KR20100082256A - Linear compressor - Google Patents

Abstract

PURPOSE: A control method of a linear compressor is provided to accurately measure the displacement of a piston even though the original position of the piston is changed by a load. CONSTITUTION: A control method of a linear compressor comprises the following steps. The displacement of a top dead center direction from the initial position of a piston(101) is controlled in a first step. The displacement of a bottom dead center direction from the initial position of a piston is controlled in a second step. The first step and the second step are independently or alternatively performed. The stroke of the piston in order to be controlled is determined based on the stroke stored in advance according to the driving condition. The first step or the second step is performed according to the stroke of the piston determined. When the linear compressor is driven, the driving condition is detected.

Description

Linear compressor control method {LINEAR COMPRESSOR}

The present invention relates to a control method of a linear compressor, and more particularly, to a control method of a linear compressor capable of producing a load-sensitive cooling power by smoothly controlling the displacement of the piston as well as accurately measuring the displacement of the piston.

In general, the reciprocating compressor is configured to compress the refrigerant while the piston reciprocates linearly within the cylinder by forming a compression space in which the working gas is absorbed and discharged between the piston and the cylinder.

Recently, the reciprocating compressor includes a component such as a crank shaft in order to convert the rotational force of the drive motor to the reciprocating linear kinetic force of the piston, there is a problem that a large mechanical loss caused by the movement change occurs. Many linear compressors have been developed for this purpose.

Such a linear compressor, in particular, allows the piston to be directly connected to a linear motor in reciprocating linear motion, thereby eliminating mechanical loss due to motion switching, thereby improving compression efficiency, and having a simple structure, and controlling power input to the linear motor. Since the operation can be controlled, the noise is lower than that of other compressors, so it is widely applied to home appliances such as refrigerators used indoors.

1 is a side cross-sectional view showing a part of an example of a general linear compressor.

A general linear compressor includes a frame (1), a cylinder (2), a piston (3), an intake valve (4), a discharge valve assembly (5), a motor cover (6), a supporter (7) inside a shell (not shown), The structure consisting of the back cover 8, the main springs S, the muffler assembly 9, and the linear motor 10 is installed to be elastically supported.

The cylinder 2 is fitted to the frame 1 so that the discharge valve assembly 5 composed of the discharge valve 5a, the discharge cap 5b, and the discharge valve spring 5c blocks one end of the cylinder 2. On the other hand, the piston 3 is inserted inside the cylinder 2, and a thin suction valve 4 is installed to open and close the outlet 3a of the piston 2.

The motor cover 6 is bolted to the frame 1 while supporting the outer stator 12 of the linear motor 10 in the axial direction so as to fix the outer stator 12 of the linear motor 10, and the back cover. (8) is coupled to the motor cover (6), wherein between the motor cover (6) and the back cover (8) the supporter (7) connected to the other end of the piston (3) is axially oriented by the main springs (S). It is installed so as to be elastically supported, and the muffler assembly 9 for sucking the refrigerant is also fastened together with the supporter 7.

In this case, the main springs S include four front springs and four rear springs at positions symmetrically up and down with respect to the supporter 7, and the front springs and the rear as the linear motor 10 is operated. The springs behave in reverse, cushioning the piston 3 and the supporter 7. In addition, the refrigerant on the compression space P side acts as a kind of gas spring to cushion the piston 3 and the supporter 7.

The linear motor 10 is installed so that the permanent magnet 13 can reciprocate linearly while maintaining an air gap between the inner stator 11 and the outer stator 12, and the permanent magnet 13 is a connecting member. It is installed so as to be connected to the piston (3) by the (14), while the permanent magnet (13) reciprocating linear movement by mutual electromagnetic force between the inner stator (11), the outer stator (12) and the permanent magnet (13) Activate 3). At this time, the linear motor 10 is controlled by a microcomputer (not shown), the microcomputer can control the power supplied to the outer stator 12 of the linear motor 10 according to the load, accordingly The stroke of the piston 3 can be adjusted.

Therefore, when the linear motor 10 is operated, the piston 3 and the muffler assembly 9 connected thereto are reciprocated linearly, and the suction valve 4 and the discharge valve assembly are changed as the pressure in the compression space P is varied. The operation of (5) is automatically adjusted, and by this operation, the refrigerant is compressed past the intake pipe on the shell side, the opening of the back cover 8, the muffler assembly 9, and the inlets 3a of the piston 3. It is sucked into the space P and compressed, and then exits through the discharge cap 5b, the roof pipe and the outlet pipe on the shell side.

