Air-conditioning control unit

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioning control unit used for an air conditioning system that performs heating operation using a refrigerant of a fuel car, electric car or the like as a heat source.

2. Description of the Related Art

A Well-known conventional air conditioning system adjusts temperature of air in a cabin by mixing hot air from a heat exchanger of a radiator for an engine as a heat source and cold air from a cooler using refrigerant as disclosed in a patent brochure, Japanese Patent Application Laid-Open No. 2002-274147.

In the case where cooling water in the radiator for the engine is used as a beat source, the above described conventional air conditioning system would be effective to control the temperature of air in the cabin.

However, in the case where no heat source of the engine exists, as in the electric vehicle by fuel cell, since the air conditioning system is required another heat source, structure and control of the system becomes complex and manufacturing cost thereof is raised.

SUMMARY OF THE INVENTION

The present invention has been achieved with such points in mind.

It therefore is an object of the present invention to provide a air-conditioning control unit used in a air conditioning system where temperature of the air in the cabin of vehicle can be more accurately controlled, and manufacturing cost thereof can be reduced.

To achieve the object, according to a first aspect of the present invention, there is provided an air-conditioning control unit (26) used in a air conditioning system (1) which comprises: a refrigerant circuit (2); a first indoor heat exchanger (10) having a low refrigerant temperature; a second indoor heat exchanger (4) having a high refrigerant temperature; controlled components (5, 12); a first air passage (21); and a second air passage (22) and a third air passage (23) which are distributed by an airflow distributing door (16) from the first air passage (21), wherein the air-conditioning control unit (26) controls the controlled components (5, 12) and the airflow distributing door (16); wherein the first indoor heat exchanger (10) is provided in the first air passage (21); wherein the second indoor heat exchanger (4) is provided in the second air passage (22); wherein adjusting air sent from the first air passage (21) is distributed into the second air passage (22) and the third air passage (23) by controlling the airflow distributing door (16); wherein switching is carried out between an air flowing state during heating in which air is distributed mainly into the second air passage (22) and an air flowing state during cooling in which air is distributed mainly into the third air passage (23); wherein switching between a cooling operation state and a heating operation state is carried out by controlling the controlled components (5, 12) and thereby performing switching between a cooling control mode and a heating control mode in the refrigerant circuit (2); and wherein, in switching from the cooling operation state to the heating operation state, the flow of the adjusting air in the second air passage (22) is increased by controlling the airflow distributing door (16) by the air-conditioning control unit (26) prior to the switching of refrigerant circuit from the cooling control mode to the heating control mode.

In the structure according to the first aspect of the present invention, when cooling operation is switched to heating operation, the airflow distributing door (16) is controlled so as to increase the quantity of adjusting air flowing into the second air passage (22) prior to switching of the refrigerant circuit from the cooling control mode to the heating control mode. As a result, since high-temperature air stagnating during cooling operation is discharged, the temperature of the adjusting air can be detected more accurately by the air temperature sensor (25) provided at the downstream of the second indoor heat exchanger (4).

According to a second aspect of the present invention, as it depends from the first aspect, there is provided an air-conditioning control unit (26) wherein the airflow distributing door (16) is controlled so as to flow smaller quantity of adjusting air into the second air passage (22) than the air flowing into the third air passage (23) in the air flowing state during cooling.

In the structure according to the second aspect of the present invention, since the airflow distributing door (16) is controlled so that smaller quantity of adjusting air flows into the second air passage (22) than the air flowing into the third air passage (23) during cooling operation, rapid change in temperature of the adjusting air can be suppressed.

According to a third aspect of the present invention, as it depends from the first or the second aspect, there is provided an air-conditioning control unit (26) wherein the airflow distributing door (16) is controlled so as to flow smaller quantity of adjusting air into the third air passage (23) than the air flowing into the second air passage (22) in the air flowing state during heating.

In the structure according to the third aspect of the present invention, since the airflow distributing door (16) is controlled so that smaller quantity of adjusting air flows into the third air passage (23) than the air flowing into the second air passage (22) during heating operation, rapid change in temperature of the adjusting air can be suppressed.

According to a fourth aspect of the present invention, as it depends from one aspect among the first to the third aspect, there is provided an air-conditioning control unit (26) wherein the second air passage (22) is connected to an air outlet on the lower side in the room and the third air passage (23) is connected to an air outlet on the upper side in the room.

