KR100690153B1 - Linear compressor - Google Patents

Abstract

The present invention synchronizes the operating frequency of the linear motor with the natural frequency of the movable member that varies depending on the load, and simultaneously changes the stroke of the movable member depending on the load, thereby quickly eliminating the load and increasing the compression efficiency. It relates to a linear compressor that can be. 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 reciprocating linearly in the axial direction within the fixed member, and the movable member is connected to the movable member. At least one or more springs installed to elastically support in the movement direction and varying a spring constant depending on a load, and connected to the movable member to reciprocally linearly move the movable member in the axial direction, and move the movable member according to a predetermined cooling force. The stroke of the member is variable, but the movable member is made of a linear motor to perform a reciprocating linear motion to the top dead center.

Description

Linear Compressor {LINEAR COMPRESSOR}

The present invention synchronizes the operating frequency of the linear motor with the natural frequency of the movable member which is variable depending on the load, and simultaneously / separately varies the stroke of the movable member depending on the load, thereby quickly eliminating the load and compressing the load. The present invention relates to a linear compressor capable of increasing efficiency.

In general, a compressor is a mechanical device that increases pressure by receiving power from a power generator such as an electric motor or a turbine to compress air, refrigerant, or various other working gases. It is widely used throughout.

These compressors are classified into a reciprocating compressor which compresses the refrigerant while linearly reciprocating the inside of the cylinder by forming a compression space in which the working gas is absorbed and discharged between the piston and the cylinder. And a rotary compressor for compressing the refrigerant while the roller is eccentrically rotated along the inner wall of the cylinder to form a compression space in which the working gas is sucked and discharged between the eccentrically rotating roller and the cylinder. As a scroll compressor that compresses the refrigerant while the rotating scroll rotates along the fixed scroll to form a compression space in which the working gas is absorbed and discharged between the orbiting scroll and the fixed scroll. Divided.

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.

In general, a linear compressor sucks, compresses, and discharges a refrigerant by using a linear driving force of a motor. A compression unit including a cylinder and a piston for compressing a refrigerant gas is large, and a linear motor supplying driving force to the compression unit. It is divided into included driving parts.

Specifically, the linear compressor is installed so that the cylinder is fixed inside the sealed container, the piston is installed in the cylinder to reciprocate linear movement, the compression space in the cylinder as the piston reciprocating linear movement in the cylinder It is configured to compress and then discharge the refrigerant into the inlet, the inlet and outlet valve assembly is installed in the compression space to adjust the inflow and discharge of the refrigerant in accordance with the pressure in the compression space.

In addition, the linear motor for generating a linear motion force to the piston is installed so as to be connected to each other, the linear motor is provided with an inner stator and an outer stator configured to be laminated in a circumferential direction around the cylinder with a predetermined gap, The coil is wound around the inner stator or the outer stator, and a permanent magnet is installed in the gap between the inner stator and the outer stator so as to be connected to the piston.

At this time, the permanent magnet is installed to be movable in the direction of movement of the piston, and the reciprocating linear motion in the direction of movement of the piston by the electromagnetic force generated as the current flows in the coil, the linear motor is a constant operation Not only is it operated at frequency f _c , but it also causes the piston to reciprocate linearly with a predetermined stroke S.

On the other hand, the piston is provided with a variety of springs to be elastically supported in the direction of movement even if the linear motor reciprocating linear movement, specifically, a coil spring which is a kind of mechanical spring to the closed container and the cylinder in the direction of movement of the piston It is installed to be elastically supported, and the refrigerant sucked into the compression space also acts as a gas spring.

At this time, the coil spring has a constant mechanical spring constant (K _m ), the gas spring has a gas spring constant (K _g ) that is variable according to the load, the mechanical spring constant (K _m ) and gas spring constant (K Taking into account _g ), the natural frequency f _n of the piston (or linear compressor) is calculated.

The calculated natural frequency f _n of the piston determines the operating frequency f _{c of} the linear motor, and the linear motor matches the operating frequency f _c with the natural frequency f _n of the piston. In other words, the efficiency can be increased by operating in the resonance state.

Therefore, in the linear compressor configured as described above, when a current is applied to the linear motor, an electromagnetic force is generated by interacting with the outer stator and the inner stator as a current flows in the coil, and the permanent magnet and The piston connected to this causes the reciprocating linear motion.

At this time, the linear motor operates at a constant operating frequency f _c , and the operating frequency f _c of the linear motor coincides with the natural frequency f _n of the piston to operate in a resonance state to maximize efficiency. Can be.

As such, the pressure inside the compression space is changed as the piston reciprocates linearly in the cylinder, and the refrigerant is sucked into the compression space according to the pressure change of the compression space, and then compressed and discharged.

The linear compressor configured as described above has a natural frequency f _n of the piston which is calculated by the mechanical spring constant K _m of the coil spring and the gas spring constant K _g of the gas spring under the load considered by the linear motor in design. Since the linear motor is configured to operate at an operating frequency f _c corresponding to the linear motor operates in a resonance state only under the load considered in the design, the efficiency can be increased.

However, in the linear compressor as described above, as the actual load varies, the gas spring constant K _g of the gas spring and the natural frequency f _n of the piston calculated by considering the same change.

Specifically, in the linear motor, as shown in FIG. 1A, the operating frequency f _c is determined to match the natural frequency f _n of the piston in the middle load region during design, and the constant constant determined as described above even if the load is variable. Although operated at an operating frequency f _c , the natural frequency f _n of the piston increases as the load increases.

