JP2000018065A - Control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize heat efficiency so as to obtain a maximum horsepower by setting a throttle opening to the minimum opening corresponding to an engine load while carrying out a stable operation when an engine is started, by reducing an air excessive ratio until an engine rotating speed exceeds a specified value just after the engine is started. SOLUTION: In the case where the operation of an engine is stabilized, it is judged whether an engine start command is outputted from a system every a constant time or not, while an engine is stopped. In the case where the engine start command is outputted, it is judged whether engine rotating speed is not less than a predetermined value or not. In the case where the engine rotating speed is less than the predetermined value, a fuel control valve is fully opened for setting an air excessive ratio to the minimum level. When a throttle opening is regulated so as to generate the maximum horsepower corresponding to an operating condition of the engine, namely, corresponding to a load, it is judged whether the load is outside a range of a predetermined value or not every a constant time. In the case where the load is outside of the range of the predetermined value, it is judged whether a present throttle opening is in the minimum level or not. As a result, in the case where the present throttle opening is not in the minimum level, the air excessive ratio, an ignition timing, and the are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an internal combustion engine.

[0002]

2. Description of the Related Art In a conventional internal combustion engine, a throttle is closed when a load is small. Conventionally, 1000
r. p. m. In order to stably rotate the engine at the following rotational speeds, a mixer is used that mechanically reduces the excess air ratio, that is, makes the engine rich.

Conventionally, a test has to be performed to determine a threshold value (limit value) of the throttle opening, and the threshold value is not an accurate boundary value due to a load, but a stable engine start. It was difficult.

Further, since the throttle opening varies depending on the opening of the fuel control valve, the relationship between load and throttle is one-to-one.
However, even if the threshold value of the throttle opening is selected, the accuracy is lacking, and it is difficult to perform stable operation (including starting) of the engine.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method for an internal combustion engine that can perform stable engine operation.

[0006]

According to a first aspect of the present invention, there is provided a control method for an internal combustion engine, wherein the excess air ratio is reduced from immediately after starting until the engine speed reaches a predetermined value.

A second aspect of the present invention is a method for controlling an internal combustion engine, characterized in that thermal efficiency is optimized by setting a throttle opening to a minimum opening corresponding to a load applied to the engine.

[0008]

FIG. 1 is a graph showing a predetermined operating range S of an internal combustion engine, in which the vertical axis represents the in-cylinder average effective pressure and the horizontal axis represents the engine speed. There are 12 mode points to test when evaluating the NOx amount (nitrogen oxide amount) of a gas engine heat pump engine. At these 12 points, the NOx amount is measured, multiplied by the load factor, and the NOx amount of the engine to be tested is evaluated. Control performed in a range (predetermined operation range S) surrounding the dotted mode point is referred to as constant combustion fluctuation control.

Here, the engine speed A is plotted on the horizontal axis of FIG.
The values of F to F and the average effective pressures a to g on the vertical axis should be different depending on the engine used and the operating conditions. In the present embodiment, the following values are used. The engine speeds A to F (rpm) are, for example, A = 500,
B = 1000, C = 1500, D = 2000 and E = 2
500 (rpm), and the average effective pressures a to f
(MPa) is, for example, a = 0.2, b = 0.25, c
= 0.3, d = 0.35, e = 0.4, f = 0.45, and g = 0.5 (MPa).

FIG. 2 shows a fuel control valve map showing the relationship between the excess air ratio, the engine speed and the average effective pressure in the cylinder. This fuel control valve map is created based on the results of an experiment conducted with a base engine having a designed compression ratio and a swirl ratio under the standard atmospheric conditions of ISO.

The fuel control valve map shown in FIG. 2 is input to a controller (not shown) system in advance. This fuel control valve map makes it possible to set the excess air ratio while keeping the combustion fluctuation constant. The control of the combustion fluctuation of the internal combustion engine and the relationship between the combustion fluctuation and the excess air ratio are described in detail in Japanese Patent Application No. 10-163419 filed by the present applicant.

