Patent Application
20210054767
The present disclosure relates generally to a lifter used in engines and fuel pumps, and more particularly, to a lifter providing improved cam lobe lubrication.
Flow control components of an internal combustion engine such as intake and exhaust valves and fuel injectors are typically driven by a cam arrangement that is operably connected to a crankshaft of the engine. Rotation of the crankshaft results in a corresponding rotation of a camshaft that drives one or more cam followers or lifters. The movement of the lifters results in reciprocating motion of the intake and exhaust valves and actuation of the fuel injectors. The shape of cam lobes on the camshaft governs the timing and duration of opening and closing of the intake and exhaust valves and of the fuel injection. Each lifter may include, among other things, a cam roller in contact with a cam lobe of the camshaft, and a bushing, roller bearing, or needle bearing that rotatably supports the cam roller at one end of a body of the lifter.
Conventional camshaft internal combustion engines typically utilize valve lifters, push rods, and valve springs along with rocker arms to open and close the intake and exhaust valves of the engine to allow air and fuel to enter and exhaust to exit the cylinders of the engine during combustion. These components are collectively referred to as the “valve train.” In conventional cam engines as opposed to those of over-head design, a valve lifter with a pushrod rides on the cam lobes of the camshaft, which is rotated by the crankshaft. As the lifter reciprocates up and down, the push rod seated in the lifter also reciprocates and communicates this up and down motion via a rocker arm to either an intake or exhaust valve. A high tension spring ranging from approximately 200 to 1000 ft-lbs, surrounds the stem of the valve and when the spring is compressed, the valve is pushed into the cylinder. During the up stroke of the piston in the cylinder, the intake valve opens to allow fuel and air to enter the combustion chamber. Somewhere near the very top of the up stroke, both the intake and the exhaust valves close and the spark plug creates a spark to ignite the air-fuel mixture which is under compression by the piston. This results in a high temperature explosion which forces the piston downward, called the “power stroke,” thereby translating this movement via a connection rod to rotate the crankshaft which, in turn, translates this angular motion to the wheels of the vehicle via a set of gears. Near the bottom of the power stroke, the exhaust valve opens to expel the burnt fuel mixture out of the cylinder. After the piston changes directions and begins the up stroke, the exhaust valve continues to remain open, thereby forcing any remaining spent gases out of the cylinder. However, during this same time, the intake valve begins to open to recharge the cylinder with fuel. It is not until the piston has started to travel upward that the exhaust valve closes. Thus, at various times during the compression cycle, both the intake and exhaust valves will be open and closed at the same time. The timing of the opening and closing of the valves is controlled by the physical design of the oval shaped cam lobes on the camshaft. As the valve lifter is pushed upward by the cam lobe of the camshaft, the valve lifter pushes the pushrod up which drives the rocker arm downward, causing the valve to open. Likewise, as the lifter and pushrod travel downward, the rocker arm raises and the valve closes due to the biasing action of the valve spring.
In high speed engines, characterized by a high number of revolutions per minute (RPM), the valve train components are under extreme stress and high temperatures. To increase engine performance and decrease component wear that may eventually lead to failure, various valve lifter configurations have been designed. Solid and hydraulic valve lifters are the most common designs used in conventional cam engines. Hydraulic lifters are typically used in relatively low RPM engines, up to 6,500 RPM, whereas solid valve lifter designs are preferred in high RPM applications such as racing and high performance applications. Conventional hydraulic and solid lifters have a flat surface that is fixed or integral with the body of the lifter and is adapted to engage and ride on the cam lobes of the camshaft. The engagement between the fixed surface of the lifter body and the camshaft lobe creates high frictional forces, causing the surfaces of the lobes to wear. Therefore, the higher the RPM of the engine, the greater the wear and the likelihood of material being removed from the cam lobe. As material is removed from the surface of the cam lobe, the timing of the opening and closing of the valve also changes. This change in timing may hamper engine performance such as by allowing excess fuel to enter the cylinder causing a rich condition. Conversely, improper timing may permit air-fuel mixture that has not been completely combusted to escape through the exhaust valve which results in a lean condition, increased fuel consumption, and increased pollution. Either of these conditions will affect cylinder pressure and decrease performance and may cause misfiring of the cylinder and engine damage. Furthermore, if this improper timing allows a valve to remain open when the piston is near the top of the compression stroke, the piston will strike the valve resulting in bent pushrods and valves, broken valve springs and lifters and will eventually lead to catastrophic engine failure.