Equation 1

Where f _n is the natural frequency of the piston, K _m and K _g are the mechanical spring constant and the gas spring constant, and M is the mass of the piston.

In general, the gas spring constant (K _g ) is small because the ratio of the gas spring constant (K _g ) to the total spring constant (K _T ) at the time of design is not considered or the gas spring constant (K _g ) is set to a constant value. In addition, since the mass (M) and the mechanical spring constant (K _m ) of the piston also has a constant value, the natural frequency (f _n ) of the piston is also calculated as a constant value depending on Equation (1).

In practice, however, the more the load increases, the pressure and temperature of the coolant increases in a limited space, which results the elastic force of the gas spring itself increases the gas spring constant (K _g) is large, and yield to be proportional to such a gas spring constant (K _g) The natural frequency f _n of the piston is also increased.

Therefore, as shown in FIGS. 1A and 1B, the piston operates in such a way as to reach the top dead center because the operating frequency f _c of the linear motor and the natural frequency f _n of the piston coincide in the intermediate load region. The compression operation is performed, and the operation is performed in a resonance state, thereby maximizing the efficiency of the compressor.

However, in the low load region, the piston's natural frequency (f _n ) is smaller than the operating frequency (f _c ) of the linear motor, so that the piston is excessively moved above the top dead center, so that the excessive compression force is applied as well as the piston and the cylinder. Friction and abrasion occurs, and the compressor efficiency is lowered because it is not operated in a resonance state.

Similarly, in the high load region, the piston's natural frequency f _n is greater than the operating frequency f _c of the linear motor, so that the piston is operated to fall below the top dead center, so that the compression force is lowered and the compressor is not operated in a resonance state. Inefficient

As a result, in the conventional linear compressor, the natural frequency f _n of the piston is variable as the load is varied, whereas the linear motor is not operated in a resonance state because the operating frequency f _{c of} the linear motor is constant. There is a problem in that the efficiency is lowered and the load cannot be released quickly due to the failure to actively respond to the load.

On the other hand, the conventional linear compressor adjusts the magnitude of the voltage (or current) input to the linear motor in order to quickly eliminate the load, so that the piston 6 is inside the cylinder 4 as shown in FIGS. 2A and 2B. In the high cooling power mode or low cooling power mode to be operated, the stroke (S) of the piston in accordance with each operation mode is to vary the compression capacity.

As shown in FIG. 2A, voltage V1 is for high cold power mode and voltage V2 is for low cold power mode. When these voltages V1 and V2 have a positive value with respect to zero, a compression stroke is made, and when they have a negative value, a suction stroke is made. Here, the peak values of voltages V1 and V2 should be below the maximum voltage limit V _{p that} can be output from the linear compressor.

Since the peak-peak value of the voltage is a factor in determining the stroke of the piston 6, the stroke of the piston 6 is controlled by changing this peak-peak value. In the high cooling mode, the peak-peak value of this voltage (V1) becomes equal to the peak-peak value (2V _p ) according to the maximum voltage limit (V _p ) so that the piston 6 can reach top dead center (TDC). (High cooling force mode stroke S1) In the low cooling force mode, the peak-peak value of this voltage V2 is reduced so that the piston 6 does reciprocating linear motion without reaching top dead center TDC.

Here, the linear compressor is operated in a high cooling power mode under a relatively large load, and in the high cooling power mode, the piston is operated so that the operating frequency f _c of the linear motor matches the natural frequency f _n of the piston. The piston is operated to reach the top dead center TDC while maintaining the predetermined stroke S1.

However, the linear compressor is operated in a low cooling mode under relatively low load. In the low cooling mode, the compression capacity can be reduced by reducing the voltage input to the linear motor, but at the same time the mechanical spring and the gas spring are As the stroke S2 of the piston decreases in a state in which the piston 6 is elastically supported in the movement direction of the piston 6 with a predetermined elastic force, the piston does not reach the top dead center (TDC), and the natural frequency of the variable piston (f _n ) and the movement frequency (f _c ) is different, thereby causing a problem that the efficiency and compression force of the compressor falls.

Accordingly, the present invention effectively adjusts the operating frequency (f _c ) of the linear motor and / or the stroke (S) of the piston even if the natural frequency (f _n ) of the piston varies depending on the load, thereby effectively compressing the capacity according to all the loads. An object of the present invention is to provide a linear compressor capable of varying the temperature.

In addition, an object of the present invention is to provide a linear compressor that provides maximum efficiency by varying the stroke S of the piston and allowing the piston to always reach top dead center to reciprocate linearly.

Linear compressor according to the present invention for achieving the above object is a fixed member including a compression space therein, a movable member for compressing the refrigerant sucked into the compression space while reciprocating linear movement in the axial direction inside the fixing member, and At least one spring installed to elastically support the movable member in the direction of movement of the movable member, the spring constant being variable depending on the load, and connected to the movable member to reciprocally linearly move the movable member in the axial direction, The stroke of the movable member is variable according to a predetermined cooling force, and the linear member is configured to perform the reciprocating linear motion to the top dead center.

In this case, the linear compressor is installed in a refrigeration / air conditioning cycle, and the load is different from a pressure (condensation pressure) at which the refrigerant condenses in the refrigeration / air conditioning cycle and a pressure (evaporation pressure) at which the refrigerant evaporates in the evaporator. It is preferable to calculate in proportion.

In addition, the load is preferably further calculated in proportion to the pressure (average pressure) which is the average of the condensation pressure and the evaporation pressure.

In addition, the linear motor preferably synchronizes the driving frequency fc to the resonance frequency f n of the movable member, which varies in proportion to the load.

In addition, the linear motor includes an inner stator configured to stack a plurality of laminations in a circumferential direction so as to surround the fixing member, and an outer stator configured to stack a plurality of laminations in a circumferential direction with a predetermined distance between the inner stator and the outer stator. A coil winding in which a coil is wound so as to generate an electromagnetic force between the inner stator and the outer stator, and a coil winding body wound around the inner stator and the outer stator, and installed to be connected to the movable member so as to be connected to the movable member. The linear motor includes a permanent magnet linearly reciprocating by interaction, and the linear motor includes a power supply unit rectifying an external AC voltage and applying a DC voltage, and receiving an DC voltage from the power supply unit to generate an AC voltage according to a predetermined inverter control signal. By creating The inverter unit applied to the coil winding body and the variable amount of the stroke of the movable member according to the cooling force are set, and the inverter control signal for generating the asymmetrical AC voltage according to the variable amount is generated and applied to the inverter unit. It is preferable to include a control unit.

It is also preferable that the positive peak value of the asymmetric alternating voltage is equal to the positive peak value of the maximum voltage limit value of the inverter section.

In addition, the asymmetric alternating voltage is preferably asymmetric with respect to zero.

In addition, the asymmetric alternating voltage is preferably symmetrical with respect to a predetermined offset voltage.

In addition, it is preferable that the movable member performs a compression stroke when the asymmetric alternating voltage is greater than the offset voltage, and the movable member performs a suction stroke when it is less than the offset voltage.

The controller may vary the stroke of the movable member by varying the peak-peak value of the asymmetric alternating voltage.

In addition, when the cooling force is a low cooling force, the peak-peak value of the asymmetric alternating voltage is preferably smaller than the peak-peak value according to the maximum voltage limit of the inverter unit.

In addition, the offset voltage is preferably a positive value.

In addition, when the cooling force is a high cooling force, the peak-peak value of the asymmetric alternating voltage is preferably larger than the peak-peak value according to the maximum voltage limit of the inverter unit.

In addition, the offset voltage is preferably a negative value.

Further, it is preferable that the negative peak value of the asymmetric alternating voltage is varied according to the variable amount.

In addition, it is preferable that the movable member performs a compression stroke when the asymmetric alternating voltage is greater than the zero point, and the movable member performs a suction stroke when it is less than the zero point.

Further, when the cold force is low cooling force, the negative peak value of the asymmetrical alternating voltage is proportionally smaller than the positive peak value in proportion to the variable amount, and when the cold force is high cold force, the negative peak value of the asymmetric alternating voltage is positive It is preferable to be larger in proportion to the variable amount than the peak value.

In addition, the control apparatus of the linear compressor according to the present invention for achieving the above object is a power supply unit for rectifying the external AC voltage to apply a DC voltage, and receives the DC voltage from the power supply unit to generate an AC voltage according to a predetermined inverter control signal By setting the variable amount of the stroke of the inverter member applied to the coil winding of the linear motor and the movable member of the linear compressor according to the cooling force, generating the inverter control signal for generating the asymmetrical AC voltage according to the variable amount The controller is applied to the inverter unit.

In addition, the control method of the linear compressor according to the present invention for achieving the above object is to set the asymmetric alternating voltage on the basis of the variable amount of the stroke of the movable member of the linear compressor according to the cold power, and for generating the asymmetric alternating voltage Generating an inverter control signal.

The features and advantages of the present invention may be better understood with reference to the following accompanying drawings in conjunction with the following detailed description of embodiments of the invention, of which:

1A is a graph showing a stroke according to load in a linear compressor according to the prior art,

1B is a graph showing the efficiency according to the load in the linear compressor according to the prior art,

2 is a block diagram showing a stroke according to the operation mode of the linear compressor according to the prior art,

3 is a sectional view showing a linear compressor according to the present invention;

Figure 4A is a graph showing the stroke according to the load in the linear compressor according to the present invention,

4B is a graph showing the efficiency according to the load in the linear compressor according to the present invention,

5 is a graph showing a change in the gas spring constant (K _g ) according to the load in the linear compressor according to the present invention,

6 is a view showing the configuration of the linear motor shown in FIG.

7A to 7D are graphs relating to a first embodiment for setting a sine wave driving voltage in the linear motor of FIG. 6;

8A and 8B are state diagrams in which the stroke of the piston 6 is variable.

9 is a result graph according to the first embodiment of FIG. 6,

10A and 10B are graphs relating to a second embodiment of setting a sine wave driving voltage in the linear motor of FIG. 6;

FIG. 11 is a result graph according to the second embodiment of FIG. 6.

Description of the Preferred Embodiments

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.

