JPH0613895B2 - Magnetic fluid damper - Google Patents

Description

The present invention relates to a magnetic fluid damper capable of surely injecting and filling a magnetic fluid into a magnetic fluid damper.

Conventionally, precision instruments such as an optical experimental device and a precision balance are installed on a vibration isolation table to absorb the vibration of the outside and the instrument itself. The anti-vibration base generally has a structure in which an air spring, a rubber base, a steel spring, etc. are attached to a highly rigid surface plate.

However, such an anti-vibration table is effective for absorbing vibrations of several tens of Hz or higher, but cannot absorb and damp vibrations of less than that, for example, 3 Hz or lower.

Therefore, conventionally, as shown in FIG. 1, it has been proposed to perform vibration isolation by combining a magnetic fluid damper 2 in parallel with an air spring vibration isolation device 1.

As shown in FIG. 2, this magnetic fluid damper is connected to a high-rigidity surface plate, which is one of the components of the anti-vibration table, and the cylindrical magnetic circuits 5, 6 and 7 (5 are the surface plate and the soft magnetic disk). A shaft for connecting the circular plates 7, 6 is a permanent magnet laminated so as to have the same poles from the surfaces of the magnetic poles facing each other via the soft magnetic plate 7)
Is housed in a non-magnetic fluid container 8 having the same cylindrical shape, and a magnetic fluid 9 is filled in the gap between the container 8 and the magnetic circuits 5, 6, 7. The magnetic fluid 9 is obtained by uniformly dispersing ferromagnetic fine particles such as ferrite in various solvents such as water, kerosene and various hydrocarbons. In the magnetic fluid damper having such a structure, the magnetic field diverging in the radial direction by the disc-shaped soft magnetic material 7 is filled between the non-magnetic material container 8 and the cylindrical magnetic circuits 6 and 7 in the magnetic fluid 9. To control the viscosity of the fluid, control the movement (flow velocity) of the magnetic fluid 9 due to the vibration inside and outside the vibration isolation table, and adjust the damping constant to absorb and dampen mechanical vibrations of 10 Hz or less. It was made to let.

When constructing the damper, such a damper first fills the nonmagnetic container 8 with the magnetic fluid 9 in a specified amount, and then inserts the cylindrical magnetic circuits 5, 6, 7 into the container 8.

However, as shown in FIG. 5, when the magnetic circuits 6 and 7 are inserted into the magnetic fluid 9 filled in the bottomed cylindrical container 8 from above, as shown in FIG. Since the magnetic fluid 9 existing in the container 8 concentrates and swells on the portion of the soft magnetic body 7 where the magnetic field strength is strong, on the contrary, a gap B is formed at the boundary with the inner wall of the container 8. Further, by inserting the magnetic circuit downward, the strong magnetic field generated by the soft magnetic body 7 at the lower end causes the magnetic fluid to contact the inner wall of the interface of the magnetic fluid in an attempt to form a magnetic path with the inner wall of the container 8. Thus, the first air layer A is formed. When it is further lowered, the magnetic field is concentrated by the second soft magnetic material 7 from the bottom, and the second bulge occurs. However, since the magnetic field of the soft magnetic material 7 at the lower end is strong, the air layer A is not broken. Therefore, an annular air layer A is generated one after another at a place where the soft magnetic body 7 is present. This air layer A will significantly reduce the viscous resistance between the container 8 and the magnetic circuits 6, 7 gap,
This is not a preferable phenomenon because it deteriorates the performance of the magnetic fluid damper.

In order to prevent such an unfavorable phenomenon, the present invention has a structure in which the magnetic circuit is separated from the shaft 5 and installed outside the container, so that the air layer that deteriorates the damping effect during assembly is sealed in the magnetic fluid. The main object of the present invention is to provide a magnetic fluid damper that is prevented from being mixed.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

Example 1. FIG. 3 is a sectional view showing an example of the present invention, and the same parts as those shown in FIG.

The structure of this example is such that a bottomed cylindrical container 8 made of a non-magnetic material such as aluminum containing a magnetic fluid 9 and a magnetic pole surface is arranged in the axial direction of the bottomed cylindrical container 8 and the permanent magnets face each other. Through holes having the same diameter as the bottomed cylindrical container 8 are bored in the permanent magnets 6 laminated so that their surfaces to be poled and the soft magnetic body 7 in close contact with both magnetic pole surfaces of the laminated permanent magnets 6 The magnetic circuit assembly in which the permanent magnet 6 and the soft magnetic material 7 laminated on the outer peripheral portion of the bottomed cylindrical container 8 are inserted and fitted and fixed from the bottom of the bottomed cylindrical container 8 and the vibration isolation table is fixed. It is composed of a cylindrical container 8 having a bottom and a non-magnetic shaft 10 such as SUS304 concentrically installed in the magnetic fluid 9 in a floating state, which is connected to the lower part of the board.

The magnetic circuit assembly may be composed of one permanent magnet and a soft magnetic material that is closely fixed to both magnetic pole surfaces of the permanent magnet.

