Automotive air conditioning system

Abstract: An air conditioning system (100) for a vehicle has a first cycle including a compressor (L), a first condenser (3), a liquid tank (4a), an expansion valve (5a) and an evaporator (12) which are connected through pipes to form a first refrigerant circulation circuit through which a refrigerant flows from an outlet of the compressor to an inlet of the compressor while changing the phase. The first cycle causes the evaporator (12) to act as a cooler when operated. The system further has a second cycle including the compressor (1), the second condenser (21), the liquid tank (4a), the evaporator (22) which are connected through pipes to form a second refrigerant circulation circuit through which the refrigerant flows from the outlet of the compressor to the inlet of the compressor while changing the phase. The second cycle causes the condenser (21) to act as a heater and the evaporator (22) to act as a cooler when operated. The first and second cycles are switched by switch means. The system further has an air duct case having an air flow passage (20) in which the second condenser (21) and the evaporator (22) are installed. The air flow passage is connected at its downstream part to a passenger room of the vehicle. The air conditioning system further comprises heater means (30) for heating a returning refrigerant which, under operation of the second cycle, flows in the pipe extending from an outlet of the evaporator to the inlet of the compressor.

Description: The present invention relates to an air conditioning system of a vehicle. Hitherto, various types of air conditioning systems have been proposed and put into practical use particularly in the field of motor vehicles. Some are of the above-mentioned double function type. In long body passenger cars, such as one-box type vehicle or the like, there have been also used a so-called duel air conditioning system which comprises a first air conditioning unit for conditioning air in a relatively front part of a passenger room and a second air conditioning unit for conditioning air in a relatively rear part of the passenger room. Nowadays, for obtaining advantages of the double function type, some of the dual air conditioning systems employ the principal of the double function type. That is, for example, the first air conditioning unit comprises an evaporator constituting part of an air conditioning system of double function type and a heater core fed with engine cooling water, and the second air conditioning unit comprises another evaporator connected to the air conditioning system and a condenser connected in series with the evaporator to serve as a heater. However, due to inherent construction, the air conditioning systems of the above-mentioned dual type have failed to give users satisfaction. That is, the second air conditioning unit of the systems has failed to provide the rear part of the passenger room with a satisfactorily warmed air particularly in cold seasons. An air conditioning system as indicated above is provided with a first air flow passage connected with a first part of the passenger room and a second air flow passage connected to a second part of the passenger room of the vehicle. Moreover, air conditioning systems with a condenser and an evaporator which can be operated as cooling means as well as a heating means are known. In particular, prior art document JP-A-7101227 teaches a heater pump type air conditioner for a vehicle. Said air conditioner comprises a compressor and a heat exchanger which performs a heat exchange between refrigerant and outside air. Said heat exchanger is connected with a further heat exchanger being arranged in a single air duct. Said further heat exchanger which is arranged in the air duct is connected with a still further heat exchanger also arranged in that air duct. Between said heat exchangers being arranged in the air duct, an expansion valve is provided. A liquid tank is provided between said expansion valve and the first mentioned heat exchanger being arranged in the air duct. An outlet of the second mentioned heat exchanger being arranged in the air duct is connected with a heater which is provided with cooling water from an electric motor. The outlet of said heater is connected with the inlet of the compressor. In order to switch between a flow circuit routed through the heat exchanger placed outside of the air duct and a flow circuit which bypasses said heat exchanger, valves are provided. A further prior art document US 4,903,495 teaches an air conditioning system which comprises a compressor driven by a prime mover. In consideration of a first circuit, said compressor is connected with a condenser coil, a heat exchanger and an expansion valve and an evaporator coil. Said evaporator coil is connected to an accumulator tank wherein the accumulator may be heated by a coolant from the prime mover. A