JP2016161244A - Refrigerant shortage determination device, refrigeration cycle having the same, and refrigerant shortage determination method of refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerant shortage determination technology which prevents the erroneous determination of the shortage of a refrigerant amount even if the refrigerant amount in a refrigeration cycle is proper, and can accurately determine the presence or absence of the shortage of the refrigerant amount in a short time.SOLUTION: A refrigerant shortage determination device comprises: first determination means which temporarily determines the shortage of a refrigerant amount in a refrigeration cycle when a difference between a temperature Tev which is detected by an evaporator temperature detection sensor and a target temperature To reaches a first prescribed value α or higher; and second determination means which temporarily determines the shortage of the refrigerant amount in the refrigeration cycle when a difference between first refrigerant saturation pressure PHL which is introduced from an outside temperature which is detected by an outside temperature detection sensor, and second refrigerant saturation pressure PSa being the pressure of a refrigerant which is detected by a refrigerant pressure detection sensor reaches a second prescribed value β1 or higher. When the first determination means temporarily determines that the refrigerant amount in the refrigeration cycle is in shortage, and the second detection means determines that the refrigerant amount in the refrigeration cycle is in shortage, the refrigerant shortage determination device defines the determination of the shortage of the refrigerant amount in the refrigeration cycle.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for accurately determining the presence or absence of refrigerant shortage in a refrigeration cycle used in a vehicle air conditioner or the like.

The refrigeration cycle used in the vehicle air conditioner has the following inconveniences when the amount of refrigerant circulating in the cycle is insufficient.
That is, if the amount of refrigerant circulating in the cycle is insufficient,
1. Lubricating oil discharged from the compressor together with the refrigerant does not return sufficiently to the compressor, the lubricating oil in the compressor is insufficient, and the compressor is seized, or
2. The endothermic effect in the evaporator is reduced and sufficient cooling capacity cannot be obtained.

  Therefore, conventionally, before starting the compressor (before operating the refrigeration cycle), the pressure inside the cycle is detected, and the detected refrigerant pressure is within a predetermined range from the saturated vapor pressure of the refrigerant determined by the outside air temperature. In the case where the amount of refrigerant in the refrigeration cycle is insufficient, a technique for preventing the compressor from starting is proposed (see Patent Document 1).

  Such a technique is effective when detecting a state in which the amount of refrigerant in the refrigeration cycle is insufficient to induce burn-in of the compressor, but an evaporator that operates without causing the burn-in of the compressor. It is not possible to effectively detect a state in which the amount of refrigerant in the refrigeration cycle is reduced to such an extent that the cooling capacity of the refrigerant decreases and the temperature of the air cooled by the evaporator deviates from the target temperature.

  Therefore, conventionally, a technique has been proposed in which when the air temperature immediately after passing through the evaporator is higher than a predetermined temperature (target temperature) determined based on the evaporation pressure in the evaporator, the refrigerant amount is insufficient. (See Patent Document 2). If the detected high pressure is below the appropriate range of the high pressure determined by the outside temperature based on the outside temperature detected by the outside temperature sensor and the high pressure of the refrigeration cycle detected by the high pressure sensor, the refrigerant A technique for determining that a leak has occurred is also known (see Patent Document 3).

Japanese Patent Laid-Open No. 2-78874 JP 10-185372 A JP-A-6-123529

  However, in the conventional configuration (configuration shown in Patent Document 2) that determines the shortage of the refrigerant amount by the difference between the air temperature immediately after passing through the evaporator and the target temperature, even if the refrigerant amount in the refrigeration cycle is appropriate There are cases where it is erroneously determined that the amount of refrigerant is insufficient.

  This point will be described with reference to FIG. 7 showing the relationship between the refrigerant amount in the refrigeration cycle and the temperature of the evaporator during cycle operation (or the air temperature immediately after passing through the evaporator). At the time of load (when the external heat load is not high), as indicated by the solid line, when the compressor is a fixed capacity type, the amount of refrigerant in the refrigeration cycle gradually decreases from the appropriate state. The temperature of the evaporator at the time of cycle operation (or the air temperature immediately after passing through the evaporator) becomes higher in proportion to this. In addition, if the compressor is a variable capacity type, the target temperature can be maintained even if the amount of refrigerant is insufficient as long as the capacity can be varied. If it decreases so that it cannot be performed, the temperature of the evaporator at the time of cycle operation (or the air temperature immediately after passing through the evaporator) increases in proportion to the decrease in the refrigerant amount. Therefore, if the heat load is not high, an alarm should be issued when the actual evaporator temperature (or the air temperature immediately after passing through the evaporator) becomes higher than the target temperature. It becomes possible to accurately grasp the shortage of the refrigerant amount.

  However, when the outside air temperature is high and the heat load is high (when the external heat load is high), the amount of heat released from the condenser is insufficient, and even if the amount of refrigerant in the refrigeration cycle is appropriate, the evaporator If the temperature (or the air temperature immediately after passing through the evaporator) does not reach the target temperature and becomes higher than the target temperature, as shown by the broken line, the alarm indicating that the refrigerant amount is insufficient is false. There is an inconvenience that is issued.

  On the other hand, when the detected high pressure is below the appropriate range of the high pressure determined by the outside air temperature, the refrigerant amount in the refrigeration cycle is insufficient due to the configuration that determines that the refrigerant is insufficient. The presence / absence determination is performed as shown in FIG.

