JPH01138957A - Magnetic circuit - Google Patents

Abstract

PURPOSE:To make the flux density in a gap constant, by a method wherein the sectional area of one part of a yoke is formed so as to be narrow while the narrow part is provided with a ferromagnetic member. CONSTITUTION:A magnetic circuit is provided with a magnet 1, a rectangular yoke 2, attached above a gap 3 at the center of the magnet, and iron screws 4, screwed into screw holes 9 provided at the upper part of the yoke 2. The magnet 1 is magnetized in up-and-down direction shown in a diagram and a magnetic circuit, in which flux is conducted into the yoke 2 through the gap 3 and returns to the magnet 1 through the yoke 2, is constituted. A coil is passed through the gap 3 whereby a linear motor is constituted. The iron screws 4, screwed into the screw holes 9 of the yoke 2, are formed of the same material as the yoke 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic circuit, and particularly to a magnetic circuit used in a linear motor.

[Prior art] Conventionally, this type of magnetic circuit used in linear motors is
It consisted of a magnet and a yoke, and both the magnet and yoke were fixedly formed.

In addition to the magnetic circuit formed by a yoke with one gap and one magnet, with the advancement and miniaturization of devices, gaps 8a and 8b are provided above and below the yoke 8 as shown in FIG. 6, for example. A top and bottom type magnetic circuit in which the magnets 1 are attached to the gaps 8a and 8b, and a twin body type in which magnetic circuits are attached to both sides of the driven body are also used.

[Problems to be Solved by the Invention] Since there are variations in the characteristics of magnet materials, variations occur in the magnetic flux density of the assembled magnetic circuit. When using a single magnetic circuit, the variation in magnetic flux density is only due to the difference in force, but when using the above-mentioned upper and lower type magnetic circuit or a double-barrel type placed on both sides of the driven body, There has been a problem in that unnecessary moments are generated due to differences in magnetic flux densities in the magnetic circuits, which impedes higher speeds.

[Means for Solving the Problems] The present invention has been made in order to solve the above-mentioned conventional problems, and as a means for solving the problems, a magnetic circuit including a magnet and a yoke for passing the magnetic flux of the magnet is provided. , a magnetism characterized in that a part of the yoke is formed to have a narrow cross-sectional area, and a ferromagnetic member that can block part or all of the narrow cross-sectional area is provided in the narrow cross-sectional area. It provides a circuit.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a side view showing a magnetic circuit according to a first embodiment of the present invention.

The magnetic circuit includes a magnet 1, a rectangular yoke 2 in which the magnet 1 is attached to a gap 3 in the center, and an iron screw 4 that is fitted into a screw hole 9 provided at the top of the yoke 2.

The magnet 1 is magnetized in the vertical direction in the figure and generates magnetic flux. The magnetic flux flows into the yoke 2 through the gap 3, passes through the yoke 2, and returns to the magnet 1, forming a magnetic circuit. A coil (not shown) is passed through this gap 3 to constitute a linear motor. Further, the iron screw 4 fitted into the screw hole 9 of the yoke 2 is made of the same material as the yoke 2.

FIG. 2 is a sectional view taken along the line AA in FIG. 1.

In Fig. 2, the desired magnetic flux density at gap 3 is Bg,
The area of the magnet 1 is set to Ag, the thickness of the yoke 2 is set to t, the width is set to W, the saturation magnetic flux density of the material of the yoke 2 is set to ρ, and the average diameter of the screw hole is set to D. Therefore, the magnetic flux passing through the cross section of the yoke 2 is set so that it becomes saturated when the iron screw 4 is inserted by half the thickness t of the yoke 2.

The thickness t of the yoke 2 is set as follows. Therefore, as shown in FIG. 3, the magnetic flux is saturated when the iron screw 4 is inserted halfway into the screw hole 9, and the magnetic flux density in the gap 3 at this time becomes the desired magnetic flux density. Incidentally, the magnet 1 is a magnet capable of supplying a magnetic flux exceeding the magnetic flux saturation.

Next, a usage example of this embodiment will be explained.

If the magnetic flux density in the gap 3 is small due to variations in the material of the magnet 1, screw in the iron screw 4 as shown in Figure 4. As a result, the resistance of the entire magnetic circuit decreases, and the magnetic flux density in the gap 3 decreases. It can be made larger.

When the magnetic flux density of the gap 3 is large, the number of screws of the iron screw 4 is reduced as shown in FIG.

As a result, the resistance of the magnetic circuit increases, and the magnetic flux density in the gap 3 can be reduced.

By inserting and removing the iron screw 4 from the screw hole 9 as described above, the magnetic flux density in the gap 3 can be made constant regardless of variations in the material of the magnet 1.

FIG. 5 is a side view showing a magnetic circuit according to a second embodiment of the invention.

The yoke 5 of this embodiment is provided with a handle portion 5a formed by thinly cutting both ends of the upper portion. A required number of iron plates 6 made of the same material as the yoke 5 can be attached to the handle portion 5a using screws 7.

In Fig. 5, the thickness of the iron plate 6 is U, and the thickness of the handle 5a is V.
, other variables are set the same as in the first embodiment. Therefore, the number n of iron plates 6 that can be attached is set so that the magnetic flux is saturated when the number of iron plates 6 is all. That is, as a result, when there is only one iron plate 6, the magnetic flux density in the gap 3 is the target magnetic flux density.

With the above configuration, if the magnetic flux density of the gap 3 is large due to variations in the material of the magnet 1,
If the number of iron plates 6 is reduced and the magnetic flux density is low, the resistance of the magnetic circuit can be changed by increasing the number of iron plates 6, and as a result, the magnetic flux density of the gap 3 can be adjusted.

The other configurations and functions are the same as those of the magnetic circuit shown in FIG.

[Effects of the Invention] As explained above, in the magnetic circuit of the present invention, a part of the yoke has a narrow cross-sectional area, and the narrow cross-sectional area is partially or completely closed. Since a ferromagnetic member that can be used is provided, there is an effect that the magnetic flux density in the gap can always be kept constant even when there are variations in the material of the magnet.

[Brief explanation of the drawing]

FIG. 1 is a side view of a magnetic circuit according to a first embodiment of the present invention, FIGS. 2 to 4 are cross-sectional views taken along the line A-A in FIG.
The figure is a side view of a magnetic circuit according to a second embodiment of the present invention, and FIG. 6 is a side view showing an example of a conventional magnetic circuit. 1: Magnet 2: Yoke of the first embodiment 3: Gap 4: Iron screw 5: Yoke of the second embodiment 6: Iron plate 7: Screw 8: Yoke with a gap above and below 9: Screw hole

Claims (1)

[Claims] In a magnetic circuit including a magnet and a yoke that passes the magnetic flux of the magnet, a part of the yoke has a narrow cross-sectional area, and a narrow cross-sectional area is provided in the narrow cross-sectional area. A magnetic circuit characterized by being provided with a ferromagnetic member that can be partially or completely blocked.