Magnetic viscous fluid device

Abstract

To provide a magnetic viscous fluid device that has a simple structure, and can enhance the accuracy of a separation dimension between two yokes forming a space in which a magnetic viscous fluid is packed.SOLUTION: A magnetic viscous fluid device 1 comprises a rotating plate 20 fixed to a rotating shaft 10, a first yoke 30 comprising first opposed surfaces 34a and 34b opposed to one principal surface of the rotating plate 20 via a first gap, a second yoke 40 comprising a second opposed surface 41 opposed to the other principal surface of the rotating plate 20 via a second gap, a magnetic viscous fluid 50 packed in the first and second gaps, and a coil 60 for forming a magnetic path passing through the first yoke 30, the second yoke 40, the rotating plate 20, and the magnetic viscous fluid 50 at the time of energization. A spacer 70 made of a non-magnetic body is interposed between the first yoke 30 and the second yoke 40 while being in contact with the first yoke 30 and the second yoke 40 radially outside an outer peripheral surface of the rotating plate 20.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 components that are arranged to be rotatable relative to one another, and the torque transmitted between the components is variable by changing the strength of the magnetic field applied to the magnetorheological fluid. [Background technology]

[0002] This type of magnetorheological fluid device is disclosed, for example, in Patent Documents 1 and 2. The magnetorheological fluid devices disclosed in Patent Documents 1 and 2 include a rotating plate and yokes arranged on both sides of the rotating plate, facing each other. A minute gap is formed between the rotating plate and the yoke, and this gap is filled with a magnetorheological fluid. A magnetic field is formed between the yokes arranged on both sides of the rotating plate, penetrating the rotating plate and the magnetorheological fluid. This causes the magnetorheological fluid to develop a viscosity that corresponds to the strength of the magnetic field, and torque that corresponds to the strength of the magnetic field is transmitted between the rotating plate and the yoke. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-181778 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-044215 Summary of the Invention [Problem to be solved by the invention]

[0004] In the magnetorheological fluid device, the torque transmitted between the rotating plate and the yoke varies depending on the size of the gap filled with magnetorheological fluid. Therefore, in order to transmit the torque between the rotating plate and the yoke as designed (i.e., to enable the magnetorheological fluid device to perform as designed), it is important to first increase the accuracy of the separation dimension between the two opposing yokes.

[0005] However, in conventional magnetorheological fluid devices such as those described in Patent Documents 1 and 2, the spacing between the two yokes is formed by combining multiple components, so the tolerance for the spacing between the two yokes is the cumulative value of the dimensional tolerances of the multiple components, making it difficult to improve the accuracy of the spacing dimension.

[0006] The present invention was devised in consideration of such problems, and aims to provide a magnetorheological fluid device that has a simple structure and can improve the accuracy of the spacing dimension between two yokes that form a space filled with magnetorheological fluid. [Means for solving the problem]

[0007] 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 an 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 filled in the first gap and the second gap, and a coil that forms a magnetic path passing through the first yoke, the second yoke, the rotating plate, and the magnetorheological fluid when energized. The rotating plate is rotatable relative to the first yoke and the second yoke. A spacer made of a nonmagnetic material is interposed between the first yoke and the second yoke radially outward from the outer circumferential surface of the rotating plate and in contact with the first yoke and the second yoke.

[0008] According to a magnetorheological fluid device having such a configuration, the spacer can easily increase the accuracy of the distance between the first opposing surface of the first yoke and the second opposing surface of the second yoke.

[0009] 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 spacer has a ring shape.

[0010] A magnetorheological fluid device according to a third aspect of the present invention is a magnetorheological fluid device according to the first or second aspect, in which the first yoke and the second yoke are inserted into a cylindrical casing made of a non-magnetic material and fixed to each other via the casing, and the spacer is arranged adjacent to the inner surface of the casing.

