JP3465786B2 - Linear actuator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator used in FA (factory automation) field and the like.

[0002]

2. Description of the Related Art In a device or the like for transporting semiconductor components, a vertical movement operation is performed when the semiconductor components are taken out from a stocker. The vertical movement operation is performed by a linear actuator. The linear actuator provided in the carrier is required to be small. Conventionally, an air cylinder has been used as a linear actuator in order to reduce the size of the structure.

FIG. 7 is a diagram showing a configuration example of a linear actuator using an air cylinder. In FIG. 7, the piston 1 moves up and down in the AA ′ direction by the compressed air supplied to the cylinder 2. For example, when compressed air is supplied to the cylinder 2, the piston 1 is pushed out of the cylinder 2 and moves downward, and when the compressed air supply is stopped,
The piston 1 is drawn into the cylinder 2 by the restoring force of a spring (not shown) in the cylinder 2.

The air supply means 3 supplies compressed air to the cylinder 2. The rail 4 is fixed to the cylinder 2 and extends in the vertical direction. The slider 5 is movably attached to the rail 4 and is connected to the piston 1.
The rail 4 and the guide 5 are provided to guide the piston 1 so that the moving direction of the piston 1 is the vertical direction.

The suction means 6 is attached to the lower end of the piston 1. When the piston 1 moves downward and the suction means 6 is pressed against the component 8 in the stocker 7, the suction means 6 suctions the component 8. The piston 1 moves upward in the sucked state, and the component 8 is taken out from the stocker 7. The suction operation of the suction means 6 is performed by utilizing the supply air pressure of the air supply means 3.

However, the conventional example of FIG. 7 has the following problems. Positioning of the piston 1 in the vertical direction was realized by a mechanical stopper. Therefore, the positioning cannot be performed at an arbitrary position. Since the piston 1 and the cylinder 2, and the rail 4 and the slider 5 are in contact with each other, wear shortens the life.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and by forming a linear pulse motor in a linear motion guide and using a magnetostrictive sensor as a position sensor, It can be positioned at any position with high accuracy and uses a magnetostrictive sensor.
The purpose of the present invention is to realize a linear actuator that can control the commutation of a motor with a long life.

[0008]

The present invention is a linear actuator having the following structure.

(1) In a linear actuator for linearly moving an object, a rail on which teeth are formed at a constant pitch along a length direction, the object is held, and the rail is movably attached to the rail. The slider and the slider are formed integrally with each other, and teeth are formed at a constant pitch in the same direction as the arrangement direction of the rail teeth, and a magnetic attraction force is generated between the teeth and the rail teeth. A linear pulse motor for moving a slider along a rail, a magnetostrictive scale made of a magnetostrictive material and arranged in parallel with the rail, and a magnetostrictive head mounted on the slider, and an end portion of the magnetostrictive scale. Further, an exciting means is provided on one side of the magnetostrictive head and a receiving means is provided on the other side, and the ultrasonic signal generated in the magnetostrictive scale by the exciting means is detected by the receiving means. Time and magnetostrictive sensor for detecting the absolute position of the slider on the basis of a position control section for feedback controlling a position of the slider on the basis of the deviation of the detected position of the magnetostrictive sensor and command position required for the next The calculation of
I multiply the decimal part of the calculated value N by 360 °
Phase to find the phase difference between the teeth of the motor and the teeth of the linear pulse motor
If the teeth and the linear pulse motor of the teeth of the phase rail: and displacement detecting _{means, N = (S n -S 0} ) / ΔS S 0
The detection value S _n of the magnetostrictive sensor when it is set : The detection of the magnetostrictive sensor obtained in the positioning operation.
Output value ΔS: The slider moved by one pitch of the rail teeth.
The amount of change in the detected value of the magnetostrictive sensor at this time is based on the phase shift detected by this phase shift detection means.
And a commutation controller for controlling commutation of the actuator.

(2) The linear actuator according to (1), characterized in that the rail and the magnetostrictive scale are arranged with the longitudinal direction being the vertical direction.

(3) A velocity detecting means for differentiating the detection signal of the magnetostrictive sensor to detect the moving velocity of the slider, and the velocity of the slider based on the difference between the command velocity and the detected velocity of the velocity detecting means. The linear control according to (1), further comprising a speed control unit for feedback control.
Actuator.

[0012]

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. This figure is a diagram showing the mechanical structure of a linear actuator according to the present invention. In FIG. 1, the rail 20 is
The teeth 21 are formed at a constant pitch along the length direction. The slider 22 holds an object (not shown) and is movably attached to the rail 20. Rail 20
The slider 22 constitutes a linear motion guide. When a linear actuator is used in a semiconductor component transfer device or the like, the rail 20 is arranged so that the length direction thereof is the vertical direction.

The linear pulse motor 23 includes a slider 22.
And the teeth 24 are formed at a constant pitch along the same direction as the arrangement direction of the teeth 21.
A magnetic attraction force is generated between the slider 22 and the rail 2
Move along 0. The pitch of the teeth 21 and the teeth 24 is equal.

The magnetostrictive scale 25 is made of a magnetostrictive material and is arranged in parallel with the rail 20. The magnetostrictive head 26 is mounted on the slider 22, generates an ultrasonic signal in the magnetostrictive scale 25, and determines the absolute position of the slider 22 based on the time required for the ultrasonic signal to reach both ends of the magnetostrictive scale 25. To detect. The magnetostrictive scale 25 and the magnetostrictive head 26 form a magnetostrictive sensor 27.

FIG. 2 is an explanatory view of the detection principle of the magnetostrictive sensor. In FIG. 2, the pulse generator 261 is an excitation coil 262.
An excitation pulse is applied to generate a pulse signal in the magnetostrictive scale 25. The excitation coil 262 moves together with the slider 22. In this example, the case where the pulse signal is generated is described, but an ultrasonic signal other than the pulse signal may be generated.

The receiving coils 263 and 264 are arranged at both ends of the magnetostrictive scale 25 and detect the pulse signal propagated through the magnetostrictive scale 25. The comparison amplifiers 265 and 266 are
The pulse waveforms received by the receiving coils 263 and 264 are shaped. The position detecting means 267 detects the absolute position of the slider based on the time required from the generation of the pulse signal by the exciting coil 262 to the detection of the pulse signal by the receiving coils 263, 264. This detection method will be described.

FIG. 3 shows the excitation pulse and reception coil 263.
8 is a time chart of signal waveforms of H.264 received pulses. As shown in FIG. 3, the reception pulses are detected by the reception coils 263 and 264 after the time T1 and T2 from the generation of the excitation pulse, respectively. Times T1 and T2 are measured.

Distances from the position of the magnetostrictive head 26 (position of the slider 22) to the left end and the right end of the magnetostrictive scale 25 are L1 and L2, respectively. The total length of the magnetostrictive scale 25 is L = L1 + L2. The distances L1 and L2 are given by the following equations. L1 = T1.v L2 = T2.vv: speed at which the pulse propagates through the magnetostrictive scale 25 where P = (T1-T2) / (T1 + T2) = (L1-L2) / (L1 + L2) = (2L1-L ) / L Thereby, L1 = {L (P + 1)} / 2 (1) Since T1 and T2 are known, P is also known. Therefore,
The distance L1 is detected from the equation (1). In this way, the position of the slider 22 is detected.

FIG. 4 is a block diagram showing the configuration of the control unit of the linear actuator according to the present invention. In FIG. 4, A / D
The converter 30 performs A / D conversion (analog / digital conversion) of the analog voltage position command signal into a digital signal position command signal.

Magnetostrictive I / F section (magnetostrictive interface section) 4
Reference numeral 0 is an interface that connects the magnetostrictive sensor 27 and the control unit, and generates a signal for performing position control, speed control, and commutation control of the linear pulse motor 23. The speed detecting means 41 differentiates the position detection signal of the position detecting means 267 to detect the moving speed of the slider 22.

The phase shift detecting means 42 calculates the phase shift of the teeth of the linear pulse motor by performing the following calculation. Perform the following calculation. N = (S _n −S ₀ ) / ΔS (2) S ₀ : Detection value S _n of the position detecting means 267 when the phases of the teeth of the rail and the linear pulse motor are aligned S _n : Position detecting means obtained in the positioning operation 26
Detected value ΔS of 7: Change amount of detected value of position detecting means 267 when slider moves by one pitch of tooth of rail 263 Multiplies the decimal part of the calculated value N of the formula (2) by 360 ° to obtain tooth 21. The phase shift of 24 is calculated.

