Assembly for simultaneously actuating two valves of an internal

Details Assembly for simultaneously actuating two valves of an internal Assembly for simultaneously actuating two valves of an internal

1993-01-19

1993-11-16

Cross, E. Rollins

Internal-combustion engines

Poppet valve operating mechanism

Plural valve trains, single actuator

123 905, 123 9055, F01L 126

Patent

active

052613615

DESCRIPTION:

BRIEF SUMMARY
The invention concerns an assembly for simultaneously actuating two valves of an internal combustion engine, comprising a beam-shaped bridge which is guided by at least one column, and in whose end regions lash adjusters engaging stem ends of the valves are arranged, the bridge being guided by the column parallelly to longitudinal axes of the valves in the cylinder head, and a rotatably mounted roller adapted to be engaged directly by a control cam being arranged in a central region of the bridge between the two lash adjusters.
Such an assembly is known from FR-A-484,035. This prior-art assembly likewise comprises a beam-shaped bridge for simultaneously actuating two engine valves. A roller projecting beyond the bridge in the direction of the camshaft is arranged at the center of the bridge and is engaged by a control cam. The bridge is guided parallel to the longitudinal axes of the valves by a telescope-type guide made as a hollow cylinder and extending away from the control cam. For valve lash adjustment, in this case, however, only between the roller and the base circle of the control cam, the valve stem ends are provided with a thread. In the bridge, this thread is provided in the region of end clamping jaws. For lash adjustment, these clamping jaws have to be removed in a complicated procedure during a standstill of the engine and the valve stem has to be turned relative to the bridge.
Further disadvantages of this solution are that no automatic valve lash adjustment is achieved, and the structure of the cylinder head for telescopically guiding the bridge is relatively complicated. Moreover, due to the fact that the roller projects beyond the bridge forming a hub-like nose, a relatively large design space is required.
In another assembly of the pre-cited type, known from U.S. Pat. No. 4,924,821, two engine valves are simultaneously actuated by a rocker arm acting via a bridge. A spherical end portion of the rocker arm is received in a cup-shaped lodging in a central portion of the bridge. Hydraulic valve lash adjusting means are arranged in the end regions of the bridge. This type of valve control by a rocker arm is disadvantageous with regard to its rigidity and the number of components involved and, moreover, in this case too, there is a relatively high design space requirement and again, an additional screw is provided for adjusting the rocker arm relative to the bridge. A further disadvantage is that complicated means are required for oil supply to the hydraulic lash adjusters through a longitudinal bore in the rocker arm and said adjusting screw.
It is therefore the object of the invention to provide an assembly for simultaneously actuating two engine valves, which is free of the disadvantages discussed above, and in which, particularly valve lash adjustment is effected automatically and by simple means, with a low design space requirement.
This object is achieved by the invention in accordance with the characterizing features of claim I by the fact that valve lash occurring between the bridge and the stem ends of the valves is adjusted by automatically acting hydraulic lash adjusters, a bore whose lower end opens into an oil channel of the cylinder head being provided in at least one column, and said bore being connected with at least one cross-bore for supplying oil to the lash adjusters. By reason of this construction, no mechanical adjustment of valve lash is required during the entire operating life of the internal combustion engine. The type of oil supply described here can be realized by simple and inexpensive means even in already fabricated cylinder heads, the columns at the same time permitting an exactly parallel guidance of the bridge relative to the axes of the valves. Further, design space requirement as compared to the known State of the Art, is relatively low, and at the same time, the number of moved parts involved is reduced and an adequate rigidity of the valve gear is assured. Advantageously, the bridge of this construction is made of a light-weight material like aluminium, p

REFERENCES:
patent: 4677723 (1987-07-01), Greene, Sr.
patent: 4773359 (1988-09-01), Titolo
patent: 4805567 (1989-02-01), Heimburg
patent: 4924821 (1990-05-01), Teerman
patent: 5150672 (1992-09-01), Fischer et al.

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