JP6439989B2 - Flow control device for intake passage - Google Patents

Description

  The present invention relates to a flow control device for an intake passage, and more particularly to an intake passage having a curved portion in an engine that injects fuel into a combustion chamber during an intake stroke and / or a compression stroke according to an operating region of the engine. The present invention relates to a flow control device for an intake passage for controlling the flow of flowing intake air.

  Conventionally, improvement of engine combustion has been performed by applying a swirl flow such as a tumble flow or a swirl flow to the intake air flowing into the combustion chamber from the intake passage. For example, in a spark ignition type direct injection engine, there is one in which an air-fuel mixture is collected in a cavity by a tumble flow or transported to the vicinity of an electrode of a spark plug (for example, see Patent Document 1).

JP 2001-342836 A

  By the way, in an engine that injects fuel into the combustion chamber during the compression stroke, if the vortex due to the tumble flow remains up to the compression stroke, the temperature of the cylinder gas increases due to the convection heat transfer between the cylinder gas and the cylinder wall surface. Therefore, the vaporization of the fuel injected during the compression stroke is not sufficiently promoted, and the combustion stability cannot be improved.

  In addition, in an engine that performs compression ignition combustion by premixed compression self-ignition (Homogeneous-Charge Compression Ignition: HCCI), in order to ensure that the air-fuel ratio lean air-fuel mixture is self-ignited, the temperature of the in-cylinder gas is changed during the compression stroke. It needs to be high enough. However, as described above, if the vortex due to the tumble flow remains until the compression stroke, the convection heat transfer between the cylinder gas and the cylinder wall surface suppresses the temperature increase of the cylinder gas accompanying the pressure increase. The stability of ignition cannot be improved.

  The present invention has been made to solve the above-described problems of the prior art, and by controlling the flow of the intake air flowing through the intake passage, the vortex caused by the tumble flow during the compression stroke is suppressed, and during the compression stroke. An object of the present invention is to provide a flow control device for an intake passage that can promote the temperature rise of the in-cylinder gas and can sufficiently vaporize the fuel injected during the compression stroke to improve the combustion stability. To do.

In order to achieve the above object, a flow control device for an intake passage according to the present invention provides a curved portion in an engine that injects fuel into a combustion chamber during an intake stroke and / or a compression stroke, depending on an operating region of the engine. A flow control device for an intake passage for controlling a flow of intake air flowing through an intake passage having an intake air flowing along an outer wall surface of the bending portion and an intake air flowing along an inner wall surface of the bending portion in the intake passage The airflow generating means for generating an airflow in the direction of reducing the flow velocity difference between the engine and the engine operating region, when the engine operating region is an operating region in which compression ignition combustion is performed and fuel injection is performed during the compression stroke, the airflow generating unit is operated. by suppressing the tumble flow by, and having a control means for Ru abolished vortex by tumble flow during the compression stroke.
In the present invention configured as described above, an air flow is generated in a direction to reduce the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion of the intake passage and the intake air flowing along the inner wall surface of the curved portion. Since the airflow generating means is provided, the control means operates the airflow generating means when the engine operating area is an operating area where compression ignition combustion is performed and fuel injection is performed during the compression stroke. The flow velocity of the intake air flowing along the outer wall surface and the inner wall surface of the curved portion on the downstream side can be made substantially equal. Thereby, the tumble flow can be canceled by the flow in the direction opposite to the tumble flow in the combustion chamber, and the vortex due to the tumble flow is suppressed in the compression stroke. Accordingly, the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder during the compression stroke is suppressed, so that convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder is suppressed, and the temperature of the in-cylinder gas during the compression stroke is increased. The fuel injected during the compression stroke can be sufficiently vaporized to improve the combustion stability.

In the present invention, preferably, the air flow generation means generates an air flow in a direction toward the combustion chamber of the engine along the inner wall surface of the curved portion.
In the present invention configured as described above, the direction of the airflow generated by the airflow generating means can be matched with the direction of the intake air toward the combustion chamber, thereby reducing the intake air charging efficiency of the engine. The vortex caused by the tumble flow during the compression stroke can be suppressed, and the temperature rise of the in-cylinder gas during the compression stroke can be promoted.

