Magnetorheological fluid clutch

Abstract

To provide a compact and inexpensive magnetic viscous fluid clutch.SOLUTION: A magnetic viscous fluid clutch 1 includes: a first rotating shaft 5; a second rotating shaft 6; a first rotary plate 8 connected to the first rotating shaft 5 and rotatable integrally with the first rotating shaft 5; a second rotary plate 9 connected to the second rotating shaft 6 and rotatable integrally with the second rotating shaft 6; a stationary housing 12 surrounding the first rotary plate 8 and the second rotary plate 9; a magnetic viscous fluid 20 for filling a space between the first rotary plate 8 and the second rotary plate 9; a coil 22 retained by the stationary housing 12 and generating magnetic field to be applied to the magnetic viscous fluid 20; and an electric current supply device 25 allowing electric current to flow in the coil 22.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetorheological fluid clutch, and particularly to a clutch using a magnetorheological fluid typified by an MR (magnetorheoelastic) fluid.

Background Art

[0002] As a mechanism for transmitting the rotation of a drive shaft to a driven shaft, a clutch has been conventionally used. The clutch connects the drive shaft and the driven shaft as needed, and transmits the rotation (or torque) of the drive shaft to the driven shaft to rotate a load connected to the driven shaft. Further, by disengaging the clutch, the drive shaft can stop the rotation of the driven shaft while rotating. Such a clutch may be used in a rotating machine such as a liquid pump device. Generally, clutches used in rotating machines include a mechanical clutch (friction multi-plate clutch) and a fluid coupling.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, conventional clutches such as mechanical clutches and fluid couplings have drawbacks such as a large installation area and high cost. Further, usually, most conventional clutches are designed for horizontal installation only, and the applicable range is limited. Furthermore, in a mechanical clutch, wear of the clutch plates that are in sliding contact with each other inevitably occurs. A fluid coupling does not have clutch plates, and it is possible to control the rotational speed and torque transmitted from the drive shaft to the driven shaft according to the amount of fluid present inside. However, an oil unit for controlling the amount of such fluid is required, which involves high cost and a large installation area.

[0005] Therefore, the present invention provides a compact and inexpensive magnetorheological fluid clutch.

Means for Solving the Problems

[0006] In one aspect, there is provided a magnetorheological fluid clutch including a first rotating shaft, a second rotating shaft, a first rotating plate connected to the first rotating shaft and rotatable integrally with the first rotating shaft, a second rotating plate connected to the second rotating shaft and rotatable integrally with the second rotating shaft, a stationary housing surrounding the first rotating plate and the second rotating plate, a magnetorheological fluid filling a space between the first rotating plate and the second rotating plate, a coil held by the stationary housing and generating a magnetic field applied to the magnetorheological fluid, and a current supply device for flowing a current through the coil.

[0007] In one aspect, the magnetorheological fluid clutch further includes a first bearing for rotatably supporting the first rotating shaft and a second bearing for rotatably supporting the second rotating shaft, and the first bearing and the second bearing are held by the stationary housing. In one aspect, the magnetorheological fluid clutch further includes a rotating housing fixed to the first rotating shaft and a rotating member fixed to the second rotating shaft, and the first rotating plate and the second rotating plate are located within the rotating housing, the first rotating plate is fixed to the rotating housing, and the second rotating plate is fixed to the rotating member. In one aspect, the magnetorheological fluid clutch further includes a sealing device for sealing a gap between the rotating housing and the rotating member. In one aspect, the magnetorheological fluid fills a sealed space formed at least by the first rotating plate, the second rotating plate, the rotating housing, the rotating member, and the sealing device.

[0008] In one aspect, the current supply device is configured to flow the current through the coil according to a preset current supply pattern. In one aspect, the magnetorheological fluid clutch further includes a first speed measuring device that measures the rotational speed of the first rotating shaft and a second speed measuring device that measures the rotational speed of the second rotating shaft, and the current supply device starts flowing the current to the coil after the rotational speed of the first rotating shaft reaches a preset speed, and is configured to increase the current while maintaining the rate of increase of the rotational speed of the second rotating shaft below a predetermined upper limit value. In one aspect, the magnetorheological fluid clutch further includes an AC power supply that alternately supplies a positive current and a negative current to the coil.

