KR20040079686A - Heater System of an Automobile - Google Patents

Abstract

PURPOSE: A heater system of a vehicle is provided to prevent the break down of the system and keep an optimal heating condition by effectively controlling the rise of discharge pressure generated by changeable external conditions as RPM(Revolution per Minute) of a compressor and the air temperature of an evaporator. CONSTITUTION: A heater system of a vehicle is composed of a refrigerant circulation passage passing through a compressor, a condenser, a first expansion valve, and an evaporator in order; a first refrigerant branch passage branched off from the refrigerant circulation passage between the compressor and the condenser, returned to the refrigerant circulation passage between the first expansion valve and the evaporator, and installed with a second expansion valve; a second refrigerant branch passage branched off from the refrigerant circulation passage between the evaporator and the compressor, returned to the refrigerant circulation passage between the condenser and the first expansion valve, and installed with an opening and closing valve; a flow direction regulating valve for controlling the flow direction of refrigerant to the refrigerant circulation passage and the first refrigerant branch passage; and a control unit for controlling the opening degree of the second expansion valve to regulate the discharge pressure of the compressor to the temperature of air flowing into the evaporator.

Description

Heater System of an Automobile

The present invention relates to a heater system for heating the interior of a vehicle, and more particularly, it is possible to adjust the discharge pressure of the compressor according to the outside temperature to prevent damage to the heater system due to excessive increase in the discharge pressure in advance The present invention relates to a heater system of a vehicle to obtain optimal heating performance.

In recent years, the existing heater system using only cooling water is insufficient as a heat source for heating the interior of the car at the beginning of the winter season and thus does not exhibit heating performance that meets the needs of the passengers. Research into using the HotGas Heater System is actively underway.

Referring to Figure 1, a brief description of a conventional hot gas heater system as follows.

In the summer, the compressor 18 is rotated by the driving of the engine E as in the normal cooling system. The refrigerant 18 is compressed to high temperature and high pressure by the rotation of the compressor 18, and then the open / close valve 17 and the condenser are opened. Condensation passes through (15) one after the other. At this time, since the opening / closing valve 16 is closed, no refrigerant flows to the hot gas bypass line 13. Then, the condensed refrigerant expands to low temperature and low pressure while passing through the check valve 14 to prevent the reverse flow of the refrigerant, and then passes through the first expansion valve 11 to absorb cooling heat in the evaporator 20 to improve cooling performance. Will be exercised.

On the other hand, in winter, the on / off valve 17 for opening and closing the refrigerant flow to the condenser 25 is blocked, and the on / off valve 16 of the bypass line 22 is opened to drive the hot gas heater system to the compressor toward the bypass line 22. The high temperature and high pressure refrigerant discharged from (7) is sent. The high temperature and high pressure refrigerant passing through the open / close valve 16 expands to high temperature and low pressure while passing through the second expansion valve 12 and then passes through the evaporator 20 to cool air (for example, −20 ° C.). Heat exchange with to raise the temperature of outside air. The outdoor air whose temperature is raised through the above process passes through the heater core 5 through which the coolant of the engine passes, so that the temperature is further increased, thereby rapidly increasing the indoor temperature of the vehicle compared to the conventional heating system in which hot gas is not used. It can be ascended quickly. Thus, the hot gas heater system is particularly advantageous for diesel engines and the like, in which the cooling water is not easily warmed up initially.

2 illustrates a cooling mode applied to the summer, and FIG. 3 illustrates a hot gas mode applied to the winter. The hot gas mode serves as an auxiliary heater system for raising the temperature of the cold outside air introduced into the evaporator in winter, and the operation of the hot gas operates only in the superheated region of the refrigerant, as shown in FIG. Since there is no evaporation process, it is different from the cooling cycle in that it is a gas cycle that uses heat entry by sensible heat.

On the other hand, the conventional hot gas heater system described above has the following problems.

When the hot gas system is operated to assist the heating of the vehicle interior and the on-off valve 17 is blocked, no refrigerant flows to the condenser 15. Therefore, the overall volume of the hot gas system is reduced by the volume occupied by the condenser 15 as compared to the cooling system in which the refrigerant flows to the condenser 15. In other words, the volume occupied by the refrigerant from the outlet of the compressor 18 to the inlet of the second expansion valve 12 is only the volume of the pipeline used for the refrigerant flow.

