Engine System

Abstract

To suppress the knocking of an engine.SOLUTION: An engine system 1 is equipped with a combustion chamber 34 formed in a cylinder 30, an air injector 80 that opens a nozzle 82 to the combustion chamber 34 and jets air in a tangential direction of an inner peripheral surface 36 of the cylinder 30, and an air jet control portion 12a that controls the jetting of air by an air injector 80. The air jet control portion 12a makes the air injector 80 jet air before ignition, thereby collecting a rich mixture existing in the combustion chamber 34 in a center area of the combustion chamber 34, and forming a layer flow of air circulating along the inner peripheral surface 36 of the cylinder 30 between the center area and the inner peripheral surface 36 of the cylinder 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an engine system having an engine. [Background technology]

[0002] For example, Patent Document 1 discloses an example of an engine system that aims to prevent engine knocking. Note that knocking is also called knocking. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-3428 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, high-pressure air is injected into the combustion chamber in conjunction with the ignition timing of the air-fuel mixture, generating turbulence in the combustion chamber. As a result, the technology of Patent Document 1 aims to improve the combustion speed in the later stage of combustion and suppress knocking. However, even when the technology of Patent Document 1 is applied, knocking is not sufficiently suppressed. For this reason, it is desired to suppress knocking more appropriately.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS In view of the above, an object of the present invention is to provide an engine system capable of suppressing engine knock. [Means for solving the problem]

[0006] In order to achieve the above object, an engine system of the present invention includes a combustion chamber formed in a cylinder, an air booster pump that generates high-pressure air at a pressure higher than the pressure inside the combustion chamber, an air injector having a nozzle opening into the combustion chamber and that injects the high-pressure air generated by the air booster pump in a tangential direction of an inner peripheral surface of the cylinder, and an air injection control unit that controls injection of high-pressure air by the air injector, wherein the air injection control unit causes the air injector to inject high-pressure air after injection of fuel into the combustion chamber has been completed and during the compression stroke of the engine and before ignition, thereby collecting a rich mixture present in the combustion chamber in a central area of ​​the combustion chamber and forming a laminar flow of high-pressure air that flows along the inner peripheral surface of the cylinder between the central area and the inner peripheral surface of the cylinder. The intake amount, the fuel injection amount, and the supply amount of the high-pressure air through the air injector are adjusted so that the entire gas, which is a combination of the mixture in the central area and the high-pressure air flowing along the inner circumferential surface of the cylinder, is stoichiometric. .

[0007] Additionally, a plurality of air injectors may be arranged at equal intervals around the circumference of the cylinder. Effect of the Invention

[0008] According to the present invention, it is possible to suppress engine knocking. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an engine system according to this embodiment. [Diagram 2] FIG. 2 is a perspective plan view of the cylinder head and the combustion chamber as viewed from above the cylinder head. [Diagram 3] FIG. 3 is a diagram illustrating the supply timing of high-pressure air. [Figure 4] FIG. 4 is a diagram for explaining the state inside the combustion chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0011] 1 is a schematic diagram showing the configuration of an engine system 1 according to this embodiment. The engine system 1 is applied to, for example, a hybrid vehicle or an internal combustion engine vehicle. The engine system 1 includes an engine 10, an engine control unit 12, and an air intake unit 14. The engine 10 includes a cylinder block 20, a piston 22, a cylinder head 24, an intake valve 26, and an exhaust valve 28.

[0012] A plurality of cylinders 30 are formed in the cylinder block 20. Pistons 22 are slidably housed in the cylinders 30. The pistons 22 are connected to a crankshaft (not shown) through connecting rods 32. The crankshaft rotates in accordance with the reciprocating motion of the pistons 22.

[0013] The cylinder head 24 is provided on the cylinder block 20 on the opposite side to the crankshaft. The cylinder head 24 is disposed on the cylinder 30 so as to close the cylinder 30, and is connected to the cylinder block 20. A combustion chamber 34 is formed within the cylinder 30. Specifically, the combustion chamber 34 is surrounded by an inner circumferential surface 36 of the cylinder 30, a crown surface of the piston 22, and an inner surface of the cylinder head 24.

[0014] A gap 40 is formed between the cylinder block 20 and the cylinder head 24. The gap 40 is an annular space that is positioned so as to surround the periphery of the combustion chamber 34 and is in communication with the combustion chamber 34. A gasket 42 is disposed on the outside of the gap 40 between the cylinder block 20 and the cylinder head 24. The gasket 42 is sandwiched between the cylinder block 20 and the cylinder head 24. The gap 40 is closed by the gasket 42.

