JP2013155615A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of startability caused by fuel leak during stop of an internal combustion engine.SOLUTION: The amount of fuel leaked out into an intake passage or a cylinder from an injector or the like during stop of an engine is estimated from a fuel temperature or a fuel pressure. The amount of intake air to be filled in the cylinder is increased and decreased in accordance with the amount of integrated leakage amount during engine start-up.

Description

  The present invention relates to start-up control of an internal combustion engine mounted on a vehicle or the like.

  Generally, when starting an internal combustion engine, a pinion gear of a starter motor (cell motor) is meshed with a ring gear on the outer periphery of a flywheel (MT vehicle) or a drive plate (AT vehicle), and the engine is driven to rotate by the starter motor. I do. Then, from the first explosion to the consecutive explosion, when the engine speed exceeds a threshold determined according to the cooling water temperature (engine temperature) etc., it is considered that the explosion has been completed and cranking is terminated (for example, (See Patent Document 1).

  By the way, while the internal combustion engine is stopped, the injector for injecting the fuel is naturally closed, but in reality, a small amount of fuel is injected into the intake port (intake port injection type) from the valve seat portion of the injector. ) Or in the cylinder (in-cylinder direct injection type).

  Conventionally, during the cranking period, a predetermined amount of fuel is injected in accordance with the behavior of the engine speed. In addition, the opening degree of the throttle valve or the idle speed control valve is kept constant. Therefore, depending on the amount of fuel leaked while the engine is stopped, the atmosphere in the cylinder becomes overrich with a high concentration of fuel components (particularly HC), and combustion may not occur well, leading to a start failure.

  In order to deal with the above events, at the time of start-up in a situation where the influence of fuel leakage is large, the start of fuel injection is delayed from the start of cranking, and the amount of air sucked into the cylinder is increased to increase the amount of air in the intake passage or the It is considered to scavenge the fuel component leaked in advance (for example, see Patent Document 2 below).

  However, it takes a long time to complete the explosion of the engine and there is a concern that unburned HC may be discharged as it is into the outside air through the exhaust passage, which is not always a preferable method.

JP-A-10-169535 Japanese Patent Application Laid-Open No. 09-088672

  An object of the present invention is to improve the startability of an internal combustion engine.

  In order to solve the above-described problems, in the present invention, the amount of fuel leaking from the injector or the like into the intake passage or the cylinder while the engine is stopped is estimated from the fuel temperature or the fuel pressure, and the amount of leakage is reduced during engine startup. A control device for an internal combustion engine is configured to increase or decrease the amount of intake air charged into a cylinder according to the amount of integrated amount.

  When the time elapsed from the engine stop to the restart is longer than a certain level, the amount of fuel leaked from the injector or the like gradually decreases due to a decrease in fuel temperature or pressure. In addition, the fuel component leaked from the injector or the like is diffused and diluted over a wide range of the intake passage and / or the exhaust passage, and the problem of over-riching the cylinder at the start is alleviated. Therefore, when the elapsed time from the engine stop is longer than a predetermined time, it is preferable to reduce the integrated amount of leakage as the elapsed time increases.

  According to the present invention, the startability of the internal combustion engine can be improved.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The flowchart which shows the procedure of the process which the control apparatus of this embodiment performs. The figure which shows the relationship between the fuel temperature and fuel pressure which the control apparatus of this embodiment estimates, and the amount of fuel leaks. The figure which shows the relationship between the elapsed time after a stop of an internal combustion engine, fuel temperature, fuel pressure, the amount of fuel leaks, etc. FIG.

  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 in the present embodiment. The internal combustion engine of the present embodiment is, for example, a three-cylinder four-stroke engine, a plurality of cylinders 1 (one of which is shown in FIG. 1), and an injector 36 that injects fuel into each cylinder 1. An intake passage 3 for supplying intake air to each cylinder 1, an exhaust passage 4 for discharging exhaust from each cylinder 1, and an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3; And an external EGR device 2 that recirculates EGR (Exhaust Gas Recirculation) gas from the exhaust passage 4 toward the intake passage 3.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream side.

  The internal combustion engine in the present embodiment is of an intake port injection type, and an injector 36 for injecting fuel is disposed in the vicinity of the intake port, specifically, in the intake manifold 35.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage is connected to a predetermined location downstream of the electronic throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are also provided on the external EGR passage.

  An ECU (Electronic Control Unit) 0 that controls operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The input interface outputs a vehicle speed signal a output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from a rotation speed sensor that detects the engine rotation speed, and an accelerator sensor that detects the amount of depression of the accelerator pedal. An accelerator opening request signal c, an intake air temperature / intake pressure signal d output from a temperature / pressure sensor that detects intake air temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), an internal combustion engine A coolant temperature signal e output from a water temperature sensor that detects the coolant temperature of the engine, a crank angle signal and a cylinder discrimination signal f output from a timing sensor at the end of the intake camshaft, and an end of the exhaust camshaft An exhaust cam signal g output from the timing sensor every rotation of a predetermined crank angle, and an outside air temperature signal h output from a temperature sensor that detects the outside air temperature An ignition switch (or ignition key) Ignition operation signal i or the like to be output from is input. From the output interface, the opening operation signal j for the EGR valve 22, the opening operation signal k for the electronic throttle valve 33, the fuel injection signal m for the injector 36, and the ignition plug (ignition coil). Ignition signal n etc. are output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h, i necessary for operation control of the internal combustion engine via the input interface, and based on them, the intake air amount and the required fuel injection amount The ignition timing, the required EGR rate (or EGR amount), etc. are calculated. Then, various control signals j, k, m, and n corresponding to the calculation result are applied through the output interface. Since the calculation method of the control inputs j, k, m, and n can be the same as the known operation control of the internal combustion engine, a detailed description is omitted. In addition, when starting the internal combustion engine, the ECU 0 energizes a starter motor (not shown) to operate it.

  FIG. 2 shows a procedure of processing executed when the ECU 0 as the control device of the present embodiment starts the internal combustion engine. When the ECU 0 senses that an operation for restarting the engine has been performed, for example, the ignition switch is switched from OFF to ON while the engine is stopped, or the driver's foot is released from the brake pedal during the idle stop. (Step S1), the restart of the engine is started. That is, a start command is input to the starter motor to operate the starter motor (step S3), and cranking is performed. At the same time, the electronic throttle valve 33 is opened (step S2), and fuel injection control and ignition control are started (step S4).

  When the internal combustion engine has gone from the first explosion to the continuous explosion and the speed of the sensed internal combustion engine exceeds or exceeds the threshold value (step S5), it is considered that the internal combustion engine has completely exploded and the starter motor is transferred to. Is interrupted, the starter motor is stopped, and the cranking is finished (step S6). The threshold is determined with reference to the cooling water temperature of the internal combustion engine. Basically, the threshold value is set to a larger value as the rotational load of the internal combustion engine at the time of starting increases. For example, the threshold value is increased as the coolant temperature at the start of starting is lower.

  Here, the opening degree of the electronic throttle valve 33 in step S2, in other words, the amount of intake air charged into the cylinder 1 during the start of the internal combustion engine is the sum of the fuel leaked from the injector 36 into the intake passage 3 while the engine is stopped. Increase or decrease according to quantity.

  More specifically, when starting the engine, the ECU 0 estimates the fuel temperature and the fuel pressure from the stop of the engine to the start of the engine, and estimates the amount of fuel leakage and the integrated amount from the fuel temperature and the fuel pressure. .

  FIG. 3 shows the relationship between the fuel temperature and fuel pressure and the amount of fuel leaked per unit time. The amount of leakage increases as the fuel temperature increases and increases as the fuel pressure increases, but the influence of the fuel temperature is significant.

  The memory of the ECU 0 stores map data that defines the relationship between the estimated fuel temperature and estimated fuel pressure and the expected amount of fuel leakage per unit time. The ECU 0 searches this map using the estimated fuel temperature and fuel pressure as keys to know the amount of fuel leakage per unit time. Accordingly, the accumulated amount is calculated by accumulating or integrating the leakage amount per unit time, and as the accumulated amount increases, the opening degree of the electronic throttle valve 33 is greatly opened in step S2, and a larger amount of intake air is obtained. Is sucked into the cylinder 1.

  FIG. 4 illustrates a transition pattern of the fuel temperature, the fuel pressure, the amount of fuel leakage, and its integrated amount after the internal combustion engine is stopped.

  In a relatively short period T1 immediately after the engine is stopped, the rotation of the fuel pump (typically, an electric pump disposed in the fuel tank) stops with the stop of the internal combustion engine. Due to fuel leakage from the tank into the tank, the fuel pressure suddenly drops as soon as the engine is stopped, and then continues to decrease consistently. On the other hand, since the internal combustion engine itself is still at a high temperature, the cooling water temperature of the engine and the temperature of the intake air remaining in the intake passage 3 tend to increase. The temperature of the fuel also increases over time. When the temperature of the fuel rises, the viscosity of the fuel decreases, so that the fuel easily leaks from the injector 36. Therefore, the amount of leakage of fuel per unit time increases, and its integration gradually increases.

  In a period T2 after a certain amount of time has elapsed since the engine stopped, the internal combustion engine itself cools, so that the once-increasing cooling water temperature and intake air temperature begin to decrease. Similarly, the temperature of the heated fuel also decreases. When the temperature of the fuel decreases, the viscosity of the fuel increases and it becomes difficult to leak from the injector 36 or the like. Therefore, the amount of leakage of fuel per unit time is reduced. Then, the speed of increase in the cumulative amount of fuel leakage declines.

