JPH09217641A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsiveness of a pump solenoid valve in a common rail type fuel injection device. SOLUTION: It is possible to change a state where a capacitor of a booster circuit 48 for pilot injection and a driving solenoid 38 of a solenoid type fuel injection valve are connected to each other and a state where the capacitor of the booster circuit 48 for pilot injection and driving solenoids 15c, 16c of a pump solenoid valve are connected to each other over to each other. An ECU makes the state where the capacitor of the booster circuit 48 for pilot injection and the driving solenoid 38 of the solenoid type fuel injection valve are connected to each other at the time of setting a pilot injection mode and changes it over the state where the capacitor of the booster circuit 48 for pilot injection and the driving solenoids 15c, 16c of the pump solenoid valve are connected to each other at the time of seeting a normal injection mode by controlling switches SW3, SW5.

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 an internal combustion engine.

[0002]

2. Description of the Related Art A common rail fuel injection system for a diesel engine is shown in FIG. The crankshaft 71 of the diesel engine 70 and the drive shaft 73 of the supply pump 72 are drivingly connected, and the cams 74 and 75 are fixed to the drive shaft 73 with a phase shift, and the inside of the cylinders 76 and 77 are rotated by the rotation of the cams 74 and 75. The pistons 78, 79 slide on the valve body 8 of the solenoid valves 80, 81.
The fuel from the fuel tank 82 is pressurized in the cylinders 76, 77 while the 0a, 81a are moved, and the high-pressure fuel is discharged and sent to the common rail 83. Then, the fuel is delivered from the common rail 83 to each injector 84 provided in each cylinder of the diesel engine 70. Further, the ECU 85 controls the injector 84 so as to inject a predetermined injection amount at a predetermined time.

Further, the solenoid valves 80, 81 (driving solenoid 80b,
81b), the ECU 85 controls the drive signals SG _pomp 1, SG _pomp 2 as shown in the timing chart of FIG.
To the drive circuit 86 to apply a battery voltage to the drive solenoids 80b, 81b of the pump solenoid valves 80, 81 to close the solenoid valves 80, 81. At this time, the pump solenoid valve 8
The discharge amount from the supply pump 72 is adjusted by controlling the valve closing timing of 0 and 81, and the pressure of the common rail 83 is controlled to the pressure required by the diesel engine 70.

[0004]

However, the pump solenoid valves 80, 81 are used for medium- and large-sized engines having a low rotational speed.
Although a predetermined pump discharge amount can be secured by a method of applying a battery voltage to the drive solenoids 80b and 81b, the common rail fuel injection device has been widely applied to a small engine having a high rotational speed in recent years. However, there has been a problem that the pump solenoid valve cannot respond in time and a predetermined discharge amount cannot be secured. That is, in the battery voltage application method, the rise of current is slow and the pump solenoid valve 8
The response of 0 and 81 is bad and a predetermined discharge amount cannot be secured. If the target common rail pressure cannot be secured in this way, problems such as the occurrence of smoke will occur.

Therefore, an object of the present invention is to improve the responsiveness of a pump solenoid valve in a common rail fuel injection device.

[0006]

According to the first aspect of the present invention, the main injection booster circuit boosts and stores the battery voltage in the capacitor connected to the drive solenoid of the electromagnetic fuel injection valve, The pilot injection booster circuit boosts and stores a battery voltage in a capacitor connected to a drive solenoid of an electromagnetic fuel injection valve. Then, the injection control means sets either the normal injection mode or the pilot injection mode according to the operating state of the internal combustion engine, and when the normal injection mode is set, the current from the capacitor of the booster circuit for main injection is set to the electromagnetic fuel injection valve. The main solenoid is supplied to the drive solenoid for the main injection, and when the pilot injection mode is set, the current from the condenser of the pilot injection booster circuit is supplied to the drive solenoid of the electromagnetic fuel injection valve to perform the pilot injection before the main injection. Also do.

As described above, the capacitor voltage boosted by the booster circuit is used when driving the electromagnetic fuel injection valve. On the other hand, the changeover control means controls the changeover switch so that the capacitor of the pilot injection booster circuit and the drive solenoid of the electromagnetic fuel injection valve are connected when the pilot injection mode is set, and the pilot injection is set when the normal injection mode is set. The capacitor of the booster circuit for use and the drive solenoid of the pump solenoid valve are switched to the connected state. As a result, when the normal injection mode is set, the capacitor of the booster circuit for pilot injection is connected to the drive solenoid of the pump solenoid valve, and when the pump solenoid valve control means energizes the drive solenoid of the pump solenoid valve, the booster circuit is turned on. The capacitor voltage boosted higher than the battery voltage is supplied to the drive solenoid of the pump solenoid valve. As a result, a large current flows through the drive solenoid, and the pump solenoid valve has excellent responsiveness.

As described above, also in the common rail type fuel injection device adapted to a small engine having a high rotational speed, the response of the pump solenoid valve can be improved and a predetermined discharge amount can be secured.

Moreover, since the pilot injection booster circuit is used without providing the booster circuit dedicated to the pump solenoid valve, there is no increase in size, increase in the number of parts, and cost.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is embodied in a common rail fuel injection system for a vehicle-mounted small diesel engine. FIG. 1 shows the overall configuration.

This system is equipped with a two-cylinder type supply pump (pressurizing pump) 1. The supply pump 1 is provided with a drive shaft 2, and the drive shaft 2 is drivingly connected to a crankshaft 4 of a 4-cylinder diesel engine (internal combustion engine) 3.
Elliptical cams 5 and 6 are fixed to the drive shaft 2. Further, the supply pump 1 is provided with cylinders 7 and 8, and inside the cylinders 7 and 8, pistons 9 and 10 that slide while contacting the cam surfaces of the cams 5 and 6 are arranged. The downward movement of the pistons 9 and 10 associated with the rotation of the cams 5 and 6 causes the pressurizing chambers 11 in the cylinders 7 and 8 to
The fuel in the tank 14 is supplied to 12 via the low-pressure pump 13.

Discharge amount control solenoid valves 15 and 16 as pump solenoid valves are arranged above the cylinders 7 and 8, and these solenoid valves 15 and 16 open and close a fuel supply passage from the low pressure pump 13. is there. That is, the solenoid valve 15 is the valve body 15
a, spring 15b, drive solenoid (coil) 15
c, and the valve body 15a is closed by moving the drive solenoid 15c against the urging force of the spring 15b from the valve open state up to that point. Similarly, solenoid valve 1
6 includes a valve body 16a, a spring 16b, and a drive solenoid (coil) 16c.
When the valve is opened, the spring 16
The solenoid valve 16 is closed by moving the valve body 16a against the biasing force of b. When the pistons 9 and 10 move upward with the discharge amount control solenoid valves 15 and 16 closed, the pressurizing chambers 11 and 1
At 2, the fuel pressurization operation is performed. The amount of fuel discharged can be adjusted by adjusting the closing timing of the solenoid valves 15 and 16 during the pressurizing operation. Here, the two cams 5 and 6 are arranged with a 90-degree phase shift. That is, the cam 5 and the cam 6 are the pistons 9 (or 1
When 0) is at top dead center, the other piston 10 (or 9) is at bottom dead center. Further, the discharge amount control solenoid valves 15 and 1
The valve 6 is opened at the top dead center of the cam lift to open the pressurizing chambers 11 and 12.
The fuel pressurization and the fuel discharge operation are completed.

Further, the pressurizing chambers 11 and 12 of the supply pump 1
The fuel supply pipes 17 and 18 are connected to a high pressure accumulating pipe common to each cylinder, that is, a so-called common rail 19. A check valve 20 is provided at the pump-side end of the fuel supply pipe 17,
A check valve 21 is provided at the pump-side end of the fuel supply pipe 18. The check valves 20 and 21 allow the supply of fuel from the supply pump 1 side to the common rail 19 side, and regulate the passage of fuel from the common rail 19 side to the supply pump 1 side.

An electromagnetic fuel injection valve (injector) 23 for each cylinder of the diesel engine 3 is connected to the common rail 19 by a branch pipe 22. Also, the fuel injection valve 2
3 is provided with a three-way solenoid valve 24. By controlling the solenoid valve 24, the fuel injection valve 23 to the common rail 19 can be controlled.
High-pressure fuel can be injected into each cylinder.

