JP2013204520A - Start control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve start control capable of securing preferable startability in an engine mounted on a vehicle or the like.SOLUTION: When oil tight leakage from an injector during a stop of an engine is large and an oil tight leakage determination condition is satisfied, an injection amount of a fuel from the injector is corrected in engine start, by subtraction from a fuel injection amount in the case where the oil tight leakage determination condition is not satisfied. Thus, an air-fuel ratio of an air-fuel mixture in engine start is made proper and startability can be improved. When the oil tight leakage determination condition is satisfied, opening control of a throttle valve 5 may also be performed together.

Description

  The present invention relates to a start control device for an internal combustion engine mounted on a vehicle or the like, and more particularly to measures against so-called oil-tight leakage, in which fuel leaks from a nozzle hole of a fuel injection valve while the engine is stopped.

  An internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle or the like, for example, guides an air-fuel mixture obtained by mixing air flowing through an intake passage and fuel injected from a fuel injection valve (hereinafter also referred to as an injector) into a combustion chamber. The air-fuel mixture is ignited with an ignition plug to burn and explode, and the crankshaft is rotated by energy (power) generated by the combustion and explosion of the air-fuel mixture. Such an engine is started by cranking the engine with a starter (motor) connected to a crankshaft, supplying fuel in accordance with the cranking, and igniting.

  In an engine that supplies fuel with an injector, it is known that fuel leaks from the injector nozzle hole when the engine is stopped (during soak), so-called oil-tight leakage may occur (for example, (See Patent Documents 1 to 3).

JP 2008-025521 A JP 2010-037984 A JP 2010-053787 A

  By the way, the oil tight leakage of the injector becomes large depending on the operating condition and the environmental condition when the engine is stopped. For example, if the fuel temperature (fuel temperature) and fuel pressure (fuel pressure) are high when the engine is stopped during low-speed and high-load driving or climbing, etc., or if the outside air temperature is high and the fuel temperature and fuel pressure are high, such as in summer In this case, the oil leakage of the injector is increased. When the oil tight leak of the injector increases, the concentration of HC (hydrocarbon) in the intake manifold (intake port) increases. If the air-fuel ratio of the air-fuel mixture becomes rich and exceeds the range of the combustible air-fuel ratio due to the increase in the HC concentration, the combustion state may deteriorate and the engine may fail to start.

  The present invention has been made in view of such a situation, and an object of the present invention is to realize start control capable of ensuring good startability in an internal combustion engine mounted on a vehicle or the like.

  The present invention provides an internal combustion engine start control device that obtains power by combusting an air-fuel mixture of intake air and fuel injected from a fuel injection valve in a combustion chamber, wherein an oil-tight leak judgment condition for the fuel injection valve is satisfied. In this case, the technical feature is that when the engine is started, the fuel injection amount by the fuel injection valve is corrected to decrease from the fuel injection amount when the oil-tight leak determination condition is not satisfied.

  According to the present invention, when the oil-tight leak of the fuel injection valve is large while the engine is stopped and the oil-tight leak determination condition is satisfied, the fuel injection amount by the fuel injection valve is corrected to decrease when the engine is started. Therefore, the enrichment of the air-fuel ratio at the time of starting the engine is suppressed and approaches an appropriate value within the combustible range. As a result, the deterioration of the combustion state at the time of starting the engine is suppressed, the engine speed (engine speed) increases rapidly, and the startability of the internal combustion engine is improved.

  In the present invention, when the oil tight leak determination condition is satisfied, scavenging control for increasing the intake air amount to facilitate scavenging of the air-fuel mixture may be executed. In this way, even if the oil-tight leak of the fuel injection valve when the engine is stopped and the concentration of HC in the intake manifold (intake port) is high, during the cranking of the internal combustion engine at the time of engine start, However, it is possible to scavenge a high concentration mixture early. Therefore, it is advantageous for optimizing the air-fuel ratio when starting the engine.

  In addition, since the richness of the air-fuel ratio of the air-fuel mixture is suppressed by the increase in the intake air amount, it is possible to moderate the decrease in the fuel injection amount, and to optimize the air-fuel ratio when starting the engine. The torque can be increased while increasing the starting performance of the internal combustion engine.

  As a specific configuration of the present invention, there is a configuration in which the amount of intake air is increased by controlling (opening control) the opening of a throttle valve provided in an intake passage leading to a combustion chamber of an internal combustion engine when the engine is started. be able to. In this case, the opening of the throttle valve when the intake air amount is increased (during scavenging control) is controlled so that the intake passage on the downstream side of the intake flow of the throttle valve does not become negative pressure, and the new air amount is reduced. It is preferable to control so as to be maximized.

  In this case, the throttle valve opening may be set based on the engine water temperature and the engine speed. In this way, an increase in the intake air amount at the time of starting the engine can be appropriately set according to the conditions at the time of starting the engine, so that a stable scavenging effect can be obtained. That is, for example, the opening of the throttle valve may be increased in accordance with an increase in the cranking rotational speed when the engine is started.

  On the other hand, the fuel reduction correction amount is preferably determined in accordance with the concentration of HC in the intake manifold (intake port), that is, the size of the oil-tight leak. It is only necessary to correct the weight loss.

  As a more specific configuration, it is preferable that the first fuel injection amount by the fuel injection valve is set to zero when the engine is started when the oil leak detection condition is satisfied. If the oil tight leak is large and the concentration of HC in the intake manifold (intake port) is high, a combustible air-fuel mixture can be introduced into the combustion chamber and ignited and burned without performing the first fuel injection. Because it can.

  That is, if the internal combustion engine has a plurality of cylinders and the fuel injection valve is provided for each cylinder, the cylinders can be used when the oil-tight leak determination condition is satisfied. It is preferable to set the first fuel injection amount for each time to zero. Also, the second fuel injection amount for each cylinder may be zero, but may be corrected by a predetermined amount. Further, it is preferable that the third and subsequent fuel injection amounts are not reduced and are injected by the same amount as when the oil-tight leak determination condition is not satisfied. In other words, it is preferable that the fuel injection amount reduction correction control is completed until the second fuel injection for each cylinder.

  On the other hand, when control for increasing the intake air amount (throttle valve opening control) is performed, this control can sufficiently scavenge an air-fuel mixture having a predetermined engine speed (for example, HC has a high concentration). Or the engine speed increase rate is equal to or higher than a predetermined value (for example, the speed increase rate at which HC can sufficiently scavenge a high-concentration air-fuel mixture). It is preferable to end when it becomes.

  Alternatively, the control for increasing the intake air amount at the time of starting the engine (throttle valve opening control) ends when the engine speed is equal to or higher than a predetermined value and the rate of increase in the engine speed is equal to or higher than a predetermined value. Alternatively, it may be terminated when the number of rotations of the internal combustion engine becomes equal to or greater than a predetermined value.

  Further, in the present invention, as a condition for determining the oil leak of the fuel injection valve, for example, a water temperature decrease value from the previous engine stop to the engine restart ([water temperature at previous stop] − [water temperature at restart] ]) Is a predetermined value or more, and the intake air temperature at the time of restarting is a predetermined value or less. Moreover, you may set the conditions that the water temperature fall value is more than the determination value set for every water temperature at the time of last stop. In other words, as for the oil leak condition, various determination conditions are conceivable so that the deterioration of combustion at restart (engine start failure) due to the oil leak of the fuel injection valve while the engine is stopped can be determined.

  According to the present invention, when the oil-tight leak of the fuel injection valve is large while the engine is stopped and the oil-tight leak judgment condition is satisfied, the fuel injection amount at the time of starting the engine is reduced and corrected. By ensuring that is not excessively rich, good startability can be ensured. If scavenging control for increasing the intake air amount is also performed, torque can be increased while optimizing the air-fuel ratio, and the startability of the internal combustion engine can be further improved.

It is a schematic block diagram which shows an example of the engine (internal combustion engine) to which this invention is applied. It is a block diagram which shows the structure of the control system of the engine shown in FIG. It is a flowchart which shows an example of the engine starting control which ECU performs. It is a figure which shows an example of the map which calculates | requires a water temperature fall determination value. 4 is a timing chart showing an example of injection timing and ignition timing for each cylinder by normal start control of the engine. It is a timing chart which shows an example of changes, such as injection timing for every cylinder by ignition control at the time of oil tight leak judgment, ignition timing, and engine speed. It is a figure which shows an example of the map which calculates | requires the throttle opening at the time of engine starting. 6 is a flowchart of a modified example in which the ignition timing is retarded when the engine is started. 4 is a timing chart showing changes in engine speed and the like when retarding the ignition timing. FIG. 6 is a view corresponding to FIG. 3 according to another embodiment that does not perform throttle opening control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

-Configuration of internal combustion engine-
First, an internal combustion engine (hereinafter also referred to as an engine) to which the present invention is applied will be described. FIG. 1 is a diagram showing a schematic configuration of an engine to which the present invention is applied. FIG. 1 shows only the configuration of one cylinder of the engine.

  The engine 1 in this example is a port injection type four-cylinder gasoline engine mounted on a vehicle, and a piston 1c that reciprocates in the vertical direction is provided in a cylinder block 1a constituting each cylinder. The piston 1c is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1c is converted into rotation of the crankshaft 15 by the connecting rod 16.

  The crankshaft 15 of the engine 1 is connected to a transmission (not shown) via a torque converter (or clutch) or the like, and transmits the power from the engine 1 to the drive wheels of the vehicle via the transmission. Can do.

  The transmission is, for example, a stepped automatic transmission that sets a gear position (for example, six forward speeds and one reverse speed) using a friction engagement element such as a clutch and a brake and a planetary gear mechanism. Each range (parking range P, reverse range R, neutral range N, drive range D) of the transmission is switched by operating the shift lever 50 (see FIG. 2). The shift operation position (P, R, N, D range) of the shift lever 50 is detected by the shift position sensor 41. The transmission may be a continuously variable transmission such as a belt type continuously variable transmission.

  The crankshaft 15 of the engine 1 is connected to a starter (motor) 10 that is started when the engine 1 is started, and the cranking of the engine 1 can be performed by starting the starter 10.

  A signal rotor 17 is attached to the crankshaft 15. A plurality of teeth (projections) 17a are provided on the outer peripheral surface of the signal rotor 17 at equal angles (in this example, for example, 10 ° CA (crank excessive)). Further, the signal rotor 17 has a missing tooth portion 17b in which two teeth 17a are missing.

  A crank position sensor 31 that detects a crank angle is disposed near the side of the signal rotor 17. The crank position sensor 31 is an electromagnetic pickup, for example, and generates a pulsed signal (voltage pulse) corresponding to the teeth 17a of the signal rotor 17 when the crankshaft 15 rotates. The engine speed Ne can be calculated from the output signal of the crank position sensor 31.

  A water temperature sensor 32 for detecting the coolant temperature of the engine cooling water is disposed in the cylinder block 1a of the engine 1. A cylinder head 1b is provided at the upper end of the cylinder block 1a, and a combustion chamber 1d is formed between the cylinder head 1b and the piston 1c. A spark plug 3 is disposed in the combustion chamber 1 d of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (Electronic Control Unit) 200.

  An oil pan 18 for storing lubricating oil (engine oil) is provided below the cylinder block 1 a of the engine 1. Lubricating oil stored in the oil pan 18 is pumped up by an oil pump (not shown) through an oil strainer that removes foreign matters during operation of the engine 1, and the engine such as the piston 1 c, crankshaft 15, connecting rod 16, etc. It is supplied to each part and used for lubrication and cooling of each part. The lubricating oil supplied in this way is used for lubrication and cooling of each part of the engine, then returned to the oil pan 18 and stored in the oil pan 18 until it is pumped up again by the oil pump. .

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 d of the engine 1. A part of the intake passage 11 is formed by an intake port 11a and an intake manifold 11b. A surge tank 11 c is provided in the intake passage 11. A part of the exhaust passage 12 is formed by an exhaust port 12a and an exhaust manifold 12b.

  In the intake passage 11 of the engine 1, an air cleaner 7 that filters the intake air, a hot-wire air flow meter 33, an intake air temperature sensor 34 (built in the air flow meter 33), a throttle valve 5 for adjusting the intake air amount of the engine 1, etc. Is arranged.

