JPH11117788A - Fuel injection controller for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection controller for a diesel engine, capable of setting a proper injection amount of fuel all times, whenever split injection is executed or not, for more startability. SOLUTION: A fuel injection controller 2 for an engine 1 has a fuel injection nozzle 4, an injection pump 5, an electromagnetic spill valve 21 to control the injection amount and timing of fuel, a timing control valve 20 and an electronic control unit(ECU) 8. The ECU 8 controls the fuel injection controller 2 when the engine 1 is judged to be in a cold starting condition in accordance with the detection results of a water temperature sensor 23 and others, so that its can split a required amount of fuel several times to execute split injection. In the ROM of the ECU 8, two maps are prepared for the calculation of a starting fuel injection amount during executing split injection at starting or not, so that the maps can be changed for the calculation of the injection amount corresponding to an injection method at starting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for a diesel engine, and more particularly to an improvement in fuel injection control which is effective in improving the startability of the engine.

[0002]

2. Description of the Related Art In a diesel engine employing electronically controlled fuel injection, a fuel injection amount and a fuel injection timing are controlled by an electronic control unit (hereinafter referred to as an ECU) mainly composed of a computer. The fuel injection amount and the fuel injection timing are determined based on various conditions such as the number of revolutions and load of the engine. The fuel injection amount is determined with reference to a control map stored in the ECU in advance.

[0003] When the engine is in a cranking state by a starter, such as when the engine is started, since the rotational fluctuation of the diesel engine is extremely large, the fuel injection amount at the time of starting is obtained from a control map during normal operation. It is necessary to further increase the amount. However, if the fuel injection amount at start-up is uniformly increased by a fixed amount, in situations where the fuel is difficult to ignite, such as during low-temperature start-up, the rate of misfires is high, and the startability of the engine is adversely affected. Getting worse. In addition, at the time of restart after complete warm-up, unburned substances and the like in the exhaust gas increase due to an excessive amount of fuel injection, and smoke is generated.

Therefore, conventionally, to solve such a problem,
For example, in "Diesel engine fuel injection amount control method" described in Japanese Patent Application Laid-Open No. 63-186939, the fuel injection amount at the time of low temperature start is calculated using a map different from that during normal operation. . FIG. 15 shows an example of the fuel injection amount control map at the time of such a low temperature start.

As shown in FIG. 15, in this fuel injection amount control, when the fuel injection amount QSTA at the time of starting is determined from the engine speed NE and the accelerator opening ACCPA, the engine speed NE is set to 0. In the section from to Na, the fuel injection amount QSTA is set to a constant amount according to the accelerator opening ACCPA. In the section where the engine speed NE is from Na to Nb, the fuel injection amount QSTA is gradually reduced to a predetermined amount Qa with an increase in the engine speed NE.

[0006] As described above, in a diesel engine, usually,
When the engine speed NE rises to some extent (a section from Na to Nb in FIG. 15) at the time of starting, the rotation fluctuation becomes remarkable, and misfire easily occurs. At this time, if excessive fuel is being injected, the combustion chamber is cooled by the unburned fuel. When the temperature in the combustion chamber is reduced in this way, the period during which fuel rises to a temperature at which self-ignition can be performed is shortened, so that misfire is more likely to occur, and low-temperature startability is reduced.

In this regard, according to the method described in the publication, the fuel is reduced in the engine rotation range where misfiring easily occurs, whereby the temperature inside the combustion chamber is prevented from lowering, and the low temperature startability is improved. Become like

On the other hand, conventionally, not only the fuel injection amount is adjusted in this manner, but also the fuel injection method itself, such as a "fuel injection device for a diesel engine" described in JP-A-5-86932. There is also known a technique for improving the startability by changing according to the condition.

That is, in the apparatus described in the above publication, when the engine is started, during a period in which the cooling water temperature THW is low and the engine speed NE is low, a required fuel injection amount is divided into a plurality of injections and injected into the combustion chamber. Is executed, and normal injection is executed in other periods. By performing the split injection until the engine speed NE rises to a predetermined engine speed at the time of low-temperature start with a low coolant temperature THW, it is possible to appropriately avoid the decrease in the cylinder temperature due to the heat of vaporization of the fuel, A more stable starting can be achieved.

[0010]

Normally, the optimum fuel injection amount at the time of each of the cooling water temperatures THW greatly differs between the time of the split injection and the time of the normal injection. However, if the fuel injection amount during the split injection or the normal injection is uniquely calculated based on the target fuel injection amount and the actual fuel pressure as in the above-described conventional apparatus, it is difficult to adapt the calculation, and the cooling water temperature or Depending on the region of the engine speed, the variation in the injection amount cannot be ignored. Although split injection is an extremely effective injection method for improving the startability as described above, if the injection amount variation becomes large in this way, the startability may be degraded.

Further, the fuel injection amount per injection usually has some errors due to the temperature, the viscosity of the fuel, the accuracy of the fuel injection device, and the like. In the case of split injection in which the required fuel injection amount is divided into a plurality of injections, such errors are accumulated, so that the injection amount variation is larger than in the normal injection. Therefore, the fuel injection amount at the time of such split injection needs to be particularly strictly controlled.

