KR20010038561A - Control algorithm of linear compressor - Google Patents

Abstract

PURPOSE: A linear compressor control algorithm is provided to achieve an optimum operation of the compressor by avoiding the unstable resonance section caused by environmental change during operation. CONSTITUTION: An algorithm is executed in such procedures that the unstable section is searched by increasing the stroke value from the lower limit point of the stroke voltage where the unstable section starts to appear, the stroke is maintained constant at the level immediately upper from the detected unstable section by increasing the voltage value when the unstable section is detected, and the stroke voltage value is decreased after an elapse of a predetermined time. When the unstable section is detected, the stroke value is increased again. Thus, the compressor operation point is maintained at the level immediately upper from the detected unstable section.

Description

Control algorithm of linear compressor {CONTROL ALGORITHM OF LINEAR COMPRESSOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control algorithm of a linear compressor, and more particularly, to a control algorithm of a linear compressor that enables operation at the highest operating point while tracking a high efficiency point during the initial operation and during operation of the linear compressor.

Since the linear compressor is driven by a linear oscillating motor, there is no crankshaft for converting rotational motion into linear motion, so that friction loss is low and resonance is used. Therefore, it is known that the compressor is more efficient than other compressors.

In addition, when such a compressor is used in a refrigerator or an air conditioner, the compression ratio may be varied as the stroke of the motor is varied, which may be used for variable cooling power control.

The operation of the linear compressor used in the refrigerator or the air conditioner will be described as follows.

Fig. 1 is a block diagram of a conventional linear compressor control device. The configuration of the present invention is a linear oscillating motor 10 for adjusting a cooling force by varying a stroke by a vertical movement of a piston, and alternating current according to a gate driving signal. The electric circuit unit 20 controls the power applied to the linear oscillating motor 10 by intermitting a power supply, and a stroke command value according to the input temperature information and a stroke voltage applied to the linear oscillating motor 10. The control unit 30 controls the estimated strokes to coincide with each other, and provides the timer driving signal to the electric circuit unit 20 accordingly.

The controller 30 receives the temperature information and estimates the stroke value by receiving the stroke command value determiner 31 for determining and outputting a stroke command value corresponding to the temperature and the stroke voltages V0-V3 supplied to the linear oscillating motor. And a sensorless stroke estimator 32 that outputs the estimated stroke value, and a stroke estimated by the sensorless stroke estimator 32 to follow the stroke command value determined by the stroke command value determiner 31 well, and accordingly A stroke controller 33 for outputting a timer command value, a zero-cross detector 34 for detecting a zero-cross point from an input voltage waveform and outputting a zero-cross signal thereto, and the zero-cross detector 34 Estimated by the stroke controller 33 at the time when the zero-cross signal output from Depending on the value comprises a timer 35 for providing gate drive signals.

Referring to the prior art configured in this way in detail as follows. When a 220V power supply voltage as shown in FIG. 2A is supplied from the power supply voltage terminal, the power supply voltage is supplied to the linear oscillating motor 10 through the current sensing resistor R, the triac Tr, and the capacitor C of the electric circuit unit 20. Is supplied. As a result, current flows in the linear oscillating motor 10. Thereafter, the piston 11 of the linear oscillating motor 10 reciprocates, and the reciprocating stroke of the piston 11 is a stroke. By varying this stroke, the cooling power is varied. That is, to adjust the cold power of the refrigerator or air conditioner.

At this time, when the user sets the temperature of the refrigerator or the air conditioner, the set temperature information is received by the stroke command value determiner 31 of the controller 30. The stroke command value determiner 31 which has received the temperature information in this way determines the stroke command value corresponding to the set temperature, and provides the determined stroke command value signal to the stroke controller 33.

At this time, the sensorless stroke estimator 32 is a voltage V1 between the power voltage terminal and the current sensing resistor R, the current sensing resistor R and the triac from the electric circuit unit 20 for supplying current to the linear oscillating motor 10. A stroke information and a current are received by receiving a voltage V1 between Tr, a voltage V2 supplied from the triac Tr to the linear oscillating motor 10, and a voltage V3 supplied to the linear oscillating motor 10 via the capacitor C. The information is estimated, and the estimated stroke information and current information are transmitted to the stroke controller 33.

