JPS58104465A - Controller for refrigeration cycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the state of a refrigeration cycle in a refrigeration system or air conditioner using an electric expansion valve such as a thermoelectric expansion valve, in order to constantly maintain the refrigeration cycle efficiently. The present invention relates to a refrigeration cycle control device that controls and optimizes a refrigeration cycle using an electric expansion valve, and in particular, constantly maintains a stable degree of superheat in the refrigeration cycle.

Traditionally, as a means of optimizing the refrigeration cycle, a method has been adopted that attempts to maintain the difference between the temperature of the generator and the temperature of the suction section of the compressor, that is, the degree of superheat, at a predetermined value. . Conventionally, in this method, when superheating was controlled using an expansion valve for electricity, a proportional or proportional-integral operation was performed depending on the difference, or deviation, between the detected degree of superheating and a set value; Regardless of the operating state (throttling state) of the expansion valve, the voltage applied to the expansion valve was increased or decreased in response to the magnitude of the deviation. Therefore, when the expansion valve throttle is large or small, the proportional constant or integral constant of the control circuit is constant or almost constant,
For example, when the amount of squeezing is large, superheated Betsugo Tokusugi is stable, but when the amount of squeezing is small, it becomes unstable and may enter a vibration state. This means that the relationship (transfer function) between the degree of superheating and the amount of throttling in the refrigeration cycle differs depending on the amount of throttling (refrigerant flow: size of amount), and when the amount of throttling is large (refrigerant flow rate is small), the amount of throttling is small. This is because a change in the temperature causes a large change in the degree of superheating.

If the conventional superheat degree control becomes unstable, it is not possible to constantly optimize the refrigeration cycle, which makes it difficult to constantly improve the efficiency of the refrigeration and air conditioning equipment.

Therefore, the present invention aims to solve the above-mentioned conventional problems, stabilize the controllability in controlling the degree of superheating, constantly optimize the refrigeration cycle, and further improve the efficiency of the refrigeration and air conditioning equipment. In order to solve the conventional difficulties, the present invention has been developed to reduce the throttle of the expansion valve in view of the fact that the magnitude of the electric signal (applied voltage) to the expansion valve has a predetermined relationship with the throttle amount in superheat degree control. The larger the refrigerant flow rate (lower refrigerant flow rate), the smaller the rate of change in the electrical signal to the expansion valve relative to the difference (deviation) between the degree of superheat and its set value, aiming to stabilize the control system. .

The refrigeration cycle control device of the present invention will be explained below based on the accompanying drawings.

'1゜Figure 1 is a schematic diagram showing an embodiment of the refrigeration cycle control device according to the present invention, and the figure particularly shows the case where it is used in a cooling device.

In the figure, 1 is a compressor, 2 is a condenser, 3 is a blower for the condenser 2, 4 is an expansion valve whose valve opening can be adjusted by an electric signal (here, a thermoelectric expansion valve) 6 is an evaporator, 6 is a blower for the evaporator 5, 7 is a temperature sensor provided at the inlet of the evaporator 6, 8 is a temperature sensor provided at the suction section of the compressor 1, and 9 is input temperature signals from temperature sensors 7 and 8. and expansion valve 4
This is a control circuit that outputs an electrical signal (DC voltage) to the

The expansion valve 4 is an energized open type here, and when a DC voltage is applied to the expansion valve, the amount of throttling increases in accordance with the voltage, and the refrigerant flow rate changes depending on the voltage vT applied to the expansion valve 4 and the refrigerant. An example of the characteristics of the flow rate Q is shown in FIG.

In the figure, QL and QH indicate the minimum and maximum range of the refrigerant flow rate Q passing through the expansion valve when the compressor 1 is operating, and the reason why there are two curves is due to hysteresis characteristics. It's for a reason.

Therefore, in the configuration shown in FIG. 1, the refrigerant is compressed by the compressor 1 into the condenser 2. Expansion valve 4. Evaporator 5. It circulates through the suction section of the compressor 1 and outputs cooling capacity in the evaporator 5. In the operation of this refrigeration cycle, ideally, the most efficient operating state is when the refrigerant evaporated in the evaporator a6 becomes dry saturated vapor at its outlet.

