Rapid cold starting method for engine

Abstract

The invention provides an engine rapid cold starting method which comprises the steps of collecting air inlet temperature data of an engine, determining a current starting control strategy according to a pre-calibrated cold starting strategy, controlling and executing engine operation dragging duration according to the current starting control strategy, and controlling an oil sprayer, a spark plug and a variable valve mechanism to act. Further, the residence time of the mixed gas of the fuel oil and the air in the cylinder is controlled; and collecting exhaust temperature data of the engine, and controlling an engine starting device, an oil sprayer, a spark plug and a variable valve mechanism to execute an idle speed control strategy when determining that the thermodynamic state in the cylinder at present meets a stable combustion condition according to the stored calibration data. When the piston engine is started in the extremely cold environment, the time of fuel oil mixed gas staying in the cylinder can be controlled according to the cold environment temperature condition, it is guaranteed that fuel oil is fully combusted to release heat, the combustion chamber is heated, the stable combustion condition is rapidly achieved, and rapid cold starting is achieved.

Description

Technical Field

[0001] This application belongs to the field of engine technology, and in particular relates to a method for rapid cold start of an engine. Background Technology

[0002] Piston engines are highly efficient power machines widely used in transportation, agriculture, national defense, industry, and other fields. However, in extremely cold environments, such as winter temperatures in northern regions where the lowest temperature can drop to -30 to -40 degrees Celsius, and in polar environments where temperatures can even reach -65 degrees Celsius, piston engines face exceptionally difficult cold starts, causing great inconvenience.

[0003] In the existing technology, by closing the intake and exhaust valves and using the starter motor to drive the engine to rotate, the engine combustion chamber is heated during the engine compression and expansion to achieve the purpose of quickly starting the engine; however, the temperature of the gas in the cylinder will decrease during the expansion stroke, resulting in low heating efficiency; at the same time, it will cause the cold start speed to be slowed down at extremely low temperatures. Summary of the Invention

[0004] In view of this, this application aims to propose a method for rapid cold starting of an engine to solve the problems of low heating efficiency and slow cold starting speed at extremely low temperatures.

[0005] To achieve the above objectives, the technical solution of this application is implemented as follows: This application provides a method for rapid cold starting of an engine, including: The system collects engine intake air temperature data and determines the current start control strategy based on a pre-calibrated cold start strategy. It then controls the duration of engine operation according to this strategy, as well as the actions of the injectors, spark plugs, and variable valve timing mechanism, thereby controlling the residence time of the fuel-air mixture in the cylinder. The cold start strategy includes an injection / ignition strategy, a variable valve timing strategy, and a starter motor strategy. The engine exhaust temperature data is collected, and based on the stored calibration data, it is determined that the current thermodynamic state in the cylinder meets the conditions for stable combustion. Then, the engine starting device, injectors, spark plugs, and variable valve timing mechanism are controlled to execute the idle speed control strategy.

[0006] Furthermore, in response to the first fuel injection and ignition, the cold start strategy is calibrated. By acquiring different intake air temperature data, the fuel injection strategy and ignition strategy are determined based on the air-fuel ratio under cold start conditions and engine limitations. Based on the determined fuel injection and ignition strategies, the fuel injector and spark plug are controlled to perform fuel injection / ignition actions, and the variable valve timing mechanism is controlled to close the intake valve and exhaust valve. After several cycles, the intake and exhaust valves are switched to the normal valve phase of the engine through the variable valve timing mechanism to discharge the exhaust gas from the cylinder and record the exhaust temperature, as well as the number of cycles in which the intake / exhaust valves close after fuel injection. By judging the change in exhaust temperature and using the current calibrated exhaust temperature as the condition for determining valve opening, the current calibrated valve closing time strategy, fuel injection strategy, and ignition strategy are used as the initial cold start strategy.

[0007] Furthermore, the calibration strategy for the injector, spark plug, and variable valve timing mechanism is fixed after the first injection. The execution strategy of the variable valve timing mechanism after the second injection is then calibrated. By introducing a strategy for delayed exhaust valve closing or secondary opening of the variable valve timing mechanism, the process of calibrating the variable valve timing mechanism, injector, and spark plug strategy during the first injection ignition is repeated. This calibrates the number of engine cycles in which the air-fuel mixture remains in the engine cylinder after injection ignition, as well as the exhaust temperature at this time.

[0008] Furthermore, by comparing the changes in exhaust temperature during two cold starts, if the exhaust temperature increases, the number of engine cycles in which the air-fuel mixture remains in the cylinder is increased. If the temperature is reduced, the number of engine cycles in which the air-fuel mixture remains in the cylinder is shortened until the degree of change in exhaust temperature meets the preset conditions. Then, the number of engine cycles in which the air-fuel mixture remains in the engine cylinder after fuel injection and ignition is calibrated.

[0009] Furthermore, during the calibration of cold start, the strategy changes of the variable valve timing mechanism, injectors, and spark plugs during cold start are obtained as the number of engine cycles in which the in-cylinder mixture remains in the combustion chamber are changed. The corresponding exhaust temperature is obtained as a result of the number of engine cycles in which the in-cylinder mixture remains in the combustion chamber, and this is used to determine the strategy of the variable valve timing mechanism, injectors, and spark plugs to be executed in the next injection.

[0010] Furthermore, in response to the determination that the thermodynamic state inside the engine cylinder does not meet the stable combustion conditions, the cold start strategy for the next injection cycle is determined based on the exhaust temperature information and temperature changes, and based on the calibrated strategy information. The duration of engine operation is controlled according to the cold start strategy for the next injection cycle, and the actions of the injectors, spark plugs and variable valve timing mechanism are controlled until the stable combustion conditions are met.

[0011] Furthermore, the piston engine is equipped with an electronic controller, which is connected to an intake temperature sensor installed at the intake end and an exhaust temperature sensor installed at the exhaust end. The intake air temperature sensor obtains the engine's intake air temperature and feeds it back to the electronic controller, while the exhaust air temperature sensor detects changes in the engine's exhaust air temperature during cold start and feeds it back to the electronic controller. The electronic controller controls the spark plug, the variable valve timing mechanism, and the fuel injector to perform corresponding ignition, variable valve timing, and fuel injection actions, and controls the duration for which the engine starting device drives the engine to run.

[0012] Compared with the prior art, the engine rapid cold start method described in this application has the following advantages: The engine rapid cold start method described in this application enables a piston engine to start in extremely cold environments by controlling the time the fuel-air mixture remains in the cylinder according to the ambient temperature, ensuring that the fuel burns completely and releases heat to heat the combustion chamber, quickly reaching the conditions for stable combustion and achieving rapid cold start. Compared with the cold start strategy of closing the intake and exhaust valves and using compressed air to heat the combustion chamber, this method can start faster and consume less electrical energy. Attached Figure Description

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the cold start process of the piston engine described in the embodiments of this application; Figure 2 This is a schematic diagram of the cold start control strategy calibration process described in the embodiments of this application; Figure 3 This is a schematic diagram of the piston engine structure described in an embodiment of this application.

[0014] Explanation of reference numerals in the attached figures: 1-Intake air temperature sensor; 2-Spark plug; 3-Variable valve timing mechanism; 4-Electronic controller; 5-Injector; 6-Piston engine; 7-Exhaust air temperature sensor; 8-Engine starting device. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0016] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0017] The purpose of this embodiment of a rapid cold start method for an engine is to improve the cold start performance of a piston engine in extremely cold environments. By controlling the variable valve timing mechanism to control the residence time of the fuel-air mixture in the cylinder, and by fully conducting combustion and exothermic reactions during multiple compression and expansion processes, the combustion chamber is rapidly heated, the thermodynamic state is improved, and rapid cold start is achieved.

[0018] The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0019] Please see Figure 1 As shown, this embodiment provides a method for rapid cold starting of an engine, including: The system collects engine intake air temperature data and determines the current start control strategy based on a pre-calibrated cold start strategy. It then controls the duration of engine operation according to this strategy, as well as the actions of the fuel injector 5, spark plug 2, and variable valve timing mechanism 3, thereby controlling the residence time of the fuel-air mixture in the cylinder. The cold start strategy includes a fuel injection / ignition strategy, a variable valve timing strategy, and a starter motor strategy. The engine exhaust temperature data is collected, and the current thermodynamic state in the cylinder is determined based on the stored calibration data to meet the conditions for stable combustion. The engine starting device 8, injector 5, spark plug 2 and variable valve timing mechanism 3 are then controlled to execute the idle speed control strategy.

