Patent Description:
Internal combustion engine systems such as in a locomotive engine, rocker arm assemblies are used for actuation of cylinder valves. During operation of the engine, components of the rocker arm assembly is supplied with a lubricating oil to facilitate relative movement of the rocker arm components. Lubricating oil may be supplied from a cylinder head to a rocker arm assembly via channels in a rocker pedestal supporting components of one or more rocker arm assemblies. After lubricating the rocker arm assembly, the excess oil may be drained from components of the rocker arm assembly such as a valve stem.

A constant supply of lubricating oil to a rocker arm tip over an engine cycle, oil may flood the valve system coupled to the tip. Oil supplied to a valve system when the valve is not being actuated may cause oil stagnation and stagnated oil may not be effectively drained from the valve system. Also, by concurrently dividing the total supplied oil between both cylinder valves, a lower amount of oil may be supplied to the valve being actuated, thereby reducing the amount of oil being supplied moving components of the rocker arm assemblies. It may be desirable to have a system and method that differs from those that are currently available. Examples of prior art can be found in, e.g., <CIT>, <CIT>and <CIT>.

The present invention provides a method for an engine according to independent claim <NUM> and a system for an engine according to independent claim <NUM>.

The following description relates to embodiments of a system for intermittently supplying lubricating oil to a tip of a rocker arm of an internal combustion engine.

In one embodiment, a cylinder may be coupled to two rocker arm assemblies with one coupled to the intake valve and another coupled to an exhaust valve. During engine operation, lubricating oil may be delivered from a cylinder head to a tip of a rocker arm via a vertical via oil channels formed in a rocker pedestal supporting the rocker shaft coupled to one or more rocker arms. The oil may be constantly supplied to each rocker arm tip throughout an engine cycle even if the valve coupled to the rocker arm tip is not being operated at the time.

In one example, a method for an engine may include selectively supplying lubricating oil to a tip of a rocker arm via oil channels aligned only during opening of a valve coupled to the tip. In this way, by intermittently supplying oil to the rocker arm tip that is being actuated to open a valve, undesired oil supply to a closed valve may be reduced.

In a first embodiment, in the engine, oil may travel from an oil sump at a cylinder head to a rocker arm via a first, vertical channel on a rocker pedestal supporting one or more rocker arms. The first channel may terminate at the center of a rocker shaft about which one or more rocker arms rock. The oil may then travel via a second, horizontal channel passing through the central axis of the rocker shaft. At locations along the rocker shaft where a bush bearing of a rocker arm surrounds the inner wall of the rocker shaft, a third, vertical oil channel originating from the second, horizontal channel may carry oil to a fourth, horizontal channel passing through a central axis of the rocker arm via a supply groove. The fourth, horizontal channel may fluidically couple the supply groove to a tip of the rocker arm. When the valve coupled to the rocker arm is closed, the supply groove may be offset with the third, vertical oil channel such that oil may not flow to the rocker arm tip and instead may flow to the bush bearing via draining channels. When the rocker arm is tilted during opening of the valve coupled to it, the supply groove may align with the third, vertical oil channel enabling oil to flow from the second, horizontal channel to the rocker arm tip via the third, vertical oil channel and the supply groove.

As another example, in a second embodiment, oil may travel from an oil sump at a cylinder head to a rocker arm via the first, vertical channel on a rocker pedestal supporting one or more rocker arms. The first channel may terminate at the center of a rocker shaft about which one or more rocker arms rock. The oil may then travel via the second, horizontal channel passing through the central axis of the rocker shaft. At locations along the rocker shaft where a bush bearing of a rocker arm surrounds the inner wall of the rocker shaft, a third, vertical oil channel originating from the second, horizontal channel may carry oil to a supply groove. When the valve coupled to the rocker arm is closed, the supply groove may be offset with the third, vertical oil channel such that oil may not be splashed out of the supply groove and instead may flow to the bush bearing via draining channels. When the rocker arm is tilted during opening of the valve coupled to it, the supply groove may align with the third, vertical oil channel enabling oil to flow from the second, horizontal channel to the supply groove. Oil from the supply groove may be splashed upwards towards a cover of the rocker arm. The cover may be equipped with features such as protrusions and slopes that allow oil impinging on the cover to drip back to the rocker arm tip.

In this way, by selectively supplying oil to a tip of a rocker arm only when the valve coupled to the tip is being opened, oil supply to the open valve may be increased facilitating availability of sufficient amount of oil to moving components during opening of the valve. The technical effect of the intermittent oil supply to the valve being actuated is that flooding of the valve systems may be reduced. By reducing stagnation of oil in components of the rocker arm assembly, active draining of oil may be reduced. Further, by suppling oil to the bush bearing, friction between adjacent metallic surfaces may be reduced, thereby reducing wear of interface. Overall, a lower volume of lubricating oil as desired for operation of the rocker arm assembly may flow through the cylinder head without the need for drainage of excess oil.

Engine systems according to embodiments of the invention may be suitable for use in mobile applications and stationary applications. Suitable stationary applications may include stationary power generation applications. Suitable mobile applications may include vehicles, such as may be used in the rail, mining, marine, aviation, trucking, and related industrial markets. A locomotive that is configured for the rail market is used herein for illustration purposes. The rail market may include mainline freight haulage, passenger rail, switchers, shunters, and the like.

An engine system, such as the engine system shown by <FIG>, includes rocker arm assemblies for actuating cylinder valves. An example rocker arm assembly coupled to a cylinder valve is shown in <FIG>. Two rocker arms may pivot about a shared rocker shaft, as shown in <FIG>. Lubricating oil may be transferred from a cylinder head to the tip of a rocker arm via oil channels in the rocker shaft and a rocker pedestal supporting the rocker shaft, as shown in <FIG>. <FIG> shows positions of first embodiments of rocker arms coupled to an intake valve and an exhaust valve, respectively, during valve actuation. <FIG> shows positions of second embodiments of rocker arms coupled to an intake valve and an exhaust valve, respectively, during valve actuation. The second embodiment of rocker arms may be covered by a cover shown in <FIG>. A plot showing durations of valve opening and oil supply to a rocker arm tip is shown in <FIG>. Intermittent supply of lubricating oil to a tip of a first rocker arm is carried out via a method elaborated in <FIG>. Intermittent supply of lubricating oil to a tip of a second rocker arm is carried out via a method elaborated in <FIG>.

Referring to <FIG>, a block diagram of an embodiment of a vehicle system <NUM> (e.g., engine system) is shown. In the illustrated embodiment, the vehicle system is a rail vehicle <NUM> (e.g., locomotive) that can run on a rail <NUM> via a plurality of wheels <NUM>. The engine system may be disposed in a vehicle. As depicted, the vehicle includes an engine <NUM>, and the engine includes a plurality of combustion chambers (e.g., cylinders). The cylinders of the engine may receive fuel (e.g., diesel fuel) from a fuel system <NUM> via a fuel conduit <NUM>. In some examples, the fuel conduit may be coupled with a common fuel rail and a plurality of fuel injectors.

