engine

Abstract

To appropriately execute a warm-up operation of an engine.SOLUTION: An engine comprises: a cylinder head in which a main combustion chamber and a sub combustion chamber are defined by a chamber partition wall as a boundary; a fuel injector which injects a fuel into the main combustion chamber; and an air injector which injects air into the sub combustion chamber. The engine comprises an ignition device including an ignition electrode disposed in the sub combustion chamber. The engine comprises a control system which controls the fuel injector, the air injector and the ignition device. In a compression process at the time of a warm-up operation, the controls system causes the fuel injector to inject the fuel over a first period and causes the air injector to inject the air over a second period which at least partially overlaps the first period.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an engine that ignites an air-fuel mixture using an electric spark.

Background Art

[0002] Regarding engines that are internal combustion engines, techniques have been proposed for injecting flames from a sub-combustion chamber of a cylinder head into a main combustion chamber (see Patent Documents 1 to 3). By injecting a flame from the sub-combustion chamber toward the main combustion chamber in this manner, a lean air-fuel mixture in the main combustion chamber can be appropriately combusted.

Prior Art Literature

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problem to be Solved by the Invention

[0004] Incidentally, during the warm-up period after the initial engine start, ignition retard control is implemented to retard the ignition timing in order to quickly warm up the catalytic converter in the exhaust system. At the same time, stratified combustion control is implemented to inject a large amount of fuel during the compression stroke in order to reduce nitrogen oxides (NOx) in the exhaust gas. Furthermore, since the main and sub-combustion chambers are at low temperatures during warm-up, combined with the ignition retard control which reduces the combustion stability of the air-fuel mixture, it has been difficult to properly burn the air-fuel mixture during warm-up. In other words, if the partition wall separating the sub-combustion chamber is at a low temperature, the fuel injected into the main combustion chamber during the compression stroke for stratified combustion may adhere to the partition wall, locally increasing the fuel concentration and potentially increasing hydrocarbons (HC) in the exhaust gas. For this reason, it is necessary to properly warm up the engine by ensuring good combustion of the air-fuel mixture even during warm-up.

[0005] The objective of this invention is to properly perform engine warm-up. [Means for solving the problem]

[0006] An engine according to one embodiment is an engine that ignites a fuel-air mixture using an electric spark, and comprises a cylinder head having a chamber partition wall in which a plurality of through holes are formed, with the chamber partition wall separating a main combustion chamber and a sub-combustion chamber; a fuel injector provided in the cylinder head for injecting fuel into the main combustion chamber; an ignition device having an ignition electrode located in the sub-combustion chamber and discharging between the ignition electrode and the chamber partition wall; and a control system comprising a processor and memory that are communicatively connected to each other, for controlling the fuel injector, the air injector and the ignition device, wherein the control system injects fuel from the fuel injector for a first period during the compression stroke of warm-up operation, and injects air from the air injector for a second period that overlaps with at least a portion of the first period; and injects fuel from the fuel injector and then discharges between the ignition electrode and the chamber partition wall during the expansion stroke of warm-up operation. [Effects of the Invention]

[0007] According to one aspect of the present invention, the control system injects fuel from a fuel injector for a first period during the compression stroke in warm-up operation, and injects air from an air injector for a second period that overlaps with at least a portion of the first period. This allows the air-fuel mixture to burn well and enables proper engine warm-up operation. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a vehicle equipped with an engine according to one embodiment of the present invention. [Figure 2] This is a diagram showing an example of an engine. [Figure 3] This figure shows the main combustion chamber and its vicinity formed in the cylinder head. [Figure 4] This figure shows the pre-chamber partition and its vicinity. [Figure 5] This is a cross-sectional view showing the pre-chamber partition along line AA in Figure 4. [Figure 6] This diagram shows an example of the basic structure of an electronic control unit. [Figure 7] Control Example 1 is a timing chart showing an example of the execution status of combustion control. [Figure 8] This figure shows the operation status of the air injector and fuel injector at crank angles CA1 to CA4 as shown in Figure 7. [Figure 9] Figure 7 shows the operation status of the fuel injector and ignition device at crank angles CA5 to CA7. [Figure 10] This timing chart shows an example of the combustion control execution status during normal operation. [Figure 11] This figure shows the operation of the fuel injector at crank angles CA11 to CA12, as shown in Figure 10. [Figure 12]Figure 10 shows the operation status of the ignition device at a crank angle of CA13. [Figure 13] As control example 2, this is a timing chart showing another example of the combustion control execution status. [Figure 14] Control Example 3 is a timing chart showing another example of the combustion control execution status. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, identical or substantially identical components and elements will be denoted by the same reference numerals, and repeated descriptions will be omitted.

