KR100283152B1 - Apparatus for measuring pressure in a linear compressor - Google Patents

Abstract

The present invention relates to an internal pressure measuring apparatus of a linear compressor, and in the related art, attaching a pressure sensor to measure the internal pressure of the linear compressor is difficult to attach, expensive, and loses the characteristics of the compressor due to the interference of the sensor. There is a problem that may be. Accordingly, the present invention provides a first adder that adds a piston average position and an arbitrary position x of the piston, and firstly differentiates the arbitrary position x, and the first differential position value. And the second differentiator for outputting the second derivative and the second derivative for the second derivative. And a fourth multiplier for outputting a multiplier, a first multiplier for multiplying a spring constant (k) by a position value added by the first adder, a second multiplier for multiplying a damping coefficient (c) by a position value differentiated in the third differentiator, and A third multiplier that multiplies the moving value m by the position value differentiated in the fourth differentiator, a fourth multiplier that multiplies the motor constant α by the current i supplied to the motor, and the first to third A second adder for obtaining the force (F) applied to the linear compressor by receiving the output value of the multiplier as an inverting terminal and the output value of the fourth multiplier as a non-inverting terminal, and a fifth multiplier for multiplying the output force by 1 / A. And a third adder for calculating the internal pressure P (x) of the linear compressor by adding the value output from the fifth multiplier and the suction pressure Ps, thereby adjusting the position of the compressor piston and the motor current without attaching the pressure sensor. Measure the internal pressure and use it to Improve performance by controlling values, and will allow one to reduce the price by not attaching the sensor.

Description

Internal pressure measuring device of linear compressor {APPARATUS FOR MEASURING PRESSURE IN A LINEAR COMPRESSOR}

The present invention relates to an internal pressure measuring device of a linear compressor that can determine the internal pressure by measuring the position of the compressor piston and the motor current without attaching a pressure sensor inside the linear compressor. The present invention relates to an internal pressure measuring device of a linear compressor that detects a position value of a piston or finds an internal pressure by using position information of a piston obtained by using a position sensor of the piston.

2 is a block diagram of a sensorless position sensing device of a conventional linear compressor. As shown in FIG. 2, a current detection unit detecting a current applied to a linear compressor for adjusting cooling power by changing a piston position by vertical movement of a piston (21), a current differentiator 22 for differentiating the current detected by the current detector 20, a voltage detector 23 for detecting a voltage between both ends of the linear compressor, and a voltage between both ends of the linear compressor. And a speed calculator 24 for inputting the detection current and the current differential value to calculate the speed, and an integrator 25 for integrating the speed calculated above to obtain the position x of the piston.

Referring to the prior art configured as described above in detail.

Unlike the reciprocating compressor, the linear compressor has more efficiency since there is no loss of converting the rotation operation into linear movement.

The linear compressor requires piston position control because the piston is not fixed and the piston head may collide, and the capacity must be varied.

For the piston position control, the position sensor can be attached or positioned without the sensor using the voltage and current of the compressor motor.

Then, the process of finding out the position (x) of the piston using the voltage and current of the compressor motor without the sensor will be described based on FIG. 1 and FIG. 2.

When a power supply voltage is supplied to the linear compressor of FIG. 1, a current flows to the compressor, whereby the piston reciprocates.

Then, the position (x) of the piston changes, and the position of the changed piston is obtained as follows.

First, the current detector 21 detects a current supplied to the linear compressor and supplies the current to the speed calculator 24 and the current differentiator 22, respectively.

Then, the current differentiator 22 performs a differential operation on the detected current to obtain a current differential value, and supplies the obtained current differential value to the speed calculator 24.

The voltage detector 23 detects a voltage between both ends when the linear compressor is driven, and supplies the detected voltage to the speed calculator 24.

Accordingly, the speed calculator 24 calculates the speed υ by receiving the current and voltage detected through the current and voltage detectors 23 and 23, and the current derivatives obtained through the current differentiator 24, respectively.

Then, the speed calculation unit 24 obtains the speed υ and provides it to the integrator 25. The integrator 25 receives the speed υ calculated by the speed calculation unit 24 and integrates the piston. The position (x) of is obtained as in Equation 1 below.

Where α is the compressor motor constant value, Is the voltage between both ends of the linear compressor, Is the electrical resistance of the compressor motor, i is the current flowing through the motor, : Reactance of motor.

