JP2540514Y2 - Fuel supply device for internal combustion engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine, and more particularly to a case where an alcohol-mixed fuel is used. The present invention relates to a fuel supply device for an internal combustion engine capable of correcting a fuel injection amount in accordance with an alcohol concentration to be injected and supplying fuel by a fuel injection valve.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, as shown in FIG. 7, a fuel in a fuel tank 1 is pumped up by a fuel pump 2 immersed in the fuel tank 1, and the fuel is injected through a fuel passage 3 into a fuel injection valve. 4 to be pumped. At this time, surplus fuel is returned into the fuel tank 1 via the return passage 5 by a pressure regulator (not shown).

[0003] In recent years, an alcohol-mixed fuel obtained by mixing alcohol such as methanol with gasoline has been proposed as an alternative fuel for an internal combustion engine for an automobile. When such an alcohol-mixed fuel is used, the stoichiometric air-fuel ratio changes according to the alcohol concentration. Therefore, it is necessary to detect the alcohol concentration of the supplied alcohol-mixed fuel and control the fuel supply amount based on the alcohol concentration. (See, for example, JP-A-56-958540).

Therefore, an alcohol sensor 6 that outputs an electric signal corresponding to the alcohol concentration in the fuel is interposed in the fuel passage 3 to detect the alcohol concentration in the fuel.

[0005]

An invention is, however, in such a conventional apparatus and are located at the upstream side L ₃ minutes only the alcohol sensor 6 Distance fuel passage 3 from the fuel injection valve 4, the alcohol sensor The fuel whose alcohol concentration is detected by the fuel injection valve 6 and the fuel injected from the fuel injection valve 4 may have different alcohol concentrations.

In other words, when fuel having a different alcohol concentration is mixed with a fuel having an alcohol concentration of Cold used so far, the fuel tank 1 is filled with fuel having an alcohol concentration of Cnew. At the time of refueling, there is a boundary, if not clear, between the fuel and the fuel having the alcohol concentration Cold already filled in the fuel passage 3. Therefore, as shown in FIG. 8, the boundary reaches the position of the alcohol sensor 6 (time t ₁ ), passes through the fuel passage 3 at a distance L ₃ , and reaches the position of the fuel injection valve 4 (time t ₂ ). During this period, as described above, the fuel (solid line) whose alcohol concentration is detected by the alcohol sensor 6 and the fuel (dashed line) injected from the fuel injection valve 4 have different alcohol concentrations. Therefore, if the fuel injection amount is corrected based on the correction value set based on the electric signal output from the alcohol sensor 6 during this time, the correction becomes impractical and the air-fuel ratio control cannot be properly performed. There was a problem.

In view of such a conventional problem, the present invention corrects the fuel injection amount based on the alcohol concentration in the fuel injected from the fuel injection valve regardless of the position of the alcohol sensor. An object of the present invention is to provide a fuel supply device for an internal combustion engine that can perform appropriate air-fuel ratio control.

[0008]

Therefore, according to the present invention, as shown in FIG. 1, the fuel injection amount correcting means (a) for correcting the fuel injection amount by the fuel injection valve according to the alcohol concentration in the fuel is provided. In a fuel supply device for an internal combustion engine, an upstream alcohol sensor and a downstream alcohol sensor are provided on a fuel passage from a fuel tank to a fuel injection valve, a first predetermined distance between both sensors, and a downstream alcohol sensor and a fuel Injection valves are arranged so as to have a second predetermined distance, and a first delay time required for fuel to move from the upstream alcohol sensor to the downstream alcohol sensor is measured based on a difference between output change timings of the two sensors. A first delay time measuring means (b) for performing the fuel supply on the downstream alcohol sensor based on the measured first delay time and a ratio of the second predetermined distance to the first predetermined distance. Second delay time calculating means (c) for calculating a second delay time required to move from the second alcohol to the fuel injection valve, and an alcohol concentration detected by the downstream alcohol sensor before the calculated second delay time. And a data delay unit (d) for correcting the fuel injection amount by the fuel injection amount correction unit.