valve is provided to switch between a circle using the condenser coil and a circle wherein the outlet of the compressor is directly connected with the evaporator section. Said air conditioning system is also applied to a single flow passage. It is an objective of the present invention to provide an air conditioning system for a vehicle which can ensure suitable heating and cooling performance even if said air conditioning system is used in a long body passenger car. According to the present invention, that objective is solved by an air conditioning system for a vehicle having the features of independent claim 1. Preferred embodiments are laid down in the dependent claims. Hereinafter the present invention will be illustrated and explained by means of the accompanying drawings. In the drawings, wherein: Fig. 1 is a schematic view of a one-box car to which a dual air conditioning system of the present teaching is practically applied; Fig. 2 is a schematically illustrated circuit of an automotive dual air conditioning system which is a first embodiment; Fig. 3 is a perspective view of an extra heat exchanger employed in the system of the first embodiment; Fig. 4 is a view similar to Fig. 2, but showing an automotive dual air conditioning system which is a second embodiment; Fig. 5 is a view of an essential portion of the dual air conditioning system of the second embodiment; Fig. 6 is a view similar to Fig. 2, but showing an automotive dual air conditioning system which is a third embodiment; Referring to Figs. 1 to 3, there is shown an automotive dual air conditioning system of a first embodiment which is generally designated by numeral 100A. As is seen from Fig. 1, the dual air conditioning system 100A generally comprises a first air conditioning unit 10 mounted on a relatively front portion of a vehicle "V", a second air conditioning unit 20 mounted on a relatively rear portion of the vehicle "V" and interconnecting means which operatively connects the first and second units 10 and 20 in such a manner as will be described hereinafter. As is understood from the drawing, the first and second air conditioning units 10 and 20 are arranged and constructed to condition air blown into relatively front and rear portions of a passenger room, respectively. That is, the first unit 10 selectively takes outside air (viz., air outside the vehicle) and/or inside air (viz., air in the passenger room) and conditions the air before discharging the same to the front portion of the passenger room, while, the second unit 20 takes inside air and conditions the same before discharging the same to the rear portion of the passenger room. The automotive dual air conditioning system 100A is schematically illustrated in Fig. 2. As is understood from this drawing, the first air conditioning unit 10 comprises an air intake housing having an air flow passage 10f through which air is forced to flow in a direction indicated by arrows. Although not shown in the drawing, an intake door and an electric blower are installed in an upstream portion of the air flow passage 10f. A first heat exchanger 12 and a heater core 11 are installed in the air flow passage 10f in the illustrated manner. Although not shown in the drawing, the air flow passage 10f has at its downstream end air blow openings exposed to the front part of the passenger room. Although not shown, a known air mix door is arranged at a position just upstream of the heater core 11 to control the ratio in quantity between hot air and cooled air fed to an air mix chamber from which the temperature controlled air is led to the passenger room. Usually, the air mix door can have a position to fully close the air passage for the heater core 11. Between the heater core 11 and a water jacket of an engine 2, there is arranged a main hot water flow circuit "Wm" having an Open/Close valve 11a installed therein. That is, when the valve 11a is open, the warmed engine cooling water in the engine water jacket is fed to the heater core 11. The second air conditioning unit 20 comprises an air intake housing having an air flow passage 20f through which air is forced to flow in a direction indicated by an arrow. Although not shown in the drawing, an electric blow is employed for producing the air flow. A second heat exchanger 22 and a second condenser 21 are installed in the air flow passage 20f in the illustrated manner. Although not shown in the drawing, the air flow passage 20f has at its downstream end air block openings exposed to the rear part of the passenger room. A known air mix door (not shown) is arranged at a position just upstream of the second condenser 21 to control the ratio in quantity between hot air and cooled air fed to an air mix chamber from which the temperature controlled air is led to the passenger room. Usually, the air mix door can have a position to fully close the air passage for the second condenser 21. A first