WO2010011085A1

WO2010011085A1 - Linear compressor

Info

Publication number: WO2010011085A1
Application number: PCT/KR2009/004068
Authority: WO
Inventors: 김종권; 박신현; 강계룡; 강희동; 이정욱; 김현
Original assignee: 엘지전자 주식회사
Priority date: 2008-07-22
Filing date: 2009-07-22
Publication date: 2010-01-28

Abstract

The present invention relates to a linear compressor, and more particularly, to a linear compressor which supplies a necessary cooling capacity through a natural cooling capacity modulation and a forcible cooling capacity modulation, and to a cooling system using the linear compressor. The linear compressor of the present invention includes a compression space (P) into which refrigerant is sucked, a movable member (36) which linearly reciprocates to compress the refrigerant sucked into the compression space (P), one or more springs (38a, 38b) which are installed to elastically support the movable member (36) in a motion direction of the movable member (36), a motor unit which includes a motor and a capacitor connected in series to the motor so as to make the movable member (36) linearly reciprocate, and a motor control unit which performs a natural cooling capacity modulation, according to a load, by reciprocation of the movable member (36).

Description

Linear compressor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear compressor, and more particularly, to a linear compressor for supplying necessary cooling power through a natural cooling force variable and a forced cooling force variable, and a cooling system using the same.

In general, a motor is also provided in a compressor, a mechanical device that increases power by compressing air, refrigerant, or various working gases by receiving power from a power generator such as an electric motor or a turbine. Or widely used throughout the industry.

In particular, when the compressor is largely classified, a reciprocating compressor for compressing the refrigerant while linearly reciprocating the piston inside the cylinder is formed by forming a compression space in which the working gas is absorbed and discharged between the piston and the cylinder. Rotary compressor that compresses the refrigerant while the roller is eccentrically rotated along the inner wall of the cylinder so that a compression space for absorbing and discharging the working gas is formed between the reciprocating compressor and the eccentrically rotating roller and the cylinder. Scroll compressor that compresses the refrigerant while the rotating scroll rotates along the fixed scroll by forming a compression space for absorbing and discharging the working gas between the orbiting scroll and the fixed scroll. Are divided into

Recently, among the reciprocating compressors, in particular, the piston is directly connected to the reciprocating linear motion drive motor, so that there is no mechanical loss due to the motion conversion to improve the compression efficiency as well as a simple linear compressor has been developed a lot.

1 is a block diagram of a motor control device applied to a linear compressor according to the prior art.

As shown in FIG. 1, the motor control apparatus applies a diode bridge 11 for receiving and rectifying an AC power, which is a commercial power source, and outputting the rectified part, a rectifying unit including a capacitor C1 smoothing the rectified voltage, and applying a DC voltage. A motor including an inverter unit 12, a motor 13, and a capacitor C2 connected in series with the motor 13, which are converted into an AC voltage according to a control signal from the controller 17 and provided to the motor unit. And a voltage detector 14 that detects the voltage across the capacitor C1, a current detector 15 that detects a current flowing in the motor unit, a sense voltage from the voltage detector 14, and a current detector 15 A calculation unit 16 for calculating the counter electromotive force (EMF) from the sense current from the control unit 16, and a control unit 17 for generating a control signal by reflecting the deferred power from the calculation unit 16 and the sense current from the current detection unit 15. )

In this control device, the calculation unit 16 calculates the counter electromotive force according to Equation 1 below.

Equation 1

Here, L is the inductance of the motor 13, V is the voltage applied to the inverter unit 12, R is the resistance value of the motor.

That is, the calculator 16 calculates the counter electromotive force EMF according to the sensed current from the current detector 5.

FIG. 2 is a graph of variable cooling power of the linear compressor of FIG. 1. The graph of FIG. 2 shows the result of the control of the control unit 17 in order to obtain the required cooling power when the inverter unit 12 of the motor control device applies the BLDC inverter.

As the temperature, which is the load, rises, the controller 17 controls the inverter unit 12 to forcibly raise the AC voltage applied to the motor 13, thereby acquiring the cooling force required according to the load. As shown in the figure, as the temperature rises from 10 ° C to 50 ° C, the controller 17 may obtain a desired cooling power or cooling power ratio through four forced voltage rising controls.

In the case of acquiring the cooling force through such a plurality of forced voltage rise control or forced voltage drop control, a plurality of controls by the controller 17 must be performed, and for such a forced voltage rise and fall control, the motor due to the continuous voltage variable, The reliability of the components in the control device is a serious problem. In addition, a protection device (protection circuit) for such a plurality of voltage variations should be additionally provided.

An object of the present invention is to provide a linear compressor and a cooling system using the same to simplify the cooling control process by performing the variable control of the natural cooling force corresponding to the load, and selectively performing a forced cooling variable control by the power control as needed. do.

In addition, an object of the present invention is to provide a linear compressor and a cooling system using the same to implement a variable power cooling control, to implement a power impact on the components and simplification of the components.

In addition, the present invention provides a linear compressor capable of supplying the cooling device with a simple control and a required cooling power even with a small number of compressors, especially in a linear compressor connected to at least one cooling device, especially in the case of a large variation in the required cooling power. It is an object to provide a cooling system using the same.

In addition, an object of the present invention is to provide a motor control device and a linear compressor using the same so as to use only a voltage value, not a current value, when calculating the counter electromotive force.

In addition, an object of the present invention is to provide a motor control device for improving the accuracy of voltage sensing and a linear compressor using the same.

It is also an object of the present invention to provide a linear compressor which allows a voltage having a substantially fixed voltage and frequency characteristic or a voltage having a variable voltage and frequency characteristic to be applied to a motor using a motor control device.

In addition, an object of the present invention is to provide a linear compressor using a motor control device so that the output of a constant voltage and a constant frequency is applied to the motor even if the external power source is variable.

The linear compressor of the present invention includes a compression space in which the refrigerant is sucked, a movable member for compressing the refrigerant sucked into the compression space while reciprocating linear movement, at least one spring installed to elastically support the movable member in the direction of movement of the movable member, and In order to reciprocally linearly move the member, the motor comprises a motor, a motor unit including a capacitor connected in series with the motor, and a motor control unit that performs a natural cooling force variable by reciprocating motion of the movable member in response to a load.