The present invention has been made in view of the above circumstances, and has as its object to always set an appropriate fuel injection amount regardless of whether split injection is performed or not, thereby further improving startability. It is an object of the present invention to provide a fuel injection control device for a diesel engine which can achieve the following.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, the required fuel injection amount is divided into a plurality of injections and the injection is performed exclusively in response to the split injection. First fuel injection amount calculating means for calculating the starting fuel injection amount according to the present invention, and second fuel injection amount calculating means for calculating the starting fuel injection amount for the normal injection other than the split injection exclusively. When performing one of the split injection and the normal injection based on a predetermined parameter at the time of engine start, the fuel injection control is performed based on the start-time fuel injection amount calculated by the first injection amount calculation means at the time of split injection. Control means for performing fuel injection control based on the starting fuel injection amount calculated by the second injection amount calculation means during normal injection. That.

According to a second aspect of the present invention, in the fuel injection control device for a diesel engine according to the first aspect, the first and second injection amount calculating means include a cooling water temperature and an engine speed as parameters. The gist is that the starting fuel injection amount is calculated based on each of the different maps.

According to these configurations, the injection amount at the start is determined completely independently between the time when the split injection is executed and the time when the split injection is not executed. Therefore, an appropriate starting fuel injection amount is applied when split injection is executed and when split injection is not executed, so that the startability is further improved.

According to a third aspect of the present invention, in the fuel injection control apparatus for a diesel engine according to the first or second aspect, the post-start fuel injection corresponding to the normal injection only after the engine is started corresponds to the normal injection. The fuel injection control apparatus further includes a third injection amount calculation unit that calculates an amount, wherein the control unit executes the fuel injection control based on the post-start fuel injection amount calculated by the third injection amount calculation unit after the engine is started. Is the gist.

According to this configuration, the fuel injection amount at the start and after the start is calculated by completely independent means. Therefore, regardless of the first injection amount calculating means or the second injection amount calculating means, the fuel injection amount at the time of starting is determined as the optimum injection amount regardless of the fuel injection amount after the engine is started. Is calculated.

According to a fourth aspect of the present invention, in the fuel injection control apparatus for a diesel engine according to the third aspect, the third fuel injection amount calculating means is provided by the first and second injection amount calculating means. The post-start fuel injection, which calculates a larger value of the calculated injection fuel injection amount obtained by gradually changing the start fuel injection amount and the basic injection amount calculated based on the accelerator opening and the engine speed. The gist is to make the amount.

According to this configuration, the fuel injection amount from the start to the start is smoothly changed. Normally, the upper limit of the selected post-start fuel injection amount is guarded by the maximum allowable injection amount of the engine.

According to a fifth aspect of the present invention, in the fuel injection control device for a diesel engine according to the fourth aspect, the third injection amount calculating means determines the gradually changing speed of the starting fuel injection amount by using a cooling water. The gist is to determine based on the temperature.

According to this configuration, by determining the gradually changing speed of the fuel injection amount at the start based on the cooling water temperature, the length of the transition period from the start to the start after the start is optimal according to the temperature state of the engine. It is said. For example, during a cold operation of an engine that has not been warmed up, the gradual change speed is slowed down to extend the transition period, and the engine is warmed up. In this way, a problem caused by a sudden change in the fuel injection amount is more suitably avoided.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a fuel injection control device for a diesel engine according to the present invention will be described in detail.

First, the configuration of the fuel injection control device according to the present embodiment will be described with reference to FIG. The fuel injection control device 2 includes a fuel injection nozzle 4 provided for each cylinder 3 of a diesel engine (hereinafter simply referred to as an engine) 1 and an injection pump for supplying high-pressure fuel distributed to each fuel injection nozzle 4. 5, an electronic control unit (hereinafter, referred to as an ECU) 8 for controlling these components, various sensors for detecting the operating state of the engine 1, and the like.

A drive shaft 11 is rotatably supported by the injection pump 5. The drive shaft 11 is drivingly connected to a crankshaft 6 which is an output shaft of the engine 1, and rotates in conjunction with the crankshaft 6. It should be noted that the crankshaft 6 and the drive shaft 11 are maintained in a 2: 1 rotational speed relationship by setting the connecting portion, and the drive shaft 11 rotates at half the rotational speed of the crankshaft 6. .

On the other hand, in the injection pump 5, the drive shaft 11 is provided with a feed pump 12 composed of a vane type pump (shown in FIG. 1 as being expanded by 90 degrees). This feed pump 12
By rotating together with the drive shaft 11, the fuel stored in the fuel tank 7 is sucked and the fuel is pressure-fed into a pump chamber 27 provided in the injection pump 5.

At the base end of the drive shaft 11, a disc-shaped signal gear plate 13 is provided. Further, the base end of the drive shaft 11 is connected to the cam disk 16 via a coupling. The cam disk 16 is rotatably supported in the injection pump 5 and slidable along its axis. The cam disk 16 rotates integrally with the drive shaft 11.

Between the signal gear plate 13 and the cam disk 16, there is provided a roller ring 15 which is rotated and adjusted according to the fuel injection timing. A plurality of rollers corresponding to the number of cylinders of the engine 1 are mounted along the circumference of the roller ring 15 on the side facing the cam disk 16.

A plurality of face cams corresponding to the number of cylinders of the engine 1 are formed on the surface of the cam disk 16 facing the roller ring 15. The cam disk 16 is urged by a spring and is always in contact with the roller ring 15. Accordingly, the cam disk 16 reciprocates in the axial direction, that is, in the left-right direction in FIG. 1 in accordance with the engagement between the face cam and the roller of the roller ring 15 with the rotation. Specifically, while the crankshaft 6 of the engine 1 makes two rotations, it performs a reciprocating motion for one rotation and the number of cylinders.

