JP2020133592A - Controller of internal combustion engine - Google Patents

Abstract

To further enhance stability of starting of an internal combustion engine.SOLUTION: A controller of internal combustion engine is configured to expand the opening of a throttle valve in a case where an oxygen concentration in an intake passage at startup is low compared to the opening in a case where the oxygen concentration in the intake passage at startup is higher, by correcting the opening of the throttle valve at the time of starting the internal combustion engine according to at least one of the temperatures in an engine compartment at the time when the internal combustion engine is stopped and at startup after that, the elapsed time from the stop to the start of the internal combustion engine, and the temperatures of cooling water at the time when the internal combustion engine is stopped and at startup after that.SELECTED DRAWING: Figure 3

Description

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

As is well known, when starting a stopped internal combustion engine, the crankshaft, which is the output shaft of the internal combustion engine, is rotationally driven by an electric motor, fuel is injected from an injector, and this is burned in the cylinder to burn the crankshaft. Perform cranking to accelerate rotation. Cranking is 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 the judgment value determined according to the temperature of the cooling water of the internal combustion engine, the explosion is completed. It is considered as and ends.

It is also known that the fuel injection amount when starting an internal combustion engine is adjusted based on the temperature of the cooling water at the time of starting the internal combustion engine (see, for example, the following patent documents).

Japanese Unexamined Patent Publication No. 2014-202176

The oxygen concentration in the intake passage at the time of starting the internal combustion engine is not constantly constant. If the rotation of the internal combustion engine stops while the intake valve and exhaust valve of any cylinder are open, exhaust gas is discharged from the exhaust passage side to the intake passage side via the cylinder during the stop period. It can flow backwards. Then, the oxygen concentration in the intake passage is lowered. Nevertheless, if the throttle valve opening and fuel injection amount are set to normal when starting the internal combustion engine, the amount of oxygen supplied to the combustion chamber of the cylinder will be insufficient, resulting in destabilization of fuel combustion or misfire. There is a concern that it may lead to a start delay or a start failure.

The present invention has been made by paying attention to the above problems for the first time, and an object of the present invention is to improve the starting stability of an internal combustion engine.

In order to solve the above-mentioned problems, in the present invention, the temperature in the engine compartment when the internal combustion engine is stopped and when it is started thereafter, the elapsed time from the stop to the start of the internal combustion engine, when the internal combustion engine is stopped and when it is started thereafter. By correcting the opening of the throttle valve at the time of starting the internal combustion engine according to at least one of the temperatures of the cooling water, the opening of the throttle valve when the oxygen concentration in the intake passage at the time of starting is low. Constructed a control device for an internal combustion engine that expands in comparison with the opening degree when the oxygen concentration in the intake passage at the time of starting is higher.

According to the present invention, the starting stability of the internal combustion engine can be further improved.

The figure which shows the schematic structure of the internal combustion engine for a vehicle and the control device in one Embodiment of this invention. A timing diagram showing the stroke of each cylinder of a three-cylinder internal combustion engine and the crank angle in which the valve overlaps. The flow chart which shows the procedure example of the process which the control device of the internal combustion engine of the same embodiment executes according to a program. The figure which shows the relationship between the length of the stop time of an internal combustion engine and the oxygen concentration of the air which stays in an intake passage. The figure which shows the relationship between the length of the stop time of an internal combustion engine and the correction amount of the throttle valve opening at the time of the subsequent start of an internal combustion engine.

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 in the present embodiment is a spark-ignition type 4-stroke engine, and includes a plurality of cylinders 1 (for example, three cylinders, one of which is shown in FIG. 1). An injector 11 for injecting fuel toward the intake port is provided in the vicinity of the intake port of each cylinder 1. 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 and induces a spark discharge between the center electrode and the ground electrode.

The 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 from the upstream on the intake passage 3.

The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of 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 external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high-pressure loop EGR. The EGR device 2 includes an external EGR passage 21 that connects 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, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21. The element is an EGR valve 23 that opens and closes and controls the flow rate of the 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, specifically, the surge tank 33.

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 is output from the vehicle speed signal a output from the vehicle speed sensor that detects the actual vehicle speed of the vehicle, the rotation angle of the crankshaft of the internal combustion engine, and the crank angle sensor (engine rotation sensor) that detects the engine rotation speed. Crank angle signal b, accelerator opening signal c output from a sensor that detects the accelerator pedal depression amount or throttle valve 32 opening as accelerator opening (engine output requested by the driver, required load factor), brake The brake depression amount signal d output from the sensor that detects the pedal depression amount or the sensor that detects the master cylinder pressure, which is the pressure of the hydraulic fluid discharged from the master cylinder, is in the intake passage 3 (particularly, the surge tank 33). Intake temperature / intake pressure signal e output from the temperature / pressure sensor that detects the intake air temperature and pressure, and cooling output from the water temperature sensor that detects the temperature of the cooling water of the internal combustion engine (indicating the temperature of the internal combustion engine). From the water temperature signal f, the cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake cam shaft, and the temperature sensor that detects the temperature in the engine compartment (or engine room) accommodating the internal combustion engine in the vehicle body. The output engine compartment temperature signal h and the like are input.