FIG. 2 shows a sectional view of the fuel injection valve 23. The fuel injection valve 23 includes a fuel injection valve body 25 and a three-way solenoid valve 24, and high-pressure fuel from the common rail 19 is supplied to the fuel injection valve body 25 and the three-way solenoid valve 24. A needle valve 27 is arranged in a fuel chamber 26 of the fuel injection valve main body 25. The needle valve 27 is connected to a piston 28 and is biased by a spring 29 in a direction to close the injection port. The three-way solenoid valve 24 has a housing 3
0, and the outer valve 31 is supported in its inner hole 30a so as to be vertically slidable. First in housing 30
A port (fuel intake port) 32, a second port 33, and a drain port 34 are provided. The first port (fuel intake port) 32 is the common rail 19 and the second port 33.
Is connected to the upper space of the piston 28, and the drain port 34 is connected to the drain tank 35. The outer valve 31 has a port 36 corresponding to the first port 32,
A port 37 corresponding to the second port 33 is provided.

A drive solenoid (coil) 38 is provided on the upper side of the housing 30. When the drive solenoid 38 is not energized, the outer valve 31 is urged downward by the spring 39, the first port 32 of the housing 30 and the port 36 of the outer valve 31 communicate with each other, and the second port 33 of the housing 30 and the outer valve 31. Communicates with the port 37. Therefore, the high-pressure fuel from the common rail 19 is supplied to these ports 32, 36, 37,
It is applied to the upper surface of the piston 28 through 33 and the inner hole 31a of the outer valve 31, and this pressure pushes the needle valve 27 downward to close the injection port.

Further, when the drive solenoid 38 is energized, the outer valve 31 is suctioned up, the port 32 is closed, and the port 33 and the port 34 are communicated with each other. Therefore, the pressure applied to the piston 28 passes through the port 33 and the port 34 and the drain tank 3
It leaks to the 5 side (low pressure side). Therefore, the needle valve 27
Rises by the high-pressure fuel in the fuel chamber 26, opens the injection port, and injects the high-pressure fuel in the common rail 19.

In FIG. 1, a crank angle sensor 4 is provided in an electronic control unit (hereinafter referred to as ECU) 40 as pump solenoid valve control means, injection control means, and switching control means.
1, a cylinder discrimination sensor 42 and an accelerator opening sensor 43 are connected. Further, the ECU 40 includes a solenoid valve drive circuit 4
4 are connected. Further, a common rail pressure sensor 45 is connected to the ECU 40, and the sensor 45 detects the common rail pressure. When the diesel engine 3 is started, the cams 5 and 6 of the supply pump 1 rotate, and the pistons 9 and 10 reciprocate with this rotation, so that fuel from the low-pressure pump 13 is supplied to the supply pump 1 and high-pressure fuel is supplied. Is supplied to the common rail 19 through the fuel supply pipes 17 and 18, and the fuel is accumulated in the common rail 19. Here, the ECU 40 controls the discharge amount of the supply pump 1 so that the common rail pressure by the common rail pressure sensor 45 becomes an optimum value according to the accelerator opening degree and the rotation speed.

Further, the ECU 40 controls the opening and closing of the three-way solenoid valve 24 of the fuel injection valve 23 to inject a fuel amount corresponding to the operating state of the diesel engine 3 and injects the fuel in the common rail 19 into each cylinder of the diesel engine 3. To do.

Next, the solenoid valve drive circuit 44 described above will be described in more detail.
This will be described in detail. FIG. 3 shows a specific example of the solenoid valve drive circuit 44.
The configuration is shown. The solenoid valve drive circuit 44 includes a constant current circuit 46.
And a main injection booster circuit (main injection booster circuit) 47
And a booster circuit 48 for pilot injection. Constant power
The flow circuit 46 injects fuel into each cylinder via the diode 49.
It is connected to the drive solenoid 38 of the valve 23. Also, each
The drive solenoid 38 of the fuel injection valve 23 of the cylinder is switched.
Via SW1a, SW1b, SW1c, SW1d
Have been The main injection booster circuit 47 is a switch
Drive of the fuel injection valve 23 of each cylinder via SW2
Connected to the switch 38. Pilot injection booster circuit 4
8 is the fuel injection valve 23 of each cylinder via the switch SW3
Of the drive solenoid 38. Switch SW
1a, SW1b, SW1c, SW1d from the ECU 40
Drive signal SG_inj1-SG_injOpen and close by 4 (on
OFF), and the switch SW2 is a drive signal from the ECU 40.
SG_MOpen and close (on / off) by 1 and switch SW3
Is the drive signal SG from the ECU 40._piOpen and close by 1 (on
・ Turn off). And switch SW2 or switch
With SW3 closed, switches SW1a, SW1b,
When SW1c and SW1d are closed, the drive solenoid 38
Energizing current I_inj1, I _inj2, I_inj3, I_inj4 is
Flow, the fuel injection valve 23 opens and fuel injection is performed.