FIG. 8 shows the relationship between the amount of refrigerant in the refrigeration cycle and the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during cycle operation, but at the time of low heat load with low outside air temperature (external heat load). If the compressor is a fixed capacity type, as shown by the solid line, when the refrigerant amount in the refrigeration cycle gradually decreases from the appropriate state, the cycle operation is almost proportional to it. The refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line at that time is lower than the refrigerant saturation pressure (refrigerant saturation pressure when the amount of refrigerant is appropriate) derived from the outside air temperature. In addition, when the compressor is a variable capacity type, it is possible to maintain the saturation pressure when the refrigerant amount is appropriate even if the refrigerant amount is insufficient within the range in which the capacity can be varied. When the amount of refrigerant in the cycle decreases to a point where it cannot be handled with a variable capacity, the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during the cycle operation is also approximately proportional to the decrease in refrigerant amount. It becomes lower than the pressure (refrigerant saturation pressure when the amount of refrigerant is appropriate).
Therefore, if the heat load is not high, if the alarm is issued when the refrigerant pressure (refrigerant saturation pressure) on the high-pressure side line during the cycle operation falls outside the appropriate range and becomes low, the refrigerant amount is insufficient. It becomes possible to capture this.

Even when the outside air temperature is high and the heat load is high (when the external heat load is high), if the refrigerant amount in the refrigeration cycle gradually decreases from the appropriate state, the compressor is either a fixed capacity type or a variable capacity type. Regardless of this, as indicated by the broken line, the refrigerant pressure (refrigerant saturation pressure) of the high-pressure side line during cycle operation is derived from the outside air temperature in proportion to the refrigerant saturation pressure (refrigerant saturation when the amount of refrigerant is appropriate). If the alarm is issued when the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line in the refrigeration cycle falls outside the proper range and becomes low, the refrigerant amount is insufficient. Can be captured.
Therefore, when this determination method is used, there is no inconvenience that an alarm indicating that the refrigerant amount is insufficient is erroneously issued even when the outside air temperature is high and the heat load is high (when the external heat load is high).

However, in such a configuration, although the variation of the determination due to the fluctuation of the heat load is reduced, whether the detected high pressure is low is due to the leakage of refrigerant (insufficient amount of refrigerant) or other There is an inconvenience that is unclear whether it is caused by a factor. For example, the outside air temperature sensor is often arranged in front of the vehicle. When the vehicle stops, the hot air in the engine room may be transmitted to the outside air temperature sensor. In this case, the refrigerant saturation pressure derived from the outside air temperature is It will be set higher. Even if there is no refrigerant leakage, it is considered that the refrigerant saturation pressure derived from the refrigerant pressure in the high-pressure side line has fallen out of the proper range and is low, and the probability that an alarm indicating that the refrigerant amount is insufficient is erroneously issued. Rises. Further, the refrigerant pressure in the high-pressure side line is constantly fluctuating due to factors such as the number of revolutions of the traveling engine, the speed of the vehicle, the wind direction around the vehicle, etc., and the accuracy is not high in detecting the shortage of the refrigerant amount.
Thus, it is more direct to evaluate whether or not the cooling capacity is lowered based on the temperature of the evaporator (or the air temperature immediately after passing through the evaporator).

  Therefore, in Patent Document 3, the excess or deficiency of the refrigerant is checked a plurality of times based on the detection value of the outside air temperature sensor and the detection value of the high pressure sensor, and the presence or absence of the refrigerant decreasing tendency is determined based on the check result. When it is determined that there is a method, a method of displaying the determination result or issuing an alarm has been proposed.

  However, according to such a method, the detection accuracy of refrigerant leakage (refrigerant shortage) can be improved, but the refrigerant excess / deficiency is determined several times over time based on the detection value of the outside air temperature sensor and the detection value of the high pressure sensor. Since it is necessary to check and determine whether or not there is a tendency to decrease the refrigerant, there is a disadvantage that it takes time to obtain a determination result.

  The present invention has been made in view of such circumstances, and prevents erroneous determination that the amount of refrigerant is insufficient even when the amount of refrigerant in the refrigeration cycle is appropriate. The main object is to provide a refrigerant shortage determination technique capable of accurately determining whether there is a shortage.

  In order to achieve the above object, a refrigerant shortage determination apparatus according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a refrigerant condensed by the condenser. A refrigerant shortage determination device used in a refrigeration cycle having an expansion device that decompresses and an evaporator that evaporates refrigerant flowing out of the expansion device, and flows through a refrigerant path between the compressor and the expansion device A refrigerant pressure detector for detecting the pressure of the refrigerant, an evaporator temperature detector for detecting the temperature of the evaporator or the air temperature immediately after passing through the evaporator, and a thermal load outside the air-conditioned space are detected. Detected by the external thermal load detector, the internal thermal load detector that detects the internal thermal load of the air-conditioned space, the temperature setting device that sets the control temperature of the air-conditioned space, and the external thermal load detector Heat load, The target temperature calculation means for calculating the target temperature of the air immediately after passing through the evaporator or the evaporator based on the thermal load detected by the internal load detector and the control temperature set by the temperature setter When the difference between the temperature detected by the evaporator temperature detector and the target temperature calculated by the target temperature calculating means is equal to or greater than a first predetermined value, the refrigerant amount in the refrigeration cycle is insufficient. First determination means for temporary determination, a first refrigerant saturation pressure derived from a thermal load detected by the external thermal load detector, and a second refrigerant saturation pressure that is a refrigerant pressure detected by the refrigerant pressure detector When the difference between the refrigerant amount and the second predetermined value is equal to or greater than a second predetermined value, the refrigerant amount in the refrigeration cycle is temporarily determined by a second determination unit that provisionally determines that the refrigerant amount is insufficient in the refrigeration cycle, and the first determination unit. It is insufficient When the provisional determination is made and the second determination means temporarily determines that the amount of refrigerant in the refrigeration cycle is insufficient, the refrigerant shortage determination is confirmed to determine the refrigerant amount shortage determination in the refrigeration cycle. And means.

