JPH01278252A - Multipolar linear dc motor - Google Patents

Abstract

PURPOSE:To reduce a thrust irregularity generated by the end effect of a movable core by varying the shape of the core. CONSTITUTION:The movable core 5' and the coil 4 of a linear DC motor are attached to a movable section 2 of a stage or the like, and a direct-move guiding mechanism for guiding in the moving direction of the motor of the stage is provided. Magnets 7 for generating alternating magnetic field are aligned on a stationary core 6 at the stationary side, and its magnetic flux is circulated through a path passing the core 5' and again returning to the magnet 7. A current flowing to the coil 4 is switched in response to the direction of the magnetic flux to generate a thrust of the same direction. In this motor, the core 5' is formed at both end faces in a crest shape, and when the length of one magnet 7 is represented by (a), the height of the crest represented by (x) is set to (a)-2a. Thus, thrust irregularity generated by the end effect of the core 5' is reduced to easily position it accurately.

Description

[Detailed Description of the Invention] [Summary] Regarding a multi-polar linear DC motor, an object of the present invention is to provide a multi-polar linear DC motor that reduces thrust unevenness caused by the end effect of the movable part core. The present invention is also a multi-polar linear DC motor in which an attractive force acts between the movable core and the magnet, and the end of the movable core that is orthogonal to the traveling direction of the movable core is formed into a chevron shape.

[Industrial application field]

The present invention relates to a multipolar linear direct current (DC) motor.

Compared to conventional actuators that combine a rotary motor and a ball screw, multi-pole linear DC motors can generate direct thrust and drive over a long range of motion without contact, so they require precise positioning. It is used for the XX stage etc.

The above multi-polar linear DC motor is composed of a movable part such as a stage to which a movable part core and a coil are attached, and a fixed part in which magnets that generate an alternating magnetic field are arranged on the fixed part core. In this configuration, since the core of the movable part is shorter than the total length of the magnets in the fixed part, the uneven thrust caused by the end effect of the core of the movable part impedes high-precision positioning, so something with less uneven thrust is desired. .

[Conventional technology]

FIG. 5 is a diagram of a conventional single-sided multipolar linear DC motor.

In the figure, a coil movable one-sided linear DC motor 1 (having a fixed core on only one side) has a movable part 2 and a fixed part 3.
The movable part 2 has a coil 4 and a movable part core 5, and the fixed part 3 has magnets 7 arranged on the fixed part core 6 to generate an alternating magnetic field. The magnetic flux emitted from the magnet 7 circulates through a path that passes through the movable part core 5 and returns to the magnet 7 again. Furthermore, by switching the current flowing through the coil 4 according to the direction of the magnetic flux, thrust in the same direction can be generated.

[Problem to be solved by the invention]

In the single-sided multipolar linear DC motor 1, the coil 4 and the movable part core 5 can be directly fixed to the movable part 2.
It has the characteristics that it is easy to support and the rigidity of the support part can be high. However, this method has the disadvantage that since the movable part core 5 is shorter than the total length of the magnets 7 of the fixed part 3, a force is applied such that one end of the movable part core 5 stays in the middle of one magnet 7. be.

That is, when the movable part core 5, which is in a relative position as shown in FIG. 6(a) with respect to the magnet 7 of the fixed part 3, is slightly displaced to the left in the figure as shown in FIG. 6(b), the end Due to the effect, the original Figure 6 (
A force like Fl acts to return to the state of a), and the 6th
Even if it is displaced in the opposite direction as shown in Fig. 6(C), a force like F2 will still act to return it to its original state as shown in Fig. 6(a).

There was a problem in that this force resulted in uneven thrust of the linear DC motor, which obstructed high-precision positioning.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multipolar linear DC motor that eliminates thrust unevenness caused by the end effect of the movable core.

[Means to solve the problem]

The above problem is as shown in FIGS. 1(a) and (b).
The movable part core 5' moves, and the movable part core 5' and the magnet 7
The movable core 5 is a multipolar linear DC morph in which an attractive force acts between the movable core 5' and the movable core 5'.
This problem is solved by the multi-polar linear DC motor of the present invention, in which the ends of ``are chevron-shaped.''

[Effect]

In the present invention, the end of the movable core 5' is formed into a chevron shape to reduce thrust force unevenness due to the end effect. The principle behind the occurrence of thrust unevenness will be explained. For simplicity, 1 as shown in Figure 3 (a)
Consider a movable core 5 having the same width as each magnet 7.

When the center of the movable core 5 is located at the boundary between the magnets 7 as shown in FIG. 3(a), the magnetic flux ■ flowing into the movable core 5 and the magnetic flux ■ flowing from the movable core 5 are balanced, Since the magnetic flux ■'■' leaking from both sides of the core 5 is also equal, the movable part core 5 is pulled by the same Fl from both sides,
It does not move in either direction.

However, when the movable core 5 is slightly displaced to the right as shown in FIG.
The amount of magnetic flux (■) flowing out from the magnetic flux increases, and the leakage magnetic flux (■') decreases. The force that pulls the movable core 5 left and right increases in proportion to the square of the magnetic flux density of the leakage magnetic flux, so the force Fl that pulls the movable core 5 to the left is the force that pulls the movable core 5 to the right. It is larger than F2. Therefore, the movable core 5 is subjected to a force that returns it to the state shown in FIG. 3(a). The same applies when the movable part core 5 shifts to the opposite side.

