IES20010349A2 - A dual purpose vehicle air conditioning system - Google Patents

Abstract

A vehicle air conditioning system (1) of the vapour compression type is provided. This is an enclosed system containing a refrigerant fluid. There is a heat exchanger (5) in the passenger compartment or thereabouts and a heat exchanger (6) usually in the engine compartment and generally sited near the engine cooling radiator of the motorcar. In heating use (reverse cycle or heating mode), the heat exchanger (5) operates as a condenser and the heat exchanger (6) as an evaporator. The system includes a compressor (15) and a reversing device (12). There is an expansion leg (22), which includes two expansion devices (22,23). In cooling use, the reversing device (12) is switched to operate as an air conditioner. Low pressure refrigerant liquid is evaporated in the heat exchanger (5) absorbing heat from the inside of the car (27) and it is then compressed in a compressor (15) and delivered to the heat exchanger (6). As high pressure, high temperature fluid, it rejects heat and is then fed through the device where it becomes a low-pressure fluid which is evaporated in the evaporator (5) and the cycle is repeated. This is conventional. The flow reversing valve (12) allows the vehicle air conditioning system (1) to operate in reverse, thus causing the in-car heat exchanger (5) to act as a condenser (putting heat into the passenger compartment) and the heat exchanger (6) to act as an evaporator (absorbing heat from the atmosphere). <Figure 1>

Description

OPEN TO PUBUC INSftOTON UNDER SECTION 28 AND RULE 23 compression type for working in a vehicle havfagan independently operable heating'1 system and associated climate management system, the system comprising an enclosed system containing a refrigerant fluid, a pair of heat exchangers, one heat exchanger sited in the passenger compartment acting as an evaporator, and the other heat exchanger sited outside the passenger compartment acting as an condenser, and associated pipework connecting the heat exchangers to form a compressor leg and an expansion leg, a compressor in the compressor leg and an expansion device in the expansion leg, the direction of fluid flow being from the heat exchanger in the passenger compartment through the compressor through the heat exchanger outside the passenger compartment through the expansion device and back through the heat exchanger in the passenger compartment. All vehicle air conditioning systems currently operating are of this vapour compression type. It is the most convenient type of air conditioning system for a vehicle and the most commonly used in other industries.

Most heating systems in the modern car are extremely effective, except at start-up. This can be a particular problem in locations where the ambient temperature is low. Such is the situation in many countries of the world where ambient temperature during winter time and for many months of the year can be below what is required for human comfort. However, it has long been recognised by the major car manufacturers that driver discomfort, particularly during the initial phase of a journey, is a cause of accidents. Very often, drivers start and operate their vehicles, particularly initially in conditions where the ambient temperature of the passenger compartment is such that it is extremely uncomfortable to sit in and secondly, very 0 often, because the ambient temperature of the passenger compartment is relatively low, the visibility is restricted due to condensation and freezing water on the windows of the vehicle. Thus, having a passenger compartment where the ambient temperature is below freezing, is to be avoided, firstly from a safety viewpoint and secondly, for comfort. Indeed, various devices have been provided to reduce the discomfort for drivers and passengers on first entering a vehicle in such conditions. For example, it is known to provide heated seats which are electrically heated which undoubtedly improve passenger comfort and go a minor way towards elevating the ambient temperature within the passenger compartment of the vehicle.

Most vehicle heating systems are relatively efficient and usually within 10 to 15 minutes of start-up from cold, depending on the outside temperature which effectively influences the initial ambient temperature of the vehicle, will attain an internal temperature within the passenger compartment which is adequate and satisfactory. Most of these heating systems work off the coolant system of the engine, whether it be, as in most cases, a water cooled system or, in some now rare cases, an air cooled system. They are therefore dependent on the coolant fluid attaining the desired temperature to allow the heating system operate effectively. The heating system is generally operated by means of a fan blowing across a heat exchanger. This heat exchanger contains engine coolant liquid and, as mentioned above, in rare cases, air that has itself been blown across the engine. Thus, while known heating systems for vehicles are extremely efficient in use, they are relatively inefficient in the initial start-up phase of the engine.

In a conventional vapour compression air conditioning system, certain terms are used by those skilled in the art to identify the heat exchangers as evaporator and condenser respectively, and the pipework forming the leg between the compressor and the evaporator as the suction leg, and that from the compressor to the condenser and from there back to the evaporator as the discharge leg. The terms high and low pressure sections are also used. For reasons which will become apparent when reading this specification, such terms are inappropriate when describing this invention. Accordingly, in this specification, the pipework between the heat exchangers which contains the compressor is identified as the compressor leg, and rest of the pipework between the heat exchangers and the expansion device is identified as the compressor leg.

The present invention is directed towards providing a system which will allow the passenger compartment of a vehicle to be heated more rapidly than is possible with the conventional heating system.

Statements of Invention According to the invention, there is provided a vehicle air conditioning system of the vapour compression type for working in a vehicle having an independently operable heating system and associated climate management system, the system comprising an enclosed system containing a refrigerant fluid, a pair of heat exchangers, one heat exchanger sited in the passenger compartment acting as an evaporator, and the other heat exchanger sited outside the passenger compartment acting as an condenser, and associated pipework connecting the heat exchangers to form a compressor leg and an expansion leg, a compressor in the compressor leg and an expansion device in the expansion leg, the direction of fluid flow being from the heat exchanger in the passenger compartment through the compressor through the heat exchanger outside the passenger compartment through the expansion device and back through the heat exchanger in the passenger compartment characterised in that there is provided a flow reversing device to reverse the flow of fluid through the system to cause the system to operate in reverse mode as a vehicle air heating system. It will be appreciated that the advantage of this is that when the passenger compartment is very cold, obviously the air conditioning system would not be required and the air conditioning system can be used as a booster for the conventional heating system. When the engine coolant rises in temperature to an acceptable temperature, the reversing device can revert back to air conditioning position rendering the system available for cooling.

In one embodiment of the invention, the flow reversing device is a reversing valve and associated pipework to reverse the flow of fluid between the heat exchangers. This is a very neat and efficient way of carrying out the invention and requires the minimum of changes to the system.

Ideally, the expansion device is a flow restrictor and in one embodiment of the invention is a capillary tube incorporated in the expansion leg.

In some embodiments of the invention, the expansion device comprises an additional flow restrictor which may be a capillary tube and associated one-way check valve whereby when operating in the reverse heating mode, the liquid refrigerant is delivered through both flow restrictors and, in the cooling mode, through the check valve and the other flow restrictor. The reason for this it may be necessary in the heating mode to have additional restriction to balance refrigerant flow.

Ideally, when the system is operating in reverse mode, the engine heating system is adapted to supply heat to the heat exchanger sited outside the passenger compartment. This will allow the most efficient use of the system.

In one embodiment of the invention, the air conditioning system and the heating system are controlled by the climate management system whereby the air conditioning and heating systems can both operate independently, either alone or jointly, and can both operate to heat the vehicle. Indeed, in this latter system, the climate management system has means for sensing the engine coolant conditions in the heating system and when the engine coolant temperature is below a preset temperature, the climate management system causes the air conditioning system to operate in the heating mode until the engine coolant temperature reaches the preset temperature so as to allow the heating system operate on its own for heating the vehicle. ideally, the preset coolant temperature is of the order of 40°C. Needless to say, the temperature may be changed, depending on the conditions.

In one embodiment of the invention, the flow reversing device includes a timer to limit the length of time the system operates in the heating mode. In this way, when the heating system is turned on, the air conditioning system may be automatically operated in the heating mode so as to always provide the quickest possible heating of the engine compartment. Generally, such a timer will operate for 10 to 15 minutes.

In one embodiment of the invention, the flow climate management system comprises:a temperature sensor within the passenger compartment: and 0549 controls operable by an occupant of the vehicle to control the temperature within the vehicle.

In another embodiment of the invention, the flow reversing device is adapted to cause the system to operate in the heating mode when the heating system is started and the conditions in the heating system are not such as to allow the heating system operate satisfactorily.

It is further envisaged that when the climate management system comprises a heating control system including a temperature sensor for the passenger compartment and means for setting a desired temperature and the flow reversing device is adapted to cause the air conditioning system to operate in the heating mode until the temperature sensed within the passenger compartment reaches the desired level set by the heating control system.

Detailed Description of the Invention The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:Fig. 1 is a schematic view of a vehicle air conditioning system according to the invention operating in a cooling mode, Fig. 2 is a schematic view similar to Fig. 1 showing the vehicle air conditioning system operating in a heating mode, and Fig. 3 shows the air conditioning system mounted in a vehicle.

Referring to the drawings and initially to Figs. 1 and 2, there is illustrated schematically a vehicle air conditioning system, indicated generally by the reference numeral 1, portion of which is sited within the passenger compartment of the car or at least is sited for use with the passenger compartment of the car which is identified by the reference numeral 2 and the remainder is sited outside the passenger compartment of the car which is, for ease, called the engine compartment, and identified by the reference numeral 3. Practically, it will be noted that, for example, portions of the beat exchangers that are identified as being inside the passenger compartment, may actually be sited in the engine compartment 3 but the outlet therefrom will be into the passenger compartment 2. The engine heating system is not illustrated.

The vehicle air conditioning system 1 is of the vapour compression type and comprises an enclosed system containing a refrigerant fluid such as one sold under the designation Refrigerant 134A but any suitable refrigerant fluid may be used. The system 1 comprises an in-car heat exchanger 5 and an engine compartment heat exchanger 6. Both heat exchangers 5 and 6 have associated therewith fans 7 and 8 respectively which operate in conventional manner, for blowing air through the heat exchangers, the fan 7 being a conventional vehicle air conditioning fan and the fan 8 would generally be the radiator fan, since, in most cases, the engine heat exchanger 6 is mounted adjacent the vehicle radiator.

In the conventional vapour pressure air conditioning system, the engine compartment heat exchanger is fitted in what is described as a series arrangement with the engine heating coil or radiator. Essentially, the two heat exchangers, namely, the engine heat exchanger or radiator, and the air conditioning heat exchanger are placed one beside the other and the radiator fan delivers air through both heat exchangers.

The vehicle air conditioning system has a compressor leg, part of which, as explained above, for the totally conventional vapour compression air conditioning system, would normally be called the suction leg is indicated generally by the reference numeral 10. The compressor leg 10 incorporates pipework 11 connecting the in-car heat exchanger 5 through a reversing valve 12 with a conventional compressor 15 which is in turn connected through the reversing valve 12 with the engine heat exchanger 6 by further pipework 16 which completes the compressor leg 10. A pipe 17 connects the reversing valve 12 to the compressor 15 as does a pipe 18.

An expansion leg, indicated generally by the reference numeral 20, comprises pipework 21 feeding from the engine heat exchanger 6 through a pair of expansion -----------devices formed by capillary tubes 22 and 23, the in-car heat exchanger 5. It will be noted that the capillary tube 22 is mounted across a one-way check valve 24 which is in the pipework 21. A conventional strainer 25 and charging pipe 26 are provided.

Fig. 3 shows the approximate location of the various portions of the vehicle air conditioning system 1 within a vehicle, identified by the reference numeral 26. It will be appreciated that the actual physical location is largely irrelevant, except for making sure that the necessary components operate in the manner in which they should. It is also essential that the piping is adequately insulated to ensure that the system operates correctly.

Cooling Mode Dealing firstly with Fig. 1 which illustrates the air conditioning system operating in the cooling mode, i.e. in the normal way, the direction of the flow of fluid is shown by arrows. Low pressure vapour is compressed in the compressor 15 to increase its temperature above ambient as well as its pressure and is then delivered through the pipe 18 to the reversing valve 12 where it is delivered through the pipe 16 to the engine heat exchanger 6 which is acting as a condenser so that the high temperature high pressure vapour gives up heat and is now condensed down into a high pressure lower temperature liquid (sub cooled). This heat is referred to as the heat of rejection. The refrigerant liquid passes through the check valve 24. Then this refrigerant liquid is delivered to the capillary tube 23 where its pressure is reduced and now becomes low pressure liquid which is then evaporated in the incar heat exchanger 5 drawing in heat which allows the fan 7 to deliver cool air into the passenger compartment 2. This evaporation takes place at a low temperature.

This evaporation means that the liquid has now become low pressure vapour which is delivered to the compressor 15 through the pipe 11, reversing valve 12 and pipe 17. The cycle is then repeated.

Heating Mode In the heating mode, the reversing valve 12 is reversed so that the high pressure vapour delivered from the compressor 15 to the reversing valve 12 is delivered as high pressure high temperature high temperature gas through the pipe 11 to the incar heat exchanger 5 which now operates as a condenser so as to condense the high pressure high temperature gas into a high pressure liquid which is then delivered through the capillary tube 23 to expand and reduce the pressure. It is then delivered to the check valve 24 and is diverted through the second capillary tube 22. Extra restriction is required in the heating mode to balance refrigerant flow. This relatively cool low pressure liquid is then delivered through the engine heat exchanger 5 which is now acting as an evaporator where the liquid now absorbs heat, expands and becomes low pressure vapour which is delivered through the pipe 16 to the reversing valve 12 and from the reversing valve 12 through the pipe 17 into the compressor 15. It will be noted that the direction of flow of fluid through the compressor 15 does not change.

Essentially, it will be appreciated that what has happened is that in the in-car heat exchanger 5, the hot high temperature gas has been cooled down to about 20°C which is then evaporated at temperatures below 0°C. It will be appreciated that the outside temperature, depending on where you are in the world, will be above the evaporating temperature. Therefore, in the engine heat exchanger 6, there will be a temperature difference so that the air conditioning system 1 will operate effectively as a heating system. It must be further considered that the energy absorbed by the compressor will also add to the heat available from the evaporator. This compressor energy is commonly known as the heat of compression.

It should be further noted that since evaporation takes place below the freezing point of water (during the heating cycle), a possibility of the formation of ice will occur on the evaporator coil. The time taken for the formation of this ice will depend mainly on the moisture content of the ambient air. However, during the period of ice formation, the engine cooling system is preparing itself to take over from the reverse cycle and will do so in time for the formation of ice not to cause a problem. Even if, in certain situations, it were to be a problem, suitable pipe embracing heating means such as electrical heating coils, could be provided.

Many automobiles include a climate management system, which can operate the conventional heating system and the air conditioning system simultaneously to provide heating, cooling and dehumidification (anti-mist) control. For example, for de-misting, the management system will simultaneously enable heating and cooling. If passenger compartment temperatures are correct, a valve within the conventional heating system will close or open, balancing the sensible heat with the sensible cooling, thus (for mist control only) providing a simple reduction in moisture and no increase or decrease in temperature. Simple software changes within the climate management controls will enable the reverse cycle system to be incorporated.

If no conventional heat (heat generated by the engine) is available for the first 10 to 15 minutes of driving, no dehumidification or mist control can occur. It is obvious that the system of reverse cycle will provide heat and dehumidification much faster than the conventional heating system thus making driving safer and more comfortable.

It is envisaged that the climate management system may include a monitor for sensing the conditions in the heating system (engine coolant) such that the temperature in the heating system would enable or disable the reversing valve (reversing device). Similarly, it is envisaged that when the temperature within the passenger compartment is sensed to be below a preset ambient temperature and the engine coolant liquid used in the conventional heating system is below a preset coolant temperature, then the flow reversing means may be operated to cause the system to operate in the heating mode thus acting as a booster for the heating system.

While above, it has been presumed that a sophisticated climate management system may be incorporated, it will be appreciated that less sophisticated systems may be used which may require more driver intervention and which may not necessarily carry out all the functions envisaged. However, such systems can be readily adapted to operate in accordance with the present invention. Indeed, there are virtually no heating systems now which do not have reasonably sophisticated control systems. While there may not be a full climate management system which links both the air conditioning when it is available and the heating system, it will be appreciated that such systems can be readily easily adapted for use with the present invention.

It will be appreciated that many ways of operating the system according to the present invention may be provided which will balance the heating and air conditioning requirements for the vehicle.

While in the embodiment described above, a reversing valve was used in conjunction with the compressor to facilitate flow reversal, it will be appreciated that, for example, a totally duplicate pipework system could be used for reversing the flow. However, this would not be the most efficient way of doing it. Those skilled in the art will immediately perceive other ways of reversing flow.

It will also be appreciated that various other expansion valves, other than a capillary tube, may be used.

Further, it will be appreciated that if there are, or become available, other air conditioning systems whose operation can be reversed as with the vapour compression system in accordance with the present invention, then such an air conditioning system could be used with the present invention.

In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims (5)

1. ... A vehicle air conditioning system (1) of the vapour compression type for working in a vehicle (26) having an independently operable heating system and associated climate management system, the system comprising an enclosed system containing a refrigerant fluid, a pair of heat exchangers (5, 6), one heat exchanger (5) sited in the passenger compartment acting as an evaporator, and the other heat exchanger (6) sited outside the passenger compartment acting as an condenser, and associated pipework connecting the heat exchangers (5, 6) to form a compressor leg (10) and an expansion leg (20), a compressor (15) in the compressor leg (10) and an expansion device in the expansion leg (20), the direction of fluid flow being from the heat exchanger (5) in the passenger compartment through the compressor (15) through the heat exchanger (6) outside the passenger compartment through the expansion device and back through the heat exchanger (5) in the passenger compartment characterised in that there is provided a flow reversing valve (12) to reverse the flow of fluid through the system (1) to cause the system (1) to operate in reverse mode as a vehicle air heating system.

2. A system (1) as claimed in claim 1, in which the expansion device comprises an expansion device and associated one-way check valve (24) whereby when operating in the reverse heating mode, the liquid refrigerant is delivered through both expansion devices and, in the cooling mode, through the check valve (24) and the other expansion device.

3. A system (1) as claimed in any preceding claim in which the air conditioning system and the heating system are controlled by the climate management system whereby the air conditioning and heating systems can both operate independently, either alone or jointly, and can both operate to heat the vehicle.

4. A system (1) as claimed in claim 4, in which the climate management system has means for sensing the engine coolant conditions in the heating system and when the engine coolant temperature is below a preset temperature, the climate management system causes the air conditioning system to operate in -----------------the heating mode until the engine coolant temperature reaches the preset--------temperature so as to allow the heating system operate on its own for heating 5. The vehicle.

5. A vehicle air conditioning system substantially as described herein with reference to and as illustrated in the accompanying drawings.