JP3479747B2 - Cooling cycle controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling cycle provided in a vehicle air conditioner or a home air conditioner, which uses a carbon dioxide gas as a refrigerant. The present invention relates to a cooling cycle control device for controlling. [0002] Conventional cooling cycle control devices include:
For example, as shown in Japanese Patent Application Laid-Open No. 4-161759, a compressor for compressing a refrigerant, a condenser for condensing a high-pressure refrigerant, an expansion valve for expanding the condensed refrigerant, and vaporizing the refrigerant that has become wet vapor. And at least an evaporator, and especially in the current automotive air conditioner, the refrigerant is Freon (for example,
Those using R-12, R-134a) are known. [0003] However, CFCs are used as a refrigerant in the present application in order to produce problems such as a large warming effect and destruction of the ozone layer when released into the atmosphere. (CO ₂ ) and a system configuration based on the current cooling cycle. However, carbon dioxide (CO ₂ ) has a low critical temperature (about 31 ° C.), and condensate cannot be liquefied in a condenser in a normal operating temperature range, so that there is a problem that sufficient capacity and efficiency cannot be secured. [0004] For this reason, the present invention focuses on the fact that when carbon dioxide gas is used as a refrigerant, there is an optimum high pressure value that is efficient with respect to the refrigerant temperature on the outlet side of the condenser. It is an object of the present invention to provide a cooling cycle control device capable of securing cooling capacity and efficiency with a similar system configuration. As shown in FIG. 1, the present invention relates to a compressor for compressing a refrigerant composed of carbon dioxide gas, a condenser for cooling the refrigerant compressed by the compressor, and a condenser for cooling the refrigerant. In the cooling cycle, an expansion valve 4 that expands the refrigerant cooled by the expansion valve 4 and an evaporator that cools air that passes through by an endothermic effect of the refrigerant expanded by the expansion valve 4 are connected in series at least in series. And a high-pressure pressure detecting means 100 for detecting the pressure of the refrigerant flowing through the high-pressure passage from the discharge side of the expansion valve to the inflow side of the expansion valve. Refrigerant temperature detecting means 110 for detecting the temperature of the refrigerant; Refrigerant temperature determining means 150 for determining whether or not the detected refrigerant temperature is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas, and when the refrigerant temperature is higher than or equal to the predetermined temperature by the refrigerant temperature determining means 150 In addition, 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 converted to the optimum high pressure calculated by the optimum high pressure calculating means. High pressure determination means 130 for determining whether the temperature is greater than
0, when the refrigerant temperature is determined to be lower than the predetermined temperature, the opening of the expansion valve 4 is fixed to the predetermined opening,
The high pressure detection means 1 is provided by the high pressure determination means.
When it is determined that the high pressure detected by 10 is large, the opening degree of the expansion valve 4 is increased, and the high pressure detected by the high pressure detection means 110 is determined by the high pressure determination means 130 to be small. Expansion valve control means 1 for reducing the opening of the expansion valve 4
40. According to the present invention, the refrigerant temperature 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 is determined. the determination unit 150 is provided, when the refrigerant temperature is determined to be equal to or higher than the predetermined temperature by the refrigerant temperature judging means 150, calculates the optimal high pressure by the optimal high pressure calculating unit 120, the optimum pressure against refrigerant temperature In a remarkable refrigerant temperature range, specifically, in a temperature range equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas,
When it is determined that the high pressure is high, the expansion valve control means 140 controls the opening of the expansion valve 4 in a direction to increase the opening to reduce the high pressure, and when it is determined that the high pressure is small, is der what can be controlled to increase the control to high <br/> pressure pressure in a direction to reduce the opening degree of the expansion valve 4 by the expansion valve control means 140
You . Further, it is determined that the refrigerant temperature is lower than a predetermined temperature.
Is expanded by the expansion valve control means 140.
The opening of the valve 4 is fixed at a predetermined opening.
