JPS6251384B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention aims to maintain the refrigeration cycle efficiently at all times in a refrigeration system or air conditioner using an electric expansion valve such as a thermoelectric expansion valve. The aim is to stably control and optimize the refrigeration cycle using valves. Conventionally, one method of optimizing the refrigeration cycle has been to maintain the difference between the temperature of the evaporator and the temperature of the suction section of the compressor, or the degree of superheat, 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 proportional-integral-differential control is performed continuously according to the value of the deviation. This method has good characteristics under stable control conditions, but on the other hand, there are cases in which the degree of superheat changes in response to changes in the state of the refrigeration cycle, which can be slow on the order of minutes or fast on the order of seconds, and There is also the problem of the response speed of the valve, and it has become extremely difficult to configure a control device that can always maintain the degree of superheat at the set value in response to these situations. Changes in the load status of the refrigeration cycle, etc.
Controlling the degree of superheating often results in large oscillations under various conditions, and stable control has not yet been achieved. Conventionally, in order to alleviate the above problems, the degree of superheating and the set value are compared, and detection is performed in two areas, positive and negative.
There is one that adds or subtracts the voltage applied to the expansion valve by a predetermined value at predetermined time intervals or when the sign changes depending on the sign. In this method, the control characteristic of the degree of superheat is basically in an oscillating state, but if 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 refrigeration cycle is under low load, that is, when the refrigerant flow rate is low, control results in large vibrations, making it easy to fall into a situation where liquid backs up to the compressor.
Attempts to improve controllability under low loads result in extremely slow control response under normal conditions, both of which have drawbacks in terms of stability and efficiency. The present invention eliminates the conventional difficulties as much as possible, stably controls the degree of superheating, and improves the efficiency of the refrigeration cycle to improve the efficiency of refrigeration and air conditioning equipment (so-called EER, SEER).
The aim is to achieve improvements in In particular, the present invention divides the difference between the degree of superheating and the set value, that is, the deviation, into three or more regions (conventionally, two regions, positive and negative), in view of the advantages over the conventional method described above.
To provide a refrigeration cycle control device which can constantly optimize a refrigeration cycle by providing a method for changing the amount of change in output according to the magnitude of deviation performed in proportional control, aiming at early stabilization and suppressing vibration amplitude. It is something. The configuration of the refrigeration cycle control device of the present invention will be explained below based on the drawings. FIG. 1 is a block diagram showing one embodiment of a refrigeration cycle control device based on the present invention, and 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, 4 is an expansion valve whose opening degree can be adjusted by an electric signal (here, it is a thermoelectric expansion valve), and 5 is a thermoelectric expansion valve. Evaporator, 6 is a blower for evaporator 5, 7
8 is a temperature sensor provided at the inlet of the evaporator 5; 9 is a temperature sensor provided at the suction section of the compressor 1; 9 inputs temperature signals from temperature sensors 7 and 8;
This is a control circuit that outputs an electrical signal (DC voltage) to the FIG. 2 is a structural sectional view showing the internal structure of the expansion valve 4 shown in FIG. In FIG. 2, 41 is a case of the expansion valve 4, 42 is an electric heater, 43, 4
4 is bimetallic. The bimetals 43 and 44 are a pair and are held in parallel by a plate 45, and the electric heater 42 is provided on the bimetal 43. The bimetal 44 is for atmospheric temperature correction. 46 is a terminal to which a DC voltage supplied from the control circuit 9 is connected. 47 is a spindle connected to the bimetal 44, 48 is a spring that pushes up the spindle 47, and 49 is a seat that serves as a valve seat for the spindle. In this expansion valve 4, when DC voltage is supplied to the electric heater 42, the bimetal 43 is heated, and the bimetal 43 is heated.
Due to this deformation, the spindle 47 is pushed down via the plate 45 and the bimetal 44. The spindle 47 is balanced at a position corresponding to the magnitude of the DC voltage by the stress of the spring 48 and the bimetal 43 and the pressure of the refrigerant, thereby giving the degree of opening of the refrigerant passage and changing the refrigerant flow rate. become. The structure shown in Fig. 2 is a closed energized type, and if the DC applied voltage supplied to the expansion valve 4 (this is set as V _T ) is increased, the refrigerant flow rate (this is set as Q) is increased.
When Q is decreased, the refrigerant flow rate Q is increased. FIG. 3 shows an example of the characteristics of the refrigerant flow rate Q with respect to the applied voltage V _T . In the figure, Q _L and Q _H indicate the minimum and maximum range of the refrigerant flow rate Q when compressor 1 is operating, and the reason there are two curves is due to the hysteresis characteristic. . Therefore, in the configuration shown in FIG.
