KR20180096264A - Linear Actuator based on Magneto-rheological Fluid - Google Patents

Abstract

The present invention prevents friction between metals. A magnetorheological fluid-based linear actuator having a multi-stack disk structure according to an embodiment of the present invention comprises: a housing in which a storage chamber in which MR fluid is filled is formed; a piston coupled to the inner surface of the storage chamber; and a plurality of discs provided below the storage chamber and spaced apart from each other.

Description

[0001] The present invention relates to a linear actuator based on a magneto-rheological fluid,

The present invention relates to a magnetorheological fluid-based linear actuator having a multi-stack disk structure.

Generally, a magnetorheological fluid is a non-colloidal solution containing ferromagnetic particles having a size of 10 ^-4 to 10 ^-3 cm. When the magnetic field is not applied, the magnetorheological fluid has a viscosity of 0.20 to 0.30 Pa-sec at a room temperature, When a magnetic field of ㎄ / m (2 ~ 3 kOe) is applied, it has a high yield stress of 50 ~ 100.. In addition, the magnetorheological fluid has a fast response time [1 to 2 msec (10 ^-3 sec)], although the maximum yield stress is limited by magnetic saturation, and the operating range of -40 to 150 ° C And has a characteristic that it is considerably insensitive to the influent impurities. In a magnetorheological fluid with such a characteristic, when the magnetic field is applied, the particles contained in the fluid form a chain, and the shear yield stress of the fluid changes. Therefore, when the magnetic field is not applied, it shows the behavior of the newtonian fluid, but when the magnetic field is applied, the particles dispersed in the fluid form a chain, so that even in the state where the shear strain is not generated, It shows the behavior of bingham fluid with increasing torque dissipation. That is, the magnetorheological fluid changes into the gel state when the magnetic field is applied, when the magnetic field is not applied.

Using magnetorheological fluid, it can be used for shock absorbers such as passenger cars, trucks, military vehicles, trains, engine mounts, brake systems, anti-collision systems, fan clutch systems, and haptic systems.

Korean Patent Registration No. 10-0445988 discloses a "shock absorber using a magnetorheological fluid ". Korean Patent Registration No. 10-1153447 discloses an external force-responsive stiffness generating apparatus using a magnetorheological fluid and a haptic providing apparatus using the same. Korean Patent Registration No. 10-1357183 discloses "a multi-mode kinesthetic-tactile generator using fluid and its design method, a damper device and a portable device using a kinesthetic-tactile generator, a resistance generating method and a recording medium thereof" .

However, in the conventional actuator using the shear mode, metal friction occurs because the gap between the piston and the outer housing must be narrowed, which may act as a durability weakening factor. In addition, when the compression mode is used in the actuator, the resistance of the actuator can be strengthened. However, since the resistance is not constant depending on the distance that the actuator is pressed, a separate control device and sensor are needed. Also, in the compression mode, there is a disadvantage that the generation interval of the resistance is not efficient as the stroke distance becomes longer.

In order to solve the above-described problems, the embodiment of the present invention is a magnetorheological fluid-based linear actuator which can be constantly generated according to the pressing force of the actuator, and friction does not occur between the metals because the fluid flows between the magnetic bodies. .

According to an aspect of the present invention, there is provided a linear actuator based on a magnetorheological fluid, comprising: a housing having a housing chamber in which MR fluid is filled; A piston coupled to an inner surface of the containing chamber; And a plurality of discs disposed at a lower portion of the containing chamber and spaced apart from each other; Wherein the plurality of discs may include a first disc in which a first passage is formed and a second disc in which a second passage is formed at a position not overlapping the first passage, have.

A main body disposed under the housing and having a disk array space therein; And a solenoid coil provided inside the main body to enclose the side surfaces of the plurality of discs; As shown in FIG.

Further, the lower portion of the housing may be coupled to the main body so as to be located above the plurality of discs.

In addition, the piston is located above the chamber and pressurizes the MR fluid underneath through the lowering operation to allow the MR fluid to flow between the plurality of disks.

In addition, a pressure plate connected to the piston by a rod may be provided on the upper portion of the housing.

The upper end of the rod may be connected to the lower surface of the pressure plate through the upper surface of the housing, and the lower end of the rod may be connected to the upper surface of the piston located in the receiving chamber.

