Ignition system, engine and method for controlling combustion in a lean burn engine

Abstract

An ignition system for an engine of a vehicle, an engine and a method for controlling combustion in a lean burn engine are disclosed. The ignition system comprises: a spark plug comprising: a ground electrode and a center electrode electrically connected to an ignition coil, wherein the spark plug ignites a mixture of fuel and air in a normal mode of the engine; a high speed pulse generator for igniting the mixture of fuel and air in a lean burn mode of the engine; a pulse generator controller for controlling the high speed pulse generator to ignite the mixture of fuel and air in the lean burn mode of the engine; an engine control unit determines the normal mode and the lean burn mode based on an engine speed and an engine load, and controls the ignition of the pulse generator controller and the spark plug based on the determined mode in the normal mode and the lean burn mode.

Description

Technical Field

[0001] This disclosure relates to an internal combustion engine having an ignition system for dual modes. Background Technology

[0002] The statements in this section are provided only as background information in connection with this disclosure and may not constitute prior art.

[0003] Typically, an internal combustion engine introduces fuel and air into the cylinder during the intake stroke, and the fuel-air mixture is ignited by a spark produced by a spark plug in the combustion chamber. The combustion chamber consists of the cylinder, the piston housed within the cylinder, and the engine's cylinder head.

[0004] Specifically, the mixture injected into the combustion chamber is compressed during the compression stroke and ignited by the spark plug's discharge. The air-fuel mixture burns in the combustion chamber, thus resisting the expansion of the movable piston, which in turn drives the crankshaft to generate power for the engine, allowing the vehicle to operate using the power from the engine.

[0005] Spark plugs, located in internal combustion engines (e.g., gasoline engines), ignite a compressed mixture by sparking, where the spark is generated by a high-voltage current produced by an ignition coil.

[0006] In the case of a typical gasoline engine, combustion is primarily based on a stoichiometric air-fuel ratio (14.7:1, λ = 1). However, in the case of lean-burn combustion, defined by λ > 1, the air-fuel ratio may be approximately 30:1 (λ = 2). In this case, the mixture in the combustion chamber contains very little injected fuel compared to the amount of air, so even if a spark plug discharges, the mixture may not ignite (e.g., misignition) or may undergo incomplete combustion.

[0007] Therefore, it is necessary to develop spark plugs to achieve lean combustion.

[0008] We have found that due to the high proportion of fuel and air in the mixture compared to air, it is difficult to achieve sustained, complete and thorough combustion in the main combustion chamber because the flame propagation speed is relatively slow. Summary of the Invention

[0009] This disclosure provides a dual-mode ignition system that enables an internal combustion (IC) engine to operate with a high-speed pulse (HSP) spark plug under low engine load conditions with lean-burn conditions (λ>1.4, lean-burn mode), while operating with a conventional spark plug under high load conditions in a conventional mode (i.e., rich-burn conditions, stoichiometric λ<=1). This utilizes the performance advantages of conventional spark plugs under high loads and relaxes the limitations on the ignition stability of lean air / fuel mixtures (high air content fuel-air mixtures) under low loads, thereby improving overall engine thermal efficiency and performance throughout the entire operating range.

[0010] In one form of this disclosure, an ignition system for an engine includes: a spark plug including a ground electrode and a center electrode electrically connected to an ignition coil, wherein the spark plug is configured to ignite a fuel-air mixture in a normal mode of the engine; a high-speed pulse generator configured to ignite the fuel-air mixture in a lean-burn mode of the engine, wherein in the lean-burn mode, the fuel-air mixture is mixed at a lean-burn air / fuel ratio; a pulse generator controller configured to control the high-speed pulse generator to ignite the fuel-air mixture in the lean-burn mode of the engine; and an engine control unit (ECU) configured to determine a normal mode and a lean-burn mode based on engine speed and engine load, and to control the ignition of the spark plug based on the mode determined in the normal mode and the lean-burn mode.

