WO2007049876A1

WO2007049876A1 - Driving controlling apparatus for linear compressor and method thereof

Info

Publication number: WO2007049876A1
Application number: PCT/KR2006/004223
Authority: WO
Inventors: Hyeung-Ju Kim; Ji-Won Sung; Chel-Woong Lee
Original assignee: Lg Electronics Inc.
Priority date: 2005-10-28
Filing date: 2006-10-18
Publication date: 2007-05-03
Also published as: KR20070095518A

Abstract

An apparatus for controlling a driving of a linear compressor capable of precisely controlling a linear compressor and enhancing a reliability of the linear compressor by calculating a motion distance of a piston connected to a motor inside the linear compressor, and a method thereof. The apparatus for controlling a driving of a linear compressor comprises a controlling unit for comparing a detected top dead center (TDC) and a detected bottom dead center (BDC) with a reference TDC and a reference BDC corresponding to a stroke command value, and outputting a stroke control signal to control a stroke based on the comparison result.

Description

DRIVING CONTROLLING APPARATUS FOR LINEAR COMPRESSOR AND METHOD THEREOF

Technical Field

[1] The present invention relates to a compressor, and more particularly, to a driving controlling apparatus for a linear compressor and a method thereof. Background Art

[2] Generally, a compressor sucks refrigerant gas, compresses it, and then discharges it by linearly reciprocating a piston in a cylinder. The compressor is divided into a reciprocating compressor and a linear compressor according to a driving method of the piston.

[3] In the reciprocating compressor, a crankshaft is coupled to a rotary motor and a piston is coupled to the crankshaft, thereby converting a rotation force of the rotary motor into a reciprocation force.

[4] In the linear compressor, a piston connected to a mover of a linear motor is linearly moved.

[5] The linear compressor is not provided with a crank shaft for converting a rotation motion into a linear motion thus not to have a frictional loss due to the crank shaft, thereby having a high compression efficiency.

[6] When the linear compressor is applied to a refrigerator or an air conditioner, a compression ratio of the linear compressor is varied by varying a voltage applied to a motor inside the linear compressor. Accordingly, a cooling capacity of the refrigerator or the air conditioner is controlled.

[7] When the linear compressor is applied to a refrigerator or an air conditioner, a compression ratio of the linear compressor is varied by varying a stroke voltage applied to the linear compressor. Accordingly, a cooling capacity of the refrigerator or the air conditioner is controlled. Herein, the stroke denotes a distance between an upper dead point of the piston and a lower dead point of the piston.

[8] The related art linear compressor will be explained with reference to FlG. 1.

[9] FlG. 1 is a block diagram showing a driving controlling apparatus for a linear compressor in accordance with the related art.

[10] As shown in FlG. 1, the related art driving controlling apparatus for a linear compressor comprises a current detecting unit 4 for detecting a current applied to a motor (not shown) of the linear compressor 6; a voltage detecting unit 3 for detecting a voltage applied to the motor of the linear compressor 6; a stroke calculating unit 5 for calculating a stroke estimation value of the linear compressor based on the detected current, the detected voltage, and a parameter of the motor; a comparing unit 1 for comparing the calculated stroke estimation value with a preset stroke command value, and outputting a difference value therebetween; and a stroke controlling unit 2 for controlling a turn-on period of a triac (not shown) serially connected to the motor based on the difference value so as to vary a voltage applied to the motor, and thereby controlling a stroke of the linear compressor 6.

[11] Hereinafter, the driving controlling apparatus for a linear compressor will be explained with reference to FlG. 1.

[12] The current detecting unit 4 detects a current applied to a motor (not shown) of the linear compressor 6, and outputs the detected current to the stroke calculating unit 5.

[13] The voltage detecting unit 3 detects a voltage applied to the motor of the linear compressor 6, and outputs the detected voltage to the stroke calculating unit 5.

[14] The stroke calculating unit 5 calculates a stroke estimation value (X) of the linear compressor by substituting the detected current, the detected voltage, and a parameter of the motor into a following equation 1. Then, the stroke calculating unit 5 applies the calculated stroke estimation value (X) to the comparing unit 1.

[15]

^{X =} _a J^"(K" ^{~ Rl ~ Li}">^di Formula 1

[16] The R denotes a resistance of the motor, the L denotes an inductance of the motor, the denotes a constant of the motor, the V M denotes a voltage applied to the motor, the

/ denotes a current applied to the motor, and the

denotes a variation ratio of the current applied to the motor according to time. That is, the

is a differential value of the (di/dt)

[17] The comparing unit 1 compares the stroke estimation value with the stroke command value, and applies a difference value therebetween to the stroke controlling unit 2. [18] The stroke controlling unit 2 varies a voltage applied to the motor of the linear compressor 6 based on the difference value, thereby controlling the stroke of the linear compressor 6. [19] FlG. 2 is a flowchart showing a method for controlling a driving of a linear compressor in accordance with the related art.