Further, a spring may be provided between the press plate and the main body.

In addition, a central axis passing through the center of the plurality of disks is provided in the center of the body, and the upper portion of the central axis can be coupled to the inside of the rod.

A sealing member, which is in close contact with a sidewall of the chamber, may be coupled to the side surface of the piston.

Further, the sealing member may be an O-ring.

An MR fluid flow path for allowing the MR fluid in the chamber to move to the upper portion of the chamber through the space between the first and second disks when the piston is lowered; As shown in FIG.

The MR fluid flow path may include a first main body flow path provided on a main body partition wall between the containing chamber and the disk array space; A disk passage communicating an upper end section with the first main flow path and providing a path for allowing the MR fluid to move between the first disk and the second disk; A second main flow path in which a lower end section is communicated with a lower end section of the disk flow path, the flow path being provided inside the main body partition wall between the plurality of disks and the solenoid coil; A housing main body having a housing main body and a housing main body; a housing main body having a housing main body; . ≪ / RTI >

The first path of the first disk and the second path of the second disk form a zigzag flow path, and the first path of the first disk is located at the center side edge, The two passages are located at the outer edge, and the first and second discs may be alternately layered.

A gap maintaining disc may be interposed between the first disc and the second disc.

In addition, the first passageway of the first disk and the second passageway of the second disk may be formed in a radiation pattern.

Also, the gap-maintaining disc may be provided with a third passage in a radial manner, and the third passage may communicate with the first passage of the first disc and the second passage of the second disc.

In addition, it is preferable that a gap maintaining disk is provided at the uppermost end of the disk array space, a first disk is located under the gap maintaining disk, a third passage is radially provided in the gap maintaining disk, The first main passage and the first passage of the first disc.

In addition, a bottom disk may be provided at the lowermost end of the disk array space, and the first disk may be arranged above the bottom disk.

In addition, the bottom disk is provided with a fourth passage having the same structure as the first passage of the first disk, a plurality of feet projecting downward along the bottom edge are formed, and a fifth passage is provided between the plurality of feet The plurality of feet may be brought into close contact with the bottom of the disk array space.

A gap retaining disc is interposed between the first disc and the bottom disc, a third passage is provided in a radial form in the gap retaining disc, and the third passageway is formed between the first passage of the first disc and the bottom disc And can communicate with the fourth passage.

According to the magnetorheological fluid-based linear actuator according to the embodiment of the present invention, the resistance of the actuator can be constantly generated according to the pressing distance.

Further, since the MR fluid flows between the magnetic bodies, no friction occurs between the metals.

Further, it is possible to provide an actuator having a constant resistive force for each stroke distance.

In addition, the actuator resistance range can be controlled according to the number and thickness of the disks installed in a stacked structure.

1 is a perspective view of a preferred embodiment of the present invention.
2 is an exploded perspective view of a preferred embodiment of the present invention.
3 is a side cross-sectional view of a preferred embodiment of the present invention.
4 is an enlarged cross-sectional view of a main body according to a preferred embodiment of the present invention.
5 is an enlarged cross-sectional view of a housing according to a preferred embodiment of the present invention.
Figure 6 is a flow diagram of a MR fluid in accordance with a preferred embodiment of the present invention.
7 is a view illustrating a state in which a plurality of disks are separated according to a preferred embodiment of the present invention.
8 is an enlarged view of a plurality of discs according to a preferred embodiment of the present invention.
9 is an enlarged view of a bottom disk according to a preferred embodiment of the present invention.
10 is a view showing a flow of a magnetic field according to a preferred embodiment of the present invention.
11 is a view showing a MR fluid when a magnetic field is not loaded according to a preferred embodiment of the present invention.
12 is a view showing MR fluid in a magnetic field load according to a preferred embodiment of the present invention.
13 is a view showing MR fluid in a strong magnetic field load according to a preferred embodiment of the present invention.
14 is a simulation result of a magnetic field of a conventional actuator.
15 is a simulation result of a magnetic field according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In addition, the preferred embodiments of the present invention will be described below, but it is needless to say that the technical idea of the present invention is not limited thereto and can be variously modified by those skilled in the art.

First, the configuration of a magnetorheological fluid-based linear actuator according to an embodiment of the present invention will be described.

1 and 2, a magnetorheological fluid-based linear actuator according to an embodiment of the present invention includes a main body 10 positioned below a housing 40, a plurality of disks 20 installed inside the main body 10, A solenoid coil 30 mounted inside the main body 10 to enclose the plurality of discs 20; a housing 40 in which the MR fluid 90 is received; a MR fluid 90 And a MR fluid flow path for providing a path of movement of the MR fluid 90. [

As shown in FIGS. 3 and 4, a disk array space 11 and a coil receiving space 13 are defined in the main body 10. In the disk array space 11, a plurality of disks 20 are accommodated. A solenoid coil (30) is accommodated in the coil receiving space (13). The disk array space 11 is located at the center of the main body 10 and the coil receiving space 13 is formed to surround the disk array space 11. [

The disk array space 11 and the storage chamber 41 are partitioned by the main body partition 14 between the disk array space and the storage chamber. The upper center of the body 10 is recessed. A lower portion of the housing 40 is inserted into the depression of the main body 10. The depressed portion of the main body 10 is formed to conform to the lower portion of the housing 40.

A center axis 12 may be provided at the center of the main body 10. The central axis 12 is located in the center of the disk array space 11. [ The upper end of the central axis 12 is located inside the rod 70. The center shaft 12 functions to guide the piston 50 in a downward direction. A plurality of discs 20 may be layered below the central axis 12. The central axis 12 may be a hollow hollow axis.

The plurality of disks 20 is a multi-stacked disk structure. The plurality of discs 20 are provided in the lower part of the storage chamber 41 so as to form a layer in the disc arrangement space 11 of the main body 10. The plurality of discs 20 may include a first disc 221 having a first passage 231 formed therein and a second passage 232 at a position not overlapping the first passage 231, And a second disk 222 located at a second position.

In FIG. 3, a plurality of disks 20 are arranged to form sixteen layers, but the present invention is not limited thereto. For example, the number of the plurality of disks 20 should be designed in consideration of the resistance of the actuator. By adjusting the number and thickness of the plurality of disks 20, the actuator resistance range can be initially changed.

The solenoid coil 30 is disposed in the coil accommodating space 13 inside the main body 10 in such a manner as to surround the side surfaces of the plurality of discs 20. When power is applied to the solenoid coil 30, a magnetic field is generated.

As shown in FIGS. 3 and 5, the housing 40 is disposed above the main body 10. A housing chamber (41) is provided in the housing (40). The MR fluid 90 is filled in the containing chamber 41. The lower portion of the housing 40 is coupled to the body 10 at the upper center. The lower portion of the housing 40 is located above the plurality of discs 20.

A pressure plate 60 is positioned on the upper portion of the housing 40. The pressure plate 60 is installed at a predetermined distance from the housing 40. When the pressure plate 60 is pressed, the piston 50 descends. The pressure plate 60 is connected to the piston 50 by a rod 70. The upper end of the rod 70 penetrates the upper surface of the housing 40 and is connected to the bottom surface of the pressure plate 60. The lower end of the rod (70) is connected to the upper surface of the piston (50) located in the containing chamber (41).

A spring (80) is provided between the pressure plate (60) and the main body (10). When the pressure plate 60 is pressed, the piston 50 is lowered and the spring 80 is compressed. When the pressing force of the pressure plate 60 disappears, the compressed spring 80 is stretched to push up the pressure plate 60 upward. The pressure plate 60 is returned to its original state before being pressurized by the extension of the spring 80.

The piston (50) is located above the containing chamber (41). The MR fluid 90 is filled in the region of the chamber 41 below the piston 50. The MR fluid 90 in the storage chamber 41 moves to the plurality of discs 20 positioned below when the piston 50 located above the storage chamber 41 performs the lowering operation.

When the MR fluid 90 flows between the plurality of disks 20 in the state where power is applied to the solenoid coil 30, the magnetic chain is strongly formed as the strength of the magnetic field is increased. When the magnetic chain is strongly formed, the viscosity of the MR fluid 90 increases and the resistance of the actuator increases.

Grooves are formed on side surfaces of the piston (50). A sealing member 51 is coupled to the groove of the piston 50. The sealing member 51 is brought into close contact with the inner wall surface of the housing chamber 41 to perform a sealing action. The sealing member 51 may be an O-ring or a packing.