Since the movement of the linear compressor varies depending on the load, that is, the pressure inside the compressor, the pressure inside the compressor is measured to precisely control the position of the compressor obtained in Equation 2 and to control the capacity of the refrigeration cycle having good performance. It is necessary to know the load accurately.

At this time, the pressure inside the compressor is attached to the pressure sensor to find out the pressure.

Thus, find out the position (x) of the piston obtained by using the internal pressure of the compressor found by using the pressure sensor, the current and voltage applied to the linear compressor, and use the pressure and the position of the piston to drive the linear compressor. Control cycle performance well.

However, in the prior art as described above, there is a problem that attaching the pressure sensor to measure the internal pressure of the linear compressor is difficult to attach, expensive, and the characteristics of the compressor may be lost due to the interference of the sensor. .

Therefore, an object of the present invention for solving the conventional problems as described above is to provide an internal pressure measuring apparatus of the linear compressor to obtain the internal pressure of the compressor only by the position information by the position sensor.

It is another object of the present invention to provide an internal pressure measuring apparatus of a linear compressor that obtains a piston position by using a current and a voltage applied to a motor, and obtains the internal pressure of the compressor with the position.

1 is a structural diagram of a conventional linear compressor.

Figure 2 is a block diagram of a sensorless position sensing device of a conventional linear compressor.

3 is a volume-pressure characteristic diagram showing a compression process in a linear compressor.

Figure 4 is a circuit diagram of the internal pressure measuring device of the linear compressor of the present invention.

FIG. 5 is a circuit configuration diagram for obtaining a piston average position in FIG. 4. FIG.

6 is a circuit diagram illustrating a suction pressure in FIG. 4.

FIG. 7 is a circuit diagram illustrating a top dead center and a bottom dead center in the compression operation.

*** Explanation of symbols for main parts of drawing ***

41: first adder 42: third quarter

43: fourth mill 44-47, 49: multiplier

48: second adder 50: third adder

51-53: Sample holding unit 54: Weight calculation unit

68,69: volume calculation section 70: suction pressure calculation section

The present invention for achieving the above object is a first adder that adds the piston average position (x _av ) and the arbitrary position (x) of the piston, and firstly differentiates the arbitrary position (x), and the first derivative Position value And the second differentiator for outputting the second derivative and the second derivative for the second derivative. And a fourth multiplier for outputting a multiplier, a first multiplier for multiplying a spring constant (k) by a position value added by the first adder, a second multiplier for multiplying a damping coefficient (c) by a position value differentiated in the third differentiator, and A third multiplier that multiplies the moving value m by the position value differentiated in the fourth differentiator, a fourth multiplier that multiplies the motor constant α by the current i supplied to the motor, and the first to third The output value of the multiplier is an inverting terminal, the output value of the fourth multiplier is a non-inverting terminal, and a second adder for obtaining the force (F) applied to the linear compressor, and the inverse of the cross-sectional area (A) of the compressor to the force output from the multiplier. And a third adder for multiplying a multiplier and a third adder for calculating an internal pressure P (x) of the linear compressor by adding a value output from the fifth multiplier and a suction pressure Ps.

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

FIG. 5 is a block diagram of the internal pressure measuring apparatus of the linear compressor according to the present invention. As shown therein, the first adder 41 adds the piston average position x _av and an arbitrary position x of the piston, respectively. And the first derivative of the arbitrary position (x), and the first derivative of the position value. Second derivative of the third differentiator 42 and the differentiated position value, and the second differentiated position value A fourth differentiator 43 for outputting the first multiplier 43, a first multiplier 44 for multiplying a spring constant k by a position value added by the first adder 41, and a position value differentiated in the third differentiator 42; The second multiplier 45 multiplying the damping coefficient (c), the third multiplier 46 multiplying the moving mass (m) by the position value differentiated in the fourth differentiator 43, and the current supplied to the motor ( i) The fourth multiplier 47 multiplying by the constant α and the output values of the first to third multipliers 44-46 are input as inverting terminals, and the output values of the fourth multiplier 47 are input as non-inverting terminals. A second adder 48 for receiving the force F applied to the linear compressor, a fifth multiplier 49 for multiplying the force output from the above by 1 / A, and a value output from the fifth multiplier 49 The third adder 50 obtains the internal pressure P (x) of the linear compressor by adding the excess suction pressure Ps.