Due to the compression action of the refrigerant, the refrigerant circulates through the condenser 2, 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 liquid compression (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, in order to achieve such an operating state, the temperature sensor 7
The voltage V _T applied to the expansion valve 4 is set so that the difference between the temperatures detected by the expansion valve 4 and the temperature difference detected by the expansion valve 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 piping). This is to change the amount of refrigerant and control the amount of 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, 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. 4, 10 is an area determination section, 11 is an arithmetic processing section, and 12 is a signal output section. )
It consists of 13 parts. The area determining section 10 includes resistors 14 and 15, a differential amplifier 16, a D/A converter 17, and a comparator 18 in addition to a part of the microcomputer 13. In addition to a part of the microcomputer 13, the signal output section 12 includes 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 determination section 10 will be explained. A voltage V _E corresponding to the temperature T E at the inlet of the evaporator 5 is transmitted from the temperature sensor 7 and the resistor 14, and a voltage V E corresponding to the temperature T _E at the inlet of the evaporator 5 is transmitted from the temperature sensor 8 and the resistor 15 to the compressor. A voltage VS corresponding to the inlet temperature TS of 1 is obtained and input to the differential amplifier 16, respectively. This differential amplifier 16 amplifies and outputs the difference between the voltages VS and VE, and its output has a value corresponding to the degree of superheating SH=TS-TE. Here, if the set value of the degree of superheat is SHd, the deviation △SH is △SH = SH - SHd. Now, as shown in Figure 5, the area A of deviation △SH
are defined as four areas (A ₁ , A ₂ , A ₃ , A ₄ ), and the boundaries thereof are assumed to be ΔSH=−2.5, 0, and +2.5 degrees. Therefore, the microcomputer 13 sets △SH=-2.5,
By inputting the digital amount of SHd + △SH to the D/A converter 17 in three ways, 0 and +2.5 degrees, and comparing the output SHR (=SHd + △SH) and the degree of superheating SH by the comparator 18. , the degree of superheating at that time
The difference between SH and the set value SHd, that is, the area A of the deviation ΔSH is determined. The four areas shown in Figure 5 are deviations △
There are two regions each for positive and negative values centered around SH=0deg. Next, the operation of the arithmetic processing section 11 will be explained. The arithmetic processing section 11 determines the value of the applied voltage V _T to the expansion valve 4 to be 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 processes changes in area A (for example,
A ₃ to A ₄ , etc.) and every time a predetermined time (for example, 2 minutes) elapses in the same area A, the increase/decrease e corresponding to each state, that is, the applied voltage V
The amount of change for changing _T is added or subtracted from the value of the applied voltage V _T up to that point, and the value of the applied voltage V _T to be newly output is determined. In this case, the increase/decrease e is as shown in Table 1, for example. "AF" in the table
indicates the area when the applied voltage V _T was changed last time, and the symbol “AP” indicates the area in which the applied voltage V _T was changed this time. If AF≠AP, the area A This is the case when AF=AP changes, and AF=AP
This is the case where a predetermined time has elapsed in the same area A.

[Table] For example, the increase/decrease amount e is shown in concrete numerical values as shown below. e ₁₁ = 25 mV e ₁₂ = 50 mV e ₂₁ = 50 mV e ₂₂ = 0 mV e ₂₃ = 100 mV In these values, the area where the absolute value of deviation △SH is large, ie A ₁ and A ₄ , is the smaller area, ie A ₂ , A ₃ , the increase/decrease e when AF=AP is set to a large value (e ₁₂ >e ₁₁ ). This is similar to the method used in proportional control to give the amount of change in response to the size of the deviation, and the deviation △SH
This is to increase the increase/decrease e as the value increases, and to perform a large correction operation so that the deviation ΔSH=0deg is achieved quickly. In addition, in the operation of AF≠AP, when A ₁ to A ₂ or A ₄ to A ₃ , that is, when the deviation △SH changes from a large area to a small area, the increase/decrease is
e ₂₂ = 0mV and no increase and decrease in the opposite case e ₂₁ = 50mV
There is a distinction between This is a desirable characteristic since the direction of change of deviation △SH is △SH = 0deg, so if e ₂₂ = e ₂₁ at this time, then
On the contrary, this is to prevent the superheat degree SH from becoming oscillating due to excessive overshoot. Further, when the area A changes from A ₂ to A ₃ and from A ₃ to A ₂ , the increase/decrease e ₂₃ is 100 mV. this is,
Since the deviation △SH changes at an approximately appropriate value, it is appropriate not to take any corrective action, but the relationship between the applied voltage V _T of the expansion valve 4 and the refrigerant flow rate Q is as shown in Fig. 3. _As shown _{in FIG .} Considering the subsequent processing, e ₂₃ is set to 100 mV, and an increase or decrease corresponding to hysteresis is given. Through the above operation, the arithmetic processing unit 11 calculates the new applied voltage V, assuming that the applied voltage after the previous change is V _TF .
