JP2020133593A - Internal combustion engine - Google Patents

Abstract

To enhance vaporization of a fuel injected from an injector in a port injection type internal combustion engine.SOLUTION: An internal combustion is constituted so that an injector 112 for injecting a fuel in a direction A not directed to an intake port is disposed on an intake passage 3 connected to the intake port of a cylinder 1, and the fuel is injected from the injector 112 at a timing when an intake valve 13 of the cylinder 1 is opened and intake air once sucked to the cylinder 1 flows back near the injector 112 in the intake passage 3 after an intake bottom dead center of the cylinder 1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a port injection type internal combustion engine mounted on a vehicle or the like.

An internal combustion engine for a vehicle equipped with a variable valve timing mechanism capable of variably controlling the opening / closing timing of an intake valve of a cylinder is known (see, for example, the following patent documents).

One of the uses of the VVT mechanism is the realization of the Miller cycle (Atkinson cycle). That is, by setting the valve timing so that the intake valve opens at a timing later than the exhaust top dead center and / or closes at a timing later than the intake bottom dead center, the stroke length of the compression stroke is effectively expanded. Shorter than the stroke length of the stroke. The Miller cycle, in which the actual expansion ratio is larger than the actual compression ratio, is advantageous in that the amount of exhaust heat can be reduced and the thermal efficiency can be increased.

Japanese Unexamined Patent Publication No. 2014-125881

In a port-injection type internal combustion engine that injects fuel toward the intake port of the cylinder, port wetness occurs in which the liquid fuel injected from the injector adheres to the inner wall surface of the intake port and the umbrella part of the valve body of the intake valve. To do. Then, the fuel of the port wet may flow down into the combustion chamber of the cylinder in the liquid phase without vaporizing.

Fuels that maintain a liquid phase in the combustion chamber cause pool combustion or have a steam-burning appearance, producing particulate matter (Particulate Matter) or locally enriching the air-fuel ratio. , Causes deterioration of emissions.

An object of the present invention is to promote vaporization of fuel injected from an injector in a port injection type internal combustion engine.

In order to solve the above-mentioned problems, in the present invention, an injector for injecting fuel in a direction not directed to the intake port is provided on the intake passage connected to the intake port of the cylinder, and after the intake bottom dead point of the cylinder, the cylinder An internal combustion engine is configured to inject fuel from the injector at the timing when the intake valve is open and the intake air once sucked into the cylinder flows back in the vicinity of the injector in the intake passage.

According to the present invention, in a port injection type internal combustion engine, it is possible to promote vaporization of fuel injected from an injector.

The figure which shows the schematic structure of the internal combustion engine and the control device in one Embodiment of this invention. A side sectional view showing an intake passage, an injector, an intake port and a combustion chamber of the internal combustion engine of the same embodiment. The plan view which shows typically the intake passage, the injector, the intake port and the combustion chamber of the internal combustion engine of the same embodiment. The figure which shows the intake valve timing and fuel injection timing controlled by the control device of the same embodiment. The figure which shows the relationship between the intake valve timing controlled by the control device of the same embodiment, and a fuel injection amount.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine of the present embodiment is a spark-ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (for example, three cylinders, one of which is illustrated in FIG. 1). In a 4-stroke engine, a series of intake stroke-compression stroke-expansion stroke-exhaust stroke of cylinder 1 is set as one cycle.

The internal combustion engine of the present embodiment is a so-called port injection type, and is an injector 111 for supplying fuel to the cylinder 1 in the vicinity of the intake port connected to each cylinder 1 upstream of the intake valve 13 of each cylinder 1. , 112 are provided. In the present embodiment, fuel is injected from a plurality of injectors 111 and 112 into the same cylinder 1. As shown in FIG. 2, one of the injectors 111 points to the intake port of the target cylinder 1 as in the existing port injection type internal combustion engine. In other words, the injector 111 injects fuel toward the intake port, that is, injects fuel in a direction along the flow of intake air flowing through the intake passage 3 toward the cylinder 1.

On the other hand, the injector 112 does not direct the intake port of the target cylinder 1 unlike that in the existing port injection type internal combustion engine. The vector (directivity spindle) A in the direction in which the injector 112 injects fuel is opposite to the vector in the direction in which the injector 111 injects fuel, and does not overlap the intake port of the cylinder 1. After all, the injector 112 does not inject fuel into the intake port of cylinder 1. The vector A in the direction in which the injector 112 injects fuel contains a component α in a direction opposite to the flow of intake air flowing through the intake passage 3 toward the cylinder 1.

As shown in FIG. 3, a plurality of intake ports may be formed in each cylinder 1, and the intake port in which the injector 111 is arranged may be different from the intake port in which the injector 112 is arranged. Of course, both injectors 111 and 112 may be arranged for one intake port.

Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives an induction voltage generated by the ignition coil to cause a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally built in the coil case together with the igniter which is a semiconductor switching element.

The intake passage 3 for supplying intake air to the cylinder 1 takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream on the intake passage 3.

The exhaust passage 4 for discharging the exhaust gas from the cylinder 1 guides the exhaust gas generated by burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4.

The exhaust gas recirculation device 2 realizes a so-called high-pressure loop EGR, and is an external EGR that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3. The elements are a passage 21, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined position downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined position downstream of the throttle valve 32 in the intake passage 3, particularly a surge tank 33.

The internal combustion engine of the present embodiment is accompanied by a VVT mechanism 5 capable of changing the opening / closing timing of the intake valve 13 of each cylinder 1. For example, the VVT mechanism 5 changes the rotation phase of the camshaft that drives the intake valve 13 of each cylinder 1 with respect to the crankshaft by the hydraulic pressure (lubricating hydraulic pressure) or the electric motor, thereby advancing the opening / closing timing of the intake valve 13. / It is a retardation. The camshaft receives engine torque from the crankshaft, which is the output shaft of the internal combustion engine, and rotates in accordance with the crankshaft. A winding transmission device (not shown) for transmitting torque is interposed between the crankshaft and the camshaft. The winding transmission device includes a crank sprocket (or pulley) provided on the crankshaft side, a cam sprocket (or pulley) provided on the camshaft side, and a timing chain (or pulley) to be wound around these sprockets (or pulleys). , Timing belt) and. The VVT mechanism 5 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the camsprocket, thereby changing the opening / closing timing of the intake valve 13.

The internal combustion engine of the present embodiment can perform the Miller cycle operation by delaying the closing timing of the intake valve 13 by more than the intake bottom dead center (for example, 55 ° CA (crank angle) or more), if necessary. .. The valve opening timing of the intake valve 13 during the Miller cycle operation is retarded to a timing near the exhaust top dead center or slightly delayed from the exhaust top dead center (for example, about 5 ° CA).

The specific mode of the VVT mechanism 5 is arbitrary and is not uniquely limited. In addition to the one that advances / retards the rotation phase of the camshaft with respect to the crankshaft, the one that prepares a plurality of cams that open and drive the intake valve 13 and use those cams appropriately, and the lever ratio of the rocker arm is the electric motor. It is known that the intake valve 13 is an electromagnetic solenoid valve and the like, and the intake valve 13 is used as an electromagnetic solenoid valve, and it is permitted to select and adopt from these various mechanisms.

The ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine of the present embodiment, is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The ECU 0 may be a plurality of ECUs or controllers connected to each other so as to be communicable with each other via a telecommunication line such as CAN (Control Area Network).

The input interface of ECU0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft and the engine rotation speed, and an accelerator pedal. Accelerator opening signal c output from a sensor that detects the amount of depression or the opening of the throttle valve 32 as the accelerator opening (so to speak, the required engine load factor), output from the water temperature sensor that detects the cooling water temperature of the internal combustion engine The cooling water temperature signal d, the intake air temperature / intake pressure signal e output from the temperature / pressure sensor that detects the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and the brake pedal are depressed. The brake signal f output from a sensor (brake switch, master cylinder pressure sensor, etc.) that detects the amount of depression of the brake pedal, and the cam angle signal g output from the cam angle sensor at multiple cam angles of the intake camshaft. , The atmospheric pressure signal h or the like output from the atmospheric pressure sensor that detects the atmospheric pressure is input.