[0011] A magnetorheological fluid device according to a fourth aspect of the present invention is the magnetorheological fluid device according to the first or second aspect, wherein the coil is wound in a ring shape on one main surface side of the rotating plate with the axis on the inside, the first yoke has a first yoke extension portion located between the first opposing surface and the coil, and further includes a cylindrical short-circuit magnetic path prevention member made of a non-magnetic material located radially outward from the outer peripheral surface of the first yoke extension portion.

[0012] A magnetorheological fluid device according to a fifth aspect of the present invention is the magnetorheological fluid device according to the second aspect, wherein the spacer and the casing are integrally formed. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a magnetorheological fluid device that can improve the accuracy of the distance dimension between two yokes that form a space filled with magnetorheological fluid, with a simple structure. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing a magnetorheological fluid device according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a cross-sectional view showing a magnetorheological fluid device according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] A magnetorheological fluid device 1 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, "upward" refers to one side of the axis N direction, and "downward" refers to the other side of the axis N direction. Of course, the use state of the magnetorheological fluid device 1 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.

[0016] First Embodiment As shown in FIG. 1, the magnetorheological fluid device 1 according to this embodiment includes a rotating shaft 10, a rotating plate 20, a first yoke 30, a second yoke 40, a magnetorheological fluid 50, a coil 60, a spacer 70, and a casing 80.

[0017] The rotating shaft 10 is supported so as to be rotatable about an axis N via a bearing 90 press-fitted into a shaft hole 31 formed in the first yoke 30. The rotating shaft 10 is formed with, in order from the top, a general portion 11, a first small diameter portion 12, a medium diameter portion 13, a second small diameter portion 14, a flange portion 15, and a tip portion 16.

[0018] The first small diameter portion 12 and the second small diameter portion 14 have a smaller diameter than the general portion 11. The flange portion 15 has a larger diameter than the general portion 11. The medium diameter portion 13 has a larger diameter than the general portion 11 and a smaller diameter than the flange portion 15. The tip portion 16 has a smaller diameter than the first small diameter portion 12 and the second small diameter portion 14, and has a shape in which the diameter becomes even smaller downward due to a step. The tip portion 16 is inserted into the through hole 23 of the rotating plate 20. The material of the rotating shaft 10 is preferably a non-magnetic material such as stainless steel.

[0019] A retaining ring 17 is attached to the general portion 11 of the rotating shaft 10, so that downward movement of the axis N is restricted relative to the bearing 90. The bearing 90 may be a plain bearing or a rolling bearing. In this embodiment, the rotating shaft 10 is rotatably supported by the bearing 90 attached to the first yoke 30, but a bearing may also be provided in the second yoke 40, and the rotating shaft 10 may be supported by this bearing.

[0020] The rotating plate 20 is, for example, a circular disk. 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. A through hole 23 is formed in the center of the rotating plate 20. The through hole 23 has a shape in which the diameter becomes smaller at the bottom due to a step. The tip portion 16 of the rotating shaft 10 is inserted into the through hole 23, and the rotating plate 20 is fixed to the rotating shaft 10 in a state of abutting against the lower surface of the flange portion 15, and the rotating plate 20 rotates integrally with the rotating shaft 10.

[0021] In this embodiment, the first yoke 30 and the second yoke 40 function as yokes through which a magnetic path, indicated by the dashed arrowed line P and formed around the coil 60, passes. 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 are fixed to each other via a casing 80. Within the first yoke 30, a space for accommodating the coil 60 and a space for accommodating the bearing 90 and the rotating shaft 10 are formed. Between the first yoke 30 and the second yoke 40, a space for rotatably accommodating the rotating plate 20 and a space for accommodating the magnetorheological fluid 50 are formed. Torque is transmitted between the first yoke 30, the second yoke 40, and the rotating plate 20 via the magnetorheological fluid 50.

[0022] As shown in FIG. 1, the first yoke 30 is disposed above the rotating plate 20. The first yoke 30 has an annular groove 32 centered on the axis N for arranging the coil 60. The annular groove 32 opens downward. The radial center of the annular groove 32 coincides with the axis N. The space within the annular groove 32 serves as a space for accommodating the coil 60. In this embodiment, the first yoke 30 is formed in a substantially annular shape centered on the axis N.

