Engine System

Abstract

To properly combust air-fuel mixture in an auxiliary chamber and a main chamber in an engine system having the main combustion chamber and the auxiliary chamber.SOLUTION: A system comprises a main combustion chamber, an auxiliary chamber, a fuel injection device for injecting fuel to the main combustion chamber, a main ignition device for igniting air-fuel mixture in the main combustion chamber, and an auxiliary ignition device for igniting air-fuel mixture. In a supercharging area and a non-supercharging area, after the main ignition device is caused to execute ignition, the auxiliary ignition device is caused to execute ignition. The main ignition device and the auxiliary ignition device are controlled so that an ignition phase difference that is a retard angle amount of the auxiliary ignition timing to the main ignition timing becomes smaller in the supercharging area than in the non-supercharging area.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to an engine system having a main combustion chamber and an auxiliary combustion chamber. [Background technology]

[0002] In the past, in engines mounted on vehicles, etc., it has been considered to provide a main combustion chamber and a pre-chamber communicating therewith in order to improve fuel economy and exhaust gas performance. Specifically, by providing a main combustion chamber and a pre-chamber communicating therewith and ejecting the flame generated in the pre-chamber into the main combustion chamber, it is possible to increase the combustion speed in the main combustion chamber and improve fuel economy, and also to suppress the remaining unburned air-fuel mixture and improve exhaust gas performance.

[0003] For example, Patent Document 1 discloses an engine including a main combustion chamber (main chamber in Patent Document 1) defined by a cylinder block, a cylinder head, and a piston, an auxiliary chamber communicating with the main combustion chamber, a main fuel injection valve provided in an intake port for supplying fuel to the main combustion chamber through the intake port, a main chamber spark plug for igniting the mixture in the main combustion chamber, a auxiliary fuel injection valve for directly injecting fuel into the auxiliary chamber, and an auxiliary chamber spark plug for igniting the mixture in the auxiliary chamber. In this engine, the mixture formed in the main combustion chamber, which is a mixture of fuel and air injected from the main fuel injection valve, is first ignited by the main chamber spark plug, and then the mixture formed in the auxiliary chamber, which is a mixture of fuel and air injected from the auxiliary fuel injection valve, is ignited by the auxiliary chamber spark plug. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-255370 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the engine of Patent Document 1, fuel is injected separately into the main combustion chamber and the auxiliary combustion chamber, and two fuel injection valves are required for one cylinder. This makes the structure complicated and is disadvantageous in terms of cost. In response to this, in an engine having a main combustion chamber and an auxiliary combustion chamber, it is possible to provide a fuel injection valve only in the main combustion chamber. However, in a configuration in which a fuel injection valve is provided only in the main combustion chamber, the combustion state of the mixture in the auxiliary combustion chamber and the main combustion chamber changes depending on the flow rate of the mixture from the main combustion chamber to the auxiliary combustion chamber. Therefore, ingenuity is required in terms of introducing an appropriate amount of mixture from the main combustion chamber to the auxiliary combustion chamber and appropriately burning the mixture in the main combustion chamber and the auxiliary combustion chamber.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to appropriately combust an air-fuel mixture in an engine system equipped with a main combustion chamber and an auxiliary combustion chamber. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a cylinder block and a cylinder head which define a cylinder, a piston housed in the cylinder so as to be capable of reciprocating motion, a main combustion chamber defined by the cylinder block, the cylinder head, and the piston, an auxiliary chamber which is separated from the main combustion chamber by a partition wall and which communicates with the main combustion chamber through a communication hole formed in the partition wall, a fuel injection device which injects fuel into the main combustion chamber, a main ignition device which ignites the air-fuel mixture in the main combustion chamber, an auxiliary ignition device which ignites the air-fuel mixture in the auxiliary chamber, a supercharger capable of supercharging intake air introduced into the cylinder, and a combustion system including the fuel injection device, the main ignition device, and the auxiliary ignition device. A control device electrically connected to the ignition device and outputting an electrical signal for control to each of the devices, the control device comprising: The engine load is higher than the specified switching load. a supercharging region in which supercharging by the supercharger is performed; When the engine load is below the switching loadIn a non-supercharging region adjacent to the supercharging region where supercharging by the supercharger is not performed, the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition, and when an ignition phase difference is an amount of retardation of an auxiliary ignition timing, which is the ignition timing of the auxiliary ignition device, relative to a main ignition timing, which is the ignition timing of the main ignition device, the control device controls the main ignition device and the auxiliary ignition device so that the ignition phase difference in the supercharging region is smaller than the ignition phase difference in the non-supercharging region. The air-fuel ratio of the mixture in the main combustion chamber in the supercharging region is set to be the same as the air-fuel ratio of the mixture in the main combustion chamber in the non-supercharging region. , characterized in that

[0008] In the present invention, ignition is performed by the main ignition device in the supercharging region and the non-supercharging region, and then ignition is performed by the auxiliary ignition device. Therefore, the mixture is burned in the main combustion chamber by ignition by the main ignition device, and the resulting pressure increase in the main combustion chamber is used to push the mixture into the auxiliary chamber.

[0009] Moreover, in the present invention, the ignition phase difference, which is the amount of retardation of the auxiliary ignition timing with respect to the main ignition timing, is made smaller in the supercharged region than in the non-supercharged region. In other words, the period from when the mixture starts being introduced into the auxiliary chamber due to the pressure rise in the main combustion chamber to when ignition by the auxiliary ignition device is performed is shorter when supercharging is performed than when not performed. Therefore, when the mixture is likely to enter the auxiliary chamber due to the increase in pressure in the main combustion chamber caused by supercharging, an excessive amount of mixture can be prevented from flowing into the auxiliary chamber, and the mixture can be properly burned in the main combustion chamber and the auxiliary chamber. Specifically, if an excessive amount of mixture flows into the auxiliary chamber, the mixture may combust explosively in the auxiliary chamber, causing abnormal combustion accompanied by high-frequency pressure waves in the auxiliary chamber and the main combustion chamber, but this abnormal combustion can be prevented. Also, when the mixture is difficult to enter the auxiliary chamber due to the pressure in the main combustion chamber being relatively low without supercharging, a sufficient amount of mixture can be flowed into the auxiliary chamber, and proper combustion of the mixture in the main combustion chamber and the auxiliary chamber can be achieved.

[0010] In the present invention, an example of a configuration for making the ignition phase difference in the supercharging region smaller than the ignition phase difference in the non-supercharging region is a configuration in which the control device controls the main ignition device and the auxiliary ignition device so that the auxiliary ignition timing in the supercharging region is more advanced than the auxiliary ignition timing in the non-supercharging region (claim 2).

[0011] In addition, in the present invention, an example of a configuration for making the ignition phase difference in the supercharging region smaller than the ignition phase difference in the non-supercharging region is a configuration in which the control device controls the main ignition device and the auxiliary ignition device so that the main ignition timing in the supercharging region is retarded relative to the main ignition timing in the non-supercharging region (claim 3).

[0012] The present invention also relates to a cylinder block and a cylinder head which define a cylinder, a piston housed in the cylinder so as to be capable of reciprocating motion, a main combustion chamber defined by the cylinder block, the cylinder head, and the piston, an auxiliary chamber which is separated from the main combustion chamber by a partition wall and communicates with the main combustion chamber through a communication hole formed in the partition wall, a fuel injection device which injects fuel into the main combustion chamber, a main ignition device which ignites the air-fuel mixture in the main combustion chamber, an auxiliary ignition device which ignites the air-fuel mixture in the auxiliary chamber, a supercharger capable of supercharging intake air introduced into the cylinder, and the fuel injection device and the main ignition device. and a control device electrically connected to the auxiliary ignition device and outputting an electric signal for control to each of the devices, wherein the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition in a supercharging region where supercharging by the supercharger is performed and in a non-supercharging region where supercharging by the supercharger is not performed and is adjacent to the supercharging region, and when a retard amount of the sub-ignition timing, which is the ignition timing of the sub-ignition device, relative to a main ignition timing, which is the ignition timing of the main ignition device, is set as an ignition phase difference, the control device controls the ignition phase difference in the supercharging region to be smaller than the ignition phase difference in the non-supercharging region, and The main ignition device and the auxiliary ignition device are controlled so that the ignition phase difference becomes smaller as the engine load becomes higher in the supercharging region. The present invention provides an engine system characterized by: (Claim 4).

[0013] With this configuration, in addition to supercharging, the pressure in the main combustion chamber becomes particularly high due to a high engine load, which particularly promotes the flow of the mixture from the main combustion chamber to the auxiliary combustion chamber. At this time, the ignition phase difference is made small, so that excessive flow of the mixture into the auxiliary combustion chamber can be reliably prevented.

[0014] The present invention also relates to a cylinder block and a cylinder head which define a cylinder, a piston housed in the cylinder so as to be capable of reciprocating motion, a main combustion chamber defined by the cylinder block, the cylinder head, and the piston, an auxiliary chamber which is separated from the main combustion chamber by a partition wall and communicates with the main combustion chamber through a communication hole formed in the partition wall, a fuel injection device which injects fuel into the main combustion chamber, a main ignition device which ignites the air-fuel mixture in the main combustion chamber, an auxiliary ignition device which ignites the air-fuel mixture in the auxiliary chamber, a supercharger capable of supercharging intake air introduced into the cylinder, and the fuel injection device and the main ignition device. and a control device electrically connected to the auxiliary ignition device and outputting an electric signal for control to each of the devices, wherein the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition in a supercharging region where supercharging by the supercharger is performed and in a non-supercharging region where supercharging by the supercharger is not performed and is adjacent to the supercharging region, and when a retard amount of the sub-ignition timing, which is the ignition timing of the sub-ignition device, relative to a main ignition timing, which is the ignition timing of the main ignition device, is set as an ignition phase difference, the control device controls the ignition phase difference in the supercharging region to be smaller than the ignition phase difference in the non-supercharging region, and The main ignition device and the auxiliary ignition device are controlled so that the ignition phase difference becomes smaller as the engine load becomes higher in the non-supercharging region. The present invention provides an engine system characterized by: (Claim 5).

[0015] With this configuration, even in the non-supercharging region where supercharging is not performed, it is possible to reliably prevent an excessive amount of mixture from flowing into the auxiliary chamber when the engine load is high, and to reliably allow a sufficient amount of mixture to flow into the auxiliary chamber when the engine load is low. Effect of the Invention

[0016] As described above, according to the engine system of the present invention, the air-fuel mixture can be appropriately combusted in the auxiliary combustion chamber and the main combustion chamber. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of an engine system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an engine body. [Diagram 3] 4 is a partial cross-sectional view of the tip portion of the sub-ignition unit as viewed from the side. FIG. [Figure 4] FIG. 4 is a plan view of the tip portion of the auxiliary ignition unit. [Diagram 5] FIG. 2 is a diagram showing a control block of the engine. [Figure 6] 2 is a map showing an operating range of an engine. [Figure 7] FIG. 4 is a diagram showing an example of a drive pulse, a main ignition timing, and an auxiliary ignition timing of an injector in a non-supercharging region. [Figure 8] FIG. 11 is a diagram showing another example of the injector drive pulse, the main ignition timing, and the auxiliary ignition timing in the supercharging region. [Figure 9] FIG. 4 is a diagram showing the relationship between the engine load and each parameter in a high speed range. [Figure 10] FIG. 4 is a diagram showing the relationship between the engine speed and each parameter in a high speed region. [Figure 11] 5 is a flowchart showing a control procedure for the supercharging motor and the spark plug in a high speed region. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (Overall engine configuration) 1 is a schematic diagram showing a preferred embodiment of an engine system of the present invention. The engine system 1 includes an engine body 2, an intake passage 4 through which air (intake air) introduced into the engine body 2 flows, an exhaust passage 6 through which exhaust gas discharged from the engine body 2 flows, and an EGR device 50. The engine system 1 is mounted on a vehicle as a power source for driving the vehicle. The engine body 2 is a four-stroke gasoline engine that mainly uses gasoline as fuel, and fuel containing gasoline is supplied to the engine body 2.

[0019] FIG. 2 is a schematic cross-sectional view of the engine body 2. In this embodiment, the engine body 2 is a multi-cylinder engine having a plurality of cylinders 22. For example, the engine body 2 has four cylinders 22 arranged in a row (arranged in a direction perpendicular to the paper surface of FIG. 1). The engine body 2 includes a cylinder block 52 in which the plurality of cylinders 22 are formed, a cylinder head 54 having a bottom surface 54a that closes the upper end openings of each cylinder 22 and attached to the upper surface of the cylinder block 52, and a plurality of pistons 24 accommodated in each cylinder 22 so as to be reciprocally slidable. In this embodiment, the side from the cylinder block 52 toward the cylinder head 54 is treated as the top, and the opposite side is treated as the bottom, but this is for convenience of explanation and is not intended to limit the installation posture of the engine.

[0020] A main combustion chamber 26 is defined above the piston 24 of each cylinder 22. The main combustion chamber 26 is defined by an inner circumferential surface 22a of the cylinder 22 formed in a cylinder block 52, a bottom surface (lower surface) 54a of a cylinder head 54, and a crown surface 24a of the piston 24. Fuel is supplied to the main combustion chamber 26 by injection from an injector 28, which will be described later. The piston 24 reciprocates up and down due to the expansion force caused by the combustion of the mixture of fuel and air.

[0021] A crankshaft 20, which is an output shaft of the engine body 2, is provided at the lower part of the cylinder block 52 (below the pistons 24). The crankshaft 20 is connected to the pistons 24 of the cylinders 22 via connecting rods 21, and rotates about its central axis in response to the reciprocating motion of the pistons 24.

[0022] In the cylinder head 54, an intake port 8 for introducing air supplied from the intake passage 4 into the main combustion chamber 26 and an exhaust port 12 for leading exhaust gas generated in the main combustion chamber 26 to the exhaust passage 6 are formed for each cylinder 22. In the cylinder head 54, an intake valve 10 for opening and closing the opening of the intake port 8 on the main combustion chamber 26 side and an exhaust valve 14 for opening and closing the opening of the exhaust port 12 on the main combustion chamber 26 side are provided for each cylinder 22. In this embodiment, two intake valves 10 and two exhaust valves 14 are provided for each cylinder 22.

[0023] The intake valve 10 and the exhaust valve 14 are driven to open and close in conjunction with the rotation of the crankshaft 20 by valve mechanisms 16, 18, respectively, disposed in the cylinder head 54. The valve mechanism 16 for the intake valve 10 is provided with a variable valve lift mechanism (intake S-VT) 16a that electrically variably controls the valve lift amount and opening and closing timing of the intake valve 10. Similarly, the valve mechanism 18 for the exhaust valve 14 is provided with a variable valve lift mechanism (exhaust S-VT) 18a that electrically variably controls the valve lift amount and opening and closing timing of the exhaust valve 14.

[0024] The cylinder head 54 is provided with one set of injector 28, main spark plug 32, and sub-ignition unit 30 for each cylinder 22. The injector 28 corresponds to the "fuel injection device" in the claims, and the main spark plug 32 corresponds to the "main ignition device" in the claims.

[0025] The injector 28 is an injection valve that injects fuel into the main combustion chamber 26. An injection port for injecting fuel is formed at a tip 28x of the injector 28. The injector 28 is attached to the cylinder head 54 so that the tip 28x faces the main combustion chamber 26 from above. In this embodiment, the injector 28 is disposed so that the tip 28x is located at the center of the ceiling surface of the main combustion chamber 26 (more specifically, on the axis of the cylinder 22).

[0026] The main ignition plug 32 ignites the air-fuel mixture in the main combustion chamber 26 by spark discharge. An electrode portion 32x for discharging a spark is provided at the tip of the main ignition plug 32. This electrode portion 32x includes a center electrode 32a and a side electrode (earth) 32b. The main ignition plug 32 is attached to the cylinder head 54 so that the electrode portion 32x faces the main combustion chamber 26 from above. In this embodiment, the main ignition plug 32 is disposed so that the electrode portion 32x is located on the intake port 8 side of the tip portion 28x of the injector 28 on the ceiling surface of the main combustion chamber 26.

[0027] The auxiliary ignition unit 30 is a device for ejecting a flame into the main combustion chamber 26. The auxiliary ignition unit 30 will be described in detail later.

[0028] The intake passage 4 is connected to one side of the cylinder head 54 so as to communicate with the intake ports 8 of each cylinder 22. The intake passage 4 is provided with, in this order from the upstream side, an air cleaner 34 that removes foreign matter in the intake air, a turbocharger 35 that supercharges the intake air flowing through the intake passage 4, an intercooler 39 that cools the intake air discharged from the turbocharger 35, an openable / closable throttle valve 36 that adjusts the flow rate of the intake air, and a surge tank 38.

[0029] The downstream end of the intake passage 4 branches into multiple passages. Each branch passage is connected to one intake port 8. For each cylinder 22, the branch passage connected to one of the two intake ports 8 is provided with a swirl valve 56 (see FIG. 5) that opens and closes the branch passage.

[0030] In this embodiment, the supercharger 35 is an electric supercharger, and the engine system 1 has a motor 37 (hereinafter, referred to as the supercharging motor 37) that drives the supercharger 35 to rotate.

[0031] The exhaust passage 6 is connected to one side of the cylinder head 54 (the side opposite to the intake passage 4) so ​​as to communicate with the exhaust ports 12 of each cylinder 22. The exhaust passage 6 is provided with a catalytic device 40 incorporating a catalyst 41 such as a three-way catalyst.

[0032] The EGR device 50 is a device for recirculating a part of the exhaust gas as EGR gas to the intake passage 4 and introducing (recirculating) the EGR gas into the main combustion chamber 26 that is connected to the intake passage 4 via the intake passage 4. The EGR device 50 has an EGR passage 42 that communicates the exhaust passage 6 with the intake passage 4, and an EGR valve 46 and an EGR cooler 44 that are respectively provided in the EGR passage 42. The upstream end of the EGR passage 42 is connected to the downstream end of the catalytic device 40 and the exhaust passage 6 downstream of the catalyst 41, and the downstream end of the EGR passage 42 is connected to the surge tank 38. The EGR valve 46 is a valve that opens and closes the EGR passage 42 to adjust the flow rate of the EGR gas. The EGR cooler 44 is a heat exchanger that cools the EGR gas. The EGR cooler 44 is disposed downstream of the EGR valve 46.

