JPS6334467Y2 - - Google Patents

Description

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

For example, in a floppy disk device,
It is necessary to move the head carriage linearly in the radial direction of the floppy disk, and an actuator is used for this purpose. 1 and 2 show examples of conventional actuators of this type. The example in FIG. 1 shows an example of a linear actuator, in which flat permanent magnets 2 and 3 magnetized in the thickness direction are fixed to the upper and lower inner sides of a box-shaped yoke 1, respectively. These permanent magnets 2,
A moving coil 4 is disposed between the heads 3 and 3, and the moving coil 4 is integrally connected to a head carriage 5. The head carriage 5 is supported by guide rails 6, 6, and when the drive coil 4 is energized and a thrust is generated in the direction according to the direction of energization, the head carriage 5 moves along with the coil 4 to the rails 6, 6.
It is designed to be able to move linearly along 6. A position signal generating member 7 is attached to the head carriage 5, and a position sensor 8 is arranged close to and facing the member 7. Further, a speed detection coil 9 is provided substantially integrally with the head carriage 5, and a magnet 10 is provided so as to surround the coil 9. The example shown in FIG. 2 is a rotary stepping motor type actuator, in which a head carriage 13 is linearly fed by a feed screw 12 which is rotationally driven by a stepping 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 like the one shown in Figure 1, it is necessary to know the position of the actuator at that time, so a position sensor is required, and the speed of the actuator needs to be controlled at a constant level. Requires speed sensor. Therefore, when using a linear actuator, consideration must be given to space allocation for the speed sensor required.

An object of the present invention is to provide a linear actuator that requires a speed sensor and has improved space efficiency by considering the placement of the speed sensor.

The feature of this invention is that a magnetic circuit is provided with a flat permanent magnet magnetized in the thickness direction as a magnetic flux generation source.
In a linear actuator in which a flat drive coil is placed in this magnetic circuit and thrust is obtained in accordance with the direction of current flowing through the drive coil,
The magnetic flux from the permanent magnet, which is a magnetic flux generation source for applying thrust to the drive coil, is also used for the speed sensor.

Hereinafter, the present invention will be explained with reference to the embodiments shown in FIGS. 3 to 6, which show examples in which the present invention is applied to a floppy disk device.

3 to 5, a chassis 21 of the floppy disk device is provided with a driving motor (not shown) for rotationally driving a disk 23 housed in a disk case 22. A linear actuator 27 is provided for linearly moving a head carriage 26 holding a magnetic head 25 for writing or reading information signals. disk case 22
is positioned and placed on a plurality of support positioning pins (not shown) fixedly planted on the substrate. The centering hub of the disk 23 in the case 22 is placed on a chucking head (not shown) which is rotationally driven by the motor, and the centering hub is mounted on a rotation stopper 31 provided on the chucking head. An engaging portion 32 provided at the disk 23 is engaged, and the drive motor is driven to rotate, thereby urging the disk 23 to rotate. Head carriage 26
is supported at two points by one guide bar 33 and at one point by another guide bar 34, and the disk 23 is supported along these two guide bars 33 and 34.
It is designed to be able to move linearly in the radial direction. The two guide bars 33 and 34 have a round bar shape, and both ends thereof are fixed by a pressing plate 35.

The linear actuator 27 is a box-shaped yoke 3
6, flat plate-shaped permanent magnets 37, 38 fixed to the upper and lower inner surfaces of the yoke 36, and a drive coil disposed within the gap between these permanent magnets 37, 38. Each of the permanent magnets 37 and 38 is magnetized in the thickness direction, with N and S poles 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. The upper and lower magnets are arranged so that the opposite polarity faces each other. The permanent magnets 37 and 38 serve as magnetic flux generation sources and are vertically opposed to each other with a predetermined gap therebetween, and together with the yoke 36 constitute a magnetic circuit.

The drive coil 39 integrally has a connecting portion 40, and the connecting portion 4 passes through the window hole 30 of the yoke 36.
0 is connected to the head carriage 26, so that the head carriage 26 moves linearly together with the drive coil 39. A position information recording medium 41 is fixed to the side of the head carriage 26, and a position sensor 42 is provided close to and facing the medium 41. Location information recording medium 41
For example, position information is recorded magnetically, and this information is detected by a magnetoresistive element or the like. However, recording and detection of position information may be performed by other means, such as optical means. The position of the magnetic head 25 is controlled by signals obtained from the medium 41 and the position detecting section 43, which is a position sensor 42, so that the magnetic head 25 matches each track of the disk 23 and stops. .

