EGR (Exhaust Gas Recirculation) control device and method for fuel gas heavy truck in high and cold environment

Abstract

The invention relates to a gas heavy truck high cold environment EGR control device and method, and relates to the field of engines, the gas heavy truck high cold environment EGR control device comprises an engine, an EGR cooler and an EGR valve, the EGR valve is arranged at an outlet of the EGR cooler, a valve seat of the EGR valve is provided with a circulating water heating device, an inlet of the EGR valve is provided with an EGRT temperature sensor, and an outlet of the engine is provided with a water temperature sensor; when an engine operates, the EGR valve is continuously heated through engine circulating water, when the environment temperature is high or the water temperature of the engine is high, the temperatures of the EGR valve and pipelines in front of and behind the EGR valve are high, water in EGR waste gas exists in a water vapor state, and an EGR system works normally. In the cold starting process of an engine or long-time idling or long-time reverse towing operation in the high and cold environment, condensate water and condensate water icing of EGR waste gas on the surfaces of cold parts are reduced, condensate water entering an air cylinder is reduced, and the influence of the EGR waste gas condensate water and condensate water icing on engine operation is reduced to the maximum extent.

Description

Technical Field

[0001] The present invention relates to the field of engine technology, and in particular to an EGR control device and method for a gas heavy truck in a cold environment. Background Art

[0002] The National VI heavy-duty gas vehicles adopt equivalent combustion and three-way catalytic converters to meet the National VI emission and power requirements, but the engine exhaust temperature and heat load increase greatly. The cylinder head, exhaust pipe, supercharger and other parts of the original vehicle engine cannot withstand high heat loads and need major design improvements. During equivalent combustion, the gas mixture is diluted by EGR (exhaust gas recirculation), which can effectively reduce the heat load of parts, reduce the temperature resistance level of materials and development costs. EGR technology is a key technology for National VI gas engines, affecting the engine's emissions, power, economy and reliability. The EGR valve of the gas heavy truck is arranged at the outlet of the EGR cooler, close to the intake manifold, to improve the responsiveness of the engine. A heater is installed at the base of the EGR valve. When the engine is running, the EGR valve is continuously heated by the engine circulating water. When the ambient temperature is high or the engine water temperature is high, the temperature of the EGR valve and the pipelines before and after the EGR valve is high. The water in the EGR exhaust gas exists in the form of water vapor, which does not affect the operation of the engine. The water vapor content in the EGR exhaust gas of a gas engine reaches 21%. When the ambient temperature is below minus 30°C, during the cold start phase of the engine, the temperature of the EGR cooler outlet pipe, the EGR valve, the pipes before and after the EGR valve, and the intake manifold wall is below 0° for a long time. The EGR exhaust gas condenses into water and freezes on the surface of cold parts, affecting the operation of the engine. In severe cases, the engine cannot start, the combustion deteriorates, the post-processor is damaged, and a large amount of condensed water enters the cylinder and damages the cylinder parts. In order to reduce the impact of EGR pipe condensation and condensed water freezing on engine operation, it is necessary to develop an EGR control method in a high-cold environment. Summary of the invention

[0003] When the engine is cold started in a high-cold environment, the temperature of the EGR cooler outlet pipe, EGR valve, pipes before and after the EGR valve, and the intake manifold wall is below 0° for a long time, and the EGR exhaust gas condenses into water and freezes on the surface of cold parts, affecting the operation of the engine. In severe cases, the engine cannot start, the combustion deteriorates, and the post-processor is damaged. A large amount of condensed water enters the cylinder and damages the cylinder parts. In view of the long-term condensation and freezing of EGR exhaust gas on the surface of cold parts in a high-cold environment, a gas heavy truck EGR control method needs to be proposed.

[0004] In order to achieve the above-mentioned purpose, the technical solution of the present invention provides an EGR control device for a gas heavy-duty truck in a high-cold environment, including an engine, an EGR cooler and an EGR valve. The EGR valve is arranged at the outlet of the EGR cooler, the valve seat of the EGR valve is provided with a circulating water heating device, the inlet of the EGR valve is provided with an EGRT temperature sensor, and the outlet of the engine is provided with a water temperature sensor. When the engine is running, the EGR valve is continuously heated by the engine circulating water. When the ambient temperature is high or the engine water temperature is high, the temperature of the EGR valve and the pipelines before and after the EGR valve are high, the moisture in the EGR exhaust gas exists in the state of water vapor, and the EGR system works normally.

[0005] The technical solution of the present invention also provides an EGR control method for a gas heavy truck in a cold environment, comprising the following steps:

[0006] Determine whether the ambient temperature is below -20°C. If so, proceed to the next step. Otherwise, turn on the EGR system.

