JPH04281171A - Shortage of refrigerant deciding device for refrigerating cycle - Google Patents

Abstract

PURPOSE:To provide a shortage of refrigerant deciding device, which is prevented from judging whether the circulating amount of refrigerant is proper or not when the abnormality of superheating is detected by mistake by a superheat switch even though the circulating amount of refrigerant of a refrigerating cycle is proper. CONSTITUTION:A pressure control valve 60 controls the pressure of refrigerant from an evaporator 50 to a compressor 10 so as not to become lower than a predetermined lower limit value under a condition that a refrigerating cycle R is circulating the refrigerant. When a superheat switch 100 generates a superheat detecting signal based on the refrigerant, which flows out of the pressure control valve 60 under a condition that said circulating amount of refrigerant is proper, a shortage of refrigerant deciding device is prohibited from judging about the circulating amount of refrigerant.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a refrigeration cycle for a cooling system, an air conditioning system, a refrigeration system, etc., and in particular, when the amount of refrigerant circulating in the refrigeration cycle is insufficient, it is possible to determine the shortage. The present invention relates to a refrigerant shortage determination device suitable for.

0002

[Prior Art] Conventionally, in this type of refrigerant shortage determination device, a super heat switch is provided downstream of an evaporator of an air conditioner installed in a vehicle, as shown in Japanese Patent Publication No. 63-54987, for example. At the same time, a temperature sensor is installed on the discharge side of the compressor, and when the superheat of the refrigerant flowing out from the evaporator rises inappropriately due to insufficient amount of circulating refrigerant, and the temperature of the refrigerant discharged from the compressor rises inappropriately, the superheat is detected. A switch detects an inappropriate increase in superheat, and a temperature sensor detects an inappropriate increase in refrigerant temperature. Based on both detection results, the remaining amount of circulating refrigerant due to leakage, etc. of the circulating refrigerant is detected. There are some things that are determined to be insufficient.

0003

[Problem to be Solved by the Invention] However, in such a configuration, when the temperature of the outside air is low, when the air conditioner is operated in the inside air introduction mode, the pressure difference of the refrigerant before and after the expansion valve of the air conditioner increases. As a result, the amount of refrigerant circulating in the cooling system decreases, so even though the amount of refrigerant remaining in the cooling system is originally appropriate, there is a problem in which the super heat increases inappropriately and causes the super heat switch to malfunction. . In addition, if a pressure control valve is provided downstream of the evaporator to prevent the evaporator from freezing during low loads, this pressure control valve will control the pressure of the refrigerant flowing out from the evaporator to a predetermined lower limit pressure (for example, 1
．． 8 kg/km2G) or less, a problem arises in that superheat cannot be detected in a state where the pressure of the outflowing refrigerant is lower than the predetermined lower limit pressure. Therefore, in order to cope with this problem, the present invention provides a refrigeration cycle equipped with a pressure control valve as described above, in which the superheat detection means detects the occurrence of superheat even though the amount of circulating refrigerant is appropriate. It is an object of the present invention to provide a refrigerant shortage determination device that does not determine whether or not the amount of circulating refrigerant is appropriate when an abnormality is detected incorrectly.

0004

[Means for Solving the Problems] In solving the above problems, the structural features of the present invention are as illustrated in FIG.
a compressor that sucks and compresses circulating refrigerant and discharges it as a high-temperature, high-pressure compressed refrigerant; a condenser that condenses the compressed refrigerant as a condensed refrigerant; a conversion means that converts the condensed refrigerant into a low-temperature, low-pressure refrigerant; In a refrigeration cycle comprising an evaporator that cools a fluid to be cooled and returns the refrigerant to the compressor, and a pressure control valve that controls the pressure of the refrigerant returned from the evaporator to the compressor so that it does not fall below a predetermined reduced pressure. , a superheat detection means 1 which is interposed between the pressure control valve and the compressor and generates a superheat detection signal when the superheat of the refrigerant flowing out from the pressure control valve rises to a predetermined value; and determining means 2 for determining that the amount of the circulating refrigerant is insufficient in response to the heat detection signal, and when the super heat detection signal occurs in a state where the amount of the circulating refrigerant is appropriate, This is because the prohibition means 3 for prohibiting the judgment operation of the judgment means 2 is provided.