[0011] In another form, both the spark plug and the high-speed pulse generator are located in the cylinder of the engine and configured to ignite the fuel-air mixture, the fuel-air mixture having the lean-burn air / fuel ratio, and / or exhaust residue in the combustion chamber of the cylinder based on a determined pattern.

[0012] The high-speed pulse generator is configured to produce non-thermal plasma in the combustion chamber and promote multi-point volumetric combustion in lean-burn mode.

[0013] In one configuration, the ECU can determine regenerative mode and electric vehicle (EV) mode based on engine speed and engine load. In regenerative mode, the power generated by the engine is at least partially used to charge the vehicle's battery, while in EV mode, the vehicle operates solely on power supplied by the battery. Specifically, the ECU is further configured to control a high-speed pulse generator controller to disable ignition in both regenerative and EV modes.

[0014] In another form, the high-speed pulse generator is configured to deliver pulse power of at least 40,000 volts in less than 100 nanoseconds.

[0015] Normal mode includes cold starts and medium to high engine loads. Normal mode operates by burning a fuel-air mixture with a lower air / fuel ratio than the aforementioned lean-burn air / fuel ratio.

[0016] In another form of this disclosure, the engine may include: an engine block defining cylinders; a cylinder head configured to cover the cylinders; a combustion chamber at least partially defined by the cylinders in the engine block and the cylinder head; a fuel delivery system including low-pressure fuel injectors and / or high-pressure direct injectors located in the intake port, or including direct injection injectors leading to the combustion chamber; and an ignition system including: spark plugs and a high-speed pulse generator, the spark plugs configured to ignite a fuel-air mixture in normal engine mode, and the high-speed pulse generator configured to... The engine ignites a fuel-air mixture in a lean-burn mode, wherein the fuel-air mixture is mixed at a lean-burn air / fuel ratio; a piston configured to reciprocate within a cylinder and configured to move upward during the engine's compression stroke to compress the fuel-air mixture; and an engine control unit (ECU) configured to determine a normal mode and a lean-burn mode based on engine speed and engine load, and to control a high-speed pulse generator and spark plugs based on the mode determined in the normal mode and the lean-burn mode.

[0017] In one configuration, both the spark plug and the high-speed pulse generator are exposed to the combustion chamber and are configured to ignite a fuel-air mixture and a fuel-air mixture having a lean-burn air / fuel ratio, respectively, in the combustion chamber.

[0018] In another form of this disclosure, a method for controlling combustion in a lean-burn engine includes: providing a lean-burn engine comprising a combustion chamber having a spark igniter and a high-speed pulse generator; providing a fuel-air mixture to the combustion chamber in a normal engine mode, wherein the lean-burn engine operates under medium and high engine loads by spark ignition using the spark igniter; providing a lean-burn air / fuel mixture to the combustion chamber in a lean-burn engine mode, wherein the lean-burn engine operates in the combustion chamber by multi-point volume combustion using the high-speed pulse generator; and igniting and promoting multi-point volume combustion of the lean-burn air / fuel mixture by non-thermal plasma generated in the combustion chamber by the high-speed pulse generator in the lean-burn engine mode. Specifically, the lean-burn air / fuel mixture has a λ value greater than 1.4.

[0019] In another form, the method further includes: determining a lean-burn engine mode when the lean-burn engine is operating at low engine load; determining a normal engine mode when the lean-burn engine is operating in the medium to high engine load range; and switching from the lean-burn engine mode to the normal engine mode upon receiving an acceleration input.