As shown in Fig. 6, the circuit configuration for calculating the suction pressure Ps includes the first differentiator 61 which firstly differentiates the arbitrary position x of the piston, and the position value differentiated above. A fourth sample holding part 62 for holding a sample according to a bottom dead center state pulse inputted to the second differentiator 63 and the first differentiated position value output from the first differentiator 61; A fifth sample holding part 64 for holding a sample of the second differential position value output from the second differentiator 63 according to the bottom dead center state pulse, and a current supplied to the motor to the bottom dead center state pulse. A sixth sample holding part 65 for holding a sample according to the present invention, a seventh sample holding part 66 for holding a sample according to a top dead center state pulse inputting the arbitrary position x, and the arbitrary position An eighth sample holding unit 67 for holding a sample according to a bottom dead center state pulse; and the seventh and eighth sample holding units 66 and 67; The volume calculation unit 68, 69 calculates the volume of the value outputted from the inside, and uses the position value and the volume at the top dead center and the bottom dead center calculated by each unit, and the piston average position (x _av ). It consists of the calculation part 70 which calculates pressure Ps.

In addition, the circuit for calculating the piston average position (x _av ) in the above, as shown in Fig. 5, the current (i) supplied to the motor in accordance with the suction state pulse, the arbitrary position (x) of the piston, and Second derivative of any position value The first to the third sample holding unit (51-53) for holding the sample, respectively, and the weight calculation unit 54 for calculating the average position of the piston by calculating the current and position value held in the sample.

Referring to the operation and effect of the present invention configured as described in detail as follows.

First, the operation of the linear compressor will be described based on FIG. 3. Part (a) is the same time as the suction pressure Ps and the pressure P inside the cylinder with the suction valve open, and the part (b) is the compressor. (C) is the same time as the discharge pressure (Pd) and the pressure (P) inside the cylinder with the discharge valve open, and (d) is the process of expanding the remaining gas inside the cylinder. .

When the operation of the linear compressor as described above is changed to kinetic energy, it can be expressed as Equation 2 below.

here Silver moving mass, Is the damping factor, k is the spring constant, Is the compressor motor constant, A is the piston cross-sectional area, x is any piston position, x _av is the average position of the piston, P (x) is the internal pressure, Is the suction pressure.

Then, a method of determining the average position (x _av ) of the piston (Piston) of the linear compressor in Equation 2 will be described based on FIG.

In the suction phase, the derivative value of the position of the piston is 0, and since the pressure inside the cylinder is equal to the suction pressure Ps, there are no terms of force due to pressure and attenuation by damping.

Therefore, the pulse in the suction state occurs when the position of the piston is X <0 and dX / dt = 0.

Accordingly, when a suction phase pulse is input, the first sample holding part 51 performs second derivative position values with respect to an arbitrary piston position value. Generated by holding the sample Is outputted to the weight calculation unit 54, and the second sample holding unit 52 receives a value of an arbitrary piston position and generates the sample by holding it. Is output to the weight calculation unit 54, and the third sample holding unit 53 receives the motor current i supplied to the motor and sample-holds the current value i _o generated by the weight calculation unit 54. )

Then, the weight calculation unit 54 receives the values generated by the sample holding units 51-53 and calculates the equations as shown in Equation 3 below to obtain a piston average position x _av .

And the compressor internal pressure And the volume inside the compressor The sum of has a constant value as shown in Equation 4 below.

Equation 4 is an equation representing a polytropic process established when the gas inside the linear compressor is a process of part (??) and part (??) in FIG. 3, and n is a refrigerant value used in the compressor.

Internal pressure in Equation 2 Can be obtained as in Equation 5 below.

The term unknown in Equation 5 is the internal pressure Ps, which can be seen in part (b) of FIG.

In Fig. 3, the pressure Pa at the bottom dead center ((a) point) is equal to the suction pressure Ps, and the volume at this point is called Va, and compression is performed from this point to the top dead center ((b) point). Using Equation 6 shown below, the internal pressure Ps can be obtained as follows.

here Is the volume at the top dead center (b point), and x _b is the position of the piston.

Next, a method of obtaining the suction pressure Ps in the process of compressing the bottom dead center (b point) from the top dead center (a point) using Equation 6 will be described with reference to FIG. 6.

