JPH06284670A - Linear actuator - Google Patents

Abstract

PURPOSE:To allow highly accurate control and to realize downsizing while enhancing general purpose performance by disposing a pair of driving coils on the stator side and a radially magnetized tubular permanent magnet on the mover side. CONSTITUTION:When predetermined currents are fed in same direction through inner and outer driving coils 4, 2 constituting a stator 1, the currents circulate through inner and outer yokes 5, 3 where the coils 4, 2 are disposed. Consequently, a so-called inclining field having field strength increasing from the axial center toward the opposite end parts is formed in the air gap. When a radially magnetized tubular permanent magnet 8 is disposed in thus air gap, thrust is generated in the permanent magnet 8 through interaction of the field and the magnetic moment of the permanent magnet 8 itself and the mover 7 is moved linearly in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator, and more particularly, by disposing a pair of drive coils on the stator side and a cylindrical permanent magnet magnetized in the radial direction on the mover side, The present invention relates to a linear actuator which has high versatility, is relatively simple in structure, and can be reduced in size and weight.

[0002]

2. Description of the Related Art As a linear actuator, a voice coil motor (VCM) conventionally used as a magnetic head positioner of a hard disk drive (HDD) device is known. In this voice coil motor (hereinafter referred to as VCM), since the mover is composed of a coil and a bobbin supporting the coil and the mover itself is lightweight, it has excellent responsiveness and precise position control. It has advantages such as being possible. However, since the VCM itself has been improved with a focus on its adoption in hard disk drive devices (hereinafter referred to as HDD devices),
It is hard to say that the configuration is necessarily suitable for use in applications other than the HDD device.

The applicant of the present application has previously proposed various types of devices such as a precision positioning device, an NC control device for hydraulic and pneumatic valves, a robot arm, an assembly device, etc., which takes advantage of the inherent advantages of the VCM for the purpose of expanding the applications of the VCM. A highly versatile linear actuator that can be used for various purposes has been proposed (JP-A-4-1016).
57). One example thereof will be described with reference to FIGS. 6a and 6b. FIG. 6a is a side view of the linear actuator,
FIG. 6b is a partially longitudinal front view. The stator 20 includes a cylindrical outer yoke 21, a cylindrical inner yoke (center yoke) 22, a yoke portion that concentrically integrates these and a side yoke 23 that magnetically connects them, and a cylindrical portion. It is constituted by a cylindrical permanent magnet 24 magnetized in the radial direction and fixed inside the outer yoke 21. The mover 25 is composed of a triangular pyramid-shaped bobbin 26, a coil 27 fixed to the outer peripheral portion of the inner end surface of the bobbin 26, and an output shaft 28 inserted and fixed to the central portion of the inner end surface of the bobbin 26. . 29 in the figure
Is so that smooth movement is not hindered by air trapped in the mover 25 when the mover 25 moves.
It is an air vent through hole formed at a predetermined position of the bobbin 26. The mover 25 is linearly movable via an output shaft 28 supported by bearings 31 arranged at both ends of the through hole 30 in the central axis direction of the inner yoke 22. Reference numeral 32 in the figure is a lead wire for supplying a current to the coil 27, and a controller (not shown) via the connector 33.
Connected to. In this configuration, the mover 25
It is necessary to dispose a rotation prevention mechanism on the actuator side or the controlled object side so that does not rotate about the output shaft 28 during linear movement.

In the linear actuator having the above structure, a uniform magnetic field is axially formed in the space formed by the inner peripheral surface of the permanent magnet 24 and the outer peripheral surface of the inner yoke 22 which form the stator 20. When a required current is applied to the coil 27 that is formed and placed in the gap,
Thrust is generated in the mover 25 by the interaction between the magnetic field and the current. Therefore, the mover 25 linearly moves in proportion to the input current to the coil 27, and it becomes possible to highly accurately control the movement of the controlled object arranged outside the linear actuator via the output shaft 28. .