On the other hand, the discharge amount control solenoid valves (pump solenoid valves) 15, 16 are connected to the battery 50 via the diode 51.
Drive solenoids 15c and 16c are connected.
The drive solenoids 15c and 16c are the switch SW4.
It is grounded via a and SW4b. The pilot injection booster circuit 48 is connected to the drive solenoids 15c and 16c of the discharge amount control units 15 and 16 via the switch SW5. The switches SW4a and SW4b are the ECU 40.
_Are opened / closed (on / off) by drive signals SG _pomp 1 and SG _pomp 2 from, and the switch SW5 is opened / closed (on / off) by a drive signal SG _pi 2 from the ECU 40. And
When the switches SW4a and SW4b are closed, the energizing currents I _pomp 1 and I _pomp 2 flow to the drive solenoids 15c and 16c, the discharge amount control solenoid valves (pump solenoid valves) 15 and 16 are closed, and the fuel to the common rail 19 is closed. The ejection operation is performed. At this time, if the switch SW5 is closed, electric power from the pilot injection booster circuit 48 is supplied to the drive solenoids 15c and 16c.

Here, the switches SW1a to SW1d,
SW2, SW3, SW4a, SW4b, and SW5 are semiconductor switching elements such as transistors, and can be opened / closed (on / off) by adjusting the voltage applied to a control terminal (base terminal or gate terminal). Has become.

FIG. 4 shows the circuit configurations of the main injection booster circuit 47 and the pilot injection booster circuit 48. In the main injection booster circuit 47, the primary coil 53a of the transformer 53 and the transistor Tr1 are connected to the battery terminal 52.
And are connected in series. The secondary coil 53b of the transformer 53, the diode 54, and the capacitor 55 are connected in series. A connection point a between the diode 54 and the capacitor 55 is connected to an output terminal via the diode 56, and this output terminal serves as a connection terminal to the drive solenoid 38 of the fuel injection valve 23 in FIG. The connection point b between the capacitor 55 and the diode 56 in FIG. 4 is grounded via the two resistors 57 and 58 connected in series. The connection point c between the resistors 57 and 58 is the comparator 5
9 is connected to one input terminal. Comparator 5
The other input terminal of 9 is connected to the ECU 40. Further, the output terminal of the comparator 59 is connected to the ECU 40.

The base terminal of the transistor Tr1 is E
It is connected to the CU40, and the transistor Tr is
A charge pulse is output to the base terminal of 1. This charge pulse turns on / off the transistor Tr1. The transformer 53 is turned on by turning on the transistor Tr1.
Secondary current I _c2 in the secondary coil 53b of the transformer 53 flows by turning off the transistor Tr1 with primary current flows I _c1 in the primary coil 53a of the voltage stored in the capacitor 55. By repeating the on / off operation of the transistor Tr1, the voltage of the capacitor 55 rises. This capacitor voltage is divided by the voltage dividing resistors 57 and 58. The comparator 59 compares the divided voltage of the capacitor 55 with the boost completion command value voltage from the ECU 40. When the divided voltage of the capacitor 55 reaches the boost completion voltage, the output terminal is changed from the H level to the L level. To do. The ECU 40 stops the output of the charge pulse to the transistor Tr1 by this L level signal and ends the boosting operation (ON / OFF operation of the transistor Tr1).

