Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1998-12-10
2000-03-07
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9022, 123 904, F01L 1300
Patent
active
060326247
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to engine valve actuating devices that can switch the valve-lift characteristic in three steps in accordance with the engine operating state.
BACKGROUND ART
Regarding a conventional engine valve actuating device, there is known a device as described, for example, in a document of JP-A 4-72403. The outline will be described. A rocker arm for opening and closing an intake valve or an exhaust valve is swingably supported by a rocker shaft, and two sub-rocker arms are arranged on the same axis as the rocker shaft and in parallel, which come in slide contact with low-speed and high-speed cams in the engine operating state, respectively. Moreover, a selectively connecting mechanism is arranged for selectively connecting said two sub-rocker arms to the rocker shaft.
Said selectively connecting mechanism is provided with a connecting plunger arranged in the rocker shaft along its radial direction, and a hydraulic circuit for selectively supplying a working hydraulic pressure to the connecting plunger. When the connecting plunger is in engagement with a through hole of the sub-rocker arm by a working hydraulic pressure, the sub-rocker arm is in connection with the rocker shaft.
Moreover, when the connecting plunger is in non-engagement with the through hole of the sub-rocker arm, the sub-rocker arm is in non-connection with the rocker shaft.
In such selectively connecting mechanism, since one end of the connecting plunger arranged in the rocker arm is selectively engaged with the through hole of the sub-rocker arm, it is limited to set to a large value the diameter of the connecting plunger in the rocker shaft having a predetermined diameter due to a problem of the mechanical strength. Moreover, it is necessary to increase the accuracy of engagement of the outer peripheral surface of the connecting plunger with respect to the through hole of the sub-rocker arm. As a consequence, there arises a problem to fail to achieve an improvement in wear resistance of the connecting plunger and a sufficient reduction in manufacturing cost thereof.
Regarding an improvement proposal in such a case, as shown in JP-U 6-073301, in place of arranging the connecting plunger in the rocker shaft, one lever member as a connecting member and corresponding to each sub-rocker arm is rotatably supported by the rocker arm, and is disposed along the center axis of the rocker shaft, wherein when one end of each lever member is selectively in engagement with an engaged portion of the corresponding sub-rocker arm, the lift characteristic of an intake valve or an exhaust valve swung by the rocker arm is varied.
However, as described above, since one lever member as a connecting member and corresponding to each sub-rocker arm is rotatably supported by the rocker arm, and is disposed along the center axis of the rocker shaft, there is a limit to a relative reduction in the width of rocker shaft in the selectively connecting mechanism.
Taking account of the above problem, the present invention aims to provide engine valve actuating devices that can switch the valve-lift characteristic in three steps in accordance with the engine operating state, and that allow a reduction in size of a selectively connecting mechanism.
DISCLOSURE OF THE INVENTION
For achieving the above object, an engine valve actuating device relative to the present invention is provided with a camshaft having three cam portions with different cam-lift heights, which are arranged on the outer peripheral surface; a rocker arm having a base end that is rotatably supported to a rocker shaft and for opening and closing an engine valve in accordance with rotation of the first cam portion with the minimum cam-lift height; a first sub-rocker arm having a base that is disposed adjacent to the base end of said rocker arm and rotatably supported to the rocker arm, and swinging in accordance with rotation of said second cam portion with higher cam lift than the first cam portion; a second sub-rocker arm having a base that is disposed adjacen
REFERENCES:
patent: 5085182 (1992-02-01), Nakamura et al.
patent: 5159905 (1992-11-01), Sugiuchi et al.
patent: 5613469 (1997-03-01), Rygiel
patent: 5794576 (1998-08-01), Hara et al.
Sawada Takanori
Tsuruta Seiji
Lo Weilun
Unisia Jecs Corporation
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