KR20010026151A - The method for controlling piston position of a linear compressor - Google Patents

Abstract

PURPOSE: A piston location control method for linear compressor is provided to prevent noise caused by amplitude vibration by controlling the piston location through the use of power factor. CONSTITUTION: A method comprises a first step(S101,S102) of detecting the current being introduced into the compressor and the voltage flowing at both ends of the compressor; a second step(S103) of obtaining a power factor by using the current and voltage detected in the first step; a third step(S104) of sensing the slope of the power factor obtained in the second step; a fourth step(S105) of detecting an inflection point of the slope of the power factor sensed in the third step; and a fifth step(S106-S108) of controlling the compressor by outputting a voltage command valve if the inflection point is not detected in the fourth step, and changing the voltage command vale into the current voltage value and supplying the changed voltage value to the compressor so as to control the piston location for the compressor, if the inflection point is detected in the fourth step.

Description

The piston position control method of the linear compressor {THE METHOD FOR CONTROLLING PISTON POSITION OF A LINEAR COMPRESSOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston position control method of a linear compressor for controlling the piston position of a linear compressor by detecting an amount of change of a power factor, particularly after an inflection point at which the increment of PF becomes negative. It relates to a piston position control method of a linear compressor to operate so as to prevent the generation of noise due to the vibration shaking phenomenon.

1 is a block diagram of a piston position control apparatus for a linear compressor according to a conventional sensorless method. As shown in FIG. 1, a compressor 11 for adjusting a cooling force by varying a stroke by vertical movement of a piston, and a switching signal The switch element 12 for regulating the voltage applied to the compressor 11 by intermitting the AC power input according to the present invention, the current detector 13 for detecting the current applied to the compressor 11, and the compressor ( 11) The stroke is calculated using the voltage detector 14 detecting the voltage between both ends, the current i detected by the current detector 13 and the voltage V detected by the voltage detector 14, The stroke calculation unit 15 outputs the calculated stroke measurement value, the rectification unit 16 for smoothing the stroke measurement value calculated by the stroke calculation unit 15 to remove unnecessary portions, and the rectifying unit 16. A comparator 17 for comparing an output stroke measurement value with a stroke command value to obtain an error, and a control unit 18 for outputting a stroke for allowing the stroke measurement value to follow the stroke command value using the error provided by the comparator 17. ) And a smoothing unit 19 for smoothing the stroke output from the control unit 18 to the switch element 12.

Looking at the prior art configured in this way in detail as follows.

When 220V AC power is supplied from the power supply voltage terminal, the AC power is supplied to the compressor 11 through the current sensing resistor R and the switch element 12.

Accordingly, a voltage is supplied to the compressor 11.

Then, the piston 21 of the compressor 11 shown in FIG. 2 reciprocates, and the reciprocating stroke distance of the piston is a stroke, and this stroke is varied to change the cooling force.

In this case, since the piston is driven by a linear motor, the friction loss can be reduced, resulting in high efficiency.

The piston of the compressor 11 performs the optimum movement according to the pressure of both ends of the piston with respect to the applied voltage.

In addition, in order to produce the required cooling force and maintain a high efficiency of compression, the operation should be performed while maintaining a top clearance, which is a distance between the top dead center of the piston 21 and the discharge valve 22, at a constant distance.

Therefore, when the user sets the temperature of the refrigerator or the air conditioner, a stroke command value proportional to the set temperature information is input to the controller 18 via the comparator 17.

Then, the controller 18 turns on or off the switch element 12 in accordance with the input stroke command value to adjust the voltage supplied to the compressor 11.

Accordingly, the compressor 11 operates, and at this time, the current detector 13 detects the input current i supplied to the compressor 11 through the current sensing resistor R and provides the stroke current to the stroke calculator 15. The voltage detector 14 detects the voltage V across the compressor 11 and provides the voltage V to the stroke calculator 15.

Accordingly, the stroke calculator 15 calculates the stroke using the current i and the voltage V provided by the two detectors 13 and 14 as follows.

Where V _M is the voltage across the compressor, Rac is the body resistance in the compressor, i is the inrush current, and L is the reactance.

When the calculated stroke is output to the rectifier 16, the rectifier 16 rectifies to remove the unnecessary portion and outputs the rectified stroke measurement to the comparator 17.

The comparator 17 then compares the current stroke measurement value with the stroke command value and transmits it to the control unit 18.

Accordingly, when the stroke measurement value is larger than the stroke command value, the control unit 18 outputs a correction stroke for turning off the switch element 12 to the smoothing unit 19 to reduce the voltage supplied to the compressor 11.

The smoothing unit 19 smoothes the stroke and outputs the switch element 12 to the switch element 12 so that the switch element SW is turned off to reduce the voltage supplied to the compressor 11.

When the stroke measurement value is smaller than the stroke command value, a correction stroke for turning on the switch element 12 is output to the smoothing unit 19 in order to increase the voltage supplied to the compressor 11.

The smoothing unit 19 smoothes the correction stroke and outputs it to the switch element 12 to turn it on.

As the switch element 12 is turned on, the voltage supplied to the compressor 11 increases.

Thus, the stroke top dead center is adjusted by decreasing or increasing the voltage supplied to the compressor 11.

In other words, after calculating the stroke with the motor resistance and the motor inductance, the current (i) and voltage (V) detected by the linear compressor (11) are calculated, and the stroke command value can be followed by comparing this value with the stroke command value. Control to maintain the top clearance between the piston top dead center of the compressor and the discharge valve at a constant distance.