In this way, the voltage of the battery is boosted to a predetermined voltage by the transformer 53 and stored in the capacitor 55. The pilot injection booster circuit 48 also has the same configuration as the main injection booster circuit 47, and the description thereof will be omitted by giving the same reference numerals to the components. As the operation of the pilot injection booster circuit 48, the transistor Tr1 is turned on / off by a charge pulse from the ECU 40 to the base terminal of the transistor Tr1, and the primary current I _c1 is supplied to the primary side coil 53a of the transformer 53 by turning on the transistor Tr1. The secondary current I _c2 flows through the secondary coil 53b of the transformer 53 as the transistor Tr1 is turned off, and the voltage is stored in the capacitor 55. By repeating the on / off operation of the transistor Tr1, the voltage of the capacitor 55 rises, the voltage of this capacitor is divided by the voltage dividing resistors 57 and 58, and the capacitor 55 is divided by the comparator 59.
When the divided voltage of the capacitor 55 reaches the boost completion voltage, the output terminal is changed from the previous H level to the L level. The ECU 40 stops the output of the charge pulse to the transistor Tr1 by this L level signal and ends the boosting operation (ON / OFF operation of the transistor Tr1).
In this way, also in the pilot injection booster circuit 48, the battery voltage is boosted to a predetermined voltage by the transformer 53 and stored in the capacitor 55.

Next, the operation of the fuel injection control device for the diesel engine thus constructed will be described. Figure 5 shows EC
It is a flow chart which shows the contents of processing which U40 performs. This process will be described with reference to the timing chart of FIG.

In FIG. 6, the output signal (reference pulse) of the cylinder discrimination sensor 42, the switches SW3, SW2 and SW.
1a to SW1d states, energization currents I _inj 1, I _inj 2, I of the drive solenoid 38 of the fuel injection valve 23 in each cylinder.
_inj 3, I _inj 4, the lift amount of the cam 5, the lift amount of the cam 6, the states of the switches SW5, SW4a, SW4b, the energization currents I _pomp 1, I _{pomp of the} discharge amount control solenoid valves 15, 16.
2, the valve lift states of the discharge amount control solenoid valves 15 and 16 and the common rail pressure are shown. Further, in FIG. 6, the solid line shows the behavior when only the main injection is performed, and the broken line shows the behavior when the pilot injection is performed.

The ECU 40 detects the engine speed by the crank angle sensor 41 in step 100 of FIG. Then, in step 101, the ECU 40 detects the accelerator opening (engine load state) by the accelerator opening sensor 43.

Then, in step 102, the ECU 40 calculates the target fuel injection amount according to the operating state of the engine based on the engine speed and the accelerator opening. Furthermore, EC
In step 103, the U40 calculates the target fuel injection pressure according to the operating state of the engine based on the engine speed and the accelerator opening. That is, the common rail pressure at the maximum amount of pump cam lift (top dead center of the cylinder) shown at t20 in FIG. 6 is calculated. In step 104, the ECU 40 calculates the pump discharge amount according to the operating state of the engine based on the engine speed and the accelerator opening.

Then, the ECU 40 determines in step 105 whether pilot injection is necessary. More specifically,
From the engine load state by the accelerator opening sensor 43 and the engine speed by the crank angle sensor 41, it is determined whether or not pilot injection is necessary using the map shown in FIG. FIG. 7 shows a region Z1 in which only the main injection is performed and a region Z2 in which pilot injection is also performed in the relationship between the engine speed and the accelerator opening. As can be seen from FIG. 7, only the main injection is performed at high rotation speed and high load.

When the ECU 40 determines in step 105 that pilot injection is necessary, it sets the pilot injection mode and executes the following processing. First, the ECU
In step 106, the switch 40 opens the switch SW5 in FIG. Furthermore, the ECU 40 switches the switch S in step 107.
The closing timing (ON timing) TF1 of W4a and SW4b is calculated. The closing timing (ON timing) TF1 is also shown in FIG.

In step 108, the ECU 40 calculates the pilot injection timing and amount according to the operating state of the engine based on the engine speed and the accelerator opening. That is, the closing timing (ON timing) TTP and the closing period (ON period) TQP of the switches SW3, SW1a to SW1d are calculated.
The closing timing TTP and the closing period TQP are also shown in FIG.

Then, in step 109, the ECU 40 calculates the main injection timing and amount according to the operating state of the engine based on the engine speed and the accelerator opening. That is, the closing timing (ON timing) TTM and the closing period (ON period) TQM of the switches SW2, SW1a to SW1d are calculated.
The closing timing TTM and the closing period TQM are also shown in FIG.

