JP2699252B2 - Permanent magnet variable magnetic field generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet variable magnetic field generator. This device is used in the field of electronic and electrical materials and electronic materials where a variable magnetic field needs to be applied.

[0002]

2. Description of the Related Art When it is necessary to apply a variable magnetic field, conventionally, an electromagnet or a solenoid coil has been generally used.

When an electromagnet or a solenoid coil is used, the intensity of the generated magnetic field can be easily changed by increasing or decreasing the current flowing through the coil. When a unipolar power supply is used for the electromagnet, the intensity of the generated magnetic field is changed from 0 G to a value (for example, 20 kG) determined by the saturation magnetization of the iron material of the electromagnet.
Super). If a bipolar power supply is used, the direction of the generated magnetic field can be reversed.

However, since the magnetomotive force source of the electromagnet or the solenoid coil is a coil, the ratio of the coil to the entire apparatus is large (in terms of both volume and cost), and it is difficult to produce a small and inexpensive variable magnetic field generator.

Further, in the case of an electromagnet or a solenoid coil, a current flows through the coil to generate a magnetic field, so that there is a problem that a large amount of power is consumed. In addition, when a magnetic field is constantly generated, heat generation due to coil resistance also poses a problem.

Further, when an electromagnet or a solenoid coil is used, alternating current is converted to direct current by a smoothing circuit. At this time, electric noise is likely to occur due to a high current value.
Therefore, there is a problem that surrounding electronic devices are likely to malfunction.

[0007] Therefore, there has been a demand for a device capable of generating a variable magnetic field which is small and does not use a large amount of electric power. For this reason, a variable magnetic field generator using a permanent magnet has been considered.

FIG. 3 shows an example of a variable magnetic field generator using a permanent magnet. In this conventional example, the yokes 10a, 10b, 1
0c and the permanent magnets 12a and 12b. The yoke 10b is moved by the ball screw 14, and the permanent magnets 12a and 12b are moved.
The size of the gap 16 between b is changed. Thereby, the intensity of the magnetic field generated between the gaps 16 can be changed. For convenience, a mechanism for rotating the ball screw 14 to move the yoke 10b is collectively represented by a square 18.

Although the structure of the conventional example shown in FIG. 3 can be very simple, when the gap 16 becomes large to some extent, the magnetic field intensity gradually decreases. In addition, there is a problem that the magnetic field strength cannot be reduced to 0G.

In addition, since the size of the gap 16 between the permanent magnets is changed, the size of the apparatus is disadvantageously increased.

Further, as the size of the gap 16 between the permanent magnets changes, not only the magnetic field strength but also the magnetic field generation region changes. There is also a problem that the larger the gap 16 between the permanent magnets, the worse the uniformity of the magnetic field becomes.

Therefore, the variable magnetic field generator as shown in FIG. 3 has not been practically used.

FIG. 4 shows another conventional example using a permanent magnet. This is called a magnet stand, and can change the magnetic attractive force at the lower part of the apparatus.

The columnar permanent magnet 20 is composed of iron yokes 22a,
2b and spacers 24a and 24b made of a non-magnetic material. The space indicated by reference numeral 26 in the figure is a space.

When the magnetization direction indicated by the arrow 28 is horizontal as shown in FIG. 4A, the flow of the magnetic force lines coming out of the columnar permanent magnet 20 becomes as shown by a dotted line 30, and the table 32 can be attracted. On the other hand, when the magnetization direction is perpendicular as shown in FIG. 4B, the table cannot be attracted because the flow of the lines of magnetic force does not pass through the lower part of the apparatus as shown by dotted lines 34a and 34b.

As described above, the magnet stand increases or decreases the magnetic attraction generated at the lower portion of the apparatus by changing the magnetization direction of the columnar permanent magnet. The ability to increase or decrease the magnetic attraction force is used, for example, it is used to install a measuring instrument or the like on the surface of a large-sized device. Further, a magnet chuck in which a plurality of magnet stands are arranged is used, for example, for fixing an iron plate during milling.

Although the magnet stand is a very practical device as described above, it is not suitable for generating a variable magnetic field in a certain area. When the spacer 24a is removed and this is used as a magnetic field generation region, FIG.
In this state, the magnetic field in this magnetic field generation region can be 0 G (ideal case), but the cylindrical permanent magnet 20 is rotated until the state of FIG. 4A (without the table 32). This is because the magnetic field lines coming out of one pole of the magnet 20 flow through both the spacers 24a and 24b to the opposite pole of the magnet 20 when moving. That is, the lines of magnetic force are distributed up and down, and the strength of the magnetic field decreases. Another reason is that the direction of the magnetic field in the magnetic field generation region changes, and the magnetic field in a certain direction does not increase.

