JPS6353454B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a refrigeration cycle control device that 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.
The purpose is to stably control the refrigeration cycle using an electric expansion valve, improve responsiveness to sudden load fluctuations, optimize it, and maintain efficiency at all times. Conventionally, as a means of optimizing the refrigeration cycle, the difference between the temperature of the evaporator and the temperature of the suction part of the compressor,
That is, a method is adopted in which the degree of superheat is maintained at a predetermined value. Conventionally, as a control device of this type, a method has been considered in which, in order to maintain the degree of superheat at a set value, proportional integral or differential integral control is continuously performed according to the value of the deviation. Although this method has good characteristics in a stable control state, the degree of superheat changes in response to changes in the state of the refrigeration cycle, which may be slow on the order of minutes or fast on the order of seconds. Due to the problem of response speed, it has become extremely difficult to configure a control device to always maintain the degree of superheat at the set value in response to these situations. Controlling the degree of superheating often results in large oscillations due to various conditions such as changes in the load condition of the refrigeration cycle, and stable control has not yet been achieved. Conventionally, in order to alleviate the above-mentioned problems, the degree of superheating is compared with a set value, detected in two regions, positive and negative, and depending on the sign, the voltage applied to the expansion valve is set at a predetermined time interval or when the sign changes. I found something that only adds and subtracts values. In this method, the control characteristic of the degree of superheat is basically in an oscillating state, but when the load on the refrigeration cycle is large and the flow rate of refrigerant is large, the degree of superheat can be controlled to be approximately equal to the set value. However, when the load on the refrigeration cycle is low, that is, when the refrigerant flow rate is low, control results in large vibrations, making it easy to cause liquid backflow to the compressor. In order to improve controllability at low loads, the voltage values to be added and subtracted are reduced, but when load fluctuation occurs and the degree of superheat deviates significantly from the set value, the recovery operation takes an extremely long time, which poses a problem in terms of responsiveness. It had become something I had. Therefore, the present invention aims to eliminate the conventional difficulties as much as possible, improve stability and responsiveness in controlling the degree of superheating, optimize the refrigeration cycle, and improve the efficiency (so-called EER and SEER) of refrigeration and air conditioning equipment. It is something to do. In particular, the present invention normally changes the voltage applied to the expansion valve in a relatively small voltage range to perform stable control with extremely low vibration, and also to prevent the degree of superheat from deviating significantly from the set value due to load fluctuations, etc. When this state continues for a certain period of time, a corrective action is performed with a large voltage width in order to hasten the recovery to normal stable control. Hereinafter, the refrigeration cycle control device of the present invention will be explained based on the accompanying drawings. FIG. 1 is a block diagram showing one embodiment of a refrigeration cycle control device based on the present invention, and the figure particularly shows the case where it is used in a cooling device. In Fig. 1, 1 is a compressor, 2 is a condenser,
3 is a blower for the condenser 2, and 4 is an expansion valve (here, a thermoelectric expansion valve) whose opening degree can be adjusted by an electric signal. 5 is an evaporator, 6 is a blower for the evaporator 5, 7 is a first temperature sensor provided at the inlet of the evaporator 5, 8 is a second temperature sensor provided at the suction portion of the compressor 1, and 9 is a blower for the evaporator 5. This is a control circuit that inputs temperature signals from temperature sensors 7 and 8 and outputs an electric signal (DC voltage) to the expansion valve 4. The expansion valve 4 is an energized closed type thermoelectric expansion valve, and when a DC voltage is applied to the expansion valve 4, a refrigerant flow rate is given in accordance with the voltage. Refrigerant flow rate Q with respect to applied voltage Vt to expansion valve 4
An example of the characteristics is shown in Fig. 2. In Figure 2, Ql and Qh
shows the minimum and maximum range of the refrigerant flow rate Q when the compressor 1 is operating, and the reason there are two curves is because of the hysteresis characteristic. Therefore, in the configuration shown in FIG. 1, the refrigerant is compressed by the compressor 1 into the condenser 2,
It circulates through the expansion valve 4, the evaporator 5, and the suction section of the compressor 1, and the evaporator 5 outputs cooling capacity.
