JP2003059020A - Linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear actuator which can reduce leakage flux further than a conventional structure. SOLUTION: The linear actuator is provided with a fixing part 20 and a movable part 30 which relatively moves in a direction along one shaft of the fixing part 20. The fixing part 20 has a pair of yokes 21b and 21c provided with a pair of permanent magnets 22 and 23 disposed oppositely around the one shaft, respectively. The movable part 30 has an air-core coil 32 excited by turning on electricity. A portion corresponding to the side part of the permanent magnets 22 and 23 of the yokes 21b and 21c is bent by its thickness so as to cover the side faces of the permanent magnets 22 and 23. Then, the yoke is further bent, as a method for reducing the magnetic leakage flux so as to be parallel to the extended direction of the permanent magnets 22 and 23.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a DLT (Digital Digitizer).
tal Linear Tape) and LTO (Line
The present invention relates to a linear tape storage system represented by ar Tape Open), and more particularly to an electromagnetic linear actuator that can be used as a head feeding mechanism of a magnetic tape head actuator assembly used therein.

[0002]

2. Description of the Related Art This kind of linear tape storage system has been developed for backup of computer systems, and various types have been proposed. For example, a digital linear tape drive as a DLT is disclosed in Japanese Patent Laid-Open No. 9-198639.

A digital linear tape drive (hereinafter, also simply referred to as "drive device", "tape drive", or "drive") is a tape cartridge having a single reel (supply reel) (hereinafter, also simply referred to as "cartridge"). It is intended to receive, and contains a take-up reel inside. When the tape cartridge is mounted on the drive device, the magnetic tape is pulled out from the tape cartridge and wound on the take-up reel via the head guide assembly (HGA). The head guide assembly is for guiding the magnetic tape (hereinafter, also simply referred to as “tape”) pulled out from the tape cartridge to the magnetic head. The magnetic head exchanges information with the tape. The head guide assembly generally consists of an aluminum plate in the shape of a boomerang and six large guide rollers using bearings.

Incidentally, the head guide assembly is also called a tape guide assembly, and it is, for example, a table 9
It is disclosed in Japanese Patent Laid-Open No. -500573. An example of the guide roller is disclosed in Japanese Patent Laid-Open No. 2000-100025.

In general, a tape drive includes a substantially rectangular parallelepiped housing having a common base, as described in, for example, Japanese Patent Publication No. 2000-501547. The base has two spindle motors (reel motors). The first spindle motor has a spool (take-up reel) permanently attached to the base, the spool being sized to receive a relatively fast flowing magnetic tape. The second spindle motor (reel motor) is adapted to receive a removable tape cartridge. The removable tape cartridge is manually or automatically inserted into the drive through a slot formed in the drive housing. When the tape cartridge is inserted into the slot, the cartridge engages a second spindle motor (reel motor). Prior to rotating the first and second spindle motors (reel motors), a mechanical buckling mechanism connects the tape cartridge to a permanently mounted spool (take-up reel). Many rollers (guide rollers) located between the tape cartridge and the permanent spool guide it as the magnetic tape moves back and forth at a relatively high speed between the tape cartridge and the permanently mounted spool. To do.

A digital linear tape drive of such construction requires a device for the take-up reel to pull the tape from the supply reel. Such a pulling device is disclosed in, for example, Japanese Patent Publication No. 3-7595. According to this publication, take-up leader means (first tape leader) is connected to the take-up reel, and supply tape leader means (second tape leader) is fixed to the tape on the supply reel. The first tape leader has a tab at one end, the second tape leader has a locking hole, and the tab is engaged with the locking hole.

Further, a mechanism for joining the first tape leader to the second tape leader is also required. Such a joining mechanism is disclosed in, for example, Japanese Patent Publication No. 6-39027.

Further, in Japanese Unexamined Patent Publication No. 2000-100116, the end portion of the leader tape is attached to the tape end of the tape cartridge without the need for an ear piece protruding laterally of the leader tape (second tape leader). A "locking part structure of a leader tape" that can be locked to a hooking part is disclosed.

Japanese Laid-Open Patent Publication No. 11-86381 discloses a lock system for preventing the take-up reel of the tape drive from rotating when the tape cartridge is not inserted in the drive.

