JPH0444405B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic drive device, and more particularly to an electromagnetic drive device that converts electrical energy used for positioning means of a magnetic head in an electromagnetic disk device into mechanical kinetic energy by electromagnetic action. The present invention relates to a method of magnetizing a magnetic circuit to be incorporated.

A moving coil type electromagnetic drive device called a voice coil type motor is generally used as a positioning means for the magnetic head of a magnetic disk device.

First, a method of magnetizing a magnetic circuit in a conventional electromagnetic drive device of this type will be explained based on the drawings.

Here, FIG. 1 is a side view of a magnetic circuit of a conventional electromagnetic drive device, and FIG. 2 is a cross-sectional plan view taken along the line A--A in FIG.

In Figures 1 and 2, 1 is a yoke piece, 2
is a center pole, 3, 3a are side yokes, 4, 4a and 4b are bolts for fixing the side yokes 3, 3a and the center pole 2 to the yoke piece 1, respectively, 5 and 5a
are permanent magnets fixed to the side yokes 3 and 3a, respectively.

When magnetizing the magnetic circuit with the above configuration, the gap distance between the side yoke 3 and the center pole 2 is small, so the magnetizing coil cannot be inserted after they are assembled as shown in Figures 1 and 2. Conventionally, the permanent magnets 5 and 5a were individually magnetized before assembly, or the permanent magnets 5 and 5a were magnetized by the side yokes 3 and 5a, respectively.
I assembled it after magnetizing it while it was fixed to 3a.

By the way, permanent magnets that have a characteristic of having an inflection point in the second quadrant of the hysteresis curve (hereinafter referred to as permanent magnets with an inflection point) have a small permeance coefficient and are Even if magnetized, the operating point will be below the inflection point, so the operating point magnetic flux density Bd will be small, and even if assembled in this state, the air gap magnetic flux density Bg will be small and the performance as a magnetic circuit will be insufficient.

Therefore, in conventional magnetization before assembly, permanent magnets without an inflection point (for example, RCO ₅ series magnets for rare earth cobalt magnets) or even if there is an inflection point, reasonable price was considered. It is necessary to use a magnet (for example, a ferrite magnet) whose permeance coefficient, which is determined by the size ratio, is below the operating point on the demagnetization characteristic curve.

However, rare earth cobalt magnets are RCO ₅ series and
They are roughly divided into two types: R ₂ CO ₁₇ series, but because the permeance coefficient of the magnetic circuit is small, the operating point magnetic flux density does not increase even if magnetized before assembly.
Uses RCO ₅ series rare earth cobalt magnets.
There was a problem that the magnetic flux density could not be increased.

The object of the present invention is to overcome the above-mentioned conventional drawbacks and
An object of the present invention is to provide a magnetization method that allows magnetization after assembly of a magnetic circuit.

The magnetization method of the present invention provides a voice coil having an E-shaped yoke made of a ferromagnetic material including a pair of side yokes and a center yoke, and a permanent magnet fixed to a surface of each of the side yokes facing the center yoke. In a method for magnetizing a magnetic circuit for a motor, after assembling a magnetic circuit using a rare earth magnet having an inflection point in a demagnetization curve as the permanent magnet, arranging a plurality of magnetizing coils around the permanent magnet, The present invention is characterized in that these magnetizing coils are combined to form a rectangular magnetizing coil, and then the permanent magnet is magnetized by energizing the magnetizing coil.

The details of the present invention will be explained below with reference to the drawings.

3A and 3B are a perspective view showing a state before magnetization and a plan view showing a state in which a magnetizing coil is set on a permanent magnet, respectively, for explaining an embodiment of the magnetizing method of the present invention.

First, in Figure 3A, the configuration of the magnetic circuit is
Although it is similar to the figure or FIG. 2, the magnetizing coil is divided into a U-shaped magnetizing coil 6 and a rod-shaped magnetizing coil 7. The magnetizing coils 6 and 7 are rods made of a rigid conductor such as copper or aluminum, and the parts other than the junction 8 (see Figure 3 B) are made of non-green material such as vinyl tape (not shown). covered with. Further, the width W ₂ of the magnetizing coil B is set to be narrower than the gap W ₁ between the end face of the permanent magnet 5 and the yoke piece 1. Lead wires 9 and 9a are connected to one ends of the magnetizing coils 6 and 7, respectively.
Further, a magnetizing coil 10 is fixed to the magnetizing coil to prevent a short circuit between the + pole and the - pole. 11,11
A is a bolt for coupling the magnetizing coils together.

