Internal-combustion engines – Poppet valve operating mechanism – Plural valve trains – single actuator
Patent
1995-11-30
1997-04-22
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Plural valve trains, single actuator
123 904, 123 9042, 123 9043, 123 9046, 74559, F01L 118, F01L 124, F01L 126
Patent
active
056221460
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a finger lever for the actuation of gas exchange valves of an internal combustion engine.
STATE OF THE ART
A finger lever used in internal combustion engines for actuating a gas exchange valve is generally pivoted at one end on the cylinder head and bears at its opposite end against the end of the shaft of the gas exchange valve. The central region of the finger lever is contacted by a cam of a camshaft.
A finger lever of a generic type known from GB-A 21 79 700 is used together with a camshaft for actuating gas exchange valves of an internal combustion engine. For actuating two gas exchange valves simultaneously, the finger lever is configured as a forked finger lever which is supported at one end on a support element and bears at an opposite fork-shaped end against the ends of shafts of two gas exchange valves. The support element comprises a device for compensating valve clearance.
From EP-A-04 53 416, a valve drive comprising two oppositely oriented finger levers is known, each of which is supported at one end by a spherical cup mounting on a hydraulic clearance compensation element inserted into the cylinder head, while the opposite end of each finger lever bears against the end of a shaft of a gas exchange valve. A cam of a camshaft arranged off-center above the finger levers causes an oscillating movement of the finger levers which is then transmitted to the gas exchange valves. A disadvantage of this structure is that two separate finger levers and a broad cam are required.
A valve bridge assembly for the simultaneous actuation of two gas exchange valves known from U.S. Pat. No. 4,924,821, aims at avoiding an oblique force application on an actuating lever of the gas exchange valves. This bridge assembly comprises a central cup-shaped recess engaged by a guide element arranged on the actuating lever. A disadvantage of such bridge-type structures, however, is that, particularly in high-speed engines, the opening cycles of the two gas exchange valves do not correspond precisely enough to the calculated valve lifting curves. Thus there is the danger of undesired valve vibrations which, in the extreme case, can lead to uncontrolled abutments of the valve heads. This, in turn, results in higher wear of the valve seats and has a negative influence on the noise level.
OBJECT OF THE INVENTION
It is an object of the invention to assure a clearance-free actuation of the gas exchange valves in a multi-valve internal combustion engine as compactly as possible without disadvantageously increasing the mass of the forked finger lever.
THE INVENTION
The finger lever of the invention comprises a clearance compensation element on at least one of its fork ends facing the ends of the shafts of the gas exchange valves. The measure of arranging an insertion element in one of the fork ends of the finger lever of the invention makes it possible to effectively compensate a difference in dimension between the shaft ends of the gas exchange valves so that, advantageously, an inclined position of the finger lever and a resulting edge pressure on the cam-contacting surface are also avoided. This configuration of the invention guarantees an effective valve clearance compensation which advantageously compensates tolerances of the components of the gas exchange valves to be simultaneously actuated.
In an advantageous development of the invention according to Claim 2, an insertion element in the form of a hydraulic clearance compensation element is inserted into one fork end of the finger lever. The arrangement of a hydraulic insertion element in combination with a support element as provided by the invention results in a reliable valve drive with a long operating life and low noise development even when a compensation of a dimension difference at the shaft ends of the gas exchange valves is required due to manufacturing tolerances.
Another embodiment teaches the use of an insertion element having a reduced compensation stroke. The use of such an insertion element with a limited stroke of compensati
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INA Walzlager Schaeffler KG
Lo Weilun
LandOfFree
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