On the other hand, as an example of a tape cartridge mounted in a digital linear tape drive, an example thereof is disclosed in Japanese Patent Laid-Open No.
No. 000-149491.

Further, Japanese Unexamined Patent Publication (Kokai) No. 11-316991 discloses a "tape drive" in which a tape leader can be pushed from a tape cartridge to a take-up reel without using a buckling mechanism or a take-up leader. There is.

It should be noted that the tape drive further includes a magnetic tape head actuator assembly (hereinafter also simply referred to as "actuator assembly"), the actuator assembly being on a tape path defined by a plurality of rollers, a take-up spool and a tape. Positioned between the cartridge. In operation, the magnetic tape flows back and forth between the take-up spool and the tape cartridge, and closely approaches the actuator assembly while flowing over the defined tape path. An example of such an actuator assembly is disclosed in the above Japanese Patent Publication No. 2000-501547.

The actuator assembly comprises a tape head assembly (hereinafter also simply referred to as "head assembly") and a head feeding mechanism. The head assembly is a magnetic head (head) extending vertically.
And a pair of flexible printed circuits (FPC) for electrically connecting the magnetic head and an external circuit.

On the other hand, the head feeding mechanism is for raising and lowering the head assembly while holding the head assembly. A conventional head feeding mechanism is provided with a lead screw with a thread (a shaft with a thread) as disclosed in the above Japanese Patent Publication No. 2000-501547, and by rotating the lead screw,
The head assembly is mechanically moved up and down (linear movement). In other words, a "mechanical linear actuator" is used as the conventional head feeding mechanism.

However, in such a mechanical linear actuator, since the position control of the head assembly is performed by the open loop control, it is difficult to accurately control the elevation position of the head assembly to a desired position.

Therefore, in order to solve the problem in such a mechanical linear actuator, an "electromagnetic linear actuator" that electromagnetically moves the head assembly up and down (linear motion) is adopted as a head feed mechanism.
It is considered that the position control of the head assembly is performed by closed loop (feedback) control.

In such an electromagnetic linear actuator, a fixed portion, a movable portion that holds the head assembly (object to be lifted and lowered) vertically with respect to the fixed portion, and a movable portion of the movable portion ( It has a guide for restraining (regulating) movements other than in the (up and down) direction, and a base for mounting this guide.

Here, the electromagnetic linear actuator is
It can be divided into two types. The first type is a "movable magnet type" electromagnetic linear actuator, which has a magnet in the movable part and a coil in the fixed part. The second type is a "moving coil type" electromagnetic linear actuator in which a fixed portion is provided with a magnet and a movable portion is provided with a coil. The present invention relates to a "moving coil type" electromagnetic linear actuator.

FIG. 12 is a perspective view showing a conventional electromagnetic linear actuator, and FIG. 13 is a transverse sectional view of the electromagnetic linear actuator of FIG.

Referring to FIGS. 12 and 13, the electromagnetic linear actuator 100 includes a fixed part 120 and a head assembly 110 for the fixed part 120.
13, upward, in FIG. 13, a movable portion 130 that holds the movable portion 130 so as to be able to ascend and descend along the vertical direction of the paper surface, and a guide portion 140 that restrains (restricts) movement of the movable portion 130 in a direction other than the movable (elevating) direction. Have and. This guide part 14
0 is attached to the fixed part 120.

The fixed portion 120 includes a yoke base 121 having a U-shaped cross section, a pair of plate magnets 122 and 123 housed in the yoke base 121, and a center yoke 12.
4 and a yoke base cover (upper yoke) 125. The yoke base 121 includes a bottom yoke 121a,
It has a front wall yoke 121c extending upward from the front end of the bottom yoke 121a and a rear wall yoke 121b extending upward from the rear end of the bottom yoke 121a. That is, the front wall yoke 121c and the rear wall yoke 121b are spaced apart from each other and arranged to face each other. Front wall yoke 121c
And a rear wall yoke 121b, a center yoke 124 is erected from the center of the bottom yoke 121a. Then, one magnet 123 is attached to the front wall yoke 121c.
Is attached, and the other magnet 122 is attached to the rear wall yoke 121b. Upper yoke 125
Covers the yoke base 121 and the center yoke 124 from above and is fixed by screws 126.