2 is a graph showing the displacement of the piston according to the operation of the general linear compressor, Figure 3 is a graph showing the displacement of the piston according to the load in the general linear compressor.

As shown in Fig. 2, when the linear compressor is initially started, the stroke of the piston, i.e., the total displacement of the piston is actuated the largest in order to quickly release the load, and the overall displacement of the piston decreases in stages as the load decreases. Is operated. At this time, the total displacement of the piston can be adjusted by controlling the power supplied to the linear motor, that is, voltage and current. Of course, in order to give the total displacement of the piston corresponding to the load, the total displacement of the piston is measured by calculating the voltage and current input to the linear motor for each load in advance, and the voltage and current values for each load are stored in advance. It is.

As shown in FIG. 3, as the load increases, the temperature and pressure of the refrigerant flowing into the linear compressor are increased, so that the piston reciprocates linearly in a state in which the piston elastically supported by the refrigerant gas is pushed in the bottom dead center direction. Done. That is, based on the initial position of the piston (hereinafter referred to as the initial value) in the low load operation, the piston is operated to have a predetermined stroke in a state where the initial value of the piston is pushed in the lower dead center direction at a heavy load than the low load, At high loads, the piston is operated to have a predetermined stroke with the initial value of the piston further pushed toward the bottom dead center. Of course, since the linear compressor generates the cooling force through linear motion, the total displacement of the piston represents the cooling force.

However, the control method of the linear compressor as described above adjusts the overall displacement of the piston according to the pre-loaded voltage value and current value for each load, but as the initial position of the piston changes as the load increases, the overall displacement of the piston is accurately Not only is it difficult to measure, it is difficult to accurately control displacement of the piston for each load, and there is a problem in that precision and reliability of such displacement control of the piston are deteriorated.

In addition, the control method of the linear compressor as described above regards the total displacement of the piston calculated from the voltage and current supplied to the linear motor as the stroke of the piston. As the displacement of the piston decreases in the top dead center direction, the top dead center operation cannot be performed, while the displacement of the piston increases in the bottom dead center direction. Therefore, when the piston is pushed as the load increases, there is a large difference between the top dead center displacement of the piston and the bottom dead center displacement of the piston, based on the initial value of the piston. It is not possible to accurately represent the size of the cooling force, even if the overall displacement of the piston is adjusted according to the load, it is difficult to solve the load quickly, there is a problem that the efficiency is lowered.

The present invention has been made to solve the above problems of the prior art, it is an object of the present invention to provide a control method of a linear compressor that can precisely control the displacement of the piston for each load without additional sensor installation.

In the control method of the linear compressor according to the present invention for solving the above problems, in the control method of the linear compressor to adjust the cooling force by varying the stroke (X) of the piston, the control method is a top dead center direction from the initial position of the piston A first step of controlling the displacement (X _TDC ) and a second step of controlling the bottom dead center direction displacement (X _BDC ) from the initial position of the piston, and independently or alternately performing the first or second step do.

The control method may further include a third step of determining the stroke X of the piston to be controlled based on the pre-stored stroke X according to the operating condition before the first and second steps, and According to the stroke X, it is preferable to perform the first step or the second step.

In addition, the control method preferably includes a fourth step of detecting a driving condition during operation.

In addition, the pre-stored stroke X is preferably stored as a _top dead center displacement (X _TDC ) and a bottom dead center displacement (X _BDC ) from the initial position of the piston.

In addition, in the fourth step, the operating condition is a load determined by the refrigerant temperature, and as the load decreases, the stroke X of the piston is preferably set smaller.

Further, in the first or second stage, it is preferable that the _top dead center direction displacement X _TDC of the piston is controlled so that the piston runs in top dead center regardless of the load.

In addition, in the first or second stage, the top dead center displacement (X _TDC ) of the piston and the bottom dead center displacement (X _BDC ) of the piston are controlled by a voltage and a current input to a linear motor providing a driving force to the piston. It is preferable.

In the control method of the linear compressor according to the present invention configured as described above, in order to have a stroke of the piston corresponding to the load, the top dead center direction displacement and the bottom dead center direction displacement are separately controlled from the initial position of the piston according to the load Even if the initial position of the piston is changed, it is possible to accurately measure the total displacement of the piston, and thus there is an advantage that the displacement control of the piston can be precise as well as reliable.