However, in the actual configuration, there is a temperature drop due to the passage resistance of the refrigerant piping from the evaporator 5 to the suction part of the compressor 1, and the compressor 1 is in the refrigerant gas-liquid mixing area. In order to prevent suction and liquid compression (although this is not necessarily the case if an acheimulator is provided), it is appropriate to operate the refrigerant gas in a slightly superheated region. Therefore, in order to achieve such an operating state, the difference between the respective temperatures detected by the temperature sensors 7 and 8 (this is referred to as the degree of superheating SH) is always set at a set value of 5Hd (for example, several do, although it varies depending on the refrigerant piping). j) Expansion valve 4
The refrigerant flow rate is controlled by changing the voltage VT applied to the refrigerant.

Note that the degree of superheating SH is not the degree of superheating (superheat) in the strict sense, as there is a temperature drop due to the passage resistance of the refrigerant piping as described above, compared to that in the ideal refrigeration cycle, but here, The values obtained by temperature sensors 7 and 8 shown in FIG. 1 are shown.

Next, the configuration of the control circuit 9 is shown in FIG. 10 of the processes constituting this circuit 9 is an area determination section, 11 is an arithmetic processing section, 1
Reference numeral 2 denotes a signal output section, and a part of the arithmetic processing section 11 and the area determination section 1o is constituted by a microcomputer (hereinafter referred to as microcomputer) 13. The area determination section 10 includes resistors 14, 15, differential amplifiers 16, . D/
A converter 17. It is composed of a comparator 18. The arithmetic processing section 11 consists of a part of the microcomputer 13 and a D/A converter, and the signal output section 12 consists of an operational amplifier 20. Resistance 21. It is composed of a transistor 22.

In this configuration, the operation of the region determination section 10 will be explained.
From the voltage vE corresponding to , the temperature sensor 8 and the resistor 15,
A voltage Vs corresponding to the temperature Ts of the compressor is input to the differential amplifier 16.

This differential amplifier 16 increases the difference between voltage vs and Vg T B
-TE This is a value corresponding to E. Here, if the set value of the superheat degree is SHd, the deviation ΔSH is ΔSH25H−8
It is Hd. As shown in Figure 4, in order to define the area of deviation ΔSH as four areas (A1.A2.A3.A4), the boundaries are set as Δ5H=-2.5, O, +2.5deg.Therefore, the microcomputer 13 , Δ5H=-2.5, 0°+2・5
The digital signal of SHd+ΔS)I is input to the D/A converter 17 in three ways, and the output is 5HR (=
By comparing the superheat degree SH (SHd+ΔSH) with the superheat degree SH using the comparator 18, it is possible to determine the difference between the current superheat degree SH and the set value SHd, that is, the area Ai of the deviation ΔSH.

The 7!1 area shown in FIG. 4 has a deviation Δ5H=od e
With g as the center, there are 2" areas for positive and negative values, respectively.

Next, the operation of the arithmetic processing section 11 will be explained.

The arithmetic processing section 11 determines the value of the voltage vT applied to the tension valve 4, which is output from the signal output section 12, based on the region A of the deviation ΔSH divided by the region determination section 10. This arithmetic processing unit 11 changes area A (for example, from A3 to A4).
etc.) and in the same area A for a predetermined time (e.g. 2
The applied voltage vT is subjected to calculation processing to be changed every time (minutes) elapses in accordance with each state, and is outputted to the signal output section 12 via the D/A converter 19.

The arithmetic processing in the arithmetic processing unit 11 is performed by a microcomputer 13 using digital quantities, and a calculation signal is obtained by adding or subtracting an increase/decrease X corresponding to a change in the area A or every predetermined time period. Output format of microcomputer 13 and D/
The configuration of the A converter 19 is as shown in FIG.
The output of No. 3 is output terminal P7, and output terminals P6 to
The same applies to PO. The D/A converter 19 is
Ladder circuit '2 is used to weight each output terminal PO to P7.
4 are connected. For weighting, resistors RO to R6 in the ladder circuit 24 have twice the resistance value of 0 in sequence, R6=2R5:4R4=・-=64
It is RO.

The resistor R7 and the resistor R8 are selected so as to give the lowest value of the applied voltage VT during normal control.

Therefore, the output voltage v0 of the D/A converter 19 is
When the transistors 23, etc. of the output terminals P7 to Po of the microcomputer 13 are all off, v0 = Ov, and only the transistor 23 is on, and vo = voL1. All the transistors 23, etc. are on (all output terminals P7 to po are vcc). The highest value is V. ”vOH.The output state of the output terminals P7 to Po of this microcomputer 13 is set to 1.
An example of the characteristics of the output voltage vo of the D/A converter 19 when expressed in two hexadecimal digits (P7 is the most significant) is shown in FIG. Note that the output of the microcomputer 13 is such that when the output terminal P7 is off, all other output terminals P6 to po are off, that is, the output state of the microcomputer 13 is changed from "oO" and "8o" to "F".
It is assumed that the value of F'Ji can be taken.

