JPH0552134B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention selectively energizes or moves current through superconducting coils arranged in segments, and drives a movable member by a permanent magnetic field formed by the persistent current. ,
This invention relates to a linear actuator that is stopped.

[Prior Art] Electrical technology is used to determine the stopping position of a movable member of an actuator steplessly or stepwise at fine discrete pitches, and to drive the moving member quickly from the stopping point to the next arbitrary stopping point. Linear actuators have a wide range of applications as they allow for control.
For example, it can generally be used as a drive source for an X stage or an XY stage, and specific examples include cases where it is used as a stage for a machine tool or a pen drive device for an XY plotter. Also, in the category of electronic equipment, for example, head feeding mechanisms for magnetic disk memories such as floppy disks and hard disks,
It is used in similar head feeding mechanisms for optical disks. Furthermore, with the advancement of automatic focus detection technology, electronic drive control mechanisms are becoming commonplace for objective lenses in optical equipment such as still cameras and video cameras. It can be used as a drive source to perform similar straight-line control, including other examples.

To generally explain such an electrically controllable linear drive system using the example of FIG. 7, reference numeral 11 in the figure is a fixed member for supporting the entire system. This same member 11 has a movable member 15 which will be described later.
The motor 12 is provided with a motor 12 that applies rotational force to the motor 12, and a threaded portion 13a that converts rotational motion into linear motion.
The rotation of the motor 12 is transmitted to a movable member 15 through a gear transmission system 14, and the movable member 15 has a threaded portion 13b that is removably engaged with the threaded portion 13a.
is provided, and as a result of rotation, it moves in a straight line. The positioning of the movable member 15 is generally performed using an encoder (not shown), which may be optical, mechanical, electrical, or magnetic. A method is used to control the driving direction and driving force of the motor based on the position information output by the motor.

The method illustrated in FIG. 7 is a method adopted when the movable member 15 may rotate, and is specifically preferably used for focus adjustment of an optical lens, zooming, etc. It is also possible, of course, to provide a second movable member whose axial rotation is restricted beyond the movable member 15 and to link the axial movement, and to design the mechanism so that only linear motion is transmitted. Such examples are often employed in head feeding mechanisms of disk devices. Note that a similar linear drive system can be constructed by using a rack and pinion type gear combination or using linear gears.

[Problems to be solved by the invention] The above-mentioned mechanism that has been used conventionally has a motor, a rotation-linear conversion system of a power transmission system, a movable member bearing, etc. as essential elements, and is composed of a linkage structure of each of these elements. There are inherently unavoidable problems with the mechanism. That is, there are issues such as energy efficiency, spatial size constraints, driving speed, stability at a stopping point, and furthermore, feed accuracy.

For example, the energy utilization efficiency of conventionally used mechanisms is extremely low, and this is due to the heat generated by the motor, friction loss, loss in the power transmission system, loss in the rotation-linear conversion system, etc., as well as the stability of the position when stopped. This is because a structure with a frictional engagement relationship is adopted between the movable member and the fixed member in order to obtain flexibility. In order to ensure positional stability when stopping, it is possible to use strong interlocking gears, screws, etc., and independent sliding members, but friction is essentially required to maintain stable stopping when stopping. shall be. Although there is a method of inserting a friction member only when the vehicle is stopped, such a configuration impairs the responsiveness of the drive. In applications that require quick response, it is common to achieve this requirement by applying friction and applying strong power to overcome the friction. There is also an example of an automatic focusing lens for a video camera that continues to be energized and operates continuously even when the lens is stopped. Since the true energy required to stop driving a movable member is only the acceleration and deceleration energy corresponding to the mass of the movable member, the conventional drive method can be said to have a large loss.

Actuators used in electronic devices, portable optical devices, and the like are generally required to be compact, but compactness and drive speed are contradictory requirements. For example, in order to obtain high-speed response, it is necessary to use a motor with a powerful torque, but this results in an increase in the size of the device. Furthermore, since electromagnetic motors are current driven, the large current needed to obtain strong torque leads to thicker windings, which in turn leads to larger motors, and also promotes larger mechanical parts. For this reason, small precision devices such as those described above are subject to many restrictions in terms of system configuration.

