KR20180109262A - Linear compressor and method for controlling linear compressor - Google Patents

Abstract

According to the present invention, a linear compressor comprises: a piston reciprocating inside a cylinder; a motor providing a driving force for movement of the piston; and a control unit controlling the motor to stop operation of the motor when the piston is at a top dead center.

Description

TECHNICAL FIELD [0001] The present invention relates to a linear compressor and a control method for a linear compressor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear compressor and a control method thereof, and more particularly, to a linear compressor having an increased driving efficiency.

Generally, a compressor is a device for converting mechanical energy into compressive energy of a compressible fluid, and is used as a part of a refrigeration apparatus, 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 an operating gas is sucked or discharged is formed between a piston and a cylinder, so that the piston linearly reciprocates within the cylinder and compresses the refrigerant. The rotary compressor compresses the refrigerant while eccentrically rotating the roller along the inner wall of the cylinder so that a compression space in which the working gas is sucked or discharged is formed between the roller and the cylinder. In the scroll type compressor, a compression space is formed between an orbiting scroll and a fixed scroll to suck or discharge an operating gas, thereby compressing the refrigerant while the newbear scroll is rotated along the fixed scroll.

The reciprocating compressor sucks, compresses, and discharges the refrigerant gas by linearly reciprocating the inner piston inside the cylinder. Reciprocating compressors are largely divided into Recipro type and Linear type depending on the method of driving the pistons.

In the reco-pro system, a crankshaft is coupled to a rotating motor, and a piston is coupled to a crankshaft to convert a rotational motion of the motor into a linear reciprocating motion. On the other hand, the linear system refers to a system in which a piston is connected to a mover of a motor that linearly moves, and the piston reciprocates by rectilinear motion of the motor.

Such a reciprocating compressor includes an electric unit that generates a driving force and a compression unit that receives a driving force from the electric unit and compresses the fluid. Generally, a motor is used as the electric unit, and a linear motor is used in the case of the linear type.

In the linear motor, since the motor itself generates a linear driving force, a mechanical conversion device is not necessary, and the structure is not complicated. In addition, the linear motor can reduce losses due to energy conversion, and has no connecting parts where friction and abrasion occur, thus greatly reducing noise. When a reciprocating compressor of a linear type (hereinafter referred to as a linear compressor) is used for a refrigerator or an air conditioner, the compression ratio is changed according to the change of the stroke voltage applied to the linear compressor. And can be used for variable control of freezing capacity.

On the other hand, since the linear compressor reciprocates in a state in which the piston is not mechanically constrained in the cylinder, when the voltage suddenly becomes excessive, the piston hits against the cylinder wall, or the piston can not advance due to a large load, This can not be done properly. Therefore, a control device for controlling the motion of the piston with respect to the load variation or the voltage variation is essential.

On the other hand, in general, the refrigerator to which the reciprocating compressor is applied is a household appliance that operates for 24 hours, and the power consumption of the refrigerator may be the most important technical factor in the refrigerator technology field. Among them, the efficiency of the compressor can be greatest, and therefore, the efficiency of the compressor must be increased in order to reduce the power consumption of the refrigerator.

At this time, one of the methods for increasing the efficiency of the linear compressor is to reduce the loss due to friction.

In order to reduce the friction loss, the stroke can be reduced by moving the initial value of the piston (or the position of the piston on the cylinder in the assembled or stopped state) toward the compression space of the cylinder (or the top dead center).

However, the initial value of the piston determines the maximum cooling capacity. As the initial value is reduced, the friction area per hour between the cylinder and the piston decreases, the friction loss decreases, and the efficiency increases. There is a problem that the cooling capacity is reduced and it is difficult to cope with the overload.

On the other hand, if the initial value of the piston is moved not to the compression space but to the opposite side, the maximum cooling capacity of the compressor is increased. However, the movement distance of the piston (distance between top dead center and bottom dead center) There is a problem in that the loss due to the increase in efficiency is reduced

Here, the TDC is an abbreviation of " Top Dead Center ", which physically means the position of the piston in the cylinder at the completion of the compression stroke. In this specification, the point at which the TDC is zero (or the point where the distance from the cylinder end (or in-cylinder discharge valve) to the end of the piston is zero) will be briefly referred to as " top dead center point ".

Likewise, bottom dead center (BDC) is an abbreviation of "bottom dead center" and may physically refer to the position of the piston at the completion of the suction stroke of the piston.

Consequently, the compressor efficiency and the maximum cooling power due to the initial value of the piston may be in a trade off relationship.

Therefore, there is a limit in the technique of adjusting the compressor efficiency using only the initial value of the piston, and a technique for securing the compressor efficiency and the maximum cooling power is needed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and it is an object of the present invention to provide a linear compressor control apparatus and control method for increasing the maximum cooling power of a compressor by limiting a driving time point of a motor, .

In order to solve the above-mentioned problems, the linear compressor disclosed in this specification includes a piston reciprocating inside a cylinder, a motor for providing a driving force for the movement of the piston, and a motor for stopping the driving of the motor when the piston is in top dead center And a control unit for controlling the motor to rotate the motor.

In one embodiment, the controller controls the motor to start driving the motor when the piston is a bottom dead center.

In one embodiment, the apparatus further includes an inverter unit including a plurality of switches for transmitting electric power to the motor, wherein the controller includes a pulse width modulation (PWM) control unit for controlling operation of the switch when the piston is at the top dead center Signal is turned on,

And turns off the PWM control signal when the piston is at the top dead center.

In one embodiment, the apparatus further includes a sensing unit sensing a motor voltage and a motor current associated with the motor, the control unit estimating a stroke of the piston using the motor voltage and the motor current, and based on the estimated stroke, And detects whether the current position of the piston is a top dead center or a bottom dead center.

In one embodiment, the control unit supplies the PWM control signal to the inverter unit so that power is supplied to the motor while the piston moves from a bottom dead center to a top dead center.

In one embodiment, the control unit gradually decreases the duty cycle of the PWM control signal when the piston moves from a bottom dead center to a top dead center.

In one embodiment, the control unit reduces the duty width so that the PWM control signal is turned off when the piston reaches the top dead center.

In one embodiment, the apparatus further comprises a timer, which is initialized when the piston is bottom dead center, and measures the elapse of time for each cycle of the piston, wherein the controller starts driving the motor when the timer is initialized And stops driving the motor when the measured value of the timer exceeds a predetermined first time interval.

In one embodiment, the controller sets the predetermined first time interval based on information related to the period of the piston.

In one embodiment, the inverter includes two pairs of switches for transmitting electric power to the motor, and receives a PWM (Pulse Width Modulation) control signal of first and second phases respectively corresponding to the two pairs of switches And the control unit turns off the PWM control signal of the second phase when the piston reaches the top dead center.

In one embodiment, the control unit turns off the PWM control signal of the second phase when a predetermined second time interval elapses after the inverter unit starts receiving the PWM control signal of the second phase.

In one embodiment, the control unit compares the phase of the stroke of the piston with a time point at which the PWM control signal of the first phase and the second phase is applied, and based on the result of the comparison, .

In one embodiment, the control unit applies the PWM control signals of the first phase and the second phase to the inverter unit at an intersection.

The linear compressor and the control method thereof according to the present invention can increase the maximum cooling power of the compressor or improve the driving efficiency of the compressor by reducing the number of switching operations performed during the reciprocating motion of the piston.

Further, the linear compressor and the control method thereof according to the present invention can improve the driving efficiency of the compressor in the low-cooling power band, and reduce the power consumption of the electronic product having such a compressor.

Further, the linear compressor according to the present invention and the control method thereof have the effect of improving the control stability of the linear compressor by limiting the time when the motor is driven.

FIG. 1A is a conceptual diagram showing an example of a reciprocating compressor of a general reciprocating type. FIG.
FIG. 1B is a conceptual view showing an example of a conventional linear-type anvil-type compressor. FIG.
1C is a graph relating to various parameters used for top dead center control of a general linear compressor.
2 is a block diagram showing components of a linear compressor;
3 is a sectional view showing an embodiment of a linear compressor according to the present invention.
4 is a conceptual diagram showing an embodiment of a linear compressor according to the present invention.
5A to 5C are conceptual diagrams showing embodiments related to the operation mode of the linear compressor.
6A is a graph showing an embodiment related to a control method of a linear compressor according to the present invention.
6B is a flow chart showing a control method of a linear compressor in relation to the graph shown in FIG. 6A;
7A is a graph showing another embodiment related to a control method of a linear compressor according to the present invention.
FIG. 7B is a flowchart showing a control method of a linear compressor related to the graph shown in FIG. 7A. FIG.
8A is a graph showing another embodiment related to a control method of a linear compressor according to the present invention.
8B is a flow chart showing a control method of a linear compressor related to the graph shown in Fig.
9A is a graph showing another embodiment related to a control method of a linear compressor according to the present invention.
FIG. 9B is a flowchart showing a control method of a linear compressor related to the graph shown in FIG. 9A. FIG.
10 is a circuit diagram of an inverter for performing a control method of a linear compressor according to the present invention.

The invention disclosed in this specification can be applied to a control device of a linear compressor and a control method of a linear compressor. However, the invention disclosed in this specification is not limited to the present invention, but may be applied to all existing compressor control devices, compressor control methods, motor control devices, motor control methods, noise testing devices for motors, It can also be applied to noise test methods.

Further, in the description of the technology disclosed in this specification, a detailed description of related arts will be omitted if it is determined that the gist of the technology disclosed in this specification may be obscured. It is to be noted that the attached drawings are only for the purpose of easily understanding the concept of the technology disclosed in the present specification, and should not be construed as limiting the spirit of the technology by the attached drawings.

In the following FIG. 1A, an example of a reciprocating type compressor of a general reciprocating type will be described.

As described above, the motor provided in the reciprocating compressor can be combined with the crankshaft 1a, whereby the rotational motion of the motor can be converted into a linear reciprocating motion.

