JPS5951661B2 - fuel injected engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to controlling the fuel injection amount when the throttle valve of a fuel injection engine is fully opened using a Karman vortex air flowmeter or the like.

Conventionally, a Karman vortex air flow meter or hot wire flow meter, which has a simple structure and is inexpensive, is used as a flow meter for engine intake air, and the fuel injection amount is controlled according to the detected flow rate to achieve a predetermined air-fuel ratio mixture. A fuel-injected engine designed to obtain airflow has been proposed.

For example, Karman vortex flowmeters utilize the phenomenon that when a cylindrical body is placed in a flow, a vortex train (Karman vortex) is generated regularly downstream, and the period of generation of the vortex is precisely proportional to the flow velocity. The flowmeter is designed to measure the flow rate by detecting the period of occurrence of the occurrence, and is becoming widely used as a flowmeter with a simple structure and low cost (for example, Japanese Patent Application Laid-Open No. 54-24
(See No. 058).

However, when the throttle valve is fully open, the influence of intake pulsation extends to the metering section upstream of the throttle valve, which disrupts the generation of vortices and reduces the accuracy of flow rate measurement, making it impossible to accurately control the air-fuel ratio. The problem arises that it becomes impossible to do so.

These problems also apply to the hot wire type.

The present invention has been made in view of the above-mentioned problems, and is aimed at an engine using a detection means such as a Karman vortex type or hot wire type intake flow rate sensor in which the accuracy of intake flow rate detection decreases near the fully open throttle valve. The purpose is to make it possible to obtain an air-fuel mixture with a predetermined air-fuel ratio even when the throttle valve is fully open.

As shown in FIG. 7, the present invention utilizes an intake flow rate detection means such as a Karman vortex flowmeter or a hot wire flowmeter, whose detection accuracy is affected by intake pulsation near the fully open throttle valve, and an engine speed detection means. In a fuel injection engine comprising: a detection means; and a means for controlling a fuel injection amount as a reference for the detection signals of both of the detection means; When the opening degree is near full open, the fuel injection amount is controlled based on the intake flow rate estimated only from the detection signal of the engine rotational speed detection means.

Therefore, in the normal operating range, the fuel injection amount is calculated accurately based on the outputs of the intake flow rate detection means such as the Karman vortex flowmeter and the rotational speed detection means, and the Karman vortex flowmeter is not affected by the intake pulsation. In the throttle valve fully open range, where the detection accuracy is low -1, the fuel injection amount is calculated based on the engine speed signal, which is highly reliable as a signal representative of the intake flow rate. Stable fuel control is possible from low to high speed and high load ranges.

This will be explained below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 1 is a means for detecting the rotational speed of the engine, 2 is a means for detecting the intake air flow rate (for example, a Karman vortex sensor), and 3 is a means for detecting the representative temperature of the engine. 4 is a means (for example, a throttle valve switch) for detecting when the throttle valve is fully open.

5 is microprocessor → force, 6 is read-only memory,
7 is a random access memory, 8 is an input/output control circuit, and these form a microcomputer 9.

10 is a fuel injection valve. The microcomputer 9 is
The signals from the detection means 1 to 4 are input as signals indicating the operating state, and the opening degree of the fuel injection valve 10, that is, the fuel injection amount is controlled according to the input signal, and the air-fuel ratio of the air-fuel mixture is adjusted to the operating state. Control or roll to a predetermined value depending on the value.

As a specific method, for example, an on-off type solenoid valve is used as the fuel injection valve 10, and this solenoid valve is driven to open and close using a pulse signal with a frequency synchronized with the engine rotation.
A method is used in which the average valve opening degree is increased or decreased by increasing or decreasing the pulse width.

Next, the execution of programming of the microcomputer 9 is shown in flowchart I in Figure 2 and in Figures 3 to 3.
This will be explained with reference to the characteristic diagram shown in FIG.

First, the throttle valve opening is read from the signal from the throttle valve opening detecting means 4.

When the Karman vortex-type intake flow rate detection means 2 becomes unable to accurately measure the intake flow rate due to the influence of intake pulsation, there is a valve below a predetermined set opening degree (for example, 70 degrees), that is, the intake flow rate detection means 2 In order to accurately detect the intake flow rate, after determining the reference pulse width from the rotational speed detection means 1 and the intake flow rate detection means 2, the reference pulse width is determined based on the input from the representative temperature detection means 3, etc. is corrected to determine the most favorable pulse width, and a signal with this pulse width is sent to the fuel injector 10.
Output to.

Next, if the throttle valve is opened more than the set opening degree, that is, if the detection means 2 is no longer able to accurately detect the intake flow rate, first read the engine rotation speed and use the one-dimensional table. A reference pulse width Tp (FIG. 4) corresponding to the rotational speed is determined in advance by lookup.

In other words, when the intake valve is fully open or close to fully open, the intake flow rate changes in accordance with the engine rotational speed. This determines the reference pulse width.

At this time, the actual intake air flow rate slightly depends on the throttle valve opening, but in a region where the absolute amount of the throttle valve opening is large, for example, even if the value when the throttle valve is fully open is fixed, this will cause The error in estimating the intake flow rate that occurs is negligible compared to the absolute amount of the intake flow rate, so there is almost no problem.

For example, as shown in FIG. 3, an area C (shaded area) where the intake flow rate detection means 2 shows an accurate value and an area D where the intake flow rate detection means 2 does not show an accurate value.
At point B on the border with (blank area), the same flow rate of fuel is injected as at point A when the throttle valve is fully open at the same rotational speed, but the difference in intake flow rate at the two points is compared to the absolute amount. Since the air-fuel ratio is so small that it can be ignored, it can be said that the air-fuel ratio itself is almost the same.

Note that whether the opening degree of the throttle valve is greater than or equal to a predetermined value may be detected by using an intake pipe pressure sensor or a pressure switch based on whether the intake pipe pressure is greater than or equal to a predetermined value.

Next, the engine representative temperature, for example, the engine cooling water temperature, is read and the corresponding correction coefficient F1 (FIG. 5) is determined by a one-dimensional table lookup.

Next, after reading the drive voltage of the injection valve 10 and calculating the corresponding correction pulse width Ts (Fig. 6), the above-mentioned reference pulse width Tp is corrected by the correction coefficient Ft and the correction pulse width Ts to obtain the optimum value. A negative pulse width T-Tpx Ft + Ts is calculated and a signal with that pulse width is output.

In this way, when the intake flow rate detecting means 2 cannot detect an accurate value in a state where the throttle valve is fully open or close to fully open, the intake flow rate is determined from the engine rotational speed that changes in accurate correspondence with the intake flow rate. Accordingly, the pulse width of the signal that drives the fuel injection valve 10 is controlled to control the fuel injection amount so that a mixture having a predetermined air-fuel ratio is obtained.

As explained above, the present invention calculates the weight flow rate of intake air from the engine rotation speed in the range where the intake flow rate sensor is fully open or close to fully open, where the accuracy of the intake flow rate sensor decreases, especially when the throttle valve is fully open or close to fully open. As a result, it is possible to achieve stable and highly accurate air-fuel ratio control with a relatively inexpensive system from the low flow range to the high flow range of the engine intake air amount. Improved output and fuel efficiency.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a flowchart 1 to 1 of the microcomputer in Fig. 1, and Fig. 3 shows how the intake flow rate detection means in Fig. 1 detects an accurate value. FIG. 4 is a characteristic diagram of the reference pulse width Tp, FIG. 5 is a characteristic diagram of the correction coefficient Ft, and FIG. 6 is a characteristic diagram of the corrected pulse width Ts. FIG. 7 is a diagram corresponding to claims of the present invention. DESCRIPTION OF SYMBOLS 1... Rotation speed detection means, 2... Intake flow rate detection means, 3... Representative temperature detection means, 4... Throttle valve opening detection means, 9... Microcomputer, 10... Fuel injection valve.

Claims (1)

[Claims] 1. An intake flow rate detection means such as a Karman vortex flowmeter or a hot wire flowmeter whose detection accuracy is affected by intake pulsation near the fully open throttle valve, an engine rotation speed detection means, and both of these. A fuel injection engine comprising means for controlling the fuel injection amount based on a detection signal of the detection means, a means for detecting that the throttle valve opening is near full open, and a means for detecting that the throttle valve opening is near full open. and means for controlling a fuel injection amount based on an intake air flow rate estimated only from a detection signal of the engine rotational speed detection means. 2. The fuel injection engine according to claim 1, wherein the means for detecting that the throttle valve opening is close to fully open detects whether the throttle valve opening is equal to or higher than a set value. 3. The fuel injection engine according to claim 1, wherein the means for detecting that the throttle valve opening is close to fully open detects whether the intake pipe pressure is equal to or higher than a set value.