  The throttle valve 5 is provided on the upstream side (upstream side of the intake flow) of the surge tank 11 c and is driven by the throttle motor 6. The opening of the throttle valve 5 is detected by a throttle opening sensor 35. The throttle opening of the throttle valve 5 is driven and controlled by the ECU 200.

  Specifically, the optimum intake air amount (target) according to the engine 1 operating state such as the engine speed Ne calculated from the output signal of the crank position sensor 31 and the accelerator pedal depression amount (accelerator opening) of the driver. The throttle opening of the throttle valve 5 is controlled so that the intake amount) is obtained. More specifically, the actual throttle opening of the throttle valve 5 is detected using the throttle opening sensor 35, and the actual throttle opening matches the throttle opening (target throttle opening) at which the target intake air amount can be obtained. Thus, the throttle motor 6 of the throttle valve 5 is feedback controlled. Such a control system for the throttle valve 5 is referred to as an “electronic throttle system” and can control the throttle opening independently of the driver's operation of the accelerator pedal. For example, it is possible to execute an increase control of the intake air amount when starting the engine, which will be described later.

A three-way catalyst 8 is disposed in the exhaust passage 12 of the engine 1. In the three-way catalyst 8, oxidation of CO and HC and reduction of NOx in the exhaust gas exhausted from the combustion chamber 1d to the exhaust passage 12 is performed, and these are made harmless CO ₂ , H ₂ O, and N ₂ . In this way, the exhaust gas is purified.

A front air-fuel ratio sensor 37 is disposed in the exhaust passage 12 upstream of the three-way catalyst 8 (upstream of the exhaust flow). The front air-fuel ratio sensor 37 is a sensor that exhibits linear characteristics with respect to the air-fuel ratio. A rear O ₂ sensor 38 is disposed in the exhaust passage 12 on the downstream side of the three-way catalyst 8. The rear O ₂ sensor 38 generates an electromotive force according to the oxygen concentration in the exhaust gas. When the output is higher than a voltage (comparison voltage) corresponding to the theoretical air-fuel ratio, the rear O ₂ sensor 38 determines that the output is rich. When the output is lower than the comparison voltage, it is determined as lean. The output signals of the front air-fuel ratio sensor 37 and the rear O ₂ sensor 38 are used for air-fuel ratio feedback control (for example, refer to the technique described in Japanese Patent Laid-Open No. 2010-007561).

  An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1d. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1d are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1d. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1d are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft 21 and the exhaust camshaft 22 to which the rotation of the crankshaft 15 is transmitted via a timing chain or the like.

  In the vicinity of the intake camshaft 21, a cam position sensor 39 is provided that generates a pulse signal when the piston 1c of a specific cylinder (for example, the first cylinder) reaches the compression top dead center (TDC). . The cam position sensor 39 is, for example, an electromagnetic pickup, and is disposed so as to face one tooth (not shown) on the outer peripheral surface of the rotor provided integrally with the intake camshaft 21. When the shaft 21 rotates, a pulse signal (voltage pulse) is output. Since the intake camshaft 21 (and the exhaust camshaft 22) rotates at a half speed of the crankshaft 15, the cam position sensor 39 becomes 1 each time the crankshaft 15 rotates twice (720 ° rotation). Two pulse signals are generated.

  In the intake passage 11, an injector (fuel injection valve) 2 is arranged for each cylinder so as to inject fuel into the intake port 11 a as an example. These injectors 2 are connected to a common delivery pipe 101, and fuel is supplied to the delivery pipe 101 from a fuel tank 104 of a fuel supply system 100 described later. The drive of the injector 2 is controlled by the ECU 200, and fuel injection is performed at a predetermined timing for each cylinder.

  Thus, the fuel injected from the injector 2 into the intake port 11a is mixed with intake air and introduced into the combustion chamber 1d in each cylinder as the intake valve 13 is opened. This air-fuel mixture is ignited by the spark plug 3 at the end of the compression stroke of the cylinder and burns and explodes. The piston 1c is pushed down by the high-temperature and high-pressure combustion gas generated at this time (expansion stroke), and driving torque is output from the crankshaft 15. The combustion gas is discharged to the exhaust passage 12 when the exhaust valve 14 is opened.

  The fuel supply system 100 includes a delivery pipe 101 commonly connected to the injector 2 of each cylinder, a fuel supply pipe 102 connected to the delivery pipe 101, a fuel pump (for example, an electric pump) 103, and a fuel tank 104. The fuel stored in the fuel tank 104 can be supplied to the delivery pipe 101 via the fuel supply pipe 102 by controlling the drive of the fuel pump 103 by the ECU 200 described below. Then, the fuel is supplied to the injector 2 of each cylinder by the fuel supply system 100 having such a configuration.

-ECU-
As shown in FIG. 2, the ECU 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, a backup RAM 204, and the like.

  The ROM 202 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 201 executes various arithmetic processes based on various control programs and maps stored in the ROM 202. The RAM 203 is a memory that temporarily stores calculation results of the CPU 201, data input from each sensor, and the backup RAM 204 is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

  The CPU 201, the ROM 202, the RAM 203, and the backup RAM 204 are connected to each other via the bus 207, and are connected to the input interface 205 and the output interface 206.

The input interface 205 includes a crank position sensor 31, a water temperature sensor 32, an air flow meter 33, an intake air temperature sensor 34, a throttle opening sensor 35, an accelerator opening sensor 36 that outputs a detection signal corresponding to the depression amount of the accelerator pedal, a front Various sensors such as an air-fuel ratio sensor 37, a rear O ₂ sensor 38, a cam position sensor 39, and a shift position sensor 41 for detecting a shift operation position of the shift lever 50 are connected. Further, the ignition switch 40 is connected to the input interface 205, and when the ignition switch 40 is turned on, cranking of the engine 1 by the starter 10 is started.

  The output interface 206 is connected to the injector 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, the starter 10, the fuel pump 103 of the fuel supply system 100, and the like.

