KR102023281B1 - Apparatus and method for controlling driving of reciprocating compressor - Google Patents

Abstract

According to an embodiment of the present invention, a device for controlling the driving of a reciprocating compressor includes: a rectification part rectifying and outputting AC power inputted from an external power source; an inverter part converting a DC voltage outputted from the rectification part into an AC voltage to provide the voltage to a motor; a current detection part detecting a driving current applied to the motor; a stroke detection part detecting a stroke of a piston reciprocating in accordance with the operation of the motor; and a control part calculating a phase difference between the stroke and the driving current in the dead center of the piston, determining whether to calibrate the dead center based on the phase difference, and calibrating the dead center by applying a control signal, which makes the AC voltage supplied to the motor become zero, to the inverter part during a preset dead center calibration section.

Description

Operation control apparatus and method of reciprocating compressors {APPARATUS AND METHOD FOR CONTROLLING DRIVING OF RECIPROCATING COMPRESSOR}

The present invention relates to an operation control apparatus of a reciprocating compressor.

Compressors are mechanical devices that increase pressure by compressing refrigerant or various other working gases, and are widely used in refrigerators and air conditioners.

Compressors can be classified into various types according to the internal structure and the operating principle. Compressor is a reciprocating compressor (eccentric rotation) for compressing the refrigerant while the piston is a linear reciprocating motion inside the cylinder is formed a compression space between the piston (cylinder) and the cylinder (cylinder) is formed A compression space is formed between the roller and the cylinder to inhale and discharge the working gas, and a rotary compressor, orbitting scroll and fixed scroll, which compresses the refrigerant while the roller is eccentrically rotated along the inner wall of the cylinder. A compressed space in which working gas is sucked in and discharged is formed between the fixed scrolls, and the rotating scrolls may be classified as a scroll compressor that compresses the refrigerant while rotating along the fixed scrolls.

The reciprocating compressor may be classified into a recipro method and a linear method according to a method of driving a piston.

Recipro method combines a crank shaft to a rotary motor and a piston to the crank shaft to convert the rotational force of the rotary motor into a linear reciprocating motion, while the linear method uses a piston to move the linear motor. It is a method of reciprocating the piston by the linear motion of the motor by connecting directly.

Since the linear reciprocating compressor has no friction loss because there is no crankshaft for converting the rotational motion used in the recipe to linear motion, the compression efficiency is higher than that of the recipe compressor.

Various techniques for increasing the operation efficiency of such a reciprocating compressor have been proposed. For example, Korean Patent Publication No. 10-0608657 discloses a method of increasing the operating efficiency of a reciprocating compressor through the variable control of the operating frequency as follows.

1 is a flowchart illustrating a control method of a reciprocating compressor according to the prior art.

Referring to FIG. 1, first, a current applied to a compressor when the compressor is driven is detected (SP12), and then a stroke of a piston reciprocating inside the compressor is detected (SP22).

Next, for adjusting the operating frequency of the compressor, the stroke value (stroke (min)) when the current for one cycle is minimum is calculated (SP32).

Thereafter, the magnitude of the stroke (min) when the current during one cycle is the minimum is compared with a predetermined reference value of 0 ± δ, and an operating frequency command value is generated based on the comparison result. do.

 In other words, when the stroke value (min) when the current for one cycle is minimum is a value within '0 ± δ', the current operating frequency is generated as the operating frequency command value without frequency change. In addition, if the stroke value (stroke (min)) when the current for one period is minimum is greater than '0 + δ' (SP42), the present operating frequency is increased by a predetermined level, and the increased operating frequency is generated as the operating frequency command value. (SP52). In addition, if the stroke value (stroke (min)) when the current for one cycle is minimum is less than '0-δ' (SP62), the current operating frequency is reduced by a predetermined level, and the reduced operating frequency is changed to the operating frequency command value. To generate (SP72).

As described above, according to the related art, the size of the current applied to the motor inside the compressor is measured and the stroke of the piston is estimated to control the operation frequency of the compressor to match the mechanical resonance frequency of the compressor. However, when using this method, it is difficult to accurately calculate the mechanical resonance frequency of the compressor.

In addition, the control method according to the related art does not reflect the inherent characteristics of the compressor's stroke cycle, such as the compression stroke or the suction stroke, and considers only the current and the stroke, thereby limiting the operation efficiency of the compressor and improving the power consumption.

The present invention provides an operation control apparatus and method for a reciprocating compressor that can improve the operation efficiency of the compressor and improve the power consumption by controlling the operation of the compressor by reflecting inherent characteristics of the compressor's stroke cycle, such as a compression stroke or a suction stroke. It aims to provide.

In addition, the present invention provides a reciprocating compressor operation control apparatus and method that can improve the phenomenon that the direction of the force applied to the piston by the motor in the piston reciprocating movement during the reciprocating motion of the compressor can be improved. It aims to provide.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention, which are not mentioned above, can be understood by the following description, and more clearly by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

Mismatch between the operating frequency and the resonance frequency of the compressor due to various factors that occur during the operation of the compressor, for example, the volume or pressure change of the refrigerant flowing into the compression space of the cylinder, or the force loss due to friction between the piston and the cylinder. Appears.

