JP2024134191A - Magnetorheological Fluid Device - Google Patents

Abstract

[Problem] To suppress a pressure rise caused by the expansion of a gas sealed in a space filled with a magnetorheological fluid together with the magnetorheological fluid. [Solution] The present invention comprises a first part 100, a second part 200 provided so as to be movable relative to the first part 100, a magnetorheological fluid 303 interposed between the first part 100 and the second part 200, a magnetic field generating part 201 for applying a magnetic field to the magnetorheological fluid 300, and an enclosed space forming part 308 for forming an enclosed space 307 in which the magnetorheological fluid 303 is sealed, and a part of the enclosed space forming part 308 is configured using an oil-proof and ventilating means 202 that allows the gas to pass out of the enclosed space forming part without allowing the liquid contained in the magnetorheological fluid 303 to pass through. [Selected Figure] Figure 1

Description

The present invention relates to a magnetorheological fluid device that changes the force transmitted between components by interposing a magnetorheological fluid between the components and changing the strength of the magnetic field applied to the magnetorheological fluid.

This type of magnetorheological fluid device is disclosed, for example, in Patent Document 1. The magnetorheological fluid device disclosed in this document has a magnetorheological fluid interposed between a first part (100) and a second part (200), and changes the torque transmitted between the first part (100) and the second part (200) by changing the strength of the magnetic field applied to the magnetorheological fluid. In this magnetorheological fluid device, sealing materials are used in each gap to prevent the magnetorheological fluid sealed inside the device from leaking out.

In the magnetorheological fluid disclosed in the document, the magnetorheological fluid enclosed in the device expands in volume due to a rise in temperature, and in order to prevent the magnetorheological fluid from leaking out from gaps blocked by sealing material, a diaphragm (202) is provided that operates to expand and contract the volume of the space (307) in which the magnetorheological fluid is enclosed in response to the expansion and contraction of the volume of the magnetorheological fluid.

JP 2017-44215 A

When filling a magnetorheological fluid device with magnetorheological fluid, it is necessary to fill the space into which the magnetorheological fluid is to be filled while expelling gas such as air. However, if the space into which the magnetorheological fluid is to be filled has a shape that makes it difficult to expel gas, gas may remain in the space. Furthermore, when filling the magnetorheological fluid, fine air particles may get mixed in between the magnetic particles of the magnetorheological fluid, or air may end up dissolved in the magnetorheological fluid.

In this way, if gas remains or gets mixed in the space that contains the magnetorheological fluid, and the temperature of the magnetorheological fluid rises, the magnetorheological fluid itself will expand in volume, and the gas in the space will also expand in volume, which may exceed the allowable pressure reduction limit of the diaphragm or the pressure resistance limit of the seal. If this happens, there is an increased possibility that the magnetorheological fluid will leak to the outside.

The present invention aims to provide a magnetorheological fluid device that can suppress the pressure increase caused by the expansion of gas sealed together with the magnetorheological fluid in the space filled with the magnetorheological fluid.

The magnetorheological fluid device according to the first aspect of the present invention comprises a first part, a second part arranged to be movable relative to the first part, a magnetorheological fluid interposed between the first part and the second part, a magnetic field generating part for applying a magnetic field to the magnetorheological fluid, and an enclosed space forming part for forming an enclosed space that encloses the magnetorheological fluid. A part of the enclosed space forming part is configured using an oil-proof and ventilating means that allows gas to pass out of the enclosed space forming part without allowing liquid contained in the magnetorheological fluid to pass through.

The magnetorheological fluid device according to the second aspect of the present invention is a magnetorheological fluid device having the above configuration, and the oil-venting and blocking means is arranged to include positions where clusters will not be formed if the oil-venting and blocking means is removed, the portion from which the oil-venting and blocking means has been removed is filled with the same material as the enclosed space forming portion surrounding the portion where the oil-venting and blocking means was provided, and the magnetorheological fluid is subjected to a magnetic field.

