JP4897419B2 - Small electric actuator - Google Patents

Description

  The present invention relates to a small electric actuator that reciprocally linearly moves a rod using an electric motor as a drive source.

  As a small actuator, a solenoid driven by electromagnetic force or a small air cylinder driven by air pressure is used.

  An electric actuator is also known as a small actuator other than the above. In this small electric actuator, the rotation of the electric motor, which is a drive source, is decelerated by a speed reduction mechanism and transmitted to the screw shaft, and the rod that is removably engaged with the screw shaft is reciprocated linearly by the rotation of the screw shaft. is there.

Incidentally, it has been well known that a variable resistor is used as means for detecting the absolute position of a moving object such as a rod (for example, see Patent Documents 1 and 2).
JP 58-096311 A JP-A-6-019551

  By the way, since a solenoid as one of small actuators drives an actuator in an ON / OFF manner by electromagnetic force and spring force, it is impossible to control the position and moving speed of the actuator. In addition, there is a disadvantage that the self-holding of the actuator is impossible or the self-holding force is weak even if it is possible.

  Small air cylinders can control the speed to some extent. However, pneumatic equipment such as a compressor and flow rate adjustment valve is required for speed control, and the entire system becomes larger. Has the disadvantage of complicated control.

  In fact, there is no conventional small electric actuator that can control the position and moving speed of the rod with a simple configuration.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a small electric actuator capable of controlling the position and moving speed of a rod with a simple configuration.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a screw shaft comprising: a rod that is rotated by a reduction mechanism to reduce the rotation of an electric motor that is a drive source and transmits the rotation to the screw shaft; In a small electric actuator that reciprocally moves linearly by rotating, a variable resistor is disposed along the movement direction of the rod, and a slider of the variable resistor is fixed to the rod, and the slider is moved. The position of the rod is controlled based on a voltage change caused by a change in resistance of the variable resistor, and the slider of the variable resistor is fixed to the rod and slides together with the rod. In addition to changing the resistance of the vessel, it also functions as a detent for the rod .

  According to a second aspect of the present invention, in the first aspect of the present invention, the electric motor is constituted by a variable speed motor, and the moving speed of the rod is controlled based on a rate of change in voltage due to a resistance change of the variable resistor. It is characterized by that.

  According to the invention of claim 1, the slider of the variable resistor moves together with the rod, and the output voltage of the variable resistor changes due to the resistance change of the variable resistor accompanying the movement of the slider. Based on this voltage change, the position of the rod can be controlled with a simple configuration. In addition, since the linear movement of the rod is performed by the rotation of the screw shaft, the movement of the rod is stopped at an arbitrary position when the rotation of the screw shaft stops, and an intermediate stop is possible. The movement is locked and the rod is held at the stop position with a strong self-holding force.

  According to the second aspect of the invention, by controlling the speed of the variable speed motor based on the rate of change of the voltage due to the resistance change of the variable resistor, the moving speed of the rod can be freely controlled with a simple configuration. it can.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is an external perspective view of a small electric actuator according to the present invention, FIG. 2 is a side view of the small electric actuator, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. FIG. 5 is a cross-sectional view taken along line BB in FIG. 4.

  A small electric actuator 1 according to the present invention includes a rectangular parallelepiped body 2, and a DC motor 3 as a drive source is attached to one end of the body 2 in the longitudinal direction at a right angle. Here, the body 2 is vertically divided into an upper body 2A and a lower body 2B, and one body 2 is configured by joining and integrating the upper body 2A and the lower body 2B. In the present embodiment, the mass of the small electric actuator 1 is set to 80 g, and the length, width, and height of the body 2 are set to 60 mm × 20 mm × 25 mm. The power supply voltage of the DC motor 3 is 5V.

  As shown in FIGS. 3 and 4, a screw shaft 4 is disposed in the longitudinal direction inside the body 2, and a hollow disposed in the longitudinal direction of the body 2 is also provided on the outer periphery of the screw shaft 4. The nut-integrated rod 5 is screwed so as to be able to advance and retract. Here, a part of the rod 5 protrudes from the body 2, and from the most contracted state shown by the solid line in FIGS. 3 and 4 to the front (right side in FIGS. 3 and 4) It can move linearly to the extended position, its maximum stroke S is set to 40 mm, the thrust is set to 80 N, and the maximum moving speed is set to 30 mm / sec.

