JP2767345B2 - Fuel supply control 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 control device for an internal combustion engine, and more particularly, to an internal combustion engine in which the adsorbed fuel vapor is purged from the interior of a canister for adsorbing fuel vapor into an intake system of the engine. It relates to fuel supply control technology.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, an evaporative fuel purging system (evaporation purge system) for purging adsorbed evaporative fuel into an intake system of an engine from inside a canister for adsorbing evaporative fuel such as gasoline from a fuel tank. System) is known. Such techniques are specifically
A purge passage that passes through the interior of the canister and reaches the intake system of the engine is provided, and a purge valve that controls the amount of fuel vapor purge is provided in the purge passage.

[0003] The adsorbed evaporative fuel is adsorbed on activated carbon or the like in a canister, and the adsorbed evaporative fuel is returned to an intake system in a predetermined operation state of the engine. That is, the evaporated fuel adsorbed on the activated carbon in the canister is separated from the activated carbon and is purged into the intake passage in a separate system from the normal fuel injection path by the suction negative pressure effect of the intake system,
Provided for combustion.

[0004]

However, in an internal combustion engine provided with the above-described conventional fuel vapor purge system, the structure for controlling the fuel injection amount in consideration of the purge amount of the fuel vapor is conventionally known. It is not adopted, and the air-fuel ratio is enriched by the purge of the evaporated fuel, resulting in deterioration of drivability and emission.

Further, in the future, it is necessary to increase the purge amount of the evaporated fuel due to the revision of the law, so that the conventional open-loop control of the fuel supply amount cannot cope with the problem, and the above-mentioned operability and emission deteriorate. There is a problem that. In view of the above-mentioned conventional problems, an object of the present invention is to improve the fuel supply control, thereby preventing the air-fuel ratio from being enriched by purging the evaporated fuel, and improving the drivability and emission.

[0006]

Therefore, a fuel supply control device for an internal combustion engine according to the present invention, as shown in FIG. 1, passes through an interior of a canister that adsorbs fuel vapor from a fuel tank and an intake system of the engine. An engine operating state detecting means for detecting an engine operating state in an internal combustion engine provided with a purge passage for controlling an amount of evaporative fuel purged in the purge passage. Fuel supply amount control means for controlling the fuel supply amount to the engine; air-fuel ratio calculation means for calculating an air-fuel ratio according to the fuel supply amount when a predetermined operating state is detected by the engine operation state detection means; Detecting a combustion pressure when a predetermined operating state is detected, and measuring an air-fuel ratio according to the combustion pressure.
Air-fuel ratio measuring means, purge valve control means for opening the purge valve for a predetermined time when a predetermined operating state is detected, detecting the combustion pressure after opening the purge valve, and measuring the air-fuel ratio according to the combustion pressure A second air-fuel ratio measuring unit that performs the fuel supply amount according to a comparison result between the air-fuel ratio calculated by the air-fuel ratio calculating unit and the air-fuel ratio measured by the first and second air-fuel ratio measuring units. And a fuel supply amount reduction correcting means for reducing the fuel supply amount controlled by the control means.

[0007]

In this configuration, the final fuel is determined based on the comparison result between the air-fuel ratio measured from the combustion pressure when the purge valve is closed and the combustion pressure when the purge valve is opened and the calculated air-fuel ratio derived from the actual fuel supply amount before the purge. The supply is reduced and controlled. Therefore, it is possible to prevent the air-fuel ratio from being enriched by purging the evaporated fuel, to control the air-fuel ratio to an appropriate value, and to improve the drivability and the emission.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. In FIG. 2 showing a system configuration of an embodiment of the present invention, air is sucked into an internal combustion engine (hereinafter referred to as an engine) 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. . In the branch section of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder.
Is provided. The fuel injection valve 6 is an electromagnetic fuel injection valve that is energized by a solenoid and opens, and is deenergized and closed by being energized by a drive pulse signal from a control unit 12 described later. Fuel which is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator is injected and supplied.

An ignition plug 7 is provided in each combustion chamber of the engine 1, and the air-fuel mixture flowing into the combustion chamber is spark-ignited by opening the intake valve 21 to ignite and burn the air-fuel mixture. Then, exhaust gas is discharged from the engine 1 through an exhaust valve (not shown), an exhaust manifold 8, an exhaust duct 9, and the like. The control unit 12 includes a CPU,
A microcomputer including a ROM, a RAM, an A / D converter, an input / output interface, and the like;
It receives detection signals from various sensors and performs arithmetic processing as described later to control the operation of the fuel injection valve and the like.