From the above, it can be seen that the conventional example shown in FIGS. 3 and 4 cannot generate a variable magnetic field in a fixed direction between the fixed gaps. Therefore, there is a need for a variable magnetic field generator capable of generating a variable magnetic field in a fixed direction between fixed gaps.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a variable magnetic field generator using only permanent magnets and capable of changing the magnetic field between fixed gaps.

[0020]

According to a magnetic field generator which comprises a yoke having a fixed gap and two or more permanent magnets arranged in parallel in the yoke and generating a magnetic field in the fixed gap, At least one of them is fixed, and at least one is rotatable or movable, and the total magnetic flux of the permanent magnet capable of rotating or moving is larger than the total magnetic flux of the fixed permanent magnet,
Further, the gap of the yoke at the portion where the rotatable or movable permanent magnet is sandwiched is made smaller than the fixed gap between the yokes.

[0021]

1 shows an example of a permanent magnet variable magnetic field generator according to the present invention. On the iron yoke 40, a permanent magnet 42 whose magnetization direction is fixed and a permanent magnet 44 whose magnetization direction can be changed are provided in parallel. Arrows 46 and 48 indicate the directions of magnetization of the permanent magnets 42 and 44, respectively.

There are two methods for changing the direction 48 of magnetization of the permanent magnet 44 as follows. One method is to rotate the permanent magnet 44 to change the direction of magnetization. Permanent magnet 4
4 is constituted by connecting a plurality of permanent magnets whose magnetization directions are slightly different from each other back and forth (in a direction perpendicular to the paper), and moving this permanent magnet 44 back and forth (in a direction perpendicular to the paper) to change the direction of magnetization. One way to change is. In the case of a method of moving the permanent magnet back and forth, a prismatic permanent magnet may be used. However, in the case of this method, it goes without saying that the front-rear width of the apparatus is slightly increased.

The fixed permanent magnet 42 and the movable permanent magnet 44 need not be provided one by one as shown in FIG. 1, but a plurality of permanent magnets may be provided in parallel according to the required strength of the generated magnetic field. .

The flow of lines of magnetic force in the permanent magnet variable magnetic field generator according to the present invention will be described with reference to FIG. 1 are given the same reference numerals.

In the state shown in FIG. 2A, the magnetization direction 46 of the permanent magnet 42 and the magnetization direction 48 of the permanent magnet 44 are the same. Therefore, the magnetic force lines 50 flow as shown in the figure. Therefore, two lines of magnetic force from the permanent magnets 42 and 44 flow through the fixed gap 52 between the yokes.

On the other hand, in the state of FIG. 2B, the magnetization direction 46 of the permanent magnet 42 and the magnetization direction 48 of the permanent magnet 44
Is the opposite. Therefore, the magnetic force lines 54 flow as shown in the figure. For this reason, the lines of magnetic force do not flow in the fixed gap 52 between the yokes, and the magnetic field in the fixed gap 52 is 0.
G.

The direction of magnetization 48 of the permanent magnet 44 is shown in FIG.
By gradually changing the state shown in FIG. 2B to the state shown in FIG. 2A, the strength of the magnetic field generated in the fixed gap 52 can be gradually increased.

If the relationship between the angle between the magnetization direction 48 of the permanent magnet 44 and the horizontal and the strength of the magnetic field generated in the fixed gap 52 is measured in advance, the permanent magnet 44 is rotated to generate the magnetic field in the fixed gap 52. The intensity of the applied magnetic field can be arbitrarily changed.

By rotating the permanent magnet 44, the direction of magnetization 48
When changing, even if the rotation of the permanent magnet 44 is performed manually,
It may be performed by motor drive. Further, by providing the angle measuring device, it is possible to precisely control the magnetic field intensity.
When the permanent magnet is rotated by driving the motor, the motor and the permanent magnet may be directly connected, but the motor torque can be reduced by using a gear. This makes it possible to reduce the size and cost of the entire apparatus, and furthermore, it is easy to stop the gear at an arbitrary rotation angle by locking the gear.

