JP7660381B2 - Magnetorheological Fluid Device - Google Patents

Description

The present invention relates to a magnetorheological fluid device in which a magnetorheological fluid is interposed between relatively rotatable members, and the torque transmitted between the members can be changed by changing the strength of the magnetic field applied to the magnetorheological fluid.

This type of magnetorheological fluid device is disclosed in, for example, Patent Document 1. The magnetorheological fluid device disclosed in FIG. 14 of the document (referred to as "rotational resistance generating unit (104)" in the document) comprises a relatively rotatable disk (128) and yokes (129), (130), and the torque transmitted between the disk (128) and the yokes (129), (130) can be changed by changing the strength of the magnetic field applied to the magnetorheological fluid interposed between them. The magnetorheological fluid device (104) disclosed in the document is built into a portable grip (100). A current is supplied to the coil (131) of the magnetorheological fluid device (104) from a battery (201) in a power supply unit (200) worn on the user's waist.

In recent years, many portable electronic devices and electronic devices that can be worn on a part of the body use lithium-ion batteries with a rated voltage of approximately 3.7 V. Lithium-ion batteries have the highest energy density of all the secondary batteries currently in widespread use, and can be said to be the ideal battery for making devices smaller and lighter. It is also desirable to use lithium-ion batteries as the driving battery for magnetorheological fluid devices built into portable devices and devices that can be worn on a part of the body.

JP 2020-017159 A

Incidentally, the transmission torque (hereinafter simply referred to as "transmission torque") generated between relatively rotatable members in a magnetorheological fluid device changes according to the magnetomotive force of the magnetic circuit. The magnetomotive force is expressed as the product of the number of turns of the coil [T] and the current flowing through the coil [A]. Therefore, when the specifications of the coil in a magnetorheological fluid device (electrical resistance and number of turns) are predetermined, the maximum value of the transmission torque depends mainly on the rated voltage of the battery.

In order to increase the maximum value of the "transmission torque," for example, a battery pack consisting of multiple lithium-ion batteries connected in series, or another type of battery with a higher rated voltage than a lithium-ion battery, can be used. However, such batteries are relatively large and heavy, and therefore are not suitable for use in magnetorheological fluid devices built into portable equipment or equipment worn on a part of the body.

Furthermore, by providing a boost circuit, it is possible to increase the voltage applied to the coil of the magnetorheological fluid device without changing to a battery with a higher rated voltage. However, providing a boost circuit increases the number of parts and causes energy loss, which is problematic.

The present invention was devised in consideration of the above-mentioned problems, and aims to provide a magnetorheological fluid device that can increase the maximum torque transmitted between relatively rotatable members without changing the number of turns and cross-sectional area of the coil or the rated voltage of the battery.

The magnetorheological fluid device according to the first aspect of the present invention is based on the premise that it comprises a first part and a second part that are arranged to be rotatable relative to one another around an axis, a magnetorheological fluid interposed between the first part and the second part, and an electromagnet that generates a magnetic field to be applied to the magnetorheological fluid, and the coil that constitutes the electromagnet is made up of multiple coil wires connected in parallel and wound in an aligned fashion.

The magnetorheological fluid device according to the second aspect of the present invention is based on the premise that it comprises a first part and a second part that are arranged to be rotatable relative to one another around an axis, a magnetorheological fluid interposed between the first part and the second part, and an electromagnet that generates a magnetic field to be applied to the magnetorheological fluid, and the coil that constitutes the electromagnet is made of multiple coil wires wound in an aligned manner, and the device comprises a switching control unit that switches the connection state of the multiple coil wires between a parallel connection and a series connection.

A magnetorheological fluid device according to a third aspect of the present invention is the magnetorheological fluid device according to the second aspect, further comprising: a voltage control unit that controls a voltage applied to the coil in accordance with a required output;
and a battery that supplies power to the voltage control unit. The switching control unit changes the connection state of the multiple coil wires to a parallel connection when the required output exceeds a predetermined threshold output, and changes the connection state of the multiple coil wires to a series connection when the required output does not exceed the predetermined threshold output. The predetermined threshold output is an output generated when the connection state of the multiple coil wires is a series connection and the voltage applied to the coil is the rated voltage of the battery, or is smaller than that output.

