KR20070033215A - Control Device and the Same Method of Supercritical Refrigants System for Air Conditioner - Google Patents

Abstract

A control device and a method of a supercritical refrigerants system for an air conditioner are provided to optimally control the system regardless of a loss of a coolant by determining excessive heating of an intake side of a target compressor. In a control device of a supercritical refrigerants system for an air conditioner, a compressor(10) compressively discharges a coolant and is capable of changing an amount of discharge. A gas cooler(11) condenses the coolant. A throttle valve(13) drops pressure of the coolant. An evaporator(14) cools the air by using an evaporation of the coolant. A first sensor unit(21) detects a pressure and a temperature of the coolant by being installed on an intake side of the compressor. A second sensor unit(22) senses a pressure and a temperature of the coolant by being installed on a discharge side of the compressor. And, a controller(20) controls an opening degree of the throttle valve and the discharge amount of the compressor according to the signals of the first sensor unit, the second sensor unit, and an intake side sensor(23) of an engine.

Description

Control Device and the Same Method of Supercritical Refrigants System for Air Conditioner

1 is a configuration diagram showing a supercritical refrigerant system control structure for a conventional air conditioner.

2 is a block diagram showing a control structure of a supercritical refrigerant system for an air conditioner according to the present invention.

3 is a flowchart illustrating a control method of a supercritical refrigerant system for an air conditioner according to the present invention.

4 is a flow chart when operating the system in acceleration mode.

5 is a flow chart when operating the system in maximum performance mode.

6 is a flow chart when operating the system in maximum efficiency mode.

7 is a graph showing the change in superheat degree of the target compressor suction side according to the refrigerant density.

8 is a graph showing the change in the sexual coefficient according to the suction side superheat degree.

9 is a graph showing a change in the coefficient of performance (COP) according to the amount of refrigerant charge when the outside temperature of 45 ℃.

10 is a graph showing the change in the superheat degree of the compressor suction according to the refrigerant filling amount at the maximum COP.

11 is a graph showing the change in the discharge pressure of the compressor according to the amount of refrigerant charge at the maximum COP.

12 is a graph showing the change in compressor discharge temperature according to the amount of refrigerant charge at the maximum COP.

13 is a graph showing the air outlet temperature change of the evaporator according to the amount of refrigerant charge at the maximum COP.

14 is a vapor pressure line diagram of carbon dioxide used as a refrigerant.

<Explanation of symbols for the main parts of the drawings>

10: Compressor 11: Gas Cooler

12: internal heat exchanger 13: throttling valve

14: evaporator 15: accumulator

20: controller 21: first sensor unit

22: second sensor unit 23: intake side sensor

T1: Compressor suction side refrigerant temperature P1: Compressor suction side refrigerant pressure

T2: compressor discharge side refrigerant temperature P2: compressor discharge side refrigerant pressure

The present invention is to control a supercritical refrigerant system for an air conditioner for cooling in a vehicle using a supercritical refrigerant, in particular, the amount of refrigerant charge is calculated and the throttling valve according to the refrigerant charge amount and the superheat degree of the compressor suction. The present invention relates to a control structure and a method of a supercritical refrigerant system for an air conditioner, by controlling the opening degree and the discharge capacity of the compressor to optimally control the system, improve cooling performance, and to maintain the system with high efficiency.

Refrigerant is the working fluid of the refrigeration cycle, a generic term for an object that takes heat from a low temperature object and transfers it to a high temperature object. Refrigerants currently widely used include ammonia, fluorohydrocarbon-based refrigerants (freons), azeotropic mixed refrigerants, chloromethyl, and the like. The refrigeration effect can be enhanced by selecting a refrigerant suitable for each characteristic according to the capacity of the refrigerator, the type of the compressor, and the use.

The conditions to be provided as a refrigerant include: evaporation at a pressure above atmospheric pressure even at low temperature, and liquefaction at relatively low pressure at room temperature; second, less power required for the same freezing capacity; third, high critical temperature, low solidification temperature, and fourth heat of evaporation. The large and small specific heat of liquid, the ratio of liquid specific heat to evaporation heat should be low, the fifth volume of refrigerant gas is small for the same freezing capacity, and the sixth chemically bond is good, so the refrigerant gas is decomposed by compressed heat. No other gas is generated, and the seventh price should be low.

Freon gas most satisfies the above-mentioned condition of the refrigerant, which is known as the main culprit for destroying the ozone layer and is currently limited in use. Therefore, there is a need for an environmentally friendly refrigerant that does not adversely affect the environment, and research on this has been actively conducted.