The magnetorheological fluid device according to the third aspect of the present invention is the magnetorheological fluid device according to the second aspect, wherein the first part has a shaft provided so as to be rotatable relative to the second part, and a protruding part provided so as to rotate integrally with the shaft and protruding outward in the radial direction of the shaft from the shaft. The protruding part is disposed within the enclosed space so as to be entirely covered by the magnetorheological fluid. The magnetic field generating part forms a magnetic flux penetrating an inner annular region of the protruding part which is annular when viewed from the axial direction of the shaft, and an outer annular region of the protruding part which is spaced outward from the inner annular region. The oil-proof ventilation means is provided in a portion of the enclosed space forming part which is inner than the inner annular region when viewed from the axial direction.

The magnetorheological fluid device according to the fourth aspect of the present invention is the magnetorheological fluid device according to the second aspect, wherein the first part has a shaft provided so as to be rotatable relative to the second part, and a protruding part provided so as to rotate integrally with the shaft and protruding outward in the radial direction of the shaft from the shaft. The protruding part is disposed within the enclosed space so as to be entirely covered by the magnetorheological fluid. The magnetic field generating part forms a magnetic flux penetrating an inner annular region of the protruding part that is annular when viewed from the axial direction of the shaft, and an outer annular region of the protruding part that is spaced outward from the inner annular region. The oil-proof ventilation means is provided at the maximum diameter part of the enclosed space forming part that is outside the outer annular region when viewed from the axial direction.

A magnetorheological fluid device according to a fifth aspect of the present invention is the magnetorheological fluid device according to any one of the first to third aspects, further comprising a communication passage for communicating the oil-proof and venting means with the outside,
The communication passage is provided with one or more oil-proof/ventilation means separate from the oil-proof/ventilation means.

The present invention makes it possible to suppress the pressure increase caused by the expansion of gas sealed in the magnetorheological fluid-filled space together with the magnetorheological fluid.

1 is a cross-sectional view of a magnetorheological fluid device according to an embodiment of the present invention. 2 is a view of a disk provided in the magnetorheological fluid device according to the embodiment, viewed from the axial direction of the shaft. FIG. FIG. 2 is an enlarged view of part III in FIG. FIG. 11 is a cross-sectional view of a magnetorheological fluid device according to a modified example of the present embodiment. 7 is a cross-sectional view of a magnetorheological fluid device according to another modified example of the present embodiment, taken along line VV of FIG. 6. FIG. 11 is a side view of a magnetorheological fluid device according to another modified example of the present embodiment. FIG. 7 is an enlarged view of part VII in FIG. 5 .

The magnetorheological fluid device according to the embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the magnetorheological fluid device 1 according to this embodiment comprises a first part 100 and a second part 200 that are arranged to be rotatable relative to each other, and a bearing 301, a seal material 302, a magnetorheological fluid 303, etc., interposed between them.

The first part 100 is composed of a shaft 101, a disk 102, etc.

The shaft 101 is rotatably supported via bearings 301 in an axial hole formed in the casing 203 described below. It is preferable that a non-magnetic material is used for the shaft 101. The shaft 101 illustrated in FIG. 1 has four large-diameter portions with diameters larger than the diameter of the portion supported by the bearings 301.

The disk 102 is a protruding portion that protrudes from the shaft 101 in the radial direction of the shaft 101. The disk 102 is fixed to the shaft 101 so as to rotate integrally with the shaft 101. In this embodiment, the disk 102 is fixed to the end of the shaft 101. It is preferable that a magnetic material be used for the disk 102.

The second part 200 is composed of a magnetic field generating part 201, an oil-proof ventilation means 202, etc.

The magnetic field generating unit 201 applies a magnetic field to the magnetorheological fluid 303 interposed between the disk 102 and the casing 203. In this embodiment, the magnetic field generating unit 201 is composed of the casing 203, the coil 204, etc.