You. Thereby, an efficient cooling cycle operation can be performed corresponding to a wide range of the refrigerant temperature. Embodiments of the present invention will be described below with reference to the drawings. A cooling (refrigeration) cycle 1 shown in FIG. 2 is mounted, for example, on an air conditioner for a vehicle, and includes a compressor 2, a condenser 3, an expansion valve 4, an evaporator 5, and an accumulator 6 connected in series with pipes. It is composed. Since the compressor 2 uses carbon dioxide as a refrigerant for 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 constituting a first high-pressure passage 8, and the outflow side of the condenser 3 forms a condenser outlet-side high-pressure passage (second high-pressure passage) 9. The connection pipe is connected to the inflow side of the expansion valve 4. The first high-pressure passage 8 and the second high-pressure passage 9 constitute a high-pressure passage. The expansion valve 4 is, for example, a proportional solenoid valve.
The degree of opening of the flow path can be adjusted in proportion to the output from the control unit 7. An outflow side of the expansion valve 4 is connected to an evaporator 5 disposed on an 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 accumulator 6 has a discharge side connected to the suction side of the compressor 2 and temporarily stores the refrigerant flowing out of the evaporator 5 and performs gas-liquid separation. In the cooling cycle 1, the compressor 2 is connected to the gas refrigerant (carbon dioxide) via the accumulator 6.
Inhale and compress. This compression stroke is indicated 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 an isentropic curve. Thereafter, the refrigerant is sent to the condenser 3 and radiates heat, thereby reducing enthalpy (i). The radiating stroke represented by M ₂ ~M _3. In a normal cooling cycle, condensed and liquefied is performed in this heat radiation process. However, in the case of carbon dioxide, the condensed and liquefied gas is not condensed and liquefied in this process because the critical temperature is low (about 31 ° C.). Thereafter, the refrigerant that has radiated heat and cooled down passes through the expansion valve 4 and is expanded. This expansion stroke is indicated by M _{3 to} M ₆ . In this expansion stroke, the pressure of the refrigerant is reduced by passing through the expansion valve 4.
With the decrease of the pressure changes at the stage of passing the saturated liquid line L ₁ (M ₅₎ to wet steam. In the state of this wet steam, it is sent to the evaporator 5 and absorbs the heat of the air passing through the evaporator 5 to evaporate. This evaporation process is M
₆ shown in the ~M _1. Incidentally, between the M ₁₁ and M ₁ is a superheat for preventing liquid back to the compressor 2 (superheat). In this embodiment, the degree of superheat is close to zero. According to the above process, since the heat absorbed from the evaporator 5 can be radiated from the capacitor 3, the air passing through the evaporator 5 can be cooled. In the cooling cycle 1, a pressure sensor 10 for detecting a high-pressure pressure of the refrigerant is attached to a high-pressure passage (first high-pressure passage 8 and second high-pressure passage 9). A temperature sensor 11 for detecting the temperature of the refrigerant is mounted on the passage 9. In this embodiment, the pressure sensor 10 is provided near the inflow side of the condenser 3, and the temperature sensor 11 is mounted near the outflow side of the condenser 3 to detect the temperature of the refrigerant. Have 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 described with reference to FIGS. 1 and 2. A compressor 2 for compressing a refrigerant composed of carbon dioxide gas, and a condenser 3 for cooling the refrigerant compressed by the compressor 2 A cooling system comprising an expansion valve 4 for expanding the refrigerant cooled by the condenser 3 and an evaporator 5 for cooling the air passing therethrough by absorbing heat of the refrigerant expanded by the expansion valve 4, at least in series piping. In cycle 1, a pressure sensor as a 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 10; an optimum high-pressure calculating means 120 for calculating an 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; High pressure determining means 130 for determining whether or not the high pressure detected by the above is higher than the optimum high pressure calculated by the optimum high pressure calculating means 120;