[0010] [vehicle] Figure 1 shows an example of a vehicle 11 equipped with an engine 10, which is one embodiment of the present invention. As shown in Figure 1, the vehicle 11 is equipped with a power unit 13 consisting of an engine 10 and a transmission 12. The output shaft 14 of the power unit 13 is connected to the rear wheels 17 via a propeller shaft 15 and a differential mechanism 16. As will be described later, the engine 10 shown is a horizontally opposed engine, but is not limited to this, and may be an inline engine, a V-type engine, or a single-cylinder engine. Also, the power unit 13 shown is a power unit for rear-wheel drive, but is not limited to this, and may be a power unit for front-wheel drive or all-wheel drive.

[0011] [engine] Figure 2 shows an example of an engine 10. As shown in Figure 2, the engine 10 has a cylinder block 20 that constitutes one cylinder bank, a cylinder block 21 that constitutes the other cylinder bank, and a crankshaft 22 supported by the pair of cylinder blocks 20 and 21. A cylinder bore 23 is formed in each cylinder block 20 and 21, and a piston 24 is housed in each cylinder bore 23. The crankshaft 22 and the piston 24 are connected to each other via a connecting rod 25.

[0012] Each of the cylinder blocks 20 and 21 is fitted with a cylinder head 31 provided with a valve mechanism 30 and the like. The cylinder head 31 is formed with an intake port 32 that opens into the main combustion chamber 32, and an intake valve 34 that opens and closes the intake port 33 is assembled therewith. The cylinder head 31 is also formed with an exhaust port 35 that opens into the main combustion chamber 32, and an exhaust valve 36 that opens and closes the exhaust port 35 is assembled therewith. Furthermore, an exhaust system 39 including a catalytic converter 37, a muffler 38 and the like is connected to the cylinder head 31 for guiding exhaust gas from the exhaust port 35 to the outside.

[0013] FIG. 3 is a diagram showing the main combustion chamber formed in the cylinder head 31 and the vicinity thereof. As shown in FIG. 3, the cylinder head 31 is formed with the main combustion chamber 32 communicating with the intake port 33 and the exhaust port 35. In the present specification, the space defined by the cylinder head 31, the cylinder bore 23 and the piston 24 is described as the main combustion chamber 32. The cylinder head 31 is provided with a fuel injector 40 that injects fuel into the main combustion chamber 32, and is also provided with a pre-chamber partition wall (chamber partition wall) 43 formed with a plurality of through holes 41, 42. Further, the fuel injector 40 and the pre-chamber partition wall 43 are arranged closer to the center CL1 of the main combustion chamber 32 than the intake valve 34 and the exhaust valve 36. A high-pressure fuel pump or the like (not shown) is connected to the fuel injector 40.

[0014] Figure 4 shows the pre-chamber partition 43 and its vicinity. As shown in Figure 4, the pre-chamber partition 43 has a base portion 44 attached to the cylinder head 31, a cylindrical side wall portion 45 provided on the base portion 44, and a hemispherical dome portion 46 provided on the side wall portion 45. By providing such a pre-chamber partition 43 on the cylinder head 31, the cylinder head 31 is divided into a main combustion chamber 32 and a sub-combustion chamber 47 with the pre-chamber partition 43 as the boundary. In other words, the cylinder head 31 has the main combustion chamber 32 outside the pre-chamber partition 43 and the sub-combustion chamber 47 inside the pre-chamber partition 43. The pre-chamber partition 43 is formed using a conductive material such as metal.