From the output interface of ECU0, the ignition signal i for the igniter of the spark ignition device, the fuel injection (valve opening) signal j1 for the injector 111, the fuel injection (valve opening) signal j2 for the injector 112, and the throttle valve 32. The opening operation signal k is output to the EGR valve 23, the opening operation signal l is output to the EGR valve 23, the intake valve timing control signal m is output to the VVT mechanism 5, and the like.

The processor of ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine via the input interface, and obtains the current operating range of the internal combustion engine [engine rotation speed, accelerator]. The opening degree (or the intake pressure in the surge tank 33, the amount of air (fresh air) sucked into the cylinder 1)] is known. Then, the required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR gas amount), intake valve 13 corresponding to the intake air amount. Determine various operating parameters such as the target opening / closing timing of. The ECU 0 applies various control signals i, j, k, l, and m corresponding to the operation parameters via the output interface.

The ECU 0 significantly delays the opening / closing timing of the intake valve 13 of the cylinder 1 via the VVT mechanism 5 in a relatively low rotation and / or low load operating region, and operates the internal combustion engine in the Miller cycle. FIG. 4 shows the opening / closing timing of the intake valve 13 and the exhaust valve 14 of the cylinder 1 at that time. In the figure, the dashed arrow E represents the period during which the exhaust valve 14 is open, and the solid arrow I represents the period during which the intake valve 13 is open. The intake valve 13 during the Miller cycle operation opens near the exhaust top dead center of the cylinder 1 or at a timing slightly delayed from the exhaust top dead center, and closes at a timing significantly delayed from the intake bottom dead center.

Therefore, a part of the required fuel injection amount required to achieve the required engine torque indicated by the accelerator opening operated by the driver is set to the original fuel injection timing t0, that is, the intake valve 13 of the cylinder 1. Is injected from one of the injectors 111 immediately before the valve is opened, at the same time as the valve is opened, or immediately after the valve is opened. Further, the rest of the required fuel injection amount is injected from the timing t2 during the period T1 until the intake valve 13 closes after the intake bottom dead center in the compression stroke of the cylinder 1, and from the other injector 112.

FIG. 5 shows the relationship between the opening / closing timing of the intake valve 13 embodied by the ECU 0 via the VVT mechanism 5 and the fuel injection amount injected from each of the two injectors 111 and 112. In the figure, the horizontal axis is the crank angle at the timing of closing the intake valve 13 opened for the intake stroke, and means that the valve closing timing of the intake valve 13 is retarded toward the right. The intake valve timing depends on the operating area of the internal combustion engine at that time. The vertical axis is the percentage of the amount of fuel injected from each injector 111, 112 to the supplied fuel injection amount. The broken line represents the ratio of fuel injection by the injector 112, and the solid line represents the ratio of fuel injection by the injector 111.

In a relatively low speed or low load operating region, the ECU 0 should open the injector 111 at the original timing t0 synchronized with the opening of the intake valve 13 in the intake stroke of the cylinder 1 and supply the injector 111 to the cylinder 1. Inject a part of the fuel. In addition, the injector 112 is opened at the timing t1 within the period T1 before the intake valve 13 is closed after the intake bottom dead center in the compression stroke of the cylinder 1, and the remaining portion of the fuel to be supplied to the cylinder 1 is injected.

During the period T1 from the intake bottom dead center to the closing of the intake valve 13, the piston that moves in the cylinder 1 from the intake bottom dead center to the compression top dead center is a part of the intake air once sucked into the cylinder 1. Is pushed back to the intake port and the intake passage 3 side. The injector 112 injects fuel in a direction along the backflow flow at the timing t1 when the intake air that is pushed out from the cylinder 1 and flows back through the intake passage 3 flows in the vicinity of the injector 112. The backflow intake air receives heat from the ceiling of the combustion chamber of the cylinder 1 and the cylinder bore to raise the temperature. Therefore, the liquid fuel ejected from the injector 112 is efficiently vaporized by the heat of the backflow intake air.

