JPH02280690A - Linear motor driving circuit - Google Patents

Abstract

PURPOSE:To prevent malfunction by a method wherein a voltage judging circuit, putting a conduction current control circuit OFF when the output of an absolute value circuit is smaller than a preset given value, is provided between the absolute value circuit and the conduction current control circuit. CONSTITUTION:The output of an absolute value circuit 24 is not inputted directly into a conduction current control circuit 27 but is inputted through a voltage judging circuit 26 and, therefore, the conduction current control circuit 27 is put OFF by the voltage judging circuit 26 when the output of an adding circuit 23 is stagnated at zero potential. Accordingly, current is not conducted through the coil 29 of a linear DC motor 28 and the malfunction of the conduction current control circuit 27 will never be generated by the output of a code judging circuit 25. According to this method, malfunction upon switching the direction of a current, conducted through the coil 29 of the linear motor 28, may be prevented.

Description

[Detailed Description of the Invention] Overview This invention relates to a linear motor drive circuit, particularly a drive circuit that moves a linear DC motor forward or backward while slightly vibrating it, without causing malfunction when switching the direction of current flowing through the coil of the linear motor. In order to provide a linear motor drive circuit, the output of a first oscillation circuit that oscillates a rectangular voltage waveform and the output of a second oscillation circuit that oscillates a sawtooth voltage waveform are input to an adder circuit. The output of the linear DC motor is input through an absolute value circuit and a sign determination circuit to a current control circuit that controls the magnitude of the current flowing through the coil of the linear DC motor, and the linear DC motor is moved forward or backward while causing minute vibrations. In addition to the motor drive circuit, a voltage determination circuit is provided to turn off the energizing current control circuit when the value of the absolute value circuit is smaller than a preset constant value.

INDUSTRIAL APPLICATION FIELD The present invention relates to a linear motor drive circuit, and more particularly to a drive circuit that moves a linear DC motor forward or backward while causing minute vibrations.

Many devices that move or position a controlled object on a one-dimensional or two-dimensional plane use a rotary motor and a mechanism that converts rotational motion into linear motion. In contrast, recent advances have been in the development of linear motors in which a controlled object is attached directly to the motor and the motor is driven in a straight line. Linear motors have a simple structure and have excellent features such as longevity and precision, and are expected to be used in a wide range of fields, including the field of OA equipment.

As an example of the application of such a linear motor, a linear DC motor is moved forward while making minute vibrations, and a metal electrode attached to the linear motor is inserted into the germinated roots of a plant that has sprouted in space, for example, to determine the potential distribution of the germinated roots. A method of using it for measurement is being considered. This usage example of the linear DC motor will be further explained with reference to the third rgJ. In the figure, reference numeral 1 denotes a coil-moving linear DC motor, in which a coil 3 is wound around a yoke 2 to serve as a mover, and magnets 4.5 are arranged on the stator side. A metal electrode 6 is attached to the linear DC motor 1, and this metal electrode is connected to a potential measuring circuit (not shown). Depending on the direction of the current flowing through the coil 3 of the linear DC motor 1, the linear DC motor 1 moves forward or backward.

This linear DC motor 1 has minute vibrations (for example, 100 to 1
It is a linear motor that moves slowly with an amplitude of 20 um) at 000 Hz, and measures the potential distribution of the sprouted roots 7 by impinging the electrode 6 on the sprouted roots 7 of the sprouts sprouted in space. Since outer space is a zero-gravity state, gravity is artificially generated in any direction to measure the relationship between the growth direction of germinated roots and the potential distribution. In such applications, in order to facilitate the insertion of the electrode into the germinated root, a method is often used in which the electrode is moved forward while being slightly vibrated back and forth as described above.

FIG. 4 is a graph showing how the linear motor shown in FIG. 3 moves, and as is clear from this graph, the linear motor gradually moves forward while vibrating slightly back and forth.

BACKGROUND OF THE INVENTION FIG. 5 is a circuit diagram of a conventional drive circuit used to move a linear DC motor forward while slightly vibrating it back and forth.

