JPH10252538A - Common rail type fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent valve closing misoperation due to coil current carrying of delivery amount control valve during fuel feed period. SOLUTION: A transistor 51 is connected to a solenoid coil 19 of a delivery amount control valve set up in a supply pump, a current is carried in the coil 19 by on-action. In a microcomputer 42, for a prescribed period in a forced feed stroke of the supply pump, the transistor 51 is turned on, the delivery amount control valve is closed, a fuel delivery amount to a common rail is controlled. In the microcomputer 42, in a non-forced feed stroke of the supply pump when the delivery amount control valve is opened, the transistor 51 is repeatedly turned on/off, flyback energy is accumulated in capacitors 54, 55 in a forced feed stroke of the supply pump when the delivery amount control valve is opened, the transistor 51 is forcibly turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a common rail fuel injection control device for a diesel engine,
More specifically, the present invention relates to a common rail fuel injection control device having a function of accumulating energy necessary for driving an injector of a diesel engine by pulsating a coil of a discharge control valve (PCV) provided in a supply pump. is there.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 8-210170 discloses a technique for driving an injector using flyback energy generated when an electromagnetic coil is driven in a common rail fuel injection control device for a diesel engine. As shown in FIG. 9, this is provided with a diesel engine 80, a supply pump 81, and a common rail 82, and a flyback generated when a normally open electromagnetic discharge control valve (PCV) 83 provided in the supply pump 81 is driven. The energy is stored in the capacitor, and this energy is used when the electromagnetic coil of the injector 84 is energized. That is, in recent years, there has been an increasing need to drive the injector with a high voltage and a large current in order to improve the engine performance and to instantaneously open the injector and inject fuel. The injector drive voltage at this time is shown in FIG. Thus, 100 volts or more and a current of about 8 amps are required. For this purpose, energy generated when the power supply of the electromagnetic coil is cut off by the discharge amount control valve (PCV) 83 is accumulated as energy for driving the injector, and discharged when the injector is driven. Also, instead of accumulating the energy necessary to drive the injector by energizing the charging coil, the electromagnetic coil of the discharge amount control valve (PCV) 83 is used instead of the coil,
Cost reduction can be achieved with a small number of parts.

More specifically, the energization of the electromagnetic coil generates magnetic energy defined by the coil inductance L and the energizing current, and this energy is stored in the charging capacitor. This allows the capacitor to store more than 100 volts of energy. The injector is driven at a timing defined by the engine speed, the battery voltage, and the like. When the injector is driven, energy of 100 volts or more previously stored in the charging capacitor is discharged to the injector.

[0004] Referring to the drive for charging the discharge amount control valve (PCV) 83, since the discharge amount control valve 83 is a fuel intake opening / closing valve, the fuel intake / pumping timing specified by the engine speed and the like. When the flyback energy at this time is charged in the capacitor, the flyback energy of the discharge amount control valve 83 only by the pressure feeding drive follows the injector injection timing. It is difficult to fully charge the charging capacitor.

In order to compensate for the insufficient voltage for the full charge, it is conceivable to output a boosting pulse continuously from the timing of t50 immediately after the end of the pressure feeding drive as shown in FIG. Here, the specification of the ON time and the OFF time of the pressure increasing pulse is such that the discharge amount control valve 83 does not shift from the open state to the closed state by the pressure increasing pulse.
Make the coil current flow. This is because the period of the boost pulse output is during the period when the discharge amount control valve 83 is in the open state, and the discharge amount control valve 83 must not be closed by the boost pulse. The discharge amount control valve 83 is provided as shown in FIG.
As shown in (a), the electromagnetic coil 90 and the fixed core 91
When the electromagnetic coil 90 is energized, the movable core 92 is attracted to the fixed core 91 against the urging force of the spring 93, and the valve element 94 also moves to the right in the figure to move the plunger chamber. The communication between the fuel passage 95 and the fuel passage 96 is interrupted, and the valve is closed. As shown in FIG. 12B, when the electromagnetic coil 90 is de-energized, the movable core 92 is separated from the fixed core 91 by the urging force of the spring 93, and the valve element 94 also moves to the left in the figure. The plunger chamber 95 communicates with the fuel passage 96 to open the valve.

[0006]

However, as shown in FIG. 11, when the discharge amount control valve 83 outputs a pressure-increasing pulse that does not close during the valve-opening period during the non-pressure-feeding period (suction stroke), The valve state can be assured during the non-pressure feeding stroke of the supply pump (suction stroke). When the pump enters the fuel pressure feeding stroke, the valve can not be maintained in the open state. This is because when the pump enters the pumping period, as shown in FIG. 12B, the fuel in the pump is raised to a pressure of 1000 Pa or more, and at this time, the discharge amount control valve 83 is moved to the valve closing side. Pressure (force F in the figure) is applied. If the discharge amount control valve 83 is driven by the step-up pulse in this state, there is a high risk that the current will not be closed during the non-pressure feeding period but will be easily closed during the pressure feeding period. Thus, if the valve is closed during the valve opening period, the risk of malfunction of the fuel injection system increases.

It is an object of the present invention to provide a common rail type fuel injection control device having a function of recovering flyback energy by energizing a coil of a discharge amount control valve. An object of the present invention is to provide a common rail fuel injection control device that can prevent a valve malfunction.

[0008]

According to a first aspect of the present invention, there is provided a common rail type fuel injection control device, wherein (1) a switching element is repeatedly turned on / off in a non-pressure feeding stroke of a supply pump when a discharge amount control valve is opened. First switching element control means for accumulating flyback energy in the charging means, and (2) second switching element for forcibly turning off the switching element in the pressure feed stroke of the supply pump when the discharge amount control valve is opened. And control means.

Accordingly, the operation of accumulating flyback energy in the charging means by the first switching element control means is prohibited in the pressure feeding process of the supply pump.

Therefore, the discharge amount control valve is in an environment where it is easily closed by the fuel pressure during the pressure feeding stroke of the supply pump, but the valve is kept open, so that a valve closing malfunction can be avoided.

According to a third aspect of the present invention, there is provided a common rail type fuel injection control device, wherein (1) the switching element is repeatedly turned on and off in the non-pressure feeding stroke of the supply pump when the discharge amount control valve is opened to charge the flyback energy. First switching element control means stored in the means;
(2) Flyback by repeatedly turning on / off the switching element in an on-time shorter than the on-time of the switching element in the first switching element control means in the pressure feed stroke of the supply pump when the discharge amount control valve is opened. And a second switching element control means for storing energy in the charging means.

Thus, the operation of accumulating the flyback energy in the charging means is such that the switching element operates in a shorter on-time than the non-pressure-feeding stroke of the supply pump in the pressure-feeding stroke of the supply pump when the discharge amount control valve is opened. It is possible to set the electromagnetic coil energizing current in a range in which the discharge amount control valve is driven and does not open.

Therefore, the discharge amount control valve is in an environment where it is easily closed by the fuel pressure during the pressure feeding stroke of the supply pump, but the valve open state is maintained and the valve closing malfunction can be avoided.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings.

FIG. 1 shows the overall configuration of a common rail fuel injection control device (diesel engine fuel injection system). This device (system) is mounted on an automobile. That is, the present invention is applied to a vehicle-mounted diesel engine.

The present system is provided with a one-cylinder type supply pump (high-pressure pump) 1. FIG. 2 is a sectional view showing a specific configuration of the supply pump 1. FIG.
1, a drive shaft 2 is provided in the supply pump 1, and the drive shaft 2 is drivingly connected to a crankshaft 4 of a six-cylinder diesel engine 3. Further, a triangular cam 5 is fixed to the drive shaft 2. Furthermore, a cylinder 7 is provided in the supply pump 1, and a plunger 9 that slides while contacting the cam surface of the cam 5 is arranged in the cylinder 7. The fuel in the tank 14 is sucked into the plunger chamber (pressurizing chamber) 11 in the cylinder 7 via the feed pump (low pressure pump) 13 by the downward movement of the plunger 9 accompanying the rotation of the cam 5.

Here, the feed pump 13 is built in the pump main body as shown in FIG. 2, and supplies the fuel in the tank 14 to the plunger chamber 11 by the movement of the vane accompanying the drive of the drive shaft 2.

A normally open type electromagnetic discharge control valve (PCV) 15 is disposed above the cylinder 7.
The discharge amount control valve 15 opens and closes a fuel supply passage from the feed pump 13. That is, the discharge amount control valve 15 includes the valve element 17, the spring 18, and the electromagnetic coil (solenoid coil) 19. The valve body 17 is moved and closed. When the plunger 9 moves upward with the discharge amount control valve 15 closed, the fuel pressurizing operation (pressure feeding operation) is performed in the plunger chamber 11. The fuel discharge amount can be adjusted by adjusting the closing timing of the discharge amount control valve 15 during this pressurizing operation.

