JP4134413B2 - Diesel engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a so-called direct injection type diesel engine provided with a fuel injection valve for injecting fuel into an in-cylinder combustion chamber of the engine, and particularly to a technical field related to fuel injection control for improving low temperature startability of the engine.
[0002]
[Prior art]
  Conventionally, it is known that the startability of an internal combustion engine deteriorates as the outside air temperature decreases. For example, in the case of an automobile diesel engine,1)If the outside air temperature is low, the battery voltage will drop, so the output of the starter motor will not be sufficient,2)Since the viscosity of the engine oil also increases, the resistance to cranking also increases, so the reason that the engine speed cannot be increased easily,3)This is because the vaporization and atomization state of the fuel is deteriorated at a low temperature, and the compression temperature of the cylinder does not become so high because the temperature of the combustion chamber and the intake air itself is low, so that the fuel is difficult to self-ignite.
[0003]
  In contrast to the deterioration of startability at such a low temperature, an additional fuel is conventionally added in addition to normal fuel injection (main injection) at the time of low temperature start, as disclosed in, for example, Japanese Patent Laid-Open No. 6-117316. It is known to perform injection (pre-injection). In this system, the total amount of fuel is increased by performing pre-injection in addition to main injection so that a sufficient amount of air-fuel mixture for ignition can be obtained even at low temperatures where the vaporization and atomization state of the fuel is poor. . Further, by performing the pre-injection earlier than the main injection, the pre-injection increases the activity of the air-fuel mixture so that the fire type is generated earlier.
[0004]
[Problems to be solved by the invention]
  However, in extremely cold conditions where the outside air temperature is extremely low, the compression temperature of the cylinder immediately after the start of cranking may not reach the self-ignition temperature of the fuel (for example, about 600 ° C.). Even if the fuel injection amount is increased as in the example, since the fuel is not self-ignited, the startability is not improved. This increased amount of fuel does not contribute to engine start until the temperature of the combustion chamber rises due to cranking, and is discharged into the atmosphere in an unburned state, resulting in a lot of wasted fuel. Not only from the viewpoint of environmental protection.
[0005]
  In addition, since the fuel supply pump is driven for such a wasteful fuel injection, the extra load consumes the driving force of the starter motor. As a result, the engine speed does not increase so easily. There is also a problem that the cold startability of the engine is further deteriorated.
[0006]
  The present invention has been made in view of such various points, and its object is to improve the low temperature startability of the engine by devising a fuel injection procedure at the start of the diesel engine, It is also intended to suppress the discharge of unburned fuel during cold start.
[0007]
[Means for Solving the Problems]
  To achieve the above object, the present inventionSolution ofThe determination means determines that the fuel can be ignited during cranking at the time of starting the engine, and then, for the first time, fuel injection for starting is performed.
[0008]
  Specifically, as illustrated in FIG. 1, the invention described in claim 1 is mechanically driven by the engine 1 and a fuel injection valve 5 that injects fuel into the in-cylinder combustion chamber 4 of the engine 1. Control of a diesel engine comprising a fuel supply pump 8 for supplying high-pressure fuel to the fuel injection valve 5 and a start injection control means 40b for injecting fuel by the fuel injection valve 5 during cranking at the time of engine start. Assume device A. An ignition determining means 40a is provided for determining that the fuel injected by the fuel injection valve 5 is in an ignitable state in which self-ignition is possible. The start injection control means 40b includes:Until it is determined by the ignition determination means 40a that the ignition is possible, an ignition determination fuel smaller than the starting injection amount is injected for the determination in the compression stroke of the cylinder,When it is determined that the ignition is possible, the fuel is injected at a start injection amount necessary for starting the engine 1.In addition, when the engine speed exceeds a preset reference speed during cranking, the ignition determination means 40a detects that the ignition determination fuel has self-ignited and determines that the ignition is possible. The reference rotational speed is set so that the lower the engine temperature state, the lower the rotational speed.
[0009]
  With the above-described configuration, when the engine 1 is started, the fuel injection valve 5 injects a starting injection amount of fuel necessary for starting the engine 1 only when the ignition determining means 40a determines that the ignition is possible. Thus, the fuel is self-ignited, so that the engine 1 is in an operating state. That is, for example, when the engine 1 is started at a low temperature, if the fuel injection amount is reduced below the start injection amount until the ignition determination means 40a determines that the ignition is possible, the fuel supply pump Since the driving load of FIG. 8 is reduced, the engine speed at the time of cranking can be increased faster than that in which the fuel of the starting injection amount is injected from the beginning as in the conventional example. 1 can be improved. Also, the amount of fuel discharged into the atmosphere in an unburned state is reduced.
[0010]
  Moreover,Based on the fact that the injected fuel for determining ignition has actually self-ignited, it is possible to reliably determine the ignitable state.ShiSince the injected ignition discrimination fuel enhances the sealing performance between the piston and the inner wall of the cylinder, the compression temperature of the cylinder is increased, which can also improve the engine startability.