On the other hand, the movable part 130 holds the head assembly 110 and moves vertically in the vertical direction, that is, in FIG.
31 and an air-core coil 132 wound around the center yoke 124 at a distance from each other. More specifically, the carriage 131 has a box shape having a front frame 131a, a right frame 131b, a lower bridge portion (not shown), and an upper bridge portion.

The air core coil 132 is housed in a space surrounded by a lower bridge portion, an upper bridge portion, a right frame 131b, and a left frame 131c (not shown).

Here, the carriage 131 is provided with an adhesive groove used for easily fixing the air-core coil 132 to the carriage 131 with an adhesive.

The guide portion 140 has a guide shaft 141 extending along the vertical direction on the left side between the bottom yoke 121a and the upper yoke 125. That is, the lower end portion and the upper end portion of the guide shaft 141 are fixed to the bottom yoke 121a and the upper yoke 125, respectively, while being fitted in the guide mounting holes 211a and 125a. As a result, the verticality of the guide 140 with respect to the yoke base 121 is maintained.

An upper damper 142 and a lower damper 143 are mounted on the upper end and the lower end of the guide shaft 141 in contact with the upper yoke 125 and the bottom yoke 121a, respectively.

On the other hand, the left frame 1 of the carriage 131
31c is a pair of annular projecting portions 313a, 313 projecting outward from the upper and lower ends thereof toward the guide shaft 141 side.
b. The guide shaft 141 connects the pair of annular protrusions 313a and 313b to the pair of metal bearings 144.
It penetrates through a and 144b. In other words, the pair of metal bearings 144a and 144b are fitted in the holes of the pair of annular protrusions 313a and 313b. That is, the pair of metal bearings 144a and 144b slide along the guide shaft 141. As a result, the carriage 131 becomes slidable in the vertical direction with respect to the guide shaft 141.

When the movable part 130 moves up and down, the pair of annular protrusions 313a and 313b of the carriage 131 abut the upper damper 142 and the lower damper 143.
The stroke of the movable part 130 is restricted, and the upper damper 14
2 and the lower damper 143 absorb the shock.

The conventional electromagnetic linear actuator 100 further includes a position sensor 150 for detecting the vertical position of the movable part 130. This position sensor 15
0 is provided so as to extend in the ascending direction from the bottom yoke 121a and above a mounting hole (not shown).

More specifically, the position sensor 150 includes a hollow sensor bobbin 152 around which a sensor coil 151 is wound.
And a sensor shaft 154 whose one end 154b side is inserted into the hollow portion of the sensor bobbin 152 and which extends in the up-down direction (vertical direction). The outer diameter of the sensor shaft 154 is substantially equal to the inner diameter of the sensor bobbin 152. The position sensor 150 detects the insertion amount of the sensor shaft 154 with respect to the sensor bobbin 152 based on a change in the value of the inductance, thereby detecting the current elevating position of the movable part 130 with respect to the yoke base 121 (fixed part 120) as a detection position. is there.

[0031]

The head of an electromagnetic linear actuator (head actuator) according to the prior art is an MR head (magneto-res).
Since it is used, leakage of magnetic flux from the permanent magnet may cause a problem in writing and reading, and therefore it is desired to make it as small as possible.

Conventionally, the leakage magnetic flux is suppressed by making the yoke thicker than the magnet or by extending and covering the magnet longer than the portion facing the coil.

Therefore, one technical object of the present invention is to provide a linear actuator which can further reduce the leakage flux as compared with the conventional structure.

Further, another technical problem of the present invention is to provide a linear actuator in which the influence of the leakage flux on the MR head can be reduced by reducing the leakage flux.

[0035]

According to the present invention, there is provided a fixed part (20) and a movable part (30) which relatively moves in a direction along an axis of the fixed part (20), and the fixed part (20). )
Is a pair of permanent magnets (2
2, 23) each having a pair of yokes (21b, 21)
c; 21b ', 21c'), and the movable part (30)
Is an air-core coil (3
2) in the linear actuator (1, 2), the yoke (21b, 21c; 21b ', 21c
′) Is bent by a thickness such that a portion of the permanent magnet (22, 23) corresponding to a side portion of the permanent magnet faces a side portion of the permanent magnet (22, 23). 1, 2)) is obtained.

