JP2009089460A - Linear motor having differential capacitance position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor having a differential capacitance position detector wherein it is possible to keep low the amount of heat generated by a motor device and yet reduce its size and enhance its thrust and to achieve accurate positioning. <P>SOLUTION: Compressed air is guided into an air intake port 31 and the compressed air goes through a sensor housing 17 and a motor housing 6 and is discharged to an air discharge port. A mover assembly is linearly moved by passing current through a coil 14 and a glass tube dielectric 18 is moved between a common electrode 20 and split electrodes 21, 22. The capacitance formed between the split electrodes 21, 22 and the common electrode 20 changes, and a signal obtained as the result of this is processed at a control circuit and the position of the axis of the mover assembly is detected. The position of the mover assembly in the axial direction is adjusted with high thrust and accuracy by feedback-controlling the current passed through a coil 9 using a position detection signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear motor having a differential capacity type position detector used in a single-axis linear motion system for microfeeding used in the semiconductor, biotechnology, and optical fields.

Normally, a linear motor is excellent in high speed and high response, but is not suitable for obtaining a high thrust, becomes large, and generates a large amount of heat (power consumption).
As means for solving this, Patent Document 1 has been proposed.
Patent Document 1 is a linear actuator that combines a linear motor mechanism and an air cylinder mechanism. Since the linear motor mechanism and the air cylinder mechanism are individually arranged, there is a limit to downsizing.

In order to maintain airtightness, air cylinders usually have an elastic body such as rubber packing in contact with and slide between the movable and fixed parts. There is a problem that feed, repeat accuracy, and constant speed performance are affected. Therefore, there is a possibility that the advantages of the linear motor cannot be fully exhibited.
JP 2002-27732 A

  An object of the present invention is to provide a linear motor having a differential capacitance type position detector that can realize miniaturization, high thrust, and high-accuracy positioning while keeping the motor device low in heat generation.

In order to achieve the above object, according to the first aspect of the present invention, a large number of coils are arranged in parallel, a movable part having a large number of magnets fixed to a shaft is inserted into the coil, and an electric current is passed through the coil to generate electromagnetic force. A linear motor mechanism configured by moving the movable part forward and backward, and mounting a dielectric on the end of the linear motor mechanism and moving the dielectric back and forth between the common electrode and the divided electrode A differential capacitance type position detector that detects the position of the shaft by changing the capacitance of the capacitor formed between the common electrode and the divided electrode and processing the signal of the capacitance change, and The moving position of the moving object engaged with the shaft tip of the linear motor mechanism is controlled.
According to a second aspect of the present invention, in the first aspect of the invention, the linear motor mechanism includes a motor housing, a number of coils fixed to the inner wall of the motor housing, a shaft having spline outer cylinders fixed to both ends, and the shaft. Including a magnet assembly in which coin-shaped magnets and coin-shaped yokes are alternately arranged, and the plurality of coils are formed so that gaps are formed between the inner wall surfaces of the plurality of coils and the outer peripheral surface of the magnet assembly. The differential capacitance type position detector is formed by inserting a magnet assembly, and a dielectric fixed to a pedestal extending from the end of the movable part of the linear motor mechanism, and the spline outer cylinder fixed inside. A common electrode fixed to an inner boss having a cavity, and a divided electrode disposed on an outer surface of the common electrode, wherein the dielectric is advanced and retracted between the common electrode and the divided electrode. The voltage change with respect to the position of the dielectric is detected by converting the difference between the capacitance change signals output from the two electrodes of the divided electrode into a voltage, and the coil is adjusted to a target position. A full-closed loop control circuit for controlling the driving position of the linear motor by controlling the current to flow is provided.
According to a third aspect of the present invention, in the second aspect of the present invention, a gas is introduced into the gap to cool the linear motor.
According to a fourth aspect of the present invention, in the second aspect, the linear motor mechanism is a three-phase linear motor mechanism.
According to a fifth aspect of the present invention, in the second aspect of the present invention, the dielectric is a glass tube, a ceramic tube or a plastic tube dielectric.
According to a sixth aspect of the present invention, in the third aspect of the present invention, the linear motor is provided with a gas inlet and an outlet, respectively, and the gas introduced from the gas inlet is between the outer surface of the common electrode and the inner surface of the cradle. And passing through the gaps between the inner surfaces of the multiple coils and the outer surface of the magnet assembly, pushing the end of the magnet assembly, and discharging to the exhaust port, cooling the linear motor mechanism The movable part of the linear motor mechanism is pressed.
According to a seventh aspect of the present invention, in the sixth aspect of the present invention, a compressed gas supply source for introducing a compressed gas is connected to the gas intake port, and a gas having a predetermined pressure is introduced into the gas intake port. The linear motor is pressed by pressing the movable part in the direction of the moving object and energizing the moving part of the linear motor mechanism in the direction of the moving object or in the opposite direction by passing an electric current through the coil of the linear motor mechanism. The tip of the shaft of the mechanism is controlled to a predetermined movement position.

