Magnetic viscous fluid device

Abstract

To provide a magnetic viscous fluid device that allows a state of magnetic viscous fluid inside the magnetic viscous fluid device to be checked from outside of the device body without disassembling the magnetic viscous fluid device.SOLUTION: A magnetic viscous fluid device 1 includes: first parts 10, 20; second parts 30, 40 rotatable relative to the first parts 10, 20; a magnetic viscous fluid 50 sealed inside a device body having the first parts 10, 20 and the second parts 30, 40 and interposed between the first parts 10, 20 and the second parts 30, 40; and magnetic field generation parts 30, 40, 60 for generating a magnetic field to be applied to the magnetic viscous fluid 50. A part of the device body is made of a transparent member 100 so that the magnetic viscous fluid 50 sealed inside the device body is visible from outside of the device body.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] One of the major factors in determining whether a magnetorheological fluid device performs as designed is the state of the magnetorheological fluid. Depending on the usage conditions of the magnetorheological fluid device, the state of the magnetorheological fluid may change, resulting in a decrease in the performance of the device. Therefore, in order to confirm the performance of a magnetorheological fluid device, it is effective to check the state of the magnetorheological fluid (fluid filling volume, gas contamination in the magnetorheological fluid, abnormal or deteriorated state of the magnetorheological fluid particles or dispersion medium, etc.).

[0005] In conventional magnetorheological fluid devices such as those disclosed in Patent Documents 1 and 2, the magnetorheological fluid filled in the magnetorheological fluid device cannot be seen from the outside, so the only way to check the state of the magnetorheological fluid is to disassemble the magnetorheological fluid device. However, once a magnetorheological fluid device has been disassembled, it is difficult to reassemble it, so it is practically impossible to check the magnetorheological fluid inside the magnetorheological fluid device.

[0006] The present invention was devised in light of these problems, and aims to provide a magnetorheological fluid device that allows the state of the magnetorheological fluid inside the magnetorheological fluid device to be easily checked from the outside without having to disassemble the magnetorheological fluid device. [Means for solving the problem]

[0007] A magnetorheological fluid device according to a first aspect of the present invention comprises a first part, a second part rotatable relative to the first part, a magnetorheological fluid enclosed within a device body having the first and second parts and interposed between the first and second parts, and a magnetic field generating unit that generates a magnetic field to be applied to the magnetorheological fluid. A part of the device body is made of a transparent material so that the magnetorheological fluid enclosed within the device body can be seen from outside the device body.

[0008] According to the magnetorheological fluid device having such a configuration, the magnetorheological fluid can be seen from the outside through the transparent member.

[0009] A second aspect of the present invention relates to the magnetorheological fluid device of the first aspect, wherein the first unit includes a rotating shaft that rotates about an axis and a rotating plate fixed to the rotating shaft, and the second unit includes a first yoke having a first opposing surface facing one main surface of the rotating plate across a first gap, and a second yoke having a second opposing surface facing the other main surface of the rotating plate across a second gap. The magnetorheological fluid is filled in the first gap and the second gap. The magnetic field generating unit includes a coil, the first yoke, and the second yoke. When the coil is energized, a magnetic path is formed that passes through the first yoke, the second yoke, the rotating plate, and the magnetorheological fluid. The transparent member is positioned so as to overlap the rotating shaft when viewed axially of the rotating shaft. [Effects of the Invention]

[0010] According to the present invention, the state of the magnetorheological fluid in the magnetorheological fluid device can be easily confirmed from the outside without disassembling the magnetorheological fluid device. [Brief explanation of the drawings]

[0011] [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. 4 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. [Figure 5] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a fifth embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a sixth embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing a magnetorheological fluid device according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] First Embodiment As shown in Fig. 1, the magnetorheological fluid device 1 according to this embodiment comprises a first section including a rotating shaft 10 and a rotating plate 20, a second section including a first yoke 30 and a second yoke 40, a magnetorheological fluid 50, a coil 60, a spacer 70, a casing 80, and a transparent member 100. The second section is rotatable relative to the first section. In the magnetorheological fluid device 1, the first yoke 30, the second yoke 40, and the coil 60 function as a magnetic field generating section that generates a magnetic field to be applied to the magnetorheological fluid 50 when current is applied. The rotating shaft 10, the rotating plate 20, the first yoke 30, the second yoke 40, and the casing 80 constitute the device main body.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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 magnetorheological fluid-filled space is formed in which the rotating plate 20 is rotatably accommodated and in which a magnetorheological fluid 50 is filled. The first yoke 30, the second yoke 40, and the rotating plate 20 transmit torque to each other via the magnetorheological fluid 50.

