JPS59136912A - Rein-bonded rare-earth cobalt magnet - Google Patents

Abstract

PURPOSE:To facilitate multipolar magnetization of a high coercive force magnet, and to realize high magnetic flux density inside of a resin-bonded rare-earth cobalt magnet when the device is to be injection molded by a method wherein thickness of the magnet is made to be specified value or less. CONSTITUTION:Thickness of a resin-bonded rare-earth cobalt magnet is made to 0.8mm. or less as to enable to perform easily multipolar magnetization of the magnet to be manufactured according to the injection molding method. For example, a material obtained by kneading R2TM17 magnetic powder of 60vol% and nylon 6 of 40vol% is made as raw material, a radially anisotropic magnet of 18mm. outer diameter, 5mm. height, 0.5 or 0.8mm. thickness is manufactured according to the magnetic field injection molding method, and is magnetized to 24 poles by a pulse magnetizer. The reason why thickness is limited to 0.8mm. or less is because width per one pole required for the present magnet is 2mm. or less, and moreover coercive force of the magnet is 7KOe or more, and sufficient magnetization can not be attained when thickness is not made to 1/3 or less even at the lowest.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin-bonded rare earth cobalt magnet manufactured by injection molding.

The demand for rare earth cobalt cornerstone is increasing year by year as the third type of magnet after ferrite and alnico. The types are
By alloy type, there are R, O05 type and R2TM17 type (R = rare earth element, TM = transition metal, mainly cobalt), and by manufacturing method, there are sintering method and resin bonding method. There are three resin bonding methods: compression molding, injection molding, and extrusion molding. The RCo5 system was the first alloy system to be magnetized and currently occupies the mainstream of sintered magnets. on the other hand,
Although the R2TM17 series was developed later than the ReO2 series, its performance is superior. Currently, the sintering method that produces the maximum energy product (BH) max = 50 MGOe is R
tTMl, system. In this way, manufacturing using the sintering method is used to achieve high performance. However, sintered rare earth cobalt magnets have the disadvantage of being hard and brittle, which poses problems in manufacturing and use. To compensate for this drawback, a resin-bonded rare earth cobalt magnet was developed. Since this magnet contains resin, which is a non-magnetic material, its performance is lower than that produced by sintering, but it has many other advantages. To list them: ■Low cost; ■Mechanical strength, no worries about cracking and chipping; ■Dimension accuracy can be achieved easily; ■The shape of the magnet follows the shape of the mold, so it is possible to use straw-shaped magnets, oval shapes, and gears. It can be made into any irregular shape, such as 8-stone magnets, ■ It is easy to manufacture magnets with anisotropy in the radial direction, and ■ It can be processed by normal cutting.
Some of the advantages are that even a relatively small amount of S stone can be manufactured at low cost; (1) magnets can be assembled with other parts; (2) variations between magnets are small.

In recent years, as the field of application of magnets has expanded, the use of multi-pole magnetized magnets has increased. Examples include magnetic couplings and small motors. Especially in the field of small motors, multi-pole magnetized fC8'5 is in high demand.

For small motors, PM type stepping motor magnets are the most common.

The magnets used in PM-type stepping motors are so-called radial anisotropic magnets, which can be magnetized from the inside to the outside or from the outside to the inside, as shown in FIG. 1, and can be easily multipolarized. Initially, ferrite magnets were used for this type of magnet, but as motors became smaller and higher performance, rare earth cobalt magnets were used.
It's 2. However, new problems have arisen with the use of rare earth cobalt magnets. In other words, sufficient magnetization cannot be achieved due to high cost and high coercive force. In the first place, in terms of cost, it is competitive with motors that use ferrite magnets, so the price of raw material powder is 3 times higher than that of ferrite.
Cobalt, a rare earth element that is 0 to 50 times more expensive, cannot compete without a very good design.

Therefore, a magnet must be used to bring out 70% of the characteristics of rare earth cobalt. Therefore, it is necessary to create a magnet that is completely magnetically saturated with multi-pole deposition and is stable, in addition to the problem of broken or chipped 9's.

The present invention has been made to overcome such problems. In other words, by molding a resin-bonded magnet by injection molding to produce a radially anisotropic ring-shaped magnet or a flat magnet with a wall thickness of 0, s mm or less, the magnetization of a high coercive force magnet can be completely achieved. Can be done IC7z, 9,
Higashi Takada density can be achieved inside the device, and in addition, the weight is reduced and injection molding is used, so the pressing cost can be reduced, the cost of the device can be reduced, and the cost performance of the device as a whole can be improved. Here, set the wall thickness to 0
．． The reason why we limited it to 8 mm or less is because the width per pole required for current magnets is 2 m or less, and the coercive force of the grinding stone is 7 KOθ or more, so at least the wall thickness should not be less than A. This is because flNml is not sufficient.

The present invention will be described below with reference to Examples.

Example 1 A radially anisotropic magnet as shown in No. 1 (9) was produced by a magnetic field injection molding method. The outer diameter of the grinding stone is 18m.
There are three types: 5mm in height, 0.5mm in thickness, 0.8mm in thickness, and 1.1mm in thickness. The raw material for injection molding was obtained by kneading 60 volumes of R2T, M17-based millet powder and 40 volumes of nylon 6. The obtained 7-length sample was magnetized with 24 poles by pulse magnetization. Measure the magnetic flux density of the sample by rotating the magnet using a Yuhaul element. The data obtained is a graph as shown in the 21st graph. The results are shown in Table 1. However, the permeance series numbers are all 1.2. Table 1 shows that if the wall thickness is large, the magnetization is not perfect.

[1.87 Bm or less is desirable.

Example 2 A magnet as shown in FIG. 6 was produced by magnetic field injection molding. The injection raw material was as in Example 1. I used the same one.

The magnetization direction is indicated by an arrow in the figure.

t is 50711m, W is 1'oim, t is 0.4 to 2
．． A total of 17 types of magnets were produced every 0.1 mm up to 0 mm. These grinding stones were cut into 10 pieces in the manner shown in Figure 5.
It was magnetized to 0 pole. The permeance was set to 1.5, and the surface magnetic flux density Bd was measured by moving the Hall element in the t direction. The results are shown in Figure 4. It can be seen that high magnetic performance is achieved when t is 0.8 or less.

The magnet produced by the method of the present invention can be widely used in the fields of step motors and linear motors, and has made a significant contribution to the consumer and industrial fields.

[Brief explanation of the drawing]

FIG. 1 shows a multi-pole magnetized ring-shaped radial anisotropic grinding stone. FIG. 2 shows an example of measuring the magnetic flux density of a multipolar magnetized radial anisotropic grinding stone. FIG. 6 shows a multi-pole magnetized flat magnet. FIG. 4 shows the relationship between the thickness and surface magnetic flux density of a child-like magnet with multi-pole N magnetization. Above, 1st f, = Figure 2, 30j ρ, 9 /, ρ t5 ,
ρ1(,,ni) → Fig. 4

Claims (1)

[Claims] Rare earth pebbles manufactured by injection molding method (A) have a wall thickness of 0.8 mm so that multipolar Ns can be easily formed.
A resin-bonded rare earth cobalt magnet characterized by having the following properties: