Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
1999-11-17
2001-08-21
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C123S090150, C123S316000, C123S405000
Reexamination Certificate
active
06276316
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 on operating condition of the engine/vehicle operating conditions.
2. Description of the Prior Art
In recent years, there have been proposed and developed various electronically-controlled variable valve timing systems which are capable of operating intake and exhaust valves electromagnetically or hydraulically. One such electronically-controlled variable valve timing system having electromagnetically-operated valve units has been disclosed in Japanese Patent Provisional Publication No. 8-200025. In the Japanese Patent Provisional Publication No. 8-200025, intake and exhaust valves are electronically arbitrarily controlled by means of an electromagnetic-solenoid valve controller, in place of a typical cam-drive mechanism. Japanese Patent Provisional Publication No. 7-317516 has disclosed an electronically-controlled, hydraulically-operated variable valve timing system having a pair of slidable plungers defining a pressure chamber therebetween, and an electromagnetic spill valve provided for each engine cylinder and fluidly connected to the pressure chamber for the purpose of working-fluid supply and working-fluid cut-off to the pressure chamber. The upper plunger is permanently pressed on the cam profile of a cam for producing reciprocating motion of the upper plunger during rotation of the cam, whereas the lower plunger is in abutted-engagement with the upper end of the valve stem. Thus, the motion of the cam is transmitted from the upper plunger via the working oil fed into the pressure chamber to the lower plunger. The working fluid in the pressure chamber can be exhausted therefrom via a flow-restricting orifice to cause a dampening effect. An intake valve closing point or an intake valve close timing (often abbreviated to “IVC”), an intake valve open timing point (often abbreviated to “IVO”), an exhaust valve closure timing (often abbreviated to “EVC”), and/or an exhaust valve open timing (often abbreviated to “EVO”) can be adjusted by electronically controlling the activation and de-activation of the spill valve for each engine cylinder.
SUMMARY OF THE INVENTION
On internal combustion engines with an electronically-controlled variable valve timing system having electromagnetically-operated or hydraulically-operated valve units, it is possible to change the quantity of intake air entering an engine cylinder by varying an intake valve open timing (IVO) or an intake valve closure timing (IVC). For instance, assuming that the intake valve open timing (IVO) is set at or fixed to a predetermined crank angle, it is possible to control the quantity of intake air introduced into the engine cylinder by varying the intake valve closure timing (IVC). Alternatively, assuming that the intake valve close timing point (IVC) is set at or fixed to a predetermined crank angle, it is possible to control the quantity of intake air introduced into the engine cylinder by varying the intake valve open timing (IVO). Especially in controlling the intake-air quantity by means of an electromagnetically-operated intake valve unit, however, it is difficult to rapidly close the intake valve for a brief moment just after the intake valve is opened. That is to say, there is a possibility that the intake-air quantity cannot be adequately reduced to a small value required for during high speed and light load, or during vehicle deceleration, owing to operating characteristics of the electromagnetically-operated intake valve unit (containing an operating speed, and a minimum operating time period from valve open action to valve close action). The controllable band for engine output torque (engine power output) would be narrowed. In order to enhance one of the operating characteristics of the electromagnetic intake-port valve unit, that is, to shorten the minimum valve operating time period, the electromagnetic intake-port valve unit requires more electric power. This results in an increase in electric-power consumption. Also, an excessively short operating time period deteriorates the durability of the electromagnetic intake-port valve unit. The inventors of the present invention pay their attention to the fact that a volumetric capacity of an engine cylinder is same when a downstroke position of the piston on the intake stroke is identical to an upstroke position of the piston on the compression stroke. From the view point discussed above and to avoid the previously-described problems, the inventors of the invention discovers that, if the intake valve cannot be closed during an intake stroke due to the valve operating characteristics, it is desirable to close the intake valve during a compression stroke following the intake stroke.
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 providing a required intake-air quantity without increasing electric power consumption, during high speed and light load, or during vehicle deceleration.
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 an intake valve, comprises a control unit which controls an intake-air quantity of air entering an engine cylinder on the basis of an intake valve closure timing of the intake valve, the control unit comprising a determination section which determines whether the intake valve should be closed during an intake stroke or during a compression stroke following the intake stroke, on the basis of at least engine operating conditions, a valve closure timing setting section which sets an intake valve closure timing on the intake stroke and an intake valve closure timing on the compression stroke, on the basis of the engine operating conditions, and a valve closure timing control section which closes the intake valve at either one of the intake valve closure timing on the intake stroke and the intake valve closure timing on the compression stroke, on the basis of a decision of the determination section.
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 an intake valve, comprises an intake-valve side actuator adjusting an opening of the intake valve, a control unit configured to be electronically connected to the intake-valve side actuator, for controlling the opening timing of the intake valve, and for controlling an intake-air quantity of air entering an engine cylinder on the basis of an intake valve closure timing of the intake valve, the control unit comprising a target intake-air quantity arithmetic-calculation section which calculates a target intake-air quantity on the basis of engine operating conditions including an accelerator opening and engine speed, an intake valve closure timing arithmetic-calculation section which calculates both an intake valve closure timing on an intake stroke and an intake valve closure timing on a compression stroke, on the basis of the target intake-air quantity and the engine speed of the engine operating conditions, a valve operating time period arithmetic-calculation section which calculates an operating time period of the intake valve from an intake valve open timing to an intake valve closure timing, on the basis of the engine speed of the engine operating conditions, a comparator which compares an intake-valve operating crank angle corres
Arai Masahiro
Nagaishi Hatsuo
Foley & Lardner
Lo Weilun
Nissan Motor Co,. Ltd.
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