Advantages of the Invention

[0009] According to the present invention, a compact and inexpensive clutch is realized, and by controlling the current flowing through the coil, various modes of torque transmission such as instantaneous connection and instantaneous disconnection between the first rotating shaft and the second rotating shaft, and control of the rotational speed of the second rotating shaft with respect to the rotational speed of the first rotating shaft become possible.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a magnetorheological fluid clutch. As shown in FIG. 1, the magnetorheological fluid clutch 1 includes a first rotating shaft 5, a second rotating shaft 6, a first rotating plate 8, a second rotating plate 9, and a stationary housing 12. The first rotating plate 8 is connected to the first rotating shaft 5 and is rotatable integrally with the first rotating shaft 5. The second rotating plate 9 is connected to the second rotating shaft 6 and is rotatable integrally with the second rotating shaft 6. The first rotating plate 8 and the second rotating plate 9 are surrounded by the stationary housing 12.

[0012] The first rotating shaft 5 and the second rotating shaft 6 are arranged in a straight line and are each independently rotatable. In the present embodiment, the first rotating shaft 5 is a drive shaft connected to a prime mover (for example, an electric motor, a diesel engine, a gas turbine engine, etc.) not shown, and the second rotating shaft 6 is a driven shaft connected to a load such as a fan. In one embodiment, the second rotating shaft 6 may be a drive shaft connected to a prime mover, and the first rotating shaft 5 may be a driven shaft connected to a load.

[0013] The magnetorheological fluid clutch 1 further includes a first bearing 15 that rotatably supports the first rotating shaft 5 and a second bearing 16 that rotatably supports the second rotating shaft 6. The first bearing 15 and the second bearing 16 are held by the stationary housing 12. The magnetorheological fluid clutch 1 further includes an intermediate bearing 17 that rotatably supports both the first rotating shaft 5 and the second rotating shaft 6. Angular ball bearings that can receive both radial loads and axial loads are employed for the first bearing 15, the second bearing 16, and the intermediate bearing 17. However, the first bearing 15, the second bearing 16, and the intermediate bearing 17 may be other types of bearings.

[0014] The magnetic viscous fluid clutch 1 includes a magnetic viscous fluid 20 that fills the space between a first rotating plate 8 and a second rotating plate 9, a coil 22 that is held by a stationary housing 12 and generates a magnetic field applied to the magnetic viscous fluid 20, and a current supply device 25 that supplies a current to the coil 22. As a specific example of the magnetic viscous fluid 20, an MR fluid (magnetorheological fluid) can be mentioned. The MR fluid is a fluid in which magnetic particles such as iron are dispersed in a fluid medium such as oil. When a magnetic field is applied to the magnetic viscous fluid 20, the magnetic particles contained in the magnetic viscous fluid 20 are connected in a chain shape, and the magnetic viscous fluid 20 solidifies. The solidified magnetic viscous fluid 20 connects the first rotating plate 8 and the second rotating plate 9. On the other hand, when the application of the magnetic field to the magnetic viscous fluid 20 is stopped, the magnetic viscous fluid 20 liquefies, and the connection between the first rotating plate 8 and the second rotating plate 9 is released.

[0015] The coil 22 is disposed in the stationary housing 12 so as to surround the first rotating plate 8 and the second rotating plate 9. The coil 22 is located radially outside the first rotating plate 8 and the second rotating plate 9. However, the position of the coil 22 is not particularly limited as long as the magnetic field generated by the coil 22 acts on the magnetic viscous fluid 20 between the first rotating plate 8 and the second rotating plate 9. In one embodiment, the coil 22 may be located outside in the axial direction of the first rotating plate 8 and the second rotating plate 9.

[0016] The start and stop of the current supply to the coil 22 are performed by the current supply device 25. The current supply device 25 is configured to be able to change the magnitude and temporal change of the current supplied to the coil 22. When the current supply device 25 supplies a current to the coil 22, the coil 22 generates a magnetic field, and the magnetic viscous fluid 20 present in the gap between the first rotating plate 8 and the second rotating plate 9 is placed in the magnetic field.

[0017] In this embodiment, the current supply device 25 is configured to pass a current through the coil 22 according to a preset current supply pattern. For example, the current supply device 25 can instantaneously connect the first rotating shaft 5 and the second rotating shaft 6 by instantaneously supplying a rated current to the coil 22. In another example, the current supply device 25 can achieve soft start by gradually increasing the current from 0 to the rated current over a preset time.

