Control apparatus for internal combustion engine

Internal-combustion engines – Charge forming device – Fuel injection system

Reexamination Certificate

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Details

C123S492000, C123S677000, C123S678000, C701S104000

Reexamination Certificate

active

06666191

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a control apparatus for an internal combustion engine, and in particular to a control apparatus for an internal combustion engine, which can precisely control the volume of fuel or air in a fuel-priority type internal combustion engine wherein the flow rate of air is controlled by an electronic control valve.
BACKGROUND OF THE INVENTION
These years, even in the technical field of automobiles, there has been demanded internal combustion engines of low fuel consumption type on the background of worldwide efforts for energy saving measures. As to internal combustion engines which can satisfy the above-mentioned demand, lean-burn type internal combustion engines have been most preferable. Among the lean-burn type internal combustion engines, a cylinder injection type internal combustion engine can, in particular, perform combustion with an air-fuel ratio higher than 40 by directly injecting fuel into an engine cylinder so as to stratify the mixture, thereby it is possible to aim at reducing pumping loss.
In comparison with control systems for conventional internal combustion engine, a control system for the above-mentioned lean-burn cylinder injection type internal combustion engine utilizes, in general, an electronic throttle for electronically controlling an air flow rate since no proportional relationship is present between the air flow rate and the torque of the engine.
Further, the control system for a lean-burn internal combustion engine requires torque demand control in order to obtain a toque the driver desires over a broad air-fuel ratio range. There has been two types of the torque demand, that is, an air priority type and a fuel priority type.
As to the air priority type, as shown in
FIG. 14
, a desired torque computing means and a desired air-fuel ratio computing means determine a desired torque and a desired air-fuel ratio, and a desired air-fuel volume computing means computes a desired air volume with which the desired torque and the desired air-fuel ratio can be obtained. Then, an electronic throttle controls the air-volume while an air volume sensor detects an actual air volume, and a fuel injection volume computing means determines a fuel injection volume from the actual air volume and the desired air-fuel ratio.
On the contrary, as to the fuel priority type, as shown in
FIG. 15
, a desired torque computing means determines a desired torque, and a fuel injection volume computing means determines a fuel injection volume with which the desired torque is obtained. Further, a desired air-volume computing means computes a desired air volume from the desired fuel injection volume and a desired air-fuel ratio, and then an electronic throttle controls the air volume. Further, with the fuel priority type, F/B control can be made for the air volume in accordance with an output value from an air-flow rate sensor.
By the way, as mentioned above, in the fuel priority type, a technique for computing a desired fuel volume with which a desired torque can be obtained, from an accelerator opening degree and a speed of the internal combustion engine, is in general used. Accordingly, it is required to previously determine the relationship between the accelerator opening degree and the desired fuel volume, depending upon a performance of the internal combustion engine.
Meanwhile, it is required to maintain the air-fuel ratio at a constant value in order to efficiently purify exhaust gas from an internal combustion, and accordingly it is required to set the maximum value of the fuel volume to a value corresponding to an air volume in an engine cylinder upon full opening of a throttle. Should a fuel volume greater than the value corresponding to an air volume in an engine cylinder upon full opening of the throttle be fed into the internal combustion engine, fuel would be excessive, resulting in deterioration of HC and CO.
However, the air-volume in the engine cylinder upon full opening of the throttle varies, depending upon the atmospheric pressure and the atmospheric temperature or EGR, opening and closing timing of intake and exhaust valves and the like. For example, when the atmospheric pressure lowers and the air volume in an engine cylinder decreases upon full opening of the throttle, fuel becomes excessive if a predetermined fuel volume as mentioned above is fed into the internal combustion engine upon full opening of accelerator, resulting in deterioration of exhaust gas.
On the contrary, if, for example, the opening and closing timing of the intake and exhaust valves varies so that the air volume in the engine cylinder upon full opening of the throttle increases, the throttle does not reach its full opening even though the accelerator is fully opened, and accordingly, a maximum torque cannot be obtained, thereby it is possible to raise such a problem that the performance of the internal combustion engine cannot be sufficiently used.
Further, the fuel volume fed into the internal combustion engine is in general divided mainly into a part for an internal loss and a part for a shaft torque. However, the internal loss is not uniform, but varies due to such causes as unevenness in mass production and aging effect. As mentioned above, the fuel volume to be fed is limited to the value corresponding to an air volume in an engine cylinder upon full opening of the throttle, and accordingly, there has been raised such a problem that since the internal loss varies, the shaft torque should be adjusted accordingly.
In view of the facts as mentioned above, the control for the fuel priority type internal combustion engine requires changing the maximum value of the fuel supply volume in accordance with an air volume in the engine cylinder upon full opening of the throttle, and further, requires changing the fuel volume for the shaft torque in view of a maximum value of the fuel supply volume and an internal loss. With the provision of these functions, it can be expected to enhance the exhaust performance and the operating performance.
As prior art of control for the fuel priority fuel injection type internal combustion engine, there has been proposed (Japanese Laid-Open H11-159317) a control device for controlling the throttle opening degree in order to compensate a delay of air from the throttle to the cylinder. Further, as to prior art of another control for the fuel priority cylinder injection type internal combustion engine, there has been proposed (Japanese Laid-Open Patent No. H11-159377) a control device for adjusting the fuel volume to a phase of an air volume in the cylinder is proposed.
However, any of those of the above-mentioned prior art concerns a control device for compensating a difference between the transmission characteristic of air from the throttle to the engine cylinder and the transmission characteristic of fuel, but does not concerns with a variation in air-volume in the engine cylinder and variation in internal loss upon full-opening of the throttle, that is, no consideration has been made for these variations.
SUMMARY OF THE INVENTION
The present invention is devised in view of the above-mentioned problems, and an object of the present invention is to provide a control apparatus for a fuel priority type internal combustion engine, which is highly robust against variation in various conditions so as to cope with variation in air volume in an engine cylinder, variation in internal loss and the like upon full opening of a throttle throughout the control of the fuel priority cylinder injection internal combustion.
To the end, according to the present invention, there is provided a control apparatus for a fuel priority type internal combustion, which basically computes a desired fuel volume, and then computes a desired air volume from this desired fuel volume and a desired air-fuel ratio, characterized by means for detecting an operating condition of the internal combustion engine, means for detecting an environmental condition surrounding the internal combustion engine, and a means for computing a desired fuel for

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