JPH055433A - Fuel supply device for internal combustion engine - Google Patents

Abstract

PURPOSE:To accurately judge alcohol concentration even when an alcohol sensor is deteriorated with passage of time. CONSTITUTION:At the time of starting, a detection value of an alcohol sensor is read (S2 to S4) when supply oil is decided, and a read value of this detection is corrected (S10) by a memory value (S8), read when a sensor output is stabilized, and by alcohol concentration estimated(S9) when air-fuel ratio is feedback- controlled.

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 supplying a mixed fuel obtained by mixing a fuel such as methanol and another fuel such as gasoline to an engine.

[0002]

2. Description of the Related Art The following is a conventional example of a fuel supply system for an internal combustion engine (Japanese Patent Laid-Open No. 2-102346).
(See the official gazette). That is, after calculating the basic injection amount from the detected intake air flow rate and the engine rotation speed, this basic injection amount is corrected by the alcohol concentration detected by the alcohol sensor, the correction coefficient of the air-fuel ratio detected by the oxygen sensor, etc. Then, the fuel injection amount is obtained. Then, an injection pulse signal corresponding to the calculated fuel injection amount is output to the fuel injection valve to inject and supply the fuel to the engine.

Here, the alcohol sensor is constructed by immersing a pair of electrodes in fuel, and detects the alcohol concentration according to the dielectric constant depending on the mixing ratio of the fuel by energizing these electrodes immediately after refueling. Is (actual Kaihei 1
-14952). Further, when an abnormality occurs in the alcohol sensor, the alcohol concentration is clamped to a fixed value (for example, M50) and the alcohol concentration is estimated from the deviation of the actual air-fuel ratio detected by the oxygen sensor during the air-fuel ratio feedback control from the theoretical air-fuel ratio. After that, the fuel injection amount is calculated based on this estimated alcohol concentration.

[0004]

The alcohol sensor is energized immediately after refueling to detect the alcohol concentration. However, when the alcohol sensor deteriorates, the sensor output changes and the alcohol concentration cannot be accurately detected. However, there is a problem that the drivability and the exhaust property are deteriorated. Further, in order to prevent deterioration of drivability due to deterioration over time of fuel injection valves and the like, there is one that performs learning control of the air-fuel ratio during air-fuel ratio feedback control. With this, learning progresses even if the alcohol sensor deteriorates. In the stage, it does not adversely affect the drivability. However, since it takes time until the learning progresses, there is a problem that the drivability deteriorates and the air-fuel ratio control response delay occurs during the transient operation until the learning is almost completed.

The present invention has been made in view of the above circumstances, and provides a fuel supply device for an internal combustion engine which can accurately determine the fuel composition of a mixed fuel even if the alcohol sensor is deteriorated.

[0006]

Therefore, the present invention is to supply a fuel mixed with a plurality of kinds of fuel to an engine, and to detect the fuel composition of the mixed fuel, and a fuel composition detecting means A. Air-fuel ratio detecting means B for detecting the air-fuel ratio, refueling detection means C for detecting that the fuel tank has been refueled with mixed fuel, and the fuel composition when it is determined that refueling of the mixed fuel has been performed at startup. Reading means D for reading the detection value of the detection means A, output determination means E for determining whether or not the output of the fuel composition detection means is stable after starting, and detection of the fuel composition detection means A when the output is stable. A storage unit F that reads and stores a value, a feedback control unit G that feedback-controls the air-fuel ratio so that the detected air-fuel ratio of the air-fuel ratio detection unit B becomes a target air-fuel ratio, and during the operation of the feedback control unit G. A fuel composition estimating means H for estimating the fuel composition of the mixed fuel based on the detected air-fuel ratio of Kisora ratio detecting unit B, and a fuel composition which read by said reading means D,
Based on the stored fuel composition and the estimated fuel composition, based on the estimated fuel composition from the operation of the fuel composition correction means I and the feedback control means G to the next refueling determination, From the time of refueling to the operation of the feedback control means, the fuel supply amount setting means J for setting the fuel supply amount based on the corrected fuel composition, and the fuel supply means K for driving control based on the set fuel supply amount And a drive control means L that operates.