The magnetorheological fluid device of the present invention can increase the maximum torque (maximum output) transmitted between relatively rotatable members without changing the number of turns and cross-sectional area of the coil or the rated voltage of the battery. For example, in a case where a lithium-ion battery with a rated voltage of approximately 3.7 V is unable to generate the original maximum output of the magnetorheological fluid device, applying the present invention makes it possible to generate the original maximum output of the magnetorheological fluid device.

1 is a cross-sectional view of a magnetorheological fluid device according to a first embodiment. FIG. 1 is a schematic circuit diagram including a coil and a battery. FIG. 4 is a cross-sectional view of a magnetorheological fluid device according to a second embodiment.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetorheological fluid device according to a first embodiment of the present invention will now be described with reference to the drawings. A magnetorheological fluid device 1 shown in FIG.

The device body A is composed of a first part and a second part that are arranged to be relatively rotatable around an axis N. The device body A includes a disk 2, yokes 3 and 4, a coil 5, a magnetorheological fluid 6, a case 7, and a rotating shaft 8. The first part includes the disk 2 and the rotating shaft 8. The second part includes the yokes 3 and 4, the coil 5, and the case 7.

The disk 2 rotates around the axis N relative to the second part. A rotating shaft 8 is connected vertically to the center of the back surface 2b of the disk 2. The rotating shaft 8 rotates around the axis N relative to the second part together with the disk 2. The rotating shaft 8 is supported in a shaft hole 11 provided in the yoke 4 via a bearing 10. It is preferable that the disk 2 is made of a magnetic material and the rotating shaft 8 is made of a non-magnetic material.

The yoke is composed of a first yoke 3 and a second yoke 4. The first yoke 3 has an opposing surface that faces the surface 2a of the disk 2 with a small gap between them. The first yoke 3 is composed of a disk-shaped member. This first yoke 3 is fitted and fixed in the cylindrical case 7.

The second yoke 4 has an opposing surface 4a that faces the rear surface 2b of the disk 2 with a small gap between them. This second yoke 4 is also fitted and fixed inside the cylindrical case 7.

A sphere 12 made of a non-magnetic material is housed in the space formed by a recess formed in the center of the first yoke 3 and a recess formed in the center of the end face of the rotating shaft 8.

The coil 5 is disposed in an annular groove formed in the second yoke 4. The coil 5, together with the first yoke 3 and the second yoke 4, constitutes an electromagnet 13. The coil 5 in this embodiment is formed by arranging and winding multiple coil wires (two in this embodiment) connected in parallel to each other. In other words, the coil 5 in this embodiment is formed by "bifilar winding" two coil wires.

The magnetorheological fluid 6 is sealed in the gap between the disk 2 and the first and second yokes 3 and 4. The magnetorheological fluid 6 is a liquid in which magnetic particles are dispersed in a dispersion medium. The magnetic particles may be, for example, nano-sized metal particles (metal nanoparticles). The magnetic particles are made of a magnetizable metal material, and although there is no particular restriction on the metal material, soft magnetic materials are preferred. Examples of soft magnetic materials include alloys such as iron, cobalt, nickel, and permalloy. The dispersion medium is not particularly limited, but one example is hydrophobic silicone oil. The amount of magnetic particles in the magnetorheological fluid may be, for example, 3 to 40 vol%. Various additives may also be added to the magnetorheological fluid to obtain various desired characteristics.

When a current flows through the coil 5 in the device main body A having the above configuration, a magnetic path is formed in the disk 2, first yoke 3, and second yoke 4, for example along the direction indicated by the arrow P in FIG. 1. This magnetic path penetrates the magnetorheological fluid 6 present in the gap between the front surface 2a of the disk 2 and the first yoke 3, and the magnetorheological fluid 6 present in the gap between the back surface 2b of the disk 2 and the second yoke 4. As a result, the magnetorheological fluid 6 develops a viscosity (shear stress) that corresponds to the strength of the magnetic field, and the torque transmitted between the disk 2 and the yokes 3 and 4 increases in accordance with the strength of the magnetic field.

Next, the power supply unit B will be described. The power supply unit B supplies a current of a desired current value to the coil 5. The power supply unit B is, for example, a portable unit that can be attached to a part of the operator's body. As shown in FIG. 1, the power supply unit B includes a battery 20 and a voltage control unit 21.

The voltage control unit 21 controls the voltage applied to the coil 5 according to predetermined input information (required output). The battery 20 supplies power to the voltage control unit 21.

In the magnetorheological fluid device 1 according to this embodiment, the coil 5 is made up of multiple parallel-connected coil wires wound in an orderly fashion, so that the maximum value (maximum output) of the torque transmitted between the disc 2 and the yokes 3 and 4 can be increased without changing the number of turns and cross-sectional area of the coil 5 or the rated voltage of the battery 20, compared to when the coil 5 is made up of a single coil wire.

For example, as shown in FIG. 2(a), when a coil wire (hereinafter also referred to as the "first coil wire") with a wire diameter D, length L, electrical resistance 20 [Ω], and number of turns 500 [T] is used as a coil and a voltage of 3.7 [V] is applied, the magnetomotive force Fm is 3.7 [V]/20 [Ω] x 500 [T] = 92.5 [AT]. In contrast, when two coils with half the length of the "first coil wire" are used as coils as shown in FIG. 2(b), that is, when two coil wires with a wire diameter D, length L/2, electrical resistance 10 [Ω], and number of turns 250 [T] are connected in parallel and a voltage of 3.7 [V] is applied, the magnetomotive force Fm is 3.7 [V]/10 [Ω] x 250 [T] x 2 = 185 [AT].

In this way, the magneto-rheological fluid device 1 according to this embodiment can increase the magnetomotive force Fm without changing the number of turns and cross-sectional area of the coil 5 or the rated voltage of the battery 20. The higher the magnetomotive force Fm, the stronger the magnetic field applied to the magneto-rheological fluid 6, and therefore the transmission torque (output) between the disk 2 and the yokes 3 and 4 can be increased.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to Fig. 3. In the magnetorheological fluid device 1A according to the second embodiment, the coil 5 constituting the electromagnet 13 in the magnetorheological fluid device 1 according to the first embodiment is formed by winding a plurality of coil wires (two in this embodiment) in an aligned manner, and a control unit 30 and a battery 20 are provided in a power supply unit BA. The control unit 30 includes the voltage control unit 21 and the switching control unit 22 described above. Below, differences from the first embodiment will be described, and the same components as those in the first embodiment will be denoted by the same reference numerals in the drawings and will not be described.

The switching control unit 22 switches the connection state of the multiple coil wires (two in this embodiment) that make up the coil 5 between parallel connection and series connection. When the specified input information (required output) input to the control unit 30 exceeds a specified "threshold output", the switching control unit 22 sets the connection state of the multiple coil wires to a parallel connection, and when the input information (required output) does not exceed the specified "threshold output", the switching control unit 22 sets the connection state of the multiple coil wires to a series connection when the input information (required output) matches the "threshold output". Note that when the input information (required output) matches the "threshold output", the switching control unit 22 may set the connection state of the multiple coil wires to a series connection instead of a parallel connection.