To decrease cam lobe wear in high performance engines, a cam roller has been added to the body of the valve lifter for riding on the cam lobe of the camshaft. The cam roller allows the use of a camshaft with cam lobes having steeper ramp angles to provide faster valve opening and closing for accommodating high RPM engines. The cam roller engagement with the rotating cam lobe reduces the frictional forces generated therebetween. Not only does the presence of the cam roller decrease cam lobe and valve lifter wear, it also provides smoother transitions as the cam roller travels over the peak of the cam lobe, thereby decreasing valve train noise. Likewise, various bearing and sleeve configurations have been utilized to decrease friction and wear of the shaft rotatably mounting the cam roller to the valve lifter. For high performance engines, needle bearings have replaced solid cam rollers, cam roller bushings, and conventional ball bearings to decrease wear and more evenly spread the load over the surface of the shaft. However, even with cam rollers that include bearings or bushings, proper functioning of a cam roller and cam roller-to-cam lobe interface depends on a continuous supply of a lubricant to the cam roller and to the interface with a cam lobe. From the ground up, a typical engine is configured with an oil pan for holding oil and an oil pump that feeds the oil to various locations in the engine. Above the oil pan sits the engine block and the crankshaft, such that a portion of the crank rotates in the oil. In a typical “V”-style engine, that is, one having cylinders at an angle to the left and right sides of the block in a “V” pattern with the crankshaft positioned at the apex of the “V”, the camshaft is typically located directly above and in parallel with the crank. In straight cylinder configuration engines wherein all cylinders are aligned in a row, the crankshaft and cylinders are located in the same plane and camshaft is positioned to one side so as to not interfere with the travel of the connecting rods. The valve lifters in an “V” style engine are located in a lifter galley. The lifters are lubricated by oil in the engine block and receive direct lubrication from one or more transverse oil passageways in the engine block that intersect the bores in which the valve lifters are positioned and indirectly from oil that is sprayed into the lifter galley from the rotation of the crankshaft and connecting rods. Various methods have been employed to increase the lubrication of the valve lifters and camshaft. One method used to increase the movement of oil to the valve lifters and camshaft is the addition of small holes to the crankshaft and the dynamic balance weights of the crank. These holes, or oil squirters, pickup oil from the pan and any oil on the surface of the crank and throw the oil to the camshaft and valve lifter as the crankshaft and rotates. This method is also employed in engines having steel connecting rods to lubricate the cylinder wall by placing a through-hole on the end that connects to the piston and to the lifters by adding a squirter to the “big end” or end that connects to the crankshaft. However, the machining of the oil squirter reduces the strength of the crankshaft and has been found to severely weaken aluminum connecting rods used in high performance, high RPM engines.
Another method of directing oil to the lifters and camshaft involves adding separate oil feed lines to the lifter galley. This is accomplished by drilling a feed hole into an oil passageway of the engine block to tap the oil pressurized by the oil pump and adding metal tubing to direct the oil to the desired location such as above the camshaft. However, adding components to the internals of engine is not always practical due to the limited amount of space. Furthermore, these added components may also fail and create shrapnel that will be run through the engine which can damage precision surfaces such as on the camshaft, crankshaft, pistons, etc.
An exemplary cam follower is disclosed in U.S. Pat. No. 9,222,376 that issued to Massing et al. on Dec. 29, 2015 (“the '376 patent”). Specifically, the '376 patent discloses a cam follower including a tappet (lifter body) positioned between a cylinder valve and a camshaft, with the tappet configured to drive the cylinder valve, a cam roller, and a pin coated with a diamond-like carbon coating that couples the roller to the tappet. The pin is provided with a depressed contour on an outer surface of the pin. The depressed contour on the pin purportedly reduces edge loading due to concentrated contact between the pin and the cam roller.
Although the cam follower of the '376 patent may be suitable for some applications, it may still be less than optimal. For example, the structure disclosed in the '376 patent is intended to reduce wear and degradation of the pin that couples the cam roller to the tappet, but does not do anything to improve the lubrication of the high load surfaces at the interface between the cam roller and the cam lobe.
The lifter of the present disclosure is directed towards overcoming one or more of the problems set forth above and/or other problems of the prior art.
One aspect of the present disclosure is directed to a cam follower assembly including a cam roller. The cam follower assembly may include a generally cylindrical body having an outer peripheral surface configured to be reciprocally slidable within a bore of an engine component. The body rotatably mounts the cam roller with the cam roller being configured to engage with a cam lobe on a camshaft of the engine, wherein the cam lobe is operative to drive the body to a position at which the cam follower assembly causes one of opening of a valve or actuation of a fuel injector of the engine. A groove is formed in the body inset from the outer peripheral surface and extending axially along the outer peripheral surface parallel to the longitudinal axis of the body and aligned with an axial median plane of the cam roller and the cam lobe.