[20] Referring to FlG. 2, a stroke estimation value obtained by the stroke calculating unit 5 is applied to the comparing unit 1 (Sl). Then, the comparing unit 1 compares the stroke estimation value with a preset stroke command value (S2), and outputs a difference value therebetween to the stroke controlling unit 2.

[21] When the stroke estimation value is smaller than the stroke command value, the stroke controlling unit 2 increases a voltage applied to the motor so as to control a stroke of the linear compressor (S3). On the contrary, when the stroke estimation value is larger than the stroke command value, the stroke controlling unit 2 decreases the voltage applied to the motor (S4).

[22] Herein, the voltage applied to the motor is increased or decreased by controlling a turn-on period of a triac (not shown) electrically connected to the motor.

[23] The stroke command value is varied according to a size of a load of the linear compressor. More concretely, when the load is large, the stroke command value is increased thus to increase the stroke of the piston, thereby preventing decrease of a cooling capacity. On the contrary, when the load is small, the stroke command value is decreased thus to decrease the stroke of the piston, thereby preventing increase of the cooling capacity and preventing a collision between the piston and the cylinder due to an over stroke.

[24] In the related art method for controlling a driving of a linear compressor, a voltage and a current applied to the motor of the linear compressor are detected. Then, a stroke estimation value of the linear compressor is calculated based on the detected current and the detected voltage in a sensorless manner, thereby controlling the voltage applied to the motor of the linear compressor.

Disclosure of Invention Technical Problem

[25] However, the related art apparatus and method for controlling a driving of a linear compressor have the following problems. When a load applied to the linear compressor is increased, the piston connected to the motor inside the linear compressor is backwardly moved towards a bottom dead center with a certain distance.

[26] When the load applied to the linear compressor is decreased, the piston connected to the motor inside the linear compressor is forwardly moved towards a top dead center with a certain distance.

[27] When the piston of the linear compressor is backwardly or forwardly moved, it may collide with a peripheral device such as a discharge valve or a suction valve. The reason is because the stroke of the linear compressor was controlled by detecting only the stroke of the motor inside the linear compressor without considering a motion of the piston in backward and forward directions occurring due to a load variation of the linear compressor.

Technical Solution

[28] Therefore, an object of the present invention is to provide an apparatus for controlling a driving of a linear compressor capable of precisely controlling a linear compressor and enhancing a reliability of the linear compressor by calculating a motion distance of a piston connected to a motor inside the linear compressor, and a method thereof. Advantageous Effects

[29] As aforementioned, in the apparatus for controlling a driving of a linear compressor and the method thereof according to the present invention, a motion distance of the piston connected to the motor inside the linear compressor is calculated, thereby precisely controlling the linear compressor and enhancing a reliability of the linear compressor. Brief Description of the Drawings

[30] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

[31] In the drawings:

[32] FlG. 1 is a block diagram showing an apparatus for controlling a driving of a linear compressor in accordance with the related art;

[33] FlG. 2 is a flowchart showing a method for controlling a driving of a linear compressor in accordance with the related art;

[34] FlG. 3 is a block diagram showing an apparatus for controlling a driving of a linear compressor according to the present invention; and

[35] FlG. 4 is a flowchart showing a method for controlling a driving of a linear compressor according to the present invention. Best Mode for Carrying Out the Invention

[36] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[37] Hereinafter, will be explained an apparatus for controlling a driving of a linear compressor capable of precisely controlling a linear compressor and enhancing a reliability of the linear compressor by calculating a motion distance of a piston connected to a motor inside the linear compressor, and a method thereof.

[38] FlG. 3 is a block diagram showing an apparatus for controlling a driving of a linear compressor according to the present invention. [39] As shown in FlG. 3, the apparatus for controlling a driving of a linear compressor according to the present invention comprises a current detecting unit 100, a voltage detecting unit 200, a stroke calculating unit 300, a comparing unit 400, a controlling unit 500, a TDC and BDC detecting unit 600, and a storing unit 700. [40] The current detecting unit 100 detects a current applied to a motor of the linear compressor, and the voltage detecting unit 200 detects a voltage applied to the motor of the linear compressor. [41] The stroke calculating unit 300 calculates a stroke estimation value of the linear compressor based on the detected current and the detected voltage. [42] The comparing unit 400 compares the calculated stroke estimation value with a preset stroke command value, and outputting a difference value therebetween. [43] The storing unit 700 stores a reference TDC and a reference BDC corresponding to the preset stroke command value. [44] The TDC and BDC detecting unit 600 detects a TDC and a BDC of a piston connected to the motor inside the linear compressor. [45] The controlling unit 500 outputs a stroke control signal to control the stroke of the linear compressor based on the difference value outputted from the comparing unit