Accordingly, the developed carbon dioxide refrigerant has better cooling performance and higher efficiency than the existing freon refrigerant, and thus can be applied to a vehicle air conditioner. However, since carbon dioxide is sublimed to become gaseous carbon dioxide in dry ice under normal pressure, it is used as a refrigerant after making it into a supercritical state by applying an appropriate pressure. The supercritical state is a state in which the liquid state and the gas state cannot be accurately distinguished, and have both liquid and gas properties.

Particularly, in the case of carbon dioxide, when the temperature is above 31 ° C., no matter how much pressure is applied, the carbon dioxide in the supercritical state satisfies the conditions of the above refrigerant, and thus constitutes a supercritical refrigerant system using carbon dioxide as a refrigerant. can do. The supercritical refrigerant system needs control such as adjusting the capacity of the compressor or changing the opening amount of the throttling valve in order to maintain the refrigerant in the supercritical state and improve the efficiency of the system.

In the conventional supercritical refrigerant system control structure, as shown in FIG. 1, the compressor 51 compresses and discharges the refrigerant and an oil separator separating the oil contained in the refrigerant discharged from the compressor 51. 52, a gas cooler 53 for condensing the refrigerant passing through the oil separator 52, and an expansion valve 55 for reducing the pressure of the refrigerant condensed in the gas cooler 53; ), An evaporator 56 for evaporating the refrigerant to cool the surrounding air, an accumulator 57 for separating the liquid refrigerant contained in the refrigerant from the evaporator 56, and the accumulator. Detects the refrigerant pressure immediately before passing through the internal heat exchanger 54 and the throttling valve 53 where heat exchange between the refrigerant from 57 and the refrigerant from the gas cooler 53 is performed. Capacity and phase of the compressor 51 Controller for controlling the opening degree of the throttle valve 55; consists of (Controller 50).

The conventional supercritical refrigerant system control structure configured as described above adjusts the compressor capacity and the opening degree of the throttling valve according to the pressure of the refrigerant so that the refrigerant system can be operated in an optimal state.

The refrigerant discharged from the compressor (51) is separated from the oil in the oil separator (52), condensed in the gas cooler (53) and passed through the throttling valve (55), and the pressure drops, and the ambient air is evaporated in the evaporator (56). To cool the room. After the refrigerant from the evaporator 56 passes through the accumulator 57, the liquid refrigerant is separated and passes through the internal heat exchanger 54 to completely vaporize the refrigerant from the gas cooler 53 through heat exchange. Return to (51).

At this time, the controller 50 senses the refrigerant pressure immediately before the throttling valve 55 using the pressure sensor 58 to adjust the opening degree of the throttle valve 55 or to change the capacity of the compressor 51 to optimize the refrigerant system. To operate at an efficiency. The opening degree of the throttling valve 55 and the capacity adjustment of the compressor 51 according to the refrigerant pressure vary depending on the configuration form of each system, and various control methods for improving the efficiency of the refrigerant system have been proposed.

In the vehicle air conditioner disclosed in Japanese Patent Laid-Open Publication No. 2003-002048, by varying the discharge capacity of the compressor by sensing the air temperature immediately after passing through the evaporator, the power consumption of the compressor is prevented from being excessively increased, and the compressor or rubber This prevents the parts and the like from being thermally damaged. That is, the discharge capacity of the compressor is controlled so that the air temperature immediately after passing through the evaporator is approximately 0 ° C., so that the flow rate of the refrigerant discharged from the compressor does not exceed a predetermined flow rate. Therefore, the refrigerant pressure and the refrigerant temperature on the high pressure side are not excessively increased, and the power consumption of the compressor is not excessively increased, and thermal damage to the compressor or the rubber parts used at each connection part can be prevented. .

In addition, the air conditioner disclosed in Japanese Patent Laid-Open No. 2000-234811 makes it possible to protect the system by sensing the pressure and temperature at the discharge side of the compressor. To this end, a discharge pressure controller for enclosing a refrigerant that can be in a supercritical state on the heat dissipation side and changing the opening degree of the throttling valve according to the discharge pressure, a discharge temperature controller for controlling the opening degree of the throttling valve according to the discharge temperature, and a discharge temperature According to the present invention, a throttling valve opening manipulator for controlling the opening degree of the throttling valve by selecting the discharge pressure controller and the discharge temperature controller is provided.

The air conditioning apparatus protects the system by preventing the refrigerant pressure and temperature of the high pressure side from being excessively increased by adjusting the opening degree of the throttling valve according to the temperature and pressure of the refrigerant discharged from the compressor. However, the above air conditioning apparatus has only a function of protecting the system and has a disadvantage in that the system cannot be optimally controlled.

