JP2023147996A - Control device of internal combustion engine - Google Patents

Abstract

To suppress the smoldering of an ignition plug of an internal combustion engine, and to avoid a start delay or a start failure.SOLUTION: A control device of an internal combustion engine is constituted such that information related to an in-cylinder temperature immediately before a stop of an operation of the internal combustion engine is stored and held, and after the operation is started by cold-operating the internal combustion engine, when the in-cylinder temperature is a low temperature which is equal to or lower than a determination value in a situation that an engine rotation number or a vehicle speed is higher than a prescribed value, a fuel injection amount is reduced. By this constitution, an air-fuel ratio is leaned, a temperature rise of the in-cylinder temperature is promoted, and deposits adhering to the ignition plug can be thereby easily combusted.SELECTED DRAWING: Figure 3

Description

The present invention relates to a control device that controls the operation of an internal combustion engine installed in a vehicle or the like.

Generally, when an internal combustion engine is cold started, the entire internal combustion engine is at a low temperature, and the fuel injected from the injector into the cylinder does not fully vaporize. Therefore, the fuel injection amount is temporarily increased to enrich the air-fuel ratio. In cold regions, the fuel injection amount may be further increased.

On the other hand, due to the low temperature inside the cylinder (the temperature inside the combustion chamber of the cylinder), fuel components that have not been completely vaporized will undergo incomplete combustion under low oxygen conditions, promoting the formation of carbon, etc., which will become deposits. It adheres to the inner wall of the cylinder bore and the spark plug. That in spark plugs is called smoldering. When deposits accumulate on the insulator that separates the center electrode and the ground electrode of a spark plug, the insulation resistance between the center electrode and the ground electrode changes, which impedes the discharge between the electrodes and, ultimately, the spark ignition of the air-fuel mixture. (See the patent documents below).

The above-mentioned smoldering phenomenon depends more on how the vehicle is used than on the distance traveled by the vehicle. If the engine is often operated at low temperatures and the operating time is short each time, the internal combustion engine will not reach a high temperature and the smoldering spark plug will not be burned out, resulting in the problem of delayed or poor starting of the internal combustion engine.

It is also possible to install a thermoedge on the spark plug to burn out smoldering, but this increases the cost of the hardware.

Unexamined Japanese Patent Publication No. 2017-115607

The present invention aims to suppress smoldering of a spark plug of an internal combustion engine and to avoid starting delays or starting failures.

In the present invention, information regarding the cylinder temperature immediately before the operation of the internal combustion engine is stopped is stored and retained,
After the internal combustion engine has been cold-started and started operating, the fuel injection amount is reduced if the cylinder temperature is lower than the determination value under a condition where the engine speed or vehicle speed is higher than a predetermined value. A control system for an internal combustion engine was constructed.

The cylinder temperature is estimated based on, for example, the engine rotational speed, intake air amount, and air-fuel ratio during operation of the internal combustion engine.

More specifically, after the internal combustion engine has been cold-started and started operating, in a situation where the engine speed or vehicle speed is higher than a predetermined value and the cooling water temperature of the internal combustion engine is higher than a predetermined value, When the cylinder temperature is lower than the determination value, the fuel injection amount is reduced.

According to the present invention, it is possible to suppress smoldering of a spark plug of an internal combustion engine and avoid starting delay or starting failure.

1 is a diagram showing a schematic configuration of an internal combustion engine and a control device in an embodiment of the present invention. FIG. 3 is a flowchart showing an example of a procedure of processing executed by the control device for an internal combustion engine according to the embodiment according to a program. FIG. 3 is a flowchart showing an example of a procedure of processing executed by the control device for an internal combustion engine according to the embodiment according to a program.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of a vehicle internal combustion engine in this embodiment. The internal combustion engine in this embodiment is a spark ignition four-stroke gasoline engine, and includes a plurality of cylinders 1 (for example, a three-cylinder engine; one of them is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 is provided for each cylinder 1 to inject fuel toward the intake port. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 causes a spark discharge between a center electrode and a ground electrode upon application of an induced voltage generated in an ignition coil. The ignition coil is integrally built into the coil case together with the igniter, which is a semiconductor switching element.

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. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream.

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

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 that opens and closes the EGR passage 21. The element includes an EGR valve 23 that controls the flow rate of EGR gas flowing through the passage 21. The entrance 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).

An ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine in this embodiment, is a microcomputer system including a processor, a memory, an input interface, an output interface, and the like. The ECU0 may include a plurality of ECUs or controllers connected to each other so as to be communicable via a telecommunication line such as a CAN (Controller 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 (or wheel rotation speed), and detects the rotation angle and engine rotation speed of the crankshaft, which is the output shaft of the internal combustion engine. A crank angle signal b output from a crank angle sensor that detects the amount of depression of the accelerator pedal by the driver or the opening degree of the throttle valve 32 from a sensor that detects the accelerator opening degree (so to speak, the required engine load factor or engine torque). The accelerator opening signal c that is output, the intake temperature and intake pressure that are output from the temperature and pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly the surge tank 33 or intake manifold 34) connected to the cylinder 1. A signal d, a cooling water temperature signal e outputted from a water temperature sensor that detects the cooling water temperature of the internal combustion engine, an air-fuel ratio signal f outputted from an air-fuel ratio sensor that detects the air-fuel ratio of gas flowing through the exhaust passage 4, the outside temperature and the engine. A signal g output from a temperature sensor that detects the temperature inside the compartment (engine room), an atmospheric pressure signal h output from an atmospheric pressure sensor that detects atmospheric pressure, etc. are input.

