JP2024091252A - Active vibration isolation device and its manufacturing method - Google Patents

Abstract

An active vibration isolation device of the present invention suppresses performance degradation caused by settling of magnetic powder of a magnetorheological fluid in a fluid chamber without increasing the volume of the fluid chamber filled with the magnetorheological fluid.
[Solution] The active vibration isolation device 1A has an electromagnetic coil 12 (magnetic field generating unit) that generates a magnetic field, a magnetic body that forms a magnetic path by the magnetic field, a first liquid chamber 15 filled with a magnetorheological fluid 20b, and a second liquid chamber 21 adjacent to the first liquid chamber 15 and filled with liquid 20a, and the electromagnetic coil 12, the magnetic body, the first liquid chamber 15, and the second liquid chamber 21 are arranged radially between the inner tube 3 and the outer tube 2, the first liquid chamber 15 and the second liquid chamber 21 are separated by a flexible member 14, and the first liquid chamber 15 has an orifice portion 15a located on the magnetic path.
[Selected figure] Figure 4

Description

The present invention relates to an active vibration isolation device and its manufacturing method.

In recent years, efforts to provide access to sustainable transport systems that take into consideration vulnerable transport participants such as the elderly, people with disabilities and children have been gaining momentum. To achieve this, we are focusing on research and development to further improve transport safety and convenience through development of vehicle livability.
Conventionally, active vibration isolation devices have been proposed for use in subframe mounts, suspension bushes, etc., for the purpose of improving the habitability of vehicles by suppressing noise and vibrations in the vehicle cabin (see, for example, Patent Document 1). Specifically, this active vibration isolation device has two liquid chambers filled with magnetorheological fluid connected to each other by a flow path, and is equipped with an excitation coil that forms a magnetic path in a direction intersecting the flow path. This active vibration isolation device controls the flow of the magnetorheological fluid by varying the magnetic flux density generated by the excitation coil when the magnetorheological fluid tries to flow through the flow path from one liquid chamber to the other liquid chamber in response to the magnitude of the input vibration amplitude. This allows the active vibration isolation device to exhibit flexible damping characteristics in response to the magnitude of the input vibration amplitude.

JP 2021-71117 A

In conventional active vibration isolation devices (see, for example, Patent Document 1), the volume of the liquid chamber can be increased to improve response performance to the input vibration amplitude, but this increases the amount of relatively heavy and expensive magnetorheological fluid that is filled into the liquid chamber, which contains magnetic powder. This creates new problems for active vibration isolation devices, such as increased manufacturing costs and an increased weight for the vehicle in which they are installed. Furthermore, with active vibration isolation devices, as the amount of magnetorheological fluid used increases, the absolute amount of magnetic powder contained in the magnetorheological fluid that settles also increases, which can lead to a decrease in the performance of the active vibration isolation device.

The present invention aims to provide an active vibration isolation device and a manufacturing method thereof that can improve response performance to external forces such as input vibrations and loads without increasing the volume of the liquid chamber filled with magnetorheological fluid, and can also suppress performance degradation due to settling of magnetic powder in the magnetorheological fluid in the liquid chamber. This will ultimately contribute to the development of sustainable transportation systems.

The active vibration control device of the present invention, which solves the above problem, is an active vibration control device having an outer tube, an inner tube arranged on the inner periphery of the outer tube, a magnetic field generating unit that generates a magnetic field, a magnetic body that forms a magnetic path by the magnetic field, a first liquid chamber filled with a magnetorheological fluid, and a second liquid chamber adjacent to the first liquid chamber and filled with liquid, wherein the magnetic field generating unit, the magnetic body, the first liquid chamber, and the second liquid chamber are provided radially between the inner tube and the outer tube, the first liquid chamber and the second liquid chamber are separated by a flexible member, and a part of the first liquid chamber forms a flow path for the magnetorheological fluid located on the magnetic path.

The present invention, which solves the above problem, is a manufacturing method for the active vibration isolation device, which includes an injection process for injecting the magnetorheological fluid into the first liquid chamber, and is characterized in that the injection process is carried out by combining the magnetic field generating unit, the magnetic body, and the flexible member in a liquid consisting of the magnetorheological fluid.

The active vibration isolation device and manufacturing method of the present invention can improve response performance to external forces such as input vibrations and loads without increasing the volume of the liquid chamber filled with magnetorheological fluid, and can also suppress performance degradation due to precipitation of magnetic powder in the magnetorheological fluid in the liquid chamber.

1 is a side view of an active vibration isolation device according to a first embodiment of the present invention; FIG. 1B is a plan view of the active vibration isolation device as viewed from the IB direction in FIG. 1A. FIG. 2 is a partially cutaway perspective view of an active vibration isolation device including a cross section along line II-II of FIG. 1B. FIG. 1B is an exploded perspective view of the active vibration isolation device shown in FIG. 1A. FIG. 2 is a cross-sectional view taken along line II-IV of FIG. 1B. 4 is a partially cutaway perspective view of an assembly of a first liquid chamber forming portion and a magnetic field forming portion in an active vibration isolation device. FIG. 13A and 13B are diagrams illustrating the action of the liquid in the second liquid chamber when a load is applied to the inner cylinder in a direction perpendicular to the axis. 11A and 11B are diagrams illustrating the movement of a magnetorheological fluid when the bottom wall of a flexible member is bent. 6A and 6B are schematic diagrams showing the behavior of magnetic powder when a magnetic field is applied to an orifice portion of a first liquid chamber. FIG. 5 is a cross-sectional view of an active vibration isolation device according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view of an active vibration isolation device according to a third embodiment of the present invention. FIG. 11 is a cross-sectional view of an active vibration isolation device according to a fourth embodiment of the present invention. FIG. 13 is an exploded perspective view of an active vibration isolation device according to a fifth embodiment of the present invention. FIG. 8B is a perspective view of the second magnetic path forming member shown in FIG. 8A. 13 is a partially cutaway perspective view of an assembly of a first liquid chamber forming portion and a magnetic field forming portion in an active vibration isolation device according to a fifth embodiment of the present invention. FIG. FIG. 13 is a partially cutaway perspective view showing a state in which a magnetic path is formed in an orifice portion by an electromagnetic coil to which a current is applied in an active vibration isolation device according to a fifth embodiment of the present invention. FIG. 13 is a cross-sectional view of an active vibration isolation device according to a sixth embodiment of the present invention. FIG. 12 is a partially enlarged cross-sectional view of part XII in FIG. 11 . 13 is a partially enlarged cross-sectional view showing a state in which a magnetic path is formed in an orifice portion by an electromagnetic coil to which a current is applied in an active vibration isolation device according to a sixth embodiment of the present invention. FIG. FIG. 13 is a cross-sectional view of an active vibration isolation device according to a seventh embodiment of the present invention. FIG. 15 is a partially enlarged cross-sectional view of part XV in FIG. 14 . 13 is a partially enlarged cross-sectional view showing a state in which a magnetic path is formed in an orifice portion by an electromagnetic coil to which a current is applied in an active vibration isolation device according to a seventh embodiment of the present invention. FIG. FIG. 13 is an exploded perspective view of an active vibration isolation device according to an eighth embodiment of the present invention. FIG. 13 is a vertical cross-sectional view of an active vibration isolation device according to a ninth embodiment of the present invention. 13 is an overall perspective view of a first liquid chamber forming portion/magnetic field forming portion assembly in an active vibration isolation device according to a ninth embodiment. FIG. 13 is an exploded oblique view of a first liquid chamber forming portion/magnetic field forming portion assembly in an active vibration isolation device according to a ninth embodiment. FIG. 21 is an overall perspective view of the flexible member shown in FIG. 20 as viewed from the rear surface side. This is a cross-sectional view of XXIb-XXIb in Figure 21A. 21 is an overall perspective view of the first magnetic path forming member shown in FIG. 20 as viewed from the front surface side. 21 is an overall perspective view of the second magnetic path forming member shown in FIG. 20 as viewed from the back surface side. 21 is an explanatory diagram of the operation of the first liquid chamber forming portion shown in FIG. 20. FIG. 20 is a partially enlarged cross-sectional view of part XXV in FIG. 18 .

Next, embodiments (first to ninth embodiments) for carrying out the active vibration isolation device of the present invention will be described in detail with reference to the drawings as appropriate.
[First embodiment]
Fig. 1A is a side view of an active vibration isolation device 1A according to a first embodiment of the present invention, Fig. 1B is a plan view of the active vibration isolation device 1A as viewed from the IB direction in Fig. 1A.