The engine <NUM> may receive intake air for combustion from an intake passage <NUM>. The intake air includes ambient air from outside of the vehicle flowing into the intake passage through an air filter <NUM>. The intake passage may include and/or be coupled to an intake manifold of the engine. Exhaust gas resulting from combustion in the engine is supplied to an exhaust passage <NUM>. Exhaust gas flows through the exhaust passage, to a muffler <NUM>, and out of an exhaust stack <NUM> of the vehicle.

Each cylinder of engine <NUM> may include one or more intake valves and one or more exhaust valves. For example, a cylinder may include at least one intake valve and at least one exhaust valve located at an upper region of cylinder. The intake valve and the exhaust valve may be actuated via respective cam actuation system coupled to respective rocker arm assemblies. Cam actuation systems may each include one or more cams and may utilize one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (WT) and/or variable valve lift (VVL) systems that may be operated by controller to vary valve operation. The position of intake valve and exhaust valve may be determined by valve position sensors. In alternative embodiments, the intake and/or exhaust valve may be controlled by electric valve actuation. For example, a cylinder may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and/or VCT systems.

In one example, the vehicle is a diesel-electric vehicle. As depicted in <FIG>, the engine is coupled to an electric power generation system, which includes an alternator/generator <NUM> and electric traction motors <NUM>. In one example, the alternator/generator may include a direct current (DC) generator. In other embodiments, the engine may be a diesel engine, a gasoline engine, a biodiesel engine, an alcohol or hydrogen engine, a natural gas engine (spark or compression ignition), or a combination of two or more of the foregoing that generates a torque output during operation. That torque may be transmitted to the electric generator or alternator through a mechanical coupling from the engine. As depicted herein, six pairs of traction motors correspond to each of six pairs of motive wheels of the vehicle. In another example, alternator/generator may be coupled to one or more resistive grids <NUM>. The resistive grids may dissipate excess engine torque and/or electricity generated by traction motors in dynamic braking mode via heat produced by the grids from generated electricity The vehicle system may include a turbocharger <NUM> that may be arranged between the intake passage and the exhaust passage. In some embodiments, the turbocharger may be replaced with a supercharger. The turbocharger increases air charge of ambient air drawn into the intake passage in order to provide greater charge density during combustion to increase power output and/or engine-operating efficiency. As shown in <FIG>, the turbocharger may include a compressor <NUM> (disposed in the intake passage) which is at least partially driven by a turbine <NUM> (disposed in the exhaust passage). While in this case a single turbocharger may be included, the system may include multiple turbine and/or compressor stages. A temperature sensor <NUM> may be positioned in the exhaust passage, upstream of an inlet of the turbine. As shown in <FIG>, a wastegate <NUM> may be disposed in a bypass passage around the turbine and may be adjusted, via actuation from controller <NUM>, to increase or decrease exhaust gas flow through the turbine. For example, opening the wastegate (or increasing the amount of opening) may decrease exhaust flow through the turbine and correspondingly decrease the rotational speed of the compressor. As a result, less air may enter the engine, thereby decreasing the combustion air-fuel ratio.

The vehicle system may also include a compressor bypass passage <NUM> coupled directly to the intake passage, upstream of the compressor and upstream of the engine. In one example, the compressor bypass passage may be coupled to the intake passage, upstream of the intake manifold of the engine. The compressor bypass passage may be configured to divert airflow (e.g., from before the compressor inlet) away from the engine (or intake manifold of the engine) and to atmosphere. A compressor bypass valve (CBV) <NUM> may be positioned in the compressor bypass passage and may include an actuator actuatable by the controller to adjust the amount of intake airflow diverted away from the engine and to atmosphere.

In some embodiments, the vehicle system may further include an aftertreatment system coupled in the exhaust passage upstream and/or downstream of the turbocharger. In one embodiment, the aftertreatment system may include a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF). In other embodiments, the aftertreatment system may additionally or alternatively include one or more emission control devices. Such emission control devices may include a selective catalytic reduction (SCR) catalyst, three-way catalyst, NOx trap, or various other devices or systems.

The vehicle system shown in <FIG> does not include an exhaust gas recirculation (EGR) system. However, in alternate embodiments, the vehicle system may include an EGR system coupled to the engine. The EGR system may route exhaust gas from the exhaust passage of the engine to the intake passage downstream of the turbocharger. In some embodiments, the exhaust gas recirculation system may be coupled exclusively to a group of one or more donor cylinders of the engine (also referred to a donor cylinder system). Also not shown in <FIG> is an alternative embodiment that includes an aftertreatment system that receives exhaust coming from the engine during operation.

The vehicle may further include the engine controller (referred to herein as the controller) to control various components and operations related to the vehicle. As an example, various components of the vehicle system may be coupled to the controller via a communication channel or data bus. In one example, the controller includes a computer control system. The controller may additionally or alternatively include a memory holding non-transitory computer readable storage media (not shown) including code for enabling on-board monitoring and control of vehicle operation.

The controller may receive information from a plurality of sensors and may send control signals to a plurality of actuators. The controller, while overseeing control and management of the vehicle, may receive signals from a variety of engine sensors. The signals may be used to determine operating parameters and operating conditions, and correspondingly adjust various engine actuators to control operation of the vehicle. For example, the engine controller may receive signals from various engine sensors including, but not limited to, engine speed, engine load (derived from fueling quantity commanded by the engine controller, fueling quantity indicated by measured fuel system parameters, averaged mean-torque data, and/or electric power output from the alternator or generator), mass airflow amount/rate (e.g., via a mass airflow meter), intake manifold air pressure, boost pressure, exhaust pressure, ambient pressure, ambient temperature, exhaust temperature (such as the exhaust temperature entering the turbine, as determined from the temperature sensor), particulate filter temperature, particulate filter back pressure, engine coolant pressure, exhaust oxides-of-nitrogen quantity (from NOx sensor), exhaust soot quantity (from soot/particulate matter sensor), exhaust gas oxygen level sensor, or the like. Correspondingly, the controller may control the vehicle by sending commands to various components such as the traction motors, the alternator/generator, cylinder valves, fuel injectors, a notch throttle, the compressor bypass valve (or an engine bypass valve in alternate embodiments), a wastegate, or the like. Other actively operating and controlling actuators may be coupled to various locations in the vehicle.

<FIG> depict example cross-section <NUM> of a rocker arm assembly <NUM> in an internal combustion engine (such as engine <NUM> in <FIG>). The rocker arm assembly may include a rocker arm <NUM> which is configured as an oscillating lever that conveys radial movement from a cam lobe into linear movement at a poppet valve to open it. A rocker arm assembly may be coupled to each valve, such as an intake valve and an exhaust valve in an engine cylinder.