Therefore, the calculation number obtained by the calculation processing section 11 is 1
A two-digit hex value is output from the output terminals P7 to Po, and depending on this output state, the output voltage V is converted from a digital quantity to an analog quantity as shown in FIG. is converted to That is, the calculation signal calculated by the microcomputer 13 is expressed as a value obtained by adding or subtracting the above-mentioned increase/decrease x to the value corresponding to the applied voltage VT (=output voltage v0) at that time. This increase/decrease X is as shown in the following table, for example. The symbol r AF J in the table is the area in which the last addition/subtraction was performed, and the symbol "APJ is the area in the state where the addition/subtraction should be performed this time. If p, AF, = QAP, it is the time when area A has changed, and the symbol AF =AP means that a predetermined time has elapsed in the same area.

For example, the increase/decrease amount X in the table is expressed as a specific numerical value (2 digits in hexadecimal) as follows.

x =02 x =01 x3=041
2 x =OOx5206 In this increase/decrease X, x5 is a case where the sign of the deviation is reversed, and in order to eliminate the influence of hysteresis as shown in FIG. 2, an amount corresponding to hysteresis is included. When the above concrete number 1 is converted to the output voltage V0 as shown in FIG. 6, the amount of change is, for example, x2==01, Vo=7
．． It is about 30 m'V ffi degrees near oV. V again. −■. Approximately 20mVNfflj near 428.6v
&, v0=voL=4. Around oV, about e o m V
It will be about. Similarly, ■ for X 1 t X 3 to x6 at that time. It changes depending on the value of.

Therefore, the calculation process performed by the microcomputer 13 is based on the deviation Δ81
The increase/decrease amount X is simply added or subtracted in relation only to the region -f, and the calculated signals are outputted to the terminals P7 to P.

However, as shown in FIG. 6, the D/A converter 19 generates an output voltage vO in a curved manner depending on the state in which the arithmetic signal is required to be output.

The signal output section 12 has an output voltage V. Since the applied voltage vT is applied to the expansion valve 4 at a low impedance 3 due to , the larger the amount of backward movement of the expansion valve 4 and the larger the rate of change in the degree of superheating S) with respect to the change in the amount of throttling, the smaller the rate of change in the applied voltage vT becomes, and the more stable the operation of the control system is expanded. ing.

Furthermore, as shown in FIG. 2, not only changes in the transfer function on the refrigeration cycle due to changes in the refrigerant flow rate, but also changes in the refrigerant flow rate Q with respect to the applied voltage vT are not linear in the expansion valve 4 itself, as shown in FIG. The smaller the refrigerant flow rate Q, the larger the rate of change (gain) becomes, and it is optimal to provide a transfer function for superheat degree control by combining these factors, and the A/D converter 1
The conversion characteristics of No. 9 are also configured to correspond to this.

FIG. 7 shows an example of characteristics of superheat degree control according to the embodiment shown in FIGS. 1 to 6. In the figure, 01 to e6 are applied voltage v
T=7. v for increase/decrease x1 to x5 in the vicinity of ov
It shows the amount of change in T. Further, Tc indicates a predetermined time (here, 2 minutes) in which vT should be changed when the deviation area A is the same area. This characteristic example shows all cases after the degree of superheating SH is about to increase due to load fluctuations in the refrigeration cycle from time 1=1o. This characteristic example shows the applied voltage v7=7. oV
Although they are close to each other, as mentioned above, as vT becomes higher, the 81~e5 value in the figure becomes smaller, and as vT becomes lower, 81~
The value of e5 becomes large, and the degree of superheating Sf can be controlled more stably to the same degree as in FIG. 7.

Although the refrigeration cycle control device according to the present invention has been described above with reference to the embodiments shown in the accompanying drawings, other configurations of the embodiments are possible.

