KR20000052189A - Linear motor and amplitude of mover detecting method thereof - Google Patents

Abstract

PURPOSE: A linear electric motor and a method of detecting amplitude of operation shaft are provided to detect an amplitude of operation shaft by utilizing voltage and current applied to a stator , so control the amplitude of operation shaft. CONSTITUTION: A linear electric motor comprises a stator and an operation shaft which reciprocates in accordance with a lengthwise direction of the stator. The linear electric motor further comprises a power supply unit, a compressor driving circuit unit(45) for supplying power from the power supply unit to the stator, an amplitude detecting circuit(40) for detecting an amplitude of the operation shaft on the basis of the voltage value and current value from the power supply unit, and a control unit(10) for controlling driving signal output from the compressor driving circuit unit in accordance with the amplitude of the operation shaft detected from the amplitude detecting circuit.

Description

LINEAR MOTOR AND AMPLITUDE OF MOVER DETECTING METHOD THEREOF}

The present invention relates to a linear motor and a movable shaft amplitude detection method thereof. More specifically, the linear motor including a movable shaft which is a movable magnet and a stator having a winding, and detects the amplitude of the movable shaft by using a voltage and a current applied to the stator, and controls the amplitude of the movable shaft; The movable shaft amplitude detection method is provided.

1 is a cross-sectional view of a linear compressor that is one embodiment of a linear electric motor. A general linear motor has a stator 2 formed of a cylindrical core wound with a coil, as in the linear compressor shown in FIG. 1, and a cylindrical movable shaft 3 accommodated inside the stator 2. The movable shaft 3 is formed in inverse 'Ｕ' shape in cross section. In the central region of the movable shaft 3, a connecting shaft portion 5 connecting the piston 12 and the movable shaft 3 is formed along the axial direction of the movable shaft 3. The axial direction and the longitudinal direction of the cylinder 11 are formed in the same direction. One end of the connecting shaft 5 is connected to the piston 12, and the other end is connected to the resonant spring 4 fixed to the casing.

When power is applied to the linear motor, AC power is applied to the stator 2, and the movable shaft 3 repeatedly protrudes and returns in the longitudinal direction of the stator 2 according to the phase of the AC power, and resonates. The moving width of the movable shaft 3 is amplified by the resonance force of the spring 4. Accordingly, the piston 12 reciprocates in the cylinder 11.

By the way, such a linear motor is not provided with any limiting device for limiting the position of the piston 12 or the movable shaft 3 during the reciprocating motion of the movable shaft 3.

As a result, the amplitude of the movable shaft 3 fluctuates in accordance with the variation of the voltage applied to the stator 2, and when the amplitude of the movable shaft 3 becomes excessively large, the movable shaft 3 is in the other region of the electric motor. Can generate noise and damage the linear motor.

On the other hand, in the case of a compressor, as the amplitude of the piston 12 changes, the amount of refrigerant compression of the compressor changes, and the amount of refrigerant compression of the compressor depends on the temperature of the refrigeration system, and the heat exchange efficiency of the refrigeration cycle may decrease. There is a problem.

In order to solve this problem, several sensors have been proposed for detecting the position of the movable shaft, that is, the position of the piston. However, when the sensor is used, there is a problem that the cost increases, the reliability is lowered, and wires for power supply and communication from the outside must be installed.

It is therefore an object of the present invention to provide a linear motor and a method for detecting the amplitude of the movable shaft which can control the amplitude of the movable shaft by detecting the amplitude of the movable shaft using the voltage and current applied to the stator.

1 is a cross-sectional view showing an embodiment of a linear electric motor,

2 is an electrical equivalent circuit diagram of a linear motor;

3 is a block diagram of the movable shaft amplitude detection circuit of the linear motor according to the present invention;

4 is a circuit diagram of the movable shaft amplitude detection circuit of FIG. 3.

<Description of the symbols for the main parts of the drawings>

5: power supply unit 10: control unit

12: piston 15: current detection unit

20: voltage detector 25: speed calculator

30: speed integral part 35: top and bottom dead center detection unit

40: amplitude calculation unit 45: compressor drive circuit

According to the present invention, there is provided a linear electric motor having a stator and a movable shaft reciprocating along a longitudinal direction of the stator, comprising: a power supply unit; A compressor driving circuit unit for supplying power to the stator; An amplitude detection circuit for detecting an amplitude of the movable shaft based on a voltage value and a current value from the power supply unit; And a control unit for adjusting a drive signal from the compressor drive circuit section in accordance with the amplitude of the movable shaft detected from the amplitude detection circuit.