In the present invention, preferably, the air flow generation means includes a plasma actuator disposed in the intake passage, and the plasma actuator includes a dielectric disposed along a wall surface of the intake passage, and an intake passage side of the dielectric. And an embedded electrode disposed on the opposite side of the exposed electrode across the dielectric, and the embedded electrode is disposed downstream of the exposed electrode in the direction of the airflow generated by the airflow generating means. Is done.
In the present invention configured as described above, when the operation region of the engine is an operation region in which fuel injection is performed during the compression stroke, the control means applies high-frequency and high-voltage alternating voltages during the intake stroke and the exposed electrodes and Applying to the embedded electrode induces a flow from the exposed electrode to the embedded electrode along the inner wall surface of the curved portion of the intake passage, and the intake air flowing along the outer wall surface of the curved portion and the inner wall surface of the curved portion The flow velocity difference from the intake air flowing along the can be reduced. Thereby, the eddy by the tumble flow during the compression stroke can be suppressed, and the temperature rise of the in-cylinder gas during the compression stroke can be promoted.

In the present invention, it is preferable that the air flow generation means reduce the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion and the intake air flowing along the inner wall surface of the curved portion in the intake passage. EGR gas inflow means for allowing EGR gas to flow into.
In the present invention configured as described above, the EGR gas is introduced in the direction of reducing the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion of the intake passage and the intake air flowing along the inner wall surface of the curved portion. Since the EGR gas inflow means is provided, the EGR gas is caused to flow from the EGR gas inflow means into the intake passage during the intake stroke when the engine operation area is an operation area in which fuel injection is performed during the compression stroke. The flow velocity of the intake air flowing along the outer wall surface and the inner wall surface of the bending portion on the downstream side of the bending portion can be made substantially equal. Thereby, the tumble flow can be canceled by the flow in the direction opposite to the tumble flow in the combustion chamber, and the vortex due to the tumble flow is suppressed in the compression stroke. Accordingly, the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder during the compression stroke is suppressed, so that convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder is suppressed, and the temperature of the in-cylinder gas during the compression stroke is increased. The fuel injected during the compression stroke can be sufficiently vaporized to improve the combustion stability.

In the present invention, it is preferable that the control means controls the airflow generation means so that the generated airflow becomes stronger as the engine speed is higher.
In the present invention configured as described above, as the intake air flow rate increases and the tumble flow becomes stronger as the engine speed increases, the air flow generated by the air flow generating means is strengthened and the tumble flow is reliably suppressed. be able to. As a result, vortexes caused by tumble flow during the compression stroke are suppressed regardless of changes in the engine speed, and convective heat transfer between the cylinder gas and the inner wall surface of the cylinder is suppressed. The temperature rise of the gas can be promoted.

  According to the flow control device of the intake passage according to the present invention, by controlling the flow of the intake air flowing through the intake passage, vortex caused by the tumble flow during the compression stroke is suppressed, and the temperature rise of the in-cylinder gas during the compression stroke is promoted. The fuel injected during the compression stroke can be sufficiently vaporized to improve the combustion stability.

1 is a schematic configuration diagram of an engine to which a flow control device for an intake passage according to an embodiment of the present invention is applied. It is a block diagram which shows the electrical structure regarding the flow control apparatus of the intake passage by embodiment of this invention. It is a conceptual diagram which shows the basic composition of the plasma actuator by embodiment of this invention. It is sectional drawing which shows arrangement | positioning of the plasma actuator in the intake passage by embodiment of this invention. 3 is an engine operation control map according to an embodiment of the present invention. It is sectional drawing which shows the in-cylinder flow of an engine in the case of the operation area | region of the engine by embodiment of this invention being an operation area | region where fuel injection is not performed during a compression stroke. It is sectional drawing which shows the operation | movement in the intake stroke of a plasma actuator in case the operating area | region of the engine by embodiment of this invention is an operating area | region where fuel injection is performed during a compression stroke. It is sectional drawing which shows arrangement | positioning of the EGR gas inflow means by the modification of embodiment of this invention.

  Hereinafter, a flow control device for an intake passage according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  First, an apparatus configuration of an engine according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram of an engine to which an intake passage flow control device according to an embodiment of the present invention is applied, and FIG. 2 shows an electrical configuration of the intake passage flow control device according to an embodiment of the present invention. It is a block diagram.

  In FIG. 1, reference numeral 1 denotes an engine. The engine 1 is a gasoline engine that is mounted on a vehicle and supplied with a fuel containing at least gasoline. The engine 1 includes a cylinder block 4 provided with a plurality of cylindrical cylinders 2 (in FIG. 1, only one cylinder 2 is shown, but for example, four cylinders 2 are provided in series), and this cylinder A cylinder head 6 disposed on the block 4 and an oil pan 8 disposed on the lower side of the cylinder block 4 and storing lubricating oil are provided. In each cylinder 2, a piston 14 connected to the crankshaft 12 via a connecting rod 10 is removably fitted and slidably inserted into the inner peripheral surface of the cylinder 2. The cylinder head 6, the cylinder 2, and the piston 14 define a combustion chamber 16. The shape of the combustion chamber 16 is not limited to the shape illustrated. For example, the shape of the top surface of the piston 14 and the shape of the ceiling surface of the combustion chamber 16 can be appropriately changed.