[0015] An intake port 50 and an exhaust port 52 are formed in the cylinder head 24. The intake port 50 and the exhaust port 52 communicate with the combustion chamber 34.

[0016] The intake valve 26 is provided in an intake port 50. A valve body of the intake valve 26 is located at the opening of the intake port 50 on the combustion chamber 34 side. The base end side of the intake valve 26 abuts against an intake cam 54. The intake cam 54 is connected to an intake camshaft 56. The intake camshaft 56 rotates in conjunction with the crankshaft. The intake cam 54 rotates in conjunction with the intake camshaft 56. The intake valve 26 opens and closes the intake port 50 in accordance with the rotation of the intake cam 54. When the intake port 50 is opened by the intake valve 26, air is sent into the combustion chamber 34 through the intake port 50.

[0017] The exhaust valve 28 is provided in the exhaust port 52. The valve body of the exhaust valve 28 is located at the opening of the exhaust port 52 on the combustion chamber 34 side. The base end side of the exhaust valve 28 abuts against an exhaust cam 58. The exhaust cam 58 is connected to an exhaust camshaft 60. The exhaust camshaft 60 rotates in conjunction with the crankshaft. The exhaust cam 58 rotates in conjunction with the exhaust camshaft 60. The exhaust valve 28 opens and closes the exhaust port 52 in accordance with the rotation of the exhaust cam 58. When the exhaust port 52 is opened by the exhaust valve 28, gas within the combustion chamber 34 is sent out through the exhaust port 52.

[0018] An injector 62 and a spark plug 64 are provided in the cylinder head 24. The injector 62 and the spark plug 64 are located near the central axis of the cylinder 30. The injector 62 is arranged with an injection port facing the combustion chamber 34. The injector 62 injects fuel such as gasoline into the combustion chamber 34 at a predetermined timing. The spark plug 64 is arranged with an electrode facing the combustion chamber 34. The spark plug 64 ignites the mixture of air and fuel at a predetermined timing to cause combustion. This combustion causes the piston 22 to reciprocate within the cylinder 30.

[0019] The engine control unit 12 is composed of a semiconductor integrated circuit including a central processing unit, a ROM in which programs and the like are stored, a RAM as a work area, and the like. The engine control unit 12 controls each part of the engine 10 by executing the programs. For example, the engine control unit 12 controls the fuel injection timing of the injector 62 and also controls the ignition timing of the spark plug 64. The engine control unit 12 also functions as an air injection control unit 12a by executing the programs. The air injection control unit 12a will be described in detail later.

[0020] The air supply section 14 includes an air booster pump 70 , an air common rail 72 , air piping 74 and an air injector 80 .

[0021] The air pressure booster pump 70 includes a pump main body 90 and a pressurizing mechanism 92. An inlet 94 of the pump main body 90 is connected to an inlet pipe 96. The inlet pipe 96 is connected to, for example, an intake pipe between an air cleaner (not shown) and a throttle valve. Air that has passed through the air cleaner is fed into the pump main body 90 through the inlet pipe 96. The inlet pipe 96 may be connected to a filter separate from the air cleaner of the intake pipe. In this case, air obtained separately from the intake air flowing through the intake pipe is fed into the pump main body 90 through the inlet pipe.

[0022] The pressurizing mechanism 92 pressurizes air introduced into a pressurizing chamber in the pump body 90 through an inlet pipe 96, and sends the pressurized air out from an outlet 98 of the pump body 90. Hereinafter, the pressurized air may be referred to as high pressure air, or simply as air.

[0023] Specifically, the pressurizing mechanism 92 includes a pump cam 100 and a plunger 102. The pump cam 100 is connected to the intake camshaft 56 and rotates in conjunction with the intake camshaft 56. The base end side of the plunger 102 abuts against the pump cam 100. The tip side of the plunger 102 is inserted into a pressurizing chamber in the pump body 90. The plunger 102 slides in conjunction with the rotation of the pump cam 100, and pressurizes the air in the pressurizing chamber.

[0024] The pressurizing mechanism 92 may be provided with a plurality of pump cams 100 having different shapes or sizes. In this case, the engine control unit 12 switches the pump cam 100 that contacts the plunger 102 according to the operating conditions such as the throttle opening. This makes it possible to change the degree of pressurization of the air or the pressurization timing. The engine control unit 12 may also advance or retard the intake camshaft 56. Since the pump cam 100 is connected to the intake camshaft 56, the phase is changed according to the advance or retard of the intake camshaft 56. This makes it possible to change the pressurization timing of the air.