Further, according to the present invention, in the linear actuators (1, 2), the yokes (21b, 2) are
1c) is a linear actuator (1), characterized in that the permanent magnet (22, 23) is provided with portions extending outward from both sides of the permanent magnet (22, 23) outward in the width direction of the permanent magnet.
Is obtained.

Further, according to the present invention, in the linear actuators (1, 2), the magnetic tape head assembly (1) provided on the outer side surface of the movable part (30).
A linear actuator (1) is obtained which is used for position adjustment of (0) along the one axis.

The reference numerals in the above parentheses are given to facilitate understanding of the present invention and are merely examples, and the present invention is not limited to these.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a linear actuator according to the first embodiment of the present invention. 2 is a plan view of the linear actuator of FIG. 1, and FIG. 3 is III-I of FIG.
FIG. 4 is a cross-sectional view taken along line II, FIG. 4 is a perspective view of the linear actuator of FIG. 1 seen obliquely from the front, and FIG. 5 is a perspective view of the linear actuator of FIG. 1 seen from the rear side. FIG. 6 is an exploded perspective view of the linear actuator. 7 is a front view of the linear actuator, and FIG. 8 is VIII-V of FIG.
FIG. 9 is a sectional view taken along line III, FIG. 9 is a bottom view of the linear actuator of FIG. 1, and FIG. 10 is a bottom view showing a method of fixing the slip-off and stop spring of the actuator shown in FIG.

1 to 9, the electromagnetic linear actuator 1 according to the first embodiment of the present invention is
It is a "moving coil type" electromagnetic linear actuator, and is applied to a horizontal type tape drive. The illustrated electromagnetic linear actuator can be applied to a vertical tape drive, but in the following,
The case where it is applied to a horizontal type tape drive will be described. This electromagnetic linear actuator is a linear motor composed of a voice coil motor (VCM).

The electromagnetic linear actuator uses the tape drive head assembly 10 as an object to be lifted and lowered.
It is for moving back and forth along the direction perpendicular to the paper surface. The head assembly 10 includes a magnetic tape head 11 that extends in the vertical direction and a head holder 12 that holds the magnetic tape head 11. Head holder 12
Is attached to the movable unit 30. Magnetic tape head 1
1 is a flexible printed circuit (FPC) not shown
Is electrically connected to an external circuit (not shown) via. As the magnetic tape head 11, the MR (mag
A neto-resistive head is used.
The MR head is a device that is very sensitive to static electricity and weak in static electricity resistance. Therefore, care must be taken when handling the MR head. Anyway, the electromagnetic linear actuator is used as a head feeding mechanism of the head assembly 10.

The electromagnetic linear actuator 1 includes a fixed portion 20 and the head assembly 10 with respect to the fixed portion 20.
A movable part 30 for holding the movably along the vertical direction,
It has a guide portion 40 for restraining the movement of the movable portion 30 other than the movable direction.

Referring to FIGS. 1 and 3, the fixing portion 20 is provided.
Has a yoke base 21, a pair of plate magnets 22 and 23 housed in the yoke base 21, and a yoke base cover (upper yoke) 25 having center yokes 24 and 24.

As best shown in FIG. 6, the yoke base 21 has a U-shaped cross section and has a bottom yoke 21a.
And a front wall yoke 21c extending upward from the front end of the bottom yoke 21a, and a rear wall yoke 21b extending upward from the rear end of the bottom yoke 21c. That is,
The front wall yoke 21c and the rear wall yoke 21b are spaced apart from each other and face each other. Center yokes 24, 24 are provided in parallel with each other in the upper yoke 25, and the bottom yoke 21a is provided between the front wall yoke 21c and the rear wall yoke 21b.
Center yokes 24 are inserted into both sides of the guide shaft in the central portion of the.

As is apparent from FIG. 6, in the yoke base 21, the bottom yoke 21a and the front wall yoke 21 are arranged.
c and the rear wall yoke 21b are integrally formed. One plate-shaped magnet 2 is attached to the front wall yoke 21c.
3 is attached, and the other plate-shaped magnet 22 is attached to the rear wall yoke 21b.