As a result, the ideal supply of the drive current according to the movement direction or position of the piston is not achieved. In other words, if the operating frequency and the resonant frequency of the compressor are inconsistent, a force in a direction opposite to the direction of movement of the piston can be supplied to the piston by the motor, which leads to a decrease in the operating efficiency of the compressor and an increase in power consumption.

The present invention is to solve this problem, and the dead center correction is performed based on the phase difference between the stroke of the piston and the drive current supplied to the motor due to the mismatch of the operating frequency and the resonance frequency of the compressor. By such dead point correction, it is possible to prevent the phenomenon that the force in the direction opposite to the movement direction of the piston is supplied to the piston.

An operation control apparatus for a reciprocating compressor according to an embodiment of the present invention includes a rectifying unit rectifying and outputting AC power input from an external power source, and an inverter unit converting a DC voltage output from the rectifying unit into an AC voltage and providing the motor to an AC voltage. And a current detector for detecting a drive current applied to the motor, a stroke detector for detecting a stroke of a piston reciprocating in accordance with the driving of the motor, and a phase difference between the drive current and the stroke at a dead center of the piston. A control unit configured to calculate the dead point correction based on the phase difference, and apply a control signal to the inverter unit so that the AC voltage supplied to the motor becomes 0 during a preset dead point correction period; Include.

In one embodiment of the present invention, the control unit calculates the difference between the phase corresponding to the zero crossing point of the driving current and the phase corresponding to the maximum or minimum value of the stroke as the phase difference.

Further, in an embodiment of the present invention, the controller determines that the dead point correction is performed only when the phase difference exceeds a predetermined reference value.

Further, in an embodiment of the present invention, the length of the dead point correction interval is set to be proportional to the magnitude of the phase difference.

In addition, in one embodiment of the present invention, the dead point correction interval is set based on the maximum value or the minimum value of the stroke.

In an embodiment of the present invention, the dead center includes a top dead center and a bottom dead center.

In addition, the operation control method of the reciprocating compressor according to an embodiment of the present invention, detecting the drive current applied to the motor, detecting the stroke of the piston reciprocating in accordance with the drive of the motor, the dead point of the piston calculating a phase difference between the driving current and the stroke at a dead center, determining whether to perform dead point correction based on the phase difference, and allowing the AC voltage supplied to the motor to be zero during a preset dead point correction period And applying the control signal to the inverter unit to perform the dead point correction.

In one embodiment of the present invention, calculating a phase difference between the driving current and the stroke may be performed between a phase corresponding to a zero crossing point of the driving current and a phase corresponding to a maximum or minimum value of the stroke. Calculating the difference as the phase difference.

Also, in an embodiment of the present disclosure, determining whether the dead point correction is performed based on the phase difference includes determining that the dead point correction is performed only when the phase difference exceeds a predetermined reference value.

Further, in an embodiment of the present invention, the length of the dead point correction interval is set to be proportional to the magnitude of the phase difference.

In addition, in one embodiment of the present invention, the dead point correction interval is set based on the maximum value or the minimum value of the stroke.

In an embodiment of the present invention, the dead center includes a top dead center and a bottom dead center.

According to the present invention, by controlling the operation of the compressor by reflecting inherent characteristics of the compressor's stroke cycle, such as a compression stroke or a suction stroke, it is possible to increase the operating efficiency of the compressor and to improve power consumption.

In addition, according to the present invention there is an advantage that can improve the phenomenon that the direction of the force applied to the piston by the motor and the direction of movement of the piston in the process of reciprocating the piston inside the compressor.

1 is a flowchart illustrating a control method of a reciprocating compressor according to the prior art.
2 is a perspective view of a refrigerator including a reciprocating compressor according to an embodiment of the present invention.
3 is a cross-sectional view of a reciprocating compressor according to an embodiment of the present invention.
4 is a block diagram of an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention.
Figure 5 shows the position of the piston and the waveform of the current applied to the motor according to the stroke cycle of the reciprocating compressor.
Figure 6 shows the waveform of the current applied to the stroke and the motor measured by the operation control device of the reciprocating compressor in one embodiment of the present invention.
FIG. 7 illustrates waveforms of voltages applied to a motor by an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention when the waveforms shown in FIG. 6 appear.
FIG. 8 illustrates waveforms of voltages applied to a motor by an operation control device of a reciprocating compressor according to another embodiment of the present invention when the waveforms shown in FIG. 6 appear.
Figure 9 shows the waveform of the current applied to the stroke and the stroke measured by the operation control device of the reciprocating compressor in another embodiment of the present invention.
FIG. 10 illustrates waveforms of voltages applied to a motor by an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention when the waveforms shown in FIG. 9 appear.
FIG. 11 illustrates waveforms of voltages applied to a motor by an operation control apparatus of a reciprocating compressor according to another embodiment of the present invention when the waveforms shown in FIG. 9 appear.
12 is a flowchart illustrating an operation control method of a reciprocating compressor according to an embodiment of the present invention.