  Therefore, the difference between the temperature detected by the evaporator temperature detector and the target temperature set by the target temperature setting means is greater than or equal to the first predetermined value by the first determination means, and the amount of refrigerant in the refrigeration cycle is increased. Insufficient provisional determination is made, and the second determination means determines the first refrigerant saturation pressure derived from the thermal load detected by the external thermal load detector and the refrigerant pressure detected by the refrigerant pressure detector. When the difference from the refrigerant saturation pressure is equal to or greater than the second predetermined value and it is temporarily determined that the refrigerant amount is insufficient in the refrigeration cycle, the refrigerant shortage determination determining unit determines whether the refrigerant amount is insufficient in the refrigeration cycle. Therefore, whether there is a shortage of refrigerant in the refrigeration cycle is evaluated based on the temperature of the evaporator that directly affects the cooling capacity (or the air temperature immediately after passing through the evaporator), and variations in judgment due to fluctuations in the heat load Less There it is possible to perform both of the evaluation based on the refrigerant saturation pressure, it is possible to prevent the refrigerant quantity in the refrigerant cycle is erroneously determined to be insufficient even appropriate.

  That is, in the state where the first determination means temporarily determines that the refrigerant amount is insufficient in the refrigeration cycle, the temperature detected by the evaporator temperature detector does not reach the target temperature when the external heat load is high. Although there is a risk of erroneous determination, since the determination by the second determination means with little determination variation due to fluctuations in the thermal load is further added to this, the risk of erroneous determination is eliminated.

  In addition, since it is not necessary to perform the determination by the first determination unit and the determination by the second determination unit with a time lapse, it is possible to perform the determination result of whether or not the refrigerant amount is insufficient in the refrigeration cycle without taking time. In addition, it can be installed in a vehicle as a pressure sensor arranged in the high-pressure side flow path of the refrigerant as a refrigerant pressure detector, an evaporator as an evaporator temperature detector or a thermo sensor arranged immediately after it, and an external thermal load detector. Since existing sensors such as a vehicle interior temperature sensor and a vehicle interior temperature sensor installed in a vehicle as an internal thermal load detector can be used, additional components can be eliminated.

Here, the second determination means for temporarily determining the shortage of the refrigerant amount in the refrigeration cycle is the first refrigerant derived from the thermal load detected by the external thermal load detector instead of the first refrigerant saturation pressure. A saturation temperature may be used, and a second refrigerant saturation temperature determined from the second refrigerant saturation pressure may be used instead of the second refrigerant saturation pressure.
Since the saturated refrigerant has a relationship in which pressure and temperature uniquely correspond to each other, it is possible to use not only the saturation pressure but also the saturation temperature in the second determination means, and the design flexibility of the determination means is expanded. It becomes possible.

Further, the magnitude of the second predetermined value may be changed according to the magnitude of the heat load outside the air-conditioned space.
In such a configuration, the threshold value for determining whether or not the refrigerant amount is insufficient in the second determination means is changed according to the magnitude of the heat load outside the air-conditioned space. It becomes possible to further eliminate the possibility of determination.

Furthermore, the apparatus further comprises third determination means for determining whether or not the refrigerant pressure detected by the refrigerant pressure detector before starting the compressor is lower than a predetermined pressure value. When it is determined that the refrigerant pressure before starting the compressor is lower than a predetermined pressure value, it is preferable not to start the compressor.
With such a configuration, it is possible to determine a refrigerant shortage enough to burn in the compressor before operating the compressor, and it is possible to avoid inconvenience that the compressor operates and burns in.

  Note that the compressor in which the above-described refrigerant shortage determination device is used may be a fixed capacity type or a variable capacity type. Moreover, you may make it integrate the refrigerant | coolant shortage determination apparatus mentioned above with a refrigerating cycle.

  In order to achieve the above object, a refrigerant shortage determination method for a refrigeration cycle according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and the condenser. A refrigerating cycle having an expansion device for depressurizing the condensed refrigerant, an evaporator for evaporating the refrigerant flowing out of the expansion device, and a pressure of the refrigerant flowing through a refrigerant path between the compressor and the expansion device. A refrigerant pressure detector to detect, a temperature detector to detect the temperature of the evaporator, or an air temperature immediately after passing through the evaporator, and an external thermal load detector to detect a heat load outside the air-conditioned space An internal thermal load detector that detects a thermal load inside the air-conditioned space, a temperature setter that sets a control temperature of the air-conditioned space, a thermal load detected by the external thermal load detector, For internal load detector Target temperature calculating means for calculating a target temperature of air immediately after passing through the evaporator or the evaporator, based on the detected thermal load and the control temperature set by the temperature setter. The difference between the temperature detected by the evaporator temperature detector and the target temperature calculated by the target temperature calculation means is determined to be greater than or equal to a first predetermined value, and the external heat The difference between the first refrigerant saturation pressure derived from the thermal load detected by the load detector and the second refrigerant saturation pressure, which is the refrigerant pressure detected by the refrigerant pressure detector, is determined to be greater than or equal to a second predetermined value. In this case, it is determined that the amount of refrigerant in the refrigeration cycle is insufficient.

Here, instead of the first refrigerant saturation pressure, the first refrigerant saturation temperature derived from the thermal load detected by the external thermal load detector is used, and the second refrigerant saturation pressure is substituted for the second refrigerant saturation pressure. The second refrigerant saturation temperature determined from the above may be used.
In order to further eliminate the possibility of erroneous determination, the magnitude of the second predetermined value may be changed according to the magnitude of the thermal load outside the air-conditioned space.

  Further, in order to avoid the burn-in of the compressor, when it is determined that the refrigerant pressure detected by the refrigerant pressure detector before starting the compressor is lower than a predetermined pressure value, the compressor is It is better not to start.