[0025] It should be noted that the pump cam 100 is not limited to being linked to the intake camshaft 56. For example, the pump cam 100 may be connected to the exhaust camshaft 60. In this case, the timing of pressurizing the air may be changed depending on whether the exhaust camshaft 60 is advanced or retarded. The pump cam 100 may also be connected to a camshaft that is independent of the intake camshaft 56 and the exhaust camshaft 60. In this case, the timing of pressurizing the air may be changed depending on whether the independent camshaft is advanced or retarded.

[0026] The air common rail 72 is formed, for example, in a tubular shape, and is connected to an outlet 98 of the pump body 90. The air common rail 72 is disposed on the cylinder head 24 and extends across the multiple cylinders 30. The air common rail 72 can store the high-pressure air delivered from the outlet 98 of the pump body 90 while maintaining the pressure.

[0027] An opening 110 is formed on a side surface of the air common rail 72. An air pipe 74 is connected to the opening 110. The air pipe 74 is connected to an air injector 80 provided in the cylinder head 24. High pressure air stored in the air common rail 72 is supplied to the air injector 80 through the air pipe 74.

[0028] The air injector 80 is disposed above and alongside the gap 40. A nozzle 82 of the air injector 80 opens into the combustion chamber 34. Under the control of the air injection control unit 12a, the air injector 80 injects high-pressure air supplied from the air common rail 72 into the combustion chamber 34 at a predetermined timing. Specifically, the tip of the nozzle 82 is normally blocked by a plunger (not shown). The plunger is electromagnetically slidable by, for example, a solenoid. When a current flows through the solenoid and the plunger is attracted to the solenoid, the tip of the nozzle 82 opens and high-pressure air is injected.

[0029] 2 is a perspective plan view of the cylinder head 24 and the combustion chamber 34 as viewed from above the cylinder head 24. A plurality of air injectors 80 are arranged at equal intervals in the circumferential direction of the cylinder 30. For example, two air injectors 80 are arranged at 180 degree intervals. The number of air injectors 80 is not limited to two, and may be at least one. Furthermore, the air injectors 80 are not limited to being arranged at equal intervals in the circumferential direction of the cylinder 30, and may be arbitrarily distributed in the circumferential direction of the cylinder 30.

[0030] The high-pressure air generated by the air booster pump 70 is supplied to the combustion chamber 34 by the air injector 80. With this in mind, the pressure inside the combustion chamber 34 when the high-pressure air is supplied to the combustion chamber 34 is defined as the reference pressure. The air booster pump 70 generates high-pressure air at a pressure higher than the reference pressure. Because the pressure of the high-pressure air is higher than the reference pressure inside the combustion chamber 34, the air injector 80 can inject the high-pressure air into the combustion chamber 34.

[0031] 2, the air injector 80 is disposed so that the opening direction of the nozzle 82 is tangent to the inner circumferential surface 36 of the cylinder 30. Therefore, the air injector 80 injects air (i.e., high-pressure air) in the tangent direction to the inner circumferential surface 36 of the cylinder 30. Then, the injected air flows along the inner circumferential surface 36 of the cylinder 30 as shown by the arrow in FIG. 2.

[0032] In this way, in the peripheral area of ​​the combustion chamber 34 around the inner circumferential surface 36 of the cylinder 30, the high-pressure air flows along the inner circumferential surface 36 of the cylinder 30, so that it is possible to prevent turbulence from occurring in the air-fuel mixture in the combustion chamber 34. Furthermore, a laminar flow of the high-pressure air can be formed in the peripheral area around the inner circumferential surface 36. The action of the high-pressure air will be described in detail later.

[0033] 3 is a diagram for explaining the timing of supplying high-pressure air. The engine 10 repeats each stroke in the order of the intake stroke, compression stroke, expansion stroke, and exhaust stroke. The intake stroke is performed while the piston 22 moves from the top dead center to the bottom dead center. The compression stroke is performed after the intake stroke, while the piston 22 moves from the bottom dead center to the top dead center. The expansion stroke is performed after the compression stroke, while the piston 22 moves from the top dead center to the bottom dead center. Although not shown, the exhaust stroke is performed after the expansion stroke, while the piston 22 moves from the bottom dead center to the top dead center.

[0034] The engine 10 takes in air through the intake port 50 during the intake stroke. The engine control unit 12 injects fuel from the injector 62 during the intake stroke, as shown by the cross-hatched area A10 in Fig. 3. As a result, an air-fuel mixture is generated in the combustion chamber 34 by mixing the intake air during the intake stroke with the fuel from the injector 62. Timing TA in Fig. 3 indicates the timing at which the intake stroke switches to the compression stroke.