In the linear compressor according to the present invention, as shown in FIG. 3, an inlet tube 2a and an outlet tube 2b through which a refrigerant flows in and out are installed at one side of the sealed container 2, and the inside of the sealed container 2 is provided. The cylinder 4 is installed to be fixed, and the piston 6 is installed in the cylinder 4 so as to reciprocate linear movement so as to compress the refrigerant sucked into the compression space P inside the cylinder 4. At the same time, a variety of springs are installed to elastically support the movement direction of the piston (6), the piston (6) is installed to be connected to the linear motor 10 for generating a linear reciprocating drive force, the natural frequency of the piston (f) Even though _n ) varies depending on the load, the linear motor 10 controls its operating frequency f _c so as to be synchronized with the natural frequency f _n of the piston as shown in FIGS. 4A and 4B. Remind that the capacity is variable The stroke S of the piston 6 is controlled.

In addition, a suction valve 22 is installed at one end of the piston 6 in contact with the compression space P, and a discharge valve assembly 24 is provided at one end of the cylinder 4 in contact with the compression space P. ) Is installed, and the suction valve 22 and the discharge valve assembly 24 are automatically adjusted to open and close according to the pressure inside the compression space P, respectively.

Here, the airtight container (2) is installed so that the upper and lower shells are coupled to each other so that the inside is sealed, the inlet pipe (2a) and the outlet pipe (2b) for the coolant flow in one side is installed, the The piston 6 is installed inside the cylinder 4 so as to be elastically supported in the movement direction for reciprocating linear motion, and the linear motor 10 is assembled to each other by the frame 18 outside the cylinder 4. The assembly is installed to be elastically supported by a support spring 29 on the inner bottom surface of the sealed container (2).

In addition, a predetermined oil is contained in the bottom surface of the airtight container (2), and an oil supply device (30) for pumping oil is installed at the bottom of the assembly, and oil is provided in the lower frame (18) of the assembly. An oil supply pipe 18a is formed to be supplied between the 6 and the cylinder 4, so that the oil supply device 30 is operated by vibration generated by the reciprocating linear motion of the piston 6. The oil is pumped, and this oil is supplied along the oil supply pipe 18a to the gap between the piston 6 and the cylinder 4 for cooling and lubrication.

Next, the cylinder 4 is formed in a hollow shape so that the piston 6 can reciprocate linearly, and a compression space P is formed at one side thereof, and one end is located close to the inside of the inflow pipe 2a. It is preferable to be installed on the same straight line as the inflow pipe (2a) in the state.

Of course, the cylinder (4) is installed in one end close to the inlet pipe (2a) so as to reciprocate linear movement, the discharge valve assembly ( 24) is installed.

At this time, the discharge valve assembly 24 is provided to open and close the discharge cover 24a which is installed to form a predetermined discharge space on one end side of the cylinder 4, and one end of the compression space P side of the cylinder. And a discharge valve 24b and a valve spring 24c, which is a kind of coil spring that imparts an elastic force in the axial direction between the discharge cover 24a and the discharge valve 24b, and at one end of the cylinder 4 The O-ring (R) is installed in the fitting so that the discharge valve 24a is in close contact with one end of the cylinder (4).

In addition, a bent loop pipe 28 is installed between one side of the discharge cover 24a and the outlet pipe 2b. The loop pipe 28 guides the compressed refrigerant to be discharged to the outside. In addition, the vibration caused by the interaction of the cylinder 4, the piston 6, and the linear motor 10 buffers the transmission of the entire sealed container 2.

Therefore, when the pressure of the compression space P becomes equal to or greater than a predetermined discharge pressure as the piston 6 reciprocates linearly in the cylinder 4, the valve spring 24c is compressed and the discharge valve ( 24b) is opened, and the refrigerant is discharged from the compression space P, and then completely discharged along the loop pipe 28 and the outlet pipe 2b.

Next, the piston 6 has a coolant flow path 6a formed at the center thereof so that the coolant flowing from the inlet pipe 2a flows, and one end close to the inlet pipe 2a is connected to the connection member 17. In addition, the linear motor 10 is installed to be directly connected to each other, and the suction valve 22 is installed at one end of the inflow pipe 2a opposite to the inflow pipe 2a, and is elastically formed by various springs in the movement direction of the piston 6. It is installed to be supported.

At this time, the suction valve 22 is formed in a thin plate shape so that the center portion is partially cut to open and close the refrigerant passage 6a of the piston, and one side is fixed by a screw to one end of the piston 6a. It is installed as possible.

Therefore, as the piston 6 reciprocates linearly in the cylinder 4, when the pressure of the compression space P becomes lower than or equal to a predetermined suction pressure lower than the discharge pressure, the suction valve 22 is When the refrigerant is opened and sucked into the compression 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 closed while the suction valve 22 is closed. Is compressed.

In particular, the piston 6 is installed so as to be elastically supported in the movement direction, specifically, the piston flange 6b protruding radially at one end of the piston 6 proximate to the inlet pipe 2a is a machine such as a coil spring or the like. Resiliently supported in the movement direction of the piston (6) by the spring (8a, 8b), the refrigerant contained in the compression space (P) on the opposite side to the inlet pipe (2a) acts as a gas spring by its elastic force The piston 6 is elastically supported.

Here, the mechanical springs (8a, 8b) has a constant mechanical spring constant (K _m ) irrespective of the load, the mechanical spring (8a, 8b) is the linear motor (10) relative to the piston flange (6b) It is preferable that the predetermined support frame 26 and the cylinder 4 are fixed to the cylinder 4 side by side in the axial direction, respectively, the mechanical spring (8a) and the cylinder (4) supported by the support frame 26 It is preferable that the mechanical spring 8a to be installed in is 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, but the gas contained in the compression space (P) increases its elastic force as the pressure of the refrigerant increases as the ambient temperature increases As the gas spring loads, the gas spring constant K _g 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 total spring constant is also variable depending on the load, piston according to the above equation (1) The natural frequency f _n of also varies depending on the gas spring constant K _g .

