JPS6042858B2 - air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air conditioner in which a refrigeration cycle is formed by a compressor, a heat exchanger, an electric expansion valve whose valve opening degree can be adjusted by an electric signal, and more particularly to The purpose is to improve the reliability of expansion valve control.

Conventionally, electric expansion valves combine a heater and a bimetal, and adjust the amount of heat generated by the amount of electricity applied to the heater.
There were some that adjusted the valve opening by changing the position of a bimetal, and others that used a motor to adjust the valve opening.

FIG. 9 shows a schematic configuration of a refrigeration cycle using an electric expansion valve. In FIG. 9, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve, and 4 is an evaporator. 5A is a first temperature sensor provided at the middle part (or the inlet side) of the evaporator 3, and 5B is a second temperature sensor provided at the outlet side of the evaporator 3. The control circuit 5 outputs an electric signal to control the valve opening degree of the electric expansion valve 3 so that the detected temperature difference SH'' becomes constant.

Said temperature here? H'' is the degree of superheating SH if the refrigerant pressure drop in the evaporator 4 is zero, but if the refrigerant pressure drop is zero, it is the value obtained by subtracting the temperature ΔT equivalent to the pressure drop from the H during superheating, that is, SH ″=SH−ΔT. Therefore, if ΔT is negligibly small compared to SH or ΔT is constant, the temperature difference SH'' will be the superheat degree SH or S.
The value corresponding to SH is obtained by subtracting a certain value from H, and the temperature difference SH''
By keeping SH substantially constant, an optimal operating state of the refrigeration cycle in which the degree of superheating SH is constant can be realized. FIG. 10 shows the relationship between the temperature difference SH'' and the valve opening degree PV of the electric expansion valve 3.If the refrigeration cycle is currently operated on the curve of cycle 1, then the cycle optimum superheat degree SH''1 The valve opening degree 0V to obtain is 0V1. Also, for example, due to changes in the capacity of the compressor 1, changes in the internal and external temperatures, and changes in the speed of the blower fan (not shown) of the condenser 2 or evaporator 4, the refrigeration cycle changes to the cycle 2 curve! If the engine is operated above, the valve opening degree 0V to obtain the optimum superheat degree SH is 0V2. It is assumed that the refrigeration cycle 1 is being operated, and that the valve opening degree 0V is controlled to 0V1 and SH'' is controlled to SH''1. When there is a sudden change from this state to cycle 2, the first and second refrigeration cycle state detectors
Due to the delay in the response of the temperature sensor, this change cannot be recognized, or the change is detected and the valve opening degree is changed from 0V1 to 0.
Even if a signal to change the value to 2 is output, the valve opening degree 0V does not immediately change from 0V1 to 0V2 due to the response delay of the electric expansion valve 3. Therefore, if the valve opening degree 0V remains 0V1 in cycle 2, the temperature difference SH'' becomes SH''2. This temperature is S
Since H″2<SH″1, the control circuit 5 is in cycle 2.
Since the valve opening cannot be distinguished from point C, an attempt is made to reduce the valve opening p■ to increase the temperature difference SH''.However, since the current operating point is point B, the valve opening 0V will become smaller from now on. Therefore, the temperature difference SH'' becomes smaller and smaller, which causes the valve opening PV to be further reduced.In such a state, the opening of the electric expansion valve 3 ends up reaching φ, and the refrigeration The optimum state (point A'') in the state of cycle 2 cannot be obtained. The change from cycle 1 to cycle 2 changes due to various factors as described above, so in terms of refrigeration cycle control, the cycle can be normally controlled by controlling the valve opening degree PV, that is, in cycle 1, the valve opening is degree PV is 0VM1 or more, and in cycle 2, the valve opening degree is 0V.
The valve opening PV must be controlled in a range of M2 or more,
If the refrigeration cycle cannot be controlled to the optimum state by controlling the valve opening degree 0V as described above, it is necessary to correct the valve opening degree QV to a normal range by some method. Conventional control circuits did not have such a function, so once they entered the above-mentioned uncontrollable range, there was no way out and normal air conditioning operation was no longer possible. . The present invention solves the drawbacks of the conventional example, and if the above-mentioned uncontrollable range is entered, the valve opening is forcibly corrected to 0 V, and the air conditioner is equipped with a control device that has the function of returning the valve to the normal range. It provides a harmonization device.

