JPH04178101A - Magnetic levitation carrier - Google Patents

Abstract

PURPOSE:To realize a stabilized levitation carrier by disposing lifting and lowering electromagnets opposing vertically, a guide electromagnet and a levitation position sensor on a vacuum carrying path for moving a carrier while levitating magnetically. CONSTITUTION:Linear motors 2, 2 are disposed on the opposite sides of a vacuum tunnel 1 and a carrying rail 3 is laid on the bottom in the center of the tunnel 1. Lifting and lowering electromagnets 4, 5 are disposed oppositely to each other at the lower part on the opposite sides of the vertical axis of the rail 3, guide electromagnets 6a, 6b are disposed on the opposite sides of a horizontal axis normal to the paper face at the upper part on the opposite sides of Z axis, and a brake electromagnet 7 is disposed oppositely above the Z axis. A levitation position sensor 8 is disposed in the center of function of the lowering electromagnet 5 and guide position sensors 9a, 9b are disposed in the center of function of the guide electromagnets 6a, 6b. A brake pole 13 is disposed in the center of a work mounting table 11 in a carrier 10 whereas a guide pole 14 and a levitation pole 15 are disposed on the opposite side boards 12. According to the constitution, electromagnet is eliminated from the carrier and stabilized levitation control is realized easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic levitation transport device that moves a transport platform in a vacuum transport path in a non-contact manner using magnetic levitation.

[Prior Art] Such devices are known and are particularly used for transporting wafers between steps in semiconductor manufacturing.

[Problems to be Solved by the Invention] In such devices, the levitation electromagnet and/or the guiding electromagnet have conventionally been provided on the transport platform, and power is supplied to the electromagnet using an overhead wire system, which poses a problem in dustproofness. Moreover, it was troublesome to manage the heat generated by the electromagnetic coil. 'Furthermore, since the levitation electromagnet installed on the carrier was provided with a suspension or lifting magnet, there was a problem with the stability of the carrier's movement.

In addition, the levitation position detection sensor has a characteristic that the area with a large detection gap is nonlinear, and in conventional technology, the levitation position was measured using a nonlinear area, so the measurement accuracy has not improved much. I can't. Furthermore, since it is difficult to accurately measure the flying height depending on the measurement position, stable flying control cannot be performed.

In a conveyance device in which floating and guiding electromagnets are installed on the conveyance path side, the number of electromagnets that can act in the conveyance direction is generally 2.
Since there were only one or three pieces, stable levitation control could not be achieved.

Furthermore, the conveyance direction guiding sensor could not suppress unnecessary disturbances of the conveyance platform, and stable levitation control could not be achieved.

The present invention has been made in view of the above-mentioned problems, and provides a magnetically levitated transport device that has good dustproof properties, has high accuracy in measuring the flying height using a floating position detection sensor, and is capable of stable floating control. The purpose is to

[Means for Solving the Problems] The magnetic levitation conveyance device of the present invention is a magnetic levitation conveyance device that moves a conveyance table in a vacuum conveyance path by magnetic levitation in a non-contact manner. A levitation electromagnet for suspending the carrier and a levitation electromagnet for lifting the carrier;
An electromagnet for guiding the direction of conveyance is provided, and a floating position detection sensor is provided below the member of the conveyance table on which the floating electromagnet acts and at the center of action of the floating electromagnet.

Here, in the transport direction, it is preferable to provide magnetic poles so that at least four sets of the levitation electromagnets can act on the transport table.

Furthermore, according to the present invention, the conveyance direction guide position detection sensors are arranged on the left and right sides of the horizontal axis, and the signals from these two sensors are processed to generate a signal corresponding to the displacement in the guide direction, and A guide control means is provided for canceling a component signal generated when the conveyance table makes a tilting motion about an axis intersecting with the conveyance table.

[Function] According to the magnetic levitation conveyance device of the present invention configured as described above, since the levitation electromagnet and the guide electromagnet are provided in the conveyance path, power can be supplied to both types of magnets without using an overhead wire system. Supply can be carried out continuously and heat generation can be easily controlled.

Furthermore, since the lifting and hanging electromagnets are provided vertically and oppositely, the stability of movement of the conveyance table can be improved.

In the present invention, a floating position detection sensor is provided below the member of the conveyance platform on which the levitation electromagnet acts, and the detection gap to be measured by the sensor becomes smaller when the conveyance platform is lowered. The floating position of the carrier can be accurately measured using the straight line portion of the nonlinear detection characteristic. As a result, stable floating control becomes possible.

Regarding the transport direction, if magnetic poles are provided so that at least four sets of levitation electromagnets can act on the transport platform, stable levitation control is possible.

