Active vibration isolation device

Abstract

To provide an active type vibration control device which inhibits its performance from being deteriorated by sedimentation of a magnetic powder of a magnetic viscoelastic fluid in a liquid chamber without increasing a volumetric capacity of the liquid chamber to be filled with the magnetic viscoelastic fluid.SOLUTION: An active type vibration control device 1A includes: an electromagnetic coil 12 (a magnetic field generation part) which generates a magnetic field; a magnetic body forming a magnetic path by the magnetic field; a first liquid chamber 15 filled with a magnetic viscoelastic fluid 20b; and a second liquid chamber 21 located adjacent to the first liquid chamber 15 and filled with a liquid 20a. The electromagnetic coil 12, the magnetic body, the first liquid chamber 15, and the second liquid chamber 21 are provided in a radial space between an inner cylinder 3 and an outer cylinder 2. The first liquid chamber 15 is partitioned from the second liquid chamber 21 by a flexible member 14. The first liquid chamber 15 has an orifice part 15a located on the magnetic path.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an active vibration isolation device. Place Regarding. [Background technology]

[0002] In recent years, efforts to provide access to sustainable transport systems that take into consideration vulnerable transport users 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 the development of vehicle livability. Active vibration isolation devices have been proposed for use in subframe mounts, suspension bushings, and the like, with the aim of improving vehicle comfort by suppressing noise and vibration within the vehicle cabin (see, for example, Patent Document 1). Specifically, this active vibration isolation device has two fluid chambers filled with magnetorheological fluid connected 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 attempts to flow through the flow path from one fluid chamber to the other 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-71117 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 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 increases the manufacturing cost of the active vibration isolation device and creates new problems, such as an increase in the weight of the vehicle in which it is installed. Furthermore, with an active vibration isolation device, as the amount of magnetorheological fluid used increases, the absolute amount of magnetic powder contained in the magnetorheological fluid that settles also increases, which could result in a decrease in the performance of the active vibration isolation device.

[0005] The present invention provides an active vibration isolation device that can improve response performance to external forces such as input vibrations and loads without increasing the volume of a liquid chamber filled with a magnetorheological fluid, and can also suppress performance degradation due to the settling of magnetic powder in the magnetorheological fluid in the liquid chamber. Place This will ultimately contribute to the development of sustainable transport systems. [Means for solving the problem]

[0006] The active vibration damping device of the present invention, which solves the above-mentioned problems, comprises an outer cylinder, an inner cylinder arranged on the inner circumferential side of the outer cylinder, a magnetic field generating unit that generates a magnetic field, and a magnetic body that forms a magnetic path by the magnetic field. a first fluid chamber filled with a magnetorheological fluid; and a second fluid chamber adjacent to the first fluid chamber. non-magnetic and a second liquid chamber filled with liquid, wherein the magnetic field generating unit, the magnetic body, the first liquid chamber, and the second liquid chamber are arranged 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 portion of the first liquid chamber forms a flow path for the magnetorheological fluid located on the magnetic path. [Effects of the Invention]