  As described above, according to the present invention, when the difference between the temperature detected by the evaporator temperature detector and the target temperature set by the target temperature setting means becomes equal to or greater than the first predetermined value, the refrigeration cycle. Tentatively determined that the amount of refrigerant in the tank is insufficient, and was detected by the first refrigerant saturation pressure (or first refrigerant saturation temperature) derived from the thermal load detected by the external thermal load detector and the refrigerant pressure detector. When the difference from the second refrigerant saturation pressure (or the second refrigerant saturation temperature determined from the second refrigerant saturation pressure), which is the pressure of the refrigerant, exceeds the second predetermined value, the refrigerant amount in the refrigeration cycle When the shortage is provisionally determined and both of these provisional determinations are made, the shortage determination of the refrigerant amount in the refrigeration cycle is fixed, so that even if the refrigerant amount in the refrigeration cycle is appropriate, the refrigerant amount is insufficient. It is possible to prevent erroneous determination

  In addition, since the determination by the first determination unit and the determination by the second determination unit can be performed at the same time, it is possible to instantaneously perform the determination result of whether or not the refrigerant amount is insufficient in the refrigeration cycle. It becomes possible to accurately determine whether or not the refrigerant amount is insufficient in time.

  In addition, a pressure sensor arranged in the high-pressure side flow path of the refrigerant as a refrigerant pressure detector, an evaporator thermosensor as an evaporator temperature detector, an outside temperature sensor as an external heat load detector, and a vehicle interior as an internal heat load detector Conventionally used sensors such as a temperature sensor can be used, so that additional parts can be dispensed with, and an increase in cost can be avoided.

  Here, the size of the second predetermined value (threshold value for determining the shortage of the refrigerant amount of the second determination means) is changed in accordance with the size of the heat load outside the air-conditioned space. Whether or not the refrigerant amount is insufficient can be appropriately determined according to the heat load outside the space, and the possibility of erroneous determination can be further eliminated.

  In addition, when the refrigerant pressure before starting the compressor is lower than a predetermined pressure value, by not starting the compressor, it is determined before starting the compressor that the refrigerant is short enough to burn the compressor. It is possible to avoid the disadvantage that the compressor operates and burns in.

FIG. 1 is a diagram showing an overall configuration of a refrigeration cycle mounted on a vehicle. FIG. 2 is a processing flow for determining the shortage of the refrigerant amount in the refrigeration cycle. FIG. 3 is a characteristic diagram showing a change in the temperature of the evaporator during the cycle operation (or the air temperature immediately after passing through the evaporator) with respect to the change in the refrigerant amount in the refrigeration cycle. FIG. 4 is a characteristic diagram showing a change in refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during cycle operation with respect to a change in refrigerant amount in the refrigeration cycle. FIG. 5 is another processing flow for determining the shortage of the refrigerant amount in the refrigeration cycle. FIG. 6 is a characteristic diagram showing a change in refrigerant temperature (refrigerant saturation temperature) in the high-pressure side line during cycle operation with respect to a change in refrigerant amount in the refrigeration cycle. FIG. 7 is a characteristic diagram showing the relationship between the amount of refrigerant in the refrigeration cycle and the temperature of the evaporator during cycle operation (or the air temperature immediately after passing through the evaporator). It is a figure explaining the conventional method to determine. FIG. 8 is a characteristic diagram showing the relationship between the refrigerant amount in the refrigeration cycle and the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during the cycle operation, and shows a conventional method for determining whether or not the refrigerant amount is insufficient. It is a figure explaining.

  Hereinafter, the refrigerant shortage determination device of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a vehicle air conditioner mounted on a vehicle.
The vehicle air conditioner 1 includes an HVAC unit 2, a refrigeration cycle 3, and a control unit 4 that monitors and controls the refrigeration cycle 3.

  The HVAC unit 2 is disposed closer to the cabin room than a fire board (not shown) that partitions the engine room and the cabin of the vehicle, and includes an air conditioning case 21 in which an air flow path is formed. The air conditioning case 21 houses an evaporator 34 constituting a part of the refrigeration cycle 3 and a heat exchanger for heating (not shown) that uses engine cooling water as a heat source, and is upstream of the evaporator 34 in the air flow path. The blower 22 is arranged in the front.

  Further, an intake door (not shown) that switches the inlet of the air introduced into the air-conditioning case 21 between the outside air inlet and the inside air inlet is arranged upstream of the blower 22. Therefore, air is introduced into the air conditioning case through the outside air inlet or the inside air inlet selected by the intake door by the rotation of the blower 22, and the introduced air is pumped to the downstream side of the air flow path.

  The refrigeration cycle 3 includes a compressor 31 that rotates by receiving power from a traveling engine (not shown), a condenser 32 that radiates and condenses the high-temperature and high-pressure refrigerant compressed by the compressor 31, and the condenser 32. An expansion device 33 that decompresses the cooled refrigerant to form a low-temperature and low-pressure gas-liquid mixed refrigerant, and an evaporation housed in the air conditioning case 21 that evaporates and vaporizes the low-temperature and low-pressure gas-liquid mixed refrigerant sent from the expansion device 33. The unit 34 is connected by piping in this order.

  The compressor 31 has a pulley 31a that is belt-driven as the traveling engine rotates, and the pulley 31a and the rotation shaft of the compressor 31 are connected and disconnected via an electromagnetic clutch 31b. Drive is controlled. Further, when the compressor 31 is a variable capacity type, a capacity variable mechanism for controlling the discharge capacity of the compressor 31 based on an external control signal is provided.