[0020] Other applicable areas will become apparent from the description provided herein. It should be understood that the descriptions and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0021] To better understand this disclosure, various forms will now be described by way of example with reference to the accompanying drawings, in which:

[0022] Figure 1 This is an example diagram of an engine having an ignition system of one form disclosed herein;

[0023] Figure 2 This is an electrical diagram of an ignition system of one form disclosed herein, which implements dual-mode ignition;

[0024] Figure 3 This is a view showing the overall construction of one form of spark plug according to the present disclosure;

[0025] Figure 4 yes Figure 1 An enlarged partial cross-sectional side view showing the arrangement of the injectors, spark plugs and high-speed pulse generator in the cylinder head;

[0026] Figure 5 This is a schematic diagram showing the operating state of an engine of one form disclosed herein;

[0027] Figure 6 This illustrates a nonthermal plasma generated by a high-speed pulse generator of one form of this disclosure;

[0028] Figure 7 This is a schematic diagram showing the operating state of an engine of one form of the present disclosure for a hybrid electric vehicle;

[0029] Figure 8 This disclosure illustrates one form of dual-mode ignition method for controlling a lean-burn engine; and

[0030] Figure 9 and Figure 10 The diagrams show improvements in fuel efficiency achieved through one form of ignition system disclosed herein.

[0031] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure in any way. Detailed Implementation

[0032] The following description is exemplary in nature only and is not intended to limit this disclosure, its application, or its uses. It should be understood that throughout the drawings, the same reference numerals denote similar or identical parts and features.

[0033] This disclosure does not describe the form of all components, and will not describe general information or repetitive information between the various forms in the art to which this disclosure pertains.

[0034] It should be understood that although this document may use terms such as "first" and "second" to describe multiple components, these components should not be limited by these terms. These terms are only used to distinguish one component from another.

[0035] The reference numerals used in the operation are provided for ease of description and do not describe the order of operations. Operations may be performed in a different order than the order described unless a specific order is explicitly specified in the context.

[0036] The operating principles and exemplary forms of this disclosure will now be described with reference to the accompanying drawings. As is known in the art, some exemplary forms may be shown in the drawings from the perspective of functional blocks, units, and / or modules. Those skilled in the art will understand that such blocks, controllers, units, and / or modules are physically implemented by electronic (or optical) circuitry, such as logic circuits, discrete components, processors, hardwired circuitry, storage devices, and wiring connections.

[0037] When blocks, units, and / or modules are implemented by a processor or other similar hardware, they can be programmed and controlled by software (e.g., code) to perform the various functions discussed in this specification. Furthermore, each block, unit, controller, and / or module can be implemented by dedicated hardware or a combination of dedicated hardware for performing certain functions and a processor (e.g., one or more programming processors and associated circuitry) for performing another function.

[0038] In one respect, reference Figure 1 This disclosure provides an engine 10 having an ignition system 20 capable of using spark plugs 40 and a high-speed pulse generator (HSP) 60 to improve the ignition performance of a lean-burn fuel-air mixture. In the engine's normal mode, the spark plugs ignite the fuel-air mixture, and in the engine's lean-burn mode, the high-speed pulse generator ignites the lean-burn fuel-air mixture. The engine 10 includes an ECU (engine control unit) 160 that determines whether the engine is operating in lean-burn mode or normal mode based on engine load and engine speed (i.e., revolutions per minute "RPM").

[0039] In lean-burn mode, the fuel and air mixture is mixed at a lean air / fuel ratio, for example, a λ value greater than 1.4. Here, the normal mode of the engine is defined as operating the engine with a fuel and air mixture having a λ value less than 1.4.

[0040] refer to Figure 1 In one embodiment of this disclosure, the engine 10 further includes: a cylinder block 12; a cylinder head 14 disposed on the cylinder block 12; an injector 30 mounted on the cylinder head; and a piston 70 reciprocating in each cylinder 90 of the engine. An ignition system 20 having a spark plug 40 and an HSP (high-speed pulse generator) 60 is mounted on the cylinder head 14, and the injector 30 may be located between the intake valve V1 and the exhaust valve V2.

[0041] In another embodiment, the engine 10 may further include: a valve control device 55 for changing the operating timing (e.g., opening and closing timing) and opening duration of each of the intake and exhaust valves disposed on the upper part of the cylinder; and an exhaust gas recirculation (EGR) valve for recirculating exhaust gas from the exhaust manifold. This exhaust gas is discharged from the engine 10 to the intake manifold I through the exhaust manifold. In one embodiment, the valve control device 55 may include: continuously variable valve timing (CVVT) devices 51, 52 for adjusting the opening and closing timing of the intake or exhaust valve; and continuously variable valve duration (CVVD) devices for adjusting the opening duration of the intake and exhaust valves.