In the above VCM type linear actuator, the permanent magnet is arranged on the stator side and the coil is arranged on the mover side, but recently, FIGS. 7a and 7b are used.
The so-called MM type (Mov
ing Magnet Type) linear actuators have been researched and developed. 7a is a front view and FIG. 7b is a side view. That is, a pair of rod-shaped yokes 40 each having a rectangular cross section and arranged in parallel with each other to form a predetermined space.
a, 40b, and a driving coil 41a, 41b wound on the outside thereof in the form of a solenoid so as to constitute a stator, and in the gap, the same direction as the facing direction of the rod-shaped yokes 40a, 40b (vertical direction in the figure) It is a linear actuator having a structure in which a mover made of a permanent magnet having a rectangular cross section magnetized in is arranged. In such a configuration, when a current I is applied to the drive coils 41a and 41b in the directions indicated by arrows a and b, respectively, in the gap between the pair of rod-shaped yokes 40a and 40b, both ends of the gap from the axial center are formed. A so-called gradient magnetic field is formed in which the magnetic field strength increases as it moves to the part. When the permanent magnet to be the mover is arranged in the gap where the gradient magnetic field is formed, a thrust is generated in the permanent magnet due to the interaction between the magnetic field and the magnetic moment of the permanent magnet itself, and the axial direction (X in the figure). Direction) move linearly.

[0006]

In the VCM type linear actuator described above, the magnetic circuit portion forming the stator and the coil forming the mover are arranged in the bearing and the mover arranged in the magnetic circuit. Since they are integrated via the output shaft, they have come to be widely used in addition to the conventional HDD device by effectively utilizing the advantages of the VCM itself. However, recent linear actuators are required to be more compact and lightweight and to be controlled with high precision, and it has become difficult for the VCM type linear actuator having the above-mentioned configuration to satisfy those requirements in a specific application. . On the other hand, although various improvements have been made also in the MM type linear actuator, since the above-mentioned configuration is the basic, the thrust itself generated in the mover is small, and it is difficult to employ it in a wide range of applications.

The present invention is capable of highly accurate control required for the recent linear actuators as described above,
The purpose of the present invention is to provide a linear actuator that can be made compact and lightweight and has high versatility.

[0008]

As a result of various studies to achieve the above-mentioned object, the present invention has the VC described above.
The present invention has been completed by discovering that synergistic effects that cannot be predicted only by the respective linear actuators can be obtained by positively utilizing the advantages of the M-type linear actuator and the MM-type linear actuator. That is, according to the present invention, an outer yoke formed by winding a driving outer coil inside and an inner yoke formed by winding a driving inner coil outside are concentrically arranged via a spacer made of a non-magnetic material. And a radial outer surface of which faces the driving outer coil, an inner surface of which faces the driving inner coil, and which is externally fitted to the inner yoke so as to be movable in the axial direction. And a mover made of a cylindrical permanent magnet magnetized in a direction.

[0009]

The operation of the linear actuator of the present invention will be described based on an embodiment shown in FIG. 1 is a front view in vertical section. In FIG. 1, reference numeral 1 denotes a stator, which has a cylindrical outer yoke 3 formed by winding a driving outer coil 2 in a solenoid shape on an inner side, and a driving inner coil 4 arranged in a solenoid shape on an outer side. The cylindrical inner yoke 5 is formed so as to be concentrically integrated with the substantially disk-shaped spacer 6 made of a non-magnetic material such as aluminum or brass. Reference numeral 7 denotes a mover, the outer peripheral surface of which faces the driving outer coil 2, the inner peripheral surface of which faces the driving inner coil 4 and which is fitted onto the inner yoke 5 to move in the axial direction. A cylindrical permanent magnet 8 magnetized in a radial direction which is arranged as possible, and a magnet holder 9 made of a lightweight non-magnetic material such as aluminum for holding the cylindrical permanent magnet 8.
Further, it is composed of an output shaft 10 which is inserted and fixed in the central portion of the magnet holder 9. In addition, mover 7
Is linearly movable via an output shaft 10 pivotally supported by bushes (bearings) 12 arranged at both ends of the through hole 11 in the central axis direction of the inner yoke 5. The electric current is supplied to the driving outer coil 2 and the driving inner coil 4 from the outside of the actuator through a lead wire drawing hole (not shown) formed in the spacer 6. In this configuration, since the coil is not disposed on the side of the mover 7, smooth movement of the mover 7 is not hindered by the lead wire or the like, and the mover 7 is intentionally operated.
Although it is not necessary to dispose the rotation prevention mechanism, it is desirable to select whether or not to dispose the rotation prevention mechanism on the actuator side or the control target side according to the control target.

