Control device for linear compressor

Abstract

A control device for a linear compressor, according to one aspect of the present disclosure, comprises: an inverter unit that supplies an alternating voltage to the linear compressor on the basis of a control signal; and a control unit that supplies the control signal to the inverter unit so as to control reciprocating motion of a piston, wherein the control unit performs control such that a first alternating voltage having a first amplitude is supplied to a motor in a first cycle, and a second alternating voltage having a second amplitude smaller than the first amplitude is supplied to the motor in a second cycle.

Description

Control device for a linear compressor

[0001] The present disclosure relates to a compressor control device, and more specifically, to a control device for a linear compressor capable of efficiently controlling a linear compressor.

[0002] A compressor is generally a device that increases pressure by compressing refrigerants or various other working gases, and is widely used in refrigeration equipment, such as refrigerators and air conditioners.

[0003] Compressors are broadly classified into reciprocating compressors, rotary compressors, and scroll compressors.

[0004] In a reciprocating compressor, a compression space is formed between the piston and the cylinder where the working gas is drawn in and discharged, and the piston compresses the refrigerant as it moves in a straight line back and forth inside the cylinder.

[0005] In a rotary compressor, a compression space is formed between an eccentrically rotating roller and a cylinder where working gas is drawn in and discharged, and the roller compresses the refrigerant as it rotates eccentrically along the inner wall of the cylinder.

[0006] In a scroll compressor, a compression space is formed between an orbiting scroll and a fixed scroll where working gas is drawn in and discharged, and the orbiting scroll compresses the refrigerant as it rotates along the fixed scroll.

[0007] Among them, reciprocating compressors can be classified into reciprocal type (reciprocal compressor) and linear type (linear compressor) depending on the method of driving the piston.

[0008] Specifically, the reciprocating method converts the rotational force of a rotary motor into linear reciprocating motion by connecting a crankshaft to the crankshaft and a piston to the crankshaft, whereas the linear method directly connects a piston to the actuator of a linear motor to cause the piston to reciprocate using the motor's linear motion.

[0009] Such reciprocating compressors consist of an electric unit that generates driving force and a compression unit that receives driving force from the electric unit and compresses the fluid. Motors are generally used as the electric unit, and in the case of the aforementioned linear type, a linear motor is used.

[0010] When the above reciprocating compressor is used in a refrigerator or air conditioner, the voltage input to the reciprocating compressor is varied to vary the compression ratio of the reciprocating compressor, and accordingly, the freezing capacity can be controlled.

[0011] As mentioned above, linear reciprocating compressors have lower friction losses because they lack a crankshaft that converts rotational motion into linear motion, so they have higher compression efficiency than reciprocating compressors.

[0012] Meanwhile, the reciprocating compressor for the refrigerator controls the operating frequency, and the linear compressor controls the stroke size to implement variable cooling power.

[0013] Linear compressors control the size of the piston stroke according to the load to ensure efficient operation through appropriate variable cooling power.

[0014] Prior Art 1 (Korean Published Patent Application No. 10-2010-0104952) does not detect TDC under general load conditions where full stroke control is not required, detects a characteristic point where the phase difference (or gas spring constant) between the motor current and the stroke numerically matches the load power according to the compressor load, drives the motor by supplying input power corresponding to the detected characteristic point, and thereby reduces power consumption by changing the cooling power accordingly.

[0015] Meanwhile, the aforementioned TDC is an abbreviation for "Top Dead Center," which is the English notation for the piston's top dead center in a linear compressor; physically, it refers to the stroke at the completion of the piston's compression stroke. Similarly, Bottom Dead Center (BDC) is an abbreviation for "Bottom Dead Center" and physically refers to the stroke at the completion of the piston's intake stroke.

[0016] Prior art document 2 (Korean Published Patent Application No. 10-2015-0072167) designs the initial value of the piston based on the normal operating range and increases the maximum cooling power by adding DC current to the motor current in the high-load operating range to increase the initial value of the piston. However, in the low-load operating range, efficiency may decrease as friction losses and re-expansion losses increase.

[0017]

[0018] The problem that the present disclosure aims to solve is to provide a control device and method for a linear compressor capable of improving efficiency.

[0019] The problem that the present disclosure aims to solve is to provide a control device and method for a linear compressor capable of reducing losses during low-cooling power control.

[0020] The problem that the present disclosure aims to solve is to provide a control device and method for a linear compressor capable of improving low-cooling efficiency through variable voltage control.

[0021] The problem to be solved by the present disclosure is to provide a control device and method for a linear compressor capable of operating in an optimal operating mode according to the load.

[0022] The problems of the present disclosure are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0023]

[0024] To achieve the above or other purposes, a control device for a linear compressor according to one aspect of the present disclosure can improve efficiency through variable voltage control when controlling low cooling power.

[0025] To achieve the above or other purposes, a control device for a linear compressor according to one aspect of the present disclosure can reduce losses and improve efficiency by utilizing a cycle in which no discharge occurs.

[0026] A linear compressor according to one aspect of the present disclosure comprises a piston and a motor.

[0027] Additionally, a linear compressor according to one aspect of the present disclosure comprises a motor, a cylinder, a piston disposed inside the cylinder, a discharge valve disposed at one end of the cylinder, and a suction valve disposed at one end of the piston.

[0028] A control device for a linear compressor according to one aspect of the present disclosure includes an inverter unit that supplies an alternating current voltage to the linear compressor based on a control signal, and a control unit that supplies the control signal to the inverter unit to control the reciprocating motion of the piston.

[0029] The above control unit controls the motor to supply a first alternating current voltage having a first amplitude in a first cycle and to supply a second alternating current voltage having a second amplitude smaller than the first amplitude in a second cycle.

[0030] The above control unit controls the intake valve and the discharge valve to be open in the first cycle, and in the second cycle, the intake valve to be open and the discharge valve not to be opened.

[0031] The above control unit can control the discharge valve to open once every two cycles in a first operating mode, and control the discharge valve to open once every one cycle in a second operating mode where the load is greater than in the first operating mode.

[0032] The above control unit controls the linear compressor with the first cycle and the second cycle in the first operating mode, and controls the linear compressor only with the first cycle in the second operating mode, where the load is greater than in the first operating mode.

[0033] The above first cycle and the above second cycle may be performed alternately.

[0034] When the first cycle is performed once, the second cycle may be performed two or more times.

[0035] The amplitude of the first alternating current voltage may be 60% or less of the amplitude of the second alternating current voltage.

[0036] The operating frequency of the first cycle above may be different from the operating frequency of the second cycle above.

[0037] The above control unit can control the stroke of both the first cycle and the second cycle to be smaller than the maximum value.

[0038] A control device for a linear compressor according to one aspect of the present disclosure may further include a phase difference detection unit that detects a phase difference between a motor current applied to the motor and a stroke, and a power calculation unit that calculates a load power based on a motor voltage applied to the motor and a motor current applied to the motor.

