JP2651732B2 - Linear drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a linear drive device that can be used as an XY stage for wafer exposure that requires precise positioning control.

<Prior Art> FIG. 3 is a schematic view of a conventional linear drive device. 1 in the figure
Denotes a rectangular vibration isolator. A plurality of vibration absorbing members 4 of air springs (4 in FIG.
) Are provided. On the vibration isolation table 1, both a mover 3 and a magnetic field forming member 2, which are main components of the linear drive device, are provided. The movable element 3 is linearly movable in the direction of the arrow on the vibration isolator 1 by a guide shaft (not shown), while the magnetic field forming member 2 is fixed on the vibration isolator 1.

That is, when a predetermined exciting current is supplied to the mover 3 in a state where the magnetic flux from the magnetic field forming member 2 is linked, the propulsive force F acts on the mover 3 and is supplied to the mover 3. By adjusting the excitation current, positioning control of a moving object (not shown) connected to the mover 3 is performed.

In order to enhance the accuracy of the positioning control, the influence of vibration transmitted from the floor 5 when a person walks around the floor becomes a problem. The vibration absorbing member 4 absorbs the vibration from the floor 5 so that the vibration is not transmitted to the vibration isolation table 1.

<Problems to be Solved by the Invention> However, in the case of the above-described conventional example, the following disadvantages are pointed out.

The first disadvantage is that when an exciting current is supplied to the mover 3 and a propulsion force F acts, a reaction force Fr acts on the magnetic field forming member 2 as a reaction of the propulsion force F and is also transmitted to the vibration isolation table 1.
As a result, inconveniences such as vibration or deformation of the vibration isolation table 1 occur. In particular, this disadvantage is promoted when the object to be moved is moved at high acceleration.

As a second disadvantage, the position of the center of gravity of the vibration isolation table 1 also changes with the movement of the moving target connected to the mover 3, and this change causes a problem that the vibration isolation table 1 is inclined. In particular, this disadvantage is exacerbated when the apparatus is enlarged.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a straight line that does not vibrate or tilt even when a reaction force acts on a magnetic field forming member. A drive device is provided.

<Means for Solving the Problems> A linear drive device according to the present invention is provided on a vibration isolation table mounted on a floor via an air spring or other vibration absorbing member, and a magnetic flux from a magnetic field forming member is provided. A device that applies a propulsive force to the mover to linearly reciprocate the moving target attached to the mover, wherein the position of the center of gravity of the mover, the moving target, and the magnetic field forming member is always substantially constant. Thus, the reaction force exerted on the magnetic field forming member as a reaction of the driving force of the mover allows the magnetic field forming member to move freely in the direction of the anti-propulsion force.

<Operation> When the propulsive force F acts on the mover in response to the magnetic flux from the magnetic field forming member, the moving target connected to the mover moves linearly on the vibration isolation table. At the same time, a reaction force Fr acts on the magnetic field forming member as a reaction of the propulsion force F, and the magnetic field forming member moves linearly on the vibration isolation table in the direction of the reaction force, that is, in the direction of the anti-propulsion force. Therefore, the reaction force Fr acting on the magnetic field forming member is not transmitted to the vibration isolation table.

Also, when the moving target moves in the propulsion direction together with the mover, the magnetic field forming member also moves in the anti-propulsion direction,
There is no change in the position of the center of gravity of the anti-vibration table with the movement of the moving target.

<Embodiment> Hereinafter, an embodiment of a linear drive device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a linear drive device showing an initial state, and FIG. 2 is a view corresponding to FIG. 1 showing a state after operation.

The linear driving device described here is a linear motor for an XY stage for wafer exposure. In FIGS. 1 and 2, it is necessary to move a wafer (not shown) to be moved in the X direction. It is a diagram schematically showing the configuration,
The configuration required for moving in the Y direction is not shown.

In the drawing, reference numeral 1 denotes a rectangular vibration isolation table. A plurality of (four in the figure) vibration absorbing members 4 of air springs are provided at the back side edge of the vibration damping table 1, and the vibration absorbing members 4 absorb vibrations from the floor surface 5 to remove vibrations. It is not transmitted to the platform 1.

On the anti-vibration table 1, both a mover 3 and a magnetic field forming member 2, which are main components of a linear motor, are provided.

Although not shown, the mover 3 has a structure in which a polyphase coil is attached to a yoke, and is movable linearly in the X direction by a guide shaft. On the other hand, although the magnetic field forming member 2 is not shown, a permanent magnet is used for the stator yoke and an N pole,
It has a structure in which it is magnetized alternately with the S-pole, and is similarly linearly movable in the X-direction by another guide mechanism.

That is, in the linear drive device, when a predetermined exciting current is supplied to the mover 3 in a state where the magnetic flux from the magnetic field forming member 2 is linked, the driving force F acts on the mover 3 and the mover 3 is connected to the mover 3. The moved object moves in the X direction. The same applies to the configuration for moving the moving object in the Y direction (forward direction in the drawing). The position of the moving object is controlled in the XY plane by adjusting the exciting current supplied to the mover 3. The basic configuration is as follows.

In the linear drive device configured as described above, no vibration occurs in the vibration isolation table 1 regardless of the movement of the moving target, and the position of the center of gravity does not change. Hereinafter, this principle will be described in detail with reference to FIG. 1 and FIG.