[0023] The first yoke 30 has two first opposing surfaces 34a, 34b that face the first main surface 21 of the rotating plate 20 across a first gap S1. The first opposing surface 34a is located radially inward of the annular groove 32, and the first opposing surface 34b is located radially outward of the annular groove 32.

[0024] The first yoke 30 has a shaft hole 31 in the center for passing the rotating shaft 10 therethrough. A first large diameter portion 31b is formed above an intermediate portion 31a of the shaft hole 31. The first large diameter portion 31b has an inner diameter larger than that of the intermediate portion 31a. A bearing 90 is press-fitted into the first large diameter portion 31b and fixed to the first yoke 30. Furthermore, a second large diameter portion 31c is formed below the intermediate portion 31a of the shaft hole 31. The outer periphery of the flange 15 of the rotating shaft 10 is inserted into the second large diameter portion 31c. The inner diameter of the second large diameter portion 31c is set to be slightly larger than the outer diameter of the flange 15 of the rotating shaft 10.

[0025] When the rotating shaft 10 is inserted from below into the shaft hole 31, the flange 15 of the rotating shaft 10 is inserted into the second large diameter portion 31c. At this time, when the side surface of the flange 15 near the outer periphery abuts against the step between the second large diameter portion 31c and the intermediate portion 31a, the rotating shaft 10 is unable to move upward along the axis N. When the rotating shaft 10 is fixed with the retaining ring 17 so as not to move downward along the axis N relative to the bearing 90, the rotating shaft 10 is positioned in the direction of the axis N so as to be rotatable relative to the first yoke 30. Furthermore, because the rotating plate 20 is fixed to the rotating shaft 10, the rotating plate 20 is also positioned in the direction of the axis N so as to be rotatable relative to the first yoke 30.

[0026] Shaft seal members 91 are provided between the inner circumferential surface of the intermediate portion 31a of the shaft hole 31 and the first small diameter portion 12 and the second small diameter portion 14 of the rotating shaft 10. The shaft seal members 91 seal between the first yoke 30 and the rotating shaft 10 to prevent the magnetorheological fluid 50 (described later) from leaking upward. For example, an O-ring or a Y-packing is used as the shaft seal member 91. The shaft seal members 91 are arranged above and below the medium diameter portion 13 of the rotating shaft 10.

[0027] The outer peripheral surface of the first yoke 30 is provided with a step 33, with the diameter being smaller on the lower side than on the upper side. The portion of the outer peripheral surface of the first yoke 30 below the step 33 is inserted into and fixed to the inside of the casing 80. An annular groove 301 is provided on the lower side of the outer peripheral surface of the first yoke 30, and an O-ring 92 is inserted into the annular groove 301. The O-ring 92 seals the gap between the first yoke 30 and the casing 80.

[0028] 1, the second yoke 40 is provided so that the rotating plate 20 is interposed between the second yoke 40 and the first yoke 30. The second yoke 40 has a disk shape that extends in a direction perpendicular to the axis N and is centered on the axis N. The second yoke 40 has a second opposing surface 41 that faces the second main surface 22 of the rotating plate 20 across a second gap S2. The second opposing surface 41 is disposed at a predetermined distance from the first opposing surfaces 34a and 34b of the first yoke 30.

[0029] The second yoke 40 is inserted into and fixed to the inside of a cylindrical casing 80. The second yoke 40 is fixed to the first yoke 30 via the casing 80. An annular groove 44 is provided on the outer circumferential surface of the second yoke 40, and an O-ring 92 is inserted into the annular groove 44. The O-ring 92 seals the gap between the second yoke 40 and the casing 80.

[0030] 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 the space formed between the first opposing surfaces 34a, 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40, excluding the rotating plate 20. In FIG. 1 , the accommodation space for the magnetorheological fluid 50 is the area shaded gray. 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.

[0031] 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 hydrophobic silicone oil is one example. The amount of magnetic particles in the magnetorheological fluid 50 may be, for example, 3 to 40 vol%. Various additives can also be added to the magnetorheological fluid 50 to obtain various desired properties.

