A control method for improving urea crystallization in a hybrid diesel engine

Abstract

The present invention discloses a control method for improving urea crystallization in a hybrid diesel engine, belonging to the technical field of diesel engine urea injection technology, and solving the technical problem of urea injection crystallization in hybrid diesel engines. The control method adopts a scheme for prematurely stopping urea injection. Specifically, the scheme comprises: the hybrid vehicle controller sends a pre-shutdown message to the engine ECU before the engine shuts down. The pre-shutdown message is one of: establishing an engine pre-shutdown instruction or revoking an engine pre-shutdown instruction; when the engine ECU receives the established engine pre-shutdown instruction, the engine ECU controls the after-treatment system to immediately stop urea injection and controls the engine injector to correct the injector timing; when the engine ECU receives the revoked engine pre-shutdown instruction, the engine ECU controls the after-treatment system to immediately resume urea injection and cancels the injector timing correction. This can reduce NOx emissions at the moment of shutdown, lowering urea demand and reducing the risk of crystallization.

Description

Technical Field

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

[0002] Hybrid engines frequently start and stop during vehicle operation, for example Figure 1 As can be seen in the figure, during actual operation, the engine starts and stops 20 times in 2000 seconds, an average of 1.5 minutes of start-stop cycles. This rapid engine shutdown from a high-load condition (corresponding to a large urea injection volume) can lead to two problems: 1. Urea injection is not shut off in time, resulting in a small amount of urea continuing to be injected after the engine stops; 2. Urea injected before shutdown is not fully hydrolyzed, not having enough time to react with the exhaust, and remains in the post-treatment mixer. Regardless of which of these situations occurs, more and more urea will remain in the mixer. If not promptly removed through regeneration, urea crystals will eventually clog the mixer. Therefore, the amount of post-treatment crystals limits the hybrid regeneration range. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art. The purpose of the present invention is to provide a control method for improving urea crystallization in a hybrid diesel engine, which can achieve improved crystallization while ensuring qualified NOx emissions.

[0004] The technical solution of the present invention is: a control method for improving urea crystallization in a hybrid diesel engine, which adopts a scheme of stopping urea injection in advance. The specific scheme is:

[0005] The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops. The pre-stop message is one of the following: establishing an engine pre-stop command or canceling an engine pre-stop command.

[0006] When the engine ECU receives the engine pre-stop instruction, the engine ECU controls the after-treatment 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 cancellation of the engine pre-stop instruction, the engine ECU controls the after-treatment 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 operates according to vehicle speed, power and torque requirements - accelerator pedal position, and battery SOC value:

[0009] When the battery SOC value is less than the battery set value, it indicates that the battery is low, and the vehicle starts from 0 speed and enters the hybrid mode; when the vehicle speed is within the first speed range, the vehicle remains in the hybrid mode and is charged to the target SOC during driving, and the pre-shutdown message information indicates that the engine pre-shutdown command is canceled;

[0010] When the battery SOC value is ≥ the battery set value, it means that the battery is not depleted, and the entire vehicle starts from 0 speed and enters the pure electric mode. When the vehicle speed is within the second speed range, the engine stops and does not work, and the pre-stop message information is the establishment of the engine pre-stop instruction.

[0011] Furthermore, when the battery is depleted and high power is required, the engine will operate at peak torque.

[0012] Furthermore, 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 pure electric mode is switched to the hybrid mode, and the pre-shutdown message information is the cancellation of the engine pre-shutdown instruction.

[0013] Furthermore, when the battery is not depleted and in pure electric mode, after the vehicle speed exceeds the third speed, the pure electric mode is switched to hybrid mode. According to the power requirements of the entire vehicle, the engine tries to operate in the optimal area to maintain power balance, and the pre-shutdown message information is the cancellation of the engine pre-shutdown command.

[0014] Furthermore, when the vehicle is coasting or braking or the vehicle's required power is less than the pure electric power, the engine is shut down, and the pre-shutdown message information is established as an engine pre-shutdown instruction.

[0015] Furthermore, during the coasting or braking process of the vehicle, the engine enters a high-speed stop-injection and rotation mode or stops to enter a pure electric mode, and the pre-stop message information is used to establish an engine pre-stop instruction.

[0016] Furthermore, when the vehicle speed is higher than the fourth speed, the hybrid mode is switched to the pure engine mode, and the engine is directly driven. The drive motor works in the second gear for power assistance or neutral parking according to the needs of the whole vehicle.