In the structure according to the fourth aspect of the present invention, since the second air passage (22) is connected to the air outlet on the lower side in the room and the third air passage (23) is connected to the air outlet on the upper side in the room, the upper side in the room can be maintained at relatively low temperatures, improving comfortability during heating operation.

According to a fifth aspect of the present invention, as it depends from one aspect among the first to the fourth aspect, there is provided an air-conditioning control unit (26) wherein position of the airflow distributing door (16) is changed so as to decrease a difference between blowing temperature of the adjusting air and control target temperature.

In the structure according to the fifth aspect of the present invention, the position of the airflow distributing door (16) is changed so as to decrease a difference between the blowing temperature of adjusting air and the control target temperature, rapid change in temperature of the adjusting air can be suppressed.

BRIEF DESCRIPTION OF THE ACCOMPANYNG DRAWINGS

FIGS, 1A and 1B are views showing position of an airflow distribution door of an air conditioning system during cooling operation (FIG. 1A) and heating operation (FIG. 1B) in accordance with the embodiment of the present invention,

FIG. 2 is a view showing an improved air conditioning system comprising an air-conditioning control unit in accordance with an embodiment of the present invention (cooling operation state).

FIG. 3 is a view showing an improved air conditioning system comprising an air-conditioning control unit in accordance with the embodiment of the present invention (heating operation state).

FIG. 4 is a flowchart showing an example of a control procedure of the air-conditioning control unit in accordance with the embodiment of the present invention.

FIG. 5 is a flowchart showing an example of a control procedure of the air-conditioning control unit in accordance with the embodiment of the present invention (continued from FIG. 4).

FIG. 6 is a flowchart showing an example of a control procedure of the air-conditioning control unit in accordance with the embodiment of the present invention (continued from FIGS. 4 and 5).

FIG. 7 is a view showing a control example of the airflow distribution door in accordance with the embodiment of the present invention in the cooling operation state.

FIG. 8 is a view showing a control example of the airflow distribution door in accordance with the embodiment of the present invention in the heating operation state.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There will be detailed below the preferred embodiments of the present invention with reference to the accompanying drawings. Like members are designated by like reference characters.

FIGS. 1A and 1B show a first embodiment of the present invention. The drawings show an arrangement of a first air passage 21 which are divided by a wall into a second air passage 22 and a third air passage 23 in a duct 20. There is provided with a first indoor heat exchanger 10 in the first air passage 21, and with a second indoor heat exchanger 4 in the second air passage 22. Furthermore, at the end of the wall which is located between the second air passage 22 and the third air passage 23, there is provided with a airflow distribution door 16 which is swungly controlled by an air-conditioning unit 26 according to the present invention.

In the above described arrangement shown in FIGS. 1A and 1B, air passes through the first indoor heat exchanger 10 (at low temperate) and airflow flowing into the second indoor heat exchanger 4 (at high temperature) are mixed or adjusted at an appropriate ratio by the airflow distributing door 16 so as to adjust temperature of the air which blow into the cabin of the vehicle or car.

In this case, as shown in the state shown in FIG. 1A for during cooling operation, control is carried out by using an air temperature sensor 24 which is located at the downstream end of the first indoor heat exchanger 10. Further, during cooling operation, for the improvement of efficiency, cooling level is adjusted by controlling the number of revolutions of a compressor and basically, no air is flown to the side of the second indoor heat exchanger 4. For this reason, high-temperature air may stagnate in the vicinity of the second indoor heat exchanger 4 during cooling operation.

In addition to the above arrangement, another air temperature sensor 25 is located at the downstream end of the second indoor heat exchanger 4. When heating operation mode (as shown in FIG. 1A) is carried out right after cooling operation mode (as shown in FIG. 1B), since control is carried out based on the temperature detected by an air temperature sensor 25 immediately since switching from the cooling operation mode to the heating operation mode, it is wrongly determined that air in the second air passage is sufficiently heated although not sufficiently heated in fact. This may lead to inadequate control.

A second embodiment of the air conditioning system 1 including the air-conditioning control unit 26 will be described hereinbelow with referring to the accompanying drawings, FIG. 2 to FIG. 8. The second embodiment is improved in such point described in the former paragraph.