When an arbitrary piston position value x is input, the value obtained by performing the first derivative in the first differentiator 61 and performing the first derivative Is output to the second differentiator 63 and the fourth sample holding unit 62.

At the same time, the seventh and eighth sample holding part 66 receives an arbitrary piston position value x from the seventh and eighth sample holding parts 66 and 67, and the seventh sample holding part 66 has a bottom dead center state pulse (a phase). Outputs _a position value x _a generated by holding a sample when a pulse is input, and the eighth sample holding unit 67 generates a sample by holding a sample when a top dead center state pulse is input. Print the value (x _b ).

Then, the volume calculators 68 and 69 receive the position values output from the seventh and eighth sample holding units 66 and 67, respectively, and calculate the volume Va (Vb) of the positions. The volume Va (Vb) is provided to the calculation unit 70.

In addition, the position value x _b of the sample held by the eighth sample holding unit 67 is provided to the calculation unit 70.

In addition, the fourth sample holding unit 62 may firstly differentiate the position value when the top dead center state pulse is input. Generated by holding the sample Is output to the calculation unit 70, and the fifth sample holding unit 64 is the second derivative position value when a b-phase pulse is input. Generated by holding the sample The sixth sample holding unit 65 outputs the current value (i _b ) generated by holding the current (i) when the top dead center state pulse (b phase pulse) is input. Output to the calculator 70.

The piston average position value x _av is input to the calculation unit 70.

Therefore, the calculation unit 70 is the position value, volume value and current, average position values output from each unit Calculate the suction pressure (Ps).

As can be seen in Figure 6 the position of the piston obtained by the position sensor And knowing the current applied to the motor can know the suction pressure (Ps).

In addition, the position (x) of the piston can be obtained through the circuit as in FIG.

Since the piston average position (x _av ) obtained in FIG. 5, the suction pressure (Ps) obtained in FIG. 6, and the current (i) supplied to the motor can be known, the internal pressure (P (x)) of the linear compressor can be obtained. The internal pressure P (x) can be obtained based on FIG. 4 as follows.

First, the average position (x _av ) of the piston and the arbitrary position (x) of the piston are input from the first adder 41 and added (x / x _av ) to the first multiplier 44, and the arbitrary position ( differential value obtained by performing the first derivative with x) input from the third differentiator 42 Are output to the fourth differentiator 43 and the second multiplier 45, respectively.

Then, the fourth differentiator 43 performs the second derivative again to obtain the derivative value Is output to the third multiplier 46.

Accordingly, the first multiplier 44 multiplies the position adder value (x / x _av ) output from the first adder 41 by the spring constant k (k (x / x _av )), which is the second adder. Output to the inverting terminal (-) of (48).

The second multiplier 45 is the first differential position value output from the third differentiator 42. And multiply by the damping factor (c) This is output to the inverting terminal (-) of the second adder 48.

The third multiplier 46 is the second derivative of the position value in the fourth differentiator 43 And multiply by the moving mass (m) This is output to the inverting terminal (-) of the second adder 48.

The fourth multiplier 47 receives the current value i supplied to the motor, multiplies it by a constant α, and outputs it to the non-inverting terminal (+) of the second adder 48.

Therefore, the second adder 48 obtains the force obtained by adding and subtracting the values input to the inverting terminal (-) and the non-inverting terminal (+), respectively, and the force (F (x)) applied to the piston of the linear compressor. , And the calculated force F (x) is outputted to the fifth multiplier 49.

The fifth multiplier 49 receives the force F (x) output from the second adder 48 and multiplies 1 / A. This is output to the non-inverting terminal (+) of the third adder 50. Where A is the cross-sectional area of the piston.

The suction pressure Ps is input to another non-inverting terminal (+) of the third adder 50.

Therefore, the third adder 50 obtains the internal pressure P (x) of the linear compressor by adding the value output from the fifth multiplier 49 and the suction pressure Ps.

As described above, the internal pressure of the linear compressor is obtained from the average position (x _av ) of the piston and the suction pressure (Ps).

FIG. 7 illustrates a circuit for obtaining a bottom dead center (a) and a top dead center shown in FIG. 3. The bottom dead center (a) is a point where dF / dt = 0 to dF / dt> 0, and a top dead center (b) is dF / dt> 0 to dF / dt = 0, where the signal indicating that the half wave of dF / dt rises is a point, and the signal indicating that it is b point when the half wave of dF / dt falls It is.