In order to realize such control, (1) the valve opening degree is 0V;
Detection of whether the temperature difference SH'' is in an uncontrollable state that cannot be controlled by the control of It is necessary to realize three elements: detection of the condition when the condition occurs and termination of forced correction control.

(1) Detection of an uncontrollable state.

The following three methods can be considered for detecting an uncontrollable state. (1-1) Output signal of control circuit 5 to electric expansion valve 3.

FIG. 1 shows the relationship between the applied voltage VT and the valve opening degree of 0 V of a thermoelectric expansion valve (energized closed type) that combines a heater and a bimetal.

Considering changes in the refrigeration cycle, the valve opening degree is 0V.
min to 0Vmax, and the corresponding voltage is VTmin
and VTmax. Now assume that the cycle in FIG. 10 is cycle 1 and 0V1=0Vmin. At this time, the applied voltage ■T
is ■τMax. If the cycle changes from cycle 1 to cycle 2, the control circuit 5 outputs a voltage larger than VTmax in the direction of decreasing the valve opening degree 0V, as described above. Therefore, if the appropriate voltage VD larger than V,max>2 becomes larger than Tmax, it is clearly in the uncontrollable range, so that an uncontrollable state can be detected. In terms of an electrical circuit, this can be easily realized using, for example, the circuit shown in FIG. In FIG. 2, 50 is a control circuit, and a thermistor 5A as a first temperature sensor 5A.
1. Based on the temperature difference detected by the thermistor 5B as the second temperature sensor 5B, the voltage applied to the thermoelectric expansion valve 3 is controlled to keep the temperature difference of 2 degrees approximately constant. 60 is a detection circuit, and voltage ■ is generated by resistors 6B and 6C.

The voltage comparator 6A gives the voltage ■. Compare and voltage VT, and if ■. 〉■ If T (normal), the voltage comparator 6A output is Hi (in this case, the output format is open collector 2), ■
If it is T (abnormal), the 6A output will be b. In this embodiment, in the case of an abnormality, the output voltage of the control circuit 5 = the applied voltage TV of the thermoelectric expansion valve 3 is forcibly set to φ■, and the valve opening degree is set to be fully open. In this embodiment, an abnormality can be reliably detected using three extremely simple circuits. (1-2) Evaporator temperature TOV
The temperature detected by the first temperature sensor 5A of the AO evaporator 4, that is, the evaporator temperature TEVA, is relatively low during normal operation because the refrigerant is in a gas-liquid two-phase state.

However, if the electric expansion valve 3 is insufficiently opened, the amount of refrigerant circulated will be insufficient, and the refrigerant will all evaporate near the inlet of the evaporator 4, causing the evaporator temperature TO to decrease.
i rises. If the current evaporator temperature TεVA is higher than the maximum value TEVAmax of the possible range of the evaporator temperature TEVA during normal operation of cycle 4, this is an abnormal state. An example of an electric circuit that specifically implements this method is the circuit shown in FIG. 51 is an embodiment of the control circuit 5. In this circuit, the temperature TEVA detected by the thermistor 5A as the first temperature sensor and the voltage E in the figure have a linear relationship within a predetermined temperature range if the resistor 5C is appropriately selected. becomes.

In other words, it can be expressed by the following equation. Therefore, the voltage VO when A: proportionality constant and B: constant is as follows.

This voltage ▼P-111141f116V^11μ
Voltage ■ than ′llll υ. If becomes smaller, the evaporator temperature TEVA becomes TBVA>TIll:VAmax.
61 is a detection circuit, which divides the power supply by resistors 61A and 61B to obtain a voltage of 5 min, and this voltage Tllll:M
in<5TE by the voltage comparator 61C, and TE
> Tε n (normal), the voltage comparator 61C output is Hi.
．． TIll: If TOmin (abnormal), voltage comparator 61
The C output becomes b, and in this embodiment, the applied voltage to the expansion valve 3 is forcibly set to zero, and the valve opening degree is set to be fully open.

