JPH0233449A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To perform evasive running by lowering the fuel pressure in a common rail to the pressure at which a solenoid valve can be opened by the mounted power voltage with a pressure control means when detecting an abnormality of a high-voltage generating means in a Diesel engine or the like. CONSTITUTION:Driving pulses tau1-tauN and charge pulses are applied to a high- voltage generating section 10 from an ECU 50 calculating the fuel injection quantity and injection timing, the high voltage is generated on a capacitor C1, a three-way solenoid valve drive control section 30 quickly raises the current to three-way solenoid pieces V1-VN, a discharge is completed when it reaches the peak current. The hold current is fed from a constant current circuit section 20 by the signal from a current detecting circuit 31. When an abnormality detecting circuit section 40 detects that the high-voltage generating section 10 does not generate the necessary high voltage for some reasons, the CPU of the ECU 50 sets the command injection pressure to the common rail pressure at which the three-way solenoid valves V1-VN can be driven by the mounted power B voltage. Fuel injection is continued to perform evasive running, the device can be made fail-safe.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a fuel injection control device having a pressure accumulation pipe (common rail) used in a diesel engine or the like.

``Prior Art'' Recently, various electronically controlled fuel injection devices for diesel engines have been developed.For example, as shown in the general configuration diagram of a conventional system shown in FIG. 7, pressure is accumulated in the common rail b in the injector a. Apply high pressure fuel and needle C
A method has been proposed in which the lift of the boat is controlled by a three-way solenoid valve d (Japanese Patent Application Laid-Open No. 62-258160). When the three-way solenoid valve d is de-energized, boats X and Y are connected, and high-pressure fuel is supplied to the hydraulic piston e. When the needle C is guided to the top and its pressure prevents the lift of the needle C, when the current is applied, the outer valve f is sucked up and the boat x is blocked, and the boat Y and the boat Z are
Because of the communication, the pressure applied to the hydraulic piston e is the boat Y.
, leaks to the low pressure side via boat Z. Therefore, the needle C rises due to the fuel pressure, opens the injection port, and injects the fuel. When de-energized, the outer valve f
is a downward force F=gPe(D+"-Dz')/4+Fs (however, Pc
: common rail pressure, Fs: spring force), so in order to connect boat Y and boat Z and inject the high pressure fuel in common rail b, suction energy sufficient to overcome force F is required. If the suction action of outer valve f is not performed at high speed, boat X and boat Z
is in communication, causing fuel to leak to the low-pressure side.Furthermore, in order to precisely control the injection start timing, the suction operation of the outer valve f must be performed at extremely high speed.Therefore, the higher the common rail pressure Pc, the higher the common rail pressure Pc. large three-way solenoid valve d
of suction energy is required.

In this system, the purpose of which is 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 Acep, engine speed Ne, and intake air temperature. , calculates fuel injection timing and fuel injection amount from various information such as cooling water temperature, and outputs a solenoid valve drive pulse port.As shown in Fig. 8, the drive pulse port is distributed to each cylinder by a decoder g and interface h to the solenoid valve drive circuit. The decoder g is a high-speed CMOS decoder TC7 manufactured by Toshiba.
It uses 4HC138, and the output Y is determined by the 3-bit code applied to terminals A, B, and C from the CPU.
One of the outputs 0 to Y becomes operable and outputs a solenoid valve drive pulse C (low active) to the solenoid valve drive circuit. The solenoid valve drive pulse port is outputted with high precision using the so-called timer function (output conveyor function) of the CPU. In addition, the input A of the decoder g
, B, and C are also controlled by the CPU vote.

In other words, the solenoid valve drive pulse C output from the CPU by the timer function (output conveyor function) is
, C terminal allows drive pulses for all cylinders to be controlled with high precision.

While the three-way solenoid valve drive pulse is at a high level, the three-way solenoid valve d is energized, but in order to quickly operate the solenoid valve d against the fuel pressure, which reaches a maximum of 150 MPa, the on-vehicle power supply voltage (battery voltage) is exceeded. Generate high voltage,
At the same time as the three-way solenoid valve drive pulse that is sent to the solenoid valve drive circuit rises, it discharges and supplies high voltage to the three-way solenoid valve d.This sharp rise in current causes a sudden increase in magnetic flux, which causes the magnetic flux to rise under high fuel pressure. However, a quick response is possible.

On the other hand, the common rail pressure is controlled to an optimum value according to the engine load and engine speed Ne with the aim of improving fuel efficiency and purifying exhaust gas. The lift of the cam is used to generate high pressure between the time when energization of the solenoid valve j of the high-pressure feed pump i starts and the time when energization ends. In this system, the energization end time is set at a specific timing according to the engine rotation speed, and the energization start time and T2 are calculated after T, (see) from a standard set at a certain timing corresponding to the engine rotation speed. The common rail pressure is controlled to the optimum value by changing the pressure. The method of calculating the timing T for starting energization of the solenoid valve of the pump will be described below.