In addition, the motor control unit preferably maintains the magnitude and frequency of the voltage applied to the motor unit to be substantially constant to perform the natural cooling force variable.

In addition, the linear compressor of the present invention includes a compression space in which the refrigerant is sucked, a movable member for compressing the refrigerant sucked into the compression space while reciprocating linear movement, and at least one spring provided to elastically support the movable member in the direction of movement of the movable member; In order to reciprocally move the movable member, the motor unit includes a motor, a motor unit including a capacitor connected in series with the motor, and a motor controller configured to vary the stroke of the movable member in response to a change in the refrigerant, thereby performing natural cooling force variation.

In addition, the motor control unit may detect a voltage corresponding to a commercial power applied from the outside or a power applied to the motor unit, and control the motor unit based on the detected voltage.

In addition, the motor control unit may vary the magnitude or frequency of the voltage applied to the motor unit to perform the forced cooling force variable.

In addition, the motor control unit changes the magnitude or frequency of the voltage applied to the motor unit to a plurality of values to perform forced cooling force variation, and then maintains the magnitude or frequency of the variable voltage constant, thereby maintaining the maintained AC voltage in the motor unit. It is preferred to perform the natural cold power variable by applying to.

In addition, the motor control unit preferably varies the magnitude or frequency of the voltage in response to the cooling force variable command from the cooling control device.

The motor controller may further include a rectifier that receives an AC power and outputs a DC voltage, an inverter that receives a DC voltage, converts the AC voltage according to a control signal, and provides the motor to the motor, and detects a voltage applied to the inverter. A first voltage detector, a second voltage detector for detecting a voltage corresponding to the voltage across the capacitor, or a voltage between the capacitor and the ground; a first voltage from the first voltage detector; and a second voltage from the second voltage detector. The control unit may be configured to include a control unit corresponding to the first and second voltages to generate and apply a control signal to the inverter unit to substantially maintain the magnitude and frequency of the AC voltage.

The controller may adjust the sampling time of the second voltage detector for detecting the second voltage.

The controller may calculate a counter electromotive force corresponding to the first and second voltages to generate a control signal according to the calculated counter electromotive force.

In addition, the cooling system of the present invention is connected to supply at least one cooling device, the refrigerant to the cooling device, the natural cold power variable control to naturally vary the cooling power in response to the load, and the cooling power in response to the load or cooling control command And a compressor for supplying a refrigerant to the cooling device by forcibly varying the forced cooling force variable control, and a refrigerant pipe connecting the cooling device and the compressor.

In addition, the cooling system of the present invention is connected to supply at least one cooling device and the refrigerant to the cooling device, and performs only a natural cold power variable control to naturally vary the cooling power in response to the load, to supply the refrigerant to the cooling device And a refrigerant pipe connecting the cooling device and the compressor.

The present invention performs the variable control of the natural cold power corresponding to the load, and optionally to perform the forced cold variable control by the power control to simplify the cooling control process, while supplying the necessary cooling power while reducing the applied power It works.

In addition, the present invention has the effect of implementing the natural cooling power control, the power impact on the components and the simplification of the components.

In addition, the present invention is a linear compressor connected to at least one cooling device, especially in the case of a large variation in the required cooling power, it is possible to stably supply the required cooling power to the cooling devices even with simple control and a small number of compressors. It works.

The present invention of such a configuration has the effect of performing the control of the motor accurately by accurately calculating the acting power by using only the voltage value, not the current value, when calculating the counter electromotive force.

In addition, the present invention by applying a voltage having a substantially fixed magnitude and frequency characteristics or a voltage having a variable magnitude and frequency characteristics to the motor provided in the linear compressor, there is an effect that the cooling power is variable according to the load.

In addition, the present invention has the effect of improving the reliability of the linear compressor by allowing the output of substantially constant voltage and constant frequency to be applied to the motor even under the input of a variable external power source.

FIG. 2 is a graph of variable cooling power of the linear compressor of FIG. 1.

3 is a block diagram of a motor control device applied to the linear compressor according to the present invention.

4 to 6 are first to third embodiments of the detection circuit of the voltage detector of FIG. 3.

7 and 8 are operational circuit diagrams of the inverter of FIG. 3.

9-11 are graphs of sensed voltages.

12 is a sectional view of a linear compressor according to the present invention.

13 through 16 are cooling capacity graphs of the linear compressor of FIG. 12.

17 is a diagram illustrating an example of a cooling system to which the linear compressor of FIG. 3 is applied.

18 is a configuration diagram showing an example of a refrigeration cycle constituting a cooling system according to the present invention.

19 is a block diagram illustrating an example of a cooling system according to the present invention.

DETAILED DESCRIPTION Hereinafter, embodiments of the present invention in which the above object can be specifically realized are described with reference to the accompanying drawings.

The motor control apparatus shown in FIG. 3 includes a rectifying unit including a diode bridge 21 for receiving and rectifying an AC power, which is a commercial power source, and outputting a rectifier, a capacitor C1 for smoothing the rectified voltage, and a control unit receiving a DC voltage. A motor section including an inverter section 22, a motor 23, and a capacitor C connected in series with the motor 23, which are converted into an AC voltage and provided to the motor section in accordance with the control signal from 27; The voltage detector 24 detects the voltage across the capacitor C1 or the divided voltages of the voltage divider resistors R1 and R2, and the voltage V1 between the capacitor C and the voltage V1 between the capacitor C and the ground. ) Is calculated from the voltage detector 25, the voltage detected by the voltage detector 24, the calculated voltage from the voltage detector 25, and the calculator 26 and the calculator 26. Reflects the counter electromotive force of and the sensed voltage from the voltage detector 25, Control comprises a control unit 27 for generating a signal. In the present invention, the control unit 27 does not describe a process of generating a control signal according to the counter electromotive force and the sensed voltage, but this process is only a degree that is clearly understood by those skilled in the art.

In addition, the controller 27 may be configured by the calculator 26 and a single element or a circuit.