The casing 203 is composed of a first casing part 203A and a second casing part 203B made of a magnetic material, and a cover part 203C made of a non-magnetic material. The first casing part 203A and the second casing part 203B also function as a yoke for the magnetic field generating part 201. The first casing part 203A and the second casing part 203B have an approximately cylindrical external shape. The first casing part 203A and the second casing part 203B face each other with a ring-shaped member 205 made of a non-magnetic material between their outer peripheral edges, and are fitted into the cylindrical cover part 203C. The ring-shaped member 205 is inscribed in the inner peripheral surface of the cover part 203C over the entire circumference. A seal material 211 is provided between the outer peripheral surface of the second casing part 203B and the inner peripheral surface of the cover part 203C to seal the gap between them. This sealing material 211 seals the gap between the outer circumferential surface of the second casing part 203B and the inner circumferential surface of the cover part 203C, preventing the magnetorheological fluid 303 from leaking out of the gap.

In the first casing part 203A, there is formed an annular groove in which the coil 204 is disposed, and an axial hole through which the shaft 101 passes. In addition, a flat cylindrical space is formed between the first casing part 203A and the second casing part 203B by interposing the annular member 205. In this embodiment, this cylindrical space constitutes the majority of the enclosed space 307 that encloses the magnetorheological fluid 303.

A bearing 301 is fitted into the shaft hole formed in the first casing part 203A, and a seal material 302 that seals the gap between the shaft 101 and the shaft hole is provided at a position closer to the disk 102 than the bearing 301. This seal material 302 seals the gap between the shaft 101 and the shaft hole formed in the first casing part 203A, preventing the magnetorheological fluid 303 from leaking out of the gap.

The second casing portion 203B has a communication passage 208 that connects a part of the enclosed space forming portion 308 that forms the enclosed space 307 with the outside. In this embodiment, this communication passage 208 is provided on an extension of the shaft 101.

As described above, the coil 204 is wound in an annular groove formed in the casing 203, and a current is supplied from the outside via the lead wire 306. When a current is applied to the coil 204, a magnetic circuit is formed that passes through the first casing part 203A, the second casing part 203B, the disk 102, and the magnetorheological fluid 303 interposed between them, for example along the direction indicated by the arrow P in FIG. 1.

When a current is applied to the coil 204, the first casing part 203A and the second casing part 203B functioning as a yoke respectively generate a magnetic flux that penetrates the inner annular region S1, which is annular when viewed from the axis N direction of the shaft 101, in the disk 102 in the axis N direction, and the outer annular region S2, which is spaced outward from the inner annular region S1, in the axis N direction, as shown in FIG. 2. The multiple through holes 102a formed in the disk 102 are provided to prevent the magnetic flux from being directed toward the second casing part 203B side, and to prevent the main magnetic circuit from being formed between the first casing part 203A and the disk 102.

The oil-proof and venting means 202 allows gas to pass through without allowing liquid and magnetic particles contained in the magnetorheological fluid 303 to pass through. For example, a porous membrane having a surface coated with an oil repellent having oil repellency against the dispersion medium of the magnetorheological fluid 303 can be used as such an oil-proof and venting means 202. The oil-proof and venting means 202 constitutes a part of the enclosed space forming part 308 that forms the enclosed space 307 that encloses the magnetorheological fluid 303 in the magnetorheological fluid device 1. Therefore, in this embodiment, the enclosed space forming part 308 is composed of the wall surface surrounding the enclosed space 307 and the oil-proof and venting means 202. In this embodiment, the oil-proof and venting means 202 is provided at the end of the communicating passage 208 on the enclosed space 307 side so as to block the communicating passage 208. The oil-proof and venting means 202 provided at the end of the communication passage 208 on the enclosed space 307 side is fitted into an annular fitting groove formed at that end of the communication passage 208 using an adhesive (liquid seal). This prevents liquid from leaking out from around the oil-proof and venting means 202 to the communication passage 208 side.

The oil-proof and ventilating means 202 is provided at the end of the communication passage 208 on the enclosed space 307 side, and another oil-proof and ventilating means 202 is provided in the middle of the communication passage 208. As shown in FIG. 1, the second casing part 203B includes an outer member 203Ba arranged on the disk 102 side, and an inner member 203Bb fitted into a cylindrical recess formed in the outer member 203Ba. The oil-proof and ventilating means 202 provided in the middle of the communication passage 208 is sandwiched between the outer member 203Ba and the inner member 203Bb. This prevents liquid from leaking out of the communication passage 208 from around the oil-proof and ventilating means 202. The oil-proof and ventilating means 202 provided at the end of the communication passage 208 on the enclosed space 307 side can also be attached by a sandwiching structure like the oil-proof and ventilating means 202 provided in the middle of the communication passage 208.

