Method for improving urea crystallization of a hybrid engine

Abstract

The application discloses a method for improving urea crystallization of a hybrid engine and belongs to the technical field of engine exhaust treatment. The method comprises the following steps: obtaining a shutdown condition, when the shutdown condition is met, sending a shutdown signal to an engine controller ECU by a hybrid vehicle controller HCU, at the same time, judging a delayed shutdown condition, and synchronously sending a signal indicating whether the engine can be delayed to shutdown, if the delayed shutdown condition is met, a delayed shutdown signal is sent, at this time, the engine is delayed to shutdown for n seconds, and urea injection is immediately stopped or reduced, if the delayed shutdown condition is not met, a non-delayed shutdown signal is sent, at this time, the engine is immediately shutdown, then, a urea injection stop condition is judged, and if the urea injection stop condition is met, urea injection is stopped. The method makes the mixer have enough time to clean the residual urea, so that the crystallization amount in the mixer is greatly reduced, and even no crystallization exists in the DPF regeneration cycle.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust gas treatment technology, and in particular to a method for improving urea crystallization in hybrid engines. Background Technology

[0002] Selective catalytic reduction (SCR) technology is an important technical route for engines to meet China VI emission standards. However, hybrid engines experience frequent start-stop cycles, approximately 20 times in 2000 seconds, averaging once every 1.5 minutes. During these start-stop cycles, the engine rapidly drops from a high-load condition (corresponding to a large urea injection volume) to a standstill, leading to the following two situations:

[0003] First, the urea injection could not be shut off in time, resulting in a small amount of urea continuing to be injected even after the engine stopped.

[0004] Secondly, the urea injected before the engine stops is not fully hydrolyzed and does not have enough time to react with the exhaust gas, so it continues to remain in the aftertreatment mixer.

[0005] In either of these situations, more and more urea will remain in the mixer, eventually leading to urea crystals clogging the mixer. Summary of the Invention

[0006] The objective of this invention is to address the aforementioned problems by providing a method for improving urea crystallization in hybrid engines. This method allows the mixer sufficient time to clear residual urea, thereby significantly reducing the amount of crystallization within the mixer, and even eliminating crystallization during the DPF regeneration cycle.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for improving urea crystallization in a hybrid engine, the method comprising: acquiring shutdown conditions; when the shutdown conditions are met, the hybrid vehicle controller (HCU) sends a shutdown signal to the engine controller (ECU); simultaneously, by judging the delayed shutdown conditions, a signal indicating whether the engine can delay shutdown is sent: if the delayed shutdown conditions are met, a delayed shutdown signal is sent, in which case the engine shuts down after a delay of n seconds and immediately stops or reduces urea injection; if the delayed shutdown conditions are not met, a non-delayed shutdown signal is sent, in which case the engine shuts down immediately; then, the urea injection stop condition is judged, and if the urea injection stop condition is met, urea injection is stopped.

[0009] Furthermore, the shutdown conditions include vehicle speed, battery SOC value, and operating mode, specifically:

[0010] When the battery is fully charged, the vehicle starts in pure electric mode between 0kph and 28kph. When the shutdown conditions are met, the engine stops.

[0011] When the battery SOC value is less than 20%, the vehicle starts from 0 speed and enters hybrid mode. It maintains hybrid mode between 0kph and 80kph speed to charge the battery to the target SOC value and meet the shutdown conditions, at which point the engine stops.

[0012] During coasting and braking, the E2 motor recovers energy and stops when the shutdown conditions are met.

[0013] Furthermore, the delayed shutdown conditions include: there is no forced shutdown fault or other request in the current operating mode; the current battery SOC value has not reached the target SOC value or has reached the target SOC value but exceeds the SOC safety threshold.

[0014] Furthermore, the n seconds in the engine shutdown delay of n seconds is obtained by calibrating the time during which emissions do not exceed the standard.

[0015] Furthermore, the conditions for immediately stopping or reducing urea spraying are as follows: if the ammonia storage is greater than the target value, urea spraying is stopped; otherwise, urea spraying is reduced.

[0016] Furthermore, the urea shutdown conditions include a shutdown signal, SCR temperature, and ammonia storage.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects:

[0018] This invention adds a judgment on whether the engine can be delayed in stopping, so that the engine can be delayed in stopping when the delay conditions are met. This allows the mixer enough time to clean the residual urea, thereby greatly reducing the amount of crystallization in the mixer, or even eliminating crystallization during the DPF regeneration cycle. Attached Figure Description

[0019] Figure 1 This is a flowchart of the improved urea crystallization method for hybrid engines according to the present invention.

[0020] Figure 2 This invention aims to improve the urea crystallization situation in the mixer of automobiles using the urea crystallization method for hybrid engines.

[0021] Figure 3 This describes the urea crystallization situation in the mixer of a car using the original hybrid engine control method. Detailed Implementation

[0022] The specific implementation of the invention will be further described below with reference to the accompanying drawings.

[0023] like Figure 1As shown, in one embodiment of the present invention, a method for improving urea crystallization in a hybrid engine is provided. The method includes: acquiring shutdown conditions; when the shutdown conditions are met, the hybrid vehicle controller (HCU) sends a shutdown signal to the engine controller (ECU); simultaneously, by judging the delayed shutdown conditions, a signal indicating whether the engine can delay shutdown is sent: if the delayed shutdown conditions are met, a delayed shutdown signal is sent, in which case the engine shuts down after a delay of n seconds and immediately stops or reduces urea injection; if the delayed shutdown conditions are not met, a non-delayed shutdown signal is sent, in which case the engine shuts down immediately; then, the urea injection stop condition is judged, and if the urea injection stop condition is met, urea injection is stopped.

[0024] Compared to the original hybrid engine control method: when the shutdown conditions are met, the hybrid vehicle controller (HCU) sends a shutdown signal to the engine controller (ECU), and the engine immediately shuts down. Then, it judges the urea injection shutdown conditions. If the urea injection shutdown conditions are met, the urea injection stops.

[0025] The control method of the present invention adds a judgment on whether the engine can be delayed in stopping, so that the engine is delayed in stopping when the delay conditions are met, so that the mixer has enough time to clean the residual urea, thereby greatly reducing the amount of crystallization in the mixer, or even eliminating crystallization during the DPF regeneration cycle.

[0026] In this embodiment, the shutdown conditions specifically include vehicle speed, battery SOC value, and operating mode, specifically:

[0027] When the battery is fully charged and the vehicle starts in pure electric mode, the speed range between 0kph and 28kph (calibrable) is pure electric (EV) mode. When the shutdown conditions are met, the engine will stop.

[0028] When the battery SOC value is less than 20%, the vehicle starts from 0 speed and enters hybrid mode. It maintains hybrid mode between 0kph and 80kph speed to charge the battery to the target SOC value and meet the shutdown conditions, at which point the engine stops.

[0029] During coasting and braking, the E2 motor recovers energy and stops when the shutdown conditions are met.

[0030] That is, when one of the above conditions is met, i.e. the shutdown condition is met, the hybrid vehicle controller (HCU) will send a shutdown signal to the engine controller (ECU).

[0031] The above shutdown conditions are only partial shutdown conditions. The shutdown conditions vary from car manufacturer to car manufacturer. The specific shutdown conditions should be determined based on the actual situation.

[0032] In this embodiment, specifically, the delayed shutdown conditions mainly include: no forced shutdown faults or other requests in the current operating mode; the current battery SOC value has not reached the target SOC value or has reached the target SOC value but exceeds the SOC safety threshold. Specifically, to protect the battery from deep discharge and overcharging, the SOC value is 100% when fully charged, but in actual use, the maximum SOC value allowed is only 90% (the definition varies by manufacturer), i.e., 90% is the target SOC value. However, sometimes for special needs, exceeding this target SOC value is allowed, but there is an upper limit, such as 95%, i.e., 95% is the SOC safety threshold. Long-term exceedance of this value will reduce battery life. Therefore, the battery SOC value reaching the target SOC value but exceeding the SOC safety threshold is one of the main conditions for delayed shutdown.

[0033] That is, when the above-mentioned delayed shutdown conditions are met, the hybrid vehicle controller (HCU) will send a delayed shutdown signal at the same time as sending a shutdown signal to the engine controller (ECU); otherwise, it will send a non-delayed shutdown signal.

[0034] In this embodiment, specifically, the n seconds in the engine's n-second delay shutdown is obtained by calibrating the time required to ensure emissions do not exceed standards. If the delay time is too long, urea will not be injected midway, the ammonia storage in the aftertreatment system will be interrupted and empty, and NOx emissions will exceed standards due to the lack of reducing agent. Therefore, calibration is required to obtain the specific value of n, which represents the minimum requirement to ensure emissions do not exceed standards.

[0035] In this embodiment, specifically, the conditions for immediately stopping or reducing urea spraying are: if the ammonia storage is greater than the target value, urea spraying is stopped; otherwise, urea spraying is reduced.

[0036] In this embodiment, the specific conditions for stopping urea spraying include a shutdown signal, SCR temperature, and ammonia storage. Urea spraying is stopped only when these conditions are met.

[0037] By applying the above-mentioned methods for improving urea crystallization to Yutong vehicles, only a small amount of urea crystals accumulated in the mixer after 1000km of mileage, such as... Figure 2 As shown. However, in Yutong vehicles using traditional control methods, a large amount of urea crystals have already accumulated in the mixer after only 500km, such as... Figure 3 As shown.

[0038] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for improving urea crystallization in a hybrid engine, characterized in that, The method includes: Upon obtaining the shutdown conditions, the hybrid vehicle controller (HCU) sends a shutdown signal to the engine controller (ECU) when the shutdown conditions are met. Simultaneously, by judging the delayed shutdown conditions, it sends a signal indicating whether the engine can delay shutdown: if the delayed shutdown conditions are met, a delayed shutdown signal is sent, in which case the engine shuts down after a delay of n seconds and immediately stops or reduces urea injection; if the delayed shutdown conditions are not met, a non-delayed shutdown signal is sent, in which case the engine shuts down immediately, and then the urea injection stoppage conditions are judged. If the urea injection stoppage conditions are met, urea injection stops.

2. The method for improving urea crystallization in a hybrid engine according to claim 1, characterized in that, The shutdown conditions include vehicle speed, battery SOC value, and operating mode, specifically: When the battery is fully charged, the vehicle starts in pure electric mode between 0kph and 28kph. When the shutdown conditions are met, the engine stops. When the battery SOC value is less than 20%, the vehicle starts from 0 speed and enters hybrid mode. It maintains hybrid mode between 0kph and 80kph speed to charge the battery to the target SOC value and meet the shutdown conditions, at which point the engine stops. During coasting and braking, the E2 motor recovers energy and stops when the shutdown conditions are met.

3. The method for improving urea crystallization in a hybrid engine according to claim 1, characterized in that, The delayed shutdown conditions include: no forced shutdown fault or other request in the current operating mode; the current battery SOC value has not reached the target SOC value or has reached the target SOC value but exceeds the SOC safety threshold.

4. The method for improving urea crystallization in a hybrid engine according to claim 1, characterized in that, The n seconds in the engine shutdown delay is obtained by calibrating the time during which emissions do not exceed the standard.

5. The method for improving urea crystallization in a hybrid engine according to claim 1, characterized in that, The conditions for immediately stopping or reducing urea spraying are as follows: if the ammonia storage is greater than the target value, urea spraying is stopped; otherwise, urea spraying is reduced.

6. The method for improving urea crystallization in a hybrid engine according to claim 1, characterized in that, The conditions for stopping urea spraying include a shutdown signal, SCR temperature, and ammonia storage.

Images