[0032] The coil 60 has a shape that wraps around the axis N, and is disposed in the annular groove 32 of the first yoke 30. In this embodiment, the coil 60 is formed by winding a coil conductor around a bobbin 61, and the coil 60 and the bobbin 61 are disposed in the annular groove 32. In this embodiment, the coil 60 uses the bobbin 61, but it is also possible to dispose the coil 60 in the annular groove 32 of the first yoke 30 without using the bobbin 61. Regarding the arrangement of the coil 60, in this embodiment, the coil 60 is disposed above the rotating plate 20, but it is also possible to dispose the coil 60 below the rotating plate 20 or radially outward from the rotating plate 20.

[0033] An external current supply device supplies current to the coil 60 via a power line (not shown). The current supply device controls the value of the current 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, and the second yoke 40 along the direction indicated by the dashed arrow line P in FIG. 1. A magnetic field corresponding to the value of the current applied to the coil 60 is then applied to the magnetorheological fluid 50 present in the first gap S1 and the second gap S2.

[0034] The spacer 70 has a ring shape and is made of a non-magnetic material. The spacer 70 is interposed between the first yoke 30 and the second yoke 40 radially outward from the outer circumferential surface of the rotating plate 20, in a state of contact with the first yoke 30 and the second yoke 40. In this embodiment, the spacer 70 is interposed between the first opposing surface 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40. The outer circumferential surface of the spacer 70 is in contact with the inner circumferential surface of the casing 80.

[0035] In this embodiment, the spacer 70 is ring-shaped with a rectangular cross section, but it can also be a shape with a portion of the ring cut out, a shape with the ring divided into multiple pieces, or a form in which multiple pins are arranged at predetermined intervals in the circumferential direction.The cross-sectional shape of the spacer 70 is not limited to a rectangle, and various cross-sectional shapes such as a trapezoid, a triangle, or a circle are also possible.

[0036] The dimension of the spacer 70 in the direction of the axis N is the same as the distance between the first opposing surfaces 34a, 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40. The spacer 70 is sandwiched between the first yoke 30 and the second yoke 40 with no gap in the direction of the axis N. The first yoke 30 and the second yoke 40 are fixed to each other by the casing 80 with the spacer 70 interposed therebetween. As a result, the distance between the first opposing surfaces 34a, 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40 is determined by the spacer 70.

[0037] The casing 80 has a cylindrical shape and is made of a non-magnetic material. In this embodiment, the height of the casing 80 is approximately half the height of the magnetorheological fluid device 1, and the entire second yoke 40 and a part of the first yoke 30 are inserted into and fixed in the casing 80. The height of the casing 80 is not particularly limited, and it may be the same height as the magnetorheological fluid device 1 or less than half the height of the magnetorheological fluid device 1.

[0038] (Action and effect) According to the magnetorheological fluid device 1 of the first embodiment described above, by interposing a high-precision spacer 70 between the first yoke 30 and the second yoke 40 while the spacer 70 is in contact with the first yoke 30 and the second yoke 40, the distance between the first opposing surfaces 34a, 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40 can be easily determined, thereby improving the accuracy of the distance.

[0039] Furthermore, in the magnetorheological fluid device 1, the spacer 70 is ring-shaped and in contact with the first yoke 30 and the second yoke 40, making it difficult for the magnetorheological fluid 50 to get between the spacer 70 and the first yoke 30 and the second yoke 40. As a result, compared to when the spacer 70 is not present, the magnetorheological fluid 50 is prevented from leaking outside the containing space, which is the area shaded gray in the drawing, resulting in a device structure that is less susceptible to fluid leakage.

[0040] Furthermore, according to the magnetorheological fluid device 1, the step between the second large diameter portion 31c and the intermediate portion 31a of the axial hole 31 can be utilized to accurately position the rotating shaft 10 and the rotating plate 20 relative to the first yoke 30, thereby improving the dimensional accuracy of the gap dimensions of the first gap S1 and the second gap S2.

[0041] Furthermore, according to the magnetorheological fluid device 1, the spacer 70 does not come into contact with the rotating plate 20, which can prevent excess frictional force from occurring between the spacer 70 and the rotating plate 20 when the rotating plate 20 rotates.

[0042] Furthermore, since the spacer 70 is disposed at a position overlapping the O-ring 92 when viewed from the axial direction, it has little effect on the magnetic path in the magnetorheological fluid device 1 and is unlikely to reduce output.

[0043] Second Embodiment A magnetorheological fluid device 1A according to a second embodiment of the present invention will be described below. In the following description, if the functions of the components constituting each part are the same as those in the magnetorheological fluid device 1 described in the first embodiment, the same reference numerals as in the first embodiment will be used and the description will be omitted even if the shape or the like is slightly different.

[0044] As shown in FIG. 2, the magnetorheological fluid device 1A according to this embodiment includes a rotating shaft 10, a rotating plate 20, a first yoke 30A, a second yoke 40A, a magnetorheological fluid 50, a coil 60A, a spacer 70A, and a member 71 for preventing a short-circuit magnetic path.

[0045] In this embodiment, the first yoke 30A and the second yoke 40A function as a single yoke through which the magnetic path formed around the coil 60A, indicated by the dashed arrowed line P, passes, and also functions as a casing for the magnetorheological fluid device 1A. The first yoke 30A and the second yoke 40A are fastened to each other with bolts B. The first yoke 30A and the second yoke 40A are each made of a magnetic material.

[0046] As shown in FIG. 2, the first yoke 30A is disposed above the rotating plate 20 and has an annular recess 35 that accommodates the coil 60. The recess 35 opens radially outward. The rotating shaft 10 is inserted into an axial hole 31 formed in the first yoke 30A. The first yoke 30A has a first opposing surface 34c that faces the first main surface 21 of the rotating plate 20 across a first gap S1. In this embodiment, the first yoke 30A is formed in a substantially annular shape centered on the axis N.

[0047] The first yoke 30A has a first yoke base 37 extending in the direction of the axis N, a first yoke first extension 38 extending radially outward from a lower portion (the other portion in the direction of the axis N) of the first yoke base 37, and a first yoke second extension 39 extending radially outward from an upper portion (one portion in the direction of the axis N) of the first yoke base 37.

[0048] The first yoke 30A defines the recess 35 by a first yoke base 37, a first yoke first extension 38, and a first yoke second extension 39. The space inside the recess 35 serves as a space for accommodating the coil 60A.

[0049] First yoke base 37 has a generally cylindrical shape, and the radially inner space is axial hole 31. Bearing 90 and rotating shaft 10 are housed within axial hole 31. The lower surface of first yoke base 37 forms part of first opposing surface 34c that faces first main surface 21 of rotating plate 20 across first gap S1.

[0050] An axis N passes through the shaft hole 31 of the first yoke base 37. The shaft hole 31 has a first large diameter portion 31b into which the bearing 90 is press-fitted and fixed, an intermediate portion 31a, and a second large diameter portion 31c into which the outer periphery of the flange portion 15 of the rotating shaft 10 is inserted.

[0051] The first yoke base 37 has an outer peripheral surface 37a, which is the radially outer surface. A coil 60A having a shape that goes around the axis N is arranged around the outer peripheral surface 37a. The coil 60A is formed by winding a coil conductor in a circular shape around the outer peripheral surface 37a. The radial center of the outer peripheral surface 37a coincides with the axis N.

[0052] The first yoke first extension portion 38 extends radially outward from the first yoke base 37 between the rotating plate 20 and the coil 60A. In this embodiment, the first yoke first extension portion 38 extends in a flange-like manner from a lower portion of the first yoke base 37. In this embodiment, in order to provide a short-circuit magnetic path prevention member 71 (described later), the outer diameter of the first yoke first extension portion 38 is larger than the outer diameter of the rotating plate 20 and smaller than the outer diameter of the first yoke second extension portion 39. The lower surface of the first yoke first extension portion 38, together with the lower surface of the first yoke base 37, forms a first opposing surface 34c that faces the first main surface 21 of the rotating plate 20 with a first gap S1 between them.