However, when the rotational speed (RPM) of the compressor 18 is rapidly increased, a large amount of refrigerant is discharged from the compressor 7 and the discharged refrigerant is gas-expanded while passing through the second expansion valve 12. For the same reason, the discharge pressure of the system rises sharply (see FIG. 5, as is the case when the inlet air temperature of the evaporator 6 rises as shown in FIG. 4). This is because the gas has a larger specific volume than the liquid, and the opening of the orifice of the second expansion valve 29 is required to be much larger than before. However, when the opening of the orifice approaches the pipe diameter, the expansion performance is large. Because of this reduction, heating performance cannot be achieved properly, there is a limit to increasing the opening of the orifice, and the flow rate no longer increases when choking occurs at the orifice when the fluid expands. This is because of the nature of the orifice that is not.

In conclusion, the conventional hot gas heater system sends a refrigerant to the second expansion valve after shutting off the refrigerant circulation to the condenser, and uses it for heating the entire amount, there is no way to control when the discharge pressure rises In other words, there was a problem that the risk of fatal damage to the entire heater system was always present.

The present invention has been made to solve the above problems, and by efficiently controlling the rise of the discharge pressure caused by changing external conditions such as compressor rotation speed, evaporator inlet air temperature, etc. to prevent damage to the heater system and optimal An object of the present invention is to provide a heater system that can maintain the heating state of the.

1 is a schematic diagram of main components of a heater system of a conventional vehicle.

2 shows the p-h diagram in the cooling mode.

3 shows a p-h diagram in the hot gas mode.

4 is a graph showing a change in the discharge pressure relative to the evaporator inlet air temperature.

5 is a graph showing a change in the discharge pressure relative to the compressor rotational speed.

6 is a schematic diagram showing main components of a heater system according to the present invention.

7 is a graph showing a change in heating capacity relative to the number of revolutions of a compressor.

8 is a p-h diagram for illustrating a change in the heating performance of the heater system according to the change in the compressor rotation speed.

Fig. 9 is a p-h diagram for showing a drop in discharge pressure at the same compressor rotation speed by the control action of the heater system according to the present invention.

10 is a graph showing a change in heating capacity according to a PWM duty (Pulse Width Modulation Duty).

11 is a graph showing the optimum compressor discharge pressure according to the outside air temperature.

12 is a block diagram showing the control logic of the heater system according to the present invention.

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

1 ... refrigerant circulation flow path, 2 ... 1st refrigerant pond,

3 ... 2nd refrigerant zone, 5 ... Heater Core,

11 ... 1st expansion valve, 12 ... 2nd expansion valve,

13 ... Hot Gas By-pass Line,

14 ... check valve, 15 ... condenser,

16, 17 ... opening and closing valve, P1 ... pressure sensor,

T1 ... Temperature sensor.

In order to achieve the above object, the present invention, the refrigerant circulation passage through the compressor, the condenser, the first expansion valve, the evaporator in turn, and branched from the refrigerant circulation passage between the compressor and the condenser, the first expansion A heater system of a motor vehicle having a first refrigerant passage equipped with a second expansion valve and returning to the refrigerant circulation passage between a valve and the evaporator, the heater system being branched from the refrigerant circulation passage between the evaporator and the compressor, A second refrigerant passage returning to the refrigerant circulation passage between the condenser and the first expansion valve and equipped with an on / off valve; A flow direction control valve for controlling a flow direction of the refrigerant toward the refrigerant circulation passage and the first refrigerant passage; And a control unit for controlling the opening degree of the second expansion valve to adjust the discharge pressure of the compressor according to the temperature of the air introduced into the evaporator.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 6, an embodiment according to the present invention includes a refrigerant circulation passage sequentially passing through a compressor, a condenser, a first expansion valve, and an evaporator constituting a cooling cycle of an automobile, and the compressor and the condenser. Branched from the refrigerant circulation passage, returning to the refrigerant circulation passage between the expansion valve and the evaporator, branching from the first refrigerant passage equipped with a second expansion valve, and the refrigerant circulation passage between the evaporator and the compressor; And a second refrigerant passage returning to the refrigerant circulation passage between the condenser and the first expansion valve and equipped with an on / off valve. Here, the second expansion valve is preferably an electronic expansion valve.

In addition, a three-way valve is provided at a branch point from the refrigerant circulation passage to the first refrigerant passage. In the present embodiment, a three-way valve is used, but as in the conventional heater system, between the point A where the first refrigerant passage branches from the refrigerant circulation passage and the second expansion valve, the point A and the condenser It is also possible to provide separate on-off valves in between.