FIG. 1 shows an initial state of the mover 3. here,
The mass of the movable element 3, including the moving object M _3, mass M ₂ of the magnetic field forming member 2, the center of gravity of the thing, including both the G. When the distance between the position of the center of gravity of the mover 3 and the position of the center of gravity G is L ₃ , and the distance between the position of the center of gravity of the magnetic field forming member 2 and the position of the center of gravity G is L ₂ , the following relational expression is established.

M ₂ · L ₂ = M ₃ · L _{3 In} this state, when a predetermined exciting current is supplied to the multi-phase coil of the mover 3, a propulsive force F acts on the mover 3 and the mover 3 At the same time, the moving target moves linearly in the propulsion direction (X direction).

 FIG. 2 shows a state after the operation of the mover 3.

Along with the movement of the mover 3, the reaction force Fr acts on the magnetic field forming member 2 as a reaction of the propulsion force F, and the magnetic field forming member 2 linearly moves in the direction of the counter propulsion force (X direction). Therefore, the reaction force Fr is not transmitted to the anti-vibration table 1, and no vibration occurs in the anti-vibration table 1.

Further, a process in which the mover 3 and the magnetic field forming member 2 move will be described in detail. First, the [Delta] x ₃ the movement of the movable element 3 when the propulsion force acting on the movable element 3 and the F (t).
Then, reaction force Fr (t) = acting on the magnetic field forming member 2 - F (t) ··· becomes, thereby the magnetic field forming member 2 is moved in the counter-thrust direction by [Delta] x _2.

Here, in an ideal state with no loss such as a sliding load, the following relational expression holds.

Δx ₃ = ∫∫F (t) / M ₃ dt ² ··· Δx ₂ = ∫∫Fr (t) / M ₂ dt ² ··· When the equation is transformed using the equation, Δx ₂ = − (M ₃ / M ₂ ) · Δx ₃ On the other hand, when the moving distances of the mover 1 and the magnetic field forming member 2 with respect to the initial position G of the center of gravity are L ₂ ′ and L ₃ ′, respectively, the following relational expression is established.

L ₂ ′ = L ₂ + │Δx ₂ │ L ₃ ′ = L ₃ + │Δx ₃ │ ・ ・ ・ Therefore, the rotational moment MM ₃ of the mover 3 with respect to the position G of the center of gravity is represented by the following equation. _{3 = M 3 · L 3 '} = M 3 · L 3 + M 3 │Δx 3 becomes │ ···.

On the other hand, the rotational moment MM ₂ of the magnetic field forming member 2 with respect to the position G of the center of gravity is calculated by using the following equation: MM ₂ = M ₂ · L ₂ ′ = M ₂ (L ₂ + │Δx ₂ │) = M ₂ · L _{2 + M 2 │- (M 3} / M 2) · Δx 3 a _{│ = M 2 · L 2 +} M 3 │Δx 3 │ ··.

Therefore, according to the formula, the formula, the formula, MM ₃ = MM ₂ ,
Here, it is proved that the position G of the center of gravity after the movement of the mover 3 and the magnetic field forming member 2 does not change from the initial state. If the position of the center of gravity G does not change, the position of the center of gravity of the anti-vibration table 1 does not naturally change. However, the description regarding the position of the center of gravity is based on an ideal state in which there is no loss such as a sliding load. Even if the target moves, there is no change in the position of the center of gravity of the vibration isolation table 1 that causes a problem.

In the case of the linear drive device described above, X-
No matter how the object to be moved is moved in the Y plane, no vibration occurs in the vibration isolation table 1 and no inconvenience such as tilting of the vibration isolation table 1 occurs. Therefore, it has great significance in improving the accuracy of the positioning control of the linear drive device. In particular, there is a great advantage particularly when the driven object performs a high acceleration motion or when the apparatus is large.

It should be noted that any type of linear drive device according to the present invention and a vibration isolation table can be applied as long as it has a vibration isolation table, and the vibration isolation table has a structure that can be kept horizontal. Anything is fine.

<Effects of the Invention> As described above, the linear drive device according to the present invention is configured such that the reaction force Fr acting on the magnetic field forming member is not transmitted to the vibration isolation table. Does not vibrate or deform. In addition, when the mover connected to the driven object moves linearly, the magnetic field forming member also moves in the opposite direction. The inconvenience of tilting of the shaking table does not occur. In particular, there is a great merit particularly when the driven object moves at high acceleration or when the device is large.

[Brief description of the drawings]

1 and 2 are views for explaining one embodiment of the linear drive device according to the present invention, wherein FIG. 1 is a schematic view of the linear drive device showing an initial state, and FIG. And FIG. 3 is a view corresponding to FIGS. 1 and 2 for explaining a conventional linear drive device. DESCRIPTION OF SYMBOLS 1 ... Vibration isolation table 2 ... Magnetic field forming member 3 ... Mover 4 ... Vibration absorption member 5 ... Floor surface

Claims (1)

(57) [Claims] 1. A movable member provided on a vibration isolating table mounted on a floor surface via an air spring or another vibration absorbing member to apply a propulsive force to the movable member by a magnetic flux from a magnetic field forming member. In a linear drive device that linearly reciprocates the moving target attached to the, the movable element, the moving target and the center of gravity of the magnetic field forming member are always substantially constant,
A linear drive device wherein the magnetic field forming member is free to move in the direction of the anti-propulsion force by the reaction force exerted on the magnetic field forming member as a reaction of the driving force of the mover.