  The ECU 200 controls the drive of the injector 2 (control of the fuel injection amount and injection timing), the control of the ignition timing by the spark plug 3, the throttle motor 6 of the throttle valve 5 based on the detection signals of the various sensors described above. Various controls of the engine 1 including drive control (control of intake air amount), air-fuel ratio feedback control, and the like are executed. Furthermore, the ECU 200 executes the following “engine start control”.

  With the program executed by the ECU 200 described above, the internal combustion engine start control device of the present invention is realized.

-Engine start control-
First, in the engine 1 including the injector 2, as described above, there may be an oil-tight leak in which fuel leaks from the injector 2 while the engine is stopped (during soak). The oil tight leakage of the injector 2 increases depending on operating conditions and environmental conditions when the engine was stopped last time. For example, when the fuel temperature / pressure is high when the engine is stopped in a low-speed / high-load operation state or in an uphill driving state, or when the outside air temperature is high and the fuel temperature / fuel pressure is high, such as in summer, the oil leak from the injector 2 Becomes larger. When the oil tight leak of the injector 2 increases, the concentration of HC in the intake manifold 11b (intake port 11a) increases. If the air-fuel ratio of the air-fuel mixture becomes rich and exceeds the range of the combustible air-fuel ratio due to the increase in the HC concentration, the combustion state may deteriorate and the engine 1 may become poorly started.

  Therefore, in the present embodiment, in consideration of such oil-tight leakage of the injector 2 when the engine is stopped, the fuel injection amount by the injector 2 for each cylinder is corrected to be reduced when the engine is started, and the intake air when the engine is started By increasing the amount, the air-fuel ratio of the air-fuel mixture is optimized. Hereinafter, an example of the control (engine start control) will be described with reference to the flowchart of FIG. The control routine of FIG. 3 is executed in the ECU 200.

  The control routine of FIG. 3 is started (START) when the ignition switch 40 is turned on (IG-ON). First, in step ST101, the water temperature and the intake air temperature at the time of engine start (at the time of restart) are recognized from the output signals of the water temperature sensor 32 and the intake air temperature sensor 34, the water temperature and the intake air temperature at the time of the engine restart, Based on the water temperature and the intake air temperature when the engine 1 is stopped, it is determined whether or not the oil leak leakage determination condition of the injector 2 is satisfied.

  Specifically, it is determined whether or not all the following conditions J1, J2, and J3 are satisfied.

Condition J1: The water temperature at the previous engine stop is equal to or higher than a predetermined water temperature determination value, and the intake air temperature at the previous engine stop is equal to or higher than a predetermined intake temperature determination value. Condition J2: The water temperature at engine restart is The water temperature at the time of restarting the engine relative to the water temperature at the time of the last engine stop ([[ The water temperature at the time of previous stop]-[water temperature at the time of restart]) is equal to or higher than the water temperature decrease determination value set for each water temperature at the time of previous stop. Each condition J1 to J3 will be described.

(Condition J1)
When the water temperature and the intake air temperature when the engine 1 is stopped are high, the oil-tight leak of the injector 2 when the engine is stopped increases. In consideration of this point, the oil leak detection condition is that the water temperature at the previous engine stop is equal to or higher than a predetermined water temperature determination value and the intake air temperature at the previous engine stop is equal to or higher than a predetermined intake temperature determination value. One of them.

  As for the water temperature judgment value when the engine is stopped, the relationship between the water temperature when the engine is stopped and the amount of oil-tight leak that may deteriorate the startability of the engine 1 is obtained by experiments, simulations, etc. Based on the relationship, the water temperature (water temperature at the time of stoppage) at which startability may deteriorate is obtained. Then, a suitable value (water temperature determination value) is set based on the result. Also, a value adapted to the intake air temperature determination value when the engine is stopped is set by the same processing.

  Here, the reason why the two parameters of the water temperature at the previous engine stop and the intake air temperature at the previous engine stop are used in the condition J1 will be described.

  For example, when the engine 1 is stopped after the engine is started until the water temperature reaches a warm-up temperature (a temperature at which the warm-up of the engine 1 can be considered to be completed: for example, about 80 ° C.), the water temperature is lower than the intake air temperature. Therefore, if the determination is made only with the water temperature, the determination does not reflect the actual temperature of the injector 2. Further, depending on the operating state of the engine 1, the intake air temperature may be lower than the water temperature. If the determination is made only with the intake air temperature (the temperature of the intake air near the air cleaner 7), an accurate determination can be made. There may not be. Considering such points, in this example, the condition J1 is set with the water temperature and the intake air temperature as parameters.

(Condition J2)
Considering the fact that the longer the engine stop time (soak time) from the previous engine stop to the restart time, the greater the oil-tight leakage of the injector 2, the water temperature at the time of engine restart is below a predetermined water temperature judgment value. In addition, one of the oil-tight leak determination conditions is that the intake air temperature when the engine is restarted is equal to or lower than a predetermined intake air temperature determination value. That is, when the water temperature and the intake air temperature when the engine is stopped are equal to or higher than the above determination values, the longer the engine stop time (soak time), the lower the water temperature and the intake air temperature during the restart. In addition, the fact that the intake air temperature is equal to or lower than the determination value is set as one of the oil leak leakage determination conditions.

  Note that the water temperature determination value and the intake air temperature determination value at the time of engine restart are set to suitable values through experiments and calculations in consideration of the relationship between the soak time and the amount of oil leak. Also in this condition J2, the condition J2 is set using the water temperature and the intake air temperature as parameters for the same reason as the condition J1 described above.

(Condition J3)
When the water temperature when the engine is stopped is, for example, 90 ° C. or higher and the oil temperature is 90 ° C. or higher, the water temperature tends not to decrease due to the influence of the temperature of the lubricating oil (oil temperature). In consideration of this point, in addition to the above condition J2, with respect to the water temperature, the water temperature drop value at the time of the engine restart relative to the water temperature at the time of the previous engine stop (the water temperature at the time of the previous engine stop)-[ It is a condition that the engine water temperature]) is equal to or higher than the water temperature decrease determination value set for each water temperature during stoppage. The water temperature decrease determination value used for this condition J3 is obtained with reference to the map (table) in FIG. 4 based on the water temperature when the engine is stopped.