  The engine 1 is set to a relatively high geometric compression ratio of 15 or more for the purpose of improving the theoretical thermal efficiency and stabilizing the compression ignition combustion described later. In addition, what is necessary is just to set a geometric compression ratio suitably in the range of about 15-20.

  In the cylinder head 6, two independent intake ports 18 and two exhaust ports 20 are formed for each cylinder 2, and these intake ports 18 and exhaust ports 20 are formed on the combustion chamber 16 side. An intake valve 22 and an exhaust valve 24 for opening and closing the intake port and the exhaust port are provided.

  The cylinder head 6 is also provided with an injector 26 (fuel injection valve) for directly injecting fuel into the cylinder 2 for each cylinder 2. The injector 26 directly injects an amount of fuel into the combustion chamber 16 at an injection timing set according to the operating state of the engine 1 and according to the operating state of the engine 1.

  A spark plug 28 for forcibly igniting the air-fuel mixture in the combustion chamber 16 is attached to the cylinder head 6 for each cylinder 2. The spark plug 28 is disposed through the cylinder head 6 so as to extend downward from the center of the ceiling surface of the combustion chamber 16.

  Further, a cavity 14 a that is recessed downward is formed at the center of the top surface of the piston 14. The cavity 14a is formed so that the planar shape when viewed from the axial direction of the cylinder 2 is substantially circular. An injector 26 is disposed directly above the center of the cavity 14a, and a spark plug 28 is disposed in the recess of the cavity 14a.

  A plasma actuator 30 is disposed in the intake port 18. Details of the plasma actuator 30 will be described later.

  As shown in FIG. 1, an intake system 32 is connected to one side of the engine 1 so as to communicate with the intake port 18 of each cylinder 2. On the other hand, an exhaust system 34 that exhausts burnt gas (exhaust gas) from the combustion chamber 16 of each cylinder 2 is connected to the other side of the engine 1.

  An air cleaner 36 that filters intake air is disposed at the upstream end of the intake system 32, and a throttle valve 38 that adjusts the amount of intake air to each cylinder 2 is disposed downstream thereof. A surge tank 40 is disposed near the downstream end of the intake system 32. The intake system 32 on the downstream side of the surge tank 40 is an intake manifold 48 that branches for each cylinder 2, and the downstream end of each branch of the intake manifold 48 is connected to the intake port 18 of each cylinder 2. The intake air flow path from the outlet of the surge tank 40 to the intake port (that is, the intake manifold 48 and the intake port 18) corresponds to the intake passage in the present invention.

  The upstream portion of the exhaust system 34 is constituted by an exhaust manifold having an independent passage branched for each cylinder 2 and connected to the outer end of the exhaust port 20 and a collecting portion where the independent passages gather. A direct catalyst 42 and an underfoot catalyst 44 are connected downstream of the exhaust manifold in the exhaust system 34 as exhaust purification devices for purifying harmful components in the exhaust gas. Each of the direct catalyst 42 and the underfoot catalyst 44 includes a cylindrical case and, for example, a three-way catalyst disposed in a flow path in the case.

  The surge tank 40 in the intake system 32 and the portion of the exhaust system 34 upstream of the direct catalyst 42 are connected via an EGR passage 50 for returning a part of the exhaust gas to the intake system 32. . The EGR passage 50 includes a main passage 51 in which an EGR cooler 52 for cooling the exhaust gas with engine coolant is disposed. The main passage 51 is provided with an EGR valve 511 for adjusting the amount of exhaust gas recirculated to the intake system 32.

  The engine 1 is controlled by a powertrain control module (hereinafter referred to as PCM) 32. The PCM 46 includes a microprocessor having a CPU, a memory, a counter timer group, an interface, and a path connecting these units. This PCM 46 constitutes a controller.