[0015] The cylinder head 31 is provided with an air injector 50 that injects air into a sub-combustion chamber 47 within a pre-chamber partition 43. The air injector 50 and the pre-chamber partition 43 are connected to each other via a connecting pipe 51. A high-pressure air pump, etc. (not shown), is connected to the air injector 50. Furthermore, as shown in Figures 3 and 4, the cylinder head 31 is provided with an ignition device 54 comprising an ignition electrode 52 located in the sub-combustion chamber 47 and an energizing circuit section 53 consisting of an ignition coil and an igniter. The ignition electrode 52 is located approximately in the center of the pre-chamber partition 43, and an insulating insulator 55 is provided between the base section 44 of the pre-chamber partition 43 and the ignition electrode 52. The tip 52a of the ignition electrode 52 extends to the vicinity of the central through-hole 41 of the dome section 46, which will be described later. In this ignition device 54, by applying a high voltage to the ignition electrode 52 from the energizing circuit 53, a discharge can be caused between the ignition electrode 52 and the pre-chamber partition wall 43, thereby generating an electric spark between the ignition electrode 52 and the pre-chamber partition wall 43.

[0016] Furthermore, the dome portion 46 of the pre-chamber partition wall 43 has multiple through-holes 41 and 42 formed therein for ejecting flames. Specifically, the pre-chamber partition wall 43 is provided with multiple through-holes 41 and 42, including a central through-hole (first through-hole) 41 formed in the center of the dome portion 46 and facing the tip 52a of the ignition electrode 52, and multiple side through-holes (second through-holes) 42 arranged to surround the central through-hole 41 and facing the side surface 52b of the ignition electrode 52. Here, Figure 5 is a cross-sectional view showing the pre-chamber partition wall 43 along line AA in Figure 4. As shown in Figure 5, the multiple side through-holes 42 formed in the pre-chamber partition wall 43 are arranged at predetermined intervals in the circumferential direction and open in the tangential direction to the inner circumferential surface 46a of the dome portion 46. In other words, the center line CL2 of the side through-holes 42 formed in the pre-chamber partition wall 43 is inclined with respect to the radial direction Dr1 of the ignition electrode 52. In the illustrated example, since the ignition electrode 52 is positioned in the center of the pre-chamber partition wall 43, the radial direction Dr1 of the ignition electrode 52 and the radial direction of the cylindrical side wall portion 45 coincide with each other.

[0017] [Control System] As shown in Figure 3, the engine 10 is equipped with a control system 61 consisting of an electronic control unit 60 to control the fuel injector 40, air injector 50, ignition device 54, etc. Sensors connected to the electronic control unit 60 include a vehicle speed sensor 62 for detecting vehicle speed, an accelerator sensor 63 for detecting the amount of accelerator pedal operation, and a brake sensor 64 for detecting the amount of brake pedal operation. Sensors connected to the electronic control unit 60 also include a crank rotation sensor 65 for detecting the rotation angle of the crankshaft 22, a coolant temperature sensor 66 for detecting the coolant temperature of the engine 10, and an airflow sensor 67 for detecting the amount of intake air of the engine 10. Furthermore, sensors connected to the electronic control unit 60 include a catalyst temperature sensor 68 for detecting the temperature of the catalytic converter 37, and an air-fuel ratio sensor 69 for detecting the air-fuel ratio from the oxygen concentration of the exhaust gas. In addition, the electronic control unit 60 is equipped with a start switch 70 that is manually operated when starting or stopping the control system 61.