closed refrigeration cycle is provided, which comprises a compressor 1, a first condenser 3, a liquid tank 4a, a first Open/Close valve V1, a first expansion valve 5a and the first heat exchanger 12. The compressor 1 is driven by the engine 2. A second closed refrigeration cycle is further provided, which comprises, in addition to the above-mentioned compressor 1, the first condenser 3 and the liquid tank 4a, a second Open/Close valve V2, the second condenser 21, a liquid tank 4b, a second expansion valve 5b, the second heat exchanger 22 and an extra heat exchanger 30. That is, an outlet line from the liquid tank 4a is forked into two branches to which the first and second Open/Close valves V1 and V2 are connected respectively, as shown. An outlet line from the first heat exchanger 12 and an outlet line from the second heat exchanger 22 are joined before being connected to an inlet line of the extra heat exchanger 30. In order to achieve heating operation as well as cooling operation, there is arranged a bypass circuit 3B which bypasses the first condenser 3. A two-way valve 7 is provided for switching the first condenser 3 and the bypass circuit 3B. That is, under the heating operation, compressed refrigerant from the compressor 1 is led to the bypass circuit 3B, while, under the cooling operation, the refrigerant is led to the first condenser 3. Switching between the above-mentioned first and second closed refrigeration cycles is carried out by operating the first and second Open/Close valves V1 and V2. If desired, a four-way valve may be used in place of the two-way valve 7. In this case, a return circuit "m" is further provided as is illustrated by a broken line. That is, upon starting of the heating operation, the return circuit "m" functions to return a marked amount of refrigerant kept in the first condenser 3 to an inlet of the compressor 1. It is to be noted that the extra heat exchanger 30 is placed outside of the air flow passages 10f and 20f of the first and second air conditioning units 10 and 20. The extra heat exchanger 30 is shown in detail in Fig. 3, which comprises a refrigerant passage with inlet and outlet lines 30a-1 and 30a-2 and a water passage with inlet and outlet lines 30b-1 and 30b-2. Although not shown in the drawing, the refrigerant passage is surrounded by the water passage to achieve an effective heat exchange between a refrigerant in the refrigerant passage and water in the water passage. As shown, the two passages are defined in a housing having a plurality of heat radiation fins (no numeral). Referring back to Fig. 2, the refrigerant inlet and outlet lines 30a-1 and 30a-2 of the extra heat exchanger 30 are connected to the outlet line of the first heat exchanger 12 (and thus the outlet line of the second heat exchanger 22) and the inlet of the compressor 1, respectively. The water inlet and outlet lines 30b-1 and 30b-2 of the extra heat exchanger 30 are connected through a sub hot water flow circuit "Ws" to going and coming lines of the above-mentioned main hot water flow circuit "Wm", respectively. An Open/Close valve 11b is installed in the sub hot water flow circuit "Ws". That is, when the valve 11b is opened, warmed engine cooling water is fed to the extra heat exchanger 30 to warm the refrigerant flowing in the exchanger 30. As will be described in detail hereinafter, under heating operation of the air conditioning system, isoentropic compression is effectively carried out by the compressor 1 due to warming of the returning refrigerant. That is, effective heating is achieved by the air conditioning system. A bypass circuit 31 is provided, which bypasses the extra heat exchanger 30 and has an Open/Close valve 32 installed therein. Due to provision of this bypass circuit 31, excessive warming of the returning refrigerant is suppressed. That is, by controlling the valve 32, abnormal discharging pressure of the compressor 1 is suppressed. For controlling the valve 32, the temperature and pressure of the returning refrigerant, those of discharged refrigerant from the compressor 1 and over-heating degree of the returning refrigerant may be used as control factors. For achieving this control, various sensors are employed, which are fixed to inlet and outlet portions of the compressor 1 and outlet portions of the first and second heat exchangers 12 and 22. That is, if at least one of the sensors detects an abnormal condition of the refrigerant, a control unit (not shown) issues a control signal to the valve 32 to open the same. By detecting the temperature, pressure and over-heating degree of the returning refrigerant, undesired overload of the closed refrigeration system is prevented. In the following, operation of the dual air conditioning system 100A of the first embodiment will be described. (1) Initial Stage of Heating Operation For heating both front and rear portions of a passenger room, the first