As shown in Figures 1A and 1B, the active vibration isolation device 1A of this embodiment comprises an outer tube 2, an inner tube 3 arranged approximately coaxially on the inner side of the outer tube 2, and a damping section main body 4 arranged between the outer tube 2 and the inner tube 3.
1A, reference symbol Sp1 denotes a first support member that supports the active vibration isolation device 1A, and reference symbol Sp2 denotes a second support member that supports the active vibration isolation device 1A. The first support member Sp1 and the second support member Sp2 are indicated by virtual lines (two-dot chain lines).
<Outer cylinder>
The outer cylinder 2 is formed of a cylindrical body having a larger diameter than the inner cylinder 3. In this embodiment, the outer cylinder 2 is formed of a non-magnetic material.
Examples of non-magnetic materials include, but are not limited to, aluminum alloys, non-ferritic SUS, copper, and engineering plastics.
As shown in FIG. 1A, the outer periphery of the outer cylinder 2 is supported by the first support member Sp1.

<Inner cylinder>
1A, the inner cylinder 3 is formed to be longer in the axial direction than the outer cylinder 2. The axial end of the inner cylinder 3 protrudes slightly axially outward from the end of the outer cylinder 2. Note that the inner cylinder 3 in this embodiment is assumed to be made of a non-magnetic material.

As shown in Fig. 1A, a shaft member Sf having threaded portions at both ends is inserted into the inner periphery of the inner cylinder 3. In Fig. 1A, the shaft member Sf is indicated by a virtual line (two-dot chain line).
A nut N1 is fastened to one end of the shaft member Sf disposed so as to penetrate the second support member Sp2, and a nut N2 is fastened to the other end of the shaft member Sf protruding from the inner cylinder 3. In Fig. 1A, the nuts N1 and N2 are indicated by virtual lines (two-dot chain lines).
As a result, the inner cylinder 3 is supported by the second support member Sp2.
Also, although not shown in the figure, the inner tube 3 can be configured so that both ends of the shaft member Sf pass through a pair of second support members Sp2 and are respectively fastened with nuts N1 and N2 so as to be clamped between the pair of second support members Sp2.

In such an active vibration isolation device 1A, vibrations from a specific vibration source or external loads (hereinafter sometimes simply referred to as "vibrations, etc.") are input to the outer cylinder 2 via the first support member Sp1, or to the inner cylinder 3 via the second support member Sp2, or to the outer cylinder 2 and inner cylinder 3 via the first support member Sp1 and the second support member Sp2.

<Damping unit body>
Next, a description will be given of the damping body 4 (see FIG. 1B). The damping body 4 damps vibrations and the like input from at least one of the outer cylinder 2 (see FIG. 1B) and the inner cylinder 3 (see FIG. 1B).
Fig. 2 is a perspective view of the active vibration isolation device 1A including a cross section taken along line II-II of Fig. 1B. Fig. 3 is an exploded perspective view of the active vibration isolation device 1A.
2, the damping portion main body 4 is disposed radially between the inner cylinder 3 and the outer cylinder 2. The damping portion main body 4 has a first liquid chamber 15 filled with a magnetorheological fluid 20b, and a second liquid chamber 21 filled with a liquid 20a that is a vibration transmission medium, which will be described later.

Specifically, as shown in FIG. 3, the damping unit main body 4 is mainly composed of a first liquid chamber forming section 6, a second liquid chamber forming section 7, and a magnetic field forming section 5. Here, we will explain the second liquid chamber forming section 7, and then explain the assembly As in which the first liquid chamber forming section 6 and the magnetic field forming section 5 are integrated together.

(Second liquid chamber forming portion)
As shown in Figure 3, the second liquid chamber forming portion 7 has a liquid chamber partitioning portion 22 that defines the second liquid chamber 21 on the outer circumferential side of the inner tube 3, and an elastic support portion 23 that elastically supports this liquid chamber partitioning portion 22 on the outer circumferential surface of the inner tube 3.
The liquid chamber partition 22 has a generally top-like shape including a cylindrical shaft portion 22a that accommodates the inner cylinder 3 therein, and a columnar portion 22b that is larger in diameter than the shaft portion 22a.
The second liquid chamber 21 is formed by partially removing the cylindrical portion 22b of the liquid chamber partition portion 22 in the circumferential direction.

When such a liquid chamber partition 22 is positioned on the inner side of the outer tube 2, it further divides the internal space formed by partially dividing the inner tube 3 and the outer tube 2 in the axial direction, thereby forming a pair of second liquid chambers 21 on the outer side of the inner tube 3.
As shown by hidden lines (dotted lines) in FIG. 1B, the pair of second liquid chambers 21 are formed to face each other with a phase difference of 180 degrees between them, sandwiching the inner cylinder 3 therebetween.
As shown in FIG. 2, the inner wall of the second liquid chamber 21 on the outer circumferential side is formed by the inner wall of the outer cylinder 2.

In addition, as shown in Figure 3, the second liquid chamber 21 has a communicating groove 21a consisting of an arc-shaped slit so as to face the groove-like recess 16 of the flexible member 14 described below that constitutes the first liquid chamber forming portion 6 when the second liquid chamber forming portion 7 and the first liquid chamber forming portion 6 are overlapped.
Specifically, as shown in Figure 4, which is a cross-sectional view taken along line II-IV of Figure 1B, the communication groove 21a is formed so as to face the groove-like recess 16 of the flexible member 14 at approximately the center in the radial direction of the cylindrical portion 22b that constitutes the liquid chamber partitioning portion 22. The bottom wall 17 that constitutes the groove-like recess 16 of the flexible member 14 forms a part of the second liquid chamber 21, and also forms a part of the first liquid chamber 15, as will be described in detail later.
In this embodiment, the liquid chamber partition 22 is assumed to be made of a non-magnetic material. As the liquid 20a filled in the second liquid chamber 21, for example, a known hydraulic oil such as silicone oil or ester oil can be suitably used.

Next, the elastic support portion 23 (see FIG. 3) will be described.
As shown in Figure 4, the elastic support portion 23 is composed of a cylindrical main body portion 23a arranged on the outer peripheral surface of the inner tube 3, and a covering portion 23b that partially covers the cylindrical portion 22b of the liquid chamber partition portion 22.
Incidentally, the covering portion 23b is also formed on the outer circumferential surface of the cylindrical portion 22b and on the inner wall surface of the cylindrical portion 22b that defines the second liquid chamber 21. The main body 23a of the elastic support portion 23 and the covering portion 23b formed on the outer circumferential surface of the cylindrical portion 22b are continuous with each other via the covering portion 23b formed on the inner wall surface of the second liquid chamber 21.

The elastic support portion 23 in this embodiment is assumed to be made of synthetic rubber, such as silicone rubber, and is vulcanization bonded to the inner tube 3 and the cylindrical portion 22b.
The main body 23a of the elastic support 23 allows relative displacement in the direction perpendicular to the axis between the inner tube 3 and the outer tube 2. In addition, the covering portion 23b of the elastic support 23 ensures sealing of the liquid 20a filled in the second liquid chamber 21.

(Assembly)
Next, a description will be given of a generally cylindrical assembly As (see FIG. 3) in which the first liquid chamber forming portion 6 (see FIG. 3) and the magnetic field forming portion 5 (see FIG. 3) are assembled so as to be integral with each other.
3, the first liquid chamber forming portion 6 is mainly composed of a flexible member 14, a first magnetic path forming member 8, and a second magnetic path forming member 9. The first magnetic path forming member 8 and the second magnetic path forming member 9 also serve as components of the magnetic field forming portion 5.

As shown in FIG. 3, the flexible member 14 has a ring shape, and is disposed inside the cylindrical first magnetic path forming member 8 .
As described above, the flexible member 14 has a pair of arcuate groove-like recesses 16 .
FIG. 5 is a partially cutaway perspective view of the assembly As having a cross section corresponding to the cross section II-IV of FIG. 1B.

As shown in Figure 5, the portion of the flexible member 14 where the groove-shaped recess 16 is formed has a liquid chamber recess 19 on the opposite side of the groove-shaped recess 16 across the bottom wall 17, which cooperates with the second magnetic path forming member 9 to define the first liquid chamber 15.
The liquid chamber recess 19 of the flexible member 14 is formed in an arc shape in the circumferential direction so as to correspond to the groove-shaped recess 16. That is, as shown in Figure 4, the second liquid chamber 21 and the first liquid chamber 15 are separated by the bottom wall 17 of the flexible member 14, which has flexibility.

