JPH01185157A - Linear motor - Google Patents

Abstract

PURPOSE:To reduce a thrust ripple while making use of merits of a multipolar type linear motor by setting a relative dimension between a multipolar magnet and a polyphase coil properly and driving selectively only a coil of a phase in a region where the density of magnetic flux is flat. CONSTITUTION:A polyphase coil unit 24 is constituted of coils 24A-24C, and the coil unit 24 moves an air space 5 provided on a multipolar magnet 11. Where bf is the length of the flat region with the distribution of the density of magnetic flux, tau is the pitch of magnetic pole and l is the effective length in the direction of the movement of one phase of coils 24A-24C, a relative dimension between the multipolar magnet 11 and the coil unit 24 must set to satisfy bf/l=m at 2 or more integer, tau-b/l=m' at 1 or more integer and the number of phases of coils 24A-24C at n=m+m', and only a coil of a phase (m-1) in a region where the density of magnetic flux is flat is driven selective ly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a linear motor, and more specifically to a stage drive mechanism of a semiconductor exposure apparatus, a pickup drive mechanism used in a large capacity storage device of a magneto-optical memory, and a pickup drive mechanism used in a printer. The present invention relates to a linear motor suitable for carriage drive mechanisms and the like.

[Prior Art] Conventionally, linear motors of the type shown in FIGS. 5 and 6 have been used in the above-mentioned mechanism. In Fig. 5, 1 is a unipolar magnet arranged along the entire length of the movable area along the traveling direction, 2 and 3 are upper and lower yokes that hold the unipolar magnet 1, and 4 is movable along the yoke 2. It is a single-phase coil that is held, and when the single-phase coil 4 is energized, a thrust is generated by interaction with the single-pole magnet 1 and the single-phase coil 4 can be moved along the yoke 2. can.

In addition, in (A) of FIG. 6, 11 is a multipolar magnet in which a large number of N poles and S poles are magnetized alternately along the traveling direction, and 12 and 13 are arranged above and below the magnet 11. The yoke 14 is a multi-phase coil (two-phase in this example) that is selectively driven according to the relative position of the magnet 11, and generates thrust by the interaction that occurs between the multi-phase coil 14 and the magnet 11. , for example, in the X direction.

[Problem to be Solved by the Invention J] However, in the case of the linear motor shown in FIG.
The magnetic flux from the unipolar magnet l is concentrated at both ends of the yokes 2 and 3. Therefore, in order to prevent the yokes 2 and 3 from reaching such a saturated state, it is necessary to set the cross-sectional area of the yokes 2 and 3 corresponding to the length direction of the monopolar electrode 1. In other words, the longer the stroke of the linear motor, the larger the yoke cross-sectional area must be, and while stable thrust is maintained over the entire stroke, the disadvantage is that the cross-sectional area in the direction perpendicular to the direction of movement becomes large. was there.

In addition, in the case of the method shown in FIG. 6, since the multipolar magnets 11 are arranged over the entire movable area as shown in (A), the magnetic flux does not concentrate at both ends of the yoke. Therefore, the cross-sectional area can be reduced. However, if a current in the direction indicated by 00 is applied to the phase 14B of the coil 14, the magnetic flux densities in the multipolar magnet 11 become as indicated by (B), so that the coil 14 becomes (
Among the positions of (() (0) (A) shown in C), (A)
The thrust is smaller in position (a) than in position (b). Note that (8) shows a state in which the energization is switched to the phase 14A. In other words, the closer the ends of each coil in the multiphase coil 14 are to the boundaries of the magnetic poles, the lower the thrust is. This means that a thrust ripple occurs every time the phase of the coil 14 is switched, and the Difficult to maintain sufficient thrust.

The purpose of the present invention is to focus on the conventional problems as mentioned above,
In order to solve this problem, it is an object of the present invention to provide a linear motor that uses a combination of multi-polar magnets and multi-phase coils and that can obtain stable thrust without generating thrust ripples throughout the stroke.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a multi-pole magnet consisting of a multipolar magnet in which different poles are arranged alternately along the direction of movement and a plurality of coils arranged in the direction of movement. It has a phase coil,
In a linear motor that moves by generating relative thrust between the multi-pole magnet and the multi-phase coil by selectively energizing the individual coils of the multi-pole magnet, When the length of the flat region of magnetic flux density in multipole is bf, the pitch between each pole is τ, the effective length of one phase of the coil in the moving direction is °C, and the number of phases of the coil is n, then bf/
Set the relative dimensions between the multipolar magnet and the multiphase coil so that Il=m is an integer of 2 or more, T-bf/IL=m' is an integer of 1 or more, and the relationship n=m+m' is obtained. , is characterized in that only the (m-1) phase coils in the region where the magnetic flux density is flat are selectively driven.

[Function] According to the present invention, each phase of the multiphase coil is driven only at the relative position of the magnetic pole region where the magnetic flux density is flat, so it is possible to generate a constant and stable thrust over the entire stroke. can.

[Examples] Examples of the present invention will be described below in detail and specifically based on the drawings.

FIG. 1 shows an embodiment of the invention. In this example, in a three-phase linear motor, the effective length in the moving direction of each coil in one phase is taken as a percentage of the length bf of the magnetic pole part where the magnetic flux density is flat in eight poles, and the magnetic pole This is an example in which (τ - bf) is equal to 1 above, where τ is the pitch of . That is, the ratio of bf/It is m, r-
This is the case where, when the ratio of bf/IL is m', the number of phases is n=3 and m=2.degree. m'=1.

