KR101665695B1 - Linear compressor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear compressor, and more particularly, to a linear compressor capable of changing natural cooling power while removing a capacitor connected to a motor.

The linear compressor according to the present invention includes a fixed member including a compression space therein, a movable member for compressing the refrigerant sucked into the compression space while linearly reciprocating in the fixed member, and a movable member installed to elastically support the movable member in the direction of motion of the movable member At least one spring, a motor which is provided so as to be connected to the movable member so as to linearly reciprocate the movable member in the axial direction, an AC voltage applied to the motor so that the stroke of the movable member and the magnitude of the AC voltage applied to the motor are proportional, And a motor control unit for performing the cooling power change by the reciprocating motion of the movable member in response to the load.

Description

[0001] LINEAR COMPRESSOR [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear compressor, and more particularly, to a linear compressor capable of changing natural cooling power while removing a capacitor connected to a motor.

Generally, a motor is also provided with a compressor, which is a mechanical device that receives power from an electric motor or a power generating device such as an electric turbine and compresses air, refrigerant or various other operating gases to increase the pressure, Or widely used throughout the industry.

Particularly, when such a compressor is broadly classified, a reciprocating compressor (hereinafter, referred to as " compressor ") which compresses the refrigerant while linearly reciprocating the piston inside the cylinder is formed so as to form a compression space in which a working gas is sucked and discharged between the piston and the cylinder A rotary compressor for compressing the refrigerant while eccentrically rotating the roller along the inner wall of the cylinder so as to form a compression space in which a working gas is sucked and discharged between a roller and a cylinder, A scroll compressor for compressing a refrigerant while rotating the orbiting scroll along a fixed scroll so that a compression space in which an operating gas is sucked and discharged is formed between an orbiting scroll and a fixed scroll, ).

In recent years, among the reciprocating compressors, in particular, the piston is directly connected to the driving motor which reciprocates linearly, so that there is no mechanical loss due to the switching of the motion.

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

As shown in FIG. 1, the motor control apparatus includes a rectifying section including a diode bridge 11 for receiving and rectifying AC power as a commercial power supply, a capacitor C1 for smoothing the rectified voltage, An inverter 12 for converting the AC voltage into an AC voltage in accordance with a control signal from the control unit 17 and providing it to the motor unit, a motor 13, and a motor C2 including a capacitor C2 connected in series to the motor 13. [ A current detection unit 15 for detecting a current flowing in the motor unit; a detection voltage from the voltage detection unit 14; a current detection unit 15 for detecting the voltage across the capacitor C1; A control unit 17 for generating a control signal by reflecting the smoke power from the arithmetic unit 16 and the sense current from the current detection unit 15; ).

The prior art linear compressor of Fig. 1 requires a cost and space for providing this capacitor C2 to the linear compressor due to the capacitor C2 connected in series to the motor 13. [ In the prior art, it is not easy to change the capacity of the capacitor C2, and a plurality of capacitors are provided to selectively connect the capacitors C2, Is also costly, space - and design - complicated.

Fig. 2 is a graph of change in input voltage and stroke of the motor in Fig. 1. Fig. In the conventional linear compressor, when the capacitor C2 is simply removed, as shown in Fig. 2, at a larger stroke, i.e., in a region close to the TDC, the voltage applied to the motor decreases (Jump phenomenon) occurs, and the under-stroke operation becomes impossible. In the graph of FIG. 2, the closer to 0.00, the closer to TDC.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a linear compressor capable of controlling variable cooling power while removing a capacitor connected to a motor of a linear compressor.

Another object of the present invention is to provide a linear compressor capable of adjusting the natural cooling force variable rate according to the load capacity.

It is another object of the present invention to provide a linear compressor that prevents a stroke jump phenomenon during control of the linear compressor.

The linear compressor according to the present invention includes a fixed member including a compression space therein, a movable member for compressing the refrigerant sucked into the compression space while linearly reciprocating in the fixed member, and a movable member installed to elastically support the movable member in the direction of motion of the movable member At least one spring, a motor which is provided so as to be connected to the movable member so as to linearly reciprocate the movable member in the axial direction, an AC voltage applied to the motor so that the stroke of the movable member and the magnitude of the AC voltage applied to the motor are proportional, The motor control unit includes a rectifying unit that receives the AC power and outputs the AC power as a DC voltage, and a control unit that receives the DC voltage and outputs the DC power according to a control signal An inverter unit for converting the AC voltage into an AC voltage and providing it to the motor, (1 / Cr) by multiplying the integrated value by a constant (1 / Cr), integrating the current from the current sensing unit, calculating an attenuation voltage, and outputting an alternating current corresponding to the difference between the set voltage and the attenuation voltage And a control section for generating a control signal for generating a voltage and applying the control signal to the inverter section. The constant (1 / Cr) is variable.