[0011]
  Particularly in the above-described configuration, when the ignition discrimination fuel self-ignites, and the rotational force acts on the crankshaft due to the combustion, increasing the engine speed during cranking and exceeding a preset reference engine speed. , Which detects that the fuel has self-ignited, The lower the engine temperature, the lower the speed.
[0012]
  That is, in general, the engine speed during cranking changes depending on the engine temperature state, so that the lower the engine temperature state, the lower the reference engine speed for detecting self-ignition to correspond to the change. By setting to, detection accuracy can be increased.
[0013]
  Claim2In the described invention, the claims1In the described invention, the fuel injection amount of the ignition discrimination corresponds to the substantially minimum valve opening time of the fuel injection valve. Here, the substantial minimum valve opening time of the fuel injection valve is the minimum valve opening time in a range where atomization of the fuel spray is not significantly impaired. The fuel injection amount for discrimination of ignition can be reduced as much as possible without significantly impairing atomization. Therefore, the driving load of the fuel supply pump and the discharge of unburned fuel can be minimized.
[0014]
  Claim3In the described invention, the claims1In the described invention, the injection amount of the ignition discrimination fuel is 1/10 or less of the start injection amount. Thus, the injection amount of the fuel for determining ignition is realized.
[0015]
  Claim4In the described invention, the claims1In the described invention, the injection amount of the ignition discrimination fuel is the same as the minimum fuel injection amount when the engine is in the practical operation range. In other words, if the injection amount of the ignition discrimination fuel is too small, the fuel may not self-ignite even though it is actually in an ignitable state. By injecting the same amount of fuel as the minimum fuel injection amount at a certain time, it is possible to reliably determine that the ignition is possible. That is, it is possible to reduce the driving load of the fuel supply pump and the discharge of unburned fuel while ensuring the reliability of the ignition determination stably.
[0016]
  Claim5In the described invention, the claims4The minimum fuel injection amount in the practical operation region of the described invention is the minimum fuel injection amount in the low-load low-rotation operation region excluding the idle state. Thus, the injection amount of the fuel for determining ignition is realized.
[0017]
  Claim6In the described invention, the claims1In the described invention, there is provided an injection prohibiting means for prohibiting fuel injection by the fuel injection valve from the start of cranking until the set period elapses, and the start injection control means is for determining ignition after the set period has elapsed. The fuel injection is started. The set period may be, for example, a period from the start of operation of the starter motor until the crankshaft of the engine rotates a predetermined number of times, or may be a period of time after the starter motor starts operation. .
[0018]
  As such, by prohibiting fuel injection only during a period when the cranking resistance immediately after the start of cranking is particularly large and reducing the drive load of the fuel supply pump as much as possible, the engine cold startability can be further improved..
[0019]
  Claim7In the described invention, the claims1The starting injection control means in the described invention is configured to immediately terminate the fuel injection for the ignition determination when it is determined by the ignition determination means that the ignition is possible. As a result, when the fuel is in a self-igniting state, the start of the engine can be completed quickly by immediately terminating the injection of the ignition discrimination fuel and injecting the fuel amount of the starting injection amount by the fuel injection valve. .
[0020]
  Claim8In the described invention, the claims1When the ignition determination fuel injection timing in the described invention is set earlier than the fuel injection for starting the engine, and the start injection control means determines that the ignition determination means is in an ignitable state, the ignition The fuel injection for determination and the fuel injection for starting the engine are both performed at least once.
[0021]
  Thus, immediately after the fuel shifts from the non-self-ignited state to the ignitable state, a small amount of ignition discrimination fuel is injected at least once earlier than the fuel injection of the starting injection amount by the fuel injection valve. The accidental misfire can be avoided by sufficiently evaporating the fuel to promote the formation of fire types.
[0022]
  Claim9In the described invention, the engine according to the first aspect of the present invention has a plurality of cylinders, the ignition determining means determines that each cylinder is in an ignitable state, and the start injection control means is The fuel injection valve is controlled for each cylinder according to the discrimination result by the ignition discrimination means.
[0023]
  That is, in general, in an engine having a plurality of cylinders, the temperature state and the intake air amount are slightly different for each cylinder. Therefore, it is determined that each cylinder is in an ignitable state, and each cylinder is determined according to the determination result. By controlling the fuel injection valve for each cylinder, the function and effect of the invention of claim 1 can be sufficiently obtained.
[0024]
  Claim10In the described invention, the engine according to the first aspect of the present invention has a plurality of cylinders, the ignition determining means determines that each cylinder is in an ignitable state, and the start injection control means is When it is determined by the ignition determining means that any one of the cylinders is in an ignitable state, fuel injection for starting the engine is started from the cylinder that performs fuel injection next to the cylinder.
[0025]
  As a result, in an engine having a plurality of cylinders, although the temperature state and intake air amount differ slightly for each cylinder, if any one of the cylinders can be ignited, the other cylinders can be ignited. Therefore, when it is determined that any one of the cylinders can be ignited, the engine is injected by injecting a starting injection amount of fuel from the cylinder that performs fuel injection next to the cylinder. Can be completed in the shortest possible time.