_T is given as V _T =V _TF ±e (+ means addition, - means subtraction). Next, the signal output section 12 inputs the digital signal of the value of the new applied voltage V _T given by the arithmetic processing section 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 V _T 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, and FIG. 6 shows an example of the characteristics such as the deviation ΔSH in the degree of superheating when the device shown in FIG. 1 is operated using the control circuit 9 shown in FIG. 4. Shown below. FIG. 6a shows the characteristics when the refrigerant flow rate is low and the airflow rate of the blower 6 is at its lowest, and FIG. 6b shows the characteristics when the airflow rate of the blower 6 is at its maximum under standard conditions. Moreover, the set value of the degree of superheating is approximately SHd=4deg. In the figure, t ₀ in a and t ₁ in b both have the same area and indicate a predetermined time when changing the applied voltage V _T , where t ₀ = 2 minutes 12 seconds, t ₁ = 2 minutes (because of the power supply frequency standards of 50Hz and 60Hz, respectively). As is clear from the figure, the deviation △SH in a stable state
Regarding the variation situation, b is better, and a is a vibration of about ±1 degree. Although it is desirable to make it more constant, even in case a, this degree of vibration does not pose a problem in terms of the refrigeration cycle, and the efficiency is almost satisfactory. In addition, in a, in a stable state, the area changes to A ₂ and A ₃ (the sign of the deviation △SH is reversed) only by increasing/decreasing e ₂₃ , but this is because e ₂₃ is smaller than the hysteresis width shown in Figure 3. This is because it was a little too big,
It would be appropriate to set e ₂₃ to a slightly smaller value.
Furthermore, in order to further improve the characteristics of a, it is conceivable to set e ₁₁ to a slightly smaller value. However, if the aforementioned e ₂₃ and e ₁₁ are made smaller, b
Since it is conceivable that the responsiveness in , the response time may deteriorate, it is desirable to select the increase/decrease e by taking these factors into consideration. Here, the first increase/decrease e for the area A is
In the table, e ₂₃ = 100mV, but e ₂₃ =
0mV, and the increase/decrease corresponding to the hysteresis is e ₀ = 100mV, compared to the previous addition/subtraction process.
Only when the current process is reversed, each increase/decrease e
You can think of it as adding e ₀ . in this case,
Regardless of changes in region A, etc., the present invention can be applied even when processing is to change the applied voltage V _T by a predetermined value, and the applicable range is expanded. Next, FIG. 7 shows a case where the number of area divisions in the area processing section 10 is increased. In the figure,
It is divided into a total of 8 regions of 1 degree each around the deviation △SH=0 degree. Specific examples of increases and decreases e for these areas A are shown in Table 2. In this Table 2, both areas A ₄ and A ₅ are considered as so-called dead zone areas,
Even if a predetermined time elapses in this area, or even if the area changes to this area from other areas, e ₀ equivalent to hysteresis will occur.
Except for = 100 mV (when changing from A ₄ to A ₅ or from A ₅ to A ₄ ), the increase/decrease e = 0 mV is always assumed. Therefore, as long as these dead zone areas A ₄ and A ₅ ,
The applied voltage V _T is increased or decreased by the amount equivalent to hysteresis e ₀ =
No changes are made except for a 100mV change. Also, for example, when changing from A ₅ to A ₆ , it is 20 mV, and when a predetermined time has elapsed at A ₆ , it is 15 mV.In addition to increasing the increase/decrease when the area changes, the larger the absolute value of the deviation △SH, the more the increase/decrease. is increasing. Also,
When the absolute value of the deviation △SH changes from a large area to a small area, the increase/decrease e is basically zero, but A ₇ is larger than A ₈ where the deviation △SH is the largest.
And only in the case of A ₂ than A ₁ , give a slight increase or decrease,
We are trying to improve responsiveness.

[Table] The operation of the area determination section 10 and the calculation processing section 11 based on this FIG. performance, responsiveness, and efficiency). In addition, in the increase/decrease e based on Fig. 7, the hysteresis equivalent e ₀ = 100mV is changed from A ₄ to A ₅ or A ₅
Therefore, it is given when changing to A ₄ , but as another method, rather than addition/subtraction processing where the previous increase/decrease e is not zero, this time, it is equivalent to hysteresis only when the process is the opposite of the previous one and the increase/decrease e is not zero. If e ₀ is added to the increase/decrease, the applied voltage V _T will not be changed at all in the areas A ₄ and A ₅ . These methods are preferably determined depending on the state of controllability. Next, FIG. 8 shows an example of the simplest area division having a dead zone area. This figure is a highly simplified version of the one shown in FIG. 7, and the dead zone area is _A2 . In this case, the controllability is inferior to that shown in FIG. 6, but the configuration of the region determining section 10 and the operation of the arithmetic processing section 11 are simpler.