[0033] (Sub-ignition unit 30) Fig. 3 is a partial cross-sectional side view of the tip portion 30x of the sub-ignition unit 30. Fig. 4 is a plan view of the tip portion 30x of the sub-ignition unit 30 (viewed from the tip side).

[0034] The auxiliary ignition unit 30 has an auxiliary spark plug 62 that ignites the air-fuel mixture by spark discharge. An electrode portion 62x for discharging sparks is provided at the tip of the auxiliary spark plug 62. The electrode portion 62x includes a center electrode 62a and a side electrode (earth) 62b. The auxiliary ignition unit 30 has a cover member 64 that is provided at its tip portion 30x and covers the electrode portion 62x of the auxiliary ignition plug 62. A sub-chamber 60, which is a predetermined space, is defined inside the cover member 64. In other words, the auxiliary ignition plug 62 is disposed so that its electrode portion 62x faces the sub-chamber 60, and ignites the air-fuel mixture in the sub-chamber 60. The cover member 64 has a hollow hemispherical shape that bulges out toward the tip side of the auxiliary ignition unit 30. The auxiliary ignition plug 62 corresponds to the "auxiliary ignition device" in the claims, and the cover member 64 corresponds to the "partition wall" in the claims.

[0035] 2, the auxiliary ignition unit 30 is attached to the cylinder head 54 so that its tip portion 30x faces the main combustion chamber 26 from above. In this embodiment, the auxiliary ignition unit 30 is attached to a position on the ceiling surface of the main combustion chamber 26 closer to the exhaust port 12 than the injector 28. In this embodiment, in this attached state, almost the entire cover member 64 is located inside the main combustion chamber 26.

[0036] The cover member 64 is formed with a plurality of communication holes 66 that penetrate the front and back of the cover member 64 and communicate between the main combustion chamber 26 and the auxiliary chamber 60. The inner space of the cover member 64, i.e., the auxiliary chamber 60, communicates with the main combustion chamber 26 via these communication holes 66. In this manner, in this embodiment, by attaching the auxiliary ignition unit 30 configured as described above to the engine body 2, the auxiliary chamber 60 that is separated from the main combustion chamber 26 by the cover member 64 and communicates with the main combustion chamber 26 via the communication holes 66 is formed in the engine body 2.

[0037] In this embodiment, three communication holes 66 are formed in the cover member 64. As shown in Fig. 4, the three communication holes 66 are formed at 120 degree intervals around the axis of the cover member 64 passing through the apex A of the cover member 64. Also, as shown in Fig. 3, each communication hole 66 is formed at a position 45 degrees from the apex A in a side view. The radius and thickness of the cover member 64 are 5 mm and 1 mm, respectively, and the diameter of each communication hole 66 is 1.2 mm.

[0038] The auxiliary ignition unit 30 ejects a flame into the main combustion chamber 26. Specifically, when fuel is injected from the injector 28 into the main combustion chamber 26 and a mixture of air and fuel is formed in the main combustion chamber 26, a part of this mixture is introduced into the auxiliary chamber 60 through the communication hole 66. When a spark discharge is generated by the auxiliary spark plug 62 with a sufficient amount of mixture present in the auxiliary chamber 60, the mixture starts to burn in the auxiliary chamber 60, and a flame propagates from the vicinity of the electrode portion 62x of the auxiliary spark plug 62 to the surroundings. Then, this flame is ejected / released into the main combustion chamber 26 through the communication hole 66 and propagates to the mixture in the main combustion chamber 26.

[0039] Here, as described above, when ignition is performed by the main spark plug 32, the flame also propagates from the vicinity of the electrode portion 32x of the main spark plug 32 to the surroundings. As a result, if ignition is performed by both the main spark plug 32 and the sub-spark plug 62 and the mixture is appropriately combusted in the main combustion chamber 26 and the sub-chamber 60, the flame will propagate from multiple positions to the mixture in the main combustion chamber 26, increasing the combustion speed of the mixture in the main combustion chamber 26 and improving fuel efficiency, while suppressing the occurrence of knocking and the remaining of unburned mixture.

[0040] (Control system) Fig. 5 is a block diagram showing the control system of the engine. The ECU 100 shown in this figure is a device that controls the engine overall, and is composed of a microcomputer including a processor (CPU) that performs various arithmetic processing, memories such as ROM and RAM, and various input / output buses. The ECU 100 corresponds to the "control device" in the claims.

[0041] Information detected by various sensors is input to the ECU 100. For example, the ECU 100 receives detection values ​​from an airflow sensor SN1, an intake air temperature sensor SN2, an intake pressure sensor SN3, a water temperature sensor SN4, and a crank angle sensor SN5 provided in the engine system 1, and an accelerator opening sensor SN6 provided in the vehicle. The airflow sensor SN1 detects the flow rate of intake air passing through the intake passage 4 and introduced into the engine body 2. The intake air temperature sensor SN2 and the intake pressure sensor SN3 respectively detect the temperature and pressure of the intake air introduced into the engine body 2. The water temperature sensor SN4 detects the temperature of engine cooling water that cools the engine body 2. The crank angle sensor SN5 detects the crank angle, which is the rotation angle of the crankshaft 20, and the engine speed. The accelerator opening sensor SN6 detects the accelerator opening, which is the opening of an accelerator pedal (not shown) provided in the vehicle.

[0042] The ECU 100 performs various determinations and calculations based on input signals from various sensors. The ECU 100 is electrically connected to the injector 28, the main spark plug 32, the sub spark plug 62, the EGR valve 46, the supercharging motor 37, etc., and outputs control electrical signals to these devices based on the results of the calculations, etc.

[0043] 6 is a map showing the engine operating range with the horizontal axis representing engine speed and the vertical axis representing engine load. As shown in FIG. 6, the engine operating range is divided into a plurality of ranges according to the control contents of the injector 28, the spark plugs 32 and 62, the EGR valve 46, and the supercharging motor 37. Specifically, the engine operating range is roughly divided into a low-speed range R1 where the engine speed is equal to or lower than a predetermined first speed N1, and a high-speed range R2 where the engine speed is higher than the first speed N1. The low-speed range R1 is divided into three ranges A1 to A3 (first range A1, second range A2, third range A3), and the high-speed range R2 is divided into two adjacent ranges B1 and B2 (non-supercharging range B1, supercharging range B2).

