JPH07236290A - Rotary actuator - Google Patents

Abstract

PURPOSE:To transmit large torque to a rotor with regard to a rotary actuator, which turns the rotor by utilizing the magnetostriction generated in magnetostriction material. CONSTITUTION:A stator 10 having a plurality of grooves is formed at one end of a cylinder member by using super-magnetostriction material. A winding is wound along the circumference of the stator 10, and a first electromagnetic coil 14 is constituted. A winding is hooked in a groove 12 and wound around the stator 10, and a second electromagnetic coil 16 is constituted. A rotor 20 is arranged at the upper side of the stator 10 with the specified space interval being provided. The stator 10 and the rotor 20 are brought into contact with the magnetic field generated from the first electromagnetic coil 14. Then, torsion is generated in the stator 10 with the synthetic magnetic field of the magnetic fields generated from the first and second electromagnetic coils 14 and 16. The rotation caused by the torsion is transmitted to the rotor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary actuator, and more particularly to a rotary actuator that rotates a rotor by utilizing magnetostriction generated in a magnetostrictive material.

[0002]

2. Description of the Related Art Conventionally, as a rotary actuator using a magnetostrictive material, one disclosed in, for example, Japanese Patent Laid-Open No. 2-205653 is known. This rotary actuator is provided with a plurality of protrusions made of a magnetostrictive material on one end surface of a cylindrical member along its circumference, and a stator provided with an electromagnetic coil independently for each protrusion, and It is composed of a mover provided in contact with the protrusion, and generates a rotational force according to the following principle.

That is, when a current is applied to the electromagnetic coil provided in the stator, a magnetic field along the axis of the electromagnetic coil is applied to the projection provided with the electromagnetic coil. Here, since the protrusion is made of a magnetostrictive material that causes magnetostriction when a magnetic field is applied, when the magnetic field is applied as described above, the protrusion is distorted according to the applied magnetic field.

Therefore, if a current is supplied only to a specific electromagnetic coil, it is possible to cause distortion only to a specific protrusion, and further to sequentially change the electromagnetic coils along the circumference of the stator. If electricity is applied, the strain generated on the one end surface of the stator rotates along the circumference.

Here, the rotor is in contact with the stator as described above, and when the above-mentioned rotational distortion occurs on the contact surface, the rotation of the distortion is transmitted to the rotor to drive the electromagnetic coil. Rotational force is generated according to the state.

[0006]

However, in the conventional rotary actuator described above, a part of the plurality of protrusions facing the rotor is distorted, and the rotation of the distorted part is used to generate a rotating torque. Therefore, in the driven state, only some of the protrusions are inevitably brought into contact with the rotor.

That is, since it is only a part of the plurality of protrusions that gives the rotating torque to the rotor and the momentary contact area is small, a large driving torque cannot be obtained. Had.

The present invention has been made in view of the above points, and a magnetostrictive material is formed into a cylindrical shape to form a stator,
By obtaining the driving torque by utilizing the torsional strain generated when a magnetic field in the spiral direction is applied to the stator,
It is an object of the present invention to provide a rotary actuator that solves the above problems.

[0009]

The above object is to provide a stator formed by molding a magnetostrictive material into a cylindrical shape, a first electromagnetic coil for applying an axial magnetic field to the stator, and the fixed member. This is achieved by a rotary actuator that includes a second electromagnetic coil that applies a magnetic field in the circumferential direction to the child, and a rotor that faces the stator at a predetermined interval in the axial direction of the stator. .

[0010]

In the rotary actuator according to the present invention,
When a current is applied to the first electromagnetic coil, a magnetic field is applied to the rotor in its axial direction. Further, when a current is applied to the second electromagnetic coil together with this, a magnetic field in the circumferential direction of the rotor generated by the second electromagnetic coil and a magnetic field in the axial direction generated by the first electromagnetic coil. And are combined, and a helical magnetic field is applied to the stator.

Therefore, when a current is applied only to the first coil, axial distortion occurs in the stator, and as a result, the stator and the mover come into contact with each other. Then, when a current is further applied to the second coil from that state, the stator is twisted, and the twist is transmitted to the stator to generate a rotational torque.

