JPH07294033A - Cooling cycle controller - Google Patents

Abstract

PURPOSE:To maintain the optimum operation of a cooling cycle by calculating the optimum high pressure of refrigerant by detecting the temperature of the refrigerant flowing through a high-pressure passage between a compressor and an expansion valve and controlling the opening of the valve in response to a difference from the actual high pressure. CONSTITUTION:The cooling cycle controller comprises high-pressure detecting means 100 for detecting the pressure of refrigerant flowing through a high pressure passage from the discharge side of a compressor to the inlet side of an expansion valve, and refrigerant temperature detecting means 110 for detecting the temperature of the refrigerant flowing through the passage. The optimum high pressure of the refrigerant flowing through the passage is calculated from the detected temperature by optimum high-pressure calculating means 120, and the calculated optimum high pressure is compared with the detected pressure by high pressure deciding means 130. If it is decided from the comparison result that the detected pressure is larger than the optimum high pressure, the opening of the valve 4 in the cycle is controlled to be increased by expansion valve control means 140, while if it is decided that the detected pressure is smaller than the optimum pressure, the opening of the valve 4 is controlled to be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling cycle control device for controlling a cooling cycle which is provided in a vehicle air conditioner or a domestic air conditioner and uses carbon dioxide as a refrigerant.

[0002]

2. Description of the Related Art As a conventional cooling cycle control device,
For example, as disclosed in Japanese Unexamined Patent Publication No. 4-161759, a compressor that compresses a refrigerant, a condenser that condenses a high-pressure refrigerant, an expansion valve that expands the condensed refrigerant, and a refrigerant that becomes wet vapor are vaporized. At least composed of an evaporator, especially in the current automobile air conditioner, the refrigerant is CFC (for example,
Those using R-12, R-134a) are known.

[0003]

[SUMMARY OF THE INVENTION However, Freon, in order to turn out problems destruction of large greenhouse and ozone layer when released into the atmosphere, in the present application, carbonic acid gas as the refrigerant (CO ₂ ) Is used, and it is assumed that the system configuration is based on the current cooling cycle. However, carbon dioxide (CO ₂ ) has a low critical temperature (about 31 ° C.) and cannot be condensed and liquefied in a condenser in a normal operating temperature range, so that sufficient capacity and efficiency cannot be secured.

For this reason, in the present invention, when carbon dioxide gas is used as a refrigerant, attention is paid to the fact that there is an optimum high pressure value that is efficient with respect to the refrigerant temperature at the condenser outlet side, and the present cooling cycle An object of the present invention is to provide a cooling cycle control device capable of ensuring cooling capacity and efficiency with the same system configuration.

[0005]

Therefore, according to the invention of claim 1, as shown by a solid arrow in FIG. 1, a compressor for compressing a refrigerant made of carbon dioxide gas and a refrigerant compressed by this compressor are cooled. A condenser, an expansion valve 4 that expands the refrigerant cooled by the condenser, and an evaporator that cools the passing air by the endothermic action of the refrigerant expanded by the expansion valve 4 are connected in series by pipe connection. In the cooling cycle,
High pressure detection means 100 for detecting the pressure of the refrigerant flowing in the high pressure passage from the discharge side of the compressor to the inflow side of the expansion valve, and the condenser outlet side high pressure passage from the outflow side of the condenser to the inflow side of the expansion valve. Refrigerant temperature detecting means 110 for detecting the temperature of the refrigerant flowing through, an optimum high pressure calculating means 120 for calculating the optimum high pressure of the refrigerant flowing through the high pressure passage from the refrigerant temperature detected by the refrigerant temperature detecting means 110, and the high pressure. The high pressure detected by the detecting means 100 is the optimum high pressure calculating means 120.
High pressure determination means 130 for determining whether the pressure is higher than the optimum high pressure calculated by
When the high pressure detected by the high pressure detecting means 110 is determined to be large by 30, the opening degree of the expansion valve 4 is increased, and the high pressure determining means 130 detects the high pressure by the high pressure detecting means 110. The expansion valve control means 140 is provided to reduce the opening degree of the expansion valve 4 when it is determined that the high pressure is small.