A rocker arm <NUM> may be coupled to an intake valve <NUM>. Rocker arm <NUM> may be configured to oscillate (rock) about a pivot point <NUM> at a center of a rocker shaft <NUM>. The rocker arm may include a rocker shaft <NUM> counted on a bush bearing to facilitate the oscillating motion of the rocker arm <NUM>. The rocker shaft <NUM> may be shared between a plurality of rocker arms, such as a first rocker arm coupled to an intake valve and a second rocker arm coupled to an exhaust valve of an engine cylinder.

The rocker arm <NUM> conveys radial movement from the lobe of cam <NUM> into linear movement at poppet intake valve <NUM> to change a valve lift amount. By changing the lift of the intake valve <NUM>, the actuator may selectively open and close the intake port <NUM> of combustion chamber <NUM> defined in cylinder head <NUM> of engine. Camshaft <NUM> is formed with intake valve drive cam <NUM> for actuating the intake valve. The inner end <NUM> of the rocker arm is raised and lowered by the rotating lobes of cam <NUM> to allow the rocker arm to engage and activate valve stem <NUM>. The drive cam <NUM> may be coupled to the inner end <NUM> of the rocker arm <NUM> via a lifter <NUM> and a pushrod <NUM>. In alternate embodiments, the drive cam <NUM> may be directly in face sharing contact with the rocker arm <NUM>. The motion at the outer end <NUM> of the rocker arm (also referred herein as tip of rocker arm) is transmitted to the valve stem <NUM>.

As the cam lobe rotates on the camshaft <NUM>, it causes the inner end <NUM> of the rocker arm <NUM> to be raised while at the same time the outer end <NUM> presses down on the valve stem <NUM>, thereby opening the intake valve <NUM>. When the rotating cam lobe causes the inner end <NUM> of the rocker arm to be lowered, the outer end <NUM> rises causing the return spring <NUM> to close the valve. While the depicted examples only show an intake valve drive cam, it will be appreciated that similar configurations may be present for an exhaust valve drive cam. Further the exhaust valve drive cam may be located axially next to the intake valve drive cam along the camshaft.

In order to facilitate the oscillating motion of the rocker arm <NUM> and the actuation of the valve <NUM>, lubricating oil is supplied to the rocker arm and further to the outer end, tip, <NUM> of the rocker arm. During a first condition, lubricating oil may be routed to a tip of a rocker arm via a supply groove fluidically connecting a first channel carrying the lubricating oil to a second channel leading to the tip of the rocker; and during a second condition, flow of lubricating oil to the tip may be suspended by offsetting the first channel from the second channel. The first condition may include a valve coupled to the tip of the rocker arm in an open position, and the second condition includes the valve coupled to the tip of the rocker arm in a closed position, the valve being one of an intake valve and an exhaust valve. The first channel may carry lubricating oil from a cylinder head to the second channel though one or more of a pillar of a rocker pedestal and a rocker shaft passing through a pivot point of the rocker arm, the rocker arm oscillating about the pivot point. During each of the first condition and the second condition, at least a portion of the lubricating from the first channel may be routed to a set of draining channels leading to a bearing configured to oscillate the rocker arm. <FIG> shows oil channels supplying lubricating oil to the rocker arm assembly.

<FIG> an example arrangement <NUM> of a first rocker arms assembly <NUM> and a second rocker arm assembly <NUM> coupled to an engine cylinder housed within an engine block <NUM>. A first end (tip) of a first rocker arm <NUM> may be coupled to a first valve lift mechanism <NUM> of an intake valve and a first end (tip) of a second rocker arm <NUM> may be coupled to a second valve lift mechanism <NUM> of an exhaust valve of the engine cylinder. Each of the first valve lift mechanism <NUM> and the second valve lift mechanism <NUM> may include a pair of return springs coupled to a valve stem and a valve attached to an end of the valve stem distal from the return springs. A second end of the first rocker arm <NUM> may be coupled to a first drive cam via a first pushrod <NUM> and a second end of the second rocker arm <NUM> may be coupled to a second drive cam via a second pushrod (not shown).

Each of the first rocker arm <NUM> and the second rocker arm <NUM> may have openings (rocker bores) in center. A continuous rocker shaft <NUM> may pass through each of the respective central openings in the first rocker arm <NUM> and the second rocker arm <NUM> along a A-A' axis. A first bush bearing <NUM> may surround an inner wall of the rocker shaft <NUM> within the first central opening in the first rocker <NUM> and a second bush bearing <NUM> may enclose the rocker shaft within the second central opening in the second rocker <NUM>. Each rocker arm may oscillate about the rocker shaft <NUM> to selectively open and close the valve coupled to the rocker arm.

Pillars of a rocker pedestal <NUM> may support portions of the rocker shaft <NUM> not passing through openings within the rocker arms such as a portion of the rocker shaft <NUM> between two rocker arms or beyond the second rocker arm <NUM>. The rocker pedestal <NUM> may include pillars in face sharing contact with such portions of the rocker shaft <NUM> not passing through openings within the rocker arms. While the portion of the rocker shaft <NUM> that passes through the openings within the rocker arms are not in contact with the pillars of rocker pedestal <NUM>. The pillars of the rocker pedestal <NUM> may be positioned between the cylinder head housed within the engine block <NUM> and the rocker shaft <NUM>. As further elaborated in relation to <FIG>, lubricating oil may be supplied from an oil sump at the cylinder head to the rocker arms via each of the pillars of rocker pedestal <NUM> and the rocker shaft <NUM>.

<FIG> shows an example cross-section <NUM> of the rocker shaft <NUM> passing through a first rocker arm <NUM> and a second rocker arm <NUM>. The cross-section of the rocker shaft <NUM> is taken along a horizontal plane formed by the axes A-A' and B-B' in <FIG>. The components of the rocker assembly arrangement as previously introduced are numbered similarly and not reintroduced.

A central, first horizontal oil channel <NUM> may pass through the center of the rocker shaft <NUM> along the axis A-A'. Oil may be supplied to the first horizontal oil channel <NUM> from vertical oil channels within the rocker pedestal <NUM> via a first inlet <NUM> and a second inlet <NUM> (as further shown in <FIG>). A first set of draining oil channels may be located at a center of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM>. The center of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM> is the pivot point (such as pivot point <NUM> in <FIG>) for oscillation of the first rocker arm <NUM>. The first set of draining oil channels may include a first passage <NUM>, a second passage <NUM>, and a third passage <NUM>. Each of the first passage <NUM>, the second passage <NUM>, and the third passage <NUM> may lead to a bush bearing surrounding the opening (bore) of the first rocker arm <NUM>. Similarly, a second set of draining oil channels may be located at a center of the portion of the rocker shaft <NUM> that is within an opening of the second rocker arm <NUM>. The center of the portion of the rocker shaft <NUM> that is within an opening of the second rocker arm <NUM> is the pivot point (such as pivot point <NUM> in <FIG>) for oscillation of the second rocker arm <NUM>. The second set of draining oil channels may include a fourth passage <NUM>, a fifth passage <NUM>, and a sixth passage <NUM>. Each of the fourth passage <NUM>, the fifth passage <NUM>, and the sixth passage <NUM> may lead to a bush bearing surrounding the opening (bore) of the second rocker arm <NUM>.