Thereafter, the stroke controller 33 controls the stroke command value determined by the stroke command value determiner 31 to be equal to the estimated stroke value. The timer command value thus obtained is transferred to the timer 35. At this time, the zero cross detector 34 receives a zero-cross point by receiving a voltage V0 between the power supply voltage terminal and the current sensing resistor R in the electric circuit unit 20 or the voltage V4 before passing the capacitor C from the power supply voltage terminal. Detect and provide the detected zero-cross signal to the timer 35.

The timer 35 then accepts the zero-cross signal as a start terminal. When the zero-cross signal is input to the start terminal, the timer 35 sets the time t1 shown in FIG. 2C by the timer command value provided by the stroke controller 33.

When the time t1 is set as above, the timer 35 outputs the gate driving signal to the gate G of the triac Tr of the electric circuit unit 20. For example, if t1 is small as shown in FIG. 2C, the gate driving signal is set shortly from the zero-cross point of time as shown in FIG. 2C, and a large amount of current flows as shown in FIG. When large as shown in FIG. 2E, the gate driving signal is far from the zero-cross time point, so that a small current flows as shown in FIG.

When the gate driving signal is output to the gate G of the triac Tt of the electric circuit unit 20, the triac Tr is turned on to supply a current to the linear oscillating motor 10, and thus the linear oscillating motor. The piston of (10) moves up and down to adjust the cooling power of the refrigerator or air conditioning. When the input current is applied to the cycle function, the piston movements have the same cycle, and the appearance varies depending on the suction and discharge pressures.

One example is shown in FIG. When the period of the piston is referred to as T, the stroke is defined as follows because the stroke represents the maximum displacement within one period.

here Actual value and error because it is estimated by sensorless May be present.

The theoretical basis for the piston's movement when modeling the linear oscillating motor 10 with a counter electromotive force RL circuit as shown in Fig. 3 is described by two nonlinear simultaneous differential equations as shown in the following equations (1) and (2). Where Equation (1) is a mechanical equation of motion, and Equation (2) is an electrical equivalent equation.

Where x is the displacement of the piston, i is the current through the motor, m is the mass of the piston, C is the damping coefficient, k is the equivalent spring constant, and P is the force applied by the piston, and E is the equivalent inductance. Coefficient, R: equivalent resistance, r: resistance for detecting current magnitude r R, V: external voltage.

In the above formula, Fp represents the force due to the pressure difference between the suction and the discharge side. As shown in FIG. 5, the compressor varies nonlinearly with the suction-compression-discharge process.

Therefore, when the voltage V increases, the right side of the equation (2) increases, so that the current on the left side also increases, and as the current increases, the right side of the equation (1) increases, so that the displacement of the piston on the left side also increases. That is, the stroke distance of the piston is changed by the applied voltage, and when the triac, which is a semiconductor switching element, is used, the applied voltage can be controlled by switching and the same effect can be obtained.

The linear compressor is the most efficient at the resonance point and generates the lowest noise. However, at this resonance point, as shown in FIG. 6, the operation of the piston is not kept constant, and a trembling instability often occurs. This resonance frequency is expressed by the following equation (3) in the case of using a commercial AC power supply of 60 Hz (50 Hz).

Where f is a frequency, Kg is a gas spring (pressure: Pd, Ps), Ks is a spring constant, and m is a piston mass. Therefore, when the frequency f becomes 60 Hz (50 Hz), mechanical resonance occurs. Here, m and Ks are constants, and only Kg values, which are influences of pressures Ps and Pd expressed by gas springs, act as variables. In products using compressors such as refrigerators and air conditioners, this Kg value changes from time to time because the pressure constantly changes. Thus, the stroke of the resonance point also changes as the pressure continues to change. Since the resonance point is the most efficient and the least noise point, it is important to operate the variable stroke to track this resonance point well.

An object of the present invention is to optimize the operation by tracking and avoiding the resonance instability area caused by various environmental changes during the operation of the linear compressor.

In order to achieve this object, the present invention searches for an unstable region by increasing the stroke value by a predetermined voltage value from the lower limit of the stroke voltage at which the unstable region starts to appear, and when the unstable region is detected, the constant voltage value is increased again. The stroke is kept constant just above the unstable area, and when a predetermined time elapses, the stroke voltage value is decreased by a certain value. When an unstable area is detected, the stroke value is increased again and the operation is repeated. It provides a control algorithm of the linear compressor to control to be located at the top.