If the movable core 5 is further displaced to the right while maintaining the state shown in FIG. 3(b), the state shown in FIG. 3(c) will occur, and magnetic flux ■' will now flow from another magnet 7. . Even in this state, the force F1 that pulls the movable core 5 to the left is larger than the force F2 that pulls it to the right, but since the magnetic flux ■' flowing into the movable core 5 from the right side increases, the difference between Fl and F2 becomes smaller. It's coming.

Then, when the movable core 5 is displaced to the state shown in FIG. 3(d), magnetic flux flows into the movable core 5 from the left and right.
' become equal, and the movable core 5 is pulled left and right by the same force Fl', as in FIG. 3(a). However, if the movable core 5 is slightly displaced to the left or right from this state, the tensile force on the displaced side becomes larger, and the state returns to the state shown in FIG. 3(a). It becomes stable. Therefore, the force that returns to the state shown in FIG. 3(a) causes thrust unevenness.

Now, if the state shown in Fig. 3 (a'') is viewed from directly above, it becomes as shown in Fig. 4, and since the leakage magnetic flux ■'■' coincides with the moving direction 8 of the movable part core 5, this leakage It can be seen that the difference in the tensile force IF8-FB I due to the magnetic flux ■'■' affects the thrust. Therefore, the direction of the leakage magnetic flux ■'■' is
What is necessary is to make it as close to perpendicular to the direction of travel as possible.

In the present invention, the end face of the movable core 5 is formed into a chevron shape so that the direction of this leakage magnetic flux is different from the direction of movement. The principle is shown in FIGS. 1(a) and 1(b). By making the end of the moving part core 5' into a chevron shape, the direction of the leakage magnetic flux is
Changes like ′■′. Therefore, the directions of the tensile forces FA and FB due to the leakage magnetic flux ■'■' are tilted by an angle θ from the traveling direction as shown in the same figure, so the influence on the thrust is l FA COS θ−FBCO5θ1, and the Compared to the conventional example shown in FIG. 4, the thrust force unevenness is reduced by a factor of COSθ. Note that by making the end of the movable core 5' into a chevron shape, the force FAsin can also be applied in the direction perpendicular to the direction of movement.
θ-FBsin θ is applied, but since this cancels out each other on both sides of the chevron, no force is applied to the movable portion core 5'.

Therefore, by making the end of the movable part core 5' into a chevron shape,
Thrust force unevenness caused by end effects can be reduced.

〔Example〕

An embodiment of the present invention is shown in FIG. Note that common symbols throughout all figures indicate the same objects.

In FIG. 2, the movable part core 5' has both end faces in a chevron shape,
In the embodiment, the length of this chevron is, for example, a for one magnet 7, and the height of the chevron is x=a to 2a. This moving part core 5
' and the coil 4 are attached to a movable part 2 such as a stage, and the stage etc. is further provided with a linear guide mechanism (not shown) that guides the multipolar linear DC motor in the traveling direction. . Furthermore, on the fixed side, magnets 7 that generate an alternating magnetic field are arranged above the fixed part core 6, and the magnetic flux emitted from the magnet 7 circulates through a path that passes through the movable part core 5' and returns to the magnet. ing. Further, by switching the current flowing through each coil 4 according to the direction of the magnetic flux, thrust in the same direction can be generated.

In this multipolar linear DC motor, the movable part core 5'
By making both ends into a chevron shape, it was possible to reduce the thrust unevenness, which was ±530 gf before the experiment, to ±50 gf in the experiment.

Therefore, the thrust force unevenness caused by the end effect of the movable part core is reduced, thereby facilitating high-precision positioning of the X-Y stage and the like on the movable part side.

〔Effect of the invention〕

As explained above, according to the present invention, thrust force unevenness caused by the end effect of the movable part core can be reduced by a simple method of changing the core shape. In experiments, it was possible to reduce the conventional thrust unevenness by about 90%.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams explaining the present invention in detail, Figure 2 is a diagram explaining one embodiment of the present invention, and Figure 3 (a)
-(d) are diagrams explaining the principle of occurrence of thrust unevenness, and FIG. 4 is a diagram explaining the direction of leakage magnetic flux. FIG. 5 is a diagram of a conventional single-sided multipolar linear DC motor, and FIGS. 6(a) to (c) are diagrams illustrating thrust unevenness of the linear DC motor. In the figure, 1' is a multipolar linear DC motor, 2 is a moving part, 3 is a fixed part, 4 is a coil, 5' is a moving part core, 6 is a fixed part core, (α) Thrust force 5t/ ! , Logic 2 word first moesu figure 6 figure 5 Fifth
Figure 1 change 1 direction CC) Lini? DC 7-or Yue Riki Z Uwo 8? Hsu 2 Figure 6

Claims (1)

[Claims] The movable part core (5') moves and the movable part core (5'
) and a magnet (7), the end of the movable core (5') perpendicular to the direction of movement of the movable core (5'), A multi-polar linear DC motor characterized by its chevron shape.