More specifically, the discharge amount control valve 15 is arranged as shown in FIG.
The configuration shown in FIG. That is, the discharge amount control valve (PC
V) 15 is, as shown in FIG.
0, fixed-side core 91, movable-side core 92, and spring 93
When the electromagnetic coil 90 is not energized, the spring 9
Due to the urging force of 3, the movable-side core 92 moves in the direction away from the fixed-side core 91 (to the left in the figure), and the valve body 94 moves in the same manner, causing the plunger chamber 95 and the fuel passage 96 to move. Connect and open the valve. As shown in FIG. 12A, the energization of the electromagnetic coil 90 causes the movable-side core 92 to be attracted to the fixed-side core 91 against the urging force of the spring 93, and the valve element 94 also moves to the right in the figure. Moving plunger room 95
The communication with the fuel passage 96 is cut off.

In FIG. 1, the plunger chamber 11 of the supply pump 1 is connected to a high-pressure accumulating pipe common to each cylinder, a so-called common rail 25, by a fuel supply pipe 23. A check valve 26 is provided at an end of the fuel supply pipe 23 on the pump side. The check valve 26 allows the supply of fuel from the supply pump 1 side to the common rail 25 side, and the supply pump The passage of fuel to one side is regulated.

Injectors (fuel injection valves) 29, 30, 31, 32, 33, and 34 for each cylinder of the diesel engine 3 are connected to the common rail 25 through a branch pipe 28. The injectors 29 to 34 have three-way solenoid valves 3.
5, 36, 37, 38, 39, and 40 are provided, and the injectors 29 are controlled by controlling the solenoid valves 35 to 40.
To 34, high-pressure fuel from the common rail 25 can be injected into each cylinder.

Electronic control unit (hereinafter referred to as ECU)
Reference numeral 41 denotes a microcomputer (hereinafter referred to as a microcomputer) 42 and a drive circuit 43. The microcomputer 42 receives information on the engine speed and the accelerator opening from a crank angle sensor 44, a cylinder discrimination sensor 45, and an accelerator opening sensor 46. You. Here, the cylinder discriminating sensor 45 has a gear 45a fixed to the drive shaft 2 of the pump as shown in FIG. 2, and generates a pulse signal when the drive shaft 2 rotates and the gear 45a passes. Is done. Then, the microcomputer 42 controls the three-way solenoid valve 35 via the drive circuit 43 so that the optimal injection timing and injection amount are determined according to the engine state determined by these signals.
To 40 are driven and controlled.

More specifically, the microcomputer 42 opens and closes the three-way solenoid valves 35 to 40 of the injectors 29 to 34 so as to inject fuel at a timing and an amount corresponding to the operating state of the diesel engine 3 (engine speed and accelerator opening). The fuel in the common rail 25 is injected into each cylinder of the diesel engine 3 under control. Here, in this example, at the time of fuel injection in each cylinder, main injection and pilot injection preceding it are performed. That is, the pilot injection signal P and the main injection signal M are generated as the injection pulse of the injector in FIG.

Further, the electromagnetic coil 19 of the discharge amount control valve 15 is connected to the microcomputer 42 of FIG. 1 through a drive circuit 43, and the electromagnetic coil 19 is energized or de-energized to control the opening and closing of the discharge amount control valve 15. You can do it. Further, the microcomputer 42 inputs a common rail pressure detection signal from a common rail pressure sensor 47 provided on the common rail 25, and sets the discharge amount control valve 15 so that the common rail pressure is set to an optimum value according to the accelerator opening and the number of revolutions.
Is controlled to adjust the discharge amount of the supply pump 1.

More specifically, when the diesel engine 3 starts, the cam 5 of the supply pump 1 rotates, and with this rotation, the plunger 9 reciprocates and the feed pump 13 rotates.
Is supplied to the supply pump 1 and high-pressure fuel is supplied to the common rail 25 through the fuel supply pipe 23, and the fuel is accumulated in the common rail 25. Here, the microcomputer 42 controls the discharge amount of the supply pump 1 so that the common rail pressure by the common rail pressure sensor 47 is set to an optimum value according to the accelerator opening and the number of revolutions.

Hereinafter, the microcomputer 42 and the driving circuit 43 will be described.
The ECU 41 will be described. FIG. 3 shows the ECU 4
1 shows a specific configuration. In brief, a microcomputer 42 for controlling fuel injection, an electromagnetic coil 19 of a discharge amount control valve installed in the supply pump 1, a MOS transistor 51 for energizing the coil 19, and switching of the transistor 51 A capacitor 53 as a charging means for storing flyback energy at the time, and a solenoid valve 35 of the injector using the stored energy.
, And MOS transistors 57 to 62 for driving.