Next, magnetization is performed using the above magnetizing coil in the following manner.

First, the magnetizing coil 6 is inserted into the gap of the magnetic circuit, and then the magnetizing coil 7 is fixed to the magnetizing coil 6 with bolts 11 and 11a, and is attached around the permanent magnet 5 as shown in FIG. Attach the magnetic coil.
and terminals 12 and 1 of leads 9 and 9a.
2a are each connected to a capacitor magnetizer (not shown), and magnetization is performed by momentarily passing a direct current through the magnetizing coil. In addition, if the terminals 12 and 12a are connected to the + side and the - side, respectively, in FIG. 3B, a current flows through the magnetizing coil in the direction of the arrow shown. After magnetization, the bolts 11, 11a may be removed and the magnetizing coils 6 and 7 may be taken out to the magnetic circuit.

According to this method, the magnetic circuit can be magnetized above the inflection point on the demagnetization curve because the magnetic circuit is in a state after assembly, that is, a state with a high permeance coefficient.

Next, the magnetic characteristics of the magnetic circuit using the above magnetization method will be explained based on FIG. 4 in comparison with a conventional example.

FIG. 4 is a diagram showing the demagnetization curve of each rare earth cobalt magnet, and A and B in the figure are respectively
The demagnetization curves, X and Y of RCO ₅ and R ₂ CO _17- based rare earth cobalt magnets (Hitachi Metals H18B and H23) are the side yoke 3 and Y shown in Fig. 1, respectively.
A magnetic circuit in which permanent magnets 7 and 7a are fixed to 3a, that is, the permeance coefficient before assembly and Fig. 3A,
Figure B shows the permeance coefficient of the magnetic circuit after assembly.

Therefore, referring to Fig. 4, according to the conventional magnetization method before assembly, the permeance coefficient is low as shown by the straight line X, so the operating point magnetic flux density after assembly is
In order to increase Bd, it is necessary to use an RCO ₅ rare earth magnet (curve A) that has a large coercive force and has no inflection point. However, since the RCO ₅ -based rare earth magnet has the demagnetizing characteristic shown by the curve A, the operating point magnetic flux density Bd ₁ in the case of the permeance coefficient shown by the above-mentioned straight line X is only about 5500G.

On the other hand, according to the magnetization method of this embodiment shown in FIG. 3A and B, the permeance coefficient is
As shown in Figure 2, the demagnetization resistance is significantly improved even if R ₂ CO _17- based rare earth magnets (curve B) are used, and the magnetic flux density Bd ₂ between the magnetic gaps is approximately It can be made more than 7000G.

As described above, according to the present invention, the permeance coefficient of the magnetic circuit is significantly improved, and the electromagnetic drive device can be made smaller, lighter, and higher in performance.

[Brief explanation of drawings]

Figure 1 is a side view showing an example of a conventional electromagnetic drive device, Figure 2 is a view taken along arrow A-A in Figure 1, Figure 3 is
B is a perspective view and a side view for explaining one embodiment of the present invention, and FIG. 4 is a diagram showing demagnetization curves of various permanent magnets. 1: Yoke piece, 2: Center pole, 3,3
a: Side yoke, 5, 5a: Permanent magnet, 6,
7: Magnetizing coil.

Claims (1)

[Claims] 1. Magnetization of a magnetic circuit for a voice coil motor having an E-shaped yoke made of a ferromagnetic material including a pair of side yokes and a center yoke, and a permanent magnet fixed to a surface of each side yoke facing the center yoke. In the method, after assembling a magnetic circuit using a rare earth magnet having an inflection point in a demagnetization curve as the permanent magnet, a plurality of magnetizing coils are arranged around the permanent magnet, and these magnetizing coils are arranged around the permanent magnet. A method of magnetization, characterized in that the permanent magnet is magnetized by combining the permanent magnets to form a rectangular magnetization coil and then energizing the magnetization coil.