JP7218051B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for controlling a port-injection internal combustion engine that injects fuel from an injector toward an intake port connected to a cylinder.

A needle valve is often used for an injector that injects fuel to be combusted in a cylinder of an internal combustion engine (see, for example, Patent Document 1 below).

In a port-injection internal combustion engine, the timing of injecting fuel from an injector must match the opening timing of the intake valve of a target cylinder. Typically, the injector is opened to start fuel injection before the intake valve is opened, and the injector is closed to end the fuel injection substantially at the same time as the intake valve is opened. The optimum fuel injection timing also changes depending on the valve opening timing of the intake valve implemented by a variable valve timing mechanism (see, for example, Patent Document 2 below).

In some cases, the injector is left open even after the intake valve is opened. In a port-injection internal combustion engine, part of the fuel injected from the injector becomes liquid and adheres to the wall surface of the intake port, the head portion of the intake valve, and the like, causing port wetness. If the injector is opened after the intake valve is opened, the amount of port wetting can be reduced and the fuel can be reliably sucked into the combustion chamber of the cylinder.

JP-A-05-340320 JP 2016-094908 A

In a naturally aspirated engine or even in a turbocharged engine, when the supercharger is not supercharging, the air pressure downstream of the throttle valve in the intake passage falls below the atmospheric pressure. As is well known, intake negative pressure is generated when an intake valve of a cylinder opens and the cylinder draws in air. In the extremely light load operating region where the throttle valve is almost completely closed, the intake negative pressure becomes very large.

Under a situation where the intake negative pressure around the injector is enormous, if an operation to close the injector that had been open is executed, there will be a gap between the valve disc and the valve seat of the injector that should have been closed as a control. Fuel enters and causes unintended leakage of fuel from the nozzle hole of the injector. For example, coarse fuel particles are formed, or the valve disc does not sit on the valve seat and fuel continues to leak. The leaked fuel over-riches the air-fuel ratio of the air-fuel mixture filled in the cylinder, causing poor combustion and deterioration of emissions.

SUMMARY OF THE INVENTION It is an object of the present invention to avoid or reduce the problem of fuel being sucked out and leaking from a closed injector.

The present invention controls a port-injection internal combustion engine in which fuel is injected from an injector into an intake port connected to a cylinder. Even if the injector is controlled to close by opening the valve, if it is assumed that it will be larger than a predetermined value that will cause unintended fuel leakage from the nozzle hole of the injector , Compared to other cases , the injector valve closing timing is advanced when the engine speed, accelerator opening, and intake valve opening timing are the same, and the intake valve of the cylinder to which the injector is directed is opened. I have constructed a control device for an internal combustion engine that closes the injector before .

Advantageous Effects of Invention According to the present invention, it is possible to avoid or suppress the problem of fuel being sucked out of a closed injector and leaking in a port injection type internal combustion engine.

1 is a diagram showing a schematic configuration of an internal combustion engine and a control device according to an embodiment of the present invention; FIG. FIG. 2 is a flow chart showing an example of the procedure of processing executed by the control device for an internal combustion engine according to the embodiment according to a program;

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine according to this embodiment. The internal combustion engine in this embodiment is a spark-ignited four-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel toward the intake port is provided for each cylinder. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1 . The spark plug 12 receives an induced voltage generated by an ignition coil and induces spark discharge between a center electrode and a ground electrode. The ignition coil is integrally built into the coil case together with the igniter, which is a semiconductor switching element.

An intake passage 3 for supplying intake air 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 which is an intake throttle valve, a surge tank 33, and an intake manifold 34 are arranged in this order on the intake passage 3 from upstream.

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

Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage 4 are installed upstream and/or downstream of the catalyst 41 in the exhaust passage 4 . The air-fuel ratio sensors 43 and 44 may be linear A/F sensors having output characteristics proportional to the air-fuel ratio of the exhaust gas, or O ₂ sensors having non-linear output characteristics with respect to the air-fuel ratio of the exhaust gas. There may be.

The exhaust gas recirculation device 2 realizes so-called high-pressure loop EGR, and is an external EGR device 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. 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 to control the flow rate of EGR gas flowing through the EGR passage 21 are elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33. As shown in FIG.

The internal combustion engine may be accompanied by a VVT mechanism 5 capable of variably controlling the opening/closing timing of the intake valve of each cylinder 1 . The VVT mechanism 5 is of a vane type in which the rotational phase of the camshaft that drives the intake valve of each cylinder 1 with respect to the crankshaft is changed by hydraulic pressure (lubricating oil pressure), or an electric type in which the rotational phase is changed by an electric motor (motor drive VVT mechanism). ). As is well known, the camshaft receives rotational driving force from the crankshaft, which is the output shaft of the internal combustion engine, and rotates following the crankshaft. A winding transmission device (not shown) for transmitting rotational driving force is interposed between the crankshaft and the camshaft. The winding transmission device consists of 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 , timing belt). The VVT mechanism 5 changes the rotation phase of the camshaft with respect to the crankshaft by rotating the camshaft relative to the cam sprocket, thereby changing the opening/closing timing of the intake valve.