Open/Close valve V1 is closed and the second Open/Close valve V2 is opened, and the valve 7 is turned to make the bypass circuit 3B operative while blocking the first condenser 3. Upon energization of the compressor 1, the high temperature high pressure refrigerant discharged from the compressor 1 is forced to flow through the valve 7, the bypass circuit 3B, the liquid tank 4a, the second Open/Close valve V2, the second condenser 21, the liquid tank 4b, the second expansion valve 5b and the second heat exchanger 22 into the extra heat exchanger 30, and the refrigerant from the extra heat exchanger 30 is forced to return to the compressor 1. During this flow, the valves 11a and 11b are both opened and thus engine cooling water is fed to both the heater core 11 and the extra heat exchanger 30. The temperature of the engine cooling water is gradually increased with increase of time. Due to closed condition of the first Open/Close valve V1, the first heat exchanger 12 does not operate. However, air flowing in the air flow passage 10f of the first air conditioning unit 10 is somewhat warmed by the heater core 11 to which somewhat heated engine cooling water is being fed. Accordingly, somewhat warmed air is blown to the front portion of the passenger room. In the second air conditioning unit 20, the high temperature and high pressure refrigerant from the compressor 1 is led through the second Open/Close valve V2 into the second condenser 21. Thus, heat exchange is carried out between the second condenser 21 and air flowing in the air flow passage 20f of the second air conditioning unit 20. After heating air, the refrigerant, which has medium temperature and high pressure, is subjected to an adiabatic expansion in the second expansion valve 5b to become a lower temperature lower pressure refrigerant and led into the second heat exchanger 22 which, serving as an evaporator, cools the air flowing in the air flow passage 20f. The low temperature low pressure refrigerant discharged from the second heat exchanger 22 is then led into the extra heat exchanger 30. That is, air flowing in the air flow passage 20f of the second air conditioning unit 20 is cooled by the second heat exchanger 22 and then warmed by the second condenser 21, and thus, the second unit 20 feeds the rear portion of the passenger room with a conditioned (more specifically, dehumidified and warmed) air. Due to provision of the extra heat exchanger 30, the heating effect of the second condenser 21 is much increased. That is, the low temperature low pressure refrigerant flowing in the extra heat exchanger 30 absorbs heat from surrounding air and the engine cooling water before being led back to the compressor 1. More specifically, before being compressed by the compressor 1, the returning refrigerant is warmed to a certain level at the second heat exchanger 22 and at the extra heat exchanger 30 while changing its entropy. That is, before being compressed, the returning refrigerant is subjected to two warming steps. Thus, the refrigerant discharged from the compressor 1 can have a higher temperature and thus the second condenser 21 can exhibit a higher heating effect. This effect becomes marked with increase of time. Thus, instant warming for the rear portion of the passenger room is achieved. With increase of time, the temperature of engine cooling water from the engine 2 increases, and thus, the heating effect of the heater core 11 in the air flow passage 10f of the first air conditioning unit 10 gradually increases. That is, after a while, the first unit 10 becomes to feed the front portion of the passenger room with a sufficiently warmed air. (2) Stable Stage of Heating operation With increase of time, both the first and second units 10 and 20 become to provide the passenger room with sufficiently warmed air. Upon this, the first Open/Close valve V1 is opened to permit the high temperature high pressure refrigerant from the compressor 1 to flow also into the first heat exchanger 12 of the first unit 10 through the first expansion valve 5a. Thus, under this condition, the first heat exchanger 12 serves as an evaporator to cool air flowing in the air flow passage 10f of the first unit 10. That is, the first unit 10 feeds the front portion of the passenger room with a conditioned (more specifically, dehumidified and warmed) air. Under this stable stage of heating operation, various heating modes are available by controlling the three Open/Close valves 11a, 11b and 32. Controlling these valves may be electrically achieved by using a control unit. (2-1) First Mode This mode is provided by opening the valves 11a and 11b and closing the valve 32. Under this mode, warmed engine cooling water from the engine 2 is fed not only to the heater core 11 through the main hot water flow circuit "Wm" but also to the extra heat exchanger 30 through the sub hot water flow circuit "Ws". Thus, the first and