KR100690164B1 - Control method for a linear compressor - Google Patents

Abstract

The present invention relates to a linear compressor in which a piston is driven by a linear motor to suck, compress, and discharge refrigerant while reciprocating linearly in a cylinder. The elastic force of a mechanical spring and a gas spring that elastically supports the piston in the movement direction is loaded. In consideration of the variable frequency, the operating frequency of the linear motor is synchronized to the natural frequency of the piston, so that even if the load is variable, it is possible to maximize the efficiency by operating in a resonant state, and to change the actual stroke of the piston according to the load. Therefore, not only can it actively respond to loads, but also can reduce power consumption.

Linear compressor, control, resonance, spring, constant, natural frequency, operating frequency

Description

CONTROL METHOD FOR A LINEAR COMPRESSOR

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

3A is a graph showing a stroke according to load in a linear compressor according to the present invention;

3B is a graph showing the efficiency according to the load in the linear compressor according to the present invention,

4 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,

5 is a graph showing a change in the gas spring constant according to the ambient temperature, the mass of the piston, the mechanical spring constant, the natural frequency in the linear compressor according to the present invention,

6 is a configuration diagram in which a stroke according to a load is displayed on a part of a linear compressor according to the present invention;

7A to 7C are side cross-sectional views showing an operating state of the linear compressor according to the present invention.

<Description of Tavern on Major Parts of Drawing>

4-cylinder 6-piston

8-spring 10-linear motor

12-inner stator 14-outer stator

16-permanent magnet 17-connecting member

The present invention relates to a linear compressor control method that not only actively copes with a load but also efficiently operates by synchronizing an operating frequency to a natural frequency of a movable member that varies depending on a load.

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 to be connected to each other, the linear motor is installed with a predetermined gap between the inner stator and the outer stator configured to be laminated in a circumferential direction around the cylinder The coil is wound around the inner stator or 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.

In this case, 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 _n 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 be operated at a driving frequency f _c corresponding to, the efficiency can be increased by operating the linear motor in a resonance state only under a load considered in the design.

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

At this time, the f _n Is the natural frequency of the piston, K _m and K _g are the mechanical and constant gas springs, 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 (Km) of the piston also have 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 the resonance state because the operating frequency f _{c of} the linear motor is constant. The efficiency is low, there is a problem that can not resolve the load quickly because it does not actively respond to the load.

On the other hand, the conventional linear compressor to change the operating frequency (f _c ) of the linear motor by adjusting the input current in proportion to the load in order to more quickly respond to the load more actively, especially the operation of the linear motor at low load Since the frequency f _c is controlled to be lowered, the compression efficiency is not achieved in the actual resonance state, so the compressor efficiency is greatly reduced, but the efficiency of the entire refrigeration cycle is increased, so that the overall efficiency is not so much increased.

Therefore, in order to achieve a compression operation in a resonance state even at a low load, the operating frequency f _c of the linear motor is controlled to be operated in the low frequency region to match the natural frequency fn of the piston, but in fact, a mechanical spring In the linear compressor having a large constant (K _m ), it is difficult to control the operating frequency (f _c ) of the linear motor to operate at a low frequency by adjusting the input current, and furthermore, it is difficult to efficiently change the compression capacity.

Accordingly, the present invention synchronizes the operating frequency (f _c ) of the linear motor with the natural frequency (f _n ) of the piston even if the natural frequency (f _n ) of the piston varies depending on the load so that it can be operated in a resonance state even if the load varies. It is an object of the present invention to provide a linear compressor.

In addition, the present invention is to provide a linear compressor that can efficiently change the compression capacity by operating the linear motor at the same time or separately to adjust the operating frequency (f _c ) of the piston according to the load or separately. For the purpose of

In one aspect of the present invention for achieving the above object and a fixed member including a compression space therein; A movable member for compressing the refrigerant by introducing the refrigerant into the compression space while reciprocating linearly in the axial direction; At least one spring installed to elastically support the movable member in a movement direction of the movable member and varying a spring constant K _T depending on a load; And a linear motor installed to be connected to the movable member to reciprocate linearly the movable member in the axial direction and to synchronize the driving frequency f _c to the natural frequency f _n of the piston. Provides a linear compressor.

Here, the spring is configured such that the spring constant is variable in proportion to the load, the linear motor is preferably operated so that the operating frequency (f _c ) is variable in proportion to the load.