In addition, the increase/decrease amount e ₀ corresponding to hysteresis in Fig. 7
is given by A ₁ from A ₂ or A ₃ from A ₂
, and it is time to perform addition/subtraction processing that is the opposite of the previous one. Although the refrigeration cycle control device based on the present invention has been described above using the embodiment shown in the drawings, the following configurations are possible in addition to this embodiment. 1. Temperature sensors 7 and 8 can be placed at any position from the inlet of the evaporator 5 to the middle part, and at any position from the outlet of the evaporator 5 to the inlet of the compressor 1, A similar operation is possible by determining the relationship between the detected temperature and the degree of superheating at each position and providing the set value. 2. Although the control circuit 9 is configured mainly using the microcomputer 13, it can also be configured using other digital integrated circuits or analog circuits. 3. Although a so-called thermoelectric expansion valve shown in FIG. 2 was used as the expansion valve 4, the same type of control is possible with an electric expansion valve having another configuration. In addition, as a characteristic of the expansion valve 4, as shown in FIG. 3, 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 section 11,
There is no need to provide an increase/decrease amount e ₀ corresponding to hysteresis, which simplifies the process. 4 In the configuration in which the degree of superheating SH and the comparison data SHR are compared in the region determination section 10, if a differential is given to the comparator 18 or the comparison data SHR, malfunctions at the time of region determination can be reduced and ensured. This makes it possible to make accurate judgments.
In addition, temperature signals detected by temperature sensors 7 and 8
The TE and TS may be directly converted into digital signals by an A/D converter, and the area may be determined from these signals, and it is desirable to select them depending on the intended use in terms of cost, performance, etc. 5 In the embodiment, the characteristics and operation were explained in a situation where the degree of superheat SH is relatively stable. However, when the compressor 1 is stopped or immediately after starting, the voltage V _T applied to the expansion valve 4 is kept at a predetermined constant value. (including full opening) and perform the control operation shown in the example at the time when the refrigeration cycle becomes relatively stable after the start of the compressor 1, that is, several minutes after the start of the compressor 1, or After increasing or decreasing the applied voltage V _T by a predetermined value at predetermined intervals until the deviation △SH reaches a predetermined value, the control operation shown in the embodiment is performed to reliably and quickly shift to a stable control state. becomes possible. 6 Although Figure 1 shows the cooling system,
In addition, it is clear that it can be applied to heat pump type air-conditioning equipment and refrigeration equipment, and it can be expected to contribute to increasing the efficiency of equipment for both. The refrigeration cycle control device of the present invention has been described above in detail.According to the present invention, the difference between the degree of superheat and its set value, that is, the deviation, is detected in at least three or more regions, and expansion is performed according to the state. The electric signal to the valve is finely changed by increasing or decreasing the predetermined amount, and this changes the control characteristics of the degree of superheat.
Its stability and responsiveness can be sufficiently improved,
The refrigeration cycle can be maintained efficiently at all times. It is also expected to improve the efficiency of the refrigeration cycle, especially SEER, and can be extremely effective in terms of energy conservation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a refrigeration cycle control device based on the present invention, FIG. 2 is a structural sectional view showing an example of the expansion valve in FIG. 1, and FIG. 3 is a structural diagram of an example of the expansion valve shown in FIG. Characteristics diagram, FIG. 4 is a configuration diagram of the control circuit in FIG. 1, FIG. 5 is an explanatory diagram of the area classification detected by the area determination section, and FIGS. 6 a and b are the implementations shown in FIGS. 1 to 5. FIGS. 7 and 8 are explanatory diagrams of other embodiments of the area classification detected by the area determining section, respectively. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Condenser, 4... Expansion valve, 5... Evaporator, 7... First temperature sensor, 8... Second temperature sensor, 9... Control circuit, 10... Area determining unit, 11...
Arithmetic processing unit, 12... signal output unit, 13... microcomputer.

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 at the outlet of the evaporator or the suction portion of the compressor. inputting temperature signals from the provided second temperature sensor and the first and second temperature sensors;
a control circuit that issues an electric signal to the expansion valve; the control circuit includes a region determining section that compares the difference between the two temperature signals and a set value thereof, and classifies the deviation into at least three or more regions; , when the area obtained by the area determining section changes, or every time a predetermined period of time elapses in the same area, add or subtract a predetermined increase or decrease corresponding to each state, and add or subtract the value of the electric signal sent to the expansion valve. an arithmetic processing unit that determines
A refrigeration cycle control device comprising: a signal output section that outputs an electric signal given by the arithmetic processing section to the expansion valve. 2. The expansion valve mainly includes an electric heater to which an electric signal generated by a control circuit is supplied, a bimetal that deforms due to the heat generated by the electric heater, and a spindle that changes the opening degree of the refrigerant passage by deforming the bimetal. A refrigeration cycle control device according to claim 1.