[0009]

In the above arrangement, the first delay time measuring means determines the first delay time required for fuel to move from the upstream alcohol sensor to the downstream alcohol sensor by determining the difference between the output change timings of the two sensors. Knowing by measuring, the first delay time measured by the second delay time calculating means
Calculates the time required to travel the fuel path through the second predetermined distance (the delay time from the downstream alcohol sensor to the fuel injection valve) based on the delay time of the first predetermined distance and the ratio of the second predetermined distance to the first predetermined distance. I do.

The fuel injection amount is corrected by the fuel injection amount correction means based on the alcohol concentration detected by the downstream alcohol sensor before the calculated second delay time by the data delay means. Thus, using an alcohol sensor installed upstream of the installation location of the fuel injection valve, knowing the alcohol concentration in the fuel actually injected from the fuel injection valve, and correcting the fuel injection amount based on this. Becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, the fuel in the fuel tank 11 is pumped up by a fuel pump 12 immersed in the fuel tank 11 and is fed to a fuel injection valve 14 through a fuel passage 13. At this time, excess fuel is returned to the return passage 16 by the pressure regulator 15 which opens at a predetermined pressure or higher.
And is returned to the fuel tank 11 via the

Further, on the fuel passage 13, downstream alcohol sensor to the second predetermined distance L ₂ upstream position from the fuel injection valve 14
17 are arranged, it is further arranged upstream alcohol sensor 18 to a first predetermined distance L ₁ upstream position than this. And
Downstream alcohol sensor 17 and upstream alcohol sensor
From 18, an electric signal corresponding to the alcohol concentration in the fuel is output to the control unit 19. The air flow meter 20 and the crank angle sensor 21 output electric signals corresponding to the intake air flow rate Q and the engine speed N, respectively. Then, a microcomputer shown in the flowchart of FIGS. 4 and 5 is performed by a microcomputer (not shown) in the control unit.

As shown in FIG. 3, signals from both alcohol sensors 17 and 18 are selectively taken in by an analog switch 31 switched by a signal from a control unit 19, and an oscillation circuit 32 and a frequency dividing circuit 33 are provided. , FV (frequency-voltage) conversion circuit 34 and amplification circuit 35, and then input to the control unit 19. And
The latest predetermined number of data is stored and held for each of the alcohol sensors in a RAM (not shown) in the control unit 19, and is used for determination each time as shown in steps 1 and 3 (described later).

The routine shown in the flowchart of FIG. 4 will be described. In step 1 (referred to as S1 in the figure, the same applies hereinafter), it is determined whether or not the alcohol concentration in the fuel has changed based on a signal from the upstream alcohol sensor 18, and
If the determination is YES, the process proceeds to step 2, the timer starts counting by a timer (not shown), and the process proceeds to step 3. If NO, the routine ends. In step 3, it waits until there is a similar change in the alcohol concentration based on the signal from the downstream alcohol sensor 17, and if there is a change (YES), the process proceeds to step 4, ends the time measurement, and sets the timer. Nde read timing value T _1, the process proceeds to step 5. That is,
The counted value T ₁ is the time required for the fuel to travel the _first predetermined distance L ₁ .

In step 5, the fuel flows through the fuel passage 13
Is calculated, the time required to move the predetermined distance L ₂ , that is, the arrival delay time T ₂ (= T ₁ · L ₂ / L ₁ ) of fuel from the downstream alcohol sensor 17 to the fuel injection valve 14 is calculated. finish. Here, steps 1 to 4 correspond to first delay time measuring means, and step 5 corresponds to second delay time calculating means.

The fuel injection amount calculation routine shown in the flowchart of FIG. 5 will be described. In step 11, the intake air flow rate Q detected based on the signal from the air flow meter 20
In step 12, the engine speed N calculated based on the signal from the crank angle sensor 21 is input. In step 13, a basic fuel injection amount Tp (= K · Q / N; K is a constant) is calculated based on the intake air flow rate Q and the engine speed N.

