JPH01163439A - Fuel control device for engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of failure in ignition during acceleration of an engine, by a method wherein, during acceleration of the engine, the computing timing and the injection timing of a fuel amount are advanced, and in which case, when a suction pressure is changed to a value higher than a set value, the computing and injecting timings are set to a value delaying than the advanced computing and injection timings. CONSTITUTION:The acceleration state of an engine 1 is detected by an acceleration detecting means 26, and the computing and injecting timings of a fuel amount are advanced by a correction means 27. Meanwhile, a suction pressure is detected by a suction pressure detecting means 17, and when a suction pressure is changed to a value higher than a set value, a computing and an injection timing are corrected to a value delaying than the respective increased timings. This constitution feeds all of a fuel amount necessary to a cylinder under a suction stroke, and prevents the occurrence of failure in ignition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improving a fuel control device for an engine equipped with a fuel injection valve. Concerning things that improve performance.

(Prior Art) Conventionally, as a fuel control device for an engine equipped with a fuel injection valve, one that continuously injects and supplies fuel from the fuel injection valve in synchronization with the intake stroke of the cylinder of the engine is known. . For example, in the method disclosed in Japanese Patent Application Laid-Open No. 57-108428, four fuel injection valves are provided corresponding to each cylinder in a four-cylinder engine, and each cylinder is injected into the corresponding cylinder each time the intake stroke begins. An appropriate amount of fuel is injected and supplied to the engine from the fuel injection valve.

(Problem to be solved by the invention) By the way, when the engine accelerates, the amount of fuel to be supplied to each cylinder increases in accordance with the increase in the amount of intake air, and this required amount of fuel increases within the cylinder during the intake stroke. If all of the fuel is not supplied, the amount of fuel will be insufficient, resulting in poor combustion of the air-fuel mixture, which may lead to a misfire (see Figure 7 (a)). Therefore, the timing of calculating the amount of fuel and the timing of injection should be changed from those during steady operation. It is desirable to supply all the required amount of fuel to the cylinders during the intake stroke as early as possible to ensure good combustibility of the air-fuel mixture.

However, if the fuel amount calculation timing and injection timing are advanced when the engine accelerates as described above, at the beginning of acceleration when the throttle valve opening changes greatly, the intake stroke does not start until after that, as shown in Figure 7 (b). It has been found that the combustibility of the air-fuel mixture in the cylinder is reduced, which can lead to misfires, causing acceleration shock and deteriorating acceleration performance.

Therefore, the inventor conducted an experiment to understand the situation during acceleration in detail, and found that at the initial stage of acceleration, the output of the air flow sensor that detects the intake air amount changes greatly, as shown in Figure (C). The intake pressure of the engine is also changing significantly, and the fuel amount calculated when the fuel amount calculation timing is advanced does not correspond to the amount of intake air when it is actually supplied to the cylinder during the intake stroke. The amount of fuel is insufficient compared to the required amount, and as a result, the combustibility of the mixture decreases,
It was learned that there was a concern that this could lead to misfires.

The present invention has been made in view of this point, and in particular, the situation during acceleration ascertained through the above experiment, as shown in Figure 8, shows that at the beginning of acceleration, as can be seen from Figure (A), the engine While the intake pressure (intake negative pressure) Pl gradually increases (approaches atmospheric pressure) as the throttle valve opens, the in-cylinder pressure P2 of the cylinder in the intake stroke suddenly decreases as the piston descends. The intake pressure decreases to less than 21,
Due to this pressure difference, the fuel injected from the fuel injection valve is quickly sucked into the cylinder, and in the middle to late stages of acceleration, the intake pressure P1
This focuses on the fact that the cylinder pressure P2 and the cylinder pressure P2 are almost the same pressure, and the fuel is not quickly sucked in due to the pressure difference as in the early stage of acceleration.