[0019] 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 in which the coil 60 is disposed. 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 1, the second yoke 40 has a through hole 45 in the center. The through hole 45 has a circular cross section. The through hole 45 passes through the second yoke 40 from top to bottom. The through hole 45 communicates with the magnetorheological fluid-filled space and the outside.

[0027] 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.

[0028] In this embodiment, the magnetorheological fluid 50 is sealed in a magnetorheological fluid-sealed space within the first yoke 30, the second yoke 40, and the casing 80 that constitute the device main body. The magnetorheological fluid-sealed space is a space formed between the first opposing surfaces 34a and 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 magnetorheological fluid-sealed space is the gray area, and includes a first gap S1 between the rotating plate 20 and the first yoke 30 and a second gap S2 between the rotating plate 20 and the second yoke 40. The magnetorheological fluid 50 is present in the first gap S1 and the second gap S2 and transmits torque according to its viscosity.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The spacer 70 has a ring shape. The spacer 70 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.

[0033] 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.

[0034] As shown in FIG. 1 , the transparent member 100 is fixed in the through-hole 45. When viewed from the direction of the axis N, the transparent member 100 is disposed at a position overlapping with the rotation axis 10. The transparent member 100 is disposed so that the magnetorheological fluid 50 can be seen from outside the device body. The transparent member 100 is large enough to fill the entire through-hole 45. The magnetorheological fluid-filled space is sealed by the transparent member 100. The transparent member 100 has a substantially cylindrical shape. When the transparent member 100 is viewed from below in the direction of the axis N, the magnetorheological fluid 50 in the magnetorheological fluid-filled space can be seen through the transparent member 100.

[0035] The transparent member 100 may be any transparent member that allows the magnetorheological fluid 50 in the magnetorheological fluid-enclosed space to be viewed from the outside. The material of the transparent member 100 is not particularly limited, and any transparent material may be used, such as resin. In this embodiment, the transparent member 100 has a thickness that fills almost the entire through-hole 45, but the transparent member 100 may be made thinner so that a portion of the through-hole 45 is filled with the disc-shaped transparent member 100.

[0036] According to the magnetorheological fluid device 1 of the first embodiment described above, it is possible to easily check the state of the magnetorheological fluid 50 in the magnetorheological fluid-enclosed space from the outside through the transparent member 100 without disassembling the magnetorheological fluid device 1. This also makes it easier to determine whether a deterioration in the performance of the magnetorheological fluid device 1 is due to the state of the magnetorheological fluid 50.

[0037] Furthermore, according to the magnetorheological fluid device 1, the transparent member 100 is disposed in the center of the second yoke 40, so that it has little effect on the magnetic path in the magnetorheological fluid device 1 and is less likely to reduce output.

[0038] 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.

[0039] In the magnetorheological fluid device 1 according to the first embodiment, the transparent member 100 is disposed in the center of the second yoke 40, but the transparent member 100 can also be disposed in another location on the second yoke. In the magnetorheological fluid device 1A according to the second embodiment shown in Fig. 2, the transparent member 101 is disposed below the coil 60 on the second yoke 40A.

[0040] The second yoke 40A of the magnetorheological fluid device 1A of the second embodiment has one through-hole 45A formed therein, which communicates with the magnetorheological fluid-filled space. The through-hole 45A passes through the second yoke 40A from top to bottom. In this embodiment, the through-hole 45A is disposed below the coil 60. The through-hole 45A has a circular cross-section. The cross-sectional shape of the through-hole 45A may be other than circular.

[0041] A cylindrical transparent member 101 is fixed inside the through-hole 45A. The transparent member 101 is large enough to fill the entire through-hole 45A. The magnetorheological fluid-sealed space is sealed by the transparent member 101. In this embodiment, the transparent member 101 does not need to be elastically deformable, and it is sufficient that the transparent member 101 is transparent so that the magnetorheological fluid 50 inside the magnetorheological fluid-sealed space can be seen from the outside through the transparent member 101.

[0042] In this embodiment, the transparent member 101 has a thickness that fills the entire through hole 45A, but the transparent member 101 may be thinner and only partially fill the through hole 45A. The transparent member 101 is only required to be arranged so that the magnetorheological fluid 50 can be seen from outside the device body. The shape of the transparent member 101 may also be other shapes that match the shape of the through hole 45A. The positions of the transparent member 101 and the through hole 45A in the second yoke 40A are not limited, but are preferably in a location that has little effect on the magnetic path.

[0043] According to the magnetorheological fluid device 1A of the second embodiment described above, the transparent member 101 can be positioned at a desired position on the second yoke 40A taking into consideration various conditions, and the state of the magnetorheological fluid 50 in the magnetorheological fluid-enclosed space can be easily checked from the outside through the transparent member 101 without disassembling the magnetorheological fluid device 1A.

[0044] <Third embodiment> In the magnetorheological fluid devices 1, 1A according to the first and second embodiments, the transparent members 100, 101 are provided on the second yokes 40, 40A, but it is also possible to use the casing 80 constituting the device body as the transparent member without providing the transparent member 101 on the second yokes 40, 40A. In the magnetorheological fluid device 1B according to the third embodiment shown in Figure 3, the casing 81 is used as the transparent member.

[0045] In this embodiment, a casing 81 made of a transparent material is used as the transparent member. As shown in Fig. 3, the magnetorheological fluid device 1B does not use a spacer, and therefore the inner circumferential surface of the casing 81 is in contact with the magnetorheological fluid 50. Therefore, the magnetorheological fluid 50 in the magnetorheological fluid-enclosed space can be seen from outside the device body along the entire periphery of the casing 81 in a direction perpendicular to the axis N.

[0046] Although no spacer is used in this embodiment, a transparent spacer or a spacer integrated with the casing can be used together with the casing as the transparent member. Furthermore, when the casing is used as the transparent member, the entire casing does not need to be transparent, and the casing may be partially transparent. For example, a through-hole communicating with the magnetorheological fluid-enclosing space may be formed in an opaque casing, and a transparent member may be fixed to the through-hole.

[0047] According to the third embodiment of the magnetorheological fluid device 1B, the casing 81 is arranged on the outer periphery of the first yoke 30 and the second yoke 40B, so that the transparent member has almost no effect on the magnetic path in the magnetorheological fluid device 1B, and there is almost no risk of reducing output.

[0048] <Fourth embodiment> In the magnetorheological fluid devices 1, 1A according to the first and second embodiments, the transparent members 100, 101 are provided on the second yokes 40, 40A, but it is also possible to provide the transparent members on the first yoke instead of the second yoke. In the magnetorheological fluid device 1C according to the fourth embodiment shown in Fig. 4, a transparent member 102 is provided on the first yoke 30C.

[0049] A through hole 36 is formed in the first yoke 30C radially outward from the annular groove 32. The through hole 36 has a circular cross section. The cross-sectional shape of the through hole 36 may be other than circular. The through hole 36 passes through the first yoke 30C in the vertical direction and communicates with the magnetorheological fluid sealing space of the magnetorheological fluid 50. The position of the through hole 36 is not limited, and it may be formed, for example, between the axial hole 31 and the annular groove 32. The through hole 36 may also serve as a fluid filling port for filling the magnetorheological fluid 50, a gas vent hole, or the like.

[0050] The cylindrical transparent member 102 is fixed within the through hole 36, filling the entire through hole 36. The transparent member 102 seals the magnetorheological fluid-filled space. The transparent member 102 is in contact with the magnetorheological fluid 50. In this embodiment, the transparent member 102 is thick enough to fill the entire through hole 36. However, the transparent member 102 may be thinned so that only a portion of the through hole 36 is filled with the transparent member 102. The transparent member 102 only needs to be positioned so that the magnetorheological fluid 50 can be seen from outside the device body. The shape of the transparent member 102 may also be other shapes to match the through hole 36. The positions of the transparent member 102 and the through hole 36 in the first yoke 30C are not limited, but a location that minimizes the effect on the magnetic path is preferable. When the through hole 36 also serves as a fluid filling port, a gas vent, or the like, the transparent member 102 is fixed within the through hole 36 after filling with the magnetorheological fluid 50 is completed.

[0051] According to the magnetorheological fluid device 1C of the fourth embodiment described above, if the through-hole 36 doubles as a fluid filling port, a gas vent hole, etc., the transparent member 102 can be attached without providing a new through-hole in the first yoke 30C. This makes it possible to easily check the state of the magnetorheological fluid 50 in the magnetorheological fluid-enclosed space from the outside through the transparent member 102 without disassembling the magnetorheological fluid device 1C.