Thereafter, when only the energization of the first electromagnetic coil is stopped, the axial magnetic field applied to the stator disappears, and the stator applies a predetermined rotational displacement to the mover. Separated from the mover.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining the overall configuration of a rotary actuator according to the present invention. FIG.
The stator 1 which is the main part of the rotary actuator of this embodiment
0 and a perspective view of the rotor 20 are shown.

As shown in FIG. 1A, the stator 10 is
It is a cylindrical member having a plurality of grooves 12 of uniform depth on the upper end surface in the figure. Here, the stator 10 is made of a giant magnetostrictive material that expands in the magnetic field direction when a magnetic field is applied. In this embodiment, Tb0.
3 Dy0.7 Fe1.9 is used.

The rotor 20 is composed of a disc portion 22 having substantially the same diameter as that of the stator 10 and a rotating shaft 24 fixed to the center of the disc portion 22. It is rotatably supported about the rotating shaft 22 with a space therebetween.

1B and 1C, the stator 10 has a first electromagnetic coil 14 and a second electromagnetic coil 16 mounted on the stator 10.
A plan view and a side cross-sectional view of the wound state (and (B) of the figure) are respectively shown.

As shown in the drawings, the first electromagnetic coil 14
Is formed by a winding wire wound around the central axis of the stator 10, that is, along the circumference of the stator 10. The second electromagnetic coil 16 is formed by a winding wire wound around the groove 12 and wound around the side surface of the stator 10.

In this case, the second electromagnetic coil 16 has the groove 1
Although it is formed as a plurality of electromagnetic coil groups due to the structure wound around 2, these electromagnetic coil groups may be any one as long as they form a magnetic field in the same direction when an electric current is applied as described later. The coils may be formed independently or in series.

By the way, FIG. 2A is generated when a predetermined current is applied to the electromagnetic coil 14a formed by winding a winding wire around the axis of the stator 10, that is, along the circumference of the stator 10. Although the state of the magnetic field H ₁ is shown, the direction of the magnetic field H ₁ generated in this case is parallel to the axial direction of the electromagnetic coil 14 a, that is, the axial direction of the stator 10.

In this case, the stator 10 is Tb-as described above.
Since it is made of Dy-Fe giant magnetostrictive material, when a magnetic field in the axial direction as described above is generated around the inner circumference of the electromagnetic coil 14a, that is, around the stator 10, the magnetic field is distorted in the axial direction. The result is stretching.

Therefore, in the rotary actuator of this embodiment shown in FIG. 1, when a current is applied to the first electromagnetic coil 14, as a result, the stator 10 expands in the axial direction. In this embodiment, when the stator 10 is extended in this way, the positional relationship between the stator 10 and the rotor 20 is such that the upper end of the stator 10 abuts on the disc portion of the rotor 20, The magnitude of the current supplied to the first electromagnetic coil 14 is set.

Next, as shown in FIG. 2B, the electromagnetic coil 1
A case will be described in which a current is supplied to the electromagnetic coil 16a including a winding wound around the side wall of the stator 10 together with 4a. In this case, the magnetic field H ₁ is generated from the electromagnetic coil 14a in the axial direction of the stator 10, as described above.
A magnetic field H ₂ is generated in a direction intersecting with a, that is, in the circumferential direction of the stator 10.

That is, a magnetic field H which is a combination of the magnetic fields H ₁ and H ₂ generated by the _two is applied to the stator 10, and the direction of the magnetic field H at this time is the circumferential direction of the stator 10. The spiral direction is such that it winds up and drifts in its axial direction. Since the stator 10 is a member that expands in the direction of the applied magnetic field, when the spiral magnetic field is applied, the stator 10 is expanded in the axial direction and twisted about the axis. become.

Therefore, in the rotary actuator of this embodiment shown in FIG. 1, when the first electromagnetic coil 14 and the second electromagnetic coil 16 are both energized with a predetermined current, the stator 10 is However, when the lower end of the stator 10 is fixed, the upper end surface of the stator 10 rotates around the axis in accordance with the twist that has occurred. It will rotate.

Further, in this embodiment, when the first electromagnetic coil 14 is energized with current, the stator 10 and the rotor 20 which are initially separated are in contact with each other,
Then, if a predetermined current is applied to the second electromagnetic coil 16, the rotation generated on the upper end surface of the stator 10 is directly transmitted to the rotor 20.