[0007] Determine whether the engine water temperature is lower than 60°C. If so, turn off the EGR system, otherwise proceed to the next step;

[0008] Determine whether the EGRT temperature is greater than 30°C, if so, proceed to the next step, otherwise repeat this step;

[0009] Conduct ice breaking stuck test;

[0010] Determine whether the ice breaking jam test is passed. If so, turn on the EGR system, otherwise return to the previous step.

[0011] Preferably, the EGR control system is turned off, the EGR valve is normally closed, the EGR exhaust gas cannot flow, and EGR condensed water is only formed in front of the EGR valve. There is less condensed water and ice, and the condensed water cannot enter the intake manifold and cylinder through the EGR valve. At the same time, the ignition advance angle is delayed and the engine torque is limited to prevent excessive exhaust temperature and detonation.

[0012] Preferably, the temperature of the EGR valve and the surrounding pipeline walls increases, there is no condensed water or condensed water freezing, and the EGR control system performs an EGR valve ice-breaking test. If the test passes, the EGR system operates normally, and the ignition advance angle and boost pressure return to normal values.

[0013] Preferably, after the engine has been running for a long time, towing downhill or idling for a long time, if the water temperature is lower than 60°C or the EGRT temperature is lower than 30°C, the EGR control system is turned off to prevent ice and jamming during operation. Perform an ice-breaking test until the thawing conditions are met, and then turn on the EGR system after the ice-breaking test is passed.

[0014] Preferably, the EGR system is shut down when the water temperature of the engine is lower than 60°C during the warm-up phase after a cold engine start, so as to reduce EGR exhaust gas condensation and condensation water freezing and prevent condensation water from entering the cylinder.

[0015] Preferably, when the EGR system is turned off, the engine advance angle is delayed to prevent knocking, and the engine load is limited to prevent excessive exhaust temperature and engine overload.

[0016] Preferably, a progressive step test is performed during the oil cut-off period of the ice-breaking test. The target opening position of the first EGR valve test is 25%. If the EGR valve opening is normal, the EGR valve test opening is increased to 50%, 75%, and 100% in sequence. If each test is normal, the EGR valve ice-breaking test passes and the EGR valve is fully controlled. Otherwise, wait for the next test.

[0017] The beneficial effects of the present invention are as follows: the EGR control device and method for a gas heavy truck in a cold environment of the present invention is beneficial to reducing the condensation of EGR exhaust gas on the surface of cold parts and the condensation of water freezing during the cold engine start-up process or long-term idling or long-term reverse operation in a cold environment, reducing the condensation of water entering the cylinder, and minimizing the impact of EGR exhaust gas condensation and condensation of water freezing on engine operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a control flow chart of the EGR system of a gas heavy truck in a cold environment of the present invention;

[0019] Figure 2 This is a structural diagram of the gas EGR control system of a gas heavy truck of the present invention;

[0020] Figure 3 It is the condensation water and ice area of ​​EGR exhaust gas when the EGR valve of the gas heavy truck of the present invention is opened;

[0021] Figure 4 It is the condensation water and ice area of ​​EGR exhaust gas when the EGR valve of the gas heavy truck of the present invention is normally closed;

[0022] Figure 5 It is a pulse spectrum of ignition advance angle and a pulse spectrum of boost pressure when the EGR valve of the gas heavy truck of the present invention is opened;

[0023] Figure 6 It is an ignition advance angle pulse spectrum table and a boost pressure pulse spectrum table when the gas EGR valve of the gas heavy truck of the present invention is normally closed. DETAILED DESCRIPTION

[0024] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0025] An embodiment of the present invention discloses an EGR control device and method for a gas heavy truck in a cold environment. A heater is installed at the EGR valve base. When the engine is running, the EGR valve is continuously heated by the engine circulating water. When the ambient temperature is high or the engine water temperature is high, the temperature of the EGR valve and the pipelines before and after the EGR valve are high. The moisture in the EGR exhaust gas exists in the form of water vapor, and the EGR system operates normally.