[0018] The electronic control unit 60 sets control targets for the fuel injector 40, air injector 50, and ignition device 54, etc., based on the output signals from each sensor. The electronic control unit 60 then outputs control signals set according to each control target to the fuel injector 40, air injector 50, and ignition device 54, etc. For example, the electronic control unit 60 controls the fuel injection amount and fuel injection timing of the fuel injector 40 based on the engine speed and intake air volume. The electronic control unit 60 also controls the ignition timing of the ignition device 54 to the air-fuel mixture based on the engine speed and intake air volume.

[0019] Figure 6 shows an example of the basic structure of an electronic control unit 60. As shown in Figure 6, the electronic control unit 60 that constitutes the control system 61 has a microcontroller 82 into which a processor 80 and main memory (memory) 81 are incorporated. A predetermined program is stored in the main memory 81, and the program is executed by the processor 80. The processor 80 and the main memory 81 are connected to each other so as to be able to communicate with each other. Note that the microcontroller 82 may incorporate multiple processors 80, and the microcontroller 82 may also incorporate multiple main memory 81.

[0020] The electronic control unit 60 also includes an input circuit 83, a drive circuit 84, a communication circuit 85, an external memory 86, and a power supply circuit 87. The input circuit 83 converts signals input from various sensors into signals that can be input to the microcontroller 82. The drive circuit 84 generates drive signals for various devices such as the fuel injector 40 based on signals output from the microcontroller 82. The communication circuit 85 converts signals output from the microcontroller 82 into communication signals for other electronic control units. The communication circuit 85 also converts communication signals received from other electronic control units into signals that can be input to the microcontroller 82. Furthermore, the power supply circuit 87 supplies a stable power supply voltage to the microcontroller 82, the input circuit 83, the drive circuit 84, the communication circuit 85, and the external memory 86. The external memory 86, which consists of non-volatile memory, stores programs and various data.

[0021] [Warm-up operation control] During the initial engine start, i.e., a cold start, it is necessary to raise the catalyst temperature quickly to activate the catalytic converter 37. Therefore, the control system 61 performs engine warm-up control of the engine 10. In this warm-up control, for example, idle-up control is performed to raise the idling speed higher than normal, and ignition retard control is performed to retard the ignition timing. This allows the catalyst temperature to be raised quickly, and the catalytic converter 37 to be activated early. The warm-up control continues until predetermined termination conditions are met. Examples of termination conditions for the warm-up control include the catalyst temperature reaching a specified temperature, the coolant temperature reaching a specified temperature, or the warm-up execution time reaching a specified time.

[0022] However, during warm-up operation when warm-up control is performed, the pre-chamber partition wall 43 in the main combustion chamber 32 is also at a low temperature, making it difficult to retard the ignition timing while ensuring proper combustion of the air-fuel mixture. In other words, when the pre-chamber partition wall 43 is at a low temperature, the fuel injected into the main combustion chamber 32 adheres to the pre-chamber partition wall 43, locally increasing the fuel concentration, which may increase hydrocarbons (HC) and particulate matter (PN) in the exhaust gas. For this reason, it is necessary to ensure proper combustion of the air-fuel mixture even during warm-up operation so that the warm-up control of the engine 10 can be performed appropriately.

[0023] [Combustion control: Control example 1] Therefore, during warm-up operation when warm-up operation control is performed, the control system 61 performs combustion control that controls the air injector 50, fuel injector 40, and ignition device 54. Here, Figure 7 is a timing chart showing an example of the execution status of combustion control as control example 1. Figure 8 is a diagram showing the operation status of the air injector 50 and fuel injector 40 at crank angles CA1 to CA4 shown in Figure 7, and Figure 9 is a diagram showing the operation status of the fuel injector 40 and ignition device 54 at crank angles CA5 to CA7 shown in Figure 7. Note that "OPEN" in Figure 7 means that the nozzles of the fuel injector 40 and air injector 50 (not shown) are opened, and "CLOSE" in Figure 7 means that the nozzles of the fuel injector 40 and air injector 50 (not shown) are closed.