In the linear actuator having the above structure, the driving outer coil 2 and the driving inner coil 4 constituting the stator 1 are in the same direction (for example, the coils 2 and 4 are both clockwise or counterclockwise). Direction)
When a predetermined current is applied, the current flows between the outer yoke 3 and the inner yoke 5 where the coils 2 and 4 are arranged. Due to these magnetic fluxes, a so-called gradient magnetic field is formed in the air gap, in which the magnetic field strength increases as it moves from the axial center to both ends. When the cylindrical permanent magnet 8 that is magnetized in the radial direction and that constitutes the mover 7 is arranged in the space where the gradient magnetic field is formed, the permanent magnet is generated by the interaction between the magnetic field and the magnetic moment of the permanent magnet 8 itself. A thrust force is generated at 8, and the mover 7 linearly moves in the axial direction (left-right direction in the drawing).

The shape of each member constituting the actuator, the means for integrating the stator 1 and the mover 7 (bearing arrangement means), etc. are not limited to the shapes and means shown in FIG. As shown in FIG. 2, the holder 9 also has a triangular pyramid-shaped tip and an air vent through hole 13 is formed at a predetermined position to reduce the weight of the magnet holder 9 and to move the mover 7 when the mover 7 moves. It is desirable to consider that the air trapped inside does not hinder the smooth movement. The cylindrical permanent magnet 8 that is magnetized in the radial direction and that constitutes the mover 7 does not necessarily have to be configured as an integral product, and may be a configuration in which a plurality of cross-sectional sector-shaped permanent magnets are integrated in a cylindrical shape. Further, the effect of the present invention can be obtained by using any known material such as a ferrite magnet and a rare earth magnet as the material of the permanent magnet, but the magnetization (or residual magnetic flux density Br) is particularly large and the effect is high. A rare earth-iron-boron magnet having a large magnetic force Hc is effective.

As is clear from the above description, the technical concept of the MM type linear actuator shown in FIG. 7 is used as the basic operating principle of the linear actuator of the present invention. However, as described above, although the thrust of the original MM type linear actuator is not very large, in the linear actuator of the present invention, each configuration of a pair of coaxially arranged yokes, a pair of drive coils and a cylindrical permanent magnet is used. By arranging the members effectively, it becomes possible to efficiently apply a magnetic field to the permanent magnets forming the mover, and the heat generated from the driving outer coil 2 and the driving inner coil 4 causes these coils to move. Since the temperature rise of the coils 2 and 4 can be suppressed by being radiated to the outside of the actuator through the outer yoke 3 and the inner yoke 5 which are arranged, the temperature rise of the coil can be suppressed as described in detail in the following embodiments. It is possible to increase the value of the low and substantially continuous energizing current, and to increase the thrust in practical use. In particular, regarding the heat dissipation of the coils 2 and 4, respectively, the air in and out through the air venting through hole 13 formed in the magnet holder 9 shown in FIG. Adopting certain aluminum etc. is also a factor that enhances the heat dissipation effect,
Further, if necessary, the outer periphery of the outer yoke 3 and the outer surface of the spacer 6 may be processed into a fin shape, or fins made of separate members may be arranged at predetermined positions or the entire outer periphery to further enhance the heat dissipation effect. Become. FIG. 1 shows a configuration in which the output shaft 10 connected to the mover 7 penetrates through the shaft center portion of the inner yoke 5. However, between the pair of yokes coaxially arranged by the spacer 6, that is, the outer peripheral surface of the inner yoke 5. Driving coils 2 and 4 are wound around the inner peripheral surface of the outer yoke 3, and a cylindrical permanent magnet 8 magnetized in the radial direction is arranged as a mover 7 between the pair of opposing driving coils 2 and 4. Since it has a configuration, the mover 7 may be rotatably supported by any of the constituent members, and can be rotatably supported by, for example, the spacer 6, the outer peripheral surface of the inner yoke 5, and the inner peripheral surface of the outer yoke 3. The controlled side to which the shaft is connected may take various forms according to the application, but it may be pivotally supported by these separate members.