[0052] Fifth Embodiment While the magnetorheological fluid devices 1, 1A, 1B, and 1C using casings 80 and 81 have been described above, a transparent member can also be provided in a magnetorheological fluid device that does not use a casing. As shown in FIG. 5 , a magnetorheological fluid device 1D according to a fifth embodiment includes a first section including a rotating shaft 10 and a rotating plate 20, a second section including a first yoke 30D and a second yoke 40D, a magnetorheological fluid 50, a coil 60D, a magnetic short-circuit prevention member 71, and a transparent member 103. In the magnetorheological fluid device 1D, the first yoke 30D, the second yoke 40D, and the coil 60D function as a magnetic field generating section. The first yoke 30D, the second yoke 40D, and the magnetic short-circuit prevention member 71 constitute the device main body.

[0053] In this embodiment, the rotating shaft 10 is supported rotatably about the axis N via a bearing 90 press-fitted into a shaft hole 31 formed in the first yoke 30D. 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.

[0054] 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 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 contact with the lower surface of the flange portion 15, so that the rotating plate 20 rotates integrally with the rotating shaft 10.

[0055] In this embodiment, the first yoke 30D and the second yoke 40D function as a single yoke through which the magnetic path formed around the coil 60D, indicated by the dashed arrowed line P, passes, and also functions as a casing for the magnetorheological fluid device 1D. The first yoke 30D and the second yoke 40D are fastened to each other with bolts B. The first yoke 30D and the second yoke 40D are each made of a magnetic material.

[0056] As shown in FIG. 5, the first yoke 30D is disposed above the rotating plate 20 and has an annular recess 35 that accommodates the coil 60D. The recess 35 opens radially outward. The rotating shaft 10 is inserted through an axial hole 31 formed in the first yoke 30D. The first yoke 30D 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 30D is formed in a substantially annular shape centered on the axis N.

[0057] The first yoke 30D has a first yoke base 37 extending in the direction of the axis N, a first yoke first extension portion 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 portion 39 extending radially outward from an upper portion (one portion in the direction of the axis N) of the first yoke base 37.

[0058] The first yoke 30D 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 is a space for accommodating the coil 60D.

[0059] 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.

[0060] 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.

[0061] The first yoke base 37 has an outer peripheral surface 37a, which is the radially outer surface. A coil 60D having a shape that circles around the axis N is arranged around the outer peripheral surface 37a. The coil 60D is formed by winding a coil conductor in an annular shape around the outer peripheral surface 37a. The radial center of the outer peripheral surface 37a coincides with the axis N.

[0062] The first yoke first extension portion 38 extends radially outward from the first yoke base 37 between the rotating plate 20 and the coil 60D. 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 across a first gap S1.

[0063] 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 60D and the outer diameter of the rotating plate 20 in order to provide a short-circuit magnetic path prevention member 71 (described later).

[0064] 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 30D is made of a single member without any dividing surface. This prevents magnetic resistance due to dividing surfaces within the first yoke 30D, and efficiently forms a magnetic path that passes through the first yoke 30D.

[0065] 5, the second yoke 40D is disposed so that the rotating plate 20 is interposed between it and the first yoke 30D, and a portion of the second yoke 40D extends upward to cover the opening of the recess 35 of the first yoke 30D. The second yoke 40D has a second opposing surface 41D that faces the second main surface 22 of the rotating plate 20 across a second gap S2. The second opposing surface 41D of the second yoke 40D is disposed at a predetermined distance from the first opposing surface 34c of the first yoke 30D.

[0066] The second yoke 40D 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 a radially outer portion of the second yoke base 42 toward the coil 60D (upward) in the direction of the axis N. The second yoke 40D has a bottomed cylindrical shape with the second yoke base 42 as the bottom and the second yoke extension 43 as the cylindrical wall.

[0067] The second yoke base 42 has a through-hole 45D in the center. The through-hole 45D passes through the second yoke base 42 in the vertical direction and communicates with the magnetorheological fluid-filled space. The through-hole 45D has a circular cross-section. The outer diameter of the second yoke base 42 is set larger than the outer diameter of the first yoke first extension 38.

[0068] 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 60D, 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 60D. The upper end of the second yoke extension 43 and the first yoke second extension 39 are fastened to each other with bolts B.

[0069] 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.