A plunger 17 is rotatably mounted on the cam disk 16 integrally with the cam disk 16. The plunger 17 is inserted into a cylinder 28 formed on the injection pump 5. A space surrounded by the right end of the plunger 17 in FIG. 1 and the inner wall of the cylinder 28 is a high-pressure chamber 29. The plunger 17 is moved with the reciprocating motion of the cam disk 16.
Moves back, fuel is introduced into the high pressure chamber 29, and the plunger 17 moves forward, whereby the fuel in the high pressure chamber 29 is compressed and pressurized.

A distribution passage 30 is formed in the cylinder 28 and communicates with each fuel injection nozzle 4. On the other hand, the same number of distribution ports 31 as the fuel injection nozzles 4 are formed in the plunger 17 so as to communicate with the high-pressure chamber 29. The distribution passage 30 and the distribution port 31 are configured such that the ones corresponding to the predetermined fuel injection nozzles 4 coincide with each other at a predetermined rotation phase as the plunger 17 rotates. Then, along with the forward movement of the plunger 17, the fuel in the high-pressure chamber 29 is pressure-fed to a predetermined fuel injection nozzle 4 via the delivery valve 18. Delivery valve 18
Is a valve for preventing backflow from the fuel injection nozzle 4 to the injection pump 5. The fuel pumped in this way is
The fuel is injected from the fuel injection nozzle 4 into the combustion chamber 10 of the engine 1.

Further, the high pressure chamber 29 is provided with the pump chamber 2
An oil passage for fuel overflow (spill) communicating with the spill valve 7 is formed.
1 is provided. The electromagnetic spill valve 21 is a normally-open type valve having a solenoid. When the solenoid 21 is not energized and the valve 21 is open, the high-pressure chamber 29 and the pump chamber 27 communicate with each other. The inside of the high-pressure chamber 29 is maintained at a reduced pressure. On the other hand, when the solenoid is energized, the electromagnetic spill valve 21 is closed, and the spill oil passage is closed. That is, the electromagnetic spill valve 21 is closed before the forward movement of the plunger 17 is started, and the electromagnetic spill valve 21 is opened during the forward movement of the plunger 17 in correspondence with each fuel injection nozzle 4, so that the high-pressure chamber is opened. The fuel in the fuel tank 29 is reduced in pressure, and the fuel injection from the fuel injection nozzle 4 is immediately stopped. Therefore, by controlling the opening timing of the electromagnetic spill valve 21 during the forward movement of the plunger 17, the end timing of the fuel injection from the fuel injection nozzle 4 is changed, and the fuel injection amount is adjusted. The energization of the electromagnetic spill valve 21 is controlled by the ECU 8.

Also, during the forward movement of the plunger 17, the electromagnetic spill valve 21 is once opened to temporarily reduce the pressure of the fuel in the high-pressure chamber 29, and then closed again. Fuel injection can be performed. Further, by repeatedly opening and closing the plunger 17 many times during the forward movement of the plunger 17, the fuel injection can be divided into a plurality of times and executed. Thus, the above-described split injection can be performed.

On the other hand, the injector pump 5 has a timer piston 19 (90 in FIG. 1) which rotates the roller ring 15 by reciprocating by a difference in oil pressure before and after the mechanism as a mechanism for changing the fuel injection timing. And a timing control valve 20 for changing the position of the timer piston 19 by adjusting the hydraulic pressure difference between the front and rear thereof.

The timer piston 19 is slidably fitted in a cylindrical space formed in the injector pump 5. In this space, two pressure chambers are formed by being partitioned by the timer piston 19. One of these pressure chambers communicates with the pump chamber 27, and is supplied with high-pressure fuel. The timer piston 19 is biased by a spring from the other pressure chamber side. The position of the timer piston 19 is determined by the balance between the urging force of the spring and the fuel pressure difference between the two pressure chambers.

Further, the injector pump 5 is provided with a passage communicating with the pressure chambers, and a timing control valve 20 is provided in the passage. The timing control valve 20 is an electromagnetic valve that is opened and closed by a duty-controlled signal, and the amount of fuel flowing from one of the two pressure chambers to the other is adjusted by the degree of opening. Then, the pressure difference between the two pressure chambers is changed, and the position of the timer piston 19 is adjusted. The duty ratio of the signal applied to the timing control valve 20 is controlled by the ECU 8.

When the position of the timer piston 19 is changed in this way, the roller ring 15 rotates in conjunction with the change. Due to this rotation, the rotation phase in which the roller of the roller ring 15 and the face cam of the cam disk 16 are engaged is changed,
The timing of the reciprocating operation of the plunger 17 is changed. Therefore, the fuel injection timing can be adjusted by these mechanisms.

The ECU 8 determines the fuel injection amount and the fuel injection timing based on the operating state of the engine 1 detected by various sensors. Next, these sensors will be described.