[0013]

The features of the linear actuator of the present invention will be described in more detail with reference to the following examples. Example 1 The outer yoke 3 and the inner yoke 5 made of soft iron are concentrically arranged by a spacer 6 made of aluminum, and the outer diameter 6 is set.
A stator 1 having a length of 0 mm and a length of 60 mm was prepared. In addition,
Inside the outer yoke 3, a drive outer coil 2 (number of turns: 505) made of a coated copper wire having an outer diameter of 0.4 mm is arranged, and on the outer side of the inner yoke 5, a coated copper wire having an outer diameter of 0.5 mm. Drive inner coil 4 (number of turns: 409)
Times). Moreover, the residual magnetic flux density Br11.6 kG and the coercive force Hc1 are applied to the magnet holder 9 made of aluminum.
A cylindrical permanent magnet 8 formed by arranging a plurality of radial-anisotropic permanent magnets having a fan-shaped cross section and made of a rare earth-iron-boron-based magnet having 1.1 kOe is fixed, and at the center of the magnet holder 9. The output shaft 10 was inserted and fixed to produce the mover 7. By combining the stator 1 and the mover 7 described above, a linear actuator of the present invention having the configuration shown in FIG. 1 was produced. At this time, the total mass of the actuator is 1.02 kg, and the weight of the mover 7 is 152 g.
(Of which, the weight of the cylindrical permanent magnet 8 was 80 g). When a DC current of 2.0 A was applied to the driving outer coil 2 and the driving inner 3 coil 4, a thrust of 3 kgf could be obtained. The thrust / volume ratio of the linear actuator of the present invention was calculated to be 173.3 N / L, which was confirmed to be improved by 20% or more as compared with the conventional VCM type linear actuator shown in FIG. It was confirmed that it is possible to reduce the size and weight.

Example 2 In the linear actuator of the present invention obtained in Example 1, a DC current of 2.0 A is continuously applied to the driving outer coil 2 and the driving inner coil 4 in an environment of room temperature of 24 ° C. When the temperature rise value of the coil was measured, the temperature was 86 ° C. Since the temperature of the conventional VCM type linear actuator shown in FIG. 6 rises to about 100 ° C., the practically allowable power consumption of the linear actuator of the present invention can be made larger than that of the conventional VCM type linear actuator. Therefore, the large thrust as shown in the first embodiment can be obtained. As described above, the temperature rise value of the coil is relatively low, as described above.
This is because the heat generated from the heat is dissipated to the outside of the actuator via the outer yoke 1 and the inner yoke 5 in which these coils are arranged.

Third Embodiment In the linear actuator of the present invention obtained in the first embodiment, the magnetic flux density distribution formed between the outer yoke 3 and the inner yoke 5 (in the air gap) is shown by the movable element 7.
Was measured by a Gauss meter in the state where no is arranged, and the result is shown in FIG. The displacement shown in the figure is
The position corresponding to the center of the driving outer coil 2 is used as the origin to represent the distance to each measurement position. It can be seen that a so-called gradient magnetic field is formed in the void so that the magnetic field strength increases as it moves from the axial center to both ends.

Fourth Embodiment In the linear actuator of the present invention obtained in the first embodiment, the thrust force (static thrust force) acting on the mover 7 at each displacement.
Was measured by a load cell, and the result is shown in FIG. The displacement shown in the figure represents the distance to the center of the mover 7 with the position corresponding to the center of the driving outer coil 2 as the origin. The values calculated by the inventor of the present application are also shown. As is clear from the figure, it can be seen that uniform thrust acts on a wide range. When the current applied to the coil is 2 A, the thrust is slightly displaced. However, according to the estimation by the inventor of the present application, the size of the inner yoke 5 is not optimal, and the magnetic flux is saturated in a part of the inner yoke 5. It is believed that the same thrust force as in the case of 1 A can be obtained by correcting the dimension.