In addition, the control method of the linear compressor according to the present invention responds to the load because the top dead center direction displacement and the bottom dead center direction are separately controlled based on the initial value of the piston even if the piston is pushed in the bottom dead center direction as the load increases. It is not only easy to control the stroke of the piston, but also the piston can be controlled to operate the top dead center, so that the displacement of the piston to represent the magnitude of the cooling force to quickly eliminate the load and increase the efficiency There is this.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a configuration diagram showing the control structure of the linear compressor according to the present invention.

An example of the linear compressor according to the present invention is a sealed container (not shown) through which refrigerant flows in and out, as shown in FIG. 4, a cylinder (not shown) provided inside the sealed container, and an initial position inside the cylinder. To the piston 101 for reciprocating linear motion between the top dead center (TDC) and the bottom dead center (BDC), the linear motor (102) for providing a driving force to the piston (101), and the linear motor (102) for voltage and current. It is composed of a power supply 103 for supplying, and a microcomputer 104 for controlling the operation of the power supply 103, the displacement is moved in the direction of top dead center (TDC) relative to the initial position of the piston 101 ( X _TDC ) and the control of displacement (X _BDC ) moved in the bottom dead center (BDC) direction independently or alternately to control the cooling force corresponding to the load.

In the microcomputer 104, the stroke X of the piston 101 corresponding to the load is set in advance, and the stroke X of the piston 101 is directed to the top dead center (TDC) based on the initial position of the piston 101. It can be set to the maximum value of the displacement (X _TDC ) moved to and the maximum value of the displacement (X _BDC ) moved in the bottom dead center (BDC) direction. In this case, the top dead center (TDC) direction displacement X _{TDC of the} piston 101 and the bottom dead center (BDC) direction displacement X _BDC of the piston 101 are calculated according to Equations 1 and 2 below.

At this time, the top dead center (TDC) direction displacement X _{TDC of the} piston 101 is transferred to the linear motor 102 while the piston 101 is moved in the top dead center (TDC) direction as shown in [Equation 1]. Calculated by the supplied voltage (V _TDC ) and current (i _TDC ), and similarly, the bottom dead center (BDC) direction displacement (X _BDC ) of the piston 101 is the piston 101 as shown in [Equation 2]. It is calculated by the voltage V _BDC and the current i _BDC supplied to the linear motor 102 while moving in the bottom dead center BDC direction. Of course, even if the piston 101 is pushed toward the bottom dead center (BDC) direction as the load increases, the microcomputer 104 may supply the voltage V _TDC supplied from the power supply 103 to the linear motor 102 for each load in advance. , V _BDC ) and the current (i _TDC , i _BDC ) are input, and the displacement in the top dead center (TDC) direction of the piston 101 according to the input voltage (V _TDC , V _BDC ) and the current (i _TDC , i _BDC ). (X _TDC ) and the bottom dead center (BDC) direction displacement (X _BDC ) of the piston 101 are calculated and stored separately.

Therefore, when the linear compressor is actually operated, the microcomputer 104 senses the actual load through the refrigerant temperature and the like, and corresponds to the top dead center (TDC) direction displacement (X _TDC ) of the piston 101 and the piston 101 to correspond to the load. Power supply to control the bottom dead center (BDC) direction displacement (X _BDC ) of, but to supply the pre-input voltage (V _TDC , V _BDC ) and current (i _TDC , i _BDC ) to the linear motor 102 Control 103.

5 is a graph showing the displacement of the piston according to the operation of the linear compressor according to the present invention.

As shown in Fig. 5, when the linear compressor is initially started, the stroke X of the piston, that is, the top dead center (TDC) direction displacement (X _TDC ) of the piston and the bottom dead center of the piston in order to quickly release the load. (BDC) Displacement (X _BDC ) operates the largest, and as the load decreases, the piston top dead center (TDC) direction displacement (X _TDC ) and piston bottom dead center (BDC) direction displacement (X _BDC ) independently Or alternately decrease in stages. At this time, the greater the load, the greater the pressure of the refrigerant that elastically supports the piston, the phenomenon that the piston is pushed in the bottom dead center (BDC) direction from the initial position occurs, the displacement of the piston in the bottom dead center (BDC) direction (X _BDC ) Is controlled much larger than the top dead center (TDC) directional displacement (X _TDC ) of the piston. Therefore, as the load decreases, the piston top dead center (TDC) direction displacement (X _TDC ) and the piston bottom dead center (BDC) direction displacement (X _BDC ) decrease, but the piston phenomena also decreases. The difference between the TDC) direction displacement (X _TDC ) and the piston bottom dead center (BDC) direction displacement (X _TDC ) is also controlled to decrease. At this time, the top dead center (TDC) direction displacement (X _TDC ) of the piston and the bottom dead center (BDC) direction displacement (X _BDC ) of the piston is the data stored for each load through the measurement and calculation in advance, that is, the voltage supplied to the linear motor ( V _TDC , V _BDC ) and current (i _TDC , i _BDC ) can be controlled by adjusting.