[0039] A control device for a linear compressor according to one aspect of the present disclosure may further include a voltage detection unit for detecting a motor voltage applied to the motor, a current detection unit for detecting a motor current applied to the motor, and a stroke calculation unit for calculating the stroke based on the motor voltage and the motor current.

[0040] A control device for a linear compressor according to one aspect of the present disclosure may further include a gas spring calculation unit that calculates a gas spring constant based on the motor current, the stroke, and the phase difference.

[0041]

[0042] According to at least one of the embodiments of the present disclosure, efficiency can be improved by operating in an optimal operating mode depending on the load.

[0043] The problem that the present disclosure aims to solve is that, when controlling low cooling power, losses can be reduced by reducing the displacement and speed of the piston.

[0044] According to at least one of the embodiments of the present disclosure, low cooling efficiency can be improved through variable voltage control.

[0045] The effects of the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0046] FIG. 1 is a perspective view of a refrigerator including a linear compressor according to one embodiment of the present disclosure.

[0047] FIG. 2 is a cross-sectional view of a linear compressor according to one embodiment of the present disclosure.

[0048] FIG. 3 is an internal block diagram of a control device for a linear compressor according to one embodiment of the present disclosure.

[0049] FIG. 4 is an internal block diagram of a control device for a linear compressor according to one embodiment of the present disclosure.

[0050] FIGS. 5 and FIGS. 6 are drawings referenced in the description of parameter calculation according to an embodiment of the present disclosure.

[0051] FIG. 7 is a PV diagram according to the stroke cycle of a linear compressor according to one embodiment of the present disclosure.

[0052] Figure 8 is a PV diagram showing the cycles of Figure 7 separated.

[0053] FIG. 9 is a drawing illustrating motor voltage, motor current, and stroke according to one embodiment of the present disclosure.

[0054] FIG. 10 is a drawing illustrating motor voltage, motor current, and stroke according to one embodiment of the present disclosure.

[0055] Figure 11 is a PV curve during normal operation.

[0056] FIG. 12 is a drawing referenced for the explanation of the motor voltage, suction stroke, and discharge stroke during normal operation.

[0057] FIG. 10 is a drawing referenced for the description of the motor voltage, suction stroke, and discharge stroke during delta operation according to one embodiment of the present disclosure.

[0058] FIG. 14 is a diagram illustrating a motor current according to one embodiment of the present disclosure.

[0059] FIGS. 15a to 21b are drawings referenced in the description of the stroke and piston movement during linear compressor control according to one embodiment of the present disclosure.

[0060] FIGS. 22 to 25 are drawings comparing normal operation and delta operation according to one embodiment of the present disclosure.

[0061] FIGS. 26 and FIGS. 27 are drawings referenced in the description of variable cooling operation according to one embodiment of the present disclosure.

[0062]

[0063]

[0064] Embodiments of the present disclosure will be described in detail below with reference to the attached drawings. However, the present disclosure is not limited to these embodiments and can be modified in various forms.

[0065] In the drawings, parts unrelated to the description have been omitted to clearly and briefly explain the present disclosure, and the same drawing reference numerals are used for identical or extremely similar parts throughout the specification.

[0066] Meanwhile, the suffixes "unit," "module," and "part" for components used in the following description are assigned solely for the ease of drafting this specification and do not inherently confer any particularly significant meaning or role. Accordingly, the terms "unit," "module," and "part" may be used interchangeably.

[0067] Additionally, in this specification, terms such as first, second, etc. may be used to describe various elements, but these elements are not limited by these terms. These terms are used only to distinguish one element from another.

[0068] FIG. 1 is a perspective view of a refrigerator including a linear compressor according to one embodiment of the present disclosure.

[0069] A linear compressor according to one embodiment of the present disclosure can be used in home appliances such as refrigerators and air conditioners.

[0070] Referring to FIG. 1, a main board (104) for controlling the operation of the refrigerator (100) is provided inside a home appliance such as a refrigerator (100). The control device of the linear compressor of the present invention, which is described below, can be implemented in the form of a circuit or module on the main board (104). The main board (104) is electrically connected to the linear compressor (102).

[0071] The refrigerator (100) operates by driving a linear compressor (102). In order for the internal storage compartment of the refrigerator (100) to remain cold, cold air must be supplied into the storage compartment. To supply cold air, the linear compressor (102) sucks in and compresses a refrigerant in gaseous form, and the compressed high-temperature / high-pressure refrigerant is liquefied as it passes through a condenser. The refrigerant coming out of the condenser passes through an evaporator, and through heat exchange, the temperature of the air around the evaporator is lowered to generate cold air. The refrigerant that has passed through the evaporator is supplied back to the linear compressor (102), and the circulation of the refrigerant takes place. Through the repetition of this process, cold air is supplied into the storage compartment of the refrigerator (100).

[0072] FIG. 2 is a cross-sectional view of a linear compressor according to one embodiment of the present disclosure.

[0073] Referring to FIG. 2, the linear compressor (102) includes a sealed container (32) that forms the exterior. An inlet pipe (32a) through which refrigerant flows in and an outlet pipe (32b) through which refrigerant flows out are installed on one side of the sealed container (32).

[0074] The linear compressor (102) includes a piston (36) and a motor (40). The piston (36) may be disposed inside a cylinder (34). An intake valve (52) may be disposed at one end of the piston (36). A discharge valve (54b) may be disposed at one end of the cylinder (34).

[0075] A cylinder (34) is installed so as to be fixed inside the sealed container (32). A piston (36) is positioned inside the cylinder (34). The piston (36) compresses the refrigerant sucked into the compression space (P) inside the cylinder (34) through reciprocating motion.

[0076] A spring (38) is installed at one end of the piston (36) to elastically support the piston (36) in the direction of motion. The piston (36) is connected to a motor (40) that generates driving force, and the piston (36) performs reciprocating motion according to the driving of the motor (40).

[0077] An intake valve (52) is installed at one end of the piston (36) in contact with the compression space (P), and a discharge valve assembly (54) is installed at one end of the cylinder (34) in contact with the compression space (P). Each of the intake valve (52) and the discharge valve assembly (54) is automatically controlled to open and close according to the pressure inside the compression space (P).

[0078] Oil is contained in the inner bottom surface of the sealed container (32), and an oil supply device (60) for pumping oil is placed inside the sealed container (32). An oil supply pipe (48a) is formed inside the lower frame (48) of the sealed container (32) to supply oil between the piston (36) and the cylinder (34). The oil supply device (60) pumps oil by vibrations generated as the piston (36) reciprocates, and the pumped oil is supplied along the oil supply pipe (48a) into the gap between the piston (36) and the cylinder (34) to perform cooling and lubrication.

[0079] The cylinder (34) is formed in a hollow shape so that the piston (36) can reciprocate, and a compression space (P) is formed inside.

[0080] The cylinder (34) can be installed on the same straight line as the inlet pipe (32a) with one end positioned close to the inside of the inlet pipe (32a).

