JPS614457A - Linear actuator - Google Patents

Abstract

PURPOSE:To rapidly attenuate a vibration generated from a flat movable coil by mounting the coil in a magnetic circuit with a permanent magnet as a magnetic flux generation source, and forming the mounting member of the coil of metal such as aluminums. CONSTITUTION:A linear actuator 27 is formed to linearly move a head carriage 26 of a floppy disk unit. The actuator 27 has a box-shaped yoke 36, flat permanent magnets 37, 38 secured to the upper and lower portion of the inside surface of the yoke, and a drive coil 39 provided between the magnets 37 and 38. The coil 39 is coupled through a mounting member 40 with the carriage 26, and linearly moves together with the carriage 26. In this case, the member 40 is formed of aluminum plate. A position detector 43 and a speed detector 44 are provided at the side of the carriage 26, and positioned to the prescribed position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a linear actuator having a speed detection coil for controlling movement speed.

(Prior art) For example, in a Freon Beatisf device, spatulas 1 to
It is necessary to move the carriage linearly in the radial direction of the floppy defrosk, and an actuator is used for this purpose. 4 and 5 show examples of conventional actuators of this type.

FIG. 4 shows an example of a linear actuator, in which flat permanent magnets 2°3 magnetized in the thickness direction are fixed to the upper and lower inner sides of a box-shaped yoke 1, respectively.
A drive coil 4 is arranged between these permanent magnets 2.3, and this drive coil 4 is connected to the head carriage 5 so as to be integral with it. The head carriage 5 is supported by a pair of parallel guide rails 6.6, and when the drive coil 4 is energized and a thrust is generated in the drive coil 4 in a direction corresponding to the energization direction, the head carriage 5 becomes a moving body together with the drive coil 4. The head carriage 5 is adapted to be moved linearly along the rail 6.6. A position signal generating member 7 is attached to the head carriage 5.
A position sensor 8 is arranged close to and opposite to. Also, a speed detection coil 9 is provided substantially integrally with the head carriage 5.
A magnet 10 is provided to surround the coil 9.

FIG. 5 shows an example of a rotary stepping motor type actuator, in which a head carriage 13 is linearly fed by a feed screw 12 that is rotationally driven by a stellar pink motor 11.

Among the above-mentioned actuators, the stepping motor type has a stepping function, so a position sensor or speed sensor is not required. However, when using a linear actuator as shown in Figure 4, it is necessary to know the position of the actuator, so a position sensor is required, and a speed sensor is required because the speed of the actuator needs to be controlled constant. need.

Therefore, the movable coil 4 is connected to the bed carriage 5.
A speed detection coil is integrally connected to the head carriage 5, and a magnetic flux from a magnetic flux generation source for the sensor is passed through this moving coil, so that a signal proportional to the moving speed of the head carriage 5 is obtained by moving the moving coil. ing.

(Problems to be Solved by the Invention) However, in the linear actuator shown in FIG. 4, when thrust is generated in the moving coil 4, the moving coil 4
vibrates. Therefore, noise corresponding to the vibration is induced in the signal obtained from the detection coil, and when a signal containing this noise is used as a control signal, it causes a control error and has the drawback that accurate movement and positioning/stopping control cannot be performed. .

The occurrence of such vibrations varies depending on the material of the mounting base on which the moving coil 4 is placed and held, and when the coil mounting base is made of synthetic resin mold, brass, copper, or other metal. occurs in

Figure 3 shows the waveform of the induced voltage of the speed sensor when a synthetic resin mold, brass, copper, or other copper-based material, or aluminum-based material is used for the coil mounting base. On the other hand, synthetic resin molds constantly exhibit slight vibrations, as shown in the same figure ([3)], and brass,
With copper-based materials such as copper.

As shown in FIG. 2D, although no microvibration occurs, the attenuation of the generated voltage is prolonged.

In the case of an aluminum material, as shown in FIG. 2(C), no slight vibration occurs, and the voltage attenuation ends within a short time.

An object of the present invention is to provide a linear actuator that attenuates vibrations generated from a moving coil as quickly as possible to avoid adverse effects on a speed sensor.

(Means for Solving the Problem) The present invention has a flat drive coil placed in a magnetic circuit using a permanent magnet as a magnetic flux generation source, and a thrust force is obtained in accordance with the direction of current flowing through the drive coil. In the linear actuator, the mounting member for the drive coil is formed with a groove made of aluminum-based metal.