[0026] During the cold engine start in a high-cold environment, the EGR valve and the pipelines before and after the EGR valve are judged to have potential ice based on the ambient temperature, engine water temperature, and EGR exhaust gas temperature. If the ice conditions are met, that is, when the ambient temperature is below minus 20℃, the EGR control system is turned off, the EGR valve is normally closed, the EGR exhaust gas cannot flow, and the EGR condensed water is only formed in front of the EGR valve. There is less condensed water and ice, and the condensed water cannot enter the intake manifold and cylinder through the EGR valve. At the same time, the ignition advance angle and engine torque limit are delayed to prevent excessive exhaust temperature and knock. When the ambient temperature is below minus 2 When the temperature is above 0℃ and the water temperature is greater than 60℃ and the EGRT temperature is greater than 30℃, the temperature of the EGR valve and the surrounding pipeline walls rises, there is no condensed water and the condensed water is frozen, and the EGR control system performs an EGR valve ice-breaking test. If the test passes, the EGR system operates normally, and the ignition advance angle and boost pressure return to normal values; after the engine has been running for a long time and is reversed downhill or idling for a long time, if the water temperature is lower than 60℃ or the EGRT temperature is lower than 30℃, the EGR control system is turned off to prevent ice and jamming during operation until the thawing conditions are met for the ice-breaking test. The EGR system is turned on after the ice-breaking test is passed.

[0027] The EGR control method for gas heavy trucks in cold weather is as shown in the attached Figure 1 As shown in the attached Figure 2 As shown, the EGR valve is installed at the outlet of the EGR cooler, a circulating water heating device is installed on the EGR valve seat, an EGRT temperature sensor is installed at the inlet of the EGR valve, and a water temperature sensor is installed at the outlet of the engine. Figure 3 This is the area where EGR exhaust gas condenses and freezes when the EGR valve is opened during cold start. Figure 4 It is the area where EGR exhaust gas condenses and freezes when the EGR valve is closed during cold start. The EGR control system determines whether the EGR valve and the pipelines before and after the EGR valve have potential ice formation through the water temperature and the EGR valve body temperature, and closes the EGR valve in time to prevent the EGR valve and the pipelines before and after the EGR valve from freezing in the cold weather and affecting the engine operation, thus ensuring the normal operation of the engine in the cold weather.

[0028] Furthermore, it is determined whether the EGR valve and the front and rear pipes are frozen, and a condition test is performed to determine whether the engine meets the cold engine start conditions in a high-cold environment: the ambient temperature is below minus 20°C.

[0029] Furthermore, when the water temperature of the engine is lower than 60°C during the warm-up phase after a cold engine start, the EGR system is shut down to reduce EGR exhaust gas condensation and condensation water freezing and prevent condensation water from entering the cylinder.

[0030] Furthermore, when the EGR system is turned off, the engine delays the advance angle to prevent knocking and limits the engine load to prevent excessive exhaust temperature and engine overload.

[0031] Furthermore, the engine performs an EGR valve ice-breaking test when the water temperature is greater than 60°C and the EGRT temperature is greater than 30°C. If the ice-breaking test is passed, the EGR system is turned on, the EGR system works normally, and the ignition advance angle and boost pressure return to normal values. Otherwise, continue to wait for the ice-breaking test.

[0032] Furthermore, after the engine has been idling for a long time or running in reverse for a long time, the water temperature and EGRT temperature continue to drop. When the icing conditions are met, the EGR system is turned off until the thawing conditions are met and an ice-breaking test is performed. The EGR system is turned on after the ice-breaking test is passed.

[0033] like Figure 1 The flow chart of the EGR control method for a gas heavy truck in a cold environment is shown in the figure. The control process includes the following steps:

[0034] Step one: determine whether the EGR valve and the front and rear pipes are frozen, that is, the engine meets the cold engine start conditions in a high-cold environment: the ambient temperature is below minus 20 degrees Celsius. When the ambient temperature is below minus 20 degrees Celsius, the engine warm-up time is long, the engine water temperature and the temperature of the EGR system parts rise slowly, and the EGR exhaust gas condenses into water when in contact with the cold wall of the parts, and further freezes. During the warm-up phase, the EGR system is turned off, and the EGR valve is in a normally closed state, which reduces the condensation of EGR exhaust gas on the surface of cold parts and the freezing of condensed water, prevents condensed water from entering the intake manifold and cylinders, and eliminates the impact of EGR valve freezing on engine operation.

[0035] Step 2: After closing the EGR valve during the warm-up phase, use independent ignition advance angle map and boost pressure map, such as Figure 5 , to prevent engine knock and engine overload when the EGR valve is closed.

[0036] Step three, determine whether the thawing conditions of the EGR valve and pipelines are met: during the warm-up stage, the water temperature continues to rise, and the EGR valve is heated by circulating water. When the water temperature exceeds 60°C and the EGRT temperature exceeds 30°C, the temperature of the EGR valve and the pipelines before and after the EGR valve rises, the ice in the pipeline melts, and the EGR exhaust gas no longer condenses, meeting the conditions for the EGR valve de-icing test.

