JPH0344593A - Positioning apparatus - Google Patents

Abstract

PURPOSE:To prevent occurrence of a stick slip between guide rail and a retaining stage by making the retaining stage held in a state of noncontact with the guide rail by an air pressure from an air bearing. CONSTITUTION:In a state wherein a retaining stage 4 is positioned in a place other than a prescribed stop position on a guide rail, electrification of an electromagnet 17 of a magnetic fluid damper 12 is kept interrupted. In this state, therefore, a viscous fluid R in a viscous fluid accommodating chamber 19 of the magnetic fluid damper 12 is not affected by a magnetic field from the electromagnet 17, and consequently, the viscosity resistance of the viscous fluid R is kept small. Accordingly, the precision in positioning of the retaining stage 4 can be improved. In addition, occurrence of a stick slip between the guide rail 3 and the retaining stage 4 can be prevented when the retaining stage 4 is moved.

Description

[Detailed Description of the Invention] [Objective of the Invention] [Field of Industrial Application] This invention is applicable to high-speed
This invention relates to improvements in high-precision positioning devices.

(Prior Art) Generally, high-speed, high-precision positioning devices used in, for example, semiconductor manufacturing equipment are required to have positioning accuracy on the order of submicrons. Conventionally, this type of positioning device is equipped with a stage drive mechanism that moves a holding stage for a held object disposed on an idle rail back and forth in sliding contact with a guide rail, and this stage drive mechanism is driven by a digital servo drive. A configuration is known in which the holding stage is controlled to stop at a predetermined stop position set on a guide rail. However, in a positioning device having such a configuration, stick-slip tends to occur when the frictional force between the contact surfaces of the guide rail and the holding stage is large, so there is a problem that the positioning accuracy is reduced.

Therefore, air bearings are used to hold the holding stage of the held object disposed on the guide rail in a non-contact state using air pressure, and a linear motor or the like is used to move the holding stage forward and backward along the guide rail. A linear motion stage configured in combination with a stage drive mechanism is provided, and the holding stage is held in a non-contact state with respect to the guide rail by the air bearing of this linear motion stage, thereby reducing the friction between the guide rail and the holding stage. Some ideas have been developed to improve positioning accuracy by eliminating this. However, in this case, when digital servo control is applied to the holding stage, it is difficult to stably position the holding stage within 1 pulse, so it is better to stop the holding stage at a predetermined stop position set on the guide rail. - There is a possibility that the holding stage may swing within the range of minus one pulse, which causes a positioning error of the holding stage and causes oscillation of the holding stage.

In addition, if the holding stage is mechanically clamped at a predetermined stop position set on the guide rail to prevent vibration of the holding stage, clamp i
There is a risk of dust generation when the ti and the holding stage come into contact, and misalignment is likely to occur when clamping.
There was a problem in trying to improve positioning accuracy.

(Problem to be Solved by the Invention) A stage drive mechanism is provided that moves a holding stage for a held object disposed on a guide rail back and forth in sliding contact with the guide rail, and this stage drive mechanism is controlled by digital servo control. In a positioning device configured to stop the holding stage at a predetermined stop position set on the guide rail, stick-slip tends to occur when the frictional force between the contact surface between the guide rail and the holding stage is large, resulting in poor positioning accuracy. In addition, when a linear motion stage that combines an air bearing with a stage drive mechanism such as a near motor is installed, stable positioning within one pulse is required when digital servo control is applied to the holding stage. This is difficult, and when the holding stage is stopped at a predetermined stop position set on the guide rail, there is a risk that the holding stage may swing within the range of plus or minus one pulse, which will result in positioning errors of the holding stage and ,
There was a problem that caused the holding stage to oscillate. Furthermore, if the holding stage is mechanically clamped at a predetermined stop position set on the guide rail to prevent the holding stage from swinging, dust may be generated when the clamping mechanism and the holding stage come into contact. In addition, positional deviation is likely to occur during clamping, which poses a problem in improving positioning accuracy.