As shown in Fig. 1A, a piston installed in a reciprocating compressor can perform a linear reciprocating motion within a predetermined position range by a specification of a crankshaft or a specification of a connecting rod connecting a crankshaft and a piston .

Therefore, in designing the compressor of the reciprocating type, when the specifications of the crankshaft and the common rod are determined such that the piston does not exceed the TDC stage, the piston does not apply the motor control algorithm separately, And does not collide with the discharge portion 2a disposed in the discharge opening 2a.

In this case, the discharge portion 2a provided in the compressor of the reciprocating type can be fixedly installed with respect to the cylinder. For example, the discharge portion 2a may be formed of a valve plate.

However, unlike the compressor of the linear type which will be described later, such a compressor of the reciprocating type generates friction between the crankshaft, the connecting rod and the piston, and therefore, there is more problems in the linear type compressor than the element which generates friction .

In the following Fig. 1B, an example of a general linear type reciprocating compressor will be described. 1C, a graph relating to various parameters used for top dead center control of a general linear type reciprocating compressor is shown.

Comparing FIGS. 1A and 1B, unlike a reciprocating type in which a crankshaft and a connecting rod are connected by a motor, linear compressors connect a piston to a mover of a linearly moving motor, The piston is reciprocated in motion.

As shown in Fig. 1B, an elastic member 1b may be connected between the cylinder of the linear type compressor and the piston. The piston can perform a linear reciprocating motion by the linear motor, and the control unit of the linear compressor can control the linear motor to change the direction of motion of the piston.

More specifically, the control unit of the linear compressor shown in Fig. 1B can determine when the piston collides with the discharge portion 2b when the piston reaches the top dead center (TDC), and thereby the movement direction of the piston To control the linear motor.

Referring to FIG. 1C, along with FIG. 1B, there is shown a graph associated with a typical linear compressor. Specifically, as shown in Fig. 1C, the phase difference [theta] between the motor current i and the stroke x of the piston forms an inflection point at the point when the piston reaches the top dead center (TDC).

A control unit of a general linear compressor detects a motor current (i) using a current sensor, detects a motor voltage (not shown) using a voltage sensor, and estimates a stroke (x) based on a motor current and a motor voltage . Thereby, the control unit can calculate the phase difference [theta] between the motor current (i) and the stroke (x), and when the phase difference [theta] forms the inflection point, it judges that the piston has reached the top dead center (TDC) At this time, the linear motor can be controlled so that the moving direction of the piston is switched. Hereinafter, the control of the motor such that the piston does not exceed the top dead center in order to prevent the control part of the linear compressor from colliding with the discharge part arranged at one end of the cylinder is defined as " conventional top dead center control ".

Conventional top dead center control is as follows.

In the conventional top dead center control, the control unit of the linear compressor can calculate the gas constant (K _g ) related to the reciprocating motion of the piston in real time using the detected motor current and the estimated stroke.

Specifically, the control unit can calculate the gas constant (K _g ) using the following equation (1).

In this equation, I (jw) is the peak value of one-week current, X (jw) is the peak value of one-week stroke, α is the motor constant or counter electromotive force constant, θ _{i, x} is the phase difference between current and stroke, by weight, w is the operating frequency, K _m of the motor refers to the mechanical spring constant.

Further, the equation ( ₂ ) related to the gas constant (K _g ) is derived by the above equation.

That is, the calculated gas constant K _g may be proportional to the phase difference between the motor current and the stroke.

Accordingly, the control of the linear compressor can be determined by the gas constant (K _g) and monitor the change in phase difference, and the gas constant (K _g) and phase difference by forming the turning point, the piston reaches the top dead center .

In addition, as shown in FIG. 1B, in the case of a general linear compressor that performs the conventional top dead center control as described above, the discharge portion 2b having the elastic member may be provided. Particularly, the discharge portion 2b provided in the conventional linear compressor is connected to an elastic member having a relatively weak elastic force. Therefore, the repulsive force of the discharge portion 2b and the piston is also relatively weak, so that the compression state in the cylinder is unstable.

In order to solve such a problem, the linear compressor according to the present invention can connect an elastic member having a significantly increased repulsive force to the discharge portion 2b. In this case, in the linear compressor according to the present invention, since the force with which the discharge portion 2b is bonded to the cylinder becomes strong, when the piston and the discharge portion 2b collide with each other, The repulsive force is also stronger than that of the conventional linear compressor.

In another embodiment of the linear compressor according to the present invention, a discharge portion having a valve plate at one end of the cylinder may be included. In this case, since the cylinder and the valve plate are fixedly coupled with each other, the repulsive force generated between the valve plate and the piston is stronger than that of the conventional linear compressor.

By using the fact that the repulsive force applied to the piston is increased as compared with the conventional linear compressor, the movement of the piston can be controlled without adding any additional sensor in the linear compressor of the present invention.

