CN-112282987-B - External cooling type EGR (exhaust gas recirculation) coking removal control method for gasoline engine

CN112282987BCN 112282987 BCN112282987 BCN 112282987BCN-112282987-B

Abstract

The invention discloses a gasoline engine external cooling type EGR (exhaust gas recirculation) coking removal control method. The method comprises the steps of detecting the opening voltage U of an EGR valve, if the opening voltage U is larger than or equal to a set voltage, monitoring the temperature T of an exhaust manifold of an engine, the load M and the transient load change deltaM in real time, closing the variable valve timing of air intake and exhaust when the temperature T of the exhaust manifold, the load M and the transient load change deltaM meet a first set condition, and increasing the opening of the EGR valve to enable more high-temperature exhaust to enter the EGR valve for coking removal. According to the invention, when certain conditions are met, the timing of the air inlet and outlet variable valve is closed, the engine only uses external cooling EGR, so that more high-temperature exhaust enters the EGR valve, coking is removed through the high-temperature exhaust, the method is simple, and the decoking effect is good.

Inventors

LIU WEI
CHEN LONG
Tuo Hanyun
WANG JINGBO
ZHOU MINGXING

Assignees

东风汽车集团有限公司
东风汽车集团有限公司

Dates

Publication Date: 20260421
Application Date: 20201030
Priority Date: 20201030

Claims (8)

1. Detecting an opening voltage U of an EGR valve, if the opening voltage U is larger than or equal to a set voltage, monitoring the temperature T of an exhaust manifold of the engine, the load M and the transient load change deltaM in real time, closing the timing of an air inlet and exhaust variable valve when the temperature T of the exhaust manifold, the load M and the transient load change deltaM meet a first set condition, and increasing the opening of the EGR valve to enable more high-temperature exhaust to enter the EGR valve for coking removal; The first setting condition is that the exhaust manifold temperature T > and the exhaust manifold temperature limit value T1, the load M > and the load limit value M1 and the load transient change deltaM < load transient change limit value deltaM1 are simultaneously met.
2. The method for controlling external cooling type EGR removal coking of a gasoline engine according to claim 1, wherein the set voltage U is U=N.U1, and the opening voltage when the EGR valve starts to act when U1 is not coked is 1.1-1.3, wherein N is a calibration value.
3. The method for controlling external cooling type EGR removal coking of a gasoline engine according to claim 1, wherein the exhaust manifold temperature limit T1=an EGR cooler cooling temperature difference +DeltaT, wherein the EGR cooler cooling temperature difference is directly obtained through equipment parameter information, and DeltaT is a calibration value.
4. The method for externally cooled EGR purge coking control of a gasoline engine according to claim 1, wherein the load limit M1 is determined by: And in the EGR operation area, measuring the corresponding load when the total EGR rate is greater than or equal to 5% at certain intervals, and filling the load into the load MAP at the corresponding rotation speed, wherein in the vehicle operation process, the load value at the current rotation speed is obtained through the load MAP interpolation according to the real-time rotation speed, namely the load limit value M1.
5. The method for externally cooled EGR purge coking control of a gasoline engine according to claim 1, wherein the load transient variation limit deltaM1 is determined by: when the test engine is in the coking-cleaning mode at each rotating speed, the load is accelerated to the maximum load change rate of no fire of the full load according to a certain rule, and the maximum load change rate is used as the load transient change of each rotating speed in the coking-cleaning mode, the load transient change of each rotating speed is filled into the corresponding rotating speed of the load transient change MAP, and the load transient change under the current working condition is obtained through the load transient change MAP interpolation according to the real-time rotating speed in the running process of the vehicle, namely the load transient change limit value deltaM1.
6. The method for externally cooling type EGR purge coking control of a gasoline engine according to claim 1, wherein the EGR valve opening is increased until the external EGR rate reaches the external EGR rate target value.
7. The method for externally cooled EGR purge coking control of a gasoline engine according to claim 6, wherein the target value of the external EGR rate is determined by: And starting from a load limit value at each rotating speed in the EGR operation area, closing the variable timing of the air intake and exhaust under each load, increasing the opening degree of the EGR valve to improve the external EGR rate, taking the maximum value of the external EGR rate which can be improved under the premise of not generating fire as the external EGR rate target value of the coking removal mode under the load, filling the external EGR rate target value into the corresponding rotating speed load in the external EGR rate target value MAP, and obtaining the external EGR rate target value under the current coking removal working condition through interpolation of the external EGR rate target value MAP according to the real-time rotating speed load during the running of the vehicle.
8. The method for controlling the external cooling type EGR (exhaust gas recirculation) of the gasoline engine according to claim 1, wherein in the process of removing the coking, the load transient variation and the temperature variation of an exhaust manifold are monitored in real time, and when the load, the load transient variation and the temperature of the exhaust manifold of the engine meet a second set condition, the coking is removed; The second setting condition is that the exhaust manifold temperature T is less than or equal to an exhaust manifold temperature limit value T1, the load M is less than or equal to a load limit value M1 or the load transient change deltaM is more than or equal to a load transient change limit value deltaM1.