In this case, the linear compressor is installed in a refrigeration / air conditioning cycle, and the load is calculated in proportion to the difference between the pressure (condensation pressure) at which the refrigerant condenses and the pressure (evaporation pressure) at which the refrigerant evaporates in the refrigeration / air conditioning cycle. Preferably, the load is further calculated in proportion to the pressure (average pressure) which is the average of the condensation pressure and the evaporation pressure.

In addition, the spring is installed to support the movable member in both the movement direction of the movable member and a mechanical spring having a constant mechanical spring constant (K _m ) and the gas spring is variable depending on the load of the refrigerant sucked into the compression space It is preferred to consist of a gas spring having a constant K _g .

In this case, the mechanical spring and the gas spring is such that the ratio of the mechanical spring constant (K _m ) to the total spring constant (K _T ) of the sum of the mechanical spring constant (K _m ) and the gas spring constant (K _g ) is 90% or less. It is preferred that the mechanical spring constant K _m and the gas spring constant K _g be determined so that the natural frequency f _n of the piston can be set in the low frequency region of 30-55 Hz.

In addition, the mechanical spring and the gas spring is preferably the mechanical spring constant (K _m ) and the gas spring constant (K _g ) is set so that the stroke, which is the reciprocating linear motion distance of the movable member is variable depending on the load, the machine The spring and the gas spring are more preferably set with a mechanical spring constant K _m and a gas spring constant K _{g such} that the movable member reciprocates linearly to the top dead center even if the stroke of the movable member varies. Do.

In addition, the movable member is preferably installed so that the initial position is closer to the top dead center as the mechanical spring constant is smaller so that it can be stably elastically supported by the mechanical spring and the gas spring.

On the other hand, in another aspect of the present invention and the fixing member including a compression space therein; A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly in the fixed member in the axial direction; A mechanical spring installed to elastically support the movable member in both the moving directions of the movable member and having a constant mechanical spring constant K _m ; A gas spring having a gas spring constant K _g which varies depending on a load of a refrigerant sucked into the compression space; A linear motor installed to be connected to the movable member to linearly reciprocate the movable member in the axial direction, wherein the mechanical spring and the gas spring are machined such that the stroke, which is the reciprocating linear movement distance of the movable member, is variable depending on the load. Provided is a linear compressor characterized by a spring constant (K _m ) and a gas spring constant (K _g ) being set.

Here, the linear compressor is installed in a refrigeration / air conditioning cycle, and the load is calculated in proportion to the difference between the pressure at which the refrigerant condenses (condensing pressure) and the pressure at which the refrigerant evaporates (evaporation pressure) in the refrigeration / air conditioning cycle. Preferably, the load is further calculated in proportion to the pressure (average pressure) which is the average of the condensation and evaporation pressures.

In addition, the mechanical spring and the gas spring are set by the mechanical spring constant (K _m ) and gas spring constant (K _g ) so that the movable member reciprocates linearly to the top dead center even if the stroke of the movable member is variable. It is desirable to be.

In addition, the movable member is preferably installed so that the initial position is closer to the top dead center as the mechanical spring constant (K _m ) is smaller so that it can be stably elastically supported by the mechanical spring and the gas spring.

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. 2, an inlet tube 2a and an outlet tube 2b through which 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. 3A and 3B. Resonant operation in this area And it is possible to increase the compression efficiency such that air.

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 inlet 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 .

Therefore, even if the load is variable, the mechanical spring constant (K _m ) and the mass (M) of the piston are constant, while the natural frequency (f _n ) of the piston depends on the load because the gas spring constant (K _g ) is variable. It is greatly influenced by the gas spring constant (K _g ), and the algorithm in which the natural frequency (f _n ) of the piston is varied according to the load, and thus the operating frequency (f _c ) of the linear motor is By controlling synchronization with the natural frequency (f _n ), 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 measured as shown in Figure 4 to measure the condensation temperature proportional to the condensation pressure and the evaporation temperature 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 may be determined through various experiments. Referring to FIG. 5, the mechanical spring constant K _m decreases as the mechanical spring constant K _m decreases. constant (K _m) and the gas spring constant (K _g) the sum of the total spring constant and the gas spring increases the ratio of the constant (K _g), the higher the ambient temperature, i.e., the larger the load the entire spring for the (K _T) constant and the gas spring constant (K _g) that becomes larger occupied rate, the greater is the total spring constant (K _T) additive ratio of the gas spring constant (K _g) which accounts for the natural frequency of the (K _T) (f _n ) fluctuations are large.

