JPS6389047A - Linear motor - Google Patents

Abstract

PURPOSE:To improve the response of a linear motor by forming a magnetic air gap section at the central section of a center yoke, into which a coil is inserted, and lowering the inductance of the coil. CONSTITUTION:A magnetic air gap section 5 in width of approximately 1-1.5mm is shaped at an approximately central section in the longitudinal direction of a center yoke 1 forming a linear motor. The center yoke 1 is divided into two of 1A and 1B by the magnetic air gap section 5. Magnetic flux generated by currents flowing through a coil 2 passes through two system closed magnetic circuits consisting of the magnetic air gap section 5, the center yokes 1A, 1B and yoke plates 3, 3, but magnetic flux passing through the center yoke 1 is lowered because the permeability of the magnetic air gap section 5 is made extremely smaller than that of the center yokes 1A, 1B, thus exceedingly reducing inductance displayed by the coil 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a near motor suitable for use in moving a magnetic head of a hard disk, etc., and is particularly applicable to those requiring high-speed response. It is.

[Summary of the invention]

The linear motor of the present invention includes a center yoke, a yoke plate that comes into contact with both ends of the center yoke to form a magnetic circuit, a magnet placed on an opposing surface of the yoke plate and the center yoke, and In a linear motor consisting of a coil that is fitted and supported so as to be movable in the longitudinal direction of a center yoke, a slight magnetic gap is formed approximately in the center of the center yoke, and the magnetic air is supplied to the coil by this magnetic gap. The responsiveness of the linear motor is increased by sharpening the rise of the drive current.

[Conventional technology]

A hard disk is designed to be able to write and read signals by coming into contact with a magnetic head while rotating, and is structured as shown in FIG. 3.

In this figure, a hard disk 10 is rotationally driven by a rotating means (not shown), and a rotary lever 11 is rotatably supported by a pivot bin 12 with respect to the hard disk 10.

An arm 13 supporting a magnetic head 14 is fixed to the tip of the rotating lever 11, and a lever motor 15 is attached to the other end of the one-turn lever 11.

As will be described later, the linear motor 15 is composed of a coil 20 wound around a bobbin 16, a center yoke 21, a yoke plate 22, etc. When a pulse current is passed through the coil 20, the coil 20 is moved to the center yoke 21.
It's like moving along. Therefore, the rotary lever 11 rotates around the pivot pin 12, thereby the magnetic head 14 moves in the radial direction along the recording surface of the hard disk 10, and the magnetic head 14 engages with any track on the hard disk 10. Signals are written and read by contacting the device.

The linear motor used to move the magnetic head in this conventional hard disk has a coil 2 wound around a bobbin movably arranged relative to the center yoke 1 as shown in FIGS. 4 and 5. It is constructed by attaching magnets 4, 4 to the inside of a yoke plate 3.3 placed above and below 1, and magnets 4.4
By interlinking the magnetic flux generated by the coil 2 with the current flowing through the coil 2, an electromagnetic force is generated in the coil 2, causing the center yoke l to move in the length direction.

[Problem that the invention seeks to solve]

As shown in the sectional view of FIG. 5, such a conventional linear motor has a coil 2, a center yoke l, upper and lower yoke plates 3, 3, and magnets 4.4, as shown by dashed lines. magnetic fluxes B, B,... are formed. Electromagnetic force is generated by the current flowing through the coil 2. When the current flows through the coil 2, a magnetic flux Φ is generated in two closed magnetic paths as shown by the dotted lines, and the coil 2 is proportional to the magnetic flux Φ. The inductance L increases, and the rise of the current flowing through the coil 2 is suppressed.

Therefore, even if an attempt is made to make the linear motor respond at high speed in response to a control signal, the current flowing through the coil 2 will be suppressed, resulting in a delayed response, and it will take time to move the head in the radial direction of the hard disk, requiring high-speed operation. There was a problem that it was not compatible with the device.