The above objects, features, and advantages will be described in detail with reference to the accompanying drawings, whereby those skilled in the art to which the present invention pertains may easily implement the technical idea of the present invention. In describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

2 is a perspective view of a refrigerator including a reciprocating compressor according to an embodiment of the present invention.

Referring to the drawings, the main board 204 for controlling the operation of the refrigerator 200 is provided in the refrigerator 200 according to an embodiment of the present invention. The operation control apparatus of the reciprocating compressor of the present invention described below may be implemented in a circuit or module form on the main substrate 204. The main substrate 204 is electrically connected to the reciprocating compressor 202.

The refrigerator 200 operates by driving the reciprocating compressor 202. In order for the internal storage compartment of the refrigerator 200 to be kept cold, cold air must be supplied into the storage compartment. In order to supply cold air, the reciprocating compressor 202 sucks and compresses a refrigerant in a gaseous form, and the compressed high temperature / high pressure refrigerant is liquefied while passing through a condenser. Refrigerant from the condenser passes through the evaporator and heat exchange creates a cold air by lowering the air temperature around the evaporator. The refrigerant passing through the evaporator is again supplied to the reciprocating compressor 202 to circulate the refrigerant. Through such a process, cold air is supplied into the storage compartment of the refrigerator 200.

3 is a cross-sectional view of a reciprocating compressor according to an embodiment of the present invention.

Referring to the drawings, the reciprocating compressor 202 according to an embodiment of the present invention includes a sealed container 32 forming an appearance. One side of the sealed container 32 is provided with an inlet pipe 32a through which the refrigerant flows in and an outlet tube 32b through which the refrigerant flows out.

In addition, the cylinder 34 is installed inside the sealed container 32 to be fixed. Inside the cylinder 34, a piston 36 for compressing the refrigerant sucked into the compression space P through the reciprocating linear motion is disposed. One end of the piston 36 is provided with springs 38a and 38b for elastically supporting the piston 36 in the movement direction. The piston 36 is connected to the motor 40 generating the driving force and performs a reciprocating linear motion according to the driving of the motor 40.

Further, an intake valve 52 is provided at one end of the piston 36 in contact with the compression space P, and a discharge valve assembly 54 is installed at one end of the cylinder 34 in contact with the compression space P. The intake valve 52 and the discharge valve assembly 54 are automatically adjusted to open and close according to the pressure in the compression space P, respectively.

A predetermined oil is contained in the bottom surface of the sealed container 32, and an oil supply device 60 for pumping oil is disposed. An oil supply pipe 48a for supplying oil between the piston 36 and the cylinder 34 is formed in the lower frame 48 of the sealed container 32. The oil supply device 60 is operated by the vibration generated as the piston 36 reciprocates linearly to pump oil, and the pumped oil is connected between the piston 36 and the cylinder 34 along the oil supply pipe 48a. It is supplied to the gap of to cool and lubricate.

The cylinder 34 is formed in a hollow shape so that the piston 36 can reciprocate linearly, and a compression space P is formed therein. The cylinder 34 is preferably installed on the same straight line as the inflow pipe 32a in a state where one end is located close to the inside of the inflow pipe 32a. A discharge valve assembly 54 is installed at one end of the cylinder 34 on the side opposite to the inflow pipe 32a.

The discharge valve assembly 54 includes a discharge cover 54a for forming a predetermined discharge space on one end of the cylinder 34, a discharge valve 54b for opening and closing one end of the cylinder on the compression space P side, and a discharge cover. It consists of a valve spring 54c which imparts elastic force in the axial direction between the 54a and the discharge valve 54b. O-ring (R) is fitted to one end inner circumferential surface of the cylinder 34 to closely contact the discharge valve 54a and the cylinder 34.

In addition, a bent loop pipe 58 is connected between one side of the discharge cover 54a and the outlet pipe 32b. The loop pipe 58 not only guides the compressed refrigerant to the outside but also transmits vibrations due to the interaction of the cylinder 34, the piston 36, and the linear motor 40 to the entire sealed container 32. It buffers things.

When the pressure of the compression space P reaches a predetermined discharge pressure as the piston 36 reciprocates linearly inside the cylinder 34, the valve spring 54c is compressed to open the discharge valve 54b. Accordingly, the refrigerant compressed in the compression space P is discharged from the compression space P, and then discharged to the outside along the loop pipe 58 and the outlet pipe 32b.

