JPH076436B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection control device for an internal combustion engine having a fuel injection valve for each cylinder.

(Prior Art) As a conventional device of this type, for example, JP-A-56-54929 is known.
As described in the publication, the fuel injection valve attached to each branch of the intake manifold of the engine is opened immediately before the intake stroke of the corresponding cylinder to inject fuel according to the engine demand. Known devices are

However, in such a device, since each fuel injection valve is opened and closed by one pulse signal synchronized with the rotation of the engine,
Under a condition where the engine is at a relatively low speed and a low load and the fuel injection amount is small, that is, when the fuel injection engine is relatively short, a good fuel supply can be obtained, but the fuel injection engine becomes longer as in the high speed and high load region and the fuel injection valve If the valve opening times of are overlapped, it is difficult to control the opening and closing of them accurately.

Therefore, under operating conditions in which the fuel injection engine is lengthened to some extent, it is considered that all fuel injection valves are simultaneously opened every injection of the engine to inject fuel all at once.

In this case, each fuel injection valve injects half the required amount of fuel for each revolution of the engine.

(Problems to be Solved by the Invention) However, this causes the following problems when switching from sequential injection in which fuel is sequentially injected to each cylinder to simultaneous injection.

FIG. 8 shows the injection timing in a 4-cylinder engine. In sequential injection, fuel is injected from the fuel injection valve immediately before the intake stroke in accordance with the ignition order of each cylinder # 1 to # 4. Simultaneous injection enters each cylinder #
When fuel is injected simultaneously in 1 to # 4, for example, in the cylinder # 1 in which the fuel is injected at the end of the sequential injection, the injection is continuously performed, so the fuel becomes excessive.

Further, in the simultaneous injection, half of the required fuel amount is injected at every crank angle of 360 °, so that only half the fuel is supplied to cylinder # 3 where the intake stroke comes immediately after the simultaneous injection,
As a result, normal fuel is lost during the switching transition.

(Means for Solving Problems) This invention, as shown in FIG. 1, includes fuel injection valves A to D for each cylinder, a means E for detecting a rotation angle of the engine, and an operation of the engine. Means F for detecting conditions, and a sequential injection drive circuit G for sequentially injecting fuel from the fuel injection valve in accordance with the ignition order of each cylinder based on these detection signals.
And a simultaneous injection drive circuit H that simultaneously injects fuel from each of the fuel injection valves at a predetermined rotational speed under a predetermined operating condition in stead of the sequential injection, and at the same time, in a fuel injection control device for an internal combustion engine, Means I for determining the fuel injection period
And means J for instructing the corresponding drive circuits to perform sequential injection immediately when the fuel injection period is shorter than a predetermined value, and to perform simultaneous injection immediately when the fuel injection period is longer than a predetermined value.
When switching from sequential injection to simultaneous injection, an injection amount reduction circuit K that reduces the injection amount of the fuel injection valve that performs injection immediately before simultaneous injection and a fuel injection valve for the cylinder that has an intake stroke immediately after simultaneous injection are provided. An injection amount increasing circuit L for increasing the injection amount only once is provided.

The fuel injection period means the fuel injection amount, and is typically represented by the fuel injection pulse width calculated based on the operating condition signals such as the engine speed and the intake air amount.

(Operation) Therefore, when switching from the sequential injection to the simultaneous injection, the fuel is excessive in the cylinder where the fuel is injected at the end of the sequential injection, or the fuel is insufficient in the cylinder in which the intake stroke comes immediately after the simultaneous injection. Therefore, a proper amount of fuel can always be supplied, and stable combustion can be maintained even during a transitional transition.

(Embodiment) FIG. 2 is a control block diagram showing an embodiment in which the present invention is applied to a four-cylinder engine. 1 is an air flow meter for detecting the intake air amount of the engine, and 2 is a crank angle for detecting the rotation angle of the engine. Sensors, 3 are control circuits, and A to D are fuel injection valves installed in each branch of the intake manifold.

The 720 ° signal (cylinder discrimination signal), 180 ° signal (reference angle signal) and 2 ° signal (unit angle signal) output from the crank angle sensor 2 are the CPU of the control circuit 3 together with the intake air amount signal from the air flow meter 1. (Arithmetic circuit) 4 is sent.

Based on these signals and the program stored in the ROM (memory) 5, the CPU 4 determines whether the operating conditions are sequential injection or simultaneous injection, and determines the fuel injection amount and fuel injection timing required for the engine. Is calculated and each control signal is output.

