JPH03217630A - Fuel supply of internal combustion engine - Google Patents

Abstract

PURPOSE:To secure a proper air-fuel ratio and improve startability by setting alcohol concentration according to the temperature of cooling water, compensating the alcohol concentration through the detection of fuel composition and supplying fuel through the calculation of basic supply quantity based on the compensating quantity. CONSTITUTION:Signals of an air flow meter 2, a crank angle sensor 3, an O2 concentration sensor 6, water temperature sensor 7, an alcohol concentration sensor 9 and a starter switch 10 are inputted to a microcomputer 1, and then fuel injection quantity is calculated so as to control a fuel injection valve 11. The alcohol concentration is set according to the temperature of cooling water the detected alcohol concentration is compared therewith so as to determine a compensating quantity, and then a starting timing injection quantity is calculated based on a starting timing basic injection quantity. The fuel injection valve 11 is controlled in this way so as to secure a proper air-fuel ratio with an improved startability.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply system for an internal combustion engine that uses a mixed fuel of alcohol such as methanol and gasoline, and particularly relates to a technique for improving startability.

Conventional examples of this type of fuel supply system for internal combustion engines include the following (rNIssAN RB Engine Maintenance Summary, Vol. 5, published by Nissan Motor Co., Ltd., 1985).
(See pages 3 to 63).

That is, after calculating the basic injection amount from, for example, the engine rotational speed and the intake air flow rate (engine load), the basic injection amount is corrected based on the cooling water temperature and the like to calculate the fuel injection amount. Then, an injection pulse signal corresponding to the calculated fuel injection amount is output to the fuel injection valve to supply fuel to the engine.

Furthermore, at the time of starting (during cranking), the fuel injection amount is set as follows in order to improve startability.

That is, it is determined by the starting injection amount T, which is obtained by increasing the fuel injection amount obtained at starting according to the fuel calculation formula 6 during normal operation, the cooling water temperature, the engine rotation speed, and the elapsed starting time. The starting injection amount T2 is compared, and the larger one is selected as the starting fuel injection amount to operate the fuel injection valve. During normal startup, since the cooling water temperature is low, the startup injection amount T2 is often selected.

Here, the starting injection amount T2 is the basic injection amount at starting which is set in the map to decrease as the cooling water temperature increases at starting, and the engine rotation speed during cranking is less than a predetermined value. A rotation correction coefficient that is set to 1 when the rotation speed is greater than a predetermined value and is set to decrease as the engine rotation speed increases, and a time correction coefficient that is set according to the elapsed time at startup. Multiply and get.

<Problems to be Solved by the Invention> However, in such a conventional fuel supply bag device, the basic injection amount at startup is set based on the cooling water temperature, so the basic injection amount at startup is set when high concentration gasoline is used. If this is set, the air-fuel ratio will change to O-Harin when using high-concentration alcohol, worsening starting performance, and conversely, if the basic injection amount at startup is set when using high-concentration alcohol, the air-fuel ratio will become O-hari-Sochi when using high-concentration gasoline, causing spark plug flaring. There is a problem that it worsens starting performance.

In addition, since the basic injection amount at startup with respect to the cooling water temperature is significantly different when using high concentration gasoline and when using high concentration alcohol, it is best to set the basic injection amount at startup according to the alcohol concentration and the cooling water temperature for matching. The problem is that it is difficult to In particular, if the basic injection amount at startup is set using a two-dimensional map using alcohol concentration and cooling water temperature as two parameters, there is a problem that the calculation of the basic injection amount at startup becomes complicated and the calculation time becomes long.