However, in the prior art as described above, when the top clearance is operated close to zero when controlling the piston position of the compressor, a piston amplitude oscillation phenomenon occurs in which the position of the piston fluctuates. Since the nonlinear gas pressure acts as a load, the load fluctuates due to the pressure fluctuations and the change in the top clearance, resulting in a slight phase change. When the amplitude vibration occurs, the input and cooling power of the compressor also fluctuate, causing noise increase. In FIG. 3, the stroke is shaken just before the top clearance reaches zero, which is a problem in that the conventional stroke control method is insufficient to cope with the amplitude shake.

Therefore, the present invention for solving the conventional problems as described above is to control the piston position of the compressor using a power factor (PF) in a constant voltage control method to control the piston position of the linear compressor to cope with the amplitude shaking phenomenon In providing.

Another object of the present invention is to increase the voltage applied to the compressor PF increases and then at some point to inflection and decrease to reach a stable point, so that after the inflection point to operate the position of the piston to the most optimal position To provide a piston position control method of a linear compressor.

1 is a block diagram of a piston position control device of a linear compressor by a stroke control method;

2 is a cross-sectional view of a linear compressor.

3 is a characteristic diagram of a voltage and a stroke at the time of piston position control in stroke.

Figure 4 is a block diagram of a piston position control device of the linear compressor according to the present invention constant voltage control method.

FIG. 5 is a PF change characteristic diagram according to voltage in FIG. 4.

Figure 6 is an operation flowchart for the piston position control method of the linear compressor of the present invention.

**** Explanation of symbols on the main parts of the drawing *****

101 compressor 102 switch element

103: current detector 104: voltage detector

105: PF conversion amount detecting unit 106: voltage command value changing unit

107 control unit 108 rectifier

The present invention for achieving the above object is a first step of detecting the current flowing into the compressor and the voltage across the compressor, a second step of obtaining the PF by using the detected current and voltage and the slope of the PF obtained above And a fourth step of detecting an inflection point of the PF tilt detected above, and outputting a voltage command value to control the compressor if the inflection point is not detected. And a fifth step of controlling the piston position of the compressor by providing the changed voltage value to the compressor.

Hereinafter, with reference to the accompanying drawings in detail as follows.

7 is an operation flowchart of a piston position control method of the linear compressor of the present invention. The second step (S102) of detecting the; and the third step (S103) of obtaining the PF with the detected current and voltage; the fourth step (S104) of detecting the slope of the obtained PF; A fifth step (S105) of detecting an inflection point of the PF gradient, and if the inflection point is not detected, the compressor is controlled by outputting a voltage command value (S106). A fifth step S108 of controlling the piston position of the compressor by changing the voltage command value to the current voltage value (S107) and providing the changed voltage value to the compressor.

The configuration of the piston position control device of the linear compressor according to the present invention constant voltage control method for performing the method consisting of each step in the above, as shown in Figure 4, by varying the stroke in the vertical movement of the piston to reduce the cooling force The compressor 101 to adjust, the switch element 102 to regulate the voltage applied to the compressor 101 by intermitting the AC power input in accordance with the switching signal, and detects the current applied to the compressor 101 The voltage detector 104 detects the voltage between the current detector 103 and the compressor 101, the current i detected by the current detector 103 and the voltage V detected by the voltage detector 104. PF (Power Factor) which detects a phase difference of PF and calculates the amount of change of the detected PF, and outputs a voltage command value if there is no change of PF in the PF change amount detecting unit 105. side Amount, the control unit 106 changes the voltage command value to the current voltage value, outputs a switch drive signal according to the voltage command value or the changed voltage command value, and smoothes the signal output from the control unit 106 so that the switch element ( It consists of the rectifier 107 which outputs to 102.

Referring to the operation and effect of the present invention configured as described in detail as follows.

When 220V AC power is supplied from the power supply voltage terminal, the AC power is supplied to the compressor 101 through the current sensing resistor R and the switch element 102.

Accordingly, a voltage is supplied to the compressor 101.

Then, the piston of the compressor 101 reciprocates.

In order to control the piston position of the reciprocating compressor as described above, the current detector 103 detects the current flowing into the compressor 101 and provides it to the PF change detection unit 105, and the voltage detector 9104 provides the compressor 101. The voltage across both ends of the signal is detected and provided to the PF change amount detecting unit 105.

Accordingly, the PF change detection unit 105 obtains PF, which is a phase difference between the input voltage and the current, and detects the slope of the PF.

In this case, when the voltage is sequentially increased in the compressor 101, as shown in FIG. 5, the current increases in proportion, the PF increases to a certain degree, and is inflected at point A to decrease to point B.

The point B is a stable point, the top clearance is '0', and the point is high efficiency.

When the PF change amount detecting unit 105 detects the inclination of the PF and provides it to the control unit 106, if the PF change amount is changed, the control unit 106 changes the voltage command value to the current voltage value.

Thereafter, the switching driving signal corresponding to the voltage command value changed to the current voltage value is output.

Then, it is smoothed by the smoothing unit 107 and then transmitted to the switch element 102 to perform the on operation to operate at a stable point.

Then, the linear compressor 101 operates while maintaining the top clearance, which is the distance between the top dead center of the piston and the discharge valve, at a predetermined distance to maintain high compression efficiency and produce the required cooling force.

As described in detail above, in the present invention, when the voltage is increased by the linear compressor, the PF increases and then decreases toward the negative side, and then goes to a stable point. It is effective to prevent noise caused by the phenomenon.

Claims (1)

A first step of detecting a current flowing into the compressor and a voltage across the compressor, a second step of obtaining PF using the detected current and voltage, a third step of detecting the slope of the PF obtained above, and A fourth step of detecting an inflection point of the PF slope detected by the control unit; and if the inflection point is not detected in the above, the voltage command value is output to control the compressor. And a fifth step of controlling the piston position of the compressor by providing it to the compressor.