Further, the invention according to claim 2 is, as shown by a broken line arrow in FIG. 1, a compressor for compressing a refrigerant composed of carbon dioxide gas, a condenser for cooling the refrigerant compressed by the compressor, and this condenser. Expansion valve 4 for expanding the refrigerant cooled by the expansion valve 4
In a cooling cycle configured by piping connection of at least an evaporator that cools passing air by the endothermic action of the refrigerant expanded by the refrigerant flowing through a high-pressure passage from the discharge side of the compressor to the inflow side of the expansion valve. High pressure detecting means 100 for detecting the pressure of the refrigerant, a refrigerant temperature detecting means 110 for detecting the temperature of the refrigerant flowing in the high pressure passage on the condenser outlet side from the outlet side of the condenser to the inlet side of the expansion valve, and the refrigerant temperature detection. Means 110
The refrigerant temperature determination means 150 for determining whether the refrigerant temperature detected by the refrigerant temperature is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas, and the refrigerant temperature determination means 150 determines whether the refrigerant temperature is equal to or higher than the predetermined temperature. In some cases, the optimum high pressure calculating means 120 for calculating the optimum high pressure of the refrigerant flowing through the high pressure passage from the refrigerant temperature and the high pressure detected by the high pressure detecting means 110 are calculated by the optimum high pressure calculating means. When the refrigerant temperature determining means 150 for determining whether the refrigerant temperature is higher than the optimum high pressure and the refrigerant temperature determining means 150 determines that the refrigerant temperature is lower than a predetermined temperature, the opening degree of the expansion valve 4 is opened to a predetermined value. When the high pressure detected by the high pressure detecting means 110 is determined to be large, Expansion for increasing the opening degree of the expansion valve 4 and decreasing the opening degree of the expansion valve 4 when the high pressure determining means 130 determines that the high pressure detected by the high pressure detecting means 110 is small. The valve control means 140 is provided.

[0007]

Therefore, according to the first aspect of the invention, the temperature of the refrigerant flowing through the condenser outlet side high pressure passage extending from the condenser outlet side to the expansion valve 4 inlet side is detected by the refrigerant temperature detecting means 110. The optimum high pressure of the refrigerant flowing through the high pressure passage is calculated from the refrigerant temperature by the optimum high pressure calculating means 120, and the high pressure of the high pressure passage detected by the high pressure detecting means 100 is calculated by the optimum high pressure calculating means 120. The high pressure determination unit 130 determines whether the pressure is higher than the optimum high pressure. As a result,
When it is determined that the high pressure is high, the expansion valve control means 140 controls the opening degree of the expansion valve 4 in a direction to increase the high pressure. If it is determined that the high pressure is small, the expansion valve control means 140 controls the opening degree of the expansion valve 4 to decrease,
Increase high pressure. As a result, the high pressure can be controlled so as to always match the optimum pressure, so that the above object can be achieved.

According to the second aspect of the present invention, it is determined whether the refrigerant temperature detected by the refrigerant temperature detecting means 110 is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide. The temperature determining means 150 is provided, and when the refrigerant temperature determining means 150 determines that the refrigerant temperature is equal to or higher than a predetermined temperature, the optimum high pressure calculating means 120 calculates the optimum high pressure, and the refrigerant temperature is lower than the predetermined temperature. When it is determined that the expansion valve control means 140 fixes the opening degree of the expansion valve 4 to a predetermined opening degree, the refrigerant temperature range in which the optimum high pressure significantly exists with respect to the refrigerant temperature, specifically, When it is determined that the high pressure is large in the temperature range equal to or higher than the predetermined temperature set near the critical temperature of carbon dioxide, the expansion valve control means 14
If the high pressure is determined to be small by controlling the opening degree of the expansion valve 4 to be increased by 0, and the high pressure is small, the opening degree of the expansion valve 4 is determined by the expansion valve control means 140. It was decided to control to decrease the pressure and to increase the high pressure. When the temperature is not higher than the predetermined temperature, the expansion valve is fixed at a predetermined opening. As a result, an efficient cooling cycle operation can be performed corresponding to a wide range of refrigerant temperature.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

A cooling (refrigerating) cycle 1 shown in FIG. 2 is installed in, for example, an air conditioning system for a vehicle. A compressor 2, a condenser 3, an expansion valve 4, an evaporator 5, and an accumulator 6 are connected in series by piping. It is composed.