second units 10 and 20 can feed the passenger room with dehumidified and warmed air. (2-2) Second Mode This mode is provided by opening the valve 11a and closing the valves 11b and 32. Under this mode, due to open condition of the valve 11a, the first unit 10 can provide the front portion of the passenger room with dehumidified and warmed air. While, due to closed condition of the valve 11b, the extra heat exchanger 30 fails to receive the warmed engine cooling water, more specifically, the engine cooling water is retained in the extra heat exchanger 30. Thus, for a while, the refrigerant flowing in the extra heat exchanger 30 absorbs heat from the retained engine cooling water in the exchanger 30. However, with increase of time, quantity of heat possessed by the retained engine cooling water is gradually reduced. Thus, after passing a given time, normal heating operation of the dual air conditioning system is provided. That is, at an initial stage of this second mode, a relatively hot air is provided by the first and second units 10 and 20 and thereafter, the temperature of the air is gradually reduced to a normally hot level. (2-3) Third Mode This mode is provided by openings the valves 11a and 32 and closing the valve 11b. That is, the bypass circuit 31 for the extra heat exchanger 30 Is opened. Under this mode, due to open condition of the valve 11a, the first unit 10 provides the front portion of the passenger room with dehumidified and warmed air like in the above-mentioned first and second modes. While, due to closed condition of the valve 11b and open condition of the valve 32, the refrigerant from the first and second heat exchangers 12 and 22 is forced to flow through the bypass circuit 31 as well as the extra heat exchanger 30. Due to this, heating effect applied to the refrigerant by the extra heat exchanger 30 is lowered and thus normal heating operation is provided by the dual air conditioning system. By selecting this third mode, the compressor 1 is prevented from producing an abnormally high pressure refrigerant. It is to be noted that under heating operation the valve 11a is kept open. (3) Cooling Operation In this cooling operation, three modes are available by controlling the first and second Open/Close valves V1 and V2, which are a front cooling mode, a dual cooling mode and a rear cooling mode. Under these modes, the valves 11a and 11b for the warmed engine cooling water are closed and the valve 32 is opened. (3-1) Front Cooling Mode For achieving this mode, the valve 7 is turned to a position to make the first condenser 3 operative while blocking the bypass circuit 3B. Then, the first Open/Close valve V1 is opened and the second Open/Close valve V2 is closed. With this, the high temperature high pressure refrigerant from the compressor 1 is forced to flow through the valve 7, the first condenser 3, the liquid tank 4a, the first Open/Close valve V1, the first expansion valve 5a, the first heat exchanger 12 to both the extra heat exchanger 30 and the valve 32, and the refrigerant from the extra heat exchanger 30 and the valve 32 returns to the compressor 1. With this circulation of the refrigerant, the first heat exchanger 12, serving as an evaporator, cools air flowing in the air flow passage 10f and thus provides the front portion of the passenger room with cooled air. (3-2) Dual Cooling Mode For achieving this mode, the valve 7 is turned to the position to make the first condenser 3 operative blocking the bypass circuit 3B, and the first and second Open/Close valves V1 and V2 are both opened. With this, the high temperature high pressure refrigerant from the compressor 1 is forced to flow through the valve 7 and the first condenser 3 into the liquid tank 4a, and one part of the refrigerant from the liquid tank 4a is forced to flow through the first Open/Close valve V1, the first expansion valve 5a and the first heat exchanger 12 to both the extra heat exchanger 30 and the valve 32, and the other part of refrigerant from the liquid tank 4a is forced to flow through the second Open/Close valve V2, the second condenser 21, the liquid tank 4b, the second expansion valve 5b and the second heat exchanger 22 to both the extra heat exchanger 30 and the valve 32. The refrigerant from both the extra heat exchanger 30 and the valve 32 is returned to the compressor 1. As a result of this circulation, the first heat exchanger 12, serving as an evaporator, cools air flowing in the air flowing passage 10f of the first unit 10, and the second heat exchanger 22, serving as an evaporator, cools air flowing in the air flowing passage 20f of the second unit 20. Thus, the first and second units 10 and 20 provide the front and rear portions of the passenger room with cooled air. It is to be noted that under this condition the second condenser 21 does not operate as a condenser because the refrigerant supplied thereto has been already condensed