In the operation of this refrigeration cycle, ideally the most efficient operating state is when the refrigerant evaporated in the evaporator 5 becomes dry saturated vapor at its outlet. However, in the actual configuration, there is a temperature drop due to passage resistance inside the evaporator 5 and the refrigerant piping from the evaporator 5 to the suction part of the compressor 1, and the compressor 1 sucks refrigerant in the gas-liquid mixing area. In order to prevent the refrigerant gas from compressing the liquid (although this is not necessarily the case if an accumulator is provided), it is appropriate to operate the refrigerant gas in a slightly superheated region. Therefore, temperature sensor 7 is used to achieve such an operating state.
The voltage Vt applied to the expansion valve 4 is adjusted so that the difference between the temperatures detected by the expansion valve 4 and the temperature difference 8 (this is referred to as the degree of superheating SH) is always the set value SHd (for example, several degrees, although it varies depending on the refrigerant pipe). This is to change the refrigerant flow rate and control the refrigerant flow rate. 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 mentioned above, compared to that in an ideal refrigeration cycle. 1
It is assumed that the values obtained by temperature sensors 7 and 8 shown in the figure are shown. Next, the configuration of the control circuit 9 is shown in FIG. In FIG. 3, 10 is an area determination section, 11 is an arithmetic processing section, and 12 is a signal output section. It consists of 13 microcontrollers (referred to as microcontrollers). The area determining section 10 includes a part of the microcomputer 13, as well as resistors 14 and 15, a differential amplifier 16, a D/A converter 17, and a comparator 18. The signal output section 12 includes a part of the microcomputer 13 as well as a D/A converter 19, an operational amplifier 20,
It is composed of a resistor 21 and a transistor 22. In this configuration, the operation of the region determining section 10 will be explained. A voltage Ve corresponding to the temperature Te at the inlet of the evaporator 5 is generated from the first temperature sensor 7 and the resistor 14.
Then, a voltage Vs corresponding to the temperature Ts at the inlet of the compressor 1 is input from the second temperature sensor 8 and the resistor 15 to the differential amplifier 16. This differential amplifier 16
is to amplify and output the difference between voltages Vs and Ve,
The output will be a value corresponding to the degree of superheating SH = Ts - Te. Here, if the set value of superheat degree is SHd,
The deviation △SH is △SH=SH−SHd. Now, as shown in Figure 4, the deviation △SH
For example, divide into 4 areas A ₁ , A ₂ , A ₃ , A ₄ and set the boundaries of each area as △SH=-2.5, 0, +2.5deg.
There are three ways. Therefore, the four deviation areas shown in Figure 4 are the deviation △SH = 0deg, that is, the degree of superheating.
There are two regions for each positive and negative region based on the point where SH matches the set value SHd. The value obtained by adding the set value SHd to the value of each deviation area mentioned above, that is, the digital amount of SHd + △SH is D/A.
input to converter 17, and its output SHr (SHd+△SH
By comparing the superheat degree SH outputted from the differential amplifier 16 with the analog conversion value of
It is possible to determine the difference in SHd, that is, the area of deviation ΔSH. The arithmetic processing unit 11 calculates, based on the area A of the deviation ΔSH divided by the area determination unit 10,
Voltage applied to the expansion valve 4 output by the signal output section 12
As shown in the block diagram of FIG. 7, the first timer means 11a determines the value of Vt.
, a second timer means 11b, an increase/decrease setting means 11c, and an arithmetic means 11d. The first timer means 11d includes the area determination section 10
A signal is output to the increase/decrease setting means 11c after a predetermined time Tx (for example, 4 minutes) after the area A of the deviation △SH becomes a predetermined area, and the sign of the deviation △SH is positive. and negative, the area A ₁ where the absolute value is maximum,
A timing operation is performed using _A4 as the predetermined area. The second timer means 11b operates at intervals of a certain period of time Tc (for example, 2 minutes) from when the area A changes, and the value of the deviation ΔSH is in the same area when the first timer means 11a starts timing and when it outputs. , the signal is repeatedly outputted to the increase/decrease setting means 11c at fixed time intervals Tc from the output of the first timer means 11a. This increase/decrease setting means 11c is configured to control when the area A changes and when the first and second timer means 11
A, 11b is outputted by setting a predetermined increase/decrease corresponding to the area A. In this case, the first timer means 11a in the predetermined areas A ₁ , A ₄ is set.
