JPH03270670A - Linear motor - Google Patents

Abstract

PURPOSE:To suppress thrust ripple by inclining the flux produced in a magnetic air gap by a predetermined angle with respect to the moving direction of a movable coil viewed on the drawing. CONSTITUTION:A magnet assembly 3b is constructed by securing a plurality of planar permanent magnets 3 having same dimensions, with predetermined intervals P, to a lower yoke 2 while inclining a predetermined angle theta with respect to the direction of stroke. In other words, the flux normal to the direction of stroke existing in a magnetic gap 4 is inclined with respect to the direction of stroke when viewed on the drawing. Consequently, flux density varies smoothly in the magnetic gap and an approximately sinusoidal flux distribution is realized, and the movable coil can be moved smoothly when a sine wave current is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear motor in which a moving coil moves linearly within a magnetic gap formed between opposing permanent magnets.

[Prior Art] Conventionally, as a drive device for positioning an object within a long stroke range such as a loan to 100 ann, a moving coil type linear motor as disclosed in Japanese Patent Publication No. 58-49100 has been used. is frequently used. This linear motor has multiple permanent magnets magnetized in the thickness direction, arranged facing each other in different directions of magnetization.
It has a structure in which a moving coil assembly that moves in a direction perpendicular to the magnetic flux is disposed within a gap formed between opposing permanent magnets.

In this type of near motor, there is no center yoke in the magnetic circuit section, and the magnetic flux forms multiple closed loops within the air gap, preventing the magnetic flux from concentrating on a part of the magnetic path. It is possible to generate different magnetic flux densities.

[Problems to be solved by the invention] According to the linear motor described above, it is possible in principle to obtain a magnetic flux density distribution with a -like shape even if the stroke becomes long, but in reality, the following problems occur. There is a point. In other words, in order to arrange multiple permanent magnets in the longitudinal direction, permanent magnets are usually glued to a yoke, so the magnetic flux density decreases at the joint between adjacent magnets and is not necessarily uniform over the entire length of the magnet. It cannot be said that a perfect magnetic flux density distribution can be obtained. Therefore, when driving the above-mentioned linear motor and measuring the thrust in the longitudinal direction, it was found that the thrust distribution was not uniform over the entire stroke, but was wave-shaped. When such thrust ripples occur, smooth linear motion is not possible, resulting in problems such as a decrease in positioning accuracy.

Therefore, an object of the present invention is to provide a linear motor that can reduce thrust ripple.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a pair of yokes disposed facing each other at a predetermined interval, and a thickness direction bonding member fixed to opposing surfaces of each of the yokes. A plurality of permanent magnets are magnetized and arranged in the longitudinal direction so that adjacent magnetic poles and opposing magnetic poles have opposite polarities, and are arranged so as to be movable in the longitudinal direction within the magnetic gap formed between the opposing permanent magnets. In the linear motor having a moving coil, the magnetic flux generated in the magnetic gap is inclined by a predetermined angle with respect to the moving direction of the moving coil when viewed from a plane.

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

FIG. 1 is a front view of a linear motor according to an embodiment of the present invention.

In FIG. 1, 1 is an upper yoke, and 2 is a lower yoke, both of which are made of ferromagnetic material and are formed into, for example, a flat plate shape. Numeral 3 is a flat permanent magnet magnetized in the thickness direction, and a plurality of permanent magnets are arranged so that N and S magnetic poles appear alternately on the surface, and are fixed to the upper yoke 1 to form a magnet assembly 3a. .

Similarly, the lower yoke 2 has permanent magnets 3 on its surface.
A plurality of magnetic poles are fixed so that the magnetic poles appear alternately to form a magnetic pole assembly 3b. The upper yoke i and the lower yoke 2 are fixed to an end plate 5.6 made of a non-magnetic material so that a magnetic gap 4 is formed between the magnet assemblies 3a and 3b, thereby forming a magnetic circuit section 1o. .

Since the magnet assembly 3a and the magnet assembly 3b face each other so that the N and S magnetic poles face each other, a magnetic flux perpendicular to the longitudinal direction (indicated by a broken line in the figure) exists in the magnetic gap 4.