The magnetorheological fluid 303 is enclosed in an enclosed space 307 within the magnetorheological fluid device 1, and in FIG. 1, the grey filled area represents the enclosed space 307 of the magnetorheological fluid. This magnetorheological fluid 303 is present in the gaps 307a, 307b between the disk 102 belonging to the first part 100 and the first casing part 203A and the second casing part 203B belonging to the second part 200, and transmits torque between them according to the viscosity. The disk 102 is placed in the enclosed space 307 so that it is entirely covered by the magnetorheological fluid 303.

The magnetorheological fluid 303 is a liquid in which magnetic particles are dispersed in a dispersion medium, and the magnetic particles may be, for example, nano-sized metal particles (metal nanoparticles). The magnetic particles are made of a magnetizable metal material, and although there is no particular restriction on the metal material, soft magnetic materials are preferred. Examples of soft magnetic materials include alloys such as iron, cobalt, nickel, and permalloy. The dispersion medium is not particularly limited, but one example is hydrophobic silicone oil. The amount of magnetic particles in the magnetorheological fluid may be, for example, 3 to 40 vol.%. Various additives can also be added to the magnetorheological fluid to obtain various desired properties.

In the magnetorheological fluid device 1 having the above configuration, when a current is applied to the coil 204, as described above, a magnetic circuit is formed within the casing 203 along the direction indicated by the arrow P in FIG. 1, and the magnetorheological fluid 303 present in the gaps 307a, 307b between the casing 203 and the disk 102 develops a viscosity (shear stress) according to the strength of the magnetic field. This allows torque transmission between the first part 100 (shaft 101, etc.) and the second part 200 (casing 203, etc.) according to the magnitude of the current applied to the coil 204.

In the magnetorheological fluid device 1 having the above configuration, when the magnetorheological fluid 303 and gas present in the enclosed space 307 expand in volume due to a rise in temperature, only the gas is discharged from the oil-proof and ventilating means 202 that constitutes part of the enclosed space forming part 308 of the magnetorheological fluid 303. The gas discharged from the oil-proof and ventilating means 202 is discharged to the outside through the communication passage 208. In the unlikely event that the gas expands in volume more than expected, causing the pores of the porous membrane used as the oil-proof and ventilating means 202 to expand and causing the dispersion medium of the magnetorheological fluid 303 to leak from the pores, another oil-proof and ventilating means 202 is provided in the communication passage 208, so that the dispersion medium of the magnetorheological fluid 303 is prevented from leaking out of the device.

As is clear from the above explanation, according to the magnetorheological fluid device 1 of the embodiment of the present invention, gas such as air contained in the enclosed space 307 in which the magnetorheological fluid 303 of the magnetorheological fluid device 1 is enclosed is discharged to the outside through the oil-proof ventilation means 202, so that the pressure increase caused by the expansion of the gas can be suppressed.

The region where the oil-proof and venting means 202 is provided is provided in a portion inside the inner annular region S1 where magnetic flux does not pass through the disk 102 when viewed from the direction of the axis N. This portion includes a position where the magnetorheological fluid 303 does not form a cluster even when a current is applied to the coil 204 (for example, a position near the axis N of the shaft 101). In this embodiment, the position where the cluster is not formed is a position where the magnetorheological fluid 303 does not form a cluster even if the oil-proof and venting means 202 is removed and the portion from which the oil-proof and venting means 202 is removed (and also the communicating passage 208 if it is present) is filled with the same material (magnetic material in this embodiment) as the enclosed space forming portion 308 around the portion where the oil-proof and venting means 202 was provided, and the magnetorheological fluid 303 is applied with a magnetic field. Since the magnetic particles contained in the magnetorheological fluid 303 tend to accumulate in places where they form clusters, the oil-proof and venting means 202 is provided in a part of the enclosed space forming portion 308 where the magnetic particles are unlikely to accumulate, thereby preventing clogging of the oil-proof and venting means 202.