Further, the stroke of the movable member and the magnitude of the alternating-current voltage applied to the motor are at least proportional to the region close to the top dead center of the movable member.

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Further, the variable rate of the cooling power of the compressor is varied by the variation of the constant (1 / Cr).

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The present invention is capable of controlling the variable cooling power while removing the capacitor connected to the motor of the linear compressor, thereby reducing the spatial part and the costly part of the compressor.

Further, according to the present invention, there is an effect that the natural cooling force variable rate can be adjusted according to the load capacity, so that the adjustment can be made more simply and swiftly.

Further, the present invention has the effect of preventing the stroke jump phenomenon during the control of the linear compressor.

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

FIG. 3 is a control block diagram of the linear compressor according to the present invention, and FIG. 4 is a control block diagram of the control block of FIG.

As shown in FIG. 3, the control structure of the linear compressor includes a rectifying section 21 for receiving and rectifying and smoothing the AC power supplied from a commercial power source, A motor 23 including the coil L and a coil L in the motor 23 and the inverter 22 or the motor 23, (Vmotor) to be applied to the motor 23 on the basis of the sensing current from the current sensing unit 24, and outputs the motor-applied voltage Vmotor to the inverter 23. [ A control unit 25 for generating and applying a corresponding control signal to the rectifying unit 22 and a voltage sensing unit 26 for sensing the magnitude of the direct current voltage from the rectifying unit 21. [ However, in the present control configuration, the configuration for supplying the voltage necessary for the control section 25, the current sensing section 24, the voltage sensing section 26, etc. is not limited to a technical configuration applicable to a person familiar with the technical field to which the present invention belongs. The description thereof is omitted.

The rectifying unit 21 includes a diode bridge performing a general rectifying function, a capacitor for smoothing the rectified voltage, and the like.

The inverter unit 22 is a means for receiving the DC voltage and generating and applying the AC voltage to the motor 23. The IGBT element is a switching element and the IGBT element is a switching element for turning on and off the IGBT element in accordance with a control signal from the controller 25. [ And a gate control unit for turning off the power supply. The inverter unit 22 is only a degree that is familiar to those skilled in the art to which the present invention pertains, and therefore the description thereof is omitted.

The motor 23 has a coil L similar to a motor in other mechanical configurations, but does not include a capacitor unlike the prior art.

The current sensing unit 24 senses a current flowing in the wire between the inverter unit 22 and the motor 23 or senses a current flowing in the coil L of the motor 23.

The voltage sensing unit 26 is a device that senses a DC voltage output from the rectifying unit 21. [ At this time, the voltage sensing unit 26 may sense the entire DC voltage or the DC voltage reduced at a certain rate.

The control unit 25 generates a control signal for receiving a start command of the linear compressor from the outside or applying a preset applied voltage Vin to the motor 23 when the AC commercial power is applied to the inverter 23, 22). Thus, the inverter section 22 generates an AC voltage corresponding to the applied voltage Vin and applies the generated AC voltage to the motor 23.

By the application of the AC voltage, the current sensing unit 24 senses the current i from the inverter unit 22 to the motor 23 or the current i flowing through the coil L of the motor 23.

The control unit 25 receives the current (i) from the current sensing unit 24 and performs a process as shown in FIG.

The control unit 25 includes an integrator 25a for integrating the current i from the current sensing unit 24 and an attenuator 25b for multiplying the integrated value by a constant 1 / Cr to calculate the attenuation voltage Vc, And an operation unit 25c for calculating the difference between the set applied voltage Vin and the attenuation voltage Vc. The applied voltage Vin in this embodiment corresponds to the voltage applied by the inverter in the compressor of the prior art and is fixed or variable according to the control algorithm of the linear compressor.

The integrator 25a and the attenuator 25b correspond to the attenuation calculation unit for attenuating the influence of the inductance by the coil L of the motor by using the current i flowing through the motor 23. [ That is, in this embodiment, since there is no capacitor connected to the coil L of the motor 23, the influence of the inductance by the coil L is controlled by controlling the motor applied voltage Vmotor applied to the motor 23 will be.