In general, it is very important to operate at the optimum efficiency in a supercritical refrigerant system using a supercritical refrigerant. That is, the efficiency of the system is changed a lot according to the operating state of the refrigerant system, and accordingly, the fuel consumption is changed, which greatly affects the economic operation of the vehicle.

As a result, in order to operate the vehicle economically, it is necessary to operate the air conditioner in various ways depending on the operating state of the vehicle and the needs of the user. For example, when the vehicle is operated for a long time, the refrigerant inside the refrigerant system leaks little by little, and a certain amount of refrigerant may occur after a predetermined time has elapsed. The decrease in the amount of refrigerant immediately leads to a decrease in the performance of the air conditioner, and the compressor torque is excessively increased, which is a factor that increases fuel consumption.

The present invention has been made to solve the above-mentioned conventional problems, by calculating the amount of refrigerant in the system to maximize the efficiency of the system according to the amount of refrigerant, as well as maintaining the cooling performance while controlling the system in consideration of the user's operability It is an object of the present invention to provide a control structure and a method of a supercritical refrigerant system for an air conditioner.

In addition, the present invention can reduce the fuel consumption by controlling the system to show the optimum efficiency according to the amount of refrigerant in the system, and improve the user's convenience and operability by controlling the system in accordance with the user's needs or operating conditions Another object of the present invention is to provide a control structure and a method of a supercritical refrigerant system for an air conditioner.

In addition, the present invention warns the user when the refrigerant filling amount is below a certain value or the refrigerant filling amount is rapidly reduced, so that the supercritical refrigerant for the air conditioner to prevent the increase of fuel consumption and cooling efficiency due to the lack of refrigerant It is another object to provide a control structure and a method of the system.

According to the control structure of the supercritical refrigerant system for an air conditioning apparatus of the present invention for achieving the above object, a compressor capable of compressing and discharging the refrigerant and changing the discharge capacity, a gas cooler for condensing the refrigerant, and a pressure drop of the refrigerant A supercritical refrigerant system comprising an throttling valve and an evaporator for cooling air by evaporation of a refrigerant, comprising: a first sensor unit installed at an intake side of the compressor to sense pressure and temperature of the refrigerant; A second sensor part installed at the discharge side of the pump to sense pressure and temperature of the refrigerant, and a discharge capacity of the compressor and an opening degree of the throttling valve according to signals of the first sensor part, the second sensor part, and the intake side sensor of the engine; It includes a controller to control.

In addition, according to the control structure of the supercritical refrigerant system for an air conditioner of the present invention, the controller calculates the refrigerant density according to the temperature and pressure of the refrigerant sensed by one of the first sensor unit or the second sensor unit, the refrigerant The opening degree of the throttling valve is controlled according to the density.

In addition, according to the control structure of the supercritical refrigerant system for an air conditioner of the present invention, the controller controls the opening degree of the throttling valve according to the suction side superheat degree of the compressor, and if the refrigerant density decreases, the target compressor suction side superheat degree Will increase.

In addition, according to the control method of the supercritical refrigerant system for an air conditioner according to the present invention, the step of checking whether the air conditioning mode is the acceleration mode according to the driving state of the vehicle and whether the user is operating, and if the air conditioning mode is the acceleration mode It is characterized in that it comprises the step of controlling to the acceleration mode, otherwise check whether the maximum performance mode, and if the air conditioning mode is the maximum performance mode to control the system to the maximum performance mode, otherwise to the maximum efficiency mode.

In addition, according to the control method of the supercritical refrigerant system for an air conditioner of the present invention, the acceleration mode is a first process of determining whether or not a rapid acceleration in accordance with the signal of the intake sensor 23 of the engine, and if the rapid acceleration After increasing the opening degree of the valve to a certain degree, it is fed back to the first process, otherwise it is characterized in that the second process of controlling the maximum efficiency mode after reducing the opening degree of the throttle valve.

In addition, according to the control method of the supercritical refrigerant system for an air conditioner of the present invention, the maximum performance mode is the first process of detecting the discharge pressure and temperature of the compressor, and whether the pressure and temperature detected in the first process is below the limit value A second process of checking the maximum value, and if the limit value is less than the limit value, increases the degree of superheat of the compressor suction, and then checks whether the maximum performance mode is released. Otherwise, the third process controls the maximum efficiency mode; It is characterized by consisting of a fourth step of controlling the mode and otherwise feedback to the first step.