[0035] When the compression stroke begins, the mixture in the combustion chamber 34 is compressed as the piston 22 rises, and the in-cylinder pressure, which indicates the pressure inside the combustion chamber 34, increases. Then, at a predetermined timing TC in the latter part of the compression stroke, the engine control unit 12 causes the spark plug 64 to ignite the mixture.

[0036] Here, as indicated by the cross-hatched area A12 in FIG. 3, the air injection control unit 12a supplies air to the combustion chamber 34 by causing the air injector 80 to inject air (i.e., high-pressure air) before the mixture is ignited by the spark plug 64.

[0037] Specifically, the timing at which air supply by the air injector 80 starts is set between the timing at which fuel injection ends and the timing at which ignition occurs (i.e., timing TC). A predetermined time before the timing at which ignition occurs, the air injection control unit 12a opens the nozzle 82 of the air injector 80 to start injecting high-pressure air.

[0038] 3 indicates the timing at which the air injector 80 stops supplying air. The timing at which the air injector 80 stops supplying air is set to be before the ignition timing (i.e., timing TC). Note that it is sufficient that the air injector 80 starts supplying air before the ignition timing, and the air injector 80 may stop supplying air after the ignition timing.

[0039] In this way, the combustion chamber 34 contains the mixture of intake air and fuel during the intake stroke and the high-pressure air from the air injector 80. In the engine 10, the intake air amount, the fuel injection amount, and the supply amount of high-pressure air are adjusted so that the entire gas, which is the combination of the mixture of intake air and fuel and the high-pressure air, is stoichiometric. In other words, the mixture of intake air and fuel is made rich, with a higher fuel ratio than the stoichiometric mixture, taking into account the high-pressure air.

[0040] More specifically, a rich mixture of intake air and fuel has an equivalence ratio, which indicates the ratio of fuel to air, of approximately 1.1. In other words, if the amount of air that is stoichiometric is 100%, then 90% of the amount of air that is stoichiometric is intake air, and 10% of the amount of air that is stoichiometric is air supplied by the air injector 80.

[0041] The engine control unit 12 determines the amount of air and the amount of fuel injection that will achieve stoichiometry according to the operating conditions such as the throttle opening. The air injection control unit 12a derives the amount of high-pressure air based on the amount of air that will achieve stoichiometry. The air injection control unit 12a derives the amount of air per air injector 80 based on the derived amount of high-pressure air. The air injection control unit 12a determines the timing to start supplying high-pressure air to each air injector 80 based on the derived amount of air per injector. When the determined supply start timing arrives, the air injection control unit 12a causes each air injector 80 to start injecting high-pressure air.

[0042] As shown in Figure 3, when the air-fuel mixture is ignited, the flame propagates and the heat release rate in the combustion chamber 34 increases. The heat release rate peaks and then decreases. Timing TD in Figure 3 indicates the timing at which the heat release rate peaks. Timing TE in Figure 3 indicates the timing at which combustion spreads throughout the air-fuel mixture.

[0043] Figure 4 is a diagram explaining the state inside the combustion chamber 34. Figure 4A shows the state inside the combustion chamber 34 at timing TA in Figure 3. Figure 4B shows the state inside the combustion chamber 34 at timing TB in Figure 3. Figure 4C shows the state inside the combustion chamber 34 at timing TC in Figure 3. Figure 4D shows the state inside the combustion chamber 34 at timing TD in Figure 3. Figure 4E shows the state inside the combustion chamber 34 at timing TE in Figure 3.

[0044] 4A, the combustion chamber 34 is filled with a rich mixture of intake air and fuel at the timing TA. In this state, high-pressure air is then supplied into the combustion chamber 34 by the air injector 80.

[0045] The high-pressure air is injected in the tangential direction of the inner circumferential surface 36, and therefore does not generate turbulence in the combustion chamber 34. In addition, in the peripheral area of ​​the combustion chamber 34 around the inner circumferential surface 36, the injected high-pressure air gathers and flows along the inner circumferential surface 36. Then, the rich air-fuel mixture that is already present in the peripheral area around the inner circumferential surface 36 is relatively moved by this high-pressure air in a direction toward the central axis of the cylinder 30. As a result, the rich air-fuel mixture that is already present in the combustion chamber 34 is gathered in the central area of ​​the combustion chamber 34.

[0046] That is, by injecting air from the air injector 80, the air injection control unit 12a causes the rich air-fuel mixture present in the combustion chamber 34 to gather in the central area of ​​the combustion chamber 34, and forms a laminar flow of air that flows along the inner circumferential surface 36 between the central area and the inner circumferential surface 36. When the laminar flow of air is formed, a mixture layer made of a rich air-fuel mixture is formed in the central area as shown by the hatched area A20 in Fig. 4B, and an air layer made of laminar high-pressure air is formed in the peripheral area as shown by the cross-hatched area A22 in Fig. 4B. Almost no fuel is present in the air layer because the previously existing air-fuel mixture is replaced by the high-pressure air.