[0026]
  Claim11In the described invention, the claims10The ignition determination fuel injection timing in the described invention is set earlier than the fuel injection for starting the engine, and when the start injection control means determines that the ignition is possible by the ignition determination means, the ignition determination Both the fuel injection and the fuel injection for starting the engine are performed at least once.
[0027]
  As a result, when any one of the plurality of cylinders of the engine is in an ignitable state and the start injection amount of fuel is injected from a cylinder that performs fuel injection next to the cylinder, the aforementioned ignitable state Since it is considered that the possibility of misfire is somewhat high in other cylinders, it is particularly effective to avoid a misfire by injecting a small amount of ignition discrimination fuel at least once earlier than the starting injection amount of fuel. Has an effect.
[0028]
  Claim12In the invention described in claim 1, in the invention described in claim 1, the amount of exhaust gas recirculated until it is determined by the ignition recirculation means that recirculates part of the exhaust gas to the engine intake system and the ignition determination means is in an ignition enabled state. Exhaust gas recirculation control means for controlling the exhaust gas recirculation means so as to be zero is provided.
[0029]
  As a result, when the engine is started at a low temperature, the exhaust gas temperature is usually lower than the intake air temperature until combustion is started. Can prevent the intake air temperature from decreasing.
[0030]
  Claim13In the described invention, in the invention described in the first aspect, the pressure accumulating chamber for storing the fuel in a high pressure state equal to or higher than the injection pressure includes a common rail fuel injection system interposed between the fuel supply pump and the fuel injection valve. Shall. In this case, since it is necessary to store fuel in a high-pressure state in a large-volume accumulator, the driving load of the fuel supply pump at the time of starting the engine is particularly large. Therefore, it is particularly effective to reduce the driving load of the fuel supply pump and improve the low temperature startability of the engine during cranking as in the first aspect of the invention..
[0031]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0032]
  (Embodiment 1)
  FIG. 1 shows an overall configuration of a control device A for a diesel engine according to Embodiment 1 of the present invention, and 1 is an in-line four-cylinder diesel engine mounted on a vehicle. The engine 1 has four cylinders 2, 2, 2, and 2. In each cylinder 2, pistons (not shown) are fitted so as to be capable of reciprocating in the axial direction. A combustion chamber 4 is defined inside. In addition, an injector (fuel injection valve) 5 is disposed at a substantially central portion of the upper surface of each combustion chamber 4 so as to extend along the axis of the cylinder 2, as exaggerated in the drawing. These injectors 5, 5,... Are connected to a common common rail (accumulation chamber) 6 for storing fuel in a high pressure state higher than the injection pressure, and are opened and closed at a predetermined injection timing for each cylinder. High-pressure fuel is directly supplied to the combustion chamber 4 from a plurality of injection holes provided at the tip.
[0033]
  The common rail 6 is provided with a fuel pressure sensor 6a for detecting an internal fuel pressure (common rail pressure). The common rail 6 is connected to a fuel supply pump 8 through a high-pressure fuel passage 7, and the fuel supply pump 8 is connected to a fuel tank 10 through a fuel passage 9. The fuel supply pump 8 has an input shaft 8 a that is drivingly connected to the crankshaft of the engine 1, and operates by receiving rotational input from the crankshaft. Fuel in the fuel tank 10 is passed through the fuel passage 9. The fuel is sucked while being filtered by the fuel filter 11, and the fuel is pumped to the common rail 6 by a jerk type pumping system.
[0034]
  Although not shown, the fuel supply pump 8 is provided with an electromagnetic valve that adjusts the discharge amount of the pump by allowing a part of the fuel sent out by the pressure feeding system to escape to the return passage 12. The opening degree of the electromagnetic valve is changed by a control signal from the ECU 40 (described later) in accordance with a detected value by the fuel pressure sensor 6a, and thereby the common rail pressure can be feedback controlled to a predetermined value. In the figure, reference numeral 13 denotes a pressure limiter that discharges fuel from the common rail 6 when the common rail pressure exceeds a predetermined value. The fuel discharged from the pressure limiter circulates in the return passage 14 and flows into the fuel. Returned to the tank 10. Furthermore, 15 is a return passage for returning surplus fuel from the injector 5 to the fuel tank 10.
[0035]
  Although not shown in detail in the engine 1, a crank angle sensor 16 for detecting the rotation angle of the crankshaft, a cam angle sensor 17 for detecting the rotation angle of the intake / exhaust system camshaft, and a cooling water temperature (engine water temperature). And an engine water temperature sensor 18 for detecting. The crank angle sensor 16 includes a plate to be detected provided at an end of the crankshaft and an electromagnetic pickup disposed so as to face the outer periphery of the plate, and extends over the entire outer periphery of the plate to be detected. A pulse signal is output corresponding to the passage of protrusions formed at equal intervals. Similarly, the cam angle sensor 17 includes a plurality of protrusions provided at predetermined positions on the cam shaft peripheral surface, and an electromagnetic pickup that outputs a pulse signal when each of the protrusions passes. Reference numeral 19 denotes a vacuum pump driven by a cam shaft.