(Example) In FIGS. 1 and 2, the chassis 21 of the floppy disk device is provided with a drive motor (not shown) for rotationally driving a disk 23 housed in a disk case 22. A linear actuator 27 is also provided for linearly moving a head carriage 26, which is a movable body and holds a magnetic hedge 25 for writing or reading information signals on the disk 23. The disk case 22 is positioned and placed on a plurality of support positioning pins (not shown) that are aligned on the board.

The centering hub of the disk 23 in the case 22 is placed on a chucking head (not shown) that is rotationally driven by the motor, and is further mounted on a rotation stopper 31 provided on the chucking head. When the engaging portion 32 is engaged, the drive motor is driven to rotate, thereby urging the disk 23 to rotate.

The head carriage 26 is connected by one guide bar 33.
is supported at one point by another guide bar 34,
Along these two guide bars 33, 34 the disc 2
It can move linearly in the radial direction of 3.

The two guide bars 33 and 34 have a round bar shape, and both ends of each guide bar 33 and 34 are fixed to the chassis 21 by a holding plate 35.

The linear actuator 27 includes a box-shaped yoke 36, flat plate-shaped permanent magnets 37 and 38 fixed vertically to the inner surface of the yoke 36, and a drive coil 39 disposed in the gap between these permanent magnets 37 and 38. It has

Each permanent magnet 37, 38 is magnetized in the thickness direction to form a north pole and a south pole.
The poles are formed in the thickness direction, but the magnetic poles are opposite to each other across the line that bisects each permanent magnet in the longitudinal direction, and the upper and lower magnets are arranged so that different polarities face each other. It is arranged. Each permanent magnet 37, 38 serves as a magnetic flux generation source and is vertically opposed to each other with a predetermined gap between them, and the yoke 3
Together with 6, it constitutes a magnetic circuit.

The drive coil 39 is placed on the tip of a mounting member 40 made of an aluminum plate, and is inserted into the window hole 30 of the yoke 36.
The head carriage 26 moves in a straight line together with the drive coil 39 by connecting the head carriage 26 to the head carriage 26. Position information is recorded on the side of the head carriage 26. medium 41
is fixed to the medium 41, and a position sensor 42 is provided close to and opposite the medium 41. For example, position information is magnetically recorded on the position information recording medium 41, and this information is detected by a magnetoresistive element or the like. However,
Recording and detection of position information may be performed using other means such as optical means. By the signal obtained by the position detection section 43 consisting of the medium 41 and the position sensor 42,
The position of the magnetic head 25 is controlled so that the magnetic head 25 matches each track of the disk 23 and stops.

The linear actuator 27 is provided with a speed detection section 44 for detecting the moving speed of the drive coil 39. The speed detection unit 44 includes a support arm 45 whose one end is connected to the head carriage 26, a magnet 46 attached to the case 22, a yoke 47 made of a magnetic metal plate, and a gap between the yoke 47 and the magnet 46. It has a flat detection coil 48.

By energizing the drive coil 39, the linear actuator 27 generates a thrust in a direction corresponding to the direction of the current, and the linear actuator 27 generates a magnetic force along with the head carriage 26.
5 heads 25 move in the radial direction of the disk 23. As the drive coil 39 moves, the detection coil 48 also moves to the yoke 4.
Since it moves while cutting off the magnetic flux passing through the gap between the drive coil 3 and the 7th magnet 46, the detection coil 48
A voltage signal proportional to the moving speed of 9 is detected. This detection signal, together with the position signal obtained by the position detection section 43, is input to a control and drive circuit (not shown), and this control and drive circuit moves the linear actuator 27 at a predetermined speed based on each of the above signals. It is moved to a certain position, positioned at a predetermined position, and stopped.

(Effects of the Invention) According to the present invention, which uses an aluminum-based metal plate for the mounting member of the drive coil, the viscosity due to hysteresis loss generated in the mounting member during seek improves, and the braking force, especially the influence of gravity such as in an upward posture, is improved. The effect is large in the state where it is received. Also,
During operation, as shown in FIG. 3(C), the induced voltage of the speed sensor decays quickly, so that the influence of noise on the control signal can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a plan view of a linear actuator showing an embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, Fig. 3 is a line diagram showing the induced voltage waveform of the speed sensor, and Fig. 4 and FIG. 5 are plan views showing examples of conventional linear actuators, respectively. 26... Moving body, 37.38... Permanent magnet,
39... Drive coil. Vanishing prisoner

Claims (1)

[Claims] In a linear actuator, a flat drive coil is placed in a magnetic circuit using a permanent magnet as a magnetic flux generation source, and thrust is obtained in accordance with the direction of current flowing through the drive coil.The drive coil is made of an aluminum metal plate. A linear actuator characterized in that the linear actuator is provided on a mounting member, and one end of the mounting member is fixed to a moving body.