[0008] The active vibration isolation device of the present invention PlaceAs a result, it is possible to improve response performance to external forces such as input vibrations and loads without increasing the volume of the liquid chamber filled with the magnetorheological fluid, and it is also possible to suppress performance degradation due to the settling of magnetic powder in the magnetorheological fluid in the liquid chamber. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a side view of an active vibration isolation device according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a plan view of the active vibration isolation device as seen from the direction IB in FIG. 1A. [Figure 2] FIG. 2 is a partially cutaway perspective view of the active vibration isolation device including the cross section II-II of FIG. 1B. [Figure 3] FIG. 1B is an exploded perspective view of the active vibration isolation device shown in FIG. 1A. [Figure 4] FIG. 2 is a cross-sectional view taken along line II-IV of FIG. 1B. [Figure 5] 3 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 damping device. FIG. [Figure 6A] 10 is a diagram showing 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. FIG. [Figure 6B] 10A and 10B are diagrams illustrating the movement of the magnetorheological fluid when the bottom wall of the flexible member is bent. [Figure 6C] 5 is a schematic diagram showing the behavior of magnetic powder when a magnetic field is applied to an orifice portion of a first liquid chamber. FIG. [Figure 7A] FIG. 4 is a cross-sectional view of an active vibration isolation device according to a second embodiment of the present invention. [Figure 7B] FIG. 10 is a cross-sectional view of an active vibration isolation device according to a third embodiment of the present invention. [Figure 7C] FIG. 10 is a cross-sectional view of an active vibration isolation device according to a fourth embodiment of the present invention. [Figure 8A] FIG. 10 is an exploded perspective view of an active vibration isolation device according to a fifth embodiment of the present invention. [Figure 8B] FIG. 8B is a perspective view of the second magnetic path forming member shown in FIG. 8A. [Figure 9]FIG. 11 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 damping device according to a fifth embodiment of the present invention. [Figure 10] FIG. 11 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. [Figure 11] FIG. 10 is a cross-sectional view of an active vibration isolation device according to a sixth embodiment of the present invention. [Figure 12] FIG. 12 is a partially enlarged cross-sectional view of part XII in FIG. [Figure 13] FIG. 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. [Figure 14] FIG. 10 is a cross-sectional view of an active vibration isolation device according to a seventh embodiment of the present invention. [Figure 15] FIG. 15 is a partially enlarged cross-sectional view of the XV portion of FIG. [Figure 16] FIG. 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. [Figure 17] FIG. 13 is an exploded perspective view of an active vibration isolation device according to an eighth embodiment of the present invention. [Figure 18] FIG. 13 is a vertical cross-sectional view of an active vibration isolation device according to a ninth embodiment of the present invention. [Figure 19] FIG. 13 is an overall perspective view of a first liquid chamber forming section / magnetic field forming section assembly in an active vibration isolation device according to a ninth embodiment. [Figure 20] FIG. 13 is an exploded perspective view of a first liquid chamber forming portion / magnetic field forming portion assembly in an active vibration damping device according to a ninth embodiment. [Figure 21A] FIG. 21 is an overall perspective view of the flexible member shown in FIG. 20 as viewed from the rear surface side. [Figure 21B] This is a cross-sectional view of XXIb-XXIb in Figure 21A. [Figure 22] FIG. 21 is an overall perspective view of the first magnetic path forming member shown in FIG. 20 as viewed from the front surface side. [Figure 23]21 is an overall perspective view of the second magnetic path forming member shown in FIG. 20 as viewed from the back side. FIG. [Figure 24] 21 is an explanatory diagram of the operation of the first liquid chamber forming portion shown in FIG. 20. [Figure 25] FIG. 20 is a partially enlarged cross-sectional view of part XXV in FIG. 18. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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, and Fig. 1B is a plan view of the active vibration isolation device 1A as seen from the direction IB in Fig. 1A.

[0011] 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 barrel> 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 such an outer cylinder 2 is supported by a first support member Sp1.

[0012] <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. In this embodiment, the inner cylinder 3 is assumed to be formed from a non-magnetic material.

[0013] 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 that is 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 that protrudes 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 figures, the inner tube 3 can also be configured such that both ends of the shaft member Sf pass through a pair of second support members Sp2 and are fastened with nuts N1 and N2, respectively, so that the inner tube 3 is sandwiched between the pair of second support members Sp2.

[0014] In such an active vibration isolation device 1A, vibrations from a predetermined vibration source or external loads (hereinafter sometimes simply referred to as "vibrations, etc.") are input to the outer tube 2 via the first support member Sp1, or to the inner tube 3 via the second support member Sp2, or to the outer tube 2 and inner tube 3 via the first support member Sp1 and the second support member Sp2.

[0015] <Dampening unit body> Next, we will explain the damping portion main body 4 (see FIG. 1B). The damping portion main 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 II-II in 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.

[0016] 3, the damping unit main body 4 is mainly composed of a first liquid chamber forming portion 6, a second liquid chamber forming portion 7, and a magnetic field forming portion 5. Here, the second liquid chamber forming portion 7 will be explained first, followed by an explanation of the assembly As in which the first liquid chamber forming portion 6 and the magnetic field forming portion 5 are integrated together.

[0017] (Second liquid chamber forming part) As shown in Figure 3, the second liquid chamber forming portion 7 has a liquid chamber partitioning portion 22 that partitions and forms the second liquid chamber 21 on the outer periphery of the inner tube 3, and an elastic support portion 23 that elastically supports this liquid chamber partitioning portion 22 on the outer periphery of the inner tube 3. The liquid chamber partitioning portion 22 has a generally top-like shape and includes a cylindrical shaft portion 22a inside which the inner cylinder 3 is disposed, and a columnar portion 22b having a diameter larger than that of the shaft portion 22a. The second liquid chamber 21 is formed by removing part of the columnar portion 22b of the liquid chamber partitioning portion 22 in the circumferential direction.

[0018] When such a liquid chamber partition 22 is placed on the inner periphery of the outer tube 2, it further divides the internal space formed by partially dividing the space between the inner tube 3 and the outer tube 2 in the axial direction in the circumferential direction, thereby forming a pair of second liquid chambers 21 on the outer periphery of the inner tube 3. The pair of second liquid chambers 21 are formed to face each other at a phase difference of 180 degrees with the inner cylinder 3 therebetween, as shown by hidden lines (dotted lines) in FIG. 1B. The inner wall of the outer periphery of the second liquid chamber 21 is formed by the inner wall of the outer cylinder 2, as shown in FIG.