First, the diode bridge 21 is a device that performs a general rectification function, and the capacitor C1 is a device that smoothes the rectified voltage.

The voltage divider R1 and R2 are composed of at least two series connected resistors R1 and R2, and divide the rectified voltage from the diode bridge 21. In general, since the rectified voltage of the diode bridge 21 is hundreds to thousands of volts (for example, 200 to 1000 V), it is not necessary for such a large voltage to be applied to the calculator 26 and / or the controller 27. ), And such a partial pressure is required because excessive voltage may be applied to the control unit 27. Preferably, a voltage of a predetermined magnitude (for example, about 5 V or 0.2 V) is applied to the operation unit 26 and the control unit 27, and the resistor R1 is at least several hundred to several thousand times larger than the resistance R2. Configure to have resistance value. The ratio of the resistance value or the resistance value of the resistors R1 and R2 is recognized by the calculation unit 26 and the control unit 27, and it is possible to calculate or predict the magnitude of the DC link voltage Vdc based on the divided voltage.

That is, the calculator 26 and the controller 27 read the voltage rectified from the diode rectifier circuit 11 or a part thereof.

Next, the inverter unit 22, the motor unit 23 and the voltage detection unit 24 are just enough to be easily recognized by a person familiar with the technical field to which the present invention belongs, and thus description thereof is omitted.

The voltage detector 25 detects the voltage between the capacitor C or the voltage between the capacitor C and the ground, and in particular, detects a part of the voltage between the capacitor C and the ground (ie, the divided voltage). The voltage (or sense voltage) V2 is applied to the calculator 26 and the controller 27. This voltage detector 25 is described in detail below.

Next, the calculator 26 calculates the counter electromotive force EMF from the voltage from the voltage detector 24 and the voltage V2 from the voltage detector 25. This operation is performed according to the following equations. Such mathematical operations may be implemented in hardware, middleware, and software. This embodiment corresponds to the case where the voltage Vc at both ends of the capacitor C is detected.

Equation 2

Here, i is a current flowing in the motor unit, and C corresponds to the capacitance of the capacitor (C). Here, the voltage Vc of the capacitor C is converted from equation (2) as shown in equation (3).

Equation 3

Substituting the voltage Vc according to Equation 3 into Equation 1 is as follows.

Equation 4

Here, L is the inductance of the motor 23, V is the applied voltage (Vdc) to the inverter unit 22, R is the resistance value of the motor.

Here, the voltage Vc may be defined as in Equation (5), and the derivative of the voltage Vc is as in Equation (2). In addition, the double derivative of the voltage Vc may be defined as shown in Equation 5 (3).

Equation 5

According to the definition of Equation 5, when the derivative of the voltage Vc and the double derivative are substituted into Equation 4, Equation 6 is obtained. Where ω is the kinetic frequency of the motor.

Equation 6

Equation (6) is summarized as Equation (7).

Equation 7

Accordingly, the calculator 26 and the controller 27 can calculate the counter electromotive force EMF from the voltage Vc at both ends of the capacitor C. FIG. In particular, in equation (7), a differential operation is required, such as RCdVc / dt, but in the calculation of counter electromotive force, since its magnitude is relatively significantly smaller than other values, the influence from noise is extremely reduced.

In addition, since the importance of the derivative operation is considerably lowered in the calculation of the counter electromotive force, even if the accuracy of the derivative operation is low, the influence on the calculation of the counter electromotive force is reduced, and thus, a processor (for example, a microprocessor or the like) provided in the operation unit 26. Even if the performance of) is relatively low, the back EMF can be calculated relatively accurately.

In addition, since the voltage of the capacitor C does not change abruptly even with a sudden change in external current and noise, the value of the voltage Vc does not include noise, and the operation of the total back EMF affects the noise. You rarely get

In addition, the control unit 27 calculates the speed by multiplying the counter electromotive force (EMF) from the calculating unit 26 by a specific constant, or calculates the displacement (for example, the displacement of the piston in the case of the linear compressor) by integrating the speed. It may be.

In addition, as is well known, the control unit 27 generates a PWM signal and a control signal corresponding to the PWM signal, and controls the inverter unit 22 by such a control signal. It is also well known that such a PWM signal may be calculated as a duty through a relationship with the voltage Vdc. Through the control signal and the duty ratio, the control unit 27 adjusts the cooling force in the case of the refrigeration cycle.

4 is a configuration for directly detecting the voltage Vc across the capacitor C. The voltage detector 25a is formed of an IC chip OP amp, so that the voltage Vc can be detected through a general OP amp. The detection of this direct voltage Vc does not require software for a separate voltage calculation.

The inverter unit 22 is composed of two pairs of switches SW1 and SW2 and SW3 and SW4 connected in series, and includes a motor between the switches SW1 and SW2 and between the switches SW3 and SW4. The addition is connected. In particular, when the switch SW1 is on and the switch SW2 is off, the switch SW3 is off and the switch SW4 is on (hereinafter referred to as 'first operation'). In addition, when the switch SW1 is off and the switch SW3 is on, the switch SW4 is off and the switch SW2 is on (hereinafter referred to as 'second operation'). The operation of the inverter unit 22 is equally applicable to the following.

In addition, since the voltage detection unit 25a is applied with a DC reference voltage Vcc (for example, + 12V and -12V) for the operation of the op amp, the voltage detection unit 25a is offset by a predetermined voltage value.

5 and 6 allow the sensing of a voltage to estimate for estimating a voltage close to or coincident with the voltage Vc, using only a low cost resistor, without the use of the OP amp of FIG. The voltage Vc 'corresponds to the voltage between the capacitor C and ground. The voltage detector 25b includes a resistor R connecting the capacitor C and the ground.

In Fig. 5, when the inverter section operates in the first operation, the voltage Vc 'becomes equal to the voltage Vc at both ends of the capacitor, and when the inverter section operates in the second operation, the voltage Vc' becomes (Vc). = Vc'-Vdc). Such calculation or the like should be recognized as the voltage detector 25 having the voltage detector 25b and software or firmware calculation means.

