JP3420484B2 - Fuel injection control device for diesel engine - Google Patents

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 improvement of fuel injection control effective for improving the startability of the engine.

[0002]

2. Description of the Related Art In a diesel engine that employs electronically controlled fuel injection, an amount of fuel injection and a fuel injection timing are controlled by an electronic control unit (hereinafter referred to as an ECU) mainly including a computer. The fuel injection amount and fuel injection timing are determined based on various conditions such as the engine speed and load. Of these, the fuel injection amount is determined by referring to a control map stored in advance in the ECU.

By the way, in the cranking state by the starter such as when the engine is started, the rotational fluctuation of the diesel engine is extremely large. Therefore, the fuel injection amount at the time of starting is obtained from the control map during normal operation. It is necessary to correct the increase. However, if the fuel injection amount at the start is uniformly increased and corrected, in a situation where the fuel is difficult to ignite, such as at low temperature start, the misfire rate is high and the engine startability is reversed. Getting worse. Further, at the time of restart after being completely warmed up, unburned substances and the like in the exhaust gas increase due to excessive fuel injection amount, and smoke is generated.

Therefore, conventionally, in order to solve these problems,
For example, in the "fuel injection amount control method for diesel engine" disclosed in Japanese Patent Laid-Open No. 186939/1988, a map different from that during normal operation is used to calculate the fuel injection amount at the time of low temperature start. . FIG. 15 shows an example of the fuel injection amount control map at 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 0. In the section from No. to Na, the fuel injection amount QSTA is set to a constant amount according to the accelerator opening degree ACCPA. Then, in the section where the engine speed NE is from Na to Nb, the fuel injection amount QSTA is gradually decreased to a predetermined amount Qa as the engine speed NE increases.

As mentioned above, diesel engines usually
When the engine speed NE rises to a certain extent (the section from Na to Nb in FIG. 15) at the time of start-up, the rotational fluctuation becomes significant and misfire easily occurs. At this time, if excessive fuel is injected, the combustion chamber is cooled by the unburned fuel. When the temperature in the combustion chamber decreases in this way, the period during which the fuel rises to the temperature at which it can self-ignite becomes shorter, so misfiring is more likely to occur, and low-temperature startability deteriorates.

In this respect, according to the method described in the publication, the temperature is reduced in the combustion chamber by reducing the amount of fuel in the engine rotation range where misfire easily occurs, and the low temperature startability is improved. Like

On the other hand, conventionally, not only the fuel injection amount is adjusted in this way, but also the fuel injection method itself is used as in the "fuel injection device for diesel engine" disclosed in Japanese Patent Laid-Open No. 5-86932. There is also known a technique for improving the startability by changing it in accordance with.

That is, in the device 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, the required fuel injection amount is divided into a plurality of times for split injection. Is performed, and the normal injection is performed in the other period. By performing the split injection in this manner until the engine speed NE rises to a predetermined engine speed at the time of low-temperature start with a low cooling water temperature THW, it is possible to preferably avoid the decrease in the temperature in the cylinder due to the heat of vaporization of the fuel and to reduce the engine temperature. It becomes possible to achieve a more stable start.

[0010]

By the way, usually, the optimum fuel injection amount at the time of starting at each temperature of the cooling water temperature THW greatly differs between split injection and normal injection. However, like the above-mentioned conventional device, if it is necessary to uniquely calculate the fuel injection amount at the time of split injection or normal injection based on the target fuel injection amount and the actual fuel pressure, it is difficult to adapt, and the cooling water temperature or Depending on the region of the engine speed, the variation in the injection amount cannot be ignored. As described above, the split injection is an extremely effective injection method for improving the startability, but if the injection amount variation becomes large in this way, the startability may be deteriorated.

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

The present invention has been made in view of the above circumstances, and an object thereof is to always set an appropriate fuel injection amount regardless of whether split injection is executed or not, and further improve startability. It is to provide a fuel injection control device for a diesel engine capable of achieving the above.

[0013]

In order to achieve the above-mentioned object, in the invention described in claim 1, the injection is performed corresponding to the split injection in which the required fuel injection amount is divided into a plurality of injections. Injection amount calculation means for calculating the startup fuel injection amount according to the first injection amount calculation means and second injection amount calculation means for calculating the startup fuel injection amount according to the normal injection other than the split injection operation. And so under extremely low temperatures
Based on the cooling water temperature
Based on the gradual change rate set based on
The fuel injection amount at startup calculated by the injection amount calculation means is gradually reduced.
Change the amount of injection to reduce the amount of fuel injection after start
When executing one of the split injection and the normal injection based on a third injection amount calculation means to be output and a predetermined parameter at the time of engine start, the first injection is performed at the time of split injection.
The fuel injection control is executed based on the fuel injection amount at startup calculated by the injection amount calculation means of
And executes a fuel injection control based on the start time fuel injection amount calculated by the injection amount calculating means, after the engine start,
Post-start fuel calculated by the third injection amount calculation means
The gist of the invention is to include a control unit that executes fuel injection control based on the injection amount .

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 calculation means use the cooling water temperature and the engine speed as parameters. The gist of the present invention is to calculate the fuel injection amount at start-up based on the respective different maps.

According to these configurations, the starting injection amount is completely independently determined when the split injection is executed and when the split injection is not executed. Therefore, since the appropriate starting fuel injection amount is applied when the split injection is executed and when the split injection is not executed, the startability is further improved.

[0016]

Further, according to these configurations, the fuel injection amounts at the time of starting and after the starting are calculated by completely independent means. Therefore, even in the case of the first injection amount calculation means,
Alternatively, the second injection amount calculation means calculates the fuel injection amount at the time of starting as the very optimum injection amount regardless of the fuel injection amount after the engine is started.

[0018]

Further , according to these configurations, the fuel injection amount smoothly changes from the start to the start. Normally, the above selected post-startup fuel injection amount is guarded by the maximum allowable injection amount of the engine.

[0020]

In addition , according to these configurations, the gradual change speed of the fuel injection amount at the time of starting is determined based on the temperature of the cooling water, so that the transition period from the time of starting to the time of starting is long according to the temperature state of the engine. Is the best. For example, during cold operation of an engine that has not been warmed up, the gradual change speed is slowed to lengthen the transition period, and the engine is warmed up. In this way, the problem caused by the sudden change in the fuel injection amount can be avoided more preferably.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a fuel injection control device for a diesel engine according to the present invention will be described in detail below.

First, the structure of the fuel injection control device according to the present embodiment will be described with reference to FIG. The fuel injection control device 2 is mainly provided with 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 to be distributed to each fuel injection nozzle 4. 5, an electronic control unit (hereinafter referred to as an ECU) 8 that controls these, various sensors that detect 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 held in a relationship in which the rotational speed thereof is 2: 1 due to the setting of 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 (developed by 90 degrees in FIG. 1) which is a vane type pump. 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 pumped into the pump chamber 27 provided in the injection pump 5.

A disk-shaped signal gear plate 13 is provided at the base end of the drive shaft 11. 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, and 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 whose rotation is adjusted according to the fuel injection timing. A plurality of rollers corresponding to the number of cylinders of the engine 1 are attached 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 biased by a spring and is always in contact with the roller ring 15. Therefore, as the cam disk 16 rotates, the cam disk 16 reciprocates in the axial direction, that is, in the left-right direction in FIG. 1 according to the engagement between the face cam and the roller of the roller ring 15. Specifically, while the crankshaft 6 of the engine 1 makes two revolutions, it makes one revolution and reciprocates for the number of cylinders.

A plunger 17 is rotatably attached to the cam disc 16 integrally with the cam disc 16. The plunger 17 is fitted in a cylinder 28 formed in the injection pump 5. The 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. With the reciprocating motion of the cam disk 16, the plunger 17
The fuel is introduced into the high-pressure chamber 29 by moving back, and the fuel in the high-pressure chamber 29 is compressed and pressurized by moving the plunger 17 forward.

The cylinder 28 is formed with a distribution passage 30 which communicates with each fuel injection nozzle 4. On the other hand, also in the plunger 17, the same number of distribution ports 31 as the fuel injection nozzles 4 that communicate with the high-pressure chamber 29 are formed. The distribution passage 30 and the distribution port 31 are configured so that the ones corresponding to the predetermined fuel injection nozzles 4 coincide with each other in a predetermined rotation phase as the plunger 17 rotates. Then, with the forward movement of the plunger 17, the fuel in the high pressure chamber 29 is pressure-fed to the 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 thus pumped is
The fuel is injected from the fuel injection nozzle 4 into the combustion chamber 10 of the engine 1.