The fuel injected by the injector 112 at the timing t1 after the intake bottom dead center in the compression stroke is not sucked into the cylinder 1 during the same cycle of the cylinder 1 and is pushed out from the cylinder 1 to the intake passage 3. It mixes well and continues to stay near the intake port even after the intake valve 13 is closed. This fuel is sucked into the cylinder 1 after the cylinder 1 reaches the intake stroke of the next cycle and the intake valve 13 is opened again. That is, the fuel injected at the timing t1 after the intake bottom dead center is given a time grace for sufficient vaporization during the compression stroke, expansion stroke, and exhaust stroke of the same cycle.

The fuel injected from the injector 112 at the timing t1 after the intake bottom dead center in the compression stroke is sent to the cylinder 1 in the intake stroke of the next cycle together with the fuel injected from the original timing t0 injector 111 corresponding to the intake stroke of the next cycle. Be sucked. Then, the sum of those fuels matches the required fuel injection amount required to output the required engine torque.

The ECU 0 advances the opening / closing timing of the intake valve 13 via the VVT mechanism 5 as the engine speed increases or the engine load factor increases. As a result, the intake valve 13 opens at the timing before the exhaust top dead center of the cylinder 1, and the period of valve overlap in which the intake valve 13 and the exhaust valve 14 open at the same time is extended. In addition, the length of the intake valve 13 is shortened during the period T1 after the intake bottom dead center.

The ratio of the amount of fuel injected by the injector 111 to the amount of fuel injected by the injector 112 varies depending on the opening / closing timing of the intake valve 13. As a tendency, as the valve closing timing of the intake valve 13 is retarded, that is, as the valve opening period T1 after the intake bottom dead center becomes longer, the amount of fuel injected by the injector 112 increases, and the fuel injected by the injector 111 increases. The amount decreases. When the intake valve timing takes the latest retard position, the entire required fuel injection amount is injected from the injector 112 at timing t1, and fuel is not injected from the injector 111 at timing t0. When the intake valve timing is advanced by a predetermined crank angle or more from the latest retarded angle position, the entire required fuel injection amount is injected from the injector 111 at timing t0, and fuel is not injected from the injector 112 at timing t1.

In the present embodiment, an injector 112 that injects fuel in a direction A that does not direct the intake port is provided on the intake passage 3 connected to the intake port of the cylinder 1, and after the intake bottom dead point of the cylinder 1, the intake of the cylinder 1 is taken. An internal combustion engine that opens the injector 112 and injects fuel from the injector 112 only at the timing t1 when the valve 13 is open and the intake air once sucked into the cylinder 1 flows back in the vicinity of the injector 112 in the intake passage 3. Was configured.

According to the present embodiment, the exhaust heat of a part of the intake air that is once sucked into the cylinder 1 but is pushed out from the cylinder 1 at the initial stage of the compression stroke is effectively utilized to promote the vaporization of the fuel injected from the injector 112. It becomes possible. Then, the port wet amount can be reduced, and the liquid drop fuel droplets can be effectively suppressed from entering the combustion chamber of the cylinder 1. Therefore, pool combustion does not occur in the combustion chamber, and the amount of PM produced can be reduced. In addition, it is possible to avoid locally enriching the air-fuel ratio in the combustion chamber. As a result, it is possible to reduce emissions of harmful substances such as PM, HC, and CO to improve emissions. Promoting the vaporization of the injected fuel also contributes to improving the combustion efficiency of the air-fuel mixture.

The present invention is not limited to the embodiments described in detail above. The specific configuration of each part can be variously modified without departing from the spirit of the present invention.

The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 111, 112 ... Injector 13 ... Intake valve 3 ... Intake passage 5 ... Variable valve timing (VVT) mechanism b ... Crank angle signal c ... Accelerator opening signal g ... Cam angle signal j1, j2 ... Fuel injection signal m ... Intake valve timing control signal t0 ... Original fuel injection timing t1 ... Additional fuel injection timing

Claims (1)

An injector that injects fuel in a direction that does not direct the intake port is attached on the intake passage that connects to the intake port of the cylinder.
An internal combustion engine that injects fuel from the injector at the timing when the intake valve of the cylinder is open after the intake bottom dead center of the cylinder and the intake air once sucked into the cylinder flows back in the vicinity of the injector in the intake passage.

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