On the other hand, the refrigerant introduced from the inlet pipe (32a) is introduced into the compression space (P) through the refrigerant passage (36a) formed in the center of the piston (36). One end of the piston 36 adjacent to the inlet pipe 32a is directly connected to the linear motor 40 by the connecting member 47. The suction valve 52 is formed in a thin plate shape so that the center portion is partially cut to open and close the refrigerant passage 36a of the piston 36, and one side is fixed to one end of the piston 36a by a screw. do.

As the piston 36 reciprocates linearly in the cylinder 34, when the pressure in the compression space P becomes lower than or equal to a predetermined suction pressure lower than the discharge pressure, the suction valve 52 is opened to cool the refrigerant in the compression space P. ) It is sucked into the inside. When the pressure in the compression space P reaches a predetermined suction pressure, the refrigerant in the compression space P is compressed with the suction valve 52 closed.

Referring to the drawings again, the piston 36 is installed so as to be elastically supported in the movement direction, specifically, the piston flange 36b protruding radially at one end of the piston 36 proximate to the inlet pipe 32a is a coil spring or the like. The refrigerant is elastically supported in the movement direction of the piston 36 by the same mechanical springs 38a and 38b, and the refrigerant contained in the compression space P opposite to the inflow pipe 32a acts as a gas spring by its elastic force. The piston 36 is elastically supported.

The motor 40 has a plurality of laminations 42a laminated in a circumferential direction, and an inner stator 42 installed to be fixed to the outside of the cylinder 34 by the frame 48, and a coil winding body configured to wind the coils ( The outer stator 44 and the inner which are arranged so that a plurality of laminations 44b are laminated circumferentially around 44a) and are provided with a predetermined gap with the inner stator 42 outside the cylinder 34 by the frame 48, the inner It consists of a permanent magnet 46 positioned in the gap between the stator 42 and the outer stator 44 and connected by the piston 36 and the connecting member 47. According to the embodiment, the coil winding body 44a may be fixedly installed outside the inner stator 42.

4 is a block diagram of an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention.

Referring to the drawings, the operation control device 204 of the reciprocating compressor according to an embodiment of the present invention, the rectifier 404, the inverter 408, the controller 410, the current detector 412, the voltage detector 414 ), The stroke estimating unit 416.

The rectifier 404 rectifies the AC power input from the external power source 402 and outputs a DC voltage.

The inverter unit 408 converts the DC voltage output from the rectifying unit 404 into an AC voltage and provides it to the compressor 418. The motor provided inside the compressor 418 is driven by the AC voltage provided by the inverter unit 408. The piston performs the reciprocating linear motion by the driving of the motor.

The controller 410 applies a control signal to the inverter unit 408. The inverter unit 408 is driven at a predetermined operating frequency by a control signal applied by the controller 410 to supply an AC voltage to a motor inside the compressor 418. The magnitude of the AC voltage applied to the compressor 418 is adjusted by the control signal applied by the controller 410. By controlling the magnitude of the AC voltage in this way, the reciprocating linear motion of the piston by the motor is controlled.

The current detector 412 detects the magnitude of the driving current applied to the motor inside the compressor 418 during the driving of the compressor 418. In addition, the voltage detector 414 detects the magnitude of the driving voltage applied to the motor inside the compressor 418 during the driving of the compressor 418.

The stroke estimator 416 receives a driving current and a driving voltage applied to a motor inside the compressor 418 during the driving of the compressor 418, and based on the input driving current and the driving voltage, the current position of the piston, that is, the stroke, is input. Calculate The stroke estimator 416 may calculate a stroke by substituting a driving current and a driving voltage into a known equation or algorithm. The stroke estimator 416 receives the driving current and the driving voltage in real time from the current detector 412 and the voltage detector 414, respectively.

Figure 5 shows the position of the piston and the waveform of the current applied to the motor according to the stroke cycle of the reciprocating compressor. 5 shows the respective positions (a) to (d) of the piston 702 in the cylinder along the stroke cycle. FIG. 5 also shows waveforms of the stroke x of the piston 702 estimated by the stroke estimating unit 416 and the drive current Ic applied to the motor according to the stroke cycle.

Referring to FIG. 5, the piston 702 performs a reciprocating linear motion in a compression space inside the cylinder 704.

In FIG. 5, (a) shows the state in which the piston 702 is located at the initial point S while moving from the bottom dead center (BDC) to the top dead center (TDC) in the compression stroke cycle. . Here, the initial point S is defined as an intermediate point between the top dead center TDC and the bottom dead center BDC. However, according to the exemplary embodiment, the initial point S may be defined as a point other than the middle point between the top dead center TDC and the bottom dead center BDC.

When the piston 702 is located at the initial point S as shown in (a), the drive current Ic applied to the motor represents the maximum value I1. In other words, when the piston 702 is located at the initial point S, the largest force is supplied to the piston by the motor. In the state as shown in (a), the piston 702 performs a linear motion in the direction toward the top dead center (TDC) by the force supplied by the motor and the elastic force supplied by the spring 708.