In this embodiment, the "threshold output" is an output generated when the multiple coil wires constituting the coil 5 are connected in series and the voltage applied to the coil 5 is the rated voltage of the battery 20. For example, if the coil 5 is configured using two coil wires with an electrical resistance of 10 [Ω] and a number of turns of 250 [T], and a battery 20 with a rated voltage of 3.7 V is used, the maximum magnetomotive force Fm1 when the multiple coil wires are connected in series is 3.7 [V] / 20 [Ω] × 500 [T] = 92.5 [AT]. The output generated when this maximum magnetomotive force Fm1 is realized can be the "threshold output". Note that the "threshold output" may be an output smaller (e.g., an output 0 to 30% smaller) than the output generated when the multiple coil wires constituting the coil 5 are connected in series and the voltage applied to the coil 5 is the rated voltage of the battery 20.

According to the magnetorheological fluid device 1A of the second embodiment, when the required output is smaller than the "threshold output", the multiple coil wires are connected in series, forming a circuit as shown in FIG. 2(a), and power consumption is reduced. For example, when the coil 5 is formed using two coil wires with an electrical resistance of 10 [Ω] and a number of turns of 250 [T], and a magnetomotive force of 50 [AT] is generated using a battery 20 with a rated voltage of 3.7 V, the power consumption when the coil wires are connected in series is 0.37 [W] (= 3.7 [V] x 50 [AT] / 500 [T]). In contrast, the power consumption when the coil wires are connected in parallel is 0.74 [W] (= (3.7 [V] x 25 [AT] / 250 [T]) x 2), and the power consumption is significantly smaller when the coil wires are connected in series.

In addition, when the required output is greater than the "threshold output", the multiple coil wires are connected in parallel, forming the circuit shown in FIG. 2(b), allowing the magnetorheological fluid device 1A to generate a large output that cannot be generated by series connection. For example, if the coil 5 is formed using two coil wires with an electrical resistance of 10 [Ω] and a number of turns of 250 [T], and a battery 20 with a rated voltage of 3.7 V is used, the maximum value of the magnetomotive force when the coil wires are connected in series is 3.7 [V]/20 [Ω] x 500 [T] = 92.5 [AT]. In contrast, the maximum value of the magnetomotive force when the coil wires are connected in parallel is 3.7 [V]/10 [Ω] x 250 [T] x 2 = 185 [AT], and a significantly larger magnetomotive force (output) can be generated when the coil wires are connected in parallel.

The present invention can be applied to a magnetorheological fluid device in which, for example, a magnetorheological fluid is interposed between relatively rotatable members, and the torque transmitted between the members can be changed by changing the strength of the magnetic field applied to the magnetorheological fluid.

1, 1A Magnetorheological fluid device A Device body B Power supply unit 2 Disk (first part)
3. First Yoke (Part 2)
4. Second Yoke (Part 2)
5 Coil 6 Magnetorheological fluid 13 Electromagnet 20 Battery 21 Voltage control unit 22 Switching control unit

Claims (2)

a first portion and a second portion that are provided so as to be relatively rotatable about an axis;
a magnetorheological fluid interposed between the first portion and the second portion;
an electromagnet that generates a magnetic field to be applied to the magnetorheological fluid;
A switching control unit;
In a magnetorheological fluid device comprising:
The coil constituting the electromagnet is formed by winding a plurality of coil wires connected in parallel in an aligned manner as one coil,
The coil wires have the same cross-sectional area,
the parallel connection is one of the connection states of the plurality of coil wires formed by the switching control unit,
the switching control unit is capable of switching a connection state of the plurality of coil wires from the parallel connection to the series connection and from the series connection to the parallel connection.
A magnetorheological fluid device comprising: 2. The magnetorheological fluid device according to claim 1 ,
A voltage control unit that controls a voltage applied to the coil in accordance with a required output;
a battery that supplies power to the voltage control unit;
Equipped with
the switching control unit changes a connection state of the plurality of coil wires to a parallel connection when a required output exceeds a predetermined threshold output, and changes a connection state of the plurality of coil wires to a series connection when the required output does not exceed the predetermined threshold output,
A magnetorheological fluid device characterized in that the specified threshold output is an output generated when the multiple coil wires are connected in series and the voltage applied to the coil is the rated voltage of the battery, or is smaller than that output.

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