10 is a rectangular wave oscillation circuit that oscillates a rectangular voltage waveform, and 11 is a sawtooth wave oscillation circuit that oscillates a sawtooth voltage waveform. The rectangular voltage waveform oscillated by the rectangular wave oscillation circuit 10 and the sawtooth voltage waveform oscillated by the sawtooth wave oscillation circuit 11 are added by an adder circuit 12 and input to an absolute value circuit (full-wave rectifier circuit) 13. Ru. 14 is a full bridge circuit, which is constructed by connecting four transistors in a bridge manner. The full bridge circuit 14 is connected to the coil 3 of the linear DC motor 1. The output of the absolute value circuit 13 drives a full bridge circuit 14 to control the current flowing to the coil 3 of the linear DC motor 1.

Reference numeral 15 denotes an operational amplifier (hereinafter abbreviated as operational amplifier), which adjusts the drive voltage of the full bridge circuit 14 so that the voltage due to the coil current detected by the resistor 17 becomes equal to the output voltage of the absolute value circuit 13. Further, 16 is a sign determination circuit, and its output is used as a full bridge circuit 14.
The direction of the current flowing through the coil 3 of the linear DC motor 1 is determined.

The sign determination circuit 16 compares the potential at point A and the ground potential, and when the potential at point A is positive, the output of the sign determination circuit 16 is at a high level, and when it is negative, it is at a low level. Now, when the output of the sign determination circuit 16 is at a high level, the transistors TR and T of the full bridge circuit 14
R, is turned on, and transistors TR and TR are turned on.

is turned off, the current flows through the transistor TR1 from top to bottom of the coil 3, and then through the transistor T
R, and flows to the resistor 17.

On the other hand, when the output of the sign determination circuit 16 is at low level,
Transistor TR1 and transistor TR of the full bridge circuit 14 are turned off, and transistors TR2 and T
R3 turns on. This residual current is caused by the transistor TR
, flows through the coil 3 from bottom to top, and further flows through the transistor TR and into the resistor 17. In this manner, in the conventional linear motor drive circuit, the direction of the current flowing through the coil 3 of the IJ near DC motor 1 is determined by the output of the adder circuit 12.

Problems to be Solved by the Invention In the conventional drive circuit as described above, when the indicated voltage (point A in FIG. 5) is approximately 0, as shown in FIG. The output of the determination circuit 16 oscillates and outputs a control signal requesting a high-speed current direction switch to the full bridge circuit 14. However, the full-bridge circuit 14 has a problem in that it cannot follow such high-speed current direction switching, which may result in malfunctions, partly because the drive target is a coil having inductance.

The present invention has been made in view of these points, and its purpose is to provide a linear motor drive circuit that does not cause malfunction when switching the direction of current flowing through the coil of a linear motor. It is.

Means to solve problems FIG. 1 shows a diagram of the principle of the present invention.

The output of the first oscillation circuit 21 that oscillates a rectangular voltage waveform and the output of the second oscillation circuit 22 that oscillates a sawtooth voltage waveform are input to an adding circuit 23, and the output of this adding circuit 23 is input to an absolute value circuit 24 and an output of a second oscillating circuit 22 that oscillates a sawtooth voltage waveform. The signal is input to the energizing current control circuit 27 that controls the magnitude of the current flowing through the coil 29 of the linear DC motor 28 via the sign determination circuit 25.
In the linear motor drive circuit that moves the motor 8 forward or backward while slightly vibrating the motor, the energizing current control circuit 27 is connected between the absolute value circuit 24 and the energizing current control circuit 270 when the output of the absolute value circuit 24 is smaller than a preset constant value. A voltage determination circuit 26 is provided to turn off the voltage.

Function: In the present invention, the output of the absolute value circuit 24 is not directly input to the energizing current control circuit 27, but is input via the voltage determination circuit 26, so that the output of the adder circuit 23 remains at zero potential. In this case, the energizing current control circuit 27 is turned off by the voltage determination circuit 2 days. As a result, no current flows through the coil 29 of the linear DC motor 28, and therefore, the energizing current control circuit 27 does not malfunction due to the output of the sign determination circuit 25, and a stable linear motor drive circuit can be realized. .