A magnetorheological fluid-based linear actuator according to an embodiment of the present invention further includes an MR fluid channel. The MR fluid flow path provides a path of movement of the MR fluid 90. The MR fluid 90 moves to the upper portion of the containing chamber 41 through the plurality of discs 20 when the piston 50 is lowered in the containing chamber 41.

6, the MR fluid flow path includes a first main flow path 110, a disk flow path 220, a second main flow path 120, and a housing flow path 410.

Specifically, the first main flow passage 110 is provided in the main body partition wall 14 between the accommodation chamber and the disk arrangement space. When the piston 50 descends, the MR fluid 90 in the accommodation chamber 41 moves to the disk array space 11 through the first main flow path 110.

As shown in FIGS. 7-9, the disk flow path 220 provides a path for the MR fluid 90 to move between the plurality of disks 20. The upper end of the disc passage 220 communicates with the first main passage 110. The disk channel 220 is a channel formed naturally by the arrangement of the disks. The disk channel 220 forms a zigzag-shaped channel. The disk channel 220 includes a first disk 221 having a first passage 231 at a center side edge thereof and a second disk 231 having a second passage 232 at an outer edge thereof to form a zigzag- (222) are alternately layered.

The first passage 231 of the first disk 221 and the second passage 232 of the second disk 222 are formed in a radial shape.

A gap maintaining disc 223 is interposed between the first disc 221 and the second disc 222.

A gap retaining disk 223 may be interposed between the main body partition wall 14 between the accommodation chamber and the disk array space and the first disk 221. [

And the third passage 233 is provided in a radial shape in the gap holding disk 223. The third passage 233 is positioned between the first passage 231 of the first disk 221 and the second disk 233 of the first disk 221. In this state, And communicates with the second passage (232) of the second passage (222).

A bottom disk 224 is provided at the lowermost end of the disk array space 11. Above the bottom disc 224, a first disc 221 is arranged. The bottom disc 224 is provided with a fourth passage 234 having the same structure as the first passage 231 of the second disc 221. A plurality of feet 225 projecting downward along the bottom edge of the bottom disk 224 are formed.

A fifth passage 235 is provided between the plurality of feet 225 provided on the bottom disk 224. The plurality of feet 225 are brought into close contact with the bottom of the disk array space 11.

A gap maintaining disk 223 is interposed between the bottom disk 224 provided at the lowermost end of the disk array space 11 and the first disk 221 immediately above.

The structure of the first disk 221, the second disk 222, the gap maintaining disk 223, and the bottom disk 224 arranged in the disk array space 11 will be described in more detail as follows.

A disc 223 at the top of the disc array space 11, a first disc 221 below the disc 223, a disc 223 below the disc 223 below it, a second disc 222 below the disc 223, A second disc 222 below the first disc 221, a gap maintaining disc 223 below the first disc 221, a disc 223 below the first disc 221, A second disc 222 below the first disc 221, a gap-maintaining disc 223 below the disc 223, a first disc 221 below the disc 223, , And a bottom disc 224 under the disc. The order and number of such disks can be changed according to the initial resistance design.

The MR fluid 90 is supplied to the third passage 233 of the gap maintaining disk 223 constituting the disk channel 220, the first passage 231 of the first disk 221, The second passage 232, the fourth passage 234 of the bottom disk 224, and the fifth passage 235.

The second main flow passage 120 forms a straight flow passage. The second main flow passage 120 is provided inside the main partition 15 between the plurality of discs and the solenoid coil. The lower end section of the second main flow passage 120 communicates with the lower end section of the disk flow passage 220.

The housing flow path 410 forms a straight flow path. The housing passage 410 is provided inside the housing side wall 42. The lower end section of the housing channel 410 communicates with the upper end section of the second main channel 120. The upper end section of the housing channel 410 communicates with the upper portion of the housing chamber 41. The fluid 90 in the containing chamber 41 at the time of lowering the piston 50 flows through the first main flow passage 110, the disk flow passage 220, the second main flow passage 120 and the housing flow passage 410, 50 are located.

The following describes the MR fluid flow according to the piston lowering operation of the magnetorheological fluid-based linear actuator according to the embodiment of the present invention.