Further, the detection signal in the left and right direction of the guide position detection sensor is used as a signal corresponding to the displacement in the guide direction, and the sensor is generated by tilting or rotational movement around the axis that intersects the horizontal axis and the vertical center axis, that is, the center axis in the conveyance direction. I canceled the signal of the component and made the guiding electromagnet not operate, so
It suppresses the occurrence of unnecessary disturbances and enables stable levitation control.

[Example] The present invention will be described in detail below with reference to the drawings.

In FIG. 1, linear motors 2.2 are provided on both sides of the vacuum conveying tunnel 1, and at the center of the bottom.
A transport rail 3 is provided.

One side of the transport tunnel 1 (the right side in the illustrated example) is connected to a vacuum pump passage 18 by a duct 16 via a gate valve 16 shown in FIG.

Electromagnets 4.4 for lifting and levitation and electromagnets 5.5 for suspension and levitation are provided facing each other at the bottom of both sides of the vertical central axis 2 of the transport rail 3, and on the left and right of the horizontal axis Y at the top of both sides. , a guiding electromagnet 6a around which electromagnetic coils Ca and Cb are wound, respectively.

6b, and brake electromagnets 7, 7 are respectively provided on the vertical central axis Z of the top.

A levitation position detection sensor 8 is provided at the center of action of the suspended levitation electromagnet 5.
Guide position detection sensors 9a and 9b are provided at the center of action of b.

Therefore, when the carriage 10 is lowered, the sensor 8.8
The detection gap is formed to be small.

On the other hand, the transport table, generally designated by the reference numeral 10, is provided with an upper plate 11 on which a wafer W is placed, and side plates 12, 12 extending downward from both ends of the upper plate 11. And top plate 1
1, magnetic poles 13 for the brake electromagnets 7 and 7 are vertically provided, magnetic poles 14 for the guide electromagnets 6 are provided on the upper portions of the side plates 12, and magnetic poles 14 for the guide electromagnets 6 are provided on the lower portions of the side plates 12, respectively. A magnetic pole 15 for the electromagnet 4.5 is horizontally protruded.

In FIG. 3, the carrier 1 for the levitation electromagnet 4.5
There are at least 4 sets of 0 magnetic poles 15 (4 sets in the illustrated example).
The length l is such that the levitation electromagnet 4.5 can act on the levitation electromagnet 4.5.

In FIG. 4, the guide position detection sensor 9a is connected to the electromagnetic coil Ca via a sensor amplifier 22a1, a compensation circuit 23a and a power amplifier 24a, and the sensor 9b is connected to an electromagnetic coil Ca via a sensor amplifier 22b1, a compensation circuit 23b and a power amplifier 24b. It is connected to the. These two sensors 9a, 9b are also connected to a control unit 20, and the two sensor amplifiers 22a, 2 are connected to the control unit 20 via an amplifier gain control signal generator 21, respectively.
2b is connected, and the control unit 20 and signal generator 21 constitute a guidance control means.

Therefore, levitation electromagnet 4.5, guide electromagnet 6.6
By providing all of the brake electromagnets 7 and 7 on the transport rail 3, power can be continuously and smoothly supplied to these electromagnets without relying on the conventional overhead wire system. Furthermore, it becomes easier to manage the heat generation of the electromagnetic coils of these electromagnets.

Further, since the lifting electromagnet 4 and the hanging electromagnet 5 are provided to face each other, the stability of movement of the conveyor table 10 is improved.

Further, as shown in FIG. 5, the output voltage Vs of the position detection sensor is generally linear in a region I where the detection gap is small, but has a characteristic that it becomes nonlinear in a region (2) where the detection gap is large. On the other hand, as shown in FIG. 6, the floating position detection sensor 8 is located below the magnetic pole 15 of the transport platform 10, and its reference detection gap DO is in the region I, and when the magnetic pole 15 is lowered, Since the detection gap becomes small, a linear output voltage Vs in the region (2) can always be obtained. Therefore, the detection accuracy of the detection gap is high, and stable floating control can be obtained.

Further, as shown in FIG. 7, for example, the length of the magnetic pole A relative to the levitation electromagnet 4 is 11, which is the length 11 on which the three electromagnets 4a to 4C can act. is located directly below the central electromagnet 4b, and in order to move the magnetic pole A smoothly horizontally without swinging, the control of excitation and extinction of the electromagnet 4a%4bN4c is extremely complicated. Become. If there is a difference in the attraction forces of these electromagnets, a rotational moment M1 will be generated on the transfer table.
Or M2 acts and the posture becomes unstable.

On the other hand, as shown in FIG. 8, the length of the magnetic pole 15 is such that at least four electromagnets 4a' to 4d can act on it! Therefore, the attractive forces of the two electromagnets 4a14b, 4c, and 4d act on the left and right sides of the center of gravity G, respectively. Therefore, the excitation and extinguishment of the electromagnets can be controlled by controlling every other two electromagnets, which is very easy. Furthermore, even if there is a difference in the attractive forces of these electromagnets, they cancel each other out and become negligible, resulting in stable levitation control.