5, the outer circumferential portion of the flexible member 14 is supported by the first magnetic path forming member 8. Specifically, the outer circumferential portion of the flexible member 14 where the liquid chamber recess 19 is formed is fixed by a flange portion 10a extending inward from the inner circumferential side of the first magnetic path forming member 8 to the height of the bottom wall 17, which penetrates into the solid portion of the outer circumferential portion of the flexible member 14. Furthermore, a portion 18b of the flexible member 14 not having the bottom wall 17 is fixed to a flange portion 10b extending from the inner circumferential side of the first magnetic path forming member 8 to near the inner circumferential surface of the flexible member 14.
As shown in FIG. 3, the portion 18 a of the flexible member 14 having the bottom wall 17 is formed in a pair so as to correspond to the communication grooves 21 a of the pair of second liquid chambers 21 .

5, the first liquid chamber 15 extending in the circumferential direction so as to correspond to the bottom wall 17 extends in the circumferential direction between the flange portion 10b and the second magnetic path forming member 9 in the portion 18b that does not have the bottom wall 17. As a result, the first liquid chamber 15 extending in the portion 18b that does not have the bottom wall 17 has a smaller cross-sectional area than the first liquid chamber 15 extending in the portion 18a that has the bottom wall 17.
In other words, although not shown in the figure, a pair of first liquid chambers 15 having a large cross-sectional area extending in an arc corresponding to the second liquid chamber 21 form an annular liquid chamber together with a pair of first liquid chambers 15 having a small cross-sectional area.

The first fluid chamber 15 formed in such an annular shape is filled with the magnetorheological fluid 20b as described above.
As will be described in detail later, when the magnetorheological fluid moves between the pair of large cross-sectional area first liquid chambers 15, the small cross-sectional area first liquid chambers 15 form an orifice portion 15a. That is, the orifice portion 15a forming a part of the first liquid chambers 15 forms a flow path for the magnetorheological fluid located on the magnetic path Mc (see FIG. 6B).
The magnetorheological fluid filled in the first liquid chamber 15 may be a known magnetorheological fluid (MRF) or magnetorheological compound (MRC) in which magnetic powder is dispersed in mineral oil or synthetic oil.

Next, the magnetic field generating unit 5 (see FIG. 5) will be described.
5, the magnetic field generating unit 5 is mainly configured to include, in addition to the first magnetic path forming member 8 and the second magnetic path forming member 9, an electromagnetic coil 12 and a third magnetic path forming member 11. The electromagnetic coil 12 corresponds to the "magnetic field generating unit" in the claims.
As shown in FIG. 3 , the second magnetic path forming member 9 , the electromagnetic coil 12 , and the third magnetic path forming member 11 are formed in a ring shape having a smaller diameter than the first magnetic path forming member 8 .

As shown in FIG. 5, the second magnetic path forming member 9 has an L-shaped cross section, which is made up of a flat ring portion 91 and a cylindrical portion 92 formed on the inner periphery of the ring portion 91 .
The second magnetic path forming member 9 having an L-shaped cross section cooperates with the flat plate-shaped third magnetic path forming member 11 to form a U-shaped cross section that opens radially outward.
The second magnetic path forming member 9 is arranged on the inner circumferential side of the first magnetic path forming member 8 so as to form an orifice portion 15a between the flange portion 10b of the first magnetic path forming member 8, and thus a placement chamber 13 for the electromagnetic coil 12 is formed on the inner circumferential side of the first magnetic path forming member 8, the placement chamber 13 being surrounded by the second magnetic path forming member 9 and the third magnetic path forming member 11.
At this time, the third magnetic path forming member 11 is magnetically connected to the first magnetic path forming member 8 , and the second magnetic path forming member 9 abuts against the first magnetic path forming member 8 via the flexible member 14 .

As a result, the magnetic field generating unit 5 forms a magnetic path Mc (see FIG. 6B) passing through the magnetorheological fluid 20b in the orifice portion 15a by the electromagnetic coil 12 to which a current is applied, as described below.
The first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11 are assumed to be made of a magnetic material such as iron, cobalt, nickel, or an alloy of these.
As shown in Figure 5, the above-mentioned assembly As is an approximately cylindrical body having an outer peripheral surface Os that fits inside the outer tube 2 (see Figure 4) and an inner peripheral surface Is that fits into the shaft portion 22a (see Figure 4) of the second liquid chamber forming portion 7 (see Figure 4).

As a manufacturing method for such an active vibration isolation device 1A, for example, as shown in FIG. 3, there is a method including a step of forming the inner tube 3 and the liquid chamber partition 22 integrally via the elastic support 23, a step of forming an assembly As by assembling the second magnetic path forming member 9, the electromagnetic coil 12, and the third magnetic path forming member 11 to the first magnetic path forming member 8 formed integrally with the flexible member 14, and a step of assembling the integrated inner tube 3 and the liquid chamber partition 22 to the assembly As and storing it in the outer tube 2.

In addition, in this manufacturing direction, the process of filling the first liquid chamber 15 (see FIG. 5) of the assembly As with the magnetorheological fluid (enclosing process) can be performed by combining the second magnetic path forming member 9 (magnetic body), the electromagnetic coil 12, and the third magnetic path forming member 11 (magnetic body) in a liquid consisting of the magnetorheological fluid when assembling the first magnetic path forming member 8 (magnetic body).

<Action and effect>
Next, the operation of the active vibration isolation device 1A of this embodiment will be described, along with the effects of the active vibration isolation device 1A.
Fig. 6A is a diagram showing the action of the liquid 20a in the second liquid chamber 21 when an external force L is applied to the inner cylinder 3 in the axial direction. Fig. 6B is a schematic diagram showing the movement of the magnetorheological fluid 20b when the bottom wall 17 of the flexible member 14 is deflected toward the first liquid chamber 15. Fig. 6C is a schematic diagram showing the behavior of the magnetic powder Mp when a magnetic field is applied to the orifice portion 15a of the first liquid chamber 15.

As shown in FIG. 6A, in an active vibration isolation device 1A, when an external force L such as a load or vibration amplitude is input to the inner cylinder 3 in a direction perpendicular to the axis, the relative positions of the inner cylinder 3 and the outer cylinder 2 are displaced.
6A, the inner cylinder 3 is displaced toward the outer cylinder 2, increasing the liquid pressure of the liquid 20a in the second liquid chamber 21. In the active vibration isolation device 1A, although not shown, the second liquid chamber 21 on the opposite side of the inner cylinder 3 is displaced so that the inner cylinder 3 is displaced away from the outer cylinder 2, decreasing the liquid pressure of the liquid 20a.

6A , when the liquid pressure of the liquid 20a in the second liquid chamber 21 increases, the bottom wall 17 of the flexible member 14 is pressed in a direction D toward the first liquid chamber 15. Although not shown, in the second liquid chamber 21 on the opposite side across the inner cylinder 3, when the liquid pressure of the liquid 20a decreases, the bottom wall 17 of the flexible member 14 is pulled in the direction opposite to the direction D shown in FIG 6A .
6B, in the active vibration isolation device 1A, the bottom wall 17 of the flexible member 14 bends so as to be convex toward the first liquid chamber 15. Moreover, the bottom wall 17 on the opposite side across the inner cylinder 3 (not shown) bends so as to be convex in the direction away from the first liquid chamber 15.
This causes the magnetorheological fluid 20b in the first fluid chamber 15 to generate a flow F passing through the orifice portion 15a, as shown in FIG. 6B.

On the other hand, as shown in FIG. 6B, a magnetic field generated by the energized electromagnetic coil 12 forms a magnetic path Mc across the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11. In other words, a magnetic path Mc is formed that passes through the magnetorheological fluid 20b in the orifice portion 15a.

As shown in the left diagram in FIG. 6C, the magnetorheological fluid 20b in the orifice portion 15a of the first liquid chamber 15 maintains the dispersed state of the magnetic powder Mp when no magnetic field is applied, and exhibits the desired fluidity.
In contrast, as shown in the right diagram of Fig. 6C, when a magnetic path Mc (see Fig. 6B) is formed by the generated magnetic field, the magnetic powder Mp is aligned along the magnetic flux ML. As a result, the apparent viscosity of the magnetorheological fluid 20b increases and the aligned magnetic powder Mp acts as a valve body, generating flow resistance in the orifice portion 15a.
The active vibration isolation device 1A exhibits a damping characteristic for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b in the orifice portion 15a.
The damping characteristics of this vibration or the like can be varied by controlling the value of the current flowing through the electromagnetic coil 12 in accordance with the magnitude of the input vibration or the like.