Then, the ECU 40 performs output processing in step 110. As a result, in FIG. 6, when the pilot injection start timing t2 is reached based on the reference timing (t1) based on the output signal of the cylinder discrimination sensor 42, the switch SW
3, SW1b is closed, and energization of the drive solenoid 38 of the fuel injection valve 23 is started. At this time, a current flows from the capacitor 55 of the pilot injection booster circuit 48 in FIG. 4 to the drive solenoid 38, the nozzle lift operation of the fuel injection valve 23 is performed, and the fuel injection valve 23 opens. Further, after the valve is opened, a constant current flows from the constant current circuit 46 of FIG. 3 to the drive solenoid 38, and the valve open state is maintained by the constant current. Further, in FIG. 6, pilot injection end timing t
When it becomes 3, the switches SW3 and SW1b are opened to terminate the energization of the drive solenoid 38 of the fuel injection valve 23.
As a result, the fuel injection valve 23 is closed. In this way, pilot injection is performed.

Thereafter, in FIG. 6, the main injection start timing t4
Then, the switches SW2 and SW1b are closed, and the energization of the drive solenoid 38 of the fuel injection valve 23 is started. At this time, a current flows from the condenser 55 of the main injection booster circuit 47 in FIG. 4 to the drive solenoid 38, the nozzle lift operation of the fuel injection valve 23 is performed, and the fuel injection valve 23 opens. Further, after the valve is opened, a constant current flows from the constant current circuit 46 to the drive solenoid 38, and the valve open state is maintained by the constant current. Then, at the main injection end timing t5 in FIG. 6, the energization of the drive solenoid 38 of the fuel injection valve 23 is ended. In this way, in the pilot injection mode, the drive solenoid 38 is energized twice to perform pilot injection and main injection.

On the other hand, the ECU 40 executes step 105 in FIG.
When it is determined that the pilot injection is not necessary in (1), the normal injection mode is set and the following processing is executed. First,
The ECU 40 opens the switch SW3 in FIG. 3 in step 111. Further, in step 112, the ECU 40 closes the switches SW5, SW4a, and SW4b (ON timing).
Calculate TF2. The closing timing TF2 is also shown in FIG.

The closing timing (ON timing) T of the switches SW4a and SW4b in steps 107 and 112
F1 and TF2 take values according to the pump discharge amount in step 104.

In step 109, the ECU 40 calculates the main injection timing and amount according to the operating state of the engine based on the engine speed and the accelerator opening. That is, the switch S
Closing time (ON timing) TT of W2 and SW1a to SW1d
M and the closed period (ON period) TQM are calculated.

Then, the ECU 40 performs output processing in step 110. As a result, in FIG. 6, when the main injection start timing t4 is reached based on the reference timing (t1) based on the output signal of the cylinder discrimination sensor 42, the energization of the drive solenoid 38 of the fuel injection valve 23 is started. Further, at the main injection end timing t5, the drive solenoid 38 of the fuel injection valve 23
To turn off electricity to.

Thus, in the normal injection mode, the drive solenoid 38 is energized once to perform the main injection.
When the normal injection mode is set, the capacitor 55 of the pilot injection booster circuit 48 shown in FIGS. 3 and 4 is connected to the drive solenoids 15c and 16c of the discharge amount control solenoid valves 15 and 16, and the drive solenoids 15c and 16c are energized. In doing so, the capacitor voltage boosted higher than the battery voltage is supplied to the drive solenoids 15c and 16c. As a result, steep currents I _pomp 1 and I _pomp 2 flow in the drive solenoids 15c and 16c for a short period of time indicated by t11 to t12 in FIG. 6 (large currents flow into the drive solenoids 15c and 16c).

As described above, the present embodiment has the following features. (A) As shown in FIG. 3, switches SW3 and SW5 as changeover switches are arranged to connect the capacitor 55 of the pilot injection booster circuit 48 and the drive solenoid 38 of the electromagnetic fuel injection valve 23, or It is possible to switch to a state in which the condenser 55 of the pilot injection booster circuit 48 and the drive solenoids 15c and 16c of the discharge amount controlling solenoid valve are connected to each other, and the ECU 40 as the switching control means executes the steps in FIG. 106,10
In the processing of 8, 111 and 112, the switches SW3 and S
W5 is controlled so that the capacitor 55 of the pilot injection booster circuit 48 is connected to the drive solenoid 38 of the electromagnetic fuel injection valve 23 when the pilot injection mode is set, and the pilot injection booster circuit 48 is set when the normal injection mode is set. The condenser 55 and the drive solenoids 15c and 16c of the discharge amount controlling solenoid valve are switched to the connected state. As a result, a large current is applied to the drive solenoid 15c,
16c, and the discharge amount control solenoid valves 15 and 16 have excellent responsiveness.