Here, the amplitude detection circuit includes: a voltage detector for detecting a voltage applied to the stator; A current detector for detecting a current flowing through the stator; A speed calculator which calculates the speed of the movable shaft from the voltage from the voltage detector and the current from the current detector; A speed integrating unit for integrating the speed from the speed calculating section and converting the speed signal into a displacement signal; An upper and lower dead center detection unit detecting a maximum value and a minimum value of the displacement signal; The amplitude calculation unit for calculating the amplitude of the movable shaft by using the difference between the highest value and the lowest value detected from the upper and lower dead center detection unit to detect the amplitude of the movable shaft.

On the other hand, when the amplitude detected from the amplitude calculation unit is a predetermined value or more, it is preferable that the control unit reduces the drive signal from the compressor driving circuit.

The speed calculating unit may calculate the speed of the movable shaft by the following equation (1).

Where V is the applied voltage of the stator, I is the current flowing through the stator, v is the speed of the movable shaft, and α is the proportional constant.

On the other hand, the above object, according to another field of the invention, in the movable shaft amplitude detection method of a linear motor having a stator and a movable shaft reciprocating along the longitudinal direction of the stator, detecting the voltage applied to the stator Steps; Detecting a current flowing through the stator; Calculating a speed of the movable shaft using the voltage and current; Integrating a speed of the movable shaft into a displacement signal; Obtaining a maximum value and a minimum value of the displacement signal; Obtaining an amplitude of the movable shaft according to a difference between the highest value and the lowest value of the displacement signal; According to the amplitude of the movable shaft, it can also be achieved by the movable shaft amplitude detection method of the linear motor, characterized in that it comprises the step of adjusting the drive signal to the stator.

Here, in the adjusting of the drive signal, it is preferable to reduce the drive signal to the stator when the amplitude of the movable shaft is greater than or equal to a certain level.

In the calculating of the speed of the movable shaft, the speed of the movable shaft may be calculated by the following equation (1).

(Equation 1)

Where V is the applied voltage of the stator, I is the current flowing through the stator, v is the speed of the movable shaft, and α is the proportional constant.

Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 3 and 4, the movable shaft amplitude detection circuit of the linear motor detects and drops the voltage applied to the stator 2 and the current applied to the stator 2. It includes a current detecting unit 15 for detecting, and a speed calculating unit 25 for calculating the speed of the piston 12 by using the voltage signal and the current signal detected from the voltage detecting unit 20 and the current detecting unit 15. Here, the voltage detector 20 is configured as a debit amplifier to detect the voltage drop, the current detector 15 detects the voltage generated across the resistor by using the shunt resistor, the current using the resistance value and the voltage value The value will be detected. The speed calculator 25 calculates the speed of the piston 12 by substituting the voltage value detected from the voltage detector 20 and the current value detected from the current detector 15.

On the other hand, the piston 12 amplitude circuit includes a speed integrator 30 for integrating a speed signal from the speed calculator 25 and converting the speed signal into a displacement signal, and an upper and lower dead center detector 35 for obtaining maximum and minimum values of the displacement signal. And an amplitude calculator 40 for detecting the amplitude of the piston 12 from the maximum and minimum values of the displacement signal.

According to this configuration, when the power is supplied from the power supply unit 55 to the stator 2, the drive signal from the compressor composition circuit is applied, and the piston 12 starts reciprocating, the voltage detecting unit 20 drops down. The voltage value Vin is input to the speed calculator 25, and the current detector 15 inputs the voltage value VI generated at both ends of the shunt resistor to the speed calculator 25. On the other hand, if the circuit constituting the speed calculating section 25 is analyzed, the following [Equation 2] can be obtained.

On the other hand, the electrical equivalent circuit of the linear motor shown in Fig. 2 is composed of a resistance and inductance by the coil of the stator, and back electromotive force generated by the reciprocating motion of the movable shaft, and the counter electromotive force is proportional to the reciprocating speed of the movable shaft. As shown in Equation 1 below, the speed can be known from the voltage and current applied to the stator.

(Equation 1)

Where V is the voltage applied to the stator, I is the current flowing through the circuit, R is the resistance of the stator winding, L is the inductance of the stator winding, v is the speed of the movable shaft, and α is the proportional constant.

Comparing [Equation 1] and [Equation 2], it can be seen that the right term of [Equation 1] indicating the speed of the movable shaft and the calculation of the output current Iin of the speed computation circuit are the same.