Since the compressor 2 uses carbon dioxide as the refrigerant of the cooling cycle 1, it is necessary to use a compressor having a large discharge pressure and good pressure resistance. The discharge side of the compressor 2 is connected to the inflow side of the condenser 3 by a pipe forming a first high pressure passage 8, and the outflow side of the condenser 3 constitutes a condenser outlet side high pressure passage (second high pressure passage) 9. Is connected to the inflow side of the expansion valve 4. The first high-pressure passage 8 and the second high-pressure passage 9 form a high-pressure passage.

The expansion valve 4 is, for example, a proportional solenoid valve,
The opening of the flow path can be adjusted in proportion to the output from the control unit 7. The outlet side of the expansion valve 4 is an evaporator 5 arranged on the air flow path of the air conditioner.
Connected to the inflow side of.

The outflow side of the evaporator 5 is connected to the inflow side of the accumulator 6. The discharge side of the accumulator 6 is connected to the suction side of the compressor 2, and temporarily stores the refrigerant flowing out from the evaporator 5 and performs gas-liquid separation.

In the cooling cycle 1, the compressor 2 passes through the accumulator 6 and the gas refrigerant (carbon dioxide gas).
Inhale and compress. This compression stroke is shown by M _{1 to} M ₂ in the Mollier diagram of FIG. 6, and both the enthalpy (i) and the pressure (P) of the sucked refrigerant increase. The characteristic line from M _{1 to} M ₂ ideally rises along the isentropic curve. After that, the refrigerant is sent to the condenser 3 and radiates heat, so that the enthalpy (i) is reduced. This heat dissipation process is indicated by M _{2 to} M ₃ . In a normal cooling cycle, condensation and liquefaction are performed in this heat release step, but in the case of carbon dioxide gas, it does not condense and liquefy in this step because the critical temperature is low (about 31 ° C).

After that, the heat-dissipated refrigerant whose temperature has dropped is expanded by passing through the expansion valve 4. The expansion stroke is indicated by M ₃ ~M _6. In this expansion stroke, the pressure of the refrigerant decreases as it passes through the expansion valve 4.
Along with this decrease in pressure, it changes to wet steam at the stage (M ₅ ) when it passes through the saturated liquid line L ₁ . In the wet vapor state, the heat of the air sent to the evaporator 5 and passing through the evaporator 5 is absorbed and vaporized. This evaporation process is M
_{6 to} M ₁ . The degree of superheat between M ₁₁ and M ₁ is superheat for preventing liquid back to the compressor 2. In the present embodiment, this degree of superheat is close to zero.

With the above process, the heat absorbed from the evaporator 5 can be dissipated from the condenser 3, so that the air passing through the evaporator 5 can be cooled.

Further, in the cooling cycle 1, the pressure sensor 10 for detecting the high pressure of the refrigerant is attached to the high pressure passage (the first high pressure passage 8 and the second high pressure passage 9) and the second high pressure. A temperature sensor 11 for detecting the temperature of the refrigerant is attached on the passage 9. In this embodiment, the pressure sensor 10 is provided in the vicinity of the inflow side of the condenser 3, and the temperature sensor 11 is equipped with the temperature sensor 11 for detecting the temperature of the refrigerant in the vicinity of the outflow side of the condenser 3. Has been. These sensors 10, 11
Pressure (P _R ) and refrigerant temperature (t) detected from
Is sent to the control unit 7.