[0005]

[Function] By configuring the present invention in this manner, when the compressor takes in and compresses the circulating refrigerant and discharges it as a high-temperature, high-pressure compressed refrigerant, the condenser condenses the compressed refrigerant as a condensed refrigerant. A converting means converts the condensed refrigerant into a low-temperature, low-pressure refrigerant, the evaporator cools a fluid to be cooled according to the low-temperature, low-pressure refrigerant and returns the refrigerant to the compressor, and the pressure control valve converts the refrigerant from the evaporator to the compressor. The pressure of the refrigerant returned to the refrigerant is controlled so that it does not fall below a predetermined reduced pressure. In such a state, when the superheat of the refrigerant flowing out from the pressure control valve rises to a predetermined value under the non-inhibiting action of the inhibiting means 3, the superheat detecting means 1
When the refrigerant generates a superheat detection signal, the determining means 2 determines that the amount of the circulating refrigerant is insufficient. Further, at this time, if the superheat detection signal occurs in a state where the amount of the circulating refrigerant is appropriate, the inhibiting means 3
prohibits the judgment function of the judgment means 2.

[0006]

As described above, when the superheat detection signal occurs in a state where the amount of the circulating refrigerant is appropriate, the inhibiting means 3 inhibits the determining operation of the determining means 2, so that, for example, if the outside air Even if the circulating refrigerant amount is appropriate, such as in a mode in which the temperature of the coolant is low and the airflow in the cooled space is cooled by the evaporator and circulated within the cooled space, the superheat will abnormally increase. In this case, the determining means 2 does not perform the determining operation, and as a result, there is no possibility of erroneously determining that there is a refrigerant shortage. In such a case, since the superheat detection means 1 is provided downstream of the pressure control valve, the refrigerant from the evaporator is not controlled from the same pressure control valve, and as a result, superheat detection There is no limit to the detection range of means 1.

[0007]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. Figs. 2 and 3 show an example in which the present invention is applied to a refrigeration cycle R employed in a vehicle air conditioning system AC. . The refrigeration cycle R includes a compressor 10, which compresses the suction refrigerant according to its operation, and supplies the refrigerant to the pipe P1 as a high-temperature, high-pressure compressed refrigerant.
The liquid is discharged into the air and flows into the condenser 20. The condenser 20 condenses the incoming compressed refrigerant under the air cooling action of an air cooling fan (not shown), and causes the condensed refrigerant to flow into the receiver 30 through the pipe P2. The receiver 30 separates the incoming condensed refrigerant into gas and liquid, and causes only the liquid phase component to flow into the expansion valve 40 through the pipe P3 as a circulating refrigerant. The compressor 10 operates by selectively receiving output from the engine of the vehicle as the engine operates.

[0008] The expansion valve 40 expands the incoming refrigerant according to its opening degree, and causes the expanded refrigerant to flow into the evaporator 50 through the pipe P4. However, in the inside air introduction mode of the air conditioning system AC when the outside temperature is low, even if the expansion valve 40 is fully open, the pressure difference before and after the expansion valve 40 is small, so the refrigerant circulation amount is It is starting to decrease. The evaporator 50 is provided in the air duct of the air conditioning system AC, and this evaporator 50 cools the air flow to be blown out through the air duct into the vehicle interior of the vehicle according to the inflowing and expanding refrigerant. The cooled refrigerant is made to flow into the pressure control valve 60 through the pipe P5. This pressure control valve 60 is
The refrigerant pressure in the pipe P5 near the refrigerant outlet of the evaporator 50 is set to a predetermined lower limit pressure (for example, 1.8 kg/km2G).
) while controlling the evaporator 50 to maintain the
The refrigerant is returned to the compressor 10 through the pipe P6. In this case, the predetermined lower limit pressure corresponds to a lower limit value that can prevent the evaporator 50 from freezing during low load. This means that the superheat (
This means that since the increase in superheat SHe (hereinafter referred to as superheat SHe) is limited, there may be cases where a shortage of refrigerant cannot be detected (see curve La in FIG. 4). In addition, since the refrigerant pressure at the refrigerant outlet of the pressure control valve 60 decreases significantly as the amount of circulating refrigerant decreases, the refrigerant pressure at the refrigerant outlet of the pressure control valve 60 (hereinafter referred to as superheat S)
(referred to as Hp) increases at an accelerating rate (in Fig. 5, each curve L
d, Le, Lf).