The present invention was made in view of these problems, and an object of the present invention is to improve the transient response characteristics of the device by reducing the inductance L of the coil without reducing the driving force of the linear motor. It is something to do.

Means for Solving Problem C] The linear motor of the present invention has a coil arranged in a magnetic field formed by a center yoke, a U-shaped yoke plate, and a magnet. A magnetic air gap is provided approximately in the middle of the center yoke.

[Effect]

Since a magnetic air gap is provided in the center yoke, changes in magnetic flux generated by current flowing through the coil are reduced, and back electromotive force is reduced. As a result, the inductance of the coil can be reduced without reducing the driving force.

It becomes possible to form a linear motor with good responsiveness.

〔Example〕

FIG. 1 is a cross-sectional view of the main parts of the linear motor of the present invention, and the same members as in the conventional linear motor are given the same reference numerals.

As shown in this figure, a center yoke 1 forming the linear motor of the present invention has a magnetic gap 5 with a width of about 1 to 1.5 mm formed approximately at the center in the longitudinal direction. Due to this magnetic gap 5, the center yoke is LA
, and IB.

Since the driving section of the linear motor of the present invention has the above-described structure, the magnetic flux Φ generated by the current I flowing through the coil 2 is distributed between the magnetic gap 5 and the center yoke IA, as shown in FIG. .

It passes through two closed magnetic circuits consisting of IB and yoke plate 3.3, but the magnetic permeability po of the magnetic gap 5
is extremely small compared to the magnetic permeability of the center yokes IB and IA, so the magnetic flux Φ passing through the center yokes 1 (A, B) is reduced, and the inductance L (Φ/
I) becomes extremely small.

Therefore, when a driving voltage is applied to the coil 2 at time to as shown in FIG. 2, in the case of a conventional motor with a large inductance, the rise of the driving current I is gradual as shown by the two-dot chain line a. However, in the case of the linear motor of the present invention, the inductance L exhibited by the coil 2
Since this can be made smaller, the rising edge becomes steeper as shown by the - dotted chain line, and the rising characteristic becomes closer to the ideal solid line, thereby improving the response of the head.

Further, the driving force F when the current I is passed through the coil 2 is the fifth
As shown in the figure, from the magnets 4, 4 to the center yoke l
If the magnetic flux directed toward (A, B) is B, then F = B I 5 is center yoke 1 (
A, B), the magnetic flux B from the magnets 4, 4 toward the center yoke l (A, B) hardly changes, so there is an effect that the driving force F of the coil 2 hardly decreases.

A sufficient effect can be obtained with a gap of about 1-1.5 mm in the magnetic gap 5, but in order to prevent magnetic particles from adhering to this gap, a non-magnetic material such as glass or paper should be used. It is preferable to fill it.

〔Effect of the invention〕

As explained above, the linear motor of the present invention reduces the inductance of the coil by forming a magnetic gap in the center portion of the center yoke into which the coil is inserted, so that the driving voltage can be reduced. The current that flows when applied has a steep rise, which has the effect of improving the responsiveness of the linear motor.

Further, when the linear motor of the present invention is used as a driving force for a magnetic head of a hard disk, there is an advantage that access time is shortened and information reading speed can be increased.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a linear motor that is an embodiment of the present invention, Fig. 2 is a graph showing the rise characteristics of the drive current, Fig. 3 is a schematic diagram explaining an example of the use of the linear motor, and Fig. 4 is a diagram of the linear motor. FIG. 5 is a perspective view and a sectional view showing the magnetic flux of the linear motor. In the figure, 1 is the center yoke, 2 is the coil, 3 is the upper and lower yoke plate, 4 is the magnet, 5 is the magnet.

Claims (1)

[Claims] A center yoke, a yoke plate that contacts both ends of the center yoke to form a magnetic circuit, the center yoke, a magnet placed on a facing surface of the yoke plate, and a magnet that moves in the longitudinal direction of the center yoke. What is claimed is: 1. A linear motor comprising a coil that can be fitted and supported, characterized in that a magnetic gap is formed approximately in the center of the center yoke.