Then, first, the first electromagnetic coil 14
If the cycle of stopping the power supply to the second electromagnetic coil and then stopping the power supply to the second electromagnetic coil and returning to the initial state is performed,
When the stator 10 finishes transmitting the predetermined rotation, it is separated from the rotor 20 to return to the initial state, and a cycle is realized, so that the rotor 20 can be appropriately rotated.

At this time, since the rotary actuator of this embodiment transmits the rotation in a state where the entire upper end of the stator 10 is in contact with the mover 20, the rotation is transmitted by utilizing the rotation distortion. It is possible to secure a large rotational torque that can be transmitted as compared with the rotary type actuator.

Since the large contact area is secured and the rotational torque is transmitted in this manner, slippage between the stator 10 and the rotor 20 during transmission of the rotation is suppressed, and the rotor 20 moves. It is possible to obtain the advantage of being able to ensure high accuracy in the rotation angle.

By the way, the rotation angle transmitted to the rotor 20 by executing the above cycle once, that is, the first angle
The torsion angle generated in the stator 10 when a predetermined current is passed through both the electromagnetic coil 14 and the second electromagnetic coil 16
Then, this φ can be expressed by the following equation.

Φ = θ ₂ +1/2 θ ₁ −90 deg (1) θ ₁ = 2 · sin ⁻¹ [L / √ {L ² + (πD) ² }] θ ₂ = sin ⁻¹ [( 1 + λ) ・ sin θ ₁ / √ {2 ・ (1+
1/2 · λ) (1- cos θ ₁ )}] where L is the entire length of the stator 10 and D is the stator 10
, Λ represents the amount of magnetostriction (extension rate) that occurs when a magnetic field is applied.

Here, for example, L = 10 mm, D = 20 mm,
When λ = 1000 ppm, the rotation of φ = 0.27 deg can be generated by performing the above-described one cycle process.

In this case, the magnetostriction amount λ of the magnetostrictive material is a value that varies according to the strength of the applied magnetic field, and is a concept that can be grasped as a function of the magnetic field strength. Therefore, the stator 10
If the total length L and the outer shape D are fixed values, the rotation angle φ in which only λ is a parameter can be grasped as a function of the magnetic field strength.

From this point of view, FIG. 3 shows the rotation angle φ per cycle of the rotary actuator of this embodiment.
Is a function of the magnetic field, but if the characteristics shown in the figure are clarified in advance, when the rotary actuator is used, the strength of the applied magnetic field is controlled, that is, the first and second magnetic fields. It is also possible to realize highly accurate control of a minute rotation angle by controlling the value of the current flowing through the electromagnetic coils 14 and 16.

As described above, the rotary actuator of this embodiment can transmit a relatively large rotational torque to the rotor 20 due to its structure, and the rotor 1 can generate a large torque.
It has the feature that the rotation angle φ per cycle can be controlled with high precision and in a minute width.

By the way, in order to drive the rotary actuator of this embodiment, it is necessary to drive the first and second electromagnetic coils 14 and 16 in the cycle described above. Figure 4
Shows an energization pattern for easily realizing such driving. As shown in FIG.
To the second electromagnetic coil 16 (FIG. 4 (B))
The desired energization pattern can be easily realized by performing the energization (FIG. 4A) with respect to (1) with a predetermined phase difference as shown in the figure.

Therefore, according to the pattern shown in FIG.
When driving the first and second electromagnetic coils 14 and 16, the rotary actuator of the present embodiment can be continuously driven, and further, the first and second electromagnetic coils 14 and 1 can be driven.
The rotation speed control of the rotor 20 can be easily realized by changing the drive frequency of the drive current applied to 6 or by changing the applied voltage, that is, the energization current.

In the above embodiment, a groove 12 is provided in the stator 10 so that the second electromagnetic coil 16 does not hinder the contact between the stator 10 and the rotor 20, and the second groove 12 is formed in the groove 12. Although the electromagnetic coil 12 is wound, the groove 12 is formed by processing the magnetostrictive material formed on the cylinder, and the protrusion of uniform height is joined to the end surface of the magnetostrictive material on the cylinder. It is also possible to form.

That is, in the rotary actuator of the present embodiment, the torsion generated in the cylindrical portion of the stator 10 produces the rotational force of the rotor 20, and the protrusion formed on the side portion of the groove 12 is , No function as a magnetostrictive material is required.