[0007]

The detected value when the output of the alcohol sensor is stable is stored, and the fuel composition is estimated based on the detected value of the air-fuel ratio detecting means during the air-fuel ratio feedback control. And, at the time of starting, when refueling is performed,
The output value of the alcohol sensor after refueling is corrected by the estimated fuel composition and the stored value, and the fuel supply control is performed by the corrected value until the estimation of the fuel composition by the air-fuel ratio feedback control is started. When the estimation of is started, fuel supply control is performed by the estimated value until the next refueling determination.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 2, the microcomputer 1 has an intake air amount detection signal from the air flow meter 2, a reference signal (corresponding to the engine rotation speed) and a position signal from the crank angle sensor 3, and an oxygen concentration in the exhaust gas. An oxygen concentration detection signal from an oxygen sensor 4 as an air-fuel ratio detecting means for detecting a fuel ratio, and an alcohol concentration detection signal from an alcohol sensor 5 as a fuel composition detecting means interposed in a fuel supply passage (not shown). , Has been entered. Further, the microcomputer 1 is provided with a throttle valve opening detection signal from the throttle sensor 6,
A vehicle speed detection signal from a vehicle speed sensor 7 and a fuel remaining amount detection signal from a fuel remaining amount sensor 8 as a fueling time detecting means for detecting a fuel remaining amount in a fuel tank (not shown) are input. ..

Here, the alcohol sensor 5 is constructed by immersing a pair of electrodes in fuel similarly to the conventional example, and a capacitance type which outputs a voltage according to the alcohol concentration by energizing these electrodes. It is a sensor. The microcomputer 1 also includes an I / O 1A, a CPU 1B, and an R
It is configured to include an OM1C and a RAM1D,
The fuel injection amount is calculated based on signals from the various sensors and the like, and an injection pulse signal is output to the fuel injection valve 9 as the fuel supply means.

Here, the microcomputer 1 constitutes reading means, output determining means, storage means, feedback control means, fuel composition estimating means, fuel composition correcting means, fuel supply amount setting means, and drive control means. Next, the operation will be described with reference to the flowcharts of FIGS. In S1, it is determined whether or not the starter switch is turned on, and YE
If S, the process proceeds to S2, and if NO, the process returns to S1 again.

In S2, it is determined whether or not the fuel has been refueled based on the remaining fuel amount in the fuel tank detected by the remaining fuel amount sensor 8. If YES, the process proceeds to S3, and if NO, the process returns to S2 again. In S3, energization of the electrodes of the alcohol sensor 5 is started. In S4, the alcohol sensor 5
The alcohol sensor concentration ALC1 detected by is read.

In S5, the alcohol concentration ALC1 read in S4 is corrected by the following equation to obtain the final alcohol concentration A:
Calculate LC. ALC = (ALC1 × ALC2) / ALC3 ALC2 is the detection value of the alcohol sensor 5 when the output of the alcohol sensor 5 is stable, and ALC3 is the alcohol concentration estimated during the air-fuel ratio feedback control.

At S6, it is determined whether or not the output of the alcohol sensor 5 is stable, and if YES, the routine proceeds to S7.
When it is O, the process returns to S3 again. In S7, it is determined whether or not the air-fuel ratio feedback control is started. If YES, the process proceeds to S8, and if NO, the process returns to S7. S8
Then, the alcohol concentration ALC2 detected by the alcohol sensor 5 is stored in the RAM 1D. This alcohol concentration ALC2 is used in the arithmetic expression of S5.

In S9, the power supply to the alcohol sensor 5 is stopped. In S10, the alcohol concentration is estimated based on the detection value of the oxygen sensor 4 by the air-fuel ratio feedback control according to the routine shown in the flowcharts of FIGS. The estimated value ALC2 of this alcohol concentration is the above S5.
It is used in the arithmetic expression of. Next, an alcohol concentration estimation routine by air-fuel ratio feedback control will be described with reference to FIGS.
It will be described according to the flowchart of

In S11, it is determined whether or not the estimation of the alcohol sensor is completed. If YES, the routine is ended, and if NO, the routine proceeds to S12. In S12, it is determined whether or not the alcohol concentration (alcohol correction coefficient ALC) has been clamped, and if YES, the process proceeds to S14.
When it is O, the process proceeds to S13. In S13, the alcohol concentration (alcohol correction coefficient ALC) is clamped to a fixed value (equivalent to M50), and then the process proceeds to S14.