Taking a still camera equipped with an automatic focus detection device as an example, and considering the above problems more specifically, we can see that due to miniaturization, it takes a considerable amount of time to drive the lens,
Continuous shooting frame speed limitations, delays in tracking moving subjects, etc. may occur. Furthermore, even in the case of normal automatic focus detection photography, a lens with a long focal length requires a large amount of lens drive from the initial position to the in-focus point, so it takes time, and the shutter cannot be released at the moment the photographer intended. Even the automatic focus adjustment mechanism of a video camera has a problem in that it cannot follow the movement of the subject or the movement of the screen framing due to the slow driving speed of the lens. Furthermore, in disk memory devices, there are limits to high-speed head tracking, which often places constraints on system configurations. For example, access time becomes longer in a system with a large number of tracks, and real-time performance deteriorates when performing integrated processing on data from multiple tracks. Particularly when handling analog video data such as video discs and still video floppies, integrated multitrack processing becomes difficult.

For the reasons mentioned above, if a linear actuator with high energy utilization efficiency, compact size, and high output characteristics could be obtained, it would be possible to reduce battery consumption of small portable devices, reduce heat generation, miniaturize devices, and improve system configuration. This brings extremely multifaceted benefits such as an increase in the degree of freedom for

[Means for Solving the Problems] The linear actuator of the present invention is characterized by having a first member and a second member supported so as to be movable relative to each other in one direction, and the second member is formed to surround the first member, and either the first member or the second member includes a plurality of superconducting coils for movement spaced apart in the movement direction, The other is provided with a moving magnet magnetized and disposed in the moving direction, and switches the energization of the plurality of moving superconducting coils to perform relative movement, and furthermore, the A non-contact type bearing using the Meissner effect is constructed by a bearing superconducting coil disposed on one of the two members and a bearing magnet disposed on the other.

The linear actuator of the present invention allows a large current to flow through the superconducting coil and realizes highly responsive driving.
Since the superconducting coil has no heat loss, it can be stopped at a stable position by continuously passing a persistent current through the coil at the stop position. Power utilization efficiency can be improved by transferring a circular current between a plurality of superconducting coils that can be selectively energized. Further, in the linear actuator of the present invention, the mechanism for stably holding the position at the stop position is the binding of the magnet by the permanent magnetic field generated by the superconducting coil, not friction. There is no friction between them. The linear actuator of the present invention does not require a mechanical power transmission mechanism, and the only frictional resistance is bearing friction and air viscosity. If a low-friction bearing is used, the sliding loss of the movable member is extremely reduced. In particular, if a superconducting coil is also used as a superconducting bearing that applies the Meissner effect, air bearings can be easily introduced.

[Example] An example in which the linear actuator of the present invention is used to drive an optical lens will be described below.

FIG. 1 shows a schematic diagram of this embodiment. The member 21 is a fixed lens barrel, and is mechanically fixed to a camera body (not shown) via a mount portion 27. An optical lens may be arranged inside the fixed lens barrel 21. The mount section 27 has electrical contacts for communicating information with the camera body, and also has contacts for receiving power from the camera body. A control circuit (not shown) is built inside the fixed lens barrel 21, and calculates the lens drive amount, target stop position, etc. based on command information from the main control circuit of the camera body. A plurality of superconducting coils 23 ₁ , 23 ₂ , 23 ₃ , etc. arranged at predetermined intervals in the axial direction of the lens 21 are selectively energized to drive and stop the lens. Note that the sharing ratio of the total amount of information processing calculations between the camera side and the lens side may be determined as appropriate in designing the system configuration.

Reference numeral 22 denotes a movable lens barrel, which has an optical lens (not shown) for focus adjustment therein, and is floatingly housed within the cylinder of the fixed lens barrel 21.

The movable lens barrel 22 also has an annular magnet 24 magnetized in the direction of the arrow 27 in the figure.
It is possible to move back and forth within the fixed lens barrel 21 by driving it with a strong magnetic field of a superconducting coil on the fixed lens barrel 21 side. Further, the movable lens barrel 22 is provided with at least two annular magnets 25 ₁ and 25 2 magnetized in the radial direction 26 of the lens barrel at a position relatively close to the end of the lens barrel, and the magnets 25 1 and 25 ₂ are magnetized in the radial direction 26 of the lens barrel. Superconducting coil 2
3, the movable lens barrel 22 is floatingly supported within the fixed lens barrel 21, thereby forming a non-contact type bearing. In this case, the width of the annular magnets 25 ₁ , 25 ₂ etc. needs to be wider than the pitch of the superconducting coil 23 in order to obtain a stable Meissner effect. Note that the relative relationship between the inside and outside of the superconducting coil and the magnet may be reversed, and the principle of operation does not change even if the superconducting coil is provided in the movable lens barrel and the magnet is provided in the fixed lens barrel.