Next, (b) shows a state where the piston 702 is located at the top dead center (TDC) in the compression stroke cycle. At this time, the piston 702 is maintained at the top dead center (TDC) for a predetermined time, the discharge valve 706 is opened and the refrigerant compressed in the cylinder 704 is discharged to the outside.

When the operating frequency and the resonant frequency of the compressor coincide with each other and the piston 702 ideally performs the reciprocating linear motion, the piston 702 passes the initial point S toward the top dead center TDC, that is, (a When performing the linear motion moving toward the position (b) at), the magnitude of the driving current Ic applied to the motor is maintained at a value between 0 at the maximum value I1, that is, a value greater than zero. Therefore, when the magnitude of the driving current Ic is greater than zero, it means that the motor supplies the piston 702 with a force in a direction toward the top dead center TDC.

Thereafter, when the piston 702 reaches the top dead center (TDC) as shown in (b), the magnitude of the driving current Ic becomes zero, and thus the force is not supplied to the piston 702 by the motor.

Next, (c) shows the state where the piston 702 is located in the initial point S in the middle of the suction stroke cycle from the top dead center TDC to the bottom dead center BDC.

When the operating frequency and the resonant frequency of the compressor coincide with each other and the piston 702 ideally performs the reciprocating linear motion, the piston 702 is directed toward the bottom dead center BDC, that is, the position of (b) to (c). When performing the linear movement moving toward, the magnitude of the drive current Ic applied to the motor is kept between 0 and the minimum value I2, that is, less than zero. Therefore, when the magnitude of the driving current Ic is smaller than zero, it means that the motor supplies the piston 702 with the force in the direction toward the bottom dead center BDC.

Subsequently, when the piston 702 reaches the initial point S as shown in (c), the magnitude of the driving current Ic represents the minimum value Ic. In other words, when the piston 702 is located at the initial point S, the largest force is supplied to the piston by the motor.

Next, (d) shows a state where the piston 702 is located at the bottom dead center BDC in the intake stroke cycle.

When the operating frequency and the resonant frequency of the compressor coincide so that the piston 702 ideally performs the reciprocating linear motion, the piston 702 passes the initial point S toward the bottom dead center BDC, that is, (c When performing the linear motion moving toward the position (d) at), the magnitude of the driving current Ic applied to the motor is maintained at a value between 0 at the minimum value I2, that is, a value smaller than zero.

Thereafter, when the piston 702 reaches the bottom dead center BDC as shown in (d), the magnitude of the driving current Ic becomes 0, and thus the force is not supplied to the piston 702 by the motor.

As described above, when the operating frequency and the resonant frequency of the compressor coincide with each other and the piston 702 ideally performs the reciprocating linear motion, the piston 702 is driven while moving in the direction toward the top dead center (TDC). The magnitude of the current Ic maintains a value greater than zero, and conversely, the magnitude of the drive current Ic maintains a value less than zero while the piston 702 moves in the direction toward the bottom dead center BDC.

In addition, when the piston 702 ideally performs the reciprocating linear motion because the operating frequency and the resonant frequency of the compressor coincide with each other, the two dead centers (TDC) and the bottom dead center (BDC) are respectively connected to the motor. Thereby, the force is not supplied to the piston 702, that is, the state of the drive current Ic should be kept to zero.

However, the operating frequency and the resonance frequency of the compressor are inconsistent due to various factors that occur during the operation of the compressor, for example, the volume or pressure change of the refrigerant flowing into the compression space of the cylinder, or the force loss due to friction between the piston and the cylinder. The phenomenon appears.

As a result, the ideal supply of the drive current Ic according to the movement direction or position of the piston as described above is not achieved. In other words, if the operating frequency and the resonant frequency of the compressor are inconsistent, a force in a direction opposite to the direction of movement of the piston can be supplied to the piston by the motor, which leads to a decrease in the operating efficiency of the compressor and an increase in power consumption.

The present invention is to solve this problem, and the dead center correction is performed based on the phase difference between the stroke of the piston and the drive current supplied to the motor due to the mismatch of the operating frequency and the resonance frequency of the compressor. By such dead point correction, it is possible to prevent the phenomenon that the force in the direction opposite to the movement direction of the piston is supplied to the piston.

Figure 6 shows the waveform of the current applied to the stroke and the motor measured by the operation control device of the reciprocating compressor in one embodiment of the present invention.

As mentioned above, if the operating frequency and the resonant frequency of the compressor do not match, the waveform of the stroke and the driving current as shown in FIG. 6 may appear. The controller 410 of the operation control apparatus 204 of the reciprocating compressor according to the present invention detects the driving current Ic applied to the motor as shown in FIG. 6 through the current detector 412. In addition, the control unit 410 detects the stroke x of the piston as shown in FIG. 6 through the stroke estimating unit 416.

