JPS644424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to direct-acting electric machines such as linear motors and speed sensors.

(Prior art) 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. FIG. 11 shows an example of a conventional actuator of this type.

As shown in FIG. 11, a conventional linear motor, for example, has flat permanent magnets 2 magnetized in the thickness direction on the upper and lower inner sides of a box-shaped yoke 1, respectively.
A drive coil 4 is arranged between these permanent magnets 2 and 3.
is integrally connected to the head carriage 5. The head carriage 5 is supported by a pair of parallel guide rails 6 (only one of which is shown), and when the drive coil 4 is energized and a thrust force in the direction corresponding to the energization direction is generated in the drive coil 4, the drive coil 4 and a head carriage 5, which is a moving body, can be moved linearly along a rail 6 in a direction perpendicular to the plane of the paper.

(Problem to be Solved by the Invention) However, in such a conventional linear motor, when the drive coil 4 is energized, in addition to generating a thrust in the direction perpendicular to the page, vertical thrust is also generated, which causes vibrations. occurs. This is because, as shown in the figure, the direction of the magnetic flux from the permanent magnets 2 and 3 is different between the central portion and both side portions, and in particular, the magnetic flux at both side portions is bent further outward, so that the torque acting on the drive coil 4 is reduced. It is thought that the direction is vertical.

Moreover, such a phenomenon also occurs when used as a speed sensor. That is, FIGS. 12 and 13
In the case of the speed sensor shown in the figure, the magnetic flux distribution and direction between the permanent magnet and the upper yoke are asymmetrical, as in the case of the linear motor described above, so when mechanical disturbance vibration is applied to the generator coil. , 8th
As shown in Figure A, noise occurs in the speed signal for each track, and using such a signal,
If you try to control the speed of a linear motor, etc., an error will occur.

(Means for Solving the Problem) The present invention corrects the direction of magnetic flux in a magnetic circuit to make the magnetic flux distribution uniform, thereby reducing the adverse effects on the coils arranged in the magnetic circuit. In a linear electric machine, a flat coil is placed in a magnetic circuit with a flat main permanent magnet magnetized in the thickness direction as a magnetic flux generation source, and this coil moves linearly in the magnetic circuit. A sub permanent magnet is provided in a side view parallel to the direction, this sub permanent magnet protrudes toward the coil side, and the magnetic poles of the sub permanent magnet and the main permanent magnet facing each other are magnetized to be the same polarity.

(Example) In FIGS. 1 and 2, the chassis 21 of the floppy disk device includes a disk case 22.
A drive motor (not shown) is provided for rotationally driving the disk 23 housed in the disk 23, and a head carriage 26, which is a moving body holding a magnetic hedge 25 for writing or reading information signals on the disk 23, is moved in a straight line. A linear motor 27 is provided to move the object. The 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 is further mounted on a rotation stopper 31 provided on the chucking head.
The engaging portion 32 provided on the centering hub is engaged, and the drive motor is driven to rotate, thereby urging the disk 23 to rotate.

The head carriage 26 has one guide bar 33
2 points, and 1 point due to another guide bar 34.
These two guide bars 33, 3
4 in the radial direction of the disk 23. two guide bars 3
3 and 34 are in the shape of round rods, and both ends thereof are fixed to the chassis 21 by pressing plates 35.

The linear motor 27 includes a box-shaped yoke 36, plate-shaped main permanent magnets 37 and 38 fixed vertically to the inner surface of the yoke 36, and these main permanent magnets 3.
7 and 38. Each of the main permanent magnets 37 and 38 is magnetized in the thickness direction so that an N pole and an S pole are formed in the thickness direction, but the magnetic poles are mutually separated at the line that bisects each main permanent magnet in the longitudinal direction. so that it is the other way around, and
The upper and lower magnets are arranged so that their different polarities face each other. The main 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 is placed on the tip of an arm-shaped mounting member 40, and the mounting member 40 passing through the window hole 30 of the yoke 36 is connected to the head carriage 26, so that the head carriage 26 is mounted together with the drive coil 39. It is designed to move in a straight line.

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. In the position information recording medium 41, position information is recorded magnetically, for example, and this information is detected by a magnetoresistive element or the like. However, the recording and detection of position information may be performed using other means, such as optical means. The position of the magnetic head 25 is controlled by a signal obtained by a position detecting section 43 consisting of a medium 41 and a position sensor 42, so that the magnetic head 25 matches each track of the disk 23 and stops.

The linear motor 27 is provided with a speed detection section 44 for detecting the moving speed of the drive coil 39. The speed detecting section 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 from a magnetic metal plate, and a gap between the yoke 47 and the magnet 46. It has a flat detection coil 48.

