Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2001-06-22
2002-07-30
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090170, C123S090470
Reexamination Certificate
active
06425359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve moving apparatus of an internal combustion engine having a mechanism for changing valve operating characteristic such as lift amount of at least one of an intake valve and an exhaust valve of the internal combustion engine in accordance with operating condition of the engine.
2. Description of the Related Art
Hitherto, as an apparatus for changing valve operating characteristic such as lift amount of an intake valve or an exhaust valve of an internal combustion engine in accordance with operating condition of the engine, a valve timing control apparatus of an engine disclosed in Japanese Laid-Open Patent Publication Hei 6-117207 has been known, for example. This apparatus comprises a rocking cam for opening and closing an intake valve or an exhaust valve, a driving cam for rocking the rocking cam supported on a camshaft rotated by power from a crankshaft, and a valve timing variable mechanism provided at one end of the camshaft for moving the camshaft axially and changing rotational phase of the camshaft with respect to the crankshaft. The driving cam is formed in a shape tapered in direction of axis of the camshaft.
When the camshaft is moved in one axial direction by the valve timing variable mechanism in accordance with engine operating condition, the valve is opened with a smaller lift amount and a smaller operation angle by the rocking cam rocked by the tapered driving cam which moves axially together with the camshaft. On the other hand, when the camshaft is moved in another direction, the valve is opened with a larger lift amount and a larger operation angle. Further, when the camshaft and the driving cam move axially, rotational phase of the camshaft with respect to the crankshaft is changed, and therefore a crank angle at which lift amount of the valve becomes maximum is also adjusted.
In the above prior art, since the driving cam for changing lift amount and operation angle of the valve is moved in a body with the camshaft by the valve timing variable mechanism, weight of an object to be moved by the valve timing variable mechanism (driving cam) is large, and further, sliding resistance of the camshaft supported by an engine main body is added. Therefore, response to change of the valve lift characteristic is not good. If a large driving force is desired in order to improve the response, the valve timing variable mechanism and the engine become large.
The present invention is achieved in view of the foregoing, and an object of the present invention is to provide a valve moving apparatus of an internal combustion engine that response to change of valve operating characteristic of an intake valve or an exhaust valve can be improved and the internal combustion engine can be miniaturized.
SUMMARY OF THE INVENTION
The present invention provides a valve moving apparatus of an internal combustion engine having an intake camshaft provided with at least one intake cam piece for opening and closing an intake valve, and an exhaust camshaft provided with at least one exhaust cam piece for opening and closing an exhaust valve, at least one of the intake cam piece and the exhaust cam piece being a variable cam piece provided with a variable cam section having different valve operating characteristics changing in direction of a rotary axis of the intake camshaft or the exhaust camshaft for opening and closing:the intake valve or the exhaust valve in accordance with the valve operating characteristic including lift amount and operation angle, wherein: the variable cam piece is provided on the intake camshaft or the exhaust camshaft so as to slide in direction of the rotary axis; a driving mechanism for moving the variable cam piece in direction of the rotary axis in accordance with engine operating condition to change the valve operating characteristic of the intake valve or the exhaust valve is provided; the driving mechanism comprises a movable member driven so as to reciprocate along a center axis, and arms extending from the movable member toward the intake camshaft or the exhaust camshaft having contact sections contacted with both side surfaces of the variable cam piece in direction of the rotary axis, respectively; and the center axis of the movable member is positioned near a center line of a cylinder of the internal combustion engine more than the rotary axis of the intake camshaft or the exhaust camshaft.
According to the invention, when the variable cam piece is moved in direction of the rotary axis of the camshaft to change valve operating characteristic of the intake valve or the exhaust valve, the driving mechanism moves the variable cam piece, which is provided on the camshaft so as to slide, in direction of the rotary axis of the camshaft, so that the movable cam section having different valve operating characteristics changing in direction of the rotary axis opens and closes the intake valve or the exhaust valve. Weight of the variable cam piece moved by the driving mechanism is very small compared with total weight of the driving cam and the camshaft of the above-mentioned prior art, therefore, a large driving force is unnecessary and the driving mechanism can be miniaturized.
Since the driving mechanism moves the variable cam piece of light weight when the valve operating characteristic of the intake valve or the exhaust valve is changed, the movement in direction of the rotary axis is carried out rapidly and response to change of the valve operating characteristic is improved, so that operation region that the engine is operated with a most suitable valve operating characteristic is widened and engine performance such as engine output can be improved. Further, since the driving mechanism can be miniaturized, the valve moving apparatus can be miniaturized and therefore the internal combustion engine can be miniaturized.
Since the movable member is positioned near a center of the cylinder more than the intake camshaft and the exhaust camshaft, and the contact section touching the variable cam piece to give driving force of the movable member to the variable cam piece is provided on the arm extending from the movable member toward the intake camshaft or the exhaust camshaft, the driving mechanism can be put within a width of the camshaft in direction of straight line perpendicular to the rotary axis of the camshaft. Therefore, a width of the valve moving apparatus in direction of the straight line does not become large. Further, since the contact sections touché the respective side surfaces of the variable cam piece, the contact sections does not influence rotation of the variable cam piece which rotates together with the intake camshaft and the exhaust camshaft.
As the result, the drive mechanism is disposed between the intake camshaft and the exhaust camshaft, width of the valve moving apparatus in direction of the straight line perpendicular to the rotary axis of the both camshafts does not become large, the valve moving apparatus can be miniaturized and the internal combustion engine can be miniaturized. Further, since the contact sections touch side surfaces of the variable cam piece so as not to influence rotation of the variable cam piece, the intake valve and the exhaust valve can be surely opened and closed by the variable cam piece.
Preferably, the driving mechanism comprises the movable member having a center axis parallel with the rotary axis and a pair of arms extending from the movable member toward the camshaft and having the contact sections, and the movable member has a recess for allowing passing of the rotating variable cam section.
According to this constitution, the movable member can be disposed further close by the camshaft, because of the recess provided on the movable member.
The movable member may have both ends supported by neighboring cam holders respectively. Since the movable member can be supported utilizing the neighboring cam holders, any other member for supporting the movable member is unnecessary. Therefore, number of parts can be reduc
Fujii Noriaki
Iwamoto Jun'ichi
Matsumochi Yuji
Nakamura Hiromu
Chang Ching
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Lahive & Cockfield LLP
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