The active vibration isolation device 1A of this embodiment is configured to generate a flow of the magnetorheological fluid 20b in the first liquid chamber 15 in response to a change in the liquid pressure of the liquid 20a in the second liquid chamber 21 when an external load or vibration amplitude is input to at least either the inner cylinder 3 or the outer cylinder 2. The active vibration isolation device 1A controls the damping characteristics of vibrations, etc., by the magnitude of the magnetic field (magnetic flux density) applied to the orifice portion 15a of the first liquid chamber 15.

Unlike conventional active vibration isolation devices (see, for example, Patent Document 1) which directly convert input such as external vibrations into a flow of magnetorheological fluid, this active vibration isolation device 1A generates a flow of magnetorheological fluid 20b in the first liquid chamber 15 by changing the liquid pressure of the liquid 20a in the second liquid chamber 21.
According to the active vibration isolation device 1A of this embodiment, the response performance to input vibrations, etc. can be improved by increasing the volume of the second liquid chamber 21 filled with liquid 20a without increasing the volume of the first liquid chamber 15 filled with magnetorheological fluid 20b.

In addition, unlike conventional active vibration isolation devices (see, for example, Patent Document 1), the active vibration isolation device 1A allows the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b to be relatively small, so that the amount of magnetorheological fluid 20b, which contains magnetic powder Mp and is relatively heavy and expensive, can be reduced.

In addition, unlike conventional active vibration isolation devices (see, for example, Patent Document 1), the active vibration isolation device 1A allows the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b to be relatively small, so that the absolute amount of magnetic powder Mp contained in the magnetorheological fluid 20b that settles can be reduced.

Furthermore, according to the active vibration isolation device 1A, the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, so that the settled magnetic powder Mp can be redispersed by the swirling action of the flow F of the magnetorheological fluid 20b.
Furthermore, according to the active vibration isolation device 1A, it is possible to suppress the settling of magnetic powder Mp due to aging, and therefore it is possible to maintain good vibration and other damping performance.

In the active vibration isolation device 1A, the first liquid chamber 15, the second liquid chamber 21, and the flexible member 14 are arranged to extend in the circumferential direction.
According to such an active vibration isolation device 1A, it is possible to make the device compact while maintaining good response performance to input vibrations and the like.

In addition, in the active vibration damping device 1A, the first liquid chamber forming portion 6 that forms the first liquid chamber 15, the second liquid chamber forming portion 7 that forms the second liquid chamber 21, and the magnetic field forming portion 5 having the electromagnetic coil 12 are arranged in line in the axial direction.
With such an active vibration isolation device 1A, the liquid 20a in the second liquid chamber 21 can efficiently generate a flow F of the magnetorheological fluid 20b in the first liquid chamber 15 in response to vibrations or the like input from either the inner tube 3 or the outer tube 2.

In addition, in the manufacturing method of such an active vibration isolation device 1A, the process of filling the first liquid chamber 15 (see FIG. 5) with a magnetorheological fluid (filling process) can be performed by combining the second magnetic path forming member 9 (magnetic body), the electromagnetic coil 12, and the third magnetic path forming member 11 (magnetic body) in a liquid consisting of magnetorheological fluid when assembling the first magnetic path forming member 8 (magnetic body).

In a conventional manufacturing method for an active vibration isolation device (see, for example, Patent Document 1), the active vibration isolation device is assembled as a whole, and then the liquid chamber is filled with a magnetorheological fluid through a predetermined filling hole. In such a conventional manufacturing method, there is a risk that air bubbles will remain in the liquid chamber, which may reduce the damping performance of vibrations, etc.
In contrast, in the manufacturing method of the active vibration isolation device 1A, before assembling the entire device, the assembly As is assembled in a liquid made of the magnetorheological fluid 20b, thereby filling the first liquid chamber 15 with the magnetorheological fluid 20b.
According to the manufacturing method of this embodiment, it is possible to prevent air bubbles from remaining in the magnetorheological fluid 20 b of the first liquid chamber 15 .

The above-described active vibration isolation device 1A can be suitably used in place of various conventional mount bushes and suspension bushes, which must be carefully selected taking into account safety performance, driving performance, comfort performance, ride quality, etc.

[Second embodiment]
Next, an active vibration isolation device according to a second embodiment of the present invention will be described.
FIG. 7A is a cross-sectional view of an active vibration isolation device 1B according to a second embodiment of the present invention, including a cross section corresponding to the II-IV cross section in FIG. 1B.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in Figure 7A, the active vibration damping device 1B of the second embodiment differs from the active vibration damping device 1A of the first embodiment (see Figure 4) in that it has multiple units (two in this embodiment) in the axial direction, each unit having a first liquid chamber forming portion 6 that forms the first liquid chamber 15, a second liquid chamber forming portion 7 that forms the second liquid chamber 21, and a magnetic field forming portion 5 having an electromagnetic coil 12.
According to such an active vibration isolation device 1B, it is possible to diversify the change in rigidity in the axial direction.
Furthermore, in the active vibration isolation device 1B, adjacent units are arranged in the axial direction with the second liquid chamber 21 between them, so that they can share the second liquid chamber 21. This allows the active vibration isolation device 1B to be made even more compact in size.

[Third embodiment]
Next, an active vibration isolation device according to a third embodiment of the present invention will be described.
FIG. 7B is a cross-sectional view of an active vibration isolation device 1C according to a third embodiment of the present invention, including a cross section corresponding to the II-IV cross section in FIG. 1B.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

7B, in the active vibration isolation device 1C according to the third embodiment, units each consisting of a first liquid chamber forming portion 6, a second liquid chamber forming portion 7, and a magnetic field forming portion 5 are adjacent to each other in the axial direction, and these units are arranged so that they are out of phase with each other about the axis. Specifically, in the active vibration isolation device 1C, the units are arranged so that they are out of phase with each other by 180 degrees about the axis.
According to such an active vibration isolation device 1C, the rigidity in the directions perpendicular to a plurality of axes can be made variable, and the damping performance of vibrations and the like can be further improved.

[Fourth embodiment]
Next, an active vibration isolation device according to a fourth embodiment of the present invention will be described.
FIG. 7C is a cross-sectional view of an active vibration isolation device 1D according to a fourth embodiment of the present invention, including a cross section corresponding to the II-IV cross section in FIG. 1B.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

7C, in the active vibration isolation device 1D according to the fourth embodiment, units each consisting of a first liquid chamber forming portion 6, a second liquid chamber forming portion 7, and a magnetic field forming portion 5 are adjacent to one another in the axial direction and share one magnetic field forming portion 5. Specifically, in the active vibration isolation device 1D, the units are arranged so that the first liquid chamber forming portion 6 and the second liquid chamber forming portion 7 are reversed in the axial direction, with the magnetic field forming portion 5 sandwiched between them.
In this case, adjacent units may be arranged so that they are out of phase with each other around the axis (for example, 180 degrees out of phase with each other) as shown in FIG. 7C, or they may be arranged so that they are in the same phase with each other (not shown).
According to such an active vibration isolation device 1D, the magnetic field generating section 5 of one of the adjacent units can be omitted, and the device can be simplified.

[Fifth embodiment]
Next, an active vibration isolation device according to a fifth embodiment of the present invention will be described.
Fig. 8A is an exploded perspective view of an active vibration isolation device 1E according to a fifth embodiment of the present invention, and corresponds to Fig. 3 according to the first embodiment. Fig. 8B is a perspective view of the second magnetic path forming member (magnetic body) indicated by reference numeral 9 in Fig. 8A, as viewed from its cylindrical portion side.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in Figure 8A, the active vibration isolation device 1E of the fifth embodiment, unlike the active vibration isolation device 1A of the first embodiment (see Figure 3), has a permanent magnet 9a in the second magnetic path forming member 9 (magnetic material).
Specifically, as shown in FIG. 8B, four permanent magnets 9a are arranged at equal intervals in the circumferential direction of the cylindrical portion 92 of the second magnetic path forming member 9.
The permanent magnet 9 a may be embedded in the cylindrical portion 92 , or may be formed by directly magnetizing the cylindrical portion 92 .
Incidentally, the permanent magnet 9a in this embodiment is assumed to have an N pole formed on the ring portion 91 side of the second magnetic path forming member 9, and an S pole formed on the axially opposite side.