However, the air conditioning system AC operates under the control of a microcomputer 110, which will be described later, and takes into consideration the outside temperature detection signal generated from the outside temperature sensor 70 as a correction parameter, and calculates the actual inside air inside the vehicle. The temperature of the airflow blown from the air duct into the vehicle interior is controlled so as to maintain the temperature at a desired set temperature. Further, this air conditioning system AC operates based on the indoor air mode switching signal generated from the indoor air mode switch 80.
The mode for introducing airflow into the air duct is switched to an inside air introduction mode for introducing inside air from the vehicle interior. The operation switch SW is closed when the device of the present invention and the air conditioning system AC are operated, and generates the power supply voltage from the DC power supply B via the ignition switch IG as the operation signal. The outside air temperature sensor 70 detects the actual temperature of the air outside the vehicle and generates the outside air detection signal. Further, the inside air mode switch 80 is operated to switch the air flow introduction mode into the air duct of the air conditioning system AC to the inside air mode, and generates the inside air mode switching signal.

Next, the electric circuit configuration constituting the main part of the present invention will be explained. The A-D converter 90 digitally converts the outside temperature detection signal from the outside temperature sensor 70 and generates a digital outside temperature signal. . The normally open type super heat switch 100 has a pressure control valve 6 as shown in FIG.
It is attached to piping P6 at the wake near 0.
This super heat switch 100 is a refrigeration cycle R.
It contains a predetermined amount of the same refrigerant as the circulating refrigerant, and also contains a temperature sensing member. Therefore, this super heat switch 100 increases the pressure of the built-in refrigerant in response to the temperature sensing member detecting the temperature rise of the refrigerant near the refrigerant outlet of the pressure control valve 60, and increases the pressure of the internal refrigerant to a predetermined pressure of the increased refrigerant pressure. When the temperature rises to , it detects this and closes, generating a superheat detection signal. In such a case, the operating region of the super heat switch 100 is in the shaded region indicated by the symbols Sa and Sb in FIGS. 4 and 5, respectively. Therefore, for example, the predetermined pressure is set to 2.1 (kg) so that the super heat switch 100 is closed when the remaining refrigerant amount is 50 (%).
/m2), set super heat amount SH
It can be seen that it is sufficient to set o=10 (° C.) and MOP=0.8. In addition, when the air conditioning system AC is operated in the inside air introduction mode at low outside temperatures,
As can be seen from the relationship between the curve Lg and the operating range Sc of the super heat switch 100 in FIG. It can be seen that it invites

The microcomputer 110 executes the computer program in cooperation with the internal air mode switch 80, the A-D converter 90, and the super heat switch 100 according to the flowcharts shown in FIGS. 7 and 8, and during this execution, , performs arithmetic processing necessary to drive and control the drive circuit 130 for the air conditioning system AC, timer 120, and relay 140. The timer 120 is
The time is measured under the control of the microcomputer 110. Therefore, when the timer 120 finishes timing as described later, the relay coil 130a of the relay 130
Excite. Relay 130 closes normally open relay switch 130b by energizing relay coil 130a. The relay 140 is selectively excited by the drive circuit 130 at its relay coil 140a under the control of the microcomputer 110 to close the normally open relay switch 140b. The warning lamp 150 is grounded at one end, and the other end of the warning lamp 150 is connected to the relay switch 140b of the relay 140, the relay 1
It is connected to the positive side terminal of the DC power supply B via the relay switch 130b of No. 30, the operation switch SW, and the ignition switch IG. However, this warning lamp 150
When both relay switches 130b and 140b are closed, power is supplied from DC power source B via operation switch SW and ignition switch IG to light up.

