JPS58217737A - Fuel injection timing control device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent an erroneous operation of the titled device, by arranging such that a fuel injection can be switched with the passage of predetermined time period after the recovery of electric voltage, in a control device utilizing a backup circuit to inject a fuel at the time of electric power voltage drop. CONSTITUTION:A low voltage detecting circuit 21 detects a voltage drop such that a microcomputer 18 can no longer operate properly. Upon a predetermined time period being passed after an electric power voltage recovers its normal value and the microcomputer 18 operates properly, a time limit circuit 22 reverse its output. The predetermined time period may, as for instance, be set at such a duration that allows a clock generation to be normal. In this manner, it is possible to prevent the titled device from operating erroneously at the time of electric power recovery, as injecting a fuel alternately by means of a backup circuit and the microcomputer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for an internal combustion engine, and is capable of starting the internal combustion engine smoothly and reliably even if the vanoter voltage drops during starting in cold or cold weather. A fuel injection control device for an internal combustion engine is provided.

In fuel injection systems for internal combustion engines, especially gasoline engines, engine operation is normally controlled at reference values that are representative of the engine load, such as the engine speed, the absolute pressure in the intake pipe, the amount of intake air, or the throttle valve opening. Specifications that indicate the condition, such as engine speed, absolute pressure in the intake pipe,
Engine water temperature.

The valve opening time is determined by adding and/or multiplying constants and/or coefficients depending on the throttle valve opening, exhaust oxygen concentration, vanoteri voltage, etc., and the fuel injection amount is controlled. control the air-fuel ratio of the air-fuel mixture.

In this type of fuel injection control device, the present invention performs the above calculations using a microcomputer, and when the voltage is lower than the voltage that makes the microcomputer inoperable and/or when it detects that the microcomputer has gone out of control, The present invention provides a fuel injection control device for an internal combustion engine that controls a fuel injection valve with a backup circuit and improves startability.

In a microcomputer-controlled control circuit having a backup circuit (hereinafter referred to as ECTJ), when switching between the backup circuit and the microcomputer control circuit is performed simply based on the power supply voltage or battery voltage inside the ECU, the voltage As the engine rotates, the switching voltage between the backup circuit and the microcomputer circuit is increased and decreased, and the backup circuit and
The fuel is controlled alternately by a microcomputer circuit, and each time the voltage drops, the microcomputer is reset and returns to the initial state, so this synergistically results in excess fuel, which can lead to misfires and carbon buildup due to fuel temperature at the ignition plug. This creates a risk of a non-starting condition. This can occur particularly when starting in cold weather or when using an aging battery. This situation will be explained in detail using FIG. Figure 1 shows the fuel injection at the time of start-up of the sequential injection method of the fuel injection system of the cylinder-twisted engine, which has fuel injection valves arranged for each cylinder, which the present inventors have already proposed. In Figure 1, which shows the situation when the cylinder discrimination signal does not come, after starting, the first
TDC (Top Dea) by the rotation speed sensor
(d Center, top dead center)) All cylinder fuel injection valves are operated, and thereafter, immediately after each intake stroke is obtained, fuel injections from the second time onward are performed in a predetermined order.

Figure 2 shows E between #2 inhalation and #1 inhalation in Figure 1.
This figure shows what happens when the voltage inside the CU drops and the microcomputer is set and returns to its initial state after initialization. In this case, even though all cylinders were injected the first time, all cylinders were injected again at about page 5 of the #1 intake line, and it can be seen that even by repeating this, there would be an excess of fuel.

FIG. 3 shows the state of fuel injection during backup according to the present invention, and shows the opening time of the fuel injector of each cylinder at TDC.
The valve opening time required for each cylinder is approximately 4 for each TDC in synchronization with the signal.

FIG. 4 shows a case where the power supply voltage fluctuates around the switching voltage between the backup circuit and the microcomputer circuit, and it can be seen that there is an excess of fuel.

In the present invention, even if the power supply voltage drops when the backup circuit is in operation, the microcomputer does not enter the bank up circuit, enter the control of the microcomputer, or repeat the setting and release of the microcomputer. In the control mode, all cylinders are simultaneously injected only once at startup, so once the back amplifier circuit is entered, even if the power is restored to a voltage that allows the microcomputer to operate, it will continue to be injected for a certain period of time, such as when the synchronizing signal is activated. The synchronization signal interval at the lowest detectable rotation is 6 hours (the synchronization signal level decreases as the rotation speed decreases and becomes undetectable), which is maintained smoothly and reliably by maintaining backup fuel injection control. This allows for smooth starting.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is an overall configuration diagram of an embodiment of the present invention. Reference numeral 1 is, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to this internal combustion engine 1. ,
A throttle body 3 is provided. A throttle valve opening sensor 4 connected to the throttle valve disposed inside the throttle body 3 converts the valve opening of the throttle valve into an electrical signal, and converts the valve opening of the throttle valve into an electrical signal.
(referred to as CU) 5.

A fuel injection valve 6 is provided in the main intake pipe 2 between the engine 1 and the throttle body 3 for each cylinder slightly upstream of the intake valve (not shown), and is connected to a fuel pump (not shown). The fuel injection valve 6 is electrically connected to the ECU 3, and the valve opening time of the mode-specific injection is controlled by the signal on page 7 from the ECU 3.

An absolute pressure sensor 7 and an intake air temperature sensor 8 are attached downstream of the throttle body 3, and each converts the absolute pressure of the intake pipe 2 and the intake air temperature into electrical signals and sends them to the ECU 3. A water temperature sensor 9 is provided in the engine 1 body, and sends a cooling water temperature signal to the ECU 3.

The engine rotation speed sensor 10 and the cylinder discrimination sensor 11 are installed around the camshaft or crankshaft of the engine 1, and the engine rotation speed sensor 10 detects a TDC signal, that is, a predetermined crankshaft every 18o0 revolutions of the engine crankshaft. The cylinder discrimination sensor 11 outputs one pulse at each angular position and at a predetermined crank angle position of a specific cylinder, and these pulses are sent to the ECU 3.

A three-way catalyst 13 is arranged in the exhaust pipe 12 of the engine 1 to purify exhaust gas. An oxygen concentration sensor 14 is provided upstream of the three-way catalyst 13 and supplies an oxygen concentration signal in the exhaust gas to the ECU 3.

Further, the ECU 3 is supplied with a vanoter voltage through the ignition switch 15. In addition, the on/off state of the starter switch can be changed using the starter switch 16.
Send to CUs.

Next, the operation of the above embodiment will be explained.

Based on the engine speed information from the engine speed sensor 10 and the engine load status information obtained from the absolute pressure sensor 7, the reference value for the opening time of the fuel injection valve is determined by table lookup from the basic Ti (fuel injection time) map. Calculated using the method.

Water temperature status obtained from water temperature sensor 9, intake temperature sensor 8
Based on the state of the intake temperature obtained from the oxygen concentration sensor 14 and the state of the oxygen concentration in the exhaust gas obtained from the oxygen concentration sensor 14, addition to the reference value or correction is made to the integration, and Increase in amount after starting determined by the number of pulses from rotation sensor 1Q and the engine water temperature.

The acceleration amount increase or deceleration amount decrease based on the acceleration state or deceleration state obtained from the throttle and torque valve opening sensor 4, the power increase based on the throttle opening and/or the absolute pressure in the intake pipe, etc. are further added with the correction obtained above 9 The ECUts determines the opening time of the fuel injection valve by adding or integrating the correction amount to the reference value and further adds the correction amount based on the battery voltage, and the cylinder discrimination sensor 1o and rotation speed sensor 11 determine the opening time of the fuel injection valve. is sent to the injection valve. The situation is shown in FIG.

Figure 6 is a timing chart during steady operation, where the cylinder discrimination signal is inputted one pulse at a time every 72o0 of the engine crank angle, and in parallel, the TDC signal pulse obtained from the rotation speed sensor is input at every 18o0 of the engine crank angle. is input one pulse at a time. The output timing of the injection valves (#1 injector to #4 injector) of each cylinder is set based on the relationship between these two signals. That is, every time a TDC signal comes in from the first TDC signal after the first cylinder discrimination, #1. #s, $4. The injection valve of #2 injector is driven.

The method of supplying fuel to each cylinder immediately after starting has been explained with reference to FIG. 1, and will be further explained using the flowchart of FIG. 7. Note that this FIG. 7 shows the case of 4 cylinders and N-1, and NORMAL FLAG in the figure is a FLAG that is set when normal 1o page injection is possible.