As shown in FIGS. 1 and 2, detection signals from various sensors SW 1, SW 2, SW 4 to SW 18 are input to the PCM 46. Specifically, on the downstream side of the air cleaner 36, the PCM 46 includes a detection signal of an air flow sensor SW 1 that detects the flow rate of fresh air, a detection signal of an intake air temperature sensor SW 2 that detects the temperature of fresh air, and an EGR passage 50. The detection signal of the EGR gas temperature sensor SW4 that is disposed in the vicinity of the connection portion with the intake system 32 and detects the temperature of the external EGR gas, and the intake air just before flowing into the cylinder 2 attached to the intake port 18 The detection signal of the intake port temperature sensor SW5 that detects the temperature, the detection signal of the in-cylinder pressure sensor SW6 that is attached to the cylinder head 6 and detects the pressure in the cylinder 2, and the vicinity of the connection portion of the EGR passage 50 in the exhaust system 34 And the detection signals of the exhaust temperature sensor SW7 and the exhaust pressure sensor SW8 that detect the exhaust temperature and the exhaust pressure, respectively, And is disposed on the upstream side of the Tarisuto 42, a detection signal of the linear O ₂ sensor SW9 for detecting the oxygen concentration in the exhaust gas, it is arranged between the direct catalyst 42 and underfoot catalyst 44 and oxygen in the exhaust A detection signal from the lambda O ₂ sensor SW10 that detects the concentration, a detection signal from the water temperature sensor SW11 that detects the temperature of the engine coolant, a detection signal from the crank angle sensor SW12 that detects the rotation angle of the crankshaft 12, and the vehicle A detection signal of an accelerator opening sensor SW13 that detects an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown), detection signals of intake and exhaust cam angle sensors SW14 and SW15, and a common rail of the fuel supply system And a detection signal of a fuel pressure sensor SW16 that detects the fuel pressure supplied to the injector 26. When a detection signal of the hydraulic sensor SW17 for detecting the oil pressure of the engine 1, and the detection signal of the oil temperature sensor SW18 for detecting the oil temperature of the engine 1, are input.

  The PCM 46 determines the state of the engine 1 and the vehicle by performing various calculations based on these detection signals, and in response thereto, the injector 26, the spark plug 28, the plasma actuator 30, and various valves (throttle valve and EGR). A control signal is output to the actuator of the valve. Thus, the PCM 46 operates the engine 1. Although details will be described later, the plasma actuator 30 and the PCM 46 correspond to the flow control device of the intake passage in the present invention, and the PCM 46 functions as a control means for controlling the plasma actuator 30.

Next, the basic configuration of the plasma actuator 30 according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a conceptual diagram showing a basic configuration of the plasma actuator 30 according to the embodiment of the present invention.
As shown in FIG. 3, the plasma actuator 30 includes a thin-film dielectric 60 and an exposed electrode 62 and a buried electrode 64 arranged with the dielectric interposed therebetween. The exposed electrode 62 and the embedded electrode 64 are arranged with their positions shifted along the planar direction of the dielectric 60. In FIG. 3, the exposed electrode 62 and the embedded electrode 64 are arranged so as not to overlap in the normal direction of the dielectric 60, but the exposed electrode 62 and the embedded electrode 64 are arranged so as to partially overlap. May be. An AC power supply 66 is connected to the exposed electrode 62 and the embedded electrode 64.

When an AC voltage of a high frequency and a high voltage (for example, several kHz, several tens of kV) is applied to the exposed electrode 62 and the embedded electrode 64 by the AC power source 66, as shown in FIG. Plasma P is generated in the discharge space between. The plasma P generates a volume force from the exposed electrode 62 toward the embedded electrode 64, and a gas flow (indicated by an arrow in FIG. 3) along the surface of the dielectric 60 is induced by the volume force.
The magnitude of the volume force generated by the plasma P can be controlled by the voltage and frequency applied to the exposed electrode 62 and the embedded electrode 64.

  Next, the arrangement of the plasma actuator 30 according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional view showing the arrangement of the plasma actuator 30 in the intake passage.

  As shown in FIG. 4, the intake passage from the outlet of the surge tank 40 to the intake port 18 a includes an intake manifold 48 and an intake port 18. The intake manifold 48 is connected to the outlet of the surge tank 40 opened upward in FIG. 4, and is bent downward toward the inlet of the intake port 18 and connected to the inlet of the intake port 18.

  The intake port 18 extends from the connection portion with the intake manifold 48 in a direction inclined from the axial direction of the cylinder 2, and curves downward toward the intake port 18 a that opens upward on the ceiling surface of the combustion chamber 16 of the cylinder 2. And connected to the intake port 18a.

The plasma actuator 30 serves as an air flow generating means for generating an air flow in a direction to reduce the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion of the intake passage and the intake air flowing along the inner wall surface of the curved portion. It is provided along the inner wall surface of the curved portion 18 b of the port 18.
Specifically, as shown in FIG. 4, the dielectric 60 of the plasma actuator 30 is disposed along the inner wall surface of the curved portion 18 b on the upstream side of the curved portion 18 b of the intake port 18. The exposed electrode 62 is disposed on the intake passage side (upper side in FIG. 4) of the dielectric 60, and is embedded on the opposite side of the exposed electrode 62 (that is, outside the intake passage, lower side in FIG. 4) with the dielectric 60 interposed therebetween. An electrode 64 is embedded. The embedded electrode 64 is disposed so as to be positioned closer to the intake port 18a than the exposed electrode 62.