[0019] In addition, as shown in Figure 3, the second liquid chamber 21 has a communicating groove 21a consisting of an arc-shaped slit so that it faces 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. 4, which is a cross-sectional view taken along line II-IV of FIG. 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 part of the second liquid chamber 21, and also forms 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, known hydraulic oils such as silicone oil and ester oil can be suitably used.

[0020] 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 peripheral surface of the cylindrical portion 22b and on the inner wall surface of the cylindrical portion 22b that forms the second liquid chamber 21. The main body 23a of the elastic support member 23 and the covering portion 23b formed on the outer peripheral 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.

[0021] The elastic support portion 23 in this embodiment is assumed to be made of synthetic rubber such as silicone rubber, and is bonded to the inner tube 3 and the cylindrical portion 22b by vulcanization. The main body 23a of the elastic support member 23 allows relative displacement in the direction perpendicular to the axis between the inner cylinder 3 and the outer cylinder 2. In addition, the covering portion 23b of the elastic support member 23 ensures sealing of the liquid 20a filled in the second liquid chamber 21.

[0022] (assembly) Next, a description will be given of an assembly As (see FIG. 3) having a substantially cylindrical shape in which the first liquid chamber forming section 6 (see FIG. 3) and the magnetic field forming section 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.

[0023] As shown in FIG. 3, the flexible member 14 has a ring shape and is disposed inside the first magnetic path forming member 8, which has a cylindrical shape. 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.

[0024] 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, separated by 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 to correspond to the groove-like recess 16. That is, as shown in Figure 4, the second liquid chamber 21 and the first liquid chamber 15 are separated by the flexible bottom wall 17 of the flexible member 14.

[0025] 5, the outer periphery of the flexible member 14 is supported by the first magnetic path forming member 8. Specifically, the outer periphery 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 periphery of the first magnetic path forming member 8 to the height of the bottom wall 17, which fits into the solid portion of the outer periphery of the flexible member 14. Furthermore, a portion 18b of the flexible member 14 that does not have the bottom wall 17 is fixed to a flange portion 10b extending from the inner periphery of the first magnetic path forming member 8 to near the inner periphery of the flexible member 14. As shown in FIG. 3, a pair of portions 18a having the bottom wall 17 of the flexible member 14 are formed to correspond to the communication grooves 21a of the pair of second liquid chambers 21.

[0026] 5, the first liquid chamber 15 extends in the circumferential direction to correspond to the bottom wall 17, and in the portion 18b that does not have the bottom wall 17, it extends in the circumferential direction between the flange portion 10b and the second magnetic path forming member 9. As a result, the first liquid chamber 15 that extends in the portion 18b that does not have the bottom wall 17 has a smaller cross-sectional area than the first liquid chamber 15 that extends in the portion 18a that has the bottom wall 17. That is, although not shown, a pair of first liquid chambers 15 having a large cross-sectional area that extend in an arc corresponding to the second liquid chamber 21 constitute an annular liquid chamber together with a pair of first liquid chambers 15 having a small cross-sectional area.

[0027] 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 chamber 15 forms an orifice portion 15a. That is, the orifice portion 15a forming a part of the first liquid chamber 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 MRF (Magneto-Rheological Fluid) or MRC (Magneto-Rheological Compound) in which magnetic powder is dispersed in mineral oil or synthetic oil.

[0028] 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 an electromagnetic coil 12 and a third magnetic path forming member 11 in addition to the first magnetic path forming member 8 and the second magnetic path forming member 9. The electromagnetic coil 12 corresponds to the "magnetic field generating unit" set forth 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 with a smaller diameter than the first magnetic path forming member 8.

[0029] As shown in FIG. 5, the second magnetic path forming member 9 has a flat ring portion 91 and a cylindrical portion 92 formed on the inner periphery of the ring portion 91, and has an L-shaped cross section. 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 outward in the radial direction. 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 itself and the flange portion 10b of the first magnetic path forming member 8, and thereby a placement chamber 13 for the electromagnetic coil 12 is formed on the inner circumferential side of the first magnetic path forming member 8, 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 .

[0030] As a result, the magnetic field generating unit 5 forms a magnetic path Mc (see FIG. 6B) that passes through the magnetorheological fluid 20b in the orifice portion 15a by the electromagnetic coil 12 to which a current is applied, as will be described later. It is assumed that the first magnetic path forming member 8, the second magnetic path forming member 9, and the third magnetic path forming member 11 are 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).

[0031] A manufacturing method for such an active vibration damping device 1A can include, for example, a process of integrally forming the inner tube 3 and the liquid chamber partitioning portion 22 via an elastic support portion 23, as shown in Figure 3, a process 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 process of assembling the integrated inner tube 3 and liquid chamber partitioning portion 22 into the assembly As and storing it in the outer tube 2.

[0032] Furthermore, in this manufacturing direction, the process of filling the first liquid chamber 15 (see Figure 5) of the assembly As with a 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 a magnetorheological fluid when assembling the first magnetic path forming member 8 (magnetic body).

