Magnetorheological fluid device

Abstract

To provide a magnetic viscosity fluid device which can form a magnetic path efficiently by reducing magnetic resistance of a yoke.SOLUTION: A magnetic viscosity fluid device 1 includes: a rotary plate 20; a first yoke 30 which faces the rotary plate through a first gap S1; a second yoke 40 which faces the rotary plate through a second gap S2; a magnetic viscous fluid 50 disposed between the first gap and the second gap; and a coil 60. The first yoke and the second yoke have a magnetic flux delivery part 70. The first yoke has: a first yoke base part 31 around which the coil is arranged; and a first yoke first extending part 32. The second yoke 40 has: a second yoke base part 41 disposed at a major surface 22 side of the rotary plate; and a second yoke extending part 42 which forms the magnetic flux delivery part with the first yoke first extending part while extending from the second yoke base part. The second yoke base part and the second yoke extending part are integrally formed without a parting surface being disposed therebetween.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetorheological fluid device in which a magnetorheological fluid is interposed between members that are arranged to be rotatable relative to one another, and the torque transmitted between the members can be changed by changing the strength of the magnetic field applied to the magnetorheological fluid. [Background technology]

[0002] Various magnetorheological fluid devices have been proposed. For example, a magnetorheological fluid device (100B) disclosed in Fig. 3 of Patent Document 1 includes a rotating plate (2B) fixed to a rotating shaft (1B) that rotates around an axis (N), a first yoke (3C) having opposing surfaces (37A, 37B) that face one main surface (2a) of the rotating plate (2B) across a gap, a second yoke (3B) having an opposing surface (36) that faces the other main surface (2b) of the rotating plate (2B) across a gap 61, a magnetorheological fluid (6) disposed in the two gaps, and a coil (4) provided in an annular recess of the first yoke (3C) so as to generate a magnetic flux in the first yoke (3C) when current is applied.

[0003] In the magnetorheological fluid device (100B) disclosed in Patent Document 1, the recess of the first yoke (3C) opens toward the rotating plate (2B) in the axial direction (N) so that the annular coil (4) can be loaded into the recess of the first yoke (3C). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-181778 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application have also conducted research and development into a magnetorheological fluid device 1H that includes a first yoke 30H in which the opening of the recess in the first yoke, into which the coil is loaded, faces radially outward, as shown in Fig. 11, rather than facing the rotating plate in the direction of the axis N. With this magnetorheological fluid device 1H, the opposing area between the first yoke 30H and the rotating plate 20 can be made larger than in the conventional magnetorheological fluid device (100B), and therefore the rotational resistance of the rotating plate 20 per predetermined value of current supplied to the coil can be efficiently increased.

[0006] The first yoke 30H of the magnetorheological fluid device 1H shown in Fig. 11 includes a first cylinder 31H and two annular plates 32H and 33H fixed to the outer periphery of the first cylinder 31H on both sides in the direction of the axis N. The two annular plates 32H and 33H are fastened to the first cylinder 31H with bolts or the like (not shown). The first yoke 30H defines a recess 30Hd that opens radially outward by the first cylinder 31H and the two annular plates 32H and 33H. The first yoke 30H accommodates an annular coil 60H in the recess 30Hd.

[0007] The magnetorheological fluid device 1H further includes a second yoke 40H. The second yoke 40H includes a disk 41H disposed below the rotating plate 20 and a second cylinder 42H fixed to the outer periphery of the disk 41H. The second cylinder 42H is fastened to the disk 41H with bolts B2.

[0008] When the second yoke 40H is formed by joining the second tube 42H to the disk 41H, the boundary between the disk 41H and the second tube 42H becomes the dividing surface d3 of the second yoke 40H. Since a larger magnetic resistance occurs at the dividing surface d3 than in other parts of the second yoke 40H, the magnetic resistance of the entire second yoke 40H is also larger than when the second yoke 40H is formed from a single member. The relatively large magnetic resistance occurs at the dividing surface d3 because a small gap (air) exists at the dividing surface d3.

[0009] The present invention was devised in view of the above problems, and aims to provide a magnetorheological fluid device that can efficiently form a magnetic path by reducing the magnetic resistance of the yoke. [Means for solving the problem]