Lubricating oil from the cylinder head may flow vertically through vertical oil channels within the rocker pedestal <NUM> and then enter the first horizontal oil channel <NUM> at each of the first inlet <NUM> and the second inlet <NUM>. The oil may horizontally flow through the first horizontal oil channel <NUM> and then intermittently flow to a second horizontal oil channel through the rocker arm (along its length). The intermittent flow of oil to the second horizontal oil channel is discussed in details in <FIG>. During conditions when oil is not supplied to the second horizontal oil channel in the rocker arm, oil from the first horizontal oil channel may flow through the first set of draining oil channels and the second set of draining oil channels to lubricate the bush bearings along the bores of the rocker arms. By supplying lubricating oil to the bush bearings, oscillating motion of the rocker arm about their respective pivot points in the rocker shaft <NUM> may be improved.

Further, the flow of oil to the first horizontal oil channel <NUM> from the cylinder head may be enabled, such as by opening one or more valves coupled to the vertical oil channels within the rocker pedestal, during conditions when the oil is supplied to the second horizontal oil channel, and during conditions when the oil is not supplied to the second horizontal oil channel, oil flow to the first horizontal oil channel <NUM> may be disabled by closing the one or more valves coupled to the vertical oil channels.

<FIG> shows an example cross-section <NUM> of a rocker pedestal <NUM> including oil channels, the rocker pedestal <NUM> supporting a rocker shaft <NUM> passing through a first rocker arm <NUM> and a second rocker arm. A first, vertical oil channel <NUM> may pass through a longitudinal axis C-C' of a pillar of the rocker pedestal <NUM>. The rocker pedestal <NUM> may have multiple pillars supporting portions of the rocker shaft <NUM> not passing through the rocker arms. Multiple vertical oil channels may pass through the separate pillars of the rocker pedestal <NUM>. Each vertical oil channel <NUM> may end in an inlet (such as first inlet <NUM> and a second inlet <NUM>) leading to a first, horizontal channel <NUM> passing through the rocker shaft <NUM>.

A first set of draining oil channels may originate from the first, horizontal channel 412at a center of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM>. The center of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM> is the pivot point (such as pivot point <NUM> in <FIG>) for oscillation of the first rocker arm <NUM>. The first set of draining oil channels may include a first passage <NUM>, a second passage <NUM>, and a third passage <NUM>. Each of the first passage <NUM>, the second passage <NUM>, and the third passage <NUM> may lead to a bush bearing <NUM> surrounding the opening (bore) of the first rocker arm <NUM>.

A second, vertical oil channel <NUM> may also originate from the first, horizontal channel <NUM> at a center of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM>. The second, vertical oil channel <NUM> may extend radially across the rocker shaft <NUM> from the center (pivot point) of the rocker shaft <NUM> to the periphery of the rocker shaft <NUM>. The second, vertical oil channel <NUM> may be perpendicular to the first, horizontal channel <NUM>. The second, vertical oil channel <NUM> may couple the first, horizontal channel <NUM> to a second, horizontal oil channel passing through the rocker arm (as seen in <FIG>). In one example, a diameter of the first vertical oil channel <NUM> may be higher than that of each of the second vertical oil channel <NUM>, the first passage <NUM>, the second passage <NUM>, and the third passage <NUM>.

Oil from the cylinder head may flow to the first horizontal channel <NUM> through the first vertical channel <NUM> and from thereon may be intermittently supplied to a second horizontal channel (within the rocker arm) via the second vertical channel <NUM>. Alternatively, in absence of the second horizontal channel within the rocker arm, the oil may be splashed to a rocker arm cover and from thereon, the oil may drip to the rocker arm.

<FIG> show a cross-section of the first position <NUM> and a cross-section of a second position <NUM> of a first rocker arm <NUM> coupled to an intake valve of a cylinder, respectively. <FIG> show a first position <NUM> and a second position <NUM> of a second rocker arm <NUM> coupled to an exhaust valve of the cylinder, respectively. Each of the first rocker arm <NUM> and the second rocker arm <NUM> may be a first embodiment of the rocker arm <NUM> in <FIG>.

A rocker shaft <NUM> may be shared between the first rocker arm <NUM> and the second rocker arm <NUM> and each rocker arm may oscillate about the pivot point at the center of the portion of the rocker shaft <NUM> that is within an opening of the respective rocker arm. As shown in this example, a first, horizontal oil channel <NUM> passes through the pivot point of each rocker arm. In this example, each of the first rocker arm <NUM> and the second rocker arm <NUM> may include a horizontal arm <NUM> along the S-S' axis and a triangular section <NUM> directly below the horizontal arm <NUM>. The rocker shaft <NUM> may pass through a bore in the triangular section <NUM>.

A first end (tip) <NUM> of the horizontal arm of a first rocker arm <NUM> may be coupled to a first valve lift mechanism of an intake valve and a first end (tip) <NUM> of horizontal arm of the second rocker arm <NUM> may be coupled to a second valve lift mechanism of an exhaust valve of the engine cylinder. Each of the first valve lift mechanism and the second valve lift mechanism may include a pair of return springs coupled to a valve stem and a valve attached to an end of the valve stem distal from the return springs. A second end <NUM> of the first rocker arm <NUM> may be coupled to a first drive cam via a first pushrod and a second end <NUM> of the second rocker arm <NUM> may be coupled to a second drive cam via a second pushrod.

A second horizontal channel <NUM> may be positioned through the horizontal arms of each rocker arm along the S-S' axis. The second horizontal channel <NUM> may span the entire length of a horizontal arm between the first end and the second end of the rocker arm. In one example, vertical oil channels may be positioned at each end of the second horizontal channel <NUM>. A second, vertical oil channel <NUM> may also originate from the first, horizontal channel <NUM> at a center (pivot point) of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM>. The second, vertical oil channel <NUM> may couple the first, horizontal channel <NUM> to the second, horizontal oil channel <NUM> passing through the rocker arm via a supply groove <NUM>. Based on a position of the rocker arm such as an angle of the rocker arm relative to the second, vertical oil channel <NUM>, the supply groove may be offset with the second, vertical oil channel <NUM> or aligned with the second, vertical oil channel <NUM>.

A set of draining oil channels may originate from the first, horizontal channel <NUM> at a center (pivot point) of the portion of the rocker shaft <NUM> that is within an opening of the first rocker arm <NUM> and diverge towards a bush bearing surrounding the inner wall of the rocker shaft <NUM>. The set of draining oil channels may include a first passage <NUM>, a second passage <NUM>, and a third passage <NUM>. The third passage <NUM> may be linear to the second, vertical oil channel <NUM> and extend in a direction away from the second horizontal channel <NUM>. The first passage <NUM> and the second passage <NUM> may be on either side of the third passage <NUM> with an angle between the first passage <NUM> and the third passage <NUM> being substantially equal to an angle between the second passage <NUM> and the third passage <NUM>. A third, vertical channel <NUM>, aligned with the supply groove <NUM> may continue towards the top surface of the rocker arm through the second, horizontal oil channel <NUM>.

During a first condition, as shown in <FIG>, the intake valve at the end of the valve stem coupled to the first end (tip) <NUM> of the first rocker arm <NUM> is closed. In this condition, there is an offset between the second, vertical oil channel <NUM> and supply groove <NUM>, thereby disconnecting the first horizontal channel <NUM> from the second horizontal channel <NUM>. Due to the offset between the second, vertical oil channel <NUM> and supply groove <NUM>, oil from the first horizontal channel <NUM> cannot flow to first end <NUM> of the rocker arm and the valve stem of the intake valve via the supply groove and the second horizontal channel <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the first condition may be reduced and the oil flowing through the first horizontal channel <NUM> may be routed through the draining oil channels such as the first passage <NUM>, a second passage <NUM>, and a third passage <NUM> to a bottom of rocker shaft/rocker bore to lubricate the bush bearing and the rocker shaft <NUM> enclosed within the bush bearing and thereby facilitate the oscillating motion of the rocker arm. By inhibiting oil flow to the intake valve during a closed state of the valve flooding of the valve stem seal may be reduced. Further, by suppling oil to the mechanical parts of the rocker shaft via the draining oil channels, friction between adjacent metallic surfaces may be reduced, thereby reducing wear of interface.

During a second condition, as shown in <FIG>, the intake valve at the end of the valve stem coupled to the first end (tip) <NUM> of the first rocker arm <NUM> is opened. A cam lobe rotates on a camshaft causing the first end <NUM> to press down on the valve stem, thereby opening the intake valve. In this condition, the second vertical oil channel <NUM> and supply groove <NUM> are aligned, thereby fluidically connecting the first horizontal channel <NUM> with the second horizontal channel <NUM>. Due to the alignment of the second, vertical oil channel <NUM> and supply groove <NUM>, oil from the first horizontal channel <NUM> may flow to first end <NUM> of the rocker arm and the valve stem of the intake valve via the supply groove and the second horizontal channel <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the second condition may be increased. A first portion the oil flowing through the first horizontal channel <NUM> may be routed to the valve stem of the intake valve via the second horizontal channel <NUM> and the first end <NUM> while a second portion of the oil may be routed to the draining oil channels such as the first passage <NUM>, a second passage <NUM>, and a third passage <NUM> to lubricate the bush bearing and the rocker shaft <NUM> enclosed within the bush bearing. In this way, lubricating oil may be intermittently supplied to a tip of a rocker arm and a corresponding valve stem during actuation of the valve coupled to it.

<FIG> shows a plot <NUM> of a duration of valve opening and oil supply to a tip (such as first end <NUM> in <FIG>) of a rocker arm (such as rocker arm <NUM> in <FIG>). The x-axis shows crank angle (in degree) and the y-axis shows a degree of valve opening. Plot <NUM> shows the opening valve coupled to the tip of the rocker arm. A first arrow <NUM> shows a first duration of valve opening and a second arrow <NUM> shows a second duration of oil supply from a cylinder head to a tip of a rocker arm and the valve stem of the valve coupled to the tip. As seen from the plot, instead of a continuous oil supply to the valve, lubricating oil may be supplied intermittently to cover the duration of valve opening.

Returning to <FIG>, during a third condition (as shown in <FIG>) the exhaust valve at the end of the valve stem coupled to the first end (tip) <NUM> of the second rocker arm <NUM> is closed. In this condition, there is an offset between the second, vertical oil channel <NUM> and supply groove <NUM>, thereby disconnecting the first horizontal channel <NUM> from the second horizontal channel <NUM>. Due to the offset between the second, vertical oil channel <NUM> and supply groove <NUM>, oil from the first horizontal channel <NUM> cannot flow to first end <NUM> of the rocker arm and the valve stem of the exhaust valve via the supply groove and the second horizontal channel <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the first condition may be reduced and the oil flowing through the first horizontal channel <NUM> may be routed through the draining oil channels such as the third passage <NUM>, a fourth passage <NUM>, and a fifth passage <NUM> to lubricate the bush bearing and the rocker shaft <NUM> enclosed within the bush bearing and thereby facilitate the oscillating motion of the rocker arm. By inhibiting oil flow to the exhaust valve during a closed state of the valve flooding of the valve stem seal may be reduced.

During a fourth condition, as shown in <FIG>, the exhaust valve at the end of the valve stem coupled to the first end (tip) <NUM> of the second rocker arm <NUM> is opened. A cam lobe rotates on a camshaft causing the first end <NUM> to press down on the valve stem, thereby opening the exhaust valve. In this condition, the second vertical oil channel <NUM> and supply groove <NUM> are aligned, thereby fluidically connecting the first horizontal channel <NUM> with the second horizontal channel <NUM>. Due to the alignment of the second, vertical oil channel <NUM> and supply groove <NUM>, oil from the first horizontal channel <NUM> may flow to first end <NUM> of the rocker arm and the valve stem of the exhaust valve via the supply groove and the second horizontal channel <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the second condition may be increased. A first portion the oil flowing through the first horizontal channel <NUM> may be routed to the valve stem of the exhaust valve via the second horizontal channel <NUM> and the first end <NUM> while a second portion of the oil may be routed to the draining oil channels such as the fourth passage <NUM>, a fifth passage <NUM>, and a sixth passage <NUM> to lubricate the bush bearing and the rocker shaft <NUM> enclosed within the bush bearing. In this way, lubricating oil may be intermittently supplied to a tip of a rocker arm and a corresponding valve stem during actuation of the valve coupled to it.

<FIG> shows a first example method <NUM> for intermittently supplying lubricating oil to a tip of a rocker arm. In this example, a first embodiment of rocker arm (such as first rocker arm <NUM> and second rocker arm <NUM> in <FIG>) may include a horizontal channel formed within the rocker arm to supply lubricating oil to rocker arm tips during an opening of a corresponding valve coupled to the rocker arm. Instructions for carrying out method <NUM> and the rest of the methods included herein may be executed by a controller based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to <FIG>. The controller may employ engine actuators of the vehicle system to adjust engine operation, according to the methods described below.

At <NUM>, a tip (such as a first end) of a rocker arm may be lowered to open a cylinder valve. The valve may be an intake valve or an exhaust valve. Rotation of a cam lobe on a camshaft may cause the tip of the rocker arm to press down on a valve stem of the cylinder valve, thereby opening the valve.

At <NUM>, as the tip of the rocker arm is lowered, a supply groove (such as supply groove <NUM> in <FIG>) may be aligned with a second vertical oil channel (such as second vertical oil channel <NUM> in <FIG>) which in turn may be coupled to a central first horizontal oil channel passing through the center of a rocker shaft of the rocker arm.

At <NUM>, a first portion of lubricating oil may be supplied from the central first horizontal oil channel to the tip of the rocker arm via the supply groove and a second horizontal channel (such as second horizontal channel <NUM> in <FIG>) passing through the rocker arm. Oil from a cylinder head may flow to the first horizontal channel through a first vertical channel (such as first vertical channel <NUM> in <FIG>) formed within a rocker pedestal supporting the rocker shaft. Oil at the tip of the rocker arm may lubricate a valve stem coupled to the tip.

