KR100675798B1 - Long range stage using active controlled bearing apparatus - Google Patents

Abstract

The present invention is directed to a large stroke stage using an active control bearing mechanism capable of actively controlling the air gap by controlling the current flowing through the linear motor coil even when the surface quality of the linear motion and its surface are poor or the precision is poor. It is about. To this end, the present invention includes a linear motor unit having a linear motor magnet and a linear motor coil for linear motion, in particular, the linear motor magnet is a Halbach magnet array to generate a driving force for the linear motion in the linear motor part and At the same time, it creates forces for the bearing effect to guide the smooth linear motion. In the case of using an air bearing system as a guide system, a specific direction of the forces induced in the linear motor part is used to apply a preload to the air bearing. In addition, the present invention can be equally applied to other guide systems as well as air bearing systems.

Stage, air bearing, magnet array, active control bearing

Description

Large stroke stage using active control bearing mechanism {LONG RANGE STAGE USING ACTIVE CONTROLLED BEARING APPARATUS}

1 is a cross-sectional view showing a conventional precision guide device using an air bearing system.

Figure 2 is a perspective view showing a large stroke stage according to the first embodiment of the present invention.

3 is a plan view of the large stroke stage according to the first embodiment of the present invention.

Figure 4 is an enlarged view showing a linear motor coil of a large stroke stage according to the present invention.

5 is a view showing a linear motor magnet and a linear motor coil of a large stroke stage according to the present invention.

Figure 6 is a plan view showing a large stroke stage according to a second embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: base 20, 30: first guide bar

21, 31: first air bearing 22, 32: coil fixing part

22a, 32a: linear motor coil 23, 33: linear motor magnet

40: second guide bar 50: specimen transfer unit

60: control unit

The present invention relates to a large stroke stage, and more particularly, to a large stroke using an active control bearing mechanism for maintaining a uniform air gap even when the movement surface is curved or the quality of the movement surface is deteriorated by using a specific magnet arrangement. It's about the stage.

With the development of the IT industry, the demand for large-scale administration such as semiconductor wafers and LCDs and equipment requiring high precision and high speed are increasing. Such high precision and high speed equipment requires a system that minimizes friction. Air friction and magnetic bearings can be used as a frictionless guide for realizing this, and in particular, air bearing systems are widely used. An air bearing system generally includes a surface of a precisely processed air bearing, a discharge port installed on the surface to discharge high pressure air, and an air bearing counterpart having precise surface quality and a plan view. Therefore, when air is discharged from the discharge port, a floating force is generated between the air bearing surface and its counterpart surface, so that the device can move while minimizing friction.

In this regard, US Pat. No. 5,064,318 discloses a precision guide device using an air bearing system. As shown in FIG. 1, the apparatus comprises a stage 1 having movement in one direction, an air bearing system 2, 3, 4, 5 for guiding the movement of the stage 1, and a stage. A linear drive system 6, 7 for generating a driving force of (1), and an air bearing guide 8 precisionly processed in parallel to guide the linear movement of the stage together with the air bearing system. In the air bearing system, the air bearing (2) rises from the air bearing guide (8) surface to allow movement while minimizing friction, and the adjustable air bearing (3) serves to manually preload the air bearing (2). do. In addition, the air bearing adjustment mechanism (4) serves to adjust the position of the adjustment air bearing (3), the air bearing rotary ball (5) allows the movement of the air bearing according to the shape error of the air bearing guide (8) surface Play a role.

In the above device, the stage 1 generates a driving force through the linear drive systems 6 and 7 and is guided by the air bearing 2 and the regulating air bearing 3 moving along the air bearing guide 8 so as to linearly move. Will be At this time, the air bearing 2 is moved while maintaining the air bearing guide 8 surface and the air gap of several um by the floating force by the pressure of the air.

However, if the parallelism and flatness of the plane of the air bearing guide (8) are ideal, the stage moves linearly along the guide plane without any problems by the air bearing (2) and the adjusting air bearing (3). Due to processing problems, the surface of the air bearing guide 8 has an unpredictable shape, and thus the characteristics of the system are continuously changed when the stage 1 moves. That is, the width of the air bearing guide 8 changes as the shape of the surface of the air bearing guide 8 changes, whereby the gap between the air bearing 2 and the air bearing guide 8 becomes too narrow. The friction occurs in the air bearings (2, 3) and the guide surface (8), causing a friction force that interferes with the linear motion, and conversely, if the air gap becomes too wide, motion in an unwanted direction besides the linear motion may be induced. Problems arise.

In the case of using air bearings, the precision of the guide surface is an important factor that is directly related to the stability and performance of the system. Especially in the large-stroke system, the area of the precision machining surface is widened, so that the wide surface is precisely processed and is uniform. Maintaining the floor plan is technically very difficult and thus there is a problem that the production cost is also high. On the other hand, when a magnetic bearing is used in a large-stroke system, expensive magnets and coils must be precisely installed in a large area in order to apply the magnetic bearing to a large area, and thus there are technical difficulties and cost problems.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to actively control the air gap even when the air bearing and its counter surface change when air bearing is used to guide the linear motion. It is to provide a large-stage administrative stage that can stabilize system characteristics and performance at cost.