[0070] The second yoke base 42 and the second yoke extension 43 are integrally formed without any dividing surface. That is, the second yoke 40D is made of a single member without any dividing surface. This prevents magnetic resistance due to the dividing surface within the second yoke 40D, and efficiently forms a magnetic path that passes through the second yoke 40D.

[0071] The first yoke 30D and the second yoke 40D are not limited to being integrally formed without a dividing surface as in this embodiment. The first yoke 30D and the second yoke 40D can each be formed from multiple components with dividing surfaces, and the multiple components can be combined. For example, a dividing surface can be provided between the first yoke base 37 and the first yoke second extension 39 of the first yoke 30D, and a dividing surface can be provided between the second yoke base 42 and the second yoke extension 43 of the second yoke 40D. Furthermore, the divided first yoke second extension 39 and the second yoke extension 43 can also be integrally formed. Thus, the shapes of the first yoke 30D and the second yoke 40D in this embodiment are not limited.

[0072] The magnetorheological fluid 50 is sealed in a magnetorheological fluid-sealed space within the first yoke 30D, the second yoke 40D, and the short-circuit magnetic path prevention member 71 that constitute the device main body. The magnetorheological fluid-sealed space is a space formed between the first opposing surface 34c of the first yoke 30D and the second opposing surface 41D of the second yoke 40D, excluding the rotating plate 20. In FIG. 5, the magnetorheological fluid-sealed space 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 30D and a second gap S2 between the rotating plate 20 and the second yoke 40D, and transmits torque between them according to its viscosity.

[0073] Coil 60D 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 60D, a magnetic path is formed that passes through first yoke 30D, magnetorheological fluid 50 present in first gap S1, rotating plate 20, magnetorheological fluid 50 present in second gap S2, second yoke 40D, and the magnetic flux passing portion along the direction indicated by dashed arrow line P in Fig. 5.

[0074] 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 60D. The short-circuiting magnetic path preventing member 71 has a substantially cylindrical shape.

[0075] 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.

[0076] The short-circuit magnetic path prevention member 71 prevents the magnetic path that should run from the first yoke 30D 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.

[0077] In this embodiment, as shown in FIG. 5 , a transparent member 103 is fixed to the through hole 45D. The transparent member 103 is disposed at a position overlapping the rotation axis 10 when viewed from the direction of the axis N. The space containing the magnetorheological fluid is sealed by the transparent member 103. The transparent member 103 has a substantially cylindrical shape. The state of the magnetorheological fluid 50 can be confirmed from the outside through the transparent member 103. The transparent member 103 is sized to fill the entire through hole 45D. The thickness of the transparent member 103 may be reduced and a portion of the through hole 45D may be filled with the disc-shaped transparent member 103 to seal the space containing the magnetorheological fluid.

[0078] Sixth Embodiment In the magnetorheological fluid device 1D according to the fifth embodiment, the transparent member 103 is disposed in the center of the second yoke 40D, but it may be disposed in another location on the second yoke. In the magnetorheological fluid device 1E according to the sixth embodiment shown in Fig. 6, the transparent member 104 is disposed in the second yoke 40E at a position that allows the magnetorheological fluid 50 to be viewed from a direction perpendicular to the axis N.

[0079] A through hole 45E for the transparent member 104 is formed in the second yoke extension 43E of the second yoke 40E. The through hole 45E has a circular cross section. The cross-sectional shape of the through hole 45E may be other than circular. The through hole 45E is formed in the lower part of the second yoke extension 43E at the same height as the magnetorheological fluid-sealed space. The through hole 45E penetrates the second yoke extension 43E in a direction perpendicular to the axis N.

[0080] In this embodiment, a through hole 72 for attaching the transparent member 104 is also formed in the magnetic short circuit prevention member 71E. The through hole 72 is at the same height as the through hole 45E and passes through the lower part of the magnetic short circuit prevention member 71E in a direction perpendicular to the axis N. The through hole 72 has a circular cross section. The cross-sectional shape of the through hole 72 may be other than circular as long as it is the same shape as the through hole 45E.

[0081] The transparent member 104 is fixed in the through hole 45E of the second yoke extension portion 43E and the through hole 72 of the short-circuit magnetic path prevention member 71E to seal the magnetorheological fluid-sealed space. The transparent member 104 is in contact with the magnetorheological fluid 50. The transparent member 104 has a cylindrical shape and a thickness that fills the entire through hole 45E and the through hole 72. The shape of the transparent member 104 may be other shapes to match the shapes of the through hole 45E and the through hole 72. In this embodiment, the state of the magnetorheological fluid 50 can be confirmed through the transparent member 104 from a direction perpendicular to the axis N.