At <NUM>, a second portion of the lubricating oil may flow from the central first horizontal oil channel to one or more draining oil channels leading to a lower portion of the rocker shaft/rocker bore such as to a bearing around the rocker shaft to facilitate movement of the rocker arm about the bearing. By suppling oil to the lower part of the rocker shaft via the draining oil channels, friction between adjacent metallic surfaces may be reduced, thereby reducing wear of interfaces. In one example, the first portion of oil supplied to the tip of the rocker arm may be higher than the second portion of oil routed to the draining oil channels.

At <NUM>, the tip of the rocker arm may be raised to close the open valve. Rotation of the cam lobe on the camshaft may cause the tip of the rocker arm to be raised, causing a return spring coupled to the valve stem to close the valve. Due to the change in inclination of the rocker arm, at <NUM>, the supply groove may become offset from the second vertical oil channel and oil flow from the second horizontal channel to the tip of the rocker arm via the second vertical oil channel and the supply groove may be suspended. Therefore, upon closure of a cylinder valve, oil may no longer be supplied to the tip of the rocker arm coupled to that valve.

At <NUM>, entire volume of oil may flow from the central first horizontal oil channel to the one or more draining oil channels leading to the bearing around the rocker shaft facilitating movement of the rocker arm about the bearing.

In this way, a system for an engine may comprise a first channel axially extending along a rocker arm up to a tip of the rocker arm coupled to a valve, a second channel fluidically coupled to an oil sump at a cylinder head at a first end, and a supply groove selectively aligned with the first channel based on an angle of the rocker arm. The selectively aligning may include the supply groove being aligned with the first channel upon the tip of the rocker arm being lowered during opening of the valve, and the supply groove being offset with the first channel upon the tip of the rocker ram arm being raised upon closing of the valve.

<FIG> show a cross-section of the first position <NUM> and a cross-section of a second position <NUM>, respectively, of a third rocker arm <NUM> coupled to an intake valve of a cylinder. <FIG> show a first position <NUM> and a second position <NUM>, respectively, of a fourth rocker arm <NUM> coupled to an exhaust valve of the cylinder. Each of the third rocker arm <NUM> and the fourth rocker arm <NUM> may be a second embodiment of the rocker arm <NUM> in <FIG>.

A rocker shaft may be shared between the third rocker arm <NUM> and the fourth rocker arm <NUM> and each rocker arm may oscillate about the pivot point at the center of the portion of the rocker shaft that is within an opening (bore) <NUM> of the respective rocker arm. As shown in this example, a first, horizontal oil channel <NUM> passes through the pivot point of each rocker arm. In this example, each of the third rocker arm <NUM> and the fourth rocker arm <NUM> may include a horizontal section <NUM> along the S-S' axis and a triangular section <NUM> directly below the horizontal arm <NUM>. The rocker shaft may pass through the opening <NUM> in the triangular section <NUM>.

A first end (tip) of the horizontal arm of a third rocker arm <NUM> may be coupled to a first valve lift mechanism <NUM> of an intake valve and a first end (tip) of horizontal arm of the fourth rocker arm <NUM> may be coupled to a second valve lift mechanism <NUM> of an exhaust valve of the engine cylinder. Each of the first valve lift mechanism <NUM> and the second valve lift mechanism <NUM> may include a valve adjuster shaped as an elephant foot with a rectangular upper portion and a spherical lower portion, and a pair of return springs coupled to a valve stem and a valve attached to an end of the valve stem distal from the return springs. A spherical lower portion (ball) of the elephant foot may form a spherical interface with a complementary cup (socket) shaped geometry of a valve train component. A second end of the third rocker arm <NUM> may be coupled to a first drive cam via a first pushrod system <NUM> including a lash adjuster and a second end of the fourth rocker arm <NUM> may be coupled to a second drive cam via a second pushrod system <NUM> including a lash adjuster.

A continuous cover <NUM> may be placed over each of the third rocker arm <NUM> and the fourth rocker arm <NUM>. The single cover <NUM> may enclose both the rocker arms. <FIG> shows a bottom view <NUM> of the cover <NUM> facing the rocker arms. The cover may include a casing <NUM> including an insert <NUM>. The insert <NUM> may include a u-shaped wall <NUM> along the perimeter of the insert <NUM>. The third rocker arm coupled to the intake valve may be positioned under a first side <NUM> of the cover <NUM> and the fourth rocker arm coupled to the exhaust valve may be positioned under a second side <NUM> of the cover <NUM>.

The insert may include an opening <NUM> towards one end of the cover <NUM>. A first set of protrusions including a first protrusion <NUM> and a second protrusion <NUM> may be placed on two sides of the opening <NUM>. A second set of protrusions including a third protrusion <NUM> and a fourth protrusion <NUM> may be placed proximal to another side of the cover <NUM> distal from the opening <NUM>. Each of the first protrusion <NUM>, the second protrusion <NUM>, the third protrusion <NUM>, and the fourth protrusion <NUM> may of conical shape with a broader base and a pointed tip. The first protrusion <NUM> and the second protrusion <NUM> may intersect with the wall <NUM> and may be bigger in size (such as diameter of base and distance between base and tip) compared to the third protrusion <NUM> and the fourth protrusion <NUM>.

The first protrusion <NUM> and the third protrusion <NUM> may be placed over the third rocker arm <NUM> while the second protrusion <NUM> and the fourth protrusion <NUM> may be placed over the fourth rocker arm <NUM>. The first protrusion <NUM> and the second protrusion <NUM> may be placed directly over the valve lift mechanism coupled to the respective rocker arm while the third protrusion <NUM> and the fourth protrusion <NUM> may be placed directly over the pushrod coupled to the respective rocker arm. The tips (ends) of each of the first protrusion <NUM> and the second protrusion <NUM> may directly face the valve lift mechanism while the tips (ends) of each of the third protrusion <NUM> and the fourth protrusion <NUM> may directly face the respective pushrods.

The surface <NUM> of the insert <NUM> facing the rocker arms may be inclined on each side of the axis I-I' with a ridge formed along the I-I' axis. The surface <NUM> of the insert <NUM> may slope away downward from the ridge along the axis I-I' on both sides of the ridge. Due to the slope leading away from the ridge in a first direction, a first portion of fluid from the ridge may trickle down a first segment <NUM> of the surface <NUM> leading to the first set of protrusions including (first protrusion <NUM> and second protrusion <NUM>) positioned on the first segment <NUM>. Also, due to the slope leading away from the ridge in a second direction, a second portion of fluid from the ridge may trickle down a second segment <NUM> of the surface <NUM> leading to the second set of protrusions including (third protrusion <NUM> and fourth protrusion <NUM>) positioned on the second segment <NUM>. Each of the protrusions may allow the fluid to concentrate and trickle down from the pointed ends.

