JPS629740B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a fuel-injected internal combustion engine (hereinafter referred to as EFI).
The present invention relates to a fuel control device for an engine (referred to as an engine), and particularly to a device for correcting the amount of fuel injected during acceleration. As is well known, in EFI, engine speed (hereinafter abbreviated as Ne), throttle valve opening degree (hereinafter abbreviated as θth), suction negative pressure (hereinafter abbreviated as PB)
The fuel amount is controlled by opening the nozzle for a period of time determined based on engine parameters such as (abbreviated as) and injecting fuel from this nozzle at a constant pressure. In such an EFI engine, when accelerating, a relatively rich air-fuel ratio is required compared to when cruising. For this reason, the air-fuel ratio required during acceleration becomes lean, making it impossible to obtain the output (horsepower) necessary for acceleration, and the disadvantage is that temporary output decreases and misfires tend to occur. The purpose of the present invention is to eliminate the above-mentioned drawbacks by temporarily injecting additional fuel for compensation in addition to the basic fuel injection amount by the normal EFI method when the rate of increase in θth reaches a predetermined value. An object of the present invention is to provide a fuel correction device for an EFI engine that can smoothly accelerate the engine. In order to achieve the above object, in the present invention, when the increase rate of θth exceeds the expected value,
Temporary addition of fuel is performed independently of normal basic fuel injection. Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. Matrix memory 1 contains Ne and one of the other engine parameters (θth, PB, etc.) (in the illustrated example
A required basic fuel amount, that is, a basic fuel (injection time) signal Ti, is stored in advance with PB) as a parameter. The basic fuel signal Ti read out from the memory 1 in accordance with the input Ne and PB is input to the register 5 and presets the preset down counter 6. Preset down counter 6 is controlled by sequence timer 7. Sequence timer 7
is controlled by the Ne signal, controls the preset operation and counting operation of the preset/down counter 6, and sets the flip-flop 9 at a timing determined in advance with respect to the Ne signal. Further, although not shown, the sequence timer 7 supplies necessary timing signals and clock signals to all device blocks to be described later. The output of flip-flop 9 is outputted via OR gate 10, which energizes a fuel injection solenoid (not shown) to open a nozzle (not shown) and inject fuel at a constant pressure. When the count of the preset down counter 6 advances and reaches 0, the 0 detector 8 generates an output to reset the flip-flop 9 and stop fuel injection. As described above, fuel injection is performed for a time corresponding to the basic fuel signal Ti. On the other hand, the value of θth is stored in the first register 14 at every scheduled time interval Δt by the sampling signal from the sequence timer 7, and
The contents of 4 will be stored in the second register 1 at the next sampling.
Transferred to 5. That is, θth(i) at the current sampling time is stored in the first register 14, and θth(i-1) at the immediately previous sampling time is stored in the second register 15. Shift registers can be used as the first and second registers. The contents of both registers 14 and 15 are stored in a subtracter 16.
The difference Δθth is divided by Δt in the divider 13 to calculate the rate of increase. Increase rate △
θth/Δt is applied to comparator 17. As can be seen from the above explanation, the first and second registers 14 and 15
Also, a differentiator can be used in place of the subtracter 16 and divider 13. The comparator 17 is set with three reference values B, +C, -C as shown in FIG. It is divided into areas as shown in the table, and three types of corresponding signal outputs are generated.