In step 14, before the second delay time T ₂ of the fuel calculated in step 5, the downstream alcohol sensor 17
Alcohol concentration C on the RAM, detected by
_T2 is input, and in step 15, an alcohol concentration correction value ALC corresponding to the alcohol concentration _CT2 is obtained from a map on the ROM.
Search for. Then, in step 16, the basic fuel injection amount Tp calculated in step 13 is corrected including a correction based on the alcohol concentration, and the actual fuel injection amount Ti (= Tp ·
COEF · α · ALC; COEF calculates various correction coefficients, α is an air-fuel ratio feedback correction coefficient).

Steps 14 and 15 correspond to data delay means, and step 16 corresponds to fuel injection amount correction means. Further, the two alcohol sensors are configured as an integral type as shown in FIG. That is, in the case 41, the pipe 42 whose length corresponds to the _first predetermined distance L1 is stored,
At both ends, an upstream sensor element 18a and a downstream sensor element 17a corresponding to the upstream alcohol sensor 18 and the downstream alcohol sensor 17 are arranged. Both sensor elements 17
Reference numerals a and 18a each include a cylindrical housing 43 serving as an outer electrode and a center electrode 44 inserted inside the housing 43. The inlet 45 of the upstream sensor element 18a is connected to the fuel passage 13 on the fuel pump 12 side.
The outlet 46 of the downstream sensor element is connected to the fuel passage 13 on the side of the fuel injection valve 14 (see FIG. 3).

With such an integrated sensor, it is possible to reduce the cost, to reduce the number of parts, to save labor for assembly, and to reduce the first predetermined distance L.
₁ can be accurately maintained. Further, as shown in FIG. 3, the processing circuit has a configuration in which a common signal processing circuit is provided for the two sensor element units using the analog switch 31, and this is housed in the case 41 to reduce cost. Can be achieved.

Further, since two alcohol sensors are provided, the output value is compared with a predetermined upper limit value and a lower limit value, and when the output value of the downstream alcohol sensor becomes abnormal, the output value of the upstream alcohol sensor becomes abnormal. The fuel injection amount can be corrected based on the output value of the sensor, so that a fail-safe function can be provided.

[0021]

As described above, according to the present invention, the alcohol concentration in the fuel actually injected from the fuel injection valve can be known regardless of the location of the alcohol sensor. The injection amount can be corrected. Thus, appropriate air-fuel ratio control can be performed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a block diagram of a signal processing circuit of the alcohol sensor.

FIG. 4 is a flowchart showing a routine for obtaining first and second delay times.

FIG. 5 is a flowchart showing a fuel injection amount calculation routine;

FIG. 6 is a sectional view of an integrated alcohol sensor.

FIG. 7 shows a conventional example.

FIG. 8 shows a conventional problem.

[Explanation of symbols]

 11 Fuel tank 13 Fuel passage 14 Fuel injection valve 17 Downstream alcohol sensor 18 Upstream alcohol sensor

Claims (1)

(57) [Scope of request for utility model registration] 1. A fuel supply system for an internal combustion engine having a fuel injection amount correcting means for correcting a fuel injection amount by a fuel injection valve in accordance with an alcohol concentration in fuel. A first predetermined distance between the upstream alcohol sensor and the downstream alcohol sensor, and a second predetermined distance between the downstream alcohol sensor and the fuel injection valve.
And a first delay time for measuring a first delay time required for the fuel to move from the upstream alcohol sensor to the downstream alcohol sensor based on a difference between the output change timings of the two sensors. Measuring means, and a second delay time required for the fuel to move from the downstream alcohol sensor to the fuel injector based on the measured first delay time and a ratio of the second predetermined distance to the first predetermined distance. Second delay time calculating means for calculating the calculated second delay time,
And a data delay unit for correcting the fuel injection amount by the fuel injection amount correction unit based on the alcohol concentration detected by the downstream alcohol sensor before the delay time of the fuel supply. .