The discharge amount control valve 1 is connected to the battery terminal + B.
5 and the MOS transistor 51 are connected in series. A connection point a between the electromagnetic coil 19 and the transistor 51 is connected to a main injection capacitor 53 and a pilot injection capacitor 54.

The three-way solenoid valves 35 to 40 of each injector are connected in parallel to the capacitor 53 through a MOS transistor 55 for separating the pilot injection voltage. Similarly, the capacitor 54 has a main injection voltage separating M
Through the OS transistor 56, the three-way solenoid valves 35 to 40 of each injector are connected in parallel. Each of the three-way solenoid valves 35 to 40 has a MOS transistor 57, 58, 59,
60, 61 and 62 are respectively connected in series.

Voltage dividing resistors 63 and 64 are connected to the capacitor 53, and the connection point c has a potential corresponding to the capacitor voltage. A comparator 65 is connected to the connection point c, where the voltage is compared with a predetermined voltage by the voltage dividing resistors 66 and 67. When the voltage of the capacitor 53 becomes higher than a predetermined potential (118 volts), the output of the comparator 65 becomes H level. Similarly, voltage dividing resistors 68 and 69 are connected to the capacitor 54, and the connection point d has a potential corresponding to the capacitor voltage. A comparator 70 is connected to the connection point d, and the comparator 70 compares the voltage with a predetermined voltage set by the voltage dividing resistors 66 and 67. And capacitor 5
When the voltage of No. 4 becomes higher than a predetermined potential (118 volts), the output of the comparator 70 becomes H level. The output terminals of the comparators 65 and 70 are connected to the microcomputer 42 through the AND gate 71. When both the voltage of the capacitor 53 and the voltage of the capacitor 54 become higher than a predetermined voltage (118 volts), an H level signal is output to the microcomputer 42. .
The microcomputer 42 detects whether the voltage of the capacitors 53 and 54 is higher than 118 volts based on the potential of the signal line (the output level of the AND gate 71).

The three-way solenoid valves 35 to
40 is connected to a constant current circuit 72.
2, a constant current (2 amps) for holding the valve closed as shown in FIG. 10 is supplied.

The microcomputer 42 includes the transistor 5 described above.
1,55,56,57,58,59,60,61,62
And the microcomputer 42 controls on / off of each transistor. That is, when the transistor 51 is turned on, the electromagnetic coil 19 is energized to close the discharge amount control valve 15. Further, by controlling the transistor 51 to be turned on and off, flyback energy generated when power supply to the electromagnetic coil 19 is completed can be stored in the capacitors 53 and 54. That is, the energy for the main injection is stored in the condenser 53, and the energy for the pilot injection is stored in the condenser 54.

Further, by turning on the transistors 57 to 62 corresponding to the respective injectors,
The energy of any of the three or 54
The fuel can be injected from the injectors 29 to 34 by supplying the fuel to the injectors 5 to 40. At this time, a capacitor is selected by turning on one of the transistors 55 and 56. That is, from the state where the energy is stored in the main injection capacitor 53 and the pilot injection capacitor 54, the transistor 56 is turned off and the transistor 55 is turned on and the pilot injection voltage is cut off to disconnect any one of the three-way solenoid valves 35 to 40. And the main injection of fuel is performed from the injectors 29-34.
In addition, while the transistor 55 is turned off and the transistor 56 is turned on to disconnect the main injection voltage, a capacitor voltage is supplied to any one of the three-way solenoid valves 35 to 40 to perform pilot injection of fuel from the injectors 29 to 34.

In the present embodiment, the microcomputer 42 constitutes fuel discharge amount control means, injector control means, first switching element control means, and second switching element control means. Further, a switching element is constituted by the transistor 51.

Next, the operation of the thus configured diesel engine fuel injection system will be described. FIG. 4 shows a cam lift of the supply pump 1 and a discharge amount control valve (PCV).
15, a drive pulse of the discharge amount control valve (PCV) 15, a coil energizing current of the discharge amount control valve (PCV) 15,
Also, a timing chart of drive pulses for the three-way solenoid valves 35 to 40 of each injector is shown.

Referring to FIG. 4, in the fuel suction stroke of the supply pump 1 accompanying the cam lift, the discharge amount control valve (PCV) 15 installed in the pump 1 is opened to suck fuel from the fuel tank 14. By the subsequent cam lift, the supply pump 1 enters a fuel pressure feeding stroke. In the fuel pressure feed stroke, the fuel in the pump 1 is raised to a desired fuel pressure by the pressure feed cam 5, and at this time, the discharge amount control valve (PCV) 15
From the open state to the closed state. This is because the fuel pressure does not increase when the discharge amount control valve (PCV) 15 is in the open state even when the pumping cam 5 enters the pumping state.