6 is different from FIG. 5, the voltage dividing resistor unit 25c enables the divided voltage of the voltage Vc 'of FIG. 5 to be detected. The voltage divider 25c includes the resistors Ra and Rb connected in series between the capacitor C and the ground, between the resistors Ra and Rb, and the DC reference voltage Vcc (for example, 5 V and 3.3). It consists of a resistor Rc connecting V). The voltage detector 25 senses the voltage V1 at the voltage divider 25c, and the voltage V1 has an offset voltage (for example, 2.5V) by the voltage divider 25c. , The detection or detection of the voltage can be made more accurate.

The voltage V1 in FIG. 6 is detected, and the voltage detector 25 includes a voltage divider 25c and software or firmware calculation means.

7 and 8 are operational circuit diagrams of the inverter of FIG. 3.

FIG. 7 shows the flow of current (dashed arrow) when the circuit of FIG. 6 operates in the first operation, and FIG. 8 shows the flow of current (dashed arrow) when the circuit of FIG. 6 operates in the second operation. To show.

Even in the case of FIG. 7 or FIG. 8, software or firmware calculation means such as those described in FIG. 5 must be provided. Since it is practically difficult to use all of the voltage V1 of FIG. 6 as data, the sampled voltage V2 reflecting the voltage V1 is used through a constant sampling time or switching.

In addition, since the voltage Vc 'of FIG. 5 and the voltage V1 of FIG. 6 must reflect the relationship (that is, the divided voltage and the offset voltage) due to the divided resistor 25c, the sampled voltage V2 is divided into the divided voltages. The voltage dividing ratio and / or the offset voltage of the unit 25c may be taken into consideration to calculate the voltage across the capacitor C.

9-11 are graphs of sensed voltages.

9 shows the actual voltage Vc and the voltage V1 of the capacitor C together.

FIG. 10 is an enlarged view of the S region of FIG. 9 and illustrates a process in which the voltage detector 25 samples the voltage V2 from the detected voltage V1 by the PWM signal switching. The voltage V2 is sampled at the sensing position corresponding to the edge. The sampling time (switching time or period) corresponding to this sensing position may be controlled by the control of the control unit 27 or arithmetic means. Since the sampling time is closely related to the amount of data to be processed by the voltage detector 25, the amount of data to be calculated or processed may be adjusted by adjusting the sampling time.

FIG. 11 compares the voltage Vc between the capacitor C and a voltage (final voltage) corresponding to the voltage V2 sampled in FIG. 10. The voltage (final voltage) corresponding to the sampled voltage V2 is a result of estimating the voltage across the capacitor C in consideration of the voltage division ratio and the offset voltage of the voltage divider resistor 25c. As shown in FIG. 11, the voltage (final voltage) calculated and estimated from the voltages across the capacitor C through the control device corresponding to FIGS. 6 to 10 is applied to the voltages Vc across the actual capacitor C. FIG. It can be seen that almost identical, and through this calculation and the estimated voltage, the calculator 26 can calculate the counter electromotive force (EMF).

The above-described motor control apparatus is not only capable of controlling a general BLDC motor and the like, but can also be applied to control of a linear motor of a compressor, in particular, a linear compressor.

The motor control apparatus shown in FIG. 3 may be applied to the linear compressor as shown in FIG. 12.

In the linear compressor according to the present invention, as shown in FIG. 12, an inlet tube 32a and an outlet tube 32b through which refrigerant flows in and out of one side of the sealed container 32 are installed, and a cylinder is formed inside the sealed container 32. The piston 34 is installed to be fixed, and the piston 36 is installed inside the cylinder 34 so as to reciprocate linear movement so as to compress the refrigerant sucked into the compression space P inside the cylinder 34. Various springs are installed to elastically support in the direction of movement of 36, and the piston 36 is installed to be connected to the linear motor 40 generating a linear reciprocating drive force, the natural frequency of the piston (f _n ) is dependent on the load Even if it is variable, the linear motor 40 induces a natural output change that changes the cooling force (output) in accordance with the variable load.

In addition, an intake valve 52 is installed 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.

Here, the airtight container 32 is installed so that the upper and lower shells are coupled to each other so that the inside is sealed, and an inlet tube 32a through which refrigerant is introduced and an outlet tube 32b through which the refrigerant is discharged are installed, and a cylinder ( 34, the piston 36 is installed so as to be elastically supported in the movement direction for reciprocating linear motion, and the linear motors 40 are assembled to each other by the frame 48 outside the cylinder 34 to form an assembly. The assembly is installed to be elastically supported by the support spring 59 on the bottom surface of the sealed container (32).

In addition, a predetermined oil is contained in the bottom surface of the airtight container 32, and an oil supply device 60 for pumping oil is installed at the bottom of the assembly, and oil is supplied to the inside of the lower frame 48 of the assembly. An oil supply pipe 48a is formed to be supplied between the cylinders 34, so that the oil supply device 60 is operated by the vibration generated by the reciprocating linear movement of the piston 36 to pump oil, and The oil is supplied to the gap between the piston 36 and the cylinder 34 along the oil supply pipe 48a to cool and lubricate.

Next, the cylinder 34 is formed in a hollow shape so that the piston 36 can reciprocate linearly, and a compression space P is formed at one side, and one end is located close to the inside of the inlet pipe 32a. It is preferable to be provided on the same straight line as the inflow pipe 32a.

Of course, the cylinder 34 has a piston 36 installed in one end close to the inlet pipe 32a so as to reciprocate linearly, and a discharge valve assembly 54 is installed at one end opposite to the inlet pipe 32a. .

At this time, the discharge valve assembly 54 is a discharge cover 54a is installed to form a predetermined discharge space on one end of the cylinder 34, and the discharge valve is installed to open and close one end of the compression space (P) side of the cylinder ( 54b) and a valve spring 54c, which is a kind of coil spring that imparts an elastic force in the axial direction between the discharge cover 54a and the discharge valve 54b, and has an O-ring R around one end of the cylinder 34. It is installed so that the discharge valve 54a is in close contact with one end of the cylinder (34).