  Next, the operation of the plasma actuator 30 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an operation control map of the engine according to the embodiment of the present invention, and FIGS. 6 and 7 are cross-sectional views showing the operation during the intake stroke of the plasma actuator 30 according to the embodiment of the present invention.

  FIG. 5 shows an example of the operation control map of the engine 1. For the purpose of improving fuel efficiency and exhaust emission performance, the engine 1 is not subjected to ignition by the spark plug 28 in a low load region where the engine load is relatively low, and is premixed compression self-ignition (Homogeneous-Charge Compression) Compression ignition combustion by Ignition (HCCI) is performed. However, as the load on the engine 1 increases, in the compression ignition combustion, the combustion becomes too steep and causes problems such as combustion noise. Therefore, in the engine 1, in a high load region where the engine load is relatively high, compression ignition combustion is stopped and switched to forced ignition combustion (here, spark ignition combustion (SI)) using the spark plug 28. . As described above, the engine 1 is configured to switch between the HCCI mode in which the premixed compression self-ignition combustion is performed and the SI mode in which the spark ignition combustion is performed in accordance with the operation state of the engine 1, in particular, the load of the engine 1. Yes. However, the boundary line for mode switching is not limited to the illustrated example.

Further, as shown in FIG. 5, the HCCI region in which the engine 1 is operated in the HCCI mode is divided into a low load side CI operation region and a high load side CI operation region.
Among these, in the low load side CI operation region, the PCM 46 injects fuel from the injector 26 into the combustion chamber 16 during the intake stroke. In this way, by performing fuel injection during the intake stroke, it is possible to ensure a sufficient time for fuel to be mixed in the combustion chamber, to obtain a homogeneous air-fuel mixture, and to obtain high fuel efficiency and emission performance. .

  On the other hand, in the high load side CI operation region, the fuel injection amount increases as the required load increases. In this case, if fuel is injected during the intake stroke as in the low load side CI operation region, some fuel may ignite prematurely during the compression stroke, causing abnormal combustion. Thus, in the high load side CI operation region, the PCM 46 can prevent premature ignition by injecting fuel from the injector 26 into the combustion chamber 16 during the compression stroke.

  Further, the PCM 46 does not operate the plasma actuator 30 in the low load side CI operation region in which fuel injection is not performed during the compression stroke. On the other hand, in the high load side CI operation region in which fuel injection is performed during the compression stroke, the plasma actuator 30 is operated to generate an air flow in the direction toward the combustion chamber 16 along the inner wall surface of the curved portion 18b of the intake port 18. Let

FIG. 6 shows a flow state in the combustion chamber 16 and the intake port 18 near the bottom dead center of the intake stroke when the operation region of the engine 1 is the low load side CI operation region.
As described above, when the operation region of the engine 1 is the low load side CI operation region, the PCM 46 does not operate the plasma actuator 30. In this case, the flow velocity distribution of the intake air flowing through the intake port 18 is determined by the shape of the intake passage. Specifically, as shown by the size of the arrow in FIG. 6, the flow velocity of the intake air flowing along the outer wall surface of the bending portion 18b on the downstream side of the bending portion 18b is along the inner wall surface of the bending portion 18b. It is faster than the flow velocity of the intake air flowing through.

In this case, the intake air that has flowed into the combustion chamber 16 through the gap between the intake port 18a and the intake valve 22 proceeds in the direction of the piston 14 along the inner wall surface of the cylinder 2 on the exhaust port 20a side, and reaches the top surface of the piston. The tumble flow T is formed by changing the direction along the direction toward the intake port side end of the piston top surface and rising toward the intake port 18a. On the other hand, the intake air that has flowed into the combustion chamber 16 from the intake port 18a toward the side opposite to the exhaust port 20a is straight in the direction of the piston 14 along the inner wall surface of the cylinder 2 on the side opposite to the exhaust port 20a. Proceed to
As described above, the intake air flowing into the combustion chamber 16 from the intake port 18a along the outer wall surface of the curved portion 18b of the intake port 18 burns from the intake port 18a along the inner wall surface of the curved portion 18b. Since the flow velocity is faster than the intake air flowing into the chamber 16, the tumble flow T is stronger than the flow proceeding in the direction of the piston 14 along the inner wall surface on the side opposite to the exhaust port 20 a of the cylinder 2. Therefore, the fuel injected into the combustion chamber during the intake stroke is sufficiently mixed by the tumble flow T, and a homogeneous air-fuel mixture is obtained.