Further, in the high pressure chamber 29, the pump chamber 2
An oil passage for fuel overflow (spill) communicating with 7 is formed, and an electromagnetic spill valve 2 for adjusting spill is formed in the oil passage.
1 is provided. The electromagnetic spill valve 21 is a normally-open type valve having a solenoid, and when the solenoid 21 is not energized, the high pressure chamber 29 and the pump chamber 27 communicate with each other when the valve 21 is open. The inside of the high pressure chamber 29 is maintained in a depressurized state. On the other hand, when the solenoid is energized, the electromagnetic spill valve 21 is closed and the oil passage for spill is closed. That is, by corresponding to each fuel injection nozzle 4, 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 to open the high pressure chamber. The fuel in 29 is decompressed, and the fuel injection from the fuel injection nozzle 4 is immediately stopped. Therefore, by controlling the valve opening timing of the electromagnetic spill valve 21 during the forward movement of the plunger 17, the fuel injection end timing 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.

During the forward movement of the plunger 17, the electromagnetic spill valve 21 is temporarily opened to temporarily depressurize the fuel in the high pressure chamber 29, and then closed again, so that the fuel is injected from the fuel injection nozzle 4 in two steps. Fuel injection can be performed. Further, similarly, by repeatedly opening and closing during the forward movement of the plunger 17, the fuel injection can be divided into a plurality of times and executed. In this way, the above-mentioned split injection can be executed.

On the other hand, the injector pump 5 has a timer piston 19 (90 in FIG. 1) as a mechanism for changing the fuel injection timing, which causes the roller ring 15 to reciprocate by reciprocating due to a hydraulic pressure difference before and after 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 before and after the timer piston 19).

The timer piston 19 is slidably fitted in a cylindrical space formed in the injector pump 5. Two pressure chambers are formed in this space 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 the spring from the other pressure chamber side. The position of the timer piston 19 is determined by the balance between the biasing force of the spring and the fuel pressure difference between the pressure chambers.

Further, the injector pump 5 is formed with a passage communicating with these 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 / closed by a duty-controlled signal, and the opening thereof adjusts the amount of fuel flowing from one of the pressure chambers to the other. Then, the pressure difference between both 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 it. By 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.

Above the signal gear plate 13 provided at the base end of the injector pump 5, the plate 1
A rotation speed sensor 14 for detecting the engine rotation speed NE based on the rotation speed of 3 is provided. Signal gear plate 1
A plurality of protrusions are formed on the outer peripheral side surface of the metal plate 3. These protrusions are arranged on the outer peripheral side surface of the signal gear plate 13 at substantially equal intervals, but there are some toothless portions without protrusions. The rotation speed sensor 14 is composed of a pickup coil, and outputs the electromotive force generated by the protrusion breaking the magnetic field of the coil to the ECU 8 as an electric signal. The ECU 8 forms this into a pulse wave electric signal and detects the engine speed NE based on this. Further, the rotation phases of the crankshaft 6 of the engine 1 and the drive shaft 11 of the injector pump 5 are detected with reference to the tooth missing 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 it to the ECU 8 as an electrical signal. On the other hand, the cylinder block of the engine 1 has a water temperature sensor 2 for detecting the temperature THW of the cooling water flowing therein.
3 is provided. This water temperature sensor 23 also detects the cooling water temperature THW in the same manner and uses this as an electrical signal E
Output to CU8.

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

When the engine is started, the starter 25, which is an electric motor, is driven. The starter 25 is
It is connected to the crankshaft 6 when the engine is started, and the engine 1 is started by rotating the shaft 6. The driver's seat is provided with a starter switch 26 for instructing the start / stop of the starter 25. The on / off operation information of the starter switch 26 is also fetched by 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, and 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
The reference numeral 51 performs arithmetic processing based on various control programs and data stored in the ROM 3. RAM52 is CP
It 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 saved when the engine 1 is stopped. These ROM50,
CPU51, RAM52 and backup RAM53
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,
Input the signals sent from these. On the other hand, the external output circuit 56 includes a timing control valve 20 and an electromagnetic spill valve 2.
1 is connected and outputs a control signal to them.