In addition, a curved loop pipe 58 is installed between one side of the discharge cover 54a and the outlet pipe 32b. The loop pipe 58 not only guides the compressed refrigerant to be discharged to the outside. Vibration caused by the interaction of the cylinder 34, the piston 36, and the linear motor 40 buffers the transmission of the entire sealed container 32.

Therefore, when the pressure in the compression space P becomes higher than a predetermined discharge pressure as the piston 36 reciprocates linearly in the cylinder 34, the valve spring 54c is compressed to open the discharge valve 54b. The refrigerant is discharged from the compressed space P, and then completely discharged along the loop pipe 58 and the outlet pipe 32b.

Next, the piston 36 has a refrigerant passage 36a formed at the center so that the refrigerant flowing from the inlet pipe 32a flows, and one end of the piston 36 adjacent to the inlet pipe 32a is connected by the linear motor. 40 is installed to be directly connected, and the suction valve 52 is installed at one end of the inflow pipe 32a in the opposite direction, and is installed to be elastically supported by various springs in the movement direction of the piston 36.

At this time, 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 by a screw to one end of the piston 36a. It is installed as possible.

Therefore, when the piston 36 moves reciprocally linearly in the cylinder 34, when the pressure of the compression space P becomes below a predetermined suction pressure lower than the discharge pressure, the suction valve 52 is opened to compress the refrigerant. When the suction in the space P and the pressure in the compression space P becomes equal to or greater than a predetermined suction pressure, the refrigerant in the compression space P is compressed while the suction valve 52 is closed.

In particular, the piston 36 is installed so as to be elastically supported in the movement direction. Specifically, a piston flange 36b protruding in a radial direction at one end of the piston 36 proximate to the inflow pipe 32a includes a mechanical spring such as a coil spring or the like. The refrigerant is elastically supported in the movement direction of the piston 36 by 38a, 38b, and the refrigerant contained in the compression space P on the opposite side to the inflow pipe 32a acts as a gas spring by its elastic force, thereby causing the piston 36 It will elastically support.

Here, the

mechanical springs

38a and 38b have a constant mechanical spring constant K _m regardless of the load, and the

mechanical springs

38a and 38b are fixed to the linear motor 40 based on the piston flange 36b. Preferably, the predetermined support frame 56 and the cylinder 34 are installed side by side in the axial direction, respectively, the mechanical spring 38a supported by the support frame 56 and the mechanical spring 38a installed in the cylinder 34. ) Is preferably configured to have the same mechanical spring constant (K _m ).

However, the gas spring has a variable gas spring constant (K _g ) depending on the load, the gas contained in the compression space (P) is the elastic force increases as the pressure of the refrigerant increases as the ambient temperature increases The gas spring has a larger gas spring constant K _g as the load increases.

At this time, the mechanical spring constant (K _m ) is constant, while the gas spring constant (K _g ) is variable depending on the load, so the overall spring constant is also variable depending on the load, and the natural frequency (f _n ) of the piston is also the gas It depends on the spring constant K _g .

Therefore, even if the load is variable, the mechanical spring constant (K _m ) and the mass (M) of the piston are constant, whereas the gas spring constant (K _g ) is variable, so the natural frequency (f _n ) of the piston depends on the load. It is greatly affected by the constant K _g .

Of course, this load can be measured in various ways, but since such a linear compressor is configured to be included in a refrigeration / air conditioning cycle in which the refrigerant is compressed, condensed, evaporated, and expanded, the load is the condensing pressure which is the pressure at which the refrigerant is condensed. It can be defined as the difference in the evaporation pressure, which is the pressure at which the refrigerant is evaporated, and further determined in consideration of the average pressure obtained by averaging the condensation pressure and the evaporation pressure to increase accuracy.

That is, the load is calculated to be proportional to the difference between the condensation pressure and the evaporation pressure and the average pressure, and as the load increases, the gas spring constant K _g increases. For example, the load between the condensation pressure and the evaporation pressure increases. increases, even if it is the same difference between the condensing pressure and the evaporation pressure greater the average pressure is calculated so as to increase the load, in response to this load is calculated so as to increase the gas spring constant (K _g). The linear compressor may be provided with a sensor (pressure sensor, temperature sensor, etc.) for calculating the load.

At this time, the load is measured so as to measure the condensation temperature which is substantially proportional to the condensation pressure and the evaporation temperature which is proportional to the evaporation pressure, and is proportional to the difference between the condensation temperature and the evaporation temperature and the average temperature.

Specifically, the mechanical spring constant (K _m ) and the gas spring constant (K _g ) can be determined through various experiments, and the resonance frequency of the piston is increased according to the load by increasing the ratio of the gas spring constant to the total spring constant. It can be varied in a relatively wide range.

The linear motor 40 is configured such that a plurality of laminations 42a are stacked in the 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 wound configured to wind the coils. The outer stator 44 is configured such that a plurality of laminations 44b are laminated in the circumferential direction around the hull 44a and is provided with a predetermined gap with the inner stator 42 outside the cylinder 34 by the frame 48. And a permanent magnet 46 positioned in the gap between the inner stator 42 and the outer stator 44 and installed to be connected by the piston 36 and the connecting member 47, wherein the coil winding body 44a is provided. May be installed to be fixed to the outer side of the inner stator 42.

The linear motor 40 corresponds to one embodiment of the motor 23 described above, and the capacitor C is connected in series to the coil winding 44a.

As described above, the control unit 27 calculates the counter electromotive force, and controls the inverter unit 22 accordingly, wherein an AC voltage having a constant magnitude and frequency is applied to the motor 23 (that is, the linear motor 40). By not only preventing output fluctuations caused by fluctuations in the external power source which may be fluctuating, the reciprocating stroke distance of the piston 36 is automatically adjusted according to the load (for example, low load, heavy load, high load, overload, etc.). In order to cause the above-described natural output change. That is, this natural output change is achieved by causing the reciprocating stroke distance of the piston 36 at low load and the reciprocating stroke distance of the piston 36 at overload to be different from each other. Preferably reciprocating up to TDC). Although the control unit 27 accurately controls the inverter 22 in keeping the magnitude and frequency of the voltage constant, the noise in the inverter 22 or the resistance in the conducting wire between the inverter 22 and the motor 23 or the like. Variations may occur in the magnitude and frequency of the voltage applied to the motor 23 due to various factors such as noise. However, since the magnitude of the voltage fluctuation and the frequency fluctuation, for example, the magnitude of the voltage fluctuates within ± 2% or the frequency fluctuation of the voltage within ± 1% has little effect on the change in natural output, This degree should be considered to be of constant magnitude and frequency. Thus, in the present specification, it is to be understood that the voltage applied to the motor 23 has a substantially constant magnitude and frequency.