[0081] A discharge valve assembly (54) is installed at one end of the cylinder (34) on the side opposite to the inlet pipe (32a). The discharge valve assembly (54) consists of a discharge cover (54a) that forms a predetermined discharge space on one end of the cylinder (34), a discharge valve (54b) installed to open and close one end of the cylinder on the side of the compression space (P), and a valve spring (54c) that provides axial elastic force between the discharge cover (54a) and the discharge valve (54b). An O-ring (R) is fitted onto the inner surface of one end of the cylinder (34) to tightly seal the discharge valve (54a) and the cylinder (34).

[0082] A curved loop pipe (58) is connected between one side of the discharge cover (54a) and the discharge pipe (32b). The loop pipe (58) performs the function of guiding the compressed refrigerant to be discharged to the outside, and also cushions the transmission of vibrations caused by the interaction of the cylinder (34), piston (36), and motor (40) to the entire sealed container (32).

[0083] As the piston (36) reciprocates inside the cylinder (34), when the pressure in the compression space (P) reaches a predetermined discharge pressure, the valve spring (54c) is compressed and the discharge valve (54b) is opened. Accordingly, the refrigerant compressed inside the compression space (P) is discharged from the compression space (P), and the compressed refrigerant discharged from the compression space (P) is discharged to the outside along the loop pipe (58) and the outlet pipe (32b).

[0084] The refrigerant introduced from the inlet pipe (32a) flows into the compression space (P) through the refrigerant passage (36a) formed in the center of the piston (36). One end of the piston (36) adjacent to the inlet pipe (32a) is directly connected to the motor (40) by a connecting member (47). The suction valve (52) is formed in the shape of a thin plate, with a portion of the central part cut out so that the central part opens and closes the refrigerant passage (36a) of the piston (36), and is installed so that one side is fixed to one end of the piston (36a) by a screw.

[0085] As the piston (36) reciprocates inside the cylinder (34), when the pressure in the compression space (P) becomes lower than the discharge pressure and falls below a predetermined suction pressure, the suction valve (52) is opened and the refrigerant is sucked into the compression space (P). When the pressure in the compression space (P) reaches a predetermined suction pressure, the suction valve (52) is closed and the refrigerant is compressed in the compression space (P).

[0086] The piston (36) is installed to be elastically supported in the direction of motion. Specifically, a piston flange (36b) protruding radially from one end of the piston (36) adjacent to the inlet pipe (32a) is elastically supported in the direction of motion of the piston (36) by a mechanical spring (38), such as a coil spring, and the refrigerant contained in the compression space (P) on the opposite side of the inlet pipe (32a) acts as a gas spring by its own elastic force to elastically support the piston (36).

[0087] The motor (40) may be a linear motor and consists of an inner stator (42), an outer stator (44), and a permanent magnet (46).

[0088] The inner stator (42) is configured such that a plurality of laminations (42a) are stacked in the circumferential direction and is installed to be fixed to the outside of the cylinder (34) by a frame (48). The outer stator (44) is configured such that a plurality of laminations (44b) are stacked in the circumferential direction around a coil winding body (44a) to which a coil is wound, and is installed to the outside of the cylinder (34) by a frame (48) with a predetermined gap from the inner stator (42). A permanent magnet (46) is positioned in the gap between the outer stator (44), the inner stator (42), and the outer stator (44), and is connected to the piston (36) by a connecting member (47). According to an embodiment, the coil winding body (44a) may be fixedly installed to the outside of the inner stator (42).

[0089] FIG. 3 is an internal block diagram of a control device for a linear compressor according to one embodiment of the present disclosure.

[0090] Referring to FIG. 3, the control device of the linear compressor includes an inverter unit (360) that supplies an alternating voltage to the linear compressor (102) based on a control signal, and a control unit (350) that controls the reciprocating motion of the piston (36) by supplying the control signal to the inverter unit (360).

[0091] The inverter unit (360) converts the DC voltage output from the smoothing capacitor into an AC voltage and provides it to the compressor (102).

[0092] The compressor motor (40) is driven by the alternating current voltage provided by the inverter unit (360). The piston (36) performs reciprocating motion by the driving of the motor (40). The inverter unit (360) may include at least one switching element.

[0093] The control unit (350) applies a control signal to the inverter unit (360). By the control signal applied by the control unit (350), the inverter unit (360) is driven at a predetermined operating frequency and supplies an alternating voltage to the motor (40) of the compressor (102). That is, the magnitude of the alternating voltage applied to the compressor (102) is adjusted by the control signal provided by the control unit (350). By adjusting the magnitude of the alternating voltage, the reciprocating motion of the piston (36) by the motor (40) is controlled.

[0094] The control unit (350) can generate a control signal to control the compressor (102) based on the commanded cooling value of the compressor (102) and the estimated stroke of the piston (36), and can provide the generated control signal to the inverter unit (360).

[0095] Here, the commanded cooling value can be received from the main control unit of a home appliance, such as a refrigerator, which is connected to the compressor control unit (908).

[0096] The inverter unit (600) receives a control signal from the control unit (350) and, according to the received control signal, supplies an alternating voltage to the compressor motor (40) of the linear compressor (102). The alternating voltage may be input power for driving the compressor motor (40).

[0097] During normal operation, the control unit (350) can generate a control signal to supply input power corresponding to a characteristic point.

[0098] The control device of the linear compressor may include a parameter calculation unit (320). For example, the control device of the linear compressor may include a phase difference detection unit (323) that detects a phase difference between the motor current applied to the compressor motor (40) and the stroke, and a power calculation unit (322) that calculates the load power based on the motor voltage applied to the motor (40) and the motor current applied to the motor (40).

[0099] The control unit (350) can detect a characteristic point where the phase difference and the load power match, and output a control signal to supply input power corresponding to the characteristic point. The inverter unit (360) can supply the input power to the motor (40) according to the control signal.

[0100] Additionally, the control device of the linear compressor may include one or more sensors (310). For example, the control device of the linear compressor may include a voltage detection unit (312) for detecting a motor voltage applied to the motor (40) and a current detection unit (311) for detecting a motor current applied to the motor (40).

[0101] Additionally, the control device of the linear compressor may further include a stroke calculation unit (321) that calculates a stroke based on the motor voltage and the motor current.

[0102] In another embodiment, the detected stroke can be used without calculating the stroke. To this end, the control device of the linear compressor may further include a stroke detection unit (not shown).

[0103] Meanwhile, the control device of the linear compressor may further include a power unit (380). The power unit (380) may include a rectifier unit that receives commercial AC power and converts it into DC power, and a smoothing capacitor that smooths the DC power.

[0104] The current detection unit (311) detects the motor current applied to the motor (40) of the linear compressor (102) according to the load of the compressor or the load of the refrigeration system, and the voltage detection unit (312) detects the motor voltage applied between the two ends of the linear motor (40) according to the load of the compressor.

[0105] The relationship between the motor voltage, motor current, and stroke is given by Equation (eq1) of Fig. 5. That is, the stroke calculation unit (321) can calculate the stroke using Equation (eq1) based on the motor voltage detected through the voltage detection unit (312) and the motor current detected through the current detection unit (311).