(2) The arithmetic processing section 11 in the control circuit 9 calculates the arithmetic signal by giving the increase/decrease amount
However, the increase/decrease xf is given by the value of the applied voltage vT at that time and the area A, and the calculated signal is, for example, 1 (-21
It is also possible to convert linearly into an analog quantity using a ladder circuit. In this case, it is sufficient to give a standard increase/decrease X of 16 to the area, correct the increase/decrease X by the applied voltage vT at that time (the calculation signal obtained for the previous output), and then add or subtract the increase/decrease X.

However, when doing this, if the number of output terminals of the microcomputer 13 and the number of digits for addition and subtraction handled internally are large, the sixth
Output characteristics equivalent to those shown in the figure can be obtained, but care must be taken as the smoothness of the characteristics will deteriorate if the number is small.

(2) In addition to configuring the control circuit 9 mainly using the microcomputer 13, a similar configuration may be possible using a digital circuit or an analog circuit.

■ In the area determination unit 1o, the superheat degree Sf (setting value S
In addition to forming the deviation ΔSH with respect to Hd into four regions as in the above-mentioned embodiment, it may be larger or smaller. However, the larger the number of areas, the more detailed control is possible.
I hope there's enough□゛°・.

For example, continuous or nearly continuous aversive control (P, PI).

From P, YJS1i11) becomes possible.

■ Figure 1 shows a cooling system, but heat pump type air-conditioning systems and refrigeration systems are also
4465(5) is applicable, and it is considered that the control equivalent to the present invention can be realized even if the expansion valve 4 is not only a so-called thermoelectric expansion valve but also a vented air type expansion valve.

As described above, according to the present invention, in order to always maintain the degree of superheat of the refrigeration cycle stably in response to a wide range of load conditions,
The larger the throttle amount of the expansion valve and the smaller the refrigerant flow rate, the smaller the change ratio of the voltage applied to the expansion valve with respect to the change in the degree of superheating can be made to prevent vibrations in the M1 control system. In other words, the control circuit is configured to compensate for changes in the control transfer function relative to the refrigerant flow rate in the refrigeration cycle and generate a controlled beating force. Improves tracking of fluctuations, optimizes the refrigeration cycle, and improves equipment efficiency (EEI).
R, or 5EER) can be expected to improve.
The cocoon can exert a profound effect in terms of energy.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the refrigeration cycle control device according to the present invention, Fig. 2 is a characteristic diagram of an expansion valve, and Fig. 3 is a diagram showing the characteristics of an expansion valve.
4 is a diagram explaining the operation of the control circuit, FIG. 6 is a circuit diagram of the arithmetic processing section in the control circuit, FIG. 6 is a characteristic diagram of the arithmetic processing section shown in FIG. The figure is an operational characteristic diagram of the apparatus of the present invention based on FIGS. 1 to 6. 4... Expansion valve, 6... Evaporator, 7...
...First temperature sensor, 8...Second temperature sensor, 9...Control circuit, 11... Arithmetic processing unit, 24... Weighting is ladder Circuit, ΔSH...
...deviation, x, e...increase/decrease, name of agent Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 ■→ Figure 3 Figure 4 Figure 5 Figure 7 Figure 6° -

Claims (1)

[Scope of Claims] (1) An expansion valve whose throttle amount can be adjusted by an electric signal, a first temperature sensor provided at the inlet of the evaporator or an intermediate portion, and an outlet of the evaporator or the suction of the compressor. and a control circuit that controls an electric signal to the expansion valve so as to maintain the difference between detection signals from the first and second temperature sensors at a set value, The control circuit increases or decreases the electric signal to the expansion valve depending on the deviation of the detected temperature difference from a set value, and the larger the throttle amount of the expansion valve, the smaller the rate of increase or decrease of the electric signal with respect to the deviation. A refrigeration cycle control device equipped with an arithmetic processing section. (2) The arithmetic processing unit calculates the increase/decrease in the electrical signal to the expansion valve,
The refrigeration cycle control device according to claim 1, configured to determine based on the deviation and the value of the electric signal at that time. (3) The arithmetic processing section is configured to convert the arithmetic signal into an electrical signal to the expansion valve after obtaining the arithmetic signal increased or decreased by an increase or decrease corresponding to the deviation. The refrigeration cycle control device described. (4) In the arithmetic processing section, the arithmetic signal is
4. The refrigeration cycle control device according to claim 3, wherein the means for converting the arithmetic signal into an electric signal to the expansion valve is a ladder circuit. (6) The refrigeration cycle control device according to claim 4, wherein the weight is a ladder circuit in which parts of the ladder circuit have successively twice the resistance value.