According to the first and second aspects, downsizing, high thrust, and high-definition positioning can be performed.
According to claim 3, in addition to the effect of claim 2, the linear motor mechanism can be efficiently cooled. According to the sixth aspect, in addition to the effect of the third aspect, the axial adjustment can be performed with high thrust. According to the seventh aspect, in addition to the effect of the sixth aspect, the position of the mover assembly in the axial direction can be finely adjusted in the front-rear direction with the linear motor mechanism while holding the position in the axial direction with a high thrust. Furthermore, according to claims 3 to 7, an appropriate gap is provided between the magnet assembly of the linear motor mechanism and the coil to form a pseudo piston mechanism, and a gas such as air, nitrogen or argon is directly passed through the gap. A long life can be realized by configuring a linear motor with the coil cooled and by using a ball spline as the sliding part of the mover.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1A is a cross-sectional view showing an embodiment of a linear motor having a differential capacitive position detector according to the present invention, and FIG. 1B is a cross-sectional view and a side view of FIG. 1A. 2 is a perspective view of FIG. 1, and FIG. 3 is an exploded perspective view of a motor housing and a sensor housing portion of a linear motor having a differential capacitive position detector according to the present invention.
FIG. 1A is a cross-sectional view taken along the line A-O-B, which is shown expanded.
The present invention is roughly composed of a linear motor mechanism and a differential capacitive sensor portion.
The linear motor mechanism includes a spline shaft (hereinafter referred to as “shaft”) 4, a front flange 5, a spline outer cylinder 10, 11, a motor housing 6, a coil 9, a coil case (2) 8, a magnet 12, a magnet case 13, and a yoke ( 1) 14, yoke (2) 15 and cradle 16.

  Perforated coin-shaped yokes (1) 14 and magnets 12 are alternately attached to the shaft 4, and a yoke (2) 15 having a female screw is attached to the last magnet 12. The yoke (1) 14, the yoke (2) 15 and the magnet 12 are accommodated in a cylindrical magnet case 13 as shown in FIG. The yoke (2) 15 is screwed with a cylindrical cradle 16 having notches 16a on both sides. A glass tube dielectric 18 is attached to the outer periphery of the cradle 16 with an adhesive. Thereby, a mover assembly (movable part) is formed. The shaft 4 is formed with two grooves 4a in the vertical direction, and the ball in the spline outer cylinder rolls in the grooves 4a to perform a linear motion, thereby restricting the rotation.

Coils 9 constituting the U phase, V phase, and W phase are alternately arranged on the outer periphery of the cylindrical coil case (2) 8, and these are accommodated in the coil case (1) 7 to constitute a coil assembly. . A coil assembly is accommodated in the inner periphery of the cylindrical motor housing 6, and the mover assembly is fitted and inserted inside the coil assembly to constitute a linear motor mechanism.
A slight gap 19 is formed between the inner circumference of the coil case (2) of the coil assembly and the magnet case 13 of the mover assembly, and air described later flows through this portion.

  By passing a three-phase alternating current through the U-phase, V-phase, and W-phase coils, between this and the N and S poles distributed in the magnet yoke (1) 14 and magnet yoke (2) 15 A linear motor that generates an electromagnetic force is formed, and a force for moving the mover assembly in the axial direction is generated, so that the mover assembly can move back and forth.