[0106] Here, x represents the stroke, α represents the motor constant, Vm represents the motor voltage, R represents the resistance, L represents the inductance, and i represents the motor current.

[0107] The phase difference detection unit (323) detects the phase difference between the motor current detected as above and the stroke calculated through the stroke calculation unit (321).

[0108] Meanwhile, the power calculation unit (322) calculates power by multiplying the motor current detected through the current detection unit (311) and the motor voltage detected through the voltage detection unit (312). Since the power at this time is a value determined by the load of the compressor or the power input to the linear motor (40), it is called load power.

[0109] The control unit (350) detects a characteristic point where the phase difference output from the phase difference detection unit (323) and the load power calculated through the power calculation unit (322) match. Additionally, the control unit (350) outputs a control signal to supply input power corresponding to the characteristic point.

[0110] The above characteristic point is determined from the point where the phase difference (180°-θi,x) output from the phase difference detection unit (323) and the load power (POWER) calculated through the power calculation unit (322) match.

[0111] The control unit (350) supplies a control signal to the inverter unit (360) to supply input power according to the characteristic point, thereby converting the DC power output from the power unit (800) into motor driving power through the inverter unit (360). Here, the control signal is generally a PWM signal that controls the PWM (Pulse Width Modulation) voltage duty of the inverter unit (360). The inverter unit (360) supplies the input power to the motor (40) according to the control signal.

[0112] FIG. 4 is an internal block diagram of a control device for a linear compressor according to one embodiment of the present disclosure.

[0113] Referring to FIG. 4, the control device of the linear compressor may further include a gas spring calculation unit (324) that calculates a gas spring constant based on the motor current, stroke, and phase difference.

[0114] The control unit (350) can detect a characteristic point where the gas spring constant and the load power match, and output a control signal to supply input power corresponding to the characteristic point. The inverter unit (360) can supply the input power to the motor (40) according to the control signal.

[0115] Meanwhile, various springs are installed so that the piston (36) can be elastically supported in the direction of motion even when it moves in a reciprocating linear motion by the motor (40). Specifically, a coil spring, which is a type of mechanical spring, is installed to elastically support the piston in the direction of motion of the sealed container and cylinder, 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 (Km), and the gas spring has a gas spring constant (Kg) that varies according to the load. The natural frequency (fmc) of the linear compressor is determined by considering the mechanical spring constant (Km) and the gas spring constant (Kg). The relationship between the natural frequency (fmc) and the mechanical and gas spring constants (Km, Kg) is given by Equation (eq7) in Fig. 6.

[0116] Here, fmc is the natural frequency of the piston, Km is the mechanical spring constant, Kg is the gas spring constant, and m is the mass of the piston.

[0117] That is, the gas spring constant calculation unit (324) calculates the gas spring constant according to the load of the linear compressor, and calculates the gas spring constant (Kg) based on the motor current detected through the current detection unit (311), the stroke calculated and output from the stroke calculation unit (321), and the phase difference between the current and the stroke detected through the phase difference detection unit (323). The gas spring constant (Kg) can be calculated as shown in Equation (eq5) of FIG. 6.

[0118] Here, α is the motor constant, ω is the operating frequency, Km is the mechanical spring constant, Kg is the gas spring constant, m is the mass of the piston, |I| is the peak current value for one cycle, and |X| is the peak stroke value for one cycle.

[0119] Meanwhile, the power calculation unit (322) calculates power by multiplying the motor current detected through the current detection unit (311) and the motor voltage detected through the voltage detection unit (312). Since the power at this time is a value determined by the load of the compressor or the power input to the linear motor (40), it is called load power.

[0120] The control unit (350) detects a characteristic point where the gas spring constant (Kg) output from the gas spring constant calculation unit (324) matches the load power calculated through the power calculation unit (322). Additionally, the control unit (350) outputs a control signal to supply input power corresponding to the characteristic point.

[0121] FIGS. 5 and FIGS. 6 are drawings referenced in the description of parameter calculation according to an embodiment of the present disclosure.

[0122] Figure 5 illustrates the formulas and factors for stroke and power calculation.

[0123] The parameter calculation unit (320) can calculate the stroke based on current and voltage information detected by the sensor (310). According to an embodiment, the stroke can be calculated based on the known voltage supplied to the motor (40) of the compressor (102) and the current detected by the sensor (310).

[0124] The parameter calculation unit (320) can calculate the stroke (x) by applying the voltage and current of the compressor motor (40) to the first mathematical equation (eq1) of FIG. 5.

[0125] Additionally, the parameter calculation unit (320) can calculate power based on current and voltage information detected by the sensor (310). The parameter calculation unit (320) can calculate power (P) by applying the voltage and current of the compressor motor (40) to the second mathematical equation (eq2) of FIG. 5.

[0126] The cooling power of the compressor can be defined by the distance between the bottom dead center (BDC) and the top dead center (TDC) of the piston during linear reciprocating motion. Additionally, the cooling power of the compressor may be defined by the operating frequency of the compressor motor and by the power applied to the compressor motor.

[0127] The compressor control unit (100) can increase the cooling power of the compressor if it is determined that the load of the compressor is large or that the load of the compressor has increased.

[0128] Additionally, the parameter calculation unit (320) can detect a phase difference by comparing the phase of the stroke with the phase of the motor current.

[0129] Figure 6 illustrates the calculation formulas for the gas spring (Kg), gas damping (Cg), and natural frequency (fmc).

[0130] The gas spring (Kg) constant can be calculated based on the motor current and the calculated stroke (x). The gas spring (Kg), gas damping (Cg), and natural frequency (fmc) can be calculated based on the mechanical equations exemplified in FIG. 6.

[0131] The parameter calculation unit (320) can calculate the gas spring (Kg) and gas damping (Cg). The parameter calculation unit (320) can calculate the phase difference between the motor current applied to the compressor motor (40) and the stroke (x) of the piston. The parameter calculation unit (320) can calculate the gas spring constant (Kg) based on the motor current, the stroke, and the phase difference.

[0132] Additionally, the parameter calculation unit (320) can calculate a gas damping constant (Cg) based on the motor current, the stroke, and the phase difference.

[0133] In addition, the parameter calculation unit (320) can calculate the natural frequency (fmc) using the calculated gas spring (Kg) and mechanical spring constant.

[0134] The natural frequency (fmc) of the piston (or linear compressor) is calculated by considering the above mechanical spring constant (Km) and gas spring constant (Kg). The natural frequency (fmc) of the piston is equal to the last mathematical equation (eq7) of Fig. 6.

[0135] Refrigerators have a wide range of usable temperatures, and different cooling power is required for each temperature range. At this time, the compressor has maximum operating efficiency in a specific range, and as a result, the operating efficiency of the compressor decreases when the cooling power of the refrigerator is varied. In particular, the linear compressor (102) may have reduced efficiency in the low cooling power range.

[0136] According to the present disclosure, the control unit (350) can improve efficiency through variable voltage control, which adjusts the motor voltage according to the cycle. The control unit (350) can reduce losses by reducing the displacement and speed of the piston (36) by controlling the motor voltage of some cycles to be lower than the motor voltage of other cycles. Variable voltage control is particularly effective in the low cooling power range.

[0137] The control unit (350) controls the motor (40) to supply a first alternating current voltage having a first amplitude in the first cycle and to supply a second alternating current voltage having a second amplitude smaller than the first amplitude to the motor (40) in the second cycle.

[0138] Additionally, the control unit (350) can reduce losses and improve efficiency by using a cycle in which no discharge occurs when driving the linear compressor (102). In particular, when controlling low cooling power, the control unit (350) can improve the efficiency of the low cooling power section by adding one or more cycles in which no discharge occurs.

[0139] The control unit (350) controls the suction valve (52) and the discharge valve (54b) to be open in the first cycle, and in the second cycle, the suction valve (52) is opened and the discharge valve (54b) is not opened. That is, in the first cycle, there is a discharge stroke in which the discharge valve (54b) is opened, and in the second cycle, there is no discharge stroke in which the discharge valve (54b) is opened.

[0140] In this specification, the first cycle in which discharge occurs is named the working cycle, and the second cycle in which discharge does not occur may be named the idle cycle.

[0141] Additionally, the first cycle in which discharge occurs can also be named a normal cycle or a beta cycle. The second cycle in which discharge does not occur can also be named a delta cycle.

[0142] When controlling low cooling power, the control unit (350) can sufficiently lower the motor voltage in an idle cycle where no discharge occurs to prevent discharge from occurring.

[0143] The control unit (350) can control the linear compressor (102) in an optimal operating mode by combining an idle cycle in which no discharge occurs and a working cycle in which discharge occurs.

[0144] The control unit (350) can control the linear compressor (102) with an idle cycle and a working cycle in the first operating mode (delta operating mode) when controlling low cooling power.

[0145] The control unit (350) can control the linear compressor (102) only by working cycle in the second operating mode (beta operating mode), where the load is greater than in the first operating mode (delta operating mode).

[0146] The control unit (350) can control the discharge valve (54b) to open once per 2 cycles in the first operating mode. The control unit (350) can control the discharge valve (54b) to open once per cycle in the second operating mode, which has a greater load than the first operating mode.

[0147] The control unit (350) can improve efficiency by controlling the linear compressor (102) to an optimal operating mode according to the load. For example, while performing the normal operation described above, by switching to variable voltage control in the low cooling power range, efficient operation is possible throughout the entire range.

[0148] In this specification, an operating mode including a second cycle (idle cycle) in which no discharge occurs is named a delta operating mode, and an operating mode consisting only of cycles in which discharge occurs may be named a normal operating mode or a beta operating mode.

[0149] According to the present disclosure, the magnitude of the motor voltage is reduced relative to the motor voltage of the working cycle so that the piston stroke generates suction and discharge during one cycle (working cycle) and performs only the suction stroke during the subsequent one or two or more cycles (idling cycle). Accordingly, the linear compressor (102) can be operated more efficiently under operating conditions where the required cooling power is low.

[0150] The motor voltage in the idle cycle is set to be sufficiently small, less than 60% of the motor voltage command value in the working cycle, so that discharge does not occur depending on the load conditions.

[0151] FIG. 7 is a PV diagram according to the stroke cycle of a linear compressor according to one embodiment of the present disclosure. FIG. 8 is a PV diagram showing the cycles of FIG. 7 separated.

[0152] FIG. 7 is a PV diagram illustrating the working cycle and the idle cycle together. In FIG. 7, the horizontal axis may represent the volume of the refrigerant within the compression space. Additionally, since the volume of the compression space is proportional to the displacement of the piston (36), the horizontal axis may represent the displacement of the piston (36). In FIG. 7, the vertical axis (P) represents the pressure within the compression space.

[0153] FIG. 8 briefly illustrates the working cycle and the idle cycle separately, with (a) showing the working cycle (810) and (b) showing the idle cycle (820).

[0154] The stroke cycle of the linear compressor (102) is broadly divided into a compression stroke and a suction stroke. More specifically, the stroke cycle of the linear compressor (102) may include suction, compression, discharge, and re-expansion strokes.

[0155] The linear compressor (102) can sequentially perform suction, compression, discharge, and re-expansion strokes.

[0156] The linear compressor (102) repeatedly performs a working cycle (810) and an idle cycle (820). The control device of the linear compressor (102) according to the present disclosure sets the stroke interval of the cycle as a 'control interval' and controls the magnitude of the force applied to the piston (36) by adjusting the magnitude of the alternating voltage applied to the piston (36) for each control interval.

[0157] Referring to FIGS. 7 and 8, in a working cycle (810), when the pressure in the compression space (P) reaches the discharge pressure (P706), the discharge valve (54b) opens. When the piston (36) reaches a predetermined position (P706), for example, top dead center (TDC) or the point closest to top dead center (TDC), the discharge valve (54b) begins to open.

[0158] The working cycle includes a discharge stroke in which the refrigerant is discharged. The discharge stroke is performed during the stroke E section in the direction of Top Dead Center (TDC) (section P706→P701). The discharge stroke (section P706→P701) is included in the working cycle (810).

[0159] After the discharge stroke, a re-expansion stroke is performed (P701→P702 section). During re-expansion, the piston (360) backstrokes (Stroke C) in the direction of the bottom dead center (BDC), and the volume increases. The re-expansion stroke may be included in the idle cycle (820).

[0160] Afterward, an intake stroke is performed. The piston (36) performs a linear motion in the direction of the bottom dead center (BDC) (P702→P703 section). For example, the piston (36) can move to the maximum value (P703 point) in the direction of the bottom dead center (BDC) of the idle cycle (820).

[0161] In addition, the suction valve (52) is opened so that the refrigerant flows into the cylinder (34).

[0162] The suction valve (52) is closed, and the piston (36) moves in a straight line from bottom dead center (BDC) to top dead center (TDC), and the refrigerant in the compression space (P) is gradually compressed (P703→P704 section). Accordingly, the pressure in the compression space (P) increases, and the volume of the refrigerant decreases.

[0163] In the compression stroke of the idle cycle (820), a relatively low motor voltage is applied, and accordingly, the displacement of the piston (36) is reduced, and the pressure in the compression space (P) does not reach the discharge pressure.

[0164] Again, the piston (36) moves in a straight line in the direction of the bottom dead center (BDC) (section S704->P705). For example, the piston (36) can move to the maximum value in the direction of the bottom dead center (BDC) of the working cycle (810) (point P735).

[0165] Meanwhile, in the idle cycle (820), the stroke (Stroke B) in the direction of the bottom dead center (BDC) is smaller than the stroke (Stroke A) in the direction of the bottom dead center (BDC) in the working cycle (810). Therefore, the loss corresponding to the stroke difference (Stroke D) can be reduced.

[0166] Afterward, the piston (36) moves in a straight line toward the top dead center (TDC), and a compression stroke is performed (section S705->P706). When the pressure in the compression space (P) reaches the discharge pressure (P706), the discharge valve (54b) opens.