[0020] Specifically, the starting method in this embodiment is based on an engine system, such as... Figure 3 As shown, it includes an intake air temperature sensor 1, a spark plug 2, a variable valve timing mechanism 3, an electronic control unit (ECU) 4, a fuel injector 5, a piston engine 6, an exhaust air temperature sensor 7, and an engine starting device 8. Among them, the intake air temperature sensor 1 collects the engine intake air temperature and feeds it back to the engine electronic controller 4; the spark plug 2, the variable valve timing mechanism 3 and the fuel injector 5 are controlled by the electronic controller 4 to perform the corresponding ignition, variable valve timing mechanism and fuel injection actions; the exhaust air temperature sensor 7 detects the change in exhaust air temperature during the cold start process of the piston engine 6 and feeds it back to the electronic controller 4; the engine starting device 8 is controlled by the electronic controller 4 to execute the duration of engine running and the time of disconnection from the engine; The electronic controller 4 stores the control strategies for cold starts at different intake air temperatures calibrated by the engine, as well as the corresponding control strategies based on changes in exhaust temperature during the starting process. It can control the engine starting device 8, variable valve timing mechanism 3, fuel injector 5 and spark plug 2 to execute corresponding action strategies based on the information from intake air temperature sensor 1 and exhaust air temperature sensor 7, so as to control the residence time of the fuel and air mixture in the cylinder, achieve a full combustion heat release reaction and heat the combustion chamber and cylinder wall.

[0021] The electronic controller 4 determines the corresponding starting control strategy based on the temperature information fed back by the intake air temperature sensor 1 and the pre-calibrated cold start strategy stored in it. It controls the engine starting device 8 to drive the piston engine 6 to rotate, and the fuel injector 5, spark plug 2 and variable valve timing mechanism 3 to execute the corresponding strategy. It also monitors the information of the exhaust temperature sensor 7, determines the current in-cylinder thermodynamic state based on the calibration data stored in the electronic controller 4, and gives the corresponding next control strategy until it determines that the in-cylinder thermodynamic state meets the requirements for stable combustion, and the engine starts successfully.

[0022] This application utilizes a variable valve timing mechanism 3 to control the closing and opening times of the intake and exhaust valves, thereby controlling the residence time of the fuel-air mixture in the engine cylinder. This allows the fuel-air mixture to fully react and release heat during multiple compression and expansion processes, heating the combustion chamber and improving the thermodynamic state within the cylinder, thus achieving rapid cold starting. The engine starting device 8 drives the piston engine 6 to rotate. The fuel-air mixture undergoes multiple compressions and expansions. Utilizing the high temperature inside the cylinder during engine compression and controlling the residence time of the fuel-air mixture in the cylinder for a certain period, the fuel and air fully react and release heat, increasing the temperature of the fuel-air mixture in the cylinder and heating the cylinder liner and piston, thereby improving the thermodynamic state within the cylinder. After the fuel has fully reacted and released heat in the cylinder, sufficiently heating the combustion chamber, the variable valve timing mechanism is controlled to expel exhaust gas from the cylinder. The exhaust valve is also controlled to close later or open a second time, allowing some exhaust gas to enter the cylinder to heat the fresh intake air before fuel injection and ignition. Additionally, the intake and exhaust valves are controlled to close for a certain period, allowing the fuel to fully react and heat the combustion chamber before the variable valve timing mechanism expels exhaust gas from the cylinder. Repeat the above operation until the thermodynamic state inside the cylinder reaches the conditions for stable combustion, then switch the control to the normal idle speed control strategy to complete the cold start process.

[0023] The specific control process in this embodiment is as follows: When the piston engine 6 is cold-started, the electronic controller 4 collects data from the intake air temperature sensor 1, determines the cold-start strategy to be executed based on the calibrated cold-start strategy data, and controls the fuel injector 5, spark plug 2, variable valve timing mechanism 3, and engine starting device 8 to execute the corresponding control strategy. During the starting process, the electronic controller 4 collects temperature information from the exhaust air temperature sensor 7, and judges the in-cylinder thermodynamic state of the piston engine 6 based on the temperature information and its changes, according to the stored calibration data, and determines whether the current in-cylinder thermodynamic state meets the requirements for stable combustion. When the in-cylinder thermodynamic state meets the requirements for stable combustion of the piston engine 6, the electronic controller ECU 4 controls the fuel injector 5, spark plug 2, variable valve timing mechanism 3, and engine starting device 8 to execute the calibrated idle speed control strategy, and the cold start ends.