The plate 1 is mounted on the signal gear plate 13 provided at the base end of the injector pump 5.
A rotation speed sensor 14 for detecting the engine rotation speed NE based on the rotation of the engine 3 is provided. Signal gear plate 1
A plurality of projections are formed on the outer peripheral side surface of the projection 3. These projections are arranged on the outer peripheral side surface of the signal gear plate 13 at substantially equal intervals, but there are portions where the projections are missing without any projections. The rotation speed sensor 14 is constituted by a pickup coil, and outputs to the ECU 8 an electromotive force generated when the projection interrupts the magnetic field of the coil as an electric signal. The ECU 8 shapes this into a pulse-wave-like electric signal, and detects the engine speed NE based on the electric signal. Further, the rotational phases of the crankshaft 6 of the engine 1 and the drive shaft 11 of the injector pump 5 are detected based on the toothless portion having no protrusion.

A fuel temperature sensor 22 is provided in the pump chamber 27 of the injector pump 5. The fuel temperature sensor 22 detects the temperature THF of the fuel in the pump chamber 27 and outputs the detected temperature to the ECU 8 as an electric signal. On the other hand, a water temperature sensor 2 for detecting the temperature THW of the cooling water flowing inside the cylinder block of the engine 1 is provided.
3 are provided. The water temperature sensor 23 similarly detects the cooling water temperature THW, and uses this as an electric signal to output EW.
Output to CU8.

The accelerator pedal 9 which reflects the driver's acceleration request is provided with an accelerator sensor 24 for detecting the opening of the accelerator 9. This accelerator sensor 24
Converts the depression amount of the accelerator pedal into an electric signal and outputs the electric signal to the ECU 8.

When the engine is started, the starter 25 composed of an electric motor is driven. The starter 25
When the engine is started, the engine 1 is started by being connected to the crankshaft 6 and rotating the shaft 6. The driver's seat is provided with a starter switch 26 for instructing the starter 25 to operate or stop. The on / off operation information of the starter switch 26 is also taken into the ECU 8.

Next, the electrical configuration of the fuel injection control device 2 in the present embodiment will be described with reference to FIG. The ECU 8 includes a ROM 50, a CPU 51, a RAM 52
And a logical operation circuit including a backup RAM 53 and the like.

The ROM 50 is a memory that stores various control programs and data such as maps that are referred to when executing these control programs. CPU
51 performs arithmetic processing based on various control programs and data stored in the ROM 3. The RAM 52 has a CP
This is a memory for temporarily storing the calculation result performed by U51, data input from each sensor, and the like. Backup R
The AM 53 is a non-volatile memory that stores data to be stored when the engine 1 stops. These ROM 50,
CPU 51, RAM 52 and backup RAM 53
Are connected to each other via a bus 54, and are also connected to an external input circuit 55 and an external output circuit 56.

The external input circuit 55 includes a rotation speed sensor 1
4. The fuel temperature sensor 22, the water temperature sensor 23, the accelerator sensor 24, and the starter switch 26 are connected,
The signals sent from these are input. On the other hand, the external output circuit 56 includes the timing control valve 20 and the electromagnetic spill valve 2.
1 are connected and output control signals to them.

Subsequently, the fuel injection control device 2 described above
The fuel injection control in the transition period of the engine 1 to the start mode and the normal mode will be described. First, regarding the execution determination process of the split injection in the start mode,
This will be described based on the flowchart shown in FIG.

The CPU 51 executes the split injection execution determination routine of FIG. 3 as an interrupt process at a predetermined rotation phase of the signal gear plate 13 detected by the rotation speed sensor 14.

By the way, the CPU 51 executes the starter switch 2 as a normal process separately from the process of this routine.
6 is monitored for on / off operation. Furthermore, CP
U51 calculates the engine speed NE based on the output signal of the speed sensor. And the starter switch 26
Is ON (ON) and the engine speed NE is less than the predetermined speed α, the start flag XSTAON is turned ON (O
N). On the other hand, the starter switch 26 is turned off (OF
F) Or, when the engine speed NE is equal to or more than the predetermined speed α, the start flag XSTAON is turned off (OFF). The predetermined rotation speed α is set as a value that can sufficiently grasp that the engine 1 has shifted to a stable complete explosion state.

Now, as the processing of this routine, the CPU 5
First, at step S100, it is determined whether or not the starting flag XSTAON is ON, that is, whether or not the engine is currently in a starting mode. If it is determined that the current mode is the start mode, the process of the CPU 51 proceeds to step S101. On the other hand, if it is determined that the mode is not the start mode, the process of the CPU 51 proceeds to step S
Move to 107. Then, the CPU 51 turns off a split injection execution flag XPLT, which will be described later, as the process of step S107, and then temporarily ends this routine.

In the subsequent step S101, the CP
U51 determines whether or not the start flag XSTAON was OFF when the processing of this routine was executed last time. Here, the previous start flag XSTAON is set to O.
When it is determined that the answer is N, the CPU 51 once ends the present routine. On the other hand, if it is OFF, that is, if it is determined that the start mode has been started at the time this routine is executed, the process of the CPU 51 proceeds to the subsequent step S102.

Then, the CPU 51 determines in step S10
In the process 2, the cooling water temperature THW is calculated based on the electric signals input from the fuel temperature sensor 22 and the water temperature sensor 23.
And the fuel temperature THF are read and stored in the RAM 52 provided in the CPU 51.

Thereafter, the CPU 51 executes the processing of steps S103 and S104, in which the coolant temperature THW and the fuel temperature T stored in the RAM 52 in step S102.
HF is the reference coolant temperature KTHWP for executing split injection
It is determined whether the temperature is lower than L or the reference fuel temperature KTHFPL.