[0012] In this embodiment configured as above,
It is assumed that the vehicle is driven with the engine started by closing the ignition switch IG. In this state, when an operation signal is generated from the operation switch SW, the microcomputer 110 starts executing the computer program at step 200 according to the flowcharts of FIGS. 7 and 8, and at step 210,
Performs initialization processing. Next, microcomputer 1
10, in the air conditioning control routine 220, the calculation processing required to start the compressor 10, the necessary blowing temperature of the airflow into the vehicle interior, the introduction mode of the airflow into the air duct, and the airflow from the air duct. Performs the calculation processing necessary to determine the speech bubble mode, etc. Then, the air conditioning system AC starts the compressor 10 in cooperation with the engine in accordance with each arithmetic processing by the microcomputer 110, and sets the mode for introducing the air flow into the air duct and the blowing out of the air flow from the air duct. operating so as to match the mode and the necessary blowing temperature of the air flow into the vehicle interior with the arithmetic processing result;
It operates to adjust the actual temperature inside the vehicle toward the set temperature.

When the compressor 10 is started as described above, the compressor 10 sucks and compresses the refrigerant in the pipe P6, and causes the compressed refrigerant at high temperature and high pressure to flow into the condenser 20 through the pipe P1. Then, this condenser 20 condenses the incoming compressed refrigerant under the air cooling action of the air cooling fan and passes it through the pipe P2 to the receiver 30.
The receiver 30 separates the condensed refrigerant into gas and liquid and causes the liquid phase component to flow into the expansion valve 40 through the pipe P3 as a circulating refrigerant. Next, the expansion valve 40 expands the inflowing refrigerant according to its opening degree, and causes the expanded refrigerant to flow into the evaporator 50 through the pipe P4. According to the inflowing refrigerant, this evaporator 50 cools the air flow blown into the vehicle interior under the operation of the air conditioning system AC as described above, and the cooled refrigerant is passed through the pipe P5. It is made to flow into the through pressure control valve 60. Therefore, the pressure control valve 60 controls the pressure of the incoming refrigerant so that it does not fall below the predetermined lower limit pressure, while circulating the refrigerant into the compressor 10 through the pipe P6.

Air conditioning control routine 22 as described above
After the calculation process at 0, the super heat switch 100
If it is currently in the open state, the microcomputer 110 determines "NO" in step 230. However, in this step 230, “NO”
”, the temperature of the circulating refrigerant in the pipe P6 rose, so the super heat switch 100
If the superheat detection signal is generated by the closing, the microcomputer 110 determines "YES" in step 230, and in step 230a,
The timer 120 is reset and started. Therefore, the timer 110 starts counting. At this time, the microcomputer 110 controls the timer 1 in the next step 240.
Based on the time measurement value Tt<predetermined measurement time Tto of 20, “N
O”. However, the predetermined measurement time Tto is set to be somewhat longer than the temporary rise period of superheat when the air conditioning system AC is started with an appropriate residual amount of refrigerant or when the vehicle is suddenly accelerated. .