The controller of the linear compressor performing the top dead center control according to the present invention can calculate the stroke of the piston using the sensed motor voltage and the motor current. Further, the control section may control the motor so that the piston does not collide with the valve plate, based on the calculated stroke change.

Specifically, the control unit of the linear compressor according to the present invention can continuously estimate the stroke of the piston while the piston reciprocates in the cylinder, and can detect the estimated stroke change.

When the graph of the estimated stroke is compared with the graph of the actual stroke, the estimated stroke and the actual stroke form a proportional relationship until the piston collides with the discharge portion provided at one end of the cylinder. However, after the piston collides with the discharge portion provided at one end of the cylinder, the estimated stroke and the actual stroke form an inverse relationship with each other.

As described above, since the piston of the linear compressor according to the present invention is provided with stronger repulsive force than that of the conventional linear compressor, the estimated stroke and the actual stroke can form an inverse relationship from the point of collision.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, the constitution of the present invention and the effects thereof will be described in order to solve the above problems.

In Fig. 2 below, one embodiment related to the components of the linear compressor will be described.

2 is a block diagram showing a configuration of a control apparatus for a reciprocating compressor according to an embodiment of the present invention.

As shown in FIG. 2, the controller of the reciprocating compressor according to an embodiment of the present invention may include a sensing unit that senses a motor voltage and a motor current associated with the motor.

2, the sensing unit may include a voltage detecting unit 21 for detecting a motor voltage applied to the motor, and a current detecting unit 22 for detecting a motor current applied to the motor. The voltage detection unit 21 and the current detection unit 22 can transmit information related to the detected motor voltage and the motor current to the control unit 25 or the stroke estimation unit 23, respectively.

2, the control device for a compressor or a compressor according to the present invention includes a stroke estimating part 23 for estimating a stroke based on the detected motor current, a motor voltage, and a motor parameter, A comparator 24 for comparing the stroke command value and outputting the difference as a result of the comparison, and a controller 25 for controlling the stroke by varying the voltage applied to the motor in accordance with the difference.

It is needless to say that the components of the control apparatus shown in Fig. 2 are not essential, and a compressor control apparatus having more or fewer components can be implemented.

Meanwhile, the compressor control apparatus according to an embodiment of the present invention can be applied to a reciprocating compressor, but will be described with reference to a linear compressor in the present specification.

Hereinafter, each component will be described.

The voltage detecting unit 21 detects a motor voltage applied to the compressor motor. According to an embodiment, the voltage detecting unit 21 may include a rectifying unit and a DC link unit. The rectifying unit may rectify an AC power having a predetermined voltage to output a DC voltage, and the DC link unit 12 may include two capacitors.

The current detector 22 detects the motor current applied to the motor. According to an embodiment, the current detector 22 can sense the current flowing in the coil of the compressor motor.

The stroke estimation unit 23 can calculate the stroke estimation value and apply the calculated stroke estimation value to the comparator 24 using the detected motor current, the motor voltage, and the motor parameters.

At this time, the stroke estimation unit 23 can calculate the stroke estimation value through the following equation (1).

Here, x denotes a stroke,? Denotes a motor constant or a back electromotive force constant, Vm denotes a motor voltage, im denotes a motor current, R denotes a resistance, and L denotes an inductance.

Accordingly, the comparator 24 compares the stroke estimate value with the stroke instruction value and applies a corresponding difference signal to the control unit 25, whereby the control unit 25 varies the voltage applied to the motor, Can be controlled.

That is, the control unit 25 decreases the motor application voltage if the stroke estimation value is larger than the stroke instruction value, and increases the motor application voltage when the stroke estimation value is smaller than the stroke instruction value.

As shown in FIG. 2, the control unit 25 and the stroke estimation unit 23 may be formed as one unit. That is, the control unit 25 and the stroke estimation unit 23 may correspond to a single processor or a computer.

3 is a sectional view of a linear compressor according to the present invention.

The linear compressor according to an embodiment of the present invention may be a linear compressor applicable to a linear compressor control apparatus or a compressor control apparatus, but may be any type or form of a linear compressor. The linear compressor according to an embodiment of the present invention shown in FIG. 3 is only one example, and is not intended to limit the scope of the present invention.

Generally, in a motor applied to a compressor, a winding coil is provided on a stator, and a magnet is provided on a mover, so that the mover rotates or reciprocates by interaction between the winding coil and the magnet.

The winding coils may be formed variously according to the type of the motor. For example, in the case of a rotary motor, a plurality of slots formed along the circumferential direction on the inner circumferential surface of the stator are wound concentrically or distributedly. In the case of a reciprocating motor, the coil is wound in an annular shape to form a winding coil, A plurality of core sheets are inserted and coupled along the circumferential direction on the outer circumferential surface of the coil.

Particularly, in the case of a reciprocating motor, a winding coil is formed by winding a coil on an annular bobbin made of a plastic material because the coil is wound in an annular shape to form a winding coil.

