Patent Application
20150377082
The present disclosure generally relates to engines and, more particularly, relates to rocker arm and roller assemblies used in engines.
In the manufacture and operation of engines such as diesel engines and Otto cycle internal combustion engines, it is well known to employ a cam shaft to coordinate the timing of valve opening and closing and to inject fuel. For example, with a diesel engine, an engine block is provided having a plurality of cylinders therein. A plurality of pistons are reciprocatingly mounted within each of the cylinders with a plurality of valves associated with each the cylinders to allow for inflow and outflow of air. In order to coordinate the timing of those valve openings, each valve is typically in forced contact with one end of a rocker arm or cam follower. This is typically accomplished with a push rod or other components comprising the valve train. The rocker arm itself is pivotally mounted relative to the engine block. One end of the rocker arm is provided with a rotating element called a roller which engages cams mounted on the cam shaft. Each cam is eccentrically formed so that rotation of the cam shaft causes larger and smaller diameter portions of each cam to rotate and in turn cause the rocker arm to pivot, thus opening and closing the valves and/or engaging a fuel injector plunger, as appropriate.
While effective, for such structure to operate effectively and consistently, the roller needs to be able to freely rotate at all times. Any inhibition or prevention of such rotation detrimentally affects the operation of the engine. If the roller were to seize on the rocker arm, for example, operation of the engine may be even more affected thus resulting in catastrophic failure.
With some rocker arms, the roller is mounted to the rocker arm using a complicated assembly of components. More specifically, an internal pin or axle extends between first and second sides of the rocker arm with an inner race being rotatively mounted to the pin. A bushing is then provided around the inner race with the roller itself then being mounted onto the bushing. Given the relatively small dimensions of such components, the assembly and manufacture of such a device is fairly complicated. Moreover, given the tight tolerances between the components, the bushing and inner race must be press fit together also adding to the difficulty and manufacturing cost associated with such a rocker arm assembly. In addition, such an assembly typically employs a lead tin overlay which adds to the complexity and cost of the assembly as well.
From the foregoing, it can be seen that a need exists for an improved rocker arm and roller assembly.
In accordance with one aspect of the disclosure, an engine rocker arm and a roller assembly is therefore disclosed which may comprise a rocker arm having a first end and a second end with the rocker arm adapted to pivot about a pivot aperture therein, an axle mounted in the second end with the axle having a stepped profile, and a roller rotatably mounted directly to the axle.
In accordance with another aspect of the disclosure, an axle for use in a rocker arm and roller assembly of an engine is disclosed which may comprise a first cylindrical section having a first diameter, a second cylindrical section adjacent to and integral with the first cylindrical section, the second cylindrical section having a lesser diameter than the first cylindrical section, and a third cylindrical section adjacent to and integral with the second cylindrical section, the third cylindrical section having a lesser diameter than the second cylindrical section.
In accordance with another aspect of the disclosure, an engine is disclosed which may comprise an engine block having a plurality of cylinders, a plurality of pistons reciprocatingly mounted in a plurality of cylinders, a plurality of valves operatively associated with the plurality of cylinders, a cam shaft rotating relative to the engine block and including a plurality of cams, a plurality of rocker arms with each rocker arm being operatively associated with one of the plurality of cams and one of the plurality of valves, an axle press fit into each rocker arm, and a roller mounted directly to each axle, each axle having a stepped profile and being manufactured with bronze.
These and other aspects and features of the disclosure will become more readily apparent upon reading the following detailed description when taking into conjunction the accompanying drawings.
While the present disclosure is susceptible to various modifications on alternative constructions, certain illustrative embodiments thereof will be shown and described below in detail. However, it is to be understood that the disclosure is not limited to the specific embodiments disclosed, but instead includes all modifications, alternative constructions, and equivalents thereof.
Referring now to the drawings, and with specific reference to
While not specifically depicted, one of ordinary skill in the art will appreciate that the engine 20 of
The rocker arm 32 is caused to so pivot by the engagement of the second end 36 of the rocker arm 32 with a camshaft 40. As will be noted in
Referring now to
Between the first and second lateral sides 46, 48, spans an axle 56. The axle 56 is sized so as to be press fit into the rocker arm 32 and more specifically, into the first and second apertures 52, 54. Turning now to
The diameters of the first, second and third cylindrical sections 58, 60, 62 are also of importance. More specifically, the first cylindrical section 58 includes a diameter slightly less than the diameter of the first aperture 52 so as to be press fit therein, and be held within the rocker arm by way of friction. Similarly, the third cylindrical section 62 is slightly less than the diameter of the second aperture 54 so as to be press fit and frictionally held within the second aperture 54.
Once press fit within the second end 36 of the rocker arm 32, the second cylindrical section 60 spans between the first and second lateral sides 46, 48 to form a pivot axis 63 for a roller 64 to rotate there about. It is the roller 64 which directly engages the cams 44 of the cam shaft 40 as mentioned above. The roller 64 itself includes an outer circumference 66 for direct engagement of the camshaft 40, and an inner circumference 68 for direct engagement with the axle 56. Among other things, by manufacturing the axle 56 with such a stepped configuration instead of a straight cylinder, a large bearing surface is provided, while stress is reduced in one of the rocker arm ears.
In so doing, it can be seen that the present disclosure greatly improves upon the prior art which employs a complicated structure using an interior pin, an inner race, an outer bushing, and a roller. As each of those aforementioned prior art components needed to be press fit and manufactured to exacting dimensions, they were relatively difficult to manufacture and thus costly as well. Moreover, given the very small tolerances between the components, the components may tend to seize in use, thus detrimentally or catastrophically affecting engine operation. With the present disclosure on the other hand, construction in streamlined, and maintenance and operatability are enhanced using fewer parts. Moreover, the present disclosure can be used with existing rocker arms with limited retrofit adjustments.
Referring again to
As referenced above, the axle 56 is manufactured from a specific material to allow for such ease of rotation, manufacturability and durability. While a number of different materials can be used for manufacturing the axle 56, the inventors have found that bronze forms a suitable surface for such operation. Moreover, the entire axle 56 may be manufactured from bronze. By manufacturing the entire axle 56 from a single material, the need for overlays such as lead tin overlays associated with prior art axles can be avoided. This in turn eases the manufacturability of the assembly. While the axle 56 may be made of bronze, the roller 64 may be made of steel so as to withstand the repeated loading thereof.
Turning now to
In operation, it can be seen that the present disclosure sets forth a rocker arm and roller assembly for use in a diesel or other engine which has a greatly improved axle and roller operation and manufacturability. As opposed to prior art devices which employ a complicated assembly of a pin, outer race, bushing, and a roller manufactured of specific materials and exacting dimensions, all of which need to be press fit together, the pending disclosure provides a greatly simplified approach which leads to less cost, easier manufacturing, and better durability. It does so by manufacturing the rocker arm with a roller end having first and second lateral sides, each of which include an aperture but of different diameters. In addition, the assembly employs a stepped axle which is adapted to be directly press fit into such apertures. By manufacturing the axle of distinctly diametered sections, the axle can be directly press fit into the roller end and form a rotational pivot for the roller without the need for any inner races, or bushings. Moreover, by manufacturing the axle from bronze, and the roller from steel, the consistent rotatability of the assembly is ensured.