[0044] (Control content of low speed region R1) The first region A1 is a region of the low speed region R1 where the engine load is equal to or lower than a predetermined load. The second region A2 is a region of the low speed region R1 where the engine load is higher than that of the first region A1. The third region A3 is a region of the low speed region R1 where the engine load is higher than that of the second region A2.

[0045] In the first region A1, the injector 28 and the spark plugs 32, 62 are controlled to realize HCCI combustion (Homogeneous Compression Charge Ignition). Specifically, in the first region A1, fuel is injected from the injector 28 during the intake stroke. Also, the driving of the spark plugs 32, 62 (ignition by these spark plugs 32, 62) is stopped.

[0046] As described above, the injector 28 faces the main combustion chamber 26, and the fuel injected from the injector 28 can be diffused throughout the main combustion chamber 26. Thus, in the first region A1, fuel is injected from the injector 28 during the intake stroke, so that the fuel and air are sufficiently mixed in the main combustion chamber 26 before the top dead center of compression is reached. Then, in the first region A1, the sufficiently mixed mixture (premixed air) is heated and pressurized by the compression of the piston 24, and self-ignites near the top dead center of compression. In HCCI combustion, the air-fuel ratio of the mixture (the ratio of the weight of air in the main combustion chamber 26 to the weight of fuel in the main combustion chamber 26) can be made lean (high) to a level where flame propagation is impossible, thereby improving fuel efficiency. Thus, in the first region A1, the opening of the throttle valve 36 is adjusted so that the air-fuel ratio of the mixture in the main combustion chamber 26 is leaner (higher) than the theoretical air-fuel ratio (14.7).

[0047] In the second region A2 and the third region A3, the main ignition plug 32 and the sub-ignition plug 62 are driven to realize flame propagation combustion. That is, in these regions A2 and A3, a flame kernel is generated around the electrode portions 32x and 62x by spark discharge from the electrode portions 32x and 62x of the ignition plugs 32 and 62, and the flame propagates from the flame kernel to the surroundings to realize SI combustion (SI: Spark Ignition) in which the mixture in the main combustion chamber 26 and the sub-chamber 60 is burned. In addition, in these regions A2 and A3, the opening of the throttle valve 36 is adjusted so that the air-fuel ratio of the mixture in the main combustion chamber 26 becomes close to the theoretical air-fuel ratio.

[0048] In the second region A2, fuel is injected from the injector 28 during the intake stroke, as in the first region A1. On the other hand, in the third region A3, the engine speed is low and the engine load is high, so there is a risk of pre-ignition occurring if fuel is injected from the injector 28 during the intake stroke. For this reason, in the third region A3, retarded SI combustion is performed in which fuel injection from the injector 28 is started during the compression stroke to cause SI combustion of the air-fuel mixture.

[0049] Furthermore, in regions where the engine load or engine speed is high, if EGR is performed to recirculate the EGR gas to the intake passage 4, a sufficient amount of air may not be introduced into the main combustion chamber 26. On the other hand, in regions where the engine speed and engine load are relatively low, EGR is expected to improve fuel efficiency by reducing pumping loss and cooling loss. Thus, in the second region A2, the EGR valve 46 is opened to perform EGR, and in the third region A3, the EGR valve 46 is fully closed to stop EGR.

[0050] (Control details for high speed region R2) Next, the control in the high speed region R2, which is a feature of the present invention, will be described.

[0051] The supercharging region B2 of the high speed region R2 is a region where supercharging is performed by the supercharger 35. That is, in the supercharging region B2, the supercharging motor 37 is driven and the supercharger 35 is rotationally driven by the supercharging motor 37. The supercharging region B2 is set to a region in the high speed region R2 where the engine speed is higher than a predetermined second rotation speed N2 and the engine load is higher than a predetermined switching load Tq1. The second rotation speed N2 is a rotation speed higher than the first rotation speed N1. The non-supercharging region B1 is a region where supercharging is not performed by the supercharger 35. That is, in the non-supercharging region B1, the supercharging motor 37 is stopped and the rotational drive of the supercharger 35 by the supercharging motor 37 is stopped. The non-supercharging region B1 is set to a region excluding the supercharging region B2 of the high speed region R2.

[0052] Fig. 7 is a diagram showing the drive pulse, main ignition timing tm, and auxiliary ignition timing ts of the injector 28 at an operating point P1 included in the non-supercharging region B1. Fig. 8 is a diagram showing the drive pulse, main ignition timing tm, and auxiliary ignition timing ts of the injector 28 at an operating point P2 included in the supercharging region B2. The main ignition timing tm is the timing at the crank angle at which the main ignition plug 32 ignites, i.e., produces a spark discharge. The auxiliary ignition timing ts is the timing at the crank angle at which the auxiliary ignition plug 62 ignites, i.e., produces a spark discharge.

[0053] In the high speed region R2 (both the supercharging region B2 and the non-supercharging region B1), the main spark plug 32 and the auxiliary spark plug 62 are driven to realize flame propagation combustion (SI combustion). As shown in Fig. 7 and Fig. 8, in the high speed region R2, the fuel injection timing tinj at which fuel injection from the injector 28 starts is set to a time during the intake stroke, and fuel injection from the injector 28 into the main combustion chamber 26 starts during the intake stroke. In addition, in the high speed region R2, the main ignition timing tm is set to a time on the more advanced side than the auxiliary ignition timing ts, and ignition is first performed by the main spark plug 32, and then ignition is performed by the auxiliary spark plug 62. In this embodiment, in the high speed region R2, the main ignition timing tm is set to a time during the compression stroke, and the auxiliary ignition timing ts is set to a time during the expansion stroke. In the high speed region R2, the opening of the throttle valve 36 is adjusted so that the air-fuel ratio of the mixture in the main combustion chamber 26 approaches the stoichiometric air-fuel ratio, and the EGR valve 46 is fully closed to stop EGR.