The subtractor 50 obtains the deviation between the command position output by the A / D converter 30 and the detected position of the position detecting means 267. The position control unit 51 outputs a control signal for performing position feedback control of the linear pulse motor 23 based on the deviation obtained by the subtractor 50. The subtractor 52 is the position controller 5
The deviation between the control signal 1 and the speed detecting means 41 is calculated. The speed control unit 53 outputs a control signal for speed feedback controlling the linear pulse motor 23 based on the deviation obtained by the subtractor 52.

The sin table 54 shows the amount of phase shift and s.
The in value is stored correspondingly. When the linear pulse motor 23 is a three-phase motor, the phase shift detection means 42
When the amount of phase shift is given from, the sin table 54
From sin (θ + 120 °) and sin (θ−120)
Value) is read. θ is an angle that changes depending on the amount of phase shift.

The multipliers 55 and 56 are the input signals of the signals obtained by the speed control unit 53, sin (θ + 120 °) and sin (θ-12) read from the sin table 54.
The value of 0 ° is used as the gain setting signal and Isin (θ + 12)
0 °) and Isin (θ-120 °) current command value (I
Outputs the current amplitude). The phase difference between the two command values is 120 ° because the motor is a three-phase motor. When the number of phases is different, the phase shift has another value. For example, in the case of a two-phase motor, the two command values are out of phase by 180 °.

The current sensors 57 and 58 detect the currents of the coils flowing through the coils L1 and L2 of the linear pulse motor 23. The subtracters 59 and 60 are Isin (θ + 120
°) and Isin (θ-120 °) and the detected values of the current sensors 57 and 58, respectively. The pulse width modulation circuits (which are PWM circuits) 61 and 62 are current sensors 57.
And a pulse width modulation signal (P) for feedback controlling the exciting current of the motor coil on the basis of the deviations taken at 58.
WM signal) is generated and output. Subtractor 63 is P
The PWM signals of the WM circuits 61 and 62 are subtracted. The PWM circuit 64 generates a PWM signal from the subtraction signal of the subtractor 63. The drive circuit 65 is a bridge-type inverter circuit, and drives the linear pulse motor 23 based on the three-phase PWM signals of the PWM circuits 61, 62, 64.

The commutation controller in the scope of claims includes a sin table 54, multipliers 55, 56, subtracters 59, 60, 6
3, the PWM circuit 61, 62, 64 and the drive circuit 65.

In the circuit of FIG. 4, the amount of phase shift between the teeth 21 and 24, sin (θ + 120 °) and sin (θ-120 °).
Are stored in advance in the sin table 54 in association with each other. The phase shift detecting means 42 according to the movement of the slider 22.
The current command value I corresponding to the detected value (phase shift) of
sin (θ + 120 °) and Isin (θ−120 °)
Change the value of and control commutation.

Based on the deviation between the commanded position and the detected position of the position detecting means 267, the position control unit 51 determines that the linear pulse motor 2
The position of the slider 22 of No. 3 is feedback-controlled. The speed control unit 53 feedback-controls the moving speed of the slider 22 of the linear pulse motor 23 based on the difference between the command speed (output of the position command unit 51) and the speed detected by the speed detecting unit 41.

As described above, the magnetostrictive I / F section 40 controls commutation,
Signals for position control and speed control are generated, and commutation control, position control, and speed control of the linear pulse motor 23 are performed using the generated signals.

FIG. 5 is a diagram showing another configuration example of the magnetostrictive sensor. In this magnetostrictive sensor, the exciting coil 262 is arranged at the end of the magnetostrictive scale 25, and the receiving coil 268 is provided.
Is mounted on the magnetostrictive head 26. That is, the excitation coil 262 is fixed in position, and the reception coil 268 moves.

FIG. 6 is a time chart of signal waveforms of the excitation pulse and the reception pulse of the reception coil 268. Distances from the position of the slider 22 to the left end and the right end of the magnetostrictive scale 25 are Y and X, respectively. The total length of the magnetostrictive scale 25 is L = X + Y. After the exciting coil 262 generates the exciting pulse, the receiving coil 268 has time T1 = X /
Receive the first pulse after v, time T2 = (X + 2Y)
The second pulse is received after / v. The second pulse is the pulse reflected at the end of the magnetostrictive scale 25. Here, P = (T1-T2) / (T1 + T2) = (X / L) -1 Therefore, X = L (P + 1) (3) Since T1 and T2 are known, P is also known. Therefore,
The distance X is detected from the equation (3). In this way, the position of the slider 22 is detected.