A At the time of interruption by timing 1 in FIG. 1 Step 700 in FIG. 7 → Calculation of fuel injection time in step γo1 - NORMAL FLA in step 702
Ci (FLA set up when normal injection is possible)
G, that is, FLAG that stands when there is a cylinder discrimination signal immediately before the timing pulse) is set (NORMALIF at timing 1 in Figure 1).
LAG is not set, so NO) → Step 70
3, it is determined whether or not it is the first interrupt (YES) → In step 704, it is determined whether or not there was a cylinder discrimination signal immediately before the timing pulse 1 (NO in FIG. 1, but if it is YES, the Set NORMAL FLAG to inject at the timing shown in Figure 6) →
At step 711, all injectors #1 to #4 inject - Step 717 B When the 11th page interrupts due to timing pulse 2 in FIG. Discrimination N〇-Stethopore 12
Determination of whether this route has been passed three times in NO-
In step 714, it is determined whether or not there was a cylinder discrimination signal immediately before timing pulse 2 - NO - Step 7
16, the contents of the cylinder discrimination RAM are carried forward by +1 →
Step 717 C At the time of interruption by timing pulse 3 in Fig. 1 Step 700 → 701 → 702 → 703 → 712 → YES at step 714 → Cylinder discrimination at step 715) 'Set the contents of IAM to 1 - Step 71
6→717D Step 700→701→Completion02-703→Step 7 at the time of interrupt by timing pulse 4 in FIG.
12: YES→Step 713: NORM
AL FLAG set → Step 714 → 716 →
717 E Injection of #4 injector (cylinder discrimination RA
Contents of M1. 2. 3.4, the injector is #1. $3.84. #2 is set) → 710 → 7
17 F When interrupted by timing pulse 6 in Figure 1, step 700 → 701 → 702 shout o8 → step 7
#2 injector injection at 09) → 710 → 71
7 G Step 700 → 701 → 702 → 708 → Step 7 when interrupted by timing pulse 7 in FIG.
Injection of #1 injector in 06→707→717 The above-mentioned contents are controlled by a microcomputer, but if a backup fuel control circuit page 13 is added to this, the above-mentioned problem occurs at low voltage.

The present invention eliminates the above-mentioned problem at low voltage, and this embodiment will be roughly described in detail below with reference to FIG. 8.

In FIG. 8, 18 is a microcomputer control circuit including a microcomputer, 19 is a backup circuit, and 17 is A for converting various analog inputs into digital quantities.
/D converter circuit, 20 is an internal power supply circuit, 21 is a low voltage detection circuit including a timer element, 22 is a timer circuit, 23 is the #1 to #4 injector drive signal from the microcomputer control circuit 18 and the back amplifier circuit 19 These are the switching circuit and injector drive circuit for all-cylinder drive signals from the injector.

The fuel calculation by the microcomputer control circuit 18 is as described above, but the backup circuit 19 is composed of, for example, a one-shot circuit that receives a value from a water temperature sensor and operates using a pulse from a rotational speed sensor as a trigger, as shown in FIG. The fuel injection valve (injector) opening time information obtained from page 14 is sent to the switching circuit 23. If the valve opening time information from the backup circuit 19 is selected by the switching circuit 23, all the cylinder injectors #1 to #4 are driven by that information, and one drive waveform as shown in FIG. 3 is obtained.

Next, when the low voltage detection circuit 21 detects a voltage that makes it impossible for the microcomputer control circuit 18 to operate normally, it immediately resets the microcomputer control circuit 18 and switches the output of the time limit circuit 22 between [23
and select 9 with the backup circuit. After a predetermined period of time elapses after the power supply voltage is restored and the microcomputer control circuit 18 is able to operate normally, for example, until clock generation becomes normal, the output of the low voltage detection circuit 21 is inverted and the microcomputer control circuit 18 is controlled. circuit 18
The reset is released and normal operation begins. Further, the inverted output of the low voltage detection circuit 21 is sent to the time limit circuit 22, but the output of the time limit circuit maintains the previous state and is activated for a predetermined period of time, for example, 15 pages rotation sensor and /-! After the pulse interval time obtained from the rotational speed sensor with the lowest rotational speed at which the output of the cylinder discrimination sensor can be obtained, it is reversed and sent to the switching circuit 23, and the injector is driven by a signal from the microcomputer control circuit 18. . Therefore, even if the microcomputer operates normally and outputs an output until the output signal of the timer circuit 22 is inverted, it is not used for actually driving the injector.

