JPH04153545A - Fuel characteristic judging device for internal combustion engine - Google Patents

Abstract

PURPOSE:To correctly judge the fuel characteristics such as fractional distillation property by representing the composition of the inspected fuel by a fuel model which consists of at least four kinds of single component fuel having different fractional distillation point. CONSTITUTION:An ignition timing controller 101 for carrying cut MBT control by correcting the previously set fundamental ignition timing is provided. A fuel temperature detecting means 102A detects the temperature T of the inspected fuel, and a fuel vapor pressure detecting means 102B detects the vapor pressure Pv, and a fuel specific gravity detecting means 102C detects the specific gravity rhol. A calculating means 103 calculates the composition of each fuel component of the fuel model which consists of at least four kinds of single component fuel having different fractional distillation point by a prescribed calculation equation on the basis of the ignition timing correction quantity to MBT and each detection value. Accordingly, the fuel characteristic such as fractional distillation property can be correctly judged, and the control precision in the fuel injection control and ignition timing control can be improved drastically.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is suitable for determining the fractional properties of hydrocarbon fuels such as gasoline. The present invention relates to a fuel property determination device.

(Prior art) In order to control the amount of fuel supplied to an internal combustion engine with high precision, the amount of fuel adhering to the intake pipe wall and the amount of fuel evaporating within the intake pipe are used as state variables to control the amount of fuel flowing into the engine cylinder. After setting a fuel behavior model that describes the behavior of A fuel injection 1 control device that determines the amount of fuel has been proposed (see Japanese Patent Laid-Open No. 1-271623).

(Problem to be Solved by the Invention) By the way, when calculating the required amount of fuel from a fuel behavior model as described above, calculation of the fuel state amount may affect the actual amount of fuel deposited and vaporized in the intake system. It is necessary to accurately determine the fractionation properties of fuel.

However, with conventional methods, the accuracy of detecting fuel properties was low, such as by representing the fuel properties only by the detected octane number and specific gravity, so there was a natural limit to the control accuracy of the final fuel supply amount. Particularly during transient periods, a deviation from the required amount of fuel occurs, resulting in deterioration of drivability and exhaust emissions.

The present invention was made by focusing on these problems.
The purpose is to determine the fuel properties by representing the composition of the test fuel using a fuel model consisting of four or more types of single-component fuels with different fractions.

(Means and Effects for Solving the Problems) In order to achieve the above object, the present invention, as shown in FIG. Assuming an internal combustion engine equipped with a control device 101,
Means 102A to 102C for detecting the temperature T1 vapor pressure Pv and specific gravity ρt of the test fuel F, and the α spark timing correction amount ΔAdv to the MBT and the detected values n (however,
n≧4) means 103 for calculating the composition of each fuel component of a fuel model consisting of more than one type of single fuel component.

Hereinafter, the contents of the calculation by the calculation means 103 will be explained with reference to a control block diagram (FIG. 2) showing the flow of processing.

In the present invention, first, in block A of FIG. 2, the temperature T, vapor pressure Pv, and specific gravity ρt of the fuel whose properties are to be determined are detected. Note that these values can be detected by attaching a temperature sensor, a hydrometer, and a pressure sensor to the fuel tank.

Next, based on the above detected values, blocks B and C are divided into four or more types with different α (here, 1=1 to 4).
For the saturated vapor pressure Pv and fuel density ρE of a fuel model consisting of a single component fuel of type 1), an rR relation between the mixed volume ratio Rv(i) of each fuel component of the fuel model is established as follows.

Pv = , ΣK (i> ・P v(i) ・R
v(i) - (1) as specified]) or (2), where K(i): constant Pv(i) for each fuel component: saturated vapor pressure ρj(i) of each fuel component
: Density of each fuel component 6 In addition, the saturated vapor pressure Pv(i) and ρj(i) of each fuel component
is calculated from the following formula 6 Pv(i)=Po-explK+(i)(1/Tfv(
i) 1/7N...(1゛) ρj(i)=K 2<i)・<IT/K
x(ri)13 -...(2゛)just】゛) or (
In Equation 2'), T fv(i) : boiling point K of each fuel component, , K , , K , : constant for each fuel component.

On the other hand, in block D, the correction amount jAd to the MBT ignition timing
v is read. Generally, the ignition timing I of an internal combustion engine, which is the optimum ignition timing during steady operation under certain environmental conditions, is set as the basic ignition timing, and in MBT control, this is determined based on the signal from the combustion pressure sensor, etc. under the actual operating environment. The ignition timing (M B T ) is corrected so that maximum torque can be obtained within a range that does not cause knocking.

ΔAdv in n is the seven-person period correction amount at this time.

Next, in block E, a relational expression between the ignition timing correction amount J A dv and the volume ratio Rv(i) is established as shown in the following equation (3).

J A dv = Σ, aAdv(i)・Rv(i)
'-(3) However, in equation (3), JA'dv(i) is an ignition timing correction coefficient predetermined according to the octane number of each fuel component.

In addition, in block F, a relational expression is established in which the sum of the mixing ratios of each fuel component is set to 1 using the following arithmetic expression.

1 = ΣRv(i) ... (4
) Finally, in block G, each of the above blocks B and C.

Based on each formula (1) to (4) established in E and F,
The mixing ratio Rv(i) of each component of a mixed fuel model consisting of four types of single component fuels is calculated.

When the mixture ratio Rv(i) is calculated in this way, various physical property values such as viscosity, specific gravity, It becomes possible to determine thermal conductivity, diffusion coefficient, etc. Specifically, regarding fuel behavior in the intake system, relatively light components in the fuel respond quickly during transient periods, which strongly influences the air-fuel ratio during transient periods. Once the properties are known, the influence of the light components can be known in advance, making it possible to significantly improve the control accuracy of fuel supply amount and ignition timing.

Note that, according to the present invention, it is also possible to calculate the proportions of various components not only in gasoline but also in light oil and methanol-mixed gasoline.

(Effects of the Invention) As explained above, according to the present invention, the composition of the fuel to be tested is represented by a fuel model consisting of four or more different single component fuels before fractionation. Since the properties can be determined accurately, it is possible to significantly improve the accuracy of fuel supply amount control and ignition timing control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a control block diagram showing the contents of the arithmetic processing. 101...Ignition timing control means, ]02A...Fuel temperature detection means, 102B...Fuel vapor pressure detection means, 102C...Fuel specific gravity detection means, 103...Calculates the volume ratio of fuel components means.

Claims (1)

[Scope of Claims] In an internal combustion engine equipped with an ignition timing control device that performs MBT control by correcting a preset basic ignition timing, means for detecting the temperature T, vapor pressure Pv, and specific gravity ρl of a test fuel; ,
Based on the ignition timing correction amount ΔAdv to the MBT and each of the detected values, the following equations (1) to (4) are used to calculate i (i≧4) types of single-component fuels that have different fractionation points from each other. A fuel property determination device for an internal combustion engine characterized by comprising means for calculating the composition of each fuel component of a fuel model consisting of: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) There are tables, etc.▼…(2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼…(3) ▲There are mathematical formulas, chemical formulas, tables, etc.▼…(4) However, K(i): Constant for each fuel component Pv(i): Saturated vapor pressure of each fuel component ρl(i): Density of each fuel component ΔAdv(i): Ignition timing correction coefficient predetermined according to the octane number of each fuel component.