Next, the controller 410 calculates a phase difference between the previously detected drive current Ic and the stroke x of the piston. In the present invention, the control unit 410 is a zero crossing point of the phase (time phase) and the driving current (Ic) corresponding to two dead points of the stroke x of the piston, that is, the top dead center (TDC) or the bottom dead center (BDC). The difference between the phases (time phases) at the point of zero crossing point, that is, when the driving current Ic becomes zero, is calculated as the phase difference. In the present invention, the maximum value x1 of the stroke is defined as top dead center, and the minimum value x2 of the stroke is defined as bottom dead center.

For example, the controller 410 calculates a difference between the time phase corresponding to the top dead center x1 and the time phase corresponding to the first zero crossing point z1 in FIG. 6. In this case, since the time phase corresponding to the top dead center x1 and the time phase corresponding to the first zero crossing point z1 coincide with each other, the phase difference is calculated as zero.

On the other hand, when the operating frequency and the resonant frequency of the compressor is the same as described above, when the piston reaches the bottom dead center (x2) as shown in (d) the force supplied to the piston by the motor should be zero. However, as shown in FIG. 6, when the operating frequency and the resonance frequency of the compressor are inconsistent, the magnitude of the driving current Ic is represented as a non-zero value at the bottom dead center x2. The phenomenon in which the force in the direction toward the point x2 is supplied appears.

In addition, while the piston moves from the bottom dead center (x2) to the top dead center (x1) again, the magnitude of the driving current (Ic) must be maintained to a value greater than zero so that the force in the direction toward the top dead center (x1) is supplied to the piston. do. However, if the operating frequency and the resonant frequency of the compressor is inconsistent, as shown in FIG. 6, the magnitude of the driving current Ic is maintained at a value smaller than 0 in the TX to TI period, so that the force in the direction opposite to the movement direction of the piston is decreased. The phenomenon of feeding to the piston appears.

As a result, this phenomenon occurs when the time phase TX corresponding to the bottom dead center x2 and the time phase TI corresponding to the second zero crossing point z2 do not coincide with each other.

Subsequently, the controller 410 calculates a difference (TX-TI |) between the time phase TX corresponding to the bottom dead center x2 and the time phase TI corresponding to the second zero crossing point z2 in FIG. 6. do. In this case, since the time phase TX corresponding to the bottom dead center x2 and the time phase TI corresponding to the second zero crossing point z2 do not coincide with each other, the phase difference is calculated as a non-zero value.

The controller 410 compares the phase difference (TX-TI |) calculated as described above with a preset reference value and determines whether dead points are corrected. In the present invention, the controller 410 determines that the dead point correction is to be performed when the calculated phase difference is larger than a preset reference value. Otherwise, the controller 410 determines not to perform the dead point correction. Here, the size of the reference value may be set differently according to an embodiment.

FIG. 7 illustrates waveforms of voltages applied to a motor by an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention when the waveforms shown in FIG. 6 appear. In addition, Figure 8 shows the waveform of the voltage applied to the motor by the operation control device of the reciprocating compressor according to another embodiment of the present invention when the waveform shown in Figure 6 appears.

As described above with reference to FIG. 6, when it is determined that the dead point correction is performed as a result of calculating the phase difference and comparing it with the reference value, the controller 410 performs dead point correction. In the present invention, dead point correction temporarily measures the magnitude of the AC voltage supplied to the motor of the compressor 418 by the inverter unit 408 during the dead point correction period set based on the dead point (top dead center or bottom dead center) where the phase difference occurs. It means to keep it as 0.

The controller 410 may set the dead center correction intervals k1 and k2 as shown in FIG. 7 based on a dead point where a phase difference occurs, for example, a bottom dead center x2 that is a minimum value of a stroke to perform dead point correction.

Here, the lengths of the dead center correction sections k1 and k2 may be set differently according to embodiments. For example, the controller 410 may determine the lengths of the dead center correction intervals k1 and k2 with reference to the lookup table in which the lengths of the dead center correction intervals k1 and k2 corresponding to the magnitudes of the phase differences calculated above are recorded. The lengths of the dead point correction intervals k1 and k2 may be determined as values calculated by substituting a phase difference into a preset equation.

In addition, the lengths of the dead center correction section k1 before the bottom dead center x2 and the dead center correction section k2 after the bottom dead center x2 may be set differently. In addition, the lengths of the dead point correction periods k1 and k2 may be set to be proportional to the magnitude of the phase difference previously calculated. In particular, the dead center correction interval k2 after the bottom dead center x2 is a period TX to TI between a time point TX corresponding to the bottom dead center x2 and a time point TI corresponding to the second zero crossing point z2. ) May be set.

According to an exemplary embodiment, the dead point correction includes only the periods TX to TI between the viewpoint TX corresponding to the bottom dead center x2 and the viewpoint TI corresponding to the second zero crossing point z2 as shown in FIG. 8. The interval k3 may be set.