[0036]
  Reference numeral 20 denotes an intake passage for supplying intake air (air) filtered by an air cleaner (not shown) to the combustion chamber 4 of the engine 1, and a downstream end portion of the intake passage 20 branches into each cylinder via a surge tank 21. In addition, each cylinder 2 is connected to the combustion chamber 4 by an intake port. The surge tank 21 is provided with a supercharging pressure sensor 22 that detects the pressure of intake air supercharged by a turbocharger 31 described later. In the intake passage 20, a hot film type air flow sensor 23 that detects an intake air flow rate sucked into the engine 1 in order from the upstream side to the downstream side, and a blower 24 that is driven by a turbine 29 described later to compress the intake air. An intercooler 25 that cools the intake air compressed by the blower 24 and an intake throttle valve 26 that restricts the cross section of the intake passage 20 are provided. The intake throttle valve 26 is a butterfly valve provided with a notch so that intake air can flow even in a fully closed state, and is opened and closed by an actuator (not shown).
[0037]
  Further, reference numeral 28 denotes an exhaust passage for discharging combustion gas from the combustion chamber 4 of each cylinder 2. The upstream end portion of the exhaust passage 28 is branched and connected to the combustion chamber 4 of each cylinder 2 by an exhaust port. A turbine 29 that is rotated by exhaust gas is disposed in the exhaust passage 28, and an exhaust purification catalytic converter 30 is disposed downstream thereof. Although not shown in detail, the catalytic converter 30 includes a cordierite carrier having a honeycomb structure having a large number of through holes extending in parallel with each other along the flow direction of the exhaust gas, and a plurality of catalysts are provided on the wall surfaces of the through holes of the carrier. A layer is formed, and has a function of reducing HC, CO, NOx, and particulates in the exhaust gas flowing through each through hole.
[0038]
  The turbocharger 31 composed of the turbine 29 and the blower 24 is a variable nozzle turbo in which a flap for changing a cross-sectional area of the inlet is rotatably provided at an inlet of a turbine chamber that houses the turbine 29. By rotating the flap to reduce the nozzle cross-sectional area, the supercharging efficiency can be increased even in the low rotation range of the engine 1 with a small exhaust flow rate.
[0039]
  Further, the exhaust passage 28 is branched and connected to an upstream end of an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 33 that recirculates part of the exhaust gas to the intake side at a portion upstream of the turbine 29. The downstream end of the EGR passage 33 is connected to the intake passage 20 on the intake downstream side of the intake throttle valve 26, and a negative pressure operation type whose opening degree can be adjusted near the downstream end in the middle of the EGR passage 33. An exhaust gas recirculation amount adjustment valve (hereinafter referred to as EGR valve) 34 is arranged. The EGR valve 34 is configured to be opened and closed by a negative pressure drive type actuator 35 driven by the negative pressure from the vacuum pump 19, and linearly changes the passage cross-sectional area of the EGR passage 33 so that the intake passage The flow rate of the exhaust gas recirculated to 20 is adjusted.
[0040]
  Each injector 5, fuel supply pump 8, intake throttle valve 26, EGR valve 34, and the like are configured to operate in response to a control signal from a control unit (Electronic Control Unit: hereinafter referred to as ECU) 40. On the other hand, the ECU 40 has an output signal from the fuel pressure sensor 6a, an output signal from the crank angle sensor 16 and the cam angle sensor 17, an output signal from the engine water temperature sensor 18, and an output signal from the air flow sensor 23. And an output signal from an accelerator opening sensor 36 for detecting an operation amount (accelerator opening) of an accelerator pedal (not shown) by a driver of the vehicle.
[0041]
  The fuel injection amount and the injection timing are controlled according to the operating state of the engine 1 by the operation of the injector 5, and the common rail pressure, that is, the fuel injection pressure is controlled by the operation of the high-pressure supply pump 8. The intake air amount is controlled by the operation of the intake throttle valve 26, the exhaust gas recirculation amount is controlled by the operation of the EGR valve 34, and the rotation angle of the flap of the turbocharger 31 is controlled. .
[0042]
  The characteristic part of the present invention is the fuel injection control when the engine 1 is started at a low temperature. That is, when the engine 1 is started in a low temperature state where the outside air temperature is low (for example, below 20 ° C. below zero), first, the ignition discrimination means that the fuel injected by the injector 5 is in an ignitable state where it self-ignites in the combustion chamber 4 Only when it is determined by 40a and it is determined that the ignition is possible, the start injection control means 40b injects the fuel of the start injection amount necessary for starting the engine 1. Further, the exhaust gas recirculation control means 40c holds the EGR valve 34 in the fully closed state until the ignition recognizing means 40a determines that the ignition is possible, thereby reducing the exhaust gas recirculation amount to zero. . The functions of the ignition determination means 40a, the start injection control means 40b, and the exhaust gas recirculation control means 40c are all realized by the ECU 40 executing a control program on the memory.