Returning to <FIG>, a second, vertical oil channel <NUM> may also originate from the first, horizontal channel <NUM> at a center (pivot point) of the portion of the rocker shaft <NUM> that is within respective openings of the third rocker arm <NUM> and the fourth rocker arm <NUM>. The second, vertical oil channel <NUM> may couple the first, horizontal channel <NUM> a supply channel <NUM>. The supply channel <NUM> may extend from the circumference of the opening <NUM> to the top surface of the respective rocker arm. The supply channel <NUM> may have an opening at the end facing the cover <NUM> on the rocker arms. Based on a position of the rocker arm such as an angle of the rocker arm relative to the second, vertical oil channel <NUM>, the supply channel <NUM> may be offset with the second, vertical oil channel <NUM> or aligned with the second, vertical oil channel <NUM>.

A set of draining oil channels may originate from the first, horizontal channel <NUM> at a center (pivot point) of the portion of the rocker shaft <NUM> that is within an opening of each of the third rocker arm <NUM> and the fourth rocker arm <NUM> and diverge towards a bush bearing surrounding the inner wall of the rocker shaft <NUM>. A first set of draining oil channels included in the third rocker arm <NUM> may include a first passage <NUM>, a second passage <NUM>, and a third passage <NUM>. The third passage <NUM> may be linear to the second, vertical oil channel <NUM> and extend in a direction away from the second horizontal channel <NUM>. The first passage <NUM> and the second passage <NUM> may be on either side of the third passage <NUM> with an angle between the first passage <NUM> and the third passage <NUM> being substantially equal to an angle between the second passage <NUM> and the third passage <NUM>. Similarly, a second set of draining oil channels included in the fourth rocker arm <NUM> may include a fourth passage <NUM>, a fifth passage <NUM>, and a sixth passage <NUM>.

During a first condition for the intake valve, as shown in <FIG>, the intake valve at the end of the first valve lift mechanism <NUM> coupled to the first end of the rocker arm <NUM> is closed. In this condition, there is an offset between the second, vertical oil channel <NUM> and supply channel <NUM>, thereby disconnecting the first horizontal channel <NUM> from the supply channel <NUM>. Due to the offset between the second, vertical oil channel <NUM> and supply channel <NUM>, oil from the first horizontal channel <NUM> cannot flow to the supply channel <NUM>, splash out of the rocker arm, and then drip back to lubricate the first valve lift mechanism <NUM> and first pushrod system <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the first condition may be reduced and the oil flowing through the first horizontal channel <NUM> may be routed through the draining oil channels such as the first passage <NUM>, a second passage <NUM>, and a third passage <NUM> to a bottom of rocker shaft/rocker bore to lubricate the bush bearing and the rocker shaft enclosed within the bush bearing and thereby facilitate the oscillating motion of the rocker arm. By inhibiting oil flow to the intake valve lift mechanism and the pushrod during a closed state of the valve flooding of the valve stem seal may be reduced. Further, by suppling oil to the mechanical parts of the rocker shaft via the draining oil channels, friction between adjacent metallic surfaces may be reduced, thereby reducing wear of interface.

During a second condition for the intake valve, as shown in <FIG>, the intake valve at the end of the first valve lift mechanism <NUM> coupled to the first end (tip) of the third rocker arm <NUM> is opened. A cam lobe rotates on a camshaft causing the first end to press down on the valve stem of the valve lift mechanism <NUM>, thereby opening the intake valve. In this condition, the second vertical oil channel <NUM> and supply channel <NUM> are aligned, thereby fluidically connecting the first horizontal channel <NUM> with the supply channel <NUM>. Due to the alignment of the second, vertical oil channel <NUM> and supply channel <NUM>, oil from the first horizontal channel <NUM> may flow to the opening at the end of the supply channel <NUM> and splash out of the supply channel <NUM>. A first jet <NUM> of oil ejecting out of the supply channel <NUM> may impinge on the surface <NUM> of the cover <NUM>. Upon alignment of the supply channel <NUM> and the vertical oil channel <NUM>, the opening at the end of the supply channel <NUM> may face a first segment <NUM> of the surface <NUM> on a first side of the I-I' axis proximal to the valve lift mechanism <NUM>.

The slope on the surface <NUM> allows the oil to flow towards the first protrusion <NUM> positioned vertically above the valve lift mechanism <NUM> and the third protrusion <NUM> positioned vertically above the lash adjuster of the pushrod system <NUM>. The oil flowing to the base of the first protrusion <NUM> may then trickle down the tip of the first protrusion <NUM> and a second jet <NUM> may drip on the valve lift mechanism <NUM>. Also, a portion of oil flowing to the base of the third protrusion <NUM> may then trickle down the tip of the third protrusion <NUM> and a third jet <NUM> may drip on the pushrod system <NUM>. Due to the offset (relative to the I-I' axis) alignment of the supply channel <NUM>, a higher volume of oil may flow towards the first protrusion <NUM> relative to the third protrusion <NUM>. Also, due to the first protrusion <NUM> being bigger in size relative to the third protrusion <NUM>, the second jet <NUM> may include a higher oil flow relative to the third jet <NUM> ensuring desired lubrication of the first valve lift mechanism <NUM>.

In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the second condition may be increased. A first portion the oil flowing through the first horizontal channel <NUM> may be routed to the first valve lift mechanism <NUM> of the intake valve via the supply channel <NUM> while a second portion of the oil may be routed to the draining oil channels such as the first passage <NUM>, a second passage <NUM>, and a third passage <NUM> to lubricate the bush bearing and the rocker shaft enclosed within the bush bearing.

During a first condition for the exhaust valve, as shown in <FIG>, the exhaust valve at the end of the second valve lift mechanism <NUM> coupled to the first end of the fourth rocker arm <NUM> is closed. In this condition, there is an offset between the second, vertical oil channel <NUM> and supply channel <NUM>, thereby disconnecting the first horizontal channel <NUM> from the supply channel <NUM>. Due to the offset between the second, vertical oil channel <NUM> and supply channel <NUM>, oil from the first horizontal channel <NUM> cannot flow to the supply channel <NUM>, splash out of the rocker arm, and then drip back to lubricate the second valve lift mechanism <NUM> and second pushrod system <NUM>. In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the first condition may be reduced and the oil flowing through the first horizontal channel <NUM> may be routed through the draining oil channels such as the fourth passage <NUM>, a fifth passage <NUM>, and a sixth passage <NUM> to a bottom of rocker shaft/rocker bore to lubricate the bush bearing and the rocker shaft enclosed within the bush bearing and thereby facilitate the oscillating motion of the rocker arm. By inhibiting oil flow to the exhaust valve lift mechanism and the pushrod during a closed state of the valve flooding of the valve stem seal may be reduced. Further, by suppling oil to the mechanical parts of the rocker shaft via the draining oil channels, friction between adjacent metallic surfaces may be reduced, thereby reducing wear of interface.