FIG. 7 shows a flow state in the combustion chamber 16 and the intake port 18 in the vicinity of the bottom dead center of the intake stroke when the operation region of the engine 1 is the high load side CI operation region.
As described above, when the operation region of the engine 1 is the high load side CI operation region, the PCM 46 operates the plasma actuator 30 during the intake stroke (that is, from the opening timing to the closing timing of the intake valve 22). . In this case, the flow velocity distribution of the intake air flowing through the intake port 18 is affected by the air flow generated by the plasma actuator 30 in addition to the shape of the intake passage. Specifically, when the operation region of the engine 1 is the high load side CI operation region, the PCM 46 applies a high frequency and high voltage AC voltage to the exposed electrode 62 and the embedded electrode 64 by the AC power source 66. Thereby, plasma is generated in the discharge space between the end face of the exposed electrode 62 and the dielectric 60, and the exposed electrode 62 is formed along the inner wall surface of the curved portion 18b of the intake port 18 by the volume force generated by the plasma. To the air inlet 18a is induced. That is, the intake air flowing along the inner wall surface of the bending portion 18b is accelerated, and the flow velocity difference between the intake air flowing along the outer wall surface of the bending portion 18b and the intake air flowing along the inner wall surface of the bending portion 18b is reduced. Flow occurs in the direction. As a result, on the downstream side of the bending portion 18b, the flow rates of the intake air flowing along the outer wall surface and the inner wall surface of the bending portion 18b are substantially equal.

In this case, the tumble flow T has almost the same strength as the flow proceeding in the direction of the piston 14 along the inner wall surface on the side opposite to the exhaust port 20a of the cylinder 2, and as shown in FIG. The two flows cancel each other, the tumble flow T is suppressed, and the vortex disappears in the compression stroke.
Thereby, the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder 2 during the compression stroke can be suppressed, and the convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder 2 is suppressed, so that the inside of the cylinder during the compression stroke is reduced. The temperature rise of the gas can be promoted.

  Further, when operating the plasma actuator 30 during the intake stroke in the high load side CI operation region, the PCM 46 controls the plasma actuator 30 so that the generated airflow becomes stronger as the rotational speed of the engine 1 is higher. For example, the PCM 46 controls the AC power supply 66 so that the voltage applied to the exposed electrode 62 and the embedded electrode 64 increases as the rotational speed of the engine 1 increases. As a result, the flow velocity of the intake air flowing through the intake port 18 increases as the rotational speed of the engine 1 increases, and the intake air flowing along the outer wall surface of the curved portion 18b and the intake air flowing along the inner wall surface of the curved portion 18b. When the difference in flow velocity increases, the air flow generated by the plasma actuator 30 increases accordingly, and the intake air flowing along the outer wall surface and the inner wall surface of the curved portion 18b on the downstream side of the curved portion 18b. The flow rates of are almost equal. Therefore, regardless of the engine speed, the tumble flow T has almost the same strength as the flow proceeding toward the piston 14 along the inner wall surface of the cylinder 2 opposite to the exhaust port 20a. Two flows cancel each other, the tumble flow T is suppressed, and the vortex disappears in the compression stroke.

Next, further modifications of the embodiment of the present invention will be described.
In the embodiment described above, an air flow is generated in the intake passage in a direction that reduces the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion of the intake passage and the intake air flowing along the inner wall surface of the curved portion. Although it has been described that the plasma actuator 30 is provided as the airflow generating means to be performed, an airflow generating means different from the plasma actuator may be used.

For example, as an air flow generation means, an EGR gas inflow that causes EGR gas to flow in a direction that reduces the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion of the intake passage and the intake air flowing along the inner wall surface of the curved portion. Means may be provided.
FIG. 8 is a cross-sectional view showing the arrangement of EGR gas inflow means according to a modification of the embodiment of the present invention. Specifically, the end of the EGR passage 50 on the intake system 32 side is connected not only to the surge tank 40 but also to the intake passage. As shown in FIG. 8, an end portion connected to the intake passage (hereinafter referred to as EGR gas inflow portion 53) is provided on the inner wall surface of the curved portion 18b on the upstream side of the curved portion 18b of the intake port 18. In this case, the opening 53a of the EGR gas inflow portion 53 is directed toward the intake port 18a.
The EGR gas inflow portion 53 is provided with an adjustment valve (not shown) for adjusting the inflow amount of EGR gas from the EGR gas inflow portion 53 to the intake passage.