In other words, even if the fuel amount calculation timing and injection timing are advanced from the steady state in order to supply all of the required fuel amount that increases when the engine accelerates to the cylinders during the intake stroke as described above, this is not possible at the beginning of acceleration. Even if it is later than the middle and late stages of acceleration, all of the injected fuel is reliably sucked and supplied to the cylinder during the intake stroke due to the pressure difference between the intake pressure P1 and the cylinder pressure P2, so the present invention The purpose of this is to calculate fuel amount and injection timing at the initial stage of engine acceleration later than during the mid- and late-acceleration stages. , the amount of fuel injection corresponds well to the amount of intake air when supplied to the cylinder, ensuring a good combustion state of the air-fuel mixture, and thus effectively suppressing acceleration shock caused by poor combustion at the beginning of acceleration. The purpose is to improve acceleration performance.

(Means for solving the problem) In order to achieve the above object, the solving means of the present invention is as follows.
As shown in the figure, the fuel injection means 9 injects fuel into the intake passage 5 of the engine 1, and the fuel injection means 9 is controlled to calculate and inject the amount of fuel to the engine 1 in synchronization with the intake stroke of the cylinder. The present invention is directed to a fuel control device for an engine equipped with an injection control means 25 that performs the following steps. Acceleration detection means 26 detects when the engine 1 accelerates; intake pressure detection means 17 detects the intake pressure of the engine 1; and both detection means 2
6. In response to the output of 17, when the engine 1 accelerates, the fuel amount calculation timing and injection timing are advanced, and when the intake pressure changes by more than the set value when the engine 1 accelerates, the fuel amount calculation timing and injection timing are changed as described above. A correction means 27 is provided for correcting the fuel amount calculation timing and injection timing of the injection control means 25 so that they are later than the earlier calculation timing and injection timing.

(Function) With the above configuration, in the present invention, basically, the injection control means 25 calculates the amount of fuel in synchronization with the intake stroke of the cylinder, and this amount of fuel is injected from the fuel injection means 9.

Therefore, when the engine 1 accelerates, in the middle and late stages,
The amount of fuel to be supplied to each cylinder increases in accordance with the increase in the amount of intake air, but the calculation timing of the fuel amount and the injection timing in the injection control means 25 are corrected by the correction means 27, so that the amount of fuel to be supplied to each cylinder increases compared to during steady operation. Since the combustion speed is faster, all the fuel amount necessary for good combustion of the air-fuel mixture is supplied to the cylinder during the intake stroke, ensuring good combustion of the air-fuel mixture, and no misfire occurs.

In addition, at the beginning of acceleration, the amount of intake air changes greatly, and at the calculation timing and injection timing of the fuel amount in the middle and late stages of acceleration, the calculated amount of fuel is actually supplied to the cylinder during the intake stroke. However, at the beginning of this acceleration, the calculation timing of the fuel amount and the injection timing are determined by the correction means. 27 is corrected later than in the middle and late stages of acceleration, the calculated fuel amount almost matches the required fuel amount, and at the time when the cylinder enters the intake stroke, the in-cylinder pressure and the intake pressure of the engine 1 are A pressure difference is generated between the two, and with this pressure difference, the above amount of fuel is quickly sucked and supplied to the cylinder during the intake stroke, ensuring good combustibility of the air-fuel mixture, and reducing acceleration shock at the beginning of acceleration. effectively suppressed. Therefore,
Acceleration performance will be improved.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 schematically shows the overall configuration of the engine fuel control system according to the present invention, in which 1 is a four-cylinder engine, 2 is a combustion chamber whose volume is variable by a piston 4 fitted into a cylinder 3 of the engine 1, and 5 is a combustion chamber having a variable volume. 7 has one end that communicates with the atmosphere via the air cleaner 6, and the other end that branches into four and opens into the combustion chamber 2 of each cylinder to supply intake air. This is an exhaust passage that opens into the combustion chamber 2 and has its other end open to the atmosphere to discharge exhaust gas.In the middle of the intake passage 5, there is a throttle valve 8 for controlling the amount of intake air.
A fuel injection valve 9 as a fuel injection means for injecting and supplying fuel to the engine 1 is disposed on the downstream side thereof and on the upstream side of a branch part to each cylinder.