  The map of FIG. 4 is a map of values (water temperature decrease determination value) adapted by experiment / calculation in consideration of the effect of the oil temperature, and is stored in the ROM 202 of the ECU 200. In the map shown in FIG. 4, when the water temperature is 90 ° C. or higher, the water temperature lowering determination value is set to a smaller value with respect to the side where the water temperature is lower than 90 ° C.

  In the map of FIG. 4, the water temperature decrease determination value between 80 ° C. and 90 ° C. is a constant value (10 ° C.). For the water temperature decrease determination value between 90 ° C. and 105 ° C., the water temperature decrease determination value is obtained by interpolation calculation.

  Here, as an oil leak leakage determination condition of the injector 2, other determination conditions can be used as long as the deterioration of combustion at the time of restart (engine start failure) due to the oil leak of the injector 2 when the engine is stopped can be determined. It may be. For example, the water temperature difference between the previous engine stop and the engine restart may be a predetermined value or more and the intake air temperature at the restart may be a predetermined value or less. Further, in addition to such a condition, the above condition J3 may be set.

  Returning to the flowchart of FIG. 3, if the determination result in step ST101 is negative (NO), that is, if the oil-tight leak determination condition is not satisfied, the process proceeds to step ST110. In step ST110, the engine 1 is started with the fuel injection amount and the intake air amount at the normal start. Note that the fuel injection amount and the intake air amount at the normal start time are, for example, the injection amount map and the intake air amount for the normal start time based on the engine start conditions (water temperature, intake air temperature, correction values so far, etc.), respectively. Calculated from the map.

  As an example, as shown in FIG. 5, fuel is injected in a predetermined order by each of the injectors 2 of the first to fourth cylinders during normal startup. In the example of the figure, fuel injection is performed in the order of the fourth cylinder, the second cylinder, the first cylinder, and the third cylinder, and basically, as shown on the right side of the figure, a predetermined timing ( For example, fuel is injected into the intake port 11a at the end of the expansion stroke. This fuel is mixed with intake air to become an air-fuel mixture, and is introduced into the combustion chamber 1d in each cylinder when the intake valve 13 is opened at the end of the exhaust stroke.

  Also, in order to shorten the start time as much as possible, immediately after the start of cranking by the starter 10, the first (first) fuel injection for each cylinder is different from the above as shown in the left end of FIG. It is executed at the timing. In the example shown in the figure, when the intake camshaft 21 rotates with cranking and the cam position sensor 39 generates a pulse signal (cylinder identification signal) at the compression top dead center (TDC) of the first cylinder, fuel injection by the injector 2 is performed. Is started.

  At this time, that is, at the compression top dead center of the first cylinder, the cylinder that first reaches the ignition timing (indicated by a virtual line in the figure) is the third cylinder, but the third cylinder immediately shifts to the compression stroke. Fuel cannot be supplied. Therefore, first, the injector 2 of the fourth cylinder in the intake stroke is driven, and then the injector 2 of the second cylinder in the exhaust stroke is driven to inject fuel respectively. If the injection pulses overlap, the injection amount may vary due to fluctuations in the fuel pressure of the delivery pipe 101, so the injection pulses are slightly shifted.

  Thus, the fourth cylinder for injecting fuel first is in the intake stroke, and the second cylinder for injecting fuel is in the exhaust stroke, both of which are later than the original injection timing, but one of the injected fuels. The part is mixed and introduced into the cylinder. Further, the fuel is injected into the subsequent first cylinder at substantially the original injection timing, and the injection timing into the subsequent third cylinder is earlier than the original timing. In general, fuel vaporization tends to be worse at the time of starting, so it is preferable to inject early.

  Thus, after the first fuel injection for each cylinder performed in the order of the fourth cylinder, the second cylinder, the first cylinder, and the third cylinder, for each of the cylinders, from the end stage of the compression stroke to the expansion stroke, that is, TDC It is ignited by the spark plug 3 at a predetermined timing in the vicinity, and the air-fuel mixture burns and explodes (first explosion). As a result, the rotation of the crankshaft 15 is accelerated and the engine speed rises.

  On the other hand, if the determination result in step ST101 is affirmative (YES), that is, if the oil-tight leakage determination condition for the injector 2 is satisfied, the process proceeds to step ST102, where the opening degree of the throttle valve 5 ( (Throttle opening) is set to be larger than that at the normal start, and the intake air amount is increased from that at the normal start to start the cranking as described above (scavenging control is executed at the engine start).

  The throttle opening at this time, that is, the opening of the throttle valve 5 when executing the control for increasing the intake air amount (scavenging control) may be an opening at which the intake passage 11 does not become negative pressure. Specifically, a value (throttle opening) adapted by experiment / calculation or the like may be used with the cranking rotation speed at the time of engine start as a parameter. The throttle opening for the intake air increase control may be a constant value, or may be variably set according to the cranking rotational speed or the like, as will be described later.

  Note that the throttle opening at which the intake passage 11 does not become negative pressure means that the throttle opening within a range in which intake pipe negative pressure (intake manifold negative pressure) does not occur when the throttle valve 5 is opened larger than at normal start when the engine is started. For example, it is an opening obtained by adding a margin (open side value) to the lower limit opening of the throttle opening range in which the intake manifold negative pressure does not occur. The throttle opening is set such that the amount of fresh air is maximized (the scavenging effect is maximized) within a range where intake pipe negative pressure (intake manifold negative pressure) does not occur.

  Then, in step ST103 of the flow of FIG. 3, the fuel injection amount calculated from the normal start-time injection amount map is corrected to decrease, and based on this, a control signal (injection pulse) output to the injector 2 for each cylinder. To decide. In the present embodiment, as shown in the middle stage of FIG. 6, in order to cut the first (first) fuel injection performed in the order of the fourth cylinder, the second cylinder, the first cylinder, and the third cylinder, The injection pulse width is zero.

  The initial fuel injection for each cylinder is not cut, but may be reduced by a predetermined amount, or this reduction correction amount may be variable. When variable, for example, the water temperature (water temperature at engine start) obtained from the output signal of the water temperature sensor 32 or the intake air temperature is used as a parameter. It is sufficient to map values that are suitable by, for example, and determine the amount of reduction correction with reference to this map.