[0010] A magnetorheological fluid device according to a first aspect of the present invention includes a rotating plate fixed to a rotating shaft that rotates about its axis, a first yoke having a first opposing surface facing one main surface of the rotating plate across a first gap, a second yoke having a second opposing surface facing the other main surface of the rotating plate across a second gap, magnetorheological fluid interposed in the first gap and the second gap, and a coil disposed around the first yoke to generate a magnetic flux within the first yoke when current is applied. The first yoke and the second yoke have magnetic flux transfer portions that are close to or in contact with each other so that magnetic flux is transferred between them. This magnetorheological fluid device is configured such that, when current flows through the coil, a magnetic path is formed that passes through the first yoke, the magnetorheological fluid interposed in the first gap, the rotating plate, the magnetorheological fluid interposed in the second gap, and the second yoke, and a magnetic field is applied to the magnetorheological fluid interposed in the first gap and the second gap. The first yoke has a first yoke base portion, the axis of which passes through the inside, having a peripheral surface around which the coil is arranged, and a first yoke first extension portion extending radially outward from the first yoke base portion so that the coil is interposed between the first yoke base portion and the rotating plate. The second yoke has a second yoke base portion including the second opposing surface and arranged on the other main surface side of the rotating plate, and a second yoke extension portion extending from the second yoke base portion in the axial direction, passing outside the rotating plate, and forming the magnetic flux passing portion between itself and the first yoke first extension portion. The second yoke base portion and the second yoke extension portion are integrally formed without any dividing surface therebetween.

[0011] In a magnetorheological fluid device having such a configuration, the second yoke base and the second yoke extension that constitute the second yoke are formed integrally without any dividing surface between them, so that by reducing the magnetic resistance of the second yoke, a magnetic path can be formed efficiently.

[0012] A magnetorheological fluid device according to a second aspect of the present invention is the magnetorheological fluid device according to the first aspect, wherein the first yoke further has a first yoke second extension portion extending radially outward from the first yoke base portion, passing between the rotating plate and the coil.

[0013] A magnetorheological fluid device according to a third aspect of the present invention is the magnetorheological fluid device according to the second aspect, in which a short-circuit magnetic path prevention member made of a non-magnetic material is interposed between the outer periphery of the first yoke second extension portion and the inner periphery of the second yoke extension portion.

[0014] The magnetorheological fluid device according to the fourth aspect of the present invention is the magnetorheological fluid device according to the first aspect or the magnetorheological fluid device according to the second aspect, in which a short-circuit magnetic path prevention member made of a non-magnetic material is interposed between the inner surface of the second yoke extension portion and the coil, and between the inner surface of the second yoke extension portion and the rotating plate, and the short-circuit magnetic path prevention member is sandwiched between the first yoke first extension portion and the second yoke base portion without any gap in the axial direction, thereby determining the gap dimension between the first opposing surface and the second opposing surface. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a magnetorheological fluid device that can efficiently form a magnetic path by reducing the magnetic resistance of the yoke. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing a magnetorheological fluid device according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing a first yoke of a magnetorheological fluid device according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing a second yoke of the magnetorheological fluid device according to the first embodiment of the present invention. [Figure 4] FIG. 10 is a partially enlarged cross-sectional view showing an example of a magnetic path that is short-circuited near the outer periphery of the rotating plate and the second extension portion of the first yoke, assuming that a short-circuit magnetic path prevention member is not provided in the magnetorheological fluid device according to the first embodiment of the present invention. [Figure 5] FIG. 3 is a cross-sectional view showing a magnetorheological fluid device according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a third embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a fourth embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a fifth embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a sixth embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a seventh embodiment of the present invention. [Figure 11] 1 is a cross-sectional view showing a magnetorheological fluid device developed by the inventors of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A magnetorheological fluid device according to a first embodiment of the present invention will be described below with reference to the drawings. In this specification, "axis N" refers to the axis N of the rotating shaft 10, "radial direction" refers to the radial direction of the rotating shaft 10, "downward" refers to one side of the axis N direction, and "upward" refers to the other side of the axis N direction. Of course, the use of the magnetorheological fluid device is not limited to a state in which the axis N of the rotating shaft 10 is oriented in the vertical direction in real space. In addition, the dashed line with an arrow indicated by the symbol P in the drawings illustrates a magnetic path.

[0018] First Embodiment As shown in FIG. 1, the magnetorheological fluid device 1 according to this embodiment includes a rotating portion 5, a first yoke 30, a second yoke 40, a magnetorheological fluid 50, a coil 60, and a magnetic short circuit prevention member 80.

[0019] The rotating unit 5 includes a rotating shaft 10 and a rotating plate 20. The rotating unit 5 is provided rotatable about an axis N of the rotating shaft 10 relative to the first yoke 30 and the second yoke 40.

[0020] The rotating shaft 10 is supported in a shaft hole 31h formed in the first yoke 30 via a bearing 130 so as to be rotatable about the axis N. The rotating shaft 10 has a medium-diameter section 12 fitted into the inner diameter side of the bearing 130, a small-diameter section 11 connected to the underside of the medium-diameter section 12, and a large-diameter section 13 connected to the underside of the small-diameter section 11. The small-diameter section 11 is provided with a first enlarged-diameter protrusion 14 located below the bearing 130 and expanding in the radial direction. A second enlarged-diameter protrusion 15 expanding in the radial direction is provided at a position below the first enlarged-diameter protrusion 14 and at an intermediate position in the direction of the axis N of the small-diameter section 11. It is desirable that the material of the rotating shaft 10 be non-magnetic. The bearing 130 may be a rolling bearing or a plain bearing.