FIGS. 2 and 3 show the air conditioning system 1 having the air-conditioning unit 26 according to the present invention. Especially, FIG. 2 shows the cooling operation mode and FIG. 3 shows the heating operation mode.

As shown in FIG. 2, in the cooling operation mode, a compressor 3, the second indoor heat exchanger 4, the outdoor heat exchanger 6, an internal heat exchanger 8, an expansion valve 9, the first indoor heat exchanger 10, an accumulator 11 and an internal heat exchanger 8 are connected to each other by piping in this order and a refrigerant circulates in the direction of arrows (first refrigerant cycle 2c).

The compressor 3 is disposed, for example, at the outside of the vehicle, compresses a sucked low-pressure refrigerant and discharges the compressed high-temperature and high-pressure refrigerant. The compressor 3 is, for example, an electric compressor driven by electric power.

The outdoor heat exchanger 6 is disposed at the outside of the car and exposed to outside air by driving a blowing means (not shown) such as an electric fan. The outdoor heat exchanger 6 radiates heat of the refrigerant to the outside air by exchanging heat between the high-temperature and high-pressure refrigerant passing theretrough and the outside air.

The expansion valve 9 reduces the pressure of the refrigerant, the heat of which is radiated in the outdoor beat exchanger 6.

The first indoor heat exchanger 10 is disposed in the car and air is sent into the car through the first indoor heat exchanger 10 by driving a blowing means (not shown) such as a blower fan. The first indoor heat exchanger 10 extracts heat from air flowing in the car and cools the air by exchanging heat between the low-temperature and low-pressure refrigerant and the blown air.

The internal heat exchanger 8 allows heat to be exchanged between the high-pressure refrigerant, the heat of which is radiated in the outdoor heat exchanger 6, and the low-pressure refrigerant, the heat of which is absorbed in the first indoor heat exchanger 10.

The accumulator 11 separates the refrigerant from the first indoor heat exchanger 10 into the liquid one and the gaseous one, sends only the gaseous refrigerant and stores the liquid refrigerant temporarily.

On the other hand, as shown in FIG. 3, in the heating operation mode, the compressor 3, the second indoor heat exchanger 4, the internal heat exchanger 8, the expansion valve 15, the outdoor heat exchanger 6, the accumulator 11 and the internal heat exchanger 8 are connected to each other by piping in this order and the refrigerant circulates in the direction of arrows (second refrigerant cycle 2h).

The second indoor heat exchanger 4 is disposed in the car and air is sent into the car through the second indoor heat exchanger 4 by driving a blowing means (not shown) such as a blower fan. The second indoor heat exchanger 4 heats the air flowing in the car and radiates heat of the refrigerant by exchanging heat between the high-temperature and high-pressure refrigerant passing therethrough and the blown air.

The expansion valve 15 reduces the pressure of the refrigerant, the heat of which is radiated in the second indoor heat exchanger 4.

The outdoor heat exchanger 6 is disposed at the outside of the car and exposed to outside air by driving a blowing means (not shown) such as an electric fan. The outdoor heat exchanger 6 allows the refrigerant to absorb heat by exchanging heat between the low-temperature and low-pressure refrigerant passing therethrough and the outside air.

In the case where the same operations are carried out both in the cooling operation mode and heating operation mode, description thereof will be omitted.

Reference numeral 5 designates a three-way valve, and reference numeral 12 designates a solenoid valve. The three-way valve 5 and the solenoid valve 12 are collectively constituted as controlled component 5, 12 which are controlled by the air-conditioning control unit 26. Reference numerals 7, 13 and 14 designate a check valve.

An air-conditioning control unit 26 consisting of a microcomputer controls the expansion valves 9, 15, the three-way valve 5, the solenoid valve 12, (a drive mechanism of) an airflow distribution door 16 and other equipment based on detected values of various sensors (an air temperature sensor 24 and the like) or input information of an operational panel (not shown) and the like. Among them, the three-way valve 5 and the solenoid valve 12 are controlled components relating to the switching of the refrigerant cycles.