Thus, even if the load is variable, the mechanical spring constant (K _m ) and the mass (M) of the piston are constant, while the gas spring constant (K _g ) is variable, so the inherent frequency (f _n ) of the piston depends on the load. It is greatly influenced by the gas spring constant (K _g ), which is determined using a frequency estimation algorithm in which the natural frequency (f _n ) of the piston is variable according to the load, and accordingly the operating frequency (f) of the linear motor _{By controlling c} ) to be synchronized with the natural frequency (f _n ) of the piston, not only can the compressor be more efficient but also the load can be released quickly.

Of course, the load can be measured in various ways, but such a linear compressor is configured to be included in the refrigeration / air conditioning cycle in which the refrigerant is compressed, condensed, evaporated, and expanded, so that 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, as the difference between the condensation pressure and the evaporation pressure increases, Even if the load is large and the difference between the condensation pressure and the evaporation pressure is the same, the larger the average pressure is, the larger the load is. The corresponding gas spring constant K _g is calculated to correspond to the load.

At this time, the load is actually calculated to measure the condensation temperature proportional to the condensation pressure and the evaporation temperature proportional to the evaporation pressure as shown in Figure 5, proportional to the difference between the condensation temperature and the evaporation temperature and the average temperature, This data is used to estimate the natural frequency f _n of the piston by a predetermined frequency estimation algorithm.

Specifically, the mechanical spring constant K _m and the gas spring constant K _g can be determined through various experiments. By applying a mechanical spring with a smaller mechanical spring constant than a conventional linear compressor, The resonant frequency of the piston is varied in a relatively wide range according to the load by increasing the ratio of the gas spring constant to the load, and the operating frequency of the linear motor is adjusted to the natural frequency (f _n ) of the piston that varies according to the load. You can control for easy synchronization.

Next, as illustrated in FIG. 6, the linear motor 10 is configured such that a plurality of laminations 12a are stacked in the circumferential direction, and is installed to be fixed to the outside of the cylinder 4 by the frame 18. And a plurality of laminations 14b are laminated in the circumferential direction around the coil winding body 14a configured to wind the coils so that the inner stator (outside the cylinder 4) is opened by the frame 18. 12 and an outer stator 14 provided with a predetermined gap, and positioned between the inner stator 12 and the outer stator 14 so as to be connected by the piston 6 and the connecting member 17. It is made of a permanent magnet 16 is installed, the coil winding 14a may be installed to be fixed to the inner stator 12 outside.

In particular, the linear motor 10 is installed to be connected to the piston 6 to reciprocate linear movement of the piston 6 in the axial direction, and according to a predetermined load (or cold force) to stroke the stroke of the piston 6. Variable, but the piston 6 to perform a reciprocating linear motion to the top dead center (TDC). To this end, the linear motor 10 receives a power supply unit 18 for rectifying an AC voltage and applying a DC voltage, and a predetermined inverter control signal (for example, a PWM signal) by receiving the DC voltage rectified from the power supply unit 18. A variable amount of stroke of the inverter unit 19 to generate a sinusoidal AC voltage and apply it to the coil winding 14a and the piston 6 according to the load, and asymmetrical according to this variable amount The control unit 20 generates an inverter control signal for generating an AC voltage and applies it to the inverter unit 19.

Here, the power supply unit 18 is a general rectifier circuit, and the inverter unit 19 is also used in the same manner as the inverter element conventionally used.

The controller 20 receives the temperature information as described above, so that the stroke of the piston 6 is varied according to the load (or cooling force) corresponding to the temperature information, so that a sinusoidal AC voltage asymmetric with respect to zero is generated. Generate a corresponding inverter control signal.

The control unit 20 forms the compression space P while causing the piston 6 to reciprocate linearly in the cylinder 4, even if the stroke S of the piston 6 is variable. 6 is completely compressed in the cylinder 4 so as to reciprocate linearly to a top dead center (TDC), which is a point at which the compression space P is not formed. The reciprocating linear motion to the top dead center (TDC) is such that even if the stroke (S) of the piston (6) is variable, the compression efficiency does not fall.

The operation and function of this control unit 20 will be described with reference to Figs. 7A to 7D below. In the following, the control unit 20 sets an asymmetric alternating voltage (in this case, the AC voltage is a kind of voltage command value), wherein the natural frequency f _n according to the above-described load is set according to a predetermined frequency estimation algorithm. The calculation is performed using to perform the process of setting the frequency of the asymmetrical alternating voltage (ie, the movement frequency f _c ) to be equal to the natural frequency f _n , but the description thereof is omitted below.

First, FIG. 7A is equal to the voltage V2 in FIG. 2A. That is, in order to reduce the stroke of the piston 6 according to the load (low load), the peak-peak value of the voltage V2 is reduced. However, the peak value V2 _p of this voltage V2 becomes smaller than the maximum voltage limit V _p so that the piston 6 does not reach the top dead center TDC.

Therefore, as shown in FIG. 7B, the controller 20 adds a predetermined offset voltage V _offset to the voltage V2 to set a new voltage V2 ′. At this time, the magnitude of the offset voltage V _offset is (V _p -V2 _p ) and becomes a DC voltage, and the offset voltage V _offset has a positive value.