In this embodiment, since abnormality/normality of the cycle is detected according to the operating state of the evaporator 4, the state can be detected extremely reliably. (1-3) Relationship between control circuit output and cycle response.

For example, in Figure 2, what is the temperature of each temperature detected by the first and second temperature sensors? If βH'' is larger than the predetermined temperature difference SHR, the expansion valve applied voltage ■τ becomes small and the valve opening becomes 0.
(2) is widened to try to reduce the temperature difference SH''.

In normal operation of the cycle, this operation causes temperature? H″
becomes smaller. However, in the event of an abnormality, as shown in Fig. 10, if the valve opening degree 0 is widened, the temperature difference SH'' will increase.
This can be determined based on the direction of the temperature difference SH'' with respect to the direction of the output of , 52B is the first or second temperature sensor 5A, 5 selected by the analog multiplexer 52A.
An A/D converter 52C that converts the analog output of B into a digital quantity receives the output of the A/D converter 52B,
A microcomputer that programmatically implements control to keep the temperature difference SH'' constant outputs the control result, converts it into an analog quantity with a 52D D/A converter, and outputs it to the expansion valve 3.

Here, the temperature difference SH'' is determined according to a constant sampling period Ts, and the output is held between samplings.

At a certain sampling point TSi, voltage VTi>VTi-1
(■Ti-1 is the output at time TSO-1 one sampling before) When outputting, the time TSI+ after one sampling
The temperature difference SH″i+1 measured at 1 is the sampling time T
If the relationship between the temperature difference SH″i in Si and SH″+1>SH″i is satisfied, it can be determined to be normal, and if not, it can be determined to be abnormal. All the steps described above are performed by the microcomputer 52
It can be processed by a program inside C. Therefore, the above-mentioned detection circuit is implemented by the microcomputer 52.
It is implemented programmatically in C. Since this method determines the rationality of the response to the control output, it is possible to reliably detect abnormal conditions in the cycle. (2) Abnormality control.

As already shown in the embodiments of FIGS. 2 and 3, as a forced correction operation of the valve opening degree PV, there is control to fully open the valve opening degree 0V. Here, the detection circuit that detects an abnormality and the output control circuit that controls the control circuit output based on the detection circuit output are used. With this circuit, the output can be controlled with an extremely simple and inexpensive circuit as shown. Valve opening Q
When returning the refrigeration cycle to a normal state without fully opening V, it is sufficient to set it to at least 0Vmax.

FIG. 5 shows an example of a circuit that realizes such control. 5, the difference from FIG. 2 is that an analog switch 53A is added to the control circuit 53, a pull-up resistor is added to the voltage comparator output of the detection circuit 62, and an output control circuit 70 is added to the detection circuit 62.
is added. In a normal state, the output of the detection circuit 62 is Hi, only the analog switch 53A is turned on, and control is performed based on the temperature difference SH''. If the cycle becomes abnormal and the output of the detection circuit 62 becomes LO, the output control is disabled. The output of the inverter 70A of the circuit 70 becomes Hi, the analog switch 70B turns on, and the output of the output control circuit 70 becomes the voltage ■Tmin of the power supply 70C.On the other hand, since the analog switch 53A is off, the voltage applied to the expansion valve 3 ■
T becomes VTmin, and the valve opening degree 0V becomes 0Vmax. The advantage of setting the valve opening degree from 0■ to 0Vmax is that the expansion valve 3
Since the control remains active, the rise speed becomes faster when normal control is restored by the return circuit described below. Also, depending on the cycle condition, if the valve opening PV is fully open, there is a risk that so-called liquid back may occur, where the refrigerant returns to the compressor in a liquid state.However, by keeping the valve opening PV at 0Vmin, You can reduce that risk. 3) Return to normal operation.

(3-1) Timer.

If a predetermined time period elapses from the time when an abnormality is detected and the output control to the expansion valve is started, the normal operating range will be restored regardless of the cycle state.

In certain conditions, liquid backing occurs as described above. Even if a liquid back-up occurs, the expansion valve 3 is controlled based on the temperature difference SH'', so that the temperature difference SH'' is adjusted to a predetermined temperature difference. This can be said to be within the normal operating range. Then, after a predetermined period of time has elapsed from the output control, the control is returned to control based on the temperature difference SH''. This can be realized, for example, by the circuit shown in FIG. It is.

