CROSS-REFERENCE TO RELATED APPLICATION

Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2018-0096913, filed on Aug. 20, 2018, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a linear compressor and a control method thereof.

2. Description of the Related Art

In general, a compressor is an apparatus for converting mechanical energy into compressive energy of a compressible fluid, and used as a part of a refrigerating appliance, for example, a refrigerator or an air conditioner.

Compressors are largely divided into reciprocating compressors, rotary compressors, and scroll compressors. In the reciprocating compressor, a compression space in which working gas is sucked or discharged is formed to compress refrigerant between a piston and a cylinder while the piston linearly reciprocates in the cylinder. In the rotary compressor, a compression space in which working gas is sucked or discharged is formed between a roller and a cylinder being eccentrically rotated to compress refrigerant while the roller eccentrically rotates along an inner wall of the cylinder. In the scroll type compressor, a compression space in which working gas is sucked or discharged is formed between an orbiting scroll and a fixed scroll to compress refrigerant while the orbiting scroll is rotated along the fixed scroll.

The reciprocating compressor sucks, compresses, and discharges refrigerant gas by linearly reciprocating the inner piston within the cylinder. The reciprocating compressors are largely divided into recipro methods and linear methods according to the method of driving the piston.

The recipro method is a method of coupling a crankshaft to a rotating motor, and coupling a piston to the crankshaft to convert a rotational movement of the motor into a linear reciprocating movement. On the contrary, the linear method refers to a method of connecting a piston to a mover of a linearly moving motor to reciprocate the piston by a linear movement of the motor.

Such a reciprocating compressor includes an electric motor unit for generating a driving force and a compression unit for receiving a driving force from the transmission unit and compressing the fluid. A motor is generally used as the electric motor unit, and a linear motor is used in the case of the linear method.

In the case of the linear motor, the motor itself directly generates a linear driving force, and thus a mechanical conversion device is not required and the structure is not complicated. In addition, the linear motor has features capable of reducing loss due to energy conversion and greatly reducing noise because there is no joint where friction and abrasion occur. Furthermore, when a linear type reciprocating compressor (hereinafter referred to as a linear compressor) is used for a refrigerator or an air conditioner, a stroke voltage applied to the linear compressor may be changed to change compression ratio, and thus it may be used for variable control of freezing capacity.

Typically, a linear compressor is configured such that a piston is linearly reciprocated within a cylinder by the linear motor in a closed shell to suck and compress, and then discharge refrigerant.

The linear motor is configured such that a permanent magnet is located between an inner stator and an outer stator, and the permanent magnet is driven to linearly reciprocate by a mutual electromagnetic force between the permanent magnet and the inner (or outer) stator. Furthermore, as the permanent magnet is driven in a state of being connected to the piston, the piston linearly reciprocates within the cylinder to suck and compress and then discharge the refrigerant.

In connection with such a linear compressor, Korean Patent Publication No. 10-2016-0000324 (published on Jan. 4, 2016) discloses a gas bearing technology that supplies refrigerant gas to a space between the cylinder and the piston to perform a bearing function. The refrigerant gas flows through a nozzle of the cylinder to an outer circumferential surface of the piston to perform a bearing action with respect to the reciprocating piston.

Furthermore, Korean Patent Publication No. 10-2017-0123042 (published on Nov. 7, 2017) discloses a linear compressor in which the position of a groove provided in a cylinder is optimized to improve the performance of a gas bearing supplied to the piston.

On the other hand, when the groove formed in the cylinder of the linear compressor is clogged by various substances, a gas that floats up the piston cannot pass through the hole, thereby causing friction between the piston and the cylinder. When friction occurs between the piston and the cylinder, it may reduce an operation efficiency of the linear compressor as well as wear out the piston.

The groove of the cylinder may be clogged by foreign matter generally introduced from the outside and oil injected into the compressor. At present, the structure of the linear compressor is designed to prevent foreign matter or oil from being introduced into the groove, but it is insufficient to completely block foreign matter and oil.

Therefore, there is a need for a control method of a linear compressor capable of preventing the groove of the cylinder from being blocked in order to increase the operation efficiency of the linear compressor and prevent the wear of the piston.

SUMMARY OF THE INVENTION

A technical task of the present disclosure is to solve the foregoing problems of a linear compressor in the related art, and an object of the present disclosure is to provide a linear compressor capable of preventing a groove of a cylinder from being clogged and a control method thereof.