[0043]
  (Control at engine start)
  Hereinafter, the control procedure at the time of low temperature start of the engine 1 by the ECU 40 will be specifically described with reference to the flowcharts shown in FIGS.
[0044]
  First, in the control of the common rail pressure shown in FIG. 2, in step SA1 in FIG. 2, various signals such as an output signal from the fuel pressure sensor 6a, a crank angle signal from the crank angle sensor 16, and a starter signal from the ignition switch are input. Subsequently, in step SA2, it is determined whether the engine is being started. That is, when the engine speed Ne calculated based on the crank angle signal is lower than a preset start determination rotational speed (for example, 500 rpm) and the starter signal is input, the engine is being started. YES The process proceeds to step SA3, and if not, it is determined NO when the engine is not started, and the process proceeds to a control routine other than when the engine is started although details are omitted.
[0045]
  In step SA3, the target common rail pressure at the start time recorded in the memory of the ECU 40 is read, and the read value is set as the start common rail pressure. Subsequently, in step SA4, a control signal is output to the solenoid valve of the fuel supply pump 8 to adjust the amount of pumping to the common rail 6, and in step SA5, the common rail pressure detected by the fuel pressure sensor 6a is It is determined whether or not the value set in step SA3 (set value) is exceeded. If this determination is YES, the process returns. On the other hand, if the determination value is NO and the common rail pressure has not reached the set value, the process returns to step SA4 to continue fuel pumping from the fuel supply pump 8 to the common rail 6. . That is, the fuel pressure is continued until the common rail pressure reaches the target value at the time of starting the engine to increase the common rail pressure.
[0046]
  Next, in the fuel injection control shown in FIG. 3, in step SB1 of FIG. 3, the crank angle signal, the output signal from the engine water temperature sensor 18, the output signal from the air flow sensor 23, the output signal from the accelerator opening sensor 36, Various signals such as a starter signal are input, and in subsequent step SB2, it is determined whether or not the engine is being started as in step SA2 in FIG. When this determination is NO, the process proceeds to a control routine other than at the time of engine start. On the other hand, when YES is determined at the time of engine start, the process proceeds to step SB3 to determine whether it is a low temperature start.
[0047]
  That is, in step SB3, it is determined whether or not the engine water temperature is lower than a set value (for example, −20 ° C.) based on the output signal from the engine water temperature sensor 18. Therefore, the process proceeds to step SB7, and the main injection at start-up in which each injector 5 injects the fuel of the start injection amount necessary for starting the engine 1 in the vicinity of the compression top dead center of each cylinder 2 is executed. On the other hand, if it is determined that the engine water temperature is lower than the set value and YES, the process proceeds to step SB4. The determination as to whether or not the engine 1 is at a low temperature start may be made in consideration of not only the engine water temperature but also the outside air temperature and the like.
[0048]
  In step SB4, a micro injection is performed in which a small amount of fuel (ignition determination fuel) is injected earlier than the main injection at the start in the compression stroke of each cylinder 2, and in the subsequent step SB5, the micro injection is performed. It is determined whether or not the fuel has self-ignited, that is, whether or not the fuel is ready for ignition. Note that the timing of the minute injection may be corrected to an advance side as the engine water temperature is low so that the injected fuel does not spread excessively and can be sufficiently vaporized and atomized.
[0049]
  The presence / absence of self-ignition is determined, for example, in step SC1 of the flow shown in FIG. 4 based on whether or not the engine speed Ne during cranking has exceeded a preset reference speed Ne *, and Ne> Ne * If YES, it is determined that the fuel has self-ignited, the process proceeds to step SC2, the ignition determination flag F is set to F = 1, and the process returns to step SB6 of the flow of FIG. On the other hand, if Ne ≦ Ne * and NO, it is determined that the fuel is not self-ignited, the process proceeds to step SC3, the ignition determination flag F is set to F = 0, and the process returns to step SB6 of the flow of FIG.
[0050]
  That is, if the fuel self-ignites during cranking, the engine speed Ne increases by one stage due to the combustion. Therefore, as illustrated in FIG. 5, the engine speed during cranking that is forcibly rotated by the starter motor is exemplified. When Ne exceeds a reference rotational speed Ne * higher than a normal cranking rotational speed (for example, about 120 rpm), it is detected that the fuel self-ignited.
[0051]
  The reference speed Ne * should be changed according to the engine water temperature.CageBy doing so, the detection accuracy can be increased. That is, in general, the engine speed Ne during cranking becomes lower as the temperature state of the engine 1 is lower. For example, experimentally, the lower the engine water temperature, the lower the engine speed Ne * becomes. It is only necessary to create a set table and electronically record this table in the memory of the ECU 40.