[0082] In this embodiment, the through hole 72 is formed in the short-circuiting magnetic path prevention member 71E. However, by using a transparent short-circuiting magnetic path prevention member 71E, the through hole 72 can be omitted. In this case, the transparent member 104 may be sized to fit only in the through hole 45E. Furthermore, when using a transparent short-circuiting magnetic path prevention member 71E, it is possible to use only the short-circuiting magnetic path prevention member 71E as the transparent member without attaching a transparent member to the through hole 45E. In this case, the state of the magnetorheological fluid 50 can be confirmed from outside the device body through the through hole 45E and the transparent short-circuiting magnetic path prevention member 71E. Furthermore, the transparent member can be attached to another location on the second yoke 40E, for example, by providing a through hole in a location other than the center of the second yoke base 42E.

[0083] Seventh Embodiment In the magnetorheological fluid device 1D according to the fifth embodiment and the magnetorheological fluid device 1E according to the sixth embodiment, the transparent members 103 and 104 are provided on the second yokes 40D and 40E, but it is also possible to provide the transparent members on the first yoke. In the magnetorheological fluid device 1F according to the seventh embodiment shown in Fig. 7, the transparent member 105 is provided on the first yoke 30F.

[0084] A through hole 36F is formed in the first yoke base 37F of the first yoke 30F between the axial hole 31 and the recess 35. The through hole 36F passes through the first yoke base 37F in the vertical direction and communicates with the magnetorheological fluid-filled space. The through hole 36F has a circular cross section. The cross-sectional shape of the through hole 36F may be other than circular. The through hole 36F can also serve as a fluid filling port for filling the magnetorheological fluid 50, a gas vent hole, etc. In this embodiment, no through hole is formed in the second yoke 40F.

[0085] A transparent member 105 is fixed to the through-hole 36F, and the transparent member 105 fills the entire through-hole 36F. The magnetorheological fluid-enclosed space is sealed by the transparent member 105, and the transparent member 105 is in contact with the magnetorheological fluid 50. The state of the magnetorheological fluid 50 can be confirmed from outside the device body through the transparent member 105. In this embodiment, the transparent member 105 has a thickness that fills the entire through-hole 36F, but it may be thinner so that it fills only a portion of the through-hole 36F. The shape of the transparent member 105 may also be other shapes to match the shape of the through-hole 36. [Industrial Applicability]

[0086] 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]

[0087] 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, 30C, 30D, 30F 1st Yoke 31 Shaft hole 34a, 34b, 34c 1st opposing surface 36, 36F through hole 37, 37F First yoke base 38 First yoke first extension 39 First yoke second extension 40, 40A, 40B, 40D, 40E, 40F Second Yoke 41, 41D Second opposing surface 42, 42E Second yoke base 43, 43E Second yoke extension 45, 45A, 45D, 45E through hole 50 Magnetorheological fluid 60, 60D coil 61 Bobbin 70 spacer 71, 71E Short-circuit magnetic path prevention material 72 Through hole 80, 81 Casing 90 bearings 100, 101, 102, 103, 104, 105 Transparent members B Bolt N axis P dashed line with arrow S1 First gap S2 Second gap

Claims

1. Part 1 and a second part provided so as to be rotatable relative to the first part; a magnetorheological fluid sealed inside a device body having the first part and the second part and interposed between the first part and the second part; a magnetic field generating unit that generates a magnetic field to be applied to the magnetorheological fluid; In a magnetorheological fluid device comprising: a part of the device body is made of a transparent material so that the magnetorheological fluid sealed inside the device body can be seen from the outside of the device body; A magnetorheological fluid device characterized by:

2. 2. The magnetorheological fluid device according to claim 1, The first part comprises: A rotation shaft that rotates around an axis line, a rotating plate fixed to the rotating shaft; Including, The second part comprises: 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; Including, the magnetorheological fluid is filled in the first gap and the second gap, The magnetic field generating unit is a coil, the first yoke, and the second yoke, and when the coil is energized, a magnetic path is formed that passes through the first yoke, the second yoke, the rotating plate, and the magnetorheological fluid; The transparent member is disposed at a position overlapping the rotation shaft when viewed from the axial direction of the rotation shaft. A magnetorheological fluid device characterized by:

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