The invention of the present application in the cooling cycle 1 described above will be explained with reference to FIGS. 1 and 2. A compressor 2 for compressing a refrigerant made of carbon dioxide gas, and a condenser 3 for cooling the refrigerant compressed by the compressor 2. An air-conditioning system in which an expansion valve 4 for expanding the refrigerant cooled by the condenser 3 and an evaporator 5 for cooling the air passing therethrough by the heat absorbing action of the refrigerant expanded by the expansion valve 4 are pipe-connected at least in series. In cycle 1, a pressure sensor as high pressure detection means 100 for detecting the pressure of the refrigerant flowing through the first high pressure passage 8 and the second high pressure passage 9 from the discharge side of the compressor 2 to the inflow side of the expansion valve 4. 10 and the capacitor 3
Temperature detecting means 1 for detecting the temperature of the refrigerant flowing through the second high-pressure passage 9 from the outflow side of the expansion valve 4 to the inflow side of the expansion valve 4.
A temperature sensor 11 serving as a reference numeral 10, an optimum high pressure calculating means 120 for calculating the optimum high pressure of the refrigerant flowing through the first high pressure passage 8 from the refrigerant temperature detected by the refrigerant temperature detecting means 110, and the high pressure detecting means 100. High pressure determination means 130 for determining whether or not the high pressure detected by the high pressure is greater than the optimum high pressure calculated by the optimum high pressure calculation means 120, and the high pressure determination means 130.
When it is determined that the high pressure is large, the expansion valve 4 is controlled to increase the opening degree of the expansion valve 4, and when the high pressure determination unit 130 determines that the high pressure is small, An expansion valve control means 140 for controlling the expansion valve 4 in the direction of closing the opening of the expansion valve 4 is provided.

Further, there is provided a refrigerant temperature judging means 150 for judging whether or not the refrigerant temperature detected by the refrigerant temperature detecting means 110 is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas. If the determination means 150 determines that the refrigerant temperature is equal to or higher than the predetermined temperature, the optimum high pressure calculation means 120 calculates the optimum high pressure, and if the refrigerant temperature is determined to be lower than the predetermined temperature, the expansion valve. This is because the opening of the expansion valve 4 is fixed to a predetermined opening by the control means 140.

The above invention is more specifically shown by the flow charts shown in FIGS. 3A and 3B, and is executed as a part of the air conditioning control executed by the control unit 7. Hereinafter, description will be given according to this flowchart.

In the flowchart shown in FIG. 3A, first, in step 200, the high pressure P _{R of} the first high pressure passage 8 detected by the pressure sensor 10 and the second high pressure passage 9 detected by the temperature sensor 11 of the second high pressure passage 9 are detected. Refrigerant temperature t
Is entered. The high pressure P _R indicates the pressure at the positions indicated by M ₂ , M ₂₁ , and M ₂₂ in the Mollier diagram of FIG. 6, and the refrigerant temperature t is M ₃ , M ₃₁ , M ₃₂ , and M ₃₃ . The temperature at the indicated position is shown.

Thereafter, at step 220, the optimum high pressure P _X corresponding to the refrigerant temperature t is calculated. As shown in the Mollier diagram of FIG. 6, the optimum high pressure is such that when the refrigerant temperature t is constant, for example, when the high pressure drops from M ₂₁ to M ₂ , the outflow side temperature of the condenser 3 is approximately M _31. ~
It descends along the isotherm of M ₃₃ . For this reason, M ₆ ~
Cooling capacity of the evaporator 5 represented by M ₁₁ is M ₆₃ ~M ₁₁
Therefore, it will decrease. For this reason, the optimum high pressure P _X exists for the refrigerant temperature t.

Optimal high pressure P _x in step 220
Is calculated by, for example, a predetermined refrigerant temperature t (t ₁ , t ₂ ,
optimum pressure P _X indicating the maximum efficiency for t ₃₎ (P _X1, P
_X2 , P _X3 , P _X4 ) are calculated in correspondence with the map shown in the characteristic diagram of FIG. The optimum pressure P _X calculated by this is the high pressure P in step 230.
Compared to _R.

In the comparison of step 230, when the high pressure P _R is larger than the optimum high pressure P _X , for example, as shown in FIG.
As shown in, when the high pressure P _R indicates the pressure value P _C and is larger than the optimum high pressure P _X2 , the routine proceeds to step 240, where the opening degree OR of the expansion valve 4 is controlled in the direction (+ α) to open the predetermined value. . As a result, the high-pressure pressure on the upstream side of the expansion valve 4 decreases, and the refrigerant temperature also decreases accordingly.
State of the refrigerant can shift point C (pressure P _C, temperature t _c) to the point D in the optimum temperature characteristic line from (pressure P _D, the temperature t _D).

