Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
2000-01-05
2001-05-22
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
C123S090110, C123S090150
Reexamination Certificate
active
06234144
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the improvements of an intake-air quantity control apparatus for an internal combustion engine equipped with a variable valve timing system capable of electronically arbitrarily controlling an intake- and/or exhaust-valve timing, depending upon engine/vehicle operating conditions, and specifically to techniques for controlling a quantity of intake air entering an internal combustion engine toward a desired intake-air quantity by electronically controlling an intake valve open timing (often abbreviated to “IVO”) and an intake valve closure timing (often abbreviated to “IVC”).
2. Description of the Prior Art
Recently, there have been proposed and developed various electronically-controlled variable valve timing systems which are capable of operating intake and exhaust valves electromagnetically. One such electronically-controlled variable valve timing system for an internal combustion engine having electromagnetically-operated valve units has been disclosed in Japanese Patent Provisional Publication No. 9-256823. In the Japanese Patent Provisional Publication No. 9-256823, each of intake and exhaust valves is comprised of an electromagnetic solenoid valve whose opening and closing are achieved by way of an electromagnetic force instead of the use of a typical cam-drive mechanism. Thus, an intake-valve closure timing (IVC), an intake-valve open timing (IVO), an exhaust-valve open timing (EVO), and an exhaust-valve closure timing (EVC) can be continually changed in response to command signals from an electronic control unit (ECU). In such internal combustion engines with a variable valve timing control system having electromagnetically-operated valve units, an intake-air quantity can be adjusted by properly controlling or managing an intake valve timing (an intake-valve open timing and/or an intake-valve closure timing), in place of throttle-opening adjustment. In this type of engines with electromagnetically-operated engine valve units, a throttle valve is often eliminated, or a throttle valve is installed on the engine only for the purpose of generation of a negative pressure in an intake-air passage. Suppose an internal pressure in the intake-air passage reaches a pressure level close to atmospheric pressure with the throttle kept at an extremely less throttle opening. In this case, the intake-air quantity control system based on adjustment of an intake-valve opening time period (a time interval between IVO and IVC) is superior to that based on only the throttle-opening adjustment, from the viewpoint of a pumping loss.
SUMMARY OF THE INVENTION
In the previously-discussed variable valve timing system having electromagnetically-operated engine valve units, there is a delay for opening and/or closing operations of each of the electromagnetically-operated engine valves with respect to a timing of output of a command signal from the ECU to the respective engine valve, owing to various factors, namely aged deterioration of valve-spring characteristics, increased sliding resistance caused by a dirty aperture between the sliding portion of each of the engine valves and the associated guiding inner wall portion, clogged or choked up with deposits of sooty carbon or engine oil, and fluctuations in a demagnetized timing of each engine valve. The delay time in the valve opening and/or closing operations tends to fluctuate or vary for each engine cylinder, or the delay time in the valve opening and/or closing operations tends to fluctuate or vary for each intake stroke of the same engine cylinder. In the presence of undesired fluctuations in a delay time in the valve opening/closing operations, a quantity of intake air entering a certain engine cylinder also tends to fluctuate or vary at any time. The fluctuations in the delay time in the valve opening and/or closing operations will be hereinafter referred to simply as “valve operation delay-time fluctuations”. Additionally, owing to the “valve operation delay-time fluctuations”, the intake-air quantity may vary for each engine cylinder. As can be appreciated from two diagrams of
FIGS. 17A and 17B
, showing the relationship between an error span based on the valve operation delay-time fluctuations and a total valve opening time period, the opening time period of the intake valve is generally set at a relatively small period during low engine load (see FIG.
17
A), in comparison with during high engine load (see FIG.
17
B). Note that the ratio of the error span of the valve operation delay-time fluctuations to the total valve opening time period obtained during the low engine load tends to become greater than that obtained during the high engine load. In other words, there is an increased tendency for the intake-air quantity to be remarkably affected by the valve operation delay-time fluctuations especially during low engine loads. The increased fluctuations in the intake-air quantity, which may occur due to the valve operation delay-time fluctuations occurring during low engine loads, deteriorate idling stability of the engine and driveability of the vehicle.
Accordingly, it is an object of the invention to provide an intake-air quantity control apparatus for an internal combustion engine with a variable valve timing system which avoids the aforementioned disadvantages of the prior art.
It is another object of the invention to provide an intake-air quantity control apparatus for an internal combustion engine with a variable valve timing system which is capable of stably controlling a quantity of intake air entering each engine cylinder toward a desired intake-air quantity, even when there are valve operation delay-time fluctuations in at least an intake valve.
In order to accomplish the aforementioned and other objects of the present invention, an intake-air quantity control apparatus for an internal combustion engine with a variable valve timing system associated with at least an intake valve, comprises a control unit which controls an intake-air quantity of air entering the internal combustion engine on the basis of at least one of an intake valve open timing and an intake valve closure timing of the intake valve, the control unit comprising a desired internal pressure determination section which determines a desired internal pressure in an intake-air passage on the basis of a predetermined operating parameter, an operation delay-time fluctuation rate detection section which detects an operation delay-time fluctuation rate for fluctuations in an operation delay time of at least the intake valve, a desired intake-air quantity arithmetic-calculation section which arithmetically calculates a desired intake-air quantity on the basis of engine operating conditions, a compensation section which compensates for the desired internal pressure on the basis of at least one of the operation delay-time fluctuation rate and the desired intake-air quantity to produce a compensated internal pressure, a throttle-opening control section which controls a throttle opening on the basis of both the compensated internal pressure and the desired intake-air quantity, and an intake-valve timing control section which controls the intake valve open timing and the intake valve closure timing on the basis of both the compensated internal pressure and the desired intake-air quantity.
According to another aspect of the invention, an intake-air quantity control apparatus for an internal combustion engine with a variable valve timing system associated with at least an intake valve located at each of engine cylinders, comprises a control unit which controls an intake-air quantity of air entering the internal combustion engine on the basis of at least one of an intake valve open timing and an intake valve closure timing of the intake valve, the control unit comprising a desired internal pressure determination section which determines a desired internal pressure in an intake-air passage on the basis of at least an engine temperature, an operation delay-time fluctuation rate detection se
Obata Takeaki
Takahashi Nobutaka
Yamaguchi Musashi
Foley & Lardner
Nissan Motor Co,. Ltd.
Solis Erick
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