JPH01151748A - Electronic control fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To optimize setting of a fuel injection timing in a low speed region, to enable completion of injection of fuel at a given timing, and to prevent worsening of combustibility, by a method wherein, in a given low speed region, a fuel injection time is set at a comparatively short period based on an engine running state. CONSTITUTION:A period varying injection timing computing means B inputs an output signal from a engine running state detecting means A to detect an engine running state. The period varying injection timing computing means computes a fuel injection time in the low speed region of the rotation speed of an engine at a time period comparatively shorter than that in other speed region based on an engine running state. In which case, a fuel injection means D is controlled by an injection starting control means C based on a computed latest fuel injection time so as to start injection of fuel at each cylinder so that injection of fuel is completed at a given fuel injection completion timing. An injection stop control means E is provided for correcting a given fuel injection completion timing according to a latest injection time after control of the starting of injection and stopping injection of fuel at an injection completion timing after correction.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Fields> The present invention provides a system for independently driving and controlling fuel injection means provided for each cylinder of an internal combustion engine. The present invention relates to an electronically controlled IT fuel injection device of a so-called sequential injection type that performs fuel injection in synchronization with the intake stroke of a corresponding cylinder.

<Prior Art> Conventionally, as this type of electronically controlled fuel injection device, there is one described, for example, in Japanese Patent Application Laid-Open No. 59-29733.

This is based on the operating state of the engine so that the end timing of fuel injection by the fuel injection valve provided for each cylinder is at a predetermined crank angle (for example, the opening timing of the intake valve) in accordance with the intake stroke of each cylinder. In this system, the injection start timing is variably controlled by calculating backward from the fuel injection amount (injection time) calculated every predetermined minute time, so that optimal combustion can be obtained.

In addition, in injection control in which the injection start timing is variably controlled so that the end timing of fuel injection is at a predetermined crank angle, if the required fuel amount increases and changes after injection starts under acceleration driving conditions, etc. In addition, if the injection ends at the expected end time, there will be a fuel shortage.
In order to eliminate this response delay in fuel control, as shown in FIG. 6, the injection end timing is delayed from the desired timing (target injection end timing) according to the fuel injection ITi set after the start of injection. There are some types that can respond to changes in the required fuel amount after the start of injection.

That is, in FIG. 6, at the timing to set the injection start time, the fuel injection amount Ti is set every 10 m5.
was Tio+, but the fuel injection amount Ti increased to T i (4) by the target injection end time, so
T from the injection start time set based on T i (,)
The injection end timing is delayed until the injection end time corresponding to i(,).

<Problems to be Solved by the Invention> By the way, as mentioned above, in order to cope with changes in the required fuel amount after the start of injection, the injection is ended after being extended from the intended end time. In this case, although it is possible to respond to changes in the required amount of fuel, the actual injection end time is significantly delayed and combustion occurs even though injection is originally set to end at a predetermined end time to obtain a good combustion condition. I was used to my sexuality getting worse.

This is a relatively long calculation cycle (for example, 10a +
This is because the fuel injection amount is calculated every s), so during acceleration, the calculated fuel injection amount shows large changes step by step over a relatively long cycle.

The present invention has been made in view of the above problems, and it is an object of the present invention to improve combustibility by reducing the length of time during which the injection end timing is extended due to changes in the required fuel injection amount after the start of injection.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. In an electronically controlled fuel injection device for an internal combustion engine that performs injection, the engine operating state detection means detects the engine operating state including the engine rotational speed, and the engine operating state detection means detects the engine operating state including the engine rotational speed and compares the engine rotational speed in a predetermined low speed region with other speed regions. a periodic variable injection time calculating means for calculating a fuel injection time based on the engine operating state detected by the engine operating state detecting means in a short time period; injection start control means for starting fuel injection by the fuel injection means for each cylinder in order to end fuel injection at a predetermined fuel injection end time based on the injection start control means; and the periodic variable injection time calculation means after injection start control by the injection start control means. Injection stop control that sets an injection end time by correcting the predetermined fuel injection end time according to the latest fuel injection time calculated in , and stops fuel injection by the fuel injection means for each cylinder at this injection end time. We decided to provide means and.

<Function> Here, the periodic variable injection time calculation means controls the fuel injection time based on the engine operating state detected by the engine operating state detecting means in a relatively short period in a predetermined low speed region where the microcomputer has sufficient processing capacity. The injection time (fuel injection amount) is set, and since there is no margin in the processing capacity of the microcomputer in a high speed range other than the predetermined low speed range, the fuel injection time is set at a relatively long cycle.

The injection start control means controls each fuel injection by the fuel injection means to end the fuel injection at a predetermined fuel injection end time based on the latest fuel injection time calculated as described above by the periodic variable injection time calculation means. Start each cylinder,
The injection stop control means corrects the predetermined fuel injection end time according to the latest fuel injection time to set the injection end time, and stops the fuel injection by the fuel injection means for each cylinder at this injection end time.

<Example> An embodiment of the present invention will be described below based on the drawings.

In FIG. 2, an engine 1 includes an air cleaner 2° intake duct 3. Air is drawn in via the throttle chamber 4 and the intake manifold 5.

The throttle chamber 4 is provided with a throttle valve 6 that operates in conjunction with an accelerator pedal (not shown) to control the intake air flow rate Q.

The intake manifold 5 or the intake boat of the engine 1 is provided with a fuel injection valve 7 as a fuel injection means for each cylinder. The fuel injection valve 7 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped. Fuel that is pressure-fed from the fuel pump and adjusted to a predetermined pressure by a pressure regulator is injected and supplied to the engine l.

The control unit 8 receives output signals from various sensors, determines the fuel injection amount Ti using a built-in microcomputer, and injects fuel at a predetermined timing according to the intake stroke of each cylinder using a drive pulse signal with a corresponding pulse width. Output to valve 7.

As the various sensors mentioned above, an air flow meter 9 is provided in the intake duct 3 and outputs a signal corresponding to the intake air flow rate Q. In addition, a crank angle sensor 10 is provided, such as built into a distributor (not shown), and outputs a position signal every 16 or 2" and a reference signal every 90 degrees. 2. The engine rotational speed N can be calculated by measuring the number of position signals generated or the cycle of the reference signal at Outputs the corresponding signal.

Further, a water temperature sensor 12 is provided in the water jacket of the engine l, and outputs a signal according to the cooling water temperature Tw. Furthermore, the voltage of a battery 13 is applied to the control unit 8 via an engine key switch 14 as its operating power source and for detecting the power supply voltage. Here, the air flow meter 9. Crank angle sensor 10.
The water temperature sensor 12 and the like correspond to the engine operating state detection means in this embodiment.

In this embodiment, the control unit 8 also functions as a periodic variable injection time calculation means, an injection start control means, and an injection stop control means.

Next, the fuel injection control by the microcomputer in the control unit 8 will be explained according to the flowcharts shown in FIGS. 3 to 5.

The routine shown in the flowchart of FIG. 3 is a routine for outputting an instruction to calculate the fuel injection amount Ti.
Executed every +ms.

In step (r3J in the figure, the same applies hereinafter) 1, based on the engine rotational speed N calculated based on the signal from the crank angle sensor IO, the operating state is determined to be within a predetermined low speed region. Determine whether

Then, when the speed is within a predetermined low speed region, the process proceeds to step 2, and by counting a 5 ms cycle in step 2, the process proceeds to step 4 every 5 ms. On the other hand, if the current operating state is not included in the predetermined low speed region, the process proceeds to step 3, and in step 3,
By counting the ha period, the process proceeds to step 4 every 10a+s.

In step 4, a Ti calculation command is output to execute the fuel injection amount (fuel injection time) calculation routine shown in the flowchart 1 of FIG.

That is, in a predetermined low speed region where the engine rotational speed N is below a predetermined value, the microcomputer has sufficient processing capacity to calculate the fuel injection amount Ti every 5+ss, and in a high speed region, the microcomputer's processing capacity Since there is no margin for this, the fuel injection amount TI is calculated every 5 cycles of 10 m.

The routine shown in the flowchart of FIG. 4 is a fuel injection amount calculation routine as described above, and is executed every time a calculation command is output in step 4.

In step 11, the intake air flow rate Q, engine rotational speed N, etc. detected by each sensor are read.

In step 12, the basic fuel injection amount Tp is determined based on the intake air flow rate Q and engine rotational speed N input in step 11.
(←KXQ/N; is a constant).

In step 13, various correction coefficients C0EF are mainly set based on the cooling water temperature Tw etc. detected by the water temperature sensor 12, and changes in the injection amount (effective valve opening time) of the fuel injection valve 7 based on voltage changes of the battery 13 are adjusted. A voltage correction numerator s for correction is set.

In step 14, the air-fuel ratio feedback correction coefficient LAMBDA is set in a separate routine that is omitted in this embodiment.
Read this air-fuel ratio feedback correction coefficient LAMB
DA is for correcting the basic fuel injection amount Tp so that the air-fuel ratio of the engine intake air-fuel mixture detected by an oxygen sensor installed in the exhaust system approaches the target air-fuel ratio, and is performed by proportional-integral control. Set.

In step 15, the basic fuel injection tTp is corrected by the various correction coefficients C0EF, the voltage correction numerator s, and the air-fuel ratio feedback correction coefficient LAMBDA to obtain the final fuel injection amount Ti (4-TPXCOEFXLAMBD^+Ts
) is calculated.

The routine shown in the flowchart in Fig. 5 is for starting injection and
A stop timing setting routine in which the crank angle sensor 10
The reference every 90 degrees of crank angle is executed every time a lens signal is output.

In step 21, the latest fuel injection amount Ti calculated by the fuel injection amount calculation routine shown in the flowchart of FIG.
is converted into a crank angle based on the current engine rotational speed N.

Then, in the next step 22, the injection start timing or injection stop timing is set based on the crank angle corresponding to the latest fuel injection amount Ti converted in step 21. That is, when injection has not started in a specific cylinder, a predetermined injection end timing (for example, the opening crank angle position of the intake valve) is determined.
In order to end the fuel injection at a certain time, the injection start time is set by calculating backward from the predetermined injection end time, and when injection is started in a specific cylinder, the injection amount corresponding to the fuel injection amount Ti is calculated from the crank angle position of the injection start. The crank angle position after the crank angle is set as the injection end time.

In the next step 23, the injection start timing and injection stop timing set in step 22 are set in the output register,
When the crank angle position corresponds to the injection start time, the output of the drive pulse signal to the corresponding fuel injector 7 is started, and when the crank angle position corresponds to the injection stop time, the output of the drive pulse signal to the corresponding fuel injector 7 is started. Stop outputting the drive pulse signal.

Here, in the predetermined low speed region of the engine 1, the fuel injection amount TI is calculated at a shorter cycle than in other speed regions, so the injection start timing set in step 22 is determined based on the latest engine operating state. This is based on the fuel injection amount Tt that is set according to the fuel injection amount, and as a result, as shown in FIG. This is something that can be prevented. Therefore, combustibility can be improved particularly in low speed ranges including idling operation where stability of combustion is required, and drivability can be improved.

It should be noted that the calculation period (5a
+s, 10m5) is not limited to this, and it is clear that more optimal injection timing control can be achieved by shortening the calculation cycle to the maximum extent possible.

<Effects of the Invention> As explained above, according to the present invention, the calculation cycle of the fuel injection amount is made shorter in a predetermined low speed region than in other regions, so that the fuel injection timing can be adjusted in the low speed region. The settings are optimized, and fuel injection ends close to the desired injection end time even during acceleration, making it possible to avoid deterioration in combustibility and improve engine drivability. There is.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIGS. 3 to 5 are flow charts showing fuel injection control in the above embodiment, and FIG. The figure is a time chart showing the difference between conventional fuel injection control and the fuel injection control of the present invention. 1... Engine 7... Fuel injection valve 8... Control unit 9... Air flow meter 10.
...Crank angle sensor 12...Water temperature sensor Patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 5

Claims (1)

[Claims] In an electronically controlled fuel injection system for an internal combustion engine, each cylinder is equipped with a fuel injection means, and each fuel injection means injects fuel in synchronization with the intake stroke of the corresponding cylinder. an engine operating state detection means for detecting the engine operating state; and a variable injection time calculation means for calculating the fuel injection time based on the engine operating state at a shorter time period in a predetermined low speed region of the engine rotation speed than in other speed regions. and injection start control means for starting fuel injection by the fuel injection means for each cylinder in order to end fuel injection at a predetermined fuel injection end time based on the latest fuel injection time calculated by the periodic variable injection time calculation means. , after the injection start control by the injection start control means, the predetermined fuel injection end time is corrected according to the latest fuel injection time calculated by the periodic variable injection time calculation means to set the injection end time; An electronically controlled fuel injection device for an internal combustion engine, further comprising injection stop control means for stopping fuel injection by the fuel injection means for each cylinder.