In addition, according to the control method of the supercritical refrigerant system for an air conditioner of the present invention, the maximum efficiency mode is the first to detect the temperature (T1) and pressure (P1) of the suction side of the compressor and calculates the density of the refrigerant using the same And a second process of calculating the target compressor suction superheat degree (a) using the density of the refrigerant, and the actual compressor suction superheat degree (b1) according to the temperature (T1) and the pressure (P1) of the compressor suction side. And a fourth process of adjusting the compressor discharge capacity and the opening degree of the throttling valve so that the actual compressor suction side superheat is within the target suction side superheat degree.

In addition, according to the control method of the supercritical refrigerant system for an air conditioning apparatus of the present invention, the first process is characterized in that it comprises a warning to the user when the density of the refrigerant is below a certain value.

Further, according to the control method of the supercritical refrigerant system for an air conditioner of the present invention, the second process further includes increasing the suction side superheat degree and / or reducing the compressor discharge pressure as the density of the refrigerant decreases. It is characterized by.

Further, according to the control method of the supercritical refrigerant system for an air conditioner of the present invention, the target compressor suction side superheat degree of the second process is “-0.21 × D × 76.6-10 [K] <target compressor suction side superheat degree ( a) [K] <-0.21 × D × 76.6 + 10 [K] ”, and the compressor suction side superheat degree of the third process is“ compressor suction side superheat degree (b) = T1-0.8864 × P1 + 30.636 It is characterized in that it is calculated by ".

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. Prior to this, the terms or words used in the present specification and claims are based on the principle that the inventor can appropriately define the concept of terms in order to explain the invention in the best way. It should be interpreted as meanings and concepts corresponding to

Hereinafter, a supercritical system for an air conditioner of the present invention will be described with reference to the accompanying drawings.

2 is a block diagram showing the control structure of the supercritical refrigerant system for an air conditioning apparatus according to the present invention, Figure 3 is a flow chart showing a control method of the supercritical refrigerant system for an air conditioning apparatus according to the present invention, Figure 4 5 is a flowchart when operating the system in the acceleration mode, FIG. 5 is a flowchart when operating the system in the maximum performance mode, and FIG. 6 is a flowchart when operating the system in the maximum efficiency mode.

In addition, Figure 7 is a graph showing a change in compressor superheat degree according to the refrigerant density, Figure 8 is a graph showing a change in the coefficient of performance according to the suction side superheat degree, Figure 9 is a refrigerant charge amount at ambient temperature 45 ℃ It is a graph showing the change of the sexual coefficient according to. In addition, Figure 10 is a change in the compressor intake superheat degree according to the refrigerant filling amount at the maximum COP, Figure 11 is a change in the compressor discharge pressure according to the refrigerant charge amount at the maximum COP, Figure 12 is a change in the compressor discharge temperature according to the refrigerant charge amount at the maximum COP, Figure 13 is a graph showing the air outlet temperature change of the evaporator according to the amount of refrigerant charge at the maximum COP. 14 is a vapor pressure diagram of carbon dioxide used as a refrigerant.

The control structure of the supercritical refrigerant system for an air conditioner according to the present invention includes a compressor (10) capable of compressing and discharging refrigerant and changing discharge capacity, a gas cooler (11) for condensing the refrigerant, and reducing the pressure of the refrigerant. The throttling valve 13, an evaporator 14 for cooling the air by evaporation of the refrigerant, and an internal heat exchanger in which heat exchange is performed between the refrigerant from the gas cooler 11 and the refrigerant from the evaporator 14 ( 12), an accumulator 15 for separating liquid refrigerant contained in the refrigerant from the evaporator 14, and a suction pressure P1 and a temperature T1 of the refrigerant are installed at the suction side of the compressor 10. The first sensor unit 21 for detecting the second, The second sensor unit 22 is installed on the discharge side of the compressor 10 for detecting the pressure (P2) and temperature (T2) of the refrigerant, and the first sensor unit The toe of the compressor 10 according to the signals of the 21 and the second sensor 22 and the intake sensor 23 of the engine. A controller 20 for controlling the opening degree of the displacement and the throttle valve 14.

The control structure of the supercritical refrigerant system for an air conditioner of the present invention configured as described above adjusts the opening degree of the throttle valve so that the optimum efficiency is shown according to the compressor suction side superheat degree.