[0024] As shown in Figure 7, during the compression stroke in warm-up mode, the air injector 50 opens at crank angle CA1 (symbol a1), and the fuel injector 40 opens at crank angle CA2 (symbol b1). Subsequently, the fuel injector 40 closes at crank angle CA3 (symbol b2), and the air injector 50 closes at crank angle CA4 (symbol a2). In other words, during the compression stroke in warm-up mode, air injection from the air injector 50 to the sub-combustion chamber 47 begins, followed by fuel injection from the fuel injector 40 to the main combustion chamber 32. Then, after fuel injection from the fuel injector 40 to the main combustion chamber 32 stops, air injection from the air injector 50 to the sub-combustion chamber 47 stops. Thus, the air injector 50 injects air over the first period T1, and the fuel injector 40 injects fuel over the second period T2. Furthermore, the entirety of the second period T2, which is the fuel injection period, overlaps with the first period T1, which is the air injection period.

[0025] As mentioned above, during the compression stroke in warm-up mode, air is injected from the air injector 50 into the sub-combustion chamber 47 and fuel is injected from the fuel injector 40 into the main combustion chamber 32, from crank angles CA1 to CA4. Here, as shown in Figure 8, the air injected from the air injector 50 into the sub-combustion chamber 47 passes through the through-holes 41 and 42 of the pre-chamber partition wall 43 and is released into the main combustion chamber 32, as indicated by arrow x1, forming an air layer AL that covers the pre-chamber partition wall 43. Furthermore, as shown in Figure 5 above, the center line CL2 of the side through-hole 42 is inclined with respect to the radial direction Dr1 of the ignition electrode 52. This allows the air released from the side through-hole 42 to swirl, as indicated by arrow x2, and enables the proper formation of an air layer AL that covers the pre-chamber partition wall 43. In this way, by covering the pre-chamber partition wall 43 with an air layer AL, even if fuel Fu is injected near the pre-chamber partition wall 43, the adhesion of fuel to the pre-chamber partition wall 43 can be suppressed. The orientation of the injection holes (not shown) of the fuel injector 40 is set so that a portion of the injected fuel passes near the pre-chamber partition wall 43. In other words, the orientation of the injection holes (not shown) of the fuel injector 40 is set so that a portion of the injected fuel does not collide with the pre-chamber partition wall 43.

[0026] As mentioned above, by covering the pre-chamber partition 43 with an air layer AL, fuel adhesion to the pre-chamber partition 43 can be suppressed, and an excessive increase in fuel concentration near the pre-chamber partition 43 can be prevented. As a result, the air-fuel mixture can be properly burned during subsequent ignition, thereby reducing hydrocarbons HC and particulate matter PN in the exhaust gas. However, since air is supplied to the sub-combustion chamber 47 from the air injector 50, it was difficult for the ignition electrode 52 to ignite the lean air-fuel mixture in the sub-combustion chamber 47.

[0027] Therefore, the control system 61 injects a small amount of fuel into the main combustion chamber 32 during the expansion stroke after top dead center in order to ignite the fuel mixture and ensure proper combustion. In other words, as shown in Figure 7, during the expansion stroke in warm-up mode, the fuel injector 40 opens at crank angle CA5 (symbol b3) and closes at crank angle CA6 (symbol b4). Thus, during the expansion stroke, a small amount of fuel is injected from the fuel injector 40 into the main combustion chamber 32 over a third period T3 which is shorter than the second period T2. Then, at crank angle CA7 after fuel injection, a high voltage is applied to the ignition electrode 52 in the sub-combustion chamber 47.

[0028] Here, as shown in the enlarged portion of Figure 9, at the crank angle CA7 after top dead center, the piston 24 moves away from the cylinder head 31, so an airflow is generated from the sub-combustion chamber 47 toward the main combustion chamber 32, as indicated by arrow x3. Also, the fuel Fu injected from the fuel injector 40 passes near the tip of the pre-chamber partition wall 43, entraining the air layer AL covering the pre-chamber partition wall 43, as indicated by arrow x4. In this way, an airflow is generated in and around the pre-chamber partition wall 43, as indicated by arrows x3 and x4, so an airflow is generated from the sub-combustion chamber 47 through the central through-hole 41 toward the main combustion chamber 32, and the discharge channel Ch, which is the path for the electric spark, is drawn out from the central through-hole 41 toward the main combustion chamber 32.