Fig. 9 is a partially cutaway perspective view of an assembly As (see Fig. 8A) of the first liquid chamber forming portion 6 and the magnetic field forming portion 5 in an active vibration isolation device 1E according to the fifth embodiment, and corresponds to Fig. 6B according to the first embodiment. Note that Fig. 9 shows a state in which no current is applied to the electromagnetic coil 12.
9, in the assembly As of the active vibration isolation device 1E, the permanent magnet 9a is disposed in a cylindrical portion 92 on the radially inner side of the second magnetic path forming member 9 (magnetic body) adjacent to the electromagnetic coil 12. This cylindrical portion 92 corresponds to the "side portion" in the claims.

<Action and effect>
Next, the operation of the active vibration isolation device 1E of this embodiment will be described, along with the effects of the active vibration isolation device 1E.
9, in the active vibration isolation device 1E, the permanent magnet 9a forms a magnetic field indicated by magnetic field lines MFL in the magnetic material around the permanent magnet 9a. Specifically, the magnetic field is formed in the cylindrical portion 92 of the second magnetic path forming member 9 and on the inner peripheral side of the third magnetic path forming member 11.

When the magnetic material around the permanent magnet 9a approaches a state of magnetic saturation (saturation magnetic flux density), a magnetic path Mm is formed by the permanent magnet 9a in the orifice portion 15a. Specifically, the magnetic path Mm is formed across the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11, and passes through the magnetic viscoelastic fluid 20b in the orifice portion 15a. In other words, in the active vibration isolation device 1E, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

FIG. 10 is a partially cutaway perspective view of the assembly As, showing a state in which a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 as a result of a current being applied to the electromagnetic coil 12. As shown in FIG.
10, in the active vibration isolation device 1E, a magnetic field generated by the energized electromagnetic coil 12 forms a magnetic path Mc across the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11, similar to the first embodiment (see FIG. 6B). That is, a magnetic path Mc is formed that passes through the magnetorheological fluid 20b in the orifice portion 15a. Incidentally, in this embodiment, a current is applied to the electromagnetic coil 12 so as to form a magnetic field that is opposite in direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

In other words, in this type of active vibration isolation device 1E, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled or weakened by the magnetic field formed in the orifice portion 15a by the electromagnetic coil 12. Unlike the active vibration isolation device 1A of the first embodiment (see FIG. 6B) in which the rigidity is increased by applying a current to the electromagnetic coil 12, the rigidity of the active vibration isolation device 1E is reduced by applying a current to the electromagnetic coil 12.

With the active vibration isolation device 1E described above, the magnetic viscoelastic fluid 20b in the orifice portion 15a is maintained at a high viscosity by the magnetic field formed by the permanent magnet 9a. This ensures the desired damping characteristics and rigidity even in a non-energized state where no current is applied to the electromagnetic coil 12.

Furthermore, as described above, with the active vibration isolation device 1E, unlike conventional devices, the stiffness can be reduced by applying a current to the electromagnetic coil 12, improving the degree of freedom when changing the damping characteristics and stiffness of the active vibration isolation device 1E.

In addition, with the active vibration isolation device 1E, the magnetic field of the orifice portion 15a formed by the permanent magnet 9a maintains the magnetic powder Mp in the magnetorheological fluid 20b in the orifice portion 15a at a high density. This makes it possible to suppress the settling of the magnetic powder Mp when applied to a part such as an engine mount bush that has a small stroke and is difficult to stir the magnetorheological fluid 20b. Therefore, with this active vibration isolation device 1E, it is possible to improve the response performance when applying a current to the electromagnetic coil 12 to change the viscosity of the magnetorheological fluid 20b.

In addition, in such an active vibration isolation device 1E, a current can be applied to the electromagnetic coil 12 so that the direction of the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is the same as the direction of the magnetic field formed in the orifice portion 15a by the electromagnetic coil 12.
According to such an active vibration isolation device 1E, the range of change in the designed damping characteristics and rigidity can be further increased.

Sixth Embodiment
Next, an active vibration isolation device according to a sixth embodiment of the present invention will be described.
Fig. 11 is a cross-sectional view of an active vibration isolation device 1F according to a sixth embodiment of the present invention, and corresponds to Fig. 4 according to the first embodiment. Fig. 12 is a partially enlarged cross-sectional view of an assembly As at part XII in Fig. 11.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in Figure 11, the active vibration isolation device 1F of the sixth embodiment, unlike the active vibration isolation device 1A of the first embodiment (see Figure 3), has a permanent magnet 9a in a magnetic body so as to be positioned radially inside the orifice portion 15a.
Specifically, the permanent magnet 9a is disposed between the flange portion 10a of the first magnetic path forming member 8 and the ring portion 91 of the second magnetic path forming member 9. The permanent magnet 9a magnetically connects the first magnetic path forming member 8 and the second magnetic path forming member 9. Although not shown in the figure, the permanent magnet 9a is disposed on the inner peripheral side of the orifice portion 15a extending in the circumferential direction so as to correspond to the orifice portion 15a.
Incidentally, the permanent magnet 9a in this embodiment is assumed to have an S pole formed on the second magnetic path forming member 9 side and an N pole formed on the first magnetic path forming member 8 side, as shown in FIG.

<Action and effect>
Next, the operation of the active vibration isolation device 1F of this embodiment will be described, along with the effects of the active vibration isolation device 1F.
As shown in Fig. 12, in the active vibration isolation device 1F, the permanent magnet 9a forms a magnetic field indicated by magnetic field lines MFL in the magnetic material around the permanent magnet 9a. Specifically, the magnetic field is formed across the first magnetic path forming member 8, the third magnetic path forming member 11, and the second magnetic path forming member 9. Note that Fig. 12 shows a state where no current is applied to the electromagnetic coil 12.

When the magnetic material around the permanent magnet 9a approaches a state of magnetic saturation (saturation magnetic flux density), a magnetic path Mm is formed by the permanent magnet 9a in the orifice portion 15a. Specifically, the magnetic path Mm is formed across the permanent magnet 9a, from the flange portion 10a of the first magnetic path forming member 8, the magnetorheological fluid 20b of the orifice portion 15a, and the ring portion 91 of the second magnetic path forming member 9. In other words, in the active vibration isolation device 1F, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

FIG. 13 is a partially enlarged cross-sectional view of the assembly As, showing a state in which a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 as a result of a current being applied to the electromagnetic coil 12. As shown in FIG.
13, in the active vibration isolation device 1F, a magnetic path Mc is formed across the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11 by the magnetic field generated by the energized electromagnetic coil 12. In other words, a magnetic path Mc is formed that passes through the magnetorheological fluid 20b in the orifice portion 15a. In this embodiment, a current is applied to the electromagnetic coil 12 so as to form a magnetic field that is opposite in direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

In this type of active vibration isolation device 1F, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled or weakened by the magnetic field formed in the orifice portion 15a by the electromagnetic coil 12. When a current is applied to the electromagnetic coil 12, the active vibration isolation device 1F has a low rigidity, similar to the active vibration isolation device 1E of the fifth embodiment (see FIG. 10).

According to the above-described active vibration isolation device 1F, it is possible to achieve the same effects as the active vibration isolation device 1E of the fifth embodiment (see FIG. 10).
Furthermore, according to the active vibration isolation device 1F, the permanent magnet 9a can be disposed closer to the orifice portion 15a than in the active vibration isolation device 1E of the fifth embodiment (see FIG. 10). This allows the active vibration isolation device 1F to more effectively form a magnetic field by the permanent magnet 9a in the orifice portion 15a.