by the first condenser 3. (3-3) Rear Cooling Mode For achieving this mode, the valve 7 is turned to the position to make the first condenser 3 operative blocking the bypass circuit 3B, and the second Open/Close valve V2 is opened and the first Open/Close valve V1 is closed. With this, the high temperature high pressure refrigerant from the compressor 1 is forced to flow through the valve 7, the first condenser 3, the liquid tank 4a, the second Open/Close valve V2, the second condenser 21, the liquid tank 4b, the second expansion valve 5b and the second heat exchanger to both the extra heat exchanger 30 and the valve 32. The refrigerant from both the extra heat exchanger 30 and the valve 32 is returned to the compressor 1. As a result of this circulation, the second heat exchanger 22, serving as an evaporator, cools air flowing in the air flow passage 20f of the second unit 20. Thus, the second unit 20 provides the rear portion of the passenger room with cooled air. For the above-mentioned reason, under this condition, the second condenser 21 does not operate as a condenser. Referring to Fig. 4, there is shown an automotive dual air conditioning system 100B which is a second embodiment. Since the system 100B of this second embodiment is similar to the above-mentioned system 100A of the first embodiment, only portions and parts which are different from those of the first embodiment will be described in detail in the following. Substantially same portions and parts as those of the first embodiment 100A are denoted by the same numerals. As is seen from Fig. 4, in this second embodiment 100B, there are no means which correspond to the bypass circuit 31 and the valve 32 which are used in the first embodiment 100A. Furthermore, the extra heat exchanger 30 is arranged in a refrigerant line just downstream of the second heat exchanger 22. As shown, a refrigerant line from the output of the extra heat exchanger 30 to connected to a refrigerant line which extends from an output of the first heat exchanger 12 to the compressor 1. As is well shown in Fig. 4, in this second embodiment 100B, there is employed a temperature sensor 40 which, for controlling an valve open degree of the second expansion valve 5b, senses the temperature of the refrigerant just discharged from the extra heat exchanger 30. That is, as is seen from Fig. 5, the temperature sensor 40 is mounted on the outlet line 30a-2 of the extra heat exchanger 30. Although not shown in the drawings, a known controller is incorporated with the second expansion valve 5b to control the valve open degree of the same in accordance with an information signal issued from the temperature sensor 40. That is, when the temperature of the refrigerant just discharged from the extra heat exchanger 30 is relatively high, the valve open degree of the second expansion valve 5b is increased, while, the temperature is relatively low, the open degree of the valve 5b is reduced. As is known, higher temperature possessed by a refrigerant just fed to the compressor 1 means that the heat load of a refrigeration cycle is high. Thus, by increasing the valve open degree of the second expansion valve 5b, the amount of the refrigerant returned to the compressor 1 is increased thereby to feed the second closed refrigeration cycle with a greater amount of refrigerant. With this, appropriate cooling operation is achieved by the second unit 20. While, when the temperature of the refrigerant from the extra heat exchanger 30 is relatively low, the valve open degree of the second expansion valve 5b is reduced for suitably controlling the amount of refrigerant flowing in the second closed refrigeration cycle. Operation of the system of the second embodiment 100B is substantially the same as that of the above-mentioned first embodiment 100A except the following. That is, due to provision of the added measure including the temperature sensor 40 by which the valve open degree of the second expansion valve 5b is controlled, more precise cooling operation is carried out by the second unit 20, as is described hereinabove. Referring to Fig. 6, there is shown an automotive dual air conditioning system 100C which is a third embodiment. Since the system 100C of this third embodiment is similar to the above-mentioned system 100B of the second embodiment, only portions and parts which are different from those of the second embodiment will be described in detail in the following. Substantially same portions and parts as those of the second embodiment 100B are denoted by the same numerals. As is seen from Fig. 6, in this third embodiment 100C, there is no means corresponding to the second heat exchanger 22 used in the second embodiment 100B. That is, the outlet of the second condenser 21 is connected to the inlet line 30a-1 of the extra heat exchanger 30 through the liquid tank 4b and the second expansion valve 5b. Further, there is no means