As described above, the controller 20 1) sets the (sine wave) voltage with a peak-peak value for reducing the stroke of the piston 6 according to the load, and 2) the positive peak value of the set voltage is the maximum voltage. A predetermined offset voltage V _offset is calculated and added so as to be equal to the threshold value, and a sine wave AC voltage that is asymmetric with respect to zero and symmetrical with respect to the offset voltage V _offset is set. When the control unit 20 generates an inverter control signal corresponding to the set asymmetric alternating voltage and transmits it to the inverter unit 19, the inverter unit 19 generates the set asymmetric alternating voltage according to the inverter control signal. Is applied to the coil winding 14a to cause the piston 6 to reciprocate linearly. In addition, the control unit 20 may perform the step 2) and then perform the step 1) to set the asymmetric alternating voltage, wherein the magnitude of the offset voltage (V _offset ) and the reduction width of the peak-peak value may be appropriately set. Such modifications can be easily implemented by those skilled in the art.

In detail, when the asymmetric alternating voltage V2 'is greater than the offset voltage V _offset , the controller 20 causes the piston 6 to perform a compression stroke, and when the asymmetric alternating voltage V2' is smaller than the offset voltage V _offset . The piston 6 allows the suction stroke to be carried out.

FIG. 7C shows the voltage V4 to which the offset voltage V _offset of a predetermined magnitude is added to the voltage V1 in FIG. 2A. At this time, the offset voltage V _offset is a DC voltage having a negative value.

Since the peak value V4 _p of this voltage V4 is smaller than the maximum voltage limit V _p , the peak-peak value of the voltage V4 is increased so that the peak value of the voltage V4 'is maximum as shown in FIG. 7D. Make it equal to the voltage limit (V _p ). The setting of this asymmetric alternating voltage is for increasing the stroke of the piston 6 in the case of high load (or high cooling force). This new voltage, V4 ', is also a sinusoidal alternating voltage that is asymmetrical with respect to zero and symmetrical with respect to offset voltage (V _offset ).

When the control unit 20 generates an inverter control signal corresponding to the set asymmetric alternating voltage and transmits it to the inverter unit 19, the inverter unit 19 generates the set asymmetric alternating voltage according to the inverter control signal. Is applied to the coil winding 14a to cause the piston 6 to reciprocate linearly.

The method of increasing the stroke of the piston 6 according to FIGS. 7C and 7D also first increases the peak-peak value of the voltage first, and then offset voltage which is a predetermined negative DC voltage such that the peak value of the voltage is equal to the maximum voltage limit value V _p . It may be implemented by adding (V _offset ).

In addition, when the asymmetric alternating voltage V2 'is greater than the offset voltage V _offset , the controller 20 causes the piston 6 to perform a compression stroke, and when the asymmetric alternating voltage V2' is smaller than the offset voltage V _offset , Let the piston 6 perform the suction stroke.

8A and 8B are state diagrams in which the stroke of the piston 6 is variable.

In FIG. 8A, when the control unit 20 generates an inverter control signal for the asymmetric alternating voltage set as shown in FIG. 7B and transmits the inverter control signal to the inverter unit 19, the inverter unit 19 passes from the inverter unit 19 to the coil winding 14a. The stroke S 'when applied to linearly reciprocate the piston 6 is shown. The stroke S has the same compression stroke distance and suction stroke distance with respect to a predetermined center C when the alternating current voltage (voltage V1 in FIG. 2A) is symmetric with respect to zero, and is applied, and the piston 6 It is the travel distance of the piston 6 when () reaches to top dead center (TDC).

As shown, the stroke S 'of the piston 6 due to the asymmetrical alternating voltage is reduced compared to the stroke S of the piston 6 due to the symmetrical alternating voltage, and the top dead center (TDC) reciprocating motion is performed and The piston 6 reciprocates by reaching a new bottom dead center DDC 'by a reduced stroke rather than by a previous down dead center (DDC).

On the other hand, in FIG. 8B, when the control unit 20 generates an inverter control signal for the asymmetric alternating voltage set as shown in FIG. 7D and transmits the inverter control signal to the inverter unit 19, the coil winding body (from the inverter unit 19) A stroke S " when applied to 14a) to linearly reciprocate the piston 6. The stroke S is generated by applying an alternating voltage (voltage V1 in Fig. 2A) which is symmetric with respect to zero. When the compression stroke distance and the suction stroke distance are the same with respect to the predetermined center C, it is the movement distance of the piston 6 when the piston 6 reaches to top dead center TDC.

As shown, the stroke S "of the piston 6 due to the asymmetrical alternating voltage is increased compared to the stroke S of the piston 6 due to the symmetrical alternating voltage, which is not in the prior art TDC (TDC). ) The reciprocating motion is carried out and the piston 6 reciprocates with the increased stroke reaching a new bottom dead center (DDC ") rather than the previous bottom dead center (DDC).

