JPH0389839A - Carriage scanner - Google Patents

Abstract

PURPOSE:To balance the moment of driving force to a carriage so as to improve driving properties by adjusting the shape of a permanent magnet within the magnetic circuit of a linear motor so that the driving force moment around the center of gravity of a mobile part may be balanced. CONSTITUTION:The force points P1-P4 of electromagnetic forces Fa-Fd are on corners of an oblong, and horizontal distances from the force points P1-P4 to the center of gravity G and each moment around the center of gravity by electromagnetic force Fa-Fd are sought. By changing the thicknesses of permanent magnets 7a-7d, the electromagnetic force at each force point P1-P4 is adjusted. The thicknesses of permanent magnets 7a-7d are determined so as to compensate the deviation of the center of gravity G by adjusting the magnitudes of the electromagnetic forces Fa-Fd. Hereby, the driving force moment around the center of gravity can be balanced, and the pitching and the yawing of a carriage can be removed, and the driving properties of the carriage can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carriage scanning device that moves a head that performs recording, reproduction, or erasing on a disk-shaped recording medium.

[Prior Art] Fig. 3 shows a sectional view of a conventional drive device using a beam near motor, in which an actuator for moving a head is placed on a carriage 2 on which pobbins 1 and 1, each having a coil (not shown) wound thereon, are attached on the left and right sides. 3 is attached, and a movable part 4 is constituted by integrating the pobbin 1, carry 2, ji 2, and actuator 3. The movable part 4 is slidable back and forth along a rail 5.5 passing through a bearing of the carriage 2. Yokes 6a, 6b and 6C16d are arranged above and below the left and right pobbins 1.1 in the direction of the rail 5, respectively, and yokes 6e, 6f along the direction of the rail 5 are spaced apart in the hollow part of the potbin 1.1. are located.

Permanent magnets 7a, 7b, and 7C17d are attached to the surfaces of the yokes 6a, 6b, and 6C16d facing the pobbin l, respectively, facing toward the rail 5. When current flows through the coils, the permanent magnets 7a, 7b, and 7C17d Electromagnetic forces Fa%Fb, Fc, and Fd act on the side surfaces of the coils with force points PL, P2, P3, and p4, respectively.
It is designed to drive the movable part 4.

[Problem to be solved by the invention] However, in the above-mentioned conventional example, the driving force Fa,
Since Fb, Fc, and Fd are equal, an unbalance occurs in the moment around the center of gravity G, which is not necessarily in a symmetrical position vertically and horizontally, and pitching or yawing in the direction of movement occurs when the movable part 4 moves. The drive characteristics of the movable part 4 deteriorate.

In addition, in order to eliminate pitching of the movable part 4, there is a method of positioning the 7-cut unit 3 between the rails 5.5 and aligning the center of gravity G with the center of the driving force as shown in FIG. There are drawbacks that the carriage 2 becomes larger and the rigidity near the attachment portion of the actuator 3 decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a carriage scanning device that eliminates the above-mentioned drawbacks, balances the moment of the driving force on the carriage, and improves the driving characteristics.

[Means for Solving the Problems] In order to achieve the above object, in a carriage scanning device according to the present invention, in a drive device that drives a carriage by a linear motor, the driving force moment around the center of gravity of the movable part is The present invention is characterized in that the shape of the permanent magnets in the magnetic circuit constituting the linear motor is adjusted so as to be balanced.

[Function] By adjusting the shape of the permanent magnet in the magnetic circuit, the carriage scanning device having the above configuration balances the moment around the center of gravity of the movable part due to the driving force, and can drive without pitching or yawing. conduct.

[Example] The present invention will be explained in detail based on the example illustrated in FIGS. 1 and 2. Note that the same reference numerals as in FIGS. 3 and 4 indicate the same members.

FIG. 1 is a sectional view of a drive device according to a first embodiment,
In contrast to the conventional magnet shown in FIG. 3, the thickness of each permanent magnet 7a to 7d is adjusted individually rather than uniformly. Electromagnetic force Fa
The force points P1 to P4 of -Fd are located on the vertices of the rectangle, and the horizontal and vertical distances from the force points Pi-P4 to the center of gravity G can be expressed as follows. That is, the horizontal distance is Pl, P2
from! ! , P3, P4 to x2. The vertical distance is PI, P
3 to yt, P2 and P4 to y2.

At this time, in order for the moments around the center of gravity due to the electromagnetic force F to be balanced, the following (D, (2), (3),
It is sufficient if formula (4) is satisfied.

yl ・Fa= 72 ・Fb ・・
・(1)71 ・Fc= 72 ・Fd
= (2) xl e Fa = x2 * Fc
…(3)11・Fb=! 2・Fd
...(4) These (1), (2
), (3), and (4), the thickness of the permanent magnets 7a to 7d may be changed to adjust the electromagnetic force at each force point P1 to P4. The permanent magnet of the first embodiment 7
The thicknesses a to 7d are thus determined so as to adjust the magnitude of the electromagnetic force Fa-Fd and compensate for the deviation of the center of gravity G.

FIG. 2 is a sectional view of a drive device according to a second embodiment,
Compared to the one in FIG. 3, the thickness of each of the permanent magnets 7a to 7d is constant, but the widths are different.

In this case as well, as in the first embodiment, (1), (2),
Equations (3) and (4) are the conditions for moment balance, and by changing the width of the permanent magnets 7a to 7d, the magnetic flux density across the coil is changed, and the electromagnetic force Fa-
Fd is generated. In addition, since the thickness of the permanent magnets 7a to 7d manufactured as one unit is the same, the thickness of each permanent magnet 7a to 7d is adjusted according to the effective length ratio that satisfies the condition of balance.
By cutting and separating the permanent magnets 7d, individual differences between the permanent magnets 7a to 7d can be reduced.

In the embodiment, linear motors are arranged on both sides of the carriage 2, but even if a linear motor is arranged only on one side of the carriage, balance can be maintained by adjusting the shape of the permanent magnet. .

[Effects of the Invention] As explained above, the carriage scanning device according to the present invention can balance the driving force moment around the center of gravity, eliminate pitching and yawing of the carriage, and has the effect of improving the driving characteristics of the carriage. be.

[Brief explanation of drawings]

1 and 2 are sectional views of first and second embodiments of a carriage scanning device according to the present invention, respectively, and FIGS. 3 and 4 are sectional views of a conventional carriage scanning device. . Code 1 is a bobbin, 2 is a carriage, 3 is an actuator,
4 is a movable part, 5 is a rail, 6a-6f is a yoke, 7a-
7d is a permanent magnet, PiNP4 is a point of force, and G is a center of gravity.

Claims (1)

[Claims] 1. A drive device for driving a carriage using a linear motor, characterized in that the shape of a permanent magnet in a magnetic circuit constituting the linear motor is adjusted so that the driving force moment around the center of gravity of the movable part is balanced. scanning device.