The controller 410 generates a control signal for maintaining the magnitude of the AC voltage supplied to the motor, that is, the driving voltage Vc, to 0 during the dead point correction periods k1, k2, and k3 set as described above. Supplies). By this control, the force supplied to the piston by the motor is maintained at zero during the dead point correction section k1, k2, k3. As the force supplied to the piston by the motor is maintained at 0 as described above, the piston performs the linear motion only by the inertia force according to the linear motion and the elastic force by the spring 708 during the dead point correction periods k1, k2, and k3.

In particular, as shown in FIG. 6, the driving efficiency of the compressor is lowered and the power consumption is increased by cutting off the force supplied to the piston by the motor during the period TX-TI of the force opposite to the piston's movement direction. Can prevent the phenomenon.

Figure 9 shows the waveform of the current applied to the stroke and the stroke measured by the operation control device of the reciprocating compressor in another embodiment of the present invention.

The controller 410 of the operation control apparatus 204 of the reciprocating compressor according to the present invention detects the driving current Ic applied to the motor as shown in FIG. 9 through the current detector 412. In addition, the control unit 410 detects the stroke x of the piston as shown in FIG. 6 through the stroke estimating unit 416.

Next, the controller 410 calculates a phase difference between the previously detected drive current Ic and the stroke x of the piston. In the present invention, the control unit 410 is a zero crossing point of the phase (time phase) and the driving current (Ic) corresponding to two dead centers of the stroke (x) of the piston, that is, the top dead center (TDC) or the bottom dead center (BDC), In other words, the difference between the phases (time phases) at the point where the drive current Ic becomes zero is calculated as the phase difference. In the present invention, the maximum value x1 of the stroke is defined as top dead center, and the minimum value x2 of the stroke is defined as bottom dead center.

As described above, when the operating frequency and the resonant frequency of the compressor coincide with each other, the driving current Ic is supplied such that a force in a direction toward the top dead center x1 is supplied to the piston while the piston moves toward the top dead center x1. The magnitude must be kept greater than zero. However, if the operating frequency and the resonant frequency of the compressor is inconsistent, as shown in FIG. 9, the magnitude of the driving current Ic is maintained at a value smaller than 0 in the TI to TX period, so that the force in the direction opposite to the piston moving direction is decreased. The phenomenon of feeding to the piston appears.

In addition, when the piston reaches the top dead center (x1) as shown in (b), the force supplied to the piston by the motor should be zero. However, when the operating frequency and the resonance frequency of the compressor do not match as shown in FIG. 9, the magnitude of the driving current Ic is represented as a non-zero value at the top dead center x1, so that the piston positioned at the top dead center x1 is continuously lowered. The phenomenon in which the force in the direction toward the point x2 is supplied appears.

As a result, this phenomenon occurs when the time phase TX corresponding to the top dead center x1 and the time phase TI corresponding to the first zero crossing point z1 do not coincide with each other.

In FIG. 9, the controller 410 calculates a difference | TX-TI | between the time phase TX corresponding to the top dead center x1 and the time phase TI corresponding to the first zero crossing point z1. . In this case, since the time phase TX corresponding to the top dead center x1 and the time phase TI corresponding to the first zero crossing point z1 do not coincide with each other, the phase difference is calculated as a non-zero value.

The controller 410 compares the phase difference (TX-TI |) calculated as described above with a preset reference value and determines whether dead points are corrected. In the present invention, the controller 410 determines that the dead point correction is to be performed when the calculated phase difference is larger than a preset reference value. Otherwise, the controller 410 determines not to perform the dead point correction.

FIG. 10 illustrates waveforms of voltages applied to a motor by an operation control apparatus of a reciprocating compressor according to an embodiment of the present invention when the waveforms shown in FIG. 9 appear. 11 illustrates a waveform of a voltage applied to a motor by the operation control apparatus of the reciprocating compressor according to another embodiment of the present invention when the waveform as shown in FIG. 9 appears.

As described above with reference to FIG. 9, when it is determined that the dead point correction is performed as a result of calculating the phase difference and comparing it with the reference value, the controller 410 performs dead point correction.

The controller 410 may set dead center correction sections k4 and k5 as shown in FIG. 10 based on a dead point where a phase difference occurs, for example, a top dead center x1 that is a maximum value of a stroke to perform dead point correction.

According to an exemplary embodiment, the dead point correction includes only the periods TX to TI between the time point TX corresponding to the top dead center x1 and the time point TI corresponding to the first zero crossing point z1, as shown in FIG. 11. The interval k6 may be set.

The controller 410 generates a control signal for maintaining the magnitude of the AC voltage supplied to the motor, that is, the driving voltage Vc, during the dead point correction periods k4, k5, and k6 set as described above. Supplies). By this control, the force supplied to the piston by the motor is kept at zero during the dead point correction section k4, k5, k6. As the force supplied to the piston by the motor is maintained at 0 as described above, the piston performs the linear motion only by the inertia force according to the linear motion and the elastic force by the spring 708 during the dead point correction section k4, k5, k6.