[Table] When △θth/△t exceeds B and the _K1 signal is output, the flip-flop 18 is set. As mentioned above, the basic fuel signal Ti read out from the matrix memory 1 according to Ne and PB is the limit value Tlim set by the limit value setter 21.
are compared in the comparator 22. When Ti>Tlim, the gate 19 is closed; otherwise, the gate 19 is opened. Therefore, when Ti>Tlim, the temporary (or one shot) fuel increase correction described below is prohibited. When the flip-flop 18 is set with the gate 19 open, that is, Ti<Tlim, its output passes through the gate 19 and triggers the monomulti 20. The output pulse of monomulti 20 starts preset down counter 21 and sets flip-flop 24. At this time, the preset down counter 21 is set with a temporary fuel increase correction output generated from the function generator 22 in accordance with Δθth/Δt. In this case, the function generator 22 may be omitted and the temporary correction output may be set to a fixed value. The counter 21 clocks only the preset amount.
Counting down Cl causes zero detector 23 to produce an output, so flip-flop 24 is reset. This causes flip-flop 24
produces a time Ts output corresponding to the output of the function generator 22, which is superimposed on the basic fuel signal Ti via the OR gate 10. Therefore, a temporary increased correction supply of fuel is performed for the above-mentioned period of time. In other words, as shown in the timing diagram of Fig. 3, when the value of △θth/△t exceeds the reference value B (a in the figure), the signal is activated at a timing independent of the original basic fuel signal Ti (b in the figure). Correction increase signal Ts (Figure c)
is generated. This increases the amount of fuel supplied and the engine output, so smooth and sufficient acceleration can be achieved. The reason why temporary addition correction is prohibited when the basic fuel signal Ti exceeds the limit value is when Ti is larger than a certain level - that is, when accelerating under a condition where the load is above a certain level, temporary addition is not required. It is from. Also, the amount of temporary addition correction, that is,
The output of the function generator 22 is predetermined within a range in which the added fuel amount is too large and the plug is covered, causing a misfire and a decrease in output. Moreover, although the above example shows that the temporary addition correction is performed only once, this increase can also be performed in two or more times. In this way, since the additional fuel is supplied in small portions, wetting in the intake manifold is reduced, and as a result, the fuel atomization rate is improved. This is expected to have the effect of reliably increasing output during acceleration. To do this, for example, the output of the monomulti 20 is delayed by an appropriate time (for example, the basic fuel injection cycle at that time), the preset counter 21 is started a predetermined number of times, and the flip-flop 2
Just set it to 4. Of course, at this time, the output of the function generator 22 needs to be reduced accordingly. When the value of Δθth/Δt decreases and reaches the cruise region or deceleration region below +C, the comparator 17 outputs signals CR and DL. These signals are applied to flip-flop 18 through OR gate 28, thereby resetting flip-flop 18. Incidentally, in reality, the value of Δθth/Δt often fluctuates around the reference value B, and if a temporary addition is performed every time B is exceeded, fuel will be in excess, causing a misfire. However, in this embodiment, even if △θth/△t fluctuates around B, +
The state of the flip-flop 18 does not change unless the voltage falls below C. Therefore, the monomulti 20 does not generate any output, no temporary addition of fuel is performed, and a misfire caused by the plug being covered is completely prevented. By temporarily adding fuel as described above, it is possible to quickly and reliably accelerate the engine, but if the timing of temporary addition and the timing of basic injection partially or completely overlap, the addition There is a risk that the effectiveness of the product may decrease or disappear altogether. For this purpose, in the present invention, the clock Cl is supplied to the preset down counter 6 via the AND gate 25, and the gate 25 is
It is controlled by the temporary addition signal, that is, the inverted output of the flip-flop 24. According to such a configuration, the clock supply to the preset/down counter 6 is stopped while the fuel temporary addition signal is being output, so if no counting is performed and the two signals overlap, The basic injection timing will be delayed by that amount. Therefore, the temporary addition is always performed reliably. The present invention illustrated and explained above can also be implemented using a computer such as a microcomputer. A flowchart in this case is shown in FIG. 4, and the calculation contents in each step S1 to S8 will be explained below. do. S1...Read necessary data such as Ne, θth, and set dθ
Calculate th/dt. S2...Whether dθth/dt is smaller than the reference value +C,
That is, it is determined whether the engine is in the cruise range. If No, it is in the acceleration region, and the process advances to step S3. S3: It is determined whether the basic fuel signal Ti read out according to the normal EFI control method is larger than a predetermined control value Tlim. If it is large, no temporary increase correction will be performed and the value will return to its original state. If it is small, proceed to step S4. S4... It is determined whether dθth/dt is larger than reference value B. If No, the temporary increase correction will not be performed and the original state will be restored. If Yes, proceed to step S5. S5... It is determined whether the K flag is set to 1, that is, whether the temporary increase correction has already been performed. Initially, since no temporary increase correction is performed, the determination result is No, and the process proceeds to steps S6 and S7. S6...Calculate a temporary correction amount according to the value of dθth/dt at that time, or read it from a stable prepared in advance. Note that this value may be kept constant. S7...The increase correction signal calculated or read in the previous step S6 is output, and the solenoid is energized for that period of time to perform fuel injection.
At the same time, set the K flag to 1 and return to the original state. In the next cycle, step S1→S2→……→
Even when the process advances to S5, the K flag is already set to 1, so the temporary fuel increase correction is not performed and the process returns to the original state. When acceleration ends, dθth/
Since dt becomes smaller, the determination in step S2 becomes Yes, and the process proceeds to step S8. S8... Set the K flag to 0 and return to the original state. This will restore the entire system. If the temporary increase correction is to be performed twice or more, for example, the engine rotation period may be calculated in step S7, and the fuel injection signal may be output at that time interval. As described above, the same effects as those described above with reference to FIG. 1 can be achieved by arithmetic control using a computer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
3 and 3 are time charts for explaining the operation, and FIG. 4 is a flow chart of an embodiment in which the present invention is implemented by computer control. 1... Matrix memory, 6, 21... Preset down counter, 7... Sequence timer, 8, 23... 0 detector, 9, 18, 24...
Flip-flop, 13...Divider, 14, 15
... Register, 16 ... Subtractor, 17 ... Comparator, 20 ... Monomulti, 22 ... Function generator.

Claims (1)

[Scope of Claims] 1. A device that determines a basic fuel injection time based on at least two engine parameters such as engine speed, throttle valve opening, and suction negative pressure, and a device that opens a nozzle during the basic fuel injection time. , a fuel correction device for an EFI engine, which includes a device for injecting fuel at a constant pressure, a device for obtaining an increase rate of the throttle valve opening, and a device for injecting fuel at a constant pressure; a device for additionally injecting fuel by temporarily opening a nozzle for a specified amount of time; A device that prohibits additional injection of fuel even if the increase rate exceeds the first set value;
A fuel correction device for an EFI engine, comprising a device for canceling the prohibition when the fuel decreases below a set value. 2. The fuel correction device for an EFI engine according to claim 1, wherein additional injection of fuel is prohibited when the basic fuel injection time is equal to or longer than a scheduled value.