JP2606306B2 - Fuel injection control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection control device having a pressure accumulation pipe (common rail) used for a diesel engine or the like.

2. Description of the Related Art Recently, various electronically controlled fuel injection devices for diesel engines have been developed. For example, as shown in the overall configuration diagram of the conventional system in FIG. 7, a method has been considered in which high pressure fuel stored in a common rail b is applied to an injector a and a lift of a needle c is controlled by a three-way solenoid valve d. JP-A-62-258160). When the three-way solenoid valve d is not energized, the port X and the port Y communicate with each other, high-pressure fuel is guided to the upper part of the hydraulic piston e, and the pressure increases the needle c.
Block the lift. At the time of energization, the outer valve f is suctioned up, the port X is closed, and the port Y and the port Z communicate, so that the pressure applied to the hydraulic piston e leaks to the low pressure side via the ports Y and Z. For this reason, the needle c rises due to the fuel pressure, and opens the injection port to inject the fuel. When de-energized, a downward force F = πPc the outer valve _{^{f (D 1 2 -D 2 2}} ) / 4 + Fs ( where, Pc: rail pressure, Fs: biasing force) so is acting, the port Y and the port Connect Z and common rail b
In order to inject the high-pressure fuel inside the pump, not only the suction energy required to overcome the force F is required, but also if the operation of sucking the outer valve f is not performed at a high speed, the port X and the port Z communicate and the fuel is Leak to the low pressure side. Further, in order to precisely control the injection start timing, the suction operation of the outer valve f must be performed at an extremely high speed. Therefore, the higher the common rail pressure Pc, the greater the suction energy of the three-way solenoid valve d is required.

In this system, which aims to quickly operate the three-way solenoid valve d against high fuel pressure and reduce energy consumption, the ECU uses the input actual common rail pressure Pc, accelerator opening Accp, engine speed Ne, intake air temperature. The fuel injection timing and fuel injection amount are calculated from various information such as the cooling water temperature and the like, and the solenoid valve drive pulse C is output. As shown in FIG. h to the solenoid valve drive circuit. The decoder g uses a high-speed CMOS decoder TC74HC138 manufactured by Toshiba, and one of outputs ₀ to ₇ is operable by a 3-bit code applied to terminals A, B and C from the CPU. And solenoid valve drive pulse C (low active)
Is output to the solenoid valve drive circuit. The solenoid valve drive pulse C is output with high accuracy using a so-called timer function (output compare function) of the CPU. The inputs A, B, and C of the decoder g are also controlled by ports of the CPU.
That is, by selecting the solenoid valve drive pulse C output from the CPU by the timer function (output compare function) from the A, B, and C terminals, the drive pulses of all cylinders can be accurately controlled. The three-way solenoid valve d is energized while the three-way solenoid valve drive pulse is at a high level, but exceeds the vehicle-mounted power supply voltage (battery voltage) in order to quickly operate the solenoid valve d against a fuel pressure of up to 150 MPa. A high voltage is generated and discharged at the same time as the rise of the three-way solenoid valve drive pulse sent to the solenoid valve drive circuit to supply a high voltage to the three-way solenoid valve d. As described above, the magnetic flux rapidly increases due to the steep rising current, and a quick response is possible even under a high fuel pressure.

On the other hand, the common rail pressure is controlled to an optimal value in order to improve fuel efficiency and purify exhaust gas in accordance with the engine load and the engine speed Ne. The high pressure is generated by using the lift of the cam k during the period from the start of energization to the solenoid valve j of the high-pressure feed pump i to the end of energization. In this system, the power supply end timing is set to a specific timing according to the engine speed, and the power supply start timing is T _F (sec) after a reference set to a specific timing corresponding to the engine speed.
_The common rail pressure is controlled to an optimum value by changing _F by calculation. When to start energizing the solenoid valve of the pump
The method of calculating _TF will be described below. First, a basic energization start timing is determined based on the command injection amount and the command injection pressure, and feedback control is performed by PID control according to the difference between the command injection pressure and the actual common rail pressure Pc. That is, the final energization start timing _TF is set by adding the feedback compensation amount to the basic energization start timing described above.

"Problem to be Solved by the Invention" However, in the above-described conventional system, when the high-voltage generator that supplies a high voltage to the three-way solenoid valve fails for some reason and cannot supply the high voltage, the valve is opened. The responsiveness deteriorates, the control accuracy for the fuel injection timing and injection amount decreases, fuel leakage increases and fuel consumption deteriorates.In addition, when the engine load is large and the common rail pressure is high, the three-way solenoid valve is attracted. There is a problem that the fuel injection becomes impossible because the valve is not opened due to insufficient power and the engine stops.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in the case where a high voltage generating unit fails, a high common rail pressure is reduced to control the opening and closing of a solenoid valve by a vehicle power supply voltage. It is an object to provide a control device.

Means for Solving the Problems The present invention provides a common rail that accumulates fuel at a high predetermined pressure, and a high pressure passage that introduces the fuel accumulated in the common rail to the back pressure side of the injection nozzle. An electromagnetic valve for opening the high pressure passage against the fuel pressure in the high pressure passage, opening the injection nozzle by releasing the fuel guided to the back pressure side of the injection nozzle to the low pressure side, and injecting the fuel. An electromagnetic valve driving circuit including a high voltage generating means for applying a high voltage exceeding a vehicle-mounted power supply voltage to drive the electromagnetic valve when energized, the fuel injection control device detects an abnormality of the high voltage generating means. Abnormality detecting means; and a pressure control means for decreasing fuel pressure in the common rail so that the electromagnetic valve can be opened with the vehicle-mounted power supply voltage when the abnormality detecting means detects an abnormality in the high voltage generating means. Characterized in that a and.

According to the specific means, when the abnormality detecting means detects an abnormality in the high-voltage generating means, the pressure control means reduces the fuel pressure in the common rail to a pressure at which the solenoid valve can be opened by the on-board power supply voltage. The pressure is reduced and the fuel injection is succeeded to enable so-called evacuation traveling.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a circuit configuration diagram of the device of the present invention, in which a block 40 is added to a conventional circuit composed of blocks 10, 20, and 30. Block 10 is the high voltage generator, the block 20 is a constant current circuit for supplying a hold current i _H after the pull of the three-way solenoid valves V1, V2 ... VN (referred to simply as if not be distinguished below V), block
Reference numeral 30 denotes a drive control unit of the three-way solenoid valve, and block 40 denotes an abnormality detection circuit unit of the high voltage generation unit 10.

The high voltage generator 10 includes a charge current control circuit 11 and a current detection circuit 12. Terminal 1 has a three-way solenoid valve V
Drive pulse τ distributed for each cylinder that controls ON-OFF of
1, τ2 ... τN (hereinafter simply referred to as τ) are applied. A charge pulse PLS for operating the high voltage generator 10 is applied to the terminal 2. Drive pulse τ and charge pulse P
LS is an ECU5 that calculates the fuel injection amount and fuel injection timing of the engine.
With 0, the signal is output with an appropriate phase. That is, prior to the drive pulse τ, the high voltage generation unit 10 that has received the charge pulse PLS switches the current flowing through the coil L1 for temporarily storing energy, thereby switching the high voltage to the capacitor C1 serving as high voltage storage means. Generate voltage. In this embodiment, the charge voltage V ' _CHG shown in FIG.
As shown in the waveform of FIG. In the three-way solenoid valve drive control unit 30, when the drive pulse τ applied to the terminal 1 has a high potential, the MOS field-effect transistor FET1 becomes conductive, and at the same time, the thyristor TH
2 is triggered, and the electric charge previously stored at high voltage in the capacitor C1 is rapidly discharged through the thyristor TH2, the three-way solenoid valve V, the MOS field-effect transistor FET1, and the resistor R1, so that the current flowing through the three-way solenoid valve V is also reduced. It rapidly rises and reaches the peak current i _P. When the discharge ends, the current gradually decreases and the preset hold current i _H
Reach the level of. Level of hold current i _H is to generate sufficient suction to keep the state after the valve opening, and can reduce the generation of heat, at the time of off of the MOS field-effect transistors FET1, current decays fast enough Set to level. After attenuating from the peak current i _P to the hold current i _H , a constant hold current i _H is supplied from the constant current circuit unit 20 to the three-way solenoid valve V to hold the three-way solenoid valve V. The constant current circuit section 20 employs a switching type to suppress heat generation of the power element. Hold current
i _H is supplied to the three-way solenoid valve V through the diode D1 or the diode D2. Further, the solenoid valve current flowing through the three-way solenoid valve V is detected by the current detection circuit 31 between the resistors R1 and is fed back to the constant current circuit unit 20, so that the drive pulse τ
There becomes a low potential, MOS field effect transistor FET1 is turned off, the hold current i _H is also off solenoids current is cut off.

The reference potential is input to the positive input terminal of the comparator iC1 of the abnormality detection circuit unit of the high voltage generation unit 10 indicated by the block 40 via the resistor R9. The reference potential is obtained by dividing the voltage between the constant voltage line (5V) and the ground by resistors R6 and R7, and a capacitor C3 for stabilization is added in parallel with the resistor R7. V ′ _CHG is input to the negative input terminal of the comparator iC1 via the resistor R8. V ' _CHG is the potential of the capacitor C1
It is determined by _dividing V _CHG by resistors R4 and R5. The resistor R10 connecting the output of the comparator iC1 to the positive input terminal and the capacitor C2 inserted between the positive input terminal and the negative input terminal are for providing hysteresis for preventing malfunction due to noise. Ie comparator
iC1 boosts capacitor C1, the potential level of the negative input terminal exceeds the reference voltage V _REF, and inputs to the ECU50 by inverting the output V _OUT to a low level. In the ECU 50, the solenoid valve driving pulse C shown in FIG. 2 is input to the A trigger terminal of the monostable multivibrator (TC4538 made by Toshiba) iC2, and B
By setting the terminal and the CD terminal to the high level, the output of the vibrator iC2 is inverted to the low level at the rise of the driving pulse C, and thereafter the vibrator iC2 changes the low level for the time T determined by the capacitor C4, the resistor R11 and the diode D5. After maintaining, it returns to the high level. And this output (second
Figure A) input to the CLOCK terminal of the D-type flip-flop iC3, RESET terminal, the SET terminal is at the low level, and inputs the output V _OUT of the comparator iC1 abnormality detection circuit section 40 to the DATA terminal. As a result, the level of the DATA terminal when the CLOCK terminal rises is output from the Q terminal. Therefore, if the time constant T of the monostable multivibrator iC2 is appropriately selected, the output Q of the D-type flip-flop iC3 (FIG. 2B) will be output when the high voltage generator 10 does not generate a necessary high voltage for some reason. High level. This output Q is connected to C in ECU50.
Port P1 (not shown) of PU (hereinafter referred to as abnormality detection port)
To generate an abnormality detection signal.

The circuit configuration and operation of the embodiment are the same as those described with reference to FIGS. 1 and 2, and the common rail pressure is implemented based on the output Q of the D-type flip-flop iC3 input to the CPU of the ECU 50. the pressure control P _C, is described with reference to a flow chart of the routine for calculating the energization start timing T _F of Figure 3.

Pressure control common rail pressure P _C is for performing the opening and closing of the electromagnetic valve of the high-pressure feed pump, eventually it calculates the energization start timing T _F of the solenoid valve, the pump solenoid valve control pulse is output at the timing By opening the solenoid valve of the pump.

First, in step S100 (hereinafter, the steps are omitted),
It is determined whether the level of the abnormality detection port P1 is high level or low level. If it is at the low level, the process proceeds to S101, in which the value obtained by interpolation from the two-dimensional map of the engine speed Ne and the command injection amount Q _FIN is corrected by the water temperature to calculate the command injection pressure P _FIN . If the level is high in S100, the process proceeds to S102. In S102, the command injection pressure P _FIN is set to the common rail pressure at which the three-way solenoid valve V can be driven by the vehicle power supply voltage. Specifically, P _FIN <
60MPa. Subsequently, in S103, a basic solenoid valve energization timing _TFBASE of the high-pressure feed pump is calculated by interpolation from a two-dimensional map of the command injection pressure P _FIN and the command injection amount Q _FIN .
Further, in S104, the actual common rail pressure P _C and the command injection pressure P feedback compensation amount by the PID control according to the difference of the _FIN T _FBK
Ask for. Proceeding to S105, it calculates the electromagnetic valve energization start timing T _F of the high pressure feed pump on the basis of the S103 and T _FBASE and T _FBK calculated in S104.

The failure of the high voltage generator 10 is caused by the abnormality detection port P of the CPU.
When detected by step 1, the command injection pressure P _{FIN, which} is the reference for calculating the energization start timing _TF of the solenoid valve of the high-pressure feed pump, is 60 MPa.
Set to less than. Opening a pump solenoid valve at timing T _F calculated for this, by lowering the actual common rail pressure P _C generated by the high-pressure feed pump, three-way solenoid valve V applied to the vehicle-mounted power supply voltage becomes possible opening .

As another embodiment for detecting an abnormality of the high voltage generation unit 10,
There is a method of directly monitoring the level of V _OUT of the comparator iC1 shown in FIG.

First, as shown in FIG. 4, a number is assigned to a 15 ° C. A signal (hereinafter referred to as a Ne pulse) of a rotation sensor that detects the rotation angle of the engine. First rising of Ne pulse immediately after G1 signal input
The Ne pulse number of the cylinder is set to 0, and thereafter, the Ne pulse number is counted up every time the Ne pulse rises. After the Ne pulse number 7, the count is reset to Ne pulse number 0 for the fifth cylinder according to the ignition order. The rising of the Ne pulse immediately after the input of the G2 signal is Ne pulse number 0 of the sixth cylinder.
In the following, Ne pulses are numbered based on the above method. Therefore, for example, at the 7th rising edge of the Ne pulse, V
Looking at the level of _OUT , as described in the first embodiment, it can be considered that the capacitor C1 has a high potential when the level is low, and that the high potential generating section 10 is normal and abnormal when the level is high. Subsequent processes are the same as in the first embodiment.

The step-down control process of the common rail pressure based on the above technical means will be described with reference to the flowcharts shown in FIGS.

In the Ne interrupt processing routine of FIG. 5, it is determined whether the Ne pulse number is 7 in S200. If it is not the seventh, NO is performed and no processing is performed. If it is the seventh, the process proceeds to S201, and it is determined whether or not the level of _VOUT connected to the abnormality detection port P1 is high. S2 if low level
At 02, the abnormality flag is set to "0", and if it is at the high level, it is set to "1" at S203. In the routine for calculating the solenoid valve energization start timing _{TF in} FIG. 6, the setting state of the abnormality flag is determined in S300, and if the abnormality flag is set to “1”, the flow proceeds to S302, and the command injection pressure P _FIN Is controlled at less than 60 MPa. If the abnormality flag is set to "0", the control as usual after S301 is performed. After that, S301
Steps S305 to S305 are the same as those in the first embodiment, and a description thereof will not be repeated.

According to the technical means, the level of V _OUT of the comparator iC1 can be directly monitored to control the step-down of the common rail pressure, and the monostable vibrator iC2 in the ECU can be controlled.
And the circuit configuration of the D-type flip-flop iC3 can be omitted.

The high voltage generator 10 and its abnormality detecting means are not limited to the means of the embodiment.

“Effects of the Invention” The present invention, as has been clarified in the description of the specific means and functions, when the abnormality detection means detects an abnormality in the high voltage generation means, the pressure control means detects the fuel pressure in the common rail,
The in-vehicle power supply voltage lowers the pressure to a pressure at which the solenoid valve can be opened, fuel injection can be continued, so-called evacuation traveling can be performed, and there are excellent effects such as realizing a fail-safe concept.

[Brief description of the drawings]

The accompanying drawings show an embodiment of the present invention. FIG. 1 is a circuit diagram, FIG. 2 is a time chart for explaining the operation, FIG. 3 is a flowchart of a routine for calculating an energization start timing _TF , FIG.
FIG. 5 is a time chart showing the operation of another abnormality detecting means, FIG. 5 is a flowchart showing a Ne interrupt processing routine,
FIG. 6 is a flowchart showing a routine for calculating the energization start timing _TF in another embodiment, FIG. 7 is an overall configuration diagram of a conventional system, and FIG. 8 is a time chart showing the operation thereof. FIG. 10 High voltage generator, 20 Constant current circuit, 30 Three-way solenoid valve drive controller, 40 Abnormality detection circuit, 50 ECU, L
1… Coil, C1… Capacitor, V, V ₁ , V ₂ … V _N … Three-way solenoid valve, iC1… Comparator, iC2 …… Monostable multivibrator, iC3… D-type flip-flop.

Claims (1)

(57) [Claims] 1. A common rail for accumulating fuel at a high predetermined pressure, and a high pressure passage for introducing the fuel accumulated on the common rail to the back pressure side of the injection nozzle. A solenoid valve for opening the high pressure passage, injecting fuel by opening the injection nozzle by releasing the fuel guided to the back pressure side of the injection nozzle to the low pressure side, and injecting fuel. A solenoid valve driving circuit including a high voltage generating means for applying a high voltage exceeding the on-vehicle power supply voltage in order to perform the abnormality detecting means for detecting an abnormality of the high voltage generating means; Pressure control means for reducing the fuel pressure in the common rail so that when the means detects an abnormality of the high voltage generation means, the solenoid valve can be opened with the vehicle-mounted power supply voltage. Fuel injection control device.