[0042] Figure 2 An electrical diagram of an ignition system 20 is shown, which utilizes an HSP 60 and spark plug 40 to implement dual-mode ignition (i.e., ignition in normal mode and lean-burn mode). The ignition system 20 for engine 10 may further include: a pulse generator controller 64 to control the HSP 60 to ignite the lean-burn fuel-air mixture in the engine's lean-burn mode; and an ECU (engine control unit) 160 that determines the normal mode and lean-burn mode based on engine speed and engine load, and controls the ignition of the spark plug 40 and the pulse generator controller 64 based on the mode determined in the normal mode and lean-burn mode.

[0043] like Figure 2As shown, a pair of spark plugs 40 and HSPs 60 are arranged in each cylinder 90 of the engine 10, and a pulse generator controller 64 is connected to the ECU 160 and controls each HSP 60 based on inputs from the ECU 160, which determines whether the engine operates in normal mode or lean-burn mode based on engine speed and engine load. Similarly, the ECU 160 controls the ignition coil 42 to control the ignition timing of the spark plugs 40 in each cylinder of the engine based on the engine operating state determined by the ECU, where the engine operating state includes engine speed and engine load. The vehicle's battery 50 can power the ignition system 20, which includes the HSPs 60, ignition coils 42, ECU 160, and pulse generator controller 64.

[0044] In one form, such as Figure 3 As shown, spark plug 40 is a conventional spark plug, comprising a center electrode 110 and a ground electrode 117. The center electrode is electrically connected to the ignition coil or ignition module 42, and the ground electrode forms a spark gap with the distal end of the center electrode 110. When the battery 50 supplies power to the ignition coil 42, the ignition coil 42 generates an ignition voltage under the control of the ECU 160. Spark plug 40 generates a spark discharge by applying the ignition voltage to the spark plug. In one embodiment, the center electrode 110 of spark plug 40 is made of a base metal (e.g., Ni-Cu) that is heat-resistant, corrosion-resistant, and conductive, and the distal end of the center electrode 110 serves as the spark portion.

[0045] Figure 4 yes Figure 1 An enlarged partial cross-sectional side view shows the arrangement of the injector 30, spark plug 40, HSP (High-Speed ​​Pulse Generator) 60, intake valve V1, and exhaust valve V2 in the cylinder head 14. Both the spark plug 40 and the HSP 60 are located in the cylinder 90 of the engine and are configured to ignite the fuel-air mixture in the combustion chamber 80 of the cylinder 90. Figure 4 As shown, the combustion chamber 80 is at least partially defined by the cylinder 90 and the cylinder head 14.

[0046] In another configuration, injector 30 may be located above the center of the upper surface of piston 70, and injector 30 may be connected to a fuel pump that pressurizes fuel at a predetermined level and supplies the pressurized fuel directly to the cylinder (this type of injector is a direct injector). In another configuration, injector 30 may be located in an intake port communicating with intake manifold IM (this type of injector is a port injector). The injection pattern of injector 30 is varied by duty control, and injector 30 performs at least one fuel injection during the intake stroke, selectively performs fuel injection during the compression stroke, and injects fuel immediately before or simultaneously with the operation of spark plug 40 or HSP 60 during the engine's burn-out stroke.

[0047] Because fuel is injected instantaneously during the explosion stroke, before or simultaneously with the operation of spark plug 40 or HSP 60, the fuel-air mixture around spark plug 40 and HSP 60 can be either rich or lean, depending on the amount of fuel injected by injector 30. Not only the mixture ratio, but also the type of igniter (i.e., spark plug or HSP) affects the initial flame formation and flame propagation during combustion of the mixed fuel and air in combustion chamber 80. Specifically, ECU 160 determines normal and lean modes based on engine speed (e.g., revolutions per minute, "RPM") and engine load, and controls spark plug 40 and HSP 60 based on the patterns determined in normal and lean modes, resulting in the engine consuming less fuel and operating efficiently.