Subsequently, the fuel injection control device 2 described above
The fuel injection control during 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 split injection in the start mode,
A description will be given 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 above-mentioned starter switch 2 as a normal process in addition to the process of this routine.
The on / off operation of 6 is monitored. 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-up flag XSTAON is turned on (O
N). On the other hand, the starter switch 26 is turned off (OF
F) Alternatively, when the engine speed NE is equal to or higher than the predetermined speed α, the start flag XSTAON is turned off. The predetermined rotation speed α is set as a value with which it can be sufficiently grasped that the engine 1 has shifted to a stable complete explosion state.

Now, as the processing of this routine, the CPU 5
First, as the processing of step S100, 1 determines whether or not the above-mentioned start-up flag XSTAON is ON, that is, whether or not the engine is currently in the start mode. When it is determined that the starting mode is set, 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 processing of step S107, and then temporarily ends this routine.

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

The CPU 51 then executes this step S10.
As the process of 2, the cooling water temperature THW is calculated from 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.

After that, the CPU 51 performs the processing of steps S103 and S104, and the cooling water temperature THW and the fuel temperature T stored in the RAM 52 in step S102.
Reference cooling water temperature KTHWP for HF to execute split injection
It is determined whether or not L or less than the reference fuel temperature KTHFPL.

These cooling water temperature THW and fuel temperature TH
When either one of F is lower than the reference temperature KTHWPL or KTHPL, the process of the CPU 51 proceeds to step S105. As the process of step S105, the CPU 51 turns on the split injection execution flag XPLT indicating whether or not the split injection execution condition 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
Any of F is the above-mentioned reference temperature KTHWPL or K
If it is equal to or more than THFPL, the process of the CPU 51 proceeds to step S106. As the processing of step S106, the CPU 51 causes the split injection execution flag XP to be executed.
Turn off LT. After that, the CPU 51 once ends this routine.

In the present embodiment, the reference temperatures KTHWPL and KTHPL are both -10 ° C.
Is set to. This reference temperature is a boundary temperature at which the effectiveness of split injection has been confirmed by tests and the like.

The CPU 51 determines, based on the split injection execution flag XPLT, whether or not to execute the above-mentioned split injection. That is, when the execution flag XPLT is ON, the CPU 51 determines the same flag XPLT.
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
It is executed only when either the cooling water temperature THW or the fuel temperature THF at the time when the starter 25 starts operating is less than -10 ° C. And split injection is executed only when the start mode is continued,
Normal fuel injection is switched to when the start mode ends.

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 regarding the cooling water temperature,
The flag XTHFPL is also a split injection condition flag relating to the fuel temperature, and the cooling water temperature THW, respectively.
Alternatively, when the fuel temperature THF is equal to or higher than the reference temperature KTHWPL or KTHPL, that is, equal to or higher than −10 ° C., it is turned on.

First, an example of starting time A will be described. At the time when the start-up flag XSTAON is switched from OFF to ON and the operation of the starter 25 is started, both of the split injection condition flag XTHWPL regarding the cooling water temperature and the split injection condition XTHFPL regarding the fuel temperature are OFF (that is, cooling). The water temperature THW and the fuel temperature THF are both below -10 ° C. Therefore, the split injection execution condition is satisfied, and the split injection execution flag XPLT is turned on.

After that, the split injection condition flag XTHWPL relating to the cooling water temperature and the split injection condition XTHFPL relating to the fuel temperature are often turned ON, and both are turned ON temporarily for a while. However, as described above, the condition determination regarding the cooling water temperature THW and the fuel temperature THF is performed only at the time of starting the engine start. Therefore, the execution flag XPLT remains ON until the start time flag XSTAON turns OFF. Until the split injection is executed.

Next, an example of starting time B will be described. When the startup flag XSTAON changes from OFF to ON, the split injection condition flag XT relating to the cooling water temperature
HWPL is ON, and split injection condition XTHFPL related to fuel temperature is OFF. In this case as well, the execution condition of the split injection is satisfied, so the execution flag XPLT is turned on, and the startup flag XSTAON is set.
Split injection is executed until is turned off.

Further, 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 relating to the cooling water temperature is OFF, contrary to the example at the time of starting B.
In this case also, since the execution condition is satisfied, the execution flag XPLT is turned on only during the period when the startup flag XSTAON is turned on.

On the other hand, in the example of the start time D, the start time flag X
When STAON is switched from OFF to ON, the split injection condition flag XTHWP relating to the cooling water temperature
Split injection condition XTHFP concerning L and fuel temperature
Both L are ON. Therefore, the execution condition of split injection is not satisfied, and the execution flag XPLT is OFF.
Has remained.