The various sensors include an intake duct 3
An air flow meter 13 of a hot wire type or the like is provided therein, and outputs a signal corresponding to the intake air flow rate Q of the engine. Further, a crank angle sensor 14 is provided, and outputs a reference signal and a unit angle signal. Here, the engine rotation speed N can be detected by measuring the cycle of the reference signal or the number of unit angle signals generated within a predetermined time.

Further, a water temperature sensor 15 for detecting a cooling water temperature Tw of the engine 1 and the like are provided. Further, a potentiometer type throttle valve opening sensor 17 for detecting the opening TVO of the throttle valve 4 is provided. on the other hand,
As a configuration according to the present invention, a canister 23 that adsorbs evaporated fuel such as gasoline from the fuel tank 22 is provided,
A purge passage 25 for adsorbed and evaporated fuel is provided which passes through the interior of the canister 23 and reaches an intake system of the engine 1, that is, an intake passage between the throttle valve 4 and the fuel injection valve 6.
The purge passage 25 is provided with a purge valve 24 for controlling the purge amount of the fuel vapor.

Further, a pressure sensor 26 for detecting the combustion pressure is provided. Here, in the present embodiment, when a predetermined operating state (for example, a steady operating state) is detected by various sensors as engine operating state detecting means, the fuel supply amount, that is, the final fuel injection described later Quantity T _i (= T _p
× COEF + T _s) depending on the detected air-fuel ratio calculating means for calculating an air-fuel ratio CAF, the combustion pressure when said predetermined operating condition is detected, the air-fuel ratio MAF ₁ in accordance with the combustion pressure
First air-fuel ratio measurement means for measuring the combustion pressure, purge valve control means for opening the purge valve 24 for a predetermined time when a predetermined operating state is detected, and detecting the combustion pressure after the purge valve 24 is opened, Air-fuel ratio MAF according to
₂ , the air-fuel ratio CAF calculated by the air-fuel ratio calculating means, and the air-fuel ratios MAF ₁ , M measured by the first and second air-fuel ratio measuring means, respectively.
Depending on the result of comparison between the AF ₂ provided, and the fuel supply amount reduction correcting means for decreasing correction of the controlled fuel supply amount by said fuel supply amount control means.

The microcomputer built in the control unit 12 is started at regular time intervals as shown in FIG.
Calculation processing and the like are performed in accordance with the flowchart of FIG. In this embodiment, the fuel supply amount control means, the air-fuel ratio calculation means,
The functions as the first air-fuel ratio measurement unit, the second air-fuel ratio measurement unit, the purge valve control unit, and the fuel supply amount decrease correction unit are provided by software as shown in the flowchart of FIG.

In the flowchart of FIG. 3, in step 1 (indicated as S1 in the figure, the same applies hereinafter), it is determined from a condition such as a load whether or not a predetermined operating state (for example, a steady operating state). . If it is a predetermined driving state,
Proceeding to step 2, if not in the predetermined operating state, the control ends. In step 2, the final fuel injection amount T
_The air-fuel ratio CAF is calculated according to _i (= T _p × COEF + T _s ).

Here, the intake air flow rate of the engine 1 is matched with the intake air flow rate Q detected by the air flow meter 13 and the engine rotation speed N calculated based on the output signal from the crank angle sensor 14. basic fuel injection quantity (basic fuel supply quantity) T _p is calculated according to the equation below. T _p = K · Q / N Then, the basic fuel injection amount T _p and various correction coefficients COE
F, change in the effective injection time by the power supply voltage variation of the fuel injection valve using a correction amount T _s for correcting the final fuel injection amount T _i is computed.

Here, the air-fuel ratio CAF is calculated by the following equation. CAF = a × T _i (a is an air-fuel ratio calculation coefficient) In step 3, the combustion pressure is detected, and the air-fuel ratio MAF ₁ is measured according to the combustion pressure. In this case, the air-fuel ratio MAF
₁ is represented by the following equation.

MAF ₁ = b × px where px is a combustion air-fuel ratio index determined as shown in FIG. 4 by the combustion temperature calculated from the combustion pressure, and px is 1 when the air-fuel ratio is 14.7. Is set. B is an air-fuel ratio constant. Therefore, in step 3, px corresponding to the combustion temperature at that time is read, and b × px is calculated to measure MAF ₁ .

In step 4, it is determined whether or not there is a change in the engine operating state. If there is no change, the process proceeds to step 5, and if there is, the control is terminated. In step 5, the purge valve 24 is controlled to be opened for a certain time. In step 6, to detect the combustion pressure after the purge valve open, to measure the air-fuel ratio MAF ₂ in accordance with the combustion pressure.