The constant 1 / Cr in the attenuator 25b can be fixed or variable depending on the size of the coil L of the motor 23. [ For example, when the LC resonance frequency is set to correspond to the mechanical resonance frequency of the compressor, the constant (1 / Cr) may be determined accordingly. Alternatively, even when the mechanical resonance frequency of the compressor is set higher or lower, the constant (1 / Cr) may be determined accordingly.

Thus, after the motor application voltage Vmotor is calculated, the control unit 25 generates a control signal for causing the inverter unit 22 to apply the calculated motor application voltage Vmotor to the motor 23, (22). That is, the control unit 25 allows the sensed current i to be fed back to the motor application voltage Vmotor so that the operation of the motor 23 can be controlled even when the capacitor is not connected to the motor 23 . In the present invention, the counter electromotive force is reflected in the current (i) and fed back, so that it is not necessary to consider it separately. The control unit 25 sets the motor application voltage Vmotor to the attenuation voltage obtained by integrating the initial voltage application voltage Vin and the current based on the applied motor application voltage Vmotor ) Or a second attenuation voltage by a motor-applied voltage (Vmotor) which is firstly estimated, and the like.

As the load increases, the motor-applied voltage Vmotor, which is a required voltage, increases. In the present invention, when the motor-applied voltage Vmotor (that is, the maximum value), which is a required voltage, is smaller than the DC voltage Vdc, it is determined as a low load or a heavy load. In the case of such a low load or a heavy load, the inverter section 22 applies an alternating voltage (motor-applied voltage Vmotor) having a magnitude within the direct-current voltage Vdc to the motor 23. Accordingly, the controller 25 adjusts the magnitude of the AC voltage applied from the inverter 22 to the motor 23 so that the required cooling power can be maintained.

In addition, the control unit 25 may achieve the high cooling power required by varying the frequency of the motor-applied voltage (Vmotor) from the inverter unit 22, for example, by increasing the frequency at a high load.

5 is a configuration diagram of a linear compressor according to the present invention. 5, an inlet pipe 32a and an outlet pipe 32b, through which refrigerant flows in and out of the sealed container 32, are installed. In the linear compressor of the present invention, A piston 36 is installed inside the cylinder 34 so as to reciprocate linearly so that the refrigerant sucked into the compression space P in the cylinder 34 can be compressed and the piston 34 The piston 36 is connected to the linear motor 40 for generating a linear reciprocating driving force. The piston 36 is connected to the linear motor 40 so that the natural frequency f _n of the piston depends on the load The linear motor 40 induces a natural output change that changes the cooling power (output) in accordance with the variable load.

A suction 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 suction valve 52 and the discharge valve assembly 54 are automatically adjusted to be opened or closed in accordance with the pressure inside the compression space P, respectively.

Here, the closed container 32 is provided so that the upper and lower shells are coupled to each other so as to close the inside of the closed container 32. An inlet pipe 32a through which the refrigerant flows into one side and an outlet pipe 32b through which the refrigerant flows out are provided. The linear motor 40 is assembled to the outside of the cylinder 34 by the frame 48 so as to constitute an assembly. So that the assembly is resiliently supported by the support springs 59 on the inner bottom surface of the closed container 32.

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

Next, the cylinder 34 is formed in a hollow shape so that the piston 36 can linearly reciprocate, and a compression space P is formed on one side. In the state where one end is located close to the inside of the inflow pipe 32a And it is preferably provided on the same straight line as the inflow pipe 32a.

Of course, in the cylinder 34, the piston 36 is reciprocally linearly movable in one end close to the inflow pipe 32a, and the discharge valve assembly 54 is installed at one end of the cylinder 34 opposite to the inflow pipe 32a .

The discharge valve assembly 54 includes a discharge cover 54a provided at one end of the cylinder 34 so as to form a predetermined discharge space and a discharge valve 54a provided to open and close one end of the cylinder in the compression space P And a valve spring 54c which is a kind of coil spring that applies an elastic force in the axial direction between the discharge cover 54a and the discharge valve 54b. So that the discharge valve 54a is brought into close contact with one end of the cylinder 34. [

A loop pipe 58 formed to bend is connected between one side of the discharge cover 54a and the outflow pipe 32b. The loop pipe 58 guides the compressed refrigerant to be discharged to the outside The vibrations due to the interaction of the cylinder 34, the piston 36 and the linear motor 40 are buffered in the entire hermetic container 32.