The cooling water temperature THW and the fuel temperature TH
If one of F is lower than the reference temperature KTHWPL or KTHFPL, the process of the CPU 51 proceeds to step S105. As the process of step S105, the CPU 51 turns on a split injection execution flag XPLT indicating whether or not the condition for split injection is satisfied. After that, the CPU 51 once ends this routine.

On the other hand, the cooling water temperature THW and the fuel temperature TH
F is the reference temperature KTHWPL or K
If not less than THFPL, the process of the CPU 51 proceeds to step S106. As the process of step S106, the CPU 51 executes the split injection execution flag XP
LT is turned off. After that, the CPU 51 once ends this routine.

In this embodiment, the reference temperatures KTHWPL and KTHFPL are both -10 ° C.
Is set to This reference temperature is a boundary temperature at which the effectiveness of the split injection has been recognized by a test or the like.

The CPU 51 determines whether or not to execute the above-described split injection based on the split injection execution flag XPLT. That is, when the execution flag XPLT is ON, the CPU 51
During the period until is turned off, split injection is executed through a well-known injection control routine (not shown). On the other hand, when the execution flag XPLT is OFF, the CPU 51 executes normal fuel injection through the same injection control routine.

The split injection execution determination routine is summarized as follows. Split injection is
This process is executed only when either the coolant temperature THW or the fuel temperature THF at the time when the starter 25 starts operating is lower than −10 ° C. And the split injection is executed only when the start mode is continued,
When the start mode ends, the mode is switched to normal fuel injection.

This will be described in more detail with reference to the time chart of FIG. In FIG. 4, the flag XSTAON is a start flag, and the flag XPLT is a split injection execution flag. Also, the flag XTHWP
L is a split injection condition flag relating to cooling water temperature,
The flag XTHFPL is also a split injection condition flag relating to the fuel temperature.
Alternatively, when the fuel temperature THF is equal to or higher than the reference temperature KTHWPL or KTHFPL, that is, equal to or higher than -10 ° C., it is assumed that the fuel cell is turned on.

First, an example of the starting time A will be described. When the start-time flag XSTAON is switched from OFF to ON and the operation of the starter 25 is started, the split injection condition flag XTHWPL relating to the coolant temperature and the split injection condition XTHFPL relating to the fuel temperature are both OFF (OFF), that is, cooling. The water temperature THW and the fuel temperature THF are both lower than -10 ° C. Accordingly, the condition for executing the split injection is satisfied, and the split injection execution flag XPLT is turned ON.

Thereafter, the split injection condition flag XTHWPL relating to the cooling water temperature and the split injection condition XTHFPL relating to the fuel temperature are frequently turned on, and both are temporarily turned on at one time. However, as described above, since the condition determination regarding the cooling water temperature THW and the fuel temperature THF is performed only at the start of the engine start, the execution flag XPLT remains ON until the start flag XSTAON turns OFF. , During which split injection is performed.

Next, an example of the start time B will be described. When the start flag XSTAON is changed from OFF to ON, the split injection condition flag XT relating to the coolant temperature is set.
HWPL is ON, and the split injection condition XTHFPL relating to the fuel temperature is OFF. Also in this case, since the execution condition of the split injection is satisfied, the execution flag XPLT is turned ON, and the start flag XSTAON is set.
Split injection is performed until is turned off.

In the example of the starting time C, the starting time flag X
At the time when STAON is switched from OFF to ON, only the split injection condition flag XTHWPL related to the cooling water temperature is OFF, contrary to the example at the time of starting B,
In this case as well, the execution condition is satisfied, so that the execution flag XPLT is turned ON only while the start flag XSTAON is ON.

On the other hand, in the example of the start time D, the start time flag X
When STAON switches from OFF to ON, split injection condition flag XTHWP relating to cooling water temperature
Split injection condition XTHFP related to L and fuel temperature
L are both ON. Therefore, the execution condition of the split injection is not satisfied, and the execution flag XPLT is turned off.
It remains.

Next, the process of calculating the final injection amount Q FINC during the transition period between the start mode and the normal mode, that is, the injection amount of the fuel actually injected into the combustion chamber 10 will be described.

First, the process of calculating the starting injection amount QSTA will be described with reference to the flowchart of FIG. This process is executed by the CPU 51 as an interrupt process at predetermined time intervals.

First, as a process of step S200, the CPU 51 reads the engine speed NE and the coolant temperature THW. Then, as a process of the next step S201, the CPU 51 determines whether or not the start flag XSTAON is ON. As described above, the start flag X
STAON is ON when the starter 25 is ON and the engine speed NE is less than the predetermined speed α. Here, the processing of the CPU 51 is performed at the start flag XSTA.
If ON is ON, the process proceeds to the subsequent step S202, and if OFF, the process proceeds to a post-start injection amount calculation routine described later.

When the starting flag XSTAON is ON,
In step S202, the CPU 51 determines whether or not the split injection execution flag XPLT is ON.
As described above, the execution flag XPLT indicates that the split injection is performed when it is ON, and that the normal fuel injection is performed when it is OFF.

