Systems and methods for estimating a temperature of a fluid injector used in a hot environment |
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申请号 | US12565529 | 申请日 | 2009-09-23 | 公开(公告)号 | US08688402B2 | 公开(公告)日 | 2014-04-01 |
申请人 | Christophe Viale; Christian Lang; | 发明人 | Christophe Viale; Christian Lang; | ||||
摘要 | Systems and methods of estimating a fluid injector tip temperature. A controller having a processor and a memory supplies a current to a coil of a fluid injector, a resistance of the coil is measured when the current is supplied to the coil, a coil temperature is determined based on the measured resistance, and a tip temperature of a fluid injector tip is estimated based on the determined coil temperature. | ||||||
权利要求 | What is claimed is: |
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说明书全文 | Fluid injectors, such as fuel injectors for automobiles, may be exposed to high temperatures. Exceeding a thermal limit of a tip of the injector can result in irreversible damage to the tip, which leaves the injector inoperative. Thus, it is necessary to determine a temperature of the fluid injector tip such that a cooling counter measure can be initiated when the temperature of the tip exceeds a temperature at which damage to the tip can occur. The invention relates to systems and methods for estimating a temperature of a fluid injector tip. Specifically, a resistance of a coil in the tip is used to estimate the temperature of the tip. In one embodiment, the invention provides a method of estimating a fluid injector tip temperature. A controller having a processor and a memory supplies a current to a coil of a fluid injector, a resistance of the coil is measured when the current is supplied to the coil, a coil temperature is determined based on the measured resistance, and a tip temperature of a fluid injector tip is estimated based on the determined coil temperature. In another embodiment, the invention provides a system for estimating a fuel injector tip temperature. The system includes a fluid injector having a coil, and a controller. The controller is configured to provide a signal to the coil to open the fluid injector, measure a resistance of the coil, and determine a temperature of a fluid injector tip based on the measured resistance of the coil Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. When power is applied to the coil 200, the controller 125 determines the resistance of the coil 200 (step 315) (e.g., by measuring a current draw of the coil 200 for a given voltage). Using the resistance of the coil, the controller 125 estimates, as described in more detail below, the temperature of the tip 210 of the injector 120 (step 320). The controller 125 next checks if the estimated temperature of the tip 210 exceeds a predetermined threshold (step 325). If the tip temperature is above the threshold, the controller 125 executes a tip cooling function (step 330). The controller 125 calculates the coil temperature 405 using the resistance of the coil 200. The controller 125 also receives the measured temperature 415 of exhaust gases downstream of the injector 120 from the exhaust gas temperature sensor 135, and the mass flow 420 of the exhaust gases from the exhaust gas mass flow meter 130. The controller 125 uses a three-dimensional map 425 (stored in the memory 128 during a calibration process) to determine a temperature difference between the coil 200 and the tip 210 based on the measured exhaust gas temperature 415 and mass flow rate 420. The temperature difference is an offset 427 which is filtered 430, delaying the offset 427 by a predetermined amount 435 (i.e., a delay parameter). The delayed offset 437 is added to the calculated coil temperature 405. The sum of the delayed offset 437 and the calculated coil temperature 405 is equivalent to an injector tip temperature if the injector 120 is not being used, and there is no fluid flowing through the tip 210 (i.e., a no-flow tip temperature 440). The temperature of fuel flowing through the injector 120 impacts the temperature of the tip 215. Thus, to compensate, the controller 125 subtracts a measured temperature 445 of the fuel in a tank (i.e., fuel supplied to the injector 120 via the fuel rail 115) from the no-flow tip temperature 440 to obtain a full-flow impact factor 450. If fuel were constantly flowing through the injector 120 (e.g., full flow), the temperature of the tip 210 would need to be reduced by an amount closely related to the temperature 445 of the fuel. However, during operation, the fuel injector 120 is constantly opening and closing, providing fuel to the tip 210 at a rate less than full flow. The percentage of time that the injector 120 is open, and providing fuel to the engine, is called a duty cycle 460. The impact the fuel temperature 445 has on the no-flow temperature 440 (the full-flow impact factor 450) is affected by, and, thus, needs to be modified by, the duty cycle 460. The controller 125 uses the duty cycle 460 and a two-dimensional curve 465 (stored in the memory 128 during a calibration process) to determine a duty cycle modification factor 470. The duty cycle modification factor 470 is multiplied by the full-flow impact factor 450 (i.e., the difference between the no-flow tip temperature 440 and the fuel temperature 445) to generate an offset 475. The offset 475 is equivalent to the reduction in tip temperature, from the no-flow temperature 440, as a result of the cooler fuel flowing through the injector 120. The offset 475 is subtracted from the no-flow tip temperature 440 to obtain an estimated tip temperature 480. In some embodiments, the estimated tip temperature is applied to a delay filter (not shown) before being used to determine if a tip cooling operation is necessary. Because of differences in manufacturing, and variations in the relationship between the coil resistance and temperature over time, a calibration procedure is performed periodically. In some embodiments, the calibration procedure is performed each time the injector is first used. In other embodiments, the calibration procedure is performed at predetermined intervals. The calibration procedure is performed using a temperature sensor located near the injector 120 (e.g., in an engine compartment), and is performed at a time when a relationship between the temperature sensed by the sensor (e.g., ambient air temperature) and the temperature of the coil 200 is known. For example, when an automobile engine has been turned off for an extended period, the temperatures of the engine compartment and the coil 200 are approximately equal. The controller 125 performs an intrusive injection at this time, and determines the resistance of the coil 200. The resistance of the coil is then calibrated to the temperature sensed by the sensor. Another calibration process updates the map 425, the curve 465, and the delay parameter 435 (and any other parameters such as the optional second delay filter), storing the results of the calibration (e.g., the map 425, the curve 465, and the delay parameter 435) in the memory 128. The model of While the above description describes applications incorporating liquid fluids, it is understood that the systems and methods described are applicable in systems using gaseous fluids as well. Also, in addition to the vehicular applications described, the model and calibration process can be used in other applications such as injection molding, paint booths, food processing, diesel exhaust fluid after-treatment, etc., which employ fluid injectors having a coil, and where knowing the temperature of the tip of the fluid injector is necessary. Thus, the invention provides, among other things, a model for estimating a temperature of a tip of a fluid injector. |