초록 ▼

A valve actuating apparatus for an internal combustion engine selectively operating in the normal Otto cycle or the Miller cycle is provided which enables the engine to achieve stable combustion and improved fuel economy during cruising or in a low-load engine operating region. A delayed-closing cam

A valve actuating apparatus for an internal combustion engine selectively operating in the normal Otto cycle or the Miller cycle is provided which enables the engine to achieve stable combustion and improved fuel economy during cruising or in a low-load engine operating region. A delayed-closing cam for Miller cycle operation and a normal cam having a cam profile for earlier valve-closing timing of the intake valve than a cam profile of the delayed-closing cam are provided on a camshaft. A cam profile-switching mechanism switches between the delayed-closing cam and the normal cam, for opening and closing the intake valve. An ECU controls the switching mechanism such that when a detected operating condition of the engine indicates starting or idling, the intake valve is operated by the normal cam, and when the detected operating condition indicates cruising, the intake valve is operated by the delayed-closing cam.

대표청구항 ▼

1. A valve actuating apparatus for an internal combustion engine, which actuates an intake valve of the engine for opening and closing thereof, the intake valve comprising at least a first intake valve and a second intake valve,the valve actuating apparatus comprising: a camshaft that is driven for

1. A valve actuating apparatus for an internal combustion engine, which actuates an intake valve of the engine for opening and closing thereof, the intake valve comprising at least a first intake valve and a second intake valve,the valve actuating apparatus comprising: a camshaft that is driven for rotation in synchronism with rotation of the engine; a delayed-closing cam provided on said camshaft, for operation of the engine in a Miller cycle; a normal cam provided on said camshaft and having a cam profile for earlier valve-closing timing of the intake valve than a cam profile of said delayed-closing cam; an idling cam provided on said camshaft and having a cam profile for making the first intake valve substantially idle; a switching mechanism that switches the intake cam for opening and closing the intake valve, between said delayed-closing cam and said normal cam; operating condition-detecting means for detecting an operating condition of the engine, wherein said operation condition-detecting means includes load parameter-detecting means for detecting a load parameter indicative of a load on the engine; and switching mechanism control means for controlling said switching mechanism such that when the detected operating condition of the engine indicates starting or idling of the engine, the intake valve is opened and closed by said normal cam, and when the detected operating condition of the engine is a predetermined operating condition indicating other than the starting and idling of the engine, the intake valve is opened and closed by said delayed-closing cam, wherein the predetermined operating condition of the engine includes a condition of the load parameter detected by said load parameter-detecting means being smaller than a first predetermined value, and wherein said switching mechanism control means controls said switching mechanism such that when the load parameter is smaller than a second predetermined value which is smaller than the first predetermined value, the first intake value is made substantially idle by said idling cam, and the second intake valve is opened and closed by said delayed-closing cam, and when the load parameter is equal to or larger than the second predetermined value and smaller than the first predetermined value, the first intake valve and the second intake valve are opened and closed by said delayed-closing cam. 2. A valve actuating apparatus as claimed in claim 1, wherein said normal cam comprises:a low-speed cam having a cam profile that gives a valve lift of the intake valve, which is equal to or smaller than a valve lift given by the cam profile of said delayed-closing cam, and a high-speed cain having a cam profile that gives a valve lift of the intake valve, which is larger than the valve lifts given by the respective cam profiles of said delayed-closing cam and said low-speed cam, the valve actuating apparatus further comprising: a first rocker arm in contact with said idling cam and the first intake valve, a second rocker arm in contact with said delayed-closing cam, a third rocker arm in contact with said low-speed cam and the second intake valve, and a fourth rocker arm in contact with said high-speed cam, and said switching mechanism having: a first switching device for switching between connection and disconnection of said second rocker arm and said third rocker arm, a second switching device for switching between connection and disconnection of said first rocker arm and said third rocker arm, and a third switching device for switching between connection and disconnection of said first rocker arm, said third rocker arm, and said fourth rocker arm, and wherein said first rocker arm is smaller in width along a direction of an axis of said crankshaft than said third rocker arm, and said second rocker arm is disposed between said first rocker arm and said third rocker arm, said fourth rocker arm being disposed on a side of said first rocker arm remote from said second rocker arm. 3. A valve actuating apparatus for an internal combustion engine, which actuates an intake valve or the engine for opening and closing thereof, the intake valve comprising at least a first intake valve and a second intake valve,the valve actuating apparatus comprising: a camshaft that is driven for rotation in synchronism with rotation of the engine; a delayed-closing cam provided on said camshaft, for operation of the engine in a Miller cycle; a normal cam provided on said camshaft and having a cam profile for earlier valve-closing timing of the intake valve than a cam profile of said delayed-closing cam; an idling cam provided on said camshaft and having a cam profile for making the first intake valve substantially idle; a switching mechanism that switches the intake cam for opening and closing the intake valve, between said delayed-closing cam and said normal cam; operating condition-detecting means for detecting an operating condition of the engine, wherein said operating condition-detecting means comprises load parameter-detecting means for detecting a load parameter indicative of a load on the engine; and switching mechanism control means for controlling said switching mechanism such that when the detected operating condition of the engine indicates starting or idling of the engine, the intake valve is opened and closed by said normal cam, and when the detected operating condition of the engine is a predetermined operating condition indicating other than the starting and idling of the engine, the intake valve is opened and closed by said delayed-closing cam, wherein the engine is installed on a vehicle, and wherein the predetermined operating condition of the engine corresponds to cruising of the vehicle, and wherein said switching mechanism control means controls said switching mechanism such that under the predetermined operating condition of the engine corresponding to the cruising of the engine, when the load parameter detected by said load parameter-detecting means is smaller than a predetermined value, the first intake valve is made substantially idle by said idling cam, and the second intake valve is opened and closed by said delayed-closing cam, and when the load parameter is equal to or larger than predetermined value, the first intake valve and the second intake valve are opened and closed by said delayed-closing cam. 4. A valve actuating apparatus as claimed in claim 3, wherein said normal cam comprises:a low-speed cam having a cam profile that gives a valve lift of the intake valve, which is equal to or smaller than a valve lift given by the cam profile of said delayed-closing cam, and a high-speed cam having a cam profile that gives a valve lift of the intake valve, which is larger than the valve lifts given by the respective cam profiles of said delayed-closing cam and said low-speed cam, the valve actuating apparatus further comprising: a first rocker arm in contact with said idling cam and the first intake valve, a second rocker arm in contact with said delayed-closing cam, a third rocker arm in contact with said low-speed cam and the second intake valve, and a fourth rocker arm in contact with said high-speed cam, and said switching mechanism having: a first switching device for switching between connection and disconnection of said second rocker arm and said third rocker arm, a second switching device for switching between connection and disconnection of said first rocker arm and said third rocker arm, and a third switching device for switching between connection and disconnection of said first rocker arm, said third rocker arm, and said fourth rocker arm, and wherein said first rocker arm is smaller in width along a direction of an axis of said crankshaft than said third rocker arm, and said second rocker arm is disposed between said first rocker arm and said third rocker arm, said fourth rocker arm being disposed on a side of said first rocker arm remote from said second rocker arm.