[0033]

According to the present invention, the following effects can be obtained.

According to the invention of claim 1, the following effects can be obtained. (1) In the air cylinder, since the vertical positioning is realized by the mechanical stopper, it cannot be positioned at an arbitrary position. On the other hand, in the present invention, the linear pulse motor is formed in the linear guide, the magnetostrictive sensor is used as the position sensor, and the linear pulse motor is position feedback controlled based on the detection signal of the magnetostrictive sensor. As a result, according to the present invention, it is possible to perform highly accurate positioning at any position. (2) In the air cylinder, the piston and the cylinder, and the rail and the slider are the contact portions. On the other hand, in the present invention, since the magnetostrictive sensor is a non-contact sensor, the contact portion is only the linear motion guide portion. As a result, in the present invention, the wear portion is reduced and the life can be extended. (3) Tooth position detected based on the detection signal of the magnetostrictive sensor
Commutation control of linear pulse motor using phase shift
You can

According to the second aspect of the present invention, a linear actuator can be used as a substitute for the air cylinder that has been vertically moved in the transfer device or the like.

According to the third aspect of the present invention, the linear pulse motor can be subjected to speed feedback control using the speed detection signal generated based on the detection signal of the position detecting means.

[0037]

As described above, according to the present invention, it is possible to position an arbitrary position with high accuracy, and the magnetostrictive sensor is used.
The motor can be used to control the commutation of the motor, and a long-life linear actuator can be realized, which is useful as an alternative to an air cylinder.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a detection principle of a magnetostrictive sensor.

FIG. 3 is an explanatory diagram of a detection principle of a magnetostrictive sensor.

FIG. 4 is a configuration diagram of a main part of the present invention.

FIG. 5 is a diagram showing another configuration example of the magnetostrictive sensor.

6 is a signal time chart of the magnetostrictive sensor of FIG.

FIG. 7 is a diagram showing a conventional example of a linear actuator.

[Explanation of symbols]

20 rails 21, 24 teeth 22 Slider 23 Linear pulse motor 25 Magnetostrictive scale 26 Magnetostrictive head 262 Excitation coil 263, 264 receiver coil 267 Position detecting means 41 Speed detection means 42 Phase shift detection means 51 Position controller 53 Speed controller 54 sin table 55,56 Multiplier 59,60,63 Subtractor 61, 62, 64 PWM circuit 65 drive circuit

Claims (3)

(57) [Claims] 1. A linear actuator for linearly moving an object, a rail having teeth formed at a constant pitch along a length direction, and a slider for holding the object and movably attached to the rail. And is formed integrally with the slider, and teeth are formed at a constant pitch in the same direction as the arrangement direction of the rail teeth, and a magnetic attraction force is generated between the teeth and the rail teeth. A linear pulse motor for moving the slider along the rail, a magnetostrictive scale made of a magnetostrictive material and arranged in parallel with the rail, and a magnetostrictive head mounted on the slider, and an end portion of the magnetostrictive scale and Excitation means is provided on one side of the magnetostrictive head, and reception means is provided on the other side, until the ultrasonic wave signal generated in the magnetostriction scale by the excitation means is detected by the reception means. A magnetostrictive sensor for the detecting the absolute position of the slider on the basis of time, a position control section for feedback controlling a position of the slider on the basis of the deviation of the detected position of the magnetostrictive sensor and the command position, the next operation And multiply the decimal part of the calculated value N by 360 °
Phase shift between the teeth of the rail and the teeth of the linear pulse motor
And N = (S _n −S ₀ ) / ΔS S ₀ : The phase of the tooth of the rail and the tooth of the linear pulse motor are combined.
The detection value S _n of the magnetostrictive sensor when it is set : The detection of the magnetostrictive sensor obtained in the positioning operation.
Output value ΔS: The slider moved by one pitch of the rail teeth.
The amount of change in the detected value of the magnetostrictive sensor at this time is based on the phase shift detected by this phase shift detection means.
And a commutation controller for controlling commutation of the actuator. 2. The rail and the magnetostrictive scale are arranged with the longitudinal direction being the vertical direction.
The described linear actuator. 3. A speed detecting means for differentiating a detection signal of the magnetostrictive sensor to detect a moving speed of a slider, and a speed of the slider is fed back based on a deviation between a command speed and a detected speed of the speed detecting means. The linear actuator according to claim 1, further comprising a speed control unit for controlling.