The linear actuator 27 includes a speed detection section 44 for detecting the moving speed of the drive coil 39.
is provided. The speed detection unit 44 is connected to an upper yoke 50 fixed to the upper surface of the box-shaped yoke 36 in the figure.
A lower yoke 51 is fixed to the lower magnetic pole surface of the lower permanent magnet 38, and a detection coil 48 is disposed in the gap between both the yokes 50 and 51. The upper yoke 50 is bent so that its cross section is L-shaped, and one side of this L-shape is fixed to the upper surface of the box-shaped yoke 36 and substantially serves as one magnetic pole (the upper surface) of the upper permanent magnet 37. The other side of the L-shape of the upper yoke 50 is formed to be magnetically coupled with the upper yoke 50 (the other side magnetic pole), and the tip end, which is the other side of the L-shape, hangs down on the side of the permanent magnet 37. The lower yoke 51 is also bent to have an L-shaped cross section, and one side of this L-shaped shape is fixed to the lower surface of the lower permanent magnet 38 and is magnetically coupled to one magnetic pole of the permanent magnet 38. and
The tip of the lower yoke 51, which is the other side of the L-shape, stands up vertically so as to face the tip of the upper yoke 50, and forms a predetermined gap with the tip of the upper yoke 50. There is. In this way, the driving permanent magnets 37, 38 are placed between the upper and lower yokes 50, 51.
A magnetic circuit for speed detection is formed using the magnetic flux as a magnetic flux generation source. The detection coil 48 is the drive coil 3
9 and substantially perpendicular to the plane of the drive coil 39, and the upper yoke 50
The distal end portions of the lower yoke 51 and the lower yoke 51 are disposed in a gap formed so as to face each other. Therefore, the magnetic flux from the permanent magnets 37 and 38, which are magnetic flux generation sources for applying thrust to the drive coil 39, is also used by the detection coil 48 forming the speed sensor. The detection coil 48 can be made integrally with the drive coil 39 by molding, and in the case of molding, the connecting portion 40 can also be integrally molded.

According to the embodiment of the present invention constructed in this way, the linear actuator 27 has its drive coil 39.
By energizing, a thrust is generated in a direction corresponding to the direction of the current, and the magnetic head 25 is moved along with the head carriage 26 in the radial direction of the disk 23. As the drive coil 39 moves, the detection coil 48 also moves while cutting the magnetic flux passing through the gap between the upper yoke 50 and the lower yoke 51, so the detection coil 48 outputs a voltage signal proportional to the moving speed of the drive coil 39. Detected. This detection signal is input to a control and drive circuit (not shown) together with the position signal obtained by the position detection section 43,
This control and drive circuit moves the linear actuator 27 at a predetermined speed to a predetermined position based on the above-mentioned signals, and also stops the linear actuator 27 at the predetermined position.

According to the above embodiment, the magnetic flux from the permanent magnet 37, which is the magnetic flux generation source for giving thrust to the drive coil, is also used in the magnetic circuit for the speed sensor, so the magnetic flux generation source for the speed sensor is independent. Therefore, it is possible to obtain a linear actuator with good space efficiency.

Next, the embodiment shown in FIG. 6 will be described. The embodiment of FIG. 6 uses only one permanent magnet 54 as a magnetic flux generation source, and an upper yoke 52 is attached to the upper surface of this permanent magnet.
The lower yoke 53 is placed below the permanent magnet 54 with a predetermined gap therebetween, and the drive coil 39 is placed in the gap between the permanent magnet 54 and the lower yoke 53. Bent hanging part 5 of side edge
6 and a bent rising portion 57 of one side edge of the lower yoke 53 are opposed to each other with a predetermined gap therebetween, and a detection coil 48 integrated with the drive coil 39 is disposed within this gap. According to this embodiment, since the drive magnetic circuit and the detection magnetic circuit are formed by the only permanent magnet 54 and the upper and lower yokes 52 and 53, it is easy to construct it flatly, and it takes up even more space. An efficient linear actuator can be obtained.

According to the present invention, a yoke is magnetically coupled to one magnetic pole and the other magnetic pole of a driving permanent magnet, and the tips of these yokes are made to face each other to form a gap, and the driving coil is placed within this gap. Since the speed detection coil is integrally attached to the speed sensor, the magnetic flux from the permanent magnet, which is the magnetic flux generation source for giving thrust to the drive coil, is also used for the speed sensor, so an independent magnetic flux generation source is provided. Since this is not necessary, a space-efficient linear actuator can be provided. In addition, if the plane of the drive coil and the plane of the speed detection coil are made substantially perpendicular to each other, even if the magnetic flux generated when the drive coil is energized to generate thrust reaches the speed detection coil, the speed detection Since the coil is angled so that no power is generated by the magnetic flux generated by the drive coil, the speed detection coil can accurately detect the moving speed of the drive coil.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of a conventional linear actuator, Fig. 2 is a plan view showing an example of a stepping motor type actuator, and Fig. 3 is a partially sectional plan view showing an example of the present invention. FIG. 4 is a side sectional view of the same embodiment, FIG. 5 is an exploded perspective view showing essential parts of the same embodiment, and FIG. 6 is a side sectional view showing another embodiment of the present invention. 23...Disk, 25...Magnetic head, 26
... Head carriage, 27 ... Linear actuator, 37, 38 ... Permanent magnet, 39 ... Drive coil, 44 ... Speed detection section, 48 ... Speed detection coil, 50, 51 ... Yoke, 52, 53 ……
Yoke, 54...Permanent magnet.

Claims (1)

[Claims for Utility Model Registration] (1) A magnetic circuit is provided with a flat permanent magnet magnetized in the thickness direction as a magnetic flux generation source, a flat drive coil is placed in this magnetic circuit, and electricity is supplied to the drive coil. In a linear actuator that obtains thrust according to the direction of current, yokes are magnetically coupled to one magnetic pole and the other magnetic pole of the permanent magnet, and the tips of these yokes are opposed to each other. A linear actuator in which a gap is formed and a speed detection coil integrally attached to the drive coil is disposed within the gap. (2) The linear actuator according to claim 1, wherein the speed detection coil is mounted so that its surface is substantially perpendicular to the drive coil.