[0054] Here, in the high speed region R2, the ignition order of the main spark plug 32 and the sub spark plug 62 is the same throughout the region, but the main ignition timing tm and the sub ignition timing ts are set so that the ignition phase difference dt, which is the amount of retardation of the sub ignition timing ts relative to the main ignition timing tm (i.e., the period in crank angles from the main ignition timing tm to the sub ignition timing ts), differs between the non-supercharging region B1 and the supercharging region B2. Specifically, the ignition phase difference dt in the supercharging region B2 (for example, the ignition phase difference dt at the operating point P2) is set smaller than the ignition phase difference dt in the non-supercharging region B1 (for example, the ignition phase difference dt at the operating point P1).

[0055] FIG. 9 is a graph showing the relationship between the engine load and each parameter in the high speed region R2. In detail, FIG. 9 shows the above relationship in the high speed region R2 where the engine speed is higher than the second speed N2. FIG. 10 is a graph showing the relationship between the engine speed and each parameter in the high speed region R2. In detail, FIG. 10 shows the above relationship in the high speed region R2 where the engine load is higher than the switching load Tq1. The top graphs in FIG. 9 and FIG. 10 are graphs showing the relationship between the engine load / engine speed and the ignition phase difference dt. The second graph from the top in FIG. 10 is a graph showing the relationship between the engine load / engine speed and the main ignition timing tm and the sub ignition timing ts. The graph in FIG. 9 shows the relationship between the engine load and each parameter when the engine speed is constant, and the graph in FIG. 10 shows the relationship between the engine speed and each parameter when the engine load is constant.

[0056] 9 and 10, in this embodiment, the main ignition timing tm in the supercharging region B2 is set to a timing that is more retarded than the main ignition timing tm in the non-supercharging region B1, and the sub-ignition timing ts in the supercharging region B2 is set to a timing that is more advanced than the sub-ignition timing ts in the non-supercharging region B1. This makes the ignition phase difference dt in the supercharging region B2 smaller than the ignition phase difference dt in the non-supercharging region B1.

[0057] In both the non-supercharging region B1 and the supercharging region B2, the main ignition timing tm is set to be more retarded (at the same engine speed) as the engine load increases, and more retarded (at the same engine load) as the engine speed increases. In both the non-supercharging region B1 and the supercharging region B2, the auxiliary ignition timing ts is set to be more advanced (at the same engine speed) as the engine load increases, and more advanced (at the same engine load) as the engine speed increases. In both the non-supercharging region B1 and the supercharging region B2, the ignition phase difference dt is set to a smaller value as the engine load increases and the engine speed increases.

[0058] The auxiliary ignition timing ts is set to advance in proportion to the engine load and engine speed throughout the entire high speed region R2. On the other hand, the main ignition timing tm is set to be significantly retarded when the engine speed (second engine speed N2) and engine load (switching load Tq1) at which the non-supercharging region B1 switches to the supercharging region B2 are exceeded, and the ignition phase difference dt also becomes significantly large when the engine speed and engine load at the above switching are exceeded.

[0059] In this embodiment, the main ignition timing tm and the sub ignition timing ts, which are set in advance for the engine speed and the engine load for each of the supercharging region B2 and the non-supercharging region B1 as described above, are stored in the ECU 100 as a map, and the main ignition timing tm and the sub ignition timing ts are set based on this map. Specifically, when the engine operating point is a point within the supercharging region B2, the ECU 100 extracts values ​​from the map of the main ignition timing tm and the map of the sub ignition timing ts for the supercharging region B2, and sets the extracted values ​​to the main ignition timing tm and the sub ignition timing ts. When the engine operating point is a point within the non-supercharging region B1, the ECU 100 extracts values ​​from the map of the main ignition timing tm and the map of the sub ignition timing ts for the non-supercharging region B1, and sets the extracted values ​​to the main ignition timing tm and the sub ignition timing ts.

[0060] FIG. 11 is a flowchart showing a control procedure executed by the ECU 100 for the supercharging motor 37, the main spark plug 32 and the sub spark plug 62 in the high speed range R2.

[0061] First, the ECU 100 reads various information (step S1). The ECU 100 reads the engine speed detected by the crank angle sensor SN5, the accelerator opening detected by the accelerator opening sensor SN6, and the like.

[0062] Next, the ECU 100 calculates a required torque, which is a torque required of the engine, that is, an engine load (step S2). The ECU 100 calculates the required torque (engine load) based on the engine speed and the accelerator opening degree read in step S1.

[0063] Next, the ECU 100 determines whether or not the engine operating point is in the high-speed region R2 (step S3). Specifically, the ECU 100 determines whether or not the current engine operating point is in the high-speed region R2 based on the engine speed read in step S1 and the required torque (engine load) calculated in step S2.

[0064] If the determination in step S3 is NO and the engine operating point is not a point within the high speed region R2, the ECU 100 ends the process (performs control of the low speed region R1). On the other hand, if the determination in step S3 is YES and the engine operating point is a point within the high speed region R2, the ECU 100 proceeds to step S4.

[0065] In step S4, ECU 100 determines whether or not the current engine operating point is within supercharging region B2, based on the engine speed and the engine load.

[0066] When the determination in step S4 is YES and the engine operating point is a point within the supercharging region B2, the ECU 100 drives the supercharging motor 37 to cause the supercharger 35 to perform supercharging (step S5). The ECU 100 also sets the main ignition timing tm and the sub ignition timing ts to timings for the supercharging region B2 (supercharging ignition timings) (step S6). In this embodiment, as described above, the ECU 100 extracts values ​​corresponding to the current engine speed and engine load from a map for the supercharging region B2 that is set in advance, and sets the main ignition timing tm and the sub ignition timing ts. As described above, the main ignition timing tm and the sub ignition timing ts set here are timings at which the ignition phase difference dt is relatively small (compared to the ignition phase difference dt in the non-supercharging region B1). After step S6, the process proceeds to step S9.

[0067] On the other hand, if the determination in step S4 is NO and the engine operating point is a point in the non-supercharging region B1, the ECU 100 stops the supercharging motor 37 to stop supercharging the supercharger 35 (step S7). The ECU 100 also sets the main ignition timing tm and the sub ignition timing ts to timings for the non-supercharging region B1 (non-supercharging ignition timings) (step S8). In this embodiment, as described above, the ECU 100 extracts values ​​corresponding to the current engine speed and engine load from a map for the non-supercharging region B1 that is set in advance, and sets the main ignition timing tm and the sub ignition timing ts. As described above, the main ignition timing tm and the sub ignition timing ts set here are timings at which the ignition phase difference dt is relatively large (compared to the ignition phase difference dt in the supercharging region B2). After step S8, the process proceeds to step S9.