An intake valve 1 is provided at the opening of the intake passage 5 to each combustion chamber 2.
0, and an exhaust valve 1 is installed at the opening of the exhaust passage 7 to each combustion chamber 2.
At the top of each combustion chamber 2, an ignition plug 12 for igniting the air-fuel mixture in the combustion chamber 2 is disposed.

Further, in the same figure, reference numeral 15 denotes an air flow sensor that detects the amount of intake air on the upstream side of the throttle valve 8 in the intake passage 5;
6 is an opening sensor that detects the opening of the throttle valve 8; 17;
is an intake pressure sensor serving as an intake pressure detection means for detecting the intake pressure (intake negative pressure) of the engine 1 on the downstream side of the throttle valve 8 of the intake passage 5 and on the upstream side of the branching part, and each of the sensors 15 to 18 The detection signals are input to the CPU 22 via the I10 boat 21 of the controller 20, which controls the amount of fuel from the fuel injection valve 9 and its injection timing. The controller 20 also includes a RAM.
A memory 23 including ROM and ROM is built-in. The memory 23 stores in advance the timing of fuel injection from the fuel injection valve 9, and the ignition order of the air-fuel mixture is the first one.
= 3rd = 4th = 2nd cylinder, then the first 2
The cylinders (first and third cylinders) inject fuel during the intake stroke of the first cylinder, and the latter two cylinders (fourth and second cylinders) inject fuel during the intake stroke of the fourth cylinder. The cylinders are grouped and fuel is injected in synchronization with the intake stroke of each cylinder. In particular, the fuel injection timing is set and stored according to the engine speed as shown in FIG. In the middle and late stages of acceleration, as shown by the broken line in the figure, the timing is set earlier than during steady operation of the engine 1, and in the early stage of acceleration, as shown by the solid line in the figure, the injection timing in the middle and late stages of acceleration is set. The timing is set later than the specified timing.

Next, the fuel injection control of the fuel injection valve 9 by the controller 20 will be explained based on the control flows shown in FIGS. 3 to 5.

First, starting from the main flow shown in FIG. 3, in step S1, it is determined whether or not the engine 1 is accelerating based on the rate of change in the opening of the throttle valve 8 from the opening sensor 16. In step S2, the routine proceeds to a determination routine for determining the increase in intake pressure during the intake stroke of the cylinder as shown in FIG. The process proceeds to an execution routine to perform fuel injection control, and in step S4, processes other control processing routines (not shown), and then returns.

Next, in the routine for determining the increase in intake pressure during the intake stroke of the cylinder shown in FIG. Estimate the intake pressure value P1 at the time of the intake stroke, and use this predicted intake pressure value P1 as
It is compared with the intake pressure value P1° at the previous fuel injection timing detected by the intake pressure sensor 17, and the difference (P+ -
When Plo) is less than the minimum value α (P+ −P+ °≦α), it is determined that the acceleration is in the middle or late stage, and the determination flag KFL is set.
AG -1 is set, while when P, -P, °>α, it is determined that this is the initial stage of acceleration where the intake pressure increases, the determination flag is set to KFLAG -0, and the process returns.

Subsequently, in the fuel injection execution routine shown in FIG.
The value of LAG is determined, and in the middle and late stages of acceleration of KFLAG -1, it is determined in step SF2 whether or not the fuel injection timing is in the middle and late stages of acceleration as shown by the broken line in FIG. 6, and only at this injection timing. In step SF4, the intake air amount to the engine 1 is calculated based on the detection signal of the air flow sensor 15, and in step SF5, the required fuel amount ( After that, in step SF6, the fuel injection valve 9 is controlled to execute fuel injection to inject this amount of fuel, and the process returns.

On the other hand, in step SFI above, the determination flag KFLAG-0
In the case of the initial acceleration of , in step SF3, the sixth
It is determined whether or not the fuel injection timing is at the early stage of acceleration, which is shown by the solid line in the figure, and only at the fuel injection timing at the early stage of acceleration, the amount of intake air to the engine 1 is adjusted in steps SF4 to SF6 in the same way as above. At the same time, the necessary fuel amount (fuel injection pulse width) corresponding to this intake air amount is calculated, the fuel injection valve 9 is controlled to inject this fuel amount, and the process returns.

Therefore, the fuel injection execution routine (step SF
1, SFJ to 5F6), the four cylinders of engine 1 are divided into two groups, and in synchronization with each intake stroke of the predetermined cylinders (first cylinder and fourth cylinder) of each group, An injection control means 25 is configured to control the fuel injection valve 9 to calculate and inject the amount of fuel to the engine 1.

Further, in step S1 of the control flow shown in FIG. 3, the acceleration detection means 26 is configured to detect the acceleration of the engine 1 based on the rate of change in the opening of the throttle valve 8 detected by the opening sensor 16. There is.

Furthermore, the routine for determining the increase in intake pressure during the intake stroke of the cylinder shown in FIG. 4 and step SF2 of the fuel injection execution routine shown in FIG. Acceleration detection means 2 by SF3
6 and the intake pressure sensor 17, when the engine 1 is accelerating, the calculation timing and injection timing of the fuel m to be supplied are set to the fuel injection timing characteristics shown by the broken line in FIG. In addition to setting the fuel amount calculation timing and injection timing earlier than usual, when the intake pressure P1 of the engine 1 changes by more than the set value α during engine acceleration (that is, at the beginning of acceleration), the fuel amount calculation timing and injection timing are set as shown by the solid line in Fig. 6. , a correction means 27 is configured to correct the fuel amount calculation timing and injection timing of the injection control means 25 so as to be later than the fuel amount calculation timing and injection timing indicated by the dashed line in the figure, which have been advanced. .

Therefore, in the "-2 embodiment, one cylinder group (
During the intake stroke of the first cylinder (first and third cylinders), the amount of fuel required for both cylinders is calculated by the injection control means 25, and the fuel injection valve 9 is controlled to inject this amount of fuel. , the fourth cylinder of the other cylinder groups (second and fourth cylinders)
During the intake stroke of the cylinder, the amount of fuel required for this rain cylinder is calculated by the injection control means 25, and the fuel injection valve 9 is controlled to inject this amount of fuel.

Therefore, when the engine 1 accelerates, the required amount of fuel increases as the amount of intake air increases, but with the same fuel amount calculation timing and injection timing as during steady operation, all of the increased required fuel amount is consumed by the intake air. As shown in Figure 7 (a), as the amount of fuel is insufficient because it is not inhaled into the cylinder during the stroke, the cylinder that undergoes the intake stroke for the first time after fuel injection (the first cylinder in the figure) suffers from poor combustion of the air-fuel mixture. However, according to the present invention, as shown in FIG. Since the timing characteristics are set to the timing characteristics shown by the dashed line, the timing is set earlier than during steady operation, so the entire required amount of injected fuel is supplied to the cylinder during the intake stroke.
There is no shortage of fuel, a good combustion state of the air-fuel mixture is ensured, and misfires are reliably prevented.

Moreover, at the early stage of acceleration, as shown in FIG. When calculating and injecting the amount of fuel based on the amount calculation timing and injection timing, as shown in the same figure (b), the amount of fuel is determined based on the amount of intake air at the time when fuel is actually supplied to the cylinder during the intake stroke. In the cylinder (the fourth cylinder in the figure) that undergoes the intake stroke for the first time after this initial acceleration, poor combustion of the air-fuel mixture occurs. However, in this early stage of acceleration, as shown in the same figure (c), the intake negative pressure (intake negative pressure) P+
On the other hand, in the cylinder (fourth cylinder) that undergoes the intake stroke for the first time after the initial stage of acceleration, the cylinder pressure P2 suddenly increases in response to the downward movement of the piston 4 during the intake stroke, as shown in Fig. 8 (a). This pressure difference (PHP2) causes the fuel injected from the fuel injection valve 9 to be quickly sucked into the cylinder during the intake stroke. Now, when supplying fuel to the cylinder (fourth cylinder) that undergoes the intake stroke for the first time after the initial stage of acceleration, the calculation timing of the fuel amount and the injection timing are set by the correction means 27 to the timing characteristics shown by the solid line in FIG. 6, It is corrected more slowly than those in the middle and late stages of acceleration.

