JPH0628505B2 - Non-contact flat type table - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-contact flat table suitable for use in dust-proof semiconductors and biotechnology-related factories.

(Prior Art) Conventionally, there is a direct drive type table using a linear motor. Since this table uses a linear motor that advances in synchronization with an input pulse signal as a drive unit, open-loop control is possible, and there is a feature that errors do not accumulate, and its application is expanding.

(Problems to be Solved by the Invention) However, in the conventional table of this type, the table including the work is separated from the linear motor and supported by a mechanical linear bearing. Therefore,
Since this mechanical linear bearing portion is provided, dust is generated from this portion, which is not suitable for use in a semiconductor manufacturing or clean room related to biotechnology.
Further, in a high vacuum state, there is a problem that the lubricating oil evaporates, the atmosphere is polluted, and the bearing portion is burned.
As such, conventional tables of this type have not been sufficient for use in the harsh environment described above.

The present invention eliminates the above-mentioned problems, and provides a non-contact flat type table that is driven directly by a magnetic linear magnetic pole in which floating and propulsion of a movable table are blocked by a linear motor magnetic pole. With the goal.

(Means for Solving Problems) In order to solve the above problems, the present invention provides, in a non-contact flat table, (a) a fixed body having tooth rows aligned with a constant pitch, (b) A core member having a plurality of teeth facing the tooth row and provided with at least four pole pieces arranged at predetermined intervals, and for propulsion guidance wound on each of the pole pieces. A propulsion guide magnetic pole excited by a coil, and a suction magnetic pole excited by a suction coil wound on a core member so as to excite two of the magnetic poles adjacent to the propulsion guide magnetic pole to the same pole. And a movable table having at least two linear motor magnetic poles integrated with each other in the propulsion direction, and the linear motor magnetic poles arranged in the propulsion direction are out of phase with each other by π / 4 with respect to the tooth row of the fixed body. ,
(c) Displacement detecting means for detecting relative displacement between the fixed body and the movable table, and (d) adjusting a gap between the fixed body and the movable table based on a detection value from the displacement detecting means. A control means for propelling the movable table in a magnetically levitated state is provided.

(Operation) According to the present invention, the movable table is held in a non-contact state by the magnetic force of the attraction magnetic pole in the linear motor magnetic pole, and the movable table is retained by the magnetic force of the propulsion guide magnetic pole in the linear motor magnetic pole. The control of the attitude of the movable table is performed by adjusting the exciting currents of the respective suction coils in the magnetic poles of the linear motor.

(Example) Hereinafter, the Example of this invention is described in detail, referring drawings.

First, the outline of the structure and operation of this non-contact flat table will be described with reference to FIGS. 1 to 3.

In the figure, reference numeral 1 denotes a fixed body, which comprises a bottom surface portion 1a, side surface portions 1b extending upward from both side ends of the bottom surface portion, and an extension portion 1c extending inward from the upper end of the side surface portion. There are openings before and after. Reference numeral 2 denotes a movable table, which has a table surface 2a at the upper part, and is composed of a vertical part 2b hanging from the center part to the lower part, and a shelf part 2c extending from the vertical part 2b to both sides to form a cross-section work shape. ing. Then, a tooth row having a tooth surface orthogonal to the traveling direction is formed on the lower surface of the overhanging portion 1c of the fixed body 1, and a linear motor magnetic pole 3 is arranged on the shelf portion 2c of the movable table. The magnetic poles 3 of the linear motor are opposed to each other.

(1) Holding the movable table in a non-contact state The magnetic poles of the linear motor magnetic poles 3 are excited by the suction coils of the linear motor magnetic poles 3 and the magnetic force between the tooth rows provided on the lower surface of the overhanging portion 1c of the fixed body. 3 is attracted to its dentition, the movable table is suspended and held in a non-contact state.

(2) Propulsion of movable table The movable table 2 is driven by the magnetic force between the propulsion guide magnetized by the propulsion guide coil of the linear motor magnetic pole 3 and the tooth row provided on the lower surface of the protruding portion 1c of the fixed body 1. Propel in the suspended condition.

(3) Attitude control of the movable table The attitude control of the movable table 2 is performed by adjusting the excitation current of the attraction magnetic poles in the magnetic poles of each linear motor on which the magnetic force acts on the movable table 2. That is, positioning is performed by adjusting the excitation current of the attraction magnetic poles in the magnetic poles of the linear motor so that the movable table 2 is in a predetermined state. Therefore, the gap between the movable table 2 and the attraction magnetic pole is detected by the displacement detector 4, and appropriate posture control is performed based on the detected value.

Hereinafter, one embodiment of the present invention will be sequentially described.

First, the linear motor magnetic pole will be described.