400. [46] The controlling unit 500 compares the TDC and the BDC detected by the TDC and

BDC detecting unit 600 with a reference TDC and a reference BDC corresponding to the stroke command value, and outputs a stroke control signal to control the stroke based on the comparison result. [47] More concretely, when the detected TDC is larger than the reference TDC, the controlling unit 500 decreases the stroke of the linear compressor. Also, when the detected BDC is larger than the reference BDC, the controlling unit 500 decreases the stroke of the linear compressor. [48] However, when the detected TDC is smaller than the reference TDC, the controlling unit 500 controls the stroke based on the difference value between the stroke command value and the stroke estimation value. [49] Also, when the detected BDC is smaller than the reference BDC, the controlling unit 500 controls the stroke based on the difference value between the stroke command value and the stroke estimation value. [50] Hereinafter, an operation of the apparatus for controlling a driving of a linear compressor according to the present invention will be explained with reference to FlG.

4. [51] FlG. 4 is a flowchart showing a method for controlling a driving of a linear compressor according to the present invention. [52] First, the motor of the linear compressor is operated with a certain stroke command value (SPIl). [53] Under this state, the current detecting unit 100 detects a current applied to the motor of the linear compressor, and the voltage detecting unit 200 detects a voltage applied to the motor of the linear compressor (SP 12). [54] The TDC and BDC detecting unit 600 detects a TDC and BDC of a piston connected to the motor inside the linear compressor (SP12). [55] The TDC and BDC of the piston can be detected by various methods. Herein, the

TDC and BDC are detected according to a mechanical equation. [56] In case of the linear motor, the following equations 1 and 2 are obtained by the mechanical equation. [57] [Equation 1]

[58] m_effx + C₁X_x + k_mx = ai - Fp

[59] [Equation 2]

[60]

^x ^ac ^~t^{~ X}dc [61] Herein, the

denotes a moving part including the piston of the linear compressor (hereinafter, will be called as a mover), the

denotes a factional coefficient, the

denotes a spring constant, the denotes a constant of the motor, the

denotes a pressure of the piston, and the

denotes a stroke of the piston. [62] When a suction valve of the linear motor is opened, a pressure inside the cylinder and a pressure inside the suction valve are equal to each other. Accordingly, the F_P is O'.

[63] The following equation 3 is obtained from the equations 1 and 2.

[64] [Equation 3] [65] m_effx + C₁X_0x, + k_m (x_^ + x_dc ) = ai

[66] The motion distance

* _*, of the piston is obtained from the equation 3, which is shown in the following equation

4.

[67] [Equation 4]

[68]

[69] Herein, the frictional coefficient

is O', the

X is shown in the following equation 5, and the

is shown in the following equation 6.

[70] [Equation 5]

[71] _j di - Ri )dt

^L dt

[72] [Equation 6]

[73]

2

[74] Accordingly, the TDC and the BDC are

[75] [Equation 7]

[76]

TDC — ^■—- x_dc

[77] [Equation 8]

[78]

BDC = —z V x_dc [79] The stroke calculating unit 300 calculates a stroke based on the detected current and the detected voltage (SPl 3).

[80] Then, the comparing unit 400 compares the stroke estimation value with the stroke command value, and outputs a difference value therebetween.

[81] Then, the controlling unit 500 selects a reference TDC and a reference BDC corresponding to the stroke command value from the storing unit 700, and compares the selected reference TDC and BDC with the TDC and BDC detected by the TDC and BDC detecting unit 600 (SP15, SP17).

[82] When the detected TDC is larger than the reference TDC (SP15), the controlling unit 500 decreases the stroke of the linear compressor (SP16). On the contrary, when the detected BDC is larger than the reference BDC (SP17), the controlling unit 500 decreases the stroke of the linear compressor (SP16).

[83] When the detected TDC is smaller than the reference TDC, the controlling unit 500 controls the stroke of the linear compressor based on the difference value between the stroke command value and the stroke estimation value (SPl 8).

[84] When the detected BDC is smaller than the reference BDC, the controlling unit 500 controls the stroke of the linear compressor based on the difference value between the stroke command value and the stroke estimation value (SPl 8).

[85] The reference TDC and the reference BDC are respectively set as an optimum value corresponding to the stroke by an experiment.