[0052]
  Then, after the self-ignition determination, in step SB6 of FIG. 3, it is determined whether or not the value of the ignition determination flag F is F = 1. If NO is not F = 1, the process returns to step SB4 while F = If “1” is YES, the process proceeds to step SB 7, and start-up main injection is executed for each cylinder 2. That is, for each cylinder 2 of the engine 1, it is determined that when a small amount of fuel injected in the compression stroke is actually self-ignited, the cylinder 2 is ready to be ignited. Is injected in an amount necessary for starting the engine 1.
[0053]
  The control procedure of SC1 to SC3 shown in the flow of FIG. 4 is based on the ignition discrimination means 40a for discriminating whether or not a small amount of fuel injected in the compression stroke is in a self-ignitable state depending on whether or not it is actually self-ignited. It corresponds to. Further, the control procedure of SB4 to SB7 shown in the flow of FIG. 3 is to perform minute injection for the determination until the ignition determination means 40a determines that the ignition is possible during cranking at the time of engine start. When it is determined by the ignition determination means 40a that the ignition is possible, it corresponds to the start injection control means 40b for performing the main injection at the start.
[0054]
  In this embodiment, the minute injection amount for determining the ignition is the same as the minimum fuel injection amount when the engine 1 is in the practical operation range. This is the same as the minimum fuel injection amount when the engine 1 is in the low-load low-rotation operation region excluding the idle state, for example, when the engine speed Ne = 1500 rpm and no fuel cut is performed. Depending on the specific example, 1-3mm³It is. If this amount of fuel is injected, the fuel will always be self-ignited and combusted when it is in an ignitable state, and the engine speed Ne will always be higher than the reference speed Ne * due to the combustion. It can be determined with certainty. Note that the fuel injection amount for determining the ignition does not necessarily have to be a minute amount as described above, but is preferably 1/10 or less of the main injection at the start.
[0055]
  Therefore, according to the control device A for a diesel engine according to this embodiment, when cranking is started when the engine 1 is started at a low temperature, first, as shown in FIG. A small amount of fuel is injected from the injector 5 in the compression stroke for each cylinder 2 (in the example shown, 20 ° CA before compression top dead center), and this fuel improves the sealing performance between the piston and the cylinder inner wall. . As the cranking gradually increases the temperature state of the engine 1 and the cranking resistance decreases due to the decrease in the viscosity of the engine oil, the engine speed Ne increases (see FIG. 5), and the compression temperature of the cylinder 2 increases. The fuel self-ignition temperature is reached.
[0056]
  Then, since the minute amount of fuel is actually self-ignited and combusted, the engine speed is increased by one step and exceeds the reference speed Ne *, and can be ignited by the ignition discriminating means 40a. The state is determined. Then, for the cylinder 2 that has been determined to be ignitable, the start injection control means 40b performs the start main injection near the compression top dead center as shown in FIG. 6 (b). As the injected fuel self-ignites and burns, the engine speed Ne rises quickly and the engine start is completed quickly.
[0057]
  According to such start injection control at the time of low temperature start, the fuel injection amount from the injector 5 is made very small until the ignition is possible in each cylinder 2 of the engine 1, so that each injector is connected via the common rail 6. The driving load of the fuel supply pump 8 that pumps fuel to 5 can be made extremely small. As a result, even when cranking in a low temperature state, the engine speed Ne can be quickly increased, and the compression temperature of each cylinder 2 can reach the self-ignition temperature of the fuel. Startability can be improved. Further, the amount of fuel discharged into the atmosphere in an unburned state can be reduced.
[0058]
  In particular, in this embodiment, whether or not the ignition is possible is determined based on the presence or absence of self-ignition of the actually injected fuel, so that the ignition possible state can be reliably determined. In addition, since the fuel injection amount for determining the ignition is as small as possible within the range necessary for determining the ignition, the driving load of the fuel supply pump 8 and the discharge of unburned fuel can be minimized. Can do.
[0059]
  In this embodiment, the exhaust gas recirculation control means 40c keeps the EGR valve 24 in the fully closed state until the ignition is enabled, so that the exhaust gas is not recirculated to the intake passage 20. That is, generally, the intake air sucked into the combustion chamber 4 when the engine 1 is started at a low temperature becomes a high temperature state during the compression stroke, and heat is taken away from the cylinder wall surface. Therefore, the exhaust temperature is higher than the intake air temperature until combustion is started. Also lower. Therefore, from the start of cranking until it is determined that the ignition is possible, the EGR valve 24 is fully closed so that the exhaust gas is not recirculated. 1 can be further improved in cold startability.
[0060]
  In this embodiment, when it is determined that the ignition is possible as described above, the minute injection is immediately terminated and the main injection at the start is executed. When it is determined that, both the fine injection and the main injection may be performed at least once as shown in FIG. By doing so, the fuel injected at an early stage by the micro-injection is sufficiently vaporized and atomized, and it becomes easy to generate a fire. Therefore, even if it is immediately after the ignition is possible, an accidental misfire can be avoided..