In addition, the present invention searches for an unstable region by increasing the stroke value by a predetermined voltage value from the lower limit of the stroke voltage at which the unstable region starts to appear, and detects the unstable region and decreases the constant voltage value to detect the stroke immediately below the unstable region. While maintaining constant at, the stroke voltage is increased by a certain value after a predetermined time, and when the unstable area is detected, the stroke value is decreased again and the operation process is repeated so that the operating point is always located directly below the unstable area. Provides a control algorithm for linear compression.

In addition, the present invention provides a method of controlling the operation of a linear compressor in which the stroke time is simply accelerated until the stroke value reaches a lower limit from zero.

1 is a block diagram of a conventional apparatus for controlling a linear compressor;

FIG. 2 is a signal waveform diagram of each part of the control device of the linear compressor of FIG.

FIG. 3 is an equivalent circuit diagram when modeling the linear oscillating motor of FIG. 1 into an R-L circuit with counter electromotive force. FIG.

4 is a waveform diagram showing a period of movement of a piston according to suction and discharge pressures in the linear compressor of FIG.

FIG. 5 is a waveform diagram of the force Fp on a non-linearly varying piston during the suction-compression-discharge process in the linear compressor of FIG.

FIG. 6 is a waveform diagram showing an unstable and stable case with respect to a period of movement of a piston according to suction and discharge pressures in the linear compressor of FIG.

7 is a diagram illustrating an optimal driving point search and driving algorithm of the linear compressor.

8 is a flowchart of an optimum operating point search and driving algorithm of the linear compressor.

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

s1: Stroke voltage increase value s2: Stroke voltage decrease value

V1: Lower limit stroke voltage V2: Upper limit stroke voltage

V3: Stroke Voltage in Unstable Region

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

7 is a diagram illustrating a driving algorithm for searching for an optimal driving point according to the present invention. As shown in the figure, the scanning for searching for the resonance unstable region is started from the lower limit V1 of the estimated stroke in the sensorless stroke estimator. This is to speed up scanning because there is no unstable area even in the part where the stroke is low even if there is a component deviation. Therefore, it accelerates simply from the starting point 0V to the lower limit V1 quickly. After the simple acceleration, when the stroke reaches the lower limit point V1, the stroke is increased by s1 by the time unit t1 from this point, and it is searched whether there is an unstable region. Then, when the stroke is increased in units of s1, and the search for an unstable region is present, the stroke is increased again by s1 and the stroke is maintained at this time. This is because it has been found experimentally that the best of efficiency and the least noise is just above the unstable area.

However, such an unstable region tends to move with time. Therefore, in order to maintain an optimal stroke, it is necessary to keep track of the movement of these unstable areas and keep the strokes just above the unstable areas that change from time to time. To do this, we continue to look for unstable areas in the current stroke until a certain time t2 has elapsed. If the unstable region exists in the current stroke as a result of the search, the stroke is increased by s1 again. This process is repeated until it leaves the unstable region.

If the unstable region does not occur even after a certain time t2 elapses while maintaining the stroke immediately above the unstable region, the stroke is reduced by s2 to search for instability. At this time, if an unstable region is detected, the stroke is increased by s1 again so that the stroke is immediately above the unstable region. If the unstable region is not detected even if the stroke is reduced by s2, it is determined that the unstable region has moved much downward, and the stroke value is continuously reduced by s2 in units of t2 hours. When the instability point is detected by repeating the above process, the stroke is increased by s1 to operate the compressor directly above the instability point, thereby maintaining the optimum operating state at all times. This process is shown in a flowchart as shown in FIG.

8 is a flowchart of an optimal operating point search and driving algorithm of the present invention.

When the operation is started, the stroke voltage is started to be read by the sensorless stroke estimator of the linear compressor (step S800). As described above, since there is a section in which the resonance instability region does not exist in the driving section of the compressor, it is only a waste of time when scanning to search for the resonance instability region up to this section. Accordingly, the sensorless stroke estimator searches for the resonance instability region from the lower limit point V1 of the estimated stroke. For this purpose, it is determined whether the current stroke voltage is equal to or lower than the lower limit point V1 (step S805). If the stroke voltage does not reach the lower limit, the scanning speed is increased by continuously increasing the stroke voltage without searching whether a resonance unstable region exists (step S810).