The increase and decrease at the time of output is set to a value larger than the increase and decrease at the time of output of the second timer means 11b. The calculating means 11d is for adding or subtracting the predetermined increase/decrease to the electric signal sent to the expansion valve 4. In the arithmetic processing unit 11 configured in this way, during stability control, the area A of the deviation ΔSH is, for example,
When the time changes from A ₃ to A ₄ , and when the first timer means 11a is in the same area (for example, A ₄ ) at the time of starting the time measurement and at the time of output, the timer changes from the time of output of the first timer means 11a. , a repetitive signal is outputted from the second timer means 11b to the increase/decrease setting means 11c at fixed time intervals Tc (for example, 4 minutes). Increase/decrease setting means 11 to which each of these signals is input
In c, the deviation △SH caused by each signal
Increase/decrease e corresponding to region A of , that is, applied voltage
The amount of change for changing Vt is set, and this increase/decrease setting means is output to the calculation means 11d. The calculation means 11d adds or subtracts the increase/decrease e to the value of the applied voltage Vt up to that point, determines the value of the applied voltage Vt to be newly output, and outputs the electrical signal to the signal output section 12. . The increase/decrease e in this case is as shown in the following table, for example. The symbol "A _F " in the table indicates the area when the applied voltage Vt was changed last time, and the symbol "A _P " indicates the area where the applied voltage Vt was changed this time.
This is a state area for Vt change processing,
If A _F ≠ A _P , then area A has changed,
A _F = A _P is a case where a predetermined time T _C has elapsed in the same area A.

[Table] The increase/decrease e in the table is shown in concrete numerical values, for example, as follows. e ₁ = 50mV, e ₂ = 25mV, e ₃ = 75mV, e ₄ =
0 mV, e ₅ =100 mV In this increase/decrease e, e ₅ is a case where the sign of the deviation is reversed, and the increase/decrease in the applied voltage Vt is reversed.
Therefore, in order to remove the influence of hysteresis as shown in Figure 2, _e5 should be set to the equivalent of hysteresis (for example,
75mV). Furthermore, e ₁ and e ₂ are each selected to have a value corresponding to the magnitude of the absolute value of the deviation. The above is the case during stable control, but if there is a sudden load change, such as when the air volume of the blower 6 shown in Fig. 1 is changed, the deviation area will be A ₁
Or it will shift significantly to _A4 . Always increase or decrease to recover from this area to A ₂ or A ₃ .
If you perform a corrective action every predetermined time T _C (2 minutes) with e ₁ ,
It will take an extremely long time to actually recover. Although it depends on the situation, it may take more than 30 minutes, for example. Therefore, in order to avoid such a situation, the arithmetic processing section 11 starts the first timer means 11a when a predetermined time Tx (for example, 4 minutes) has elapsed after the deviation area becomes _A1 or _A4 . According _to the output _of
Addition and subtraction are performed by the calculation means 11d every T _C (2 minutes).
After that, the area is A ₂ or A ₃ where the deviation △SH is small
When this happens, the operation shifts again to the above-mentioned stability control operation. By this operation, when the degree of superheating SH deviates significantly, the increase/decrease e ₁ is increased, and the increased value e ₁ ' can quickly restore stable control. Here, as the timing for increasing this increase/decrease e ₁ , when changing from A ₂ or A ₃ to A ₁ or A ₄ , the increase/decrease is immediately changed without waiting for a predetermined time _T
It is conceivable to add or subtract the increased e ₁ ' instead of e ₃ , and then add or subtract it every fixed time T _C (2 minutes), but if you use this method, A ₁ or A ₄ will only be added for a short period of time.
Even if this is a stable control operation, the increased e ₁ ' will be too large and there is a high risk of falling into _a large oscillating state. be. Note that _{if the predetermined} time _T . In this case, it may be easy to fall into a vibration state depending on the object of use, so it is better to select an appropriate one based on stability and responsiveness. Through the above operations, the arithmetic processing unit 11 calculates the applied voltage after the previous change.