Further, in the comparison of step 230,
When the high pressure P _R is smaller than the optimum high pressure P _X , for example, as shown in FIG. 5, when the high pressure P _R indicates the pressure value P _A and is smaller than the optimum high pressure P _X1 , the routine proceeds to step 250, where the expansion valve The opening degree OR of 4 is controlled in the direction of closing a predetermined value (-α). As a result, the high pressure on the upstream side of the expansion valve 4 rises, and the refrigerant temperature rises accordingly. Therefore, the state of the refrigerant changes from point A (pressure P _A , temperature t _A ) to B on the optimum temperature characteristic line. It is possible to move to a point (pressure P _B , temperature t _B ). As a result, the optimum cooling cycle operation can be performed in the temperature range normally used.

Further, in the flow chart shown in FIG. 3B, after the refrigerant pressure P _R and the refrigerant temperature t are input in step 200, it is determined in step 210 whether the refrigerant temperature t is higher than a predetermined temperature t _s. Make a decision. This predetermined temperature t _s is the critical temperature of carbon dioxide gas of about 31 °.
It is set near C (for example, 30 ° C.). As shown by t ₄ in the characteristic diagram of FIG. 4, this is a characteristic that when the refrigerant temperature is below the critical temperature, the higher the high pressure is, the lower the efficiency becomes, as in the normal cooling cycle. This is to show a diagram. Therefore, in the determination of step 210, when the refrigerant temperature t is equal to or lower than the predetermined temperature t _s , the routine proceeds to step 260, where the opening degree OR of the expansion valve 4 is set to the predetermined opening degree β.

When the refrigerant temperature t is equal to or higher than the predetermined temperature t _s in the determination of step 210, the expansion valve control shown in FIG. 3 (a) is executed.
From the above, when the refrigerant temperature is lower than or equal to the predetermined temperature, the opening degree of the expansion valve is fixed, and when the refrigerant temperature is higher than or equal to the predetermined temperature, the expansion valve control described above is executed. It is possible to perform an efficient cooling cycle operation in a wider refrigerant temperature range than the cycle.

[0028]

As described above, according to the first aspect of the invention, the temperature of the refrigerant flowing through the second high pressure passage extending from the outlet side of the condenser to the inlet side of the expansion valve is detected, and the temperature of the refrigerant is detected. From this, the optimum high pressure of the refrigerant flowing through the high pressure passage is calculated, and it is determined whether or not the actual high pressure of the high pressure passage is higher than the optimum high pressure. As a result, when it is determined that the actual high pressure is large, the opening degree of the expansion valve is controlled to be increased to reduce the high pressure. When it is determined that the high pressure is small, the opening degree of the expansion valve is controlled so as to be small and the high pressure is increased. This makes it possible to match the high pressure to the optimum pressure, so that even when carbon dioxide is used as a refrigerant, it can be installed in an air conditioner with the same system configuration as the current one, reducing costs and reducing man-hours. In addition to being able to be executed, the operation of the optimum cooling cycle can be maintained.

According to the second aspect of the invention, it is determined whether the refrigerant temperature is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide, and it is determined that the refrigerant temperature is equal to or higher than the predetermined temperature. When the refrigerant temperature is determined to be lower than the predetermined temperature, the optimum high pressure is significantly increased with respect to the refrigerant temperature by fixing the expansion valve opening to the predetermined opening. The expansion valve control is executed in a refrigerant temperature range existing in the above, specifically, in a temperature range of a predetermined temperature or higher set near the critical temperature of carbon dioxide. In particular,
When it is determined that the high pressure is large, the expansion valve is controlled so as to increase its opening degree, and the high pressure is decreased, and when the high pressure is determined to be small, the expansion valve opening degree is changed. It was decided to control to decrease the pressure and to increase the high pressure. Further, when the refrigerant temperature is equal to or lower than the predetermined temperature, the expansion valve is fixed to a predetermined opening degree. As a result, expansion valve control can be performed over a wide range of refrigerant temperature, and even if carbon dioxide is used as a refrigerant, it can be installed in an air conditioner with the same system configuration as the current one, thus reducing costs. It is possible to reduce the number of man-hours and man-hours, and to maintain the optimum operation of the cooling cycle.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a configuration explanatory view showing a configuration of a cooling cycle according to an embodiment of the present invention.