Next, the final injection amount QFINC in the transition period to the start mode and the normal mode, that is, the injection amount calculation process of the fuel actually injected into the combustion chamber 10 will be described.

First, the calculation process of the starting injection amount QSTA will be described with reference to the flowchart of FIG. It should be noted that this process is executed by the CPU 51 as an interrupt process at predetermined time intervals.

First, the CPU 51 reads the engine speed NE and the cooling water temperature THW as the processing of step S200. Then, as the processing of the next step S201, the CPU 51 determines whether or not the startup 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 by the startup flag XSTA.
If ON is ON, the process proceeds to the following step S202, and if OFF, the process proceeds to a post-start injection amount calculation routine described later.

When the start flag XSTAON is ON,
In step S202, the CPU 51 determines whether the split injection execution flag XPLT is ON.
As described above, the execution flag XPLT indicates that split injection is performed when ON, and normal fuel injection is performed when OFF.

Split injection execution flag XPLT is ON
In the case of, the CPU 51 proceeds to the process of step S203. In step S203, the CPU 51 calculates the starting base injection amount QSTBSE. This starting base injection amount QSTBSE is stored in the ROM 50 in the CPU 51.
Engine speed NE and cooling water temperature THW stored in
It is obtained by referring to the two-dimensional map of and. In the present embodiment, two types of this two-dimensional map are prepared: a map A dedicated to normal injection in the starting mode shown in FIG. 6 and a map B dedicated to split injection in the starting mode shown in FIG. There is. In the calculation process of step S203, the map B dedicated to the split injection of FIG. 7 is referred to.

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

When the processing of the above step S203 or step S204 is completed, the CPU 51 executes step S
The processing of 205 is executed. In 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 increasing start time t
TQSTAD is set to become longer as the cooling water temperature THW decreases.

As the processing of the next step S206, the CPU 51 reads the starting start time counter CSTAON from the built-in timer counter. The start time counter CSTAON reflects the elapsed time from the start of the start mode to the present.

After that, the CPU 51 executes the previously read start-time amount increase start time tTQ as the processing of step S207.
The start injection amount increase tQSTAD is calculated from the STAD and the start start time counter CSTAON. The injection amount increase tQSTAD at the time of start is the start time counter CSTAO.
It is obtained by multiplying the difference between N and the increase amount start time tTQSTAD at startup by a predetermined coefficient k. However, the startup injection amount increase tQSTAD is set to a value 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
51 is the start-time injection amount increase tQST thus obtained
AD and the 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 injection amount QSTA
Is the sum of the starting base injection amount QSTBSE and the starting injection amount increase tQSTAD.

The starting injection amount QSTA calculated in this way
Has the following tendency. FIG. 9 shows the transition of the starting injection amount QSTA when the engine speed NE and the cooling water temperature THW are constant.

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

After the start-up injection amount QSTA is calculated in this way, the CPU 51 executes the calculated start-up injection amount QSTA as the final injection amount QFI in step S209.
Set as NC. That is, in the starting mode, the starting injection amount QSTA 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 calculated completely independently when the split injection is executed and when it is not executed. Figure 10
The relationship between the cooling water temperature THW and the starting injection amount QSTA when split injection is executed and when split injection is not executed is shown in the case where 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 start-time injection amount QSTA when the split injection and the normal injection are selectively used is referred to not only two maps as in the present embodiment but only one map as in the conventional device. Problems 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 the straight lines in FIG. 10, but numerical values are prepared only at predetermined intervals of the parameters to be referenced. Absent. Therefore, for example, in the case of the map of FIG. 10, if the value of the fuel injection amount QSTA at the time of starting is prepared every 5 ° C. of the cooling water temperature THW, the corresponding temperature is prepared by interpolation for the temperature for which the value is not prepared. There is no choice but to obtain the fuel injection amount QSTA at startup. That is, if the split injection is executed when the cooling water temperature THW is less than -10 ° C, -15 to -15
In the region of −10 ° C., the fuel injection amount QSTA at start is calculated by interpolation of points A and B as shown by the dotted line in FIG.
There is no choice but to ask. Therefore, a value different from the actually required injection amount will be set.

In this respect, as in the present embodiment, by switching and using the two maps according to each injection method, such a problem is prevented from occurring, and the appropriate fuel injection according to the fuel injection method is performed. The quantity can be secured.