In this regard, when the differentiator 71 receives the force (F (x)) applied to the linear compressor and differentiates and provides the half wave rectifier 72, the half wave rectifier 72 half-waves the differential power to raise the rising edge detector. And output to the 73 and falling edge detectors 75, respectively.

Then, the rising edge detector 73 receives a pulse output from the half-wave rectifying unit 72 and detects the rising edge to provide a signal to the pulse generator 74.

Accordingly, the pulse generator 74 generates a top dead center state pulse.

The top dead center condition pulse is a pulse that pulses when the piston of the linear compressor reaches top dead center. When this pulse is generated, each additional operation required to know the top dead center position in FIGS. 5 and 6 is performed.

The falling edge detector 75 receives a pulse output from the half-wave rectifier 72 and provides a signal to the pulse generator 74 when the falling edge is detected.

Accordingly, the pulse generator 74 generates a bottom dead center state pulse.

The bottom dead center state pulse is a pulse that pulses when the piston of the linear compressor reaches the bottom dead center, and when this pulse is generated, each additional operation required to know the bottom dead center position in FIGS. 5 and 6 is performed.

By the above operation, the pressure inside the compressor is obtained using only the position sensor or the position information without the pressure sensor.

By using the compressor internal pressure and the piston position, the linear compressor can be used to achieve good performance.

Accordingly, the present invention can improve the performance by measuring the position of the compressor piston and the internal current by measuring the position of the compressor piston and without using a pressure sensor inside the linear compressor, by controlling the position of the piston using the sensor, There is an effect to reduce the price by not attaching.

Claims (5)

A first adder that adds the piston average position x _av and the arbitrary position x of the piston, respectively, and firstly differentiates the arbitrary position x, and the first differential position value And the second differentiator for outputting the second derivative and the second derivative for the second derivative. And a fourth multiplier for outputting a multiplier, a first multiplier for multiplying a spring constant (k) by a position value added by the first adder, a second multiplier for multiplying a damping coefficient (c) by a position value differentiated in the third differentiator, and A third multiplier that multiplies the moving value m by the position value differentiated in the fourth differentiator, a fourth multiplier that multiplies the motor constant α by the current i supplied to the motor, and the first to third The output value of the multiplier is an inverting terminal, the output value of the fourth multiplier is a non-inverting terminal, and a second adder for obtaining the force (F) applied to the linear compressor, and the inverse of the cross-sectional area (A) of the compressor to the force output from the multiplier. The internal pressure of the linear compressor comprising a fifth multiplier to multiply and a third adder to obtain the internal pressure (P (x)) of the linear compressor by adding the value output from the fifth multiplier and the suction pressure (Ps). Measuring device. The suction pressure (Ps) of claim 1, wherein the suction pressure (Ps) is the first differentiator for first-order differentiating any position (x) of the piston, the second differentiator for second-differentiating the differentiated position value, and the first differentiator. The fourth sample holding unit for holding a sample of the first differential position value outputted from the bottom dead center state pulse and the bottom dead center state pulse inputting the second differential position value output from the second differentiator. A fifth sample holding part for holding a sample, a sixth sample holding part for holding a sample according to a bottom dead center state pulse inputted to a current supplied to the motor, and a top dead center state pulse for inputting the arbitrary position x A seventh sample holding part for holding a sample, an eighth sample holding part for holding a sample according to a bottom dead center state pulse input to the arbitrary position, and a volume of values output from the seventh and eighth sample holding parts, respectively; In the volume calculation part to calculate | require and each said part An internal pressure measuring apparatus for a linear compressor, comprising a calculation unit for calculating an internal pressure Ps using the calculated position and volume at the top dead center and the bottom dead center, and the piston average position x _av . The piston average position (x _av ) is the current (i) supplied to the motor according to the suction state pulse, and any position of the piston. And the second derivative of the arbitrary position value. The first to third sample holding unit for holding each of the sample and the internal pressure measuring device of the linear compressor, characterized in that the weight calculation unit for calculating the average position of the piston by calculating the current and the position holding the sample. The internal pressure measuring apparatus of the linear compressor according to claim 3, wherein the average piston position is obtained by the following equation. The position of the piston according to claim 1 or 2, wherein The internal pressure measuring apparatus of the linear compressor, characterized in that to use the position information obtained by the position sensor or the position information calculated by the current and voltage of the drive motor.