From the output interface, the ignition signal i for the igniter of the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation signal l for the EGR valve 23. Etc. are output.

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, obtains the engine speed, and is sucked into the cylinder 1. Estimate the amount of air. Then, various operations such as 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), etc., corresponding to the intake air amount. Determine the parameters. The ECU 0 applies various control signals i, j, k, l corresponding to the operation parameters via the output interface.

Further, when the ECU0 starts the stopped internal combustion engine (it may be a cold start or a restart from an idling stop), the electric motor (starter motor or ISG (Integrated Starter Generator)) is not shown. ), The control signal o is input, and cranking for fuel injection and spark ignition is executed while the crankshaft is rotationally driven by the electric motor. Cranking ends when the internal combustion engine goes from the initial explosion to the continuous explosion and the engine speed exceeds the judgment value determined according to the cooling water temperature of the internal combustion engine, etc., assuming that the internal combustion engine has completely exploded. ..

When the operation of the internal combustion engine is stopped, the intake valve and the exhaust valve of any cylinder 1 may be in a valve overlap state in which both are open. As shown in FIG. 2, in a three-cylinder engine, the timing T at which one cylinder 1 approaches the compression stroke from the intake stroke, in other words, the piston of the same cylinder 1 reaches the compression top dead center after reaching the intake bottom dead center. Sometimes it stops when it starts to rise. In this case, any of the other cylinders 1 is approaching the intake stroke from the exhaust stroke, and both the intake valve and the exhaust valve of the cylinder 1 are opened.

If the exhaust gas flows back from the exhaust passage 4 side to the intake passage 3 side via the cylinder 1 while the internal combustion engine is stopped in that state, a portion downstream of the throttle valve 32 of the intake passage 3, particularly a surge. The oxygen concentration of the air staying in the tank 33 and / or the intake manifold 34 is reduced. After that, when cranking is started to start the internal combustion engine, intake air having a low oxygen concentration flows into the cylinder 1 from the intake passage 3, and the amount of oxygen supplied to the combustion chamber is insufficient, so that the fuel of the air-fuel mixture becomes insufficient. It may cause instability of combustion or misfire.

Therefore, as shown in FIG. 3, when the ECU 0 of the present embodiment starts the internal combustion engine, the stroke of each cylinder 1 when the latest internal combustion engine is stopped, in other words, the position of the piston of each cylinder 1 when stopped. Is determined, and it is confirmed whether or not the intake valve and the exhaust valve are both stopped in the valve overlapping state in which the valve is opened in any of the cylinders 1 (step S1). In step S1, the ECU 0 refers to the output signals b and g of the crank angle sensor and the cam angle sensor in the process of stopping the engine rotation, and actually measures the stroke of each cylinder 1 when the internal combustion engine is stopped. presume.

If any of the cylinders 1 is in the valve overlap state when the internal combustion engine is stopped most recently, the ECU 0 performs the correction control in step S2 or lower when the internal combustion engine is started thereafter. First, the execution of cranking is started with the normal throttle valve 32 opening degree and fuel injection amount (equivalent to the case where the condition of step S1 is not satisfied). Then, it is confirmed whether or not the first explosion has occurred without any particular delay (step S2). In step S2, for example, when the engine speed exceeds a certain threshold value, which is known by referring to the crank angle signal b, or when the amount of increase (acceleration) of the engine speed per unit time exceeds a certain threshold value. Is regarded as the time when the first explosion occurred, and it is determined whether or not the first explosion occurred within the required time from the start of cranking. If the first explosion occurs within the required time from the start of cranking, the cranking will continue as in normal control.

On the other hand, if the initial explosion does not occur even after the required time has passed from the start of cranking and the initial explosion is delayed, the ECU 0 determines the opening and / or fuel of the throttle valve 32 during cranking. A correction is added to the injection amount (step S3). More specifically, the opening degree of the throttle valve 32 during cranking is expanded more than usual, and / or the fuel injection amount during cranking is reduced than normal. In step S3, the ECU 0 determines the temperature in the engine compartment at the time of the latest internal combustion engine stop and subsequent start, the stop time of the internal combustion engine, that is, the elapsed time from the latest internal combustion engine stop to the subsequent start, and the latest. The amount of correction is determined according to at least one of the temperatures of the cooling water when the internal combustion engine is stopped and when the internal combustion engine is started thereafter.

FIG. 4 shows the length of the stop time when one of the cylinders 1 is in the valve overlapping state and the internal combustion engine is stopped, and the oxygen of the air staying in the portion downstream of the throttle valve 32 of the intake passage 3. The relationship with the transition of concentration fluctuations is shown. While the internal combustion engine is stopped, the exhaust gas flows back from the exhaust passage 4 side to the intake passage 3 side via the cylinder 1 in the valve overlapping state, and as a result, the oxygen concentration of the air remaining in the intake passage 3 increases. It gradually decreases. The oxygen concentration in the intake passage 3 decreases as the internal combustion engine is stopped for a long time, and becomes extremely minimum when several hours have passed since the internal combustion engine was stopped. In FIG. 4, the region where the length of the internal combustion engine stop time exceeds D is the region where there is a high risk of causing a delay or failure in the subsequent start of the internal combustion engine.

In step S3, ECU 0 obtains the difference between the temperature in the engine compartment or the cooling water temperature when the most recent internal combustion engine is stopped and the temperature in the engine compartment or the cooling water temperature when the engine is started after that, and based on this, obtains the difference between the temperature in the engine compartment or the cooling water temperature. Estimate the length of stop time from the most recent stop to the subsequent start. As a general rule, it is considered that the larger the difference between the temperature at the latest stop and the temperature at the start, the longer the stop time of the internal combustion engine. Of course, the ECU 0 may directly count the elapsed time from the latest stop of the internal combustion engine to the subsequent start.

On top of that, the longer the stop time before starting the internal combustion engine, that is, the lower the oxygen concentration of the air in the portion downstream of the throttle valve 32 of the intake passage 3 at the time of starting, the higher the opening degree of the throttle valve 32. A correction is made to widen the valve and / or reduce the fuel injection amount from the injector 11. FIG. 5 shows the relationship between the stop time of the internal combustion engine and the correction amount added to the throttle valve 32 opening and / or the fuel injection amount in step S3. If the length of the internal combustion engine stop time is less than D, there is a low risk of causing an internal combustion engine start delay or start failure. Therefore, the throttle valve 32 opening and / or fuel injection amount is corrected in step S3. There is no need to add.

In the present embodiment, of the temperature in the engine compartment when the internal combustion engine is stopped and when it is started thereafter, the elapsed time from the stop of the internal combustion engine to the start, and the temperature of the cooling water when the internal combustion engine is stopped and when it is started thereafter. By correcting the opening degree of the throttle valve 32 at the time of starting the internal combustion engine according to at least one of (step S3), the throttle valve 32 is opened when the oxygen concentration in the intake passage 3 at the time of starting is low. The control device 0 of the internal combustion engine is configured to increase the degree as compared with the opening degree when the oxygen concentration in the intake passage 3 at the time of starting is higher.

According to the present embodiment, even when any of the cylinders 1 is in a valve overlapping state and the internal combustion engine is stopped, it is possible to reliably start the internal combustion engine thereafter.

The present invention is not limited to the embodiments described in detail above. For example, in the above embodiment, after the start of cranking for starting the internal combustion engine, the throttle valve 32 opening and / or fuel injection during cranking is confirmed on condition that the delay of the initial explosion is confirmed (step S2). It was supposed to correct the amount. However, when any of the cylinders 1 is in a valve overlapping state and the internal combustion engine is stopped, the throttle valve 32 opening and / or the fuel injection amount during cranking is adjusted regardless of whether or not the initial explosion is delayed. It may be corrected.

In addition, the specific configuration of each part, the content of the process, and the like can be variously modified without departing from the spirit of the present invention.

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

0 ... Control unit (ECU)
1 ... Cylinder 11 ... Injector 12 ... Spark plug 3 ... Intake passage 32 ... Throttle valve 4 ... Exhaust passage b ... Crank angle signal e ... Intake temperature / intake pressure signal f ... Cooling water temperature signal g ... Cam angle signal h ... Engine compartment temperature Signal i ... Ignition signal j ... Fuel injection signal k ... Opening operation signal o ... Control signal of electric motor for cranking

Claims (1)

At least one of the temperature in the engine compartment when the internal combustion engine is stopped and then started, the elapsed time from the internal combustion engine stop to the start, and the temperature of the cooling water when the internal combustion engine is stopped and then started. By correcting the opening of the throttle valve at the time of starting the internal combustion engine accordingly, the opening of the throttle valve when the oxygen concentration in the intake passage at the time of starting is low can be adjusted to the oxygen concentration in the intake passage at the time of starting. A control device for an internal combustion engine that expands compared to the opening when is higher.

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