JPH069171B2 - Electromagnetic actuator - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electromagnetic actuator applied to various actuators.

[Prior Art] As a conventional electromagnetic actuator, a magnetic bearing using a mutual attraction force using an iron core made of a ferromagnetic material and a permanent magnet or an electromagnet has been put into practical use. On the other hand, a magnetic levitation train is being developed as a system that uses a superconducting coil to levitate using its repulsive force, but research is also being conducted on the use of superconductors in electromagnetic actuators. Therefore, the conventional electromagnetic actuator using the electromagnet is configured as shown in FIG. In the figure, reference numeral 20 is a casing made of a non-magnetic material, in which drive coils 21 and 22 are concentrically arranged with a predetermined interval. The coils 21 and 22 are connected to a driving power source via lead wires (not shown). The drive plate 23 is arranged between the two coils 21 and 22. A drive shaft 24 is attached to the drive plate 23 and is integrally configured. The drive shaft 24 is a bearing coil 2 provided above and below the drive coils 21 and 22.
The position is maintained by 5, 26. The bearing coils 25 and 26 are lead wires (not shown).
Is connected to the driving power supply via.

However, in the case of the above configuration, the driving coil 2
Since 1, 22 and the bearing coils 25, 26 are provided separately and independently, they have drawbacks such as a complicated structure, complicated assembly, and reduced reliability.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and an object thereof is to provide a highly reliable electromagnetic actuator which has a smooth operation and is easy to control and assemble. And

[Means for Solving the Problems] According to the present invention, two coils are concentrically arranged in a casing with a predetermined space therebetween, and a drive shaft provided along a central axis of the coil is provided between the two coils. Driven by a superconducting plate attached to the drive shaft so as to be located at,
With the superconducting shafts provided on the drive shaft so that the two coils face each other on both sides of the superconducting plate, the drive shaft does not deviate from the central axis of the coil before and after driving. is there.

[Operation] When an arbitrary current is applied to the two coils, a repulsive force is generated by the Meissner effect that occurs when the superconductor is placed in a magnetic field, and this becomes a driving force and a bearing reaction force, which controls the position and braking of the drive shaft. Do.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a conceptual concept of an electromagnetic actuator according to an embodiment of the present invention. And FIG. 1 (a)
Is a perspective view showing a casing with a part cut away, and FIG. 1 (b) is a longitudinal sectional view thereof. Inside the cylindrical casing 1 made of a non-magnetic material, two coils 2 and 3 are concentrically arranged with a predetermined gap (L) between them. (Fixing metal fittings, lead wires, etc. are not shown.) At this time, the driving distance (l) is l ≦ L−t ₀ , where t ₀ is the plate thickness of the superconducting plate 4 described later. The drive shaft 5 made of a non-magnetic material is integrally formed with the superconducting plate 4, the superconducting shafts 6 and 7, and is arranged between the coils 2 and 3, and the superconducting shaft 6 is located in the coil 2 and the superconducting shaft 7 is located in the coil 2. It is arranged at a position facing the coil 3. The superconducting shafts 6 and 7 have lengths (a, b) that do not deviate from the coils 2 and 3 facing each other so that a sufficient bearing reaction force can be secured at any driving position. It has a length of ≧ l and b ≧ l. Here, the superconductors of the superconducting plate 4, the superconducting shafts 6 and 7 are in a superconducting state during operation. In the figure, the arrows show the cooling concept for cooling below the critical temperature of the superconductor used. A cooling gas or liquid with a temperature below the seaside temperature is used. In this case, cooling is not required as long as superconductivity can be obtained at room temperature, such as superconducting ceramics.
The coils 2 and 3 may be normal conducting coils or superconducting coils. Further, the distance (L) between the coils 2 and 3 is naturally larger than the required drive distance, but an appropriate value is selected in consideration of the magnetic force that is the drive power determined by the current passed through the coil.

FIG. 2 is a diagram schematically showing an operation concept of the actuator having the above structure. When driving upward from the position shown in FIG. 2 (a), the coil 3 in FIG.
A predetermined current I _{B is} passed through. At this time, due to the Meissner effect peculiar to the superconductor, the skin current i ₁ flows concentrically in the superconductor plate 4 as a function of the magnetic field at the position of the superconductor, that is, the coil energization amount, and the magnetic field based on the skin current i ₁ and the coil 3 driving force Fa by repulsion to the original magnetic field based on the current I _B flowing through the
Occurs and is driven upward in the figure. Here, assuming that an average magnetic field between the coil 3 and the superconducting plate 4 is B ₃₄ , Fa ∝ A / 2μ ₀ · B ₃₄ ² (where A is the area of the superconducting plate 4 and μ ₀ is the vacuum permeability). Becomes Strictly speaking, it is obtained from the integral form for the magnetic field B ₃₄ which is a function of position. The current _{I A} of the coil 2 to the superconducting shafts 6 and 7, the skin currents _i 2, _{i 3} flows concentrically according to the current _{I B} and the like of the coil 3, the original current _I A and the magnetic field based on this, repulsion between the magnetic field due to I _B (hereinafter, referred to as the bearing reaction force) by and held in the most stable center position. FIG. 2B shows a state in which the drive shaft is driven in this way and the superconducting plate 4 approaches the coil 2. At the same time that the repulsive force from the coil 3 decreases due to the distance from the coil 3, an increase in the repulsive force between the magnetic field of the coil 2 and the magnetic field due to the skin current i ₁ of the superconducting plate 4 is superimposed, so that the driving force Fb is the initial value. It becomes considerably smaller than the value Fa. Here, if an average magnetic field between the coil 3 and the superconducting plate 4 is B _34, and an average magnetic field between the coil 2 and the superconducting plate 4 is B ₂₄ , F
Biarufaei / a ^{_{2μ 0 · (B 34 2 -B}} 24 2). Then, as shown in FIG. 2 (c), the repulsive forces reach the final position due to the balance between the repulsive forces. However, the above does not consider the direction of action of gravity. In this way, the drive shaft 5 is driven upward.