During the repetition of the "NO" determination in step 240, the super heat switch 100
Timer 1 is activated upon generation of superheat detection signal from
20 time measurement value Tt≧predetermined measurement time Tto is established,
The microcomputer 110 determines "YES" in step 240 and advances the computer program to step 250. At the same time, the timer 120 excites the relay coil 130a of the relay 130 to close the relay switch 130b. At this stage, if the value of the digital outside temperature signal from the A-D converter 90 (hereinafter referred to as outside temperature Tam) is equal to or higher than the predetermined low temperature value Tamo, the microcomputer 110 in step 250
YES” is determined. After that, if the current air flow introduction mode into the air duct of the air conditioning system AC is not the inside air introduction mode, the microcomputer 1
10 determines "NO" in the next step 260,
And in step 260a, a relay output signal necessary to excite relay coil 140a of relay 140 is generated. However, the predetermined low temperature value Tamo is set in order to avoid determining that there is a refrigerant shortage due to the closing operation of the super heat switch 100 due to a decrease in the amount of circulating refrigerant in the refrigeration cycle R when the outside air temperature is low and the inside air introduction mode is set. , is set to an appropriate value (for example, 15 (° C.)) and is stored in advance in the ROM of the microcomputer 110.

As mentioned above, the microcomputer 110
When a relay output signal is generated from , the drive circuit 130 excites the relay coil 140a of the relay 140 and closes the relay switch 140b. Therefore, the warning lamp 15
When the relay switch 140b is closed while the relay switch 130b is closed, power is supplied from the DC power source B through the ignition switch IG and the operation switch SW, and the light is turned on to warn of refrigerant shortage. In such a case, the warning lamp 150 lights up on the premise that the determination is "YES" in both steps 240 and 250 and the determination is "NO" in step 260, so that the warning lamp 150 lights up when the vehicle suddenly accelerates or when the air conditioner It can be seen that this is not caused by a temporary increase in superheat when the system AC is started, or by the inside air introduction mode when the outside temperature is low. Therefore, the warning lamp 150 in such a case
Illumination of the symbol means that a precise warning is given that the amount of remaining refrigerant in the refrigeration cycle R is insufficient due to leakage of the refrigerant or the like. Moreover, the super heat switch 100 is
This super heat switch 1 is installed in the pipe P6 near the refrigerant outlet of the pressure control valve 60.
The refrigerant in the pipe P6, which is the object of detection of 00, is directly controlled by the pressure control valve 60, like the refrigerant in the pipe P5.
As a result, a situation where the super heat switch 100 becomes unable to detect super heat does not occur.

[0017] Furthermore, when the computer program proceeds to step 250 as described above, if the determination at step 250 is "NO", it is determined that there is an appropriate amount of refrigerant remaining in the refrigeration cycle R. Nevertheless,
Based on the determination that the low outside temperature will inappropriately reduce the amount of circulating refrigerant, the microcomputer 110 prohibits the computer program from proceeding to step 260, advances the computer program to step 250a, and sets timer 1.
After stopping 20, the computer program returns to step 220. Also, when the computer program proceeds to step 260 as described above, step 26
If the determination in 0 is "YES", the air conditioning system AC is in the inside air introduction mode under the low outside temperature, so even though there is an appropriate amount of residual refrigerant in the refrigeration cycle R. Regardless, the microcomputer 110 determines that the amount of circulating refrigerant will be inappropriately reduced.
The computer program is prohibited from proceeding to step 260a, the computer program is advanced to step 250a, and after stopping the timer 120, the computer program is returned to step 220. Therefore, when the outside temperature is too low or when the inside air introduction mode is in this state, the warning lamp 150 will not light up even if the super heat switch 100 is closed in the malfunction area shown in FIG.
There is no possibility of mistakenly recognizing that there is a refrigerant shortage.