[0048] As described above, the ECU (Engine Control Unit) 160 controls the spark plug 40, HSP 60, valve control device 55, and injector 30. The ECU 160 controls the injector 30 to control injection timing and fuel quantity, such that the fuel-air mixture in cylinder 90 can be selected to be stoichiometrically either a rich or dilute value. Here, the ECU's control of the engine can be implemented in a hardware manner (e.g., a processor), a software manner, or a combination of hardware and software (i.e., a series of commands) to perform at least one function or operation. The ECU receives various signals indicating the engine's operating state (including the engine speed (RPM) signal) and engine load corresponding to the engine torque required to satisfy the desired output for vehicle operation from various sensors coupled to the engine.

[0049] Figure 5This is a schematic diagram illustrating the operating states of an engine in one form of this disclosure. The engine load-engine speed diagram shows a “SP-Cold Start” region ①, a “HSP-Lean Burn” region (i.e., lean burn mode) ②, and a “Normal Spark Plug” region ③ (i.e., normal mode). In the “SP-Cold Start” region ①, the ECU 160 controls the current supplied to the ignition coil 42 of the spark plug 40 to generate a spark discharge by applying an ignition voltage to the spark plug. When the engine is started from a stop, and the engine temperature and catalyst temperature are both below a threshold, the ECU 160 determines that the engine is in a cold start state. This cold start state differs from an engine hot start state (such as engine restart), in which the engine restarts quickly after a previous engine stop, causing the engine temperature and / or catalyst temperature to be above a threshold. Based on the engine's operating state, the ECU determines the transition between the aforementioned regions, such as... Figure 5 As indicated by the middle arrow.

[0050] Upon receiving an acceleration input, the engine operation shifts to the "HSP lean-burn" region (i.e., lean-burn mode)②. In the "HSP lean-burn" region (i.e., lean-burn mode)②, the ECU 160 is electrically connected to the pulse generator controller 64, and each HSP 60 is controlled based on inputs from the ECU 160 when the ECU determines that the engine is operating in lean-burn mode based on engine speed and engine load. When the engine operates at low speeds (800 RPM-1500 RPM) or medium speeds (1500 RPM-2500 RPM) and the engine load is in a low range (2 bar-8 bar mean effective braking pressure), the engine may not require high torque to keep the vehicle running and can operate in lean-burn mode to improve fuel efficiency. However, when using conventional spark plugs to ignite a lean-burn fuel-air mixture (e.g., a fuel-air mixture with a λ value greater than 1.4), the engine struggles to ignite the lean-burn fuel-air mixture.

[0051] As described above, this disclosure provides an HSP 60 for igniting a lean-burn fuel-air mixture in lean-burn mode, enabling the engine to implement a dual-mode ignition system using a novel high-speed pulse generator ignition system (low load) and a conventional spark plug 40. The HSP 60 is a non-thermal high-speed pulse generator that produces high-pressure nanosecond pulses with low total energy. The HSP 60 creates a highly efficient non-thermal ignition process for lean-burn (λ>1.4) combustion engines.

[0052] More specifically, the HSP 60 generates nonthermal plasma in the combustion chamber and promotes multi-point volumetric combustion in lean-burn mode. Figure 6A non-thermal plasma generated by a high-speed pulse generator in one form of this disclosure is shown. An initial flame core forms a ring around the central electrode and develops faster than a spark plug. Specifically, the HSP60 releases electrons that influence fuel or air molecules and generate free radicals that serve as precursors to the flame ignition core. The HSP60 employs a discharge / non-thermal plasma in a gaseous medium to activate fuel from the fuel injector, promoting more efficient and effective combustion. In non-thermal plasma, electrons are “hot,” while ions and neutral matter are “cold”—resulting in less enthalpy wasted in the process gas stream. This contrasts with thermal plasma, where the energy of electrons, ions, and neutral matter is thermally balanced (or “hot”) and significant waste heat exists in the process gas.