In FIG. 9, when the operation switch (not shown) is ON (step S1 is YES), the control unit 20 detects the output voltages Va and Vb of the guide position detection sensors 9a and 9b (steps S2 and S3). , Vb are equal (step S4). If YES,
That is, if the detection gaps of both sensors 9a and 9b are equal (i), the process returns to step S2 without performing subsequent control. Further, as shown in FIG. 10, when the conveyance table 10 tilts around the intersection axis of the horizontal axis , the detection gap D1a of the sensor 9a is larger than the detection gap D2a, and the detection gap Dlb of the sensor 9b is larger than the detection gap D2.
Of course, the detection gap D2a is larger than b.
D2b are equal. Therefore, the component due to the tilting movement of the conveyor table 10 around the axis 7 is canceled in step S4. Next, the control unit 20 determines whether the output voltage Va is larger than the output voltage vb (step S5).
. If YES, that is, if the detection gap Dla is larger than the detection gap Dlb, the amplifier gain control signal generator 21 outputs a control signal to the sensor amplifier 22a, increases the gain of the output signal of the sensor 9a, and attracts the electromagnetic coil Ca. Increase the force (step S6).

Next, the output voltage Va of both sensors 9 a s 9 b,
Vb is detected (steps S7, S8). Therefore, the output voltages VaSVb become equal (step S9 is YES).
, and when the output voltages Va and Vb become zero, that is, when the conveyance platform 10 moves and the gap is no longer detected (step S14 is YES), the power supply to both electromagnetic coils Ca and Cb is cut. (Step 515), returning to step S1.

Moreover, if step S5 is No, that is, the detection gap D
If lb is larger than the detection gap Dla, steps SIO to S13, which are substantially the same as steps 86 to S9, are executed for the sensor amplifier 22b, and the process moves to step S14.

Note that the above-described embodiments are merely illustrative, and are not intended to limit the present invention to what is illustrated. For example, even if the circuit shown in FIG. 4 is replaced with the circuit shown in FIG. 11, favorable effects can be obtained.

The embodiment shown in FIG. 11 is distinguished from the embodiment shown in FIG. 4 in that it includes a square root circuit, but its structure and operation and effect are the same, so a description thereof will be omitted.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to continuously and smoothly supply current to the electromagnet, to easily manage the heat generation of the electromagnetic coil, and to achieve stable levitation control. It can be carried out.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are cross-sectional views perpendicular to the conveyance direction of the conveyance tunnel side and the gate valve side showing one embodiment of the present invention;
Figure 3 is a side sectional view of Figure 1, Figure 4 is a control block diagram of guidance control, Figure 5 is a characteristic diagram of the detection gap to output voltage of the position detection sensor, and Figure 6 is the floating position detection sensor and magnetic pole. FIGS. 7 and 8 are side views showing the relationship between the levitation electromagnet and the length of the magnetic poles. 11 is a control flowchart of guidance control, FIG. 10 is a diagram orthogonal to the conveyance direction explaining the tilting movement of the conveyance table in guidance control, and FIG. 11 is a control block showing another embodiment of guidance control of the present invention. It is a diagram. 1...Transportation tunnel 3...Transportation rail 4...
Lifting and levitation electromagnet 5... Suspension and levitation electromagnet 6g, 6b... Guide electromagnet 8... Levitation position detection sensor 9a, 9b... Guide position detection sensor 20... Control unit 21... Sensor gain control signal generator

Claims (3)

[Claims] (1) In a magnetic levitation conveyance device that moves a conveyance platform in a vacuum conveyance path by magnetic levitation in a non-contact manner, a levitation electromagnet that suspends and lifts up the conveyance platform that vertically opposes the conveyance path; A magnetic levitation conveyance device comprising: an electromagnet for guiding the conveyance direction; and a levitation position detection sensor provided below the member of the conveyance table on which the levitation electromagnet acts and at the center of action of the levitation electromagnet. . (2) Claim (1), wherein magnetic poles are provided so that at least four sets of the levitation electromagnets act on the conveyance table in the conveyance direction.
The magnetic levitation transport device described. (3) Conveying direction guide position detection sensors are arranged on the left and right sides of the horizontal axis, and the signals from these two sensors are processed to generate a signal corresponding to the displacement in the guiding direction, and the sensor is arranged at the intersection of the horizontal axis and the vertical central axis. 2. The magnetic levitation conveyance apparatus according to claim 1, further comprising a guide control means for canceling a signal component generated when the conveyance table makes a tilting motion.