[0033] <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 direction perpendicular to the axis. 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 bent 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.

[0034] As shown in FIG. 6A, in the 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. Furthermore, in the active vibration damping 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 moves away from the outer cylinder 2, decreasing the liquid pressure of the liquid 20a.

[0035] 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 direction D toward the first liquid chamber 15. Furthermore, although not shown, in the second liquid chamber 21 on the opposite side of 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 direction D shown in FIG. That is, in the active vibration damping device 1A, as shown in Fig. 6B, the bottom wall 17 of the flexible member 14 bends so as to 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 convex in a 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 that passes through the orifice portion 15a, as shown in FIG. 6B.

[0036] 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.

[0037] As shown in the left diagram in Figure 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 and exhibits the desired fluidity when no magnetic field is applied. 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 particles Mp are aligned along the magnetic flux ML. As a result, the apparent viscosity of the magnetorheological fluid 20b increases, and the aligned magnetic powder particles Mp act as valve bodies, generating flow resistance within 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.

[0038] The active vibration damping device 1A of this embodiment is configured so that, when an external load or vibration amplitude is input to at least either the inner cylinder 3 or the outer cylinder 2, a flow of the magnetorheological fluid 20b in the first liquid chamber 15 is caused to occur in accordance with a change in the liquid pressure of the liquid 20a in the second liquid chamber 21. The active vibration damping 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.

[0039] Unlike conventional active vibration damping devices (see, for example, Patent Document 1) that directly convert input such as external vibrations into a flow of magnetorheological fluid, this active vibration damping device 1A generates a flow of magnetorheological fluid 20b in the first liquid chamber 15 by changing the liquid pressure of liquid 20a in the second liquid chamber 21. According to the active vibration damping 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.

[0040] Furthermore, according to the active vibration damping device 1A, unlike conventional active vibration damping devices (see, for example, Patent Document 1), the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, so that the amount of magnetorheological fluid 20b used, which is relatively heavy and expensive and contains magnetic powder Mp, can be reduced.

[0041] Furthermore, according to the active vibration damping device 1A, unlike conventional active vibration damping devices (see, for example, Patent Document 1), the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, thereby reducing the absolute amount of magnetic powder Mp contained in the magnetorheological fluid 20b that settles.

[0042] Furthermore, according to the active vibration damping 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 lifting action of the flow F of the magnetorheological fluid 20b. Furthermore, the active vibration isolation device 1A can suppress the precipitation of magnetic powder Mp over time, and therefore can maintain good vibration and other damping performance.

[0043] In the active vibration damping 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.

[0044] 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 damping 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 input from either the inner cylinder 3 or the outer cylinder 2.

[0045] Furthermore, in the manufacturing method of such an active vibration damping device 1A, the process of filling the first liquid chamber 15 (see Figure 5) with a magnetorheological fluid (sealing process) can be carried out 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 a magnetorheological fluid when assembling the first magnetic path forming member 8 (magnetic body).

[0046] In a conventional manufacturing method for an active vibration isolation device (see, for example, Patent Document 1), after assembling the entire active vibration isolation device, a magnetorheological fluid is filled into the liquid chamber through a predetermined filling hole. With such a conventional manufacturing method, there is a risk that air bubbles will remain in the liquid chamber, reducing the damping performance of vibrations, etc. In contrast, in the manufacturing method of the active vibration damping device 1A, before assembling the device as a whole, 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 20b of the first liquid chamber 15.

[0047] The active vibration isolation device 1A described above 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.

[0048] [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, and includes a cross section corresponding to the II-IV cross section of 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.

[0049] 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 (two in this embodiment) units arranged 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 that has 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 damping device 1B, adjacent units are arranged in the axial direction with the second liquid chamber 21 sandwiched between them, allowing them to share the second liquid chamber 21. This allows the active vibration damping device 1B to be made even more compact in size.

[0050] [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, and includes a cross section corresponding to the II-IV cross section of 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.

[0051] 7B, in the active vibration damping device 1C according to the third embodiment, units each consisting of a first liquid chamber forming section 6, a second liquid chamber forming section 7, and a magnetic field forming section 5 are adjacent to one another in the axial direction, and these units are arranged so that they are out of phase with one another around the axis. Specifically, in the active vibration damping device 1C, the units are arranged so that they are out of phase with one another by 180 degrees around the axis. According to such an active vibration isolation device 1C, the rigidity in a plurality of directions perpendicular to the axes can be varied, and the damping performance of vibrations and the like can be further improved.

[0052] [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, and includes a cross section corresponding to the II-IV cross section of 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.