[0053] The basic working principle of nonthermal plasma is to cause electrons to collide with gases, thereby producing chemical reactants for catalytic combustion, which enhances ignition and stabilizes lean combustion. The discharge of single-unit nonthermal transient plasma in air advantageously alters the chemical and physical properties required for pre-combustion.

[0054] HSP 60 delivers a pulse of at least 40,000 volts of power in less than 100 nanoseconds. HSP 60 is a multi-point ignition source that helps the mixture burn more efficiently in the combustion chamber and can ignite mixtures with a very high air-fuel ratio (λ>1.4). In other words, during low-load operation common in most vehicle driving cycles, HSP60 provides more energy than conventional spark plugs to ignite the lean fuel-air mixture in the combustion chamber. Therefore, HSP ignition technology relaxes the limitations of ignition stability and can improve engine operating efficiency by 20% and reduce NOx emissions by more than 50%. Increased ignition stability in the lean fuel-air mixture also contributes to better fuel economy and results in ultra-low NOx and particulate emissions from the engine.

[0055] While HSP 60 improves the upper limit of the air-to-fuel ratio for lean-burn combustion under low-load conditions (e.g., lean-burn mode), it is ineffective under high-load conditions (e.g., normal mode). Therefore, conventional spark plug 40 is used under high-load conditions. For example, when the engine load becomes higher in response to an increase in engine torque and / or engine speed, ECU 160 controls injector 30 to increase the amount of fuel and thus the fuel-air mixture becomes more fuel-rich, for example, to give the mixture a λ value of less than 1.4. ECU then determines that the engine is operating in normal mode (i.e., the "conventional spark plug" region) and stops the operation of HSP 60, and uses spark plug 40 to ignite the fuel-air mixture in normal mode.

[0056] As described above, this disclosure provides a dual-mode ignition system that enables an internal combustion (IC) engine to operate with HSP under low load conditions with lean-burn conditions (λ>1.4) and under high load conditions with rich-burn conditions (0.9<λ<1.4) using conventional spark plugs, thereby enabling the engine to operate with dual-mode ignition functionality, thereby making the most efficient use of the air-fuel mixture according to the engine speed and load conditions.

[0057] In another form, the engine 10, including the ignition system 20, can be used in a hybrid electric vehicle (HEV) having an electric motor capable of driving the vehicle when the engine 10 is stopped. Typically, HEVs offer multiple modes, including: a pure electric mode (EV mode), where the HEV allows the vehicle to operate using only the electric motor without the engine; a hybrid mode, where both the engine and the electric motor are used; and a regenerative mode, where the electric motor operates as a generator to charge the battery using the engine's power when the ECU receives a braking signal. In regenerative and EV modes, the ECU controls the pulse generator controller to prevent the HSP 60 from igniting. Figure 7 This is a schematic diagram illustrating the operating states of an engine used in HEVs. When the engine operates at a mean effective braking pressure of 2-8 bar and a speed of 800-2500 RPM, the high-speed pulse mode is the effective combustion mode. When switching from HSP to SP+EV mode (e.g., at 800-5000 RPM and under a load above 8 bar), the EV motor activates.

[0058] Figure 8 This is a flowchart illustrating a method for controlling dual-mode ignition in a lean-burn engine according to one form of the present disclosure. As described above, the present disclosure relates to a lean-burn engine 10 that operates in either a lean-burn mode or a normal mode based on the engine's operating state. The lean-burn engine 10 improves the ignitability of the lean-burn fuel-air mixture by selectively using a spark igniter (e.g., a spark plug) 40 to ignite the fuel-air mixture charged in the combustion chamber in normal mode, or by using a high-speed pulse generator (HSP) 60 to ignite the lean-burn fuel-air mixture in the engine's lean-burn mode.