In particular, as shown in FIG. 9, the driving efficiency of the compressor is lowered and the power consumption is increased by cutting off the force supplied to the piston by the motor during the period TI to TX where the force in the direction opposite to the movement direction of the piston is supplied to the piston. Can prevent the phenomenon.

12 is a flowchart illustrating an operation control method of a reciprocating compressor according to an embodiment of the present invention.

When the compressor is driven, the controller 410 detects the magnitude of the drive current applied to the motor of the compressor through the current detector 412 (S802).

In addition, the control unit 410 detects the stroke of the piston inside the compressor through the stroke estimating unit 416 (S804).

Next, the control unit 410 calculates a phase difference between the detected drive current of the motor and the stroke of the piston (S806). The controller 410 has two zero dead center points (time phase) corresponding to two dead center points (TDC) or a bottom dead center point (BDC) and zero crossing points of the driving current, that is, the driving current Ic is zero. The difference between the phases (time phases) at the time points at which they are obtained is calculated as phase difference.

The controller 410 compares the phase difference between the calculated driving current of the motor and the stroke of the piston with a preset reference value (S808). As a result of the comparison, if the previously calculated phase difference is equal to or less than the reference value, the controller 410 returns to step S802.

As a result of the comparison, if the phase difference is larger than the reference value, the controller 410 determines to perform dead point correction, and sets a dead point correction section for performing dead point correction (S810). The dead point correction section may be set based on the maximum or minimum value of the previously detected stroke. In addition, the length of the dead point correction interval may be set to be proportional to the magnitude of the phase difference calculated previously.

When the dead point correction section is set, the controller 410 applies a control signal to the AC unit, that is, the driving voltage to be 0, which is supplied to the motor during the dead point correction section previously set, and performs dead point correction (S812).

By such dead center correction, the force transmitted to the piston by the motor is maintained at zero during the dead center, that is, the dead center correction interval set based on the top dead center or the bottom dead center. Accordingly, the piston performs the linear motion only by the inertia force and elastic force by the spring during the dead point correction interval. Therefore, the phenomenon in which force is transmitted to the piston in a direction opposite to the movement direction of the piston as in the related art can increase the operation efficiency of the compressor and at the same time prevent the phenomenon of increased power consumption.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by.

Claims (12)

A rectifier for rectifying and outputting AC power input from an external power source;
An inverter unit converting a DC voltage output from the rectifier into an AC voltage and providing the same to a motor;
A current detector for detecting a drive current applied to the motor;
A stroke detection unit detecting a stroke of a piston reciprocating in accordance with driving of the motor;
Calculate the phase difference between the driving current and the stroke at the dead center of the piston, determine whether to perform dead point correction based on the phase difference, and the AC voltage supplied to the motor during the preset dead point correction period is 0 And a controller configured to apply a control signal to the inverter unit to perform the dead point correction.
Operation control device of reciprocating compressor.
The method of claim 1,
The control unit
Calculating a difference between a phase corresponding to a zero crossing point of the driving current and a phase corresponding to a maximum or minimum value of the stroke as the phase difference
Operation control device of reciprocating compressor.
The method of claim 1,
The control unit
Determining that the dead point correction is performed only when the phase difference exceeds a predetermined reference value.
Operation control device of reciprocating compressor.
The method of claim 1,
The length of the dead point correction interval is set to be proportional to the magnitude of the phase difference
Operation control device of reciprocating compressor.
The method of claim 1,
The dead point correction section is set based on the maximum or minimum value of the stroke.
Operation control device of reciprocating compressor.
The method of claim 1,
The dead center includes a top dead center and a bottom dead center
Operation control device of reciprocating compressor.
Detecting a drive current applied to the motor;
Detecting a stroke of a piston reciprocating in accordance with driving of the motor;
Calculating a phase difference between the drive current and the stroke at a dead center of the piston;
Determining whether to perform dead point correction based on the phase difference; And
Performing a dead point correction by applying a control signal to the inverter unit such that the AC voltage supplied to the motor becomes 0 during a preset dead point correction period;
Operation control method of reciprocating compressor.
The method of claim 7, wherein
Calculating the phase difference between the drive current and the stroke
Calculating a difference between a phase corresponding to a zero crossing point of the driving current and a phase corresponding to a maximum or minimum value of the stroke as the phase difference.
Operation control method of reciprocating compressor.
The method of claim 7, wherein
Determining whether dead point correction is performed based on the phase difference
Determining that the dead point correction is to be performed only when the phase difference exceeds a predetermined reference value;
Operation control method of reciprocating compressor.
The method of claim 7, wherein
The length of the dead point correction interval is set to be proportional to the magnitude of the phase difference
Operation control method of reciprocating compressor.
The method of claim 7, wherein
The dead point correction section is set based on the maximum or minimum value of the stroke.
Operation control method of reciprocating compressor.
The method of claim 7, wherein
The dead center includes a top dead center and a bottom dead center
Operation control method of reciprocating compressor.

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