[0053] 7C, in an active vibration damping device 1D according to the fourth embodiment, units each consisting of a first liquid chamber forming section 6, a second liquid chamber forming section 7, and a magnetic field forming section 5 are adjacent to one another in the axial direction and share a single magnetic field forming section 5. Specifically, in the active vibration damping device 1D, the units are arranged so that the first liquid chamber forming section 6 and the second liquid chamber forming section 7 are reversed in the axial direction, with the magnetic field forming section 5 sandwiched between them. In this case, adjacent units can be configured to be arranged so that they are out of phase around the axis (for example, 180 degrees out of phase), as shown in Figure 7C, or they can be configured so that they are in the same phase, although this is not shown. According to such an active vibration isolation device 1D, it is possible to omit the magnetic field generating section 5 of one of the adjacent units, thereby simplifying the device.

[0054] [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) designated 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.

[0055] As shown in Figure 8A, the active vibration damping device 1E of the fifth embodiment differs from the active vibration damping device 1A of the first embodiment (see Figure 3) in that it has a permanent magnet 9a in the second magnetic path forming member 9 (magnetic body). 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 9a 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 opposite side in the axial direction.

[0056] 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 damping device 1E according to the fifth embodiment, and corresponds to Fig. 6B according to the first embodiment. Note that Fig. 9 shows the state when no current is applied to the electromagnetic coil 12. 9, in the assembly As of the active vibration damping device 1E, the permanent magnet 9a is arranged 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" referred to in the claims.

[0057] <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 damping 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.

[0058] When the magnetic material around the permanent magnet 9a approaches a state of magnetic saturation (saturated 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 magnetorheological fluid 20b in the orifice portion 15a. In other words, in the active vibration damping device 1E, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

[0059] FIG. 10 is a partially cutaway perspective view of the assembly As, showing how a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 when a current is applied to the electromagnetic coil 12. As shown in FIG. 10, in the active vibration damping 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 in the opposite direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

[0060] That is, in this active vibration isolation device 1E, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled out 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 increases when a current is applied to the electromagnetic coil 12, the rigidity of the active vibration isolation device 1E decreases when a current is applied to the electromagnetic coil 12.

[0061] According to the active vibration isolation device 1E described above, the magnetorheological fluid 20b in the orifice portion 15a is maintained at a high viscosity by the magnetic field generated by the permanent magnet 9a, thereby ensuring the desired damping characteristics and rigidity even in a non-energized state where no current is applied to the electromagnetic coil 12.

[0062] Furthermore, as described above, according to the active vibration isolation device 1E, unlike conventional devices, the rigidity can be reduced by applying current to the electromagnetic coil 12, thereby improving the degree of freedom when changing the damping characteristics and rigidity of the active vibration isolation device 1E.

[0063] Furthermore, with the active vibration damping device 1E, the magnetic field of the orifice portion 15a formed by the permanent magnet 9a maintains the magnetorheological fluid 20b in the orifice portion 15a in a state where the density of the magnetic powder Mp is high. This makes it possible to suppress the settling of the magnetic powder Mp when the active vibration damping device 1E is applied to a part, such as an engine mount bush, that has a small stroke and is difficult to agitate the magnetorheological fluid 20b. Therefore, with this active vibration damping 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.

[0064] In addition, in such an active vibration isolation device 1E, 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, it is possible to further widen the range of change in the designed damping characteristics and stiffness.

[0065] [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 the 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.

[0066] As shown in Figure 11, the active vibration damping device 1F of the sixth embodiment differs from the active vibration damping device 1A of the first embodiment (see Figure 3) in that it has a permanent magnet 9a in the 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 drawings, the permanent magnet 9a is disposed on the inner 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 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.

[0067] <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. 12, in an active vibration damping device 1F, a 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 in which no current is applied to the electromagnetic coil 12.

[0068] When the magnetic material around the permanent magnet 9a approaches a state of magnetic saturation (saturated 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 damping device 1F, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

[0069] FIG. 13 is a partially enlarged cross-sectional view of the assembly As showing how a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 when a current is applied to the electromagnetic coil 12. As shown in FIG. 13, in the active vibration damping device 1F, 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. In this embodiment, a current is applied to the electromagnetic coil 12 so as to form a magnetic field in the opposite direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

[0070] In such an active vibration isolation device 1F, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled out 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 reduced rigidity, similar to the active vibration isolation device 1E of the fifth embodiment (see FIG. 10).

[0071] According to the active vibration isolation device 1F 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 1F, the permanent magnet 9a can be arranged 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.

[0072] [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 the 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.

[0073] As shown in Figure 14, the active vibration damping device 1G of the seventh embodiment, unlike the active vibration damping device 1A of the first embodiment (see Figure 3), has a permanent magnet 9a in the 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 drawings, 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.

[0074] <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 damping 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 where no current is applied to the electromagnetic coil 12.

[0075] 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 damping device 1G, the orifice portion 15a is positioned on the magnetic path Mm formed by the permanent magnet 9a.