This invention was made in view of the above-mentioned circumstances, and prevents the occurrence of stick-slip between the guide rail and the holding stage and the vibration of the holding stage when the holding stage is stopped at the stop position on the guide rail. It is an object of the present invention to provide a positioning device that can improve positioning accuracy by preventing dust from being generated when a holding stage is stopped.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a damper body in which a movable member interlocked with the movement of a holding stage is disposed in a storage chamber for a viscous fluid made of a magnetic fluid, and a damper body for storing a viscous fluid in the storage chamber. A stage that is equipped with a viscous resistance adjusting member that adjusts viscous resistance, a magnetic fluid damper that adjusts the operating resistance of the holding stage as the viscous resistance of the viscous fluid in the storage chamber changes, and that moves the holding stage forward and backward along a guide rail. A stop position control function that uses digital servo control to control the operation of the drive mechanism to stop the holding stage at a predetermined stop position set on the guide rail, and a state in which the holding stage is located at a location other than the stop position on the guide rail. to reduce the viscous resistance of the viscous fluid in the viscous fluid storage chamber of the magnetic fluid damper, and increase the viscous resistance of the viscous fluid in the viscous fluid storage chamber when the holding stage has moved to the stop position on the guide rail. A control section with a viscous resistance control function is provided to control the adjustment member.

(Function) By holding the holding stage in a non-contact state with respect to the guide rail by air pressure from the air bearing, it prevents stick-slip between the guide rail and the holding stage when the holding stage moves. , the control unit controls the viscous resistance adjustment member of the magnetic fluid damper according to the movement state of the holding stage, and the magnetic fluid damper accommodates the viscous fluid when the holding stage is located at a location other than the stop position on the guide rail. By reducing the viscous resistance of the viscous fluid in the chamber to increase the movement speed of the holding stage, and by increasing the viscous resistance of the viscous fluid in the viscous fluid storage chamber when the holding stage has moved to the stop position on the guide rail. , the holding stage is prevented from wobbling when the holding stage is stopped at a stop position on the guide rail, thereby improving positioning accuracy, and preventing the generation of dust when the holding stage is stopped.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows the schematic configuration of the entire positioning device.
is the substrate of this positioning device. A pair of supporting legs 2a and 2b are provided at both ends of the upper surface of the board 1, and are spaced apart from each other and facing each other, and a guide rail 3 having a rectangular cross section is installed between these supporting legs 2a and 2b. A holding stage 4 for holding an object to be held is attached to this guide rail 3. This holding stage 4 is formed into a substantially rectangular frame shape,
This holding stage 4 is attached so as to be movable along the guide rail 3. In this case, the guide rail 3 incorporates an air bearing that holds the holding stage 4 against the guide rail 3 in a non-contact state using air pressure. Furthermore, linear protruding members 5 and 6 are protruded from both sides of the holding stage 4, respectively.

Furthermore, a linear motor (stage drive mechanism) 7 for moving the holding stage 4 forward and backward along the guide rail 3 is disposed on the upper surface of the substrate 1 . This linear motor 7 is formed by a stator 7a arranged parallel to the guide rail 3 and a movable element 7b that reciprocates along the stator 7a.

In this case, the stator 7a is installed between a pair of support legs 8a and gb that are spaced apart from each other at both ends of the upper surface of the substrate 1. Further, the tip end of the protruding member 5 on one side of the holding stage 4 is fixed to the movable element 7b of the linear motor 7. When the linear motor 7 is in operation, the movement of the movable element 7b is transmitted to the holding stage 4 side via this protruding member 5, and the holding stage 4 moves back and forth along the guide rail 3 in conjunction with the movement of the movable element 7b. It's supposed to work.

On the other hand, the protruding member 6 on the other side of the holding stage 4 includes a pair of pulleys 9a arranged facing each other at both ends of the upper surface of the substrate 1.
Both ends of the non-expandable operating wire 10 stretched between the wires 9b are fastened. In this case, one pulley 9a is connected to the substrate 1
It is rotatably supported by a support [11] protruding from one end of the upper surface.

Furthermore, the other pulley 9b is fixed to the tip of the rotating shaft 12a of the magnetic fluid damper 12 disposed at the other end of the upper surface of the substrate 1. When the holding stage 4 is in operation, the operating wire 10 moves forward and backward in accordance with the movement of the holding stage 4, and the pulley 9a moves in conjunction with the forward and backward movement of the operating wire 10.
, 9b rotates, and as the pulley 9b rotates, the rotating shaft 12a of the magnetic fluid damper 12 rotates integrally, so that the rotating speed of the pulley 9b is controlled by the magnetic fluid damper 12. It has become.

Further, FIG. 2 shows a schematic configuration of the magnetic fluid damper 12. This magnetic fluid damper 12 includes a damper body 13.
A rotor (movable member) 15 is housed in a substantially cylindrical case 14.
A stator 16 and an electromagnet (viscous resistance adjusting member) 17 are respectively provided. In this case, the base end portion of the rotating shaft 12a is fixed to the rotor 15. Further, the case 14 of the damper body 13 is provided with a bearing portion 18 and a storage chamber 19 for a viscous fluid R made of magnetic fluid, which are partitioned through a partition wall 14a. And bearing part 18
Inside is a pair of bearings 20a.

20b are spaced apart from each other, and the rotating shaft 12a is rotatably supported by these bearings 20a, 20b. Further, an electromagnet 17 is disposed at the inner bottom of the storage chamber 19 for the viscous fluid R, and the stator 16 is fixed onto the electromagnet 17. This stator 16 is formed by a thick inner disk 21, and this thick inner disk 21
A pair of concentric circular IIJs 22a and 22b are formed on the surface of each of the two concentric circles. Further, the rotor 15 is formed by a thick inner disk 23 which is arranged to face the stator 16 at a distance, and a pair of concentric cylindrical projections 24 are provided on the surface of the thick disk 23 facing the stator 16. a, 24
b are provided in a protruding manner.

These cylindrical projections 24a, 24b are inserted into the respective circular grooves 22a, 22b of the stator 16, respectively. Further, a flat propeller 2 is provided at the base end of the rotating shaft 12a of the rotor 15 disposed in the viscous fluid storage chamber 19.
5 is fixed.

Note that magnetic fluid is a fluid whose viscosity changes significantly when influenced by a magnetic field, and by changing the magnetic field inside the case 14 of the damper body 13 in accordance with the energization control of the electromagnet 17, the viscosity inside the viscous fluid storage chamber 19 can be changed. The configuration is such that the viscous resistance of the fluid R is changed to control the rotational speed of the rotor 15 and the pulley 9b.

Further, the electromagnet 17 of the magnetic fluid damper 12 is connected to a control section 26 formed by, for example, a microcomputer and its peripheral circuits. Furthermore, this control section 26
A linear motor 7 is connected to both, and a position sensor 27 of the holding stage 4 is connected to both. This position sensor 27 is installed at a predetermined stopping position of the holding stage 4 set on the guide rail 3, and a detection signal from this position sensor 27 is manually inputted to the control section 26. Then, the controller 26 controls the beam near motor 7.
Stop position control a! that digitally servo controls the operation of and stops the holding stage 4 at a predetermined stop position set on the guide rail 3. By keeping the electromagnet 17 of the magnetic fluid damper 12 de-energized while the holding stage 4 is located at a position other than the stop position on the guide rail 3, the viscosity in one viscous fluid storage chamber is reduced. The viscous resistance of the fluid R is reduced, and the holding stage 4 is attached to the guide rail 3.
A viscous resistance $-111 function controls the electromagnet 17 of the magnetic fluid damper 12 so as to increase the viscous resistance of the viscous fluid R in the viscous fluid storage chamber 19 by energizing the electromagnet 17 when the magnet 17 is moved to the upper stop position. Each is provided.

Next, the operation of the above configuration will be explained.

First, when the holding stage 4 is located at a location other than a predetermined stop position on the guide rail 3, that is, while the holding stage 4 is moving, the electromagnet 17 of the magnetic fluid damper 12 is kept de-energized.

Therefore, in this state, the viscous fluid R in the viscous fluid storage chamber 19 of the magnetic fluid damper 12 is not affected by the magnetic field from the electromagnet [7], so that the viscous resistance of the viscous fluid R is maintained in a small state. In this case, for example, when water is used as the base solvent of the viscous fluid R, the viscous resistance is close to 0 when the magnetic field is O, so the holding stage 4 can be moved smoothly without being affected by the magnetic fluid damper 12. It is possible to move the holding stage 4, and the moving speed of the holding stage 4 can be increased.