[0018] In the embodiment shown in FIG. 1, the magnetorheological fluid clutch 1 further includes a rotating housing 31 fixed to the first rotating shaft 5 and a rotating member 32 fixed to the second rotating shaft 6. The first rotating plate 8 is fixed to the rotating housing 31, and the second rotating plate 9 is fixed to the rotating member 32. Therefore, the first rotating shaft 5, the rotating housing 31, and the first rotating plate 8 rotate integrally, and the second rotating shaft 6, the rotating member 32, and the second rotating plate 9 rotate integrally. The first rotating shaft 5, the rotating housing 31, and the first rotating plate 8 are non-contact with the second rotating shaft 6, the rotating housing 31, and the second rotating plate 9, and the first rotating shaft 5 can rotate independently of the second rotating shaft 6. Further, the rotating elements including the first rotating shaft 5, the rotating housing 31, the first rotating plate 8, the second rotating shaft 6, the rotating member 32, and the second rotating plate 9 are non-contact with the stationary housing 12 and the coil 22 which are fixed-side elements.

[0019] When the first rotating plate 8 and the second rotating plate 9 are rotating, the stationary housing 12 and the coil 22 do not rotate. In other words, the rotating body including the first rotating shaft 5, the rotating housing 31, the first rotating plate 8, the second rotating shaft 6, the rotating member 32, and the second rotating plate 9 can rotate relative to the stationary housing 12 and the coil 22.

[0020] The first rotating plate 8 and the second rotating plate 9 are located within the rotating housing 31. The rotating housing 31 has a cylindrical first base 31A fixed to the first rotating shaft 5, a circular connecting wall 31B extending radially outward from the first base 31A, an outer peripheral wall 31C extending axially from the outer peripheral portion of the connecting wall 31B, and a cover wall 31D extending radially inward from the outer peripheral wall 31C. The first rotating plate 8 is fixed inside the outer peripheral wall 31C. The rotating member 32 has a cylindrical second base 32A fixed to the second rotating shaft 6 and a circular block 32B extending radially outward from the second base 32A. The second rotating plate 9 is fixed to the outer peripheral portion of the circular block 32B.

[0021] The first bearing 15 is located between the cylindrical first base 31A and the stationary housing 12. The first rotating shaft 5 is rotatably supported by the first bearing 15 via the first base 31A. The second bearing 16 is located between the cylindrical second base 32A and the stationary housing 12. The second rotating shaft 6 is rotatably supported by the second bearing 16 via the second base 32A. The intermediate bearing 17 is disposed between the first base 31A and the second rotating shaft 6. The first rotating shaft 5 is rotatably supported by the intermediate bearing 17 via the first base 31A, and the second rotating shaft 6 is directly rotatably supported by the intermediate bearing 17. In one embodiment, the intermediate bearing 17 may be disposed between the second base 32A and the first rotating shaft 5.

[0022] In the present embodiment, a plurality of first rotating plates 8 and a plurality of second rotating plates 9 are provided, and the first rotating plates 8 and the second rotating plates 9 are arranged alternately along the axial direction. The space between the first rotating plate 8 and the second rotating plate 9 is filled with the magnetorheological fluid 20. In one embodiment, a single first rotating plate 8 and a single second rotating plate 9 may be provided.

[0023] The magnetic viscous fluid clutch 1 further includes seal devices 35 and 37 that seal the gap between the rotating housing 31 and the rotating member 32. More specifically, a first seal device 35 is provided between the connecting wall 31B of the rotating housing 31 and one side of the circular block 32B of the rotating member 32, and a second seal device 37 is provided between the cover wall 31D of the rotating housing 31 and the opposite side of the circular block 32B of the rotating member 32. The specific configurations of the first seal device 35 and the second seal device 37 are not particularly limited, and examples include oil seals, mechanical seals, O-rings, gland packings, and the like.

[0024] The magnetic viscous fluid 20 fills the sealed space formed by at least the first rotating plate 8, the second rotating plate 9, the rotating housing 31, the rotating member 32, and the two seal devices 35 and 37.

[0025] Next, the operation of the magnetic viscous fluid clutch 1 configured as described above will be described. When the current supply device 25 passes a current through the coil 22, the coil 22 generates a magnetic field, and the magnetic field solidifies the magnetic viscous fluid 20 present between the first rotating plate 8 and the second rotating plate 9. The solidified magnetic viscous fluid 20 connects the first rotating plate 8 and the second rotating plate 9, and thereby the rotation (torque) of the first rotating shaft 5 is transmitted to the second rotating shaft 6. In an embodiment where the second rotating shaft 6 is the driving shaft and the first rotating shaft 5 is the driven shaft, the rotation (torque) of the second rotating shaft 6 is transmitted to the first rotating shaft 5. When the current supply device 25 stops supplying current to the coil 22, the magnetic viscous fluid 20 liquefies, and thereby the connection between the first rotating shaft 5 and the second rotating shaft 6 is released.