As described above, on the lower surface of the overhanging portion 1c of the fixed body 1, tooth rows aligned at a certain pitch are formed so as to be orthogonal to the propulsion direction, and a gap facing the tooth row is formed. The linear motor magnetic pole 3 is arranged at the holding position. As shown in FIG. 4, in this linear motor magnetic pole 3, a suction coil of the movable table 2 is wound around the base of the core member 21, and a propulsion guide coil is wound around the tip of the movable table 2. That is, a magnetic pole for attraction that magnetically attracts the movable table 2 for non-contact support and a magnetic pole for propulsion guide that magnetically propels the movable table 2 are integrally formed. This core member 21 is formed by stacking ferromagnetic materials such as electromagnetic steel plates punched in a concatenated shape having a concave shape, and suction coils 26 and 27 are provided on the outer periphery of each recess of the core member 21. They are wound so that they have opposite magnetism. Each tip of this core member is composed of a first pole piece, a second pole piece, a third pole piece, and a fourth pole piece, and each pole piece has a propulsion guide coil 28, 29, 3 respectively.
0, 31 are wound, the first magnetic pole 22, the second magnetic pole 23, the third magnetic pole 2
4, the fourth magnetic pole 25 is formed. These magnetic poles 22, 23, 24,
The pitch of each tooth provided on 25 is the same as the pitch of the teeth of the fixed body, but the pitch of the teeth between the magnetic poles is deviated from the pitch of the magnetic pole teeth, and with reference to the first magnetic pole 22, , The second magnetic pole 23 is 1/2 pitch, the third magnetic pole
24 is a quarter pitch, and the fourth magnetic pole 25 is arranged so as to be displaced by a quarter pitch relative to the tooth pitch of the fixed body.

Next, the operation of the magnetic poles of this linear motor will be described with reference to FIG.

(1) When a current in the direction indicated by the arrow in FIG. 5 (the positive direction) is applied only to the suction coils 26 and 27, magnetic flux flows as shown in FIG. Occurs.

(2) When a current is applied only to the propulsion guide coils 28 and 29 that excite the first magnetic pole 22 and the second magnetic pole 23, a magnetomotive force is generated, and FIG.
Magnetic flux flows as shown in (b). When a current is passed in the negative direction, the direction of magnetomotive force is reversed and the magnetic flux also flows in the opposite direction. The same applies to the propulsion guide coils 30 and 31 that excite the third magnetic pole 24 and the fourth magnetic pole 25.

Here, a certain constant current Ic is passed through the suction coils 26 and 27. That is, when the magnetomotive force shown in FIG. 5 (a) is generated to flow the magnetic flux and at the same time the positive current Ia is passed through the propulsion coils 28 and 29, the first magnetic pole 22 generates the current Ic and the current Ia. The magnetomotive forces strengthen each other, while the current I
The magnetomotive forces of c and the current Ia cancel each other out, and the movable table 2
Generates a stable restoring force at the position shown in Fig. 5 (b). That is, an attempt is made to stabilize at a position where the convex portions of the teeth of the first magnetic pole 22 and the convex portions of the teeth of the fixed body 1 coincide.

Next, if the current Ia is made zero and the current Ib is made positive, the third
A magnetic flux is about to flow through the magnetic pole 24, and thrust is generated on the movable table 2 so as to stabilize at the position shown in FIG.
Step by pitch.

Next, if the current Ib is made zero and the current Ia is made negative, the second
Since the magnetomotive force with respect to the magnetic pole 23 is strengthened and the magnetic flux flows, the step advances by 1/4 pitch.

In this way, Ia (positive) → Ib (positive) → Ia (negative)
→ By switching the currents of the propulsion guide coils 28, 29 and 30, 31 such as Ib (negative), the movable table 2 is stepped every ¼ pitch.

With such a configuration, non-contact support of the movable table and propulsion of the movable table can be achieved by a compact linear motor magnetic pole, and a conventional mechanical bearing mechanism such as a rolling bearing can be completely abolished.

Next, the attitude control of the movable table will be described with reference to FIGS.

As shown in these figures, the shelves 2 of the movable table 2
In c, four linear motor magnetic poles 3 are arranged in two rows in the traveling direction of the movable table and face the tooth row on the lower surface of the overhanging portion 1c of the fixed body 1 with a predetermined gap. Displacement detectors 4 are arranged near the central portion of the linear motor magnetic pole 3 to detect the relative displacement of the gap between the fixed body 1 and the movable table 2.

Here, first, the origin position of the movable table 2 is determined by a dog switch or the like, and the movable table 2 is supported in a non-contact manner at this position. In other words, an exciting current is made to flow through the magnetic poles of the linear motor in advance via the drive circuit 9 to balance the weight of the movable table 2 and the magnetic attraction force to balance the weight of the movable table 2 and the magnetic attraction force to magnetically levitate the movable table 2. And bring them into non-contact state.