Fifth Embodiment Using the measuring apparatus used in the fourth embodiment, in the linear actuator of the present invention obtained in the first embodiment, the relationship between the thrust (static thrust) and the current at the position where the displacement is 0 mm is measured. The results are shown in FIG. The values calculated by the inventor of the present application are also shown. From the figure, it can be seen that the thrust increases almost proportionally as the current value increases. Considering together with the result of Example 4, it became clear that the linear actuator of the present invention enables highly accurate position control.

[0018]

As is apparent from the embodiments, in the linear actuator according to the present invention, the permanent magnets that form the mover by effectively arranging the components such as the drive coil and the yoke that form the stator. The magnetic field can be efficiently applied to the magnets, and the heat generated from the drive coils is dissipated to the outside of the actuator through the yokes in which these coils are arranged, and the temperature rise of each coil can be suppressed. Therefore, it becomes possible to increase the value of the substantially continuous energizing current, and the thrust can be practically increased. That is, the thrust / volume ratio can be improved by 20% or more compared to the conventional VCM type linear actuator, and the size and weight can be reduced. Further, the rate of change of thrust with respect to the displacement of the mover is small, and highly accurate position control is possible. Since it is not necessary to dispose a lead wire for supplying current on the mover itself, the lead wire is not laid around when the mover moves, and such a configuration also enables highly accurate position control. It is a factor. As is clear from the above description, according to the present invention, it is possible to provide a linear actuator having high versatility, a relatively simple structure, and a reduction in size and weight.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional front view of a linear actuator that is an embodiment of the present invention.

FIG. 2 is a partial vertical cross-sectional front view of a mover that constitutes a linear actuator that is an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the displacement and the magnetic flux density when the mover is not arranged in the linear actuator that is an embodiment of the present invention.

FIG. 4 is a graph showing the relationship between displacement and thrust in a linear actuator that is an embodiment of the present invention.

FIG. 5 is a graph showing the relationship between current and thrust in a linear actuator that is an embodiment of the present invention.

6A and 6B are a side view and a partial vertical sectional front view showing the outline of a conventional VCM type linear actuator.

7A and 7B are a front view and a side view showing an outline of a conventional MM type linear actuator.

[Explanation of symbols]

 1 stator 2 outer coil for driving 3 outer yoke 4 inner coil for driving 5 inner yoke 6 spacer 7 mover 8 cylindrical permanent magnet 9 magnet holder 10 output shaft 11 through hole 12 bush

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[Procedure amendment]

[Submission date] May 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

In the linear actuator having the above structure, the driving outer coil 2 and the driving inner coil 4 constituting the stator 1 are in the same direction (for example, the coils 2 and 4 are both clockwise or counterclockwise). Direction)
When a predetermined current is applied, the current flows back between the outer yoke 3 and the inner yoke 5 where the coils 2 and 4 are arranged.
A magnetic flux will be generated . Due to these magnetic fluxes, a so-called gradient magnetic field is formed in the air gap, in which the magnetic field strength increases as it moves from the axial center to both ends. When the cylindrical permanent magnet 8 that is magnetized in the radial direction and that constitutes the mover 7 is arranged in the space where the gradient magnetic field is formed, the permanent magnet is generated by the interaction between the magnetic field and the magnetic moment of the permanent magnet 8 itself. A thrust force is generated at 8, and the mover 7 linearly moves in the axial direction (left-right direction in the drawing).

Claims (1)

[Claims] 1. An outer yoke having an outer drive coil wound inside and an inner yoke having an inner drive coil wound outside are concentrically arranged with a spacer made of a non-magnetic material interposed therebetween. And a radial direction in which an outer peripheral surface faces the driving outer coil, an inner peripheral surface faces the driving inner coil, and the outer yoke is fitted to the inner yoke so as to be movable in the axial direction. And a mover made of a magnetized cylindrical permanent magnet.