By the way, the applicant of the present application has discovered the starting injection amount characteristic, that is, the starting basic injection amount characteristic, which can ensure the optimum air-fuel ratio at the time of starting regardless of the alcohol concentration and the cooling water temperature, as follows. That is, as shown in Fig. 4, the basic injection amount at startup is set at 1 degree alcohol ALCTW,
It has a characteristic that changes approximately linearly depending on the alcohol concentration with different gradients in the low alcohol concentration region and the high alcohol concentration region. Furthermore, the basic injection amount at startup has a characteristic that increases as the cooling water temperature decreases.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a fuel supply device for an internal combustion engine that takes the above-mentioned characteristics into account and can improve startability while simplifying the calculation of the starting injection amount. do.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention supplies a mixed fuel containing alcohol to an engine, and the starting supply amount supplied to the engine at the time of starting is controlled. , comprising: a starting supply amount setting means A that sets the starting basic supply amount based on the starting starting supply amount; and a drive control means C that drives and controls the fuel supplying means B based on the set starting starting supply amount. A fuel composition detection means D detects the composition of the mixed fuel, a temperature detection means E detects the engine cooling water temperature or a state related thereto, and a setting is made based on the detected cooling water temperature or a state related thereto. an alcohol concentration setting means F for setting an alcohol concentration; a concentration determining means G for determining whether the alcohol concentration is below the set alcohol concentration based on the detected fuel composition; and when the alcohol concentration is below the set alcohol concentration. and basic supply amount calculation means H for calculating the basic supply amount at startup based on different correction amounts for when the alcohol concentration exceeds the set alcohol concentration, respectively.

In this way, after considering the above characteristics and setting the set alcohol concentration that changes depending on the cooling water temperature from the cooling water temperature or related conditions, the detected alcohol concentration and the set alcohol concentration are set. Compare with. Then, the basic supply amount at startup is calculated based on different correction amounts when the alcohol concentration is below the set alcohol concentration and when it exceeds the set alcohol concentration. Then, the starting supply amount is set from this starting basic supply amount to drive and control the fuel supply means.

<Example> An example of the present invention will be described below based on FIGS. 2 to 5.

In FIG. 2, a microcomputer 1 receives an intake air flow rate signal from an air flow meter 2, a reference signal (corresponding to the engine rotation speed) and a position signal from a crank angle sensor 3, and an exhaust passage 5 of an engine 4. An oxygen concentration signal from an interposed oxygen sensor 6 that detects the air-fuel ratio from the oxygen concentration in exhaust gas, a cooling water temperature signal from a water temperature sensor 7 serving as a temperature detection means, and a fuel interposed in the fuel supply passage 8. A concentration detection signal from an alcohol concentration sensor 9 serving as a composition detection means and an on/off signal from a starter switch 10 that is turned on during cranking are input.

The microcomputer 1 has an I/OIA and a CPU.
The fuel injection valve is configured to include an IB, a ROMIC, and a RAMLD, and calculates the amount of fuel to be injected based on signals from the various sensors, etc., and serves as a fuel supply means installed in the intake system of the engine. 11 to output an injection pulse signal.

Here, the control device 1 constitutes a starting supply amount setting means, a drive control means, an alcohol concentration setting means, a concentration determining means, and a basic supply amount calculation means.

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

In S1, it is determined whether the starter switch 10 is on or not, and when it is YES, it is determined that cranking is in progress and the process proceeds to S2.
When o, the routine is terminated.

In S2, the cooling water temperature detected by the water temperature sensor 7 is read.

In S3, the standard starting basic injection amount TTST (see FIG. 4) for pure gasoline is searched from the map based on the detected cooling water temperature. This standard starting basic injection amount T
TST is set to decrease as the cooling water temperature increases.

In S4, the set alcohol ALCTW is searched from the map based on the detected cooling water temperature.

As shown in FIG. 5, the set alcohol concentration ALCTW is set to increase as the cooling water temperature increases.

In S5, the alcohol concentration ALC detected by the alcohol concentration sensor 9 is read.

In S6, it is determined whether the detected alcohol concentration ALC is less than the searched set alcohol concentration ALCTW, and if YES, the process proceeds to S7, and if NO, the process proceeds to S9.

In S7, based on the detected cooling water temperature, the first
Search the alcohol concentration gradient KALCI (see Figure 4) from the map.

In S8, the searched reference starting basic injection amount TTS
T and the detected alcohol concentration ALC and the first searched
Based on the alcohol concentration gradient KALCI, the starting basic injection amount TST is calculated using the following equation.

TST=TTST-1-KALCIX (ALC-AL
CMIN) ALCMIN is the alcohol concentration corresponding to the reference starting basic injection amount TTST (see FIG. 4).

In S9, based on the detected cooling water temperature, the first
The alcohol concentration gradient KALCI and the second alcohol concentration gradient KALC2 are searched from the map.

