Patent Application
20160376935
The present disclosure relates to a valvetrain for an engine.
Diesel engines use a much leaner air-to-fuel ratio than gasoline engines. The larger amount of air in the intake gas promotes more complete fuel combustion and better fuel efficiency, and thus lower emissions of hydrocarbons and carbon monoxide than gasoline engines. However, with the higher pressures and temperatures in the diesel engine, nitrogen oxides emissions, which include nitrogen oxide (NO) and nitrogen dioxide (NO2), known collectively as NOx, tend to be higher because the high temperatures cause the oxygen and nitrogen in the intake air to combine.
To comply with increasingly stringent government mandates regarding NOx emissions, engine manufacturers have developed several NOx reduction approaches. One such approach is exhaust gas recirculation (EGR), in which a percentage of the exhaust gas is drawn or forced back into the intake and mixed with the fresh intake gas and fuel that enters the combustion chamber. Another approach is selective catalytic reduction (SCR). The SCR process reduces NOx to diatomic nitrogen (N2) and water (H2O) using a catalyst and anhydrous ammonia (NH3) or aqueous NH3, or a precursor that is convertible to NH3, such as urea.
In addition to NOx emissions, diesel engines also produce particulate matter (PM), or soot, which is produced in comparatively larger amounts than that of gasoline engines. PM is a complex emission that includes elemental carbon, heavy hydrocarbons derived from the fuel, lubricating oil, and hydrated sulfuric acid derived from the fuel sulfur. One approach for reducing or removing PM in diesel exhaust is a diesel particle filter (DPF). The filter is designed to collect PM while allowing exhaust gases to pass through it.
These example approaches as well as others may result in, or require, cylinder pressures that are relatively high, as compared to cylinder pressures in systems not using such approaches. These higher cylinder pressures create higher forces, and these higher forces are then applied to the intake and exhaust valves. These forces are then translated to other components in the valvetrain, including the rockers and pushrods, among other things. Such forces may result in failures to these and other components in the valvetrain.
Disclosed is a valvetrain with a rocker support, a fulcrum, and a rocker. The rocker support is mounted to the cylinder head of an internal combustion engine and is fixed relative thereto. The rocker support includes an axial aligning groove. The rocker is positioned about the rocker support and partially in the axial aligning groove. The fulcrum is sandwiched between the rocker support and the rocker. A first end of the rocker receives forces from and applies forces to a push rod, and a second end of the rocker receives forces from and applies forces to a valve. The rocker oscillates about the fulcrum, as the forces are received and applied to the first end and the second end thereof.
The detailed description of the drawings refers to the accompanying figures in which:
Like reference numerals in the various drawings indicate like elements.
Referring to
The engine 100 must receive the intake gas and dispel the exhaust gas at precise internals using a valvetrain 112. During an intake stroke of a piston, its respective intake valve 102 is generally open, and during an exhaust stroke, the respective exhaust valve 104 is generally open. During the other strokes, both the intake valve 102 and the exhaust valve 104 are generally closed. The valvetrain 112 may include a camshaft 110 that turns at one half of the speed of the crankshaft, so that the intake valves 102 and the exhaust valves 104 are closed once during the two revolutions of the crankshaft. Push rods 114 may be used for providing motion of the camshaft 110 to a rocker 116.
Springs 111 may be positioned around the intake valves 102 and exhaust valves 104, so as to keep them closed until respectively opened by the camshaft 110. The springs 111 may be cylindrical springs, and in some cases, there may be two springs used for each of the valves 102, 104, so as to minimize spring vibration and valve flutter. The springs 111 may be designed based, in part, on the mass of the other components in the valvetrain 112. For example, heavier components may require stiffer, stronger springs 111.
An exhaust system of the engine 100 may include an aftertreatment system for reducing, among other things, particulate matter and NOx. It may include an oxidation catalyst, and a diesel particulate filter (for reducing the particulate matter), and a SCR catalyst (for removing the NOx). A reductant may be injected into the exhaust downstream of the diesel particulate, but upstream of the SCR catalyst. Some examples of the power system may also include an EGR system that reroutes a portion of the exhaust gas (EGR gas) and mixes it with a fresh intake gas, so as to form a mixed intake gas that is combusted in the engine 100. The inclusion of the EGR gas lowers the combustion temperatures and, thus, reduces NOx levels exiting the combustion chamber.
Referring to
Each rocker 116 is positioned about the rocker support 120 and is partially in an axial aligning groove 122 of the rocker support 120. The rocker 116 oscillates about the fulcrum 118, as the forces are received and applied to the first and second ends of the rocker 116. The rocker 116 may be made of, for example, 1010, 1018, or 1020 steel that is stamped and then formed, and it may further go through a nitriding or carbonizing process for increasing the strength thereof.