FIG. 1A shows a longitudinal section of the linear motor, where 24 is a multi-phase coil unit, and 25 is a space provided above the magnet 11 for the coil unit 24 to move. Furthermore, ■ and O indicate the direction in which current flows in each phase. In this example, it is also a multipolar magnet! At 1, the magnetic flux density changes as shown in (B).

Now, when the coil unit 24 is located at the position shown in (A), if a current is passed through one of the coils 24B in the direction shown, the coil unit 24 moves in the X direction within a constant magnetic flux density. do. In this way, when the coil unit 24 moves by τ/3 and moves from position (a) to position (b) in (C), the position is detected by the coil position detection means (not shown), and the coil unit 24 is moved by τ/3. The energization to the coil 24B is stopped and the coil 24C is energized. As a result, the coil unit 24 receives thrust and moves in the X direction.
The current is continued until it moves roughly by τ/3, and (
When the coil reaches the position 8), switch the current to the coil 24A. Following the same steps, (d), (ne), (f), ()
) By switching the energization every time the coil advances by τ/3, the coil unit 24 always maintains a constant thrust.
can be moved in the X direction.

FIG. 2 shows a second embodiment of the invention. This example also has m
=2. In this example, three-phase coils 24A, 24B, and 24C constitute one unit 24, and three units form a multi-phase coil. However, in this case, each coil 24
A, 24B, and 24C are connected in series or in parallel for the same phase, but the polarity is such that only the middle unit has the opposite polarity. The thrust constant is thus increased, and the operating procedure is exactly the same as the example shown in FIG. 1, so detailed explanation thereof will be omitted. In this example as well, the energization to the coils 24A, 24B, and 24C of each layer is switched in accordance with the timing when the multiphase coil unit 34 moves by τ/3, and thereby the magnetic flux density is kept in a flat region. By sequentially driving only the phase coils, stable thrust with extremely small thrust fluctuations can be achieved. Note that here, 6 is a coil support member.

FIG. 3 shows a third embodiment of the invention. Here, the distance between the centers of adjacent coils of each phase is maintained at (τ+τ/3), and a flat coil is used for each phase coil. In this case, these coils are arranged in the order of 24C, 24A, and 24B from the left as shown in the figure. Even in the case of this configuration, each coil 24C, 24A is
By sequentially and selectively driving 24B and 24B, it is possible to obtain thrust with extremely little fluctuation in thrust.

FIG. 4 shows an embodiment of the invention. In this example, the movable unit 4
4 is a multipolar magnet 11. It is composed of yokes 12 and 13 and a side plate 15. Such a movable unit 44 moves along the coil support member 6 into which the coils 24A to 24G are fitted.
Assume that the left end of the coil 24G is located further to the left by τ/6 in FIG. 4, that is, the center of the coil 24G is located at the boundary between the magnets. Here, the multipolar magnet 11
When currents in ten directions are first passed through the coil 24E, with the direction of the coil current such that the magnetic flux points vertically upward as + and the opposite direction as -, the movable unit 44 moves to the right. Thus, after moving by τ/3, the coil 24
By applying a current in the child direction to F, it is further moved to the right by τ/3, and then a current in the child direction is applied to coil 24G, and thereafter, every time the coil 24G moves by τ/3, the current is applied to 24E, 24F, and 24G one after another. By supplying current in the direction, only the coils in the flat area of magnetic flux density are energized.
In the same manner as in the embodiment described above, stable thrust with extremely little fluctuation can be obtained.

[Effects of the Invention] As explained above, according to the present invention, in a multi-pole linear motor, the length of the flat region of magnetic flux density distribution is bf, the magnetic pole pitch is τ, and the direction of movement of one phase of the coil is When the effective length is the base, bf/Il=m is an integer of 2 or more,
τ-bf/jl=m' is an integer greater than or equal to 1, the number of phases of the coil n
The relative dimensions of the multipolar magnet and multiphase coil are set so that = m + m', and the magnetic flux density is in a flat region (m
-1) Since only the phase coils are selectively driven, it is possible to take advantage of the advantages of a multi-station linear motor while suppressing thrust ripples to an extremely small level and obtaining stable thrust with little fluctuation. Ta.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the first embodiment of the linear motor of the present invention, and FIGS. 2, 3, and 4 are exploded views of the second, third, and fourth embodiments of the present invention, respectively. FIG. 5 is a perspective view showing an example of the configuration of a conventional single-pole linear motor, and FIG. 6 is an explanatory diagram of the operation of a conventional multi-pole linear motor. 5... Space, 6... Coil support member, 11-... Multipolar magnet, 12, 13... Yoke, 15... Side plate, 24... Coil unit, 24A to 24G... Coil , 34-... Multiphase coil unit, 44... Movable unit. Second implementation of non-invention? J is disassembled and assembled into uz 2nd figure and half invention 4th actual catch I sequence S is disassembled and shown

Claims (1)

[Scope of Claims] 1) A multi-polar magnet in which different poles are arranged alternately along the moving direction and a multi-phase coil consisting of a plurality of coils arranged in the moving direction, the multi-phase coil comprising: A linear motor in which movement is performed by generating relative thrust between the multi-polar magnet and the multi-phase coil by selectively energizing individual coils, wherein each of the multi-polar magnets When the length of the flat region of magnetic flux density at the pole is bf, the pitch between each pole is τ, the effective length of one phase of the coil in the moving direction is l, and the number of phases of the coil is n, then bf /l=m is an integer greater than or equal to 2, τ-bf/l=
The relative dimensions between the multipolar magnet and the multiphase coil are set so that m' is an integer of 1 or more and the relationship n=m+m' is obtained, and the magnetic flux density is in a flat region (m -1) A linear motor characterized in that only phase coils are selectively driven.