Therefore, the material of the protrusions is arbitrary, and if they are formed by joining, the productivity can be improved without causing any functional problem. Further, since these protrusions are also a region where stress is concentrated when the rotary actuator is driven, if they are made of a material having higher rigidity, such as an iron-based steel material, instead of a magnetostrictive material, durability is improved. Advantageous effects can also be obtained in terms of the above.

By the way, for a giant magnetostrictive material such as that used as the material of the stator 20 in this embodiment, if a pre-pressurization is applied in advance in the direction in which a magnetic field is applied to cause magnetostriction, It is known that a large magnetostriction can be obtained with respect to the applied magnetic field.

FIG. 5 shows applied magnetic field-displacement characteristics when three different types of pre-pressurization are applied to the stator 10 of this embodiment, and when large pre-pressurization is applied, the same characteristics are obtained. It shows that a larger displacement can be taken out with respect to the magnetic field.

On the other hand, the contact and separation of the stator 10 and the rotor 20 are controlled by utilizing the extension of the stator 10 due to the magnetic strain, and the rotor 20 is utilized by utilizing the twist of the stator 10 due to the magnetic strain. In order to configure a rotary actuator having a configuration for transmitting rotation, it is desirable that the displacement amount of the stator 10 is large from the viewpoints of securing dimensional tolerance, securing a rotation angle, and the like.

Therefore, when the rotary actuator according to the present invention is constructed, if pre-pressurization can be applied to the stator 10, it is possible to obtain more excellent characteristics than the rotary actuator shown in FIG. it can.

From this point of view, FIG. 6 shows that the pressing members 30 and 32 are arranged between the upper and lower ends of the stator 10, respectively.
Further, an example of the structure in which these pressurizing members 30 and 32 are connected by a connecting shaft 34 to secure a desired preliminary pressurization is shown.

In this case, a desired pre-pressurization can be obtained by, for example, a structure in which the connecting shaft 34 is bolted at the lower part of the pressing member 32, and the first and second electromagnetic coils 14,
If 16 is incorporated to apply a magnetic field, a large rotation angle can be obtained, and the stator 10 and the mover 20 can be obtained.
It is possible to secure a relatively wide range of assembly tolerances and the like.

[0046]

As described above, according to the present invention, torsional strain is generated in the stator itself, which is formed by molding a magnetostrictive material into a cylindrical shape, and the torsion is directly used as the rotational torque of the mover. It is possible to secure a wide contact area between the stator and the mover when operating as a rotary actuator.

Therefore, according to the rotary actuator according to the present invention, it is possible to secure a large rotary torque as compared with the conventional rotary actuator that obtains a rotary torque by causing a rotational strain on one end surface of the stator. .

Further, in the structure of the present invention, the movable element has a rotation angle substantially equal to the twist angle generated in the stator. Therefore, as compared with the conventional rotary actuator, it is possible to realize the rotation angle control more easily and with higher accuracy, and in particular, it is possible to control the minute rotation angle.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an overall configuration of an embodiment of a rotary actuator according to the present invention.

FIG. 2 is a diagram for explaining the operation of the rotary actuator of this embodiment.

FIG. 3 is a diagram showing a relationship between a magnetic field applied to the stator of the rotary actuator of the present embodiment and a rotation angle caused by the magnetic field.

FIG. 4 is an example of a drive pattern suitable for driving the rotary actuator of this embodiment.

FIG. 5 is a diagram showing applied magnetic field-displacement characteristics of a giant magnetostrictive material with preliminary pressurization as a parameter.

FIG. 6 is an example of a configuration in which pre-pressurization is applied to the stator of the rotary actuator of this embodiment.

[Explanation of symbols]

 10 Stator 12 Groove 14 First Electromagnetic Coil 16 Second Electromagnetic Coil 20 Rotor 22 Disc Part 24 Rotating Shaft 30, 32 Pressurizing Member 34 Connection Shaft

Claims (1)

[Claims] 1. A stator formed by molding a magnetostrictive material into a cylindrical shape, a first electromagnetic coil for applying an axial magnetic field to the stator, and a magnetic field circumferentially applied to the stator. A rotary actuator comprising: a second electromagnetic coil for applying a voltage; and a rotor facing the stator at a predetermined interval in the axial direction of the stator.