Further, as best shown in FIGS. 1 and 8, the front wall yoke 21c and the rear wall yoke 21b are provided on the side surfaces of the plate-like magnets 23 and 22, respectively.
After bending by the thickness of 3, 22, the magnet 2
Each of the yokes has a shape in which the side portions of the yokes are bent outward from both side surfaces of the magnets 3 and 22 along the extending direction of the magnets 23 and 22. With this structure, the leakage flux from the permanent magnet is greatly reduced.

Further, as shown in FIGS. 2 to 7, the upper yoke 25 is provided with a pair of center yokes 24.
The center yoke 24 has a bottom wall portion 21 a of the yoke base 21.
To penetrate. At this time, the upper yoke 25 covers one end of the yoke base 21. As shown in FIGS. 9 and 10, the upper yoke 25 and the yoke base 21 (rear wall yoke 21c) are fixed by the center yoke 24 after the bottom wall portion 21a is penetrated and the retaining spring 26 is attached. Has been done.

On the other hand, as shown in FIGS. 3 and 6 and 7,
While the movable part 30 holds the head assembly 10,
It has a carriage 31 that moves in the vertical direction and an air-core coil 32 housed in the carriage 31. The air-core coil 32 is wound around the center yoke 24 with a space therebetween. More specifically, the carriage 31 is arranged near the front of the front wall yoke 21a and in front of the head assembly 1.
Front frame 31 to which the head holder 12 of 0 is attached
a, a right frame 31b extending rearward from the right end of the front frame 31a, a left frame 31c extending rearward from the left end of the front frame 31a, and a front wall yoke 21c.
In the space between the (one magnet 23) and the center yoke 24, the lower bridge portion 31d that bridges the right frame 31b and the left frame 31c at the lower end, and the rear wall yoke 2
1b (the other magnet 22) and the center yoke 24 in the space between the right frame 31b and the left frame 31c
And an upper bridge portion 31e bridging the upper end with the upper bridge portion 31e.

The air core coil 32 is mounted on the lower bridge portion 31d. In other words, the air core coil 32 includes the lower bridge portion 31d, the upper bridge portion 31e, and the right frame 31b.
It is housed in a space surrounded by the left side frame 31c. Here, it is necessary to fix the air-core coil 32 to the carriage 31 that is the mounting portion. In the present invention, as will be described later in detail with reference to the drawings,
Adhesive grooves used to easily fix the air-core coil 32 to the carriage 31 with an adhesive are cut.

The guide portion 40 has a guide shaft 41 extending so as to connect between the central portions of the bottom yoke 21a and the upper yoke 25. That is, in the guide shaft 41, the lower end portion and the upper end portion thereof are respectively attached to the bottom yoke 21a and the upper yoke 25, and the guide mounting holes 211a (see FIG. 10) and 25a (see FIG. 2).
It is fixed in the state that it is inserted into. Thereby, the perpendicularity of the guide 40 with respect to the yoke base 21 can be maintained.

The upper yoke 25 and the bottom yoke 21 are respectively provided at the upper end and the lower end of the guide shaft 41.
An upper damper 42 and a lower damper 43 for absorbing shock are mounted in a state of being in contact with a.

On the other hand, the upper and lower frames 31 of the carriage 31
The a and 31b have a pair of through holes 313a and 313b penetrating from the upper and lower ends into the carriage. The guide shaft 41 penetrates the pair of through holes 313a and 313b through the pair of metal bearings 44a and 44b. In other words, the pair of metal bearings 44a, 44b
Are fitted into the holes of the pair of through holes 313a and 313b. That is, the guide shaft 41 is supported by the pair of metal bearings 44a and 44b. As a result, the carriage 31 becomes slidable in the vertical direction with respect to the guide shaft 41.

When the movable part 30 moves up and down, the carriage 3
The pair of through holes 313a and 313b of the first upper damper 42
Since it abuts against the lower damper 43, the stroke of the movable portion 30 is restricted, and the shock is absorbed by the upper damper 42 and the lower damper 43.