In addition, the capacitor C, together with the coil winding 44a, is a component that determines the circuit operating frequency f _c of the motor control device, wherein each of the capacitor C and the coil winding 44a The magnitude should be designed to match the natural frequency f _n at the maximum output (eg, overload) of the linear motor 40 (ie, resonance point design). At this time, the natural frequency f _n is considered to be both the mechanical spring constant (K _m ) and the gas spring constant (K _g ) described above, or to make the mechanical spring constant (K _m ) small and the gas spring constant (K _g ) It is predicted and used in advance such that the influence on the natural frequency f _n is large. This design allows the piston 36 of the linear motor 40 to reciprocate to top dead center (TDC) when a load requiring a maximum output is required, and at a load below this maximum output the linear motor 40 To perform the reciprocating motion in response to the load of the piston 36 of the. That is, the natural output change according to the load is performed.

13 through 16 are cooling capacity graphs of the linear compressor of FIG. 12.

FIG. 13 illustrates a case in which the inverter unit 22 applies an AC voltage having a specific magnitude and frequency to the motor 23 in the linear compressor of FIG. 12. That is, it is a graph of cooling capacity when a certain size and frequency are kept fixed (maintaining a substantially constant size and frequency). The above-described automatic output change (ie, natural cold power variable) can be clearly recognized in the cooling capacity graph shown in FIG. 13. In other words, the cooling capacity graph shows that the cooling capacity is changing according to the load (temperature, ambient temperature, etc.) (i.e., the load of the refrigerator), especially after 40 ° C (e.g., overload area). It can be seen that it has a substantially constant size. In addition, as described above, after 40 ° C., the piston 36 reciprocates to the top dead center TDC, and below that, the piston 36 moves at a reciprocating stroke distance corresponding to the load. With this automatic output change (i.e., variable natural cold power), the cooling capacity by the control device according to the present invention is that an alternating voltage having a constant magnitude and frequency is applied to the linear motor 40 even when the external power source changes. Due to this, as shown in Fig. 13, the graph gradually changes, and the cooling cycle is driven stably. In addition, with the automatic output change and stable cooling cycle, the circuit operating frequency (f _c ) of the motor control device is made to match the natural frequency (f _n ) of the maximum output, thereby performing TDC reciprocation at the maximum output. Thus, the cooling efficiency is maximized.

FIG. 14 is a graph of cooling capacity of the linear compressor of FIG. 12. FIG. 14 is a case where the control unit 27 causes the inverter unit 22 to apply the alternating voltages having at least three characteristics (voltage magnitude or frequency, which are a plurality of different values) to the motor unit 23. That is, the control unit 27 may perform the variable control of the natural cold power corresponding to the graph (line I) indicating the cold power according to the alternating current voltage having an intermediate cold force, and the AC voltage having a magnitude higher than the AC voltage corresponding to the I line. The natural cold power variable control corresponding to the graph (line II) representing the cold power according to the present invention may be performed. In addition, the controller 27 may perform the variable natural cold power control corresponding to the graph (line III) representing the cold power according to the AC voltage having a magnitude lower than the AC voltage corresponding to the I line.

As shown in FIG. 14, the control unit 27 varies and maintains an alternating voltage applied to the motor 23 by the inverter unit 22, and performs a forced cooling force variable control through varying the alternating voltage. By maintaining a constant AC voltage, a natural cold power variable control corresponding to the variable AC voltage is performed. That is, the control unit 27 basically performs the natural cold power variable control, but can perform the forced cold power variable control as required by the cold power. This necessity of cooling power corresponds to the case where forced cooling force variable control is required in response to a load when cooling force above the cooling force that can be achieved by the natural cooling force variable control is required, or a cooling power control command from the user (increasing the cooling force, decreasing the cooling force, etc.) ), For example, a case where a forced cooling force variable control according to (for example, a special cooling command, a low cooling command, etc.) is required.

15 is a graph of cooling capacity of the linear compressor of FIG. 12. FIG. 15 is a case where the natural cold force variable control and the forced cold force variable control are simultaneously or selectively performed by increasing the AC voltages corresponding to the lines I and III of FIG. 14 (line IV).

For example, looking at the progress of the IV line, when the temperature is about 18 ° C. or less, the control unit 27 causes only the natural cooling force variable control to be performed, and at about 18-19 ° C., it is forced to apply an alternating voltage larger than before. Forced cold power variable control is performed to allow the cold power to be increased, and while performing such forced cold power variable control, the natural cold power variable control can be performed simultaneously or selectively. In addition, the controller 27 controls the inverter unit 22 so that the natural cold variable control is performed in a section in which the magnitude and frequency of the increased AC voltage during the forced cold variable control are kept constant, that is, at about 19-27 ° C. Done. That is, the controller 27 performs the natural cold power variable control and the forced cold power variable control according to the necessity of cooling or in response to the load.

FIG. 16 is a graph of cooling capacity of the linear compressor of FIG. 12. In particular, Fig. 16 shows a graph of the cooling capacity of the conventional linear compressor (line VI) (ie, the graph of Fig. 2) and the graph of the cooling capacity of the linear compressor of Fig. 12 together.

As shown, the graph VI line according to the prior art, according to the load, in order to increase the cooling power ratio, only the forced cooling power variable control is possible, so as to increase the AC voltage applied to the motor in sequential steps. Accordingly, since the cold power is varied only by the forced cold power variable control, the forced cold power variable control must be repeatedly performed several times or more.