  One end portion in the axial direction of the screw shaft 4 (left end portion in FIGS. 3 and 4) is rotatably supported by a bearing 6, and an end portion protruding from the bearing 6 of the screw shaft 4 includes As shown in FIG. 4, a worm wheel 7 is attached.

  On the other hand, as shown in FIGS. 4 and 5, the output shaft 3a of the DC motor 3 extends in a direction perpendicular to the screw shaft 4 and has a small diameter meshing with the worm wheel 7 at its end. A worm 8 is attached, and the worm 8 and the worm wheel 7 convert the rotation direction of the output shaft 3 a of the DC motor 3 to a right angle, and reduce the rotation of the output shaft 3 a and transmit it to the screw shaft 4. A deceleration mechanism (see FIGS. 6 and 7) is configured.

  As shown in FIGS. 3 and 4, a potentiometer 10, which is a variable resistor, is disposed along the rod 5 in the longitudinal direction beside the rod 5 in the body 2. The moving element 10a is fixed to the outer periphery of one end of the rod 5 and slides with the rod 5 to change the resistance value of the potentiometer 10, and also serves as a detent for the rod 5.

  Thus, when the DC motor 3 is energized and driven, the rotation of the output shaft 3a of the DC motor 3 is converted into a right angle by the worm 8 and the worm wheel 7 constituting the speed reduction mechanism 9 and decelerated. Then, it is transmitted to the screw shaft 4, and the screw shaft 4 is rotationally driven at a predetermined speed. Then, the rod 5 screwed to the screw shaft 4 moves linearly, for example, the rod 5 in the most contracted state shown by the solid line in FIGS. 3 and 4 moves forward (to the right in FIGS. 3 and 4). It is possible to stroke up to the maximum extension position indicated by the chain line. When the DC motor 3 is reversed, the screw shaft 4 is also reversed, so that the rod 5 moves rearward (leftward in FIGS. 3 and 4) and contracts. In this way, the rod 5 can reciprocate linearly to expand and contract.

  When the rod 5 reciprocates linearly as described above, the slider 10a of the potentiometer 10 moves with the rod 5, so that the resistance of the potentiometer 10 changes linearly. Therefore, the position of the rod 5 can be detected by passing a constant current through the potentiometer 10 and detecting the voltage change. Further, if the rate of change of voltage with time (dV / dt: V is voltage, t is time), that is, the rate of change of voltage is calculated, the moving speed of rod 5 can also be detected. The moving speed can be controlled.

  Examples of control systems for controlling the position and moving speed of the rod 5 are shown in FIGS. 6 and 7, respectively. 6 and 7 are block diagrams showing the configuration of the control system.

  In the example shown in FIG. 6, for example, the operator manually operates the control potentiometer 11 to control the position and moving speed of the rod 5, and the operator uses a slider (not shown) of the control potentiometer 11. When operated, a voltage corresponding to the position of the slider is continuously transmitted as a command voltage to the arithmetic processing unit 12 such as a microcomputer. Then, the arithmetic processing unit 12 calculates the change rate of the command voltage proportional to the operation speed of the slider, and outputs a control signal based on the command voltage and the change rate to the motor driver 13.

  Thus, the motor driver 13 controls the drive of the DC motor 3 based on the control signal transmitted from the arithmetic processing unit 12, and when the DC motor 3 is driven by the motor driver 13, the rotation of the output shaft 3a is performed. As described above, the direction is changed to a right angle by the speed reduction mechanism 9 constituted by the worm 8 and the worm wheel 7, and the speed is reduced and transmitted to the screw shaft 4, and the screw shaft 4 is rotationally driven at a predetermined speed. . Then, the rod 5 screwed to the screw shaft 4 moves linearly as described above, but the resistance of the position detecting potentiometer 10 changes with the movement, and the output voltage (detected voltage) of the potentiometer 10 changes. To do. Further, the change rate of the detection voltage also changes due to a change in the moving speed of the rod.

  The detected voltage output from the potentiometer 10 is transmitted to the arithmetic processing unit 12, and the arithmetic processing unit 12 calculates the rate of change of the detected voltage, and also detects the detected voltage and the command voltage, and the calculated rate of change of the detected voltage and the command. The voltage change rate is compared, and a control signal is transmitted to the motor driver 13 so that the difference between them is zero. That is, the DC motor 3 is feedback-controlled so that the position and moving speed of the rod 5 coincide with the position and moving speed of the rod 5 set by the operator, and the operator's hand operating the slider of the control potentiometer 11. The movement of the rod 5 follows this movement, and the operator can freely control the position and moving speed of the rod 5 using the control potentiometer 11 as a manipulator.