80 is a recovery circuit, in which the detection circuit 63 detects an abnormality and outputs LO.
When the transistor 80A is output, the transistor 80A turns off, the capacitor starts charging, and after a predetermined period of time, the voltage comparator 80A turns off.
The output of the voltage comparator 6A of the detection circuit 63 becomes approximately -Vcc, and the output of the voltage comparator 6A returns to the normal output of Hi.

At this time, the transistor 80A is turned on, so that the output of the voltage comparator 80B becomes Hi. The abnormal operation can be terminated by forcing a return using a timer, but this method can also be applied to the detection circuit 61 by making some changes to the circuit 80, and can also be applied to the detection circuit 61 as shown in FIG. This can be realized even more easily if the method is used. (3-2) Evaporator temperature TIll:V
If the valve opening degree 0V is controlled to be fully open or to a predetermined opening degree due to the abnormal AO operation, the evaporator temperature T will be maintained.

VA is decreasing. Therefore, the temperature T at which normal operation can occur
When EVANM is reached, the abnormal operation should be terminated.
An example of this circuit is shown in FIG. 64 is a detection circuit in which a backflow prevention diode 64A is added to the detection circuit 61.

Reference numeral 81 denotes a recovery circuit, which is composed of a transistor 81B, a resistor 81C, etc., and is a so-called hysteresis circuit.

When an abnormal operation occurs and the voltage comparator 61C becomes a normal output, the transistor 81B turns on and the voltage comparator 61C becomes TE.
．． Compare the voltage equivalent to VANM and TEVA and find that T[11:VA decreases due to abnormal operation] TεVA<TIll:
When it comes to VANM (TEVAmaX), voltage comparator 6
The 1C output becomes Hi and normal operation is restored.

This method is achieved by appropriately modifying the control circuit 50.
It can also be used for the detection circuit 60, and as shown in FIG. 4, if a microcomputer is used, it can be easily realized by a program. This has the advantage that it can be restored before the liquid returns because it is restored in accordance with the state of the evaporator temperature. (3-3) Temperature difference SH''.

By adjusting the valve opening to a predetermined valve opening due to abnormal operation, the evaporator returns to a wet state, the temperature difference SH'' gradually increases, and the damping liquid backs up further, and the temperature difference SH'' increases again. It continues to decline.

Therefore, the first method is to terminate the abnormal operation when the time gradient of the temperature difference SH'' is negative, that is, when the temperature difference SH'' tends to decrease. The second method is to terminate the abnormal movement when the temperature difference SH'' has returned to a certain level.

First, in realizing the former method, it is advantageous to use the microcomputer shown in Fig. 4. For example, after entering abnormal operation, the temperature difference SW is measured at appropriate time intervals, and The abnormal operation may be terminated when the temperature difference SH"i and the temperature ?Hi+1 after one measurement time interval satisfy the relationship SH"i>SH"i+1.

According to this method, since the abnormal operation is terminated based on the temperature difference βH'', the return to the normal operating range can be detected most reliably. An embodiment of the latter method is shown in FIG. A detection circuit 82 includes a backflow prevention diode 65A, and a return circuit 82 forms a so-called hysteresis circuit consisting of a resistor 82A and a backflow prevention diode 82B.

During abnormal operation, the voltage comparator output of the detection circuit 65 becomes red.
A resistor 6C is connected in parallel to the resistor 6B, and the temperature difference SW
When reaches an appropriate size SH″RST, the control circuit 5
The operational amplifier output 0 of 0 falls to the voltage 0RST corresponding to SH'RST, so the output of the voltage comparator 6A becomes Hi, and the abnormal operation ends.

If this method is used in combination with the abnormality detection circuit (1-1), a recovery circuit can be constructed extremely easily. In the above explanation, each of them has been explained individually, but they can also be easily combined as appropriate.