A binary-decimal converter 6 converts the sequential signals D ₀ and D ₁ input from the CPU 4 at every crank angle of 180 °, and sequentially outputs high level [1] from the output side as shown in FIG. And a signal for switching to low level [0] is generated.

The OR circuit (OR circuit) 7 sequentially opens the gates in accordance with the signal from the binary-decimal converter 6, and when the simultaneous injection signal D ₂ is input from the CPU 4, all the gates are opened.

The AND gate 8 is opened by the ejection pulse signal T sent from the CPU 4 while the gate of the OR circuit 7 is opened, and the ejection pulse signal T is opened and closed by the power transistors 9 to. Output to 12.

In the case of sequential injection, the CPU 4 outputs the injection pulse signal T ₁ having a width corresponding to the required fuel amount immediately before the intake stroke of each cylinder, and the corresponding fuel injection valves A to D via the power transistors 9 to 12.
Are opened and closed sequentially.

In the case of simultaneous injection, the CPU 4 sends the simultaneous injection signal D ₂ to the OR circuit 7.
And an injection pulse signal T ₂ having a width half the required fuel amount is output immediately before a predetermined intake stroke for each engine revolution,
The fuel injection valves A to D are simultaneously opened and closed.

When switching from the sequential injection to the simultaneous injection, the CPU 4 first sets the width of the injection pulse signal T ₁ output to the AND circuit 8 to half in the state of the sequential injection, and opens the fuel injection valve to be the final sequential injection. Reduce valve time.

For example, if an attempt is made to switch to simultaneous injection after the injection by the fuel injection valve A is completed, in sequential injection, the gate of the OR circuit 7 is switched in accordance with the output of the binary-decimal converter 6, and then the fuel injection valve B. However, the valve opening time of the fuel injection valve B is halved.

After this, when the output of the binary-decimal converter 6 is further switched to the injection timing of the fuel injection valve C, the CPU 4 outputs the injection pulse signal T ₂ having a half width and the simultaneous injection to the OR circuit 7. The signal D ₂ is output and the fuel injection valves A to D are simultaneously opened and closed.

Then, after this injection, the CPU 4 blocks the simultaneous injection signal D ₂ until the output of the binary-decimal converter 6 is switched, and in response to the completion of the injection, the single pulse signal T of half the width is also provided. ₃
Is output, and in this case, the fuel injection valve C is opened and closed again.

When this opening and closing is completed, the above-mentioned simultaneous injection for every one revolution of the engine is performed thereafter.

Next, the operation will be described based on the flowcharts of FIGS. 4 and 5.

The injection cylinder counter COUNT1 is incremented (the value is 0 to 3) in S1 due to the interruption every 180 ° of the crank angle, and the width of the injection pulse signal T with respect to the engine 1/4 rotation cycle has hysteresis in S2. It is compared with the predetermined values K ₁ and K ₂ considered, and when the width of T is small, the sequential injection routine of S3 and S4 is started.

In S3, the injection pulse signal T is selected as it is, and in S4, flags F1 = 1, F2 = 0, and F3 = 1 of the injection execution flow (not shown) are selected.

However, F1: 1 successively jetting 0 coinjected F2: 1 successively → coinjected into switching 0 sequentially or simultaneously injected F3: therefore without 1 injection execution 0 injection, a crank in accordance with the injection pulse signal T ₁ and F1, F2, F3 The fuel injection valves A to D are sequentially opened and closed at every angle of 180 °, and the required amount of fuel is injected into each cylinder immediately before the intake stroke.

In S5, the injection cylinder is set to COUNT1.

When the width of the injection pulse signal T with respect to the engine 1/4 rotation cycle from this sequential injection becomes larger than the predetermined values K ₁ and K ₂ , the reduction routine from S2, S6 to S7 to S9 is started.

In S7, the width of the injection pulse signal T is reduced (in the case of FIG. 2
K ₃ = 0.5) and the flags F1 = 0, F2 = 1 and F3 = 1 are selected in S8.

Therefore, the fuel injection valve that is opened and closed at this time has a short width of the injection pulse signal T ₁ , so that the valve opening time is shortened and the injection amount is reduced.

In S9, the interrupt injection cylinder is stored in COUNT2, that is, the fuel increase cylinder is set to the cylinder at the next 180 ° interruption.

When the next 180 ° interrupt is entered, since F1 = 0 at this time, the simultaneous injection routine from S6 to S10 to S14 is started.

At the beginning of this routine, F3 = 1, and the width of the injection pulse signal T is set to half in S11. Also, in S12, F1 = 0, F
3 = 0 is selected and the injection cylinders are set to all cylinders in S13.