In addition, a pressure sensor P1 for measuring the discharge pressure of the compressor and a temperature sensor T1 for measuring the temperature of the outside air are respectively provided at the refrigerant circulation passage and the inlet of the evaporator, and the pressure sensor P1 and the temperature are respectively provided. The sensor T1, the second expansion valve, the three-way valve, and the opening / closing valve to the second refrigerant reservoir are connected to the control unit.

On the other hand, a check valve is installed on the downstream side of the condenser (based on the flow direction of the refrigerant during cooling) to prevent the refrigerant from flowing back to the condenser when the heater system is operating. In addition, the first expansion valve may be configured as a variable orifice that varies according to the requirements of the heater system, and may be configured integrally with the check valve. In addition, although the three-way valve and the second expansion valve are separately formed in FIG. 6, the three-way valve and the second expansion valve may be integrally formed.

Hereinafter, with reference to Figure 6 will be described the operation of the embodiment according to the present invention.

During summer cooling, the three-way valve is opened in the condenser direction, and the refrigerant discharged from the compressor is condensed in the condenser and expanded while passing through the first expansion valve (orifice), and then the vehicle interior is cooled while passing through the evaporator. In this case, no refrigerant flows to the first refrigerant passage.

During the winter heating, the three-way valve opens in the direction to the first refrigerant pond, and the refrigerant flows toward the second expansion valve, for example, the electronic expansion valve, to the first refrigerant pond. Then, the discharged refrigerant gas is a high-temperature, low-pressure refrigerant while expanding through the electronic expansion valve, and heats the interior of the vehicle by heat exchange with cold air flowing into the evaporator. At this time, when the discharge pressure of the heater system is not greater than a predetermined value, the on-off valve to the second refrigerant reservoir is always kept closed so that all the refrigerant in the heater system can be used for heating.

On the other hand, Figure 7 shows the change in the heating capacity and discharge pressure according to the rotational speed (RPM) of the compressor, the amount of refrigerant discharged from the compressor and the discharge pressure increases as the number of revolutions of the compressor increases, As shown, the temperature of the refrigerant entering the inlet of the evaporator also rises, and consequently the heating performance of the heater system is improved.

However, as described above, an increase in discharge pressure results in an improvement in the heating performance of the heater system, but an unlimited increase in discharge pressure is not allowed for the protection of the entire heater system including the compressor and is constantly constant. Should be limited (eg about 28 bar). Therefore, when the pressure sensor P1 for measuring the discharge pressure provided in the downstream direction of the compressor shows a value higher than the allowable value, the open / close valve of the second refrigerant passage 3 is opened to cool the refrigerant exiting the evaporator to the low pressure condenser. The evaporator side pressure can be kept low by keeping the evaporator side pressure in the heater system equal to the pressure of the condenser (saturation pressure of the refrigerant accumulated in the condenser) to suppress the increase in the discharge pressure. In other words, when the ambient temperature is low, the saturation pressure of the refrigerant accumulated in the condenser is lowered. By simply flowing the refrigerant from the heater system to the low pressure condenser, the discharge pressure of the heater system is increased while maintaining the same compressor rotational speed. It becomes possible to suppress it. 8 shows the effect of lowering the discharge pressure when the compressor rotational speed is high by the above-described control action. As shown in FIG. 9, the on / off valve functions as a high pressure preventing safety device for protecting the heater system when the discharge pressure of the heater system is excessive.

On the other hand, in order to generate the optimal heating performance it is required to maintain the discharge pressure properly, the reason for this is as follows.

If the amount of heat generated when the refrigerant in the evaporator transfers heat to the air side is Q,

dQ / dt = dm / dt × △ h

Is

If the opening degree of the expansion valve of the heater system is decreased at the same compressor rotation speed, that is, the discharge pressure is increased, the enthalpy difference Δh increases but the flow rate m decreases, thereby reducing the heat generation amount, that is, heating performance. On the contrary, when the opening degree of the expansion valve of the heater system is increased at the same compressor speed, that is, when the discharge pressure is lowered, the flow rate m increases but the enthalpy difference Δh decreases and the heating performance decreases.

In conclusion, there is a discharge pressure in which the product of two terms (heating performance) is the maximum, which is dependent on the outside air temperature introduced into the evaporator, and FIG. 11 shows the optimum discharge pressure according to the change of the outside air temperature.

On the other hand, it is possible to adjust the discharge pressure by adjusting the pulse width modulation duty (PWM Duty) of the electronic expansion valve of the heater system (that is, adjusting the opening degree of the electronic expansion valve). 10 shows the change in heating capacity and discharge pressure according to the duty of the electronic expansion valve at the same compressor rotational speed.

