Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1998-08-24
1999-11-30
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9046, 123198F, F01L 1300, F01L 118, F01L 124
Patent
active
059923601
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a valve drive for gas exchange valves of internal combustion engines comprising a switchable rocker arm on whose one end facing a valve stem is arranged a slidably mounted tappet element which can be coupled to or uncoupled from the rocker arm by a coupling means so that a valve lift or an idle stroke is effected, the coupling means being hydraulically actuatable against the force of a spring.
BACKGROUND OF THE INVENTION
A valve drive of the precited type is known from GB-A-2 075 118. In this rocker arm, a spring-loaded pressure pin is slidably mounted with a bottom thereof bearing against a valve stem of a gas exchange valve. Above the valve stem, the pressure piston is laterally connected by a coupling means to a spring-loaded and hydraulically displaceable piston. Depending on the end position of this hydraulically displaceable position in each case, the pressure pin is either fixed in place or displaceable so that, upon a pivoting of the rocker arm, either the gas exchange valve is actuated or the pressure pin slides in the rocker arm i.e., the gas exchange valve is not actuated. A drawback of this structure is that, on the one hand, a complicated pressure oil supply comprising a plurality of oil channels is required and on the other hand, the mechanical connection between the pressure pin and the hydraulically displaceable piston is comprised of a plurality of differently configured mechanical components. The manufacture of such a switchable rocker arm is therefore very complicated and accordingly expensive.
In this connection, a switchable valve drive is known from DE 44 11 182 A1 which comprises two transmitting levers with a hydraulically actuatable locking element arranged therebetween. This hydraulically actuatable locking element is supplied with pressure from the oil supply of the valve clearance compensation element arranged in the rocker arm. A drawback of this is that this switchable valve drive is likewise very complicated and expensive to manufacture because two transmitting levers are required.
Finally, DE-GM 93 15 436 also discloses a switchable cam follower in the form of a cup tappet which is composed of two relatively displaceable units whose coupling and uncoupling are assured respectively by a compression spring and by the oil pressure of a hydraulic clearance compensation element. However, this type of switching of two relatively displaceable units is entirely unsuitable for use in a switchable rocker arm.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to create a switchable valve drive for a rocker arm which is composed of the smallest possible number of components and which can be manufactured economically.
The invention achieves this object in that an insert element is arranged in the rocker arm, which insert element receives a hydraulic clearance compensation element in a bore which is open towards a valve stem, a second end of the insert element being supported in the rocker arm via a resetting spring while a bore extending perpendicular to a longitudinal axis of the rocker arm is arranged in each of the insert element and the rear end of the rocker arm for receiving the coupling means, and the hydraulic actuation of the coupling means is effected from an oil supply of the hydraulic valve clearance compensation element which is arranged in the rocker arm.
Due to the fact that the hydraulic supply is fed from the hydraulic clearance compensation element, that is to say, it already exists, additional channels for conducting the hydraulic medium can be dispensed with. The locking under spring force without the action of pressure from the hydraulic medium, also called pressureless locking, is particularly advantageous in case all cylinders are required for an initial ignition or for a re-ignition of the internal combustion engine. On the other hand, when the internal combustion engine has been started, the oil pressure required for the supply of the hydraulic clearance compensation element is built up immedi
REFERENCES:
patent: 4141333 (1979-02-01), Gilbert
patent: 5474037 (1995-12-01), Paul
patent: 5577469 (1996-11-01), Muller et al.
patent: 5651335 (1997-07-01), Elendt et al.
Elendt Harald
Haas Michael
Ina Walzlager Schaeffler OHG
Lo Weilun
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