  Even if the first fuel injection for each cylinder is cut as described above, if the oil tight leak is large and the HC concentration in the intake manifold (intake port) is high, the combustion chamber 1a in the cylinder is flammable. Is introduced. For this reason, as shown in the upper part of FIG. 6, if the ignition plug 3 is ignited, the air-fuel mixture is combusted (initial explosion), and the engine speed rises as shown in the lower part of the figure. Then, the scavenging of the air-fuel mixture proceeds by the cranking of the engine 1, and the engine speed rapidly increases in combination with the optimization of the air-fuel ratio.

  Subsequently, in step ST104 of the flowchart of FIG. 3, it is determined whether or not the engine speed Ne calculated from the output signal of the crank position sensor 31 has reached a predetermined determination value Thne (see FIG. 6). If the determination is NO (NO), the system waits until the engine speed Ne at the start reaches this determination value Thne. Then, when the determination is affirmative (YES), that is, when the engine speed Ne at the start reaches the determination value Thne, the process proceeds to step ST105.

  The determination value Thne used in the determination of step ST104 is obtained by experiment / calculation, etc., of the engine speed at which HC can sufficiently scavenge a high-concentration mixture during cranking at the time of engine start. A value (for example, 1000 rpm) adapted to the result may be used.

  In step ST105, the intake air amount increase control is terminated, and the throttle valve 5 is controlled to the opening during normal control to return the intake air amount to the normal control state (see FIG. 6). Thereafter, this control routine is temporarily terminated (RETURN).

  As described above, in the present embodiment, when the oil tight leak of the injector 2 is large while the engine is stopped and the oil tight leak judging condition is satisfied, the fuel injection amount at the time of engine start is corrected to decrease. Thus, it is possible to suppress the enrichment of the air-fuel ratio of the air-fuel mixture that is initially introduced into the combustion chamber 1d in each cylinder. In addition, since the engine 1 is started with the intake air amount increased, the air-fuel mixture with a high concentration of HC can be quickly scavenged during cranking of the engine 1.

  In other words, it is possible to suppress the air-fuel ratio from becoming excessively rich at the time of engine start due to oil-tight leakage, and to achieve an appropriate air-fuel ratio within the combustible range, so a good combustion state is realized from the first ignition. it can. Moreover, torque can be increased by increasing the intake air amount, that is, by increasing the air-fuel mixture. As a result, as shown in the lower part of FIG. 6, the engine speed rises faster and rises faster than when the fuel is not decreased and the air amount is not increased (indicated by a broken line).

  In the present embodiment, when the oil-tight leak condition of the injector 2 is satisfied, as described above, the intake air amount that is increased when the engine is started may be a constant amount or may be set variably. Good.

  When the intake air volume that is increased when starting the engine is variably set, the engine takes into consideration that the negative pressure (intake manifold negative pressure) in the intake passage increases as the cranking speed when the engine starts increases. The intake passage 11 does not become negative pressure by increasing the opening degree of the throttle valve 5 and gradually increasing the intake air amount (or increasing it stepwise) as the cranking rotational speed at the start increases. Do it. In this case, the map shown in FIG. 7 is referred to based on the water temperature obtained from the output signal of the water temperature sensor 32 (water temperature at the time of engine start) and the cranking rotation speed (recognized from the output signal of the crank position sensor 31) by the starter 10. Then, by setting the throttle opening θ of the throttle valve 5, the intake air amount may be gradually increased (or increased stepwise) in accordance with the cranking rotation speed.

  The map shown in FIG. 7 is a map obtained by mapping the throttle opening θ at which the intake passage 11 does not become negative pressure by experiment and calculation using the water temperature and the cranking rotation number as parameters. It is stored in the ROM 202. In the map of FIG. 7, the throttle opening θ is set to be larger as the water temperature is higher and the cranking rotational speed is higher.

-Modification of engine start control-
Next, a modified example of the engine start control described above will be described with reference to the flowchart of FIG. In this modified example, when the intake air amount is increased at the time of starting the engine as in the above-described embodiment, the engine speed at the completion of the start-up rises higher than usual, so that the driver does not feel uncomfortable. In addition, the ignition timing is retarded.

  Therefore, the step of decreasing the fuel injection amount or increasing the intake air amount in the flowchart of FIG. 8 is omitted, but also in this modification, the reduction of the fuel injection amount and the increase of the intake air amount are performed in the same manner as in the above embodiment. Is called.

  Also in this modification, the ECU 200 recognizes the water temperature and the intake air temperature when the engine is stopped every time the engine 1 is stopped based on the output signals of the water temperature sensor 32 and the intake air temperature sensor 34. The water temperature and intake air temperature when the engine is stopped are sequentially stored and updated in the RAM 203 or the like.

  The control routine of FIG. 8 is started when the ignition switch 40 is turned on (IG-ON). When this processing routine is started, first, in step ST201, it is determined whether or not the oil leak leakage determination condition for the injector 2 is satisfied. Since the determination process in step ST201 is the same as the determination process in step ST101 of FIG. 3 described above, detailed description thereof is omitted here.

  If the determination result in step ST201 is negative (NO), the process proceeds to step ST210. If the determination result of step ST201 is affirmative (YES), the process proceeds to step ST202.

  In step ST202, it is determined whether or not the engine speed Ne calculated from the output signal of the crank position sensor 31 rises to a scavenging completion speed (the same value as the scavenging end determination value Thne: 1000 rpm, for example) or more. judge. When the determination result is negative (NO) (when the engine speed Ne does not increase to the scavenging completion speed), the process proceeds to step ST220.

  If the determination result in step ST202 is affirmative (YES), it is determined that the engine speed has rapidly increased due to fuel injection amount decrease correction and scavenging control (intake air amount increase control) at the time of engine start. The process proceeds to step ST203.

  In step ST203, after the scavenging control at the time of starting the engine (intake air amount increase control) is completed, ignition retard control is performed in order to prevent the engine speed Ne from being blown up. Specifically, the ignition timing C (for example, −10 ° BTDC (10 ° [CA] retarded with respect to BTDC)) is set, and the ignition timing control (retarding control) of the spark plug 3 (igniter 4) is performed. Do.