[0017] Furthermore, when the battery is low on power, the pure engine mode will switch to hybrid mode for driving and charging.

[0018] Furthermore, the process of correcting the injector timing is as follows: according to the engine speed and the injection amount, the main injection timing pre-stop correction map is queried to obtain the correction coefficient, the correction coefficient is multiplied by the pre-stop correction main injection timing coefficient to obtain the main injection timing pre-stop correction value, the main injection timing pre-stop correction value is added to the main injection timing base value to obtain the main injection timing final value, and the engine injector operation is controlled according to the main injection timing final value.

[0019] Beneficial effects

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention adopts a pre-shutdown solution to stop urea injection in advance, which significantly improves the crystallization problem in hybrid diesel engine aftertreatment. Experimental verification shows that the amount of crystallization is reduced to one-third of the original under the same operating conditions and time, and the regeneration mileage of hybrid vehicle models for crystal removal is significantly increased by more than 1 times.

[0022] 2. The present invention adopts a main injection timing correction strategy based on pre-shutdown to reduce the risk of excessive NOx emissions after urine injection is stopped. Combined with calibration optimization, it can achieve crystallization improvement while ensuring qualified NOx emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of engine start-stop monitoring;

[0024] Figure 2 This is a schematic diagram of engine shutdown and urea injection time;

[0025] Figure 3 It is a control logic schematic diagram of the present invention;

[0026] Figure 4 This is a schematic diagram for judging the hybrid vehicle controller;

[0027] Figure 5 Schematic diagram for correcting the injector timing. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the specific embodiments in the accompanying drawings.

[0029] See Figures 3 to 5 A control method for improving urea crystallization in a hybrid diesel engine adopts an early urea injection stop scheme. The specific scheme is as follows:

[0030] The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops. The pre-stop message is divided into two types of stop signals, signal 0 and signal 1. When the signal is in state 1, it means that the engine pre-stop command is established, and when it is in state 0, it means that the engine pre-stop command is cancelled. That is, the pre-stop message is one of the engine pre-stop command establishment and engine pre-stop command cancellation.

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

[0032] When the engine ECU receives the cancellation of the engine pre-stop instruction, the engine ECU controls the after-treatment system to immediately resume urea injection, and the engine ECU cancels the correction of the injector timing.

[0033] The hybrid vehicle controller operates based on vehicle speed, power and torque requirements, accelerator pedal position, and battery SOC value:

[0034] When the battery SOC value is less than the battery set value, the battery is depleted and the vehicle enters hybrid mode (CVT) from zero speed. When the vehicle speed is within the first speed range, the vehicle remains in hybrid mode and charges to the target SOC while driving. The pre-shutdown message indicates that the engine pre-shutdown command is revoked. In this embodiment, the battery set value is 20% and the first speed range is 0 kph to 90 kph. When the battery is depleted and high power is required, the engine will operate at peak torque to ensure vehicle operating stability.

[0035] When the battery SOC value ≥ the battery set value, it means that the battery is not depleted, and the whole vehicle starts from 0 speed and enters the pure electric mode (EV). When the vehicle speed is within the second speed range, the engine stops and does not work, and the pre-stop message information is the establishment of the engine pre-stop instruction; in this embodiment, the second speed range is 0kph~28kph; in the pure electric mode, when the power demand is greater than the pure electric power or there is additional mechanical accessory power demand, the pure electric mode is switched to the hybrid mode, and the pre-stop message information is the cancellation of the engine pre-stop instruction.

[0036] When the battery is fully charged and the vehicle is in pure electric mode, and the vehicle speed exceeds the third speed, the vehicle switches from pure electric mode to hybrid mode. Based on the vehicle's power requirements, the engine operates as optimally as possible to maintain power balance, and the pre-shutdown message indicates the revocation of the engine pre-shutdown command. In this embodiment, the third speed is 28 kph. When the vehicle is coasting or braking, or when the vehicle's power requirement is less than the pure electric power, the engine shuts down, and the pre-shutdown message indicates the establishment of the engine pre-shutdown command.

[0037] When the vehicle speed exceeds the fourth speed, hybrid mode switches to pure engine mode, with the engine directly driving the vehicle. The drive motor operates in second gear for power assist or neutral, depending on the vehicle's needs. In this embodiment, the fourth speed is no less than 80 kph. Of course, if the first speed range is 0 kph to 90 kph, the fourth speed can be 90 kph. When the battery is depleted, pure engine mode switches to hybrid mode for on-the-go charging. During coasting or braking, the engine enters high-speed stop-and-go mode or shuts down to enter pure electric mode. The pre-shutdown message establishes the engine pre-shutdown instruction.

