JP2023082331A - Controller of internal combustion engine - Google Patents

Abstract

To appropriately cope with oxygen deficiency causing start delay or start failure when starting a stopped internal combustion engine, to improve startability.SOLUTION: A controller of an internal combustion engine is configured to: when stopping an internal combustion engine that is being operated by firing, stop fuel injection and combustion to monitor the internal combustion engine by an electric motor; estimate an amount of air having flowed from a suction passage through a cylinder to an exhaust passage during motoring based on at least an engine speed and a motoring time; and determine whether the amount of air exceeds a threshold corresponding to the volume of the cylinder and exhaust passage.SELECTED DRAWING: Figure 2

Description

The present invention relates to a control device for controlling an internal combustion engine mounted on a vehicle or the like as a power source.

As is well known, when starting a stopped internal combustion engine, fuel is injected from an injector while executing motoring (or cranking) in which a crankshaft, which is the output shaft of the internal combustion engine, is rotationally driven by an electric motor. This is then combusted in the cylinder, accelerating the rotation of the crankshaft. This motoring for starting is performed when the internal combustion engine goes from the first explosion to the continuous explosion, and the rotation speed of the crankshaft, that is, the engine speed exceeds a judgment value determined according to the temperature of the cooling water of the internal combustion engine. , terminates assuming that a complete explosion has occurred (see, for example, the following patent document).

JP 2020-133592 A

When shutting down and shutting down an internal combustion engine, the rotation of the crankshaft may come to a standstill in a valve overlap condition in which both the intake and exhaust valves of one of the cylinders are open. A stop in the valve overlap state is relatively likely to occur in an in-line three-cylinder internal combustion engine.

When both the intake and exhaust valves of a certain cylinder are open while the internal combustion engine is stopped, the exhaust, that is, the combustion gas remaining in the exhaust passage when the internal combustion engine is stopped, is taken in from the exhaust passage side via the cylinder. Back flow may occur on the aisle side. This gas has a lower oxygen concentration than normal air (outside air). As a result, the concentration of oxygen in the intake passage leading to the cylinder decreases. In other words, the oxygen concentration in the intake passage does not become constant when the internal combustion engine is started.

After that, even if an attempt is made to restart the internal combustion engine, there is a concern that the amount of oxygen supplied to the combustion chamber of the cylinder will be insufficient, leading to unstable fuel combustion or misfiring, which in turn will lead to delayed start or poor start.

SUMMARY OF THE INVENTION An intended object of the present invention is to improve the startability of a stopped internal combustion engine by appropriately coping with oxygen deficiency that causes start delay or start failure.

In the present invention, when stopping an internal combustion engine that is operating with firing, fuel injection and combustion are stopped and the internal combustion engine is motored by an electric motor. A controller for an internal combustion engine is constructed that estimates the amount of air that has flowed based on at least engine speed and motoring time, and determines whether the amount of air exceeds a threshold corresponding to the volumes of the cylinders and the exhaust passage.

In particular, it is preferable to terminate the motoring and stop the rotation of the internal combustion engine on condition that the air amount exceeds a threshold value corresponding to the volume of the cylinder and the exhaust passage.

The amount of air can be estimated based on at least engine speed, motoring time, and intake pressure in the intake passage leading to the cylinder.

In a method for controlling an internal combustion engine according to the present invention, when stopping an internal combustion engine that is operating with firing, the steps of stopping fuel injection and combustion and motoring the internal combustion engine with an electric motor; estimating the amount of air that has flowed from the passage to the exhaust passage through the cylinder based on at least the engine speed and the motoring time; and determining whether the air amount exceeds a threshold corresponding to the volumes of the cylinder and the exhaust passage. perform the steps of:

Advantageous Effects of Invention According to the present invention, it is possible to appropriately deal with insufficient oxygen, which causes start delay or start failure when starting a stopped internal combustion engine, and to improve startability.

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

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. This internal combustion engine is a spark-ignited four-stroke reciprocating engine that uses gasoline or the like as fuel, and has a plurality of cylinders 1 (for example, an in-line three-cylinder engine, one of which is shown in FIG. 1). equipped. An injector 11 for injecting fuel toward the intake port is provided near the intake port of each cylinder 1 in the intake passage 3 . 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.