[0021] In this embodiment, the rotating plate 20 is a circular disk. The rotating plate 20 is fixed to the lower end surface of the large diameter portion 13 of the rotating shaft 10, which rotates around the axis N, and rotates integrally with the rotating shaft 10. The rotating plate 20 has a first main surface 21 located on the upper side and a second main surface 22 located on the lower side. It is desirable that the rotating plate 20 be made of a magnetic material.

[0022] In this embodiment, the first yoke 30 and the second yoke 40 function as a single yoke through which a magnetic path formed around the coil 60, indicated by the dashed arrowed line P, passes, and also function as a casing for the magnetorheological fluid device 1. The first yoke 30 and the second yoke 40 are fastened to each other with a bolt B1. The first yoke 30 and the second yoke 40 are each made of a magnetic material. The first yoke 30 and the second yoke 40 each include a space for accommodating the coil 60, a space for accommodating the bearing 130 and the rotating shaft 10, and a space for rotatably accommodating the rotating plate 20 and accommodating the magnetorheological fluid 50. Torque is transmitted between the first yoke 30, the second yoke 40, and the rotating plate 20 of the rotating unit 5 via the magnetorheological fluid 50.

[0023] As shown in FIGS. 1 and 2, the first yoke 30 is disposed above the rotating plate 20 and has an annular recess 30d that accommodates the coil 60. The recess 30d opens radially outward. The rotating shaft 10 is inserted into an axial hole 31h formed in the first yoke 30. The first yoke 30 has a first opposing surface 34 that faces the first main surface 21 of the rotating plate 20 across a first gap S1. In this embodiment, the first yoke 30 is formed in a substantially annular shape centered on the axis N.

[0024] The first yoke 30 has a first yoke base 31 extending in the direction of the axis N, a first yoke first extension 32 extending radially outward from an upper portion (one side in the axial direction) of the first yoke base 31, and a first yoke second extension 33 extending radially outward from a lower portion (the other side in the axial direction) of the first yoke base 31.

[0025] The first yoke 30 defines the recess 30d by the first yoke base 31, the first yoke first extension 32, and the first yoke second extension 33. Hereinafter, the space inside the recess 30d will be referred to as the "coil accommodating space."

[0026] First yoke base 31 has a generally cylindrical shape and accommodates bearing 130 and rotating shaft 10 in the radially inner space. Axis N passes through the inside of first yoke base 31. The diameter of the lower portion of the inner circumferential surface of first yoke base 31 is set to be slightly larger than the diameter of large-diameter portion 13 of rotating shaft 10. The diameter of the upper portion of the inner circumferential surface of first yoke base 31 is formed to be larger than the diameter of the lower portion. Bearing 130 is fitted into the upper portion of the inner circumferential surface of first yoke base 31.

[0027] The lower surface of the first yoke base 31 forms a part of a first opposing surface 34 that faces the first main surface 21 of the rotating plate 20 via a first gap S1.

[0028] A shaft seal member 90 is provided between the first yoke base 31 and the small diameter portion 11 of the rotating shaft 10. The shaft seal member 90 seals between the first yoke base 31 and the rotating shaft 10 to prevent the magnetorheological fluid 50 (described later) from leaking upward. The shaft seal member 90 is, for example, an O-ring or a Y-packing. Two shaft seal members 90 are arranged, one above the other, and the upper shaft seal member 90 is arranged between the first enlarged diameter protrusion 14 and the second enlarged diameter protrusion 15 of the rotating shaft 10. The lower shaft seal member 90 is arranged between the second enlarged diameter protrusion 15 and the large diameter portion 13 of the rotating shaft 10.

[0029] The first yoke base 31 has a peripheral surface 31c, which is the radially outer surface. A coil 60 having a shape that goes around the axis N is arranged around the peripheral surface 31c. A coil wire is wound around the peripheral surface 31c. The radial center of the peripheral surface 31c coincides with the axis N.

[0030] An insulating coating IC is preferably formed on the peripheral surface 31c to prevent leakage of the current flowing through the coil 60 to the first yoke base 31. In other words, it is preferable that an insulating coating is formed on the portion of the first yoke 30 around which the coil conductor wire is wound. The insulating coating IC is made of, for example, epoxy resin or silicone resin.