[0024] When the electronic controller 4 determines, based on the stored calibrated cold start strategy, that the thermodynamic state of cylinder 6 of the piston engine cannot meet the requirements for stable combustion, the electronic controller 4, based on the temperature information and temperature changes from the exhaust temperature sensor 7, determines and provides a new cold start strategy according to the calibrated strategy information. The electronic controller 4 controls the fuel injector 5, spark plug 2, variable valve timing mechanism 3, and engine starting device 8 to execute the corresponding calibrated strategy. This operation is repeated until it is determined that the thermodynamic state of cylinder 6 of the piston engine meets the requirements for stable combustion. At this point, the electronic controller 4 executes the idle speed strategy, and the cold start ends.

[0025] Furthermore, the cold start control strategy calibration logic stored in electronic controller 4 is as follows: When the electronic controller 4 calibrates the cold start strategy, it determines the injection and ignition strategies based on the different intake air temperatures of the intake air temperature sensor 1, the limitations of the piston engine 6 (such as the absence of spark plug 2 in a compression ignition engine), and the air-fuel ratio requirements for cold starts. The engine starter 8 drives the piston engine 6 to rotate, and the injectors 5 and spark plug 2 execute the determined injection / ignition strategies. Afterward, the variable valve timing mechanism 3 closes the intake and exhaust valves. The engine starter 8 drives the engine to run. After several engine cycles, the variable valve timing mechanism 3 controls the intake and exhaust valves to switch to the normal engine valve phase, expelling the in-cylinder mixture. The temperature of the exhaust temperature sensor 7 is recorded, as well as the number of engine cycles (time) after the intake / exhaust valves close following injection. When the engine is cold-started again, after the injector 5 and spark plug 2 execute the determined injection and ignition strategy, the variable valve timing mechanism 3 closes the intake / exhaust valves, and the engine starter 8 drives the engine to run. After the intake / exhaust valve closing time increases by N engine cycles compared to the previous time, the variable valve timing mechanism 3 controls the intake and exhaust valves to switch to the normal engine phase, expelling the in-cylinder mixture. At the same time, the temperature of the exhaust temperature sensor 7 is recorded, as well as the number of engine cycles (time) after the intake / exhaust valves close after injection.

[0026] Comparing two exhaust temperature changes, if the exhaust temperature increases, the number of engine cycles (time) the air-fuel mixture spends in the cylinder is increased; if the exhaust temperature decreases, the number of engine cycles (time) the air-fuel mixture spends in the cylinder is shortened. This process continues until the degree of change between two adjacent exhaust temperatures is small. At this point, the number of engine cycles (time) the air-fuel mixture spends in the engine cylinder after fuel injection and ignition is calibrated, along with the temperature of the exhaust temperature sensor 7. On one hand, the time when the intake / exhaust valves open at this point is used as the calibration time for opening the intake / exhaust valves after the first fuel injection during cold start at the calibrated intake temperature. On the other hand, it serves as the basis for obtaining the relationship between exhaust temperature and the variable valve timing mechanism 3 strategy during the subsequent stable ignition and combustion process during cold start, i.e., the relationship between exhaust temperature and the time the air-fuel mixture spends in the cylinder after each fuel injection and ignition. This relationship is used to determine the variable valve timing mechanism 3 strategy for assisting in the cold start process at the calibrated intake temperature.

[0027] Next, after the first fuel injection, the calibration strategies of injector 5, spark plug 2, and variable valve timing mechanism 3 are fixed, and the execution strategy of variable valve timing mechanism 3 after the second fuel injection is calibrated. At the same time, in order to accelerate cold start, it is necessary to introduce the exhaust gas discharged after the first fuel injection into the cylinder to heat the intake air. According to the existing internal EGR strategy, the strategy of delayed closing or secondary opening of the exhaust valve of variable valve timing mechanism 3 is fixed. The process of calibrating the strategies of variable valve timing mechanism 3, injector 5, and spark plug 2 during the first fuel injection ignition is repeated. After the fuel injection ignition, the number of engine cycles (time) of the air-fuel mixture staying in the engine cylinder and the temperature of the exhaust temperature sensor 7 at this time are calibrated.