Next, the principle of movement of the movable lens barrel 22 of the lens system will be explained using FIGS. 2 and 3. FIG. 2 is a cross-sectional view showing the positional relationship between the superconducting coil 23 and the annular magnet 24. Reference numerals 31, 32, etc. indicate optical lenses for focus adjustment inside the movable lens barrel 22. There is more than one method for driving the annular magnet 24 with a coil magnetic field, and it can be roughly divided into a method using the repulsive force of the magnetic field, a method using the attractive force, and a method in which both of them work together at the same time. Here is an example. FIG. 3a shows a state in which a persistent current flows through the superconducting coil _23j and is stopped as it is attracted by the magnetic field. A current flows only in the coil 23 _j , and no current flows in the other coils, or a relatively small current flows in the other coils. In this case, the magnetic field produced by the magnet 24 and the magnetic field produced by the coil 23 _j are in the same direction near the magnetic poles of the magnet, and the magnet is dynamically most stable in the vicinity of the coil.

As is well known, superconducting coils have no Joule loss due to their characteristics, so once they reach a stopped state, a circular current continues to flow forever, keeping the magnet fixed, while there is no need to supply current to the coils. In addition, since a large current can flow, the magnetic field formed is strong, and a coil with a small number of turns can effectively bind the magnet. For example, if a superconducting wire with a critical current of 10 ⁴ A/mm ² is used, a current of approximately 10 ² A can be passed through a coil with a diameter of 0.1 mm, and the pitch of the feed can be divided into small pieces by arranging the coils densely. The required lens feed pitch varies depending on the lower aperture value, but it is at least 0.1mm.
Often requires an order.

Next, a case will be described in which the movable lens barrel 22 is moved in the axial direction.

To drive the magnet 24 from the vicinity of the coil 23 _j in the direction of the coil 23 _j+1, move the coil 2 as shown in FIG. 3b.
It is sufficient to reduce the ring current of 3 _j and start flowing the ring current in the same direction to the coil 23 _j+1 . The magnet 24 is attracted by the magnetic field created by the coil 23 _j+1 and starts moving. When this energization switching process is completely completed, the current in coil 23 _j becomes 0, and coil 23 _j+1
If the current becomes dominant, the magnet 24 will move the coil 23
It stops stably near _j+1 . In this series of processes, the current flowing through the coil 23 _j+1 may be newly supplied from the power supply, or the current flowing through the coil 23 _j may be moved by a known method. In that case, for example, JP-A-59-61443, JP-A-61-109434
The technique disclosed in et al. can be used. This method can significantly reduce energy loss.

In any case, to carry out this type of energization switching control, a switch (preferably a superconducting switch) is required in the superconducting coil.

According to the above drive method, the number of turns of each divided superconducting coil can be reduced, and in this embodiment, where the coil inductance is small, extremely high-speed drive control can be performed. In other words, the rise of the coil current when a constant voltage is applied is inversely proportional to the inductance, so the smaller the inductance, the faster the drive can be performed.

In the driving method of this embodiment, if the current movement is stopped midway and, for example, a current equal to the superconducting coil 23 _j and superconducting coil 23 _j+1 in FIG. 3 is passed, the movable lens barrel 22 can be stopped at an intermediate position. . Furthermore, by controlling the current division to an arbitrary ratio, it is possible to continuously stop not only at intermediate positions but also at arbitrary points. The restraining force of the movable member when stopped depends on the shape of the coil, the shape of the annular magnet, the relative positional relationship between the two, the coil magnetic field, the magnetic field of the annular magnet, etc., and can be designed to a desired value.

[Other Examples] A second example in which the present invention is applied to an optical lens will be described with reference to FIG.