As described above, even in the common rail type fuel injection device adapted to a small engine having a high rotational speed, the responsiveness of the pump solenoid valves (15, 16) can be improved and a predetermined discharge amount can be secured. Becomes

Further, since the pilot injection booster circuit 48 is used without providing a booster circuit dedicated to the pump solenoid valve, there is no increase in size, increase in the number of parts, and cost.

The present invention is not limited to the above embodiment. For example, in the above embodiment, two pumps for controlling the discharge amount are used in the pump 1, but the two cylinder type pump is used. ) It may be embodied when only one is used (one-cylinder type pump) or when three or more are used.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a common rail fuel injection system according to an embodiment.

FIG. 2 is a sectional view of a fuel injection valve.

FIG. 3 is an electrical configuration diagram of a solenoid valve drive circuit.

FIG. 4 is a configuration diagram of a booster circuit.

FIG. 5 is a flowchart for explaining the operation.

FIG. 6 is a timing chart for explaining the operation.

FIG. 7 is a map showing a region.

FIG. 8 is an overall configuration diagram of a common rail fuel injection system for explaining a conventional technique.

FIG. 9 is a timing chart for explaining a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Supply pump as pressurizing pump, 3 ... Diesel engine (internal combustion engine), 15 ... Discharge control solenoid valve as pump solenoid valve, 15c ... Drive solenoid, 16 ...
Discharge amount control solenoid valve as pump solenoid valve, 16c ... Drive solenoid, 19 ... Common rail, 23 ... Electromagnetic fuel injection valve, 38 ... Drive solenoid, 40 ... Pump solenoid valve control means, injection control means, switching control means ECU,
47 ... Main injection booster circuit (main injection booster circuit), 4
8 ... Pilot injection booster circuit, 55 ... Capacitor, S
W3 ... Changeover switch, SW5 ... Changeover switch

Claims (1)

[Claims] 1. A pressurizing pump having a pump solenoid valve, which pressurizes fuel by rotation accompanying the drive of an internal combustion engine and discharges pressurized fuel by energizing a drive solenoid of the pump solenoid valve, A common rail for storing pressurized fuel discharged from the pressurizing pump; pump solenoid valve control means for controlling energization of a drive solenoid of the pump solenoid valve to control the fuel discharge amount of the pressurizing pump; An electromagnetic fuel injection valve that opens by energizing a solenoid to inject high-pressure fuel in the common rail, and a main injection that boosts and stores a battery voltage for a capacitor connected to a drive solenoid of the electromagnetic fuel injection valve A booster circuit for pilot injection, which boosts and stores a battery voltage in a capacitor connected to a drive solenoid of the electromagnetic fuel injection valve, Either the normal injection mode or the pilot injection mode is set according to the operating state of the fuel engine, and when the normal injection mode is set, the current from the condenser of the main injection booster circuit is supplied to the drive solenoid of the electromagnetic fuel injection valve. Main injection is performed, and when the pilot injection mode is set, the current from the capacitor of the pilot injection booster circuit is supplied to the drive solenoid of the electromagnetic fuel injection valve to perform pilot injection prior to the main injection. A fuel injection control device for an internal combustion engine comprising injection control means, wherein a capacitor of the pilot injection booster circuit and a drive solenoid of the electromagnetic fuel injection valve are connected, or the pilot injection booster A switching switch for switching between the circuit capacitor and the drive solenoid of the pump solenoid valve. And a switch for controlling the pilot injection mode so that the pilot injection booster capacitor and the solenoid drive valve drive solenoid are connected, and the normal injection mode is set to the pilot injection mode. A fuel injection control device for an internal combustion engine, comprising: a switching control means for switching to a state in which the capacitor of the booster circuit for use and the drive solenoid of the pump solenoid valve are connected.