Apparatus for controlling internal combustion engine equipped with variable valve timing control device

An apparatus for controlling an internal combustion engine equipped with a variable valve timing control device includes the variable valve timing control device for restricting a relative rotation between a crankshaft and an exhaust camshaft at a starting of the internal combustion engine at a most advanced angle phase or at an intermediate angle phase between the most advanced angle phase and a most retarded angle phase. An apparatus for controlling an internal combustion engine equipped with a variable valve timing control device further includes a throttle valve control means for controlling an opening of the throttle valve provided at an intake passage of the internal combustion engine. The throttle valve control means controls the throttle valve to be opened when the internal combustion engine is started, thereby to restrict the relative rotation between the crankshaft and the exhaust camshaft.

This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2002-158134 filed on May 30, 2002, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to an apparatus for controlling an internal combustion engine equipped with a variable valve timing control device.

BACKGROUND OF THE INVENTION

A known variable valve timing control device for an internal combustion engine is disclosed in Japanese Patent Laid-Open Publication No. 11-294121. The disclosed variable valve timing control device is provided in the drive train that transmits a drive force from a crankshaft of the internal combustion engine to a camshaft for opening and closing an exhaust valve of the combustion engine. The known variable valve timing control device includes a housing member rotating with the crankshaft and a vane member rotating with the camshaft and accommodated in a receiving space formed within the housing member so as to rotate relative to the housing member within a predetermined angle. The variable valve timing control device further includes a switching valve for controlling an operation oil supply to an advanced angle chamber defined in the receiving space by the vane member and which volume becomes larger as the vane portion is rotated in an advanced angle direction relative to the housing member by virtue of the supply of the operation oil, and a retarded angle chamber defined in the receiving space by the vane member and which volume becomes larger as the vane member is rotated in a retarded angle direction relative to the housing member by virtue of the supply of the operation oil. Furthermore, the variable valve timing control device includes an oil pump for generating the operation oil, and a torsion spring for biasing the vane member to the advanced angle side (i.e., the direction that enlarges the advanced angle chamber) relative to the housing member. The biasing force of the torsion spring is set higher than or equal to an average torque of the camshaft at idling of the combustion engine under a high oil temperature for ensuring restarting performance of the engine.

According to the above-mentioned variable valve timing control device, if the engine is stopped irregularly under a low oil temperature, the biasing force of the torsion spring may become under the average torque of the camshaft due to a high viscosity of the operation oil. The engine cannot be sopped under the condition that the vane member is surely retained to the most advanced angle side. After the variable valve timing control device is stopped at any positions other than a most advanced angle phase (i.e., a phase of the camshaft is most advanced relative to the crank shaft) or an initial position, i.e. an intermediate angle phase positioned between the most advanced angle phase and a most retarded angle phase (i.e., the phase of the camshaft is most retarded relative to the crank shaft), a valve overlap period during which the exhaust valve and an intake valve are open at the same time is set longer when a sufficient oil is not generated by cranking rotations of the combustion engine for operating the variable valve timing control device for the exhaust valve at restarting of the combustion engine. Therefore, in the intake process, the exhaust gas inflows from the exhaust side and thus a new air-fuel mixture cannot inflows from the intake side. A stable ignition of the internal combustion engine is impossible, thereby enabling to start the internal combustion engine.