[0076] FIG. 16 is a partially enlarged cross-sectional view of the assembly As showing how a magnetic path Mc is formed in the orifice portion 15a by the electromagnetic coil 12 when a current is applied to the electromagnetic coil 12. As shown in FIG. 16, in the active vibration damping device 1G, 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. In this embodiment, a current is applied to the electromagnetic coil 12 so as to form a magnetic field in the opposite direction to the magnetic field formed in the orifice portion 15a by the permanent magnet 9a.

[0077] In such an active vibration isolation device 1G, the magnetic field formed in the orifice portion 15a by the permanent magnet 9a is canceled out 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 reduced rigidity, similar to the active vibration isolation device 1E of the fifth embodiment (see FIG. 10).

[0078] According to the active vibration isolation device 1G 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 arranged 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.

[0079] Furthermore, by being positioned on the outer periphery of the orifice portion 15a, the permanent magnet 9a of the active vibration damping device 1G can have a larger circumferential length than the permanent magnet 9a positioned on the inner periphery in the active vibration damping device 1F of the sixth embodiment (see Figure 11). This allows the active vibration isolation device 1G to more effectively form a magnetic field by the permanent magnet 9a in the orifice portion 15a compared to the active vibration isolation device 1F (see FIG. 11).

[0080] [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.

[0081] As shown in Figure 17, the active vibration damping device 1H of the eighth embodiment differs from the active vibration damping device 1A of the first embodiment (see Figure 3) in that it is equipped with a permanent magnet 24 as a magnetic field generating unit instead of the electromagnetic coil 12.

[0082] <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, in this active vibration isolation device 1H, the permanent magnet 24 can constantly generate a magnetic field in the orifice portion 15a (see FIG. 4).

[0083] As a result, in the active vibration isolation device 1H, the magnetic powder Mp is aligned along the magnetic flux ML due to the generated magnetic field, as shown in the right diagram of Fig. 6C. 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 within the orifice portion 15a. The active vibration isolation device 1H becomes hard.

[0084] 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. According to such an active vibration isolation device 1H, even if the magnetic field cannot be controlled by the electromagnetic coil 12, the active vibration isolation device 1H can be switched between two levels of stiffness depending on the magnitude of the input load to the active vibration isolation device 1H.

[0085] [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, the active vibration isolation device 1J differs from the active vibration isolation device 1A according to the first embodiment (see FIG. 2) in that it has a flange 3a at one end of the inner cylinder 3. In addition, the active vibration damping 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 damping device 1A (see Figure 3).

[0086] Furthermore, as shown in Figure 18, the active vibration damping device 1J does not have the liquid chamber partition 22 (see Figure 3), and instead has an elastic support portion 23 consisting of an approximately cylindrical elastic body that is vulcanized and 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 damping device 1J is formed on the inner circumferential side of the outer cylinder 2 such that the elastic support portion 23 is partially removed in the circumferential direction.

[0087] 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 Figure 3) of the active vibration damping device 1A (see Figure 3).

[0088] Next, the first liquid chamber forming section 6 (see FIG. 18) and the magnetic field forming section 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 made up 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 encloses a magnetorheological fluid 20b.

[0089] The first liquid chamber 35 is configured to include 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 than 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 of the first embodiment (see FIG. 6A), and serves as a flow path for the magnetorheological fluid 20b.

[0090] 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 the third magnetic path forming member 41. As will be described later, the magnetic field forming unit 5 forms a magnetic path Mc in the parallel liquid chamber 35b.

[0091] 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 to be integrated. As shown in Figure 19, the assembly As has a generally cylindrical shape so as to fit inside the outer cylinder 1 (see Figure 18). In Figure 19, reference numeral 34 denotes a flexible member that constitutes the first liquid chamber forming portion 6, reference numeral 38 denotes a first magnetic path forming member (partition wall) that constitutes the first liquid chamber forming portion 6, and reference numeral 39 denotes a second magnetic path forming member that is 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 that constitutes the magnetic field forming portion 5. Note that the electromagnetic coil 12 (see Figure 18) has been omitted from Figure 19 for ease of illustration.

[0092] FIG. 20 is an exploded perspective view of the assembly As. As shown in FIG. 20, the 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 a ring-shaped electromagnetic coil 12 (magnetic field generating unit), a second magnetic path forming member 39, a first magnetic path forming member 38 (partition wall), and a flexible member 34 in this order on the inner circumferential side of the third magnetic path forming member 41, which is an approximately bottomed cylindrical body.

[0093] The flexible member 34 has a pair of arc-shaped bottom walls 37 on the surface thereof, 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 seen from the rear surface side, and Fig. 21B is a cross-sectional view taken along line XXIb-XXIb in Fig. 21A.

[0094] 21A and 21B, the flexible member 34 has a symmetrical structure on the front and back sides. A groove-shaped adjacent liquid chamber 35a is formed on the back side of the flexible member 34 so as to be symmetrical with the groove-shaped recess having a bottom wall 37 (see FIG. 21B) on the front side. A magnetorheological fluid 20b (see FIG. 18) is sealed in this adjacent liquid chamber 35a by bringing the back side of the flexible member 34 into close contact with the surface of the first magnetic path forming member 38 (see FIG. 20).