  When the operation region of the engine 1 is the high load side CI operation region, the PCM 46 opens the adjustment valve, and causes EGR gas to flow into the intake passage from the EGR gas inflow portion 53. In this case, the flow velocity distribution of the intake air flowing through the intake port 18 is affected by the flow of EGR gas flowing from the EGR gas inflow portion 53 in addition to the shape of the intake passage. Specifically, when the operation region of the engine 1 is the high load side CI operation region, when the PCM 46 opens the adjustment valve, the EGR gas inflow portion 53 extends along the inner wall surface of the curved portion 18b of the intake port 18. The EGR gas flows from the opening 53a toward the intake port 18a. That is, the intake air flowing along the inner wall surface of the bending portion 18b is accelerated, and the flow velocity difference between the intake air flowing along the outer wall surface of the bending portion 18b and the intake air flowing along the inner wall surface of the bending portion 18b is reduced. Flow occurs in the direction. As a result, on the downstream side of the bending portion 18b, the flow rates of the intake air flowing along the outer wall surface and the inner wall surface of the bending portion 18b are substantially equal.

In this case, the tumble flow T has almost the same strength as the flow proceeding in the direction of the piston 14 along the inner wall surface opposite to the exhaust port 20a of the cylinder 2, so that these two flows cancel each other. The tumble flow T is suppressed, and the vortex disappears in the compression stroke.
Thereby, the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder 2 during the compression stroke can be suppressed, and the convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder 2 is suppressed, so that the inside of the cylinder during the compression stroke is reduced. The temperature rise of the gas can be promoted.

  In addition, as an airflow generation means, either the plasma actuator 30 or the EGR gas inflow portion 53 may be provided, or both may be provided.

In the above-described embodiment, the PCM 46 does not operate the plasma actuator 30 in the low load side CI operation region in which fuel injection is not performed during the compression stroke, and performs the high load side CI operation in which fuel injection is performed during the compression stroke. Although it has been described that the plasma actuator 30 is operated in the region, the plasma actuator 30 may be controlled based on more detailed conditions.
For example, the operation region of the engine 1 includes a first operation region in which fuel injection is not performed during the compression stroke, a second operation region in which fuel injection is performed by being divided into an intake stroke and a compression stroke, and only the compression stroke. PCM 46 does not operate plasma actuator 30 in the first operation region, operates plasma actuator 30 in the second operation region, and is divided into the third operation region in which fuel injection is performed in FIG. In the third operation region, the plasma actuator 30 may be operated so as to generate a stronger airflow than the second operation region.

  Next, effects of the above-described embodiment of the present invention and the flow control device for the intake passage according to the modification of the embodiment of the present invention will be described.

  First, a plasma actuator is used as an air flow generating means for generating an air flow in a direction to reduce the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion 18b of the intake port 18 and the intake air flowing along the inner wall surface of the curved portion 18b. 30 is provided, the PCM 46 operates the plasma actuator 30 during the intake stroke when the operation region of the engine 1 is a high load side CI operation region in which fuel injection is performed during the compression stroke. The flow velocity of the intake air flowing along the outer wall surface and the inner wall surface of the curved portion 18b on the downstream side of the curved portion 18b can be made substantially equal, and the tumble flow T and the flow in the direction opposite to the tumble flow T are canceled out. Accordingly, the tumble flow T is suppressed, and the vortex can be eliminated in the compression stroke. Thereby, since the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder 2 during the compression stroke can be suppressed, the convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder 2 can be suppressed, and the cylinder during the compression stroke can be suppressed. The temperature rise of the internal gas can be promoted, and the fuel injected during the compression stroke can be sufficiently vaporized to improve the combustion stability.

  Further, since the plasma actuator 30 generates an air flow in the direction toward the combustion chamber 16 of the engine 1 along the inner wall surface of the curved portion 18b, the direction of the air flow generated by the plasma actuator 30 is changed to the intake chamber. It is possible to match the direction of travel, thereby suppressing the vortex caused by the tumble flow during the compression stroke without reducing the charging efficiency of the engine 1 and promoting the temperature rise of the in-cylinder gas during the compression stroke. it can.