[0167] The linear compressor (102) is driven by a linear motor (40), which reduces friction losses compared to a reciprocating compressor, making it possible to design a high-efficiency compressor.

[0168] Unlike a reciprocating compressor that sets the cooling power by changing the rotational speed of the motor, a linear compressor (102) can control the cooling power by setting the operating frequency near the system resonance frequency and varying the magnitude of the motor voltage to increase or decrease the magnitude of the piston stroke.

[0169] For refrigerator compressors, the load conditions in the frequently used operating range are at the level of 30–40% of the maximum cooling power. When the motor voltage is reduced for low-cooling operation of a linear compressor, the top clearance increases along with the stroke reduction compared to full-stroke operation, which discharges all the compressed gas inside the compression space. This can cause friction losses and re-expansion losses to increase, which may lead to a decrease in efficiency. Here, top clearance refers to the gap between the head and the piston when the piston is at top dead center (TDC).

[0170] The latest refrigerators are increasingly trending toward continuous operation under ultra-low cooling conditions to improve energy efficiency and reduce internal temperature fluctuations.

[0171] According to the present disclosure, high-efficiency operation can be achieved even under low cooling conditions by controlling the stroke size such that the magnitude of the motor voltage is set differently for each cycle so that compression discharge occurs once (working cycle), and then only suction occurs without discharge through compression and re-expansion one or two times (idling cycle).

[0172] In a linear compressor (102), the magnitude of the AC motor voltage can be alternated so that an AC voltage of sufficient magnitude is applied for one cycle to cause suction and discharge, and for the following one or two cycles or more, an AC voltage of sufficiently small magnitude compared to the magnitude of the AC voltage of the previous cycle is applied so that only suction is possible without discharge, thereby reducing the magnitude of the discharge cooling power by about half and maintaining an efficient compression stroke.

[0173] The stroke and phase difference of the idle cycle (820) can be defined based on the working cycle (810). The size of the stroke in the working cycle (810) does not necessarily have to be a full stroke, and can be controlled to an appropriate stroke size according to the required cooling level (using the existing beta control as is).

[0174] According to the present disclosure, the efficiency of a linear compressor under low-load conditions can be improved solely by the operation method, without modifying the structure of the compressor. Furthermore, by extending the high-efficiency cooling range of the linear compressor, efficient operation methods for the refrigerator, such as continuous operation of the compressor, are made possible.

[0175] FIG. 9 is a drawing illustrating motor voltage, motor current, and stroke according to one embodiment of the present disclosure.

[0176] Referring to FIG. 9, the idle cycle (820) and the working cycle (810) can be performed alternately. When the idle cycle (820) is performed once, the working cycle (810) can be performed once. That is, the entire cycle consists of one idle cycle (820) and one working cycle (810).

[0177] The idle cycle (820) reduces only the amplitude while maintaining the sinusoidal waveform of the alternating voltage, making it easy to control and minimizing the possibility of distortion caused by voltage changes.

[0178] Meanwhile, the amplitude of the first alternating current voltage supplied to the idle cycle (820) may be 60% or less of the amplitude of the second alternating current voltage supplied to the working cycle (810). Accordingly, it is possible to control so that no discharge occurs in the idle cycle (820).

[0179] The amplitude of the first alternating current voltage supplied to the idle cycle (820) may be 50% or less of the amplitude of the second alternating current voltage supplied to the working cycle (810).

[0180] In particular, control can be performed most simply when the amplitude of the first alternating current voltage supplied to the idle cycle (820) is set to 50% of the amplitude of the second alternating current voltage supplied to the working cycle (810).

[0181] If the magnitude of the motor voltage in the idle cycle (820) is set to alternate to 50% of the working cycle (810), the current-stroke inertance phase (inertial resistance) is at an equivalent level compared to when operating with only the working cycle motor voltage, and the input power and cooling power are at half the level, allowing for efficient variable cooling power control even under low-load conditions such as continuous operation of the refrigerator.

[0182] Meanwhile, the driving frequency of the idle cycle (820) may be different from the driving frequency of the working cycle (810).

[0183] The driving frequency can be set to a single fixed value, but for more active resonance control, the driving frequency in the working cycle (810) and the idle cycle (820) can be alternately set differently.

[0184] In the idle cycle (820), there is no discharge stroke, and all the compressed refrigerant inside the compression chamber is re-expanded. Accordingly, the gas pressure acting on the piston head becomes greater than in the working cycle (810), and since the resonance frequencies can be different, the motor operating frequency can be set differently in an alternating manner.

[0185] FIG. 10 is a drawing illustrating motor voltage, motor current, and stroke according to one embodiment of the present disclosure.

[0186] Meanwhile, when the walking cycle (810) is performed once, the idle cycle (820) may be performed two or more times.

[0187] FIG. 10 illustrates an embodiment in which an idle cycle (820) is performed two or more times when a working cycle (810) is performed once.

[0188] The entire cycle of Fig. 10 consists of one working cycle (810) and two idle cycles (820).

[0189] Figure 11 is a PV curve during normal operation.

[0190] The stroke cycle of the linear compressor (102) is broadly divided into a compression stroke and a suction stroke. FIG. 11 shows the stroke cycle of the linear compressor (102) in the order of "P1110→P1120→P1130→P1140". In FIG. 11, the horizontal axis may represent the volume of the refrigerant in the compression space. Additionally, since the volume of the compression space is proportional to the displacement of the piston (36), the horizontal axis may represent the displacement of the piston (36). In FIG. 11, the vertical axis (P) represents the pressure in the compression space.

[0191] First, when the piston (36) is positioned at a predetermined position, for example, bottom dead center (BDC) within the cylinder (34), the suction valve (52) is opened so that the refrigerant flows into the cylinder (34).

[0192] When the inflow of refrigerant is complete, the suction valve (52) closes, and the piston (36) moves in a straight line from bottom dead center (BDC) to top dead center (TDC), and the refrigerant in the compression space (P) is gradually compressed (P1110→P1120 section). Accordingly, the pressure in the compression space (P) increases, and the volume of the refrigerant decreases.

[0193] When the piston (36) reaches a predetermined position, for example, top dead center (TDC), the discharge valve (54b) begins to open. At this time, the piston (36) remains at the top dead center (TDC) until the discharge valve (54b) is fully opened (point P1130), so the pressure in the compression space (P) is maintained, but the volume of the refrigerant continues to decrease due to the discharge of the refrigerant (P1120→P1130 section).

[0194] After this, when the discharge valve (54b) is fully opened, the compressed refrigerant is completely discharged to the outside through the discharge valve (54b). Accordingly, the pressure in the compression space (P) decreases, and the discharge valve (54b) closes (P1130→P1140 section).

[0195] When the discharge valve (54b) is closed, the piston (36) moves in a straight line again toward the bottom dead center (BDC). As a result, the compression space (P) expands, and the volume gradually increases while the pressure within the compression space (P) remains constant (P1140→P1110 section). When the piston (36) reaches the bottom dead center (BDC) (P1110 point), the suction valve (52) opens, and the inflow of refrigerant begins again.