Description

External cooling type EGR (exhaust gas recirculation) coking removal control method for gasoline engine Technical Field The invention belongs to the technical field of automobiles, and particularly relates to an external cooling type EGR (exhaust gas recirculation) coking removal control method for a gasoline engine. Background With the increasing severity of emissions and fuel consumption regulations, many gasoline engines use externally cooled EGR in order to reduce fuel consumption. In the actual operation process, the external cooling type EGR is used in a low-temperature environment, the too low temperature of exhaust gas entering the EGR valve can lead to the condensation of water vapor and sulfide in the exhaust gas to generate coking, and long-term coking accumulation can lead to the clamping stagnation of the EGR valve to lead to the failure of the external cooling type EGR, so the actual application working condition area of the external cooling type EGR is not large. In order to avoid the occurrence of failure, the application working condition area is enlarged, the external cooling type EGR is started at low temperature as much as possible to reduce fuel consumption, the coking degree of the EGR valve needs to be monitored, and when the coking degree is considered to be higher, a corresponding control strategy is adopted to remove the coking. The document CN104863731B discloses a self-cleaning method of an EGR valve, wherein an ECU of an engine controls the action of the EGR valve, and the self-cleaning method comprises the following steps that when a certain condition is met, the ECU sends a preset command signal for controlling the self-cleaning action of the EGR valve, and the EGR valve performs full-closing action and full-opening action to generate vibration until the self-cleaning process is finished. According to the method, the ECU controls the EGR valve to vibrate so that the coking is removed, the purpose of removing the coking is achieved, the requirement on the action sensitivity of the EGR valve is high, and when the coking is serious, the EGR valve can be blocked and cannot act, so that the coking removing effect is not ideal. Disclosure of Invention The invention aims to solve the defects in the prior art and provides a method for controlling external cooling type EGR (exhaust gas recirculation) coking of a gasoline engine, which is simple and high in reliability. According to the technical scheme, the external cooling type EGR (exhaust gas recirculation) coking removal control method for the gasoline engine is characterized by detecting the opening voltage U of an EGR valve, monitoring the temperature T of an exhaust manifold of the engine, the load M and the transient load change deltaM in real time if the opening voltage U is larger than or equal to a set voltage, closing the variable valve timing of the air inlet and the exhaust when the temperature T of the exhaust manifold, the load M and the transient load change deltaM meet a first set condition, and increasing the opening of the EGR valve to enable more high-temperature exhaust to enter the EGR valve for coking removal. Further, the set voltage U is u=n×u1, where N is a calibration value and is 1.1-1.3, and U1 is an opening voltage at the start of the EGR valve when no coking occurs. Further, the first setting condition is that the exhaust manifold temperature T > is an exhaust manifold temperature limit value T1, the load M > is a load limit value M1, and the load transient change deltaM is a load transient change limit value deltaM1. Further, the exhaust manifold temperature limit value t1=the cooling temperature difference +Δt of the EGR cooler, wherein the cooling temperature difference of the EGR cooler is obtained directly through the equipment parameter information, and Δt is a calibration value. Further, the load limit M1 is determined by: And in the EGR operation area, measuring the corresponding load when the total EGR rate is greater than or equal to 5% at certain intervals, and filling the load into the load MAP at the corresponding rotation speed, wherein in the vehicle operation process, the load value at the current rotation speed is obtained through the load MAP interpolation according to the real-time rotation speed, namely the load limit value M1. Further, the load transient variation limit deltaM1 is determined by: when the test engine is in the coking-cleaning mode at each rotating speed, the load is accelerated to the maximum load change rate of no fire of the full load according to a certain rule as the load transient change of each rotating speed in the coking-cleaning mode, the load transient change of each rotating speed is filled into the corresponding rotating speed of the load transient change MAP, and the load transient change under the current working condition is obtained through the interpolation of the load transient change MAP according to the real-time rotating speed in the running proce