[0068] In step S9, which follows step S6 or step S8, the ECU 100 executes ignition by the main spark plug 32 and the auxiliary spark plug 62. Specifically, the ECU 100 drives the main spark plug 32 so that ignition by the main spark plug 32 is performed at the main ignition timing tm set in step S6 or step S8, and then drives the auxiliary spark plug 62 so that ignition by the auxiliary spark plug 62 is performed at the auxiliary ignition timing ts set in step S6 or step S8.

[0069] (action, etc.) As described above, in the above embodiment, the main combustion chamber 26 and the auxiliary combustion chamber 60 are provided in the engine body 2, and the fuel consumption performance and exhaust gas performance can be improved by burning the mixture in these two combustion chambers 26, 60. Moreover, the injector 28, which is a device for injecting fuel, is provided only in the main combustion chamber 26 and not in the auxiliary combustion chamber 60, so that the structure of the engine system can be simplified and it is advantageous in terms of cost compared to the case where the injector 28 is provided in each of the main combustion chamber 26 and the auxiliary combustion chamber 60. Furthermore, since the injector 28 is disposed so as to inject fuel into the main combustion chamber 26, the fuel can be diffused more uniformly throughout the main combustion chamber 26. Therefore, appropriate HCCI combustion can be realized in the first region A1 of low speed and low load.

[0070] Here, in the configuration in which the injector 28 is provided only in the main combustion chamber 26 as described above, there is a risk that an appropriate amount of mixture (fuel) may not flow from the main combustion chamber 26 to the auxiliary combustion chamber 60. In contrast, in the above embodiment, in the high speed region R2, ignition is performed by the auxiliary spark plug 62 after ignition by the main spark plug 32. Therefore, the mixture can be pushed into the auxiliary combustion chamber 60 by utilizing the pressure increase in the main combustion chamber 26 caused by the combustion of the mixture in the main combustion chamber 26, and a shortage of the mixture in the auxiliary combustion chamber 60 can be prevented.

[0071] However, when the pressure in the main combustion chamber 26 is high, an excessive amount of mixture may flow into the auxiliary combustion chamber 60, causing the mixture to combust explosively in the auxiliary combustion chamber 60 and resulting in abnormal combustion accompanied by high-frequency pressure waves in the auxiliary combustion chamber 60 and the main combustion chamber 26.

[0072] In contrast, in the above embodiment, the ignition phase difference dt, which is the amount of retardation of the sub-ignition timing ts relative to the main ignition timing tm, is made smaller during operation in the supercharging region B2 where the pressure in the main combustion chamber 26 is high due to supercharging, than during operation in the non-supercharging region B1 where the pressure in the main combustion chamber 26 is relatively low without supercharging. If the ignition phase difference dt is made smaller, the period from when the mixture starts to flow into the sub-chamber 60 as the pressure in the main combustion chamber 26 rises to when the sub-ignition plug 62 ignites is shortened. As a result, when the ignition phase difference dt is small, the amount of mixture in the sub-chamber 60 at the time of ignition by the sub-ignition plug 62 is smaller than when the ignition phase difference dt is large. Therefore, by controlling the ignition phase difference dt as described above, according to the above embodiment, it is possible to prevent an excessive amount of mixture from flowing into the sub-chamber 60 in the supercharging region B2, and the mixture can be appropriately burned in the sub-chamber 60 and the main combustion chamber 26. Furthermore, a sufficient amount of air-fuel mixture can be caused to flow into the auxiliary combustion chamber 60 in the non-supercharging region B1, and the air-fuel mixture can be appropriately combusted in the auxiliary combustion chamber 60 and the main combustion chamber .

[0073] Furthermore, when the engine load, i.e., the required torque, is high, the heat energy generated in the main combustion chamber 26 increases, and the pressure in the main combustion chamber 26 also increases, promoting the inflow of the mixture from the main combustion chamber 26 to the auxiliary combustion chamber 60. In contrast, in the above embodiment, the ignition phase difference dt is made smaller as the engine load increases in both the supercharging region B2 and the non-supercharging region B1. This makes it possible to reliably prevent excessive inflow of the mixture into the auxiliary combustion chamber 60 in the supercharging region B2, and to reliably allow an appropriate amount of the mixture to flow into the auxiliary combustion chamber 60 in the non-supercharging region B1. Therefore, appropriate combustion of the mixture in the auxiliary combustion chamber 60 and the main combustion chamber 26 can be more reliably achieved in both the supercharging region B2 and the non-supercharging region B1.

[0074] In the above embodiment, the main ignition timing tm is set to a timing significantly retarded when the engine speed (second engine speed N2) and engine load (switching load Tq1) at which the non-supercharging region B1 switches to the supercharging region B2 are exceeded. Therefore, in the supercharging region B2 where knocking is likely to occur due to the increased pressure and temperature in the main combustion chamber 26 caused by supercharging, the increase in pressure and temperature in the main combustion chamber 26 near the compression top dead center can be suppressed, thereby preventing knocking.

[0075] (Modification) In the above embodiment, the main ignition timing tm in the supercharging region B2 is retarded more than the main ignition timing tm in the non-supercharging region B1, and the sub-ignition timing ts in the supercharging region B2 is advanced more than the sub-ignition timing ts in the non-supercharging region B1. However, only the sub-ignition timing ts may be set differently between the supercharging region B2 and the non-supercharging region B1, and the main ignition timing tm may be set to the same timing in the supercharging region B2 and the non-supercharging region B1. Conversely, only the main ignition timing tm may be set differently between the supercharging region B2 and the non-supercharging region B1, and the sub-ignition timing ts may be set to the same timing in the supercharging region B2 and the non-supercharging region B1.

[0076] In the above embodiment, a case has been described in which the supercharging region B2 is set to a region in which the engine speed is higher than the second speed N2 and the engine load is higher than the switching load Tq1, and the non-supercharging region B1 is set to another region of the high speed region R2, but the specific ranges of the supercharging region B2 and the non-supercharging region B1 are not limited to the above.