Next, in the non-contact state, the detection value from each displacement detector 4 is input to the electronic control unit 8 and the input interface 8-3
Read through, and the read value and the memory 8 in advance.
-2 is compared with the reference value (the reference void value) of each displacement detector stored in -2, and the I / O is set so that the deviation becomes zero.
In the drive circuit 9 through the interface 8-4,
Adjust the excitation current value of the suction coil in each magnetic pole of the linear motor. The CPU 8-1 is a central processing unit, and performs overall control and calculation of the electronic control unit 8. MD18-
Reference numeral 5 is a manual data input device, which can input various data. A power source 10 is connected to the drive circuit 9.

By thus performing the feedback control, it is possible to smoothly perform the attitude control of the movable table.

Also, the position of the propulsion direction is stored in advance as the origin position,
From this position, the amount of displacement can be recognized by the number of pulses applied to the magnetic poles of the linear motor, and the position of the movable table can be controlled.

Next, the micro step drive of the movable table will be described.

Here, the micro-step drive is a method in which a two-phase current having a 90 ° phase shift is applied to two windings of a linear pulse motor to drive the motor as a synchronous motor. A current waveform as shown is provided.

FIG. 7 is a block diagram for performing microstep driving, in which 41 is a ring counter and 42 and 43 are RO.
M, 44 and 45 are D / A converters, and 46 and 47 are drive amplifiers.

As shown in this figure, when a movement command is input to the ring counter 41, the waveform data stored in the ROMs 42 and 43, that is, the sine and cosine values are read out, and the D / A converters 44 and 45 are operated. An analog amount is input to the drive amplifiers 46, 47 via the amplifiers and amplified to drive guidance coils 28, 29, 30, 31.
Added to.

In the waveform, the ratio of the A phase and the B phase is determined by the electrical angle position (time), which is output according to the angular electrical angle position to move the movable table 2. If a voltage amplifier is used as the drive amplifier, passive typing can be expected. With this configuration, the movable table can move smoothly and can be positioned at a minute distance.

By the way, since the movable table is driven in a contact state, the mechanical diping with respect to the movement of the movable table is very small. Therefore, even if the micro step drive is performed, some vibration is accompanied. In order to suppress this vibration, the phases of the plurality of linear motor magnetic poles arranged in the propulsion direction with respect to the teeth of the movable table 2 are shifted from each other by π / 4. That is, at a certain point, the linear motor magnetic pole 3a,
In the propulsion guide coil 3b, the linear motor magnetic pole 3 is used to generate the magnetomotive force shown in FIG. 8 (a).
In the propulsion guide coils c and 3d, the linear motor magnetic poles are arranged so as to generate a magnetomotive force as shown in FIG. 8 (b).

Thus, the position of the magnetic pole of the linear motor is π / 4 in electrical angle.
If they are shifted, the thrust and diping characteristics will be uniform,
Smoother driving becomes possible as compared with the case of the in-phase arrangement.

In the above, the case of the micro step drive has been described.
The pattern is as shown. That is, the linear motor magnetic pole I
When the (linear motor magnetic pole 3a or 3b) is one-phase excitation, the linear motor magnetic pole II (linear motor magnetic pole 3c or 3b)
d) is two-phase excitation, and vice versa.

Here, plus and minus in the table are polarities of the coil voltage (or current) at the time of bipolar driving of the step motor.

In this way, not only during microstep driving, but also in the case of a normal step motor, dipping can be performed by shifting the excitation phase.

Furthermore, even if n × π / 4 (n = 1, 3, 5, 7) is advanced or delayed, the above-described effects can be obtained. That is, when one of the two is two-phase excitation, the other one is preferably one-phase excitation.

Next, one embodiment of the position closed loop control of this non-contact flat table will be described with reference to FIG.

Here, a traveling direction position detector 66 is provided. The linear motor magnetic pole 3 and the traveling direction detector 66 are fixed to the movable table 2. Further, the drive circuit of the suction coil 26, the gap detector, the gap control circuit, and the like are omitted.

In the figure, 51 is a deviation counter for outputting an error between the current position and the movement command value, 52 is a D / A converter, 53 is a controller including a PID controller, 54 is a code discriminator, and the phase is advanced. Delay, that is, output a plus or minus signal. 55 is an absolute value circuit and 56 is a phase output device, which is normally fixed at 90 °. 57 is a phase adder / subtractor, 58 and 59 are ROMs, 60 and 61 are D / A converters, 62 and 63 are multipliers, 64,
Reference numeral 65 is a drive amplifier, and 66 is a traveling direction position detector, which detects the phase with respect to the teeth provided on the fixed body 1. The waveform is
For example, it outputs as a sine wave and a cosine waveform. 67 is a position converter, for example, an R / D (resolver / digital) converter, which outputs the current phase output to the phase adder / subtractor 57 and outputs the speed output to the addition point 68 to form a speed loop. . The position converter 67 also outputs a current position signal to the deviation counter 51 to form a position loop.