[0029] In this way, by drawing the discharge channel Ch towards the main combustion chamber 32, ignition can be performed on the rich mixture in the main combustion chamber 32, rather than the lean mixture in the sub-combustion chamber 47. In other words, even if air is injected into the sub-combustion chamber 47 from the air injector 50 to suppress fuel adhesion to the pre-chamber partition wall 43, drawing the discharge channel Ch towards the main combustion chamber 32 allows for ignition of the mixture and proper combustion. In this way, by properly burning the mixture even during warm-up, hydrocarbons HC and particulate matter counts PN in the exhaust gas can be reduced, and the engine 10 can be properly warmed up.

[0030] Furthermore, the fuel injector 40 and the pre-chamber partition wall 43 are positioned closer to the center CL1 of the main combustion chamber 32 than the intake valve 34 and the exhaust valve 36. This allows the fuel injector 40 and the pre-chamber partition wall 43 to be brought closer to each other, so that even when injecting a small amount of fuel from the fuel injector 40, as shown in Figure 9, fuel can be properly supplied to the vicinity of the tip of the pre-chamber partition wall 43.

[0031] [Combustion control: During normal operation] Next, we will explain combustion control during normal operation after the warm-up period. Figure 10 is a timing chart showing an example of the combustion control execution status during normal operation. Figure 11 shows the operation status of the fuel injector 40 at crank angles CA11 to CA12 shown in Figure 10, and Figure 12 shows the operation status of the ignition device 54 at crank angle CA13 shown in Figure 10.

[0032] As mentioned above, for example, when the temperature of the catalytic converter 37 reaches a specified temperature, the warm-up control is terminated and the system switches to normal operation control. During the compression stroke in normal operation when this normal operation control is performed, as shown in Figure 10, the fuel injector 40 opens at crank angle CA11 (symbol c1) and closes at crank angle CA12 (symbol c2). In this way, during the compression stroke in normal operation, from crank angle CA11 to CA12, fuel Fu is injected from the fuel injector 40 into the main combustion chamber 32, as shown in Figure 11. Also, at crank angles CA11 to CA12 before top dead center, the piston 24 moves toward the cylinder head 31, so an airflow is generated from the main combustion chamber 32 toward the sub-combustion chamber 47, as indicated by arrow x5. As a result, the air-fuel mixture from the main combustion chamber 32 is supplied to the sub-combustion chamber 47, and the sub-combustion chamber 47 becomes filled with the air-fuel mixture. During normal operation, the air injector 50 is kept in a stopped state, not spraying air.

[0033] As shown in Figure 10, during the compression stroke in normal operation, a high voltage is applied to the ignition electrode 52 in the sub-combustion chamber 47 at crank angle CA13 after fuel injection. Here, as shown in the enlarged portion of Figure 12, at crank angle CA13 before top dead center, the piston 24 moves toward the cylinder head 31, so as indicated by arrow x6, an airflow is generated from the main combustion chamber 32 through the central through-hole 41 toward the sub-combustion chamber 47. As a result, the discharge channel Ch of the electric spark is drawn from the central through-hole 41 toward the sub-combustion chamber 47, and the air-fuel mixture in the sub-combustion chamber 47 can be ignited. When the air-fuel mixture in the sub-combustion chamber 47 is ignited and combusted in this way, flame jets JF are injected from the through-holes 41 and 42 of the pre-chamber partition wall 43. In other words, since high-energy flame jets JF are injected from the sub-combustion chamber 47 toward the main combustion chamber 32, the air-fuel mixture in the main combustion chamber 32 can be made lean while maintaining the combustion stability of the air-fuel mixture.