<Another embodiment 1>
In the embodiment described above, it is possible to omit one of the two oil-proof and venting means 202 provided in the communication passage 208. It is also possible to provide the oil-proof and venting means 202 at the outer end of the communication passage 208.

<Another embodiment 2>
In the above-described embodiment, the positions of the communication passage 208 and the oil-proof and venting means 202 can be changed to positions in the enclosed space forming portion 308 that overlap with the coil 204 when viewed from the axis N direction (see FIG. 4). In this case, the oil-proof and venting means 202 is provided in a portion outside the inner annular region S1 and the outer annular region S2 through which the magnetic flux does not pass with respect to the disk 102 when viewed from the axis N direction. The portion provided with the oil-proof and venting means 202 includes a position where the magnetorheological fluid 303 is less likely to form clusters or does not form clusters compared to the surrounding area even when a current is applied to the coil 204, so that clogging of the oil-proof and venting means 202 can be suppressed as described above. The communication passage 208 is perpendicular to the magnetic circuit formed along the direction of the arrow P in FIG. 4, but the magnetic resistance increased by this is slight. 4 is provided with only one oil-proof and venting means 202, a plurality of oil-proof and venting means 202 may be provided at intervals in the communicating passage 208. It is also possible to form a plurality of communicating passages 208 in a doughnut-shaped region where the coil 204 and the enclosed space forming portion 308 overlap as viewed from the direction of the axis N, and provide each of the communicating passages 208 with an oil-proof and venting means 202.

<Other embodiment 3>
In the above-described embodiment, the portion where the oil-proof and venting means 202 is provided may be changed to the portion that is the maximum diameter portion of the enclosed space forming portion 308 as shown in Figs. 5 to 7, and the communication passage 208 may be omitted. The oil-proof and venting means 202A illustrated in Figs. 5 to 7 is cylindrical and forms the outer periphery of the enclosed space forming portion 308 that forms the enclosed space 307 formed between the first casing portion 203A and the second casing portion 203B. The maximum diameter portion of the enclosed space forming portion 308 is located outside the outer annular region S2 shown in Fig. 2. This portion is where the magnetorheological fluid 303 does not form clusters even when a current is applied to the coil 204, and therefore, as described above, clogging of the oil-proof and venting means 202A can be suppressed.

When providing the oil-proofing and venting means 202A at the maximum diameter portion of the enclosed space forming portion 308, the cover portion 203C of the casing 203 is changed to the cover portion 203D as shown in Figures 5 to 7. The cover portion 203D is the cover portion 203C shown in Figure 1 with multiple slits 206 formed at the portion that intersects with the radially outward side of the disk 102.

In addition, instead of the annular member 205 provided between the first casing part 203A and the second casing part 203B, an annular oil-proof and venting means 202A having a width dimension larger than the gap dimension between the first casing part 203A and the second casing part 203B is provided. The outer peripheral surface of the annular oil-proof and venting means 202A is flush with the outer peripheral surfaces of the first casing part 203A and the second casing part 203B. In addition, annular recesses 203Aa, 203Ba into which both sides of the oil-proof and venting means 202A fit are formed at the outer peripheral ends of the first casing part 203A and the second casing part 203B. Then, the oil-proof and venting means 202A is assembled into the first casing part 203A and the second casing part 203B, which are fitted into the cover part 203D. Additionally, the cover part 203C is fixed to the first casing part 203A and the second casing part 203B. Fixing devices 207 such as screws are used for fixing.

<Other embodiment 4>
In the above-described embodiment, a particle removing means may be provided for removing magnetic particles and the like on the oil prevention and ventilation means 202, 202A in conjunction with the movement of the disk 102 relative to the oil prevention and ventilation means 202, 202A. As the particle removing means, for example, a brush may be provided on the end of the shaft 101 shown in Fig. 1. In this case, the brush can remove magnetic particles accumulated on the surface of the oil prevention and ventilation means 202 provided on the extension of the shaft 101 while rotating together with the shaft 101.