As shown in FIG. 3, the reciprocating compressor has a structure in which the frame 120 is resiliently mounted by the plurality of support springs 161 and 162 in the inner space of the closed shell 110. A suction pipe 111 connected to an evaporator (not shown) of the refrigeration cycle is connected to the inner space of the shell 110. A suction pipe 111 connected to a condenser (not shown) (112) are communicated with each other.

The outer stator 131 and the inner stator 132 of the reciprocating motor 130 constituting the driving section M are fixed to the frame 120 and the reciprocating motion is provided between the outer stator 131 and the inner stator 132 A mover 133 is provided. A piston 142 constituting a compression unit Cp is coupled to a mover 133 of the reciprocating motor 130 so as to reciprocate with a cylinder 141 to be described later.

The cylinder 141 is provided in a range overlapping with the stator 131 (132) of the reciprocating motor 130 in the axial direction. A compression space CS1 is formed in the cylinder 141. A suction channel F for guiding the refrigerant to the compression space CS1 is formed in the piston 142. The suction channel F is formed at the end of the suction channel F, And a discharge valve 145 for opening and closing the compression space CS1 of the cylinder 141 is provided on the end surface of the cylinder 141. The suction valve 143 is provided to open /

For reference, the discharge portion of the linear compressor according to the present invention may be formed in various forms.

For example, the linear compressor according to the present invention may include a discharge portion formed by a valve plate, as shown in FIG. That is, the discharge unit used in the conventional reciprocating compressor can be applied to the linear compressor according to the present invention.

In another example, the linear compressor according to the present invention may include a discharge portion having an elastic member, as shown in Fig. 1B. That is, the linear compressor according to the present invention can be applied to a discharge unit used in a conventional linear compressor.

However, the elastic force of the elastic member provided in the discharge portion of the linear compressor according to the present invention may be greater than the elastic force of the elastic member provided in a general linear compressor.

In the following FIG. 4, an embodiment showing a control method of a linear compressor according to the present invention will be described.

Referring to Fig. 4, the distance variables defined by the cylinder, the piston and the discharge portion are described.

First, the distance between the linear compressor unit is the center position of the piston and the discharge in the cylinder before the drive is defined as X _0.

When the linear compressor is in operation, the distance between the top dead center and the discharge side of the piston is defined as X _TDC .

The distance between the top dead center and the bottom dead center of the piston is defined as Stk.

The distance that the center of the piston is pushed in the cylinder after the linear compressor is driven is defined as X _dc .

Specifically, when the linear compressor starts to be driven, a stronger load is applied when the piston moves toward the top dead center than when the piston moves toward the bottom dead center. Therefore, even when the control unit outputs the same stroke command or voltage command, The position can be gradually pushed away from the discharge portion. In FIG. 4, the distance that the piston is pushed from the initial position is defined as X _dc .

In addition, at the time when the control parameter related to the piston of the linear compressor to form a turning point, the distance between the piston top dead center and the discharge portion is defined as X _v. X _v may be a constant set according to the design of the compressor.

For example, if the control parameters corresponding to a gas constant (K _g), because the inflection point of the gas constant (K _g) is generated when the theoretical piston is in contact with the discharge portion, the X _v may be set to zero, have. However, X _v is not limited to this value and can be set differently depending on the design of the compressor or the change of the control parameter.

The distance (X _TDC ) between the top dead center and the discharge portion of the piston can be calculated by the following equation (4).

In addition, the distance (X _TDC ) between the top dead center and the discharging portion of the piston can be corrected by the following equation (5).

In Equation (5), X _{TDC - C} denotes a post-update value of the X _TDC .

Also, the Equation 5 X _{v _ obj} refers to X _TDC is calculated at the time when the control parameter is formed an inflection point.

In one embodiment, the control unit 25 of the linear compressor according to the present invention can detect the load variation of the motor using at least one of the motor voltage and the motor current.

The control unit 25 can calculate a compensation value related to the position of the piston whenever a load variation of the motor is detected, and can control the absolute position of the piston using the calculated compensation value.

Specifically, the control unit 25 can estimate the stroke of the piston using the motor voltage and the motor current, and based on the estimated stroke, the control unit 25 determines, from the initial position of the piston, It is possible to calculate the pushing distance X _dc .

Further, the control unit 25 can calculate the distance (X _TDC ) between the top dead center and the discharging unit of the piston using the estimated stroke and the calculated pushing distance X _dc .

In addition, the control unit 25 can calculate the parameters related to the movement of the piston in real time using the estimated stroke and the detected motor current. The control unit 25 can calculate the distance (X _TDC ) between the top dead center of the piston and the discharging unit at the time when the calculated parameter forms the inflection point. The control unit 25 compares the preset reference distance with the X _TDC at the time when the parameter forms the inflection point, and calculates the compensation value based on the comparison result.

The control unit 25 can control the motor to keep the distance (X _TDC ) between the top dead center and the discharging unit of the piston below a predetermined limit distance.

For example, the control unit 25 may increase the stroke command value or increase the motor voltage or the motor current when the calculated X _TDC is larger than the predetermined limit distance.

The control unit 25 can detect the operation rate of the motor and determine whether the load fluctuation of the motor has occurred or not based on the detected operation rate.