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, 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 exhausting exhaust guides exhaust gas generated as a result of combustion of fuel in the cylinder 1 from an 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 gas flowing through the exhaust passage 4 are installed upstream and downstream of the catalyst 41 in the exhaust passage 4 . Each of the air-fuel ratio sensors 43 and 44 may be an O ₂ sensor having an output characteristic that is non-linear with respect to the air-fuel ratio of the exhaust gas, or a linear A/F sensor having an output characteristic that is proportional to the air-fuel ratio of the exhaust gas. There may be.

The exhaust gas recirculation device 2 includes an external EGR passage 21 that communicates the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21 to open and close the EGR An EGR valve 23 for controlling the flow rate of EGR gas flowing through the passage 21 is included as an element. The inlet of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4 . The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

The internal combustion engine may be accompanied by a VVT (Variable Valve Timing) mechanism 5 capable of variably controlling the opening/closing timing of the intake valve and/or the exhaust valve of each cylinder 1 . The VVT mechanism 5 is, for example, a vane type that changes the rotation phase of the intake camshaft and/or the exhaust camshaft with respect to the crankshaft by hydraulic pressure (lubricating oil pressure) for opening and closing the intake and exhaust valves of each cylinder 1, or an electric motor. It is an electric type (motor drive VVT) that changes by The camshaft receives rotational torque from the crankshaft and rotates following the crankshaft. A winding transmission device (not shown) for transmitting rotational torque 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 and/or the exhaust valve.

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 engine torque or the engine load factor required for the internal combustion engine); An intake temperature/pressure signal d output from a temperature/pressure sensor that detects the intake air temperature and intake pressure in the continuous intake passage 3 (downstream of the throttle valve 32, particularly the surge tank 33 or the intake manifold 34), cooling of the internal combustion engine A cooling water temperature signal e output from a water temperature sensor that detects the water temperature, a signal f output from an air-fuel ratio sensor 43 that detects the air-fuel ratio of the exhaust gas on the upstream side of the catalyst 41, and an air-fuel ratio of the exhaust gas on the downstream side of the catalyst 41. A signal g output from an air-fuel ratio sensor 44 that detects the fuel ratio, a cam angle signal h output from a cam angle sensor at a plurality of cam angles of an intake camshaft or an exhaust camshaft of an internal combustion engine, 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 solenoid of the injector 11 , an opening operation signal k for the throttle valve 32 , and an opening operation signal k for the EGR valve 23 . It outputs a control signal m for valve timing to the VVT mechanism 5, and a control signal m for the valve timing.

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, learns the engine speed, and injects into the cylinder 1. Estimate the amount of air (fresh air). Then, based on the engine speed and intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of fuel injections for one expansion stroke of one cylinder 1), fuel injection pressure, ignition timing (one It determines various operating parameters such as the number of spark ignitions for one expansion stroke of cylinder 1), the required EGR rate (or EGR gas amount), valve timing, and the like. The ECU 0 applies various control signals i, j, k, l, m corresponding to the operating parameters through the output interface.

When the stopped internal combustion engine is started (either cold start or restart from idling stop), the ECU 0 controls an electric motor (starter (starter motor), motor generator, etc.) attached to the internal combustion engine. ), the fuel is injected from the injector 11 while performing motoring (cranking) to rotationally drive the crankshaft of the internal combustion engine by the electric motor, spark ignition is performed by the spark plug 12, and the fuel is burned. Let Motoring for starting ends when the internal combustion engine progresses from the first explosion to the continuous explosion, and the engine speed accelerates and rises to exceed the complete explosion judgment value. The complete explosion determination value can fluctuate depending on the temperature of the internal combustion engine and the like. Basically, the lower the cooling water temperature of the internal combustion engine at the start, the higher the complete explosion determination value.

On the other hand, when the internal combustion engine is being driven by firing, that is, by supplying fuel to cylinder 1 and burning it, the driver of the vehicle turns the ignition switch (or ignition key or power switch) from ON to ON. When it is operated to OFF, the operation of the internal combustion engine is stopped.