6 and 7 are graphs showing the displacement of the piston and the voltage and current applied to the linear motor during the low load / high load operation of the linear compressor according to the present invention.

As shown in FIG. 6, since the piston's sliding hardly occurs in the low load state, the piston's top dead center (TDC) direction displacement (X _TDC ) and the piston's bottom dead center (BDC) direction displacement (X _BDC ) coincide. do. On the other hand, as shown in Figure 7, because the piston phenomena occur in a high load state, the piston top dead center (TDC) direction displacement (X _TDC ) and the piston bottom dead center (BDC) direction displacement (X _BDC ) coincide. The lower dead center (BDC) direction displacement X _BDC of the piston is controlled to be larger than the upper dead center (TDC) direction displacement X _TDC of the piston. At this time, the top dead center (TDC) direction displacement (X _TDC ) of the piston is the voltage (V _TDC ) and current (i T) input to the linear motor when the piston is located in the top dead center (TDC) direction relative to the initial position of the piston. _TDC ) can be controlled by adjusting, and the piston bottom displacement (BDC) direction displacement (X _BDC ) is the voltage input to the linear motor when the piston is located in the bottom dead center (BDC) direction relative to the initial position of the piston ( V _BDC ) and current (i _BDC ) can be adjusted by controlling.

Therefore, the control of the top dead center (TDC) direction displacement (X _TDC ) of the piston and the control of the bottom dead center (BDC) direction displacement (X _BDC ) of the piston are independently or alternately controlled, but as the load increases, the stroke of the piston ( X) In other words, precise control to increase the cooling power can not only solve the load quickly, but also increase the accuracy and reliability of the control, and the piston's superiority to reach the top dead center (TDC) regardless of the load. Since the point (TDC) direction displacement (X _TDC ) can also be controlled, the compression efficiency can be further increased.

In the above, the present invention has been described in detail by way of examples based on the embodiments of the present invention and the accompanying drawings. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

1 is a side cross-sectional view showing a part of an example of a general linear compressor.

Figure 2 is a graph showing the displacement of the piston according to the operation of the general linear compressor.

3 is a graph showing the displacement of the piston according to the load in a general linear compressor.

4 is a configuration diagram showing a control structure of the linear compressor according to the present invention.

5 is a graph showing the displacement of the piston according to the operation of the linear compressor according to the present invention.

Figure 6 is a graph showing the displacement of the piston and the voltage and current applied to the linear motor during low load operation of the linear compressor according to the present invention.

Figure 7 is a graph showing the displacement of the piston and the voltage and current applied to the linear motor during high load operation of the linear compressor according to the present invention.

Claims (7)

In the control method of the linear compressor for varying the cooling force by varying the stroke (X) of the piston, the control method is A first step of controlling _top dead center direction displacement (X _TDC ) from an initial position of the piston; And a second step of controlling the bottom dead center direction displacement (X _BDC ) from the initial position of the piston, wherein the first step or the second step is performed independently or alternately. The method of claim 1, The control method may include a third step of determining the stroke X of the piston to be controlled based on the pre-stored stroke X according to the operating conditions before the first and second steps, and the determined stroke of the piston ( The control method of the linear compressor characterized by performing a 1st step or a 2nd step according to X). The method of claim 2, The control method includes a fourth step of detecting an operating condition when the linear compressor is in operation. The method of claim 2, The prestored stroke (X) is stored as a top dead center displacement (X _TDC ) and a bottom dead center displacement (X _BDC ) from the initial position of the piston. The method of claim 3, In the fourth step, the operating condition is a load determined by the refrigerant temperature, and as the load decreases, the stroke X of the piston is set smaller. The method of claim 1, In the first or second stage, the top dead center direction displacement (X _TDC ) of the piston is controlled so that the piston operates in top dead center regardless of the load. The method according to any one of claims 1 to 7, In the first or second stage, the top dead center displacement (X _TDC ) of the piston and the bottom dead center displacement (X _BDC ) of the piston are controlled through a voltage and a current input to a linear motor providing a driving force to the piston. The control method of the linear compressor.

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