The microcomputer 42 controls the fuel pressure and the fuel injection amount. At this time, the microcomputer determines which timing during the pumping stroke of the pumping cam 5 to close the discharge amount control valve (PCV) 15. . When high pressure is required in the common rail 25, the valve closing operation is performed relatively early, and when low pressure is required, it is performed relatively late. Then, when the fuel on the common rail 25 rises to a desired pressure, the three-way solenoid valves 35 to 40 are energized to open the injectors 29 to 34 to inject fuel, and thereafter,
The discharge amount control valve (PCV) 15 is shifted to the open state. Since then
This operation is sequentially repeated.

Here, the microcomputer 42 determines the operating conditions of the pump and the engine, including the stroke of the pump, using the reference rotation angle pulse. That is, the sensor 44 of FIG.
A pulse signal (crank angle pulse signal) is used as a reference rotation angle pulse of the engine, the number of pulses is counted using a signal (cylinder discrimination pulse signal) from the sensor 45, and a pulse number corresponding to the corresponding engine is counted. P
The start of CV pumping, the end of pumping, and the start of fuel injection are determined.

The microcomputer 42 includes a discharge amount control valve (PCV)
15, the PCV drive transistor 51, the injector drive transistors 57 to 62, the charging capacitor 53,
A drive pulse signal for the discharge drive transistors 55 and 56 is calculated from the engine speed and the battery voltage and output. Then, during the period from t1 to t2 in FIG. 4, the microcomputer 42 turns on the transistor 51 at the fuel suction / pump timing specified by the engine speed or the like, and switches the discharge amount control valve (PCV) 15 from t1 ′ to t2 ′. Close for a period.
At this time, the electromagnetic coil 19 of the discharge amount control valve (PCV) 15
Generates magnetic energy by pulse driving.

Magnetic energy Q (unit J: joule)
Is determined by the following equation using the coil inductance L, the coil conduction peak current I, and the drive pulse frequency f. Q = (１ ／) · L · I ² · f This magnetic energy is called the flyback energy of the coil. The start time and the on-time of the pumping drive pulse are defined by the fuel injection control system.

The injector drive pulse specifications depend on the fuel injection system (number of cylinders, maximum number of revolutions) of the corresponding engine.
When the injector is driven, the transistors 57 to 62 are driven in accordance with the fuel injection timing. At this time, as shown in FIG.
Charging energy of more than 00 volts is applied to the injector. At this time, a current of about 8 amps flows through the injector, the injector is opened, and fuel is injected.
After the injector is driven at a high voltage, the constant current circuit 7 shown in FIG.
2, a constant current flows through the injector, and the closed state is maintained for a certain period.

After time t2 in FIG. 4 (after the end of the pressure feeding driving), a boosting pulse for charging the capacitors 53 and 54 is output. This is because it is difficult for the boost pulse drive to fully charge the charging capacitors 53 and 54 following the injector injection timing with the flyback energy of the discharge amount control valve (PCV) 15 by only the normal pumping drive. Therefore, in order to supplement the voltage that is insufficient for the full charge, the boosting pulse is continuously output immediately after the end of the pumping drive.

The boosting (charging) process will be described with reference to the flowchart of FIG. The microcomputer 42 performs step 1
After the energization for closing the discharge amount control valve (PCV) 15 is ended in 01, the process proceeds to step 102. Then, the microcomputer 42 waits for a predetermined time Tw (see FIG. 4) in step 102, that is, the time when the fall time of the PCV drive current due to the pressure feeding drive has elapsed after the stop of the pressure feeding pulse output is set as the start time of the step-up pulse. In step 103, it is checked whether the capacitor voltage is higher than 118 volts. Here, if the charging proceeds and the capacitor voltage is equal to or higher than 118 volts, the boosting (charging) process is terminated in step 109.

If the capacitor voltage is less than 118 volts in step 103, the microcomputer 42
In step 04, a drive pulse for boosting is output. The drive pulse causes the transistor 51 in FIG. 3 to be repeatedly turned on and off, and the flyback energy to the capacitors 53 and 54 is accumulated. Here, the specification of the on-time of the pressure increasing pulse is set to a time during which the discharge amount control valve (PCV) 15 rises to a PCV drive current value at which the discharge amount control valve (PCV) 15 does not shift from the valve open state to the valve closed state by the pressure increase pulse in the non-pressure feeding stroke. . This on-time is calculated by the microcomputer 42 as needed in accordance with the fluctuation of the battery voltage. The reason why the battery voltage is considered is that the rise time of the PCV conduction current changes due to the change in the battery voltage.