[0026] According to this embodiment, a compact and inexpensive clutch is realized. In particular, since the coil 22 is fixed to the stationary housing 12 and is stationary (non-rotating), the weight of the rotating body of the magnetorheological fluid clutch 1 is reduced. As a result, the inertial force generated when rotating the rotating body of the magnetorheological fluid clutch 1 becomes smaller, and the power required for the prime mover can be reduced. Furthermore, slip rings, brushes, etc. for supplying current to the coil in the rotating body are unnecessary, and the manufacturing cost and installation area can be reduced.

[0027] Also, by controlling the current flowing through the coil 22, various modes of torque transmission such as instantaneous connection and instantaneous disconnection between the first rotating shaft 5 and the second rotating shaft 6, and control of the rotational speed of the second rotating shaft 6 with respect to the rotational speed of the first rotating shaft 5 become possible.

[0028] The first rotating shaft 5 and the second rotating shaft 6 of the magnetorheological fluid clutch 1 shown in FIG. 1 extend in the vertical direction, but the posture of the magnetorheological fluid clutch 1 is not limited to the vertical arrangement shown in FIG. 1. For example, the magnetorheological fluid clutch 1 may be arranged horizontally or obliquely.

[0029] FIG. 2 is a cross-sectional view showing another embodiment of the magnetorheological fluid clutch 1. The configuration and operation of this embodiment that are not particularly described are the same as those of the embodiment shown in FIG. 1, so the overlapping description is omitted. As shown in FIG. 2, the magnetorheological fluid clutch 1 of this embodiment further includes a first speed measuring device 51 that measures the rotational speed of the first rotating shaft 5 and a second speed measuring device 52 that measures the rotational speed of the second rotating shaft 6. The first speed measuring device 51 and the second speed measuring device 52 are arranged adjacent to the first rotating shaft 5 and the second rotating shaft 6, respectively. The specific configuration of the first speed measuring device 51 and the second speed measuring device 52 is not particularly limited.

[0030] The first speed measuring device 51 and the second speed measuring device 52 may be fixed to the stationary housing 12, or may be fixed to another stationary member (not shown). The first speed measuring device 51 and the second speed measuring device 52 are connected to the current supply device 25, and the measured values of the rotational speed of the first rotating shaft 5 and the measured value of the rotational speed of the second rotating shaft 6 are sent to the current supply device 25.

[0031] After the rotational speed of the first rotating shaft 5 reaches a preset speed, the current supply device 25 starts to pass an electric current through the coil 22, and is configured to increase the current while maintaining the rising rate of the rotational speed of the second rotating shaft 6 below a predetermined upper limit value. That is, when the first rotating shaft 5 is rotating, the current supply device 25 starts to supply an electric current to the coil 22 and further gradually increases the current. The rotational speed of the second rotating shaft 6 gradually increases as the current increases. By such a soft start operation, an overload on the prime mover (for example, an electric motor) connected to the first rotating shaft 5 can be prevented.

[0032] FIG. 3 is a cross-sectional view showing another embodiment of the magnetorheological fluid clutch 1. The configuration and operation of this embodiment that are not particularly described are the same as those of the embodiment shown in FIG. 1, and thus the overlapping description thereof is omitted. As shown in FIG. 3, the magnetorheological fluid clutch 1 of this embodiment further includes an AC power supply 60 that alternately supplies a positive current and a negative current to the coil 22.

[0033] The reason for providing the AC power supply 60 is as follows. In the magnetorheological fluid clutch 1, a current is passed through the coil 22, and a magnetic field is applied to the magnetorheological fluid 20 through a magnetic yoke made of a magnetic material around the coil. At that time, the magnetic yoke member made of the magnetic material around the coil may be magnetized and residual magnetism may remain. Also, magnetic particles such as iron contained in the magnetorheological fluid 20 may be magnetized. As a result, even when no current is applied to the coil 22, the viscosity of the magnetorheological fluid 20 may increase, and the disconnection of the magnetorheological fluid clutch 1 may not function. Therefore, when no current is supplied from the current supply device 25 to the coil 22, the AC power supply 60 alternately and repeatedly supplies a positive-direction current and a negative-direction current to the coil 22, and gradually reduces the magnitude of the applied current over time. Examples of such alternating currents include a sine-wave alternating current, a rectangular-wave alternating current, a triangular-wave alternating current, or a sawtooth-wave alternating current. By alternately flowing a positive-direction current and a negative-direction current that gradually decreases over time through the coil 22, the direction of the magnetic field applied to the magnetic yoke member and the magnetorheological fluid 20 around the coil 22 periodically reverses and the magnetic field weakens over time. As a result, the magnetized magnetic yoke member around the coil 22 and the magnetized magnetic particles contained in the magnetorheological fluid 20 can be demagnetized.

[0034] The embodiment shown in FIG. 3 can be combined with the embodiment shown in FIG. 2.

[0035] The magnetorheological fluid clutch 1 according to the embodiment described with reference to FIGS. 1 to 3 can be suitably used for a rotating machine such as a liquid pump device. For example, the magnetorheological fluid clutch 1 can be incorporated into a vertical-axis pump device installed in a river or the like, a descaling pump device used in a steel mill, or the like. The descaling pump device is configured to instantaneously switch between the injection and the stop of high-pressure liquid, and the magnetorheological fluid clutch 1 can be suitably used for such an operation. Further, the magnetorheological fluid clutch 1 can also be used as a reverse-prevention clutch for a large pump.

[0036] FIG. 4 is a schematic view showing a vertical shaft pump device incorporating any one of the magnetic viscous fluid clutches 1 according to the embodiments described with reference to FIGS. 1 to 3. As shown in FIG. 4, the vertical shaft pump device includes a vertical shaft pump having a rotating shaft 115 extending in the vertical direction, an impeller 110 fixed to the rotating shaft 115, a pump casing 127 that houses the impeller 110 therein, a lift pipe 128 connected to the upper end of the pump casing 127, a discharge elbow 130 connected to the upper end of the lift pipe 128, and a discharge pipe 134 connected to the discharge side end of the discharge elbow 130.

[0037] The rotating shaft 115 is connected to the drive shaft 107a of the prime mover 107 by the magnetic viscous fluid clutch 1. One of the first rotating shaft 5 and the second rotating shaft 6 (see FIG. 1) of the magnetic viscous fluid clutch 1 is connected to the drive shaft 107a, and the other of the first rotating shaft 5 and the second rotating shaft 6 is connected to the rotating shaft 115. Examples of the prime mover 107 include an electric motor, a diesel engine, and a gas turbine engine. The stationary housing 12 of the magnetic viscous fluid clutch 1 and the prime mover 107 are fixed to the bracket 111.

[0038] The pump casing 127 is suspended in the suction water tank 100 by the lift pipe 128. The pump casing 127 includes a suction bellmouth 122 and a discharge bowl 124. The upper end of the discharge bowl 124 is connected to the lower end of the lift pipe 128. The suction bellmouth 122 has a suction port 122a that opens downward, and the upper end of the suction bellmouth 122 is connected to the lower end of the discharge bowl 124. The suction port 122a is formed at the lower end of the pump casing 127. The impeller 110 is housed within the pump casing 127.

[0039] The lift pipe 128 extends downward through an opening 105 formed in the pump mounting floor 102 that constitutes the upper wall of the suction water tank 100. An attachment flange 133 is fixed to the upper end of the lift pipe 128. The attachment flange 133 is fixed to the pump mounting floor 102 by foundation bolts (not shown). The rotating shaft 115 extends vertically through the discharge elbow 130 and the lift pipe 128, and the lower end of the rotating shaft 115 is located within the pump casing 127. The rotating shaft 115 is rotatably supported by an outer bearing 145 and a sliding bearing 141.

[0040] The rotating shaft 115 protrudes upward from the discharge elbow 130 and is connected to the drive shaft 107a of the prime mover 107 via the magnetorheological fluid clutch 1. The outer bearing 145 is disposed outside the discharge elbow 130 and rotatably supports the portion of the rotating shaft 115 that protrudes from the discharge elbow 130. A sliding bearing for supporting the rotating shaft 115 may be further disposed within the lift pipe 128. The outer bearing 145 is fixed to the upper part of the discharge elbow 130 and supports the upper part of the rotating shaft 115. The sliding bearing 141 is disposed within the discharge bowl 124 and supports the lower part of the rotating shaft 115. The sliding bearing 141 is immersed in the liquid during the operation of the vertical shaft pump.