With this structure, the magnetic field generated from the annular permanent magnet circuits 6 and 7 acts on the magnetic fluid 9 filled in the gap between the cylindrical container 8 and the shaft 10 through the cylindrical container 8. Therefore, the viscosity of the magnetic fluid 9 can be changed, and the viscous resistance to the shaft 10 and the container 8 which vertically vibrate the gap can be adjusted and changed, and the damping coefficient of the magnetic fluid damper can be adjusted. You can get a damper.

In the magnetic fluid damper according to this structure, when assembling the respective components, the cylindrical container 8 is filled with a specified amount of the magnetic fluid 9, the shaft 5 is inserted, and the magnetic circuits 6 and 7 are inserted into the cylindrical container 8 from below. Because it can be installed,
As shown in C, even if the magnetic fluid 9 concentrates on the portion of the soft magnetic body 7 where the magnetic field strength is strong when the magnetic circuit is inserted, an air layer is not generated, and the magnetic fluid as shown in FIGS. Does not occur such that an air layer is mixed into the magnetic fluid before the magnetic circuit is pulled up by the permanent magnet circuit and the magnetic circuit is installed at a predetermined position. Therefore, the reliability of the performance as the magnetic fluid damper is significantly improved.

Example 2. FIG. 4 is a cross-sectional view of the improved magnetic fluid damper of FIG. 3 in which the leakage magnetic field exerted on the outside of the magnetic fluid damper is reduced. That is, the outer circumferences of the magnetic circuits 6 and 7 are surrounded by the soft magnetic cylindrical body 1.
By enclosing it with 1, the leakage magnetic field generated in the example of FIG. 3 can be reduced and the magnetic field strength acting on the magnetic fluid 9 can be effectively increased.

As described above, according to the present invention, a non-magnetic bottomed cylinder containing a magnetic fluid, and one of the bottomed cylinder having a magnetic pole surface arranged in the axial direction or the facing surfaces of magnets have the same pole. A through hole having the same diameter as the bottomed cylinder is bored in the soft magnetic material that is in close contact with both the permanent magnets and the magnetic pole surfaces of the permanent magnets that are laminated as
A magnetic circuit assembly in which a permanent magnet and a soft magnetic material are fitted and fixed to the outer periphery of a bottomed cylinder from the bottom of the bottomed cylinder, and a non-magnetic shaft that is concentrically attached to the bottomed cylinder and floated in a magnetic fluid Since the magnetic fluid damper is assembled, the air layer can be prevented from being mixed into the magnetic fluid when the magnetic fluid damper is assembled, and the soft magnetic cylindrical body is fitted and fixed to the outer peripheral surface of the magnetic circuit, so that the magnetic fluid damper is externally affected. It is possible to provide a highly reliable magnetic fluid damper having the advantage of reducing the leakage magnetic field.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the principle structure of a vibration isolation table, FIG. 2 is a sectional view for explaining the structure and operation of a conventional magnetic fluid damper, and FIG. 3 is a magnetic fluid damper of the present invention. FIG. 4 is a sectional view showing an example, FIG. 4 is a sectional view showing another example of the present invention, FIG. 5 is an assembly process diagram of a conventional example, and FIG. 6 is an assembly process diagram of the present invention. 1 ... Rubber air spring having spring constant, 2 ... Magnetic fluid damper having damping coefficient, 3 ... Vibration isolation table with high rigidity mass (including precision instruments to be vibration-isolated), 4
…… Base, 6 …… Disc permanent magnets stacked so that the opposing faces of the magnets have the same pole, 7 …… Disc-shaped soft magnet closely attached to the gap of the permanent magnet and the side face of the cylindrical magnetic circuit. Magnetic material, 8 ... Non-magnetic disk-shaped container fixed to the base,
9 ... Magnetic fluid, 10 ... Non-magnetic shaft, 11 ... Soft magnetic cylinder.

Claims (2)

[Claims] 1. A non-magnetic bottomed cylinder containing a magnetic fluid, and one magnet having a magnetic pole surface arranged in the axial direction of the bottomed cylinder, or the magnets are laminated so that the surfaces facing each other have the same pole. The permanent magnet and the soft magnetic material that is in close contact with both magnetic pole surfaces of the permanent magnet are provided with through-holes of the same diameter as the bottomed cylinder, and the permanent magnet and the soft magnetic material are attached to the outer circumference of the bottomed cylinder. A magnetic fluid damper comprising a magnetic circuit assembly fitted and fixed from a bottom portion, and a non-magnetic shaft concentrically provided with a bottomed cylinder and floating in a magnetic fluid. 2. A non-magnetic bottomed cylinder containing a magnetic fluid, and one magnet having a magnetic pole surface arranged in the axial direction of the bottomed cylinder, or magnets are laminated so that the surfaces facing each other have the same pole. The permanent magnet and the soft magnetic material that is in close contact with both magnetic pole surfaces of the permanent magnet are provided with through-holes of the same diameter as the bottomed cylinder, and the permanent magnet and the soft magnetic material are attached to the outer circumference of the bottomed cylinder. A magnetic fluid damper comprising a magnetic circuit assembly fitted and fixed from the bottom and a non-magnetic shaft concentrically floating in a magnetic fluid with a bottomed cylinder. A magnetic fluid damper characterized by fitting and fixing a soft magnetic cylindrical body.