The size of the fixed permanent magnet 42 is determined in consideration of the required strength of the generated magnetic field and the performance of the permanent magnet used. When the size of the permanent magnet may be smaller than that of FIG. 2, the right end and the left end of the permanent magnet 42 may be replaced with iron yokes. In addition, it is natural that the iron yoke 40 must be designed so as not to be magnetically saturated regardless of the direction of magnetization 48 of the permanent magnet 44.

In order to function as a variable magnetic field generator, the magnetic field generated in the fixed gap 52 must be reduced to 0 G. As a result of the study by the present inventors on this point, the following has been found.

In order to reduce the magnetic field of the fixed gap 52 to 0 G, it is important to consider the balance of the amount of magnetic flux generated by the permanent magnets 42 and 44. Of course, the fixed gap 52 and the permanent magnet 44 are inserted. The difference in the size of the gap with the gap of the iron yoke (hereinafter referred to as the magnet insertion gap) is important. That is, the magnet insertion gap is preferably narrower than the fixed gap 52. This is because, in the state of FIG. 2B, the lines of magnetic force of the permanent magnets 42 flow more easily in the narrow gap insertion gap than in the wide gap fixed gap 52, and thus the magnetic field of the fixed gap 52 is 0G. It is easy to become.

If the lines of magnetic force from the permanent magnet 42 also flow through the fixed gap 52, the lines of magnetic force from the permanent magnet 44 flow in the opposite direction (to the right in FIG. 2B) through the fixed gap 52. The leftward magnetic line of force from the permanent magnet 42 is canceled, and the magnetic field in the fixed gap 52 can be made 0 G as a whole.

If the total magnetic flux of the permanent magnets 44 is slightly larger than the total magnetic flux of the permanent magnets 42, FIG.
In the state of (b), the magnetic field of the fixed gap 52 exceeds 0 G and becomes a negative value (to the right in the figure). Therefore, FIG.
Even if the magnetization direction 48 of the permanent magnet 44 is not completely leftward as shown in FIG.
Can be. Of course, if the total magnetic flux amount of the permanent magnets 44 is made much larger than the total magnetic flux amount of the permanent magnets 42, a large negative (rightward) magnetic field can be generated in the fixed gap 52.

In order to achieve the smallest possible and high magnetic field strength, the permanent magnets 42 and 44 must have 1-5
Type SmCo magnet, 2-17 type SmCo magnet, NdFeB
Rare earth magnets with high characteristics such as magnets (especially anisotropic sintered magnets)
It is better to use

In the present invention, a variable magnetic field generator was manufactured using only permanent magnets. That is, the present invention does not use an electromagnet or a solenoid coil, and does not require power for it. In addition, there is an advantage that the device can be downsized because no coil is used. For example, the permanent magnet variable magnetic field generator according to the present invention (for example, a gap interval of 20 to
30mm, the size of the device is almost 30 × 30 × tens of c
m) is only a fraction of the volume of a variable magnetic field generator using an electromagnet or a solenoid coil, which can generate a magnetic field of the same intensity.

Further, the permanent magnet variable magnetic field generator of the present invention has a great advantage that the size of the region for generating a magnetic field is invariable, that is, a variable magnetic field can be generated between fixed gaps.

[0038]

According to the variable magnetic field generator of the present invention, a variable magnetic field generator using only permanent magnets and capable of changing the magnetic field between the fixed gaps can be provided.

[Brief description of the drawings]

FIG. 1 shows an example of a variable magnetic field generator according to the present invention.

FIG. 2 is a diagram illustrating the flow of lines of magnetic force in an example of a variable magnetic field generator according to the present invention.

FIG. 3 is a conventional example of a variable magnetic field generator using a permanent magnet.

FIG. 4 is another conventional example of a variable magnetic field generator using a permanent magnet.

Claims (1)

(57) [Claims] 1. A magnetic field generator for generating a magnetic field in a fixed gap, comprising: a yoke having a fixed gap; and two or more permanent magnets arranged in parallel in the yoke, wherein at least one of the permanent magnets is provided. Is fixed, and at least one is rotatable or movable. The total magnetic flux of the permanent magnet capable of rotating or moving is larger than the total magnetic flux of the fixed permanent magnet, and A permanent magnet variable magnetic field generating device, wherein a gap of a yoke in a portion sandwiching a movable permanent magnet is narrower than a fixed gap between the yokes.