[0028] Repeat the above calibration operation to calibrate the strategy of the variable valve timing mechanism 3, injector 5, and spark plug 2 after the next fuel injection ignition (including how many engine cycles the valves open to return to normal phase), and record the exhaust temperature of the exhaust gas discharged when the corresponding exhaust valve opens; in addition, during the multiple fuel injection processes calibrated, after the intake and exhaust valves return to normal phase, the fuel injection ignition strategy is executed normally. When the intake and exhaust phase switching is normal after fuel injection ignition, stable combustion can be achieved until a cold start is successful. Record the exhaust temperature before a successful cold start as a condition for determining stable combustion.

[0029] During the aforementioned multiple cold start calibration processes, the strategies of the variable valve timing mechanism 3, injector 5, and spark plug 2 during the calibrated cold start process are obtained as the number of engine cycles (time) the in-cylinder mixture resides in the combustion chamber. The temperature of the corresponding exhaust temperature sensor 7 is also obtained as a function of the number of engine cycles (time) the in-cylinder mixture resides in the combustion chamber. This information is used to determine the strategy of the variable valve timing mechanism, injector 5, and spark plug 2 to be executed in the next injection. At this point, the cold start strategy calibration for this intake air temperature is complete. The above calibration process is repeated to calibrate the cold start strategy for the next intake air temperature, ultimately completing the cold start strategy calibration.

[0030] The engine electronic controller 4ECU stores the above-calibrated cold start control strategy. Based on the temperature information fed back by the intake air temperature sensor 1, it can determine the degree of coldness of the environment and obtain the corresponding start control strategy, controlling the engine starter 8 to drive the piston engine 6 to rotate, and the fuel injector 5, spark plug 2 and variable valve timing mechanism to execute the corresponding strategy.

[0031] When implementing the above scheme, by controlling the intake / exhaust valve timing and fuel injection / ignition, the time of the fuel-air mixture in the engine cylinder is changed, extending the reaction time of the mixture in the cylinder. The exothermic oxidation reaction of fuel and air is used to fully heat the combustion chamber of the piston engine. At the same time, the exhaust valve is opened a second time to introduce exhaust gas back into the cylinder, thereby increasing the temperature of the mixture in the cylinder and allowing highly reactive reactants produced by combustion in the exhaust gas to enter the cylinder, accelerating the combustion reaction rate.

[0032] The control method is as follows: When the engine starts in a low-temperature environment, after the intake valve closes at the end of the intake stroke, the fuel injector 5 injects appropriate fuel during the compression stroke, and the spark plug 2 ignites at the appropriate time. In the next power stroke of the compression stroke, due to the low-temperature environment, the fuel-air mixture may not burn completely. In order to ensure rapid engine preheating, the exhaust valve and intake valve are closed during the following exhaust stroke and several subsequent cycles. The engine continuously compresses and expands under the drive of the starter motor, allowing the mixture to undergo a full exothermic reaction in the compression and expansion cycle, and heating the combustion chamber and cylinder walls. After several cycles, the exhaust valve is opened to expel the exhaust gas from the cylinder. At this time, the intake / exhaust valve timing returns to normal, and the exhaust valve is closed later or opened a second time to introduce some exhaust gas to heat the fresh air in the cylinder. After exhaust, the engine repeats the above operation in the next engine cycle. After fuel injection / ignition, the combustion chamber is heated by controlling the valve closing and opening strategies.

[0033] During the aforementioned cold start process, the opening and closing times of the intake and exhaust valves are adjusted according to changes in exhaust temperature to alter the residence time of the air-fuel mixture in the cylinder. This allows for the rapid heating of the air-fuel mixture and cylinder walls through the heat released during combustion. After several cycles of this fuel injection cold start process, a stable combustion state is achieved, enabling the engine to start quickly.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0035] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A method for rapid cold starting of an engine, characterized in that, include: The system collects engine intake air temperature data and determines the current start control strategy based on a pre-calibrated cold start strategy. It then controls the duration of engine operation according to this strategy, as well as the actions of the injectors, spark plugs, and variable valve timing mechanism, thereby controlling the residence time of the fuel-air mixture in the cylinder. The cold start strategy includes an injection / ignition strategy, a variable valve timing strategy, and a starter motor strategy. The engine exhaust temperature data is collected, and based on the stored calibration data, it is determined that the current thermodynamic state in the cylinder meets the conditions for stable combustion. Then, the engine starting device, injectors, spark plugs, and variable valve timing mechanism are controlled to execute the idle speed control strategy.

