Active vibration isolation device and manufacturing method thereof

Abstract

To provide an active vibration damping device which inhibits performance deterioration caused by precipitation of a magnetic powder of a magnetorheological fluid in a liquid chamber without increasing a volumetric capacity of the liquid chamber to be filled with the magnetorheological fluid.SOLUTION: An active vibration damping device 1 of the invention includes: an electromagnetic coil 12 serving as a magnetic field generation part; an outer member 61 which is a magnetic material; and an inner member 62 which is a magnetic material. A first liquid chamber 15 and a 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 and the second liquid chamber 21 are partitioned by a flexible member 14 extending in an axial direction of the inner cylinder 3. Further, the flexible member 14 is supported by the outer member 61 which is the magnetic material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an active vibration isolation device and a method for manufacturing the same. [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. With this active vibration isolation device, 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. At this time, the active vibration isolation device controls the flow of the magnetorheological fluid by varying the magnetic flux density generated by the excitation coil. 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 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 that can also suppress performance degradation due to the settling of magnetic powder in the magnetorheological fluid in the liquid chamber, thereby contributing to the development of sustainable transportation systems. [Means for solving the problem]

[0006] The present invention is an active vibration damping device having an outer tube, an inner tube arranged on the inner side 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 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, the flexible member extends in the axial direction of the inner tube, and a portion of the first liquid chamber forms a flow path for the magnetorheological fluid located on the magnetic path.

[0007] The present invention also provides a method for manufacturing the active vibration damping device, characterized in that it includes the steps of: a fabrication process for a second liquid chamber forming portion in which the elastic body is integrally molded onto the outer surface of the inner cylinder to form the second liquid chamber; a fabrication process for a first liquid chamber forming portion in which the magnetic field generating portion, the magnetic body, and the flexible member are combined in a liquid consisting of the magnetorheological fluid to form the first liquid chamber filled with the magnetorheological fluid; a fabrication process for an assembly in which the first liquid chamber forming portion and the second liquid chamber forming portion are assembled so that the first liquid chamber and the second liquid chamber are separated by the flexible member extending in the axial direction of the inner cylinder and supported by the magnetic body, and the magnetic body and the inner cylinder are connected by the elastic body; and a fixing process in which the assembly is inserted inside the outer cylinder in the liquid to fill the second liquid chamber with the liquid and fix the assembly within the outer cylinder. [Effects of the Invention]

[0008] The active vibration damping device and its 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 the settling of magnetic powder in the magnetorheological fluid in the liquid chamber. [Brief explanation of the drawings]

[0009] [Figure 1A] 1 is a partially enlarged perspective view of a rear suspension equipped with an active vibration isolation device according to an embodiment of the present invention. [Figure 1B] 1 is an overall perspective view of an active vibration isolation device according to an embodiment of the present invention; [Figure 2A] FIG. 2 is a cross-sectional view taken along line IIA-IIA of FIG. 1B. [Figure 2B] This is a cross section taken along line IIB-IIB in FIG. 1B. [Figure 3] FIG. 1C is an exploded perspective view of the active vibration isolation device shown in FIG. 1B. [Figure 4] 1 is a perspective view of the entire assembly of a first liquid chamber forming portion and a second liquid chamber forming portion that constitute an active vibration damping device. FIG. [Figure 5]FIG. 1C is a cross-sectional view of FIG. 1B. [Figure 6] FIG. 10 is an overall perspective view of a cage embedded in a second liquid chamber forming portion. [Figure 7] FIG. 2 is an exploded perspective view of a first liquid chamber forming portion that constitutes the active vibration damping device. [Figure 8] 8 is a partially enlarged perspective view of the active vibration isolation device including the VIII-VIII cross section of FIG. 2B. [Figure 9] 5 is a schematic diagram showing the behavior of magnetic powder when a magnetic field is applied to an orifice of a first liquid chamber. FIG. [Figure 10A] FIG. 10 is an overall perspective view of an active vibration isolation device according to another embodiment of the present invention. [Figure 10B] 10B is a cross-sectional view taken along the line XB-XB in FIG. 10A. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an active vibration isolation device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following, we will use an active vibration isolation device applied to a vehicle suspension as an example, but the present invention is not limited to this and can also be applied to vehicle noise and vibration isolation devices such as mounting bushes that are placed between components connected to the vehicle frame (including the subframe). First, the overall configuration of a rear suspension to which the active vibration isolation device of this embodiment is applied will be described, and then the active vibration isolation device will be described in more detail.

[0011] <Rear suspension> 1A is a partially enlarged perspective view of a rear suspension 30 equipped with an active vibration isolation device 1 according to this embodiment. Note that the up, down, left, right, front, and rear directions in the following description are based on the directions of the arrows in FIG. 1A, which correspond to the up, down, left, right, front, and rear directions of the vehicle.

[0012] As shown in FIG. 1A, the rear suspension 30 is a semi-trailing suspension that mainly includes a suspension arm 31, a rear damper 32 that is attached at one end to the suspension arm 31 and supported at the other end on the vehicle body frame (not shown), and a coil spring 33 that is supported by the suspension arm 31.

[0013] The suspension arm 31 includes a trailing arm 34, a cross beam 35, and a knuckle 36 that is provided on the trailing arm 34 and supports a rear wheel (not shown). A bushing 37 is attached to the front end of the trailing arm 34 for swingably mounting the trailing arm 34 to a vehicle body frame (not shown). The bushing 37 is an active vibration isolation device of this embodiment, and will be referred to as an active vibration isolation device 1 hereinafter. The front end of the trailing arm 34 is attached to an outer cylinder 2 (see FIG. 2A) of the active vibration isolation device 1, which will be described later. The active vibration isolation device 1 is also attached to a predetermined bracket (not shown) provided on a vehicle body frame (not shown) via a support shaft 38. Incidentally, the support shaft 38 is inserted into an inner cylinder 3 (see FIG. 2A) of the active vibration isolation device 1, which will be described later.

[0014] <Active vibration isolation device> FIG. 1B is an overall perspective view of the active vibration damping device 1 of this embodiment. FIG. 2A is a cross-sectional view taken along line IIA-IIA of FIG. 1B. FIG. 2B is a cross-sectional view taken along line IIB-IIB of FIG. 1B. For convenience of drawing, FIG. 1B depicts, among the components of the active vibration damping device 1, the outer cylinder 2 in solid lines, and the inner cylinder 3 disposed inside the outer cylinder 2, the first liquid chamber forming portion 6, and the second liquid chamber forming portion 7 in hidden lines (dotted lines). Incidentally, in FIG. 1B, reference numeral 14 denotes a flexible member of the first liquid chamber forming portion 6 that faces the outside of the second liquid chamber forming portion 7 via a slit 7b1 of the second liquid chamber forming portion 7, which will be described later.

[0015] As shown in FIG. 1B, the active vibration isolation device 1 has a cylindrical outer shape. As shown in FIGS. 2A and 2B, the active vibration isolation device 1 includes an outer cylinder 2 and an inner cylinder 3 that is arranged on the inner periphery of the outer cylinder 2 so as to be substantially coaxial with the outer cylinder 2. In addition, between the outer tube 2 and the inner tube 3, as will be explained in detail later, there are arranged a first liquid chamber forming portion 6 (see Figure 5) that forms a first liquid chamber 15 (see Figure 5), and a second liquid chamber forming portion 7 (see Figure 5) that forms a second liquid chamber 21 (see Figure 5).

[0016] As shown in Fig. 2B, an orifice 15a is formed in the first liquid chamber forming portion 6 as part of the first liquid chamber 15. This orifice 15a forms a throttle portion with a cross-sectional area smaller than the cross-sectional area of ​​the first liquid chamber 15 as a general portion shown in Fig. 2A. As will be described in detail later, when a magnetic path Mc is formed by the magnetic field generated by the electromagnetic coil 12 (magnetic field generating portion) shown in Fig. 2B, this orifice 15a is located on this magnetic path Mc.

[0017] <Outer barrel> As shown in FIGS. 2A and 2B, the outer cylinder 2 is formed as a cylindrical body with a bottom. The outer cylinder 2 is configured to have a cylindrical outer cylinder body 24 and a lid body 25 that closes one open end of the outer cylinder body 24. The lid 25 has a disk portion 25a arranged to abut against one end surface of the inner cylinder 3, and a cylindrical elastic portion 25b made of synthetic rubber that vulcanizes and bonds the end of the outer cylinder body 24 to the lid 25. The disk portion 25a has an opening 25a1 in the center that has the same diameter as the hole 3a of the inner cylinder 3. In this embodiment, the outer cylinder body 24 and the disk portion 25a of the lid body 25 are assumed to be made of a non-magnetic material. Examples of non-magnetic materials include, but are not limited to, aluminum alloys, non-ferritic SUS, and copper.

[0018] <Inner cylinder> 2A and 2B, the inner cylinder 3 is formed to be longer in the axial direction than the outer cylinder body 24. The axial end of the inner cylinder 3 protrudes slightly axially outward from the end of the outer cylinder body 24. In this embodiment, the inner cylinder 3 is assumed to be made of a non-magnetic material. A support shaft 38 (see FIG. 1A) is inserted through the hole 3a of the inner cylinder 3 and the opening 25a1 of the disk portion 25a. As described above, the active vibration isolation device 1 is supported on the vehicle frame (not shown) via this support shaft 38 (see FIG. 1A).

[0019] <First liquid chamber forming portion and second liquid chamber forming portion> Next, the first liquid chamber forming portion 6 (FIG. 2A) and the second liquid chamber forming portion 7 (FIG. 2A) will be described. Here, the second liquid chamber forming portion 7 (FIG. 2A) will be described first, followed by the first liquid chamber forming portion 6 (FIG. 2A).

[0020] FIG. 3 is an exploded perspective view of the active vibration isolation device 1 (see FIG. 2A). As shown in FIG. 3, the second liquid chamber forming portion 7 is substantially in the shape of a top with the inner cylinder 3 as its axis. Specifically, the second liquid chamber forming portion 7 has a substantially cylindrical portion 7a that is press-fitted into the inside of the outer cylinder main body 24, and a cylindrical portion 7b into which a small-diameter cylindrical portion 61a of the first liquid chamber forming portion 6 (described later) is fitted. The substantially cylindrical portion 7a and the cylindrical portion 7b have the same outer diameter and are integrally molded so as to be coaxial with each other. The cylindrical portion 7b is press-fitted into the inside of the outer cylinder main body 24 together with the substantially cylindrical portion 7a. 3, the reference symbol R denotes ribs formed on the outer peripheral surface of the second liquid chamber forming portion 7. When the second liquid chamber forming portion 7 is press-fitted into the outer cylinder main body 24, these ribs R function as a sealing member for the second liquid chamber 21 (see FIG. 5) filled with a liquid 20a (see FIG. 5), which will be described later.

[0021] As shown in Fig. 3, a pair of grooves 7a1 are formed in the substantially cylindrical portion 7a. The pair of grooves 7a1 extend in the circumferential direction of the substantially cylindrical portion 7a at positions sandwiching the inner tube 3. The pair of grooves 7a1 are formed to face each other at a phase difference of 180 degrees with the inner tube 3 in between. That is, the pair of grooves 7a1 are formed in the substantially cylindrical portion 7a so as to sandwich a partition wall 7a2 extending in the radial direction of the substantially cylindrical portion 7a therebetween.

[0022] A pair of slits 7b1 are formed in the cylindrical portion 7b. Each of the pair of slits 7b1 extends in the circumferential direction of the cylindrical portion 7b so as to be parallel to each of the pair of grooves 7a1 in the axial direction. Furthermore, the opening of the slit 7b1, which faces the inside of the cylindrical portion 7b, is liquid-tightly sealed by the flexible member 14 when the small-diameter cylindrical portion 61a of the first liquid chamber forming portion 6 is fitted into the inside of the cylindrical portion 7b, as will be explained below.

[0023] FIG. 4 is an overall perspective view of an assembly As of the second liquid chamber forming portion 7 and the first liquid chamber forming portion 6. As shown in FIG. As shown in FIG. 4, the assembly As is configured by press-fitting the small-diameter cylindrical portion 61a (see FIG. 3) of the first liquid chamber forming portion 6 into the cylindrical portion 7b of the second liquid chamber forming portion 7. As a result, the opening of the slit 7b1 facing the inner periphery of the cylindrical portion 7b is liquid-tightly closed by the flexible member 14, which will be described in detail later. As a result, slit 7b1 forms groove 7c that extends in the circumferential direction of cylindrical portion 7b with flexible member 14 as its bottom. That is, groove 7c is formed to correspond to groove 7a1 of approximately cylindrical portion 7a.

[0024] The second liquid chamber forming portion 7 also has a groove 7d that connects the groove 7a1 and the groove 7c. In this embodiment, a pair of grooves 7d are formed from both circumferential ends of groove 7c toward groove 7a1. That is, groove 7d is formed from the approximately columnar portion 7a to the cylindrical portion 7b of the second liquid chamber forming portion 7. Such grooves 7d are formed as recesses in which the outer circumferential surfaces of the approximately columnar portion 7a and the cylindrical portion 7b are partially recessed radially inward.

[0025] Fig. 5 is a VV cross-sectional view of Fig. 1B, which shows an assembly As of the second liquid chamber forming portion 7 and the first liquid chamber forming portion 6 arranged inside the outer cylinder 2. As shown in FIG. 5, the groove 7a1 of the second liquid chamber forming portion 7 is closed by the inner circumferential surface of the outer cylinder 2 to form a main liquid chamber 21a. Furthermore, the groove portion 7c of the second liquid chamber forming portion 7 is closed by the inner peripheral surface of the outer cylinder 2, forming an adjacent liquid chamber 21b adjacent to the main liquid chamber 21a. Furthermore, the groove 7d of the second liquid chamber forming portion 7 is closed by the inner peripheral surface of the outer cylinder 2, forming a connecting passage 21c that connects the main liquid chamber 21a and the adjacent liquid chamber 21b.

[0026] The main liquid chamber 21a, the adjacent liquid chamber 21b, and the connecting passage 21c are integrated to form the second liquid chamber 21. Specifically, the second liquid chamber 21 includes an adjacent liquid chamber 21b located radially outward on the flexible member 14 side, and a main liquid chamber 21a located axially on the opposite side from the adjacent liquid chamber 21b across the elastic body 8. The active vibration damping device 1 also includes a connecting passage 21c between the cage 9 and the outer cylinder 2 that connects the main liquid chamber 21a and the adjacent liquid chamber 21b. The second fluid chamber 21 is filled with a fluid 20a that is a medium for transmitting vibrations, etc. As the fluid 20a, known hydraulic oils such as silicone oil and ester oil can be suitably used.

[0027] As shown in Figure 5, such a second liquid chamber forming portion 7 is configured to include an elastic body 8 that forms an approximately columnar portion 7a and a cylindrical portion 7b that are arranged between the outer tube main body 24 of the outer tube 2 and the inner tube 3, and an approximately cylindrical cage 9 that is embedded in the elastic body 8 so as to fit along the inner surface of the outer tube 2.

[0028] The elastic body 8 in this embodiment is assumed to be a molded product of synthetic rubber, and is bonded to the outer peripheral surface of the inner cylinder 3 by vulcanization. 5, the elastic body 8 has a tubular covering portion 8a that supports the approximately columnar portion 7a and the cylindrical portion 7b on the inner tube 3. The tubular covering portion 8a covers approximately the entire outer circumferential surface of the inner tube 3. Such elastic body 8 elastically supports the second liquid chamber forming portion 7 and the first liquid chamber forming portion 6, which is integrated with this second liquid chamber forming portion 7 via the outer cylinder 2, on the outer peripheral surface of the inner cylinder 3. In other words, the elastic body 8 cooperates with the cylindrical elastic portion 25b that constitutes the outer cylinder 2 to allow relative displacement of the inner cylinder 3 with respect to the outer cylinder main body 24 in the direction perpendicular to the axis.

[0029] The cage 9 is embedded in the elastic body 8 by insert molding. FIG. As shown in Figure 6, the cage 9 has two notches 9a formed to correspond to the main liquid chamber 21a (see Figure 5) and two notches 9b formed to correspond to the adjacent liquid chamber 21b (see Figure 5). The cage 9 is a substantially cylindrical body made of a thin metal plate, and as shown in Fig. 2B, the cage 9 contains the elastic body 8 on the radially inner side. As will be described in detail later, the cage 9 functions as a strain relief member that relieves residual strain that occurs after vulcanization molding of the elastic body 8 (see FIG. 2B) due to drawing applied to the cage 9. Examples of materials for the cage 9 include steel plates, aluminum plates, copper plates, and titanium plates, but are not limited to these as long as they can be drawn. Among these, steel plates are preferred as the material for the cage 9.

[0030] Next, the first liquid chamber forming portion 6 (see FIG. 3) will be described. As shown in FIG. 3, the first liquid chamber forming portion 6 has a flexible member 14, an outer member 61 to which the flexible member 14 is attached, and an inner member 62 that fits inside the outer member 61.

[0031] FIG. 7 is an exploded perspective view of the first liquid chamber forming portion 6. As shown in FIG. As shown in FIG. 7, the outer member 61 includes a small diameter cylindrical portion 61a and a large diameter cylindrical portion 61b having a larger diameter than the small diameter cylindrical portion 61a. A pair of circumferentially extending slit-shaped notches 61a1 are formed in the small-diameter cylindrical portion 61a. The circumferential length of these notches 61a1 corresponds to the circumferential length of the groove 7c (see FIG. 4) in the second liquid chamber forming portion 7 (see FIG. 4). The cutout portion 61a1 allows communication between the inside and outside of the small diameter cylindrical portion 61a. The outer member 61 is made of a magnetic material such as iron, cobalt, nickel, or an alloy thereof.

[0032] As shown in FIG. 7, the flexible member 14 is attached to the small diameter cylindrical portion 61a so as to cover the notch 61a1 from the outside of the small diameter cylindrical portion 61a. The flexible member 14 is formed of a long, thin plate made of synthetic rubber that curves along the outer circumferential surface of the small-diameter cylindrical portion 61a. Locked rings 14a are formed on both longitudinal ends of the flexible member 14. The locked rings 14a fit into locking projections 61a2 formed on the outer circumferential surface of the small diameter cylindrical portion 61a, thereby attaching the flexible member 14 to the outer circumferential surface of the small diameter cylindrical portion 61a. Incidentally, the flexible member 14 is disposed so that the width direction of the flexible member 14 extends along the axial direction of the inner cylinder 3, as shown in FIG. 2A.

[0033] In this embodiment, the flexible member 14 is configured to be sandwiched between the inner surface of the cylindrical portion 7b of the second liquid chamber forming portion 7 and the outer surface of the small diameter cylindrical portion 61a of the first liquid chamber forming portion 6. However, the support structure of the flexible member 14 is not limited to this, and the flexible member 14 may also be configured to be integrally connected to at least one of the cylindrical portion 7b and the small diameter cylindrical portion 61a.

[0034] As shown in Figure 7, the inner member 62 is configured to have an insertion cylindrical portion 62a that is inserted into the inside of the small diameter cylindrical portion 61a of the outer member 61, and a flange portion 62b formed at one axial end of the insertion cylindrical portion 62a. As shown in FIG. 2B, the outer diameter of the flange portion 62b is set so as to fit within the inner periphery of the large diameter cylindrical portion 61b of the outer member 61.

[0035] As shown in FIG. 2B, the fitting cylindrical portion 62a of the inner member 62 is configured by providing a coating 62a2 made of synthetic rubber on the surface of a cylindrical core material 62a1 made of a magnetic material. As shown in FIG. 2B, the coating 62a2 is formed on the entire surface of the cylindrical fitting portion 62a except for the portion where the orifice 15a, which will be described in detail later, is formed. The flange portion 62b of the inner member 62 is made of a magnetic material and is formed so as to continuously protrude from one axial end of the core material 62a1 to the outer periphery. Examples of the magnetic material forming the core material 62a1 and the flange portion 62b include iron, cobalt, nickel, and alloys thereof.

[0036] 5, when the inner member 62 is press-fitted into the outer member 61, the coating 62a2 of the fitting cylindrical portion 62a of the inner member 62 comes into liquid-tight contact with the inner circumferential surface of the small-diameter cylindrical portion 61a of the outer member 61. A slit-shaped notch 61a1 formed in the small-diameter cylindrical portion 61a forms a first liquid chamber 15 between the flexible member 14 and the fitting cylindrical portion 62a. The first liquid chamber 15 is filled with a magnetorheological fluid 20b. As the magnetorheological fluid 20b, known MRF (Magneto-Rheological Fluid) or MRC (Magneto-Rheological Compound) in which magnetic powder is dispersed in mineral oil, synthetic oil, or the like can be suitably used.

[0037] Next, the orifice 15a (see FIG. 2B) that constitutes a part of the first liquid chamber 15 (see FIG. 5) will be described in more detail. FIG. 8 is a partially enlarged perspective view of the active vibration isolation device 1 including the cross section VIII-VIII of FIG. 2B. As shown in FIG. 8, the first liquid chamber 15 extends annularly along the circumferential direction of the first liquid chamber forming portion 6, except for a separation portion 15c provided at a position opposite the orifice 15a across the inner cylinder 3. The orifice 15a, which is a part of the first fluid chamber 15, is formed to have a smaller cross-sectional area in the radial direction than the cross-sectional area of ​​the general portion 15b of the first fluid chamber 15. As described above, the general portion 15b of the first fluid chamber 15 is formed between the inner surface of the flexible member 14 and the outer circumferential surface of the fitting cylindrical portion 62a. In contrast, the orifice 15a is formed in the gap between the rectangular region Ar that does not have the coating 62a2 shown in Fig. 7 and the small-diameter cylindrical portion 61a of the outer member 61 that faces this rectangular region Ar. That is, as shown in Fig. 8, the orifice 15a is formed in a gap that corresponds to the thickness of the coating 62a2 in the fitting cylindrical portion 62a. When the active vibration isolation device 1 of this embodiment is attached to the rear suspension 30 shown in FIG. 1A, the orifice 15a is positioned vertically downward as shown in FIG.

[0038] The connecting passage 21c in the second liquid chamber forming portion 7 shown in Figure 5 is set to have a cross-sectional area that is smaller than the resistance when the liquid 20a flows through the connecting passage 21c and the resistance when the magnetorheological fluid 20b flows through the orifice 15a shown in Figure 8 when no magnetic field is applied from the electromagnetic coil 12 (magnetic field generating portion).

[0039] 7, the first liquid chamber forming portion 6 is configured so that the electromagnetic coil 12 (magnetic field generating portion) is accommodated inside the large diameter cylindrical portion 61b of the outer member 61. Specifically, as shown in FIG. 2B, the electromagnetic coil 12 is disposed in an annular space surrounded by the large diameter cylindrical portion 61b of the outer member 61 and a flange portion 62b of the inner member 62, which will be described next.

[0040] Then, as shown in FIG. 2B, when the inner member 62 is press-fitted into the inside of the outer member 61, the large diameter cylindrical portion 61b of the outer member 61 and the inner member 62 are magnetically connected. The coating 62a2 magnetically insulates the small diameter cylindrical portion 61a of the outer member 61 from the core material 62a1 of the fitting cylindrical portion 62a, except for the portion where the orifice 15a is formed. As a result, the outer member 61, the core material 62a1 of the inner member 62, and the flange portion 62b of the inner member 62 form a magnetic path Mc that passes through the magnetorheological fluid 20b in the orifice 15a due to the magnetic field generated by the electromagnetic coil 12.

[0041] The outer member 61, the core material 62a1 of the inner member 62, and the flange portion 62b of the inner member 62 constitute the "magnetic body" referred to in the claims. 5, the first liquid chamber forming portion 6 as described above is not directly connected to the elastic body 8. Specifically, the first liquid chamber forming portion 6 is fitted into the second liquid chamber forming portion 7, and is fitted inside the outer cylinder 2. In other words, the first liquid chamber forming portion 6 is disposed radially outwardly of the inner cylinder 3 and spaced apart from it.

[0042] <<Operation of the active vibration isolation device>> First, the operation of the active vibration isolation device 1 when the electromagnetic coil 12 is not energized will be described. As shown in FIG. 5, in the active vibration isolation device 1, 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. In the scene shown in Fig. 5, the inner cylinder 3 is displaced toward the outer cylinder 2, which increases the liquid pressure of the liquid 20a in the second liquid chamber 21 on the P side in Fig. 5. In addition, in the second liquid chamber 21 on the Q side, which is on the opposite side across the inner cylinder 3, the liquid pressure of the liquid 20a decreases as the inner cylinder 3 is displaced away from the outer cylinder 2.

[0043] When the liquid pressure of the liquid 20a in the P-side second liquid chamber 21 increases, the P-side flexible member 14 is pressed in a direction toward the first liquid chamber 15, i.e., toward the inner cylinder 3. Furthermore, when the liquid pressure of the liquid 20a in the Q-side second liquid chamber 21 decreases, the flexible member 14 is pulled in a direction away from the inner cylinder 3. That is, in the active vibration damping device 1, as shown in Fig. 8, the magnetorheological fluid 20b in the general portion 15b of the first liquid chamber 15 on the P side moves to the general portion 15b of the first liquid chamber 15 on the Q side. The magnetorheological fluid 20b generates a flow F that passes through the orifice 15a.

[0044] On the P side shown in FIG. 5, when the flexible member 14 is pressed toward the inner cylinder 3, the liquid 20a flows from the main liquid chamber 21a through the connecting passage 21c to the adjacent liquid chamber 21b. The liquid 20a generates flow resistance when flowing through the connecting passage 21c. The active vibration isolation device 1 exhibits damping characteristics for input vibrations and the like due to the flow resistance of the liquid 20a.

[0045] Also, as shown in FIG. 8, the magnetorheological fluid 20b generates flow resistance when it flows from the general portion 15b of the first liquid chamber 15 on the P side to the general portion 15b of the first liquid chamber 15 on the Q side via the orifice 15a. The active vibration isolation device 1 exhibits damping characteristics for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b.

[0046] Next, the operation of the active vibration isolation device 1 when the electromagnetic coil 12 is energized will be described. The magnetic field generated by the energized electromagnetic coil 12 forms a magnetic path Mc passing through the magnetorheological fluid 20b in the orifice 15a, as shown in FIG. 2B.

[0047] FIG. 9 is a schematic diagram showing the behavior of the magnetic powder Mp when a magnetic field is applied to the orifice 15a of the first liquid chamber 15. As shown in FIG. As shown in the left diagram in Figure 9, the magnetorheological fluid 20b in the orifice 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. 9, 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 15a. The active vibration isolation device 1 exhibits damping characteristics for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b in the orifice 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.

[0048] The active vibration damping device 1 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 1 controls the damping characteristics of vibrations, etc., by the magnitude of the magnetic field (magnetic flux density) applied to the orifice 15a of the first liquid chamber 15.

[0049] 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 1 causes 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.

[0050] ≪Manufacturing method≫ Next, a method for manufacturing the active vibration isolation device 1 will be described mainly with reference to the reference numerals shown in FIG. This manufacturing method includes the steps of: a manufacturing step of a second liquid chamber forming portion 7 that forms the second liquid chamber 21 by integrally molding an elastic body 8 on the outer surface of the inner cylinder 3; a manufacturing step of a first liquid chamber forming portion 6 that forms the first liquid chamber 15 filled with the magnetorheological fluid 20b by combining an electromagnetic coil 12 as a magnetic field generating portion, an outer member 61 that is a magnetic body, an inner member 62 that is a magnetic body, and a flexible member 14 in a liquid made of the magnetorheological fluid; and a manufacturing step of a first liquid chamber forming portion 6 that forms the first liquid chamber 15 and the second liquid chamber 21 in the axial direction of the inner cylinder 3. The method includes a manufacturing step of assembling the first liquid chamber forming portion 6 and the second liquid chamber forming portion 7 to form an assembly As (see FIG. 4) so ​​that the first liquid chamber forming portion 6 and the second liquid chamber forming portion 7 are separated by a flexible member 14 extending in a direction perpendicular to the surface of the inner cylinder 3 and supported by the magnetic body, and the magnetic body and the inner cylinder 3 are connected by an elastic body 8; and a fixing step of inserting the assembly As (see FIG. 4) inside the outer cylinder 2 in a liquid 20a to fill the second liquid chamber 21 with the liquid 20a and fixing the assembly As (see FIG. 4) inside the outer cylinder 2.

[0051] The fixing step in this manufacturing method further includes a step of drawing the outer cylinder body 24 of the outer cylinder 2 radially inward. In this drawing process, the outer cylinder body 24 is plastically deformed so as to slightly reduce its diameter. Furthermore, as the outer cylinder body 24 is reduced in diameter, the cage 9 disposed inside the outer cylinder body 24 also is slightly reduced in diameter. The elastic body 8 disposed between the outer cylinder body 24 and the inner cylinder 3 is compressed. As a result, residual strain generated in the elastic body 8 that has shrunk after vulcanization is released by this drawing process.

[0052] <Action and effect> Next, the effects of the active vibration isolation device 1 according to this embodiment will be described. Unlike conventional active vibration damping devices (see, for example, Patent Document 1) that directly convert external inputs such as vibrations into a flow of magnetorheological fluid, the active vibration damping device 1 of this embodiment causes 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, as described above. According to the active vibration damping device 1 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.

[0053] Furthermore, according to the active vibration damping device 1, 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.

[0054] Furthermore, according to the active vibration damping device 1, 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.

[0055] Furthermore, according to the active vibration damping device 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 settled magnetic powder Mp can be redispersed by the stirring action of the flow F of the magnetorheological fluid 20b. Furthermore, the active vibration isolation device 1 can suppress the precipitation of magnetic powder Mp over time, and therefore can maintain good vibration and other damping performance.

[0056] In the active vibration damping device 1, 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 1, it is possible to make the device compact while maintaining good response performance to input vibrations and the like.

[0057] In the active vibration damping device 1, the electromagnetic coil 12 as a magnetic field generating unit, the outer member 61 which is a magnetic body, the inner member 62 which is a magnetic body, the first liquid chamber 15, and the second liquid chamber 21 are provided radially between the inner cylinder 3 and the outer cylinder 2. The first liquid chamber 15 and the second liquid chamber 21 are separated by a flexible member 14. With such an active vibration damping device 1, 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.

[0058] In the active vibration isolation device 1, the flexible member 14 extends in the axial direction of the inner cylinder 3. With such an active vibration isolation device 1, the width of the flexible member 14 can be secured to be large in the axial direction of the inner tube 3, unlike, for example, a device in which the flexible member 14 extends in a direction perpendicular to the axis of the inner tube 3 and the width of the flexible member 14 is limited to less than the distance between the outer tube 2 and the inner tube 3. That is, with the active vibration damping device 1, the width of the orifice 15a can be expanded in the axial direction without increasing the outer diameter of the active vibration damping device 1. This allows the active vibration damping device 1 to increase the liquid column resonance frequency when no magnetic field is generated by the electromagnetic coil 12. The low spring frequency range of the active vibration damping device 1 can be increased. Furthermore, according to the active vibration isolation device 1, the width of the orifice 15a can be increased in the axial direction, so that the film rigidity of the flexible member 14 can be reduced when no magnetic field is generated by the electromagnetic coil 12.

[0059] In addition, in the active vibration isolation device 1, the flexible member 14 is held by a cage 9 located radially outward and an outer member 61 which is a magnetic material located radially inward of the cage 9, and the elastic body 8 is connected to the cage 9 and not connected to the outer member 61. According to such an active vibration isolation device 1, the elastic body 8 is not directly connected to the outer member 61 but is connected only to the cage 9, so it is possible to make the elastic body 8 (rubber feet) longer. This allows the active vibration isolation device 1 to improve the durability of the elastic body 8, which expands and contracts due to vibrations, etc.

[0060] In the active vibration isolation device 1, the outer cylinder 2 is drawn radially inward with the cage 9 inside. According to such an active vibration isolation device 1, the outer cylinder 2 and the cage 9 can be more reliably integrated. Furthermore, according to the active vibration isolation device 1, the cage 9 together with the outer cylinder 2 can be drawn radially inward, so that residual strain in the elastic body 8 during vulcanization molding can be reduced.

[0061] In the active vibration isolation device 1, the cage 9 is formed only by a cylindrical portion that extends along the outer cylinder 2. According to such an active vibration isolation device 1, the cage 9 is made up of only a cylindrical portion, which makes it easy to perform drawing.

[0062] In addition, in the active vibration damping device 1, the second liquid chamber 21 comprises an adjacent liquid chamber 21b located radially outward on the flexible member 14 side, and a main liquid chamber 21a located on the opposite side of the adjacent liquid chamber 21b in the axial direction, sandwiching the elastic body 8. In addition, the active vibration damping device 1 comprises a connecting passage 21c between the cage 9 and the outer cylinder 2 that connects the main liquid chamber 21a and the adjacent liquid chamber 21b. It is expected that the capacity of the adjacent liquid chamber 21b will decrease if the flexible member 14 is brought closer to the outer tube 2. However, with the active vibration damping device 1, the main liquid chamber 21a and the adjacent liquid chamber 21b are connected via the connecting passage 21c, thereby ensuring a large overall capacity for the second liquid chamber 21.

[0063] Furthermore, in the active vibration damping device 1, the connecting passage 21c is set to have a cross-sectional area that is smaller than the resistance when the liquid 20a flows through the connecting passage 21c and the resistance when the magnetorheological fluid 20b flows through the orifice 15a when no magnetic field is applied from the electromagnetic coil 12 (magnetic field generating unit). If the flow resistance of the liquid 20a in the connecting passage 21c becomes greater than the flow resistance of the magnetorheological fluid 20b in the orifice 15a, the range of change in stiffness when the magnetic field is changed by the electromagnetic coil 12 (magnetic field generating unit) will become smaller. In other words, it is thought that the controllable frequency band will become narrower. In contrast, the active vibration isolation device 1 can prevent the controllable frequency band from becoming narrower.

[0064] In addition, in the active vibration damping device 1, the first liquid chamber 15 is provided between the flexible member 14 and the outer member 61, which is a magnetic material, and the second liquid chamber 21 is provided between the flexible member 14 and the outer cylinder 2. According to such an active vibration damping device 1, after forming the first liquid chamber 15 filled with the magnetorheological fluid 20b, the filling process of the magnetorheological fluid 20b and the liquid 20a to form the second liquid chamber 21 filled with the liquid 20a can be easily carried out.

[0065] The manufacturing method of the active vibration damping device 1 includes the steps of: a manufacturing step of a second liquid chamber forming portion 7 that forms the second liquid chamber 21 by integrally molding an elastic body 8 on the outer surface of the inner cylinder 3; a manufacturing step of a first liquid chamber forming portion 6 that forms the first liquid chamber 15 filled with the magnetorheological fluid 20b by combining an electromagnetic coil 12 (magnetic field generating portion), an outer member 61 that is a magnetic body, an inner member 62 that is a magnetic body, and a flexible member 14 in a liquid made of the magnetorheological fluid; and a manufacturing step of a first liquid chamber forming portion 6 that forms the first liquid chamber 15 filled with the magnetorheological fluid 20b. The method includes a manufacturing step of assembling the first liquid chamber forming portion 6 and the second liquid chamber forming portion 7 to form an assembly As such that the first liquid chamber forming portion 6 and the second liquid chamber forming portion 7 are separated by a flexible member 14 extending in the axial direction of the inner cylinder 3 and are supported by an outer member 61 which is a magnetic material, and the outer member 61 and the inner cylinder 3 are connected by an elastic body 8; and a fixing step of inserting the assembly As into the inside of the outer cylinder 2 in a liquid made of liquid 20a to fill the second liquid chamber 21 with liquid 20a and fixing the assembly As inside the outer cylinder 2.

[0066] 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 1, 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.

[0067] In the manufacturing method of the active vibration isolation device 1, the fixing step further includes a step of drawing the outer cylinder 2 radially inward. According to such a manufacturing method for the active vibration isolation device 1, the outer cylinder 2 and the cage 9 can be more reliably integrated. Furthermore, according to the manufacturing method of the active vibration isolation device 1, residual strain during vulcanization molding of the elastic body 8 can be reduced.

[0068] The active vibration damping device 1 of this embodiment 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 comfort performance, etc.

[0069] 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. The active vibration isolation device 1 of the embodiment is assumed to have the orifice 15a only on the lower side in the vertical direction, as shown in FIG. 8, but the present invention is not limited to this. Fig. 10A is an overall perspective view of an active vibration isolation device 1A according to another embodiment of the present invention, and Fig. 10B is a cross-sectional view taken along the line XB-XB of Fig. 10A. In the active vibration isolation device 1A, the same components as those in the active vibration isolation device 1 of the above embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition, in Fig. 10A, the outer cylinder 2 is represented by a virtual line (two-dot chain line).

[0070] As shown in Figure 10A, when the active vibration damping device 1A is attached to the trailing arm 34 (see Figure 1A) of the rear suspension 30 (see Figure 1A), a pair of main liquid chambers 21a are formed so as to sandwich a partition wall 72a2 (first partition wall) extending in the vertical direction. Further, the adjacent liquid chambers 21b are formed as a pair so as to sandwich a partition wall 72a3 (second partition wall) which extends in a direction perpendicular to the extending direction of the partition wall 72a2 (first partition wall) when viewed in the axial direction of the inner cylinder 3.

[0071] On the other hand, as shown in FIG. 10B, the general portions 15b of the first liquid chamber 15 are provided above and below the active vibration damping device 1A in correspondence with the adjacent liquid chambers 21b (see FIG. 10A). The orifice 15a of the first fluid chamber 15 is provided in the active vibration damping device 1A in correspondence with the partition wall 72a3 (see FIG. 10A) which is the second partition wall. 10A, the partition wall 72a2 (first partition wall) and the partition wall 72a3 (second partition wall) are connected to each other in the axial direction of the inner cylinder 3. As shown in FIG. That is, as shown in Figure 10B, the orifices 15a of the active vibration isolation device 1A attached to the rear suspension 30 (see Figure 1A) are provided in pairs at positions that are displaced in phase by 90 degrees in the axial direction from the general portions 15b of the pair of upper and lower first fluid chambers 15. In other words, the pair of orifices 15a are arranged to face each other on a horizontal plane.

[0072] According to this active vibration damping device 1A, by offsetting the positions of the main liquid chamber 21a and the adjacent liquid chamber 21b, a pair of orifices 15a are arranged facing each other on a horizontal plane, so that the rigidity can be made variable even if the magnetic powder of the magnetorheological fluid 20b settles downward in the vertical direction. [Explanation of symbols]

[0073] 1. Active vibration isolation device 2 outer cylinder 3 Inner cylinder 6 First liquid chamber forming part 7 Second liquid chamber forming part 9 Cage 12 Electromagnetic coil (magnetic field generating part) 14 Flexible member 15 1st liquid chamber 15a Orifice 20a liquid 20b Magnetorheological fluid 21 2nd liquid chamber 61 Outer member (magnetic material) 62a1 Core material (magnetic material) 62b Flange part (magnetic material) Mc magnetic path

Claims

1. An outer cylinder 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, The flexible member extends in the axial direction of the inner cylinder, 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. the flexible member is held by a cage positioned radially outward and the magnetic body positioned radially inward of the cage, an elastic body disposed between the outer cylinder and the inner cylinder, and burying the cage along an inner peripheral surface of the outer cylinder; 2. An active vibration isolation device according to claim 1, wherein the elastic body is connected to the cage and is not connected to the magnetic body.

3. 3. An active vibration isolation device according to claim 2, wherein the outer cylinder is drawn radially inward with the cage inside.

4. 4. An active vibration isolation device according to claim 3, wherein the cage is formed only by a cylindrical portion extending along the outer cylinder.

5. The second liquid chamber includes an adjacent liquid chamber located radially outward of the flexible member, and a main liquid chamber located on the opposite side of the adjacent liquid chamber with the elastic body sandwiched between them in the axial direction, A connecting passage is provided between the cage and the outer cylinder, connecting the main liquid chamber and the adjacent liquid chamber.

3. An active vibration isolation device according to claim 2, wherein:

6. The active vibration isolation device is a bushing that connects the trailing arm to the vehicle body. The main liquid chamber is formed as a pair with a first partition wall extending in the vertical direction sandwiched therebetween, The adjacent liquid chambers are formed as a pair so as to sandwich a second partition wall therebetween, the second partition wall extending in a direction intersecting the extending direction of the first partition wall as viewed in the axial direction, The first liquid chamber is provided above and below the adjacent liquid chamber, 6. An active vibration isolation device according to claim 5, wherein the orifice of the first fluid chamber is provided at a position corresponding to the second partition wall.

7. An active vibration isolation device as described in claim 6, characterized in that the connecting passage is set to have a cross-sectional area such that the resistance when the liquid flows through the connecting passage is smaller than the resistance when the magnetorheological fluid flows through the orifice when no magnetic field from the magnetic field generating unit is acting.

8. the first liquid chamber is provided between the flexible member and the magnetic body, 3. An active vibration isolation device according to claim 2, wherein the second fluid chamber is provided between the flexible member and the outer cylinder.

9. A method for manufacturing an active vibration isolation device according to claim 1, comprising: a step of forming a second liquid chamber forming portion by integrally molding an elastic body on the outer surface of the inner cylinder to form the second liquid chamber; a manufacturing step of a first liquid chamber forming portion for forming the first liquid chamber filled with the magnetorheological fluid by combining the magnetic field generating portion, the magnetic body, and the flexible member in a liquid made of the magnetorheological fluid; a manufacturing process of an assembly in which the first liquid chamber forming portion and the second liquid chamber forming portion are assembled together so that the first liquid chamber and the second liquid chamber are partitioned by the flexible member extending in the axial direction of the inner cylinder and are supported by the magnetic body, and the magnetic body and the inner cylinder are connected by the elastic body; a fixing step of inserting the assembly into the outer cylinder in the liquid to fill the second liquid chamber with the liquid and fix the assembly inside the outer cylinder; A method for manufacturing an active vibration isolation device, comprising:

10. 10. The method for manufacturing an active vibration isolation device according to claim 9, wherein the step of fixing the assembly within the outer cylinder further includes a step of drawing the outer cylinder radially inward.

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