[0196] In such normal operation, the stroke is also operated consistently by operating with the same stroke.

[0197] FIG. 12 is a drawing referenced for the description of the motor voltage, intake stroke, and discharge stroke during normal operation. FIG. 13 is a drawing referenced for the description of the motor voltage, intake stroke, and discharge stroke during delta operation according to one embodiment of the present disclosure. FIG. 14 is a drawing illustrating the motor current according to one embodiment of the present disclosure, illustrating the motor current during delta operation.

[0198] The horizontal axis of Figures 12 and 13 is the time axis, and the passage of time is displayed such that the cycle repeats in units of 360 to better represent the cycle.

[0199] Referring to FIG. 12, during normal operation, the motor AC voltage is repeatedly applied as a sine wave having one amplitude and a predetermined period.

[0200] One discharge occurs at two points (1210, 1220) where the top clearance is minimized.

[0201] Referring to Figures 13 and 14, during delta operation, the idle cycle and the working cycle are repeated.

[0202] The idle cycle and the working cycle can have the same period. However, the amplitudes of the idle cycle and the working cycle are different.

[0203] The amplitude of the idle cycle can be 60% or less of the amplitude of the working cycle. In the example of FIG. 13, the amplitude of the idle cycle can be 50% of the amplitude of the working cycle. When the motor voltage decreases, the motor current also decreases, and the stroke decreases.

[0204] Therefore, in the idle cycle, the displacement of the piston (36) is reduced, and sufficient compression is not achieved, so no discharge occurs.

[0205] Only during the working cycle, a single discharge occurs at the point (1310) where the top clearance is minimized.

[0206] According to the present disclosure, by voltage variable control, the discharge valve (54b) is opened only once every two cycles. Additionally, the displacement of the piston (26) being pushed less and then moving again is shortened, thereby reducing friction.

[0207] FIGS. 15a to 21b are drawings referenced in the description of the stroke and piston movement during linear compressor control according to one embodiment of the present disclosure.

[0208] FIGS. 15a, FIGS. 16a, FIGS. 17a, FIGS. 18a, FIGS. 19a, FIGS. 20a, and FIGS. 21a illustrate the position of the piston (36) within the cylinder (34) according to the stroke cycle.

[0209] FIGS. 15a, FIGS. 16a, FIGS. 17a, FIGS. 18a, FIGS. 19a, FIGS. 20a, and FIGS. 21a respectively show the positions of the pistons corresponding to the points indicated in FIGS. 15b, FIGS. 16b, FIGS. 17b, FIGS. 18b, FIGS. 19b, FIGS. 20b, and FIGS. 21b.

[0210] Referring to the drawings, the piston (36) performs reciprocating motion within the compression space inside the cylinder (34).

[0211] Referring to FIGS. 15a and 15b, when the pressure inside the compression space reaches the discharge pressure, the discharge valve (54b) opens due to the pressure, and the refrigerant compressed inside the cylinder (34) is discharged to the outside. FIG. 15a shows the position of the piston (36) at point P1610 during the discharge stroke.

[0212] Referring to FIGS. 16a and 16b, the re-expansion stroke and the suction stroke are performed as the piston (36) moves toward the bottom dead center (BDC). FIG. 16a shows the position of the piston (36) at point P1620 during the suction stroke. The suction valve (52) opens and the refrigerant flows in.

[0213] Referring to FIG. 17a and FIG. 17b, the piston (36) can move increasingly in the direction of the bottom dead center (BDC). For example, the piston (36) can move to the maximum value (point P1630) in the direction of the bottom dead center (BDC) of the working cycle.

[0214] Referring to FIG. 18a and FIG. 18b, as the piston (36) moves toward the top dead center (TDC), a compression stroke in which the pressure increases again can be performed. For example, the piston (36) can move to point P1640.

[0215] Because the piston (36) moves a short distance toward the bottom dead center (BDC) and then moves a short distance toward the top dead center (TDC), the pressure inside the compression space does not reach the discharge pressure. Therefore, no discharge occurs during the idle cycle.

[0216] Referring to FIGS. 19a and 19b, without discharge, the piston (36) moves toward the bottom dead center (BDC). Additionally, the suction valve (52) opens, and a suction stroke is performed in which refrigerant is introduced.

[0217] Referring to FIG. 20a and FIG. 20b, the piston (36) can move increasingly in the direction of the bottom dead center (BDC). For example, the piston (36) can move to the maximum value (point P1660) in the direction of the bottom dead center (BDC) of the idle cycle.

[0218] Subsequently, the piston (36) moves in a straight line from bottom dead center (BDC) to top dead center (TDC), and the refrigerant in the compression space (P) is gradually compressed (P1660→P1670 section). Accordingly, the pressure in the compression space (P) increases, and the volume of the refrigerant decreases. Referring to FIGS. 21a and 21b, when the pressure inside the compression space reaches the discharge pressure, the discharge valve (54b) opens due to the pressure, and the refrigerant compressed inside the cylinder (34) is discharged to the outside.

[0219] The reason the cooling variable efficiency of the linear compressor (102) decreases is that the smaller the cooling variable rate, the greater the loss ratio due to speed. Friction losses, etc. are proportional to the square of the speed.

[0220] According to the present disclosure, low cooling efficiency is improved through variable voltage control. By alternately reducing the voltage magnitude to decrease the piston operating speed, friction losses can be significantly reduced.

[0221] FIGS. 22 to 25 are drawings comparing normal operation and delta operation according to one embodiment of the present disclosure.

[0222] Figure 22 illustrates the change in displacement when TDC is the same at 0.4 mm for comparison of displacement between beta control and delta control.

[0223] Figure 23 is a PV diagram of beta control and delta control, where the TDC is also shown as 0.4 mm, and the area is shown to represent the cooling power.

[0224] In FIGS. 22 and 23, Δ=37.4 represents delta control with a command value (power command value, cooling command value) of 37.4, and β=41.7 and β=83.4 represent beta control with command values ​​of 41.7 and 83.4, respectively.

[0225] Referring to FIG. 22 and FIG. 23, when comparing Δ control and β control, the top clearance of Δ has a top clearance similar to that of β twice. For example, Δ=37.4 and β=83.4 in a working cycle have almost the same displacement (2210). Also, discharge (2310) occurs at the corresponding point (2210).

[0226] Meanwhile, in the idle stroke, the stroke of Δ control is smaller than the stroke of β control. For example, the stroke for Δ=37.4 is 7.96 mm, and the stroke for β=83.4 is 12.3 mm.

[0227] In addition, Δ has a cooling capacity similar to that of β. For example, Δ=110 and β=110 can have similar cooling capacities.

[0228] When comparing the efficiency of Δ control with that of β control having the same top clearance (e.g., comparing Δ=80 and β=160), the cooling power is half (50%), and the moving loss increases slightly.

[0229] Figure 24 shows the PV curve when the cooling power is the same.