(Other embodiments)
  In addition, this invention is the said embodiment.1It is not limited and includes various other embodiments. Ie,in frontIn the first embodiment, the ignition discriminating means 40a shall discriminate whether or not each cylinder of the engine 1 is in an ignitable state, and the start injection control means 40b is based on the ignition discriminating result for each cylinder. Thus, the fuel injection control is performed for each cylinder, but the present invention is not limited to this.
[0061]
  That is, when it is determined by the ignition determination means 40a that any one of the cylinders of the engine 1 is in an ignitable state, the start injection control means 40b starts the main injection at the start in order from the cylinder that performs the next fuel injection. You may make it make it. For example7As shown, when the first cylinder of the four cylinders of the engine 1 is first determined to be in an ignitable state, the third cylinder, the fourth cylinder, the second cylinder, the first cylinder,. In this order, the main injection at the start is performed to complete the start of the engine 1, and the engine start can be completed in the shortest time.
[0062]
  At that time, as shown in the figure, in the three cylinders other than the first cylinder determined to be ignited, both the minute injection and the main injection at the start may be performed. By doing so, even if one of the three cylinders is in a state where it is difficult for the fuel to self-ignite, the fuel finely injected earlier than the main injection is sufficiently vaporized and atomized, making it easy to generate a fire type. By doing so, misfire can be avoided.
[0063]
  In each of the above embodiments, the present invention is applied to the diesel engine 1 equipped with the common rail fuel injection system. However, the present invention is not limited to this, and a unit injector is provided for each cylinder instead of the common rail fuel injection system. Of course, the present invention can be applied to various types of diesel engines including an electronically controlled fuel injection pump.
[0064]
【The invention's effect】
  As described above, according to the control device for a diesel engine according to the first aspect of the present invention, it is not until the ignition is possible because the ignition discrimination means determines that the ignition is possible when the engine is cold started. Since the fuel of the starting injection amount necessary for starting the engine is injected, the fuel injection amount is made smaller than the starting injection amount until the ignition is possible, thereby reducing the driving load of the fuel supply pump. In addition, the low temperature startability of the engine can be improved. Further, it is possible to suppress the discharge of unburned fuel when the engine is cold started.
[0065]
  MoreoverIn addition, it is possible to improve the sealability of the combustion chamber by injecting the ignition discrimination fuel, and it is possible to reliably discriminate the ignitable state because the fuel has actually self-ignited.
[0066]
  Furthermore, when the engine speed during cranking exceeds a preset reference engine speed, self-ignition of the ignition discrimination fuel can be detected, and the reference engine speed is changed according to the engine temperature state. Thus, the detection accuracy can be increased.
[0067]
  Claim2According to the described invention, the injection amount of the ignition discrimination fuel corresponds to the substantial minimum valve opening time of the fuel injection valve, thereby minimizing the driving load of the fuel supply pump and the unburned fuel discharge. Can be suppressed.
[0068]
  Claim4According to the described invention, by making the injection amount of the fuel for determining the ignition the same as the minimum fuel injection amount when the engine is in a practical operation range, the reliability of the ignition determination is stably secured, and the fuel supply pump Driving load and unburned fuel emissions can be reduced.
[0069]
  Claim6According to the described invention, by prohibiting fuel injection by the injection prohibiting means for a set period immediately after the start of cranking, the driving load of the fuel supply pump is minimized when the cranking resistance is particularly large, so that the engine can be started at low temperature. Can further improve.
[0070]
  Claim7According to the described invention, when it is determined that the ignition is possible, the start of the engine can be completed quickly by immediately terminating the injection of the ignition determination fuel and injecting the fuel amount of the start injection amount.
[0071]
  Claim8According to the described invention, when it is determined that the ignition is possible, it is possible to avoid a misfire by performing both the injection of the fuel for determining the ignition and the fuel injection for starting the engine at least once.
[0072]
  Claim9According to the described invention, the effect of the invention of the first aspect can be sufficiently obtained by performing the ignition determination and the fuel injection control for each cylinder.
[0073]
  Claim10According to the described invention, when it is determined that any one of the plurality of cylinders of the engine is in an ignitable state, fuel injection for starting the engine is started from the cylinder that performs fuel injection next to the cylinder. Thus, the engine start can be completed in the shortest time.
[0074]
  Claim11According to the described invention, it is particularly effective that misfire can be avoided by performing both the injection of the fuel for determining the ignition and the fuel injection for starting the engine.
[0075]
  Claim12According to the described invention, the exhaust gas is not recirculated until it is determined that the ignition is possible, so that a decrease in the intake air temperature due to the cold exhaust gas at the time of engine low temperature start can be prevented, and the low temperature start performance of the engine can be further improved.
[0076]
  Claim13In the described invention, in an engine equipped with a common rail type fuel injection system in which the driving load of the fuel supply pump is particularly large, reducing the driving load of the fuel supply pump during cranking is particularly effective in improving low temperature startability. become.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a control device for a diesel engine according to Embodiment 1 of the present invention.