<Other embodiment 5>
In the embodiment described above, the oil-proof and venting means 202, 202A are attached to the first casing part 203A and the second casing part 203B made of a magnetic material, but it is also possible to make the peripheral parts of the oil-proof and venting means 202, 202A (the peripheral parts of the oil-proof and venting means 202, 202A such as the first casing part 203A and the second casing part 203B) out of a non-magnetic material, which can better prevent clogging due to magnetic particles.

The configurations of each of the embodiments described above can be combined in part or in whole, unless there is a particular contradiction.

The present invention is applicable to magnetorheological fluid devices that change the force transmitted between components by interposing a magnetorheological fluid between the components and changing the strength of the magnetic field applied to the magnetorheological fluid.

N: axis line S1: inner annular region S2: outer annular region 1: magnetorheological fluid device 100: first part 101: shaft 102: disk (projection)
200 Second part 201 Magnetic field generating part 202 Oil-proof/ventilating means 202A Oil-proof/ventilating means 203A First casing part (yoke)
203B Second casing part (yoke)
204 Coil 206 Slit 208 Communication passage 303 Magnetorheological fluid 307 Enclosed space 308 Enclosed space forming portion

Claims (5)

Part 1 and
a second part provided so as to be movable relative to the first part;
a magnetorheological fluid interposed between the first portion and the second portion;
a magnetic field generating unit for applying a magnetic field to the magnetorheological fluid;
an enclosing space forming part that forms an enclosing space in which the magnetorheological fluid is enclosed;
Equipped with
a part of the enclosed space forming portion is configured using an oil-proof and ventilating means that allows gas to pass to the outside of the enclosed space forming portion without allowing the liquid contained in the magnetorheological fluid to pass therethrough;
A magnetorheological fluid device comprising: 2. The magnetorheological fluid device of claim 1,
the oil-proof and venting means is provided so as to include a position where no clusters are formed when the oil-proof and venting means is removed, the portion from which the oil-proof and venting means has been removed is filled with the same material as the enclosed space forming portion surrounding the portion where the oil-proof and venting means was provided, and a magnetic field is applied to the magnetorheological fluid.
A magnetorheological fluid device comprising: 3. The magnetorheological fluid device according to claim 2,
The first part comprises:
A shaft provided so as to be rotatable relative to the second portion;
a protruding portion provided to rotate integrally with the shaft and protruding outward in a radial direction of the shaft from the shaft;
having
the protruding portion is disposed within the enclosed space so as to be entirely covered by the magnetorheological fluid;
The magnetic field generating unit generates a magnetic flux passing through an inner annular region of the protruding portion that is annular when viewed from the axial direction of the shaft and an outer annular region of the protruding portion that is spaced outward from the inner annular region,
the oil-preventing and venting means is provided in a portion of the enclosed space forming portion that is located inside the inner annular region when viewed from the axial direction,
A magnetorheological fluid device comprising: 3. The magnetorheological fluid device according to claim 2,
The first part comprises:
A shaft provided so as to be rotatable relative to the second portion;
a protruding portion provided to rotate integrally with the shaft and protruding outward in a radial direction of the shaft from the shaft;
having
the protruding portion is disposed within the enclosed space so as to be entirely covered by the magnetorheological fluid;
The magnetic field generating unit generates a magnetic flux passing through an inner annular region of the protruding portion that is annular when viewed from the axial direction of the shaft and an outer annular region of the protruding portion that is spaced outward from the inner annular region,
the oil-preventing and venting means is provided at a maximum diameter portion of the enclosed space forming portion which is located outside the outer annular region when viewed from the axial direction,
A magnetorheological fluid device comprising: 4. The magnetorheological fluid device according to claim 1,
A communication passage is formed to connect the oil-preventing and venting means with the outside,
The communication passage is provided with one or more oil-proof and venting means separate from the oil-proof and venting means,
A magnetorheological fluid device comprising:

Images