Assuming Vtf, a new applied voltage Vt is given as Vt=Vtf±e (+ means addition, - means subtraction). Next, the signal output unit 12 inputs the digital signal of the new applied voltage Vt value given by the arithmetic processing unit 11 to the D/A converter 19, and expands the output voltage using the operational amplifier 20 and the transistor 22. applied to valve 4. The voltage Vt applied to the expansion valve 4 is always maintained at the previously applied value until the arithmetic processing section 11 performs a new addition/subtraction process.
The configuration and operation of the control circuit 9 have been explained above. Next, FIG. 5 shows an example of the characteristics of the deviation ΔSH in the degree of superheating when the device shown in FIG. 1 is operated using this control circuit 9. show. FIG. 5i shows the characteristics when the refrigerant flow rate is low and the air flow rate of the blower 6 is the lowest. In addition, in FIG. 5, the solid line characteristics are the characteristics under standard conditions and when the air volume of the blower 6 is maximum and standard, and the broken line characteristics are reference characteristics when there is no function to increase the increase/decrease e ₁ . Further, time t=t ₀ is the time when the air volume is changed from the maximum to the standard. The set value of superheating degree SHd was set to 4deg. As is clear from the figure, the deviation in the stable state △
The change characteristics of SH are better in case of , and the vibration is about ±1 degree, but even in case of , if it is suppressed to this level, there is no problem in the refrigeration cycle, and the efficiency is almost satisfied. It is something that can be achieved. In addition, in Fig. 5, there is a load fluctuation at time t = t ₀ , and the recovery operation of the superheat degree SH is performed relatively quickly, and the characteristic shown by the broken line, that is, the increase/decrease e ₁ does not increase. The characteristics are sufficiently superior to those that are controlled at a constant value. In order to further improve these characteristics shown in Figure 5, it is possible to change the value of increase/decrease _e and the predetermined time _T It is desirable to select the Here, in the arithmetic processing circuit 11 described above, an amount equivalent to the hysteresis is added to the increase/decrease e ₅ , but as an alternative method, the increase/decrease corresponding to the hysteresis is set to e ₀ , and the increase/decrease in the applied voltage V _T is reversed from the previous time. It is also possible to add e ₀ to the predetermined increase/decrease e only when performing the change in the direction. Next, another embodiment of the area determination section 10 and the calculation processing section 11 will be described. FIG. 6 simplifies the configuration of the region determination unit 10, and defines the region A with positive and negative deviations △SH.
two regions, namely A ₅ when △SH<0, △SH0
It is set as A ₆ when . For example, the increase/decrease e for the areas A ₅ and A ₆ is as follows.

[Table] e ₁ = 50mV, e ₅ = 100mV (equivalent to hysteresis)
75mV included), constant time T _C = 2 minutes, specified time T _X =
7 minutes. However, e ₁ is the same area and after T _X has elapsed, e ₁ ′=
Set to 200mV. In this case, _the predetermined time _T be. Although the characteristics shown in FIG. 6 are generally inferior to those shown in FIG. 4, they have the advantage that the structure and processing of the region determining section 10 and the arithmetic processing section 11 are simple and costs can be reduced. The above deviation area is divided into four areas in Figure 4, and
Although the area is divided into two in the figure, it is clear that the same operation can be performed by dividing the area into other numbers and determining the increase/decrease e corresponding to each area. As described above, the refrigeration cycle control device based on the present invention,
Although the embodiments shown in the accompanying drawings have been described, the following configurations are possible in addition to the embodiments. 1) Temperature sensors 7 and 8 are connected to the evaporator 5, respectively.