[0037] Step 4: EGR valve ice-breaking test: Perform an EGR valve ice-breaking test before the EGR system is operated to ensure that the ice on the EGR valve is completely melted and the EGR valve is fully controlled. Perform an ice-breaking test during the reverse towing period when the accelerator is released. Performing an ice-breaking test during reverse towing can eliminate the impact of the ice-breaking test on engine operation. Figure 6 During the oil cut-off period, a progressive step test is performed. The target opening position of the first EGR valve test is 25%. If the EGR valve opening is normal, the EGR valve test opening is increased to 50%, 75%, and 100% in sequence. If each test is normal, the EGR valve ice-breaking test is passed and the EGR valve is fully controlled. Otherwise, wait for the next test.

[0038] Step 5, EGR control system works: After the EGR valve ice breaking test is passed, the EGR valve is opened, the EGR control works normally, and the ignition advance angle and boost pressure return to normal values. Figure 6 .

[0039] Step six, repeatedly shut down the EGR system: after the engine has been idling for a long time or running in reverse for a long time, the water temperature and EGRT temperature continue to drop. When the water temperature is lower than 60℃ or the EGRT temperature is lower than 30℃, shut down the EGR system until the thawing conditions are met and perform an ice-breaking test. After the ice-breaking test is passed, open the EGR system.

[0040] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A gas heavy truck EGR control device for cold weather environment, characterized in that: It includes an engine, an EGR cooler and an EGR valve. The EGR valve is arranged at the outlet of the EGR cooler. The valve seat of the EGR valve is provided with a circulating water heating device. The inlet of the EGR valve is provided with an EGRT temperature sensor. The outlet of the engine is provided with a water temperature sensor. When the engine is running, the EGR valve is continuously heated by the engine circulating water. When the ambient temperature is high or the engine water temperature is high, the temperature of the EGR valve and the pipes before and after the EGR valve are high. The water in the EGR exhaust gas exists in the state of water vapor, and the EGR system works normally.

2. The control method of a gas heavy truck high-cold environment EGR control device according to claim 1 is characterized in that: The following steps are involved: Determine whether the ambient temperature is below -20°C. If so, proceed to the next step. Otherwise, turn on the EGR system. Determine whether the engine water temperature is lower than 60°C. If so, turn off the EGR system, otherwise proceed to the next step; Determine whether the EGRT temperature is greater than 30°C, if so, proceed to the next step, otherwise repeat this step; Conduct ice breaking stuck test; Determine whether the ice breaking jam test is passed. If so, turn on the EGR system, otherwise return to the previous step.

3. The EGR control method for a gas heavy truck in a cold environment according to claim 2, characterized in that: Turn off the EGR control system, the EGR valve is normally closed, the EGR exhaust gas cannot flow, and EGR condensed water is only formed in front of the EGR valve. There is less condensed water and ice. The condensed water cannot enter the intake manifold and cylinder through the EGR valve. At the same time, the ignition advance angle is delayed and the engine torque is limited to prevent excessive exhaust temperature and detonation.

4. The EGR control method for a gas heavy truck in a cold environment according to claim 3 is characterized in that: The temperature of the EGR valve and the surrounding pipeline walls rises, there is no condensed water or condensed water freezing, and the EGR control system performs an EGR valve ice-breaking test. If the test passes, the EGR system operates normally, and the ignition advance angle and boost pressure return to normal values.

5. The EGR control method for a gas heavy truck in a cold environment according to claim 4, characterized in that: If the engine is running and towing downhill or idling for a long time, and the water temperature is below 60℃ or the EGRT temperature is below 30℃, turn off the EGR control system to prevent ice and jamming during operation. Perform an ice-breaking test when the thawing conditions are met. Turn on the EGR system after the ice-breaking test is passed.

6. The EGR control method for a gas heavy truck in a cold environment according to claim 5, characterized in that: When the water temperature of the engine is lower than 60℃ during the warm-up phase after cold start, the EGR system is turned off to reduce EGR exhaust condensation and condensation freezing and prevent condensation from entering the cylinder.

7. The EGR control method for a gas heavy truck in a cold environment according to claim 6, characterized in that: When the EGR system is turned off, the engine advance angle is delayed to prevent knock and the engine load is limited to prevent excessive exhaust temperature and engine overload.

8. The EGR control method for a gas heavy truck in a cold environment according to claim 7, characterized in that: A progressive step test is performed during the oil cut-off period of the ice-breaking test. The target opening position of the first EGR valve test is 25%. If the EGR valve opening is normal, the EGR valve test opening is increased to 50%, 75%, and 100% in sequence. If each test is normal, the EGR valve ice-breaking test passes and the EGR valve is fully controlled. Otherwise, wait for the next test.

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