When the vehicle cooling device is operated, the refrigerant compressed by the compressor 10 is discharged, and the refrigerant is condensed while passing through the gas cooler 11. Subsequently, after passing through the high pressure side of the internal heat exchanger 12, the pressure drops while passing through the throttling valve 13, and exchanges heat with ambient air while passing through the evaporator 14. At this time, the air cooled by the heat exchange with the refrigerant in the evaporator 14 is discharged to the room to cool the room. The refrigerant from the evaporator 14 is returned to the compressor 10 via the low pressure side of the accumulator 15 and the internal heat exchanger 12. The accumulator 15 separates the liquid refrigerant which has not yet vaporized from the refrigerant passing through the evaporator 14, and the refrigerant flowing in the low pressure side by the hot refrigerant flowing in the high pressure side of the internal heat exchanger 12. Is heated and returned to the compressor completely vaporized.

Here, the controller 20 calculates the refrigerant filling amount according to the temperature (T1, T2) and the pressure (P1, P2) of the refrigerant sensed by the first sensor unit 21 or the second sensor unit 22. The opening degree of the throttling valve 13 is adjusted according to the refrigerant filling amount. In addition, the controller 20 controls the opening degree of the throttling valve 13 according to the suction side superheat degree of the compressor 10, and increases the target compressor suction side superheat degree when the refrigerant filling amount decreases. As a result, the system will operate in maximum efficiency mode.

At this time, the target compressor suction side superheat degree is within the range determined by Equation 1 according to the average density (D) of the refrigerant charged in the system.

Here, the average density (D) of the refrigerant is a value obtained by dividing the amount of refrigerant charged into the system by the internal volume of the system, and is dependent on the temperature T1 and the pressure P1 of the refrigerant sensed by the first sensor unit 21. You can get it accordingly. That is, since the refrigerant is in a saturated state or a critical state, the density of the refrigerant according to the temperature and pressure of the refrigerant can be obtained by using the vapor pressure diagram of the carbon dioxide shown in FIG. 14. At this time, the density value according to the temperature and pressure of the refrigerant shown in the steam pressure diagram is input to the controller 20 in advance, and the volume inside the system is also input to the controller 20.

When the target compressor suction side superheat degree is set by Equation 1, the controller 20 may adjust the opening degree of the throttle valve 13 to obtain the corresponding superheat degree. At this time, the opening degree of the throttling valve 13 is set in consideration of the user's request and the vehicle state, and it is preferable to maximize the coefficient of performance (COP), which is the efficiency of the system.

The control method of the supercritical refrigerant system for an air conditioner includes: checking whether an air conditioning mode is an acceleration mode according to a driving state of a vehicle and whether a user operates; If the air conditioning mode is an acceleration mode, controlling the system in an acceleration mode, and otherwise confirming whether the maximum performance mode; If the air conditioning mode is the maximum performance mode, the system is controlled to the maximum performance mode, otherwise it is controlled to the maximum efficiency mode.

Here, the acceleration mode is a first process for determining whether or not a rapid acceleration according to the signal of the intake sensor 23 of the engine, and if the acceleration is during acceleration, the opening degree of the throttle valve is increased to a certain degree and then fed back to the first process. If not, the second process is performed to reduce the opening degree of the throttle valve and then control the maximum efficiency mode.

The maximum performance mode includes a first process of detecting a compressor discharge pressure and a temperature, a second process of checking whether the pressure and temperature detected in the first process is less than or equal to a threshold, and a compressor superheating degree of the compressor if less than or equal to a threshold. A third process of checking whether the maximum performance mode is released after the increase and otherwise controlling to the maximum efficiency mode; and a fourth process of controlling to the maximum efficiency mode if the maximum performance mode is released and otherwise feeding back to the first process described above. The process takes place.

In addition, the maximum efficiency mode is a first process of detecting the temperature (T1) and the pressure (P1) of the compressor suction side and using it to calculate the density of the refrigerant, and the target compressor suction side superheat degree using the density of the refrigerant a second process of calculating (a), a third process of calculating the actual compressor suction side superheat degree (b) according to the temperature T1 and the pressure P1 of the compressor suction side, and the actual compressor suction side superheat degree And a fourth step of adjusting the compressor discharge capacity and the opening degree of the throttling valve so as to be within the range of the target suction side superheat degree.

In addition, the first process of the maximum efficiency mode includes a warning to the user when the density of the refrigerant is below a certain value.

In the second process of the maximum efficiency mode, as the density of the refrigerant decreases, the suction-side superheat is increased or the compressor discharge pressure is decreased. Of course, you can use both methods.

Also, in the second process, the target compressor suction-side superheat should be within the range calculated by Equation 1 described above.

In addition, the compressor suction side superheat degree in the third process may be approximated by Equation 2 below.

According to the control method of the supercritical refrigerant system for an air conditioning apparatus, the system can be controlled in an optimal air conditioning mode according to the driving state of the vehicle and the user's operation.