Referring to the energization of the coil, when a pulse voltage is applied to the coil, a current starts to flow gradually with a certain time constant. This time constant is determined by the inductance L of the coil, the battery voltage, and the current before the coil is magnetically saturated. Here, since the inductance L of the discharge amount control valve (PCV) 15 and the desired energization current value at which the discharge amount control valve 15 does not close are both constant, the pulse voltage is applied only for the rising time determined by the battery voltage. Then, when the current reaches a desired current value, the pulse falls and the transistor 51 is turned off. At the time when the pulse falls, a back electromotive force is generated in the coil, and the coil still functions to flow a current in the forward direction.
At this time, the magnetic energy is stored in the coil. Pulse off time is PCV coil inductance L
And the time defined by the capacitance C of the charging capacitor.

As described above, the PCV closing peak current value due to the boost pulse is set to a current value within a range in which the supply amount control valve (PCV) 15 can maintain the valve open state during the non-pressure feeding period of the supply pump 1.

Magnetic energy generated in the coil by the PCV pumping drive and the boost pulse drive is stored in charging capacitors 53 and 54. Then, the microcomputer 42 determines in steps 105, 106 and 107 in FIG. 5 that the capacitor voltage is less than 118 volts, there is no drive pulse output for the injectors 29 to 34, and
End timing tc of the non-pumping stroke of the pump (see FIG. 4)
If not, the step-up (charging) process is continued at step 108.

When the microcomputer 42 reaches the end timing tc of the non-pressure-feeding step of the pump at step 107, the microcomputer 42 shifts to step 110 to stop the output of the drive pulse and ends the above-described step-up (charging) processing.

That is, the step-up pulse drive is limited to a non-pumping stroke before the next pumping stroke from the end of the pumping drive. The step-up pulse drive during the pumping stroke increases the risk of closing the discharge amount control valve (PCV) 15 as described above, and thus is prevented. Also, during the non-pumping period,
When the charging capacitors 53 and 54 are fully charged to a desired voltage, the boost pulse driving is terminated to prevent overcharging.

As described above, the present embodiment has the following features. (A) The microcomputer 42 performs steps 104 to 108 in FIG.
In the non-pressure feeding stroke of the supply pump 1 when the discharge amount control valve 15 is opened.
1 is repeatedly turned on and off to accumulate flyback energy in the condensers 53 and 54. Further, in the processing of steps 107 and 110 in FIG. 5, the pressure feed stroke of the supply pump 1 when the discharge amount control valve 15 is opened. , The operation of forcibly turning off the transistor 51 and accumulating flyback energy in the capacitors 53 and 54 is prohibited in the pressure feeding process of the supply pump 1. Therefore, the discharge amount control valve 15 is in an environment where it is easy to close due to fuel pressure during the pressure feeding stroke of the supply pump 1, but the valve opening state is maintained, and a valve closing malfunction can be avoided.

That is, as shown in FIG. 11, when the boosting pulse is similarly output to the discharge amount control valve 15 in the non-pressure feeding stroke and the pressure feeding stroke, as shown in FIG. When the pump enters, the fuel in the pump
The pressure was raised to a pressure of 000 Pa or more. At this time, there was an increased risk of applying a pressure to move the discharge amount control valve to the valve closing side and increasing the risk of closing the valve. By forcibly turning off the transistor 51 during the pumping process of the pump 1, it is possible to prevent a valve closing malfunction due to coil energization of the discharge amount control valve 15 during the fuel pumping period. (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

FIG. 6 is a timing chart in the present embodiment corresponding to FIG. 4 in the first embodiment. In the first embodiment, as shown in FIG. 4, the transistor 51 is forcibly turned off during the pressure feeding process of the supply pump 1 when the discharge amount control valve 15 is opened. In FIG. 6, the transistor 51 is repeatedly turned on and off with an on-time shorter than the on-time of the transistor 51 in the non-pressure-feeding process of the supply pump 1 to reduce the flyback energy.
3, 54. That is, two types of boosting pulses are used.