[0059] refer to Figure 8At step S100, ECU 160 detects the engine load corresponding to the desired engine torque, engine speed (e.g., engine RPM), and air / fuel ratio. At step S120, ECU 160 determines whether the engine is performing a cold start. When a cold start is determined, the ECU controls the spark plugs to ignite the air / fuel mixture to start the engine. However, when it is determined that the engine is not in a cold start state, at step S140, the ECU determines whether the engine is in lean-burn mode based on the detected air / fuel ratio, engine load, and engine RPM. If lean-burn mode is determined at step S140, ECU 160 causes the high-speed pulse generator (HSP) to perform ignition by igniting the lean-burn fuel-air mixture via HSP 60. When the engine is not operating in lean-burn mode, the ECU determines that the engine is in normal mode (step S160) and operates the spark plugs at step S180 to ignite the air / fuel mixture in the engine's combustion chamber. Specifically, when the lean-burn engine operates under low engine load, the ECU 160 determines it to be in lean-burn mode, while when the lean-burn engine operates in the medium to high engine load range (e.g., 2 bar-8 bar and 800 RPM-2500 RPM), it determines it to be in normal mode. When an acceleration input is received, the lean-burn engine mode changes to normal engine mode.

[0060] like Figure 9 to Figure 10 As shown, the dual-mode ignition system and its control method maximize combustion stability in the lean-burn engine at low loads while utilizing low-cost conventional spark plug technology in the medium to high engine load range. The dual-mode ignition system and control method result in a 9.4% improvement in fuel efficiency (FE) at braking fuel consumption rate (“BSFC”), exceeding [a certain level]. Figure 9 The diagram shows 9 points representing the FTP75 cycle. Figure 9 The diagram shows the brake fuel consumption rate on the complete engine operation map. Nine points are considered standard criteria for comparing the fuel economy of different engines of similar size. These points are covered in the FTP75 cycle.

[0061] Figure 10 This is a graph showing the coefficient of variation of the indicated mean effective pressure of the spark plug and high-speed pulse generator (HSP) relative to the value λ. Figure 10 In this context, "cov" represents the "coefficient of variation," "IMEP" represents the "indicating mean effective pressure," and "BMEP" represents the "braking mean effective pressure." The cov of IMEP defines the cyclic variation in the indicated work for each cycle. For example... Figure 10As shown, when λ is less than approximately 1.3 (λ < 1.4), conventional spark plug ignition exhibits better cov_IMEP, while when λ is greater than approximately 1.4 (λ > 1.4), HSP ignition exhibits better cov_IMEP. Therefore, compared to spark plug ignition, HSP ignition in a lean-burn λ state has better combustion stability.

[0062] As described above with reference to the exemplary form of this disclosure, the dual-mode ignition system and control method contribute to improved fuel economy and provide improved emission control at a low cost.

[0063] While some forms of this disclosure have been shown and described above, those skilled in the art will understand that modifications can be made to these forms without departing from the principles and spirit of this disclosure.

Claims

1. An ignition system for a vehicle engine, comprising: A spark plug, comprising a ground electrode and a center electrode electrically connected to an ignition coil, the spark plug being configured to ignite a fuel-air mixture in normal mode of the engine; A high-speed pulse generator is configured to ignite a fuel-air mixture in a lean-burn mode of the engine, wherein the fuel-air mixture is mixed at a lean-burn air / fuel ratio in the lean-burn mode. A pulse generator controller is configured to control the high-speed pulse generator to ignite the fuel-air mixture in the lean-burn mode of the engine; as well as The engine control unit is configured as follows: The normal mode and the lean-burn mode are determined based on engine speed and engine load, and The spark plug ignition and the pulse generator controller are controlled based on the determined mode in the normal mode and the lean-burn mode. Both the spark plug and the high-speed pulse generator are disposed in the cylinder of the engine and configured according to a determined pattern, wherein the spark plug ignites the fuel-air mixture in the combustion chamber of the cylinder, or the high-speed pulse generator ignites the fuel-air mixture having the lean-burn air / fuel ratio in the combustion chamber of the cylinder. The high-speed pulse generator is configured to generate non-thermal plasma in the combustion chamber and promote multi-point volumetric combustion in the lean-burn mode.