  In a period T3 after a considerable time has elapsed since the engine was stopped, the fuel temperature becomes substantially constant and the amount of fuel leaked per unit time becomes very small, so that the amount of leakage hardly increases.

  The concentration of the fuel component (HC) contained in the atmosphere filled in the cylinder 1 at the start increases during the T1 period and decreases from the latter stage of the T2 period. This is partly due to the fact that the leaked fuel component diffuses over a wide range of the intake passage 3 and the exhaust passage 4 and dilutes with time.

  The ECU 0 measures the engine stop time (time elapsed between engine stop and restart, soak time), intake air temperature, cooling water temperature, outside air temperature measured and stored immediately before the engine stop, and at the start of engine start. Based on the intake air temperature, the coolant temperature, and the outside air temperature, the fuel temperature transition (time series) while the engine is stopped is estimated. The intake air temperature, the cooling water temperature, and the outside air temperature at the start of engine start may be estimated from those values measured immediately before the engine is stopped and the engine stop time. In addition, the ECU 0 estimates the transition of the fuel temperature during the engine stop based on the engine stop time.

  Then, the amount of fuel leakage per unit time at various times during the engine stop is estimated, and the integrated amount is calculated by adding the time series to determine the opening of the electronic throttle valve 33 in step S2.

  However, when the engine is started after a sufficient time has elapsed since the stop of the engine, the fuel component leaked from the injector 36 or the like diffuses over a wide range of the intake passage 3 and / or the exhaust passage 4 and becomes diluted, and the cylinder The problem of 1 being over-rich is alleviated. Therefore, in a situation where the time elapsed since the engine stop is longer than a predetermined time, for example, when the engine is started after the latter period of the period T2, the cumulative amount of fuel leakage is reduced as the engine stop time increases. To do.

  If the starting time of the engine is within the period T3 and the engine stop time is a predetermined time or longer (for example, 24 hours or longer), the integrated amount of fuel leakage may be regarded as zero.

  Incidentally, if the fuel does not leak as much as the cumulative leakage amount estimated by the ECU 0, the electronic throttle valve 33 opens too much, the intake air flow becomes excessive, and the engine speed starts to increase as the engine starts. There is a fear. Therefore, when the rotational speed of the sensed internal combustion engine exceeds an abnormal determination value that is excessively increased, a fuel cut is performed to retard the ignition timing or temporarily stop fuel injection from the injector 36. Therefore, it is desirable to reduce the rotational speed.

  According to the present embodiment, the amount of fuel leakage that leaks from the injector 36 or the like into the intake passage 3 or the cylinder 1 while the engine is stopped is estimated from the fuel temperature or fuel pressure, and the accumulated amount of the leakage amount during engine startup is estimated. Since the control device 0 of the internal combustion engine is configured to increase or decrease the amount of intake air charged into the cylinder 1 according to the amount of the engine, the atmosphere in the cylinder 1 becomes overrich at the time of start-up and the combustion becomes unstable and the start-up is started. It can effectively solve problems that cause problems.

  The present invention is not limited to the embodiment described in detail above. For example, in the above-described embodiment, the injector 36 injects fuel into the intake manifold 35. However, the present invention is also applicable to start-up control of an in-cylinder direct injection internal combustion engine that injects fuel directly into the cylinder 1. The invention can be applied.

  In the above embodiment, the opening degree of the electronic throttle valve 33 is manipulated to adjust the intake amount at the time of starting, but a bypass passage that connects the upstream side and the downstream side of the throttle valve is provided in the intake passage 3. In an internal combustion engine having an ISC (Idle Speed Control) valve that opens and closes the bypass passage, the opening of the ISC valve can be manipulated in order to adjust the intake air amount at the time of starting.

  In a hybrid vehicle, when a transition is made from a state where only an electric motor is traveling to a state where the internal combustion engine is started and traveled using this, the throttle valve opening operation in step S2 before the internal combustion engine is started. Thus, the fuel component leaking into the intake passage 3 or the cylinder 1 can be scavenged.

  In addition, the specific configuration of each unit, the processing procedure, and the like 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 33 ... Electronic throttle valve 36 ... Injector

Claims (2)

Estimate the amount of fuel leaking from the injector or the like into the intake passage or cylinder while the engine is stopped from the fuel temperature or fuel pressure,
A control apparatus for an internal combustion engine, wherein the amount of intake air charged in a cylinder is increased or decreased according to the amount of accumulated leakage amount during engine startup. 2. The control device according to claim 1, wherein when the elapsed time from the engine stop is longer than a predetermined time, the integrated amount of the leakage amount is reduced as the elapsed time increases.

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