Another aspect of the present disclosure is directed to a lifter configured for use in an engine including a plurality of flow control components and a camshaft including cams that cause reciprocating movement of the flow control components. The lifter may include a generally cylindrical body having an outer peripheral surface configured to be reciprocally slidable within a bore of an engine component. The body may rotatably mount a cam roller with the cam roller being configured to engage with a cam lobe on the camshaft of the engine, wherein the cam lobe is operative to drive the body to a position at which the lifter causes one of opening of a valve or actuation of a fuel injector of the engine. An oiling channel may be formed in the body inset from the outer peripheral surface and extending axially along the outer peripheral surface parallel to the longitudinal axis of the body and aligned with an axial median plane of the cam roller and the cam lobe.
In yet another aspect, the present disclosure is directed to a method of supplying oil to a high load area on at least one of a cam roller of a lifter or a cam lobe of a camshaft including cams that cause reciprocating movement of the lifter and flow control components of an engine, wherein the lifter may include a generally cylindrical body having an outer peripheral surface configured to be reciprocally slidable within a bore of an engine component, the cam roller may be rotatably mounted on the body and configured to engage with the cam lobe, and the cam lobe may be operative to drive the body to a position at which the lifter causes movement of at least one of the flow control components. The method may include receiving oil from an oil supply passageway of the engine component into an oil receiving annular recess formed around the outer peripheral surface of the body at a location spaced from the cam roller while the body is reciprocally sliding within the bore of the engine component, and directing the oil from the oil receiving annular recess into an oiling channel formed in the body inset from the outer peripheral surface and extending axially along the outer peripheral surface parallel to the longitudinal axis of the body and aligned with an axial median plane of the cam roller and the cam lobe.
A valve lifter as used in an internal combustion engine is designed to translate the angular motion of a camshaft to reciprocating motion to open and close intake and exhaust valves of the engine. In the exemplary embodiment of
As shown in
As best seen in the inset of
Groove 32 of lifter 30 for the exemplary cam follower assembly shown in
In the exemplary embodiment of valve lifter 30 shown in
One of ordinary skill in the art will recognize that valve lifter 30 may be symmetrical in configuration as viewed from 360 degrees around the cylindrical body of valve lifter 30, with the exception of groove 32 and bore hole 36, which are located only on one side of the body of valve lifter 30 in the embodiment shown in
While the exemplary embodiments of the cam follower assemblies shown in
As shown in
In the alternative embodiment of a cam follower assembly shown in
One of ordinary skill in the art will recognize that valve lifter 130 shown in
In the alternative embodiments of valve lifter 130 discussed above, with a groove or bore hole located on an opposite side of the valve lifter body, or with two grooves and/or bore holes located on both of opposite sides of the valve lifter body spaced 180 degrees apart from each other, the oil flow path from each of the one or more grooves or bore holes may still lead directly to an axial median plane of cam roller 140 at a midpoint between opposite axial ends of cam roller 140, such that oil is directly deposited on the highest load area of cam roller 140.
Similarly, in the exemplary embodiment of a cam follower assembly for a fuel system lifter 230 shown in
One of ordinary skill in the art will recognize that fuel system lifter 230 may be symmetrical in configuration as viewed from 360 degrees around the cylindrical body of fuel system lifter 230, with the exception of groove 232, which is located only on one side of the body of fuel system lifter 230 in the embodiment shown in
Each of exemplary lifters 30, 130, 230 includes a rotatably mounted cam roller 40, 140, 240, respectively, which rides on an engagement surface of cam lobe 50, 150, 250, respectively, of a camshaft that rotates along with a crankshaft as pistons of the engine move up and down. In various exemplary embodiments, cam rollers 40, 140, 240 may include bearing assemblies containing needle bearings, roller bearings, or bushings. Each of cam rollers 40, 140, 240 may be rotatably mounted to a respective valve lifter 30, 130, 230 by a shaft or pin extending through the bearings or bushings of the cam roller. In high performance and heavy duty application engines, especially those which maintain high engine speeds or loads for long durations, it is important to provide sufficient oiling of the cam rollers of the lifters and of the cam lobes of the camshaft as the lifters ride on the cam lobes, particularly at the point of contact, and even more particularly in the area of highest load. The highest load areas at the point of contact between the cam rollers and the cam lobes are typically located at or near the axial median planes extending through each cam roller and cam lobe, perpendicular to the central rotational axes of the cam roller and the cam lobe, and intersecting the axes at approximately a midpoint between the two opposite axial ends of the cam roller and the cam lobe. Oil receiving annular recesses 35, 135, 235 formed around the outer peripheral surfaces 31, 131, 231 of lifters 30, 130, 230, respectively, form oil pressure feed passageways that supply oil to grooves 32, 132, 232. Grooves 32, 132, 232 form oiling channels that are inset from outer peripheral surfaces 31, 131, 231 of lifters 30, 130, 230, and extend axially along the outer peripheral surfaces parallel to the longitudinal axes of the bodies of the lifters and aligned with an axial median plane of the cam roller and the cam lobe. Oil enters oil receiving annular recesses 35, 135, 235 from common transverse oil passageways in engine block 20 or the fuel pump housing that intersect the lifter bores. As the lifters reciprocate, the oil receiving annular recesses carry oil up and down the lifter bores and direct oil into the oiling channels formed by grooves 32, 132, 232 for supplying the oil directly to the engagement interface between each cam roller and cam lobe.