When the pressure plate 60 is pressed as shown in Fig. 6, the piston 50 in the containing chamber 41 descends. At this time, the spring 80 between the pressure plate 60 and the main body 10 is compressed. As the piston 50 descends, the MR fluid 90 flows along the MR fluid flow path as shown by the arrows in FIG. 6 through the plurality of disks 20 in the storage chamber 41 to the upper portion of the storage chamber 41 Move.

Specifically, the MR fluid 90 in the storage chamber 41, which is positioned below the piston 50 by the descent of the piston 50, moves to the disk channel 220 through the first main flow channel 110.

The MR fluid 90 passes through the third passage 233 of the gap maintaining disk 223, the first passage 231 of the first disk 221, the third passage 233 of the gap holding disk 223, The same channel as the second passage 232 of the disk 222 is repeatedly moved and moved through the fourth passage 234 and the fifth passage 235 of the lowermost bottom disk 224, (120).

The MR fluid 90 that has passed through the disc passage 220 moves to the housing passage 410 via the second main passage 120 provided between the plurality of discs 20 and the solenoid coil 30. The MR fluid 90 moves to the upper portion of the housing chamber 41 via the housing passage 410. [

The following describes the process in which MR fluid particles by magnetic field are arranged in a chain form.

When a power is applied to the solenoid coil 30 as shown by an arrow in FIG. 10, a magnetic field M is generated. 11, the MR fluid 90 has the property of being a liquid oil in a magnetic field no-load state. As shown in FIGS. 12 and 13, when the MR fluid 90 is affected by the magnetic field, the MR fluid 90 particles are arranged in a chain form.

Under the magnetic field load condition as shown in FIG. 12, the chain structure of the MR fluid 90 particles becomes harder when the magnetic field load state is strong as shown in FIG. As the magnetic field strength becomes stronger when the MR fluid 90 flows between the plurality of disks 20, the magnetic chain is strongly formed. When the magnetic chain is strongly formed, the viscosity of the MR fluid 90 increases, and the resistance of the actuator increases.

When the pressing force of the pressure plate 60 disappears, the compressed spring 80 is stretched to push up the pressure plate 60 upward. At this time, the piston 50 rises and returns to the upper portion of the pre-drop containing chamber 41. Conversely, the MR fluid 90, which was outside the chamber 41 at the same time as the piston 50 is lifted, is returned to the chamber 41 below the piston 50 again. This cycle is continuously and repeatedly performed by the operation of the piston (50).

14 is a simulation result of a magnetic field of a conventional actuator. 15 is a simulation result of a magnetic field according to an embodiment of the present invention.

As shown in FIG. 14, as a result of a simulation of a magnetic field of a conventional actuator, a conventional actuator has a coil and a piston coupled with each other and performs a rising operation, so that a magnetic field flows outside the main body. In addition, the magnetic force is not concentrated on the plurality of discs, which are the resistance generating unit, resulting in a result that the final resistance of the linear actuator is weakened.

As shown in FIG. 15, in the magnetic field simulation of the magnetorheological fluid-based linear actuator according to the embodiment of the present invention, the magnetorheological fluid-based linear actuator according to the embodiment of the present invention has a solenoid coil and a plurality of disks, And since the solenoid coil is fixed, the magnetic field is formed more uniformly than the conventional actuator. As a result, the resistive force due to the applied amount of current in the resistive force generating portion was constantly generated.

As described above, the magnetorheological fluid-based linear actuator according to the embodiment of the present invention can be constantly generated according to the pressing force of the resistance of the actuator. Further, since the MR fluid flows between the magnetic bodies, no friction occurs between the metals. In addition, the actuator resistance range can be controlled according to the number and thickness of the disks installed in a stacked structure.