[Seventh embodiment]
Next, an active vibration isolation device according to a seventh embodiment of the present invention will be described.
Fig. 14 is a cross-sectional view of an active vibration isolation device 1G according to a seventh embodiment of the present invention, and corresponds to Fig. 4 according to the first embodiment. Fig. 15 is a partially enlarged cross-sectional view of an assembly As at part XV in Fig. 14.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in Figure 14, the active vibration isolation device 1G of the seventh embodiment, unlike the active vibration isolation device 1A of the first embodiment (see Figure 3), has a permanent magnet 9a in a magnetic body so as to be positioned radially outside the orifice portion 15a.
Specifically, the permanent magnet 9a is disposed between the flange portion 10a of the first magnetic path forming member 8 and the ring portion 91 of the second magnetic path forming member 9. The permanent magnet 9a magnetically connects the first magnetic path forming member 8 and the second magnetic path forming member 9. Although not shown in the figure, the permanent magnet 9a is disposed on the outer circumferential side of the orifice portion 15a extending in the circumferential direction so as to correspond to the orifice portion 15a.
Incidentally, the permanent magnet 9a in this embodiment is assumed to have an N pole formed on the second magnetic path forming member 9 side and an S pole formed on the first magnetic path forming member 8 side, as shown in FIG.

<Action and effect>
Next, the operation of the active vibration isolation device 1G of this embodiment will be described, along with the effects of the active vibration isolation device 1G.
As shown in Fig. 15, in the active vibration isolation device 1G, the permanent magnet 9a forms a magnetic field indicated by magnetic field lines MFL in the magnetic material around the permanent magnet 9a. Specifically, the magnetic field is formed across the first magnetic path forming member 8, the third magnetic path forming member 11, and the second magnetic path forming member 9. Note that Fig. 15 shows a state in which no current is applied to the electromagnetic coil 12.

When the magnetic material around the permanent magnet 9a approaches a state of magnetic saturation (saturation magnetic flux density), a magnetic path Mm is formed by the permanent magnet 9a in the orifice portion 15a. Specifically, the magnetic path Mm is formed across the permanent magnet 9a, from the flange portion 10a of the first magnetic path forming member 8, the magnetorheological fluid 20b of the orifice portion 15a, and the ring portion 91 of the second magnetic path forming member 9. In other words, in the active vibration isolation device 1G, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

FIG. 16 is a partially enlarged cross-sectional view of the assembly As, showing a state in which a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 as a result of a current being applied to the electromagnetic coil 12. As shown in FIG.
16, in the active vibration isolation device 1G, a magnetic path Mc is formed across the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11 by the magnetic field generated by the energized electromagnetic coil 12. In other words, a magnetic path Mc is formed that passes through the magnetorheological fluid 20b in the orifice portion 15a. In this embodiment, a current is applied to the electromagnetic coil 12 so as to form a magnetic field that is opposite in direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

In this type of active vibration isolation device 1G, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled or weakened by the magnetic field formed in the orifice portion 15a by the electromagnetic coil 12. When a current is applied to the electromagnetic coil 12, the active vibration isolation device 1G has a low rigidity, similar to the active vibration isolation device 1E of the fifth embodiment (see FIG. 10).

According to the active vibration isolation device 1G as described above, it is possible to achieve the same effects as the active vibration isolation device 1E of the fifth embodiment (see FIG. 10) described above.
Furthermore, according to the active vibration isolation device 1G, the permanent magnet 9a can be disposed closer to the orifice portion 15a than in the active vibration isolation device 1E of the fifth embodiment (see FIG. 10). This allows the active vibration isolation device 1F to more effectively form a magnetic field by the permanent magnet 9a in the orifice portion 15a.

Furthermore, by positioning the permanent magnet 9a of the active vibration isolation device 1G on the outer periphery side of the orifice portion 15a, a larger circumferential length can be ensured compared to the permanent magnet 9a positioned on the inner periphery side in the active vibration isolation device 1F of the sixth embodiment (see Figure 11).
As a result, the active vibration isolation device 1G can more effectively form a magnetic field by the permanent magnet 9a in the orifice portion 15a than the active vibration isolation device 1F (see FIG. 11).

[Eighth embodiment]
Next, an active vibration isolation device according to an eighth embodiment of the present invention will be described.
FIG. 17 is a cross-sectional view of an active vibration isolation device 1H according to an eighth embodiment of the present invention, and corresponds to FIG. 3 according to the first embodiment.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 17, the active vibration isolation device 1H according to the eighth embodiment differs from the active vibration isolation device 1A according to the first embodiment (see FIG. 3) in that it has a permanent magnet 24 as a magnetic field generator instead of the electromagnetic coil 12.

<Action and effect>
In the active vibration isolation device 1H, for example, when the movement of the active vibration isolation device 1H is small and the bottom wall 17 of the flexible member 14 does not deform significantly, the pressure of the magnetorheological fluid 20b flowing through the orifice portion 15a is low.
On the other hand, such an active vibration isolation device 1H can constantly generate a magnetic field in the orifice portion 15a (see FIG. 4) by the permanent magnet 24.

As a result, in the active vibration isolation device 1H, as shown in the right diagram of Figure 6C, the magnetic field generates such that the magnetic powder Mp is aligned along the magnetic flux ML. This increases the apparent viscosity of the magnetorheological fluid 20b, and the aligned magnetic powder Mp acts as a valve body, generating flow resistance within the orifice portion 15a. The active vibration isolation device 1H becomes hard.

Furthermore, in the active vibration isolation device 1H, when the pressure of the magnetorheological fluid 20b exceeds a certain level, the aligned state of the magnetic powder Mp is disrupted, and the active vibration isolation device 1H becomes soft.
With such an active vibration isolation device 1H, even if it is not possible to control the magnetic field using the electromagnetic coil 12, the active vibration isolation device 1H can be switched between two levels of firmness depending on the magnitude of the input load to the active vibration isolation device 1H.

[Ninth embodiment]
Next, an active vibration isolation device according to a ninth embodiment of the present invention will be described.
FIG. 18 is a cross-sectional view of an active vibration isolation device 1J according to a ninth embodiment of the present invention.
In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
As shown in FIG. 18, an active vibration isolation device 1J has a flange 3a at one end of the inner cylinder 3, unlike the active vibration isolation device 1A according to the first embodiment (see FIG. 2).
In addition, the active vibration isolation device 1J omits the approximately top-shaped liquid chamber partition portion 22 (see Figure 3) made of a non-magnetic material that constitutes the second liquid chamber forming portion 7 (see Figure 3) in the active vibration isolation device 1A (see Figure 3).

Furthermore, as shown in Figure 18, the active vibration isolation device 1J omits the liquid chamber partition 22 (see Figure 3) and instead has an elastic support portion 23 made of an approximately cylindrical elastic body that is vulcanized bonded from the surface portion of the flange 3a facing the inner tube 3 to the outer peripheral surface of the inner tube 3.
The second fluid chamber 21 of the active vibration isolation device 1J is formed such that the elastic support portion 23 is partially removed in the circumferential direction on the inner circumferential side of the outer cylinder 2.

The second liquid chamber forming portion 7 having such an elastic support portion 23 forms a pair of second liquid chambers 21 extending circumferentially between the outer tube 2 and the inner tube 3, similar to the second liquid chamber 21 (see FIG. 3) of the active vibration isolation device 1A (see FIG. 3).

Next, the first liquid chamber forming portion 6 (see FIG. 18) and the magnetic field forming portion 5 (see FIG. 18) in the active vibration isolation device 1J will be described.
As shown in FIG. 18, the first liquid chamber forming portion 6 is composed of a flexible member 34 , a first magnetic path forming member 38 , and a second magnetic path forming member 39 which also serves as part of the magnetic field forming portion 5 .
As shown in FIG. 18, the first liquid chamber forming portion 6 forms a first liquid chamber 35 that contains a magnetorheological fluid 20b.

This first liquid chamber 35 is composed of an adjacent liquid chamber 35a that is arranged adjacent to the flexible member 34, and a parallel liquid chamber 35b that is formed shifted in a direction away from the second liquid chamber 21 from the adjacent liquid chamber 35a.
The parallel fluid chamber 35b is provided to correspond to the orifice portion 15a (see FIG. 6A) in the active vibration isolation device 1A (see FIG. 6A) of the first embodiment, and serves as a flow path for the magnetorheological fluid 20b.

As shown in FIG. 18, the magnetic field generating section 5 is made up of the second magnetic path forming member 39, the electromagnetic coil 12 (magnetic field generating section), and a third magnetic path forming member 41.
As described later, the magnetic field generating unit 5 forms a magnetic path Mc in the parallel liquid chamber 35b.