However, the control unit 25 can judge the load variation of the motor by various methods in addition to the operation rate. That is, when the user input for changing the output of the linear compressor is applied, the control unit 25 can determine that the load variation of the motor has occurred.

The control unit 25 can calculate the compensation value related to the position of the piston at the time of initial drive of the motor.

Specifically, the compensation value associated with the position of the piston may include an error of the calculation result of the stroke (Stk) estimated value and the distance (X _dc ) that the piston is pushed from the initial position.

That is, when the control unit 25 calculates the distance (X _TDC ) between the top dead center and the discharging unit of the piston, the control unit 25 controls the motor The compensation value associated with the position of the piston can be calculated every time.

A concrete method for the control unit 25 to calculate the compensation value is as follows.

First, when the driving of the compressor is started, the control unit 25 can calculate the distance (X _TDC ) between the top dead center of the piston and the discharging unit. That is, the control unit 25 can calculate the X _TDC at the first time point.

Thereafter, the control unit 25 can monitor the change in the control parameter (for example, the gas constant (K _g )) related to the movement of the piston used in the conventional top dead center control.

During monitoring, the control unit 25 can calculate the distance (X _TDC ) between the top dead center and the discharge unit of the piston at the second time point at which the control parameter forms the inflection point. At this time, the control parameter is defined at the time of forming the inflection point to the theoretical position of the piston in X _v, and X defines the _TDC is calculated at a second time to the X _{v_obj.}

Controller 25 by the sum of the result obtained by subtracting the X _v X _{v _ obj} in the X _TDC at a first point in time, it is possible to calculate the final X _TDC. That is, the controller 25 by subtracting X _{v v _ obj} in X, it is possible to calculate a compensation value related to the position of the piston.

On the other hand, the control unit 25 can calculate the compensation value related to the position of the piston even when the load fluctuation amount of the motor is equal to or less than a predetermined value for a predetermined time interval. That is, the control unit 25 can update the X _TDC by calculating the compensation value related to the position of the piston even when the load of the motor is maintained for a considerable period of time.

In one embodiment, the control unit 25 can detect the phase difference between the estimated stroke and the motor current, and calculate the pushing distance (X _dc ) of the piston using the detected phase difference. Specifically, the control unit 25 can calculate the pushing distance (X _dc ) of the piston using a predetermined equation including the phase difference between the estimated stroke and the motor current as a variable.

For example, the control unit 25 calculates the gas constant K _g and the damping constant C _g using the phase difference, and calculates the push distance (X _dc ) of the piston using the gas constant, the damping constant, and the stroke . That is, the control unit 25 can calculate the pushing distance X _dc of the piston by using a predetermined equation including the gas constant K _g , the damping constant C _g , and the stroke Stk as variables .

In another embodiment, the control unit 25 of the linear compressor according to the present invention can detect the absolute position of the top dead center of the piston when the detected amount of load variation is within a predetermined range. The control unit 25 can control the motor based on the absolute position of the detected top dead center.

That is, the control unit 25 can compare the absolute position of the detected top dead center and the stroke command value, and adjust the motor voltage based on the comparison result.

The control unit 25 can control the motor such that the absolute position of the detected top dead center falls within a predetermined distance from the discharge unit.

The control unit 25 may further include a memory (not shown) for storing information related to the mechanical characteristics of the linear compressor.

The control unit 25 detects the initial position of the piston based on information related to the mechanical characteristics of the linear compressor and can detect the absolute position of the top dead center of the piston based on the initial position of the piston.

For example, the information related to the mechanical characteristics of the linear compressor may include information related to the specifications of the cylinders of the linear compressor, the pistons, the spring provided in the pistons, and information related to the initial mounting position of the pistons in the cylinders.

The control unit 25 estimates the stroke Stk of the piston by using the sensed motor voltage and the motor current during driving of the linear compressor and calculates the stroke of the piston from the initial position of the piston based on the estimated stroke, It is possible to detect the distance (X _dc ) pushed in the opposite echo from the side on which the discharge portion is provided.

The control unit 25 can detect the absolute position of the top dead center of the piston based on the detected pushing distance X _dc and the initial position of the piston.

The control unit 25 may calculate at least one of the error of the estimated stroke value and the error of the detected pushing distance X _dc and may update the absolute position of the top dead center of the piston by reflecting the calculated error.

5A to 5C, various operation modes of the linear compressor will be described.

Referring to FIG. 5A, a graph relating to an asymmetric control operation among operation modes of a linear compressor is shown.

5A, the control unit of the linear compressor performing the asymmetric control operation moves the piston by a first stroke distance from the center position of the piston in the first direction, and moves the piston in the second direction opposite to the first direction And can be moved by the second stroke distance. At this time, the first stroke distance may be set different from the second stroke distance.

Referring to FIG. 5B, a graph relating to a general control operation among operation modes of the linear compressor is shown.

As shown in FIG. 5B, the control unit of the linear compressor performing the general control operation can reciprocate the piston based on the center position of the piston. That is, the first stroke distance and the second stroke distance at this time can be set to be the same.