When the stroke voltage reaches the lower limit V1 through the simple acceleration section, it starts to search whether the unstable region exists by increasing the stroke voltage step by step (step S815). In this step, if an unstable region is not detected at each set stroke voltage, the unstable region is considered to exist above the current stroke voltage and the stroke voltage is increased by s1 (step S820). Then, it is searched whether there is an unstable region at the increased stroke voltage (step S815). This process is repeated to continuously increase the stroke voltage until the presence of an unstable region is detected.

In step S915, if an unstable region is detected at a constant stroke voltage, the stroke voltage is increased again by s1 (step S825). Thereafter, the state of instability is checked (step S830), and if the unstable region is still detected, the stroke voltage is increased again by s1 (step S835). After that, it is again checked for instability. This process is repeated until the unstable region is not detected.

If the unstable region is no longer detected in step S830, the operation is continued while maintaining the stroke voltage at that time (step S840). In this way, the stroke voltage is present just above the unstable region, so that stable and efficient operation can be continued, and high efficiency and low noise operation are possible.

However, as the operation continues, the unstable region may fluctuate from time to time. For optimal operation, it is necessary to keep track of the unstable region and operate to control the stroke immediately above the unstable region. To this end, in step S840, the stroke voltage is kept constant to detect whether an unstable region exists at the current stroke voltage. That is, it is currently operating while being raised by s1 from the unstable area, and it detects whether the unstable area is raised by s1 again. At this time, the time is set to t2 to detect whether the instability continues until this set time elapses. If an unstable area exists within t2 time, the stroke is increased by s1 again (step S835), and the unstable area occurs during t2 time. Otherwise, the stroke is reduced by s2 in consideration of the possibility that the unstable region has moved downward from the previously detected point (step S860).

In this way, after reducing the stroke by s2, it is detected whether an unstable region exists again (step S830). As a result, if there is an unstable region, it is determined that the unstable region does not move downward even after a predetermined time t2 has elapsed (step S835), and this process is repeated to operate immediately above the unstable region. On the other hand, if the unstable area does not exist after reducing the stroke by s2 and detecting the presence of the unstable area, it is determined that the unstable area has moved downward and the unstable area is maintained until a predetermined time t2 elapses while maintaining the stroke at that time. Determine if it rises. If an unstable area is detected within a certain time t2, the stroke is raised to avoid an unstable area, and if the unstable area is not detected within a predetermined time t2, the stroke is again reduced by s2 in consideration of the possibility that the unstable area has moved downward ( Step S860). By repeating such a process, the stroke of the linear compressor is always operated directly above the unstable region, thereby enabling stable and low noise operation.

In the embodiment of the present invention, when the unstable area is detected, the stroke value is increased by a constant value to avoid the problem. However, in other embodiments, it is possible to reduce the stroke value by a certain value than the unstable area. .

The linear compressor operates most efficiently at the resonance point and generates less noise. At this resonance point, there is an unstable region of the piston. The present invention seeks to operate optimally by searching for a resonance unstable region and keeping track of the region.

Claims (4)

A control algorithm of a linear compressor, wherein the control algorithm for a linear compressor is configured to search for a stroke instability area during initial operation and during operation, and to detect the instability area so as to avoid the instability area by changing the stroke voltage value. The method of claim 1, wherein the stroke value is searched by increasing the stroke value by a predetermined voltage value from the lower limit of the stroke voltage, and when the unstable area is detected, the constant voltage value is increased again to keep the stroke constant just above the unstable area. A control algorithm of a linear compressor that reduces a stroke voltage value by a predetermined value after a predetermined time and increases a stroke value again when an unstable region is detected so that an optimum operating point is always directly above the unstable region. The method of claim 1, wherein the stroke value is searched by increasing the stroke value by a predetermined voltage value from the lower limit of the stroke voltage, and when the unstable area is detected, the predetermined voltage value is decreased again to keep the stroke constant just below the unstable area. The control algorithm of the linear compressor that increases the stroke voltage value by a predetermined value after a time elapses and decreases the stroke value again when an unstable area is detected so that the optimum operating point is always immediately below the unstable area. 4. The control algorithm according to any one of claims 1 to 3, wherein the stroke value is simply accelerated from zero to the lower limit to reduce the search time.