The boosting (charging) process in the present embodiment is described in FIG.
This will be described with reference to FIGS. After terminating the energization for closing the discharge amount control valve (PCV) 15 in step 201, the microcomputer 42 proceeds to step 202 for a predetermined time T
Wait for w. Then, the microcomputer 42 determines in step 20
After confirming in step 3 whether the capacitor voltage is higher than 118 volts, in step 204, a drive pulse for boosting is output. This drive pulse causes the transistor 51 in FIG.
Flyback energy is stored. Here, the specification of the on-time of the pressure increasing pulse is set to a time during which the discharge amount control valve (PCV) 15 rises to a PCV drive current value at which the discharge amount control valve (PCV) 15 does not shift from the valve open state to the valve closed state by the pressure increase pulse in the non-pressure feeding stroke. . That is, PCV by the boost pulse
The valve closing peak current value is set to a current value within a range in which the supply amount control valve (PCV) 15 can maintain the valve open state during the non-pressure feeding period of the supply pump 1.

Then, the microcomputer 42 executes step 2 in FIG.
At 05, 206, and 207, the capacitor voltage becomes 118.
If it is less than the volt, if there is no drive pulse output from the injectors 29 to 34, and if it is not the end timing tc of the non-pressure-feeding stroke of the pump (see FIG. 6), step 20 is executed.
In step 8, the above-described step-up (charging) process is continued.

If the microcomputer 42 determines in step 207 that the pump is in the non-pressure-feeding process end timing tc, the microcomputer 42 proceeds to step 211 in FIG. 8 to increase the ON time of the transistor 51 in the non-pressure-feeding process of the supply pump 1 as a boosting pulse. A pulse signal having a shorter ON time is generated and output. That is, the on-time in the boosting pulse (pulse with a short on-time) at this time is a time corresponding to the electromagnetic coil energizing current in a range in which the discharge amount control valve 15 does not close during the pressure feeding process of the supply pump 1. The transistor 51 is repeatedly turned on / off by this pulse signal, and flyback energy is stored in the capacitors 53 and 54.

Then, the microcomputer 42 determines in step 21
2, 213, 214, the capacitor voltage is less than 118 volts, there is no drive pulse output from the injectors 29 to 34, and the drive pulse output timing t11 for closing the discharge amount control valve 15 (FIG. 6)
Otherwise, in step 215, the above-described step-up (charging) process is continued.

If the microcomputer 42 determines in step 214 that the output timing of the pulse for driving the injector is t11, the microcomputer 42 proceeds to step 216 and stops outputting the boosting pulse (pulse with a short ON time).

In this manner, the PCV pumping drive and the
Magnetic energy generated in the coil by the various types of boost pulse driving is accumulated in the charging capacitors 53 and 54.
As described above, the present embodiment has the following features. (A) The microcomputer 42 performs steps 204 to 208 in FIG.
In the non-pressure feeding stroke of the supply pump 1 when the discharge amount control valve 15 is opened.
1 is repeatedly turned on and off to store flyback energy in the capacitors 53 and 54, and
Of steps 207, 211 to 215 of
The transistor 51 is repeatedly turned on and off in an on-time shorter than the on-time of the transistor 51 in the pressure feeding process of the supply pump 1 when the discharge amount control valve 15 is opened. Thereby, the operation of accumulating the flyback energy in the capacitors 53 and 54 is performed by the transistor in the on-time shorter than the non-pressure-feeding stroke of the supply pump 1 in the pressure-feeding stroke of the supply pump 1 when the discharge amount control valve 15 is opened. The electromagnetic coil energizing current can be set within a range in which the discharge amount control valve 15 is not opened when the 51 is driven. Therefore, the discharge amount control valve 15 is in an environment where it is easy to close due to fuel pressure during the pressure feeding stroke of the supply pump 1, but the valve opening state is maintained, and a valve closing malfunction can be avoided.

In contrast to the step-up switching method in which only the non-pumping period is used as in the first embodiment, the charging period can be lengthened in the second embodiment. Further, in the step-up switching method only in the non-pumping period as in the first embodiment, the charging time is restricted by the maximum engine speed, but in the second embodiment, the charging period is also included in the pumping period. Time constraints are eased.

In addition to the embodiment described above, the present invention may be implemented as follows. Although a capacitor is used as the charging means, other devices may be used. Although a MOS transistor is used as a switching element, a bipolar transistor or an IGBT may be used instead.

In the above-mentioned example, the case where the pilot injection and the main injection are performed will be described. In the system using the main injection capacitor 53 and the pilot injection capacitor 54, a system using one charging capacitor without performing the pilot injection is described. It may be embodied.

In the above embodiment, the supply pump is a one-cylinder system and the engine has six cylinders. However, the number of cylinders and the number of cylinders are not limited.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a common rail fuel injection control device.