In carrying out the present invention, an air temperature sensor is employed to detect the actual temperature immediately before the air flow to be cooled enters the evaporator 50, and both steps 250 and 250 are
, 260, a predetermined temperature difference value Tc of the temperature difference ΔT between the air temperature detected by the air temperature sensor and the outside temperature detected by the outside temperature sensor 70 is adopted, and ΔT≧T
When c holds, step 2 of the computer program
The transition to 60a may be prohibited. Further, in implementing the present invention, the super heat switch 10
0, and a super heat switch 100A having the same configuration and functions as this (however, the super heat setting value is larger than that of the super heat switch 100).
is installed in the pipe P6 as shown in FIG. 9, and the operating range of the super heat switch 100A is designated by the symbol S in FIG.
If the selection is made within the dashed line area indicated by d, and the generation of the superheat detection signal from the superheat switch 100A is also used as the determination criterion in step 240, the superheat will be even lower at low outside temperatures. In the inside air introduction mode shown below, the arithmetic processing after step 250 is performed on the premise that a super heat detection signal is generated from the super heat switch 100A, and in other cases, the super heat switch 100
The arithmetic processing after step 250 is performed on the premise that a superheat detection signal is generated from. Note that the number of super heat switches added may be changed as appropriate. Furthermore, in implementing the present invention, the present invention is not limited to the refrigeration cycle of a vehicle air conditioning system, but may be applied to a refrigeration cycle for a vehicle refrigeration system, an air conditioning system for general buildings, etc. .

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the claims.

FIG. 2 is a circuit diagram of a refrigeration cycle in an embodiment to which the present invention is applied.

FIG. 3 is an electrical circuit diagram of the cargo rack of the same embodiment.

4 is a graph showing the relationship between the refrigerant pressure at the refrigerant outlet of the evaporator and the superheat SHe using the load condition and the remaining refrigerant amount Q as parameters, and a diagram showing the operating range of the superheat switch in FIG. 2. FIG.

[Fig. 5] The relationship between the refrigerant pressure at the refrigerant outlet of the pressure control valve and the superheat SHp according to the load condition and the residual refrigerant amount Q
FIG. 3 is a graph showing the parameters as parameters, and a diagram showing the operating range of the super heat switch of FIG. 2.

[Fig. 6] The relationship between the refrigerant pressure at the refrigerant outlet of the pressure control valve and the superheat SHp when the outside temperature is 0 (°C) and the inside temperature is 27 (°C), depending on the load condition and the remaining refrigerant amount Q.
FIG. 3 is a graph showing the parameters as parameters, and a diagram showing the operating range of the super heat switch of FIG. 2.

FIG. 7 is the first part of a flowchart showing the operation of the microcomputer in FIG. 3;

FIG. 8 is the latter part of a flowchart showing the operation of the microcomputer in FIG. 3;

FIG. 9 is a circuit diagram showing a partial modification of the refrigeration cycle of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10... Compressor, 20... Capacitor, 30... Receiver, 40... Expansion valve, 50... Evaporator, 60... Pressure control valve, 70... Outside temperature sensor, 80... Inside air mode switch, 100, 100A... Super heat switch, 110
...Microcomputer, 120...Timer, 130, 1
40...Relay, P1-P6...Piping, Refrigeration cycle...R.

Claims (1)

[Claims] 1. A compressor for sucking and compressing circulating refrigerant and discharging it as a high-temperature, high-pressure compressed refrigerant; a condenser for condensing the compressed refrigerant as a condensed refrigerant; a conversion means for converting the condensed refrigerant into a low-temperature, low-pressure refrigerant; an evaporator that cools a fluid to be cooled according to a low-pressure refrigerant and returns the refrigerant to the compressor; and a pressure control valve that controls the pressure of the refrigerant flowing from the evaporator to the compressor so that it does not fall below a predetermined reduced pressure. In the refrigeration cycle, superheat detection means is interposed between the pressure control valve and the compressor and generates a superheat detection signal when the superheat of the refrigerant flowing out from the pressure control valve rises to a predetermined value. and determining means for determining that the amount of the circulating refrigerant is insufficient in response to the superheat detection signal, and when the superheat detection signal occurs in a state where the amount of the circulating refrigerant is appropriate. A refrigerant shortage determination device for a refrigeration cycle, characterized in that a prohibition means for prohibiting the determination operation of the determination means is provided.