As shown in FIG. 2, the ECU 0 of the present embodiment stops the fuel injection from the injector 11 and the ignition combustion by the spark plug 12 (step S2) when stopping the internal combustion engine that has been running until then (step S1). ). After that, motoring is performed to rotationally drive the crankshaft of the internal combustion engine by the electric motor (step S3).

The motoring in step S3 maintains the engine rotation without fuel injection and combustion, thereby sending air containing no fuel component from the intake passage 3 to the exhaust passage 4 via the cylinder 1, and the cylinder 1 and the exhaust gas. This is a measure for scavenging and discharging the exhaust gas remaining in the passage 4 .

During the motoring in step S3, it is preferable to increase the opening of the throttle valve 32 on the intake passage 3 to a greater extent than the so-called opener opening to promote air circulation. Incidentally, the opener opening refers to the opening of the throttle valve 32 when power is not supplied to the throttle motor that drives the butterfly valve body of the electronic throttle valve 32 and no force is applied from the throttle motor to the valve body. , it may be fully closed to almost completely block the flow of intake air through the intake passage 3, or it may be slightly opened to allow the flow of intake air.

Further, during motoring in step S3, the opening/closing timing of the intake valve and/or the exhaust valve embodied by the VVT mechanism 5 is set to the initial position, that is, when the internal combustion engine is stopped or started, or when the engine is idling or at a low level close to idling. Return to the valve timing for load operation. For example, the opening/closing timing of the intake valve of cylinder 1 is returned to the most retarded timing to minimize the length of the valve overlap period during which both the intake valve and the exhaust valve are open.

The ECU 0 then estimates the amount of air that has flowed from the intake passage 3 to the exhaust passage 4 via the cylinder 1 during motoring in step S3 (step S4), and compares the calculated air amount with a threshold value (step S5). ).

In step S4, the ECU 0, based on the current engine speed and the length of the execution time of motoring in step S3, for example, according to the following equation, flows from the intake passage 3 into the exhaust passage 4 during motoring. Calculate the amount of air;
Inflow air amount [cc] = Engine speed [rpm] ÷ 60 [sec/min] ÷ 2 x Displacement specification value [cc] x Intake correction coefficient x Motoring execution time [sec]
Regarding the above formula, the "displacement specification value" is a series of cycles (intake stroke - compression stroke - expansion stroke - exhaust stroke of cylinder 1) with the opening and closing timing of the intake valve and/or exhaust valve returned to the initial position. is defined as one cycle). This displacement specification value is the sum of one minute for all cylinders included in the internal combustion engine (if it is a three-cylinder engine, the sum of three cylinders), and is obtained experimentally or set by adaptation at the design stage. is a constant. The displacement specification value is smaller than the geometric internal volume of cylinder 1, that is, the difference between the combustion chamber volume when the piston is at bottom dead center and the combustion chamber volume when it is at top dead center. In addition, the "intake correction coefficient" is obtained experimentally or is set by presuming (possible range) the intake air temperature and intake air pressure in the intake passage 3 during motoring in step S3. It is a constant set by step fitting.

Of course, the intake air temperature and intake pressure in the intake passage 3 during motoring in step S3 are actually measured with reference to the output signal d of the sensor, and are used to control the exhaust air from the intake passage 3 through the cylinder 1 during motoring. The amount of air that has flowed through passage 4 may be estimated. In that case, in step S4, the amount of inflow air is calculated according to the following formula;
Inflow air volume [cc] = Engine speed [rpm] ÷ 60 [sec/min] ÷ 2 x Displacement specification value [cc] x (Standard state temperature [K] x Measured intake pressure [kPa]) ÷ (Standard state Atmospheric pressure [kPa] x (Standard state temperature [K] + Measured intake air temperature [°C]) x Motoring execution time [sec]
Both "standard state temperature" and "standard state atmospheric pressure" are constants. The "standard state temperature" is, for example, 273.15, and the "standard state atmospheric pressure" is, for example, 101.3.