  Next, in step ST204, it is determined whether or not one of the conditions “reaching the rotation increase end determination time ta (see FIG. 9)” or “a predetermined time has elapsed after engine start” is satisfied. If the determination result is negative (NO), the retard control in step ST203 is continued. The rotation increase end determination time ta is from when the engine starts t1 (or when cranking starts) until the increase in the engine speed Ne ends when the fuel is reduced and the intake air amount is increased at the time of starting the engine. This time is adapted by experiment and calculation. Further, the elapsed time after the engine is started is, for example, the time until the engine speed is stabilized after the engine is started, and is adapted by experiments and calculations.

  Then, when the determination result in step ST204 is affirmative (YES), the process proceeds to step ST205. In step ST205, on the basis of the current engine speed Ne and the engine load factor kl calculated from the output signal of the crank position sensor 31, the ignition timing is calculated with reference to a map previously adapted by experiments and calculations. Then, a gradual change process is performed to gradually advance the ignition timing retarded in step ST203 (see FIG. 9), and the actual ignition timing is changed to the calculated value (normal control value) of the ignition timing. Thereafter, this control routine is temporarily terminated (RETURN).

  The load factor kl can be calculated, for example, as a value indicating the current load ratio with respect to the maximum engine load with reference to a map or the like based on the engine speed Ne and the intake pressure.

  On the other hand, when the determination result of step ST201 is negative (NO), that is, when the oil leak leakage determination condition of the injector 2 is not satisfied (when normal starting), the process proceeds to step ST210. In step ST210, any one of the conditions “the engine speed Ne calculated from the output signal of the crank position sensor 31 is equal to or higher than the start determination speed (see FIG. 9, for example, 500 rpm)” or “the starter signal is OFF” is satisfied. It is determined whether or not is established. If the determination result is negative, the process proceeds to step ST220. In step ST220, after setting the ignition timing A (for example, 5 ° BTDC), this control routine is temporarily terminated.

  If the determination result in step ST210 is affirmative (YES), the process proceeds to step ST211. In step ST211, ignition timing B (for example, 2 ° BTDC) is set, and ignition timing control (retarding control) of the spark plug 4 is performed.

  Next, in step ST212, any one of the conditions “reached rotation end determination time tb (see FIG. 9)”, “predetermined time has elapsed after engine start”, or “shift change to D range” is set. It is determined whether or not it is established. If the determination result is negative (NO), the ignition timing control in step ST211 is continued.

  The rotation rise end determination time tb is the time from when the engine starts at t3 (or when cranking starts) until the increase in the engine speed Ne ends when the engine is started with the intake air amount at the normal start. Yes, it can be adapted by experiment and calculation. The predetermined time after the engine is started is, for example, the time until the engine speed is stabilized after the engine is started, and is adapted by experiments and calculations.

  Then, when the determination result in step ST212 is affirmative (YES), the process proceeds to step ST213. In step ST213, based on the current engine speed Ne and the engine load factor kl calculated from the output signal of the crank position sensor 31, the ignition timing is calculated with reference to a map adapted in advance through experiments and calculations. Then, a gradual change process for gradually advancing the ignition timing is performed (see FIG. 9), and the actual ignition timing is changed to the calculated value of the ignition timing. Thereafter, this control routine is temporarily terminated.

  Next, engine start control of this modification will be specifically described with reference to the timing chart of FIG.

  First, the case where the oil leak leakage determination condition of the injector 2 is satisfied will be described.

  When the oil leak detection condition is satisfied, first, the throttle opening at the start of cranking with IG-ON is set larger than that at the normal start control, and the intake air amount is increased with respect to the normal start control. The Due to the cranking with the increase in the intake air amount, the fuel (HC) leaked from the injector 2 into the intake manifold 11b (intake port 11a) is scavenged. The air-fuel ratio is optimized. Thereby, a combustion state becomes favorable and an engine speed comes to rise rapidly. In this increase process, the increase in the intake air amount is completed at time t2 when the engine speed Ne exceeds the start determination rotation speed (for example, 500 rpm) (t1) and then reaches the scavenging completion rotation speed (for example, 1000 rpm). (Return throttle opening during normal control). Further, the ignition timing is retarded by setting the ignition timing to −40 ° BTDC. By such ignition timing retardation control, it is possible to suppress the engine speed Ne from being blown up after reaching the scavenging completion speed.

  This ignition timing retardation control is continued until the above-described rotation rise end determination time ta is reached. Then, when the rotation rise end determination time ta is reached, a gradual change process for gradually advancing the ignition timing retarded at the time t2 is performed, and the actual ignition timing is set to the normal control value after the engine start (current Ignition timing calculated based on the engine speed Ne and the load factor kl).

  Here, the control in this example is a case where the shift range is shifted from the N range to the D range by operating the shift lever 50 of the driver at the time t4, for example, while the ignition timing retarding control is continued. Even if there is, the ignition timing retard control is continued. By doing in this way, the deterioration of the drivability at the time of the shift change from N range and the rotation increase of the engine 1 (rotation increase shown with a broken line in FIG. 9) can be suppressed.

  Next, a case where the oil tight leak determination condition of the injector 2 is not established (normal start control) will be described.

  If the oil leak detection condition is not satisfied, first, the throttle opening at the start of cranking with IG-ON is set to the opening at the normal start control, and the engine starts with the intake air amount at the normal start . After the cranking is started, the ignition timing is set to the retard side at time t3 when the engine speed Ne reaches the start determination rotational speed (for example, 500 rpm). This state is continued until the above-described rotation rise end determination time tb is reached. Then, when the engine speed Ne reaches the rotation rise end determination time tb, a gradual change process for gradually advancing the ignition timing is performed, and the actual ignition timing is changed to the ignition timing (in normal control after engine startup) ( The current engine speed Ne and the load factor kl are calculated).

  Since the increase in engine speed (torque up) is smaller at the normal start time than at the time when the intake air amount is increased, for example, at the timing t4 until the rotation increase end determination time tb is reached. Even if the shift range is shifted from the N range to the D range by operating the shift lever 50, the influence on the drivability at the time of the shift change from the N range is small. Therefore, in this example, a gradual change process is performed in which the ignition timing is gradually advanced at time t4 when the shift operation is performed, so that the actual ignition timing is changed to the ignition timing at the normal control after the engine is started (FIG. 9).