Thus, a need exists for an apparatus for controlling internal combustion engine equipped with a variable valve timing control device which can start the internal combustion engine even if the variable valve timing control device is stopped at a position other than the most advanced angle phase or the Intermediate angle phase.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an apparatus for controlling an internal combustion engine equipped with a variable valve timing control device includes the variable valve timing control device provided in a drive train that transmits a drive force from a crankshaft of the internal combustion engine to an exhaust camshaft of the internal combustion engine so as to restrict or allow a relative rotation between the crankshaft and the exhaust camshaft. The variable valve timing control device controls an opening and a closing timing of an exhaust valve by restricting the relative rotation between the crankshaft and the exhaust camshaft at a starting of the internal combustion engine at a most advanced angle phase where a phase of the camshaft is most advanced relative to the crankshaft or at an intermediate angle phase between the most advanced angle phase and a most retarded angle phase where the phase of the camshaft is most retarded relative to the crankshaft, and by allowing the relative rotation between the crankshaft and the exhaust camshaft. An apparatus for controlling a variable valve timing of an internal combustion engine further includes a throttle valve control means for controlling an opening of the throttle valve provided at an intake passage of the internal combustion engine. The throttle valve control means controls the throttle valve to be opened when the internal combustion engine is started thereby to restrict the relative rotation between the crankshaft and the exhaust camshaft.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention is explained referring to attached drawings.FIG. 1is a schematic view of the present invention employed in an internal combustion engine (herein after referred to as engine)1installed in a vehicle. An apparatus for controlling an internal combustion engine equipped with a variable valve timing control device of the present invention includes the variable valve timing control device10, a cam angle sensor3afor detecting the rotational phase angle of an exhaust camshaft3for opening and closing an exhaust valve (not shown), and a crank angle sensor (engine speed sensor)5afor detecting the rotational phase angle of a crankshaft5. The control device also includes an electronic control throttle9having a throttle valve9aprovided at an intake passage100for controlling an intake air flow, a throttle sensor9bfor detecting the opening of the throttle valve9aand a throttle motor9cfor operating the throttle valve9a. The control device further includes an electronic control unit (ECU)8for controlling the electronic control throttle9and the like.

The ECU8calculates an actual valve timing of the exhaust valve by signals from the crank angle sensor5aand the cam angle sensor3a. In addition, the ECU8controls the actual valve timing so that the exhaust valve can be opened or closed at an appropriate timing being preset in the ECU8and sets an appropriate valve timing in accordance with the engine driving condition. Further, the ECU8controls the opening of the throttle valve9ain response to the engine speed calculated by a signal from the crank angle sensor5a, a signal from a timer installed in the ECU8, and a signal from the throttle sensor9b. That is, the ECU performs the operation at the engine start.

An operation of the embodiment is explained as follows.

The operation routine of the embodiment at the engine start is explained referring to a flowchart in FIG.2. The operation is carded out by the ECU8repeatedly at predetermined time intervals. At Step301, a timer installed in the ECU8is turned on for counting an elapsed time from the initiation of a starter triggered by an ignition (IG) turned on. Next at Step302, an engine speed Nes is read by the crank angle sensor5a. Then, at Step303, it is determined whether the engine speed Nes exceeds a predetermined idle speed Nea. When the engine speed Nes exceeds the predetermined idle speed Nea, the operation proceeds to Step309at which a normal control for setting an appropriate valve timing is performed depending on the engine driving condition. When the engine speed Nes is below the predetermined idle speed Nea, the operation proceeds to Step304. At Step304, it is determined whether a total starter operation time Ts is longer than a throttle control start set time Ta. When the total starter operation time Ts is shorter than the throttle control start set time Ta, the operation returns to Step302. When the total starter operation time Ts is longer than the throttle control start set time Ta, the operation proceeds to Step305at which a forced throttle control is initiated by the ECU8to open the throttle valve9a. At this time, a new air-fuel mixture can flow in the engine1and thus the combustion state of the engine can be stabilized, thereby enabling the engine start. Next, the operation proceeds to Step306at which an engine speed Net is read by the crank angle sensor5a. Then, at Step307, it is determined whether the engine speed Net exceeds the predetermined idle speed Nea. When the engine speed Net is below the predetermined idle speed Nea, the operation returns to Step306. When the engine speed Net exceeds the predetermined idle speed Nea, the operation proceeds to Step308at which the forced throttle control is stopped. At this time, the engine1is in a normal driving condition and thus the operation proceeds to Step309at which the normal control is performed for setting the appropriate valve timing depending on the engine driving state.

According to the above-mentioned embodiment, since the throttle valve is opened even if the valve overlap period during which the exhaust valve and the intake valve are open at the same time is longer at the engine restarting, the new air-fuel mixture can flow into the engine, thereby enabling the engine start.

In addition, according to the above-mentioned embodiment, a stable engine start is available since a predetermined throttle opening is set.

Further, according to the above-mentioned embodiment, an over speed of the engine at starting can be prevented, thereby protecting the engine.