At this time, the ratio of the mechanical spring constant (K _g ) to the total spring constant (K _T ) is preferably set to 90% or less.

For example, when the ratio of the gas spring constant (K _g ) to the total spring constant (K _T ) is 10% or more by lowering the mechanical spring constant (K _m ) to 35.5 kN / m or less, according to the change of ambient temperature. Since the natural frequency (f _n ) is relatively large, it is easy to control the operating frequency (f _c ) of the linear motor, so that the operation can be performed in a resonant state and the load can be released quickly, thereby reducing power consumption. Can be reduced.

However, when the mechanical spring constant (K _m ) is greater than 35.5 kN / m so that the ratio of the gas spring constant (K _g ) to the total spring constant (K _T ) is less than 10%, Since the frequency f _n is changed relatively small, it is difficult to control the operating frequency f _c of the linear motor, thereby making it difficult to operate in a resonance state.

As described above, when the ratio of the gas spring constant (K _g ) to the total spring constant (K _T ) is large, the natural frequency (f _n ) of the piston (6) is greatly changed as the load is changed In addition, the operating frequency (f _c ) of the linear motor can be controlled to be easily synchronized with the natural frequency (f _n ) of the piston (6), thereby maximizing efficiency by allowing the operation to be performed in a resonance state. Furthermore, even when the operating frequency (f _c ) of the linear motor is operated in the low frequency region, the load can be quickly released and the power consumption can be reduced by operating at maximum efficiency.

Thus, the natural frequency f _n of the piston is initially determined by the mechanical spring constant (K _m ) and gas spring constant (K _g ) and the mass (M) of the piston, which is initially determined in design. Even if set in the low frequency range of 30-55 Hz lower than (f _n ), not only can it be operated sufficiently efficiently, but it can also quickly release the load.

In particular, since the linear compressor is designed such that the mechanical spring constant K _m is set relatively small and the ratio of the gas spring constant K _g to the total spring constant K _T is set to be large, The operation frequency of the linear motor (f _c ) is matched to the natural frequency (f _n ) of the piston to operate in a resonance state to increase the efficiency of the compressor, furthermore, the linear motor 10 operates in a low frequency region This can increase the efficiency of the entire refrigeration cycle.

Next, the linear motor 10 is configured such that a plurality of laminations 12a are stacked in the circumferential direction, and the inner stator 12 and the coil are installed to be fixed to the outside of the cylinder 4 by the frame 18. A plurality of laminations 14b are laminated in the circumferential direction around the coil winding 14a configured to be wound so that a predetermined gap is formed between the inner stator 12 and the outside of the cylinder 4 by the frame 18. Permanent magnet 16 is installed in the gap between the outer stator 14 and the inner stator 12 and the outer stator 14 is installed so as to be connected by the piston 6 and the connecting member (17) The coil winding 14a may be installed to be fixed to the outer side of the inner stator 12.

As the current is applied to the coil winding 14a in the linear motor 10 as described above, an electromagnetic force is generated, and the permanent magnet 16 reciprocates by the interaction between the electromagnetic force and the permanent magnet 16. The piston 6 is linearly moved, and the piston 6 connected to the permanent magnet 16 is reciprocated linearly in the cylinder 4.

At this time, the linear motor 10 may vary the compression capacity by varying the operating frequency (f _c ) as the current is applied, but by adjusting the current input from the outside is a reciprocating linear distance of the piston (6) The compression capacity may be varied by varying the stroke S to the first stroke S1 and the second stroke S2 according to the load as shown in FIG. 6.

Of course, the piston 6 is the reciprocating linear motion inside the cylinder 4 to form the compression space (P), even if the stroke (S) of the piston is variable, the piston 6 is the cylinder ( 4) The compression efficiency is not reduced even if the stroke S of the piston is shortened by being completely compressed inside so that the compression space P is reciprocated linearly to the top dead center (TDC: Top Dead Center). It is desirable to avoid.

In this case, the linear motor 10 may control the driving frequency f _c and the stroke S of the piston to increase as the load increases, but as the load increases, only the stroke S of the piston increases. You can also control it.

