Determination method for initial temperatures of NOx sensor and differential pressure sensor mounting pipe walls of vehicle postprocessor

Abstract

The invention discloses a determination method for the initial temperatures of NOx sensor and differential pressure sensor mounting pipe walls of a vehicle postprocessor. The method comprises the following steps of 1, collecting the ambient temperature H through a vehicle ambient air temperature sensor, or reading and calculating the ambient temperature H through an intake air temperature sensor,and reading the ambient temperature H from an ECU; 2, reading postprocessor pipeline wall temperature T0 stored for the last time in nvm before parking and power-off through the ECU; and 3, calculating to obtain the initial temperatures T(t) of the mounting pipe walls according to the following formula 2 on the basis that the H is obtained in the step 1 and the T0 is obtained in the step 2, wherein the T (t) is H+(T0-H).e<-kt>, the t is the parking time, the k is the time constant, the S<-1> is the unit, and the e is the natural logarithm in the formula 2. The initial temperatures of the NOx sensor (1) and differential pressure sensor (2) mounting pipe walls of the vehicle postprocessor can be accurately evaluated, so that the accuracy of estimating dew point temperatures of the NOx sensor(1) and the differential pressure sensor (2) is improved.

Description

technical field [0001] The invention relates to a method for determining temperature, more specifically to a method for determining the initial temperature of installation pipe walls of NOx sensors and differential pressure sensors of vehicle post-processors, and belongs to the technical field of engine exhaust gas purification treatment. Background technique [0002] At present, in order to meet the strict requirements of China VI on emissions in low-temperature areas, the post-processor is usually equipped with front and rear NOx sensors and differential pressure sensors, which are used to measure the NOx content of vehicle exhaust gas in real time and measure the DPF pressure drop (used to estimate the DPF carbon load). amount); for the NOx sensor to work normally, the heating function needs to be turned on to keep the sensor at a certain temperature. When the temperature of the inner wall of the post-processing pipe is too low, the water vapor in the exhaust gas may cond...

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Problems solved by technology

However, the method for estimating the dew point temperature in the patent application for this invention is relatively extensive as a whole, and does not take into account the initial temperature of the sensor installation pipe wall. Since the entire exhaust aftertreatment system is still in a relatively hot state and has not completely cooled down, the temperature of the sensor installation tube wall will soon reach the dew point temperature after the engine is restarted, or even be directly above the dew point temperature as soon as the engine is started, and it can be started earlier. The heating function of the NOx sensor is used to obtain the sensor reading, but the adoption of the technical scheme of the patent application for this invention will cause the dew point of the NOx sensor to pass through the time equivalent to or slightly earlier than the normal cold engine start, and during this period of time without the NOx sensor reading will be SCR Injecting Urea to Treat Adverse Effects of NOx Exhaust Gas

Another example: when the ambient temperature is extremely low, such as minus 20 degrees, and the vehicle is parked for a long time, start the vehicle in a completely cooled state. Since the initial temperature of the sensor installation pipe wall is extremely low at this time, if the technical solution of the patent application for this invention is adopted , it will appear that the calculation result has reached the dew point temperature to start the NOx heating function, but the actual pipe wall temperature has not reached the dew point temperature, so that condensed water may still appear on the inner wall of the pipe, and there is a risk of failure such as cracking caused by flowing to the NOx sensor

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