[86] The TDC is an abbreviated term of a top dead center of the piston of the linear compressor, which represents a position of the piston when the piston completes a compression operation.

[87] The BDC is an abbreviated term of a bottom dead center of the piston of the linear compressor, which represents a position of the piston when the piston completes a suction operation.

[88] When the TDC is '0' , an efficiency of the linear compressor is maximized. Accordingly, the linear compressor is controlled so that the piston can be positioned at the 'TDC=O'.

[89] As aforementioned, in the apparatus for controlling a driving of a linear compressor and the method thereof according to the present invention, a motion distance of the piston connected to the motor inside the linear compressor is calculated, thereby precisely controlling the linear compressor and enhancing a reliability of the linear compressor.

[90] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

[1] An apparatus for controlling a driving of a linear compressor, comprising: a controlling unit for comparing a detected top dead center (TDC) and a detected bottom dead center (BDC) with a reference TDC and a reference BDC corresponding to a stroke command value, and outputting a stroke control signal to control a stroke based on the comparison result.

[2] The apparatus of claim 1, wherein when the detected TDC is larger than the reference TDC, the controlling unit decreases the stroke of the linear compressor.

[3] The apparatus of claim 1, wherein when the detected BDC is larger than the reference BDC, the controlling unit decreases the stroke of the linear compressor.

[4] The apparatus of claim 1, wherein when the detected TDC is smaller than the reference TDC, the controlling unit controls the stroke based on a difference value between the stroke command value and a present stroke estimation value.

[5] The apparatus of claim 1, wherein when the detected BDC is smaller than the reference BDC, the controlling unit controls the stroke based on a difference value between the stroke command value and a present stroke estimation value.

[6] The apparatus of claim 1, further comprising a TDC and BDC detecting unit for detecting a TDC and a BDC of a piston connected to a motor of the linear compressor.

[7] The apparatus of claim 1, further comprising a storing unit for storing a reference

TDC and a reference BDC corresponding to the stroke command value.

[8] An apparatus for controlling a driving of a linear compressor, comprising: a current detecting unit for detecting a current applied to a motor inside a linear compressor; a voltage detecting unit for detecting a voltage applied to the motor inside the linear compressor; a stroke calculating unit for calculating a stroke estimation value of the linear compressor based on the detected current, the detected voltage, and a parameter of the motor; a comparing unit for comparing the calculated stroke estimation value with a preset stroke command value, and outputting a difference value therebetween; and a controlling unit for controlling a stroke of the linear compressor based on the difference value, comparing a detected top dead center (TDC) and a detected bottom dead center (BDC) with a reference TDC and a reference BDC corresponding to the preset stroke command value, and outputting a stroke control signal to control the stroke based on the comparison result. [9] The apparatus of claim 8, wherein when the detected TDC is larger than the reference TDC, the controlling unit decreases the stroke of the linear compressor. [10] The apparatus of claim 8, wherein when the detected BDC is larger than the reference BDC, the controlling unit decreases the stroke of the linear compressor. [11] The apparatus of claim 8, wherein when the detected TDC is smaller than the reference TDC, the controlling unit controls the stroke based on a difference value between the stroke command value and a present stroke estimation value. [12] The apparatus of claim 8, wherein when the detected BDC is smaller than the reference BDC, the controlling unit controls the stroke based on a difference value between the stroke command value and a present stroke estimation value. [13] The apparatus of claim 8, further comprising a TDC and BDC detecting unit for detecting a TDC and a BDC of a piston connected to a motor of the linear compressor. [14] The apparatus of claim 8, further comprising a storing unit for storing a reference

TDC and a reference BDC corresponding to the stroke command value. [15] A method for controlling a driving of a linear compressor, comprising: detecting a TDC and a BDC of a piston connected to a linear compressor; and controlling a stroke of the linear compressor according to the detected TDC and the BDC. [16] The method of claim 15, wherein the controlling a stroke comprises: decreasing the stroke of the linear compressor when the detected TDC is larger than the reference TDC. [17] The method of claim 15, wherein the controlling a stroke comprises: decreasing the stroke of the linear compressor when the detected BDC is larger than the reference BDC. [18] The method of claim 15, wherein the controlling a stroke comprises: controlling the stroke based on a difference value between the stroke command value and a present stroke estimation value when the detected TDC is smaller than the reference TDC. [19] The method of claim 15, wherein the controlling a stroke comprises: controlling the stroke based on a difference value between the stroke command value and a present stroke estimation value when the detected BDC is smaller than the reference BDC. [20] The method of claim 15, further comprising storing a reference TDC and a reference BDC corresponding to the stroke command value.