Therefore, the injection pulse signal T ₂ is sent to all the fuel injection valves A to D by the 180 ° interruption, and the simultaneous injection is performed.

Upon completion of this injection, the injection end interrupt shown in FIG. 5 is entered. Since F2 = 1 at this time, the routine advances from U1 to U2 to U4.

Half the width of U2 in T (the case of FIG. 2 K ₅ = 0.5) of the injection pulse signal T ₃ is selected, sets the injection cylinder in COUNT2 in U3.

Therefore, after the end of the injection, the injection pulse signal T ₃
Only the fuel injection valve of the cylinder determined in S9 is opened again, and the fuel amount is increased.

Further, in U4, it switches to F2 = 0 so as to end this interrupt injection.

After this, when the next 180 ° interrupt is entered, the process proceeds from S10 to S14 in the simultaneous injection routine of FIG. 4, and when another 180 ° interrupt is entered, the process proceeds from S10 to S1 to S13.

As a result, all the fuel injection valves A to D are opened and closed immediately before the intake stroke of the predetermined cylinder for each engine revolution, and the simultaneous injection is performed.

A timing chart when switching from this sequential injection to the simultaneous injection is shown in FIG. 6, and therefore, the fuel is excessive in the cylinder (for example, # 1) where the fuel is injected at the end of the sequential injection, The fuel is not denied in the cylinder (# 3) where the intake stroke comes immediately after the simultaneous injection, and the required amount of fuel can always be supplied.

As a result, normal combustion can be maintained in each cylinder even during switching, torque fluctuations, etc. can be prevented, and good drivability can be ensured particularly when shifting from low speed low load to high speed high load.

FIG. 7 is a timing chart showing another embodiment of the present invention. Instead of the sequential injection, the cylinders # 1 to # 4 are arranged in groups of cylinders # 1 and # 2 and cylinders # 3 and # 4 having a close intake stroke. In this example, the fuel injection is performed for each group at a predetermined timing.

This group injection is performed once every two revolutions of the engine, but when switching to injection at the same time, the injection amount by the last group injection is reduced by a predetermined amount as in FIG. 6, and after the simultaneous injection, the injection on the other group side is performed. The amount is increased by a predetermined amount.
In this case, the reduction rate and the increase rate of the injection amount may be small.

As described above, according to the present invention, the sequential injection and the simultaneous injection are immediately switched based on the fuel injection period, while the sequential injection and the simultaneous injection are switched immediately before the simultaneous injection. In addition to reducing the injection amount of the fuel injection valve that injects into the cylinder, the injection amount of the fuel injection valve of the cylinder in which the intake stroke arrives immediately after the simultaneous injection is increased only once. Even if there is, the excess and deficiency of the fuel amount due to the switching from the sequential injection to the simultaneous injection can be surely compensated to maintain an appropriate air-fuel ratio, and thereby an effect that a good combustion state can be maintained can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a control block diagram of an embodiment, FIG. 3 is a table showing the functions of a binary-decimal converter, FIGS. 4 and 5 are flowcharts, and FIG. FIG. 6 is a timing chart, FIG. 7 is a timing chart of another embodiment, and FIG. 8 is a conventional timing chart. 1 ... Air flow meter, 2 ... Crank angle sensor, 3
...... Control circuit, 4 ... CPU, 5 ... ROM

Claims (1)

[Claims] 1. A fuel injection valve is provided for each cylinder, and means for detecting a rotation angle of the engine, means for detecting an operating condition of the engine, and a means for detecting the operating condition of the engine from the fuel injection valve to each cylinder are provided. A sequential injection drive circuit for sequentially injecting fuel in accordance with the ignition order, and a simultaneous injection drive circuit for injecting fuel simultaneously from the fuel injection valve at predetermined rotational speeds in each cylinder simultaneously under predetermined operating conditions instead of this sequential injection In a fuel injection control device for an internal combustion engine, the means for determining a fuel injection period and sequential injection immediately when the fuel injection period is shorter than a predetermined value, and simultaneous injection immediately when the fuel injection period is longer than the predetermined value. And a means for instructing the corresponding drive circuits, and an injection amount reduction for reducing the injection amount of the fuel injection valve that performs injection immediately before simultaneous injection when switching from sequential injection to simultaneous injection by a predetermined amount. Road and, a fuel injection control apparatus for an internal combustion engine, characterized by comprising the injection amount increasing circuit for a predetermined amount increasing one-time injection amount of the fuel injection valve in the intake stroke comes cylinder immediately after the simultaneous injection.