Next, driving in the opposite direction is performed by the same principle if the energization states of the coils 2 and 3 are exchanged. However, it goes without saying that gravity may be added or subtracted depending on the installation direction.

FIG. 3 relates to a case where superconducting coils are used for the coils 2 and 3 as another embodiment. In this case, a method of flowing a current I _A to the coil 2 by applying a current I _B in the coil 3 as in the above embodiment, a method is conceivable which is not energized to the coil 2. Hereinafter, a method in which the coil 2 is not energized will be described. In FIG. 3 (a), with respect to the magnetic field generated by passing the current I _B through the coil 3, i ₁ is applied to the superconducting plate 4, i ₂ , i ₃ is applied to the superconducting shafts 6 and 7, and superconductivity is caused by the Meissner effect. Skin currents such as i _A and i _A ′ flow through the coil 2. Due to the magnetic field based on these skin currents, the same driving force and bearing reaction force as those described with reference to FIG. 2 can be obtained. The situation in FIGS. 3 (b) and 3 (c) is also understood in the same manner as in FIGS. 2 (b) and (c).

When driving in the reverse direction, the current I is applied to the coil 2 contrary to the above.
Energized and _A, is driven by the coil is not energized 3.

In the description of the above embodiment, the skin currents i ₁ , i ₂ ,
Although i ₃ , i _A , i _A ′, etc. are described as being constant numerically and spatially, they have a distribution even momentarily and spatially depending on the energizing current and driving position. However, only representative ones are shown.

Then flowing current _{(I A,} I _B) by time history control, illustrating the universal values and without example driving force. For simplification, the forward drive in the case where the current I _B (t) is passed through the coil 3 and the coil 2 is not energized is taken as an example. At this time, the driving force F (t) at time t is _{generally, F (t) αI B (} t) 2 / r
There is a relationship of _B (t) ⁶ . r _B (t) is the distance from the coil 3 of the superconducting plate 4 at time t. Therefore, by detecting the distance r _B (t) at each time, I _B (t) ∝r
_{When the} energizing current I _B (t) is controlled by the control function of _B (t) ³ , the driving force F (t) can be made a substantially constant value. Similarly, the desired driving force can be set by selecting the control function. In practice, since a braking force due to the interaction with the coil 2 acts, the energizing current I _B (t) is controlled based on a strict relational expression taking this into consideration. Furthermore, I _B
(T) and I _A (t) may be controlled simultaneously.

FIG. 4 shows an embodiment of the time history control method. The position signal detected by the position detector 8 at an arbitrary time t is transmitted to the computer 9, and the initial position setting information and the above L, t
R _A (t) and r _B (t) are obtained from ₀ by the addition / subtraction calculation. Initial target setting information (required driving force, etc.) speaker 10
Based on the information from and the above r _A (t) and r _B (t),
_A predetermined function calculation is performed by the computer 11 and I _A (t), I _B
(T) is determined, and the energizing currents from the power sources 12 and 13 to the coils 2 and 3 are controlled based on this instruction.

[Effects of the Invention] As described above in detail, according to the present invention, the drive shaft and the drive plate for driving the drive shaft are made of a superconducting material, so that the drive shaft can be easily controlled and the connection of the movable portion is required. Therefore, the structure can be simplified and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view and a vertical sectional view showing a partially cutaway view of an electromagnetic actuator according to an embodiment of the present invention, FIG. 2 is an operation conceptual diagram for explaining the operation of the embodiment, and FIG. FIG. 4 is a block diagram showing a configuration of a peripheral portion for performing control of one embodiment of the present invention, and FIG. 5 is a configuration of a conventional electromagnetic actuator, for explaining the operation of another embodiment. FIG. 1 ... Casing, 2, 3 ... Coil, 4 ... Superconducting plate, 5 ... Drive shaft, 6,7 ... Superconducting shaft, 8 ... Position detector, 9, 11 ... Computer, 10 ... Transmission Vessel, 12, 13 ... Power supply.

Claims (1)

[Claims] 1. A casing, two coils provided in the casing and concentrically arranged at a predetermined interval, a drive shaft provided along a central axis of the two coils, and the two coils. A superconducting plate mounted on the drive shaft so as to be located between the coils; and a superconducting shaft provided on the drive shaft so as to face each of the two coils on both sides of the superconducting plate. Characteristic electromagnetic actuator.