Next, the injection amount calculation process during the transition period to the normal mode will be described based on the flowchart shown in FIG. The injection amount calculation routine in this transition period is performed by the start time flag XSTA 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-mentioned start mode condition is not exceeded for a while, this routine is executed after the start injection amount calculation routine is executed for a certain period.

First, in step S300, the CPU 5
1 calculates the decrease amount tQSTSUB of the starting injection amount QSTA. This decrease amount tQSTSUB is obtained by referring to the one-dimensional map of the cooling water temperature THW shown in FIG. This decrease amount tQSTSUB is set to a certain large value for a temperature of -5 ° C or higher, but it is -10 ° C.
It decreases sharply in the vicinity, and a very small value is set for cryogenic temperatures.

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

Next, the CPU 51 executes the base injection amount QBASE in the normal mode as the processing of step S302.
And the maximum injection amount QFULL are 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.

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

After that, the CPU 51 controls the timing control valve 20 based on the final injection amount QFINC thus obtained.
Also, the electromagnetic spill valve 21 is controlled to execute fuel injection.
FIG. 14 shows the accelerator opening ACCP and the cooling water temperature THW.
Final injection amount QF in the transition period when
The change of INC is shown. FIG. 14 shows the cooling water temperature THW.
Two curves are shown, one for high temperature and one for low temperature.

First, the case of high temperature will be described. In FIG. 14, the period up to time Ta is in the starting mode, and the final injection amount QFINC is the starting injection amount QST calculated by the fuel injection amount calculation routine in the starting mode.
It is A. At the time Ta, the starting mode ends and the starting injection amount QSTA gradually decreases from the time when the transition period to the normal mode starts. However, time T
Until b, the starting injection amount QSTA exceeds the base injection amount QBASE in the normal mode, so the final injection amount QF
INC is the starting injection amount QSTA. Then, at the time Tb, when the base injection amount QBASE exceeds the starting injection amount QSTA, this base injection amount QBASE
E becomes the final injection amount QFINC. In this way, the transition from the starting mode to the normal mode is smoothly performed.

Further, thereafter, the accelerator operation amount ACCPA is decreased by the driver's operation or the engine speed NE is decreased, so that the base injection amount QBASE becomes smaller and the starting injection amount QSTA becomes larger. For example, this starting injection amount QSTA is the final injection amount QFINC.
Becomes Eventually, the starting injection amount QSTA will decrease to zero due to the decrease, so after the lapse of a predetermined time, 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 No. 2, the reduction amount tTQSTSUB of the starting injection amount QSTA is set to be extremely small. Therefore, the starting injection amount QST in 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, in this way the transition period is lengthened,
After the engine temperature rises at time Tc, the mode can be shifted to the normal mode.

As described above in detail, according to the fuel injection amount control device of the present embodiment, the following effects can be obtained. The fuel injection can be performed with a more appropriate fuel injection amount at the time of starting and not executing the split injection, and the startability can be further improved.

Since the fuel injection amount at the time of starting and after the starting is calculated by completely independent means, it is possible to execute the fuel injection at a more appropriate fuel injection amount at the time of starting and after the starting. Therefore, it is possible to achieve both improved startability and improved engine performance after starting.

By gently changing the fuel injection amount during the transition period, it is possible to smoothly shift from the starting mode to the normal mode. In particular, under extremely low temperatures (-10 ° C), by reducing the deceleration rate, it is possible to eliminate engine stalls, rough idles, etc. that frequently occur during extremely low temperatures and immediately after transition. You can

By specifying the split injection effective execution region by the cooling water temperature THW and the fuel temperature THF,
The startability can be improved. By executing the split injection determination only when the start mode is started, and when the execution condition is satisfied, the split injection is continuously executed during the start mode.
It is possible to prevent the startability from deteriorating due to frequent switching between the normal injection and the split injection under an unstable condition during cranking at the time of starting.

By setting conditions for both the cooling water temperature THW and the fuel temperature THF, and determining the split injection execution condition by the logical sum of the two, if either one of the temperature detecting means fails. Also, split injection can be performed, and startability at low temperatures is ensured.

The split injection can be executed more effectively by adding the fuel temperature THF, which 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 by changing its configuration as follows. -Calculate the injection amount during split injection execution and non-execution by functional calculation. In that case as well, it is determined completely independently of whether the split injection is executed or not.

