Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1995-08-16
1998-05-05
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 906, 75568R, 251251, F01L 1300, F01L 108
Patent
active
057461660
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention refers to an apparatus and a method for changing operational characteristics of a valve of an internal combustion engine.
2. Brief Description of the Background of the Invention Including Prior Art
It is well known that the cams of internal combustion engine camshafts during the rotation cause a moving of air in intake valves and exhaust valves of the internal combustion engine, where the lift of the value depends on the cam lift. Furthermore, the cams define the time between the point in time of valve opening and the point in time of valve closing depending on the form and shape of the cam profile. The cams provide the correct timing of the valves, i.e. the opening and closing of each valve at the proper moment relative to the crankshaft position.
Internal combustion engines equipped with camshafts having fixed cams show the maximum torque and the maximum power at a specific RPM number whereas the torque and the momentum decrease at another RPM number.
Systems reducing the above-mentioned disadvantages, have been tested on a very small scale so far, and only in specific types of internal combustion engines. Such systems operate with camshaft systems with inclined fixed cams, where the entire camshaft slides back and forth along the axis of the camshaft, increasing or decreasing, respectively, the valve lift depending on the relevant position of the lifter on the inclined cam. Simultaneously, the camshaft itself has also the ability to turn to some degree with respect to its initial position, thereby changing the timing of the valves.
Other systems, like for example the VTEC system, are using camshafts with more than one fixed cam of different lift strokes, angles, or phases for each valve, and cooperating with a system of multiple rocker arms for each separate operational case.
Systems with camshafts sliding along their axis need a modification of the construction of the internal combustion engine, while in the case of "V" type engines or with the camshaft disposed on one side, the application of the camshafts sliding along their axis is impossible, since the distance between the valve lifters strictly limits any sliding movement of the camshaft.
Other systems having camshafts with a special cam form (e.g. inclined cam), entirely different from the conventional cams used in the market today, require also the use of extremely specialized equipment and machinery for the manufacturing, as well as for the reconditioning of the cams. Therefore, these camshafts cannot have a wide use and their application is extremely limited.
The VTEC system has also a limited application, since its application is not possible or extremely difficult in "V"0 type engines or in engines with the camshaft on one side because the distance between the cams is small, which causes serious problems in the complicated system of multiple rocker arms. Additionally, the application of such system requires not only the construction and manufacture of a totally new camshaft, but also the construction and manufacture of a totally new cylinder head in which the multiple rocker arm system will be fitted. It is important to note at this point that this system is impossible to operate correctly at a high number of rotations per minute (rpm) due to the inertia of the multiple rocker arms at these high velocities.
U.S. Pat. No. 5,161,429A describes a variable cam moving in an angular direction around a point located on the symmetry axis. The variable cam, apart from the complexity of the design and the use of specially shaped cooperating components for the faultless operation, allows only to change the valve timing (phase change and valve opening-closing time duration change), whereas the variable cam has no ability to change the cam lift (and consequently the valve lift).
The German printed patent document No. DE 42 22 477 A1 describes a variable cam which operates either with a movable segment of the cam or with a combination of a fixed segment and of a movable segment. The vari
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JP-A-61 201803, Sep. 6, 1986. JP-A-61 275515
Kasper Horst M.
Lo Weilun
LandOfFree
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