However, in the linear compressor, as the actual load increases, the gas spring constant (K _g ) increases, so that the elastic force of the gas spring increases, and the stroke (S) of the piston decreases than when the load is small. It is necessary to control the operation of the linear motor 10 in consideration of the reflecting mechanical spring constant K _m and the gas spring constant K _g .

In addition, the piston 6 is initially installed to be spaced apart from the top dead center (TDC) by a predetermined interval, the mechanical spring constant (K _m ) by reducing the gas spring for the total spring constant (K _T ) If the ratio of the constant K _g is designed to be greater, the smaller the mechanical spring constant K _m , the smaller the mechanical spring constant K _m is to ensure that the piston 6 reaches the top dead center TDC completely. It is preferable that the initial position of is provided to be close to the top dead center (TDC).

Looking at the operation of the linear compressor of the present invention configured as described above is as follows.

First, when a current is applied to the coil winding 14a, the electromagnetic force generated around the coil winding 14a and the permanent magnet 16 interact with each other so that the permanent magnet 16 reciprocates linearly. The pistons 6 connected to each other by the permanent magnet 16 and the connecting member 17 are linearly reciprocated together. As the pistons 6 reciprocate linearly in the cylinder 4, the cylinders ( 4) The compression space P inside is variable, and the refrigerant is sucked into the compression space P, and then compressed and discharged.

Specifically, when the piston 6 is moved in the direction in which the compression space P is expanded inside the cylinder 4, as shown in FIG. 7A, the pressure inside the compression space P is a predetermined suction. As the pressure drops, the suction valve 22 is opened, and the refrigerant sucked through the inlet pipe 2a passes through the refrigerant passage 6a of the piston and is sucked into the compression space P.

Next, when the piston 6 is moved in the direction of compressing the compression space P inside the cylinder 4, the intake valve 22 and the discharge valve 24b are closed as shown in FIG. 7B. As the pressure inside the compression space P increases in a state, the refrigerant is compressed into a gas refrigerant having a high temperature and high pressure.

Next, when the piston 6 moves in the direction of compressing the compression space P inside the cylinder 4 to reach the top dead center TDC, the compression space P as shown in FIG. 7C. ) As the pressure inside the valve is higher than a predetermined discharge pressure, the valve spring 24c is compressed to open the discharge valve 24b, and the refrigerant compressed in the compression space P passes through the discharge space and loops. It is discharged to the outside through the pipe 28 and the outflow pipe 2b.

While repeating the above process, the linear compressor compresses the refrigerant, and the operating frequency (f _c ) of the linear motor is applied to the natural frequency (f _n ) of the spring calculated in consideration of the gas spring constant (K _g ) depending on the load. ) Can be improved by operating in a resonant state by synchronizing the), and as the load increases, it adjusts the current input to the linear motor 10 to adjust the stroke (S) of the piston to quickly change the compression capacity. Not only can it respond to the load, but it can also reduce power consumption.

As such, when the mechanical spring constant is reduced in the present invention than the conventional mechanical spring constant, the influence of the gas spring in the present invention becomes larger than the conventional gas spring effect in the present invention, and the load is increased as the influence of the gas spring in the present invention increases. As it gets bigger, the natural frequency of the piston also gets bigger automatically.

Therefore, in the present invention, the natural frequency of the piston is relatively changed in accordance with the load, and the operating frequency of the linear motor can be easily synchronized to the natural frequency of the piston, which is thus varied, so that the efficiency is maximized by operating in a resonance state. In addition, the load can be quickly eliminated and further operated in the low frequency range, thereby reducing power consumption.

In addition, since the stroke of the piston can be adjusted by adjusting an external current input to the linear motor in the present invention, it is possible not only to quickly solve the load actively and to reduce power consumption.

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.

Accordingly, the present invention synchronizes the operating frequency (f _c ) of the linear motor with the natural frequency (f _n ) of the piston even if the natural frequency (f _n ) of the piston is variable depending on the load so that it can be operated in a resonance state even if the load is variable. There is an effect to provide a linear compressor.

In another aspect, the present invention provides a linear compressor that can efficiently change the compression capacity by operating the linear motor to adjust the stroke (S) of the piston at the same time or separately to vary the operating frequency (f _c ) according to the load. There is another effect.