[0047] When the mixture is ignited after such a laminar air flow is formed, a flame is generated near the center of the combustion chamber 34, and the mixture starts to burn, as shown in the white area A24 in Fig. 4C. The generated flame then propagates through the mixture, and the combustion range of the mixture expands, as shown in the white area A24 in Fig. 4D. Then, the entire mixture that has gathered in the central area is burned, as shown in the white area A24 in Fig. 4E.

[0048] Here, since a laminar air layer is formed in the peripheral area of ​​the combustion chamber 34, the flame does not propagate to this peripheral area, and the combustion does not spread to the air layer. Therefore, in the engine system 1, the flame propagation distance or the combustion distance of the mixture can be substantially shortened by the radial thickness of the air layer. As a result, in the engine system 1, the entire mixture can be combusted early before the unburned mixture self-ignites, making it possible to suppress knocking.

[0049] Furthermore, a rich air-fuel mixture is collected in the mixture layer in the central area of ​​the combustion chamber 34. Therefore, in the engine system 1, the combustion speed of the air-fuel mixture in the central area can be made faster than that of a stoichiometric air-fuel mixture. As a result, in the engine system 1, the entire air-fuel mixture can be burned earlier, and knocking can be further suppressed.

[0050] Furthermore, in the engine system 1, the air-fuel mixture is collected in the central area, so that the air-fuel mixture can be combusted more reliably. Therefore, in the engine system 1, it is possible to reduce unburned loss, which is the air-fuel mixture remaining unburned.

[0051] In addition, the air layer formed in the peripheral area of ​​the combustion chamber 34 also functions as a heat insulating layer, suppressing the transfer of heat caused by the combustion of the air-fuel mixture to the inner circumferential surface 36 of the cylinder 30. Therefore, in the engine system 1, in addition to suppressing knocking, it is possible to reduce heat loss.

[0052] Furthermore, in the engine system 1, the air injector 80 injects air in a tangential direction of the inner circumferential surface 36 of the cylinder 30. Therefore, in the engine system 1, the generation of turbulence can be appropriately suppressed, and a laminar flow of air can be appropriately formed.

[0053] If turbulence occurs in the combustion chamber 34 when high-pressure air is supplied, the substantial flame propagation distance cannot be shortened and knock cannot be sufficiently suppressed. In contrast, in the engine system 1 of the present embodiment, a laminar air layer is formed to prevent turbulence from occurring, so that the substantial flame propagation distance can be appropriately shortened and knock in the engine 10 can be more appropriately suppressed.

[0054] Furthermore, in the engine system 1, a plurality of air injectors 80 are arranged at equal intervals in the circumferential direction of the cylinder 30. Therefore, in the engine system 1, a laminar air flow can be formed more appropriately compared to an embodiment in which the air injectors 80 are not arranged at regular intervals. Also, in the engine system 1, a laminar air flow can be formed more appropriately as the number of air injectors 80 is increased compared to an embodiment in which there is only one air injector 80.

[0055] Although the embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the claims, and it is understood that such examples also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0056] 1 Engine System 12a Air injection control unit 14 Air supply section 30 Cylinder 34 Combustion chamber 36 Inner surface 80 Air Injector 82 Nozzle

Claims

1. A combustion chamber formed in a cylinder; an air booster pump for generating high-pressure air having a pressure higher than the pressure inside the combustion chamber; an air injector having a nozzle that opens into the combustion chamber and injects high-pressure air generated by the air compression pump in a tangential direction of an inner circumferential surface of the cylinder; an air injection control unit that controls the injection of the high-pressure air by the air injector; Equipped with the air injection control unit causes the air injector to inject the high-pressure air after the injection of fuel into the combustion chamber is completed, during the compression stroke of the engine, and before ignition, thereby causing a rich mixture present in the combustion chamber to gather in a central area of ​​the combustion chamber, and forming a laminar flow of the high-pressure air flowing along the inner circumferential surface of the cylinder between the central area and the inner circumferential surface of the cylinder; an engine system in which the intake volume, the fuel injection volume, and the amount of high-pressure air supplied through the air injector are adjusted so that the entire gas, which is the combination of the mixture in the central area and the high-pressure air flowing along the inner surface of the cylinder, is stoichiometric.

2. The engine system according to claim 1 , wherein the air injector is arranged at equal intervals in a circumferential direction of the cylinder.

Images