corresponding to the added measure (including the temperature sensor 40 by which the second expansion valve 5b is controlled) employed in the second embodiment 100B. Furthermore, in the third embodiment 100C, a refrigerant line from the output of the compressor 1 to the first condenser 3 has a first Open/Close valve Va installed therein, a refrigerant line from the output of the compressor 1 to the inlet of the second condenser 21 has a second Open/Close valve Vb intalled therein, and a refrigerant line from the outlet of the outlet of the first heat exchanger 12 to the inlet of the liquid tank 4a has a third Open/Close valve Vc installed therein. Due to removal of the second heat exchanger (22) from the second unit 20, the second unit 20 loses the cooling function. However, the second unit 20 can be produced compact in size and thus entire of the air conditioning system 100C of this third embodiment can be constructed compact in size. In the following, operation of the dual air conditioning system 100C of the third embodiment will be described. (1) Heating Operation For heating both front and rear portions of a passenger room, the valves 11a and 11b are both opened and the first Open/Close valve Va is closed and then the second Open/Close valve Vb is opened. Thus, engine cooling water is fed to the heater core 11. However, in the initial heating stage, the heater core 11 of the first unit 10 fails to exhibit a satisfied heating function due to lack of heat possessed by the engine cooling water. Upon energization of the compressor 1, the high temperature high pressure refrigerant discharged from the compressor 1 is forced to flow through the second Open/Close valve Vb, the second condenser 21, the liquid tank 4b and the second expansion valve 5b into the extra heat exchanger 30, and the refrigerant from the extra heat exchanger 30 is forced to return to the compressor 1. Thus, heat exchange is carried out between the second condenser 21 and air flowing in the air flow passage 20f of the second unit 20. After heating air, the refrigerant, which has medium temperature and high pressure, is subjected to an adiabatic expansion in the second expansion valve 5b to become a lower temperature lower pressure refrigerant and led into the extra heat exchanger 30. That is, by the second condenser 21, the air flowing in the air flow passage 20f of the second unit 20 is warmed. Due to provision of the extra heat exchanger 30, the heating effect of the second condenser 21 is much increased. That is, the low temperature low pressure refrigerant flowing in the extra heat exchanger 30 absorbs heat from surrounding air before being led back to the compressor 1. That is, before being compressed by the compressor 1, the returning refrigerant is warmed to a certain level changing its entropy. Thus, the second condenser 21 can exhibit a higher heating effect. This effect becomes marked with increase of time. Thus, instant warming for the rear portion of the passenger room is achieved. With increase of time, the temperature of engine cooling water increases, and thus, the heating effect of the heater core 11 of the first unit 10 gradually increases. Thus, after a while, the second unit 10 becomes to feed the front portion of the passenger room with a sufficiently warmed air. With increase of time, the temperature of the engine cooling water increases thereby gradually increasing the heating effect of the extra heat exchanger 30. Thus, the heating effect of the second condenser 21 is increased with increase of time. The refrigerant condensed by the second condenser 21 is stored by the liquid tank 4b, so that the amount of refrigerant flowing in the refrigerant line of the second unit 20 is appropriately controlled. (2) Cooling Operation Cooling operation is carried out by only the first air conditioning unit 10. For starting the cooling operation, the third Open/Close valve Vc is opened to return the refrigerant, which has been remained in the first condenser 3, to the compressor 1. Then, the first Open/Close valve Va is opened and the second and third Open/Close valves Vb and Vc are closed. Then, the compressor 1 is operated. Upon this, the high temperature high pressure refrigerant from the compressor 1 is forced to flow through the first Open/Close valve Va, the first condenser 3, the liquid tank 4a and the first expansion valve 5a into the first heat exchanger 12, and the refrigerant from the first heat exchanger 12 is forced to return to the compressor 1. With this circulation of the refrigerant, the first heat exchanger 12, serving as an evaporator, cools air flowing in the air flow passage 10f and thus provides the front portion of the passenger room with cooled air. The refrigerant condensed by the first condenser 3 is stored by the liquid tank 4a, so that the amount of refrigerant flowing in the refrigerant line of the first unit 10 is appropriately controlled.