FIG. 9 is a result graph according to the first embodiment of FIG. 6, where the X axis is an offset ratio and the Y axis is a stroke ratio. Here, the offset ratio is defined as (the pushed distance of the piston 6 by the offset voltage) / (kinematic initial value). Specifically, the pushed distance of the piston 6 by the offset voltage is the center of the stroke in FIGS. 8A and 8B described above as the travel distance in the direction of top dead center TDC of the piston 6 by the added offset voltage V _offset . This is the same as the moving distance. In other words, it means the difference between the center C of the stroke S and the centers of the strokes S 'and S "at the symmetrical alternating voltage. In addition, the mechanical initial value is the top dead center in the state where no voltage is applied. (TDC) to a fixed distance from the center C. Therefore, if the offset ratio is positive, it means that the load is pushed in the direction of top dead center (TDC) of the piston 6 when the load is low cooling force, If the offset ratio is negative, it means that the load is pushed in the direction of the bottom dead center (DDC) of the piston 6 when the load is high cooling force, and the stroke ratio is (stroke when the offset voltage is added) / ( Stroke due to symmetrical alternating voltage).

Therefore, the relationship between the offset ratio and the stroke ratio is that if the piston 6 is pushed in the direction of top dead center (TDC) by the offset voltage, that is, if the offset ratio is a positive value, the stroke ratio is 100% because the overall stroke is reduced. If it becomes smaller and the offset ratio is negative, the overall stroke is increased so that the stroke ratio is greater than 100%. Through such a pipe, the stroke can be changed through the asymmetrical alternating voltage, and the cooling force can be changed. This ability to vary cold power makes it possible to respond quickly to varying loads.

10A and 10B are graphs of a second embodiment for setting a sine wave driving voltage in the linear motor of FIG.

In this second embodiment, since the piston 6 must reach the top dead center (TDC), the positive peak values of the voltages V5 and V6 must be equal to the maximum voltage limit V _p , and thus the voltage of FIG. 2A. The positive region (compression stroke) at V2 remains the same, while the negative region (suction stroke) of the voltage V2 is changed for the stroke variation of the piston 6.

As shown in FIG. 10A, the control unit 20 sets the peak value V5 _p in the negative region of the load voltage V2 to be smaller than the maximum voltage limit V _p according to the load (low load). Such a change reduces the negative region of voltage V2 by a predetermined ratio corresponding to the load (i.e. by a variable amount of stroke), or adds a predetermined alternating voltage to correspond to the load (i.e., By a variable amount of stroke). As a result, the peak-peak value of this voltage V5 is reduced than the peak-peak value of the voltage V2, so that the stroke of the piston 6 is reduced. This reduction variable has the same result as in FIG. 8A.

As shown in FIG. 10B, the controller 20 sets the peak value V6 _p in the negative region of the voltage V2 to be greater than the maximum voltage limit value V _p . Such a change increases the negative region of the voltage V2 by a predetermined ratio corresponding to the load (i.e., by a variable amount of stroke), or adds a predetermined alternating voltage to correspond to the load (i.e., By a variable amount of stroke). Since the peak-peak value of this voltage V6 is increased than the peak-peak value of the voltage V2, the stroke of the piston 6 is increased. This increasing variation leads to the same result as in Fig. 8B.

10A and 10B, the control unit 20 sets an asymmetric alternating voltage, where the natural frequency f _n according to the load described is calculated so that the frequency of the asymmetric alternating voltage (ie, the movement frequency f _c ) is obtained. The process of setting the same as the natural frequency f _n is performed, but the description thereof is omitted.

The change in the stroke of the piston 6 due to the asymmetric alternating voltage shown in FIGS. 10A and 10B corresponds to FIGS. 8A and 8B, respectively, and the description thereof is omitted.

FIG. 11 is a result graph according to the second embodiment of FIG. 6. X axis is asymmetrical ratio, Y axis is stroke ratio. Here, the asymmetric ratio is defined as (amplitude of stroke in suction stroke) / (stroke amplitude in compression stroke), and the stroke ratio is (stroke when applying asymmetrical alternating voltage) / (stroke when applying symmetrical alternating voltage) Is defined.

In detail, it can be seen that, in the case of the asymmetrical alternating voltage having a negative peak value smaller than the positive peak value as shown in FIG. 10A, the value is smaller than '1', and the overall stroke is reduced. On the other hand, as shown in FIG. 10B, in the case of an asymmetric alternating voltage in which the negative peak value is larger than the positive peak value, the value is larger than '1', and the overall stroke is increased. Through this relationship, the stroke can be changed through the asymmetrical alternating voltage, and the cooling force can be changed. This ability to vary cold power makes it possible to respond quickly to varying loads.

In addition, as the load increases, the gas spring constant increases and the natural frequency of the piston also increases, and the frequency of the asymmetrical AC voltage is adjusted so that the operating frequency of the linear motor is also synchronized to the natural frequency of the piston by a frequency estimation algorithm. In this case, the linear compressor may operate in a resonance state to increase the compression efficiency.

In addition, as the load acts small, the gas spring constant decreases, and the natural frequency of the piston also decreases, and the frequency of the asymmetrical AC voltage is also synchronized such that the operating frequency of the linear motor is synchronized with the natural frequency of the piston by a frequency estimation algorithm. In this way, the linear compressor can operate in a resonance state to increase the compression efficiency.

As described above, in the present invention, the gas spring constant and the natural frequency vary according to the load by a frequency estimation algorithm, and the resonance frequency is achieved by synchronizing the operating frequency (that is, the frequency of the asymmetric AC voltage) of the linear motor with the natural frequency. It is possible to maximize the compression efficiency as a result of operating at.