In the present embodiment, the gradual change rate of the fuel injection amount from the starting mode to the normal mode after starting is changed based on the cooling water temperature, but this is changed regardless of the cooling water temperature. The speed may be constant 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 cooling water temperature and the fuel temperature as in the present embodiment, and for example, only one of the cooling water temperature and the fuel temperature, the engine speed or It may be changed so that the intake temperature or the like is used as the condition.

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

Even if the above reference temperature is not set to a predetermined constant value, the startability of the engine is monitored at the time of starting the engine, and feedback is provided to learn the optimum temperature condition. good. By making such changes, the optimum conditions can be set according to the engine usage conditions and individual differences.

In the present embodiment, a so-called distributed type fuel injection device is used, but the present invention is not limited to this, and the present invention can be applied to another type, for example, a column type or common rail type fuel injection device. .

[0101]

According to the invention described in claims 1 and 2,
Since the start-time injection amount is determined completely independently between the split injection execution time and the non-execution time, an appropriate start-time fuel injection amount is applied to each of the split injection execution time and the non-execution time. Further, the startability can be improved.

[0102] Further, since the fuel injection amount during startup and after startup is calculated with a completely independent means, it is at the split injection execution, it is during the non-execution, agnostic fuel injection amount after engine start, It is possible to calculate the fuel injection amount at the time of starting as the optimum injection amount.

Further , the fuel injection amount can be smoothly changed from the start to the start. In addition , by determining the gradual change rate of the fuel injection amount at startup based on the cooling water temperature, the length of the transition period from startup to after startup is optimized according to the temperature state of the engine, and the fuel injection amount Problems due to sudden changes can be avoided more suitably.

[Brief description of 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 a routine for calculating an injection amount in a starting mode.

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

FIG. 9 is a graph showing changes in the injection amount in the starting mode.

FIG. 10 is a graph showing the relationship between the cooling water temperature and the required value of the 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 starting mode to the normal mode.

FIG. 12 is a graph showing an example of a map for calculating the reduction amount of the injection amount at startup.

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

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

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

[Explanation of symbols]

1 ... Diesel engine, 2 ... Fuel injection amount control device, 4
… Fuel injection nozzle, 5… Injection pump, 8…
Electronic control unit (ECU), 14 ... Rotation speed sensor, 20 ...
Timing control valve, 21 ... Electromagnetic spill valve, 22 ... Fuel temperature sensor, 23 ... Water temperature sensor.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-42036 (JP, A) JP-A-6-33812 (JP, A) JP-A-5-86932 (JP, A) JP-A-4- 103850 (JP, A) JP 63-186939 (JP, A) JP 6-117316 (JP, A) JP 2-125939 (JP, A) JP 1-300032 (JP, A) JP-A-7-34926 (JP, A) JP-A-7-63082 (JP, A) JP-A-59-203836 (JP, A) JP-A-63-208637 (JP, A) JP-A-4-91335 (JP, A) JP 5-214981 (JP, A) Actual development 7-44552 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 41/00-41 / 40

Claims (2)

(57) [Claims] 1. A first injection amount calculation means for calculating a fuel injection amount at the time of starting, which corresponds to a split injection in which a required fuel injection amount is divided into a plurality of times and injected. Second injection amount calculating means for exclusively calculating the normal injection other than the split injection and calculating the fuel injection amount at the time of the start of the injection, and at a very low temperature so as to be gentler than otherwise.
The gradual change rate set based on the cooling water temperature
The start calculated by the first and second injection amount calculation means
The fuel injection amount that has been gradually changed to
A third injection amount calculation means for calculating the fuel injection amount, and one of the split injection and the normal injection based on a predetermined parameter at the time of engine start, and the split injection time is calculated by the first injection amount calculation means. is the running fuel injection control based on the start timing fuel injection amount, when in the normal injection executes fuel injection control based on the start time fuel injection quantity calculated by the second injection amount calculating means
In both cases, after the engine is started, the third injection amount calculation means
Perform fuel injection control based on the calculated fuel injection amount after startup.
The fuel injection control apparatus for a diesel engine, characterized in that it comprises a control means for line, the. 2. The first and second injection amount calculating means calculates the starting fuel injection amount on the basis of respective maps using the cooling water temperature and the engine speed as parameters. Item 1. A fuel injection control device for a diesel engine according to Item 1.