Therefore, as described above, the heating performance of the heater system can be improved by adjusting the opening degree of the electronic expansion valve to adjust the compressor discharge pressure to an optimum value according to the evaporator inlet air temperature, that is, the outside air temperature. That is, after reading the temperature of the air flowing into the evaporator, the opening degree of the electronic expansion valve is adjusted to give the optimum discharge pressure for the optimum heating shown in FIG. Then, the actual discharge pressure is read by the pressure sensor P1, and the opening degree of the electronic expansion valve is adjusted while comparing with the optimum discharge pressure. As described above, it is possible to adjust the discharge pressure only according to the temperature of the evaporator inlet air regardless of the increase in the compressor rotation speed.

Hereinafter, a process of controlling the heater system according to the present invention will be described in more detail with reference to FIG. 12.

1) When the operation switch of the heater system is turned on, the heater system is operated while the microcomputer (not shown) mounted on the controller is initialized.

2) The three-way valve is blocked to the condenser side and opened to the first refrigerant passage, so that no refrigerant flows toward the refrigerant circulation passage.

3) A predetermined time has elapsed so that the electric expansion valve is supplied with the maximum current until the counter (clock) is operated and the heater system has a proper pressure (preventing a sudden high pressure during the initial operation of the heater system and protecting the heater system). To do this, the opening of the electronic expansion valve needs to be increased.

4) Operate pressure sensor P1 and temperature sensor T1 to read discharge pressure and evaporator inlet air temperature.

5) If the discharge pressure is below a certain value (allowed value), go through the following normal mode process.

5-1) Read the optimum compressor discharge pressure data according to the evaporator inlet air temperature based on the data in FIG.

5-2) The actual compressor discharge pressure is read using the pressure sensor P1.

5-3) Calculate the error between the actual compressor discharge pressure and the optimum compressor discharge pressure.

5-4) The compressor discharge pressure is adjusted by adjusting the PWM duty of the electronic expansion valve based on the calculated error to adjust the opening degree of the electronic expansion valve.

6) If the discharge pressure value is larger than a certain value (allowed value), the high pressure control mode is entered and the following high pressure control operation starts.

6-1) Open the on / off valve to the second coolant port and flow the coolant to the condenser.

6-2) Supply the maximum current (maximum PWM duty) to the electronic expansion valve to the first refrigerant reservoir to facilitate the flow of the refrigerant.

6-3) The discharge pressure is read and returned to the normal mode when the discharge pressure is lower than or equal to the predetermined value. When the discharge pressure is higher than the constant value, the high pressure control mode is continuously repeated.

6-4) When returning to the normal mode, shut off the valve to the second refrigerant reservoir.

According to the present invention having the above-described configuration, the compressor discharge pressure is set to an appropriate value using an electronic expansion valve according to the outside temperature (evaporator inlet air temperature) to optimally maintain the heating performance of the heater system, and It is possible to prevent damage to the heater system by preventing an increase in discharge pressure.

In addition, by using the heater system according to the present invention, it is possible to replace the combustion heater, etc. that have been previously used for auxiliary heating at a low cost.

Claims (4)

A refrigerant circulation passage passing through the compressor, the condenser, the first expansion valve, and the evaporator in turn, and branched from the refrigerant circulation passage between the compressor and the condenser, and returned to the refrigerant circulation passage between the first expansion valve and the evaporator. In the heater system of the vehicle provided with a first refrigerant passage equipped with a second expansion valve, A second refrigerant passage branched from the refrigerant circulation passage between the evaporator and the compressor to return to the refrigerant circulation passage between the condenser and the first expansion valve and having an on / off valve; A flow direction control valve for controlling a flow direction of the refrigerant toward the refrigerant circulation passage and the first refrigerant passage; And a control unit for controlling an opening degree of the second expansion valve to adjust the discharge pressure of the compressor according to the temperature of the air introduced into the evaporator. The method of claim 1, The flow direction control valve is a three-way valve (3-way valve), the heater system of the vehicle, characterized in that located at the point where the first refrigerant branch from the refrigerant circulation passage. The method according to claim 1 or 2, The control unit includes a pressure sensor P1 for measuring the compressor discharge pressure and a temperature sensor T1 for measuring the temperature of the air flowing into the evaporator, the compressor discharge pressure value from the pressure sensor P1 and the And the compressor discharge pressure is controlled by adjusting the second expansion valve, the three-way valve, and the opening / closing valve by using the temperature value of the air from the temperature sensor (T1). The method of claim 1, And the second expansion valve and the flow direction control valve are integrally formed.