JPH0318642A - Fuel control device for engine - Google Patents

Abstract

PURPOSE:To improve startability by controlling the driving of an injector by a second control means so as to obtain the specified fuel quantity during the period of engine start-up and forbidding the operation of drive control corresponding to the engine parameter by a first control means. CONSTITUTION:The CPU 18 of an engine control device 11 retrieves the map of a first control means stored in a RAM on the basis of the intake air flow of an engine detected by sensors 6-8, a crank angle (engine speed) signal and water temperature so as to decide the fuel injection quantity and drives the injector 9 of each cylinder through a timer 20. The CPU 18, upon judging the start-up of the engine 1 with a starter switched on, also retrieves the map of a second control means on the basis of the water temperature and drives the injector 9 so as to obtain the specified fuel quantity. The switching of the first and second control means is performed synchronously with the injection timing. The characteristic at the time of start up when the battery voltage is liable to be lowered can be thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a fuel control device for an engine. [Prior Art] Fig. 6 shows the structure of a conventional fuel control system for a four-cylinder engine, where l is the engine, 2 is an intake pipe, 3 is an exhaust pipe, 4 is a throttle valve provided in the intake pipe 2, 5 is an air cleaner provided at the inlet of the intake pipe 2; 6 is a Karman vortex air flow sensor (hereinafter abbreviated as AFS) provided in the intake pipe 2; 7 is a crank angle sensor connected to the engine 1; 8 is a crank angle sensor connected to the engine 1; A water temperature sensor, 9 is an injection valve (injector) provided for each cylinder and injects fuel, 10 is a starter switch, 11 is a control unit, 12 to 14 are interfaces, 15
．． 16 is a counter, 17 is an A/D converter, 18 is R
CPU with OM and RAM, 19.20 is a timer, 2
1 is a voltage detection circuit, 22 is a watchdog detection circuit, 2
3.24 is an AND circuit, 25 is an OR circuit, 26 is a drive circuit, 27 is a 174 frequency divider circuit, 28 is a NOR circuit, and 29 is a NOT circuit. In the above structure, the AFS 6 detects the intake air amount of the engine 1, and the crank angle sensor 7 detects the crank angle reference signal (SG
T) is generated. The starter switch 10 detects the starting of the engine, and the water temperature sensor 8 detects the temperature of the cooling water of the engine 1. The control II section 1l receives each of these detection signals and performs various processes to simultaneously drive the four fuel injection valves 9 in the l direction with one rotation of the engine. Next, the operation will be explained using the timing chart shown in FIG. First, (as shown in the figure)
When turned on and cranking starts, the SGT signal is emitted from the crank angle sensor 7 (as shown in the diagram).
(e) As shown in the figure, a pulse is emitted from the timer 19 at a rate of once per engine rotation, and in response to this, the drive circuit 26 via the AND circuit 23 and the OR circuit 25 as shown in the figure (b). A drive signal for the injector 9 is generated. By the way, as shown in figure (b), the battery voltage ■.
When becomes below a predetermined value, the voltage detection circuit 2l detects this and outputs a reset signal (C) through the NOR circuit 28.
Similarly, when CPtJ1B becomes abnormal, the watchdog detection circuit 22 detects this and sends a low signal to the CPU1B via the NOR circuit 2B.
A reset signal is input to B, and cp01a stops.
On the other hand, the 1/4 frequency divider circuit 27 outputs a pulse once per engine rotation as shown in figure (f), and in response to this, the timer 20 also outputs a pulse as shown in figure (8). ．． However, when the reset signal is not generated, the NOT circuit 2
Since the output from the AND circuit 24 is a low signal, no output is generated from the AND circuit 24, and the injector 9 is not driven by the output. Here, when the reset signal is issued as described above, the timer 19 does not generate an output as shown by the dotted line, and even if it occurs, it is blocked by the AND circuit 23, and the output of the timer 20 is output by the AND circuit 24 and the OR circuit. 2
5 as a drive signal from the drive circuit 26. [Problems to be Solved by the Invention] In the conventional device described above, the injector 9 is driven by the output of the backup means, that is, the timer 20 when the CPtJ1B is not activated. however,
At startup, the battery voltage V. battery voltage V. When the timer 20 returns to normal, the reset signal is turned off and the output from the timer 20 is cut off. For this reason, as shown in FIG. 7(b), the injector drive signal is also cut off by the dotted line, making it impossible to obtain a sufficient amount of fuel injection, resulting in poor startability.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain an engine fuel control device that can improve the characteristics at the time of starting, where a drop in battery voltage is particularly likely to occur. ．． [Means for Solving the Problems] An engine fuel control device according to the present invention includes a first control means for driving and controlling an injector according to engine parameters, and a predetermined fuel control device when the first control means is not activated. The second control means drives and controls the injector so that the amount of the injector is controlled, and means for forcibly causes the second control means to drive and control the injector during the engine starting period. Further, the engine fuel control device according to the present invention includes:
In addition to the above means, there is provided means for switching the first and second control means in synchronization with the injection tie ξ sog. [Operation] In the present invention, the injector is drive-controlled by the second control means during the engine starting period, and irregularities in the injector drive at the time of switching with the first control means are eliminated. Further, in this invention, the switching between the first control means and the second control means is performed in synchronization with the injection tie, and the switching is not performed at the same time as the cranking signal and the reset signal are turned on and off. The irregularity of the injector injection is improved. [Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure shows the structure of the engine fuel control system according to this embodiment, in which each member 1 to 28 is the same as the conventional one, and 30 is a reset signal from the Noah circuit 28 and a starter switch 10.
A NAND circuit, 31, receives a cranking signal from
is a NOT circuit 32 which receives the output of the NAND circuit 30;
is a knot circuit into which the output of interface 13 is input. Next, the operation of the above-mentioned Kaikai will be explained using the flowchart shown in Fig. 3. (A) The figure shows the main program of CPU1B. First, when a reset signal is input to CPUI B, in step 101 the RAM, input/output ports, etc. in the CPU 18 are initialized, and in step 102, P,
Inverts the output, that is, the watchdog signal. Step 1
In step 03, the output of the water temperature sensor is A/D converted and stored in the RAM as WT. In step 104, the bathoteri voltage V. 7. A/D convert the data and store it in RAM as VB.
In step 105, the output signal SG of the crank angle sensor 7 is
T period T36? and AFS6's output T3. ? AN-Tays is calculated from the force cycle Taps and stored in the RAM.AN is the amount of intake air taken during one stroke of the engine. In step 106, as shown in FIG.
Data table stored in OM f. (WT), calculate the driving time T at startup, and store it in RAM. In step 107, as shown in FIG. 5, battery voltage data V. The data table f, (VB) stored in advance in the ROM of the CPU 1B is mapped by the wasted time T. Calculate and store it in RAM. Step 108
Then, use the starter switch 10 to determine whether or not to start.
Step 10 when starting with starter switch 10 on
In step 9, the driving time T1 of the injector 9 is calculated by T r − T c + T s, and when the starter switch 10 is off, step 110? T+-K+xAN+T
The driving time T, is calculated using e, and the process returns to step 102. In this way, the optimum drive time TI for the engine condition is always stored in the RAM. Note that K1 is a driving time conversion coefficient. FIG. 3(B) shows the interrupt power P of the CPU 18, that is, A
The interrupt processing program for the output signal of FS6 is shown, and in step 201, the output pulse period T'a of AFS6 is
rs is read and stored in RAM, and in step 202 T. , reset the count value of the measurement counter 15, and start measurement of the next pulse fil period of AFS6. FIG. 3(C) shows an interrupt processing program for the CPU 1B's interrupt P2, that is, the output signal SOT of the crank angle sensor 7. In step 301, the SGT period T■7
is read and stored in RAM, and in step 302 T
s t. The count value of the counter 16 for t measurement is reset and the measurement of the next SC, TIMI'#J4 is started. In step 303, a drive time T is set in the timer 19, and in step 304, the timer 19 is triggered, and the timer 19 generates an output signal with a pulse width T+. FIG. 2 is a time chart showing the operation of the above structure,
The output of the NAND circuit 30 shown in (a) to (b) is of the same birch as the conventional one.While the cranking signal generated during startup is at a high level, the output of the NAND circuit 30 is at a high level regardless of the reset signal, and the timer Each injector 9 is driven by the output of 2o.When the cranking signal becomes low level, that is, after the starting period has elapsed, each injector 9 is driven by the output of the timer 20 and the output of the timer 19 depending on the presence or absence of the reset signal.
1, but the battery voltage V. does not decrease much except at the time of starting, and after the starting period has elapsed, the injector 9 is driven mostly by the output of the timer 19. FIGS. 8 and 9 show a second embodiment of the invention;
3 is a DT clip-flop provided between the output of the NAND circuit 30 and the manual power of the AND circuit 24 and the NOT circuit 3l, which has another structure or is the same as the first embodiment. The output of this flip-flop 33 becomes a high level if the output of the NAND circuit 30 is high level when receiving the output of the 1/4 frequency divider circuit 27, and becomes a low level if the output of the NAND circuit 30 is a low level. Therefore, switching of the outputs of timers 19 and 20 in the injector drive signal is performed in synchronization with injection timing. Here, for example, if the cranking signal is
), in the first embodiment, the drive output is switched from the timer 20 to the timer l9, but the output of the timer 19 is zero and the amount of fuel decreases. However, in this embodiment, the output of the flip-flop 33 is not switched until the next output pulse of the 174 frequency divider circuit 27 is input, and the timer 20 is not switched to the timer 19. of fuel is supplied, and good starting performance can be maintained. [Effects of the Invention] As described above, according to the present invention, each control means is not switched during the starting period, the irregularity of fuel injection caused by switching is eliminated, and starting performance can be improved. Furthermore, even if the cranking signal is temporarily interrupted due to a poor connection during the startup period, the control means will not be switched immediately but at the next injection timing, so the reset signal will cause the first control means to output Switching is almost never performed when the engine cannot obtain the desired amount of fuel, and stable fuel injection can be performed, which also improves starting performance.

[Brief Description of the Drawings] Figures 1 to 3 are configuration diagrams, time charts, and flowcharts according to the first embodiment of this invention device, and Figures 4 and 5 are injection drive at startup of this invention device. Characteristic diagrams of time and waste time of fuel injection, Figures 6 and 7 are configuration diagrams and time charts of the conventional device, and Figures 8 and 9 are configuration diagrams of the second embodiment of the device of the present invention. and time chart
It is.

Claims (2)

[Claims] (1) means for detecting engine parameters; means for detecting engine starting; an injector for supplying fuel to the engine; a first control means for controlling drive of the injector according to engine parameters; a second control means for driving and controlling the injector so that a predetermined fuel amount is achieved when the control means is not operating; and a means for forcibly driving and controlling the injector by the second control means during an engine starting period. An engine fuel control device characterized by: (2) means for detecting engine parameters; means for detecting engine starting; an injector for supplying fuel to the engine; a first control means for driving and controlling the injector according to engine parameters; a second control means for driving and controlling the injector so that a predetermined fuel amount is achieved when the control means is not activated; a means for forcibly driving and controlling the injector by the second control means during an engine starting period; 1. A fuel control device for an engine, comprising means for switching between a first control means and a second control means in synchronization with injection timing.