In the above description, the present invention relates to a linear compressor for moving, moving and reciprocating linearly inside a cylinder a suction magnet type linear motor in which a moving magnet type linear motor is operated based on the embodiments of the present invention and the accompanying drawings. The example has been described in detail. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

Claims (38)

delete delete A fixing member including a compression space therein; A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly moving inside the fixing member; At least one spring installed to elastically support the movable member, the spring constant being variable depending on a load; Is installed to be connected to the movable member is a linear motor for reciprocating linear movement of the movable member, varying the stroke of the movable member in accordance with the cold force, the movable member to perform a reciprocating linear motion to the top dead center, The linear compressor is installed in a refrigeration / air conditioning cycle, and the load is proportional to a difference between a pressure (condensation pressure) at which the refrigerant condenses in the refrigeration / air conditioning cycle and a pressure (evaporation pressure) at which the refrigerant evaporates in the evaporator. Calculated, but further calculated in proportion to the pressure (average pressure) that is the average of the condensation pressure and the evaporation pressure. delete A fixing member including a compression space therein; A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly moving inside the fixing member; At least one spring installed to elastically support the movable member, the spring constant being variable depending on a load; Is installed to be connected to the movable member is a linear motor for reciprocating linear movement of the movable member, varying the stroke of the movable member in accordance with the cold force, the movable member to perform a reciprocating linear motion to the top dead center, The linear motor may include an inner stator configured to surround the fixing member, an outer stator positioned at a predetermined interval on the inner stator outer shaft, and a coil winding body in which a coil is wound between the inner stator or the outer stator, and A permanent magnet positioned in a gap between the inner stator and the outer stator and installed to be connected to the movable member, wherein the linear motor includes a power supply for rectifying an external AC voltage and applying a DC voltage, and receiving a DC voltage from the power supply; Generating an AC voltage according to a predetermined inverter control signal and setting the variable amount of the stroke of the movable member according to the cooling force and the inverter unit for applying to the coil winding body to generate an asymmetrical AC voltage according to this variable amount. Generating the inverter control signal for the inverter unit The linear compressor comprises a control unit for applying. The linear compressor according to claim 5, wherein the positive or negative peak value of the asymmetric alternating voltage corresponds to the positive or negative peak value of the maximum voltage limit of the inverter section. delete delete delete 7. The linear compressor according to claim 5 or 6, wherein the controller varies the stroke of the movable member by varying the peak-peak value of the asymmetric alternating voltage. delete delete delete delete delete delete delete A power supply unit rectifying an external AC voltage to apply a DC voltage; An inverter unit receiving a DC voltage from the power supply unit to generate an AC voltage according to a predetermined inverter control signal and to apply the DC voltage to a coil winding of the linear motor; The control unit includes a controller by setting a variable amount of a stroke of the movable member of the linear compressor according to the cooling force, generating the inverter control signal for generating an asymmetric alternating voltage according to the variable amount, and applying it to the inverter unit. Control unit of the compressor. 19. The control apparatus of a linear compressor according to claim 18, wherein a positive or negative peak value of the asymmetric alternating voltage corresponds to a positive or negative peak value of the maximum voltage limit of the inverter section. 19. The control apparatus of a linear compressor according to claim 18, wherein the asymmetric alternating voltage is asymmetric with respect to zero. The method of claim 20, And said asymmetric alternating voltage is symmetrical with respect to a predetermined offset voltage. delete 21. The control apparatus for a linear compressor according to any one of claims 18 to 20, wherein the controller varies the stroke of the movable member by varying the peak-peak value of the asymmetric alternating voltage. delete delete delete delete 21. The control apparatus of a linear compressor according to claim 20, wherein a negative or positive peak value of said asymmetric alternating voltage is varied according to said variable amount. delete delete Setting an asymmetric alternating voltage on the basis of a variable amount of stroke of the movable member of the linear compressor according to the cold force; And generating an inverter control signal for generating the asymmetric alternating voltage. 32. The method of claim 31, wherein setting the asymmetrical alternating voltage comprises causing a positive or negative peak of the asymmetrical alternating voltage to correspond to the maximum voltage limit. 33. The method of claim 32, wherein setting the asymmetric alternating voltage includes setting an offset voltage so that a positive or negative peak of the asymmetric alternating voltage corresponds to the maximum voltage limit. The method according to any one of claims 31 to 33, wherein The step of setting the asymmetric alternating voltage includes setting the peak-peak value of the asymmetric alternating voltage to be proportionally smaller than the peak-peak value according to the maximum voltage limit of the linear compressor when the cold force is low cooling force. And setting the peak-peak value of the asymmetric alternating voltage when the cooling force is a high cooling force to be proportionally larger than the peak-peak value according to the maximum voltage limit of the linear compressor. Control method. The method of claim 34, wherein And wherein the asymmetric alternating voltage is symmetrical with respect to the offset voltage, and the offset voltage is a positive value when the cold force is a low cold force and a negative value when the cold force is a high cold force. delete 33. The method of claim 32, wherein setting the asymmetric alternating voltage includes varying a negative or positive peak value of the asymmetric alternating voltage according to the variable amount. The method of claim 37, When the cold force is low cooling force, the negative peak value of the asymmetrical alternating voltage is proportionally smaller than the positive peak value, and when the cold force is high cold force, the negative peak value of the asymmetric alternating voltage is higher than the positive peak value. A control method of a linear compressor, characterized in that large in proportion to the variable amount.

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