Next, another embodiment of this non-contact flat type table will be described with reference to FIG.

In the figure, reference numeral 101 denotes a fixed body having a bottom surface portion 101a, a vertical portion 101b extending from the central portion of the bottom surface portion to an upper portion, and protruding portions 101c extending from the vertical portion to both sides, and has a sectional shape. Ten
Reference numeral 2 denotes a movable table, which includes a table surface 102a on an upper portion, side surface portions 102b extending from both ends of the table surface to a lower portion, and a shelf portion 102c extending inward from a lower end of the side surface portion.
It is shaped to embrace the 101. Reference numeral 103 denotes a linear motor magnetic pole, which is arranged on the shelf 102c. That is, in this embodiment, the movable table has an outer bar shape.

With this configuration, the waterproof and dustproof functions of the linear motor magnetic pole portion can be enhanced.

The present invention is not limited to the above embodiment,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described in detail above, according to the present invention, in a non-contact plane type table, a fixed body having tooth rows aligned at a constant pitch, and a plurality of facing members facing the tooth rows. A core member having at least four pole pieces installed at predetermined intervals and having a tooth, and a propulsion guide magnetic pole excited by a propulsion guide coil wound on each of the pole pieces. Advancing a linear motor magnetic pole that is integrated with an attraction magnetic pole that is excited by an attraction coil wound on a core member so as to excite two of the magnetic poles adjacent to the propulsion guidance magnetic pole to the same pole. A movable table in which at least two linear motor magnetic poles arranged in the driving direction are shifted in phase from each other by π / 4 with respect to the tooth row of the fixed body; and between the fixed body and the movable table. Displacement detection to detect relative displacement And a control means for adjusting the gap between the fixed body and the movable table on the basis of the detection value from the displacement detecting means to propel the movable table in a magnetically levitated state. , (1) The movable table can be propelled in a non-contact state, and its control is extremely smooth.

(2) The movable table is a direct drive type flat table, and its structure is simple and compact.

(3) The atmosphere is not polluted and maintenance can be facilitated as compared with the conventional mechanical bearing.

(4) It can be used in a high vacuum state. In this case,
Unlike conventional mechanical bearings, the lubricating oil evaporates, pollutes the atmosphere and does not burn the bearing.

As described above, the present invention has various advantages and the effects are great.

In particular, the present invention is suitable for use in a semiconductor manufacturing or clean room related to biotechnology because it can be sufficiently used even under the severe environment described above.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a non-contact flat type table showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II ′ of FIG. 1, and FIG. 4 is a perspective view of the magnetic poles of the linear motor, and FIG. 5 is an operation explanatory view of the magnetic poles of the linear motor.
6 and 8 are microstep drive current waveform diagrams,
FIG. 7 is a microstep drive system configuration diagram, FIG. 9 is an excitation sequence diagram, FIG. 10 is a closed loop control system configuration diagram, and FIG. 11 is a part of a non-contact plane type table showing another embodiment of the present invention. It is a broken perspective view. 1,101 ... fixed body, 2,102 ... movable table, 3,
103 …… Linear motor magnetic pole, 4 …… Displacement detector, 8 ……
Electronic control device, 9 ... Driving circuit, 10 ... Power supply.

Claims (3)

[Claims] 1. A fixed body having (a) a tooth row aligned at a constant pitch, and (b) at least a plurality of teeth facing the tooth row, which are installed at a predetermined interval. A magnetic pole for propulsion and guidance, which has a core member provided with four pole pieces, is excited by a propulsion and guidance coil wound around each of the pole pieces, and two of the magnetic poles are adjacent to the magnetic pole for propulsion and guidance. A linear motor having at least two linear motor magnetic poles in the propulsion direction, which are integrated with the suction magnetic poles excited by the suction coil wound on the core member so as to be excited to the same pole. A movable table whose motor magnetic poles are out of phase with each other by π / 4 with respect to the tooth row of the fixed body; (c) displacement detection means for detecting relative displacement between the fixed body and the movable table; ) Based on the detection value from the displacement detection means, the fixed body and the Adjust the gap between the dynamic table, the non-contact planar table, characterized by comprising a control means for promoting a magnetic levitation state of the movable table. 2. A means for supplying a sine-wave current and a cosine-wave current to the propulsion guide coil, and performing microstep drive by the current flowing in each of these phases. The non-contact flat table according to item 1. 3. A displacement detecting means detects displacement of the movable table in a traveling direction during the micro-step driving,
The non-contact plane type table according to claim 2, further comprising means for performing closed loop control so that a constant excitation lead angle is obtained based on the detected value.