[0031] The first yoke first extension portion 32 extends radially outward from the first yoke base 31 so that the coil 60 is interposed between the first yoke first extension portion 32 and the rotating plate 20 located below. In this embodiment, the first yoke first extension portion 32 expands in a flange shape from the upper portion of the first yoke base 31. In this embodiment, the outer diameter of the first yoke first extension portion 32 is larger than the outer diameter of the coil 60 and the outer diameter of the rotating plate 20 in order to provide a short-circuit magnetic path prevention member 80 (described later).

[0032] The first yoke second extension portion 33 extends radially outward from the first yoke base portion 31 between the rotating plate 20 and the coil 60. In this embodiment, the first yoke second extension portion 33 expands in a flange shape from the lower portion of the first yoke base portion 31. In this embodiment, in order to provide a short-circuit magnetic path prevention member 80 (described later), the outer diameter of the first yoke second extension portion 33 is larger than the outer diameter of the rotating plate 20 and smaller than the outer diameter of the first yoke first extension portion 32.

[0033] The lower surface of the first yoke second extension portion 33, together with the lower surface of the first yoke base portion 31, forms a first opposing surface 34 that faces the first main surface 21 of the rotating plate 20 across a first gap S1.

[0034] The first yoke base 31 and the first yoke first extension 32 are integrally formed without any dividing surface. Similarly, the first yoke base 31 and the first yoke second extension 33 are integrally formed without any dividing surface. In other words, the first yoke 30 is made of a single member without any dividing surface. As a result, no magnetic resistance due to the dividing surface occurs within the first yoke 30, and a magnetic path passing through the first yoke 30 is efficiently formed.

[0035] 1 and 3, the second yoke 40 is provided so that the rotating plate 20 is interposed between it and the first yoke, and a portion of the second yoke 40 extends upward to cover the opening of the coil accommodating space (recess 30d) of the first yoke 30. The second yoke 40 has a second opposing surface 44 that faces the second main surface 22 of the rotating plate 20 across a second gap S2.

[0036] The second yoke 40 has a disk-shaped second yoke base 41 that is centered on the axis N and extends in a direction perpendicular to the axis N, and a second yoke extension 42 that extends from the radially outer portion of the second yoke base 41 toward the coil side (upward) in the direction of the axis N. The second yoke 40 has a cylindrical shape with a bottom, with the second yoke base 41 as the bottom and the second yoke extension 42 as the cylindrical wall. The diameter of the second yoke base 41 is set to be larger than the outer diameter of the first yoke first extension 32.

[0037] A hole 41h is formed in the center of the second yoke base 41. A piston 110 is fitted into the hole 41h so as to be movable within a predetermined range in the direction of the axis N. The piston 110 moves in response to the pressure in the space accommodating the magnetorheological fluid 50, thereby suppressing pressure fluctuations in the space accommodating the magnetorheological fluid 50. This prevents the magnetorheological fluid 50 from leaking from the seal portion between the rotating shaft 10 and the shaft hole 31h due to a significant increase in internal pressure. An O-ring 120 is attached to the piston 110 to prevent the magnetorheological fluid from leaking from the hole 41h.

[0038] The second yoke extension 42 extends in the direction of the axis N from the outer periphery of the second yoke base 41, passing radially outside the rotating plate 20 and outside the coil 60, and extends to the outside of the first yoke first extension 32. The second yoke extension 42 has a cylindrical shape centered on the axis N, and is aligned concentrically with the first yoke base 31 and the coil 60. The upper end of the second yoke extension 42 and the first yoke first extension 32 are fastened to each other with a bolt B1.

[0039] In addition, the inner peripheral surface of the upper end of the second yoke extension portion 42 and the outer peripheral surface of the first yoke first extension portion 32 form a magnetic flux transfer portion 70 that is close to or in contact with each other so that magnetic flux is transferred between them.

[0040] The second yoke base 41 and the second yoke extension 42 are integrally formed without any dividing surface. That is, the second yoke 40 is made of a single member without any dividing surface. This prevents magnetic resistance due to the dividing surface within the second yoke 40, and efficiently forms a magnetic path that passes through the second yoke 40.

[0041] The magnetorheological fluid 50 is accommodated in the accommodation space for the magnetorheological fluid 50 within the first yoke 30 and the second yoke 40. The accommodation space for the magnetorheological fluid 50 is a space formed between the first opposing surface 34 of the first yoke 30 and the second opposing surface 44 of the second yoke 40, and is indicated by the gray area in FIG. 1 . The magnetorheological fluid 50 is present in the first gap S1 between the rotating plate 20 and the first yoke 30 and the second gap S2 between the rotating plate 20 and the second yoke 40, and transmits torque between them according to its viscosity. A gap defining plate 100 is disposed between the second main surface 22 of the rotating plate 20 and the second opposing surface 44 of the second yoke 40 to position the rotating plate 20 in the axial direction N within the accommodation space for the magnetorheological fluid 50, or in other words, to define the gap dimension of the second gap S2. The gap regulation plate 100 is made of a plate having a circular hole through which a part of the rotation shaft 10 is inserted so as to be relatively rotatable. The outer peripheral shape of the gap regulation plate 100 is not particularly limited, and may be circular or polygonal.