Of course, the specific aspect of the VVT mechanism 5 is arbitrary and is not uniquely limited. In addition to advancing/retarding the rotational phase of the camshaft with respect to the crankshaft, there are also those that prepare multiple cams that drive the opening of the intake valve and use these cams appropriately, and those that change the lever ratio of the rocker arm via an electric motor. There are known mechanisms in which the intake valve is changed by an electromagnetic solenoid valve, etc., and it is permitted to select and adopt from among these various mechanisms.

An ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine according to the present embodiment, is a microcomputer system having a processor, memory, input interface, output interface, and the like. The ECU 0 may be formed by connecting a plurality of ECUs or controllers so as to be able to communicate with each other via electric communication lines such as CAN (Controller Area Network).

The input interface of the ECU 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine and the engine speed. , an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as the accelerator opening (so to speak, the required engine load factor), the intake passage 3 (particularly, the surge tank 33 ), an intake air temperature and pressure signal d output from an intake air temperature and pressure sensor that detects the intake air temperature and pressure, and a cooling water temperature signal that is output from a water temperature sensor that detects the temperature of the cooling water indicating the temperature of the internal combustion engine. e, an air-fuel ratio signal f output from an air-fuel ratio sensor 43 that detects the air-fuel ratio of the exhaust gas upstream and/or downstream of the catalyst 41 in the exhaust passage 4, and a plurality of cam angles of the intake camshaft of the internal combustion engine. A cam angle signal g output from a cam angle sensor, an atmospheric pressure signal h output from an atmospheric pressure sensor for detecting atmospheric pressure, and the like are input.

From the output interface of the ECU 0, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an opening operation signal for the EGR valve 23. It outputs a signal l, a control signal m for the intake valve timing to the VVT mechanism 5, and the like.

The processor of the ECU 0 interprets and executes a program stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various types of information a, b, c, d, e, f, g, and h necessary for controlling the operation of the internal combustion engine through an input interface, and generates a request corresponding to the amount of intake air charged into the cylinder 1. Operation parameters such as fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR amount (or EGR rate), intake valve opening/closing timing, etc. are determined. The ECU 0 applies various control signals i, j, k, l, m corresponding to the operating parameters through the output interface.

In addition, when starting the stopped internal combustion engine (it may be a cold start or restart from idling stop), a control signal o is input to the electric motor (starter motor or ISG (Integrated Starter Generator)). Then, cranking is performed by rotating the crankshaft by the electric motor. Cranking is defined as complete explosion of the internal combustion engine when the internal combustion engine goes from the first explosion to the continuous explosion, and the engine speed exceeds a threshold determined according to the temperature of the internal combustion engine (especially the temperature of the cooling water). Consider and exit.

When determining the fuel injection amount, the ECU 0 first obtains the amount of air taken into the cylinder 1, and then, according to the intake air amount, determines the fuel injection amount that can realize the stoichiometric air-fuel ratio or an air-fuel ratio in the vicinity thereof. Determine the basic quantity TP. Needless to say, the basic injection amount TP is proportional to the amount of intake air, and increases as the amount of intake air increases. The intake air amount is estimated based on the current engine speed and the intake pressure in the surge tank 33 . If necessary, the estimated value can be corrected according to intake air temperature, atmospheric pressure, and the like. Of course, if an airflow meter is installed in the intake passage 3, it is possible to directly measure the amount of intake air via the airflow meter.

Next, this basic injection amount TP is corrected by a correction coefficient FAF that is determined according to the output signals f and g of the air-fuel ratio sensors 43 and 44 . The correction coefficient FAF is a positive number that increases and decreases around 1, and decreases when the air-fuel ratio detected via the air-fuel ratio sensors 43, 44 is richer than the stoichiometric air-fuel ratio. increases when the air-fuel ratio detected via is leaner than the stoichiometric air-fuel ratio.

Furthermore, the final fuel injection time (energization time for the injector 11) T is calculated in consideration of various correction coefficients K determined depending on the situation and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T = TP x FAF x K + TAUV
becomes. Then, the signal j is input to the injector 11 for the fuel injection time T to open the injector 11 and inject the fuel. The air-fuel ratio of the air-fuel mixture filled in cylinder 1, which is finally realized by the fuel injection amount T determined by the ECU 0, is not always the stoichiometric air-fuel ratio, and may become richer than the stoichiometric air-fuel ratio. If so, it may be leaner than the stoichiometric air-fuel ratio.