The split injection execution flag XPLT is ON.
In the case of, the CPU 51 proceeds to the process in step S203. In this step S203, the CPU 51 calculates the starting base injection amount QSTBSE. The start base injection amount QSTBSE is stored in the ROM 50 in the CPU 51.
Engine speed NE and cooling water temperature THW stored in the memory
With reference to the two-dimensional map of In the present embodiment, two types of two-dimensional maps are prepared: a map A dedicated to normal injection in the start mode shown in FIG. 6 and a map B dedicated to split injection in the same start mode shown in FIG. I have. In the calculation processing in step S203, the map B dedicated to the time of split injection in FIG. 7 is referred to.

On the other hand, if the split injection execution flag is OFF in step S202, the CPU 5
1 shifts to the processing of step S204. In this step S204, the CPU 51 calculates the base injection amount at start QSTBSE in the same manner as above, but here, the two-dimensional map A dedicated to normal injection shown in FIG. 6 is referred to.

When the processing in step S203 or S204 is completed, the CPU 51 proceeds to step S203.
The processing of 205 is executed. In this step S205, the CPU 51 calculates the start time increase start time tTQSTAD from the one-dimensional map of the cooling water temperature shown in FIG. As shown in this one-dimensional map, the start time increase start time t
TQSTAD is set to be longer as the cooling water temperature THW decreases.

The CPU 51 reads a start start time counter CSTAON from a built-in timer counter as a process of the next step S206. The start start time counter CSTAON reflects the elapsed time from the start of the start mode to the present.

After that, the CPU 51 determines in step S207 that the start-up time increase start time tTQ
The start-time injection amount increase tQSTAD is calculated from the STAD and the start start time counter CSTAON. The start-time injection amount increase tQSTAD is a start start time counter CSTAO.
This is obtained by multiplying the difference between N and the start time increase start time tTQSTAD by a predetermined coefficient k. However, the start-time injection amount increase tQSTAD is equal to or greater than zero and equal to or less than a predetermined value β.

As the processing of the next step S208, the CPU
Reference numeral 51 denotes the starting injection amount increase tQST thus obtained.
AD and previous step S204 or step S20
The starting injection amount QSTA is calculated from the starting base injection amount QSTBSE obtained in step 5. Start-up injection amount QSTA
Is the sum of the starting base injection amount QSTBSE and the starting injection amount increase tQSTAD.

The thus calculated starting injection amount QSTA
Has the following tendency. FIG. 9 shows the transition of the start-time injection amount QSTA when the engine speed NE and the coolant temperature THW are constant.

That is, the start-time injection amount QSTA immediately after the start of the engine start mode is the same as the start-time base injection amount QSTBSE, and the value thereof is the dedicated engine speed N for the ordinary fuel injection and the dedicated engine speed N for the split injection, respectively.
This is obtained from the two-dimensional maps A and B of E and the cooling water temperature THW. However, after the start-time increase start time tTQSTAD from the start of the start, the start-time injection amount QST
A is gradually increased. This increase is continued until the increase width reaches the predetermined value β.

After the start-time injection amount QSTA is calculated in this manner, the CPU 51 determines the calculated start-time injection amount QSTA as the final injection amount QFI as a process of step S209.
Set as NC. That is, in the starting mode, the starting injection amount QSTA itself calculated in step S208 is the actual injected fuel amount.

As described above, in the present embodiment,
The start-time fuel injection amount QSTA is completely independently calculated when split injection is executed and not executed. FIG.
FIG. 5 shows the relationship between the coolant temperature THW and the injection amount QSTA at the start during split injection execution and non-execution when the engine speed NE is constant. FIG. 10 shows a map A dedicated to normal injection and a map B dedicated to split injection under the above conditions.

Here, the starting injection amount QSTA in the case where the split injection and the normal injection are selectively used is not described by using two maps as in the present embodiment but by referring to a single map, for example, as in a conventional device. The problem in the calculation will be described with reference to FIG.

Normally, in such a map, the calculated parameters are not prepared as continuous values like each straight line in FIG. 10, but numerical values are prepared only at predetermined intervals of the parameter to be referred to. Absent. Therefore, for example, in the case of the map of FIG. 10, if the value of the starting fuel injection amount QSTA is prepared every 5 ° C. of the cooling water temperature THW, the temperature for which the value is not prepared is determined by interpolation. The starting fuel injection amount QSTA must be obtained. That is, even though the split injection is performed when the cooling water temperature THW is lower than −10 ° C., −15 to −15 ° C.
In the region of −10 ° C., the start-time fuel injection amount QSTA is obtained by interpolating the points A and B as indicated by the dotted line in FIG.
I have no choice but to ask. For this reason, a value different from the actually required injection amount is set.

In this regard, by switching and using two maps corresponding to the respective injection methods as in the present embodiment, the occurrence of such a problem is prevented, and appropriate fuel injection corresponding to the fuel injection method is performed. Quantity can be secured.

Next, the injection amount calculation process during the transition period to the normal mode will be described with reference to the flowchart shown in FIG. In the injection amount calculation routine in this transition period, the start time flag XSTA is set in step S201 of the injection amount calculation routine in the start mode.
It is executed when ON is OFF, that is, when the condition of the start mode is not satisfied. However, after starting the engine,
Since the above-described conditions of the start mode are not deviated for a while, this routine is executed for a certain period after the start injection amount calculation routine is executed.