  Further, the dielectric 60 of the plasma actuator 30 is disposed along the wall surface of the intake port 18, the exposed electrode 62 is disposed on the intake port 18 side of the dielectric 60, and the embedded electrode 64 is an exposed electrode with the dielectric 60 interposed therebetween. 62 in the direction of generating an air flow so as to reduce the flow velocity difference between the intake air flowing along the outer wall surface of the bending portion 18b and the intake air flowing along the inner wall surface of the bending portion 18b. Since it is arranged downstream of the exposed electrode 62, when the operating region of the engine 1 is the high load side CI operating region, the PCM 46 applies high-frequency and high-voltage AC voltages during the intake stroke to the exposed electrode 62 and the embedded electrode. 64 is applied to induce a flow from the exposed electrode 62 toward the embedded electrode 64 along the inner wall surface of the curved portion 18b of the intake port 18. It is possible to reduce the flow rate difference between the outer flow along the wall surface inlet and intake air flowing along the inner wall surface of the curved portion 18b of 18b. Thereby, the eddy by the tumble flow during the compression stroke can be suppressed, and the temperature rise of the in-cylinder gas during the compression stroke can be promoted.

  In addition, an EGR gas inflow portion 53 that causes the EGR gas to flow in a direction that reduces the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion 18b of the intake port 18 and the intake air flowing along the inner wall surface of the curved portion 18b. Therefore, when the operating region of the engine 1 is a high load side CI operating region in which fuel injection is performed during the compression stroke, EGR gas is caused to flow from the EGR gas inflow portion 53 into the intake passage during the intake stroke. Thus, the flow velocity of the intake air flowing along the outer wall surface and the inner wall surface of the curved portion 18b on the downstream side of the curved portion 18b can be made substantially equal, and the tumble flow T and the direction facing the tumble flow T can be made. It is possible to cancel the tumble flow T by canceling the flow toward each other and to eliminate the vortex in the compression stroke. Thereby, since the flow velocity of the gas in the vicinity of the inner wall surface of the cylinder 2 during the compression stroke can be suppressed, the convective heat transfer between the in-cylinder gas and the inner wall surface of the cylinder 2 can be suppressed, and the cylinder during the compression stroke can be suppressed. The temperature rise of the internal gas can be promoted, and the fuel injected during the compression stroke can be sufficiently vaporized to improve the combustion stability.

  Further, since the PCM 46 controls the plasma actuator 30 so that the generated air flow becomes stronger as the rotational speed of the engine 1 is higher, the flow velocity of the intake air becomes higher and the tumble flow T becomes stronger as the rotational speed of the engine 1 increases. As it is, the air flow generated by the plasma actuator 30 can be strengthened and the tumble flow T can be reliably suppressed. This suppresses vortices due to the tumble flow T during the compression stroke regardless of changes in the engine speed, suppresses convective heat transfer between the cylinder gas and the inner wall surface of the cylinder 2, and The temperature rise of the in-cylinder gas can be promoted.

1 Engine (Engine body)
14 Piston 14a Cavity 16 Combustion chamber 18 Intake port 18a Intake port 18b Bending portion 20 Exhaust port 20a Exhaust port 30 Plasma actuator 40 Surge tank 46 PCM
48 Intake Manifold 50 EGR Passage 53 EGR Gas Inflow Portion 60 Dielectric 62 Exposed Electrode 64 Embedded Electrode P Plasma T Tumble Flow

Claims (5)

In an engine that injects fuel into a combustion chamber during an intake stroke and / or a compression stroke according to an engine operating region, the flow control device for the intake passage controls the flow of intake air flowing through the intake passage having a curved portion. And
An airflow generating means for generating an airflow in a direction to reduce a flow velocity difference between the intake air flowing along the outer wall surface of the curved portion and the intake air flowing along the inner wall surface of the curved portion in the intake passage;
When the operation region of the engine is an operation region in which compression ignition combustion is performed and fuel injection is performed during the compression stroke, the tumble flow is suppressed by operating the air flow generating means to suppress the tumble flow. and control means Ru abolished the vortex,
A flow control device for an intake passage.   2. The flow control device for an intake passage according to claim 1, wherein the air flow generation unit generates an air flow in a direction toward the combustion chamber of the engine along the inner wall surface of the curved portion. The airflow generation means includes a plasma actuator disposed in the intake passage,
The plasma actuator includes a dielectric disposed along a wall surface of the intake passage, an exposed electrode disposed on the intake passage side of the dielectric, and an opposite side of the exposed electrode across the dielectric. Embedded electrode,
3. The intake passage flow control device according to claim 1, wherein the embedded electrode is disposed downstream of the exposed electrode in a direction of an airflow generated by the airflow generating unit.   The air flow generation means flows EGR gas into the intake passage in a direction to reduce the flow velocity difference between the intake air flowing along the outer wall surface of the curved portion and the intake air flowing along the inner wall surface of the curved portion. The flow control device for an intake passage according to any one of claims 1 to 3, further comprising an EGR gas inflow unit to be operated.   The intake passage flow control device according to any one of claims 1 to 4, wherein the control means controls the air flow generation means so that the generated air flow becomes stronger as the engine speed is higher.

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