[0042] The magnetorheological fluid 50 is a liquid in which magnetic particles are dispersed in a dispersion medium, and in particular, magnetic particles made of nano-sized metal particles (metal nanoparticles) can be used. The magnetic particles are made of a magnetizable metal material, and although there are no particular restrictions on the metal material, soft magnetic materials are preferred. Examples of soft magnetic materials include alloys of iron, cobalt, nickel, and permalloy. The dispersion medium is not particularly limited, but one example is hydrophobic silicone oil. The amount of magnetic particles in the magnetorheological fluid may be, for example, 3 to 40 vol%. Various additives can also be added to the magnetorheological fluid to achieve various desired properties.

[0043] The coil 60 is disposed around the first yoke 30 so as to generate a magnetic flux within the first yoke 30 when current is applied. In this embodiment, the coil 60 is formed by winding a coil conductor directly around the peripheral surface 31c of the first yoke base 31 without using a bobbin or other member. A current is supplied to the coil 60 from an external current supply device via a power line (not shown). The current supply device controls the current value supplied to the coil 60. When a current flows through the coil 60, a magnetic path is formed that passes through the first yoke 30, the magnetorheological fluid 50 present in the first gap S1, the rotating plate 20, the magnetorheological fluid 50 present in the second gap S2, the second yoke 40, and the magnetic flux transfer portion 70 along the direction indicated by the dashed arrowed line P in FIG. 1 . A magnetic field corresponding to the current value applied to the coil 60 is applied to the magnetorheological fluid 50 present in the first gap S1 and the second gap S2.

[0044] When a magnetic field is applied to the magnetorheological fluid 50 present in the first gap S1 and the second gap S2, a viscosity (shear stress) corresponding to the strength of the magnetic field is generated in the magnetorheological fluid 50. As a result, torque corresponding to the magnitude of the current value applied to the coil 60 is transmitted between the rotating part 5 and the first yoke 30 and the second yoke 40.

[0045] The short-circuit magnetic path prevention member 80 prevents the magnetic path that should run from the first yoke 30 through the magnetorheological fluid 50 present in the first gap S1 and the magnetorheological fluid 50 present in the second gap S2 in the thickness direction of the rotating plate 20 toward the second yoke base 41, as shown by the dashed arrowed line P in Figure 1, from short-circuiting to the second yoke extension 42 without passing through the first gap S1 and the second gap S2, or without passing only through the second gap S2, as shown, for example, by the dashed arrowed lines R1, R2, and R3 in Figure 4.

[0046] The magnetic short-circuit prevention member 80 is made of a non-magnetic material and has a lower magnetic permeability than the magnetorheological fluid 50. Examples of the magnetic short-circuit prevention member 80 include austenitic stainless steel such as SUS304 and SUS316, as well as copper, aluminum, titanium, resin, brass, ceramic, and glass. The magnetic permeability of austenitic stainless steel is 1.260×10-6 ~8.8×10 -6 [N / A 2 ], and the relative magnetic permeability of austenitic stainless steel in a vacuum is 1.0026 to 7. The magnetic permeability of aluminum is 1.256665 x 10 -6 [N / A 2 ] and the relative magnetic permeability of aluminum to a vacuum is 1.000022. The magnetic permeability of resin is 1.2567×10 -6 [N / A 2 ] and the relative magnetic permeability of the resin to a vacuum is 1.00005.

[0047] The short-circuiting magnetic path preventing member 80 has a cylindrical shape centered on the axis N and is arranged concentrically with the first yoke base 31, the coil 60, and the second yoke extension 42. The outer diameter of the short-circuiting magnetic path preventing member 80 is set to be approximately equal to the diameter of the inner circumferential surface 42i of the second yoke extension 42. The inner diameter of the short-circuiting magnetic path preventing member 80 is set to be approximately equal to the outer diameter of the first yoke second extension 33. The length of the short-circuiting magnetic path preventing member 80 in the direction of the axis N is set to be equal to the length from the upper surface (second opposing surface 44) of the second yoke base 41 to the lower surface of the first yoke first extension 32.

[0048] The short-circuiting magnetic path preventing member 80 is interposed between the inner peripheral surface 42i of the second yoke extension portion 42 and the outer peripheral portion of the first yoke second extension portion 33. The short-circuiting magnetic path preventing member 80 is also interposed between the inner peripheral surface 42i of the second yoke extension portion 42 and the coil 60. The short-circuiting magnetic path preventing member 80 is also interposed between the inner peripheral surface 42i of the second yoke extension portion 42 and the outer peripheral portion of the rotating plate 20.