During a second condition for the exhaust valve, as shown in <FIG>, the exhaust valve at the end of the second valve lift mechanism <NUM> coupled to the first end (tip) of the fourth rocker arm <NUM> is opened. A cam lobe rotates on a camshaft causing the first end to press down on the valve stem of the valve lift mechanism <NUM>, thereby opening the exhaust valve. In this condition, the second vertical oil channel <NUM> and supply channel <NUM> are aligned, thereby fluidically connecting the first horizontal channel <NUM> with the supply channel <NUM>. Due to the alignment of the second, vertical oil channel <NUM> and supply channel <NUM>, oil from the first horizontal channel <NUM> may flow to the opening at the end of the supply channel <NUM> and splash out of the supply channel <NUM>. A first jet <NUM> of oil ejecting out of the supply channel <NUM> may impinge on the surface <NUM> of the cover <NUM>.

The slope on the surface <NUM> allows the oil to flow towards the second protrusion <NUM> positioned vertically above the second valve lift mechanism <NUM> and the fourth protrusion <NUM> positioned vertically above the lash adjuster of the second pushrod system <NUM>. The oil flowing to the base of the second protrusion <NUM> may then trickle down the tip of the second protrusion <NUM> and a second jet <NUM> may drip on the second valve lift mechanism <NUM>. Also, a portion of oil flowing to the base of the fourth protrusion <NUM> may then trickle down the tip of the fourth protrusion <NUM> and a third jet <NUM> may drip on the pushrod system <NUM>. Due to the second protrusion <NUM> being bigger in size relative to the fourth protrusion <NUM>, the second jet <NUM> may include a higher oil flow relative to the third jet <NUM> ensuring desired lubrication of the second valve lift mechanism <NUM>.

In one example, oil flow from the cylinder head to the first horizontal channel <NUM> during the second condition may be increased. A first portion the oil flowing through the first horizontal channel <NUM> may be routed to the second valve lift mechanism <NUM> of the exhaust valve via the supply channel <NUM> while a second portion of the oil may be routed to the draining oil channels such as the first passage <NUM>, a second passage <NUM>, and a third passage <NUM> to lubricate the bush bearing and the rocker shaft enclosed within the bush bearing. In this way, lubricating oil may be intermittently supplied to a tip of a rocker arm and a corresponding valve stem without any horizontal oil channel within the rocker arm during actuation of the valve coupled to it.

<FIG> shows a second example method <NUM> for intermittently supplying lubricating oil to a tip of a rocker arm. In this example, a second embodiment of rocker arm (such as third rocker arm <NUM> and fourth rocker arm <NUM> in <FIG>) may not include a horizontal channel within the rocker arm but instead the rocker arm may be enclosed under a cover equipped with features such as protrusions and slopes that allow oil impinging on the cover to drip back to the rocker arm tip.

At <NUM>, a tip (such as a first end) of the rocker arm may be lowered to open a cylinder valve. The valve may be an intake valve or an exhaust valve. Rotation of a cam lobe on a camshaft may cause the tip of the rocker arm to press down on a valve stem of the cylinder valve, thereby opening the valve.

At <NUM>, as the tip of the rocker arm is lowered, a supply channel (such as supply groove <NUM> in <FIG>) may be aligned with a second vertical oil channel (such as second vertical oil channel <NUM> in <FIG>) which in turn may be coupled to a central first horizontal oil channel passing through the center of a rocker shaft of the rocker arm.

At <NUM>, a first portion of lubricating oil may be splashed to the cover of the rocker arms via the opening at the end of the supply channel facing the cover. The lubricating oil may be supplied to the supply channel from the central first horizontal oil channel. Upon impinging on the surface of the cover, due to the sloping nature of the surface, the oil may flow to two opposite ends.

At <NUM>, first rocker arm tip coupled to the valve lifting mechanism and a second rocker arm tip coupled to a pushrod may be lubricated by oil dripping from the rocker cover. The oil from the surface of the rocker cover may drip down on the rocker arms tips from protrusions on the surface directly facing the rocker arm tips. The lubricating oil may drip on the valve lifting mechanism and the pushrod from the pointed ends of the protrusions. In this way topological features on the rocker arm surface may be used to guide lubricating oil sprayed on the cover to drip and lubricate valve actuation mechanism and pushrod coupled to a rocker arm.

At <NUM>, the tip of the rocker arm may be raised to close the valve. Rotation of the cam lobe on the camshaft may cause the tip of the rocker arm to be raised, causing a return spring coupled to the valve stem to close the valve. Due to the change in inclination of the rocker arm, at <NUM>, the supply channel may become offset from the second vertical oil channel and splashing of oil onto the rocker arm cover form the supply channel may be suspended. Therefore, upon closure of a cylinder valve, oil may no longer be supplied to the tip of the rocker arm coupled to that valve.

In this way, upon aligning of oil channels only during opening of a valve coupled to a tip of a rocker arm, lubricating oil may be selectively splashed to a cover of the rocker arm and then the splashed lubricating oil may be supplied to the tip of the rocker arm via topographical features on the surface of the cover facing the rocker arm.

<FIG> and <FIG> show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a "top" of the component and a bottommost element or point of the element may be referred to as a "bottom" of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example.

Claim 1:
A method for an engine, the method comprising:
upon aligning of second vertical and supply channels (<NUM>, <NUM>) only during opening of a valve coupled to a tip of a rocker arm (<NUM>, <NUM>), selectively splashing lubricating oil to a cover (<NUM>) of the rocker arm (<NUM>, <NUM>) and supplying the splashed lubricating oil to the tip of the rocker arm (<NUM>, <NUM>),
wherein the cover (<NUM>) includes a surface (<NUM>) having one or more protrusions (<NUM>, <NUM>, <NUM>, <NUM>) thereon,
wherein the one or more protrusions (<NUM>, <NUM>, <NUM>, <NUM>) includes a first set of protrusions (<NUM>, <NUM>) on the cover (<NUM>) at a first side of the cover (<NUM>) and a second set of protrusions (<NUM>, <NUM>) on the cover (<NUM>) at a second side of the cover (<NUM>),
wherein supplying the splashed lubricating oil to the tip of the rocker arm (<NUM>, <NUM>) includes guiding the splashed lubricating oil from a ridge to the first side of the cover (<NUM>) following a first downward slope sloping downward away from the ridge and then dripping the splashed lubricating oil on the tip via the first set of protrusions (<NUM>, <NUM>), and
wherein the method further comprises supplying the splashed lubricating oil to another tip of the rocker arm (<NUM>, <NUM>) by guiding the splashed lubricating oil from the ridge to the second side of the cover (<NUM>) following a second downward slope sloping downward away from the ridge and then dripping the splashed lubricating oil on the another tip via the second set of protrusions (<NUM>, <NUM>), the another tip coupled to a drive cam via a pushrod (<NUM>, <NUM>),
wherein a first amount of oil dripped from the first set of protrusions (<NUM>, <NUM>) on the tip is higher relative to a second amount of oil dripped from the second set of protrusions (<NUM>, <NUM>) on the another tip.