Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
1999-12-16
2001-05-08
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090330, C123S090370, C074S559000, C184S006900
Reexamination Certificate
active
06227156
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The invention concerns a rocker arm for a valve train of an internal combustion engine comprising two longitudinally extending side walls enclosing an intermediate space while being connected to each other by a crossbeam to form a U- or H-shaped cross-section, the crossbeam possessing an abutment for an end of a push rod on a first end of its undersurface and a support for an end of a gas exchange valve on a second end of the undersurface, each side wall having a bearing shell arranged in the region of a central transverse plane of the rocker arm, said bearing shells being aligned to each other for receiving a pivot axle, an aperture for a supporting pedestal for fixing the pivot axle being arranged in the crossbeam in the region of the bearing shells, a top surface of the crossbeam being intersected in the region of the abutment by at least one end of at least one passage for transporting lubricant, which passage starts from the end of the push rod.
2. Background of the Invention
In a rocker arm of the pre-cited type known from U.S. Pat. No. 4,944,257, the semispherical recess for receiving an end of a push rod is intersected by a bore for lubricant. Seen from one end of the rocker arm, a splash plate spaced therefrom extends from a top surface of the crossbeam of the rocker arm towards the other end of the rocker arm. This splash plate is intended to communicate with said bore so as to disperse the oil exiting from the bore over a large region of the rocker arm.
A drawback of the rocker arm of this species-defining document is that no measures are provided for ensuring a controlled and economic lubricant supply to a contact surface of a support for an end of a gas exchange valve on the rocker arm. This leads to unnecessary wear in the region of the support particularly if cold starts are frequent. At the same time, it must be noted that this type of splash lubrication of the rocker arm requires a large amount of lubricant, and, especially following a cold start of the internal combustion engine, a considerable amount of time until, finally, the contact surface of the support of the gas exchange valve on the rocker arm is adequately lubricated.
OBJECT OF THE INVENTION
The object of the invention is therefore to create a rocker arm of the pre-cited type in which the mentioned drawbacks are eliminated and to provide, notably with the help of simple measures, a controlled lubrication of the support of the rocker arm on the end of the gas exchange valve.
SUMMARY OF THE INVENTION
The intermediate space together with the side walls having the bearing shells faces away from the gas exchange valve, a separate channel for transporting the lubricant being arranged on the top surface of the crossbeam, said channel starting from the end of the passage in the crossbeam and extending to the end of the gas exchange valve.
This separate channel serves to effectively eliminate the drawbacks of the rocker arm described hereinbefore. In particular, a high-precision lubrication of the said support of the gas exchange valve on the rocker arm is possible. The separate channel at the same time permits the entire rest of the rocker arm including the bearing shells on the side walls to be made in one piece.
In a further development of the invention, the channel extends in a bridge-like element which is fixed on the top surface of the crossbeam or on end faces of the side walls having the same orientation with respect to the top surface. Thus, at least one channel for the transport of the lubricant starting from the passage in the abutment is created in this element. It is, however, also conceivable to arrange a single “tube” or a similar element on the top surface. Said element leads in the region of the second end of the rocker arm to a bore, not specified herein, through the crossbeam directly to the support of the gas exchange valve on the undersurface of the crossbeam. Alternatively, the crossbeam may comprise a bore for splash lubrication arranged at a distance from this support. It is equally conceivable to arrange a trough on the top surface of the crossbeam in the region of the support, in which trough lubricant exiting from the element in this region is accumulated and can be conveyed to the support through a bore of the crossbeam in this region.
If the rocker arm is to be fixed on a supporting pedestal via a pivot axle, according to the invention, a recess is likewise provided in the element in the region of the aperture.
Advantageously, the element is fixed to the top surface of the crossbeam, for example, by a welded or similar joint. However, alternative joining methods such as clamping, locking and gluing are also proposed.
The element of the invention for the transport of lubricant is advantageously made of a thin-walled sheet metal material or of a light-weight material like plastic in or on which the channel for the further transport of lubricant is formed.
In a further advantageous embodiment of the invention, the entire rocker arm is made of a sheet metal material which proves to be particularly advantageous from the point of view of manufacturing cost and time. At the same time, the proposed sheet metal material guarantees the required strength of the rocker arm. Through this measure, friction in the valve drive can be reduced.
It is particularly advantageous to make also the bearing shells integrally with the rocker arm. This permits the bearing shells to be formed simultaneously with the rocker arm by a deep-drawing or similar procedure.
For a further reduction of friction in the valve train, it is proposed to arrange rolling bearings such as needle bearings in the bearing shells. Alternatively, it is also possible to use ball or roller bearings.
According to a further advantageous embodiment of the invention, the side walls may be narrowed at least in the region of one of the ends of the crossbeam. By this, the rigidity of the rocker arm can be additionally increased and, when required, its mass reduced.
Finally, the invention proposes a simple measure for mounting the end of the push rod on the first end of the crossbeam. This mounting arrangement (abutment) is configured as a semi-spherical recess. Starting from this semi-spherical recess, it is possible to realize an excellent further transport of the lubricant coming from the push rod to the channel in the separate element. At the same time, a proper guidance of the rocker arm on the end of the push rod is created.
It is understood that the scope of the invention also covers embodiments in which the rocker arm is not arranged on a separate supporting pedestal but on an axle common to a number of rocker arms. At the same time, the element provided by the invention for the transport of lubricant can also be used with other bridge-type cam followers such as oscillating arms or finger levers which have a U- or H-shaped cross-section and in which lubricant is to be transported along their longitudinal axis.
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patent: 3289657 (1966-12-01), Winter, Jr.
patent: 3410366 (1968-11-01), Winter
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patent: 5887474 (1999-03-01), Cutshall et al.
Abel Bernd
Autrey Jennifer
Doppling Horst
Frank Dale
Bierman, Muserliannnn & Lucas
Ina Walzlager Schaeffler OHG
Lo Weilun
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