In SIO, the searched reference starting basic injection amount TT
ST, detected alcohol concentration ALC, searched set alcohol concentration ALCTW, and searched first and second
Based on the alcohol concentration gradients KALC1 and KALC2, the basic injection amount TST at startup is calculated using the following equation.

TST=TTST+KALCI XALCTW+KAL
C2 (ALC-ALCMIN) When the basic injection amount TST at startup is calculated in this way, the basic injection amount TST at startup is calculated.
As shown in FIG. 4, ST increases as the alcohol concentration increases at the first alcohol concentration gradient KALCI until the alcohol concentration reaches the set alcohol concentration ALCTW. Furthermore, when the alcohol concentration is equal to or higher than the set alcohol concentration ALCTW, the basic injection amount TST at startup increases as the alcohol concentration becomes higher at the second alcohol concentration gradient KALC2.

Furthermore, the starting basic injection amount TST is set to increase as the cooling water temperature becomes lower.

Therefore, the first and second alcohol concentration gradients KALCI,
KALC2 constitutes the correction amount.

Then, the starting injection amount T2 is calculated by the following equation based on the starting basic injection amount TST calculated in S8 or S10.

T2=TSTxTCSNxTKCS TCSN is a rotation correction coefficient that is set to 1 when the engine rotation speed during cranking is less than a predetermined value, and is set to decrease as the engine rotation speed increases when it is above the predetermined value. Starter switch 1
This is a time correction coefficient that is set to 1 until 0 is turned off, and then decreases to 0 over time.

Furthermore, the calculated starting injection amount T2 is compared with the starting injection amount T1, which is obtained by increasing the fuel injection amount obtained according to the engine operating state at starting, as in the conventional example. Then, the larger one of them is selected, and an injection pulse signal corresponding to the selected starting injection amount is output to the fuel injection valve 11,
Fuel is supplied to the engine.

As explained above, since the starting injection amount T2, that is, the basic starting injection amount TST, is set by changing it according to the alcohol concentration and the cooling water temperature, it is optimal regardless of the alcohol concentration and the cooling water temperature. Since a suitable air-fuel ratio can be ensured, startability, especially at low temperatures, can be improved. At this time, the standard starting basic injection amount TTST, set alcohol concentration ALCTW, first and second alcohol concentration gradients KALCI, KALC2 are each set in a one-dimensional map (ROM, etc.) consisting of a single parameter, and these values are set. Since the starting basic injection amount TST is calculated from the starting basic injection amount TST, searching for them is much easier than before, and the time required to calculate the starting basic injection amount TST can be shortened and the calculation is also easier.

Effects of the Invention> As explained above, the present invention sets the set alcohol concentration based on the cooling water temperature or related conditions, and then sets the set alcohol concentration when the detected alcohol concentration is less than or equal to the set alcohol concentration. When the concentration exceeds the
Since the basic supply amount at startup is calculated using different correction amounts for each, the optimum air-fuel ratio can be ensured at startup regardless of alcohol concentration and cooling water temperature, improving startability and simplifying these calculations. can do.

[Brief explanation of drawings]

Fig. 1 is a claim correspondence diagram of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Fig. 3 is a flowchart of the same as above,
FIG. 4 and FIG. 5 are for explaining the same effect as above. 1...Microcomputer 2...Air flow meter 3...Crank angle sensor 7...Water temperature sensor 9...Alcohol concentration sensor 10...Starter switch 11...Fuel injection valve

Claims (1)

[Claims] A starting supply amount setting means for supplying a mixed fuel containing alcohol to the engine, the starting supply amount setting means for setting the starting supply amount supplied to the engine at the time of starting based on the starting basic supply amount; A fuel supply device for an internal combustion engine, comprising: a drive control means for controlling the fuel supply means based on a fuel supply amount at a time; a fuel composition detection means for detecting the composition of the mixed fuel; temperature detection means for detecting a related state; alcohol concentration setting means for setting a set alcohol concentration based on the detected cooling water temperature or a state related thereto; a concentration determining means for determining whether or not the alcohol concentration is below the set alcohol concentration; and calculating the basic supply amount at startup based on different correction amounts when the alcohol concentration is below the set alcohol concentration and when it exceeds the set alcohol concentration. A fuel supply device for an internal combustion engine, comprising: basic supply amount calculation means.