From the output interface of the ECU 0, an ignition signal i is sent to the igniter of the spark plug 12 of the internal combustion engine, a fuel injection signal j is sent to the injector 11, and an opening operation signal k is sent to the motor that drives the valve body of the throttle valve 32. , outputs an opening operation signal l, etc. to the motor that drives the valve body of the EGR valve 23.

The processor of ECU0 interprets and executes programs stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operational control of the internal combustion engine and the vehicle through the input interface, and determines the required fuel injection amount commensurate with the intake air amount, Determine operating parameters such as fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing (including the number of ignitions for one combustion), required EGR rate (or EGR gas amount), etc. do. ECU0 applies various control signals i, j, k, l corresponding to operating parameters via an output interface.

In addition, when starting a stopped internal combustion engine (sometimes with a cold start, sometimes with a restart from idling stop), the ECU0 controls the electric motor (starter motor (starter motor), ISG (Integrated Starter Generator), etc.). A control signal o is input to the engine (not shown), and cranking is performed in which fuel injection and spark ignition are performed while the crankshaft is rotationally driven by an electric motor. The electric motor receives the necessary power from an on-board battery. Cranking ends when the internal combustion engine goes from the first explosion to successive explosions and the rotational speed of the crankshaft, that is, the engine rotational speed, exceeds a threshold value, and the internal combustion engine is considered to have completely exploded. Usually, the threshold value is set higher as the cooling water temperature of the internal combustion engine at the time of starting is lower.

The fuel injection amount during cranking is increased so as to be richer than the normal target air-fuel ratio (stoichiometric air-fuel ratio or its vicinity). If the coolant temperature at startup is very low, the fuel injection amount is further increased compared to when the coolant temperature is higher than the coolant temperature. After the internal combustion engine has started, the fuel injection amount is gradually reduced, and eventually reaches the normal target air-fuel ratio.

The ECU 0 of this embodiment is configured to use the most recent driving opportunity (trip) to start the internal combustion engine when the ignition switch (ignition key) or power switch is turned ON, and then to stop the internal combustion engine when it is turned OFF. The period up to this point is considered to be one trip), and it is estimated to what extent the in-cylinder temperature has risen, and the fuel injection amount control for the current driving opportunity is changed accordingly.

FIG. 2 is an example of a procedure that the ECU0 executes during the most recent driving opportunity. The ECU0 determines whether or not the temperature of the cooling water rose to a predetermined level or higher before the internal combustion engine stopped operating in the most recent past driving opportunity, in other words, whether or not warm-up was completed (step S1). If warm-up is completed, it is expected that deposits will be less likely to accumulate on the spark plug 12, that is, smoldering will occur, and that the deposits will be burned off. If the condition in step S1 is true, that fact is stored and held in the nonvolatile memory (step S4).

Further, the ECU0 repeatedly estimates the current in-cylinder temperature while the internal combustion engine is operating. The in-cylinder temperature is estimated based on the engine speed, intake air amount, and air-fuel ratio. The memory of ECU0 stores in advance the operating range of the internal combustion engine [engine speed, intake air amount (or accelerator opening, intake pressure, or fuel injection amount)] and the amount of change in cylinder temperature per cycle (amount of rise). ) is stored. This map data was created experimentally on the premise that the air-fuel ratio of the air-fuel mixture filled into the cylinder 1 is a normal target air-fuel ratio. The ECU0 searches the map using the parameters of the current operating range of the internal combustion engine as a key, and learns the amount of change in the cylinder temperature per cycle. Further, the amount of change is modified depending on the current air-fuel ratio, or depending on the current cooling water temperature, outside air temperature, or engine compartment temperature. Although it depends on the absolute intake air amount and fuel injection amount, if the air-fuel ratio is rich, the temperature inside the cylinder may be difficult to rise due to the latent heat (heat of vaporization) of the fuel, and conversely, if the air-fuel ratio is lean. As a result, the temperature inside the cylinder, where the latent heat of the fuel is small, tends to rise. Needless to say, the lower the current coolant temperature, outside air temperature, or engine compartment temperature, the more difficult it is for the cylinder temperature to rise. The ECU0 calculates the estimated value of the current in-cylinder temperature by integrating (time-integrating) the amount of change in the in-cylinder temperature per cycle thus obtained. Note that the initial value of the cylinder temperature is, for example, the cooling water temperature at a cold start. The ECU0 stores and holds the estimated current in-cylinder temperature in a non-volatile memory at any time (including the time immediately before the operation of the internal combustion engine is stopped) (step S3).