Since the metal bearings 44a and 44b are cheaper than the bearings used conventionally, the cost of the electromagnetic linear actuator can be reduced. Further, in the present embodiment, the metal bearing 44a,
The inner peripheral surface of 44b is processed into a polygonal shape (a hexagon in the illustrated example). In this technical field, processing the inner peripheral surface of the metal bearing into a polygonal shape is referred to as "cutting a groove in the inner peripheral surface" or "chamfering the inner peripheral surface". By making the shapes of the inner peripheral surfaces of the metal bearings 44a and 44b polygonal, the guide shaft 41 and the metal bearing 4 can be formed.
The contact portion with 4a, 44b can be a line from the surface. Thereby, friction when the movable portion 30 moves up and down can be reduced, and the slidability of the movable portion 30 can be improved.
The polygon may be symmetrical, and the number of corners is preferably hexagon or more. However, when the number of surplus angles increases, the number of contact portions increases, so that the number of angles is naturally limited to an appropriate number.

The illustrated electromagnetic linear actuator further includes a position sensor 50 for detecting the vertical position of the movable portion 30. The position sensor 50 includes a sensor coil 51.
A hollow sensor bobbin 52 around which the sensor bobbin 52 is wound,
A screw 53 screwed to the sensor bobbin 52 via 11b.
And one end 54a is fixed to the protruding portion 312a protruding from the upper end of the right frame 31b to the outside of the position sensor 50 side, and the other end 54b side is inserted into the hollow portion of the sensor bobbin 52 and extends in the up-down direction (vertical direction). And a sensor shaft 54 that operates. That is, the outer diameter of the sensor shaft 54 is substantially equal to the inner diameter of the sensor bobbin 52. The position sensor 50 detects the insertion amount of the sensor shaft 54 with respect to the sensor bobbin 52 based on the change in the value of the inductance, thereby detecting the current lift position of the movable portion 30 with respect to the yoke base 21 (fixed portion 20) as the detection position. is there.

The position detection signal, which is detected by the position sensor 50 and indicates the current lift position (detection position) of the movable portion 30, is sent to a controller (not shown). The controller compares the detected position represented by this position detection signal with the target position of the movable part 30 and controls the amount of current flowing through the coil 32 of the movable part 30 so that these positions match. . That is, by adopting this electromagnetic linear actuator, it is possible to control the elevation position of the head assembly (object to be elevated and lowered) 10 by closed loop (feedback) control.

In this embodiment, as the material of the carriage 31, a resin containing a carbon material which is a conductive material is used. That is, the carriage 31 is manufactured as a resin molded product containing a carbon material. As a result, the static electricity generated in the MR head 11 can be quickly leaked to the outside via the carriage 31.
The content of the carbon material contained in the resin is preferably 30% or more, because if the content is too small, countermeasures against static electricity become impossible. On the other hand, since a material having too much content becomes brittle, the content of the carbon material to be contained in the resin is determined in consideration of this point.

In the present embodiment, an example in which a carbon material is used as the conductive material contained in the resin has been described, but it goes without saying that another conductive material may be used.

Further, in the present embodiment, as described above, the air core coil 32 forming the movable portion 30 may be divided into two. In this case, one split coil is
Movable part 30 including lifted object (head assembly) 10
Is used to move the lifted object 10 to a desired lifting position by exerting a lifting force against its own weight, and the other split coil stops the lifted object 10 at the desired lifting position. In addition, the lowering force is applied to the movable portion 30. With such a configuration, the lifted position of the lifted object (head assembly) 10 can be stopped at a desired position at high speed and with high accuracy. In this case, the ratio of one split coil in the entire coil 32 is 1/3, but the ratio is not limited to this, and may be 1/4, for example. Further, the other split coil is arranged on the lower side and the one split coil is arranged on the upper side, but these arrangements may be upside down.

FIG. 11 is a sectional view showing an electromagnetic linear actuator according to the second embodiment of the present invention. Figure 1
1, an electromagnetic linear actuator 2 according to a second embodiment of the present invention includes a front wall yoke 21c 'and
The rear wall yoke 21b 'has a plate-like magnet 23, 2
It has the same configuration except that it is formed so as to cover the outer surface and both side surfaces of each of the two. That is, the magnets 22 and 23 have the front wall yoke 21c 'and the rear wall yoke 2
The recesses 61a and 61b of 1b 'are mounted and configured.