FIG. 2 is a sectional view showing a specific configuration of a supply pump.

FIG. 3 is a specific configuration diagram of an ECU.

FIG. 4 is a timing chart for explaining the operation of the first embodiment.

FIG. 5 is a flowchart for explaining the operation.

FIG. 6 is a timing chart for explaining the operation of the second embodiment.

FIG. 7 is a flowchart for explaining the operation.

FIG. 8 is a flowchart for explaining the operation.

FIG. 9 is an overall configuration diagram of a common rail fuel injection control device.

FIG. 10 is a waveform diagram for driving an injector.

FIG. 11 is a time chart for explaining the operation of the common rail fuel injection control device.

FIG. 12 is an explanatory diagram for explaining opening and closing of a discharge amount control valve.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Supply pump, 3 ... Diesel engine, 9 ... Plunger, 15 ... Discharge amount control valve, 19 ... Electromagnetic coil,
25: Common rail, 29: Injector, 30: Injector, 31: Injector, 32: Injector,
33 ... injector, 34 ... injector, 42 ... microcomputer, 51 ... transistor, 53 ... capacitor, 54 ...
Capacitors.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mikio Kumano 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Kazutoshi Nishimura 1-1-1, Showa-cho, Kariya-shi, Aichi Co., Ltd. Inside DENSO

Claims (4)

[Claims] 1. A supply pump driven by a diesel engine and sucking and pumping fuel by reciprocating movement of a plunger, a common rail for storing high-pressure fuel by the supply pump, and a common rail mounted on each cylinder of the diesel engine, An injector that receives a supply of high-pressure fuel, a switching element that is connected to an electromagnetic coil of a discharge amount control valve that is installed in the supply pump, and that is energized when the coil is turned on, Fuel supply amount control means for turning on the switching element to close the discharge amount control valve during the period, and controlling the fuel discharge amount to the common rail by the supply pump accompanying the valve closing; and energizing the electromagnetic coil. The flyback energy generated when Charging means for accumulating as a driving source for the fuel injector; and an injector for driving the injector of each cylinder to inject a fuel amount corresponding to the state of the diesel engine from the injector to each cylinder at a fuel injection timing corresponding to the state of the diesel engine. A fuel injection control device comprising: a charging means for charging the flyback energy by repeatedly turning on and off the switching element in a non-pressure feeding stroke of the supply pump when the discharge amount control valve is opened. First switching element control means for accumulating in the means, and second switching element control means for forcibly turning off the switching element during the pressure feeding stroke of the supply pump when the discharge amount control valve is opened. A common rail type fuel injection control device, characterized in that: 2. The common rail fuel injection control device according to claim 1, wherein the first switching element control means sets the discharge amount control valve in a non-pressure feeding stroke of the supply pump as an ON time of a switching element. A common rail fuel injection control device characterized in that the time corresponds to a current flowing through an electromagnetic coil in a range not to be closed. 3. A supply pump driven by a diesel engine and sucking and pumping fuel by reciprocating movement of a plunger; a common rail for storing high-pressure fuel by the supply pump; and a common rail mounted on each cylinder of the diesel engine. An injector that receives a supply of high-pressure fuel, a switching element that is connected to an electromagnetic coil of a discharge amount control valve that is installed in the supply pump, and that is energized when the coil is turned on, Fuel supply amount control means for turning on the switching element to close the discharge amount control valve during the period, and controlling the fuel discharge amount to the common rail by the supply pump accompanying the valve closing; and energizing the electromagnetic coil. The flyback energy generated when Charging means for accumulating as a driving source for the fuel injector; and an injector for driving the injector of each cylinder to inject a fuel amount corresponding to the state of the diesel engine from the injector to each cylinder at a fuel injection timing corresponding to the state of the diesel engine. A fuel injection control device comprising: a charging means for charging the flyback energy by repeatedly turning on and off the switching element in a non-pressure feeding stroke of the supply pump when the discharge amount control valve is opened. A first switching element control means to be stored in a means, and an on time shorter than an on time of the switching element in the first switching element control means in a pressure feeding stroke of the supply pump when the discharge amount control valve is opened. The switching element is turned on and off repeatedly Common rail fuel injection control apparatus characterized by the flyback energy and a second switching element control means for storing in said charging means to. 4. The common-rail fuel injection control device according to claim 3, wherein the second switching element control means closes the discharge amount control valve during a pressure feeding stroke of the supply pump as an ON time of the switching element. A common rail fuel injection control device characterized in that the time corresponds to a current flowing through an electromagnetic coil in a range not to be valved.