[0095] Fig. 22 is an overall perspective view of the first magnetic path forming member 38 as seen from the front side. In Fig. 22, half 35b1 of the juxtaposed liquid chamber 35b formed on the back surface 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).

[0096] 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 connecting 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 plan view that matches the shape of one end of the flexible member 34 (see FIG. 21A) where the pair of adjacent liquid chambers 35a (see FIG. 21A) face each other.

[0097] 22, 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 shown in FIG. As shown in Figure 22, half 35b1 extends circumferentially around the first magnetic path forming member 38 from one of the 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).

[0098] As will be explained in detail later, the positions at which these connecting passages 38a (see Figure 22) are formed are preferably positioned vertically above the lowest vertical position of the parallel liquid chamber 35b (see Figure 22) when the axis of the active vibration damping device 1J (see Figure 18) is horizontal.

[0099] The groove bottom of half 35b1 is formed with concave-convex shapes 38b, in which convex portions 38b1 that convex toward second magnetic path forming member 39 and concave portions 38b2 that concave are alternately arranged in the circumferential direction. 18, the first magnetic path forming member 38 is disposed so as to separate 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 the "partition wall" referred to in the claims.

[0100] 23 is an overall perspective view of the second magnetic path forming member 39 as seen from the back side. 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 shown 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 to one end of the cylindrical portion 39c1 in a flange-like shape.

[0101] 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 this half 35b2. As shown in FIG. 23, this uneven shape 39a is formed by convex portions 39a1 that convex toward the first magnetic path forming member 38 (see FIG. 20) side and concave portions 39a2 that concave toward the first magnetic path forming member 38 (see FIG. 20) side, alternately arranged in the circumferential direction.

[0102] As shown in FIG. 20, half 35b1 of first magnetic path forming member 38 and half 35b2 of second magnetic path forming member 39 are integrated to form juxtaposed liquid chamber 35b shown in FIG. 18. In this case, convex portion 38b1 on the first magnetic path forming member 38 side shown in FIG. 22 and convex portion 39a1 on the second magnetic path forming member 39 side shown in FIG. 23 face each other with a predetermined clearance formed therebetween. The clearance (gap) formed between convex portion 38b1 and convex portion 39a1 forms an orifice portion in juxtaposed liquid chamber 35b, which serves as a flow path for magnetorheological fluid 20b. In other words, juxtaposed liquid chamber 35b has multiple orifices along its length (circumferential direction).

[0103] <Action and effect> Next, the operation of the first liquid chamber forming portion 6 (see FIG. 20) will be explained, while explaining the effects of the active vibration damping device 1J (see FIG. 18). 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 of the pair of second liquid chambers 21 that is compressed between the outer cylinder 2 and the inner cylinder 3. Furthermore, the liquid pressure of the liquid 20a decreases in the second liquid chamber 21 on the opposite side of the inner cylinder 3.

[0104] 24, which is an explanatory diagram of the operation of the first liquid chamber forming portion 6, a load P1 is applied to the bottom wall 37 of the flexible member 34 adjacent to one of the second liquid chambers 21 (see FIG. 18) in a direction that presses it. Although not shown, the bottom wall 37 bends so as to 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 that pulls the bottom wall 37. Although not shown, the bottom wall 37 bends so as to become concave toward the adjacent liquid chamber 35a.

[0105] This increases 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, while decreasing 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. 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, bypasses the parallel liquid chamber 35b, and passes through the other connecting passage 38a.

[0106] 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. This increases the apparent viscosity of the magnetorheological fluid 20b in the parallel liquid chamber 35b, and generates flow resistance within the parallel liquid chamber 35b. The active vibration isolation device 1J exhibits damping characteristics for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b in the parallel fluid 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.

[0107] 18, in the active vibration damping 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). This active vibration damping device 1J allows the magnetorheological fluid 20b to flow in the parallel liquid chamber 35b that is offset in the axial direction from the adjacent liquid chamber 35a. This allows the active vibration damping 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.

[0108] Furthermore, as shown in Figure 24, when the active vibration damping device 1J is positioned so that its axis Ax is horizontal, the connecting passage 38a is formed so that it is positioned vertically above the lowest point Bm in the vertical direction (in the direction of 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 damping device 1J, the magnetorheological fluid flows through the lowermost part Bm of the parallel fluid chamber 35b and into the connecting passage 38a, so that the influence of settling of the magnetorheological fluid can be reduced.

[0109] As shown in FIG. 24, the active vibration isolation device 1J has a concave-convex shape 39a in the parallel liquid chamber 35b that serves as a flow path for the magnetorheological fluid. According to this active vibration damping 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) with the recess 39a2.