Spline outer cylinders 10 and 11 are respectively attached to the front end side and the rear end side of the shaft 4. The motor housing 6 has four screw holes 6c for attaching the front flange 5 on the front side, and is provided with a groove 6a. A spline outer cylinder 10 is fixed inside the front flange 5. The front flange 5 has four holes 5 b provided in the flange portion 5 a and screw holes 6 c of the motor housing 6. Fixed to. Between the groove 6a of the motor housing 6 and the rear surface of the flange portion 5a of the front flange 5, a passage for discharging the air sent to cool the interior of the linear motor mechanism is formed.
On the other hand, the spline outer cylinder 11 attached to the rear end side of the shaft 4 is fixed inside the inner boss 23.
A ball receiver 3 having a recess for receiving a ball is screwed to the front end surface of the shaft 4, and a ceramic ball 1 is inserted into the recess and a ball receiving collar 2 is attached to the ball receiver 3 to push a moving object. A moving position control target connection unit is configured.

A divided electrode composed of cylindrical divided electrodes A21 and B22 is fixed to the inner peripheral surface of the cylindrical sensor housing 17 with an adhesive, thereby forming a divided electrode assembly. The divided electrodes are insulated from the sensor housing 17. As described above, the inner boss 23 has a cylindrical inner boss fixing portion 23 a for fixing the spline outer cylinder 11 and a screw hole (female) on the outer peripheral surface for fixing to the sensor housing 17. It is comprised from the flange-shaped part 23b which has the joint connection hole 29 for fixing. A common electrode 20 having upper and lower cutouts 20a is fixed to the outer periphery of the inner boss 23 with an adhesive, thereby forming a common electrode assembly (see FIG. 6). The common electrode 20 is insulated from the inner boss 23.
The common electrode assembly is inserted into the divided electrode assembly, and the four screw holes of the flange-shaped portion 23b are aligned with the four holes provided near the rear end of the sensor housing 17 and screwed. The glass tube dielectric 18 fixed to the support 16 between the outer peripheral surface of the common electrode of the common electrode assembly and the inner peripheral surface of the divided electrode advances and retreats. As a result, two variable capacitance capacitors which are differential capacitance type position detectors are formed.

A collar 27 is attached to the rear surface of the inner boss 23, and a joint 30 is fixed to the joint connection hole 29 of the inner boss 23. A pipe to which a compressed air supply source (not shown) is coupled is connected to the joint 30.
A rectangular hole 17a is formed in the lower surface of the sensor housing 17, and the preamplifier substrate 26 is accommodated in the rectangular hole 17a. As shown in FIG. 6, the divided electrodes A21 and B22 have connection ends 21a and 22a, and the land on the upper surface of the preamplifier substrate 26 is electrically connected to the connection ends 21a and 22a. Terminals 25a and 25b are provided on the lower surface of the preamplifier substrate 26, and a capacitor signal formed by the divided electrodes A21 and B22 is taken out from the terminals 25a and 25b. The common electrode 20 is connected to the signal land of the preamplifier substrate 26 by a lead wire. The ground land of the preamplifier substrate 26 is connected to a screw for fixing the cradle 16 by a lead wire.

  A case 24 that covers the preamplifier substrate 26 is attached to the lower surface of the sensor housing 17. A hole 6 b provided in the rear end surface of the motor housing 6 is screwed to a screw hole (female) 24 a provided in the front end of the case 24, and a hole 28 a provided in the lid 28 is provided in the collar 27. The screw hole (female) 27a is screwed together. The hole 28b of the lid 28 is for taking out the lead wire soldered to the output of the preamplifier substrate 26 to the outside.

FIG. 4 is a view for explaining the air flow of the linear motor having the differential capacitive position detector according to the present invention.
Compressed air is introduced into the joint 30 fixed to the joint connection hole 29. The compressed air passes through the two through holes 23c provided in the inner boss fixing portion 23a of the inner boss 23, passes through the inner boss fixing portion 23a (common electrode 20), and is fixed to the yoke (2) 15 of the mover assembly. The mounting surface of the cradle 16 is removed. The compressed air pushes the mounting surface of the cradle 16 and then cools the coil of the linear motor mechanism through the gap 19 between the coil case (2) 8 and the magnet case 13. The compressed air that has passed through the gap 19 is discharged to the front side of the linear motor mechanism, and is discharged to the outside from the discharge port formed by the groove 6a of the motor housing 6. By adjusting the degree of compression, the compressed air can always apply thrust to the mover assembly with a predetermined force in the front direction of the linear motor and simultaneously cool the linear motor mechanism.