  Therefore, when the compressor 31 is operated and the refrigerant in the refrigeration cycle 3 is sucked into the compressor 31 and compressed, the refrigerant compressed by the compressor 31 dissipates heat and condenses in the condenser 32, and has a low temperature and high pressure. The refrigerant expands in the expansion device 33 and is supplied to the evaporator 34 as a low-temperature and low-pressure refrigerant, which absorbs heat from the air passing through the evaporator 34 and evaporates, and is then sucked into the compressor 31 again. Is done.

  The control unit 4 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input / output port (I / O), and the like (not shown), and turns on and off the electromagnetic clutch 31b of the compressor 31. A control signal to be controlled is formed, and the refrigerant amount in the refrigeration cycle 3 is monitored.

That is, the refrigerant pressure detection sensor 41 for detecting the refrigerant pressure (Pref) in the high-pressure side line of the refrigeration cycle 3 (the refrigerant path from the discharge port of the compressor 31 to the expansion device 33 via the condenser 32), and the evaporator 34 An evaporator temperature detection sensor 42 which is disposed between the fins of the two or near the downstream side of the evaporator 34 and detects the temperature of the evaporator 34 or the air temperature (Tev) immediately after passing through the evaporator 34; Set by signals from sensors such as an outside air temperature detection sensor 43 for detecting the temperature (Tamb), a vehicle interior temperature detection sensor 44 for detecting the vehicle interior temperature (Tinc), and the operation of the temperature setting unit 46 on the operation panel 45. The set temperature (Tset) is input, various input signals are processed in accordance with a predetermined program given to the memory, and the electromagnetic clutch 31b of the compressor 31 is controlled to be turned on / off via the drive circuit 47. Rutotomoni, and so as to monitor the amount of refrigerant in the refrigeration cycle 3.
Here, the pressure of the high-pressure side line detected by the refrigerant pressure detection sensor 41 is provided, for example, in a pipe between the discharge port of the compressor 31 and the condenser 32 or between the condenser 32 and the expansion device 33. It may be detected by a pressure sensor (in this example, provided in a pipe between the condenser 32 and the expansion device 33).

  The refrigerant shortage determination device according to the present invention is provided separately from the refrigeration cycle 3 based on information from the above-described various sensors and the temperature setting unit 46 mounted on the vehicle air conditioner and the vehicle. Or it is comprised by the control unit 4 integrated with the refrigerating cycle 3 as an apparatus which performs the following processes.

  In FIG. 2, a processing example by the control unit 4 is shown as a flowchart. Hereinafter, the control operation of the compressor 31 and the determination of the refrigerant amount shortage in the refrigeration cycle 3 will be described based on this flowchart.

  The processing example shown here is executed after a predetermined initial setting after the ignition switch is turned on. First, in step 50, the refrigerant pressure (refrigeration cycle) of the high-pressure side line detected by the refrigerant pressure detection sensor 41 is used. It is determined whether or not (refrigerant pressure Pref in the equilibrium state at the time of stopping) is lower than a predetermined allowable refrigerant pressure γ. In Step 50, when Pref is lower than the predetermined refrigerant pressure γ, the refrigerant amount in the refrigeration cycle 3 has decreased to an unacceptable level. Therefore, when the compressor 31 is started as it is, the compressor 31 Therefore, a warning indicating that the refrigerant is insufficient is issued to call attention (step 52), and the compressor 31 is not operated and the stopped state is maintained (step 54).

  On the other hand, if it is determined in step 50 that the refrigerant pressure Pref in the high-pressure side line is equal to or higher than the predetermined pressure γ, there is no fear of seizure even if the compressor 31 is operated. Is started (step 56), and it is determined whether or not the difference between the temperature Tev detected by the evaporator temperature detection sensor 42 and the target temperature To is a predetermined value: α or more (Tev−To ≧ α) (step). 58).

The target temperature To is calculated by the following equation (1), for example, the outside air temperature (Tamb) detected by the outside air temperature detection sensor 43, and the vehicle interior temperature detected by the vehicle interior temperature detection sensor 44. (Tinc) and the target temperature of the air just after passing through the evaporator calculated by the set temperature (Tset) set via the temperature setter 46.
To = A · Tset + B · Tamb + C · Tinc + D (1)
Here, A, B, and C are calculation constants for weighting the respective signals, and D is a correction term. As described above, the target temperature To is calculated using not only the outside air temperature (Tamb) detected by the outside air temperature detecting sensor 43 but also the vehicle interior temperature (Tinc) and the set temperature (Tset). Even when the hot air is transmitted to the outside air temperature detection sensor 43 and the outside air temperature detection sensor 43 does not detect the accurate outside air temperature, the amount of deviation from the accurate temperature is limited.

  This step 58 constitutes a first determination means for temporarily determining the shortage of the refrigerant amount in the refrigeration cycle 3, and the temperature Tev detected by the evaporator temperature detection sensor 42 as a shortage of the refrigerant amount in the refrigeration cycle 3. Is to be evaluated based on

  That is, as shown in FIG. 3, when the relationship between the refrigerant amount in the refrigeration cycle 3 and the temperature of the evaporator 34 during the cycle operation (or the air temperature immediately after passing through the evaporator 34) is seen, When the heat load is not high, as shown by the solid line, when the compressor 31 is a fixed capacity type, the cycle operation is almost proportional to the refrigerant amount gradually decreasing from the proper state. The temperature of the evaporator 34 at the time (or the air temperature immediately after passing through the evaporator 34) becomes higher. Further, even when the compressor is of a variable capacity type, the target temperature To can be maintained even if the amount of refrigerant is insufficient within the range in which the capacity can be varied. If the pressure decreases so as to become unacceptable, the temperature of the evaporator 34 during the cycle operation (or the air temperature immediately after passing through the evaporator 34) increases in proportion to the decrease in the refrigerant amount. Therefore, when the heat load is not high, whether or not the actual temperature of the evaporator 34 (or the air temperature immediately after passing through the evaporator 34) has increased from the target temperature To beyond a predetermined allowable range: α. If it is determined, whether or not the refrigerant amount is insufficient can be captured.