[0110] 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 damping devices 1E, 1F, and 1G according to the fifth to seventh embodiments described above, examples have been given in which the permanent magnets 9a are arranged in three locations: the radial side surface of the electromagnetic coil 12, the radial inside of the orifice portion 15a, or the radial outside of the orifice portion 15a, but the active vibration damping device of the present invention is not limited to this. Therefore, the active vibration damping device of the present invention can also be configured in such a way that the permanent magnets 9a are arranged in two or more selected locations out of the three locations: the radial side surface of the electromagnetic coil 12, the radial inside of the orifice portion 15a, and the radial outside of the orifice portion 15a.

[0111] Furthermore, in the active vibration isolation device 1J, instead of the electromagnetic coil 12, a permanent magnet 24 similar to that of the active vibration isolation device 1H (see FIG. 17) can be arranged. According to such an active vibration isolation device 1J, like the active vibration isolation device 1H (see FIG. 17), the active vibration isolation device 1J can be switched between two levels of stiffness depending on the magnitude of the input load to the active vibration isolation device 1J. [Explanation of symbols]

[0112] 1A Active vibration isolation device 1B Active vibration isolation device 1C Active vibration isolation device 1D active vibration isolation device 1E Active vibration isolation device 1F Active vibration isolation device 1G active vibration isolation device 1H Active vibration isolation device 1J Active vibration isolation device 2 outer cylinder 3 Inner cylinder 5 Magnetic field forming part 6 First liquid chamber forming part 7 Second liquid chamber forming part 8. First magnetic path forming member (magnetic material) 9 Second magnetic path forming member (magnetic material) 9a permanent magnet 11 Third magnetic path forming member (magnetic material) 12 Electromagnetic coil (magnetic field generating part) 14 Flexible member 15 1st liquid chamber 15a Orifice 17 Bottom wall of flexible member 20a liquid 20b Magnetorheological fluid 21 2nd liquid chamber 24 Permanent magnet (magnetic field generating part) 34 Flexible member 35 1st liquid chamber 35a Adjacent liquid chamber 35b Parallel liquid chamber 38 First magnetic path forming member (partition wall) 38a Connecting 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 electromagnetic coil Mm Magnetic path formed at the orifice by the permanent magnet MFL magnetic field lines

Claims

1. An outer tube and 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 a non-magnetic 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 the radial direction, The first liquid chamber and the second liquid chamber are separated by a flexible member, An active vibration isolation device, characterized in that a part of the first fluid chamber forms a flow path for the magnetorheological fluid located on the magnetic path.

2. 2. An active vibration isolation device according to claim 1, wherein the first liquid chamber, the second liquid chamber, and the flexible member extend in a circumferential direction.

3. An outer tube and 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 the radial direction, The first liquid chamber and the second liquid chamber are separated by a flexible member, a portion of the first fluid chamber forms a flow path for the magnetorheological fluid located on the magnetic path; the first liquid chamber, the second liquid chamber, and the flexible member extend in a circumferential direction, An active vibration damping device characterized in that a first liquid chamber forming portion that forms the first liquid chamber, a second liquid chamber forming portion that forms the second liquid chamber, and a magnetic field forming portion that has the magnetic field generating portion are arranged in line in the axial direction.

4. 4. The active vibration isolation device according to claim 3, further comprising a plurality of units, each having the first liquid chamber forming portion, the second liquid chamber forming portion, and the magnetic field forming portion, arranged in the axial direction.

5. 5. An active vibration isolation device according to claim 4, wherein adjacent units are arranged so that their phases are different from each other around the axis.

6. 5. The active vibration isolation device according to claim 4, wherein adjacent units share one of the magnetic field generating portions.

7. 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 the flow path of the magnetorheological fluid is located on the magnetic path formed by the permanent magnet.

8. An active vibration isolation device as described in claim 7, characterized in that the permanent magnet is arranged in at least one location 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 in the flow path of the magnetorheological fluid, and the outer adjacent portion adjacent to the radial outside in the flow path of the magnetorheological fluid.

9. An outer tube and 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 the radial direction, The first liquid chamber and the second liquid chamber are separated by a flexible member, a portion of the first fluid chamber forms a flow path for the magnetorheological fluid located on the magnetic path; the first liquid chamber includes an adjacent liquid chamber adjacent to the flexible member, the flow path of the magnetorheological fluid is separated from the adjacent liquid chamber in the axial direction by a partition wall; An active vibration isolation device characterized in that the partition wall has a connecting passage that connects the adjacent liquid chamber with the flow path of the magnetorheological fluid.

10. The adjacent liquid chambers are formed as 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.

11. An active vibration isolation device as described in claim 9, characterized in that when the axis of the active vibration isolation device is positioned horizontally, the connecting passage is formed so as to be positioned vertically above the vertical lowest point of the flow path of the magnetorheological fluid.

12. 10. The active vibration isolation device according to claim 9, wherein the flow path for the magnetorheological fluid has an axially uneven shape.

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