FIG. 7 is a block diagram showing an embodiment of a control circuit for driving a linear motor having a differential capacitive position detector according to the present invention.
The terminals of the divided electrodes A21 and B22 and the common electrode of the capacitor forming the differential capacitance type position detector 36 are connected to the signal processing circuit 49. The signal processing circuit 49 outputs a voltage proportional to the mover position of the linear motor by performing a ratio calculation of two capacitors that share one electrode of the differential capacitance type position detector 36. The signal processing circuit 49 is implemented in Japanese Patent No. 29967413 or Japanese Patent No. 3827661. Further, the signal processing circuit can be integrated and incorporated in the linear motor.
The voltage signal output from the signal processing circuit 49 can be the position F / B (position feedback signal) of the linear motor, and is input to the subtraction unit 41 and the sine wave data calculation unit 44 of the position control unit 40. The subtractor 41 subtracts the position F / B of the signal processing circuit 49 and the position command signal of the linear motor and outputs a deviation signal. The deviation signal from the subtraction unit 41 is input to the servo circuit 42. The servo circuit 42 performs control so that the deviation signal of the subtraction unit 41 input to the servo circuit 42 becomes zero. The output of the servo circuit 42 is input to the multipliers 45 and 46 of the DC three-phase AC converter 43, respectively.

  On the other hand, the sine wave data calculation unit 44 creates sin (θ + 120 °) data that is 120 ° out of phase with the sine wave sin θ data, and the sin θ data and sin (θ + 120 °) data are input to the multiplication units 45 and 46, respectively. The current command output from the servo circuit 42 is multiplied. An AC U-phase current command signal is output from the multiplier 45, and an AC V-phase current command signal is output from the multiplier 46 and input to the two amplifiers 48a and 48b of the three-phase amplifier 48, respectively. The W-phase current command calculation unit 47 calculates a W-phase current command signal from the U-phase current command signal and the V-phase current command signal and inputs the W-phase current command signal to the three-phase amplifier 48c. The three amplifiers 48a, 48b, and 48c each output current having a phase difference of 120 °, and supply current to the corresponding coils of the linear motor mechanism to drive the linear motor.

  This circuit is a full-closed loop control circuit, and the servo circuit 42, multipliers 45 and 46, and sine wave data so that the deviation e between the position F / B signal c and the position command signal d from the signal processing circuit 49 becomes zero. Control is performed by the calculation unit 44, the W-phase current command calculation unit 47, and the three-phase amplifier 48.

The linear motor according to the present invention introduces air of a predetermined pressure from the air intake port on the rear surface of the differential capacity type position detector, and pushes the mover assembly shaft in the protruding direction to apply thrust using compressed air to the linear motor. The position of the mover assembly is detected by the differential capacitance type position detection sensor by inputting the signal of the target position, and the coil current of the mover assembly is controlled by the fully closed loop control circuit. Can be brought with high accuracy.
In other words, the mover assembly is pressed in the protruding direction by the compressed air, but the mover assembly is attached to the excess and deficiency of the compressed air by controlling the coil current so as to reach the target position by the fully closed loop control circuit. Given power, it is moved and held at a target position with high accuracy.

Although the differential capacitance type sensor of the above embodiment has shown the example of a dielectric movable type, it can also be set as the structure which moves the electrode side.
Further, it can be realized by using a voice coil type linear motor for the linear motor mechanism as a modification of the present invention. Further, it can be realized by incorporating a linear scale instead of the differential capacitance type position detector.
Furthermore, when there is a load fluctuation (load fluctuation), a pressure sensor is provided between the linear motor output shaft and the controlled object, and gas compression control is performed. A motor drive current (current flowing through the coil) is detected and gas compression control is performed. Etc. can be applied.
The bearing can be a dry bearing or a sintered bearing. As the ferroelectric, a ceramic dielectric or a resin dielectric can be used. Nitrogen or argon can be used as the gas.

  It realizes high-speed, high-thrust, and high-precision positioning as a movement control object in the semiconductor, bio, and optical fields.

It is sectional drawing which shows embodiment of the linear motor which has a differential capacitive type position detector by this invention. It is a cross-sectional view and a side view of FIG. 1A. FIG. 2 is a perspective view of FIG. 1. 1 is an exploded perspective view of a linear motor having a differential capacitive position detector according to the present invention. FIG. It is a figure for demonstrating the flow of the air of the linear motor which has a differential capacity type position detector by the present invention. It is a figure which shows the detail of a mover assembly. It is a figure which shows the detail of a division | segmentation electrode assembly, a common electrode assembly, and a glass dielectric. It is a circuit block diagram which shows embodiment of the control circuit which drives the linear motor which has the differential capacitive type position detector by this invention.

