Patent Application
20140102117
The present invention relates to a method for optimizing evaporator core temperature control using an active thermocouple array sensor.
One process for measuring evaporator core temperature is to use a single point contact temperature sensor. The single point contact temperature sensor is placed at one point on the evaporator core, measuring the temperature only at that point. A single point contact sensor does not give an accurate representation of the temperature distribution on the evaporator core.
While additional thermistors could be added, this would raise the cost and only provide information in incremental discrete locations. Using multiple thermistors requires a more sophisticated control algorithm encompassing a larger memory cache allotment. Each thermistor measures the temperature at one location and does not give an accurate representation of temperature distribution across the evaporator core.
Another process of measuring evaporator core temperature is to use non-contacting thermistors. Placing the thermistors in the airflow path measures the temperature of the air as it passes the thermistor. This process also fails to provide a representation of temperature distribution across the evaporator core.
Active thermocouple array sensors have been proposed for use in certain limited applications in a vehicle. Vehicle applications for active thermocouple array sensors include automotive blind spot detection, tire temperature monitoring, battery charging, passenger classification, and detecting passenger compartment thermal comfort. Active thermocouple array sensors have been proposed for use in an automotive air conditioning system to measure temperature in a thermal array inside the passenger compartment of the vehicle. The use of an active thermocouple array sensor in the passenger compartment does not provide any indication of temperature distribution across the evaporator core.
An accurate representation of the temperature distribution is required for optimization of the evaporator performance because temperature may vary at different points on the evaporator core. The coldest evaporator core temperature location may change based on differing operating conditions such as mode, blower speed, and ambient conditions. These changing variables make it difficult to optimize the performance of the evaporator core without the risk of freezing the core condensate on the surface of the evaporator core. The risk of freezing the core condensate leads to compromising evaporator core efficiency as a result of setting the compressor off set-point higher than the optimal minimum threshold. Setting the compressor off set-point higher than the optimal minimal threshold may increase the temperature of the air flow from the registers and reduce the comfort of the vehicle occupants.
This disclosure is directed to the above problems and other problems as summarized below.
According to one aspect of the disclosure, an apparatus is disclosed for optimizing the evaporator core performance. A multipoint thermal active thermocouple array sensor is attached to the HVAC casing of a vehicle to detect thermal radiation and measure temperatures without making contact with the evaporator core. The active thermocouple array sensor measures the temperature in an array across the surface of the evaporator core. Positioning the active thermocouple array sensor facing an airflow outlet face allows the active thermocouple array sensor to accurately measure temperature distribution across the area of the evaporator core. Ambient air enters the HVAC casing and enters the evaporator core through an airflow inlet face of the evaporator core. The air exits the evaporator core through the airflow outlet face where the temperature of the evaporator core is measured by the active thermocouple array sensor. The active thermocouple array sensor is positioned to have a line-of-sight at the air outlet face.
The array may be read as a temperature map to allow the vehicle climate control system to adjust evaporator core temperature with a finer level of granularity. Knowing the thermal properties of the evaporator core allows the vehicle to compensate for cold spot migration and optimize the energy transfer by the evaporator core.
According to another aspect of the disclosure, a method is provided for using the active thermocouple array sensor to optimize evaporator core performance. The active thermocouple array sensor is assembled to a feature inside of the HVAC casing and positioned to have a line-of-sight on an air outlet face of the evaporator core. The HVAC casing directs air into an air inlet face of the evaporator core and through an air outlet face of the evaporator core. As the air flows through the outlet face, the active thermocouple array sensor measures the temperature of the core. This gives an accurate representation of the temperature across the air outlet face of the evaporator core. Once a plurality of points is measured, the active thermocouple array sensor generates temperature distribution data based on the measurement data. The active thermocouple array sensor arranges the temperature distribution in an array, or in a temperature map. After creating a temperature distribution, the vehicle temperature control system analyzes the temperature distribution and adjusts evaporator core temperature control. The vehicle temperature control system uses a minimum temperature threshold to adjust the temperature of the evaporator core. For example, the evaporator core temperature may change to minimize the risk of icing or freeze up occurring on the evaporator core. The minimum temperature threshold varies by vehicle and ranges from approximately 32° F. to 38.5° F.
According to a further aspect of this disclosure, a vehicle temperature control system is provided that includes a heater core and an evaporator core enclosed within a HVAC casing of the vehicle, an active thermocouple array sensor, and a vehicle climate control system including a compressor. The active thermocouple array sensor is disposed within an HVAC casing of the vehicle temperature control system. Air flows through the front end of the vehicle and enters the HVAC casing. The air flow is directed by the HVAC casing into the evaporator core through an air inlet face and exits the evaporator core through an air outlet face. The active thermocouple array sensor detects and measures the temperature of the core as the air flows through the air outlet face of the evaporator core. The active thermocouple array sensor is attached to a support structure within the HVAC casing and is positioned with a line-of-sight to the airflow output face. The active thermocouple array sensor collects temperature distribution data from a plurality of temperature data measurements of the evaporator core. The temperature distribution data may be in the form of an array that is organized to provide a temperature map of the evaporator core. The vehicle climate control system analyzes the temperature distribution data from the active thermocouple array sensor to optimize performance of the evaporator core. The vehicle climate control system uses the temperature distribution data to operate the evaporator core at its minimum threshold temperature.
The vehicle climate control system analyzes the measurement data from the thermocouple array sensor to control the compressor. The minimum temperature threshold varies between vehicle styles and may range from approximately 32° F. to approximately 38.5° F. For example, when the vehicle climate control system receives a signal indicating the evaporator core temperature is below 38.5° F., the compressor turns off. Likewise, when the vehicle climate control system receives a signal that the evaporator core temperature is above 38.5° F. the compressor may be turned on. The use of the active thermocouple array sensor in the vehicle temperature control system allows for a finer granularity of the evaporator core temperature control enabling the core temperature to be controlled closer to its minimum temperature threshold. Operating the evaporator core at the minimum threshold temperature enables optimized cooling performance within the refrigerant system while preventing unwanted evaporator icing or freeze up.
The above aspects of the disclosure and other aspects will be better understood in view of the attached drawings and the following detailed description of the illustrated embodiments.
The illustrated embodiments are disclosed with reference to the drawings. It should be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the disclosed concepts.
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While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