An engine in which fuel system lifters 230 are provided may include an engine block 20 that at least partially defines a plurality of cylinders. A piston may be slidably disposed within each cylinder to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head may be associated with each cylinder. Each cylinder, piston, and cylinder head may together at least partially define a combustion chamber. A fuel injector assembly may be at least partially disposed within each cylinder head and configured to inject fuel into each respective combustion chamber to support fuel combustion within the engine. The engine may also include a crankshaft that is rotatably supported within engine block 20 by way of a plurality of journal bearings. A connecting rod may connect each piston to the crankshaft so that a sliding motion of the piston within each respective cylinder results in a rotation of the crankshaft.
A fuel injector assembly may be configured to inject or otherwise spray fuel, for example, diesel fuel, directly into each combustion chamber via a fuel port within the cylinder head in accordance with a desired timing. The fuel injector assembly may embody a mechanically-actuated, electronically-controlled unit injector that is in fluid communication with a common fuel rail (not shown). Alternatively, the fuel injector assembly may be any common rail type injector and may be actuated and/or operated hydraulically, mechanically, electrically, piezo-electrically, or any combination thereof. The common fuel rail may provide fuel to the fuel injector assembly associated with each combustion chamber.
Just as with flow control components of the engine in the form of the intake and exhaust valves, the fuel injector assemblies may be driven by a rocker arm that is pivotally coupled to a rocker shaft. Each fuel injector assembly may include an injector body, a plunger, and an injector tip. A first end of the rocker arm may be operatively coupled to the plunger of the fuel injector. The plunger of the fuel injector may be biased by a spring toward a first end of the rocker arm. In the exemplary embodiment shown in
The disclosed cam follower assemblies and lifters may be used with any internal combustion engine. The lifters of this disclosure facilitate methods of supplying oil to high load areas on at least one of a cam roller of a lifter or a cam lobe of a camshaft including cams that cause reciprocating movement of the lifter and flow control components of an engine. Each of the disclosed exemplary lifters may include a generally cylindrical body having an outer peripheral surface configured to be reciprocally slidable within a bore of an engine component. The disclosed cam rollers are rotatably mounted on the body of each lifter, at an opposite end of the lifter from an end that receives a pushrod configured to exert a force on a rocker arm operatively connected to a flow control component of an engine. Each cam roller is configured to engage with a corresponding cam lobe of a cam shaft, and the cam lobe is operative to drive the body of the lifter to a position at which the lifter causes movement of at least one of the flow control components through the pushrod and rocker arm assembly.
The disclosed methods of supplying oil to high load areas on at least one of a cam roller of a lifter or a cam lobe of a camshaft may include receiving oil from an oil supply passageway of the engine component into an oil receiving annular recess formed around the outer peripheral surface of the body of the lifter at a location spaced from the cam roller while the body is reciprocally sliding within the lifter bore of the engine component. Oil is then directed from the oil receiving annular recess into an oiling channel formed in the body inset from the outer peripheral surface and extending axially along the outer peripheral surface parallel to the longitudinal axis of the body and aligned with an axial median plane of the cam roller and the cam lobe. The location and cross sectional area of the oiling channel or groove formed along the outer peripheral surface of the lifter ensures that sufficient oil is supplied from the oil supply passageways of the engine component with negligible pressure drop directly to the high load interface between the cam roller and the engaged cam lobe. As discussed above, various alternative embodiments may include one oiling channel or groove, possibly coextensive with a bore hole through a portion of a lifter, or replaced by a bore hole through a portion of the lifter body, located on only one side of an otherwise symmetrical lifter body, or two oiling channels or grooves, possibly coextensive with one or more bore holes, or replaced by one or more bore holes through portions of the lifter body, and formed along the outer peripheral surface of the lifter body on opposite sides of the lifter body spaced 180 degrees from each other.
Each groove or oiling channel 32, 132, 232 of lifters 30, 130, 230, respectively, defines an oil flow path 15 that extends parallel to the longitudinal axis of the respective lifter and intersects with an axial median plane of at least one of cam roller 40, 140, 240, respectively, or cam lobe 50, 150, 250, respectively. The axial median plane located approximately midway between opposite axial ends of the cam roller or the cam lobe is typically the highest load area at the interface between the lifter and the camshaft, and therefore the lifters according to the various embodiments of this disclosure have been found to greatly enhance the life expectancy of the lifters and camshafts by ensuring adequate lubrication at all times to the high load areas and dramatically reducing wear of the components.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed lifters and methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