First, in step S300, the CPU 5
1 calculates a decrease amount tQSTSUB of the start-time injection amount QSTA. This decrease amount tQSTSUB is obtained with reference to a one-dimensional map of the coolant temperature THW shown in FIG. The decrease amount tQSTSUB is set to a constant large value for a temperature of -5 ° C or more, but is set to -10 ° C.
There is a sharp decrease in the vicinity, and a very small value is set for cryogenic temperatures.

At the next step S301, the CPU 51
Is a value obtained by subtracting the decrease amount tQSTSUB from the start-time injection amount QSTA determined when the present routine or the start-time injection amount calculation routine was executed last time.
STA. Therefore, the starting injection amount QS
TA decreases each time this step S301 is executed. In particular, when the temperature is lower than −10 ° C., the reduction amount t
Since the value of QSTSUB is set to be small, the start-time injection amount QSTA decreases very slowly.

Next, the CPU 51 executes the base injection amount QBASE in the normal mode as the process of step S302.
And the maximum injection amount QFULL is calculated with reference to a two-dimensional map of the accelerator opening ACCPA and the engine speed NE as shown in FIG. 13, for example.

In the subsequent step S303, the CP
U51 is the base injection amount QBASE obtained in this manner and the starting injection amount QST calculated in step S301.
A is compared with A, and the larger value is substituted for a variable x. In the subsequent step S304, the CPU 51 compares the variable x with the maximum injection amount QFULL obtained in the above step S302, and determines the smaller value as the final injection amount QF.
Set as INC.

Thereafter, the CPU 51 determines the timing control valve 20 based on the final injection amount Q FINC thus obtained.
And the electromagnetic spill valve 21 to execute fuel injection.
FIG. 14 shows accelerator opening ACCP and cooling water temperature THW.
Is constant, the final injection amount QF during the transition period
The transition of INC is shown. FIG. 14 shows the cooling water temperature THW.
Are two curves when the temperature is high and when the temperature is low.

First, the case of a high temperature will be described. In FIG. 14, the period up to time Ta is in the start mode, and the final injection amount Q FINC is the start injection amount QST calculated by the fuel injection amount calculation routine in the start mode.
A. At the time Ta, the start-up mode is ended, and the start-up injection amount QSTA gradually decreases from a point in time when a transition period to the normal mode is started. However, time T
Up to b, the starting injection amount QSTA exceeds the base injection amount QBASE in the normal mode, so that the final injection amount QF
INC is the starting injection amount QSTA. Then, at time Tb, the base injection amount QBASE becomes greater than the base injection amount QBASE exceeding the start-time injection amount QSTA.
E becomes the final injection amount QFINC. Thus, the transition from the start mode to the normal mode is smoothly performed.

After that, the base injection amount QBASE becomes smaller and the starting injection amount QSTA becomes larger because the accelerator operation amount ACCPA becomes smaller or the engine speed NE decreases due to the driver's operation. If the starting injection amount QSTA is equal to the final injection amount Q FINC
Becomes Eventually, since the starting injection amount QSTA becomes zero due to the decrease, the base injection amount QBA
SE becomes the final injection amount QFINC.

On the other hand, in the case of a low temperature of −10 ° C. or less, FIG.
As shown in the map of FIG. 2, the decrease amount tTQSTSUB of the start-time injection amount QSTA is set very small. Therefore, the starting injection amount QST during the transition period
A decreases very slowly. As described above, misfire often occurs while the engine 1 is not warmed up, and there is a possibility that the engine 1 cannot be operated in a stable state. Therefore, the transition period is thus lengthened,
After the temperature of the engine rises at the time Tc, the mode can be shifted to the normal mode.

As described in detail above, according to the fuel injection amount control device according to the present embodiment, the following effects can be obtained. -Fuel injection can be performed with a more appropriate start-up fuel injection amount at the time of execution of split injection and at the time of non-execution, so that startability can be further improved.

Since the fuel injection amount at the start and after the start is calculated by completely independent means, the fuel injection can be executed with a more appropriate fuel injection amount at the start and after the start. Therefore, it is possible to achieve both improvement of the startability and improvement of the engine performance after the start.

The transition from the start mode to the normal mode can be smoothly performed by gradually changing the fuel injection amount during the transition period. In particular, at extremely low temperatures (-10 ° C), by setting a smaller weight loss rate, it is possible to eliminate engine stalls, rough idles, etc., which occur frequently at extremely low temperatures during the transition period or immediately after the transition. Can be.

By specifying an effective execution region of the split injection based on the cooling water temperature THW and the fuel temperature THF,
Startability can be improved. By performing split injection execution determination only at the start of the start mode, and by executing split injection continuously during the start mode when the execution conditions are satisfied,
It is possible to prevent a situation in which the normal injection and the split injection are frequently switched under unstable conditions during the cranking at the time of starting and the startability is deteriorated.

The condition is set for both the cooling water temperature THW and the fuel temperature THF, and the execution condition of the split injection is determined based on the logical sum of both, so that when one of the temperature detecting means fails. Can also execute split injection, and startability at low temperatures is ensured.

The split injection can be executed more effectively by adding the fuel temperature THF that directly affects the fuel injection, such as the viscosity of the fuel, to the execution conditions of the split injection.

The present embodiment can be implemented with its configuration changed as follows. -Calculate the injection amount at the time of execution of split injection and at the time of non-execution by a function operation. In this case as well, the split injection is determined completely independently of the time of execution and the time of non-execution.