2. The method for rapid cold starting of an engine according to claim 1, characterized in that: In response to the first fuel injection and ignition, the cold start strategy is calibrated. By acquiring different intake air temperature data, the fuel injection strategy and ignition strategy are determined based on the air-fuel ratio under cold start conditions and engine limitations. Based on the determined fuel injection and ignition strategies, the injectors and spark plugs are controlled to perform fuel injection / ignition actions, and the variable valve timing mechanism is controlled to close the intake and exhaust valves. After several cycles, the intake and exhaust valves are switched to the normal valve phase of the engine through the variable valve timing mechanism to discharge the exhaust gas from the cylinder and record the exhaust temperature, as well as the number of cycles in which the intake / exhaust valves close after fuel injection. By judging the change in exhaust temperature and using the current calibrated exhaust temperature as the condition for determining valve opening, the current calibrated valve closing time strategy, fuel injection strategy, and ignition strategy are used as the initial cold start strategy.

3. The method for rapid cold starting of an engine according to claim 2, characterized in that: After the first fuel injection, the calibration strategy for the injector, spark plug, and variable valve timing mechanism is fixed. Then, the execution strategy of the variable valve timing mechanism after the second fuel injection is calibrated. By introducing a strategy of delayed exhaust valve closing or secondary opening of the variable valve timing mechanism, the process of calibrating the variable valve timing mechanism, injector, and spark plug strategy during the first fuel injection ignition is repeated. The number of engine cycles in which the air-fuel mixture stays in the engine cylinder after fuel injection ignition, as well as the exhaust temperature at this time, are calibrated.

4. The method for rapid cold starting of an engine according to claim 3, characterized in that: By comparing the changes in exhaust temperature during two cold starts, if the exhaust temperature increases, the number of engine cycles in which the air-fuel mixture remains in the cylinder is increased. If the temperature is reduced, the number of engine cycles in which the air-fuel mixture remains in the cylinder is shortened until the degree of change in exhaust temperature meets the preset conditions. Then, the number of engine cycles in which the air-fuel mixture remains in the engine cylinder after fuel injection and ignition is calibrated.

5. A method for rapid cold starting of an engine according to claim 2, characterized in that: During the cold start calibration process, the strategy changes of the variable valve timing mechanism, injectors, and spark plugs during the cold start process are obtained as the number of engine cycles in which the in-cylinder mixture stays in the combustion chamber are changed. The corresponding exhaust temperature is obtained as the change pattern of the number of engine cycles in which the in-cylinder mixture stays in the combustion chamber is used to determine the strategy of the variable valve timing mechanism, injectors, and spark plugs to be executed in the next injection.

6. The method for rapid cold starting of an engine according to claim 1, characterized in that: In response to the determination that the thermodynamic state inside the engine cylinder does not meet the stable combustion conditions, the cold start strategy for the next injection cycle is determined based on the exhaust temperature information and temperature changes, and based on the calibrated strategy information. The cold start strategy for the next injection cycle is used to control the duration of engine operation, as well as the operation of the injectors, spark plugs and variable valve timing mechanism, until the stable combustion conditions are met.

7. The method for rapid cold starting of an engine according to claim 1, characterized in that: The piston engine is equipped with an electronic controller, which is connected to an intake temperature sensor installed at the intake end and an exhaust temperature sensor installed at the exhaust end. The intake air temperature sensor obtains the engine's intake air temperature and feeds it back to the electronic controller, while the exhaust air temperature sensor detects changes in the engine's exhaust air temperature during cold start and feeds it back to the electronic controller. The electronic controller controls the spark plug, the variable valve timing mechanism, and the fuel injector to perform corresponding ignition, variable valve timing, and fuel injection actions, and controls the duration for which the engine starting device drives the engine to run.

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