[0062]

As described above, according to the present invention,
It is possible to provide a linear actuator that can further reduce the leakage flux as compared with the conventional structure.

Further, according to the present invention, it is possible to provide a linear actuator capable of reducing the influence of the leakage magnetic flux on the MR head by reducing the leakage magnetic flux.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a linear actuator according to a first embodiment of the present invention.

FIG. 2 is a top view of the linear actuator of FIG.

3 is a cross-sectional view taken along the line III-III in FIG.

4 is a perspective view of the linear actuator of FIG. 1 as viewed from the front side on the diagonal left side.

5 is a perspective view of the linear actuator of FIG. 1 viewed from the back side.

FIG. 6 is an exploded perspective view of a linear actuator.

FIG. 7 is a front view of a linear actuator.

8 is a sectional view taken along the line VIII-VIII in FIG.

9 is a bottom view of the linear actuator of FIG. 1. FIG.

FIG. 10 is a rear view showing a method for fixing the detachment of the actuator shown in FIG. 9 and the lock spring.

FIG. 11 is a sectional view showing an electromagnetic linear actuator according to a second embodiment of the present invention.

FIG. 12 is a perspective view showing a conventional electromagnetic linear actuator.

13 is a cross-sectional view of the electromagnetic linear actuator of FIG.

[Explanation of symbols]

1 Electromagnetic linear actuator 10 Head assembly 11 magnetic head 12 head holder 20 Fixed part 21 York base 21a bottom yoke 21b Rear wall yoke 21c Front wall yoke 21b 'Rear wall yoke 21c 'front wall yoke 22,23 magnet 24 Center yoke 25 Yoke base cover (upper yoke) 25a, 211a Guide mounting hole 26 Spring for retaining 30 moving parts 31 carriage 32 air core coil 31a front frame 31b Right frame 31c Left frame 31d Lower bridge section 31e Upper bridge part 313a, 313b Through hole 40 Guide 41 Guide shaft 42 Upper damper 43 Lower damper 44a, 44b Metal bearing 50 position sensor 51 sensor coil 52 sensor bobbin 53 screws 54a, 54b ends 61a, 61b depression 100 Electromagnetic linear actuator 110 head assembly 120 fixed part 121 York base 121a bottom yoke 121c front wall yoke 121b Rear wall yoke 122,123 plate magnet 124 Center yoke 125 yoke base cover (upper yoke) 125a, 211a Guide mounting hole 126 screws 130 Moving part 131 carriage 131a front frame 131b Right frame 131c Left frame 132 air core coil 140 Guide part 141 guide shaft 142 Upper damper 143 Lower damper 150 position sensor 151 sensor coil 152 sensor bobbin 153 screws 154 Sensor shaft

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eiichi Yoneyama             2 Mitsu, 8-8, Kokuryo-cho, Chofu-shi, Tokyo             Mi Electric Co., Ltd. F-term (reference) 5D095 AA01                 5E048 AB09 AC10

Claims (3)

[Claims] 1. A fixed part (20) and a movable part (30) which relatively moves in a direction along one axis of the fixed part (20), and the fixed part (20) is arranged to face the circumference of the one axis. A pair of yokes (21b, 21c; 21b ', 21c') each having a pair of permanent magnets (22, 23) are provided, and the movable part (30) is an air-core coil (excited by being energized). 32) in the linear actuator (1, 2), the yoke (21b, 21)
c; 21b ', 21c') said permanent magnets (22, 2)
The part corresponding to the side of 3) is the permanent magnet (22, 2).
A linear actuator (1, 2), characterized by being bent by a thickness so as to face the side portion of (3). 2. The linear actuator (1, 2) according to claim 1, wherein the yoke (21b, 21c).
Is a linear actuator, characterized in that it further comprises a portion extending outward in the width direction of the permanent magnet from both sides of the permanent magnet (22, 23). 3. The linear actuator (1, 2) according to claim 1, used for position adjustment of a magnetic tape head assembly (10) provided on an outer surface of the movable part (30) in a direction along the one axis. A linear actuator characterized in that