As in the previous embodiment, the fixed lens barrel 21 is fixed to the camera body (not shown) via the mount section 27.
On the other hand, the movable lens barrel 22 has annular magnets 25 ₁ and 25 ₂ magnetized in the direction of the arrow 26 in the figure, and floats due to the Meissner effect between these magnets 25 ₁ and 25 ₂ and the superconducting coil of the fixed lens barrel 21. is supported by

That is, the fixed lens barrel 21 of this embodiment has two superconducting coil groups 53 ₁ , 53 ₂ , . . . with different pitches.
and groups 58 ₁ , 58 ₂ , . . . Correspondingly, the movable lens barrel has an annular magnet 54 and annular magnet groups 59 ₁ , 59 ₂ , . Then, by selectively energizing the first superconducting coil groups 53 ₁ , 53 ₂ , . . . , the position of the annular magnet 54 is controlled to perform coarse feeding movement, while the second superconducting coil group 58 ₁ , 58 ₂ By selectively energizing ..., the positions of the annular magnet groups 59 ₁ and 59 ₂ can be controlled and fine movements can be performed. All of the second superconducting coil groups 58 ₁ , 58 ₂ . . . in this example are arranged within a length equivalent to one pitch of the coarse-pitch coil groups 53 ₁ , 53 ₂ , . Further, the annular magnet groups 59 ₁ , 59 ₂ , . . . are arranged at the same spacing as the arrangement pitch of the coarse-pitch first superconducting coil groups 53 ₁ , 53 ₂ , .
Only those objects are subject to position control. This combination of two types of coils and magnet systems with different pitches has the advantage of reducing the number of members when it is desired to move over a wide range with high feed accuracy. Furthermore, by jointly controlling the drive current by dividing it between adjacent coils as in the embodiment described above, the feeding accuracy can be further improved.

Next, a third embodiment in which the present invention is applied to a magnetic head feeding mechanism will be described with reference to FIG.

In the same figure, 61 is a fixed block, and a movable block 62 is floatingly accommodated in a hollow portion inside. This fixed block 61 has three superconducting coils 63 ₁ , 63 ₂ , 63 ₃ and coiled superconducting sheets 64 ₁ , 64 ₂ that serve as superconducting members of a non-contact bearing utilizing the Meissner effect.

The movable block 62 housed inside the fixed block 61 includes a plurality of annular magnets 65 ₁ , 65 ₂ ,
..., and a spring 66 with a magnetic head slider 67 attached to its tip. The strength, dimensions, etc. of this spring 66 are constants that depend on the flying height of the head, the relative speed of the head disk, etc. This movable block 62 includes annular magnets 65 ₁ , 65 ₂ . . .
It has a structure in which the annular magnets 65 ₁ , 64 ₂ are suspended in the air and supported in a floating manner by the magnetic repulsion between the superconducting sheets 64 1 and 64 ₂ on the fixed block side.
65 ₂ ... is indicated by arrow 68 in the figure to increase drive efficiency.
Since it is magnetized in the same direction, the magnetic efficiency of air bearings is slightly lower. It is also possible to configure the direction of magnetization to be perpendicular to the surface of the movable block, but in this case, the air bearing performance improves, but the magnetic efficiency of the drive decreases, and it is necessary to obtain the same acceleration and deceleration effects. Current must be passed through the coil. Magnetic efficiency can be improved by functionally separating the drive and Meissner bearings and using dedicated components.

Unlike the above-mentioned embodiments relating to optical lenses, this embodiment relating to a magnetic head does not allow rotation about the drive direction as an axis. Therefore, a shape that inhibits some kind of rotation is required, and in this embodiment, a rectangular block cylinder is adopted as an example.

Actuator driving in this embodiment is performed as follows. FIG. 6a shows a state in which a persistent current flows through the superconducting coil ₆₃₁ , binding the magnet _65j and stopping the movable block. Next, to move the movable block 62 to the right in the figure, (b) gradually move the current in the coil 63 ₁ to the coil 63 ₂ , or reduce the current in the coil 63 ₁ ,
At the same time, the current in the coil 63 ₂ is gradually increased from zero, and the magnet 65 _j is finally restrained under the coil 63 ₂ .

(c) Next, perform the same operation between coils 63 ₂ and 63 ₃ , and finally apply current only to coil 63 ₃ ,
As a result, a state is reached in which the magnet _65j is restrained under the coil ₆₃₃ .

(d) Transfer the persistent current from coil 63 ₃ to coil 63 ₁ so that coil 63 ₁ becomes magnet 65 _j-1
to restrain. At this time, the magnet does not move.