First, the basic energization start timing is determined based on the command injection amount and command injection pressure, and the command injection pressure and actual common rail pressure Pc
PID according to the difference! Feedback control is performed under the II control, that is, the final energization start time T is set by adding a feedback compensation amount to the above basic energization start time.

``Problems to be Solved by the Invention'' However, in the conventional system, if the high voltage generator that supplies high voltage to the three-way solenoid valve malfunctions for some reason and is no longer able to supply high voltage, it is difficult to open the valve. Not only does responsiveness deteriorate and control accuracy for fuel injection timing and injection amount decreases, resulting in increased fuel leakage and poor fuel efficiency, but also when the engine load is large and the common rail pressure is high, the three-way solenoid valve There are problems such as the valve not opening due to insufficient power, making it impossible to inject fuel, leading to the engine stopping.

The present invention has been made in order to solve the above-mentioned problems, and is a fuel injection system that can reduce the high common rail pressure and control the opening and closing of the solenoid valve using the on-vehicle power supply voltage when the high voltage generation section fails. The purpose of this invention is to provide a control device.

"Means for Solving the Problem" The specific means for achieving the above objective is to accumulate fuel at a high predetermined pressure in a common rail, and inject this fuel from an injection nozzle into each cylinder of an internal combustion engine by opening the valve. solenoid valve and
In a fuel injection control device comprising a solenoid valve drive circuit for driving the solenoid valve, the solenoid valve drive circuit includes a high voltage generating means for applying a high voltage exceeding the on-vehicle power supply voltage, and a means for holding the operating state of the solenoid valve. It includes a constant current circuit that supplies a constant @ current to the solenoid valve, and a switching circuit that controls the opening and closing of the solenoid valve, and further includes an abnormality detection means that detects an abnormality in the high voltage generation means, and an on-vehicle power supply by the abnormality detection. The present invention is characterized in that it includes pressure control means for reducing the fuel pressure in the common rail so that the solenoid valve can be opened by voltage.

"Operation" According to the specific means, when the abnormality detection means detects an abnormality in the high voltage generation means, the pressure control means increases the fuel pressure in the common rail to a pressure at which the solenoid valve can open using the onboard power supply voltage. The pressure is lowered and fuel injection continues to enable so-called evacuation driving.

"Example" Embodiments of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 is a circuit diagram of the device of the present invention, and shows block 10. Block 20. A block 40 is added to the conventional circuit composed of a block 30. block 1
0 is a high voltage generator, block 20 is a three-way solenoid valve Vl,
V2...VN (If not explained separately below, simply ■
block 30 is a drive control section for the three-way solenoid valve, and block 40 is an abnormality detection circuit section for the high voltage generation section 10.

High voltage generation section 10 includes a charge current control circuit 11 and a current detection circuit 12. Terminal 1 receives a drive pulse τ1. which is distributed for each whistle to control ON-OFF of the three-way solenoid valve ■. 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 . The drive pulse and the charge pulse PLS are output with appropriate phases by the ECU 3O, which calculates the fuel injection amount and fuel injection timing of the engine. That is, prior to the drive pulse τ,
The high voltage generation section 10 that receives the charge pulse PLS,
By switching the current flowing through the coil L1 for temporarily storing energy, a high voltage is generated in the capacitor C1 which forms the high voltage storage means. In this embodiment, the waveform of the charge voltage V'CNQ in FIG. As shown, the voltage is increased in 5 steps. In the three-way solenoid valve drive control section 30, when the drive pulse τ applied to the terminal 1 becomes a high potential, the MO3 type field effect transistor F
ETI becomes conductive and at the same time thyristor TH2 is triggered, and the charge previously stored at high voltage in capacitor C1 is transferred to thyristor TH2, three-way solenoid valve V, MO8 field effect transistor FET1. Since the current is rapidly discharged through the resistor R1, the current flowing through the three-way solenoid valve V also rises rapidly and reaches the peak current i p. When the discharge ends, the current gradually attenuates and reaches the preset hold current i- level. This hold current i
, l are set to a level that generates sufficient suction force to maintain the state after the valve is opened, generates less heat, and allows the current to attenuate sufficiently quickly when the MO8 field effect transistor FETI is turned off. has been done. After the peak current i p attenuates to the hold current 1 ++, the three-way solenoid valve V
A constant hold current iM is supplied from the constant current circuit section 2° to the three-way solenoid valve V in order to hold the current. This definition 1
! The flow circuit section 20 employs a switching type in order to suppress heat generation of the power element. Hold current i.

is supplied to the three-way solenoid valve (2) through the diode D1 or the diode D2. In addition, the solenoid valve current flowing through the three-way solenoid valve ■ is detected by the current detection circuit 31 between the resistors R1 and fed back to the constant current circuit section 2o, and when the drive pulse τ becomes a low potential, the MOS field effect transistor FET1 is turned off. However, the solenoid valve current is cut off and the hold currents i and I are also turned off.

A reference potential is input to the positive input terminal of the comparator iC1 of the abnormality detection circuit section of the high voltage generation section 10 indicated by block 40 via the resistor R9. The reference potential is a constant voltage line (
5V) and ground using resistors R6 and R7, and a stabilizing capacitor C3 is added in parallel with resistor R7. Vo is connected to the negative input terminal of the comparator iC1 via a resistor R8. ,. Enter. V'
Cll6 is the potential VB of the capacitor C1. resistor R4 and R
It is obtained by dividing the pressure by 5. Comparator LC
A resistor RIO connects the output of I and the positive input terminal, and a capacitor C2 is inserted between the positive input terminal and the negative input terminal.
is for providing hysteresis to prevent malfunction due to noise. That is, comparator iC1
, the capacitor C1 is boosted and the potential level of the negative input terminal is the reference potential V□.

If it exceeds, the output ■. U? invert to low level and press E
Input to CU3O. F, A of monostable multivibrator (TC made by Toshiba; 4538) iC2 in CU3O
By inputting the solenoid valve drive pulse port shown in Fig. 2 to the trigger terminal and setting the B and CD terminals to high level, the output Q of the vibrator IC2 is reversed to low level at the rising edge of the drive pulse port. From now on capacitor C
4. After maintaining the low level for a time T determined by the resistor R11 and the diode D5, it returns to the high level.

Then, this output Q (21st prisoner) is inputted to the CLOCK terminal of the D-type flip-flop iC3, and the RESET and SET terminals are set to low level, and the abnormality detection circuit section 40
Output of comparator iC1 ■. 1. is input 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 multi-bibreak iC2 is appropriately selected, when the necessary high voltage is not generated in the high voltage generator 10 for some reason, the D type flip-flop i
The output Q of C3 (FIG. 2 [E]) becomes high level.

This output Q is positively inputted to a CPU (not shown) in the ECU 3O (hereinafter referred to as an abnormality detection board) and used as an abnormality detection signal.

The circuit configuration of the above embodiment and its operation are as follows.
As explained based on Figure 2, C of ECU3O
Pressure control of the common rail pressure Pc performed based on the output Q of the D-type flip 70 tube iC3 input to the PU will be described with reference to the flowchart of the calculation routine for the energization start time T2 in FIG.

Pressure control of the common rail pressure Pc is performed by opening and closing the solenoid valve of the high-pressure feed pump.Finally, the timing T to start energizing the solenoid valve is calculated, and the pump solenoid valve control pulse output at this timing is used to control the common rail pressure Pc. This is done by opening the solenoid valve of the pump.

First, in step 5100 (hereinafter steps will be omitted), it is determined whether the level of the abnormality detection boat P1 is high level or low level. If the level is low, proceed to 5101,
A value obtained by interpolation from a two-dimensional map of the engine rotational speed Ne and the commanded injection amount Q Fll+ is corrected for water temperature to calculate the commanded injection pressure P Fll+. If the level is high in step 5100, the process proceeds to step 5102. In step 5102, the command injection pressure P2 is set to the common rail pressure at which the three-way solenoid valve V can be driven by the on-vehicle power supply voltage. Specifically, P, □< 60 M
Let it be P a. Subsequently, in 8103, the command injection pressure P
The basic solenoid valve energization timing T of the high-pressure feed pump is determined by interpolation from the two-dimensional map of y+++, commanded injection amount Q, and □.
Calculate □□. In addition, in 5104, feedback compensation i"ry, is calculated by PID control according to the difference between the actual common rail pressure Pa and the commanded injection pressure PFII+. Next, the process proceeds to 5105, where T, □□ calculated in 5103 and 5104, and Based on T and □, the solenoid valve energization start timing T2 of the high-pressure feed pump is calculated.

When a failure of the high voltage generating section 10 is detected by the abnormality detection boat P1 of the cPU, the command injection pressure P,1, which is the standard for calculating the timing T for starting energization of the solenoid valve of the high pressure feed pump, is
．． is set to less than 60 MPa. Therefore, when the bomb electromagnetic valve is opened at the calculated timing T2, the actual common rail pressure Pe generated by the high-pressure feed pump is reduced, and the three-way electromagnetic valve (2) to which the on-vehicle power supply voltage is applied can be opened.

As another embodiment for detecting an abnormality in the high voltage generating section 10,
V OLl ? of the comparator IC1 shown in FIG. 1 above?
One method is to directly monitor the level of

First, as shown in FIG. 4, numbers are assigned to the 15°C A signal (hereinafter referred to as Ne pulse) of the rotation sensor that detects the rotation angle of the engine. The Ne pulse number of the first cylinder is set to 0 at the rise of the Ne pulse immediately after the Gl signal is input, and the Ne pulse number is counted up every time the Ne pulse rises thereafter (the count is reset after Ne pulse number 7). According to the ignition order, the Ne pulse number of the fifth cylinder is set to 0.The rise of the Ne pulse immediately after the input of the G2 signal is the sixth cylinder.
The current Ne pulse number is set to 0, and the Ne pulses are numbered based on the method described above. Therefore, for example, at the rising edge of the seventh Ne pulse. If you look at the level of u7,
As explained in the first embodiment, when the level is low, the capacitor C1 becomes a high potential, and the high potential generating section 10 is considered normal, and when the level is high, it is considered abnormal. The subsequent processing is the same as in the first embodiment.

The common rail pressure step-down control process based on the above technical means will be explained with reference to the flowcharts shown in FIGS. 5 and 6.

In the Ne interrupt processing routine shown in FIG. 5, it is determined whether the Ne pulse number is 8200 and is number 7. If it's not the 7th, say No and do nothing, if it's the 7th, say YE.
Proceed to 8201 with S and connect to abnormality detection boat P1 ■
. . It is determined whether the level of , is high level or not.

If the level is low, the abnormality flag is set to "0" in step 5202, and if it is high, it is set to "1" in step 8203. In addition, in the calculation routine for the solenoid valve energization start timing T shown in FIG.
Proceed to step 02, and set the command injection pressure PFIM to 60 MPa. If the abnormality flag is set to "0", normal control from 8301 onwards will be performed, from now on 53
Each step from 01 to 5305 is the same as in the first embodiment, so the explanation will be omitted.

According to the said technical means, V 01 of comparator lc1
1? Step-down control of the common rail pressure is possible by directly monitoring the level of the monostable vibrator tc2 and D type flip-flop iC3 in the ECU
The circuit configuration of can be omitted.

Note that the high voltage generating section 10 and its abnormality detecting means are not limited to the means of the embodiment.

``Effect of the Invention J'' As clarified in the explanation of the specific means and operation described above, the present invention provides that when the abnormality detection means detects an abnormality in the high voltage generation means, the pressure control means controls the fuel pressure in the common rail on the vehicle. The power supply voltage lowers the pressure to a level that allows the solenoid valve to open, and continues fuel injection to enable so-called evacuation driving, which has excellent effects such as realizing the concept of fail-safe.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention, and FIG. 1 is a circuit configuration diagram, FIG. 2 is a time chart explaining the operation, FIG. 3 is a flowchart of a routine for calculating the energization start time T, and FIG.
5 is a flowchart showing the Ne interrupt processing routine, FIG. 6 is a flowchart showing the calculation routine for the energization start timing T in another embodiment, and FIG. 7 is a time chart showing the operation of another abnormality detection means. 8 is an overall configuration diagram of the conventional system, and FIG. 8 is a time chart showing its operation, and also shows a block diagram inside the ECU. 10., High voltage generation section, 20. ,, constant current circuit, 3
0. Three-way solenoid valve drive control section 40. Abnormality detection circuit section 50. ,, ECU, Ll, , Coil, C1, , Capacitor, V, V+, Vz...V
w, 3-way solenoid valve, i C1, , comparator, ic2. . , monostable multivibrator, i C3, , D type flip-flop. Figure T, X output routine Figure Figure

Claims (1)

[Claims] A fuel injection control device consisting of a solenoid valve that stores fuel at a high predetermined pressure in a common rail and injects the fuel from an injection nozzle into each cylinder of an internal combustion engine by opening the valve, and a solenoid valve drive circuit that drives the solenoid valve. In the solenoid valve drive circuit, the solenoid valve drive circuit includes a high voltage generating means that applies a high voltage exceeding the on-vehicle power supply voltage, a constant current circuit that supplies the solenoid valve with a constant current to hold the operating state of the solenoid valve, and a solenoid valve. further includes an abnormality detection means for detecting an abnormality in the high voltage generating means, and upon detection of the abnormality, lowering the fuel pressure in the common rail so that the solenoid valve can be opened using the on-vehicle power supply voltage. 1. A fuel injection control device comprising: pressure control means.