The movable part 20 is constructed by fixing a movable coil 21, which is, for example, a three-phase coil, to a carriage 23 with a coil fixture 22, as shown in FIG. 2, which is a sectional view taken along the line A-A in FIG. The carriage 23 holds the magnetic circuit section 10 between two parts.
A pair of mechanical rollers 24 are attached. On the other hand, a slide plate 7 extending longitudinally along the upper yoke 1 is assembled to the end plate 5.6. Both ends of the slide plate 7 are held on the outer periphery of the guide rollers 24, which allows the movable s20 to move in the longitudinal direction.

Next, the magnet arrangement, which is a feature of the present invention, will be explained with reference to FIG. FIG. 3 is a partially enlarged view taken along the line B--B in FIG. 1, and shows the magnet assembly 3b, but the magnet assembly 3a also has a similar magnet arrangement. Magnet assembly 3b
, a plurality of flat permanent magnets 3, all of which have substantially the same dimensions, are placed at a predetermined interval (P) and inclined at a predetermined angle (θ) with respect to the stroke direction, and the lower yoke 2 is
It is formed by adhering to. That is, the long side 3' of the permanent magnet 3 is in a relationship such that it is not orthogonal to the stroke direction indicated by the dashed line S. In short, magnetic room i! The magnetic flux perpendicular to the stroke direction existing in i4 is inclined to the stroke direction when viewed from the plane. As a result, the magnetic flux density in the magnetic gap changes smoothly, resulting in a substantially sinusoidal magnetic flux distribution shape, and by supplying a sinusoidal current to the movable coil, its movement is performed smoothly. Therefore, thrust ripple can be significantly reduced.

Furthermore, in the present invention, instead of arranging the permanent magnets 3 at an angle with respect to the stroke direction as shown in FIG. It may be made to be inclined with respect to the direction.

The linear motor of the present invention is similar to the conventional one.

Although the moving coil is energized to generate thrust, the current is made into a sine wave current, the relative position between the moving coil and the permanent magnet is detected by an appropriate detection means, and the coil in which the current flows and its direction are switched. Can be moved continuously over long strokes. In addition, from the point of view of motor efficiency, the moving coil is composed of a plurality of coils each having a coil width smaller than a fraction of the longitudinal width of one permanent magnet, as described in Japanese Patent Application Laid-Open No. 193543/1983. It is desirable to form a multiphase flat coil in which the coils are sequentially arranged next to each other on the same plane so that the central portions of the coils do not overlap, and only the central portion of the coil located within the magnetic gap has a thickness equivalent to one phase.

Further, in the present invention, the permanent magnet 3 may have a shape as shown in FIG.

[Effects of the Invention] As detailed above, according to the present invention, the magnetic flux perpendicular to the stroke direction within the magnetic gap is inclined with respect to the stroke direction when viewed from the plane, and the magnetic flux distribution approximates a sinusoidal distribution shape. By doing so, when the current flowing through the movable coil is made into a sine wave, the thrust ripple of the generated thrust due to the interaction can be reduced.

[Brief explanation of drawings]

1 is a front view of a linear motor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG.
FIG. 4 is a sectional view taken along the line BB in the figure, and is a diagram showing the shape of the magnet used in the present invention. 1: Upper yoke, 2: Lower yoke, 3: Permanent magnet, 4:
Magnetic air gap, 21: Moving coil (series)

Claims (2)

[Claims] (1) A pair of yokes facing each other at a predetermined interval, magnetized in the thickness direction and fixed to the opposing surfaces of each yoke so that adjacent magnetic poles and opposing magnetic poles have opposite polarities. In a linear motor having a plurality of permanent magnets disposed in the longitudinal direction, and a moving coil disposed so as to be movable in the longitudinal direction within the magnetic gap formed between the opposing permanent magnets, The linear motor is characterized in that the magnetic flux is inclined by a predetermined angle with respect to the moving direction of the movable coil when viewed from a plane. (2) The permanent magnets are plate magnets having a substantially rectangular parallelepiped shape, and each permanent magnet is arranged at equal intervals so that its long sides intersect at an angle with the moving direction of the moving coil. The linear motor according to claim (1).