Referring to
The rocker 116 may include just a single layer of material or, alternatively, as shown in
As shown in
Referring to
The installation end 174 of the banjo mount 108 may be accessible and positioned on an opposite side of the rocker support 120 (e.g., an opposite side of the rocker bar 121). The installation end 174 may be accessible for assembly and servicing. For example, the installation end 174 may have a hexagonal socket and may be accessible by reaching underneath the rocker 116 with, for example, an allen wrench for tightening and loosening the banjo mount 108. Or, as shown in the illustrated rocker 116, the installation opening 172 may be aligned with the installation end 174 of a banjo mount 108 by, for example, rotating the rocker 116. When aligned, the installation end 174 may be accessible through the installation opening 172 for tightening or loosening the banjo mount 108 with a tool, such as an allen wrench or a screwdriver.
As shown in
The fulcrum 118 is sandwiched between the rocker support 120 and the rocker 116. Exemplarily, the fulcrum 118 may be a sphere (e.g., a ball) or a portion of a sphere, and in such an embodiment, the rocker 116 may include a spherical receiver 136 in contact with the sphere. As another example, the fulcrum 118 may be a cylinder.
As further shown in
An inlet 175 of the banjo passage 191 may be positioned on an outer surface of the small diameter portion 182, and an outlet 177 may be positioned on an outer surface of the fulcrum 118. In the illustrated embodiment of the valvetrain 112, lubrication flows through the longitudinal lubrication supply passage 184, the retaining passages 186, and out the banjo passages 191. This lubricates the contact points between the fulcrums 118 and the rockers 116. The first diameter portion 178 and the second diameter portion 180 may be positioned in contact with the retaining aperture 176, while the small diameter portion 182 is spaced apart therefrom.
As shown in
The rocker 116 may also include a tip pad 164 and a pad retaining shaft 166 extending therefrom, wherein the pad retaining shaft 166 may be positioned in the second cylindrical portion 128 and the tip pad 164 may be positioned in contact with either one of intake valves 102 or exhaust valves 104. The tip pad 164 may be made of 52100 chrome alloy steel, having a typical hardness of about 60-67 HRC, and may be held into place in the rocker 116 with a press fit.
The opening 156 may be aligned with the actuation plane 129. The fulcrum 118 and the rocker support 120 may be positioned in the opening 156. The opening 156 of the rocker 116 does not interfere with the rocker support 120 when the valve is in a completely open position, a completely closed position, or any position therebetween.
As shown in
As shown in the illustrated embodiment of the rocker support 120, the opening 156 is large enough to fit around and slide along the rocker bar 121 when the rocker 116 is being installed. For example, the opening 156 may be aligned with the rocker support 120, then slid into an axial position on the rocker support 120, and then rotated and generally retained in the axial position. As also shown in the illustrated embodiment of the rocker support 120, the opening 156 is not large enough to fit around and slide over the entire length of the rocker bar 121 when the mounting feet 188 are mounted thereto. In such an embodiment, each rocker 116 may be installed prior to having the mounting feet 188 installed.
As shown in
An inner diameter 138 of the first cylindrical portion 124 may be larger than the thickness of the rocking plate 127, and similarly an inner diameter 140 of the second cylindrical portion 128 may also be larger than the thickness of the rocking plate 127. Such a thickness, which is quite thin relative to both the minimum outer dimension 148 and the maximum outer dimension 142, further adds to a shape that is lightweight and rigid, particularly when viewed in combination with the relatively large maximum outer dimension 142.
Also as shown in
The rocker 116 may include a rocker pivot cup 162 and a cup retaining shaft 169 extending therefrom. The illustrated pivot cup 162 defines the spherical receiver 136. As shown, the cup retaining shaft 169 may be positioned in the third cylindrical portion 168, so that the rocker pivot cup 162 extending therefrom is positioned in contact with the fulcrum 118. The cup retaining shaft 169 may be held into place in the third cylindrical portion 168 with, for example, a press fit. The rocker pivot cup 162 may be made of 52100 chrome alloy steel, having a typical hardness of about 60-67 HRC.
Repositioning the third axis 170 and the fulcrum 118, relative to the first axis 126 and the second axis 130, may be useful for adjusting the force distributions, ratios, and movements in the valvetrain 112. Such adjustments may be easily designed into some embodiments of the rocker 116, while still keeping its shape, functionality, and strength.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims.