[0049] Furthermore, the short-circuit magnetic path prevention member 80 is sandwiched between the first yoke first extension portion 32 and the second yoke base portion 41 with no gap in the direction of the axis N. This positions the first yoke 30 relative to the second yoke 40 in the direction of the axis N. By positioning in this manner, the gap dimension between the second opposing surface 44 of the second yoke 40 and the first opposing surface 34 of the first yoke 30 is defined.

[0050] (Action and effect) According to the magnetorheological fluid device 1 of this embodiment described above, the first yoke base 31 and the first yoke first extension 32 constituting the first yoke 30 are formed integrally without any dividing surface between them, so that the magnetic resistance in the first yoke 30 is reduced and a magnetic path can be formed efficiently.

[0051] Furthermore, according to the magnetorheological fluid device 1, the first yoke base 31 and the first yoke second extension 33 that constitute the first yoke 30 are formed integrally without any dividing surface between them, so that the magnetic resistance in the first yoke 30 is reduced and a magnetic path can be formed efficiently.

[0052] Furthermore, according to the magnetorheological fluid device 1, the second yoke base 41 and the second yoke extension 42 that constitute the second yoke 40 are formed integrally without any dividing surface between them, thereby reducing the magnetic resistance in the second yoke 40 and enabling the efficient formation of a magnetic path.

[0053] Furthermore, according to the magnetorheological fluid device 1, the first yoke second extension portion 33 is interposed between the rotating plate 20 and the coil 60, so the coil 60 does not come into contact with the magnetorheological fluid 50, and there is no risk of the coil 60 being worn down by the magnetic particles contained in the magnetorheological fluid 50 as the magnetorheological fluid 50 flows.

[0054] Furthermore, according to the magnetorheological fluid device 1, a short-circuit magnetic path prevention member 80 made of a non-magnetic material is interposed between the outer periphery of the rotating plate 20 and the inner periphery 42i of the second yoke extension portion 42, thereby preventing the formation of a short-circuit magnetic path R2 between the outer periphery of the rotating plate 20 and the inner periphery 42i of the second yoke extension portion 42 as shown in Figure 4, and allowing a magnetic field to be efficiently applied to the magnetorheological fluid 50 interposed in the first gap S1 and the second gap S2.

[0055] Furthermore, according to the magnetorheological fluid device 1, a short-circuit magnetic path prevention member 80 made of a non-magnetic material is interposed between the outer periphery of the first yoke second extension portion 33 and the inner periphery 42i of the second yoke extension portion 42, thereby preventing the formation of a short-circuit magnetic path R1 between the outer periphery of the first yoke second extension portion 33 and the inner periphery 42i of the second yoke extension portion 42 as shown in Figure 4, and allowing a magnetic field to be efficiently applied to the magnetorheological fluid 50 interposed in the first gap S1 and the second gap S2.

[0056] Furthermore, according to the magnetorheological fluid device 1, the lower end of the short-circuit magnetic path prevention member 80 interposed between the outer periphery of the rotating plate 20 and the inner circumferential surface 42i of the second yoke extension 42 abuts the second yoke base 41, thereby preventing the formation of not only the magnetic path R2 short-circuiting from the rotating plate 20 to the inner circumferential surface 42i of the second yoke extension 42 as shown in FIG. 4, but also the magnetic path R3 short-circuiting from the magnetorheological fluid 50 interposed in the second gap S2 to the inner circumferential surface 42i of the second yoke extension 42, and thereby enabling a magnetic field to be efficiently applied to the magnetorheological fluid 50 interposed in the second gap S2.

[0057] Furthermore, according to the magnetorheological fluid device 1, the short-circuit magnetic path prevention member 80 is sandwiched between the first yoke first extension portion 32 and the second yoke base portion 41 without any gap in the direction of the axis N, so that the gap dimension between the first opposing surface 34 and the second opposing surface 44 is determined, and therefore the total dimension of the first gap S1 and the second gap S2 can be adjusted to the design value with high precision.

[0058] Next, second to seventh embodiments will be described, each of which has a configuration that is partially different from that of the magnetorheological fluid device 1 according to the first embodiment. For each of the second and subsequent embodiments, only the differences from the magnetorheological fluid device 1 according to the first embodiment will be described, and the same components that perform the same functions as those in the magnetorheological fluid device 1 will be assigned the same reference numerals and will not be described again.

[0059] Second Embodiment In the magnetorheological fluid device 1 according to the first embodiment, the first yoke first extension portion 32 and the second yoke extension portion 42 are fastened together with bolts, with the inner peripheral surface of the tip of the second yoke extension portion 42 overlapping the outer peripheral surface of the first yoke first extension portion 32, and the magnetic flux passing portion 70 is formed parallel to the direction of the axis N. However, the fastening direction of the first yoke first extension portion 32 and the second yoke extension portion 42 is not limited to this. For example, a magnetorheological fluid device 1A according to a second embodiment shown in FIG. 5 may be used. In the magnetorheological fluid device 1A, the first yoke first extension portion 32A of the first yoke 30A extends radially longer than the first yoke first extension portion 32 of the first embodiment, and the upper end surface of the second yoke extension portion 42A of the second yoke 40A overlaps the lower surface of the first yoke first extension portion 32A. The first yoke first extension portion 32A and the second yoke extension portion 42A are fastened together by a bolt B1 along the direction of the axis N. In the magnetorheological fluid device 1A according to the second embodiment, the magnetic path passing portion 70A is formed parallel to the radial direction.

[0060] Third Embodiment In the magnetorheological fluid device 1 according to the first embodiment, the first yoke second extension 33 is interposed between the coil 60 and the rotating plate 20. However, a magnetorheological fluid device 1B according to a third embodiment shown in FIG. 6 may be configured as shown. In the magnetorheological fluid device 1B, the first yoke 30B does not have the first yoke second extension 33, and a magnetic short-circuit prevention member 80B is interposed at the position of the first yoke second extension 33. The magnetic short-circuit prevention member 80B has a base 81B and an extension 82B. The base 81B has the same shape as the magnetic short-circuit prevention member 80 according to the first embodiment. The extension 82B is interposed between the coil 60 and the rotating plate 20 and extends radially inward from the base 81B to the first yoke base 31. The lower surface of the extension 82B is aligned on the same plane as the first opposing surface 34 of the first yoke base 31, and forms a first gap S1 between itself and the first main surface 21 of the rotating plate 20.

[0061] According to the magnetorheological fluid device 1B of the third embodiment, it is possible to prevent the coil 60 from coming into contact with the magnetorheological fluid 50, and also to prevent the magnetic path from being short-circuited radially from the first yoke base 31 to the second yoke extension 42.

[0062] <Fourth embodiment> 7, the first yoke 30C may not have the first yoke second extension portion 33, and the coil 60C may be provided downward to the same position in the direction of the axis N as the lower surface (first opposing surface 34) of the first yoke base portion 31. According to the magnetorheological fluid device 1C of the fourth embodiment, the number of turns of the coil 60C can be made larger than that of the magnetorheological fluid device 1.

[0063] Fifth Embodiment In the magnetorheological fluid device 1 according to the first embodiment, the short-circuiting magnetic path preventing member 80 is interposed between the coil 60 and the second yoke extension 42. However, a magnetorheological fluid device 1D according to a fifth embodiment, as shown in FIG. 8 , may be configured as shown. In the magnetorheological fluid device 1D according to the fifth embodiment, the short-circuiting magnetic path preventing member 80 is not interposed between the coil 60 and the second yoke extension 42, and the coil 60D extends radially to the second yoke extension 42. The magnetorheological fluid device 1D according to the fifth embodiment allows for a larger number of turns of the coil 60D. Note that the magnetorheological fluid device 1D according to the fifth embodiment includes a short-circuiting magnetic path preventing member 80D that is different from the short-circuiting magnetic path preventing member 80 described in the first embodiment. The short-circuiting magnetic path preventing member 80D in the fifth embodiment is interposed between the coil 60D and the second yoke base 41 in the axial direction N and between the first yoke second extension 33, the rotating plate 20, and the second yoke extension 42 in the radial direction. The member 80D for preventing a magnetic short circuit is made of, for example, a single cylindrical member.

[0064] Sixth Embodiment In the magnetorheological fluid device 1 according to the first embodiment, the first yoke second extension 33 is interposed between the coil 60 and the rotating plate 20, and the magnetic short-circuit prevention member 80 is interposed between the coil 60 and the second yoke extension 42. However, a magnetorheological fluid device 1E according to a sixth embodiment shown in FIG. 9 may be configured as shown in FIG. 9. In the magnetorheological fluid device 1E according to the sixth embodiment, the magnetic short-circuit prevention member 80 is not interposed between the coil 60E and the second yoke extension 42, and the coil 60E extends radially to the second yoke extension 42. In addition, in the magnetorheological fluid device 1E, the first yoke 30E does not have the first yoke second extension 33, and the magnetic short-circuit prevention member 80E is interposed between the coil 60E and the rotating plate 20. According to the magnetorheological fluid device 1E according to the sixth embodiment, the number of turns of the coil 60E can be increased. Furthermore, the magnetorheological fluid device 1E according to the sixth embodiment can prevent the coil 60E from coming into contact with the magnetorheological fluid 50, and can also prevent the magnetic path from being short-circuited radially from the first yoke base 31 to the second yoke extension 42.

[0065] Seventh Embodiment In the magnetorheological fluid device 1 according to the first embodiment, the first yoke 30 is integrally formed without any dividing surface. However, the first yoke 30 may be composed of multiple components. For example, in a magnetorheological fluid device 1F according to a seventh embodiment shown in FIG. 10 , the first yoke 30F has the same shape as the first yoke 30 according to the first embodiment, but the first yoke base 31, the first yoke first extension 32, and the first yoke second extension 33 are formed as separate components. Specifically, the first yoke 30F includes a first cylinder 31F, a first upper annular plate 32F, and a first lower annular plate 33F, which correspond to the first yoke base 31, the first yoke first extension 32, and the first yoke second extension 33, respectively. The first upper annular plate 32F and the first lower annular plate 33F are fastened to the first cylinder 31F with bolts or the like (not shown).

[0066] <Other embodiments> In the magnetorheological fluid devices 1 to 1F according to the first to seventh embodiments described above, the rotating shaft 10 is arranged so as to protrude significantly toward the first yoke 30 (upward) relative to the rotating plate 20, but the rotating shaft 10 may also be arranged so as to protrude significantly toward the second yoke base 41 (downward), or the rotating shaft 10 may be arranged so as to penetrate the first yoke 30 and the second yoke 40 in the direction of the axis N. [Industrial Applicability]

[0067] The present invention can be applied to a magnetorheological fluid device in which, for example, a magnetorheological fluid is interposed between components that are arranged to be rotatable relative to one another, and the torque transmitted between the components can be changed by changing the strength of the magnetic field applied to the magnetorheological fluid. [Explanation of symbols]

[0068] 1, 1A, 1B, 1C, 1D, 1E, 1F Magnetorheological fluid device 10 Rotation axis 20 Rotating Plate 21 First main surface 22 Second main surface 30, 30A, 30B, 30C, 30E, 30F First Yoke 31 Base of the first yoke 31c Peripheral surface of the base of the first yoke 32, 32A First yoke first extension 33 First yoke second extension 34 First opposing surface 40, 40A Second Yoke 41 Second yoke base 42, 42A Second yoke extension 42i Inner surface of second yoke extension 44 Second opposing surface 50 Magnetorheological fluid 60, 60C, 60D, 60E coils 70, 70A magnetic flux transfer section 80, 80B, 80D, 80E Short-circuit magnetic path prevention material S1 First gap S2 Second gap N axis

Claims

1. a rotating plate fixed to a rotating shaft that rotates around an axis; a first yoke having a first opposing surface that faces one main surface of the rotary plate with a first gap therebetween; a second yoke having a second opposing surface that faces the other main surface of the rotary plate via a second gap; a magnetorheological fluid present in the first gap and the second gap; a coil disposed around the first yoke so as to generate a magnetic flux within the first yoke when energized; Equipped with the first yoke and the second yoke have magnetic flux passing portions that are close to or in contact with each other so that magnetic flux is passed between them, a magnetic rheological fluid device configured such that, when a current flows through the coil, a magnetic path is formed that passes through the first yoke, the magnetorheological fluid present in the first gap, the rotating plate, the magnetorheological fluid present in the second gap, and the second yoke, and a magnetic field is applied to the magnetorheological fluid present in the first gap and the second gap; The first yoke is a first yoke base having a peripheral surface through which the axis passes and around which the coil is disposed; a first yoke first extension portion extending radially outward from the first yoke base portion so that the coil is interposed between the first yoke first extension portion and the rotary plate; and The second yoke is a second yoke base portion including the second opposing surface and disposed on the other main surface side of the rotary plate; a second yoke extension portion that extends from the second yoke base portion in the axial direction, passes outside the rotary plate, and forms the magnetic flux passing portion between itself and the first yoke first extension portion; and the second yoke base portion and the second yoke extension portion are integrally formed without any dividing surface therebetween, a short-circuit magnetic path prevention member made of a non-magnetic material is interposed between an inner peripheral surface of the second yoke extension portion and the coil, and between the inner peripheral surface of the second yoke extension portion and the rotating plate; The short-circuit magnetic path prevention member is sandwiched between the first yoke first extension portion and the second yoke base portion with no gap in the axial direction, so that a gap dimension between the first opposing surface and the second opposing surface is defined. A magnetorheological fluid device characterized by:

2. 2. The magnetorheological fluid device according to claim 1, the first yoke further includes a first yoke second extension portion extending radially outward from the first yoke base portion through a gap between the rotating plate and the coil; A magnetorheological fluid device characterized by:

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