FIG. 19 is an overall perspective view of an assembly As in which the first liquid chamber forming portion 6 and the magnetic field forming portion 5 are assembled together so as to be integrated with each other.
As shown in Fig. 19, the assembly As has a generally cylindrical shape so as to be accommodated on the inner periphery side of the outer cylinder 1 (see Fig. 18). In Fig. 19, reference numeral 34 denotes a flexible member constituting the first liquid chamber forming portion 6, reference numeral 38 denotes a first magnetic path forming member (partition wall) constituting the first liquid chamber forming portion 6, and reference numeral 39 denotes a second magnetic path forming member used by both the magnetic field forming portion 5 and the first liquid chamber forming portion 6. Reference numeral 41 denotes a third magnetic path forming member constituting the magnetic field forming portion 5. Note that the electromagnetic coil 12 (see Fig. 18) is omitted in Fig. 19 for convenience of drawing.

FIG. 20 is an exploded perspective view of the assembly As.
As shown in FIG. 20, a third magnetic path forming member 41 constituting the assembly As is configured to have a bottom plate with a central hole and a cylindrical side wall.
The assembly As is constructed by stacking and fitting, in this order, a ring-shaped electromagnetic coil 12 (magnetic field generating portion), a second magnetic path forming member 39, a first magnetic path forming member 38 (partition wall), and a flexible member 34 on the inner side of the third magnetic path forming member 41, which is an approximately bottomed cylinder.

The flexible member 34 has a pair of arc-shaped bottom walls 37 on the surface of the flexible member 34, similar to the bottom wall 17 (see Figure 3) of the flexible member 14 (see Figure 3) of the active vibration isolation device 1A (see Figure 3) of the first embodiment.
Fig. 21A is an overall perspective view of the flexible member 34 as viewed from the rear surface side, and Fig. 21B is a cross-sectional view taken along line XXIb-XXIb in Fig. 21A.

As shown in Figures 21A and 21B, the flexible member 34 has a symmetrical structure on the front and back. A groove-shaped adjacent liquid chamber 35a is formed on the back of the flexible member 34 so as to be symmetrical with the groove-shaped recess having a bottom wall 37 (see Figure 21B) on the front side. This adjacent liquid chamber 35a is filled with a magnetorheological fluid 20b (see Figure 18) by closely contacting the back of the flexible member 34 with the surface of the first magnetic path forming member 38 (see Figure 20).

Figure 22 is an overall perspective view of the first magnetic path forming member 38 as seen from the front side. In Figure 22, half 35b1 of the juxtaposed liquid chamber 35b formed on the back side of the first magnetic path forming member 38 and the uneven shape 38b formed in the juxtaposed liquid chamber 35b are shown by hidden lines (dotted lines).

As shown in FIG. 22, the first magnetic path forming member 38 is formed of a ring-shaped plate.
The first magnetic path forming member 38 is formed with a pair of connection passages 38a that penetrate the first magnetic path forming member 38 in the plate thickness direction.
Each of the pair of connecting passages 38a is configured to communicate with each of the ends of a pair of adjacent liquid chambers 35a (see Figure 21A) formed between the first magnetic path forming member 38 and the flexible member 34 (see Figure 21A).
The connecting passage 38a (see FIG. 22) has a short arc shape in a plan view to match the shape of one end of the flexible member 34 (see FIG. 21A) where a pair of adjacent liquid chambers 35a (see FIG. 21A) face each other.

22, a half 35b1 of the juxtaposed liquid chamber 35b is formed on the back surface of the first magnetic path forming member 38. This half 35b1 is formed as a groove portion that opens toward the second magnetic path forming member 39 side shown in FIG.
As shown in Figure 22, half 35b1 extends circumferentially of the first magnetic path forming member 38 from one of a pair of connecting passages 38a in the opposite direction to the other connecting passage 38a, and is connected to the other connecting passage 38a.
That is, the connecting passage 38a (see FIG. 22) connects the adjacent liquid chamber 35a (see FIG. 21A) and the parallel liquid chamber 35b (see FIG. 22).

As will be described in detail later, the positions at which these connecting passages 38a (see FIG. 22) are formed are preferably located vertically above the lowermost vertical portion of the parallel liquid chamber 35b (see FIG. 22) when the axis of the active vibration isolation device 1J (see FIG. 18) is horizontal.

The groove bottom of the half 35b1 is formed with an uneven shape 38b in which convex portions 38b1 that are convex toward the second magnetic path forming member 39 side and concave portions 38b2 that are concave are alternately arranged in the circumferential direction.
18, the first magnetic path forming member 38 is disposed so as to partition the first liquid chamber 35 into an adjacent liquid chamber 35a and a side-by-side liquid chamber 35b. The first magnetic path forming member 38 corresponds to a "partition wall" in the claims.

23 is an overall perspective view of the second magnetic path forming member 39 as viewed from the back side. In addition, in FIG. 23, half 35b2 of the juxtaposed liquid chamber 35b formed on the surface of the second magnetic path forming member 39 and the uneven shape 39a formed in the juxtaposed liquid chamber 35b are indicated by hidden lines (dotted lines).
As shown in FIG. 23, the second magnetic path forming member 39 has a cylindrical portion 39c1 and a ring portion 39c2 connected in a flange-like shape to one end side of the cylindrical portion 39c1.

Half 35b2 of the parallel liquid chamber 35b is formed on the surface of the ring portion 39c2. This half 35b2 is formed as a groove that opens toward the first magnetic path forming member 38 side shown in FIG. 20. As shown in FIG. 20, half 35b2 is formed to correspond to half 35b1 of the first magnetic path forming member 38. An uneven shape 39a is formed at the bottom of the groove of such half 35b2. As shown in FIG. 23, this uneven shape 39a is formed by alternating between convex portions 39a1 that are convex toward the first magnetic path forming member 38 (see FIG. 20) side and concave portions 39a2 that are concave.

As shown in FIG. 20, half 35b1 of the first magnetic path forming member 38 and half 35b2 of the second magnetic path forming member 39 are integrated to form the parallel liquid chamber 35b shown in FIG. 18. At this time, the convex portion 38b1 on the first magnetic path forming member 38 side shown in FIG. 22 and the convex portion 39a1 on the second magnetic path forming member 39 side shown in FIG. 23 face each other with a predetermined clearance. In addition, the clearance (gap) formed between the convex portion 38b1 and the convex portion 39a1 forms an orifice portion in the parallel liquid chamber 35b that serves as a flow path for the magnetorheological fluid 20b. In other words, the parallel liquid chamber 35b has multiple orifices along its length (circumferential direction).

<Action and effect>
Next, the effects of the active vibration isolation device 1J (see FIG. 18) will be described while showing the operation of the first liquid chamber forming portion 6 (see FIG. 20).
18, when a load is input in a direction intersecting the axis via the inner cylinder 3, the liquid pressure of the liquid 20a increases in the second liquid chamber 21 that is compressed between the outer cylinder 2 and the inner cylinder 3, out of the pair of second liquid chambers 21. Also, the liquid pressure of the liquid 20a decreases in the second liquid chamber 21 on the opposite side across the inner cylinder 3.

24, which is an explanatory diagram of the operation of the first liquid chamber forming portion 6, a load P1 is applied in a direction pressing against the bottom wall 37 of the flexible member 34 adjacent to one of the second liquid chambers 21 (see FIG. 18). Although not shown, the bottom wall 37 bends so as to be convex toward the adjacent liquid chamber 35a.
24, a load P2 is applied to the bottom wall 37 of the flexible member 34 adjacent to the other second liquid chamber 21 (see FIG. 18) in a direction pulling the bottom wall 37. Although not shown, the bottom wall 37 bends so as to become concave toward the adjacent liquid chamber 35a.

As a result, the pressure of the magnetorheological fluid 20b (see FIG. 18) in one adjacent liquid chamber 35a (see FIG. 18) on the side where the bottom wall 37 (see FIG. 18) is bent convexly increases, while the pressure of the magnetorheological fluid 20b (see FIG. 18) in the other adjacent liquid chamber 35a (see FIG. 18) on the side where the bottom wall 37 (see FIG. 18) is bent concavely decreases.
The magnetorheological fluid 20b (see FIG. 18) in one adjacent liquid chamber 35a (see FIG. 18) flows to the other adjacent liquid chamber 35a (see FIG. 18).
That is, as shown in FIG. 24, the magnetorheological fluid 20b (see FIG. 18) forms a flow F that flows from one connecting passage 38a, bypassing the parallel liquid chamber 35b and passing through the other connecting passage 38a.