FIG. 2 is a flowchart showing a processing procedure of common rail pressure control at the time of engine start.
FIG. 3 is a flowchart showing a processing procedure for start-up fuel injection control.
FIG. 4 is a flowchart showing a processing procedure for self-ignition determination.
FIG. 5 is a time chart showing a change in engine speed during cranking.
FIG. 6 is an explanatory diagram illustrating the injection timing of micro injection and start-up main injection.
[Fig. 7]Description showing the fuel injection mode of each cylinder in another embodiment in which when the ignition possibility determination is made for any one cylinder of the engine, the main injection at the start is started sequentially from the other cylinder to which fuel is injected next. FIG.
[Explanation of symbols]
A Diesel engine control system
1 Diesel engine
2-cylinder
4 Combustion chamber
5 Injector (fuel injection valve)
6 Common rail (accumulation chamber)
8 Fuel supply pump
33 EGR passage (exhaust gas recirculation means)
40 Control unit
40a Ignition discrimination means
40b Start injection control means
40c Exhaust gas recirculation control means
40d Non-ignitable period estimation means

Claims (13)

A fuel injection valve for injecting fuel into a cylinder combustion chamber of the engine;
A fuel supply pump that is mechanically driven by an engine to supply high-pressure fuel to the fuel injection valve;
In a control device for a diesel engine comprising start injection control means for injecting fuel by the fuel injection valve during cranking at the time of engine start,
Ignition determination means for determining that the fuel injected by the fuel injection valve is in an ignitable state where self-ignition is provided,
The start injection control means injects an ignition determination fuel smaller than the start injection amount in the compression stroke of the cylinder for the determination until the ignition determination means determines that the ignition is possible. When it is determined that the engine is in a possible state, the engine is configured to inject a start injection amount of fuel necessary for starting the engine ,
The ignition determination means is configured to detect that the ignition determination fuel is self-ignited and determine that the ignition is possible when the engine rotation speed exceeds a preset reference rotation speed during cranking. And
The control apparatus for a diesel engine, wherein the reference rotational speed is set so as to become lower as the engine temperature is lower . In claim 1,
The diesel engine control device , wherein the injection amount of the ignition discrimination fuel corresponds to a substantial minimum valve opening time of the fuel injection valve . In claim 1 ,
Injection amount of the ignition discriminating fuel control system for a diesel engine, wherein the starting injection quantity of at 1/10 or less. In claim 1 ,
A control apparatus for a diesel engine, characterized in that the injection amount of the ignition discrimination fuel is the same as the minimum fuel injection amount when the engine is in a practical operation range . In claim 4 ,
A control device for a diesel engine, characterized in that the minimum fuel injection amount in a practical operation region is a minimum fuel injection amount in a low-load low-rotation operation region excluding an idle state . In claim 1 ,
Between the start of cranking and until the set period elapses, an injection prohibiting means for prohibiting fuel injection by the fuel injection valve is provided,
The diesel engine control device , wherein the start injection control means is configured to start injection of an ignition discrimination fuel after the set period has elapsed . In claim 1 ,
The control device for a diesel engine, wherein the starting injection control means is configured to immediately end the injection of the ignition discrimination fuel when the ignition discrimination means determines that the ignition is possible . In claim 1 ,
The timing for injecting the ignition discrimination fuel is set earlier than the fuel injection for starting the engine,
The start injection control means is configured to perform both the ignition determination fuel injection and the engine start fuel injection at least once when the ignition determination means determines that the ignition is possible. control device for a diesel engine, characterized in that there. In claim 1,
The engine has multiple cylinders,
The ignition discriminating means is configured to discriminate that each cylinder is in an ignitable state,
The control device for a diesel engine , wherein the start injection control means is configured to control the fuel injection valve for each cylinder in accordance with a determination result by the ignition determination means . In claim 1,
The engine has multiple cylinders,
The ignition discriminating means is configured to discriminate that each cylinder is in an ignitable state,
When it is determined by the ignition determining means that any one of the cylinders is in an ignitable state, the start injection control means starts fuel injection for starting the engine from a cylinder that performs fuel injection next to the cylinder. control device for a diesel engine, characterized in that it is configured to. In claim 10 ,
The fuel injection timing for determining ignition is set earlier than the fuel injection for starting the engine,
The start injection control means is configured to perform both the ignition determination fuel injection and the engine start fuel injection at least once when the ignition determination means determines that the ignition is possible. control device for a diesel engine, characterized in that there. In claim 1,
Exhaust gas recirculation means for recirculating part of the exhaust gas to the engine intake system;
An exhaust gas recirculation control means is provided for controlling the exhaust gas recirculation means so that the exhaust gas recirculation amount becomes zero until it is determined by the ignition determination means that the ignition is possible . Control device. In claim 1,
A diesel engine control device comprising a common rail fuel injection system in which a pressure accumulating chamber for storing fuel in a high pressure state equal to or higher than an injection pressure is provided between a fuel supply pump and a fuel injection valve .

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