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 is determined to be small by the high pressure determination means 130, An expansion valve control means 140 for controlling the expansion valve 4 in a direction to close the opening of the expansion valve 4 is provided. Further, there is provided a refrigerant temperature determining means 150 for determining 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. When the determining means 150 determines that the refrigerant temperature is equal to or higher than the predetermined temperature, the optimum high-pressure calculating means 120 calculates an optimum high pressure. When it is determined that the refrigerant temperature is lower than the predetermined temperature, the expansion valve The control means 140 fixes the opening of the expansion valve 4 to a predetermined opening. The above invention is more specifically shown by the flow charts shown in FIGS. 3A and 3B, and is executed as part of the air conditioning control executed by the control unit 7. Hereinafter, description will be made according to this flowchart. In the flowchart shown in FIG. 3A, first, at step 200, the high pressure PR of the first high pressure passage 8 detected by the pressure sensor 10 and the refrigerant of the second high pressure passage 9 detected by the temperature sensor 11 are shown. Temperature t
Is entered. The high pressure PR indicates a pressure at a position indicated by M ₂ , M ₂₁ and M ₂₂ in the Mollier diagram of FIG. 6, and the refrigerant temperature t is indicated by M ₃ , M ₃₁ , M ₃₂ and M ₃₃ . This indicates the temperature at the position where the temperature changes. [0022] Thereafter, in step 220, the optimum pressure P _x which corresponds to the refrigerant temperature t is calculated. The optimum pressure, as indicated by the Mollier diagram of FIG. 6, when the refrigerant temperature t is constant, for example, when the high pressure has dropped from M ₂₁ to M _2, substantially M ₃₁ outlet side temperature of the capacitor 3 ~
It descends along the isothermal line 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 is lowered. For this, it is made with the presence of optimal pressure P _x with respect to the refrigerant temperature t. The optimum high pressure P _x in step 220
Is calculated, for example, at a predetermined refrigerant temperature t (t ₁ , t ₂ , t ₃ )
Pressure P _x (P _x1 , P _x2 , P
_x3 , _Px4 ) are calculated in correspondence with the map shown in the characteristic diagram of FIG. The optimum pressure P calculated by this
_x in step 230 is compared with the high pressure P _R. In the comparison in step 230, if the high pressure P _R is larger than the optimum high pressure P _x , for example, FIG.
As shown, when the high pressure P _R is greater than the optimum pressure P _x2 indicates the pressure value P _C, performs control in the direction (+ alpha) to open a predetermined value the degree OR of the expansion valve 4 proceeds to step 240 . As a result, the high pressure on the upstream side of the expansion valve 4 decreases, and the refrigerant temperature further decreases.
The state of the refrigerant can shift from point C (pressure P _C , temperature t _C ) to point D (pressure P _D , temperature t _D ) on the optimal temperature characteristic line. In the comparison in 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 is operated. 4 is controlled in the direction (-α) to close the opening OR by a predetermined value. As a result, the high-pressure pressure on the upstream side of the expansion valve 4 increases, and the refrigerant temperature further increases. Accordingly, the state of the refrigerant changes from the point A (pressure P _A , temperature t _A ) to B on the optimal temperature characteristic line. Point (pressure P _B , temperature t _B ). As a result, an optimal cooling cycle operation can be performed in a normally used temperature range. Furthermore, in the flowchart shown in FIG. 3 (b), after entering the refrigerant pressure P _R and the refrigerant temperature t in step 200, the refrigerant temperature t in step 210 of whether greater than the predetermined temperature t _S Make a decision. This predetermined temperature t _S is a critical temperature of carbon dioxide gas of about 31 °.