You can repeat these steps as appropriate. To move in the opposite direction, the steps can be performed in the opposite direction from a state where current flows only through the coil ₆₃₃ . When using this two-phase clock method, three superconducting coils are arranged at twice the density of the annular magnet pitch, and when the current is moved or increased or decreased at each step, the current flows through the two coils. It is better to provide an intermediate state where the flow is flowing.

The head feeding mechanism as described above is not limited to magnetic heads, but can be similarly applied to disk systems based on optical or electrostatic principles.

[Effects of the Invention] As explained above, the linear actuator of the present invention is capable of extremely high-speed access operation, is highly accurate, lightweight, and has high energy efficiency, and is an electrically controllable actuator. It can be applied to linear motion control such as optical lens driving, head feeding, stage driving, etc. As the superconducting material used in the actuator of the present invention, it is desirable to use a material with a critical temperature as high as possible because of its wide practical application, but this does not particularly limit the present invention. The actuator of the present invention can be used under various cooling conditions depending on the properties of the superconducting material used. for example,
It may be an inert gas cooled with liquid nitrogen,
Superconducting materials with high critical temperatures can be used at room temperature or even higher temperatures.

In the embodiment described in the present invention, the drive system member, that is, the superconducting coil (or magnet) is also used as a component of the superconducting bearing, but this is an example of realizing the present invention, and is particularly The configuration is not limited to this.

The effects of the present invention result from the combination of the benefits of extremely reduced mechanical losses provided by the superconducting bearing and the benefits of the strong magnetic field and fast current rise provided by the annular persistent current of the divided superconducting coils that can be selectively energized. With this configuration, it is possible to provide a novel linear actuator with features such as high speed drive, high precision, small size, light weight, and high energy efficiency.

[Brief explanation of the drawing]

Figure 1 shows an example of the general configuration of an embodiment in which the linear actuator according to the present invention is applied as a drive means for a lens barrel, with the fixed lens barrel and movable lens barrel in an expanded state. FIGS. 3A, 3B, and 3C, which are partially sectional views, are diagrams for explaining the driving principle of the apparatus shown in FIG. FIG. 4 is a diagram showing an example of a general configuration of another embodiment in which the linear actuator according to the present invention is applied as a driving means for a lens barrel, with the fixed lens barrel and the movable lens barrel in an expanded state. FIG. 5 is a diagram showing an example of the general configuration of an embodiment in which the linear actuator of the present invention is applied as a magnetic head feeding means, with the fixed block and movable block in an expanded state, and FIG. 6 a, b, c, and d are FIG. 5 is a diagram for explaining the driving principle of the configuration device. FIG. 7 is a diagram illustrating an example of a general configuration using a conventional linear actuator, with the fixed member and movable member in an expanded state. 11...Fixing member, 12...Motor, 13a...
...Threaded part, 13b...Threaded part, 14...Gear transmission system, 15...Movable member, 21...Fixed lens barrel, 22
...Movable lens barrel, 23 ₁ , 23 ₂ ...Superconducting coil,
24... Annular magnet, 25 ₁ , 25 ₂ ... Annular magnet,
27...Mount part, 53 ₁ , 53 ₂ ... Superconducting coil, 54... Annular magnet, 58 ₁ , 58 ₂ ... Superconducting coil, 59 ₁ , 59 ₂ ... Annular magnet, 61...
Fixed block, 62...Movable block, 63 ₁ ,
63 ₂ , 63 ₃ ... superconducting coil, 64 ₁ , 64 ₂ ...
…Superconducting coil, 65 ₁ , 65 ₂ … Annular magnet, 6
6...Spring, 67...Slider.

Claims (1)

[Claims] 1 has a first member and a second member supported so as to be relatively movable in one direction, the second member is formed to surround the first member, and the first member
Either one of the member or the second member is provided with a plurality of superconducting coils for movement spaced apart in the movement direction, and the other is a movement magnet magnetized and arranged in the movement direction. a superconducting coil for a bearing, which switches energization to the plurality of superconducting coils for movement to perform relative movement, and further includes a superconducting coil for a bearing disposed on either the first member or the second member. A linear actuator characterized in that a non-contact type bearing using the Meissner effect is constructed by a bearing magnet placed on one side and the other side.