When the pressure in the compression space P becomes equal to or 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 And the refrigerant is discharged from the compression space P and then completely discharged to the outside along the loop pipe 58 and the outlet pipe 32b.

Next, the refrigerant passage 36a is formed at the center of the piston 36 so that the refrigerant introduced from the inlet pipe 32a can flow. One end of the piston 36 near the inlet pipe 32a is connected to the linear motor And a suction valve 52 is installed at one end of the inlet pipe 32a opposite to the inlet pipe 32a so as to be elastically supported by various springs in the direction of movement of the piston 36. [

At this time, the suction valve 52 is formed in a thin plate shape so that a central portion of the suction valve 52 is partially cut so as to open and close the refrigerant passage 36a of the piston 36. One end of the suction valve 52 is screwed to one end of the piston 36a As shown in FIG.

Accordingly, when the pressure in the compression space P becomes equal to or lower than a predetermined suction pressure lower than the discharge pressure as the piston 36 reciprocates linearly in the cylinder 34, the suction valve 52 is opened, The refrigerant in the compression space P is compressed when the suction valve 52 is closed when the pressure in the compression space P becomes equal to or higher than the predetermined suction pressure.

Particularly, the piston 36 is installed to be elastically supported in the direction of movement. Specifically, a piston flange 36b protruding radially from one end of the piston 36 close to the inflow pipe 32a is connected to a mechanical spring 38a and 38b so that the refrigerant contained in the compression space P opposite to the inlet pipe 32a acts as a gas spring due to the self- .

Here, the mechanical springs (38a, 38b) will be of a constant mechanical spring constant (K _m), regardless of the load, the mechanical spring (38a, 38b) is fixed to the linear motor (40) relative to the piston flange (36b) The mechanical spring 38a supported by the support frame 56 and the mechanical springs 38a provided on the cylinder 34 are preferably arranged parallel to the predetermined support frame 56 and the cylinder 34 in the axial direction, ) Are preferably configured to have the same mechanical spring constant (K _m ).

However, the gas spring is the to be of a varying gas spring constant (K _g), the gas contained in the compression space (P) is the higher the ambient temperature, self-elasticity depending on the pressure of the refrigerant increases, becomes larger depending on the load The gas spring constant (K _g ) increases as the load increases.

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

Therefore, even if the load is variable mechanical spring constant (K _m) and the mass (M) of the piston it has a natural frequency of a constant, while the piston since the gas spring constant (K _g) variable (f _n) is dependent on the load a gas spring Which is greatly affected by the constant (K _g ).

Of course, this load can be measured in a variety of 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 condensation pressure It can be defined as the difference in evaporation pressure, which is the pressure at which the refrigerant is evaporated. Further, it is determined in consideration of the average pressure that the condensation pressure and the evaporation pressure are averaged to increase the accuracy.

In other words, the load is above is calculated to be proportional to the condensing pressure and the car and the average pressure of the evaporation pressure, the larger the load there is be a gas spring constant (K _g) is larger, the larger the difference between the condensing pressure and the evaporation pressure as an example the load 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 have a sensor (pressure sensor, temperature sensor, etc.) for calculating the load.

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

More specifically, the mechanical spring constant (K _m ) and the gas spring constant (K _g ) can be determined through various experiments. The ratio of the gas spring constant to the total spring constant is increased so that the resonance frequency of the piston And can be varied over a relatively wide range.

The linear motor 40 includes an inner stator 42 configured to laminate a plurality of laminations 42a in the circumferential direction and to be fixed to the outside of the cylinder 34 by a frame 48, An outer stator 44 which is formed by surrounding a plurality of laminations 44b in the circumferential direction around the hull 44a and is disposed outside the cylinder 34 by a frame 48 with a predetermined clearance from the inner stator 42, And a permanent magnet 46 which is disposed in the gap between the inner stator 42 and the outer stator 44 so as to be connected by the piston 36 and the connecting member 47. The coil winding body 44a, May be fixed to the outside of the inner stator 42.

The linear motor 40 corresponds to one embodiment of the motor 23 described above.

Fig. 6 is a graph showing the conversion of the input voltage and the stroke of the motor in the linear compressor according to the present invention.