The threshold in step S5 to be compared with the amount of air obtained in step S4 means that when the internal combustion engine, which has been in firing operation until then, is stopped, exhaust gas with a lower oxygen concentration than normal air remains. is the volume of the possible area. namely;
Threshold [cc] = internal volume of cylinder [cc] + internal volume of exhaust passage [cc]
is.

The "cylinder internal volume" is the total value for 1 minute of all cylinders included in the internal combustion engine, and is a constant obtained experimentally or set by adaptation at the stage of design. The "internal volume of the exhaust passage" is a value corresponding to the entire internal volume of the exhaust passage 4 from the exhaust port to the end communicating with the outside, including the exhaust manifold 42, the catalyst 41, and the muffler downstream thereof. It is a constant obtained theoretically or set by adaptation at the design stage.

The fact that the condition of inflow air amount>threshold is established in step S5 means that the exhaust gas remaining in the exhaust passage 4 has been scavenged and replaced with air by the motoring in step S3. When the condition of step S5 is satisfied, the ECU 0 ends the motoring of the internal combustion engine (step S6) and stops the rotation of the internal combustion engine.

According to this embodiment, it is possible to accurately estimate the amount of exhaust gas with a low oxygen concentration remaining in the exhaust passage 4 when the operation of the internal combustion engine is stopped. Furthermore, it is possible to reliably scavenge and exhaust low-level exhaust gas remaining in the exhaust passage 4 . Therefore, it is possible to effectively avoid the problem that the exhaust gas flows backward from the exhaust passage 4 side to the intake passage 3 side while the internal combustion engine is stopped, and the oxygen concentration in the intake passage 3 decreases. Combustion is stable and no start delays or start failures occur.

It is not necessary to newly install an air-fuel ratio sensor ( _O2 sensor or linear A/F sensor) at the end of the exhaust passage 4, and the increase in cost can be avoided.

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 scope of the present invention.

0... Control unit (ECU)
REFERENCE SIGNS LIST 1 cylinder 11 injector 12 spark plug 2 exhaust gas recirculation (EGR) device 21 EGR passage 22 EGR cooler 23 EGR valve 3 intake passage 31 air cleaner 32 throttle valve 33 surge tank 34 intake Manifold 4 Exhaust passage 41 Catalyst 42 Exhaust manifold 43, 44 Air-fuel ratio sensor 5 Variable valve timing (VVT) mechanism a Vehicle speed signal b Crank angle signal c Accelerator opening signal d Intake temperature/intake pressure Signals e Cooling water temperature signal f, g Air-fuel ratio signal h Cam angle signal i Ignition signal j Fuel injection signal k Throttle valve opening operation signal l EGR valve opening operation signal m Valve timing Control signal o... Control signal for motor

Claims (4)

When stopping the internal combustion engine that is operating with firing,
stopping fuel injection and combustion and motoring the internal combustion engine with an electric motor;
estimating the amount of air flowing from the intake passage to the exhaust passage through the cylinder during the motoring based on at least the engine speed and the motoring time;
A control device for an internal combustion engine that determines whether or not the amount of air exceeds a threshold value corresponding to the volumes of the cylinder and the exhaust passage. 2. The control device for an internal combustion engine according to claim 1, wherein the motoring is terminated and the rotation of the internal combustion engine is stopped on condition that the air amount exceeds a threshold value corresponding to the volumes of the cylinders and the exhaust passage. . estimating the air amount based on at least the engine speed, the motoring time, and the intake pressure in the intake passage connected to the cylinder;
3. A control system for an internal combustion engine according to claim 1, wherein it is determined whether or not said air quantity exceeds a threshold value corresponding to the volume of said cylinder and said exhaust passage. When stopping the internal combustion engine that is operating with firing,
stopping fuel injection and combustion to motor the internal combustion engine with an electric motor;
estimating the amount of air that has flowed from the intake passage to the exhaust passage through the cylinder during the motoring, based on at least the engine speed and the motoring time;
and determining whether or not the air amount exceeds a threshold value corresponding to the volume of the cylinder and the exhaust passage.

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