In addition, an object of the present invention is to provide a large stroke stage that can be applied to a guide system that does not use an air bearing to smoothly guide the linear motion without being greatly affected by the surface quality and precision of the guide surface. (See Example 2)

In the large-stroke stage using the active control bearing mechanism according to the present invention for achieving this object comprises a linear motor unit having a linear motor magnet and a linear motor coil for a linear motion in a specific direction, the linear motor The magnet is characterized in that the Halbach magnet array to generate a driving force for the linear motion in the linear motor portion and at the same time generates a force for the bearing effect to guide the smooth linear motion.

In addition, the linear motor magnets are installed in a row on the outer surface of each of the pair of first guide bar arranged side by side, the linear motor coil is fixed to the second guide bar provided between the first guide bar is fixed to the first The coil fixing part installed to surround the guide bar is installed to face the linear motor magnet, and at least one side of the second guide bar is provided with a first air bearing, so that a part of the force generated in the linear motor part is It is transmitted to the second guide bar through the coil fixing portion is characterized in that to act in the opposite direction to the lifting force of the first air bearing to apply a preload.

In addition, the linear motor magnets are installed in a row on the outer surface of each of the pair of first guide bar arranged side by side, the linear motor coil is fixed to the second guide bar provided between the first guide bar is fixed to the first A pair of coil fixing parts installed to surround the guide bar are installed to face the linear motor magnets, so that a part of the force generated in each of the linear motor parts acts on the pair of coil fixing parts in opposite directions to each other. It is characterized by acting as a bearing by achieving a balance of.

In addition, the air gap between the first air bearing and the first guide bar or the gap between the second guide bar and the first guide bar is actively controlled to measure the voids to maintain a constant void and According to the result further comprises a control unit for controlling the current flowing in the linear motor coil.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. 2 is a perspective view showing a large stroke stage according to a first embodiment of the present invention, Figure 3 is a plan view showing the large stroke stage according to the first embodiment of the present invention.

As shown in Figure 2 and 3, the large stroke stage according to an embodiment of the present invention is the base 10, the first guide bar (20, 30), the second guide bar 40 and the linear motor unit and Specimen transfer unit 50 is included.

The base 10 is a rectangular flat plate, and the first guide bars 20 and 30 are mounted side by side on both sides thereof, and the base 10 is formed in a direction perpendicular to the first guide bar between the first guide bars 20 and 30. Two guide bar 40 is installed. The second guide bar 40 receives a driving force from the linear motor unit to be described below to perform a linear movement along the first guide bars 20 and 30. For convenience of description, the direction in which the first guide bars 20 and 30 are mounted is displayed in the y-axis direction, and the direction in which the second guide bar 40 is mounted is displayed in the x-axis direction.

The upper surface of the second guide bar 40 is provided with a specimen conveying portion 50 to move in the x-axis direction, the specimen conveying portion 50 is a rectangular flat plate is placed on the specimen to be worked on .

At both ends of the second guide bar 40, the first air bearing 21 to minimize friction with the first guide bars 20 and 30, which may occur when the second guide bar 40 linearly moves in the y-axis direction. , 31). In the present exemplary embodiment, air bearings are installed on both sides of the second guide bar 40, but air bearings are not necessarily installed on both sides of the second guide bar 40. It is also possible to install air bearings on either side.

On the other hand, the coil fixing parts 22 and 32 to which the linear motor coil is mounted are fixed to both sides of the second guide bar 40. The coil fixing parts 22 and 32 extend in the horizontal direction by a predetermined length from the second guide bar 40 and then extend in the vertical direction, that is, in the negative direction of the z-axis. Therefore, the horizontal extension portion of the coil fixing portion 22, 32 covers a part of the upper surface of the first guide bar 20, 30, and the vertical extension portion of the coil fixing portion 22, 32 is the first guide bar 20 , 30) to face the outer surface.

As shown in FIG. 4, the linear motor coils 22a and 32a are installed in the vertical extension portions of the coil fixing parts 22 and 32, and the linear motors together with the linear motor magnets 23 and 33 to be described below. By forming a portion, the force acting in the opposite direction to the floating force of the first air bearings 21 and 31 together with the driving force required for the linear movement of the second guide bar 40 generates a preloading force.

The linear motor magnets 23 and 33 are respectively installed on the outer surfaces of the first guide bars 20 and 30. The linear motor magnets 23 and 33 are arranged in a line along the length direction of the first guide bars 20 and 30, that is, the y-axis direction, and have a Halbach magnet array as shown in FIG. 5. 5 is a diagram illustrating a coil of a linear motor magnet and a linear motor of a large-stroke stage according to the present invention, the direction of the magnetic field (Bx, By), the direction of the current and the direction of the force induced in the linear motor unit (Fx, Fy) ) Is displayed. In the present invention, the Halbach magnet array used as the arrangement of the linear motor magnets 23 and 33 increases the size of Bx and By to obtain a higher magnetic flux density, and in the y-axis direction, which is important in the present invention. This is to enhance the strength of magnetic field By as much as that of Bx.