[0077] In the above embodiment, a case has been described in which the high speed region R2 where the engine speed is equal to or higher than a predetermined first speed N1 is divided into a supercharged region B2 and a non-supercharged region B1 and the ignition phase difference dt is made different. However, the region in which the ignition phase difference dt is made different by dividing the region into the supercharged region B2 and the non-supercharged region B1 is not limited to the high speed region R2 set as described above.

[0078] Furthermore, the control content of the low speed region R1 is not limited to the above.

[0079] The specific shape and dimensions of the cover member 64 of the auxiliary ignition unit 30 are not limited to those described above. Moreover, the number and dimensions of the communication holes 66 provided in the cover member 64 are not limited to those described above. Moreover, the mounting position of the auxiliary ignition unit 30 is not limited to those described above. For example, the auxiliary ignition unit 30 may be provided on the exhaust port 12 side with respect to the tip portion 28x of the injector 28.

[0080] Further, the detailed structure of the engine body 2, such as the number of cylinders, is not limited to the above. [Explanation of symbols]

[0081] 1 Engine System 2 Engine body 4 Intake passage 24 Piston 28 Injector (fuel injection device) 26 Main combustion chamber 30 Auxiliary ignition unit 32 Main spark plug (main ignition device) 35 Turbocharger 37 Supercharging motor 52 Cylinder block 54 Cylinder head 60 Antechamber 62 Auxiliary spark plug (auxiliary ignition device) 64 Cover material (partition wall) 66 Communication hole 100 ECU (control unit) B1 Non-supercharging area B2 Supercharging area

Claims

1. A cylinder block and a cylinder head which form a cylinder; A piston accommodated in the cylinder so as to be capable of reciprocating motion; a main combustion chamber defined by the cylinder block, the cylinder head, and the piston; an auxiliary chamber separated from the main combustion chamber by a partition wall and communicating with the main combustion chamber through a communication hole formed in the partition wall; a fuel injection device that injects fuel into the main combustion chamber; a main ignition device that ignites the air-fuel mixture in the main combustion chamber; an auxiliary ignition device that ignites the air-fuel mixture in the auxiliary chamber; a supercharger capable of supercharging the intake air introduced into the cylinder; a control device electrically connected to the fuel injection device, the main ignition device, and the auxiliary ignition device to output control electrical signals to each of the devices, the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition in a supercharging region where the engine load is higher than a predetermined switching load and supercharging by the supercharger is performed, and in a non-supercharging region adjacent to the supercharging region where the engine load is equal to or lower than the switching load and supercharging by the supercharger is not performed, when a retard amount of an auxiliary ignition timing, which is the ignition timing of the auxiliary ignition device, relative to a main ignition timing, which is the ignition timing of the main ignition device, is defined as an ignition phase difference, the control device controls the main ignition device and the auxiliary ignition device so that the ignition phase difference in the supercharging region is smaller than the ignition phase difference in the non-supercharging region, an air-fuel ratio of the mixture in the main combustion chamber in the supercharged region is set to be the same as an air-fuel ratio of the mixture in the main combustion chamber in the non-supercharged region.

2. 2. The engine system according to claim 1, The control device controls the main ignition device and the auxiliary ignition device so that the auxiliary ignition timing in the supercharging region is more advanced than the auxiliary ignition timing in the non-supercharging region.

3. 3. The engine system according to claim 1, The control device controls the main ignition device and the auxiliary ignition device so that the main ignition timing in the supercharging region is retarded more than the main ignition timing in the non-supercharging region.

4. A cylinder block and a cylinder head forming a cylinder; A piston accommodated in the cylinder so as to be capable of reciprocating motion; a main combustion chamber defined by the cylinder block, the cylinder head, and the piston; an auxiliary chamber separated from the main combustion chamber by a partition wall and communicating with the main combustion chamber through a communication hole formed in the partition wall; a fuel injection device that injects fuel into the main combustion chamber; a main ignition device that ignites the air-fuel mixture in the main combustion chamber; an auxiliary ignition device that ignites the air-fuel mixture in the auxiliary chamber; a supercharger capable of supercharging the intake air introduced into the cylinder; a control device electrically connected to the fuel injection device, the main ignition device, and the auxiliary ignition device to output control electrical signals to each of the devices, the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition in a supercharging region where supercharging by the supercharger is performed and in a non-supercharging region where supercharging by the supercharger is not performed and is adjacent to the supercharging region, an ignition phase difference is a retard amount of the auxiliary ignition timing, which is the ignition timing of the auxiliary ignition device, relative to the main ignition timing, which is the ignition timing of the main ignition device, and the control device controls the main ignition device and the auxiliary ignition device so that the ignition phase difference in the supercharging region is smaller than the ignition phase difference in the non-supercharging region and the ignition phase difference becomes smaller as the engine load in the supercharging region becomes higher.

5. A cylinder block and a cylinder head forming a cylinder; A piston accommodated in the cylinder so as to be capable of reciprocating motion; a main combustion chamber defined by the cylinder block, the cylinder head, and the piston; an auxiliary chamber separated from the main combustion chamber by a partition wall and communicating with the main combustion chamber through a communication hole formed in the partition wall; a fuel injection device that injects fuel into the main combustion chamber; a main ignition device that ignites the air-fuel mixture in the main combustion chamber; an auxiliary ignition device that ignites the air-fuel mixture in the auxiliary chamber; a supercharger capable of supercharging the intake air introduced into the cylinder; a control device electrically connected to the fuel injection device, the main ignition device, and the auxiliary ignition device to output control electrical signals to each of the devices, the control device causes the main ignition device to perform ignition and then the auxiliary ignition device to perform ignition in a supercharging region where supercharging by the supercharger is performed and in a non-supercharging region where supercharging by the supercharger is not performed and is adjacent to the supercharging region, an ignition phase difference is a retard amount of the auxiliary ignition timing, which is the ignition timing of the auxiliary ignition device, relative to the main ignition timing, which is the ignition timing of the main ignition device, and the control device controls the main ignition device and the auxiliary ignition device so that the ignition phase difference in the supercharging region is smaller than the ignition phase difference in the non-supercharging region and the ignition phase difference becomes smaller as the engine load in the non-supercharging region becomes higher.

Images