[0041] An inner bowl 125 is disposed inside the discharge bowl 124, and the inner bowl 125 is connected to the discharge bowl 124 by a plurality of guide vanes 137. The plurality of guide vanes 137 are disposed above (discharge side) the impeller 110. A liquid flow path is formed between the inner surface of the discharge bowl 124 and the outer surface of the inner bowl 125.

[0042] The torque of the prime mover 107 is transmitted to the rotating shaft 115 via the magnetorheological fluid clutch 1, and the impeller 110 is rotated together with the rotating shaft 115. When the impeller 110 rotates, the liquid in the suction water tank 100 is sucked in from the suction port 122a of the pump casing 127. The liquid is transferred to the discharge pipe 134 through the pump casing 127, the lift pipe 128, and the discharge elbow 130 by the rotation of the impeller 110.

[0043] The magnetic viscous fluid clutch 1 can reduce the rotation of the impeller 110 or stop the rotation of the impeller 110 while maintaining the rotation of the prime mover 107 as it is. In particular, for a vertical shaft pump device that handles liquids, a large load is applied to the prime mover 107 at the time of its startup. The magnetic viscous fluid clutch 1 can prevent an overload on the prime mover 107 by soft-starting the vertical shaft pump device. Further, when a problem occurs in the rotation of the impeller 110, the current supply device 25 can cut off the connection with the prime mover 107 by instantaneously stopping the current flowing through the coil 22, and can prevent an expansion of damage to the pump device.

[0044] The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is construed in the broadest scope in accordance with the technical idea defined by the claims.

Explanation of Reference Numerals

[0045] 1 Magnetic viscous fluid clutch 5 First rotating shaft 6 Second rotating shaft 8 First rotating plate 9 Second rotating plate 12 Stationary housing 15 First bearing 16 Second bearing 17 Intermediate bearing 20 Magnetic viscous fluid 22 Coil 25 Current supply device 31 Rotating housing 31A First base 31B Connecting wall 31C Outer peripheral wall 31D Cover wall 32 Rotating member 32A Second base 32B Circular block 35, 37 Seal device 51 First speed measurer 52 Second speed measurer 60 AC power supply

Claims

1. A first rotating shaft, a second rotating shaft, a first rotating plate connected to the first rotating shaft and rotatable integrally with the first rotating shaft, a second rotating plate connected to the second rotating shaft and rotatable integrally with the second rotating shaft, a stationary housing surrounding the first rotating plate and the second rotating plate, a magnetorheological fluid filling a space between the first rotating plate and the second rotating plate, a coil held by the stationary housing and generating a magnetic field applied to the magnetorheological fluid, a current supply device for flowing a current through the coil, a first speed measuring device for measuring the rotational speed of the first rotating shaft, a second speed measuring device for measuring the rotational speed of the second rotating shaft, wherein the current supply device is configured to start flowing the current through the coil after the rotational speed of the first rotating shaft reaches a preset speed, and to increase the current while maintaining the rate of increase of the rotational speed of the second rotating shaft below a predetermined upper limit value. A magnetorheological fluid clutch.

2. The magnetorheological fluid clutch further comprises: a first bearing for rotatably supporting the first rotating shaft, a second bearing for rotatably supporting the second rotating shaft, wherein the first bearing and the second bearing are held by the stationary housing. The magnetorheological fluid clutch according to claim 1.

3. The magnetorheological fluid clutch further comprises: a rotating housing fixed to the first rotating shaft, a rotating member fixed to the second rotating shaft, wherein the first rotating plate and the second rotating plate are located within the rotating housing, the first rotating plate is fixed to the rotating housing, and the second rotating plate is fixed to the rotating member. The magnetorheological fluid clutch according to claim 1 or 2.

4. The magnetorheological fluid clutch according to claim 3, further comprising a sealing device for sealing a gap between the rotating housing and the rotating member.

5. The magnetorheological fluid fills a sealed space formed at least by the first rotating plate, the second rotating plate, the rotating housing, the rotating member, and the sealing device. The magnetorheological fluid clutch according to claim 4.

6. The magnetorheological fluid clutch according to any one of claims 1 to 5, further comprising an AC power supply for alternately supplying a positive current and a negative current to the coil.

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