[0053] The first yoke second extension portion 39 extends radially outward from the first yoke base portion 37. In this embodiment, the first yoke second extension portion 39 extends in a flange-like manner from the upper portion of the first yoke base portion 37. In this embodiment, the outer diameter of the first yoke second extension portion 39 is larger than the outer diameter of the coil 60A and the outer diameter of the rotating plate 20 in order to provide a short-circuit magnetic path prevention member 71 (described later).

[0054] The first yoke base 37 and the first yoke first extension 38 are integrally formed without any dividing surface. Similarly, the first yoke base 37 and the first yoke second extension 39 are integrally formed without any dividing surface. In other words, the first yoke 30A is made of a single member without any dividing surface. This prevents magnetic resistance due to dividing surfaces within the first yoke 30A, and efficiently forms a magnetic path that passes through the first yoke 30A.

[0055] 2, the second yoke 40A is disposed so that the rotating plate 20 is interposed between the second yoke 40A and the first yoke 30A, and a portion of the second yoke 40A extends upward to cover the opening of the recess 35 of the first yoke 30A. The second yoke 40A has a second opposing surface 41A that faces the second main surface 22 of the rotating plate 20 across a second gap S2. The second opposing surface 41A of the second yoke 40A is disposed at a predetermined distance from the first opposing surface 34c of the first yoke 30A.

[0056] The second yoke 40A has a disk-shaped second yoke base 42 that is centered on the axis N and extends in a direction perpendicular to the axis N, and a second yoke extension 43 that extends from the radially outer portion of the second yoke base 42 toward (upward from) the coil 60A in the direction of the axis N. The second yoke 40A has a bottomed cylindrical shape with the second yoke base 42 as its bottom and the second yoke extension 43 as its cylindrical wall. The outer diameter of the second yoke base 42 is set larger than the outer diameter of the first yoke first extension 38.

[0057] The second yoke extension 43 extends in the direction of the axis N from the outer periphery of the second yoke base 42, passing radially outward from the rotating plate 20 and outside the coil 60A, and extends to the outside of the first yoke first extension 38. The second yoke extension 43 has a cylindrical shape centered on the axis N and is aligned concentrically with the first yoke base 37 and the coil 60A. The upper end of the second yoke extension 43 and the first yoke second extension 39 are fastened to each other with bolts B.

[0058] In addition, the inner peripheral surface of the upper end of the second yoke extension portion 43 and the outer peripheral surface of the first yoke second extension portion 39 form a magnetic flux transfer portion that is close to or in contact with each other so that magnetic flux is transferred between them.

[0059] The second yoke base 42 and the second yoke extension 43 are integrally formed without any dividing surface. That is, the second yoke 40A is made of a single member without any dividing surface. This prevents magnetic resistance due to the dividing surface within the second yoke 40A, and efficiently forms a magnetic path that passes through the second yoke 40A.

[0060] The first yoke 30A and the second yoke 40A are not limited to being integrally formed without a dividing surface as in this embodiment. The first yoke 30A and the second yoke 40A may each be formed of multiple components with dividing surfaces, and the multiple components may be combined. For example, a dividing surface may be provided between the first yoke base 37 and the first yoke second extension 39 of the first yoke 30A, and a dividing surface may be provided between the second yoke base 42 and the second yoke extension 43 of the second yoke 40A. Furthermore, the divided first yoke second extension 39 and the second yoke extension 43 may be integrally formed. Thus, the shapes of the first yoke 30A and the second yoke 40A in this embodiment are not limited.

[0061] The magnetorheological fluid 50 is accommodated in a space for accommodating the magnetorheological fluid 50 within the first yoke 30A and the second yoke 40A. The space for accommodating the magnetorheological fluid 50 is a space formed between the first opposing surface 34c of the first yoke 30A and the second opposing surface 41A of the second yoke 40A, excluding the rotating plate 20. In FIG. 2, the space for accommodating the magnetorheological fluid 50 is the area shaded gray. The magnetorheological fluid 50 is present in a first gap S1 between the rotating plate 20 and the first yoke 30A and a second gap S2 between the rotating plate 20 and the second yoke 40A, and transmits torque between them according to its viscosity.