When the air conditioner is activated, it checks whether it is accelerating and if it is accelerating, it controls the system in acceleration mode. That is, after checking whether the acceleration is accelerated through the signal of the engine intake sensor, if the acceleration is being accelerated, the opening degree of the throttle valve 13 is increased to a certain degree and then the acceleration is again checked. After reducing the opening degree to a certain degree, control the system in the maximum efficiency mode.

If the vehicle's driving status is not accelerating, check whether it is in maximum performance mode. The maximum performance mode is selected by the user to obtain cool indoor air even at the expense of driving ability of the vehicle, which can be selected by turning on the maximum performance mode switch on the control panel.

The maximum performance mode is applied when more air is required than driving the vehicle, such as when the vehicle is started in a hot summer. In the maximum performance mode, the controller 20 is configured to maximize the compressor suction side superheat within the range where the temperature T2 and pressure P2 of the compressor discharge side detected by the second sensor unit 22 are below the limit. To control.

If the air conditioning mode is not the acceleration mode or the maximum performance mode, the system is controlled in the maximum efficiency mode. In the maximum efficiency mode, after detecting the suction side temperature T1 and the pressure P1 of the compressor 10 through the first sensor unit 21, the density of the refrigerant is obtained using the steam pressure diagram shown in FIG. This is applied to Equation 1 above to calculate the range of the target suction side superheat degree (a). Next, the suction side temperature T1 and the pressure P1 of the compressor 10 are applied to Equation 2 to calculate the actual compressor suction side superheat degree b. Thereafter, the discharge capacity of the compressor 10 and the opening degree of the throttling valve 13 are adjusted such that the compressor suction side superheat degree b is within a target suction side superheat degree.

However, since the refrigerant may be leaked finely over time, it is necessary to detect the amount of refrigerant flowing in the actual system. To this end, the temperature (T1, T2) and the pressure (P1, P2) of the refrigerant is sensed using the temperature sensor and the pressure sensor of the sensor unit (21, 22) installed in the system, and the temperature (T1, T2) and pressure (P1) Calculate the amount of refrigerant using, P2). Refrigerant filling amount can be obtained through the density of the refrigerant determined according to the temperature (T1, T2) and the pressure (P1, P2) of the refrigerant.

Here, the compressor suction side superheat degree is linearly changed according to the density of the refrigerant under the same efficiency, as shown in FIG. Therefore, the target compressor suction superheat must be increased to achieve the same COP with reduced refrigerant charge.

However, if the calculated refrigerant charge amount is less than a certain amount, the target suction-side superheat is excessively increased, and as a result, the temperature (T1, T2) and the pressure (P1, P2) inside the system may be raised, which may cause overload of the entire system. have. That is, referring to FIG. 9, the change in the maximum efficiency point according to the refrigerant charge amount may be found to decrease rapidly as the refrigerant charge amount decreases below a certain value. In other words, if the amount of refrigerant charge decreases, the compressor suction side superheat value, which represents the maximum efficiency, is increased, so that the target suction side superheat degree for the efficient operation of the system is increased.

 Accordingly, when the refrigerant charge amount is less than a predetermined amount to warn the user to add the refrigerant. Therefore, the system can be optimally controlled by maintaining an appropriate amount of refrigerant charge at all times. In addition, when the refrigerant charge amount is drastically reduced by looking at the change in the refrigerant charge amount, it is determined that the refrigerant is excessively leaked in a part of the refrigerant system to warn the user. Therefore, the user can repair the leak portion of the refrigerant through the inspection of the refrigerant system to prevent the refrigerant from leaking and prevent an abnormal operation of the system due to excessive leakage of the refrigerant.

Of course, if the change in the refrigerant filling amount is small or the user ignores it, the control is performed to increase the efficiency of the system. Therefore, when the amount of refrigerant charge is reduced, the system is controlled in a direction in which the compressor suction side superheat is increased, thereby improving efficiency of the system and reducing energy consumption.

As a result, at the maximum efficiency point, the compressor suction superheat degree is linearly distributed with respect to the refrigerant charge amount, so the compressor suction superheat degree becomes an appropriate control variable in the supercritical refrigerant system for the air conditioner.

The compressor suction superheat degree, which shows optimum efficiency, varies with the internal volume of the refrigerant system. At this time, since the compressor suction-side superheat is a function of density as in Equation 1 above, in the case of the same volume, it depends on the amount of refrigerant charged. FIG. 10 is a diagram illustrating a superheat diagram of a compressor suction side according to a change in a refrigerant filling amount at a maximum efficiency state in a refrigerant system having an internal volume of about 2L.