  When the operator stops the movement of the slider of the control potentiometer 11, the movement of the rod 5 stops at that point, and the rod 5 is locked and held at that position. Here, since the linear movement of the rod 5 is performed by the rotation of the screw shaft 4, the movement of the rod 4 is stopped when the rotation of the screw shaft 4 is stopped, and an intermediate stop is possible. The movement is locked and the rod 5 is held at the stop position with a strong self-holding force. In the present embodiment, since the DC motor 3 is used as a drive source, the moving speed of the rod 5 can be easily controlled by changing the rotation speed. As a drive source, a variable speed motor such as a stepping motor or a servo motor can be used in addition to a DC motor.

  In the example shown in FIG. 7, the personal computer (hereinafter abbreviated as “PC”) 14 is operated to control the position and moving speed of the rod 5. When the position and moving speed set values are key-input, the set values are converted into analog values by a D / A (digital / analog) converter 15 and transmitted to the arithmetic processing unit 12 as command voltages and their rate of change. . Then, the arithmetic processing unit 12 outputs a control signal based on the command voltage and the rate of change thereof to the motor driver 13.

  Thus, the motor driver 13 controls the driving of the DC motor 3 based on the control signal transmitted from the arithmetic processing unit 12, and when the DC motor 3 is driven by the motor driver 13, the rod 5 is As the line moves, the resistance of the position detection potentiometer 10 changes, and the output voltage (detection voltage) of the potentiometer 10 changes. Further, the change rate of the detection voltage also changes with the change of the moving speed of the rod 5.

  The detection voltage output from the potentiometer 11 is transmitted to the arithmetic processing unit 12, and the arithmetic processing unit 12 calculates the change rate of the detection voltage, and also detects the detection voltage, the command voltage, the change rate of the detection voltage, and the command voltage. The change rate is compared, and a control signal is transmitted to the motor driver 13 so that the difference between them is zero. That is, the DC motor 3 is feedback controlled so that the position and moving speed of the rod 5 coincide with the position and moving speed of the rod 5 set by the operator, and the rod 5 moves at the moving speed set by the operator. , Stop at the specified position and lock its movement. A plurality of patterns of the moving speed of the rod 5 may be prepared, and an optimum one may be selected from the patterns.

  As described above, according to the present invention, it is possible to control the position and moving speed of the rod 5 of the small electric actuator 1 with a simple configuration.

1 is an external perspective view of a small electric actuator according to the present invention. It is a side view of the small electric actuator which concerns on this invention. It is the sectional view on the AA line of FIG. It is the bottom view which looked at the small electric actuator from the lower part by removing the lower body from the small electric actuator according to the present invention. It is the BB sectional view taken on the line of FIG. It is a block diagram which shows the structural example of the control system of the small electric actuator which concerns on this invention. It is a block diagram which shows the structural example of the control system of the small electric actuator which concerns on this invention.

Explanation of symbols

1 Small electric actuator 2 Body 2A Upper body 2B Lower body 3 DC motor (variable speed motor)
3a DC motor output shaft 4 Screw shaft 5 Rod 6 Bearing 7 Worm wheel 8 Worm 9 Reduction mechanism 10 Potentiometer (variable resistor)
10a Potentiometer Slider 11 Control Potentiometer 12 Arithmetic Processing Unit 13 Motor Driver 14 Personal Computer (PC)
15 D / A converter

Claims (2)

In a small electric actuator that decelerates the rotation of an electric motor as a drive source by a speed reduction mechanism and transmits it to a screw shaft, and reciprocally linearly moves a rod that is screwed to the screw shaft so as to advance and retract.
A variable resistor is disposed along the moving direction of the rod, and a slider of the variable resistor is fixed to the rod, so that a voltage change caused by a resistance change of the variable resistor accompanying the movement of the slider. based so as to control the position of the rod,
The slider of the variable resistor is fixed to the rod and slides with the rod to change the resistance of the variable resistor, and also serves as a detent for the rod. Small electric actuator. 2. The small electric actuator according to claim 1, wherein the electric motor is constituted by a variable speed motor, and the moving speed of the rod is controlled based on a voltage change rate due to a resistance change of the variable resistor.

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