25, which is a partially enlarged cross-sectional view of part XXV in Fig. 18, a magnetic path Mc is formed in the parallel liquid chamber 35b by the magnetic field generated by the energized electromagnetic coil 12. As a result, the apparent viscosity of the magnetorheological fluid 20b in the parallel liquid chamber 35b increases and flow resistance is generated within the parallel liquid chamber 35b.
The active vibration isolation device 1J exhibits a damping characteristic for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b in the parallel liquid chamber 35b.
The damping characteristics of this vibration or the like can be varied by controlling the value of the current flowing through the electromagnetic coil 12 in accordance with the magnitude of the input vibration or the like.

18, in the active vibration isolation device 1J, the adjacent liquid chamber 35a and the juxtaposed liquid chamber 35b that form the first liquid chamber 35 are separated in the axial direction by a first magnetic path forming member 38 (partition wall). The adjacent liquid chamber 35a and the juxtaposed liquid chamber 35b, which serves as a flow path for the magnetorheological fluid 20b, are connected by a connecting passage 38a formed in the first magnetic path forming member 38 (partition wall).
According to this active vibration isolation device 1J, the magnetorheological fluid 20b can be caused to flow in the parallel liquid chamber 35b that is shifted in the axial direction relative to the adjacent liquid chamber 35a. This makes it possible for the active vibration isolation device 1J to reduce the effects of settling of the magnetorheological fluid 20b in the parallel liquid chamber 35b where the magnetic path Mc is formed.

Furthermore, as shown in Figure 24, when the axis Ax of the active vibration isolation device 1J is positioned horizontally, the connecting passage 38a is formed so that it is positioned vertically above the lowermost point Bm in the vertical direction (indicated by the up and down arrows in Figure 24) of the parallel liquid chamber 35b (flow path of the magnetorheological fluid).
According to such an active vibration isolation device 1J, the magnetorheological fluid flows through the lowermost part Bm of the parallel liquid chamber 35b and into the connecting passage 38a, so that the effects of settling of the magnetorheological fluid can be reduced.

As shown in FIG. 24, the active vibration isolation device 1J has a concave-convex shape 39a in the parallel liquid chamber 35b which serves as a flow path for the magnetorheological fluid.
With this type of active vibration isolation device 1J, the recess 39a2 (see Figure 23) of the uneven shape 39a ensures a predetermined flow path cross-section of the parallel liquid chamber 35b, which serves as a flow path for the magnetorheological fluid, while the magnetic force in the parallel liquid chamber 35b can be increased by facing the first magnetic path forming member 38 (see Figure 22) at the recess 39a2.

Although the present embodiment has been described above, the present invention is not limited to the above embodiment and can be embodied in various forms.
In the active vibration control devices 1E, 1F, and 1G according to the fifth to seventh embodiments described above, the permanent magnets 9a are arranged in three locations: the radial side portion of the electromagnetic coil 12, the radial inside of the orifice portion 15a, and the radial outside of the orifice portion 15a. However, the active vibration control device of the present invention is not limited to this. Therefore, the active vibration control device of the present invention can also be configured to arrange the permanent magnets 9a in two or more selected locations out of the three locations: the radial side portion of the electromagnetic coil 12, the radial inside of the orifice portion 15a, and the radial outside of the orifice portion 15a.

Moreover, in the active vibration isolation device 1J, instead of the electromagnetic coil 12, a permanent magnet 24 similar to that in the active vibration isolation device 1H (see FIG. 17) can be disposed.
According to this type of active vibration isolation device 1J, similar to the active vibration isolation device 1H (see Figure 17), the active vibration isolation device 1J can be switched between two levels of firmness depending on the magnitude of the input load to the active vibration isolation device 1J.

1A Active vibration-isolating device 1B Active vibration-isolating device 1C Active vibration-isolating device 1D Active vibration-isolating device 1E Active vibration-isolating device 1F Active vibration-isolating device 1G Active vibration-isolating device 1H Active vibration-isolating device 1J Active vibration-isolating device 2 Outer cylinder 3 Inner cylinder 5 Magnetic field forming portion 6 First liquid chamber forming portion 7 Second liquid chamber forming portion 8 First magnetic path forming member (magnetic body)
9 Second magnetic path forming member (magnetic body)
9a Permanent magnet 11 Third magnetic path forming member (magnetic body)
12 Electromagnetic coil (magnetic field generating unit)
14 Flexible member 15 First liquid chamber 15a Orifice portion 17 Bottom wall of flexible member 20a Liquid 20b Magnetorheological fluid 21 Second liquid chamber 24 Permanent magnet (magnetic field generating portion)
34 Flexible member 35 First liquid chamber 35a Adjacent liquid chamber 35b Parallel liquid chamber 38 First magnetic path forming member (partition wall)
38a Connection passage 39 Second magnetic path forming member 41 Third magnetic path forming member 92 Cylindrical portion of second magnetic path forming member (radial side portion of magnetic body)
Mc: Magnetic path formed by the electromagnetic coil Mm: Magnetic path formed in the orifice by the permanent magnet MFL: Magnetic line of force

Claims (13)

An outer cylinder,
an inner cylinder disposed on the inner circumferential side of the outer cylinder;
A magnetic field generating unit that generates a magnetic field;
A magnetic body that forms a magnetic path by the magnetic field;
a first fluid chamber filled with a magnetorheological fluid;
a second liquid chamber adjacent to the first liquid chamber and filled with liquid;
An active vibration isolation device having
the magnetic field generating unit, the magnetic body, the first liquid chamber, and the second liquid chamber are provided between the inner cylinder and the outer cylinder in a radial direction,
The first liquid chamber and the second liquid chamber are partitioned by a flexible member,
An active vibration isolation device, characterized in that a portion of the first fluid chamber forms a flow path for the magnetorheological fluid located on the magnetic path. The active vibration isolation device according to claim 1, characterized in that the first liquid chamber, the second liquid chamber, and the flexible member extend in the circumferential direction. The active vibration isolation device according to claim 2, characterized in that the first liquid chamber forming portion that forms the first liquid chamber, the second liquid chamber forming portion that forms the second liquid chamber, and the magnetic field forming portion having the magnetic field generating portion are arranged to be aligned in the axial direction. The active vibration isolation device according to claim 3, characterized in that it has multiple units in the axial direction, each unit having the first liquid chamber forming portion, the second liquid chamber forming portion, and the magnetic field forming portion. The active vibration isolation device according to claim 4, characterized in that adjacent units are arranged so that they are out of phase with each other around the axis. The active vibration isolation device according to claim 4, characterized in that adjacent units share one of the magnetic field generating sections. The magnetic field generating unit is an electromagnetic coil,
2. An active vibration isolation device as described in claim 1, characterized in that the magnetic body further has a permanent magnet as the magnetic field generating unit, and a flow path of the magnetorheological fluid is located on the magnetic path formed by the permanent magnet. The active vibration isolation device according to claim 7, characterized in that the permanent magnet is disposed at least in one of the radial side portion of the magnetic body adjacent to the magnetic field generating unit, the inner adjacent portion adjacent to the radial inside of the flow path of the magnetorheological fluid, and the outer adjacent portion adjacent to the radial outside of the flow path of the magnetorheological fluid. the first liquid chamber includes an adjacent liquid chamber adjacent to the flexible member,
the flow path of the magnetorheological fluid is partitioned from the adjacent liquid chamber in the axial direction via a partition wall,
2. An active vibration isolation device according to claim 1, wherein the partition wall is provided with a connecting passage that connects the adjacent liquid chamber with the flow path of the magnetorheological fluid. The adjacent liquid chambers are formed in a pair in the circumferential direction,
10. An active vibration isolation device according to claim 9, wherein the adjacent fluid chambers communicate with each other through a flow path for the magnetorheological fluid. An active vibration isolation device according to claim 9, characterized in that, when the axis of the active vibration isolation device is arranged horizontally, the connection passage is formed so as to be positioned vertically above the lowermost point in the vertical direction of the flow path of the magnetorheological fluid. The active vibration isolation device according to claim 9, characterized in that the flow path of the magnetorheological fluid has an uneven shape in the axial direction. A method for manufacturing an active vibration isolation device according to claim 1, comprising the steps of:
a sealing step of sealing the magnetorheological fluid in the first fluid chamber,
A manufacturing method for an active vibration isolation device, characterized in that the encapsulation process is performed by combining the magnetic field generating unit, the magnetic body, and the flexible member in a liquid consisting of the magnetorheological fluid.