[0034] [Combustion control: Control example 2] In control example 1 shown in Figure 7, the entire second period T2, which is the fuel injection period, is superimposed on the first period T1, which is the air injection period. However, this is not the only option; it is sufficient if at least a portion of the first period T1 and the second period T2 overlap. Here, Figure 13 is a timing chart showing another example of the combustion control execution status as control example 2. Note that in Figure 13, crank angles and operating conditions that are the same as those shown in Figure 7 are denoted by the same reference numerals and their explanations are omitted.

[0035] As shown in Figure 13, during the compression stroke in warm-up mode, the fuel injector 40 opens at crank angle CA2 (symbol b1), and the air injector 50 opens at crank angle CA21 (symbol d1). Subsequently, the air injector 50 closes at crank angle CA24 (symbol d2), and the fuel injector 40 closes at crank angle CA3 (symbol b2). In other words, during the compression stroke in warm-up mode, fuel injection from the fuel injector 40 to the main combustion chamber 32 begins, followed by air injection from the air injector 50 to the sub-combustion chamber 47. After the air injection from the air injector 50 to the sub-combustion chamber 47 stops, fuel injection from the fuel injector 40 to the main combustion chamber 32 stops.

[0036] Thus, fuel is injected from the fuel injector 40 into the main combustion chamber 32 over a second period T2, and air is injected from the air injector 50 into the sub-combustion chamber 47 over a first period T1a which is shorter than the second period T2. In this way, even when air is injected over a first period T1a which is shorter than the second period T2, it is possible to cover the pre-chamber partition wall 43 with the air layer AL. As a result, similar to control example 1, the adhesion of fuel to the pre-chamber partition wall 43 can be suppressed, so that an excessive increase in fuel concentration near the pre-chamber partition wall 43 can be prevented, and the air-fuel mixture can be properly burned at ignition.

[0037] In the example shown in Figure 13, fuel injection from the fuel injector 40 to the main combustion chamber 32 is initiated first, followed by air injection from the air injector 50 to the sub-combustion chamber 47. However, this is not limited to this configuration, and fuel injection from the fuel injector 40 to the main combustion chamber 32 may be initiated first, followed by air injection from the air injector 50 to the sub-combustion chamber 47. Furthermore, in the example shown in Figure 13, fuel injection from the fuel injector 40 to the main combustion chamber 32 is stopped after air injection from the air injector 50 to the sub-combustion chamber 47 is stopped. However, this is not limited to this configuration, and air injection from the air injector 50 to the sub-combustion chamber 47 may be stopped first, followed by air injection from the air injector 50 to the sub-combustion chamber 47.

[0038] [Combustion control: Control example 3] In control example 1 shown in Figure 7, fuel and air are not injected during the intake stroke during warm-up, but this is not the only option. In other words, fuel may be injected from the fuel injector 40 and air may be injected from the air injector 50 not only during the compression stroke but also during the intake stroke during warm-up. Here, Figure 14 is a timing chart showing another example of the combustion control execution status as control example 3. Note that in Figure 14, the same crank angle and operating conditions as those shown in Figure 7 are denoted by the same reference numerals and their explanations are omitted.

[0039] As shown in Figure 14, during the intake stroke in warm-up mode, the air injector 50 opens at crank angle CA31 (symbol e1), and the fuel injector 40 opens at crank angle CA32 (symbol f1). Subsequently, the fuel injector 40 closes at crank angle CA33 (symbol f2), and the air injector 50 closes at crank angle CA34 (symbol e2). In other words, during the intake stroke in warm-up mode, air injection from the air injector 50 to the sub-combustion chamber 47 begins, followed by fuel injection from the fuel injector 40 to the main combustion chamber 32. Then, after fuel injection from the fuel injector 40 to the main combustion chamber 32 stops, air injection from the air injector 50 to the sub-combustion chamber 47 stops.