  Therefore, in step 58, when the difference between the temperature Tev detected by the evaporator temperature detection sensor 42 and the target temperature To is smaller than the first predetermined value: α, the difference is detected by the evaporator temperature detection sensor 42. Since the deviation of the temperature from the target temperature To is within the allowable range, the refrigerant amount in the refrigeration cycle 3 is considered to be within the appropriate range, and a normal state such as displaying the normal state is performed. Operation continues (step 60).

  However, when the outside air temperature is high and the heat load is high (when the external heat load is high), the amount of heat dissipated in the condenser 32 becomes insufficient, and even if the amount of refrigerant in the refrigeration cycle 3 is appropriate, evaporation occurs. If the temperature of the vessel 34 (or the air temperature immediately after passing through the evaporator 34) does not reach the target temperature To and becomes higher than the target temperature To exceed the predetermined allowable range α, as indicated by the broken line, an error occurs. Therefore, it may be determined that the refrigerant amount is insufficient.

  Therefore, if it is determined in step 58 that the difference between the temperature Tev detected by the evaporator temperature detection sensor 42 and the target temperature To is equal to or greater than the first predetermined value: α, the refrigerant in the refrigeration cycle 3 Although there is a possibility that the amount is insufficient, it is not clear whether this determination result is due to a lack of refrigerant amount in the refrigeration cycle 3 or due to heat load. The determination that the amount of refrigerant in the cycle is insufficient is not confirmed and the routine proceeds to step 62.

In step 62, the refrigerant saturation pressure (first refrigerant saturation pressure P _HL ) derived from the outside air temperature (Tamb) detected by the outside air temperature detection sensor 43 and the refrigerant in the high-pressure side line detected by the refrigerant pressure detection sensor 41 are detected. Whether or not the difference between the pressure (the refrigerant pressure of the high-pressure side line when the compressor is in operation and the second refrigerant saturation pressure Psa) is a second predetermined value: β1 or more (P _HL− Psa ≧ β1) is determined (step 62).

  This step 62 constitutes a second determination means for temporarily determining the shortage of the refrigerant amount in the refrigeration cycle 3, and the refrigeration cycle 3 in which the refrigerant pressure detection sensor 41 detects the shortage of the refrigerant amount in the refrigeration cycle 3. Is to be evaluated based on the pressure Psa of the high-pressure side line.

  That is, as shown in FIG. 4, when the relationship between the refrigerant amount in the refrigeration cycle 3 and the refrigerant pressure in the high-pressure side line during the cycle operation is seen, at the time of low heat load where the outside air temperature is low (external heat load is If the compressor is a fixed capacity type, the refrigerant amount in the refrigeration cycle gradually decreases from the proper state as shown by the solid line (when it is not high). The refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line of the refrigerant is lower than the refrigerant saturation pressure (refrigerant saturation pressure when the amount of refrigerant is appropriate) derived from the outside air temperature. Further, even when the compressor is a variable capacity type, it is possible to maintain the saturation pressure when the refrigerant amount is appropriate, even if the refrigerant amount is insufficient, within the range in which the capacity can be varied. When the amount of refrigerant in the refrigeration cycle decreases to a point where it cannot be handled with variable capacity, the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during cycle operation is also derived from the outside air temperature in proportion to the decrease in refrigerant amount. It becomes lower than the saturation pressure (refrigerant saturation pressure when the amount of refrigerant is appropriate). Therefore, if the heat load is not high, whether or not the refrigerant amount is insufficient is determined by determining whether or not the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during the cycle operation has fallen below the appropriate range: β1. Can be captured.

  Even when the outside air temperature is high and the heat load is high (even when the external heat load is high), if the refrigerant amount in the refrigeration cycle gradually decreases from the appropriate state, as shown by the broken line, it is almost proportional to it. Then, the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line during the cycle operation is lower than the refrigerant saturation pressure (refrigerant saturation pressure when the amount of refrigerant is appropriate) derived from the outside air temperature. If it is determined whether or not the refrigerant pressure (refrigerant saturation pressure) in the high-pressure side line has fallen below the appropriate range: β1, it is possible to detect whether or not the refrigerant amount is insufficient (the determination is based on fluctuations in the heat load). No variation occurs).

Therefore, in step 62, the refrigerant saturation pressure (first refrigerant saturation pressure P _HL ) derived from the outside air temperature Tam detected by the outside air temperature detection sensor 43 and the refrigerant pressure in the high-pressure side line detected by the refrigerant pressure detection sensor 41. When it is determined that the difference from (second refrigerant saturation pressure Psa) is smaller than the second predetermined value: β1, the refrigerant pressure Psa of the high-pressure side line is detected by the outside air temperature detection sensor 43. since even deviate within the allowable range from the refrigerant saturation pressure P _HL derived from the difference between the detected temperature Tev and the target temperature to the evaporator temperature sensor 42 in step 58 is the first predetermined value : Despite being determined to be greater than or equal to α, it has been confirmed that this determination result is not due to a shortage of refrigerant amount, so the refrigerant amount in the refrigeration cycle is determined to be within the appropriate range. The normal operation is continued (step 60).

In contrast, in step 62, the refrigerant saturation pressure (first refrigerant saturation pressure P _HL ) derived from the outside air temperature detected by the outside air temperature detection sensor 43 and the refrigerant in the high-pressure side line detected by the refrigerant pressure detection sensor 41. Is determined to be equal to or greater than a predetermined value: β1, the refrigerant saturation pressure derived from the heat load outside the passenger compartment and the actual refrigerant pressure in the high-pressure side line are determined. Even if it is determined whether or not the refrigerant amount is insufficient based on the difference between the refrigerant amount and the refrigerant amount in the refrigeration cycle is determined to be insufficient, there is no doubt that the refrigerant amount in the refrigeration cycle is insufficient. And confirming that the amount of refrigerant is insufficient (step 64), indicating that the refrigerant is insufficient on the operation panel 45 or indicating that the refrigerant is insufficient. Sent an alarm Reminders, such as to carry out (step 66).

  Therefore, according to the above refrigerant shortage determination device, even if there is a difference between the temperature Tev detected by the evaporator temperature detection sensor 42 and the target temperature To in step 58, the refrigerant amount of the refrigeration cycle 3 is not necessarily insufficient. In step 62, the determination based on the refrigerant saturation pressure with a small variation in the determination due to the variation in the thermal load (the refrigerant saturation pressure determined based on the thermal load outside the passenger compartment). If the refrigerant shortage condition is satisfied in any of the determinations, the refrigerant shortage condition is determined again by taking into account the refrigerant pressure deficiency state of the high pressure side line from the Since the determination that the refrigerant is insufficient is fixed, it is possible to eliminate erroneous determination.

In the above configuration, when determining whether or not the amount of refrigerant in the refrigeration cycle 3 is insufficient, the temperature of the evaporator that directly affects the cooling capacity or the air temperature immediately after passing through the evaporator is used. The determination to be performed based on the determination (determination by the first determination unit in step 58) is performed first, and then the determination to be performed based on the pressure in the high-pressure side line of the refrigeration cycle 3 (determination by the second determination unit in step 62). ) To confirm the suitability of the determination by the first determination means, so that the inconvenience caused by overconfidence of the determination result can be avoided while placing importance on the determination result evaluated from the cooling capacity of the evaporator. Temporarily, the order of the determination by the first determination means and the determination by the second determination means is reversed, the determination by the second determination means in step 62 is performed first, and then by the first determination means in step 58. When the determination is made and the suitability of the determination by the second determination means is confirmed, the determination result based on the refrigerant pressure of the high-pressure side line that does not directly affect the cooling capacity and constantly varies depending on the vehicle and the surrounding environment is emphasized. Therefore, there is an inconvenience that the shortage of the refrigerant amount cannot be determined with high accuracy.
Therefore, in the present invention, even when warning is given to the occupant, since it is based on the point that the shortage of the refrigerant amount in the refrigeration cycle is caught by the lack of cooling capacity, it can be determined with high accuracy, and the occupant In line with the sense of

Furthermore, in determining whether the refrigerant amount is insufficient, an evaluation based on the temperature of the evaporator (or the air temperature immediately after passing through the evaporator) and an evaluation based on the pressure of the high-pressure side line of the refrigeration cycle (refrigerant saturation pressure) Since it is not necessary to perform the measurement after a certain amount of time, it is possible to perform the determination result as to whether or not the refrigerant amount is insufficient in the refrigeration cycle without taking time.
Moreover, since it is possible to use the existing sensors (refrigerant pressure detection sensor 41, evaporator temperature detection sensor 42, outside air temperature detection sensor 43, vehicle interior temperature detection sensor 44) in determining whether or not the refrigerant amount is insufficient, a new It is not necessary to add a sensor, and it is possible to accurately determine whether or not the amount of refrigerant is insufficient without incurring costs.

In the above configuration, the refrigerant saturation pressure (first refrigerant saturation pressure) derived from the outside air temperature detected by the outside air temperature detection sensor 43 and the refrigerant pressure detection sensor in step 62 as the second determination means. When it is determined that the difference between the refrigerant pressure (second refrigerant saturation pressure) in the high-pressure side line detected by 41 is a predetermined value: β1 or more, a shortage of refrigerant amount in the refrigeration cycle is provisionally determined. However, since the refrigerant saturation pressure and the refrigerant saturation temperature have a uniquely corresponding relationship, as shown in FIGS. 5 and 6, the refrigerant derived from the outside air temperature detected by the outside air temperature detection sensor 43. using saturation pressure refrigerant saturation temperature derived from the outdoor temperature detected by the outside air temperature detection sensor 43 in place of the (first refrigerant saturation pressure) (first refrigerant saturation temperature) T _HL, test the refrigerant pressure sensor 41 It may be used second refrigerant saturation temperature Tsa determined from the second refrigerant saturation pressure Psa instead pressure of the refrigerant on the high pressure side line (second refrigerant saturation pressure).

That is, step 62 shown in FIG. 5 is performed by using the refrigerant saturation temperature (first refrigerant saturation temperature T _HL ) derived from the outside air temperature detected by the outside air temperature detection sensor 43 and the high pressure side detected by the refrigerant pressure detection sensor 41. If it is determined that the difference from the refrigerant saturation temperature (second refrigerant saturation temperature Tsa) determined from the refrigerant pressure in the line is equal to or greater than a predetermined value: β2, it is temporarily determined that the refrigerant amount is insufficient. Then, on the assumption that the refrigerant amount is insufficient in step 58, it is determined that the refrigerant amount in the refrigeration cycle 3 is insufficient (step 64), and the operation panel 45 is determined. The user may be alerted such as displaying the fact that the refrigerant is insufficient or sending an alarm indicating that the refrigerant is insufficient to the passenger (step 66).

  In the above configuration, the example in which the thresholds (β1 and β2) for temporarily determining the shortage of the refrigerant amount are set as predetermined values regardless of the magnitude of the heat load outside the passenger compartment is shown. The threshold value may be changed in accordance with the size of. For example, if the threshold values (β1 and β2) are set to be smaller as the heat load outside the passenger compartment is larger, it is possible to more accurately detect the shortage of the refrigerant amount at a high heat load where the cooling function is important. Thus, by varying the respective threshold values according to the external heat load, it is possible to more accurately determine whether there is a refrigerant shortage, and further reduce the possibility of erroneous determination.