In this embodiment, the gradual change rate of the fuel injection amount from the start mode to the normal mode after the start is changed based on the cooling water temperature. The speed may be fixed, or may be determined based on other operating state parameters.

The execution condition of the split injection is not limited to the condition of the coolant temperature and the fuel temperature as in the present embodiment. For example, only one of the coolant temperature and the fuel temperature, or the engine speed and The determination may be made based on the intake air temperature or the like as a condition.

In the present embodiment, the reference temperature for determining the execution of the split injection based on the coolant temperature and the fuel temperature is -1.
Although the temperature is set to 0 ° C., another temperature may be set according to the operating conditions of the engine and individual differences.

Even if the above-mentioned reference temperature is not set to a predetermined constant value and the startability of the engine is monitored during start-up of the engine, the optimum temperature condition is learned by feeding back the result. good. By making such changes, optimal conditions can be set in accordance with the use conditions of the engine and individual differences.

In this embodiment, a so-called distribution type fuel injection device is used. However, the present invention is not limited to this, and the present invention can be applied to other types of fuel injection devices, for example, a row type or a common rail type fuel injection device. .

[0101]

According to the first and second aspects of the present invention,
Since the starting injection amount is completely independently determined between the time of split injection execution and the time of non-execution, an appropriate start-time fuel injection amount is applied at the time of split injection execution and at the time of non-execution, respectively. Further, the startability can be improved.

According to the third aspect of the present invention, since the fuel injection amount at the start and after the start is calculated by completely independent means, the engine can be started whether the split injection is executed or not. The fuel injection amount at the time of starting can be calculated as the optimum injection amount regardless of the subsequent fuel injection amount.

According to the fourth aspect of the present invention, it is possible to smoothly change the fuel injection amount from the start to the start. According to the fifth aspect of the present invention, by determining the gradually changing speed of the fuel injection amount at the time of starting based on the coolant temperature, the length of the transition period from the time of starting to the time of after starting according to the temperature state of the engine. And the problem caused by a sudden change in the fuel injection amount can be more suitably avoided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine to which a fuel injection control device according to the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of the fuel injection control device.

FIG. 3 is a flowchart showing a split injection execution determination routine.

FIG. 4 is a time chart showing an execution condition determination mode of split injection.

FIG. 5 is a flowchart showing an injection amount calculation processing routine in a start mode.

FIG. 6 is a graph showing an example of a map for calculating a base injection amount at the start of normal injection.

FIG. 7 is a graph showing an example of a map for calculating a base injection amount at the start of split injection.

FIG. 8 is a graph showing an example of a map for calculating a start time increase start time.

FIG. 9 is a graph showing a transition of an injection amount in a start mode.

FIG. 10 is a graph showing a relationship between a cooling water temperature and a required value of a fuel injection amount at the time of starting.

FIG. 11 is a flowchart showing an injection amount calculation process during a transition period from the start mode to the normal mode.

FIG. 12 is a graph showing an example of a map for calculating a decrease amount of a start-time injection amount.

FIG. 13 is a graph showing an example of a map for calculating a base injection amount and a maximum injection amount in a normal mode.

FIG. 14 is a graph showing a transition of a final injection amount during a transition period.

FIG. 15 is a graph showing a conventional map for calculating a fuel injection amount at the time of low-temperature start.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Fuel injection amount control device, 4
... Fuel injection nozzle, 5 ... Injection pump, 8 ...
Electronic control unit (ECU), 14 ... rotational speed sensor, 20 ...
Timing control valve, 21: electromagnetic spill valve, 22: fuel temperature sensor, 23: water temperature sensor.

Claims (5)

[Claims] 1. A first injection amount calculating means for calculating a start-up fuel injection amount for a required fuel injection amount, which corresponds to a split injection in which a required fuel injection amount is divided into a plurality of injections, and A second injection amount calculating means for calculating a start-up fuel injection amount for the normal injection other than the split injection exclusively; and performing one of the split injection and the normal injection based on a predetermined parameter at the time of engine start. At the time of execution, fuel injection control is performed based on the starting fuel injection amount calculated by the first injection amount calculating means during split injection, and at the time of starting calculated by the second injection amount calculating means during normal injection. A fuel injection control device for a diesel engine, comprising: control means for executing fuel injection control based on a fuel injection amount. 2. The first and second injection amount calculating means calculates the starting fuel injection amount based on respective maps using a coolant temperature and an engine speed as parameters. Item 2. A fuel injection control device for a diesel engine according to item 1. 3. A fuel injection control apparatus for a diesel engine according to claim 1, wherein the post-starting fuel injection amount for the injection is calculated exclusively in correspondence with the normal injection after the engine is started. The fuel injection system for a diesel engine, further comprising a calculation unit, wherein the control unit executes the fuel injection control based on the post-start fuel injection amount calculated by the third injection amount calculation unit after the engine is started. Control device. 4. The fuel injection amount calculated by the first and second injection amount calculation means, wherein the fuel injection amount at the time of starting is gradually reduced and the accelerator opening degree and 4. The fuel injection control device for a diesel engine according to claim 3, wherein a larger value than the basic injection amount calculated based on the engine speed is set as the calculated post-start fuel injection amount. 5. 5. The fuel injection control device for a diesel engine according to claim 4, wherein said third injection amount calculating means determines a gradually changing speed of said starting fuel injection amount based on a coolant temperature.