-Other embodiments-
In the above-described embodiment, the fuel injection amount is corrected to decrease and the intake air amount is increased when the oil leak detection condition is satisfied when the engine is started. However, the present invention is not limited to this. That is, as shown in an example in the flowchart of FIG. 10, when the oil-tight leak determination condition is satisfied when the engine is started, the fuel injection amount by the injector 2 for each cylinder is reduced and corrected while the intake air amount is increased. (Throttle valve 5 opening control) may not be performed.

  In steps ST301, 302, and 310 in the illustrated flow, the same processing as in steps ST101, 103, and 110 in the flow shown in FIG. 3 is performed. That is, in step ST301, it is determined whether the oil leak leakage determination condition is satisfied, and in step ST302, the fuel is reduced and the engine 1 is started. At this time, the first fuel injection for each cylinder may be cut as well as the second fuel injection as in the above embodiment. Alternatively, the fuel injection amount after the second time may be reduced by a predetermined amount.

  Further, the amount of reduction correction of the fuel injection amount after the second time can be made variable. In that case, for example, using the water temperature (water temperature at the time of engine start) obtained from the output signal of the water temperature sensor 32 or the intake air temperature as a parameter, experiment / calculation so that the amount of reduction correction increases as the oil tight leak increases. It is sufficient to map the values that are suitable by the above, and determine the amount of reduction correction by referring to this map. A sensor for detecting the HC concentration in the intake manifold 11b may be provided, and the amount of reduction correction may be determined according to the output.

  In step ST303, it is determined whether or not the engine speed Ne has reached a predetermined determination value. This determination value is obtained by experiment / calculation of the engine speed at which HC can sufficiently scavenge a high-concentration air-fuel mixture without performing throttle valve 5 opening control. It may be a value adapted to the above.

  The engine waits until the engine speed Ne at the time of starting reaches the determination value (determination is NO) and continues the fuel injection amount reduction correction. If the determination value is reached (determination is YES), the process proceeds to step ST304 and fuel is supplied. Is completed, and this control routine is once ended (RETURN). When the air amount is not increased in this way, there is no fear that the engine speed will rise when the start is completed without performing the retard control of the ignition timing.

  Further, in the above-described embodiment, the timing at which the intake air amount increase control (scavenging control) is ended is the time when the engine speed reaches the determination value, but the present invention is not limited to this, for example, The rate of change dNe / dt of the engine speed at the time of engine start (see the two-dot chain line in the lower part of FIG. 6) is a predetermined determination value (for example, HC can sufficiently scavenge a high-concentration mixture) When the rotational speed increase rate) is reached, the intake air amount increase control (scavenging control) may be terminated. Further, the intake air amount increase control (scavenging control) may be terminated when the engine speed becomes equal to or higher than the determination value at the time of engine start and the rate of change of the engine speed becomes equal to or higher than a predetermined value. .

  In addition, the correction control for decreasing the fuel injection amount or increasing the intake air amount when starting the engine may be terminated when the number of rotations of the crankshaft 15 exceeds a predetermined value. In this case, every time the crankshaft 15 rotates 360 °, the count value is incremented by one, and the count value is a predetermined value (for example, a count value that enables HC to sufficiently scavenge a high-concentration mixture (engine rotation If the number of times)) or more, the correction control is terminated.

  Further, in the above-described embodiment, the example in which the present invention is applied to the start control of the port injection type engine (internal combustion engine) has been described. However, the present invention is not limited to this, and the start control of the in-cylinder direct injection type engine. It is also applicable to.

  In the above-described embodiment, the case where the present invention is applied to a four-cylinder engine has been described. However, the present invention is not limited to this, and start control of an engine having any other number of cylinders, such as a six-cylinder engine, for example. It is also applicable to. In addition to the in-line multi-cylinder engine, the present invention can be applied to start control of a V-type multi-cylinder engine.

  INDUSTRIAL APPLICABILITY The present invention can be used for a start control device for an internal combustion engine (engine) mounted on a vehicle or the like, and more specifically, can be used for a start control device for an internal combustion engine intended to ensure good startability. Can do.

1 Engine 2 Injector (fuel injection valve)
5 Throttle valve 200 ECU

Claims (7)

An internal combustion engine start control device for obtaining power by burning an air-fuel mixture of intake air and fuel injected from a fuel injection valve in a combustion chamber,
When the oil-tight leak judgment condition of the fuel injection valve is satisfied, the amount of fuel injected by the fuel injection valve at the time of engine start is reduced from the fuel injection amount when the oil-tight leak judgment condition is not satisfied. A start control device for an internal combustion engine, wherein the correction is performed. The start control device for an internal combustion engine according to claim 1,
A start control device for an internal combustion engine, characterized by executing scavenging control for increasing the amount of intake air to facilitate scavenging of an air-fuel mixture when the oil tight leak determination condition is satisfied. The start control device for an internal combustion engine according to claim 2,
When increasing the intake air amount, the opening degree of the throttle valve provided in the intake passage leading to the combustion chamber is controlled to an opening degree at which the intake passage downstream from the throttle valve does not become negative pressure. An internal combustion engine start control device. The start control device for an internal combustion engine according to claim 3,
An opening control device for an internal combustion engine, wherein the opening of the throttle valve when increasing the intake air amount is set based on an engine water temperature and an engine speed. The start control device for an internal combustion engine according to any one of claims 1 to 4,
An internal combustion engine start control device characterized in that, when the oil tight leak determination condition is satisfied, the first fuel injection amount by the fuel injection valve is made zero at the time of engine start. In the start control device for an internal combustion engine according to any one of claims 1 to 5,
The internal combustion engine has a plurality of cylinders, and the fuel injection valve is disposed for each cylinder;
An internal combustion engine start control device characterized in that, when the oil tight leak determination condition is satisfied, the first fuel injection amount for each cylinder is made zero. The start control device for an internal combustion engine according to claim 6,
An internal combustion engine start control device, wherein when the oil-tight leak judgment condition of the fuel injection valve is satisfied, the second fuel injection amount for each cylinder is also corrected to decrease.

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