In S14, it is determined whether or not the estimation condition of the alcohol concentration is satisfied (when the output of the oxygen sensor 6 is reversed). If YES, the process proceeds to S15, and if NO, the process proceeds to S18. In S15, the alcohol concentration is estimated by the routine shown in the flowchart of FIG. 6 described later.

In S16, since the estimation of the alcohol concentration is estimated, the air-fuel ratio feedback correction coefficient α is initialized to 1 to start the air-fuel ratio feedback control, and then the process proceeds to S17. In S17, after starting the air-fuel ratio feedback control, the routine is ended.

If the estimation condition is not satisfied, the routine ends in S18 after starting the NG air-fuel ratio feedback control of the alcohol sensor 5 by the routine shown in the flowchart of FIG. 5 described later. Next, the NG air-fuel ratio feedback control of the alcohol sensor 5 will be described with reference to the flowchart of FIG.

In S21, it is determined whether or not a lean flag or a rich flag described later is set (ON),
If YES, the process proceeds to S29, and if NO, the process proceeds to S22. In S22, it is determined whether or not the clamp time of the air-fuel ratio feedback correction coefficient α is determined for the first time. If YES, the process proceeds to S23, and if NO, the process proceeds to S25.

At S23, the air-fuel ratio feedback correction coefficient α is clamped to 1, and then the routine proceeds to S24. In S24, the timer is set to a predetermined clamp time (for example, 5 seconds), and then the routine is ended. In S25, it is determined whether or not the count time (clamping time) of the timer has become zero. If YES, the process proceeds to S26, and if NO, the routine ends.

In S26, it is determined whether or not the actual air-fuel ratio is clamped on the rich side of the stoichiometric air-fuel ratio based on the detection value of the oxygen sensor 6. If YES, the process proceeds to S27, and if NO, the process proceeds to S28. When the actual air-fuel ratio is clamped on the rich side, the lean flag is turned on in S27, and conversely, when the actual air-fuel ratio is clamped on the lean side, the rich flag is turned on in S28.

In S29, the count time of the timer is subtracted. In S30, it is determined whether or not the actual air-fuel ratio is clamped on the rich side based on the flag, and YES
When NO (when the lean flag is on), the process proceeds to S30. When NO (when the rich flag is on), the process proceeds to S31. In S31, the air-fuel ratio feedback correction coefficient α clamped in S33 is reduced by a predetermined amount in order to make the actual air-fuel ratio lean.

At S32, the air-fuel ratio feedback correction coefficient α is increased by a predetermined amount in order to enrich the actual air-fuel ratio. Such control is performed until the actual clamp direction of the air-fuel ratio is reversed, in other words, until the estimation condition in S15 is satisfied. Next, the estimation of the alcohol concentration is shown in FIG.
It will be described according to the flowchart of

In S41, the change amount Δα from 1 of the air-fuel ratio feedback correction coefficient α (S30 or S
At 31, the change amount until the clamp direction of the actual air-fuel ratio is reversed is calculated. In S42, a new alcohol correction coefficient ALC _NEW is calculated by the following equation from the previous alcohol correction coefficient ALC _OLD and the change amount Δα.

ALC _NEW = ALC _OLD ± ALC _OLD × Δα In S43, a new alcohol correction coefficient ALC _NEW (estimated value of alcohol concentration) is stored in the RAM. As a condition for estimating the alcohol concentration, it is assumed that the learning control of the air-fuel ratio has already been completed.

The alcohol concentration calculated in S5 of FIG. 3 is used for calculating the fuel injection amount from the time of refueling determination until the air-fuel ratio feedback control is started (correctly until the alcohol concentration estimation is completed). The alcohol concentration estimated during the air-fuel ratio feedback control is used for calculating the fuel injection amount from the time when the alcohol concentration estimation is completed to the next refueling.