FIG. 5C shows a graph related to the low load control operation among the operation modes of the linear compressor. The low load control operation is the operation mode of the linear compressor proposed in the present invention, and various embodiments related to the low load control operation will be described below.

As shown in FIG. 5C, the control unit 25 of the linear compressor performing the low load control operation can supply electric power to the motor only in a certain section during the reciprocating motion of the piston.

That is, referring to the graph of the motor current in FIG. 5C, the controller 25 can control the inverter (not shown) of the linear compressor so that the motor current flows in only one direction.

In particular, when the output of the compressor set by the user is equal to or lower than a predetermined output value, the control unit 25 can perform the low load control operation.

In order to perform the low load control operation as described above, the control unit 25 of the linear compressor according to the present invention can control the motor to stop driving the motor when the reciprocating piston in the cylinder is the top dead center.

6A and 6B, an embodiment relating to a control method of a linear compressor according to the present invention will be described.

As shown in Fig. 6A, the control unit 25 can control the motor to start driving the motor when the piston is at the bottom dead center.

More specifically, the linear compressor includes an inverter unit (not shown) including a plurality of switches for transmitting electric power to the motor, and the control unit 25 controls the operation of the PWM Width Modulation) control signal to turn on the PWM control signal when the piston is at the top dead center.

The control unit 25 can estimate the stroke of the piston based on the motor voltage and the motor current sensed by the voltage detection unit 21 and the current detection unit 22, respectively. In addition, the control unit 25 can detect whether the current position of the piston is the top dead center or the bottom dead center based on the estimated stroke.

6B, the process of this embodiment is shown.

The control unit 25 can monitor the position of the piston when the piston is in motion (S601).

The control unit 25 can determine whether the position of the piston has reached the bottom dead center (S602). If the control unit 25 determines that the position of the piston reaches the bottom dead center, the control unit 25 can turn on the PWM control signal (S604).

On the other hand, if the position of the piston is not the bottom dead center, the control unit 25 can determine whether the piston has reached the top dead center (S603). If the control unit 25 determines that the position of the piston has reached the top dead center, the control unit 25 can turn off the PWM control signal (S605).

7A and 7B, another embodiment related to the control method of the linear compressor according to the present invention will be described.

As shown in FIG. 7A, the control unit 25 may include a timer (not shown) that is initialized when the piston is bottom dead center, and measures the passage of time in each cycle of the piston.

The control unit 25 can start driving the motor when the timer is initialized and can stop driving the motor when the measured value of the timer exceeds a predetermined first time interval.

At this time, the control unit 26 may set the predetermined first time interval based on information related to the period of the piston.

Referring to FIG. 7A, the controller 25 can drive the motor when the timer is initialized to zero. In addition, the control unit 25 can stop driving the motor when the value of the timer exceeds the target value (Target Count) or reaches the target value.

In one example, the target value may correspond to a time value required for the piston to travel from the bottom dead center to the top dead center. In another example, the target value may be set to be shorter than a time value required for the piston to move from the bottom dead center to the top dead center.

For reference, the control unit 25 may stop driving the motor before the value of the timer reaches the target value, taking into consideration the phase delay occurring when the motor is driven.

The process of this embodiment is shown in Figure 7b.

When the piston is positioned at the bottom dead center, the control unit 25 can initialize the timer to zero (S701). Thereafter, the timer measures the elapsed time.

The control unit 25 can determine whether the measured value of the timer is equal to or less than the target value (S702).

If the measured value of the timer is equal to or lower than the target value, the control unit 25 can turn on the PWM control signal (S703). Conversely, if the measured value of the timer exceeds the target value, the control unit 25 can turn off the PWM control signal (S704).

In addition, the controller 25 may determine whether the measured value of the timer has reached a predetermined maximum value (S705). When the measured value of the timer reaches the maximum value, the control unit 25 again initializes the timer to zero.

8A and 8B, another embodiment related to the control method of the linear compressor according to the present invention will be described.

Referring to FIG. 8A, the controller 25 may limit the output of the PWM control signal on any one of the plurality of PWM control signals.

Specifically, the inverter unit includes two pairs of switches for transmitting electric power to the motor, and can receive PWM (Pulse Width Modulation) control signals of the first and second phases respectively corresponding to the two pairs of switches. In particular, the control unit 25 may apply the PWM control signals of the first phase and the second phase to the inverter unit at an intersection.

At this time, the control unit 25 can turn off the PWM control signal of the second phase when the piston reaches the top dead center.

For example, the control unit 25 can turn off the PWM control signal of the second phase when a predetermined second time interval elapses from when the inverter unit starts receiving the PWM control signal of the second phase.

On the other hand, the control unit 25 compares the phase of the stroke of the piston with the timing of applying the PWM control signals of the first and second phases, and sets the predetermined second time interval based on the comparison result have.