As shown in Fig. 5, when the magnetic field acting on the point P of the coil by the linear motor magnets 22 and 33 is B, the magnetic field B can be considered as the sum of the x-axis magnetic field Bx and the y-axis magnetic field By. . When current flows in the linear motor coils 22a and 32a in the direction from the ground to the ground, the y-axis force Fy is induced by the x-axis magnetic field Bx, and the x-axis force is induced by the y-axis magnetic field By. Fx is derived. Here, Fy acts as a driving force necessary for the linear movement of the second guide bar 40 in the y-axis direction, and Fx acts in the opposite direction to the flotation force of the first air bearings 21 and 31 to apply a preload. . As described above, in the present invention, the preload may be applied to the first air bearings 21 and 31 without the need for a separate additional system or preload air bearing to apply the preload by using the force in the x-axis direction generated in the linear motor unit. The whole device is simplified. In addition, since the mating surfaces of the first air bearings 21 and 31, that is, inner surfaces of the first guide bars 20 and 30 are not precisely machined, the first guide bars 20 and 30 and the first air bearings ( Even if the gap between 21 and 31 changes irregularly, it can be actively controlled to keep the above gap constant. To this end, the present invention includes a control unit 60 for sensing the air gap through a sensor or the like and controlling the current flowing through the linear motor coils 22a and 32a.

On the other hand, between the lower surface and the base 10 of the second guide bar 40 and between the lower surface and the base 10 of the specimen transfer part 50 so that the second guide bar 40 can perform a plane movement while supporting the load The second air bearing 41 is installed.

In addition, linear position sensors 22b and 32b are mounted on the upper surfaces of the coil fixing parts 22 and 32 so that the linear movement of the second guide bar 40 can be detected from both sides. Each of the linear position sensors 22b and 32b senses the linear movement of the second guide bar 40 on both sides when a rotational movement with the z-axis as the rotation axis is needed, analyzes the degree of movement thereof, and then adjusts the second guide bar accordingly. (40) The rotational motion is generated by varying the degree of movement by the linear motors on both sides.

6 is a plan view showing a large-stroke stage according to a second embodiment of the present invention. The components and operation of the large stroke stage shown in FIG. 6 are similar to those of the large stroke stage according to the first embodiment described above, except that the first air guides linear motion to both sides of the second guide bar 40. The only difference is that no bearing is installed. Thus, even if the first air bearing is not mounted, the force in the x-axis direction generated by each of the linear motor parts on both sides of the first guide bars 20 and 30 is transmitted through the coil fixing parts 22 and 32. It acts as a bearing by balancing the forces by acting in opposite directions on both sides of the guide bar 40. Therefore, the y-axis movement of the second guide bar 40 can be guided even without a separate air bearing system. In addition, even when the inner surfaces of the first guide bars 20 and 30 are not precisely processed as in the case of the first embodiment, even when the gap between the first guide bar 20 and the second guide bar 30 is changed irregularly. Through the control unit 60 capable of measuring the air gap and controlling the current of the linear motor coil, the air gap can be actively controlled and kept constant.

As described above, in the present invention, when the air bearing is used as a guide for minimizing friction, the apparatus is simplified because a separate preload system is not required by applying a preload to the air bearing by using the force generated in the linear motor unit. The production cost is reduced.

In addition, the present invention can save the cost of precision machining because it can actively control the air gap by controlling the current flowing through the linear motor coil even if the surface quality of the linear motion and its surface is poor or the precision is poor And it has the effect of improving the overall performance of the device.

In addition, the present invention has the effect that can be equally applied to other systems as well as air bearing guide system.

Claims (5)

delete delete delete A pair of first guide bars arranged side by side, a linear motor magnet arranged in a line on the first guide bar, and a second guide disposed between the pair of first guide bars to linearly move along the first guide bar A large stroke stage having a linear motor coil for interacting with the linear motor magnet to generate propulsion for linear movement of the second guide bar, The linear motor magnet is arranged to have a Halbach magnet arrangement, the large stroke stage is an air bearing for minimizing friction between the second guide bar and the first guide bar, the first air bearing and the first guide bar And a control unit for measuring the air gap so as to actively control the air gap therebetween and controlling the current flowing through the linear motor coil according to the result. A pair of first guide bars arranged side by side, a linear motor magnet arranged in a line on the first guide bar, and a second guide disposed between the pair of first guide bars to linearly move along the first guide bar A large stroke stage having a linear motor coil for interacting with the linear motor magnet to generate propulsion for linear movement of the second guide bar, The linear motor magnets are arranged to have a Halbach magnet arrangement, and the large stroke stage measures the voids to actively control the voids between the second guide bar and the first guide bar, and accordingly the linear Large stroke stage using an active control bearing mechanism characterized in that it comprises a control unit for controlling the current flowing in the motor coil.

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