The normal fuel injection timing, that is, the opening/closing timing of the injector 11 is matched with the opening timing of the intake valve of the target cylinder 1 to which fuel is to be supplied. Typically, the injector 11 is opened before the intake valve is opened to start fuel injection, and the injector is closed substantially at the same time as the intake valve is opened to end the fuel injection. The optimum fuel injection timing changes depending on the valve opening timing of the intake valve embodied by the VVT mechanism 5 .

In some cases, the opening/closing timing of the intake valve is delayed so that the injector 11 is kept open without being closed even after the intake valve is opened.

The injector 11 is located downstream of the throttle valve 32 in the intake passage 3 . The atmospheric pressure around the nozzle hole of the injector 11 becomes lower than the atmospheric pressure due to the intake negative pressure. When the internal combustion engine is started, idling, or in a very light load operating region close to idling, the throttle valve 32 is almost completely closed, and the intake negative pressure generated by the intake of air into the cylinder 1 becomes significantly large. .

In a situation where the intake negative pressure around the injector 11 is enormous (the air pressure is significantly reduced), when the injector 11 is opened and closed, the valve is closed as a control. Fuel enters between the valve body and the valve seat of the injector 11, which is supposed to be there, causing unintended fuel leakage from the nozzle hole of the injector. Leakage of fuel is never preferable because it causes an overrich air-fuel ratio and causes poor combustion, poor start-up if the internal combustion engine is started, or deterioration of emissions.

In order to avoid or suppress the problem of fuel being sucked out and leaking from the closed injector 11, the ECU 0 of the present embodiment, as shown in FIG. 60 kPa, which means that the ambient pressure around the injector 11 is 60 kPa below atmospheric pressure, if it is assumed that the ambient pressure of the injector 11 is lower than the predetermined value) (Step S1), the valve closing timing of the injector 11 is advanced compared to the case otherwise (Step S2).

In step S1, based on the transition of the intake pressure downstream of the throttle valve 32 actually measured via the intake air temperature/intake pressure sensor, it is determined whether the intake negative pressure becomes larger than a predetermined value by opening the intake valve of cylinder 1. It may be determined whether or not, the current operating range of the internal combustion engine [engine speed, accelerator opening (or engine torque, air amount filled in cylinder 1 or fuel injection amount, etc.)] and atmospheric pressure, etc. , it may be estimated whether or not the opening of the intake valve causes the intake negative pressure to become greater than a predetermined value. In the latter, the memory of the ECU 0 stores in advance map data defining the relationship between the operating range of the internal combustion engine, the atmospheric pressure, etc., and the estimated value of the intake negative pressure. Then, the ECU 0 searches the map using the current operating range and the atmospheric pressure as keys, obtains an estimated value of the intake negative pressure, and determines whether or not the estimated value exceeds a predetermined value.

To surely close the injector 11 before opening the intake valve of the cylinder 1 to which the injector 11 is directed under the condition that the intake negative pressure around the injector 11 becomes larger than a predetermined value. (Step S2). On the other hand, under the condition that the intake negative pressure around the injector 11 does not exceed a predetermined value, the injector 11 is closed at normal timing (step S3). Under the condition that other conditions such as the engine speed, the degree of accelerator opening, and the opening timing of the intake valve are the same, the closing timing of the injector 11 in step S2 is advanced from the normal closing timing of the injector 11 in step S3. corner.

After determining the valve closing timing of the injector 11 in this way, the ECU 0 determines the valve opening timing of the injector 11 so that the required fuel injection time T can be realized.

According to this embodiment, in a port injection type internal combustion engine, it is possible to avoid or suppress the problem that fuel leaks from the closed injector 11 and the air-fuel mixture filled in the cylinder 1 becomes excessively rich. Therefore, it is possible to prevent poor combustion and poor starting caused by this, and to avoid deterioration of emissions.

It should be noted that the present invention is not limited to the embodiments detailed above. Various modifications can be made to the specific configuration of each part, the procedure of processing, and the like without departing from the spirit of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1... Cylinder 11... Injector 3... Intake passage 32... Throttle valve 5... Variable valve timing (VVT) mechanism b... Crank angle signal c... Accelerator opening signal d... Intake temperature/intake pressure signal h... Atmospheric pressure signal j... Fuel injection signal

Claims (1)

A port injection type internal combustion engine that injects fuel from an injector toward an intake port connected to a cylinder,
Even if the intake negative pressure around the injector opens the intake valve of the cylinder to which the injector is directed, even if the injector is controlled to close, unintended fuel leakage from the nozzle hole of the injector may occur. If it is assumed that it will be larger than a predetermined value that causes the occurrence ,
Compared to other cases , the injector valve closing timing is advanced when the engine speed, accelerator opening, and intake valve opening timing are the same, and the intake valve of the cylinder to which the injector is directed is opened. A control device for an internal combustion engine that causes the injector to close earlier .

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