Further, when the control unit 26 detects that the holding stage 4 has moved to the stop position on the guide rail 3 based on a detection signal from the position sensor 27, the electromagnet 17 of the magnetic fluid damper 12 is energized. Therefore, in this state, the viscous fluid R in the viscous fluid storage chamber 19 of the magnetic fluid damper 12 is affected by the magnetic field from the electromagnet 17, and the viscous resistance and density of the viscous fluid R in the magnetic fluid damper 12 increase. The drag force acting on the propeller 25 of the rotating shaft 12a of the rotor 15 increases, and the rotational resistance of the pulley 9b increases. Therefore, when the holding stage 4 is stopped at the stop position on the guide rail 3 like a linear motion stage that combines a conventional air bearing and a stage drive mechanism such as a near motor, it is held within the range of plus or minus one pulse. Since the stage 4 can be prevented from swinging, the positioning error of the holding stage 4 can be reduced and the positioning accuracy of the holding step 4 can be improved.

Furthermore, since the holding stage 4 is held in a non-contact state with respect to the guide rail 3 by air pressure from the air bearing, there is no stick-slip between the guide rail 3 and the holding stage 4 when the holding stage 4 is moved. It is possible to prevent this from occurring, and it is possible to make the movement of the holding stage 4 smoother, and when the holding stage 4 is stopped, it is possible to prevent the holding stage 4 from being mechanically clamped at the stop position on the guide rail 3. It is possible to prevent the generation of dust when the holding stage 4 is stopped.

Note that this invention is not limited to the above embodiments. For example, in the above embodiment, the rotary magnetic fluid damper 12
Although the case is shown in which a direct-acting magnetic fluid damper 12 is used, a configuration may also be adopted in which the direct-acting magnetic fluid damper 12 is directly attached to the holding stage 4. Furthermore, it goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] According to the present invention, there is provided a damper body in which a movable member that is interlocked with the operation of the holding stage is disposed in a storage chamber for a viscous fluid made of magnetic fluid, and a viscous resistance that adjusts the viscous resistance of the viscous fluid in the storage chamber. A magnetic fluid damper is equipped with an adjustment member to adjust the operating resistance of the holding stage in accordance with changes in the viscous resistance of the viscous fluid in the storage chamber, and a digital servo control is used to control the operation of the stage drive mechanism that moves the holding stage forward and backward along the guide rail. A stop position control function that controls the holding stage to stop at a predetermined stop position set on the guide rail, and a stop position control function that controls the holding stage to stop at a predetermined stop position set on the guide rail. Viscous resistance that controls a viscous resistance adjusting member to reduce the viscous resistance of the viscous fluid in the storage chamber and increase the viscous resistance of the viscous fluid in the viscous fluid storage chamber when the holding stage moves to the stop position on the guide rail. A control unit with a control function is provided to prevent stick-slip between the guide rail and the holding stage and to prevent the holding stage from swinging when the holding stage is stopped at the stop position on the guide rail. It is possible to improve positioning accuracy and prevent the generation of dust when the holding stage is stopped.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic diagram of the entire positioning device, and FIG. 2 is a longitudinal sectional view showing a magnetic fluid damper. 3... Guide rail, 4... Holding stage, 7...
・Linear motor (stage drive groove), 12... Magnetic fluid damper, 13... Damper body, 15... Rotor (movable member), 17... Electromagnet (viscous resistance adjustment member)
, R... Viscous fluid, 19... Viscous fluid storage chamber, 25
... Drifter passageway, 26... Control section.

Claims (1)

[Claims] A holding stage for a held object disposed on a guide rail, an air bearing that holds the holding stage in a non-contact state with respect to the guide rail by air pressure, and movement of the holding stage back and forth along the guide rail. a damper body in which a movable member interlocked with the operation of the holding stage is disposed in a viscous fluid storage chamber made of magnetic fluid; and a viscous resistance adjustment member that adjusts the viscous resistance of the viscous fluid in the storage chamber. a magnetic fluid damper that adjusts the operating resistance of the holding stage according to a change in the viscous resistance of the viscous fluid in the accommodation chamber; and digital servo control of the operation of the stage drive mechanism to move the holding stage onto the guide rail. A stop position control function that stops the magnetic fluid damper at a predetermined stop position, and a stop position control function that stops the magnetic fluid damper at a predetermined stop position when the holding stage is located at a position other than the stop position on the guide rail. a viscous resistance control function that controls the viscous resistance adjusting member to reduce the resistance and increase the viscous resistance of the viscous fluid in the viscous fluid storage chamber when the holding stage has moved to a stop position on the guide rail; A positioning device characterized by comprising a control section.