[0062] Coil 60A is formed by winding a coil conductor directly around outer peripheral surface 37a of first yoke base 37, without using a member such as a bobbin. When a current flows through coil 60A, a magnetic path is formed that passes through first yoke 30A, magnetorheological fluid 50 present in first gap S1, rotating plate 20, magnetorheological fluid 50 present in second gap S2, second yoke 40A, and the magnetic flux passing portion along the direction indicated by dashed arrow line P in FIG.

[0063] The spacer 70A has a ring shape centered on the axis N. The spacer 70A is interposed between the first opposing surface 34c of the first yoke 30A and the second opposing surface 41A of the second yoke 40A, and is disposed radially outward from the outer circumferential surface of the rotating plate 20. While the spacer 70A is ring-shaped in this embodiment, it may also be shaped such that a portion of the ring is cut out or the ring is divided into multiple pieces. Alternatively, it may be shaped such that multiple pin-like members are arranged at intervals in the circumferential direction, and each is connected to a short-circuit magnetic path prevention member 71, which will be described later.

[0064] The spacer 70A is formed so that its dimension in the direction of the axis N is the same as the distance between the first opposing surface 34c of the first yoke 30A and the second opposing surface 41A of the second yoke 40A. The spacer 70A is sandwiched between the first yoke first extension portion 38 of the first yoke 30A and the second yoke base portion 42 of the second yoke 40A with no gap in the direction of the axis N. When the first yoke 30A and the second yoke 40A are fixed to each other by the bolt B, the distance between the first opposing surface 34c of the first yoke 30A and the second opposing surface 41A of the second yoke 40A is determined by the spacer 70A.

[0065] The short-circuiting magnetic path preventing member 71 is disposed radially between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the first yoke first extension portion 38. The short-circuiting magnetic path preventing member 71 is also disposed radially between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the coil 60A. The short-circuiting magnetic path preventing member 71 has a substantially cylindrical shape.

[0066] The outer diameter of the magnetic short circuit prevention member 71 is set to be approximately equal to the inner diameter of the inner circumferential surface of the second yoke extension portion 43. The inner diameter of the magnetic short circuit prevention member 71 is set to be approximately equal to the outer diameter of the first yoke first extension portion 38.

[0067] The short-circuit magnetic path prevention member 71 prevents the magnetic path that should run from the first yoke 30A 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 42 from short-circuiting to the second yoke extension 43 without passing through both the first gap S1 and the second gap S2, or without passing only through the second gap S2.

[0068] In this embodiment, the spacer 70A and the magnetic short circuit prevention member 71 are connected to each other, are integrally formed from a non-magnetic material, and have an L-shaped cross section as shown in Fig. 2. The spacer 70A and the magnetic short circuit prevention member 71 may also be separate members.

[0069] (Action and effect) According to the magnetorheological fluid device 1A of the second embodiment, by interposing a high-precision spacer 70A between the first yoke 30A and the second yoke 40A while the spacer 70A is in contact with the first yoke 30A and the second yoke 40A, the distance between the first opposing surface 34c of the first yoke 30A and the second opposing surface 41A of the second yoke 40A can be easily defined, thereby improving the accuracy of the distance. Furthermore, the short-circuit magnetic path prevention member 71 can efficiently apply a magnetic field to the magnetorheological fluid 50 located in the first gap S1 and the second gap S2.

[0070] <Third embodiment> In the magnetorheological fluid device 1A according to the second embodiment, the short-circuit magnetic path prevention member 71 is interposed between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the first yoke first extension portion 38, and between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the coil 60A. However, the short-circuit magnetic path prevention member 71 may be interposed only between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the first yoke first extension portion 38, as shown in FIG. 3 as the short-circuit magnetic path prevention member 71A.