Looking at the relationship between the refrigerant charge amount and the discharge pressure P2 of the compressor 10, as shown in Figure 11 it can be seen that as the refrigerant charge amount is reduced, the compressor discharge side pressure (P2) showing the optimum efficiency is also reduced. That is, when a decrease in the refrigerant filling amount is detected, the compressor discharge side pressure P2 should be controlled to be low. Otherwise, the compressor 10 is excessively operated to increase power consumption. At this time, since the change in the refrigerant filling amount and the discharge pressure P2 of the compressor 10 does not appear linearly, it can be seen that the compressor discharge pressure P2 is not suitable as a control variable.

In addition, as shown in Figure 12, it can be seen that the discharge side temperature (T2) of the compressor 10 is increased when the refrigerant charge amount is reduced. However, the refrigerant charge amount and the compressor discharge temperature (T2) also shows a non-linear distribution, it can be seen that the compressor discharge temperature (T2) is not appropriate as a variable.

In addition, as shown in Figure 13, it can be seen that when the refrigerant charge amount is reduced, the air outlet temperature of the evaporator 13 is increased. This means that the cooling performance decreases as the amount of refrigerant charged decreases, but it is also difficult to detect the amount of refrigerant charged through the air outlet temperature of the evaporator 13 because of the nonlinear distribution.

As a result, the efficiency of the supercritical refrigerant system varies depending on the amount of refrigerant charged, and the amount of refrigerant filled shows a linear distribution with the compressor suction superheat, so that the efficiency of the system can be controlled by adjusting the compressor suction superheat. The compressor suction superheat degree is determined according to the temperature T1 and the pressure P1 of the suction side detected by the first sensor unit 21, and the suction side pressure P1 is adjusted by adjusting the throttle valve 13. Can be controlled.

The adjustment of the throttling valve 13 is adjusted in conjunction with the target compressor suction-side superheat degree determined according to Equation 1, and it is preferable to adjust the throttling valve so that the maximum system efficiency appears in consideration of the user's request and the vehicle condition. Do. That is, during the initial cooling, the throttling valve 13 is controlled in the maximum performance mode to improve the cooling performance at the expense of the engine's output according to the user's selection, and when there is a sudden acceleration, the throttling valve 13 according to the acceleration mode. And the discharge capacity of the compressor 10, and in other cases, the discharge capacity of the throttle valve 13 and the compressor 10 in the maximum efficiency mode.

The maximum efficiency mode is applied to the case of the economic driving state maximizing the fuel efficiency of the vehicle except the maximum performance mode and the acceleration mode described above. That is, in the supercritical refrigerant system using carbon dioxide as the refrigerant as shown in FIG. Can be.

To this end, the compressor discharge side temperature T2 and the pressure P2 are sensed through the second sensor unit 22, and the discharge side temperature T2 or the pressure P2 of the compressor 10 does not exceed the limit. The compressor suction side superheat is raised, and by adjusting the throttling valve 13, the compressor suction side superheat can also be elevated.

In order to lower the compressor suction side superheat degree, a method of opening the throttle valve 13 to lower the compressor suction side pressure or reducing the discharge capacity of the compressor 10 is used. Of course, in order to increase the compressor suction superheat degree, a method of reducing the opening degree of the throttle valve 13 to increase the suction side pressure of the compressor or to increase the discharge capacity of the compressor 10 is used.

Although the preferred embodiments of the present invention have been described above, the scope of the present invention is not limited to such specific embodiments, and those of ordinary skill in the art are appropriately within the scope described in the claims of the present invention. Changes will be possible.

As described above, according to the control structure and method of the supercritical refrigerant system for an air conditioner according to the present invention, the amount of refrigerant charge in the supercritical refrigerant system is calculated and the target compressor suction side superheat is used to control the system. As a result, the system can be optimally controlled regardless of the loss of the refrigerant.

In addition, according to the control structure and method of the supercritical refrigerant system for an air conditioner according to the present invention, the maximum efficiency is obtained by changing the superheat degree of the target compressor inhalation according to the change of the refrigerant charge amount without adding a separate control logic. There are other effects that allow the air conditioner to run at maximum performance as well.

In addition, according to the control structure and method of the supercritical refrigerant system for an air conditioner according to the present invention, it is possible to monitor the change in the amount of refrigerant charge to quickly respond to the leakage of refrigerant and to increase the fuel consumption rate due to the lack of refrigerant. There is another effect that can be prevented.

In addition, according to the control structure and method of the supercritical refrigerant system for an air conditioner according to the present invention, since the cooling performance and the running performance is changed according to the user's operating characteristics, the driving performance is improved and the user's convenience is increased during acceleration or deceleration. There is also an effect.

