JPS6327533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention controls the increase in fuel supply when restarting fuel supply after shutoff in a fuel supply system for an internal combustion engine that has a function of shutting off fuel supply upstream of a throttle valve under specific operating conditions. Regarding the method.

When restarting the fuel supply after cutting off the fuel,
Particularly in internal combustion engines equipped with a fuel injection device that injects fuel into each cylinder intermittently, the amount of fuel may be increased by a certain amount in order to prevent engine vibrations caused by sudden torque fluctuations. In addition, in an internal combustion engine with a carburetor, the fuel that adheres to the intake pipe wall during shutoff evaporates, and even if fuel supply is restarted, some of the fuel remains on the intake pipe wall for a while, causing the air-fuel mixture to contribute to combustion. The actual air-fuel ratio of the fuel becomes extremely lean, causing the problem of emitting harmful emissions due to misfire, so although most of the fuel is cut, only a small portion
Care has been taken to ensure that the fuel continues to flow and wet the walls of the intake pipe.

However, even during fuel cutoff, supplying even a small amount of fuel to keep the intake pipe wall slanted is not useful in energy conversion of the engine, and is therefore undesirable from the standpoint of fuel conservation. In addition, if the amount is increased by a certain amount when restarting fuel supply after a complete shutoff, under certain conditions, it is possible to prevent the air-fuel ratio from becoming lean for a while as described above, but the degree of fuel evaporation on the intake pipe wall depends on the time of fuel shutoff. If this time is long, the air-fuel ratio will become lean for a while, whereas if this time is short, the air-fuel ratio will be too rich, which may temporarily generate harmful exhaust components. I understand. In particular, in systems that inject and supply fuel upstream of the throttle valve, the intake passage from the fuel injection part to each cylinder is long and the wall area of the intake passage is large. It was difficult to optimally compensate when fuel supply was resumed.

The present invention has been made in view of the above, and is a system for intermittently injecting and supplying fuel upstream of a throttle valve of an engine, in which the fuel is completely cut off under operating conditions where the fuel should be cut off, and when the fuel supply is restarted, the amount is increased. The larger the amount of time the engine is in a shut-off state or the cumulative number of engine revolutions corresponding to that time, the larger the increase in fuel amount will be, and the amount of increase will be gradually reduced over time. The aim is to further improve fuel savings without producing harmful exhaust gas components at the start of supply.

The present invention will be explained below with reference to embodiments shown in the drawings. Fig. 1 is a schematic configuration diagram showing the configuration of the present invention, in which 1 is an intake pipe that communicates with each cylinder of the engine via an intake manifold, and 2 is an electromagnetically actuated fuel injection valve that adjusts the fuel pressure to a constant level. This is a configuration in which fuel is pumped. The fuel injection valve 2 is installed directly above the throttle valve 3 that adjusts the flow rate of air flowing into the engine, and intermittently injects fuel toward the downstream side, that is, the throttle valve 3, to supply fuel to each cylinder of the multi-cylinder internal combustion engine 4. supply. 5 is a microcomputer for fuel injection control; ignition signal (rotation angle signal) of distributor 8 which serves as a rotation sensor; signal of idle switch 6 which operates in conjunction with the throttle valve and detects when the throttle valve is fully closed; and intake pipe. A signal from a pressure sensor 7 that detects the pressure of the engine and a signal from a water temperature sensor 9 that detects the temperature of cooling water of the engine are inputted, and the injection valve 2 is electrically connected to operate the injection valve 2.

FIG. 2 is a block diagram for explaining the microcomputer 5 in detail.
is a microprocessor unit (CPU) that calculates the fuel injection amount. Reference numeral 101 denotes an interrupt command unit that commands the microprocessor unit 100 to perform interrupt processing for calculation of the fuel injection amount based on the ignition signal from the distributor 8, and is connected to the common bus 123.
Information is transmitted to the microprocessor unit 100 through the microprocessor unit 100. The interrupt command unit 101 also outputs a timing signal for controlling the operation start time of a unit 106, which will be described later. Reference numeral 102 denotes a rotational speed counter unit to which an ignition signal is input and which counts the period between ignitions based on a clock signal of a predetermined frequency from the microprocessor unit 100 to calculate the engine rotational speed. 103 is a digital signal unit, which turns the idle switch 6 ON-
The OFF signal is sent to the microprocessor unit 100 as a "1"-"0" signal to be read. 1
04 is an A/D conversion processing unit including an analog multiplexer, which has the function of A/D converting the signals from the pressure sensor 7 and water temperature sensor 9 and reading them into the microprocessor unit 100. Output information from each of these units 102, 103, and 104 is transmitted to microprocessor unit 100 through common bus 123. Reference numeral 105 stores the control program for the microprocessor unit 100, and also stores the control program for each unit 101, 102, 10.
A memory unit having a function of temporarily storing output information from the microprocessor unit 100 and the common bus 123.
It is done through. Reference numeral 106 is a fuel injection time counter unit including a register, which converts a digital signal representing the valve opening time of the injection valve 2 calculated by the microprocessor unit 100, that is, the fuel injection amount, into a pulse signal with a pulse time width giving the valve opening time. do. 107 is a power amplifier that amplifies the pulse signal from this counter unit 108 and supplies it to the injection valve 2.

Next, the general operation of the above configuration will be explained with reference to the waveform diagram shown in FIG. The ignition signal (rotation angle signal) of the distributor 8 shown in FIG. 3A is waveform-shaped by a waveform shaping circuit (not shown) as shown in FIG.
Sent to 02. The interrupt command unit issues an interrupt command to the microprocessor unit 100 for injection time calculation processing and causes the counter unit 106 to start counting down in synchronization with the rotation angle signal after waveform shaping shown in FIG. 3B. Send command signals such as Microprocessor unit 100 performs the above-mentioned interrupt operation in response to this command signal, and sets the result of the operation in a register within counter unit 106. This counter unit 106 counts down the digital value set in the register in response to the command signal, converts it into an injection time, and forms the injection signal shown in FIG. 3D. On the other hand, the counter unit 102 performs counting using the clock signal sent from the microprocessor unit 100 during the time period from when this signal arrives until the next signal arrives using the rotation angle signal after the waveform shaping shown in FIG. 3B. The count result is read into the microprocessor unit and used as a rotation signal (N).

4 and 5 show a schematic flowchart of the microprocessor unit 100. When the engine starts, the mail routine is activated in step 1001, and the intake pipe pressure sensor 7 is activated in step 1002.
and the analog signal of the water temperature sensor 9 are sequentially A-D converted by the A-D conversion processing unit 104, and the digital values are temporarily stored in the memory unit 105.Next, in step 1003, the A-D conversion of the water temperature sensor signal is performed. The correction ratio α is calculated based on the value obtained by conversion. This α is, for example, the memory unit 105
This is a known method of reading values corresponding to water temperature information from a map stored in the system. Next, we proceed to the logic for measuring the fuel cut time to determine the fuel increase ratio after fuel cut, which will be described later. In other words, it is determined in 1004 whether the predetermined time (51.2ms) has elapsed,
If the time has elapsed, proceed to step 1005. This step
In step 1005, it is determined whether or not fuel is being cut using a value B that indicates whether or not fuel is being cut, which is obtained in an interrupt process to be described later.If fuel is being cut, step 1007 is performed.
Then, 1 is added to the value A stored in the RAM area in the memory unit 105. If the fuel is not being cut, the process advances to step 1006 and A is set to 0. Therefore, during fuel cut, A is counted by 1 every 51.2 ms, so the count value of A can represent the fuel cut time. Step 1006 or 1007
When the process in step 1004 is completed, or if it is determined in the process in step 1004 that 51.2 ms has not elapsed, the process returns to step 1002.

As described above, when no interrupt signal is received from the interrupt command unit 101, the main routine program shown in FIG. 4 is repeatedly executed. Once an interrupt signal is received, the microprocessor unit 100 immediately proceeds to the interrupt processing routine entry 1010 shown in FIG. 5 even if the main routine is in the middle of calculation. Next, in step 1011, the digital value (Pm) and rotation signal (N) of the intake pipe pressure signal are taken in, and in step 1012, the injection time (ti) is determined based on the Pm and N signals.
Calculate. Next, let's move on to the fuel cut logic.
In other words, in step 1013, idle switch 6
ON (that is, the throttle valve is fully closed), and in step 1014 it is determined whether the rotation speed (N) is greater than a preset rotation speed (No). This set rotational speed No. is determined from a characteristic map as shown in FIG. 7 stored in the memory unit 105 in accordance with the water temperature information at that time. When the idle switch is ON and the rotation speed is higher than the set speed, in step 1024, the value B, which indicates whether or not fuel is being cut, stored in the RAM area of the memory unit 105 is set to 1, and then in step 1025. Carry out fuel cut with ti=0. On the other hand, step 1013,
If it is determined in step 1014 that both of the above conditions are not satisfied, it is determined in step 1015 whether B=1. That is, it is determined whether or not it is the moment to start fuel injection again after fuel cut. If so, proceed to step 1016, read the fuel increase ratio γo corresponding to this value A from the value A representing the fuel cut time using the map shown in FIG. 6 stored in the memory unit 105, set γ=γo, and proceed to step B = 1017
0 indicates that fuel is not being cut.

If it is not the moment to start fuel injection again after fuel cut, the process proceeds to step 1018, and it is determined whether γ>1. That is, it is determined whether or not the amount is being increased after fuel cut, and if the amount is being increased, the process proceeds to step 1019. In step 1019, the increase ratio γ is decreased by Δγ. In other words, for each interrupt process, that is, for each number of injections, γ=
Reduce γ by Δγ until it becomes 1. step
In 1020, it is determined whether γ>1 or not (that is, γ≦
In case 1), γ=1 is set in step 1021. If γ > 1 in step 1020, or after the processing in step 1021 or after the processing in step 1017, the process advances to step 1022, and the calculated γ is stored in the memory unit 10.
5 is temporarily stored. Next, the process proceeds to step 1023, and the injection time ti is corrected using the correction ratio α obtained in step 1003 of the main routine and the increase ratio γ obtained in step 1022, that is, ti=ti×α×γ is calculated. Next, in step 1026, the injection time ti after the correction calculation or the injection time ti = 0 representing the fuel cut obtained in step 1025 is set in the register in the counter unit 106, and in step 1027, the interrupt processing is terminated and the main routine is resumed. Return to the calculation.

In the above embodiment, the fuel increase ratio γ was determined based on the fuel cut-off time, but there are also steps 1005, 1006, and 1006 of the main routine.
1007 is performed in the interrupt processing routine, and A is calculated as the cumulative number of engine revolutions corresponding to the fuel cut period.
is memorized, and the increase ratio γ is determined by this cumulative number A.
may be determined. Also, the increase ratio γ is 1
Although Δγ is subtracted every rotation (that is, every injection), it is also possible to subtract Δγ every predetermined time.

Furthermore, although the above embodiment uses a microcomputer as the control circuit, it can also be achieved by using an analog circuit.

As described above, the present invention provides a control method for a fuel supply device that has a function of cutting off fuel injection supply upstream of a throttle valve under specific operating conditions of an internal combustion engine. The larger the amount of fuel is increased and the period in which the engine is shut off or the cumulative number of engine revolutions corresponding to that period is larger, the larger the percentage of fuel is increased, and furthermore, this increase is gradually reduced. Regardless of the length of the fuel cutoff period (time), the engine can be operated at the appropriate air-fuel ratio as soon as the fuel supply is restarted, preventing harmful exhaust gas from being emitted. It has a great effect. In addition, when determining the increase rate when fuel supply is resumed based on the cumulative value of rotation during the fuel cutoff period, the evaporation of fuel adhering to the intake pipe during fuel cutoff increases as the number of rotations during that period increases. Therefore, the amount of fuel to be increased when fuel supply is restarted is optimal.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
1 is a block diagram of the microcomputer shown in FIG. 1, FIG. 3 is a waveform diagram used to explain the operation of the present invention, and FIGS. 4 and 5 are outlines of the main routines of the microprocessor unit shown in FIG. 2. A flowchart, a schematic flowchart of the interrupt processing routine, and FIGS. 6 and 7 are characteristic diagrams for explaining the operation of the present invention. 2...Fuel injection valve, 4...Internal combustion engine, 5...Microcomputer, 6...Idle switch,
7...Pressure sensor, 8...Distributor,
100...Microprocessor unit.

Claims (1)

[Scope of Claims] 1. A fuel injection valve is provided upstream of a throttle valve in an intake pipe communicating with each cylinder of an internal combustion engine, and has a function of cutting off intermittent fuel supply from this injection valve under specific operating conditions. A method for controlling a fuel supply device, the method comprising: measuring a period of fuel supply cutoff or the cumulative number of engine rotations corresponding to this period; and when restarting fuel supply from the fuel supply cutoff state, the measured value is increasing the amount of fuel supplied from the injector at a corresponding increase ratio, and increasing an initial value of this increase relative to the increase in the measured value; and after starting the increase, increasing the amount of fuel supplied from the injector multiple times. 1. A method of controlling a fuel supply device, characterized in that the increase in fuel amount is gradually reduced over the period of fuel supply. 2. The method of controlling a fuel supply device according to claim 1, wherein the measurement is based on integration of engine rotation during the period of the fuel supply cutoff.