The air cooled in the first indoor heat exchanger 10 is distributed into a second air passage 22 passing through the second indoor heat exchanger 4 and another third air passage 23 bypassing the second indoor heat exchanger 4 at an appropriate ratio by the airflow distribution door 16. In the case where a cooling and heating efficiency is maximized, however, the airflow distribution door 16 is controlled so as to positioned to block the second air passage 22 in the cooling operation state (hereinafter referred to as F/COOL) (FIG. 2) and to block the third air passage 23 in the heating operation state (hereinafter referred to as F/HOT) (FIG. 3). The air passing through the second air passage 22 and the air passing through the third air passage 23 are mixed in an air mix chamber (not shown) and blown out from an air outlet (not shown) toward the inside of the car.

Next, an example of control procedures of the airflow distribution door by the air-conditioning control unit in accordance with this embodiment will be described with reference to FIGS. 4 to 8. FIGS. 4 to 6 are flowcharts of the control procedures, FIG. 7 is a view showing an air passage running certain quantity of regulating air at the side of the second air passage in the cooling operation state and FIG. 8 is a view showing an air passage running certain quantity of regulating air at the side of the third air passage in the heating operation state. In FIGS. 4 to 6, the airflow distribution door 16 is referred to as A/MIX.

Firstly, at a step S10, the air-conditioning control unit 26 determines whether or not a time interval Ti has passed after previous control. When Ti has passed, the procedure of determining a control target position of the airflow distribution door 16 is carried out and when Ti has not passed, the procedure of controlling the airflow distribution door 16 at the control target position is carried out (FIG. 6). Preferably, this Ti is determined depending on rate of change of room air temperature. It is set to be six seconds, for example.

At a step S11, in the case of heating control mode, the air-conditioning control unit 26 carries out procedures of changing the control target position of the airflow distribution door 16 depending on an air outlet mode, position of the airflow distribution door 16 and a difference between a blowing temperature and a control target temperature (steps S12 to S19; FIG. 4). At a step S20, in the case of cooling control mode, the air-conditioning control unit 26 carries out procedures of changing the control target position of the airflow distribution door 16 depending on the number of revolutions of the compressor 3, position of the airflow distribution door 16 and a difference between a blowing temperature and a control target temperature (steps S21 to S29; FIG. 5). At a step S20, in the case where the mode is neither heating control mode nor cooling control mode, the air-conditioning control unit 26 carries out procedures of driving and controlling the airflow distribution door 16 at the control target position (steps S30 to S32; FIG. 6).

In the heating control mode, at a step S12, it is determined whether or not the air outlet mode is set at bi-level (described as B/L in the figure). The bi-level is the state where the third air passage 23 is connected to the air outlet on the upper side in the room and the second air passage 22 is the air outlet on the lower side in the room. When the air outlet mode is not set at bi-level, the target position of the airflow distribution door 16 is set at F/HOT (see FIG. 3) (step S13).

When the air outlet mode is set at bi-level, at a step S14, it is determined whether or not the airflow distribution door 16 is located closer to the F/COOL side than a second specified position (see FIG. 2). When the airflow distribution door 16 is located closer to the F/COOL side than a second specified position, the control target position is defined as the second specified position.

Here, as shown in FIG. 8, the second specified position is a position at which small quantity of adjusting air is distributed into the third air passage 23. When the airflow distribution door 16 is located at the second specified position, smaller quantity of adjusting air flows into the third air passage 23 than the air-flowing into the second air passage 22. In this state, since both of warm air and cool air are blown into the room, such control is effective especially when rapid change in temperature of the adjusting air is undesirable, for example, at switching from heating to cooling. Further, in this embodiment, the airflow distribution door 16 is located at the second specified position in the state where the air outlet mode is set at bi-level. This leads to an advantage of improving comfortability since cool air is blown to the upper side in the room and heat air is blown to the lower side in the room.

When the airflow distribution door 16 is not located closer to the F/COOL side than the second specified position at a step S14, an absolute value of temperature difference between the blowing temperature and the control target temperature is compared with a predetermined threshold value and it is determined whether or not the blowing temperature is much lower than the control target temperature at a step S16. Subsequently, when the blowing temperature is much lower than the control target temperature, the control target position of the airflow distribution door 16 is shifted toward the F/HOT side (step S17).

At a step S18, an absolute value of temperature difference between the blowing temperature and the control target temperature is compared with a predetermined threshold value and it is determined whether or not the blowing temperature is much higher than the control target temperature at a step S18. Subsequently, when the blowing temperature is much higher than the control target temperature, the control target position of the airflow distribution door 16 is shifted toward the F/COOL side (step S19). Preferably, the shift of the control target position in the steps S17 and S19 is performed in increments of a predetermined relatively minute angle (for example, an angle obtained by dividing an angle between the F/COOL and F/HOT positions by 125).

