body 2 made of the magnetorheological fluid and the nonmagnetic material intervenes. In addition, no magnetic field is applied to the magnetorheological fluid 7 _X1 interposed between the close opposing surfaces 2 a and 3 a of the cylinder 3 and the piston 3 at the position X1. In such a state, the magnetorheological fluid 7 _X1 interposed in the minute gap is in the lowest viscosity state, and the damping constant of the magnetorheological fluid damper 1 is the lowest value. Of course, in this state, no magnetic field is applied also to the magnetorheological fluid 7 existing other than between the close facing surfaces 2a and 3a.

When the piston 3 moves from the position X1 to the side between the magnetic pole portions 6N and 6S and a part of the piston 3 reaches a position X2 interposed between the magnetic pole portions 6N and 6S as shown by a two-dot chain line in FIG. In accordance with the amount of the piston 3 existing between the magnetic pole portions 6N and 6S, the magnetic resistance between the magnetic pole portions 6N and 6S decreases, and a magnetic path is formed between them. Thereby, the magnetorheological fluid 7 _X2 on the magnetic path forms a cluster to develop a shear stress, and the damping constant of the magnetorheological fluid damper 1 is largely in accordance with the amount of the piston 3 existing between the magnetic pole portions 6N and 6S. Become. Although the cylinder body 2 on the magnetic path is a non-magnetic body, its thickness is set sufficiently thin so that the magnetic path can be formed.

Next, when the piston 3 further moves from the position X2 and reaches the position X3 completely interposed between the magnetic pole portions 6N and 6S, as shown in FIG. 3, the magnetic resistance between the magnetic pole portions 6N and 6S is minimized, The magneto-rheological fluid 7 _X3 interposed in the minute gap between the cylinder body 2 and the piston 3 develops the maximum shear stress, and the damping constant of the magneto-rheological fluid damper 1 becomes the maximum value.

By the way, in the magneto-rheological fluid damper 1 according to the present embodiment, a magnetic field is not applied to the magneto-rheological fluid 7 _{W present} in the gap between the remote facing surface 3 b of the piston 3 and the remote facing surface 2 b of the cylinder body 2. There is. Therefore, the dimension between the remote facing surfaces 2b and 3b can be set large (for example, 1 mm or more). And between the remote opposing surfaces 2b and 3b, when the piston 3 moves in the cylinder body 2, it becomes a flow path of the magnetorheological fluid 7 that moves between the liquid chambers 14 and 15, so that the remote opposing surfaces 2b and 3b By sufficiently securing the dimension between 3b, the minimum damping constant of the magnetorheological fluid damper 1 can be made extremely low.

  In the magnetorheological fluid damper according to the conventional example, since the damping constant was adjusted by adjusting the flow rate at the orifice, it was difficult to increase the ON / OFF ratio of the damping constant. According to the magneto-rheological fluid damper 1 as described above, since the minimum damping constant can be set to a very low value as described above, the ON / OFF ratio of the damping constant can be easily increased.

Other Embodiments
Although the permanent magnet 8 is used as the magnetic field forming portion 6 in the embodiment described above, the yoke 18 and the coil 19 wound around the yoke 18 and the coil 19 as in the magnetorheological fluid damper 1A shown in FIG. By adopting a magnetic field forming unit 6A including a current supply device (not shown) for supplying a current to the magnetic pole portion 6N, 6S disposed at a predetermined position of the cylinder body 2 as described above to apply a magnetic field It is also good. In addition, parts other than the magnetic field formation part 6A of this magnetorheological fluid damper 1A are comprised similarly to the magnetorheological fluid damper 1 which concerns on embodiment mentioned above.

  The present invention is applicable to, for example, a direct acting damper using a magnetorheological fluid as a working fluid.

1,1A Magnetorheological Fluid Damper 2 Cylinder Body 3 Piston 4, 5 Rod 6N, 6S Magnetic Pole 7 Magnetorheological Fluid

Claims (2)

A magnetorheological fluid damper that accommodates a piston composed of a magnetic material in a cylinder body composed of a non-magnetic material so as to be capable of direct movement, and uses a magnetorheological fluid as a working fluid,
Minute gaps formed at two places between the cylinder body and the piston;
A gap larger than the minute gap formed between the two minute gaps between the cylinder body and the piston,
And a magnetic pole portion respectively disposed on the back surface of a portion of the cylinder body where the two minute gaps are formed.
Magneto-rheological fluid damper characterized by In the magnetorheological fluid damper according to claim 1,
Magnetorheological fluid dampers characterized in that rods are respectively connected to the front and rear portions of the piston in the linear movement direction, and the pistons are supported by the cylinder body through these rods so as to be linearly movable. .

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