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

10: Body
11: Disk array space
12: center axis
13: Coil receiving space
14: Body partition wall between the receiving chamber and the disk array space
15: a main body partition between a plurality of disks and a solenoid coil
20: Multiple disks
30: Solenoid coil
40: Housing
41: storage room
42: housing side wall
50: Piston
51: sealing member
60: pressure plate
70: Load
80: spring
90: MR fluid
110: first main body flow path
120: second main body flow path
220: Disk channel
221: first disk
222: second disk
223: Interval sustaining disk
224: floor disc
225: Foot
231: first passage
232: second passage
233: Third passage
234: fourth passage
235: fifth passage
410:
M: magnetic field

Claims (20)

A housing in which a housing chamber filled with MR fluid is formed;
A piston coupled to an inner surface of the containing chamber; And
A plurality of disks provided at the bottom of the containing chamber and spaced apart from each other;
/ RTI >
Wherein the plurality of discs comprise a first disc on which a first passage is formed and a second disc on which a second passage is formed in a position not overlapping the first passage and which is located under the first disc, Actuator.
The method according to claim 1,
A body disposed under the housing and having a disk array space therein; And
A solenoid coil provided inside the main body to enclose the side surfaces of the plurality of discs;
Wherein the linear actuator is a linear actuator.
The method of claim 2,
And a lower portion of the housing is coupled to the main body so as to be positioned above the plurality of discs.
The method of claim 2,
The piston,
Wherein the MR fluid is located above the chamber and pressurizes the MR fluid below through the lowering action to cause the MR fluid to flow between the plurality of discs.
The method of claim 2,
On the upper portion of the housing,
And a pressure plate connected to the piston by a rod is provided.
The method of claim 5,
Wherein the rod top is connected to the bottom surface of the presser plate through an upper surface of the housing, and the rod lower end is connected to an upper surface of the piston located in the containing chamber.
The method of claim 5,
Between the presser plate and the main body,
Wherein a spring is provided on the inner surface of the linear actuator.
The method of claim 5,
Wherein a central axis passing through the centers of the plurality of discs is provided in the center of the body, and an upper portion of the central axis is coupled to the inside of the rod.
The method of claim 2,
On the side surface of the piston,
And a sealing member that is in close contact with a sidewall surface of the inside of the accommodating chamber is coupled.
The method of claim 9,
Wherein the sealing member comprises:
Wherein the linear actuator is an O-ring.
The method of claim 2,
An MR fluid flow path for allowing the MR fluid in the chamber to move to the upper portion of the chamber through the gap between the first and second disks when the piston is lowered;
Further comprising: a linear actuator based on a magnetorheological fluid.
The method of claim 11,
The MR fluid flow path includes:
A first main body flow path provided on a main body partition wall between the containing chamber and the disk array space;
A disk passage communicating an upper end section with the first main flow path and providing a path for allowing the MR fluid to move between the first disk and the second disk;
A second main flow path in which a lower end section is communicated with a lower end section of the disk flow path, the flow path being provided inside the main body partition wall between the plurality of disks and the solenoid coil; And
A housing passage having a lower end section communicating with an upper end section of the second main flow passage and an upper end section communicating with an upper portion of the accommodating chamber;
Wherein the linear actuator is a linear actuator.
The method of claim 12,
Wherein the disk channel is formed by a first passage of the first disk and a second passage of the second disk,
Wherein the first passageway of the first disc is located at the center side edge and the second passageway of the second disc is located at the outer edge,
Wherein the first disk and the second disk are alternately arranged in layers.
The method of claim 2,
Wherein a gap maintaining disk is interposed between the first disk and the second disk.
15. The method of claim 14,
Wherein the first passage of the first disk and the second passage of the second disk are formed in a radial form.
15. The method of claim 14,
Wherein the gap maintaining disk is provided with a third passage in a radial manner and the third passage is in communication with the first passage of the first disk and the second passage of the second disk. .
The method of claim 12,
Wherein the disk storage space is provided with a gap maintaining disk, a first disk is located under the gap maintaining disk, a third passage is provided in a radial form in the gap maintaining disk, The main passage and the first passage of the first disk.
The method of claim 12,
Wherein a bottom disk is provided at the bottom end of the disk array space, and the first disk is arranged on the bottom disk.
19. The method of claim 18,
A fourth passage having the same structure as the first passage of the first disk is formed on the bottom disk, a plurality of feet projecting downward along the bottom edge are formed, a fifth passage is provided between the plurality of feet, Wherein a foot of the disk linear actuator is in close contact with a bottom of the disk array space.
The method of claim 19,
Wherein a gap retaining disc is interposed between the first disc and the bottom disc, wherein the gap retaining disc is provided with a third passageway in a radial form, and the third passageway is disposed between the first passageway of the first disc and the fourth passageway of the bottom disc And is communicated with the passage.

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