Control method for mitigating urea crystallization in hybrid diesel engine

Abstract

The present invention relates to the technical field of diesel engine urea injection, and disclosed is a control method for mitigating urea crystallization in a hybrid diesel engine, for use in solving the technical problem of crystallization during urea injection in hybrid diesel engines. The control method comprises: using a solution of stopping urea injection in advance, wherein the solution specifically comprises: a hybrid vehicle control unit sends pre-shutdown packet information to an engine ECU before engine shutdown, the pre-shutdown packet information being one of engine pre-shutdown instruction activation and engine pre-shutdown instruction deactivation; when the engine ECU receives the engine pre-shutdown instruction activation, the engine ECU controls an aftertreatment system to immediately stop urea injection, and the engine ECU controls an engine injector to correct the injector timing; and when the engine ECU receives the engine pre-shutdown instruction deactivation, the engine ECU controls the aftertreatment system to immediately resume urea injection, and the engine ECU deactivates the correction of the injector timing. The control method can reduce NOx emissions at the moment of shutdown, lower the urea demand value, and reduce the risk of crystallization.

Description

A control method for improving urea crystallization of a hybrid diesel engine TECHNICAL FIELD

[0001] The present application relates to the technical field of diesel engine urea injection, and more particularly to a control method for improving urea crystallization of a hybrid diesel engine. BACKGROUND

[0002] The hybrid engine has the phenomenon of frequent start-stop in automobile operation. As can be seen from FIG. 1, in the actual operation process, the engine starts and stops 20 times in 2000s, that is, it starts and stops in turn every 1.5 minutes on average. The engine rapidly stops from a high load condition (corresponding to a large amount of urea injection), which can cause two problems: 1. The urea injection cannot be turned off in time, resulting in a small amount of urea continuously injected after the engine stops; and 2. The urea injected before the engine stops is not fully hydrolyzed and cannot react with the exhaust gas in time, and continues to remain in the mixer of the aftertreatment system. Either of the above situations can cause more and more urea to remain in the mixer. If the urea is not burned in time through regeneration, it will eventually cause the mixer to be blocked by urea crystallization, and therefore the amount of crystallization of the aftertreatment system restricts the regeneration mileage of the hybrid engine. SUMMARY

[0003] The technical problem to be solved by the present application is to solve the above-mentioned deficiencies of the prior art. The purpose of the present application is to provide a control method for improving urea crystallization of a hybrid diesel engine, which can improve crystallization while ensuring that the NOx emission is qualified.

[0004] The technical solution of the present application is: a control method for improving urea crystallization of a hybrid diesel engine, which adopts an early stop-injection urea scheme, and the scheme is specifically as follows:

[0005] The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops, and the pre-stop message is one of an engine pre-stop instruction setup and an engine pre-stop instruction cancellation;

[0006] When the engine ECU receives the engine pre-stop instruction setup, the engine ECU controls the aftertreatment system to immediately stop urea injection, and the engine ECU controls the engine injector to correct the injector timing;

[0007] When the engine ECU receives the engine pre-stop instruction cancellation, the engine ECU controls the aftertreatment system to immediately resume urea injection, and the engine ECU cancels the correction of the injector timing.

[0008] As a further improvement, the hybrid vehicle controller works according to the vehicle speed, the power torque demand- accelerator pedal position, and the battery SOC value:

[0009] When the battery SOC value < battery set value, it indicates that the battery is out of power, the vehicle starts from 0 speed into hybrid mode, when the vehicle speed is in the first speed range, the vehicle always maintains in hybrid mode and charges to the target SOC, and the pre-stop message information is engine pre-stop instruction cancellation;

[0010] When the battery SOC value ≥ battery set value, it indicates that the battery is not out of power, the vehicle starts from 0 speed into pure electric mode, when the vehicle speed is in the second speed range, the engine stops working, and the pre-stop message information is engine pre-stop instruction establishment.

[0011] Further, under the condition of battery out of power and high power demand, the engine runs at peak torque.

[0012] Further, in pure electric mode, when the power demand is greater than the pure electric power or there is an additional mechanical accessory power demand, the mode is switched from pure electric mode to hybrid mode, and the pre-stop message information is engine pre-stop instruction cancellation.

[0013] Further, under the condition of battery not out of power and pure electric mode, when the vehicle speed is higher than the third speed, the mode is switched from pure electric mode to hybrid mode, and according to the vehicle power demand, the engine works in the optimal region to maintain the power balance, and the pre-stop message information is engine pre-stop instruction cancellation.

[0014] Further, when the vehicle is sliding or braking or the vehicle demand power is less than the pure electric power, the engine stops, and the pre-stop message information is engine pre-stop instruction establishment.

[0015] Further, during the vehicle sliding or braking process, the engine enters high-speed stop-injection rotation or stops into pure electric mode, and the pre-stop message information is engine pre-stop instruction establishment.

[0016] Further, when the vehicle speed is higher than the fourth speed, the mode is switched from hybrid mode to pure engine mode, which is directly driven by the engine, and the drive motor works in 2 gears according to the vehicle demand to assist or stop in neutral.