FIG. 3 (a) is a flowchart according to the first invention, and FIG. 3 (b) is a flowchart for cutting according to the second invention.

FIG. 4 is a characteristic diagram showing a map for calculating an optimum high pressure.

FIG. 5 is a characteristic diagram illustrating a correction state.

FIG. 6 is a Mollier diagram showing a cooling cycle according to the embodiment of the present invention.

[Explanation of symbols]

 1 Cooling Cycle 2 Compressor 3 Condenser 4 Expansion Valve 5 Evaporator 6 Accumulator 7 Control Unit 8 First High Pressure Passage 9 Second High Pressure Passage 10 Pressure Sensor 11 Temperature Sensor

Claims (2)

[Claims] 1. A compressor for compressing a refrigerant composed of carbon dioxide gas, a condenser for cooling the refrigerant compressed by the compressor, an expansion valve for expanding the refrigerant cooled by the condenser, and an expansion valve for expanding the refrigerant. In a cooling cycle configured by piping connection of at least an evaporator that cools passing air by the endothermic action of the refrigerant, the pressure of the refrigerant flowing through a high-pressure passage from the discharge side of the compressor to the inflow side of the expansion valve is detected. Refrigerant pressure detecting means for detecting the temperature of the refrigerant flowing through the condenser outlet side high pressure passage extending from the condenser outlet side to the expansion valve inlet side, and the refrigerant detected by the refrigerant temperature detecting means. An optimum high pressure calculating means for calculating the optimum high pressure of the refrigerant flowing through the high pressure passage from the temperature; The high pressure detected by the high pressure detection means,
A high pressure determination means for determining whether or not the high pressure is greater than the optimum high pressure calculated by the optimum high pressure calculation means, and when the high pressure detected by the high pressure detection means is judged to be high by the high pressure determination means. An expansion valve control means for increasing the opening degree of the expansion valve and reducing the opening degree of the expansion valve when the high pressure determining means determines that the high pressure detected by the high pressure detecting means is small. An air-conditioning cycle control device comprising: 2. A compressor for compressing a refrigerant made of carbon dioxide, a condenser for cooling the refrigerant compressed by the compressor, an expansion valve for expanding the refrigerant cooled by the condenser, and an expansion valve for expanding the refrigerant. In a cooling cycle configured by piping connection of at least an evaporator that cools passing air by the endothermic action of the refrigerant, the pressure of the refrigerant flowing through a high-pressure passage from the discharge side of the compressor to the inflow side of the expansion valve is detected. Refrigerant pressure detecting means for detecting the temperature of the refrigerant flowing through the condenser outlet side high pressure passage extending from the condenser outlet side to the expansion valve inlet side, and the refrigerant detected by the refrigerant temperature detecting means. Determines whether the temperature is above the specified temperature set near the critical temperature of carbon dioxide Refrigerant temperature determining means, and an optimum high pressure calculating means for calculating an optimum high pressure of the refrigerant flowing through the high pressure passage from the refrigerant temperature when the refrigerant temperature is equal to or higher than a predetermined temperature by the refrigerant temperature determining means; The high pressure detected by the detection means is
The high-pressure pressure determination means for determining whether or not it is higher than the optimum high pressure calculated by the optimum high-pressure calculation means, and the expansion valve when the refrigerant temperature determination means determines that the refrigerant temperature is lower than a predetermined temperature. The opening of the expansion valve is fixed to a predetermined opening, and when the high pressure detected by the high pressure detecting means is determined to be large, the opening of the expansion valve is increased to increase the high pressure. A cooling cycle control device comprising expansion valve control means for reducing the opening degree of the expansion valve when the high pressure pressure detected by the high pressure detection means is judged to be small by the judgment means.