JPS62247138A - Electronically controlled fuel injector for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the ratio of fuel to air from becoming too low and improve the accelerating property of an engine, by restricting the injected quantity of fuel, at the time of acceleration of the engine, below an upper limit higher than that to the injected quantity of fuel except at the time of acceleration of the engine. CONSTITUTION:In an electronically controlled fuel injector, a fuel injection valve D is regulated by a drive control means C depending on an injected quantity of fuel which is set by a setting means B on the basis of the output from a hot-wire flow meter A. A first upper limit memory means E for storing an upper limit to the injected quantity of fuel at the time of acceleration of an engine, and a second upper limit memory means F for storing an upper limit set to be lower than the former and used for the injected quantity of fuel except at the time of acceleration of the engine are provided. The memory means E or F is selected in terms of the result of detection by an accelerated state detection means D so that the upper limit stored by the selected memory means and the injected quantity of fuel set by the setting means B are compared with each other by a comparison means G. When the set injected quantity of fuel has exceeded the upper limit, the drive control means C is operated by a restriction means H depending on the upper limit stored by the selected memory means.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electronically controlled fuel injection device for an internal combustion engine.

<Prior art> Examples of conventional electronically controlled fuel injection devices for internal combustion engines include the following (Japanese Patent Application Laid-Open No. 59-49334).
(Refer to the publication number, etc.)

That is, a signal (for example, voltage) output from an intake air flow rate detection device such as a hot wire flowmeter in response to the intake air flow 1iQ.
The intake airflow IQ is determined in the control device based on .

Then, the basic fuel injection amount Tp (-KxQ
/N; K is a constant).

Furthermore, after calculating various correction coefficients C0EF according to engine operating conditions such as engine cooling water temperature and correction numerator s according to battery voltage, the fuel injection amount Ti (=T p x COE
F + T s ).

Here, based on the reference signal obtained from the crank angle sensor, the fuel injection valve is opened and driven to perform fuel injection in synchronization with the rotation of the engine with an injection pulse width of the fuel injection 1 Ti.

By the way, in an internal combustion engine, when an intake valve is closed when the opening degree of a throttle valve is large, a backflow or blowback of intake air generally occurs. When measuring the intake air flow rate with a hot-wire flowmeter, this blowback of the intake air is detected as the intake air flow rate, so the intake air flow rate is detected to be higher than the actual intake air flow rate by the amount of detected blowback. Based on this incorrect intake air flow rate detection result, more fuel is injected than necessary and the air-fuel ratio becomes ilA? There was a fear that this would worsen the exhaust properties and fuel consumption rate.

For this reason, conventionally the basic fuel injection amount (basic fuel injection amount)
An upper limit value is set for Tp, and correction control is performed so that the basic fuel injection rl T I) does not exceed this upper limit value.

To explain this upper limit correction based on the flowchart of FIG. 5, in step 1 (indicated as "S" in the figure, the same shall apply hereinafter), the intake air flow rate Q and engine rotational speed N are input, and in step 2, A basic fuel injection amount 'rp (=KXQ/N; K is a constant) is calculated from these values.

In step 3, the basic fuel injection amount Tp calculated in step 2 and the preset basic fuel injection [11 upper limit Tp
When Tp>Tpmax, that is, the calculated basic fuel injection rlj Tp is the upper limit Tp+
When it exceeds ma, proceed to step 4 and set the upper limit T.
If it is less than p nIax, the basic fuel injection amount Tp calculated in step 2 is returned as the set value.

In step 4, a preset upper limit value Tpmax is set as the basic fuel injection amount 'rp.

Here, the upper limit value Tpmax of the basic fuel injection 11 is:
It is set based on the amount of air taken in when the throttle valve is fully opened during steady operation, and is set to a value that will not be exceeded unless blowback is detected.

<Problems to be Solved by the Invention> By the way, in a fuel injection device of a so-called single point injection system in which a fuel injection valve is installed upstream of a throttle valve, a negative pressure state occurs on the downstream side of the throttle valve when the engine accelerates. The intake manifold (collector part) is filled with intake air before it is drawn into the cylinder, so the intake air flow rate at this time is larger than the intake air flow rate when the throttle valve is fully open during steady operation. There are times when it happens.

However, if correction control is performed so that the basic fuel injection amount Tp does not exceed the upper limit value Tpmax as described above, even though it is necessary to inject fuel to the intake air of this intake manifold filling bone, the upper limit value Since the fuel injection amount is regulated by the value T p max, there is a risk that the fuel injection amount will be insufficient and the air-fuel ratio will become too high, impairing the acceleration response of the engine.

The present invention has been made in view of the above conventional problems,
The purpose is to improve acceleration response while preventing excessive enrichment of the air-fuel ratio due to intake air blowback detection.

(Means for Solving the Problems) Therefore, in the present invention, as shown in FIG. Electronic control of an internal combustion engine in which a fuel injection amount is set by a fuel injection amount setting means based on the air flow rate, and the drive control means drives and controls the fuel injection valve according to the fuel injection amount set by the fuel injection amount setting means. The fuel injection device includes an engine acceleration state detection means for detecting an acceleration state of the engine, and a first engine that stores a preset upper limit value of the fuel injection amount at the time of engine acceleration.
an upper limit storage means; and a second upper limit storage storing an upper limit of the fuel injection amount at times other than when the engine is accelerating, which is preset to be smaller than the upper limit of the fuel injection amount stored in the first upper limit storage means. and upper limit values stored in the first and second upper limit value storage means based on the detection result of the engine acceleration state detection means, and selected as the fuel injection amount set by the fuel injection amount setting means. a comparison means for comparing the fuel injection amount with an upper limit value; and a comparison means for controlling the drive control means with the selected upper limit value when the comparison means determines that the fuel injection amount set by the fuel injection amount setting means exceeds the upper limit value. Injection amount limiting means to be activated is provided.

According to this configuration, when the fuel injection amount is set based on the intake air flow rate detected by the hot wire flowmeter during steady operation or deceleration, the set fuel injection amount and the second upper limit value When the set fuel injection amount exceeds the upper limit value by comparing it with the upper limit value stored in the storage means, the fuel injection valve is driven and controlled using the upper limit value stored in the second upper limit value storage means.

Of course, when the set fuel injection amount does not exceed the upper limit value, the fuel injection valve is driven and controlled according to the fuel injection amount that is set based on the intake air flow rate.

On the other hand, when an acceleration state is detected, the fuel injection amount based on the intake air flow rate is compared with the upper limit value stored in the first upper limit value storage means, and when the set fuel injection amount exceeds the upper limit value, The fuel injection valve is driven and controlled using the upper limit value stored in the first upper limit value storage means. When the set fuel injection amount does not exceed the upper limit even in such an engine acceleration state,
The fuel injection valve is driven and controlled according to the fuel injection amount set based on the intake air flow rate.

Here, since the upper limit value stored in the second upper limit value storage means is set smaller than the upper limit value stored in the first upper limit value storage means, the fuel injection amount regulated by the upper limit value is There will be more people.

Therefore, it is possible to secure a fuel injection amount equivalent to the amount of air filled in the intake manifold during acceleration, and a larger amount of fuel than necessary is injected by detecting blowback in all driving ranges including acceleration conditions. It is possible to prevent this from happening.

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

FIG. 2 shows the hardware configuration of the electronically controlled fuel injection system of this embodiment.

In this figure, a rotational speed signal N is the output of the rotational speed sensor l, an intake air flow rate signal Q is the output of the hot wire flowmeter 2, and a cooling water temperature signal Tw is the output of the water temperature sensor 3.
are input/output devices and storage devices.

Based on these signals, the control unit 4 sends an injection pulse signal corresponding to the fuel injection amount Ti, which is set as described later, to the throttle valve ( The signal is output to a drive circuit 6 (corresponding to drive control means) of the fuel injection valve 5 installed upstream of the fuel injection valve (not shown).

Here, the control unit 4 controls the fuel I'll tolerance setting means 2, the acceleration state detecting means, the first and second upper limit storage means, the comparing means, and the injection amount limiting means as shown in the flowchart of FIG. It is equipped with software.

Next, the operation will be explained according to the flowchart shown in FIG.

Step (indicated as “S” in the diagram, the same applies below)
1, the engine rotation speed N detected by the rotation speed sensor l, the intake air flow rate Q detected by the hot wire flowmeter 2, and the cooling water temperature T detected by the water temperature sensor 3.
Enter w.

In step 2, the engine rotation speed N manually operated in step 1 is
The basic fuel injection amount Tp (=
KXQ/N; is a constant).

In step 3, it is determined whether the engine is in an acceleration state. Specifically, it is determined whether the engine is in an accelerating state based on the rate of change in the intake airflow MtQJP and the basic fuel injection width Tp or the rate of change in the throttle valve opening detected by the throttle valve opening sensor.

If it is determined that the engine is in an accelerating state, the process proceeds to step 4, where the upper limit value Tpmax for upper limit correction control is set to the preset fuel injection 11 T p +. On the other hand, when it is determined that the engine is not in an accelerating state, the process proceeds to step 5 and the fuel injection rl? Set to Tp2.

Here, the fuel injection amount T p2 is set based on the intake air flow rate Q which is larger by a predetermined amount than the maximum intake air flow rate Q during steady operation, and normally the set basic fuel injection [ll T I) is Although this fuel injection amount Tp2 is not exceeded, the fuel injection amount TI)2 is set to be exceeded when blowback is detected and an intake air flow rate Q larger than the actual intake air flow rate Q is detected.

On the other hand, the fuel injection amount T p + is set to a value that takes into consideration intake manifold filling during engine acceleration. In other words,
When the engine is accelerating, the intake manifold under negative pressure is filled with intake air before being sucked into the engine, so more air is taken in than the maximum intake air flow rate Q during steady operation, and the fuel needs to be adjusted accordingly. In order to inject, the fourth
As shown in the figure, the fuel injection amount TpI is set larger than the fuel injection rl+T p 2.

Basic fuel injection r in step 4 or step 5
When the upper limit value Tpmax of l T p is set, the upper limit value Tpm which is Tp+ or Tp2 is set in step 6.
ax and basic fuel injection 'r calculated in step 2
When Tp>Tpmax, that is, the calculated basic fuel injection rllTI) is the upper limit Tpa+a.
When x is exceeded, proceed to step 7 and set the upper limit T p
Set taax as 'rp during final basic fuel injection.

On the other hand, when Tp≦Tpmax, that is, when the calculated basic fuel injection period 'rp is less than the upper limit value T p wax, the process proceeds to step 8, and the basic fuel injection period 'rp calculated in step 2 is used as the final Basic fuel injection rliTp
Set as .

In step 9, correction coefficients based on the respective operating conditions stored in the storage device in the control unit 4 are retrieved from the cooling water temperature 7'w detected by the water temperature sensor 3 and other engine operating conditions, and these correction coefficients are searched. The fuel injection amount Ti is set by correcting the basic fuel injection period 'rp set in step 7 or step 8 using various correction coefficients C0EF and the like obtained by calculating the correction coefficients with a calculation device.

In step 10, an injection pulse signal corresponding to the fuel injection amount Ti set in step 9 is output to the drive circuit 6 of the fuel injection valve 5.

According to the electronically controlled fuel injection device having such a configuration, the upper limit value Tpmax that regulates the maximum amount of Tp during basic fuel injection is set larger during engine acceleration than during steady operation (Tp
I<Tp2), as a result, 'rp during basic fuel injection can be set larger than during steady operation, and a fuel injection amount corresponding to the intake air filled into the intake manifold during acceleration can be obtained. Therefore, it is possible to prevent the air-fuel ratio from becoming too lean during engine acceleration, improving acceleration response, and preventing the air-fuel ratio from becoming too rich due to intake blowback detection in all driving ranges, including during acceleration, improving exhaust properties and fuel efficiency. deterioration can be avoided.

<Effects of the Invention> As explained above, according to the present invention, when the engine accelerates,
The maximum amount of fuel injection is limited by an upper limit value that is larger than the fuel injection type upper limit value during times other than acceleration.

This prevents the air-fuel ratio from becoming too lean during engine acceleration, improving acceleration performance, and prevents the air-fuel ratio from becoming too rich due to intake air blowback detection in all driving ranges, including acceleration, which improves exhaust properties and fuel efficiency. This has the effect of avoiding deterioration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a configuration block diagram showing an embodiment of the present invention, FIG. 3 is a flowchart showing control in the above embodiment, and FIG. 4 is an upper limit value diagram in the above embodiment. A time chart showing the characteristics, and FIG. 5 is a flowchart showing the conventional upper limit correction of the fuel injection amount. 1... Rotation speed sensor 2... Hot wire flow meter 3.
・・Water temperature sensor 4・・Control unit 5・
... Fuel injection valve 6 ... Drive circuit patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima Figure 3 Tokushi p>

Claims (1)

[Claims] A fuel injection valve and a hot-wire type flow meter are provided on the upstream side of the throttle valve, and a fuel injection amount is set by a fuel injection amount setting means based on the intake air flow rate detected by the hot-wire type flowmeter, and the set fuel injection amount is set. In an electronically controlled fuel injection system for an internal combustion engine, the fuel injection valve is drive-controlled by a drive control means according to the engine acceleration state detection means for detecting an acceleration state of the engine, and a preset amount of fuel injection at the time of engine acceleration. a first upper limit storage means storing an upper limit value of;
a second upper limit value storage means storing an upper limit value of the fuel injection amount at times other than when the engine is accelerating, which is preset to be smaller than the upper limit value stored in the first upper limit value storage means; and the engine acceleration state detection means. Comparing means for selecting an upper limit stored in the first and second upper limit storage means based on the detection result and comparing the fuel injection amount set by the fuel injection amount setting means with the selected upper limit; and injection amount limiting means for operating the drive control means at the selected upper limit value when the comparison means determines that the fuel injection amount set by the fuel injection amount setting means exceeds the upper limit value. An electronically controlled fuel injection device for an internal combustion engine, characterized in that: