JP2016188626A - Replacement time diagnosis method of dosing valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a replacement time diagnosis method of a dosing valve which quantitatively counts heat damage which the dosing valve receives, evaluates deterioration caused by the heat damage, and can diagnose a replacement time of the dosing valve.SOLUTION: A replacement time diagnosis method of a dosing valve 20 which injects urea water into an exhaust pipe 14 sorts exhaust temperatures to a several stages of temperature ranges, and sets DV off-timers 1 to 4 in the respective temperature ranges. The method selects the DV off-timers 1 to 4 in the temperature ranges from the exhaust temperatures of an exhaust gas when the dosing valve 20 is stopped in injection, counts a stop time, and diagnoses a replacement time of the dosing valve on the basis of an accumulation time of count values of the DV off-timers 1 to 4.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a dosing valve for injecting urea water, and more particularly to a dosing valve replacement timing diagnosis method capable of diagnosing the replacement timing when the dosing valve has deteriorated due to heat damage.

  As one device for detoxifying NOx (nitrogen oxide) contained in diesel exhaust gas, urea SCR (Selective Catalytic Reduction; hereinafter abbreviated as SCR) has been put into practical use.

  Diesel exhaust gas aftertreatment device using SCR is a dosing that injects urea upstream of the SCR, in which the DOC (oxidation catalyst), DPF (diesel particulate filter), and SCR are connected in order to the exhaust pipe of the diesel engine. It is configured with a valve.

  Exhaust gas from diesel engine is collected in DPF after unburned fuel (HC), carbon monoxide (CO), etc. in exhaust gas are oxidized in DOC, and PM (particulate matter) in exhaust gas is collected The urea water injected from the dosing valve on the inlet side of the SCR is hydrolyzed with the heat of the exhaust gas to become ammonia, and the ammonia and NOx in the exhaust gas are catalysts (selective reduction catalyst) in the SCR. It reacts and is detoxified by being reduced to nitrogen and water.

  The urea water injected by this dosing valve sucks urea water in the urea water tank by a supply pump, supplies it to the dosing valve, and directly injects urea water from the dosing valve.

JP 2012-233463 A JP 2009-121413 A JP 2010-096126 A JP 2011-080397 A

  By the way, the supply pump, etc. breaks down, or urea injection at the dosing valve stops due to other reasons. If this continues for a long time, the dosing valve is exposed to high-temperature exhaust gas, and it breaks down due to heat damage. There is.

  Conventionally, the thermal damage of the dosing valve is not diagnosed, and even if the ECU can diagnose the failure of the dosing valve, it is not predicted until the replacement time of the dosing valve.

  Therefore, an object of the present invention is to solve the above-mentioned problems, quantitatively count the thermal damage received by the dosing valve, evaluate deterioration due to the thermal damage, and diagnose the replacement timing of the dosing valve. It is to provide a method.

  In order to achieve the above object, according to the present invention, in a dosing valve replacement timing diagnostic method for injecting urea water into an exhaust pipe, the exhaust temperature is divided into several temperature ranges and a DV off timer is set for each temperature range. When the dosing valve is stopped, the DV off timer in the temperature range is selected from the exhaust temperature of the exhaust gas, the stop time is counted, and the dosing valve is based on the accumulated time of the count value of each DV off timer. This is a method for diagnosing the replacement time of a dosing valve, characterized by diagnosing the replacement time.

  When the exhaust gas temperature is 200 ° C. or higher, several stages of DV off timers are set in the exhaust gas temperature range of 50 to 100 ° C., and the threshold time of the replacement timing in each DV off timer is set, and The threshold time is preferably set to be shorter step by step as the temperature range is higher.

  The DV off timer for each temperature range preferably counts the DV stop time with an added value corresponding to the exhaust gas flow rate.

  The accumulated time of the count value of each DV off timer is preferably stored in the engine control unit, and the engine control unit preferably causes the service tool to display and output the accumulated time via a connector that outputs information.

  In the present invention, a DV off timer is set for each exhaust gas temperature range, and when the dosing valve is stopped, the DV off timer in the exhaust gas is selected and counted, thereby causing deterioration due to thermal damage of the dosing valve. It has an excellent effect of being able to diagnose and predict the replacement time.

It is the schematic of the exhaust gas aftertreatment apparatus to which the replacement timing diagnostic method of the dosing valve of the present invention is applied. It is a figure which shows the count by a DV off timer, and the chart of accumulation time in the replacement time diagnostic method of the dosing valve of this invention.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  First, an exhaust gas aftertreatment device will be described with reference to FIG.

  A turbocharger 11 including a turbine 12 and a compressor 13 is connected to an intake / exhaust system of the engine 10. A DOC (oxidation catalyst) 15 and a DPF (diesel particulate filter) are connected to an exhaust pipe 14 connected to the turbine 12. 16 and SCR 17 are connected in order to form an exhaust gas aftertreatment device 18.

  The dosing valve 20 as a urea injection nozzle is provided on the upstream side of the SCR 17. The urea water injected by the dosing valve 20 is supplied from the urea water tank 22 through the supply pump 23, and the injection amount is controlled by opening and closing the dosing valve 20 by duty control. Although not shown, excess urea water supplied to the dosing valve 20 is returned to the urea water tank 22.

  An exhaust temperature sensor 21 is provided in the exhaust pipe 14 upstream of the SCR 17, and a NOx sensor 24 is provided in the exhaust pipe 14 downstream of the SCR 17, and the detected values of these sensors 21, 24 are the engine control unit ( (Hereinafter referred to as ECU) 30.

  The ECU 30 controls the dosing valve 20 based on the detection value of the NOx sensor 24 to control the urea injection amount. Further, since the hydrolysis of urea water does not occur when the temperature of the exhaust gas is less than 200 ° C., the ECU 30 stops the injection from the dosing valve 20, and there is a failure of the supply pump 23, a malfunction of the SCR 17 or the NOx sensor 24. If there is, the injection from the dosing valve 20 is stopped.

  When the dosing valve 20 is stopped, it is inevitable that the dosing valve 20 is exposed to high-temperature exhaust gas and causes thermal degradation.

  Therefore, in the present invention, the DV off time during which the dosing valve 20 is stopped is counted in stages for each exhaust temperature to diagnose thermal damage.

  This will be specifically described.

(1) Set a cumulative timer for closing the DV for each temperature range of the exhaust temperature.
Exhaust temperature (250 ° C or higher and lower than 350 ° C): DV off timer 2
Exhaust temperature (350 ° C or higher, lower than 500 ° C): DV off timer 3
Exhaust temperature (over 500 ° C): DV off timer 4
(2) Setting of threshold time for replacement timing of DV off timers 1 to 4 DV off timer 1> 1000 hours DV off timer 2> 85 hours DV off timer 3> 1 hour DV off timer 4> 0.1 hour Each threshold time is set .

  The above (1) and (2) are counts based on the temperature of the exhaust gas, but a DV off timer in which the exhaust gas flow rate is added to the exhaust gas temperature can also be used.

(3) For each exhaust gas temperature range, set a DV closed cumulative timer that takes into account the flow rate. Addition value taking into account the exhaust temperature (over 200 ° C) and the exhaust flow rate: DV off timer 1a
Addition value considering exhaust temperature (250 ° C or higher) and exhaust flow rate: DV off timer 2a
Addition value considering exhaust temperature (300 ° C or higher) and exhaust flow rate: DV off timer 3a
Addition value considering exhaust temperature (over 400 ° C) and exhaust flow rate: DV off timer 4a
(4) The threshold time for the replacement time of the DV off timers 1a to 4a is set by adding a coefficient corresponding to the flow rate to each count value of the DV off timers 1a to 4a.

  The exhaust temperature range can be arbitrarily set stepwise within a range of 50 to 100 ° C. Further, when the exhaust flow rate is added to the exhaust temperature, it is equivalent to the DV off timers 1a to 4a counting the heat capacity of the exhaust gas, and the amount of heat received by the dosing valve 20 can be obtained more accurately.

  FIG. 2 shows a chart of accumulated times counted by the respective DV off timers 1 to 4 when the dosing valve 20 (hereinafter abbreviated as DV) is turned off and on.

  First, when the DV is new, the time is cleared, the accumulated time is 0 at time t0, the SCR is stopped due to an abnormality at time t1, and the DV output becomes 0 (no urea injection), time t1 to time Until t2, when the exhaust temperature is outside the above-mentioned exhaust temperature range (less than 200 ° C.), the DV off timers 1 to 4 do not count, and the exhaust temperature enters the above temperature range from time t2 to time t3. In addition, the DV off timer corresponding to the area is selected and the stop time is counted, and when the exhaust gas temperature is outside the area, the count is not performed, but the time is not counted when the exhaust gas temperature is outside the area, from time t4 to time t5. Sometimes, counting is performed by one of the DV off timers 1 to 4.

  After that, when the abnormality is recovered at time t5 and the SCR is activated, when the DV output is 0 or more, any DV off timers 1 to 4 are not counted even in the area, and at time t6, the SCR due to abnormality is detected. When the DV output becomes 0, when any DV off timer 1 to 4 in the area is selected and counted, the accumulated count value reaches the DV replacement threshold at time t7. DV exchange.

  The cumulative time chart counted by each of the DV off timers 1 to 4 is stored in the ECU 30.

  Therefore, when the vehicle is inspected or repaired, the connector 32 of the service tool 33 is connected to the connector 31 that outputs information to the ECU 30, and the cumulative time chart stored in the ECU 30 is displayed and output, so that the thermal degradation of the DV. Can be used to diagnose the replacement period.

  As described above, the present invention sets a DV off timer for each exhaust gas temperature range, and when the dosing valve is stopped, selects and counts the DV off timer for the exhaust gas, thereby counting the dosing valve. Deterioration can be diagnosed by heat damage and the replacement time can be predicted.

10 Engine 14 Exhaust pipe 17 SCR
20 Dosing valve 21 Exhaust temperature sensor 23 Supply pump 30 Engine control unit

Claims (4)

  In the dosing valve replacement timing diagnostic method for injecting urea water into the exhaust pipe, the exhaust temperature is divided into several temperature ranges and a DV off timer is set for each temperature range, and when the dosing valve stops injection, A DV off timer within the temperature range is selected from the exhaust temperature of the exhaust gas, the stop time is counted, and the replacement timing of the dosing valve is diagnosed based on the accumulated time of the count value of each DV off timer. How to diagnose dosing valve replacement time.   When the exhaust gas temperature is 200 ° C. or higher, several stages of DV off timers are set in the exhaust gas temperature range of 50 to 100 ° C., and the threshold time of the replacement timing in each DV off timer is set, and 2. The dosing valve replacement timing diagnosis method according to claim 1, wherein the threshold time is set to be shorter stepwise as the temperature range is higher.   3. The dosing valve replacement timing diagnosis method according to claim 1, wherein the DV off timer for each temperature range counts the stop time of the DV with an added value corresponding to the exhaust gas flow rate.   The accumulated time of the count value of each DV off timer is stored in an engine control unit, and the engine control unit causes the service tool to display and output the accumulated time via a connector that outputs information. Replacement timing diagnosis method for dosing valves described in 1.

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