Also in this case, the air-fuel ratio MAF_TwoIs given by
MAF_Two= B × px Read the px corresponding to the combustion temperature at that time, and b × px
And calculate MAF _TwoIs measured. In step 7,
Before and after opening the purge valve 24 of the air-fuel ratio according to the combustion pressure
Change in value after release (MAF_Two-MAF₁) And the actual fuel
Injection amount T_iThe difference SAF of the air-fuel ratio CAF calculated from
Determine according to the formula.

SAF = (MAF ₂ −MAF ₁ ) −CAF This SAF is based on a measured air-fuel ratio change amount caused by purging of the fuel vapor into the intake passage based on the opening of the purge valve 24 and an actual fuel injection amount before the purge. In step 8, this SAF is the difference from the calculated air-fuel ratio derived from
Was rich fraction correction amount of the fuel injection amount, the various correction is subtracted from the coefficients COEF, it is calculated based on the final fuel injection amount T _i in the following equation.

As is clear from the fuel supply control of T _i = T _p × (COEF-SAF) + T _s or more, the fuel pressure is measured from the combustion pressure when the purge valve 24 is closed and when it is opened, ie, from the combustion pressure before and after the fuel vapor purge. The final fuel injection amount _Ti is controlled based on a comparison result between the air-fuel ratio calculated from the actual fuel injection amount before the purge and the calculated air-fuel ratio derived from the actual fuel injection amount before the purge. The enrichment can be prevented, the air-fuel ratio can be controlled to an appropriate value, and the drivability and emission can be improved.

As described above, the present invention has been described with reference to the specific embodiments. However, the present invention is not limited to these embodiments, and is attached to the present invention by a person skilled in the art. Without departing from the scope of the appended claims.
It should be noted that various changes and modifications are possible.

[0023]

As described above, according to the present invention,
The air-fuel ratio calculated according to the fuel supply amount when the predetermined operation state is detected, the air-fuel ratio measured according to the combustion pressure when the predetermined operation state is detected, and the combustion pressure after opening the purge valve. Since the fuel supply amount is configured to be reduced according to the comparison result with the air-fuel ratio measured according to
Prevent enrichment of the air-fuel ratio by purging evaporated fuel,
Drivability and emission can be improved, and the usability can be easily coped with an increasing tendency of fuel vapor.

[Brief description of the drawings]

FIG. 1 is a block diagram of a fuel supply control device for an internal combustion engine according to the present invention.

FIG. 2 is a system diagram showing an embodiment of the above device.

FIG. 3 is a flowchart showing control contents of the embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a combustion temperature calculated based on a combustion pressure and a combustion air-fuel ratio index.

[Explanation of symbols]

 Reference Signs List 1 engine 6 fuel injection valve 12 control unit 22 fuel tank 23 canister 24 purge valve 25 purge passage 26 pressure sensor

Continuation of the front page (56) References JP-A-58-131343 (JP, A) JP-A-63-41632 (JP, A) JP-A-63-55357 (JP, A) JP-A-63-57841 (JP, A) JP-A-63-131843 (JP, A) JP-A-63-253142 (JP, A) JP-A-63-253143 (JP, A) JP-A-1-267338 (JP, A) 2-130240 (JP, A) JP-A-3-222841 (JP, A) JP-A-5-288107 (JP, A) JP-A-5-321772 (JP, A) JP-A-63-190541 (JP, A) U) Japanese Utility Model 1-145958 (JP, U) Japanese Utility Model 1-148043 (JP, U) Japanese Utility Model 2-85843 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) ) F02D 41/14 310 F02D 41/02 330 F02D 45/00 368 F02M 25/08 301

Claims (1)

(57) [Claims] 1. A purge passage which passes through the interior of a canister for adsorbing fuel vapor from a fuel tank and reaches an intake system of an engine is provided, and a purge valve for controlling a purge amount of the fuel vapor is provided in the purge passage. In an internal combustion engine, an engine operating state detecting means for detecting an engine operating state, a fuel supply amount controlling means for controlling a fuel supply amount to the engine based on the engine operating state, and a predetermined operation by the engine operating state detecting means. An air-fuel ratio calculating means for calculating an air-fuel ratio according to the fuel supply amount when a state is detected, and detecting a combustion pressure when a predetermined operating state is detected, and calculating an air-fuel ratio according to the combustion pressure. First air-fuel ratio measuring means for measuring, purge valve control means for opening the purge valve for a predetermined time when a predetermined operating state is detected, and detecting a combustion pressure after opening the purge valve, Second air-fuel ratio measuring means for measuring an air-fuel ratio in accordance with the combustion pressure; air-fuel ratio calculated by the air-fuel ratio calculating means; and air-fuel ratio respectively measured by the first and second air-fuel ratio measuring means. A fuel supply control device for an internal combustion engine, comprising: a fuel supply amount reduction correcting means for correcting the fuel supply amount controlled by the fuel supply amount control means in accordance with the comparison result.