8A, the control unit 25 compares the phase of the U-phase PWM control signal with the phase of the stroke so that the piston reaches the top dead center from the moment when the U phase PWM control signal is applied It is possible to detect the time interval to the time point. The controller 25 may set the detected time interval to the second time interval.

Referring to FIG. 8A, the period of the PWM control signal on the U phase and the period of the PWM control signal on the V phase may correspond to the half cycle of the stroke, respectively.

The process of this embodiment is shown in Figure 8b.

9A and 9B, another embodiment related to the control method of the linear compressor according to the present invention will be described.

Referring to FIG. 9A, the control unit 25 may gradually decrease the duty ratio of the PWM control signal when the piston moves from the bottom dead center to the top dead center.

For example, the control unit 25 may gradually decrease the duty ratio so that the PWM control signal is turned off when the piston reaches the top dead center.

The process of this embodiment is shown in Figure 9b.

First, the control unit 25 can detect the moving direction of the piston (S901). In addition, the controller 25 can determine whether the piston moves from the bottom dead center to the top dead center (S902).

When the piston moves from the bottom dead center to the top dead center, the control unit 25 can turn on the PWM control signal (S903) and gradually decrease the duty ratio of the PWM control signal after the PWM control signal is turned on (S905).

Conversely, when the piston moves from the top dead center to the bottom dead center, the control unit 25 can turn off the PWM control signal (S904).

Referring to Fig. 10, there is shown an inverter of a linear compressor according to the present invention.

As described above, the inverter section which receives the U-phase PWM control signal and the V-phase PWM control signal generally requires two pairs of switches.

On the other hand, according to the low load control operation of the linear compressor according to the present invention, the current can flow in only one direction. That is, referring to FIG. 9A, when the controller 25 controls the inverter to supply power to the motor only while the piston is moving from the bottom dead center to the top dead center, the current flows only in one direction.

Therefore, in the case of the linear compressor performing the low load control operation, two switches out of the two pairs of switches can be removed.

The linear compressor and the control method thereof according to the present invention can increase the maximum cooling power of the compressor or improve the driving efficiency of the compressor by reducing the number of switching operations performed during the reciprocating motion of the piston.

Further, the linear compressor and the control method thereof according to the present invention can improve the driving efficiency of the compressor in the low-cooling power band, and reduce the power consumption of the electronic product having such a compressor.

Further, the linear compressor according to the present invention and the control method thereof have the effect of improving the control stability of the linear compressor by limiting the time when the motor is driven.

Claims (14)

A piston reciprocating inside the cylinder;
A motor for providing a driving force for the movement of the piston; And
And a controller for controlling the motor to stop driving the motor when the piston is at the top dead center. The method according to claim 1,
Wherein,
And controls the motor to start driving the motor when the piston is at the bottom dead center. 3. The method of claim 2,
And an inverter unit including a plurality of switches for transmitting electric power to the motor,
Wherein,
A PWM (Pulse Width Modulation) control signal for controlling the operation of the switch is turned on when the piston is at the top dead center,
And turns off the PWM control signal when the piston is at the top dead center. The method of claim 3,
Further comprising a sensing unit for sensing a motor voltage and a motor current associated with the motor,
Wherein,
Estimating a stroke of the piston using the motor voltage and the motor current,
Based on the estimated stroke, whether the current position of the piston is a top dead center or a bottom dead center. The method of claim 3,
Wherein,
And supplies the PWM control signal to the inverter unit so that power is supplied to the motor while the piston moves from the bottom dead center to the top dead center. The method of claim 3,
Wherein,
Wherein the duty ratio of the PWM control signal is gradually reduced when the piston moves from the bottom dead center to the top dead center. The method according to claim 6,
Wherein,
And decreases the duty width so that the PWM control signal is turned off when the piston reaches the top dead center. 3. The method of claim 2,
Further comprising a timer that is initialized when the piston is bottom dead center and measures the passage of time for each period of the piston,
Wherein,
Wherein when the timer is initialized, driving of the motor is started,
And stops driving the motor when the measured value of the timer exceeds a predetermined first time interval. 9. The method of claim 8,
Wherein,
And sets the predetermined first time interval based on information related to the period of the piston. The method according to claim 1,
An inverter unit including two pairs of switches for transmitting electric power to the motor, and receiving first and second PWM (Pulse Width Modulation) control signals corresponding to the two pairs of switches, respectively;
Wherein,
And turns off the PWM control signal of the second phase when the piston reaches the top dead center. 11. The method of claim 10,
Wherein,
And turns off the PWM control signal of the second phase when a predetermined second time interval elapses after the inverter section starts receiving the PWM control signal of the second phase. 12. The method of claim 11,
Wherein,
Compares the phase of the stroke of the piston with the point of time when the PWM control signal of the first phase and the second phase is applied,
And sets the predetermined second time interval based on the comparison result. 13. The method of claim 12,
Wherein,
And applies the PWM control signals of the first phase and the second phase to the inverter section in an intersecting manner. 14. The method of claim 13,
Wherein the periods of the PWM control signals of the first phase and the second phase correspond to half cycles of the stroke, respectively.

Images