2. The ignition system according to claim 1, wherein, The engine control unit is further configured to determine a regenerative mode and an electric vehicle mode based on the engine speed and the engine load. In the regenerative mode, the power generated by the engine is at least partially used to charge the vehicle's battery. In the electric vehicle mode, the vehicle operates solely on the power supplied by the battery. The engine control unit is further configured to control the pulse generator controller to disable the ignition of the high-speed pulse generator in the regenerative mode and the electric vehicle mode.

3. The ignition system according to claim 1, wherein, The high-speed pulse generator is configured to deliver pulse power of at least 40,000 volts in less than 100 nanoseconds.

4. The ignition system according to claim 1, wherein, The normal mode includes cold starts of the engine and medium to high engine loads. The normal mode is operated by burning a fuel-air mixture with a lower air / fuel ratio than the lean-burn air / fuel ratio.

5. An engine, comprising: Engine block, which limits the number of cylinders; A cylinder head, configured to cover the cylinder; The combustion chamber is defined at least in part by the cylinder and the cylinder head of the engine block; An injector configured to inject fuel into the cylinder; An ignition system includes a spark plug and a high-speed pulse generator, the spark plug being configured to ignite a fuel-air mixture in a normal mode of the engine, and the high-speed pulse generator being configured to ignite a fuel-air mixture in a lean-burn mode of the engine, wherein in the lean-burn mode, the fuel-air mixture is mixed at a lean-burn air / fuel ratio. A piston is configured to reciprocate within the cylinder and to move upward during the compression stroke of the engine to compress a mixture of fuel and air. as well as The engine control unit is configured as follows: The normal mode and the lean-burn mode are determined based on engine speed and engine load, and The high-speed pulse generator and the spark plug are controlled based on the patterns determined in the normal mode and the lean-burn mode. The injector, the spark plug, and the high-speed pulse generator are disposed in the cylinder of the engine.

6. The engine according to claim 5, wherein, Both the spark plug and the high-speed pulse generator are exposed to the combustion chamber, and the spark plug is configured to ignite a fuel-air mixture in the combustion chamber, while the high-speed pulse generator is configured to ignite a fuel-air mixture having the lean-burn air / fuel ratio in the combustion chamber.

7. The engine according to claim 6, wherein, The high-speed pulse generator is configured to generate non-thermal plasma in the combustion chamber, promoting the generation of free radicals and multi-point volumetric combustion in the lean-burn mode.

8. The engine according to claim 6, wherein, The engine control unit is configured to determine a normal mode when the engine is in a cold start state or when the engine load is in the range of medium to high engine load, and to determine a lean-burn mode when the engine is operating at low engine load.

9. A method for controlling combustion in a lean-burn engine, comprising: A lean-burn engine is provided, comprising a combustion chamber having a spark igniter and a high-speed pulse generator; In normal engine mode, an air / fuel mixture is supplied to the combustion chamber, in which the lean-burn engine operates by spark ignition using the spark igniter under medium and high engine loads. In lean-burn engine mode, a lean-burn air / fuel mixture is supplied to the combustion chamber, in which the lean-burn engine operates by multi-point volume combustion in the combustion chamber using the high-speed pulse generator; as well as In the lean-burn engine mode, the lean-burn air / fuel mixture is ignited by the non-thermal plasma generated in the combustion chamber by the high-speed pulse generator, and the lean-burn air / fuel mixture is induced to undergo multi-point volume combustion.

10. The method according to claim 9, wherein, The lean air / fuel mixture has a λ value greater than 1.

4.

11. The method of claim 10, further comprising: When the lean-burn engine operates under low engine load, it is determined to be in the lean-burn engine mode; When the lean-burn engine is in a cold start state or operating in the range of medium to high engine load, it is determined to be the normal engine mode; and Upon receiving an acceleration input, the engine switches from the lean-burn engine mode to the normal engine mode.

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