On the contrary, the graph V line according to the present invention allows only natural cold power variable control to be performed up to a constant cold power ratio (for example, 60%), and forced cold power variable control and natural cold power variable control up to 60-75%. Simultaneously or selectively, the cooling power is increased, and only the natural cold power variable control is performed at the cooling power ratio of 75% or more, so that the required cooling power is achieved. In other words, it is possible to achieve a desired cooling power ratio or cold power while minimizing forced cold power variable control.

17 is a diagram illustrating an example of a cooling system to which the linear compressor of FIG. 3 is applied. The cooling system (or a combined cooling system) includes one outdoor unit 70, a kimchi refrigerator 80 that is a cooling device, a wine cellar 90, and a refrigerator 100, wherein the refrigerant is a refrigerant pipe 110 and a pipe connection ( Through 120, the outdoor unit 70 circulates between the kimchi refrigerator 80, the wine cellar 90, and the refrigerator 100. Here, the cooling device should be understood to include a device for performing cooling and the like, in addition to such a refrigeration and refrigerating device.

The outdoor unit 70 includes an accumulator 71, a linear compressor 72 according to FIG. 12, and a condenser 73 along the flow of the refrigerant. The condenser 73 may further include a fan 74, and the accumulator 71 serves to allow the refrigerant in the gas phase to enter the linear compressor 72. The refrigerant exiting the condenser 73 enters the pipe connection part 120 through the supply refrigerant pipe 111 and passes through the pipe connection part 120 to one of the kimchi refrigerator 80, the wine cellar 90, and the refrigerator 100. Supplied. This supply is controlled by

valves

131, 132, 133. The refrigerant passing through one of the kimchi refrigerator 80, the wine cellar 90, and the refrigerator 100 is recovered to the accumulator 71 through the recovery refrigerant pipe 112 and the pipe connection part 120. The pipe connection part 120 may be actually provided, but may be understood as a virtual space in which the supply refrigerant pipe 111, the recovery refrigerant pipe 112, and / or the

valves

131, 132, and 133 are located, and located on the outdoor unit 70 side. You may. The

valves

131, 132, and 133 may be located at the outdoor unit 70 and / or the refrigerator side according to a control unit (not shown) in charge of the control. The kimchi refrigerator 80, the wine cellar 90, and the refrigerator 100 are respectively connected to the outdoor unit 70 through the supply refrigerant pipe 111 and the recovery refrigerant pipe 112. The kimchi refrigerator 80 includes an evaporator 81, the wine refrigerator 90 includes an evaporator 91 and a fan 92, and the refrigerator 100 includes

evaporators

101A and 101B and

fans

102A and 102B. ). The refrigerator 100 includes a freezing compartment 103 and a refrigerating compartment 104, in which an evaporator 101A is used for freezing the freezer compartment 103 and an evaporator 101B is used for refrigerating the refrigerating compartment 104. In addition, the refrigerator 100 includes a heater 105 in the freezer compartment 103 and a valve 106 for controlling the supply of refrigerant to the freezer compartment 103 and the refrigerating compartment 104 for defrosting. It is apparent to those skilled in the art that the present invention is not limited to a refrigerator equipped with a kimchi refrigerator, a wine refrigerator, a freezer and a refrigerating chamber, provided that refrigeration or freezing is possible without departing from the basic spirit of the present invention. In addition, the kimchi refrigerator 80, the wine cellar 90 and the refrigerator 100 are provided with

temperature sensors

87, 97, 107A and 107B for measuring the temperature. Meanwhile, a control unit (not shown) for controlling the operation of the outdoor unit 70, the kimchi refrigerator 80, the wine cellar 90, and the refrigerator 100, and a cable (not shown) for transmitting and receiving signals therebetween are further included. It is provided. The control unit may be provided in each of the refrigerators and the outdoor unit, and may be provided in any one or at least one of them. Various modifications to the configuration and operation of the control unit can be found in an air conditioning system with one outdoor unit and a plurality of indoor units. The

temperature sensors

87, 97, 107A, and 107B are generally located in a refrigerator, but may be located in an evaporator, or may be located in a refrigerator and an evaporator.

The linear compressor 72 is applied to the linear compressor according to FIGS. 2 and 12 described above, and performs a natural cold power variable control and a forced cold power variable control. In addition, the linear compressor 72 may be composed of a plurality of linear compressors.

Next, the operation of the refrigeration cycle shown in FIG. 18 will be described.

In the case of cooling the freezer compartment 103, the linear compressor 72 is operated, the refrigerant is supplied to the evaporator 101A via the condenser 73, the supply refrigerant pipe 111, the recovery refrigerant pipe 112, and the accumulator. The refrigerant is circulated to the linear compressor 72 via the 71. At this time, the valve 133 is open, the

valves

131 and 132 are closed, and the valve 106 is operated to direct the refrigerant to the evaporator 101A. Fan 107A and fan 74 may also be operated together. When the temperature measured by the temperature sensor 107A becomes equal to or less than the set value (for example, -18 ° C), the supply of the refrigerant to the evaporator 101A is stopped.

In the case of cooling the refrigerating compartment 104, the valve 106 is operated so that the refrigerant is directed to the evaporator 101B, and when the temperature measured by the temperature sensor 107B is below a set value (e.g., 3 ° C), The refrigerant supply to the evaporator 101B is stopped.

In the case of cooling the refrigerator 100, according to the temperature (i.e., load) measured by the

temperature sensors

107A and 107B, the linear compressor 72 controls the natural cold power to control the cooling force corresponding to the load. To be fulfilled.

This is the case where the refrigerator, kimchi refrigerator 90, wine refrigerator 80, respectively, cooling is required, the linear compressor 72 can supply the required cooling power only by the natural cold power variable control.

Cooling of each refrigerator may be sequentially performed as described above, but when cooling for a plurality of refrigerators is required (that is, when a significantly higher cooling power is required compared to previously required cooling power) (that is, when the variation in the cooling power is large ), When the temperature in the chamber measured by the

temperature sensors

87, 97, 107A, and 107B is equal to or higher than a set value, the linear compressor 72 is a cooling controller (e.g., a controller of a refrigerator, Main control unit or the like) or a cooling control command from the cooling control device that manages the entire cooling system to perform forced cooling force variable control to achieve a cooling force that cannot be achieved by natural cooling variable control.