[0071] The magnetorheological fluid device 1B according to the third embodiment has a magnetic short-circuit path prevention member 71A that is different from the magnetic short-circuit path prevention member 71 described in the second embodiment. The spacer 70A is the same as that in the second embodiment. The magnetic short-circuit path prevention member 71A is disposed radially between the inner peripheral surface of the second yoke extension portion 43 and the outer peripheral surface of the first yoke first extension portion 38. The magnetic short-circuit path prevention member 71A has a cylindrical shape. The spacer 70A and the magnetic short-circuit path prevention member 71A are integrally formed of a non-magnetic material. The spacer 70A and the magnetic short-circuit path prevention member 71A may be separate members.

[0072] In the magnetorheological fluid device 1B according to the third embodiment, no short-circuit magnetic path prevention member 71A is interposed between the coil 60B and the second yoke extension 43, and the coil 60B extends radially up to the second yoke extension 43. According to the magnetorheological fluid device 1B according to the third embodiment, the number of turns of the coil 60B can be increased.

[0073] <Fourth embodiment> In the magnetorheological fluid device 1 according to the first embodiment, the spacer 70 and the casing 80 are formed as separate components. However, the spacer 70 and the casing 80 may be integrally formed. In a magnetorheological fluid device 1C according to a fourth embodiment, shown in FIG. 4, an annular spacer 70B and a cylindrical casing 80A are integrally formed from a non-magnetic material. The spacer 70B protrudes radially inward from the inner circumferential surface of the cylindrical casing 80A. By integrally forming the spacer 70B and the casing 80A, the number of parts and the assembly procedure can be reduced. While the spacer 70B is ring-shaped in this embodiment, the spacer 70B may have any shape as long as it protrudes radially inward from the inner circumferential surface of the casing 80A and contacts the first opposing surfaces 34a and 34b of the first yoke 30 and the second opposing surface 41 of the second yoke 40. [Industrial Applicability]

[0074] 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]

[0075] 1, 1A, 1B, 1C Magnetorheological fluid device 10 Rotation axis 20 Rotating Plate 21 First main surface 22 Second main surface 30, 30A 1st Yoke 31 Shaft hole 34a, 34b, 34c 1st opposing surface 37 Base of the first yoke 38 First yoke first extension 39 First yoke second extension 40, 40A Second Yoke 41, 41A Second opposing surface 42 Second yoke base 43 Second yoke extension 50 Magnetorheological fluid 60, 60A, 60B coils 70, 70A, 70B spacers 71, 71A Short-circuit magnetic path prevention material 80, 80A casing B Bolt N axis P dashed line with arrow S1 First gap S2 Second gap

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 filled in the first gap and the second gap; a coil that forms a magnetic path passing through the first yoke, the second yoke, the rotating plate, and the magnetorheological fluid when energized; Equipped with In the magnetorheological fluid device, the rotating plate is rotatably provided with respect to the first yoke and the second yoke, a spacer made of a non-magnetic material is interposed between the first yoke and the second yoke radially outward from the outer circumferential surface of the rotary plate in a state of contact with the first yoke and the second yoke; A magnetorheological fluid device characterized by:

2. 2. The magnetorheological fluid device according to claim 1, The spacer has a ring shape. A magnetorheological fluid device characterized by:

3. 3. The magnetorheological fluid device according to claim 1 or 2, the first yoke and the second yoke are inserted into a cylindrical casing made of a non-magnetic material and fixed to each other via the casing, The spacer is disposed adjacent to the inner circumferential surface of the casing. A magnetorheological fluid device characterized by:

4. 3. The magnetorheological fluid device according to claim 1 or 2, the coil is wound around one main surface of the rotary plate in an annular shape including the axis line therein, the first yoke has a first yoke extension portion located between the first opposing surface and the coil, a cylindrical member for preventing a magnetic short circuit, the member being made of a non-magnetic material and positioned radially outward from the outer circumferential surface of the first yoke extension; A magnetorheological fluid device characterized by:

5. 4. The magnetorheological fluid device according to claim 3, the spacer and the casing are integrally formed; A magnetorheological fluid device characterized by:

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