Claims (13)

Compressor 10 capable of compressing and discharging the refrigerant and changing discharge capacity, gas cooler 11 for condensing the refrigerant, throttling valve 13 for lowering the pressure of the refrigerant, and cooling the air by evaporation of the refrigerant In the supercritical refrigerant system for an air conditioner comprising an evaporator (14), The first sensor unit 21 is installed on the suction side of the compressor 10 to sense the pressure P1 and the temperature T1 of the refrigerant, and the pressure P2 of the refrigerant is installed on the discharge side of the compressor 10. And the compressor 10 according to the signals of the second sensor unit 22 sensing the temperature T2, the first sensor unit 21, the second sensor unit 22, and the intake sensor 23 of the engine. A control structure of a supercritical refrigerant system for an air conditioner, characterized in that it comprises a controller (20) for controlling the discharge capacity of the) and the opening degree of the throttling valve (13). The method of claim 1, The controller 20 calculates the refrigerant filling amount according to the temperature (T1, T2) and the pressure (P1, P2) of the refrigerant sensed by one of the first sensor unit 21 or the second sensor unit 22. And controlling the opening degree of the throttling valve according to the refrigerant filling amount. The method of claim 1, The controller 20 controls the opening degree of the throttling valve 13 according to the suction side superheat degree of the compressor 10 and increases the target compressor suction side superheat degree when the refrigerant filling amount is decreased. Control structure of supercritical refrigerant system for air conditioning equipment. The method of claim 3, The suction superheat degree of the target compressor is determined according to the average density (D) of the refrigerant packed in the system, and is within the following range. -0.21 × D × 76.6-10 K <Target compressor suction overheat (a) <-0.21 × D × 76.6 + 10 K In the method for controlling the supercritical refrigerant system according to claim 1, Checking whether the air conditioning mode is the acceleration mode according to the driving state of the vehicle and whether the user operates the vehicle; If the air conditioning mode is the acceleration mode, controlling the system in the acceleration mode, otherwise confirming whether the maximum performance mode, Controlling the system to the maximum performance mode if the air conditioning mode is the maximum performance mode; otherwise, controlling the system to the maximum efficiency mode. The method of claim 5, In the acceleration mode, the first process of determining whether or not there is a rapid acceleration according to the signal of the intake sensor 23 of the engine, and if the rapid acceleration is increased, the opening degree of the throttle valve is increased to a certain degree and then fed back to the first process. And a second process of reducing the opening degree of the throttling valve to control the maximum efficiency mode. The method of claim 5, The maximum performance mode may include a first process of detecting the discharge pressure and temperature of the compressor, a second process of checking whether the pressure and the temperature sensed in the first process are below a threshold value, and a superheat degree of the compressor suction side if the threshold value is less than the threshold value. A third process of checking whether the maximum performance mode is released after the increase and controlling the maximum efficiency mode if the maximum performance mode is not released; and controlling the maximum efficiency mode if the maximum performance mode is released; Control method of a supercritical refrigerant system for an air conditioning apparatus comprising a fourth process of feeding back. The method according to any one of claims 5 to 7, The maximum efficiency mode, the first process of detecting the temperature (T1) and the pressure (P1) of the compressor suction side and using this to calculate the density of the refrigerant, and the target compressor suction side superheat degree using the density of the refrigerant ( a second process of calculating a), a third process of calculating the actual compressor suction side superheat degree b according to the temperature T1 and the pressure P1 of the compressor suction side, and the actual compressor suction side superheat degree And a fourth step of adjusting the compressor discharge capacity and the opening degree of the throttling valve so as to be within the range of the target compressor suction side superheat degree. The method of claim 8, The first process is a control method of a supercritical refrigerant system for an air conditioner, comprising warning the user when the density of the refrigerant is below a predetermined value. The method of claim 8, The second process is a control method of a supercritical refrigerant system for an air conditioning apparatus, characterized in that as the density of the refrigerant decreases, the suction side superheat is increased. The method of claim 10, The second process is a control method of a supercritical refrigerant system for an air conditioner, characterized in that further comprising reducing the discharge pressure of the compressor as the density of the refrigerant is reduced. The method of claim 8, The control method of the supercritical refrigerant system for an air conditioner, characterized in that the target compressor suction side superheat degree in the second process is within the following range. -0.21 × D × 76.6-10 K <Target compressor suction overheat (a) <-0.21 × D × 76.6 + 10 K The method of claim 8, The compressor suction side superheat degree in the third process is calculated by the following equation. Compressor suction side superheat (b) = T1-0.8864 × P1 + 30.636

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