Therefore, the ECU0 determines whether or not the in-cylinder temperature rose above the determination value in the most recent past driving opportunity before the internal combustion engine stopped operating (step S2). The determination value mentioned here is set at a temperature at which the deposit attached to the spark plug 12 is expected to be burned off, for example, around 500°C. If the condition in step S2 is true, that fact is stored and held in the nonvolatile memory (step S4).

FIG. 3 is an example of a procedure that the ECU0 executes during the current driving opportunity. After a cold start of the internal combustion engine (step S5), ECU0 first determines whether the cooling water temperature or the cylinder temperature has risen to a predetermined level or higher in the most recent operating opportunity (if the conditions in step S1 or S2 are true). (step S6), and if so, the routine shifts to normal fuel injection amount control.

Otherwise, correction control is performed to burn off the deposits attached to the spark plug 12. That is, on the premise that the cooling water temperature has risen above a predetermined level (step S7), and when the engine speed or vehicle speed is higher than a predetermined level (step S8), the fuel injection amount is reduced compared to normal to adjust the air-fuel ratio. Make it lean (step S9). By making the air-fuel ratio leaner, the temperature inside the cylinder increases, and deposits attached to the spark plug 12 become easier to burn.

An upper limit guard is provided for the reduction correction of the fuel injection amount in step S9. For example, the air-fuel ratio should not exceed 17.

As already mentioned, the ECU0 repeatedly estimates the current in-cylinder temperature while the internal combustion engine is operating. If the current in-cylinder temperature rises to a predetermined level or higher (step S10), the routine thereafter shifts to normal fuel injection amount control, that is, the reduction correction of the fuel injection amount in step S9 is not performed.

In this embodiment, information regarding the cylinder temperature immediately before the most recent stop of the internal combustion engine is stored and retained, and after the internal combustion engine is cold started and started, the engine rotational speed or vehicle speed increases. A control device 0 for an internal combustion engine is configured, which performs correction control to reduce the amount of fuel injection when the cylinder temperature is lower than a determination value under a situation where the temperature is higher than a predetermined value. .

The present control device 0 estimates the cylinder temperature based on the engine rotational speed, intake air amount, and air-fuel ratio during operation of the internal combustion engine.

After the internal combustion engine has been cold-started and started to operate, this control device 0 controls the above-mentioned operation under the condition that the engine rotation speed or vehicle speed is higher than a predetermined value and the cooling water temperature of the internal combustion engine is higher than a predetermined value. If the in-cylinder temperature is lower than the determination value, correction control is performed to reduce the fuel injection amount compared to the case where this is not the case.

Note that the present invention is not limited to the embodiments detailed above. For example, the in-cylinder temperature immediately before stopping the internal combustion engine during multiple operating occasions in the recent past (for example, two consecutive trips in the recent past) was both significantly lower than the determined value (determined (the value has risen only to a certain value, for example, 200 degrees Celsius), the judgment value for the current driving opportunity is raised to make it more difficult for the condition of step S10 to be met, and the fuel injection amount is reduced in step S9. It is conceivable that the temperature inside the cylinder may be further increased through this process.

In addition, if the in-cylinder temperature immediately before stopping the internal combustion engine during multiple driving opportunities in the recent past did not rise to the judgment value, combustion is stable during steady driving during the current driving opportunity ( On the condition that the number of misfires is 0 or less than a predetermined value, it is also possible to loosen the guard on the fuel injection amount reduction correction in step S9, for example, to lean the air-fuel ratio to 17.5.

In the above embodiment, the cylinder temperature during operation of the internal combustion engine is estimated based on the engine speed, intake air amount, and air-fuel ratio. However, if a sensor for detecting the cylinder temperature is installed, The cylinder temperature can be actually measured via the sensor.

In addition, the specific configuration of each part, processing procedure, etc. can be variously modified without departing from the spirit of the present invention.

0...Control unit (ECU)
1...Cylinder 11...Injector 12...Spark plug a...Vehicle speed signal b...Crank angle signal c...Accelerator opening signal e...Cooling water temperature signal i...Ignition signal j...Fuel injection signal k...Throttle valve opening operation signal o...Cl Control signal for ranking motor

Claims (3)

Stores and retains information regarding the cylinder temperature immediately before the internal combustion engine stops operating,
After the internal combustion engine has been cold-started and started operating, the fuel injection amount is reduced if the cylinder temperature is lower than the judgment value under conditions where the engine speed or vehicle speed is higher than a predetermined value. A control device for an internal combustion engine. The control device for an internal combustion engine according to claim 1, wherein the in-cylinder temperature is estimated based on an engine rotational speed, an intake air amount, and an air-fuel ratio during operation of the internal combustion engine. After the internal combustion engine is cold-started and started to operate, the cylinder temperature is determined in a situation where the engine speed or vehicle speed is higher than a predetermined value and the cooling water temperature of the internal combustion engine is higher than a predetermined value. 3. The control device for an internal combustion engine according to claim 1, wherein the control device controls the fuel injection amount by reducing the fuel injection amount when the temperature is lower than the temperature.

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