The operation of the above embodiment will be explained with reference to FIG.

Figure 9 shows a case where the voltage was low from the time the starter switch was first turned on, and the low voltage detection circuit output was I
The microcomputer control circuit 6 is set in the state of t L It, and the microcomputer control circuit 6 is set in the state of the backup circuit ``H'' with the time element output in the state of L''.
Injector drive signal 02 is selected. The low voltage detection circuit 505 reaches T1 when the voltage exceeds the threshold voltage.
After a period of time, the output of the timer becomes I Hl'' 12 hours after the output of the low voltage detection circuit becomes H''.

The dotted line in the figure shows a state in which overconcentration occurs when the switching circuit is switched using the output of the low voltage detection circuit.

Although it is possible to shorten/or eliminate T2 time and lengthen T1 time to achieve the same purpose, there is a disadvantage that the microcomputer circuit is reset during this time and cylinder discrimination ranking is delayed.

In FIG. 8, the time limit circuit 22 can include a runaway prevention circuit. This is to set the time element output to L''' when the reset signal from the microcomputer control circuit 18 does not come during a predetermined number of pulses at a predetermined rotation speed, a predetermined time, or both. .

The above embodiment is an example of sequential injection for four cylinders, but the engine type can also be applied to internal combustion engines other than four cylinders.
It can also be applied to a type equipped with two injection valves.

As detailed above, according to the present invention, fuel injection
'If the valve control circuit includes a backup circuit, even if the power supply voltage is low when the engine ignition switch starts operating and the backup circuit controls the fuel, the microcomputer circuit will control the fuel after the power supply voltage has reliably returned. In order to start control, the backup circuit and microcomputer circuit alternately control the fuel injection, and inject all cylinders many times, which can cause misfires and carbon buildup due to the fuel temperature at the ignition plug. This has the advantage that this can be avoided and smooth and reliable startup can be achieved.

[Brief explanation of drawings]

1 to 4 are diagrams explaining the operation of a conventional fuel injection control device, FIG. 6 is a schematic diagram of a fuel injection control device according to an embodiment of the present invention, and FIG. 6 is a diagram explaining the operation of the same device. Figure 7 is a flowchart for sending an injector drive signal immediately after starting the device, and Figure 8 is a block diagram of the main parts of the device.
FIG. 9 is a timing chart of the device. 1...Engine, 2...Intake pipe, 3.
... Throttle rebody, 4... Throttle valve opening sensor, 6... Electronic control unit, pages 6 and 18... Fuel injection valve, 7...・・Absolute pressure sensor, 8
...Intake temperature sensor, 9...Water temperature sensor, 1
o...Engine speed sensor, 11...
・Cylinder discrimination sensor, 12...Exhaust pipe, 13...
...Three-way catalyst, 14...Oxygen concentration sensor,
15...Ignition switch, 16...
...Starta Ino-IF-117...A/
D converter circuit, 18...Microcomputer control circuit, 19...Backup circuit, 2
0... Power supply circuit, 21... Medium/low voltage detection circuit, 22... Time limit circuit, 23... Switching circuit and injector drive circuit. Name of agent: Patent attorney Toshio Nakao and one other person
52nd generation (Miyohina)

Claims (2)

[Claims] (1) a calculation means for calculating a fuel injection time based on predetermined input information related to the internal combustion engine; a backup means for outputting a predetermined fuel injection time signal; and a fuel injection time signal output from the calculation means; a control means for controlling the fuel injection means in synchronization with the rotation of the internal combustion engine based on a predetermined fuel injection time signal output from the backup means; a voltage detection means for detecting the magnitude of the power supply voltage with respect to the predetermined voltage; switching means for selecting the output of the backup means when the power supply voltage is lower than a predetermined voltage and selecting the output of the calculation means when the power supply voltage is higher than the predetermined voltage; A fuel injection control device for an internal combustion engine, comprising a delay means for delaying the switching operation of the switching means at a time point 1 when a predetermined time has elapsed from the time point. 2 pages (2) The fuel injection control device for an internal combustion engine according to claim 1, wherein the delay time by the delay means is set to be equal to or longer than the synchronization signal cycle at the lowest internal combustion engine rotation speed that can be detected by the synchronization signal.