Claims: An air conditioning system for a vehicle, comprising: a first air conditioning unit (10) having a first air flow passage (10f), and a second air conditioning unit (20) having a second air flow passage (20f), said first air flow passage (10f) is connected at its downstream part to a first part of a passenger room of said vehicle, and said second air flow passage (20f) is connected at its downstream part to a second part of the passenger room of said vehicle; a first cycle including a compressor (1), a first condenser (3), a second condenser (21), a liquid tank (4b), an expansion valve (5b) and an evaporator (22) which are connected through pipes to form a first refrigerant circulation circuit through which a refrigerant flows from an outlet of said compressor (1) to an inlet of said compressor (1) while changing the phase, said first cycle causing said evaporator (22) to act as a cooler when operated; a second cycle including said compressor (1), said second condenser (21), said liquid tank (4b), said expansion valve (5b) and said evaporator (22) which are connected through pipes to form a second refrigerant circulation circuit through which said refrigerant flows from the outlet of said compressor (1) to the inlet of said compressor (1) while changing the phase, said second cycle causing said second condenser (21) to act as a heater and said evaporator (22) to act as a cooler when operated; switch means (7, 11a, 11b, V1, V2) for switching said first and second cycles; said second condenser (21) and said evaporator (22) are installed in said second air flow passage (20f), and a heater core (11) is installed said first air flow passage (10f); and heater means (30) for heating a returning refrigerant which, under operation of said second cycle, flows in the pipe extending from an outlet of the evaporator (22) to the inlet of said compressor (1). An air conditioning system for a vehicle according to claim 1, wherein said heater means comprises warmed water producing means (2, 30a) for producing warmed water; and a heat exchanger (30) having a first passage (30a-1, 30a-2) through which said returning refrigerant flows and a second passage (30b-1, 30b-2) through which said warmed water flows, said first and second passages (30a-1, 30a-2, 30b-1, 30b-2) being arranged to carry out heat exchanging therebetween. An air conditioning system for a vehicle according to claim 2, wherein said warmed water producing means is a water jacket of an internal combustion engine (2) which is mounted on said vehicle. An air conditioning system for a vehicle according to claim 2 or 3, wherein said heat exchanger (30) is formed with a plurality of heat radiation fins. An air conditioning system for a vehicle according to at least one of the claims 2 to 4, wherein said heater exchanger (30) arranged in a position outside of the first and second air flow passage (10f, 20f). An air conditioning system for a vehicle according to at least one of the claims 2 to 5, wherein said first passage (30a-1, 30a-2) through which said returning refrigerant flows is provided with a bypass circuit (31) which bypasses said heat exchanger (30), said bypass circuit (31) is provided with an open/close valve (32) installed therein.

Inventors: ABE KENICHI, NODA YOSHITOSHI, OHASHI TOSHIO, TAJIMA TADAYOSHI, YAMAGUCHI HIROYUKI, YOSHIOKA HIROKI, ABE, KENICHI, NODA, YOSHITOSHI, OHASHI, TOSHIO, TAJIMA, TADAYOSHI, YAMAGUCHI, HIROYUKI, YOSHIOKA, HIROKI
Applicants: CALSONIC KANSEI CORP, CALSONIC KANSEI CORPORATION
Application year: 1997
Main classification: B60H1
IPC codes: B60H1, F28D1, F28D7