Claims (9)

delete delete A fixing member including a compression space compressing the refrigerant therein; A movable member which compresses the refrigerant by introducing the refrigerant into the compression space while reciprocating linearly in the axial direction; Spring means for providing an elastic force to the movable member by, induce resonance of the movable member; a, a gas spring having a spring constant (K _m) for having mechanical spring, a spring constant (K _g) which varies depending on the load A spring means having a spring constant K _{T that} is the sum of the spring constant K _m and the spring constant K _g ; And a linear motor installed to be connected to the movable member to linearly reciprocate the movable member in the axial direction. Calculating a load; And, And a second step of synchronizing the operating frequency f _{c with} the natural frequency f _n of the movable member which varies according to the spring constant K _T which varies depending on the load. The first step is characterized in that the load is calculated in proportion to the difference between the pressure at which the refrigerant is condensed (condensation pressure) and the pressure at which the refrigerant is evaporated (evaporation pressure) and the pressure (average pressure) which is the average of the condensation pressure and the evaporation pressure. Linear compressor control method. A fixing member including a compression space compressing the refrigerant therein; A movable member which compresses the refrigerant by introducing the refrigerant into the compression space while reciprocating linearly in the axial direction; Spring means for providing an elastic force to the movable member by, induce resonance of the movable member; a, a gas spring having a spring constant (K _m) for having mechanical spring, a spring constant (K _g) which varies depending on the load A spring means having a spring constant K _{T that} is the sum of the spring constant K _m and the spring constant K _g ; And a linear motor installed to be connected to the movable member to linearly reciprocate the movable member in the axial direction. Calculating a load; And, And a second step of synchronizing the operating frequency f _{c with} the natural frequency f _n of the movable member which varies according to the spring constant K _T which varies depending on the load. And a ratio of the mechanical spring constant (K _m ) to the total spring constant (K _T ) of the sum of the mechanical spring constant (K _m ) and the gas spring constant (K _g ) is 90% or less. A fixing member including a compression space compressing the refrigerant therein; A movable member which compresses the refrigerant by introducing the refrigerant into the compression space while reciprocating linearly in the axial direction; Spring means for providing an elastic force to the movable member by, induce resonance of the movable member; a, a gas spring having a spring constant (K _m) for having mechanical spring, a spring constant (K _g) which varies depending on the load And a spring constant (K _T ), which is the sum of the spring constant (K _m ) and the spring constant (K _g ), so that the natural frequency (f _n ) of the movable member is set in the low frequency region of 30-55 Hz. K _m ) and spring means having a spring constant K _g ; And a linear motor installed to be connected to the movable member to linearly reciprocate the movable member in the axial direction. Calculating a load; And, And a second step of synchronizing the operating frequency (f _c ) with the natural frequency (f _n ) of the movable member which is changed according to the spring constant (K _T ) which is variable in dependence on the load. . The method according to any one of claims 3 to 5, The second step is to synchronize the operating frequency f _c to the natural frequency f _n of the movable member which varies with the spring constant K _T which varies depending on the load and the reciprocating of the movable member depending on the load. A linear compressor control method, characterized in that any one of varying stroke which is a linear movement distance. The method of claim 6, The second step is a linear compressor control method, characterized in that the movable member reciprocates linearly to the top dead center even if the stroke of the movable member is variable. A fixing member including a compression space compressing the refrigerant therein; A movable member compressing the refrigerant sucked into the compression space while reciprocating linearly moving in the fixed member in the axial direction; A mechanical spring installed to elastically support the movable member in both the moving directions of the movable member and having a constant mechanical spring constant K _m ; A gas spring having a gas spring constant K _g which varies depending on a load of a refrigerant sucked into the compression space; And a linear motor installed to be connected to the movable member to linearly reciprocate the movable member in the axial direction, wherein the linear compressor is used in a linear compressor installed in a refrigeration / air conditioning cycle. Calculating a load in proportion to a difference between a pressure at which the refrigerant is condensed (condensation pressure) and a pressure at which the refrigerant is evaporated (evaporation pressure) and a pressure (average pressure) that is an average of the condensation pressure and the evaporation pressure; And, And a second step of varying a stroke, which is a reciprocating linear movement distance of the movable member, depending on the load. The method of claim 8, The second step is a linear compressor control method, characterized in that the movable member reciprocates linearly to the top dead center even if the stroke of the movable member is variable.

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