In the case of a linear motor, as shown in FIGS. 1 to 4, the main permanent magnets 37 and 3 of the linear motor 27 are
A sub permanent magnet 50 is disposed on the side surface of the magnet 8. As shown in FIG. 1, the sub permanent magnet 50 is attached to the inner surface of the yoke 36 parallel to the moving direction of the drive coil 39, and the magnetic poles near the main permanent magnets 37 and 38 are connected to the main permanent magnet 37. , 38 are magnetized to have the same polarity as the magnetic poles on the opposing surfaces. Furthermore, the magnetic poles in the direction of movement are also divided into two halves and have the same polarity, as shown in FIG.

On the other hand, in the case of a speed sensor, as shown in FIGS. 1, 2, and 5, a sub magnet 51 is disposed on the side surface of the main magnet 46 of the speed detecting section 44. As shown in FIG. 1, this sub magnet 51 is attached to the inner surface of the yoke 47 parallel to the moving direction of the detection coil 48 at right angles to the main magnet 46, and the magnetic pole on the main magnet 46 side is opposite to the coil of the main magnet 46. It is magnetized to the same polarity as the magnetic pole on the surface side.

By energizing the drive coil 39 of the linear motor 27, a thrust force is generated in a direction corresponding to the direction of the current, and the head carriage 26 and the magnetic head 25 move 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 yoke 47 and the magnet 46.
8, a voltage signal proportional to the moving speed of the drive coil 39 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 motor 27 at a predetermined speed to a predetermined position based on each of the above-mentioned signals. It is moved, positioned at a predetermined position, and stopped.

When performing such an operation, by providing the sub permanent magnet 50 or the sub magnet 51, the sixth
As shown in the figure, the magnetic flux generated from the main permanent magnet 38 causes the sub permanent magnets 50 to have the same polarity.
This repulsion prevents the magnetic flux from shifting to the left in the figure, and as a result, the magnetic flux is corrected so that it acts at right angles to the coil 39. In the absence of the secondary permanent magnet 50, the magnetic flux bends toward the right, as shown at the right end of the main permanent magnet 38. Therefore, the direction of the torque acting on the drive coil 4 is only perpendicular to the drawing due to the magnetic flux acting at right angles, and vibrations in the vertical direction are significantly reduced.

FIG. 9 shows another embodiment of the invention,
Sub-permanent magnets 61 and 62 are placed on both sides of the main permanent magnet 60.
FIG. 10 shows still another embodiment of the present invention in which the sub permanent magnet is formed integrally with the main permanent magnet 63 into a key shape. Give an example.

(Effect of the invention) By using the auxiliary permanent magnet, the direction of the magnetic flux at the end of the main permanent magnet is corrected, and the magnetic flux in the effective area is made uniform. In the case of a linear motor, as shown by the broken line in FIG. , the flat part A of the magnetic flux distribution expands, and the magnetic flux density becomes uniform.

The speed sensor is less affected by disturbance vibrations, and the generation of noise at the end of the decay of the generated voltage for each track is reduced, as shown in FIG. 8B.

[Brief explanation of drawings]

FIG. 1 is a plan view of a direct-acting electric machine showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of FIG. 1, FIG. 3 is a cross-sectional view of a linear motor, and FIG. Figure 5 is a cross-sectional view showing the speed sensor, Figure 6 is a diagram showing the direction of magnetic flux generated from the main permanent magnet, Figure 7 is a line diagram showing the magnetic flux distribution of the main permanent magnet, and Figure 5 is a cross-sectional view showing the speed sensor. FIG. 8 is a diagram showing the generation status of the speed signal of the head carriage for each track of the magnetic disk, FIG. 9 is a sectional view of a direct-acting electric machine showing another embodiment of the present invention, and FIG. 11 is a sectional view showing an example of a conventional linear motor; FIG. 12 is a sectional view showing an example of a conventional speed sensor; FIG.
FIG. 13 is a sectional view taken along the line AA in FIG. 12; 37, 38, 46, 60, 63... Main permanent magnet, 39, 48... Coil, 50, 51, 52,
53, 54, 61, 62, 64... Sub-permanent magnet.

Claims (1)

[Claims] 1 In a direct-acting electric machine in which a flat coil is placed in a magnetic circuit using a flat main permanent magnet magnetized in the thickness direction as a magnetic velocity generation source, and this coil moves linearly in the magnetic circuit, the coil A sub permanent magnet is provided on a side surface parallel to the direction of movement of the sub permanent magnet, the sub permanent magnet protrudes toward the coil side, and the magnetic poles of the sub permanent magnet and the main permanent magnet facing each other are magnetized to the same polarity. A direct-acting electric machine featuring: