Patent Application
20090242652
The present disclosure relates to an air conditioning apparatus and a method of controlling the output of a vehicle air conditioning compressor based on evaporator utilization.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Vehicle manufacturers are continuously striving to produce vehicles that overall, consume less energy. In many vehicles, specific components such as alternators, air-conditioning compressors, and cooling fans are driven by belts and pulleys that rely directly on rotation of the engine, which must consume extra fuel as opposed to a situation where components are not directly engine-driven. Accordingly, in vehicles utilizing internal combustion engines and engine-driven components, attention is being directed at improving the efficiency of engine-driven components to reduce fuel consumption.
Stated differently, because current air conditioning system logic does not consider controlling other operational points, or that is, other air conditioning components, when the cooling capacity of the evaporator has been reached, the compressor of a current air conditioning system will continue to try to cool or make the evaporator colder even when the capacity of the evaporator has been reached.
Cold storage is an area of technology that is being studied on mild hybrid systems. Mild hybrid systems are systems that occasionally turn off the engine and thus the air conditioning compressor but also usually do not operate the compressor solely on electrical power. Thus, increasing cold storage within the air conditioning system is sought to enable the evaporator to continue to remove heat from air passed through the evaporator even after the engine and compressor cease to operate. Utilization of cold storage to prolong evaporator utilization to achieve extended cool air from the exit side of the evaporator is sought to be accomplished using cooling fan logic. Such will make the air conditioner more efficient.
While efforts at increasing efficiencies may be directed at a variety of engine-driven components, a further need exists in the art for increasing the efficiency of air conditioning systems. More specifically, what is needed then is a vehicle air conditioning apparatus and a method of controlling the air conditioning apparatus that pertains to monitoring evaporator capacity and changing the speed and/or the displacement of the compressor according to the evaporator capacity. Additionally needed is air conditioning control logic to extend the time of blown cold air from an evaporator based upon the degree of cold storage within the air conditioning system.
An air conditioner control method may entail measuring an evaporator first temperature at an exit side of the evaporator, maintaining the evaporator first temperature, measuring a length of time that the evaporator maintains the evaporator first temperature, providing a user-set evaporator target temperature; and reducing a rate of refrigerant compressed by a compressor based on a relationship between the length of time that the evaporator maintains the evaporator first temperature and the evaporator target temperature. Furthermore, an air conditioner control method utilizing a condenser and a cold storage unit may entail turning off an air conditioner compressor, maintaining operation of a condenser cooling fan, closing a thermostatic expansion valve, opening a bleed port to bypass the thermostatic expansion valve, and receiving a liquid refrigerant into the cold storage unit from the condenser after the refrigerant passes through a thermostatic expansion valve bleed port and the evaporator.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Turning to the present teachings, cold storage is an area of air conditioner technology that may be utilized or implemented on mild hybrid vehicles. A mild hybrid vehicle is a type of vehicle that normally is not configured to operate its air conditioning compressor solely from electrical power when the internal combustion engine is not operating, as in a “full hybrid” type of vehicle, because of cost constraints. Therefore, the air conditioning compressor on a mild hybrid vehicle is typically only operated from mechanical energy from the engine when the engine is operating and when the engine is not operating, the compressor does not function. Alternatively, an electric compressor may be employed, but this again imposes cost constraints. Concerning mild hybrid vehicles, it remains a desire to prolong the cold air that is available from the exit side of the evaporator for as long as possible, including during periods of time when the engine is not functioning. Thus, ways of utilizing an air conditioning cold storage container on the vehicle is desired. As is known in the field of vehicle air conditioning, cold storage may be accomplished using a type of wax, such as paraffin that freezes and remains cold until it is needed. Utilizing cold storage containers may also have a savings associated with them that are not possible with different arrangements of different types of compressors and ways of powering such compressors when an engine is not operating.
Turning now to
In a refrigeration cycle, the compressor 14 discharges a superheated gas refrigerant of high temperature and high pressure, which flows into a condenser 22. In the condenser 22, heat exchange is performed with the outside air 24, which may be assisted or driven by a cooling fan 31, which normally blows forced air 29 at a higher velocity than the outside air 24, so that the refrigerant is cooled to undergo condensing. The refrigerant condensed in the condenser 22 then flows into a receiver 26, in which the refrigerant is separated into a gas and a liquid. A redundant liquid refrigerant in the refrigeration cycle is stored inside the receiver 26. The liquid refrigerant from the receiver 26 is decompressed by an expansion valve 28 into a gas-liquid double phase state of low pressure refrigerant. The low pressure refrigerant from the expansion valve 28 then flows into an evaporator 30 by way of an inlet pipe 32. The evaporator 30 is arranged inside an HVAC case 34 of the HVAC system 10. The low pressure refrigerant flowing into the evaporator 30 absorbs heat from the air inside the HVAC case 34 during evaporation. An outlet pipe 36 of the evaporator 30 is connected to the suction side of the compressor 14 so that the cycle components mentioned above constitute a closed circuit.
Continuing with
The HVAC case 34 accommodates, on the downstream side 48 of the evaporator 30, a hot water heater core 50 to exchange heat with air passing through the heater core 50. The heater core 50 includes an inlet pipe 52 and an outlet pipe 54. An engine coolant, such as water or an antifreeze solution that circulates around the vehicle engine 16, is directed to the heater core 50 through the inlet pipe 52 by a water pump 25. A water valve 58 controls the flow volume of engine coolant supplied to the heater core 50. A radiator 60 and a thermistor 62 further cooperate to control the temperature of the flowing coolant.
A bypass channel 66 exists beside the hot water heater core 46 in the HVAC case 34. An air mix door 64 is provided to adjust the volume ratio between warm air and cool air that passes through the hot water heater core 50 and the bypass channel 66, respectively. The air mix door 64 adjusts the temperature of the air blown into the passenger compartment 40 by adjusting the volume ratio between the warm air and cool air.
Additionally, a face outlet 68, a foot outlet 70, and a front windshield defroster outlet 72 are formed at the downstream end of the HVAC case 42. The face outlet 68 directs air toward the upper body portions of passengers, the foot outlet 70 directs air toward the feet of the passengers, and the defroster outlet 72 directs air toward the internal surface of a windshield. The outlets 68, 70 and 72 are opened and closed by outlet mode doors (not shown). The air mix door 64 and the outlet mode doors mentioned above are driven or adjusted by electric driving devices such as servo motors via linkages or the like.
With the inclusion of
Continuing with the inquiry at inquiry block 84, if the evaporator temperature is stable, that is consistent and not changing, and the evaporator temperature is greater than the evaporator target temperature, the flow of the control logic proceeds to inquiry block 86. However, if the evaporator temperature is not stable or if the evaporator target temperature is equal to or less than the evaporator target temperature, then the flow of control logic returns to the beginning and re-enters inquiry block 84. Generally, a reason for inquiring as to whether the evaporator temperature is stable is to prevent the deliberate changing of anything in the HVAC system 10, such as regarding operation of the air conditioning compressor 14, until the change has been completed. To determine a stable evaporator temperature, a time period, such as 10 seconds, 30 seconds, 1 minute, etc. may be set for maintaining such a temperature in order for the evaporator temperature to be considered stable. Continuing, the HVAC system has a target panel-air 68 temperature that is set by a vehicle operator 92 or other passenger 94 on an air conditioning panel 96 within the passenger compartment 40. Setting the target air temperature sets or fixes the temperature of the blowing air 98 that exits from the vents 68 or exit ports 68 within the passenger compartment 40 after the blowing air has passed through the evaporator 30 as airflow 88.
Therefore, setting a temperature on the air conditioning panel 96 adjusts the degree of work or compression of the compressor 14. Stated differently and in terms of the compressor 14, the compressor 14 compresses more or less refrigerant depending upon the temperature/amount of the air to be blown from the vents 68. By adjusting the degree of work or compression of the compressor 14 with respect to the refrigerant compressed, the amount and/or rate of refrigerant passing through the evaporator varies, as well as its temperature in the evaporator.
At block 86, upon the reply to the inquiry at block 84 being “yes,” a control unit 102 in communication with the compressor 14 adjusts or effects a change in the electrical current supplied to the compressor 14, if the compressor is electrically controlled, or adjusts the stroke or displacement of the piston that does the compression or pumping of the refrigerant in the compressor 14.
After the compression of the compressor 14 is adjusted (i.e. lessened or reduced in output) by control of the control unit 102, inquiry block 104 inquires whether the evaporator temperature has increased (become warmer) since the compression of the compressor 14 was adjusted. If the evaporator temperature has not increased, then the control returns to the inquiry block 84 to again make the inquiry as to whether the evaporator temperature is stable and greater than the evaporator target temperature. However, if the evaporator temperature has increased (become warmer), then control proceeds to block 106. At block 106, the compressor speed (current) is increased by the control unit 102 if the compressor 14 is an electric compressor, or alternatively, the current into the compressor may be increased or changed if it is a mechanical compressor 14 that has a swash plate, which is changed electrically in conjunction with a control valve. The mechanically driven compressor 14, such as driven by pulleys 18, 19, may be driven by the engine. Upon making the adjustment (increase in current or speed) of the compressor 14, the evaporator temperature may be decreased, thus resulting in colder air being discharged from the vents 68 as panel air 68.
By using the above control logic, the work or compression of the compressor is controlled so that the compressor output or work does not exceed the evaporator capacity. Stated differently, the control logic of the present disclosure permits the compressor 14 to be used only up to the cooling capacity of the evaporator 30. By preventing the compressor 14 from compressing faster or from compressing additional refrigerant when the evaporator can not be cooled or lowered in temperature, as measured at the evaporator surface, vehicle energy is conserved. Conserving vehicle energy may mean conserving gasoline that the internal combustion engine is consuming to provide the energy necessary to operate a belt-driven external—variable displacement compressor (E-VDC) at high capacity when such capacity is actually not necessary at the time that the air conditioning evaporator has reached its cooling capacity. Alternatively, in the event of an electrically driven compressor, the electric compressor may reduce its rpm, and thus capacity, at the time that the air conditioning evaporator has reached its maximum cooling capacity. A feature of the control logic is that it takes into consideration operational points where the evaporator capacity has been reached and it reduces compressor power consumption in order to reduce engine fuel consumption during periods when the compressor is run at excess capacity, which is when the evaporator capacity has been reached for example. This strategy actively reduces compressor capacity to match that of the limiting factor, to performance, in the system.
In order to effectively control the compressor in accordance with the logic disclosed, the control unit 102 may be in communication with the compressor 14, whether it is an electric compressor or a belt-driven E-VDC compressor, the thermistor 85, the resistance temperature detector 87, and the evaporator surface 90 to determine a temperature associated with the evaporator 30. Continuing, the controller 102 may also be capable of tracking time intervals between temperature readings.
Continuing now with reference to
Continuing with the system 110 of
Turning now to
Continuing, because the tubes through which refrigerant travels, as depicted by arrows 116, create a closed loop within the air conditioning system, any liquid refrigerant 124 in the condenser 22 may still be drawn through the tubes to the evaporator 30. Thus, maximizing the amount of liquid condensate present in the system, that is, increasing the amount of liquid refrigerant, after the engine 16 and compressor 14 are turned off and getting the condensate to the evaporator 30 may be accomplished by utilizing the volume of cold storage in the cold storage unit 112.
With continued reference to
To facilitate the drawing of liquid refrigerant from the condenser 22 and into the evaporator 30, a bleed port 122 or bypass tube 122 may be utilized in place of the TXV 28. Such bleed port 122 or bypass tube 122 will automatically open and thereby prevent the TXV 28 from being utilized when the engine is turned off. Stated differently, the TXV 28 is not utilized when the engine 16 and compressor 14 are turned off. As the cold storage unit 112 continues to draw liquid refrigerant from the condenser 22 and into the evaporator 30, the amount of liquid refrigerant 123 in the condenser 22 decreases, as depicted in viewing the amount of liquid refrigerant 123 in
Turning now to
To achieve the results depicted in
Therefore, in addition to the above disclosure, an air conditioner control method 80 may entail measuring an evaporator first temperature at an exit side 48 of the evaporator 30, maintaining the evaporator first temperature, measuring a length of time, such as with the controller 102, that the evaporator 30 maintains the evaporator first temperature, providing a user-set evaporator target temperature, and reducing or changing a rate of refrigerant compressed by a compressor 14 based on a relationship between the length of time that the evaporator 30 maintains the evaporator first temperature and the evaporator target temperature.
The method may further entail reducing the rate of refrigerant compressed by the compressor 14 when the length of time that the evaporator 30 maintains the evaporator first temperature is at or above a predetermined time and greater than the evaporator target temperature. Still yet, the method of control may entail measuring an evaporator second temperature at an exit side of the evaporator, and comparing the evaporator second temperature and the evaporator first temperature, and then increasing the rate of refrigerant compressed by the compressor when the measured evaporator second temperature is greater than the evaporator first temperature.
Reducing a rate of refrigerant compressed by a compressor based on a relationship between the length of time that the evaporator maintains the evaporator first temperature and the evaporator target temperature may entail reducing electrical energy to the compressor 14 if the compressor is an electrically powered compressor 14. Alternatively, in the event that the compressor is not electrically powered, but rather belt driven and engaged by a clutch, for example, the length of time that a clutch of the compressor is engaged, to drive the compression of the compressor, may be altered to alter the length of time that the compressor compresses.
Still yet, an air conditioner control method 80 may entail measuring an evaporator first temperature at an exit side 48 of the evaporator 30, measuring a length of time that the evaporator 30 maintains the evaporator first temperature, providing a user-set evaporator target temperature, reducing a rate of refrigerant compressed by the compressor 14 when the length of time that the evaporator maintains the evaporator first temperature is at or above a predetermined time and greater than the evaporator target temperature, measuring an evaporator second temperature at an exit side 48 of the evaporator 30, comparing the evaporator second temperature and the evaporator first temperature, and increasing the rate of refrigerant compressed by the compressor 14 when the measured evaporator second temperature is greater than the evaporator first temperature.
The evaporator 30 reaches its cooling capacity when increasing the rate of refrigerant compression does not lower the temperature of the evaporator 30, for instance, at an exit side of the evaporator 30. Additionally, the evaporator 30 may be said to reach its cooling capacity when, after operating the compressor 14 continuously, the evaporator 30 reaches a temperature measured at an exit side (such as in the air within approximately three inches of the evaporator exit surface) or at an exit surface of the evaporator 30 below which a lower temperature is not possible to achieve. Stated differently, additional compression of the compressor 14 such as operating the compressor 14 at a determined rate for extended periods of time (including continuously) or increasing the flow rate of refrigerant compression for a period of time, does not result in a lower evaporator surface temperature or lower temperature measured at the exit side of the evaporator 30.
In another control method of an air conditioner, a cold storage unit 112 may be utilized. The method may entail terminating operation of an air conditioner compressor 14, such as by turning off an internal combustion engine 16, which powers the compressor 14, maintaining operation of a condenser cooling fan 31, closing a thermostatic expansion valve 28, and opening a bleed port 122 as a bypass of the thermostatic expansion valve 28. Furthermore, the air conditioner control method may entail receiving liquid refrigerant into the evaporator 30 from the condenser 22, or receiving liquid refrigerant into the evaporator 30 from the condenser 22 after the liquid refrigerant passes through a bleed port 122 to bypass the thermostatic expansion valve 28. Alternatively, the control method may entail forcing a liquid refrigerant from a condenser 22 at a first pressure into a cold storage unit 112 at a second pressure, such that the first pressure is higher than the second pressure. The liquid refrigerant may pass through a bleed port 122 that bypasses the thermostatic expansion valve 28 and then into an evaporator 30 before the liquid refrigerant is forced into the cold storage unit 112.
In another example of a method of controlling an air conditioner that utilizes a condenser 22 and a cold storage unit 112, the compressor 14 may be turned off, such as by turning off the engine that mechanically powers the compressor 14. Upon turning off the compressor 14, the condenser cooling fan 31 or fans would continue to operate (spin and blow air) to continue to cool the liquid refrigerant 124 within the condenser 22. Additionally, the closing of a thermostatic expansion valve 28 would occur and the opening of a bleed port 122 to bypass the thermostatic expansion valve 28 would occur. Opening of the bleed port 122 would permit liquid refrigerant to flow through the bleed port 122 or passage without having to pass through the TXV 28. Next, because the pressure in the condenser 22, upon turning off the compressor 14, would be higher than that within the evaporator 30 or cold storage unit 112, the condenser 22 would force, due to the higher pressure, a volume of the liquid refrigerant 124 in the condenser 22 through the bleed port 122, through the evaporator 30, and into the cold storage unit 112. That is, the refrigerant would be received in the cold storage unit from the condenser 22 because of the pressure differential between the condenser 22 and the cold storage unit 112 forces such a flow of the refrigerant 124. Liquid refrigerant would not flow past the cold storage unit 112, such as to the compressor 14, when the compressor 14 is not compressing.