[0038] The process of correcting the injector timing is as follows: Figure 5As shown: According to the engine speed and the injection amount, the main injection timing pre-stop correction map is queried to obtain the correction coefficient. The main injection timing pre-stop correction map is pre-calibrated and stored in the hybrid vehicle controller. 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 pre-stop correction main injection timing coefficient is also pre-calibrated according to the engine model and stored in the hybrid vehicle controller. The main injection timing pre-stop correction value is added to the main injection timing base value to obtain the main injection timing final value. The main injection timing base value is the injection amount when urea injection is not stopped. The engine injector operation is controlled according to the main injection timing final value.

[0039] By correcting the main injection timing of the shutdown command, the NOx emissions of the engine at the moment of shutdown are reduced, the urea demand value is reduced, the crystallization risk is reduced, and the risk of excessive NOx emissions is reduced.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A control method for improving urea crystallization in a hybrid diesel engine, characterized in that: The early urea spraying stop program is adopted, and the specific program is as follows: The hybrid vehicle controller sends a pre-stop message to the engine ECU before the engine stops. The pre-stop message is one of the following: establishing an engine pre-stop command or canceling an engine pre-stop command. When the engine ECU receives the engine pre-stop instruction, the engine ECU controls the after-treatment system to immediately stop urea injection, and the engine ECU controls the engine injector to correct the injector timing; When the engine ECU receives the cancellation of the engine pre-stop instruction, the engine ECU controls the after-treatment system to immediately resume urea injection, and the engine ECU cancels the correction of the injector timing.

2. The control method for improving urea crystallization in a hybrid diesel engine according to claim 1, characterized in that: The hybrid vehicle controller works according to 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, and the vehicle starts from 0 speed and enters the hybrid mode; when the vehicle speed is within the first speed range, the vehicle remains in the hybrid mode and is charged to the target SOC during driving, and the pre-shutdown message information indicates that the engine pre-shutdown command is canceled; When the battery SOC value is ≥ the battery set value, it means that the battery is not depleted, and the entire vehicle starts from 0 speed and enters the pure electric mode. When the vehicle speed is within the second speed range, the engine stops and does not work, and the pre-stop message information is the establishment of the engine pre-stop instruction.

3. The control method for improving urea crystallization in a hybrid diesel engine according to claim 2, characterized in that: When the battery is depleted and high power is required, the engine will run 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 is greater than the pure electric power or there is additional mechanical accessory power demand, the pure electric mode is switched to hybrid mode, and the pre-shutdown message information is the cancellation of the engine pre-shutdown command.

5. The control method for improving urea crystallization in a hybrid diesel engine according to claim 2, characterized in that: When the battery is not depleted and the vehicle is in pure electric mode, after the vehicle speed exceeds the third speed, the pure electric mode is switched to hybrid mode. According to the power requirements of the entire vehicle, the engine tries to operate in the optimal area to maintain power balance. The pre-shutdown message information indicates that the engine pre-shutdown command is revoked.

6. The control method for improving urea crystallization in a hybrid diesel engine according to claim 5, characterized in that: When the vehicle is coasting or braking or the vehicle's required power is less than the pure electric power, the engine is shut down, and the pre-shutdown message information is established as the engine pre-shutdown instruction.

7. The control method for improving urea crystallization in a hybrid diesel engine according to claim 2, characterized in that: During the coasting or braking process of the vehicle, the engine enters high-speed stop-injection and rotation or stops to enter pure electric mode, and the pre-stop message information is used to establish the engine pre-stop instruction.

8. The control method for improving urea crystallization in a hybrid diesel engine according to claim 2, characterized in that: When the vehicle speed is higher than the fourth speed, the hybrid mode is switched to the pure engine mode, and the vehicle is directly driven by the engine. The drive motor works in the second gear for power assistance or neutral parking according to the needs of the vehicle.

9. The control method for improving 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 for driving and charging.

10. The control method for improving urea crystallization in a hybrid diesel engine according to claim 1, characterized in that: The process of correcting the injector timing: query the main injection timing pre-stop correction map according to the engine speed and injection amount to obtain the correction coefficient, multiply the correction coefficient by the pre-stop correction main injection timing coefficient to obtain the main injection timing pre-stop correction value, add the main injection timing pre-stop correction value to the main injection timing base value to obtain the main injection timing final value, and control the engine injector operation according to the main injection timing final value.

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