Furthermore, in the case of recovery, it also falls within the scope of the present invention to combine a timer and the temperature difference βH''.As detailed above, according to the present invention, when the refrigeration cycle becomes abnormal for some reason, , this was detected by the detection circuit, the output of the control circuit was controlled to force a return to the normal state, and the previous abnormal operation was terminated by detecting that the refrigeration cycle had entered the normal operating range. Since it returns to normal operation, it is possible to obtain an expansion valve control device with extremely high operating reliability that eliminates the drawbacks seen in conventional examples.Even if it enters the abnormal operating range, it can be restored, eliminating the drawbacks of conventional examples. The air conditioner has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the applied voltage and the valve opening degree of the energized closed thermoelectric expansion valve, FIG. 2 is a diagram showing the control circuit and detection circuit in an embodiment of the air conditioner of the present invention, and FIG. FIG. 4 is a block diagram of a control circuit according to another embodiment of the present invention, FIG. 5 is a diagram showing an output control circuit of the present invention, and FIG. 6 is a diagram showing an embodiment of the recovery circuit of the present invention, FIG. 7 is a diagram showing another embodiment, FIG. 8 is a diagram showing another embodiment, and FIG. 9 is a diagram showing a conventional refrigeration circuit. An explanatory diagram of the cycle, FIG. 10 is a characteristic diagram illustrating the relationship between the temperature difference SH'' and the opening degree of the expansion valve. 3...Electric expansion valve, 4...Evaporator ,
5, 50, 51, 52, 53...control circuit, 60
, 61, 62, 63, 64, 65... detection circuit, 70... output control circuit, 80, 81, 82...
...Return circuit.

Claims (1)

[Scope of Claims] 1. An electric expansion valve 3 whose opening degree can be adjusted by an electric signal, and an electric signal which outputs an electric signal to control the valve opening degree to the electric expansion valve 3 according to the state of a refrigeration cycle. a control circuit 5 that maintains the refrigeration cycle in a substantially optimal state; and the control circuit 5.
a detection circuit that detects that the refrigeration cycle cannot be optimized despite the operation of the refrigeration cycle and outputs an abnormal signal at that time, and controls the output electric signal of the control circuit 5 according to the output of the detection circuit. and recovery circuits 80 to 8 that detect that the refrigeration cycle is in a state that can be optimized by the control circuit 5 and output a normal signal that controls the output of the detection circuit or the output control circuit 70.
An air conditioner characterized by comprising: 2. 2. The air conditioner according to claim 1, wherein the detection circuit is a circuit 60 that outputs an abnormal signal when the output electric signal of the control circuit 5 exceeds a predetermined range. 3. The air conditioner according to claim 1, wherein the detection circuit is a circuit 61 that outputs an abnormal signal when the evaporator temperature of the air conditioner exceeds a predetermined temperature. 4. The control circuit 5 includes a first refrigerant temperature sensor 5A provided at the inlet side of the evaporator of the air conditioner or an intermediate portion of the evaporator, a second refrigerant temperature sensor 5B provided at the outlet side, and the first refrigerant temperature sensor 5B provided at the outlet side. A circuit that outputs a control signal to the electric expansion valve 3 according to the difference in output between the temperature sensor 5A and the second refrigerant temperature sensor 5B, and maintains the difference in output substantially constant,
The detection circuit is a circuit that detects the relationship between the increase and decrease of the difference in the output with respect to the increase and decrease of the control signal to the electric expansion valve 3, and outputs an abnormal signal when the relationship becomes a predetermined relationship. The air conditioner according to item 1. 5. The output control circuit 70 is a circuit that controls the output electric signal of the control circuit 5 so that the valve opening of the electric expansion valve 3 becomes a predetermined opening when the detection circuit outputs an abnormal signal. An air conditioner according to claim 1. 6. The air conditioner according to claim 1, wherein the recovery circuit is a circuit that outputs a normal signal after a predetermined time has elapsed after the detection circuit outputs the abnormal signal. 7. The air conditioner according to claim 1, wherein the return circuit is a circuit that outputs a normal signal when the temperature of the evaporator 4 of the air conditioner is below a predetermined temperature. 8 The recovery circuit is such that the output control circuit 70 is connected to the control circuit 5.
The air conditioner according to claim 1, which is a circuit that outputs a normal signal when a change in the degree of superheating of the refrigeration cycle or a corresponding temperature difference satisfies a predetermined relationship while controlling the output of the air conditioner.