As shown in Fig. 6, in the linear compressor according to the present invention, even if the piston 36 approaches the top dead center, the input voltage of the motor rises, causing no stroke jump phenomenon. Accordingly, the linear compressor according to the present invention can perform the cooling power change in a stable state. That is, the control unit 25 controls the AC voltage applied to the motor 23 so that the stroke of the piston 36 as the movable member and the magnitude of the AC voltage applied to the motor 23 are proportional to each other, So that it is possible to perform the natural cooling power change by the reciprocating motion of the motor 36.

 In particular, the stroke of the piston 36 and the magnitude of the alternating voltage applied to the motor 36 are proportional at least in the region close to the top dead center of the movable member, thereby preventing a stroke jump.

FIG. 7 is a graph of change in cooling power and load in the linear compressor according to the present invention.

The control unit 25 stores a variable constant (1 / Cr). As shown in Fig. 7, in the case of Cr (10 kPa), it is confirmed that the cooling power of the linear compressor is variable in accordance with the load.

It can be seen that as the value of Cr (1 / Cr) varies, the cooling power variation rate changes as shown in Fig.

Accordingly, the control unit 25 according to the present invention can adjust the cooling power variable rate by varying the constant (1 / Cr) (or Cr).

As Cr is varied, the difference in phase between the motor-applied voltage (Vmotor) and the current (i) decreases at a low load, so that more cooling can be exerted under the same load. That is, the LC resonance frequency is determined by the value of Cr, and the phases of the motor-applied voltage (Vmotor) and the current (i) at a constant load are determined. If Cr is changed at this time, The phase of the current i is changed, and the total power is different. Soon, the cooling power becomes larger or smaller, so that the natural cooling power variable rate becomes different.

8 is voltage graphs of a linear compressor according to the present invention. As shown in the figure, the actual motor-applied voltage Vmotor is calculated by subtracting the decaying voltage Vc calculated from the applied voltage Vin from the current i, L, the voltage applied to the motor in the circuit in which the capacitors are connected in series, so that the linear compressor can be controlled to vary the cooling power.

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 content of the following claims.

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

Fig. 2 is a graph of change in input voltage and stroke of the motor in Fig. 1. Fig.

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

4 is a control example of the control unit of Fig.

5 is a configuration diagram of a linear compressor according to the present invention.

Fig. 6 is a graph showing the conversion of the input voltage and the stroke of the motor in the linear compressor according to the present invention.

FIG. 7 is a graph of change in cooling power and load in the linear compressor according to the present invention.

8 is voltage graphs of a linear compressor according to the present invention.

Claims (9)

A fixing member having a compression space therein; A movable member that compresses the refrigerant sucked into the compression space while linearly reciprocating in the fixing member; At least one spring installed to elastically support the movable member in the direction of motion of the movable member; A motor installed to be connected to the movable member and linearly reciprocating the movable member in the axial direction; And a motor control unit for controlling the AC voltage applied to the motor so that the stroke of the movable member and the magnitude of the AC voltage applied to the motor are proportional to each other to perform the cooling power change by the reciprocating motion of the movable member in response to the load , The motor control unit includes a rectifying unit for receiving the AC power and outputting it as a DC voltage, an inverter unit for receiving a DC voltage and converting the AC voltage into an AC voltage according to a control signal to provide the AC voltage to the motor, A control unit that integrates the current from the current sensing unit and calculates an attenuation voltage by multiplying the integrated value by a constant (1 / Cr), and generates an AC voltage corresponding to the difference between the set voltage and the attenuation voltage And a control section for generating a signal and applying it to the inverter section, wherein the constant (1 / Cr) is variable. The method according to claim 1, The stroke of the movable member and the magnitude of the alternating voltage applied to the motor are proportional to at least a region close to the top dead center of the movable member. delete delete The method according to claim 1, Wherein the set voltage is variable. The method according to claim 1, Wherein a variation of the set voltage and a constant (1 / Cr) varies the cooling power variation rate of the compressor. The method according to claim 1, And the control unit compares the difference between the set voltage and the decay voltage with the DC voltage to determine the load. 8. The method of claim 7, When the difference between the set voltage and the attenuation voltage is smaller than the DC voltage, the control unit determines that the load is a low load or a heavy load. The method according to claim 1, Wherein the control unit varies the frequency of the AC voltage corresponding to the difference between the set voltage and the attenuation voltage.

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