[0017] Further, when the battery is out of power, the pure engine mode is switched to hybrid mode for driving charging.

[0018] Further, the process of correcting the fuel injector at any time is as follows: a correction coefficient is obtained by querying a main injection timing pre-stop correction map according to the engine speed and the fuel injection amount, a main injection timing pre-stop correction value is obtained by multiplying the correction coefficient and a pre-stop correction main injection timing coefficient, a main injection timing final value is obtained by adding the main injection timing pre-stop correction value and a main injection timing basic value, and the engine fuel injector is controlled according to the main injection timing final value. Advantages

[0019] Compared with the prior art, the present application has the advantages that:

[0020] 1. After the pre-stop early stop injection urea scheme is adopted, the crystallization problem of the hybrid diesel engine aftertreatment is significantly improved, and through experimental verification, the crystallization amount is reduced to one third of the original under the same working condition and time, and the regeneration mileage of the hybrid vehicle type crystallization removal is significantly improved by more than 1 times.

[0021] 2. The pre-stop based main injection timing correction strategy can reduce the risk of NOx emission exceeding the standard after urea stop injection, and combined with calibration optimization, the crystallization improvement is realized while ensuring the qualified NOx emission. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is a schematic diagram of engine start-stop monitoring;

[0023] Fig. 2 is a schematic diagram of engine stop and urea injection time;

[0024] Fig. 3 is a schematic diagram of the control logic of the present application;

[0025] Fig. 4 is a schematic diagram of hybrid vehicle controller judgment;

[0026] Fig. 5 is a schematic diagram of correcting the injector time. DETAILED DESCRIPTION

[0027] The present application will be further described below in combination with specific embodiments in the drawings.

[0028] Referring to Figs. 3-5, a control method for improving urea crystallization of a hybrid diesel engine adopts an early stop injection urea scheme, and the scheme specifically is:

[0029] The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops, and the pre-stop message is divided into two stop signals, signal 0 and 1, when the signal is state 1, it represents the engine pre-stop command is established, and when the state 0 represents the engine pre-stop command is cancelled; that is, the pre-stop message is one of the engine pre-stop command is established and the engine pre-stop command is cancelled;

[0030] When the engine ECU receives the engine pre-stop command, the engine ECU controls the aftertreatment system to immediately stop urea injection, and the engine ECU controls the engine injector to correct the injector time;

[0031] When the engine ECU receives the engine pre-stop command, the engine ECU controls the aftertreatment system to immediately stop urea injection, and the engine ECU controls the engine injector to correct the injector time;

[0032] The hybrid vehicle controller works according to the vehicle speed, power torque demand - accelerator pedal position, and battery SOC value:

[0033] When the battery SOC value is less than the battery set value, the battery is in a deficit, the vehicle starts from 0 speed and enters the hybrid mode (CVT); when the vehicle speed is in the first speed range, the vehicle always maintains the hybrid mode and performs driving charging to the target SOC, and the pre-stop message information is the engine pre-stop instruction cancellation; in this embodiment, the battery set value is 20%, and the first speed range is 0 kph-90 kph; when the battery is in a deficit and high power demand, the engine runs at the peak torque to ensure the stability of the vehicle;

[0034] When the battery SOC value is greater than or equal to the battery set value, the battery is not in a deficit, the vehicle starts from 0 speed and enters the pure electric mode (EV), the engine is stopped and does not work when the vehicle speed is in the second speed range, and the pre-stop message information is the engine pre-stop instruction establishment; in this embodiment, the second speed range is 0 kph-28 kph; when the power demand is greater than the pure electric power or there is an additional mechanical accessory power demand in the pure electric mode, the pure electric mode is switched to the hybrid mode, and the pre-stop message information is the engine pre-stop instruction cancellation.

[0035] When the battery is not in a deficit and in the pure electric mode, the vehicle speed is higher than the third speed, the pure electric mode is switched to the hybrid mode, the engine works in the optimal region as much as possible to maintain the power balance according to the vehicle power demand, and the pre-stop message information is the engine pre-stop instruction cancellation. In this embodiment, the third speed is 28 kph. When the vehicle is sliding or braking or the vehicle demand power is less than the pure electric power, the engine is stopped, and the pre-stop message information is the engine pre-stop instruction establishment.

[0036] When the vehicle speed is higher than the fourth speed, the hybrid mode is switched to the pure engine mode, which is directly driven by the engine, and the drive motor works in the 2nd gear according to the vehicle demand to assist or stop in the neutral position. In this embodiment, the fourth speed is not less than 80 kph. Of course, if the first speed range is 0 kph-90 kph, the fourth speed can be 90 kph. When the battery is in a deficit, the pure engine mode is switched to the hybrid mode for driving charging. During the vehicle sliding or braking process, the engine enters the high-speed stop injection and rotation or stops in the pure electric mode, and the pre-stop message information is the engine pre-stop instruction establishment.