Therefore, it can be seen that the output current Iin becomes equal to the speed v of the movable shaft when the device value of the speed computing circuit, that is, the resistances Rv and Ri and the capacitor CI of the circuit are adjusted to have the following values.

When the speed v of the movable shaft is obtained as described above, the speed integrating unit 30 converts the speed into a sinusoidal wave representing the displacement signal of the movable shaft. The upper and lower dead center detection unit 35 for detecting respective voltages when the movable shaft reaches the highest point and the lowest point from the displacement signal, that is, when the top dead center and the bottom dead center is reached, is composed of a diode and a capacitor. It consists of a top dead center detection unit 36 for detecting a point, and a bottom dead center detection unit 37 for detecting a bottom dead center. On the other hand, the top and bottom dead center detection unit 35 also performs a function of maintaining the sine wave displacement signal for one period.

In the amplitude calculation unit 40, the difference between the voltage value of the top dead center and the bottom dead center voltage obtained by the top and bottom dead center detection unit 35 and input to the +/− input terminals of the deceleration amplifier is obtained to determine the amplitude of the movable shaft.

The amplitude of the movable shaft thus calculated is input to the controller 10, and the controller 10 adjusts the drive signal from the compressor drive circuit 45 according to the amplitude of the movable shaft. That is, when the amplitude of the movable shaft is excessively large, the drive signal generated by the compressor drive circuit 45 is reduced, and when the amplitude of the movable shaft is small, the driving signal is increased.

Accordingly, according to the amplitude detection circuit of the movable shaft of the present invention, it is possible to easily calculate the amplitude of the movable shaft by sensing only the voltage and current applied to the motor without the need for a separate device, and thus have a relatively high linearity. The amplitude of the movable shaft can be precisely controlled.

As described above, according to the present invention, there is provided a linear motor and its movable shaft amplitude detecting method capable of controlling the amplitude of the movable shaft by detecting the amplitude of the movable shaft using the voltage and current applied to the stator.

Claims (7)

In a linear motor having a stator and a movable shaft reciprocating along the longitudinal direction of the stator, A power supply unit; A compressor driving circuit unit for supplying power to the stator; An amplitude detection circuit for detecting an amplitude of the movable shaft based on a voltage value and a current value from the power supply unit; And a control unit for adjusting a drive signal from the compressor drive circuit unit in accordance with the amplitude of the movable shaft detected from the amplitude detection circuit. The method of claim 1, The amplitude detection circuit, A voltage detector detecting a voltage applied to the stator; A current detector for detecting a current flowing through the stator; A speed calculator which calculates the speed of the movable shaft from the voltage from the voltage detector and the current from the current detector; A speed integrating unit for integrating the speed from the speed calculating section and converting the speed signal into a displacement signal; An upper and lower dead center detection unit detecting a maximum value and a minimum value of the displacement signal; And an amplitude calculator configured to calculate an amplitude of the movable shaft by using a difference between the highest value and the lowest value detected from the upper and lower dead center detection unit. The method of claim 1, And the control unit reduces the drive signal from the compressor drive circuit when the amplitude detected from the amplitude calculator is greater than or equal to a certain level. The method of claim 2, The speed calculator, the linear motor, characterized in that for calculating the speed of the movable shaft by the following equation: (Equation 1) Where V is the applied voltage of the stator, I is the current flowing through the stator, v is the speed of the movable shaft, and α is the proportional constant. In the method of detecting the amplitude of the movable shaft of a linear motor having a stator and a movable shaft reciprocating along the longitudinal direction of the stator, Detecting a voltage applied to the stator; Detecting a current flowing through the stator; Calculating a speed of the movable shaft using the voltage and current; Integrating a speed of the movable shaft into a displacement signal; Obtaining a maximum value and a minimum value of the displacement signal; Obtaining an amplitude of the movable shaft according to a difference between the highest value and the lowest value of the displacement signal; And adjusting the drive signal to the stator according to the amplitude of the movable shaft. The method of claim 5, The adjusting of the drive signal may include reducing the drive signal to the stator when the amplitude of the movable shaft is greater than or equal to a predetermined level. The method of claim 5, Computing the speed of the movable shaft, the movable shaft amplitude detection method of the linear motor, characterized in that for calculating the speed of the movable shaft by the following equation: (Equation 1) Where V is the applied voltage of the stator, I is the current flowing through the stator, v is the speed of the movable shaft, and α is the proportional constant.