The temperature is set near C (for example, 30 ° C.). This is because, as indicated by t ₄ in characteristic diagram of FIG. 4, when the coolant temperature is below the critical temperature, characteristics such as higher the normal cooling cycle and the high pressure similarly less efficient This is to show a diagram. Therefore, in the determination of step 210, when the refrigerant temperature t is lower than a predetermined temperature t _S is for setting the opening degree OR of the expansion valve 4 to a predetermined opening degree β proceeds to step 260. If it is determined in step 210 that the refrigerant temperature t is equal to or higher than the predetermined temperature t _S , the expansion valve control shown in FIG. 3A is executed.
From the above, when the refrigerant temperature is equal to or lower than the predetermined temperature, the opening degree of the expansion valve is fixed, and when the refrigerant temperature is equal to or higher than the predetermined temperature, the expansion valve control described above is executed. An efficient cooling cycle operation can be performed in a wider refrigerant temperature range than the cycle. Thus, according to the present invention, it is determined whether or not the refrigerant temperature is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide, and if the refrigerant temperature is equal to or higher than the predetermined temperature. When it is determined, the optimum high pressure is calculated, and when it is determined that the refrigerant temperature is smaller than the predetermined temperature, the opening of the expansion valve is fixed at the predetermined opening, so that the optimum high pressure with respect to the refrigerant temperature is obtained. In the remarkable refrigerant temperature range, specifically, in a temperature range equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas, the expansion valve control is performed , and a predetermined value is set.
Do not execute expansion valve control in the following temperature range.
It is something that has been done . Specifically, when it is determined that the high pressure is high, the opening degree of the expansion valve is controlled to be increased, the high pressure is reduced, and when it is determined that the high pressure is small, the expansion is controlled. controlled in a direction to reduce the opening degree of the valve, have row control for increasing the high pressure, when the coolant temperature is below the predetermined temperature is obtained so as to secure the expansion valve to a predetermined opening degree. As a result, even when carbon dioxide gas is used as the refrigerant, it can be installed in an air conditioner with the same system configuration as the current system, so that it is possible to reduce costs and reduce man-hours, and to maintain optimal cooling cycle operation. You can do it.

BRIEF DESCRIPTION OF THE 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 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 state of correction. FIG. 6 is a Mollier diagram showing a cooling cycle according to the embodiment of the present invention. [Description of Signs] 1 Cooling cycle 2 Compressor 3 Capacitor 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 (1)

(57) [Claim 1] A compressor for compressing a refrigerant made of carbon dioxide gas, a condenser for cooling the refrigerant compressed by the compressor, and an expansion valve for expanding the refrigerant cooled by the condenser And an evaporator that cools the air that passes through by the heat absorbing action of the refrigerant expanded by the expansion valve is connected at least in series with pipes. From the discharge side of the compressor to the inflow side of the expansion valve High-pressure pressure detection means for detecting the pressure of the refrigerant flowing through the high-pressure passage; refrigerant temperature detection means for detecting the temperature of the refrigerant flowing through the condenser outlet high-pressure passage from the outlet side of the condenser to the inflow side of the expansion valve; The refrigerant temperature detected by the refrigerant temperature detecting means is equal to or higher than a predetermined temperature set near the critical temperature of carbon dioxide gas. A refrigerant temperature determining means for determining whether or not the refrigerant temperature is higher than a predetermined temperature by the refrigerant temperature determining means; and an optimum high pressure for calculating an optimum high pressure of the refrigerant flowing through the high pressure passage from the refrigerant temperature. Calculating means, the high pressure detected by the high pressure detecting means,
A high pressure determining means for determining whether or not the refrigerant pressure is higher than an optimum high pressure calculated by the optimum high pressure calculating means; and the expansion valve when the refrigerant temperature determining means determines that the refrigerant temperature is lower than a predetermined temperature. The opening of the expansion valve is fixed at a predetermined opening, and when the high pressure detection means determines that the high pressure detected by the high pressure detection means is large, the opening of the expansion valve is increased, and the high pressure A cooling cycle control device, comprising: expansion valve control means for reducing the degree of opening of the expansion valve when the high pressure detected by the high pressure detection means is determined to be small by the determination means.