For example, when the rated speed is 3000 r. p.
m. In the internal combustion engine of FIG.
r. p. m. (Immediately after engine start) to C (C = 1500)
r. p. m. Until the predetermined value, the excess air ratio is made rich by fully opening the fuel control valve (not shown) regardless of the magnitude of the load applied to the engine. Therefore, immediately after the start of the engine when a heavy object is being pulled, engine stall does not occur, and the operation of the engine is very stable.

In the operating range S 'above the predetermined operating range S in FIG. 1, the throttle opening is always minimized in order to generate the maximum horsepower under each operating condition (ship speed, load magnitude, etc.). So that the excess air ratio, ignition timing,
At least one of the swirl ratio, the EGR rate, the valve timing, and the cooling water is controlled.

Here, in order to generate the maximum horsepower under each operating condition (such as the speed of the boat, the magnitude of the load, etc.), it is preferable to simultaneously operate two of the above-mentioned excess air ratio and ignition timing.

FIG. 3 is a flowchart showing a procedure for stabilizing the operation of the engine. As shown in FIG. 3, while the engine is stopped, it is determined whether or not an engine start command is issued from the system (F = 1) at regular intervals (for example, one minute).

If an engine start command has been issued, it is next checked whether or not the engine speed is equal to or higher than a predetermined value (700 to 800 rpm). If it is less than the predetermined value, the fuel control valve is fully opened to minimize the excess air ratio.

Further, the engine start flag is not F = 1 (the start command is not issued) or the engine speed is a predetermined value (7
00 to 800 r. p. m. If the above is satisfied, the engine can be stopped or operate stably, so it returns to complete the control and waits until the next control.

FIG. 4 shows a procedure for adjusting the throttle opening so as to generate the maximum horsepower according to each operating condition (the magnitude of the load). Every predetermined time (for example, 5 minutes), the load is out of the predetermined range (above and below the predetermined operation range S in FIG. 1, that is, greater than 0.45 MPa or 0.4%).
275 MPa) is checked. If it is above or below a predetermined operating range S (FIG. 1), it is determined whether or not the current throttle opening is minimum.

If the current throttle opening is not the minimum value, at least one of the excess air ratio, the ignition timing, the swirl ratio, the valve timing and the coolant temperature is controlled in the next step to optimize the thermal efficiency. I do.

[0020]

According to the first aspect of the invention, the excess air ratio is reduced from immediately after the start of the engine until the engine speed reaches a predetermined value, so that the engine can be stably started when the internal combustion engine is started. be able to.

When the invention of claim 2 is applied, the throttle opening is set to the minimum opening corresponding to the load on the engine, so that the thermal efficiency can be optimized and the maximum horsepower can be generated. Also, when horsepower is required, horsepower can be accurately generated. When the load is small, stable operation of the engine can be performed.

[Brief description of the drawings]

FIG. 1 is a graph showing a predetermined operating range of an internal combustion engine in which the vertical axis represents the in-cylinder average effective pressure and the horizontal axis represents the engine speed.

FIG. 2 is a graph showing a fuel control valve map showing a relationship between an excess air ratio, an engine speed, and an average effective pressure in a cylinder.

FIG. 3 is a flowchart showing a procedure for stabilizing the operation of the engine when the engine is started.

FIG. 4 is a flowchart of control of the engine at the time of low load and at the time of high load.

[Explanation of symbols]

 S Predetermined operating range

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Nakazono 1-32 Chayamachi, Kita-ku, Osaka-shi, Osaka F-term in Yanmar Diesel Co., Ltd. (Reference) 3G065 AA00 CA00 GA09 GA10 GA13 GA14 GA15 GA18 GA41 3G084 AA00 BA05 BA09 BA13 BA17 BA20 BA21 BA23 DA09 FA10 FA20 FA33 3G301 HA22 JA00 KA01 KA05 LA00 LA01 LA05 LA07 MA01 MA11 NE13 PA11Z PE01Z PE08Z

Claims (2)

[Claims] 1. A control method for an internal combustion engine, comprising: reducing an excess air ratio from immediately after starting until the engine speed reaches a predetermined value. 2. A method for controlling an internal combustion engine, wherein the thermal efficiency is optimized by setting a throttle opening to a minimum opening corresponding to a load applied to the engine.