DESCRIPTION OF SYMBOLS 3 Refrigeration cycle 31 Compressor 32 Condenser 33 Expansion device 34 Evaporator 41 Refrigerant pressure detection sensor 42 Evaporator temperature detection sensor 43 Outside temperature detection sensor 44 Car interior temperature detection sensor 46 Temperature setter

Claims (11)

A compressor that compresses the refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion device that depressurizes the refrigerant condensed by the condenser; and an evaporator that evaporates the refrigerant flowing out of the expansion device And a refrigerant shortage determination device used in a refrigeration cycle having:
A refrigerant pressure detector for detecting the pressure of the refrigerant flowing in the refrigerant path between the compressor and the expansion device;
An evaporator temperature detector for detecting the temperature of the evaporator or the air temperature immediately after passing through the evaporator;
An external thermal load detector that detects the thermal load outside the air-conditioned space;
An internal thermal load detector for detecting the thermal load inside the air-conditioned space;
A temperature setter for setting a control temperature of the air-conditioned space;
Passed through the evaporator or the evaporator according to the thermal load detected by the external thermal load detector, the thermal load detected by the internal load detector, and the control temperature set by the temperature setter. Target temperature calculation means for calculating the target temperature of the air immediately after,
When the difference between the temperature detected by the evaporator temperature detector and the target temperature calculated by the target temperature calculating means is equal to or greater than a first predetermined value, it is temporarily determined that the refrigerant amount is insufficient in the refrigeration cycle. First determining means for
The difference between the first refrigerant saturation pressure derived from the thermal load detected by the external thermal load detector and the second refrigerant saturation pressure, which is the refrigerant pressure detected by the refrigerant pressure detector, is equal to or greater than a second predetermined value. A second determination means for temporarily determining the shortage of the refrigerant amount in the refrigeration cycle when
The first determination means tentatively determines that the refrigerant amount in the refrigeration cycle is insufficient, and the second determination means tentatively determines that the refrigerant amount in the refrigeration cycle is insufficient. A refrigerant shortage determination determination means for determining a shortage determination of the refrigerant amount in the refrigeration cycle,
A refrigerant shortage determination device comprising:   The second determination means for temporarily determining the shortage of the refrigerant amount in the refrigeration cycle replaces the first refrigerant saturation pressure with the first refrigerant saturation temperature derived from the thermal load detected by the external thermal load detector. 2. The refrigerant shortage determination device according to claim 1, wherein a second refrigerant saturation temperature determined from the second refrigerant saturation pressure is used instead of the second refrigerant saturation pressure.   The refrigerant shortage determination device according to claim 1 or 2, wherein the second predetermined value is changed in accordance with a heat load outside the air-conditioned space. Further comprising third determination means for determining whether or not the refrigerant pressure detected by the refrigerant pressure detector before starting the compressor is lower than a predetermined pressure value;
4. The compressor according to claim 1, wherein the compressor is not started when it is determined by the third determination means that the refrigerant pressure before starting the compressor is lower than a predetermined pressure value. The refrigerant shortage determination device according to claim 1.   The refrigerant shortage determination device according to claim 1, wherein the compressor is of a fixed capacity type.   The refrigerant shortage determination device according to claim 1, wherein the compressor is a variable capacity type.   The refrigerating cycle provided with the refrigerant | coolant shortage determination apparatus in any one of Claims 1 thru | or 6. A compressor that compresses the refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion device that depressurizes the refrigerant condensed by the condenser; and an evaporator that evaporates the refrigerant flowing out of the expansion device And a refrigeration cycle having
A refrigerant pressure detector for detecting the pressure of the refrigerant flowing in the refrigerant path between the compressor and the expansion device;
A temperature detector for detecting the temperature of the evaporator or the air temperature immediately after passing through the evaporator;
An external thermal load detector that detects the thermal load outside the air-conditioned space;
An internal thermal load detector for detecting the thermal load inside the air-conditioned space;
A temperature setter for setting a control temperature of the air-conditioned space;
Passed through the evaporator or the evaporator according to the thermal load detected by the external thermal load detector, the thermal load detected by the internal load detector, and the control temperature set by the temperature setter. Target temperature calculation means for calculating the target temperature of the air immediately after,
A refrigerant shortage determination method of the refrigeration cycle configured to include:
The difference between the temperature detected by the evaporator temperature detector and the target temperature calculated by the target temperature calculation means is determined to be greater than or equal to a first predetermined value, and the heat detected by the external thermal load detector When the difference between the first refrigerant saturation pressure derived from the load and the second refrigerant saturation pressure, which is the refrigerant pressure detected by the refrigerant pressure detector, is determined to be greater than or equal to a second predetermined value, A refrigerant shortage determination method for a refrigeration cycle, wherein the refrigerant amount is determined to be insufficient.   Instead of the first refrigerant saturation pressure, the first refrigerant saturation temperature derived from the thermal load detected by the external thermal load detector is used, and the first refrigerant saturation pressure is determined from the second refrigerant saturation pressure instead of the second refrigerant saturation pressure. The refrigerant shortage determination method for a refrigeration cycle according to claim 8, wherein the second refrigerant saturation temperature is used.   10. The refrigerant shortage determination method for a refrigeration cycle according to claim 8, wherein the second predetermined value is changed according to a heat load outside the air-conditioned space. 11. The compressor is not started when it is determined that the refrigerant pressure detected by the refrigerant pressure detector before starting the compressor is lower than a predetermined pressure value. The refrigerant shortage determination method for the refrigeration cycle according to any one of the above.

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