[0040] In this way, even when fuel and air are injected from both injectors 40 and 50 during the intake stroke as well as the compression stroke during warm-up, the pre-chamber partition 43 can be covered by the air layer AL. This suppresses the adhesion of fuel to the pre-chamber partition 43, thereby preventing an excessive increase in fuel concentration near the pre-chamber partition 43, and allowing the air-fuel mixture to burn properly at ignition. In addition, during the intake stroke during warm-up, fuel injection from the fuel injector 40 may be started before air injection from the air injector 50. Also, during the intake stroke during warm-up, fuel injection from the fuel injector 40 may be stopped after air injection from the air injector 50 has been stopped.

[0041] In the example shown in Figure 14, fuel and air are injected from both injectors 40 and 50 during the intake stroke while the engine is warming up, but this is not the only option. For example, during the intake stroke while the engine is warming up, fuel may be injected from the fuel injector 40 while air injection from the air injector 50 is stopped. Alternatively, during the intake stroke while the engine is warming up, air may be injected from the air injector 50 while fuel injection from the fuel injector 40 is stopped. Even in these cases, since air is injected from the air injector 50 during the compression stroke while the engine is warming up, the pre-chamber partition wall 43 can be covered with an air layer AL, thereby suppressing fuel adhesion to the pre-chamber partition wall 43.

[0042] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. For example, in the above description, the control system 61 is configured by one electronic control unit 60, but it is not limited to this, and the control system 61 may be configured by multiple electronic control units 60. Also, the illustrated pre-chamber partition wall 43 has a hemispherical dome portion 46, but it is not limited to this, and a pre-chamber partition wall with a tip of another shape may be provided. Also, the illustrated engine 10 is an engine that uses gasoline as fuel, but it is not limited to this, and the present invention may be applied to an engine that uses a fuel other than gasoline. Also, the illustrated engine 10 is an engine used in a vehicle 11, but it is not limited to this, and the present invention may be applied to an engine used as a power source in other devices, etc. [Explanation of symbols]

[0043] 10 Engines 31 Cylinder head 32 Main combustion chamber 34 Intake valves 36 Exhaust valve 40 Fuel Injectors 41 Central through hole (through hole, first through hole) 42 Side through holes (through holes, second through holes) 43. Pre-chamber partition (chamber partition) 47. Sub-combustion chamber 50 Air Injectors 52 Ignition electrode 52a Tip 52b Side 54 Ignition devices 61 Control Systems 80 processors 81 Main memory (memory) CL1 center CL2 center line Dr1 radial direction T1, T1a First Period T2 Second Period T3 Third Period

Claims

1. An engine that uses an electric spark to ignite a fuel-air mixture, A cylinder head having a chamber partition wall with multiple through holes formed therein, the chamber partition wall separating the main combustion chamber and the sub-combustion chamber, A fuel injector provided in the cylinder head for injecting fuel into the main combustion chamber, An air injector provided in the cylinder head for injecting air into the sub-combustion chamber, An ignition device comprising an ignition electrode positioned in the sub-combustion chamber, which discharges electricity between the ignition electrode and the chamber partition wall, A control system comprising a processor and memory connected to each other in a manner that enables communication between them, for controlling the fuel injector, the air injector and the ignition device, It has, The control system is During the compression stroke in the warm-up phase, fuel is injected from the fuel injector over a first period, and air is injected from the air injector over a second period that overlaps with at least a portion of the first period. During the expansion stroke in warm-up operation, after fuel is injected from the fuel injector, a discharge is made between the ignition electrode and the chamber partition. engine.

2. In the engine according to claim 1, The chamber partition wall has a plurality of through holes, including a first through hole facing the tip of the ignition electrode and a plurality of second through holes facing the side surface of the ignition electrode. engine.

3. In the engine according to claim 2, The center line of the second through-hole is inclined with respect to the radial direction of the ignition electrode. engine.

4. In the engine according to claim 1, The fuel injector and the chamber partition are positioned closer to the center of the main combustion chamber than the intake valve and the exhaust valve. engine.

5. In the engine according to claim 1, The control system is During the expansion stroke in the warm-up operation, fuel is injected from the fuel injector for a third period shorter than the first period, and then a discharge is made between the ignition electrode and the chamber partition. engine.

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