In particular, a technical task of the present disclosure is to provide a linear compressor for determining whether or not the temperature around the linear compressor corresponds to a low temperature condition by various methods, and preheating the linear compressor according to the determination result to secure the groove opening of the cylinder and a control method thereof.

Furthermore, a technical task of the present disclosure is to provide a linear compressor for performing a preheating operation prior to performing a normal operation according to a temperature condition and a control method thereof.

In order to solve the foregoing tasks, a linear compressor disclosed herein may include a cylinder provided with at least one groove, a piston reciprocating within the cylinder, a motor configured to provide a driving force to move the piston within the cylinder, an inverter configured to perform a switching operation to transmit electric power to the motor, and a controller configured to receive temperature information from the electronic device and control the inverter to preheat the motor based on the received temperature information.

According to an embodiment, the controller may preheat the motor while the piston is stopped to increase the temperature of the linear compressor when the power of the electronic device is activated.

Specifically, the controller may control the inverter to allow a DC current of a predetermined magnitude to flow through the motor so as to preheat the motor.

According to an embodiment, the linear compressor may further include a sensing unit configured to sense a motor current flowing through the motor, wherein the controller adjusts an output voltage of the inverter based on the motor current sensed by the sensing unit subsequent to applying a DC current to the motor.

According to an embodiment, the controller may set a target DC current value for controlling a preheating operation of the motor, and control the inverter to increase the output voltage of the inverter when the motor current sensed by the sensing unit is less than the target DC current.

According to an embodiment, the controller may control the inverter to block the output of the inverter when the motor current sensed by the sensing unit is higher than a preset trip level subsequent to applying the DC current to the motor.

According to an embodiment, the controller may control the inverter to allow an AC current above a preset reference frequency to flow through the motor so as to preheat the motor.

According to an embodiment, the temperature information may include a temperature value related to a location of the electronic device, and the controller may compare the temperature value with a preset reference temperature, and preheat the motor based on the comparison result.

According to an embodiment, the temperature value may be measured by a temperature sensor provided in the electronic device, and the controller may preheat the motor prior to operating the motor according to a predetermined compressor command when the temperature value is lower than the reference temperature.

According to an embodiment, the controller may receive temperature information from any one temperature sensor disposed at a position closest to the linear compressor among a plurality of temperature sensors provided in the electronic device.

According to an embodiment, when a control command for starting the operation of the linear compressor is generated, the controller may determine whether or not to preheat the motor using temperature information received within a predetermined period of time from the time of generating the control command.

According to an embodiment, the controller may update temperature information for each predetermined offset period of time after the preheating operation of the motor is started, and end the preheating operation of the motor based on the comparison result of a temperature value included in the updated temperature information and the reference temperature.

According to an embodiment, the controller may end the preheating operation of the motor when a period of time of the preheating operation of the motor exceeds a preset reference period of time.

According to an embodiment, the controller may decrease a carrier frequency applied to the inverter when the temperature value is less than the reference temperature.

According to an embodiment, the controller may control the inverter to allow the piston to reciprocate within the cylinder based on an operation mode of the electronic device, without performing a preheating operation of the motor when the temperature value is above the reference temperature.

According to an embodiment, the controller may control the inverter to allow the piston to reciprocate within the cylinder based on an operation mode of the electronic device when the preheating of the motor ends.

Furthermore, according to another embodiment of the present invention, a temperature around the linear compressor may be estimated using a motor current and a motor voltage measured by the sensing unit of the linear compressor

Specifically, the controller may detect a resistance value of the motor using the motor voltage and the motor current sensed by the sensing unit, and control the inverter to preheat the motor based on the detected resistance value.

At this time, the controller may monitor a resistance value of the motor at predetermined intervals after the preheating operation of the motor is started, and perform a preheating operation of the motor until the resistance value of the motor increases above the reference resistance value.

The linear compressor according to the present disclosure performs a preheating operation prior to performing a reciprocating movement of the piston, thereby obtaining an effect of preventing a groove formed in the cylinder from being clogged.

Furthermore, according to the present disclosure, a preheating operation for increasing the temperature of the linear compressor prior to moving the piston of the linear compressor may be carried out, thereby preventing friction or collision between the piston and the cylinder.

Accordingly, the linear compressor according to the present disclosure has an advantage capable of securing the operation performance of the compressor even under a low temperature condition.

In addition, according to the present disclosure, the performance of the gas bearing may be secured to minimize the wear of the piston, thereby obtaining an effect of increasing the life of the mechanism and parts of the linear compressor.