Embodiments The present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 2 is a circuit diagram of an embodiment of the drive circuit of the present invention.
Components that are the same as those in the conventional example circuit diagram shown in the figure are given the same reference numerals, and some explanations thereof will be omitted. The circuit diagram of the embodiment of the present invention does not directly input the output of the absolute value circuit 13 to the operational amplifier 15 to drive the full bridge circuit 14, as in the conventional circuit diagram shown in FIG. The voltage obtained by dividing the voltage by the resistor 32 is input to the operational amplifier 15 and used as the drive control voltage for the full bridge circuit 14. The resistor 32 is connected to a negative power supply of, for example, about -0.5 .

With this configuration, when the output of the absolute value circuit 13 is higher than the breakdown voltage of the Zener diode 31,
The value obtained by subtracting the breakdown voltage of the Zener diode 31 from the output of the absolute value circuit 13 is the full bridge circuit 1.
However, when the output of the absolute value circuit 13 is smaller than the breakdown voltage of the Zener diode 31, no current flows through the resistor 32 connected in series with the Zener diode 31, and the output of the operational amplifier 15 becomes 0. Become. As a result, the drive control voltage of the full-bridge circuit 14 becomes 0, so the full-bridge circuit 14 is turned off. Therefore, when the instruction voltage of the adder circuit 12 is approximately OV, the output of the sign determination circuit 16 oscillates due to the noise contained in this instruction voltage, and a control signal is sent to the full bridge circuit 14 requesting high-speed current direction switching. Even if this is output, since the full bridge circuit 14 is off, this control signal does not affect the control signal in any way, and during this period, the power supply to the coil 3 of the linear DC motor 1 is stopped. Therefore, malfunction of the full bridge circuit 14 does not occur. If the Zener voltage is selected to be a value that is sufficiently larger than the random noise signal included in the sum signal of the signal of the rectangular wave oscillation circuit 10 and the signal of the sawtooth wave oscillation circuit 11, the full bridge circuit will not malfunction. do not have. Note that the resistor 32 may be connected to ground potential.

Effects of the Invention Since the linear motor drive circuit of the present invention is configured as detailed above, it has the effect of effectively preventing malfunctions of the linear motor drive circuit for gradually moving the linear motor forward or backward while causing minute vibrations. play.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is an embodiment circuit diagram of the present invention, Fig. 3 is a schematic diagram showing an example of the use of a linear motor, and Fig. 4 is a movement of the linear motor shown in Fig. 3. FIG. 5 is a conventional circuit diagram, and FIG. 6 is a diagram showing voltage waveforms at various points in the conventional example shown in FIG. 0... Square wave oscillation circuit, 1... Sawtooth wave oscillation circuit, 2... Adder circuit, 3... Absolute value circuit, 4... Full bridge circuit, 5... Operational amplifier, 6. ...Sign determination circuit, l...First oscillation circuit, 2...Second oscillation circuit, 3...Addition circuit, 4...Absolute value circuit, 5...Sign judgment circuit, 6... - Voltage judgment circuit, 7... Energizing current control circuit, 8... Linear DC motor, 9... Coil.

Claims (1)

[Claims] The output of the first oscillation circuit (21) that oscillates a rectangular voltage waveform and the second oscillation circuit (22) that oscillates a sawtooth voltage waveform.
) is input to the adder circuit (23), and the output of the adder circuit (23) is input to the adder circuit (23).
3) is sent to the absolute value circuit (24) and sign determination circuit (2).
5) to the coil (2) of the linear DC motor (28).
9) An energizing current control circuit (
27) in a linear motor drive circuit that moves the linear DC motor (28) forward or backward while slightly vibrating, when the output of the absolute value circuit (24) is smaller than a preset constant value, the energizing current A linear motor drive circuit comprising a voltage determination circuit (26) that turns off a control circuit (27).