The control unit 150 operates in conjunction with the linear compressor 72, the fan 74, the

temperature sensors

87, 97, 107A and 107B, the fans 32, 42A and 42B, and the

valves

106, 131, 132 and 133 to operate the cooling system. The control unit 150 receives a cooling control command by operating a user's button 152 (for example, a special cooling command, a low cooling command, etc.) (that is, an input means) or responds to a sensed temperature from a temperature sensor. A cooling control command can be generated and sent to the linear compressor 72.

The control unit 150 may correspond to a cooling control device provided in each of the

refrigerators

80, 90, and 100 of FIG. 18, and independently communicates with the linear compressor 72 to transmit a cooling control command. It may be a device.

In the above, the present invention has been described in detail based on the embodiments of the present invention and the accompanying drawings. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention should be limited only by the contents described in the claims below.

Claims

A compression space into which the refrigerant is sucked;

A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly;

At least one spring installed to elastically support the movable member in the movement direction of the movable member;

A motor unit including a motor and a capacitor connected in series with the motor for reciprocating linear movement of the movable member;

And a motor controller configured to perform a variable natural cooling force by reciprocating motion of the movable member in response to the load.
The linear compressor according to claim 1, wherein the motor control unit maintains a substantially constant magnitude and frequency of the voltage applied to the motor unit to perform natural cooling force variation.
A compression space into which the refrigerant is sucked;

A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly;

At least one spring installed to elastically support the movable member in the movement direction of the movable member;

A motor unit including a motor and a capacitor connected in series with the motor for reciprocating linear movement of the movable member;

In response to the refrigerant change, the stroke of the movable member is variable, the linear compressor, characterized in that consisting of a motor control unit for performing a variable natural cooling power.
4. The linear compressor according to claim 3, wherein the motor control unit maintains a substantially constant magnitude and frequency of the voltage applied to the motor unit, thereby performing a natural cooling force variable.
The linear compressor of claim 3, wherein the motor controller senses a voltage corresponding to a commercial power applied from the outside or a power applied to the motor, and controls the motor based on the detected voltage.
The linear compressor according to any one of claims 1 to 5, wherein the motor control unit changes the magnitude or frequency of the voltage applied to the motor unit to perform the forced cooling force variation.
The method according to claim 6, wherein the motor control unit changes the magnitude or frequency of the voltage applied to the motor unit to a plurality of values to perform forced cooling force variation, and then maintains the magnitude or frequency of the variable voltage constant to maintain the alternating current. A linear compressor characterized by applying a voltage to the motor unit to perform a natural cold power variable.
The linear compressor according to claim 6, wherein the motor control unit varies the magnitude or frequency of the voltage in response to the cooling force variable command from the cooling control device.
The motor control unit of claim 6, wherein the motor control unit is provided with a rectifying unit for receiving an AC power and outputting the DC voltage, an inverter unit receiving the DC voltage, converting the AC voltage according to a control signal, and providing the motor unit to the motor unit, and being applied to the inverter unit. A first voltage detector for sensing a voltage, a second voltage detector for detecting a voltage corresponding to the voltage across the capacitor, or a voltage between the capacitor and the ground, a first voltage from the first voltage detector, and a second voltage detector And a control unit configured to receive the second voltage and generate a control signal corresponding to the first and second voltages, and to generate a control signal to maintain the magnitude and frequency of the AC voltage substantially constant. Linear compressor.
10. The linear compressor of claim 9, wherein the controller adjusts a sampling time of the second voltage detector for detecting the second voltage.
The linear compressor of claim 9, wherein the controller calculates back EMF corresponding to the first and second voltages, and generates a control signal according to the calculated back EMF.
At least one cooling device;

It is connected to supply a coolant to the cooling device, and performs the natural cold power variable control to naturally vary the cold power in response to the load, and the forced cold variable control to forcibly vary the cold power in response to the load or cooling control command, A compressor for supplying a cooling device; And

And a refrigerant pipe connecting the cooling device and the compressor.
13. The cooling system of claim 12, wherein the compressor selectively performs natural cold variable control and forced cold variable control.
The cooling apparatus of claim 12, wherein the cooling apparatus receives an input of a cooling control command from a user, or generates and transmits a cooling control command to a compressor in response to a cooling need for a cooling space provided in the cooling apparatus. system.
The compressor according to any one of claims 12 to 14, wherein the compressor includes a compression space in which the refrigerant is sucked, a movable member for compressing the refrigerant sucked into the compression space while reciprocating linearly moving, and the movable member in the direction of movement of the movable member. Maintaining a substantially constant magnitude and frequency of a voltage applied to the motor portion, the motor portion including at least one spring provided to elastically support, and a motor, a capacitor connected in series with the motor, for reciprocating linear movement of the movable member. And a motor control unit configured to perform the variable control of the natural cold force and to perform the forced cold variable control by varying the magnitude or frequency of the applied voltage.
At least one cooling device;

A compressor which is connected to supply a coolant to the cooling device and performs only natural cold power variable control for naturally varying cold power in response to a load, thereby supplying the coolant to the cooling device;

And a refrigerant pipe connecting the cooling device and the compressor.
17. The compressor of claim 16, wherein the compressor comprises: a compression space into which the refrigerant is sucked, a movable member for compressing the refrigerant sucked into the compression space while reciprocating linearly, and at least one spring provided to elastically support the movable member in the direction of movement of the movable member. And, in order to reciprocally linearly move the movable member, a natural cold power variable control is performed by maintaining a substantially constant magnitude and frequency of a voltage applied to the motor, a motor part including a capacitor connected in series with the motor, and a voltage applied to the motor part. Cooling system comprising a motor control unit.
18. The cooling system according to claim 17, wherein the motor control unit maintains a substantially constant magnitude and frequency of the voltage applied to the motor unit, thereby performing a natural cooling force variable.
The cooling system of claim 18, wherein the motor controller detects a voltage corresponding to a commercial power applied from the outside or a power applied to the motor, and controls the motor based on the detected voltage.