Explanation of symbols

1 Ceramic balls
2 Ball receiving collar 3 Ball receiving 4 Spline shaft
5 Front flange
6 Motor housing
7 Coil case (1)
8 Coil case (2)
9 Coil 10, 11 Spline outer cylinder
12 magnet 13 magnet case 14 yoke (1)
15 York (2)
16 cradle 17 sensor housing 18 glass tube dielectric
19 Air gap
20 Common electrode 21 Split electrode A
22 Split electrode B
23 Inner Boss
24 Case 25 Terminal 26 Preamplifier Board 27 Color 28 Lid 29 Joint Connection Hole 30 Joint 31 Air Intake 35 Linear Motor Mechanism 36 Differential Capacitance Type Position Detector 40 Position Controller 41 Subtractor 42 Servo Circuit 43 DC 3 Phase AC Converter 44 Sine Wave Data Calculation Unit 45, 46 Multiplication Unit 47 W Phase Current Command Calculation Unit 48 Three Phase Amplifier 49 Signal Processing Circuit

Claims (7)

It is configured by inserting a large number of coils side by side, inserting a movable part with a large number of magnets fixed on the shaft into the coil, passing an electric current through the coil to generate electromagnetic force, and moving the movable part back and forth. A linear motor mechanism,
A dielectric is mounted on the end of the linear motor mechanism,
By moving the dielectric between the common electrode and the divided electrode, the capacitance of the capacitor formed between the common electrode and the divided electrode is changed, and the position of the axis is processed by processing the capacitance change signal. And a differential capacitance type position detector for detecting
A linear motor having a differential capacitive position detector, wherein the moving position of a moving object engaged with a shaft tip of the linear motor mechanism is controlled. The linear motor mechanism is
A motor housing;
A number of coils fixed to the inner wall of the motor housing;
A shaft with a spline outer cylinder fixed to both ends;
Including a magnet assembly in which coin-shaped magnets and coin-shaped yokes are alternately arranged on the shaft,
The magnet assembly is inserted through the multiple coils so that air gaps are formed between the inner wall surfaces of the multiple coils and the outer peripheral surface of the magnet assembly,
Differential capacitance type position detector
A dielectric fixed to a cradle extending from the end of the movable part of the linear motor mechanism;
A common electrode fixed to an inner boss having a cavity for fixing the spline outer cylinder therein;
A split electrode disposed on the outer surface of the common electrode,
The dielectric is advanced and retracted between the common electrode and the divided electrode;
A voltage change with respect to the position of the dielectric is detected by converting a difference between capacitance change signals output from the two electrodes of the divided electrode into a voltage, and a current flowing through the coil is controlled so as to be a target position. A fully closed loop control circuit that controls the drive position of the linear motor
A linear motor having a differential capacitance type position detector according to claim 1, wherein the linear motor is provided.   The linear motor having a differential capacitive position detector according to claim 2, wherein gas is introduced into the gap to cool the linear motor.   3. The linear motor having a differential capacitive position detector according to claim 2, wherein the linear motor mechanism is a three-phase linear motor mechanism.   3. The linear motor having a differential capacitive position detector according to claim 2, wherein the dielectric is a glass tube, a ceramic tube, or a plastic tube dielectric. The linear motor is provided with a gas intake port and an exhaust port,
The gas introduced from the gas inlet passes between the outer surface of the common electrode and the inner surface of the cradle, pushes the end of the magnet assembly, and gaps between the inner surfaces of the multiple coils and the outer surface of the magnet assembly. Configured to discharge to the exhaust port,
4. The linear motor having a differential capacitance type position detector according to claim 3, wherein the linear motor mechanism is cooled and a movable portion of the linear motor mechanism is pressed. Connect a compressed gas supply source for introducing compressed gas to the gas inlet, put a gas of a predetermined pressure into the gas inlet, press the movable part of the linear motor toward the moving object,
In addition, a current is applied to the coil of the linear motor mechanism to bias the movable part of the linear motor mechanism in the direction of the moving object or in the opposite direction, thereby moving the tip of the shaft of the linear motor mechanism to a predetermined moving position. The linear motor having a differential capacitance type position detector according to claim 6, wherein

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