[0230] Figure 25 is a PV diagram of beta control and delta control, in which the cooling power is shown equally and the area is shown to represent the cooling power.

[0231] In FIGS. 24 and 25, Δ=37.4 represents delta control with a command value (power command value, cooling command value) of 37.4, and β=41.7 and β=83.4 represent beta control with command values ​​of 41.7 and 83.4, respectively.

[0232] When comparing the Δ control (Δ=37.4) and β control (β=41.7) with the same cooling capacity in Figures 24 and 25 (see 2410, 2510), the TDC (0.4 mm) of the working cycle is half the level (50%) of the TDC (0.8 mm) of the idle cycle.

[0233] In addition, the stroke of the idle cycle (Δ=37.4) is about 8 mm, which is significantly smaller than the stroke of 11.6 mm of the working cycle (β=41.7). Therefore, the loss is significantly reduced.

[0234] FIGS. 26 and FIGS. 27 are drawings referenced in the description of variable cooling operation according to one embodiment of the present disclosure.

[0235] FIG. 26 illustrates the cooling power and energy efficiency ratio of a control (2600) that combines TDC control (2610) and delta control (2620) in a low cooling power range.

[0236] Referring to Fig. 26, in the normal range, TDC control (100%) is performed, and in the low cooling range, variable cooling (30%, 50%, and 70% respectively relative to TDC control (100%)) is performed.

[0237] TDC control is one of the existing control methods. For example, when a variable cooling amount is commanded from a refrigerator, the linear compressor starts and increases the stroke until TDC=0. Then, the input power at that time is calculated and stored, and using that value as a reference of 100%, the stroke is reduced so that the power value drops to the variable cooling amount commanded from the refrigerator. When the input power value reaches the corresponding variable cooling amount, the operation is maintained at that stroke.

[0238] FIG. 27 illustrates the cooling power and energy efficiency ratio of a control (2700) that combines beta control (2710) and delta control (2720).

[0239] Referring to FIG. 26, in the normal section, beta control (2610) of approximately 80% is performed, and in the low cooling section, delta control (2620) of approximately 40%, which is half the level of beta control (2610) of 80%, is performed. In addition, during each control, the efficiency was measured while varying the command value.

[0240] Comparing Fig. 26 and Fig. 27, in the normal section, there is no significant difference in efficiency between TDC control (100%) and beta control (2610).

[0241] However, in the low cooling range, the efficiency characteristics of the control (2700) combining beta control (2710) and delta control (2720) were very high.

[0242] Therefore, considering low cooling efficiency, Delta control can always operate under TDC without TDC control.

[0243] Additionally, the control unit (350) can control both the working cycle and the idle cycle so that the stroke is smaller than the maximum value (Full stroke).

[0244] Although preferred embodiments of the present disclosure have been illustrated and described above, the present disclosure is not limited to the specific embodiments described above, and various modifications can be made by those skilled in the art without departing from the gist of the present disclosure as claimed in the patent claims.

Claims

In a control device for a linear compressor including a piston and a motor, An inverter unit that supplies AC voltage to the linear compressor based on a control signal; and, A control unit that controls the reciprocating motion of the piston by supplying the control signal to the inverter unit; The above control unit is, In the first cycle, a first alternating current voltage having a first amplitude is supplied to the motor, and A control device for a linear compressor that controls the supply of a second alternating current voltage having a second amplitude smaller than the first amplitude to the motor in the second cycle. In paragraph 1, The above control unit is, In the first operating mode, the linear compressor is controlled by the first cycle and the second cycle, and A control device for a linear compressor that controls the linear compressor only by the first cycle in a second operating mode where the load is greater than in the first operating mode. In paragraph 1, A control device for a linear compressor in which the first cycle and the second cycle are performed alternately. In paragraph 1, When the above first cycle is performed once, A control device for a linear compressor in which the above second cycle is performed two or more times. In paragraph 1, A control device for a linear compressor in which the amplitude of the first alternating current voltage is 60% or less of the amplitude of the second alternating current voltage. In paragraph 1, A control device for a linear compressor in which the operating frequency of the first cycle is different from the operating frequency of the second cycle. In paragraph 1, The above control unit is, A control device for a linear compressor that controls both the first cycle and the second cycle so that the stroke is smaller than the maximum value. In paragraph 1, A phase difference detection unit for detecting a phase difference between the motor current applied to the motor and the stroke; and, A control device for a linear compressor further comprising: a power calculation unit that calculates load power based on the motor voltage applied to the motor and the motor current applied to the motor. In paragraph 8, A voltage detection unit for detecting the motor voltage applied to the above motor; A current detection unit for detecting a motor current applied to the above motor; and A control device for a linear compressor further comprising a stroke calculation unit that calculates the stroke based on the motor voltage and the motor current. In Paragraph 9, A control device for a linear compressor further comprising a gas spring calculation unit that calculates a gas spring constant based on the motor current, the stroke, and the phase difference. A control device for a linear compressor comprising a motor, a cylinder, a piston disposed inside the cylinder, a discharge valve disposed at one end of the cylinder, and a suction valve disposed at one end of the piston, An inverter unit that supplies AC voltage to the linear compressor based on a control signal; and, A control unit that controls the reciprocating motion of the piston by supplying the control signal to the inverter unit; The above control unit is, In the first cycle, the suction valve and the discharge valve are opened, and A control device for a linear compressor that controls the suction valve to be open and the discharge valve not to be open during the second cycle. In Paragraph 11, The above control unit is, In the first operating mode, the discharge valve is controlled to open once every two cycles, and A control device for a linear compressor that controls the discharge valve to open once per cycle in a second operating mode, where the load is greater than in the first operating mode. In Paragraph 11, A control device for a linear compressor in which the first cycle and the second cycle are performed alternately. In Paragraph 11, When the above first cycle is performed once, A control device for a linear compressor in which the above second cycle is performed two or more times. In Paragraph 11, A control device for a linear compressor in which the amplitude of the voltage supplied to the motor in the first cycle is 60% or less of the amplitude of the voltage supplied to the motor in the second cycle. In Paragraph 11, A control device for a linear compressor in which the operating frequency of the first cycle is different from the operating frequency of the second cycle. In Paragraph 11, The above control unit is, A control device for a linear compressor that controls both the first cycle and the second cycle so that the stroke is smaller than the maximum value. In Paragraph 11, A phase difference detection unit for detecting a phase difference between the motor current applied to the motor and the stroke; and, A control device for a linear compressor further comprising: a power calculation unit that calculates load power based on the motor voltage applied to the motor and the motor current applied to the motor. In Paragraph 18, A voltage detection unit for detecting the motor voltage applied to the above motor; A current detection unit for detecting a motor current applied to the above motor; and A control device for a linear compressor further comprising a stroke calculation unit that calculates the stroke based on the motor voltage and the motor current. In Paragraph 19, A control device for a linear compressor further comprising a gas spring calculation unit that calculates a gas spring constant based on the motor current, the stroke, and the phase difference.

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