As a result, the calculated amount of fuel almost corresponds to the amount of intake air at the time when it is actually taken into the cylinder, and all of this amount of fuel corresponds to the pressure difference (P+-P2
), the air is quickly drawn into the cylinder (fourth cylinder) undergoing the intake stroke, ensuring good combustion of the air-fuel mixture and effectively suppressing acceleration shock at the beginning of acceleration due to poor combustion. Therefore, during acceleration, a good combustion state of the air-fuel mixture can be ensured regardless of whether it is in the early, middle, or late stages of acceleration, so it is possible to effectively suppress acceleration shock in the early stages of acceleration and improve acceleration performance. .

In the above embodiment, fuel is calculated and injected during the intake stroke of each cylinder group, but fuel injection valves are provided for each cylinder, and fuel is injected during the intake stroke of each cylinder. Of course, the present invention can also be similarly applied to a configuration in which the amount of fuel from a corresponding fuel injection valve is calculated and injected.

(Effects of the Invention) As explained above, according to the engine fuel control device of the present invention, when fuel is continuously injected in synchronization with the intake stroke of the cylinder, when the engine accelerates, it is possible to The fuel amount calculation timing and injection timing are advanced from those during steady operation to supply the entire required amount of fuel to the cylinder during the intake stroke, and at the beginning of acceleration when the intake air amount increases and changes, the earlier fuel amount is The calculation timing and the injection timing are set later than the calculation timing and the injection timing, so that the amount of fuel corresponds well to the amount of intake air when being supplied into the cylinder during the intake stroke,
The entire amount of fuel is quickly sucked and supplied to the cylinder by the pressure difference between the in-cylinder pressure and the intake pressure in the cylinder during the intake stroke.

It is possible to ensure good combustibility of the air-fuel mixture not only in the later stages but also in the early stages of acceleration, and it is possible to effectively suppress acceleration shocks in the early stages of acceleration, thereby improving acceleration performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. Figures 2 to 8 show embodiments of the present invention, Figure 2 is a general schematic diagram, Figures 3 to 5 are flowcharts showing fuel injection control, and Figure 6 is an initial stage of acceleration and acceleration. Figures 7(a) to 7(c) and 8(a) and 8(b), which show the fuel injection timing characteristics in the middle and later stages, are operation explanatory diagrams. DESCRIPTION OF SYMBOLS 1... Engine, 5... Intake passage, 8... Throttle valve, 9... Fuel injection valve, 15... Air flow sensor, 17... Intake pressure sensor, 20... Controller, 25 ... injection control means, 26 ... acceleration detection means, 27 ... correction means. Patent applicant Mazda Corporation.

Claims (1)

[Claims] (1) A fuel injection means for injecting fuel into the intake passage of the engine; and an injection control means for controlling the fuel injection means to calculate and inject the amount of fuel to the engine in synchronization with the intake stroke of the cylinder. A fuel control device for an engine, comprising:
an acceleration detection means for detecting when the engine is accelerating; an intake pressure detection means for detecting the intake pressure of the engine; receiving the outputs of both the detection means, and advancing the fuel amount calculation timing and injection timing when the engine is accelerating; When the intake pressure changes by more than a set value during engine acceleration, the injection control means controls the fuel amount calculation timing and injection timing so that the fuel amount calculation timing and injection timing are later than the aforementioned earlier calculation timing and injection timing. 1. A fuel control device for an engine, comprising: a correction means for correcting timing.