An injection pulse signal corresponding to the fuel injection amount thus calculated is output to the fuel injection valve 9 to inject fuel to the engine. As described above, the ratio ALC2 / of the alcohol concentration ALC2 detected by the alcohol sensor 5 at the time of the previous refueling and the alcohol sensor concentration ALC3 estimated by the air-fuel ratio feedback control.
ALC3 is the alcohol concentration A detected during refueling this time
Since the correction is made by multiplying LC1, the following effects are obtained.

That is, when the alcohol sensor 5 deteriorates with time, the alcohol concentration ALC1 after refueling is increased.
Has a predetermined deviation from the exact alcohol concentration. On the other hand, the alcohol concentration ALC3 estimated during the air-fuel ratio feedback control is calculated by subtly changing the air-fuel ratio, and therefore the alcohol concentration is substantially accurate.
Therefore, the ratio ALC2 / ALC3 corresponds to the deterioration amount of the alcohol sensor 5. Therefore, if the detection value ALC1 of the alcohol sensor 5 immediately after the start is corrected by the ratio, even if the alcohol sensor 5 deteriorates with time, immediately after refueling. Since the alcohol concentration can be accurately detected when starting the
Exhaust properties can be greatly improved. Further, in the case where the learning control of the air-fuel ratio is performed, it is possible to avoid the influence of the deterioration of the alcohol sensor 5 with time, and it is possible to prevent the deterioration of the drivability and the delay of the control response during the transient operation. In addition, since fuel injection control is performed based on the estimated accurate alcohol concentration until refueling is performed, drivability and exhaust properties can be significantly improved even if the alcohol sensor 5 deteriorates with time.

[0029]

As described above, according to the present invention, the detected value of the fuel composition detecting means when it is determined that the fuel is supplied at the time of starting, the detected value when the output is stable, and the estimated value when the air-fuel ratio feedback control is performed. Since the correction is made based on the fuel composition, the fuel composition can be accurately detected even if the fuel composition detecting means deteriorates with time, so that the drivability and the exhaust property can be greatly improved.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

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

FIG. 3 is a flowchart of the above.

FIG. 4 is a flowchart showing an estimation routine by air-fuel ratio feedback control of the above.

FIG. 5 is another flowchart of the above.

FIG. 6 is still another flowchart of the above.

[Explanation of symbols]

1 ... Microcomputer 9 ... Fuel injection valve 4 ... Oxygen sensor 5 ... Alcohol sensor 8 ... Fuel remaining amount sensor

Claims (1)

Claim: What is claimed is: 1. A fuel for mixing a plurality of types of fuel is supplied to an engine, and a fuel composition detecting means for detecting a fuel composition of the mixed fuel and an actual air-fuel ratio are detected. Air-fuel ratio detection means, refueling time detection means for detecting that fuel has been refueled in the fuel tank, and reading of the fuel composition detection means when it is determined that refueling of the mixed fuel has been performed at startup Reading means for loading, output determining means for determining whether or not the output of the fuel composition detecting means is stable after starting, storage means for reading and storing the detected value of the fuel composition detecting means when the output is stable, Feedback control means for feedback controlling the air-fuel ratio so that the detected air-fuel ratio of the air-fuel ratio detection means becomes the target air-fuel ratio, and based on the detected air-fuel ratio of the air-fuel ratio detection means during the operation of the feedback control means. Fuel composition estimating means for estimating the fuel composition of the mixed fuel, and fuel composition correcting means for correcting the fuel composition read by the reading means on the basis of the stored fuel composition and the estimated fuel composition. A fuel for setting the fuel supply amount based on the estimated fuel composition from the time when the feedback control means is operated until the next fueling determination is made, and based on the corrected fuel composition from the time when the fueling is performed to the time when the feedback control means is operated. A fuel supply device for an internal combustion engine, comprising: a supply amount setting means; and a drive control means for drivingly controlling the fuel supply means based on the set fuel supply amount.