Such control has an advantage of suppressing rapid change in temperature of the adjusting air. As described herein, in terms of heating efficiency, it is advantageous that control is carried out so as to reduce the temperature difference only when the temperature difference between the blowing temperature and the control target temperature is large.

On the other hand, in the cooling control mode, at a step S21, it is determined whether or not the number of revolutions of the compressor 3 equals a threshold number of revolutions Nth or more. The threshold number of revolutions Nth is set to be close to the minimum number of revolutions of the compressor 3 in the state where heating operation is switched to cooling operation and vice versa. For example, when the number of revolutions of the compressor 3 ranges from 30 Hz to 120 Hz, Nth is set to be 40 Hz. By doing so, it is possible to know switching from the cooling control mode to the heating control mode in advance.

When the number of revolutions of the compressor 3 is higher than Nth, the target position of the airflow distribution door 16 is set at F/COOL (see FIG. 2) (step S22).

On the contrary, when the number of revolutions of the compressor 3 is lower than Nth, it is determined whether or not the airflow distribution door 16 is located closer to the F/COOL side than a first specified position. Then, when the airflow distribution door 16 is located closer to the F/COOL side than the first specified position, the control target position is defined as the first specified position (step S25).

Here, as shown in FIG. 7, the first specified position is a position at which small quantity of adjusting air is distributed into the second air passage 22. When the airflow distribution door 16 is located at the first specified position, smaller quantity of adjusting air flows into the second air passage 22 than the air flowing into the third air passage 23. In this state, since both of warm air and cool air are blown into the room, such control is effective especially when rapid change in temperature of the adjusting air is undesirable, for example, at switching from heating to cooling.

In this embodiment, since the adjusting air can be passed into the second air passage 22 prior to switching from the cooling control mode to the heating control mode, stagnation of high-temperature air generating in the vicinity of the second indoor heat exchanger 4 in the cooling operation state can be removed, thereby preventing false detection of an air temperature sensor 25.

When the airflow distribution door 16 is not located closer to the F/COOL side than the first specified position at a step S24, an absolute value of temperature difference between the blowing temperature and the control target temperature is compared with a predetermined threshold value and it is determined whether or not the blowing temperature is much lower than the control target temperature at a step S26. Subsequently, when the blowing temperature is much lower than the control target temperature, the control target position of the airflow distribution door 16 is shifted toward the F/HOT side (step S27).

At a step S28, for example, an absolute value of temperature difference between the blowing temperature and the control target temperature is compared with a predetermined threshold value and it is determined whether or not the blowing temperature is much higher than the control target temperature. When the blowing temperature is much higher than the control target temperature, the control target position of the airflow distribution door 16 is shifted toward the F/COOL side (step S29). Preferably, the shift of the control target position in the steps S27 and S29 is performed in increments of the above-mentioned angle.

Such control has an advantage of suppressing rapid change in temperature of the adjusting air. As described herein, in terms of cooling efficiency, it is especially advantageous that control is carried out so as to reduce the temperature difference only when the temperature difference between the blowing temperature and the control target temperature is large.

The air-conditioning control unit 26 caries out a procedure as shown in FIG. 6 to move the airflow distribution door 16 to the control target position thus determined.

That is, at a step S30, the air-conditioning control unit 26 determines whether or not a time interval T0 has passed since previous positional control. When T0 has passed, the position of the airflow distribution door 16 is controlled and when T0 has not passed, this control is finished. This prevents the airflow distribution door 16 from moving frequently, thereby suppressing uncomfortable feeling due to the frequent operation noise. T0 is set to be one second, for example.

At a step S31, a difference between the control target position and the current position of the airflow distribution door 16 is acquired. When the difference is large, the airflow distribution door 16 is shifted toward the determined control target position at a step S32 (DRIVE A/MIX). At this time, it is preferred that the airflow distribution door 16 is driven in increments of the above-mentioned angle.

The entire contents of the Japanese Patent Application 2004-104820 (filed on Mar. 31, 2004) are incorporated herein by reference,

Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments descried above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.

Air-conditioning control unit

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CPC

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Priority Claims (1)