[0037] The process of correcting the fuel injector time is shown in Figure 5: according to the engine speed and the fuel injection amount, a correction coefficient is obtained by querying the main injection timing pre-stop correction map, the main injection timing pre-stop correction map is pre-calibrated and saved in the hybrid vehicle controller, the main injection timing pre-stop correction value is obtained by multiplying the correction coefficient and the pre-stop correction main injection timing coefficient, the pre-stop correction main injection timing coefficient is also pre-calibrated according to the model and saved in the hybrid vehicle controller, the final value of the main injection timing is obtained by adding the main injection timing pre-stop correction value and the main injection timing base value, the main injection timing base value is the fuel injection amount when the urea injection is not stopped, and the engine fuel injector is controlled according to the final value of the main injection timing.

[0038] The main injection timing correction by the stop command reduces the NOx emission of the engine at the moment of stopping, reduces the urea demand value, reduces the risk of crystallization, and reduces the risk of NOx emission exceeding the standard.

[0039] The above is only the preferred embodiment of the present application, it should be pointed out that for those skilled in the art, without departing from the structure of the present application, a number of variations and improvements can be made, which will not affect the effect of the present application and the practicality of the patent.

Claims

1. A method for controlling urea crystallization in a hybrid diesel engine, characterized in that, The plan to stop urea spraying in advance is adopted, and the specific plan is as follows: The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops. The pre-stop message can be either an engine pre-stop command establishment message or an engine pre-stop command cancellation message. When the engine ECU receives the engine pre-stop command, the engine ECU controls the aftertreatment system to immediately stop urea injection, and the engine ECU controls the engine injectors to adjust the injector timing. When the engine ECU receives the engine pre-stop command cancellation, the engine ECU controls the aftertreatment system to immediately resume urea injection, and the engine ECU cancels the correction of the injector timing.

2. The method for controlling urea crystallization in a hybrid diesel engine according to claim 1, characterized in that, The hybrid vehicle controller operates based on vehicle speed, power and torque requirements, accelerator pedal position, and battery SOC value. When the battery SOC value is less than the battery set value, it indicates that the battery is low on charge, and the vehicle starts from 0 speed and enters hybrid mode; when the vehicle speed is within the first speed range, the vehicle remains in hybrid mode and charges to the target SOC while driving, and the pre-stop message information indicates that the engine pre-stop command is cancelled. When the battery SOC value is greater than or equal to the battery setting value, it means that the battery is not depleted. The vehicle starts from 0 speed and enters pure electric mode. When the vehicle speed is within the second speed range, the engine stops and does not work. The pre-stop message information is the engine pre-stop command established.

3. The method for controlling urea crystallization in a hybrid diesel engine according to claim 2, characterized in that, When the battery is low on power and high power demand is required, the engine will operate at peak torque.

4. The method for controlling urea crystallization in a hybrid diesel engine according to claim 2, characterized in that, In pure electric mode, when the power demand exceeds the pure electric power or there is an additional power demand from mechanical accessories, the system switches from pure electric mode to hybrid mode, and the pre-stop message indicates that the engine pre-stop command has been cancelled.

5. The method for controlling urea crystallization in a hybrid diesel engine according to claim 2, characterized in that, When the battery is not depleted and in pure electric mode, the vehicle speed exceeds the third speed limit, and the vehicle switches from pure electric mode to hybrid mode. Based on the power requirements of the vehicle, the engine operates in the optimal range as much as possible to maintain the battery balance, and the pre-stop message indicates that the engine pre-stop command has been cancelled.

6. The method for controlling urea crystallization in a hybrid diesel engine according to claim 5, characterized in that, When the vehicle is coasting or braking, or when the vehicle's required power is less than the pure electric power, the engine will stop, and the pre-stop message will be established as an engine pre-stop command.

7. The method for controlling urea crystallization in a hybrid diesel engine according to claim 2, characterized in that, During vehicle coasting or braking, the engine enters high-speed injection-free operation or stops and enters pure electric mode, and the pre-stop message information establishes the engine pre-stop command.

8. The method for controlling urea crystallization in a hybrid diesel engine according to claim 2, characterized in that, When the vehicle speed exceeds the fourth speed, it switches from hybrid mode to pure engine mode, and is directly driven by the engine. The drive motor works in second gear to assist or stop in neutral according to the needs of the vehicle.

9. The method for controlling urea crystallization in a hybrid diesel engine according to claim 8, characterized in that, When the battery is low on power, the pure engine mode will switch to hybrid mode to charge the battery while driving.

10. The method for controlling urea crystallization in a hybrid diesel engine according to claim 1, characterized in that, The process of correcting the injector timing is as follows: Based on the engine speed and injection quantity, the main injection timing pre-stop correction map is consulted to obtain the correction coefficient. The main injection timing pre-stop correction value is obtained by multiplying the correction coefficient with the pre-stop correction main injection timing coefficient. The main injection timing pre-stop correction value is added to the main injection timing base value to obtain the final main injection timing value. The engine injector operation is controlled based on the final main injection timing value.

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