It can be placed at any position from the inlet to the middle part of the evaporator 5, and at any position from the outlet of the evaporator 5 to the inlet of the compressor 1, and the detected temperature at each position is determined by the relationship between the degree of superheating. seek,
A similar operation is possible if the setting value is given. 2) Although the control circuit 9 is configured mainly using the microcomputer 13, it may also be configured using other digital integrated circuits or analog circuits. 3) Although a so-called thermoelectric expansion valve was used as the expansion valve 4, the same type of control would be possible with an electric expansion valve of other configuration. Furthermore, as a characteristic of the expansion valve 4, as shown in FIG. 2, we have explained the case where it has a hysteresis characteristic, but it is better if this hysteresis characteristic can be almost ignored or there is no hysteresis, and in this case, , in the arithmetic processing unit 11, there is no need to provide an increase/decrease amount e ₀ corresponding to hysteresis, and the processing is simplified. 4) In the configuration in which the degree of superheating SH and the comparison data SH _R are compared in the region determination unit 10, if a differential is given to the comparator 18 or the comparison data SH _R , malfunctions during region determination can be reduced. This makes it possible to make reliable judgments. In addition, temperature signals detected by temperature sensors 7 and 8
T _E and T _S may be directly converted into digital signals by a D/A converter, and the area may be determined based on these signals, and it is desirable to select them depending on the intended use in terms of cost, performance, etc. 5) Although FIG. 1 shows an air conditioner, it can also be applied to heat pump type air conditioning devices and refrigeration devices. The refrigeration cycle control device of the present invention has been described in detail above.According to the present invention, in order to maintain the degree of superheat at the set value, the deviation from the set value of the degree of superheat is divided into two or more regions, and the state The electric signal to the expansion valve is finely changed by a predetermined increase/decrease depending on the situation, and when the degree of superheat deviates significantly from the set value due to load fluctuations, etc., it does not recover from that range to an appropriate range within a predetermined time. The system detects this and increases the predetermined increase/decrease to speed up the recovery operation, which can sufficiently improve the stability and responsiveness in controlling the degree of superheat. This can be expected to improve the efficiency of the refrigeration cycle, especially the SEER, and can produce extremely excellent effects in terms of energy conservation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the refrigeration cycle control device based on the present invention, FIG. 2 is an example of the characteristics of the expansion valve in FIG. 1, FIG. 3 is a block diagram of the control circuit in FIG. 1, and FIG. The figure is an explanatory diagram of the area division detected by the area determination section, FIG. 5 is an operational characteristic diagram of the embodiment shown in FIGS. 1 to 4, and FIG. 6 is an illustration of another embodiment of the area division of the area determination section The explanatory diagram, FIG. 7, is a block diagram of the control circuit shown in FIG. 3. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 4... Expansion valve, 5... Evaporator, 7... First temperature sensor, 8... Second temperature sensor, 9... Control circuit, 10... Region determining unit, 11...
Arithmetic processing unit, 11a...first timer means, 11b
...Second timer means, 11c...Increase/decrease setting means,
11d...Arithmetic means, 12...Signal output section, 13...Microcomputer, △SH...Deviation, A...Area,
e...Increase/decrease, T _C ...certain time, T _X ...predetermined time, Vt
...Electrical signal (applied voltage).

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 or intermediate portion of the evaporator, and a first temperature sensor provided at the outlet of the evaporator or the suction portion of the compressor. a second temperature sensor; and a control circuit that controls an electrical signal to the expansion valve so as to maintain a difference between temperatures detected by the first and second temperature sensors at a set value, and the control circuit is such that the deviation of the detected temperature difference from the set value is at least 2
an area determination unit that divides the area into two or more areas; a first timer unit that outputs an output after a predetermined period of time has elapsed since the area becomes a predetermined area; When the value is in the same area when the first timer starts counting and when outputting, the second timer means repeats the output at the constant time interval from the time of output of the first timer means, The second timer means sets a predetermined increase/decrease corresponding to the region at the time of change and the output of the first and second timer means, and in the predetermined region, the second timer means before the output of the first timer means. For the increase/decrease in the output of
an increase/decrease setting means for setting the increase/decrease to a large value at the time of the output of the first timer means and the subsequent output of the second timer means; and arithmetic means for adding/subtracting the predetermined increase/decrease from the electrical signal. A refrigeration cycle control device comprising: an arithmetic processing section; and a signal output section that outputs an electric signal given from the arithmetic processing section to the expansion valve. 2. The area determination unit is configured to divide the deviation into three or more areas, and the first timer means of the arithmetic processing unit selects the area with the largest absolute value as a predetermined area when the sign of the deviation is positive and negative. The refrigeration cycle control device according to claim 1, wherein the refrigeration cycle control device is configured to perform a timekeeping operation.