Valve actuation system for an engine and valve tappet and rocker arm therefor

Abstract

A valve actuation system for an engine includes a rotatable camshaft, an injector actuation linkage. The valve actuation linkage includes a valve tappet, a valve pushrod, and a rocker arm. At least one of a rocker arm center plane defined by the valve rocker arm or a tappet roller center plane defined by the valve tappet is spaced apart from the pushrod axis by an offset distance, providing increased contact width between an injector roller in the injector actuation linkage and one of a plurality of cam lobes of the camshaft. The valve tappet includes a clevis defining a center plane that is spaced apart from a central axis of the valve tappet by an offset distance. The rocker arm includes a screw hole that is offset relative to a rocker arm center plane.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a valve actuation system for an engine, and more particularly to a valve actuation system configured to increase injector tappet roller contact width. BACKGROUND

[0002] A wide variety of valve actuation systems are well known and are widely used in internal combustion engines throughout the world. A typical engine configuration includes one or more intake valves and one or more exhaust valves each associated with a combustion cylinder in the engine. During an engine cycle, the valve actuation system is used to open and close the intake valves to allow fresh air, and sometimes fresh air mixed with fuel or other gases, to enter the cylinder. After a combustion or expansion stroke, the valve actuation system is used to open the exhaust valves to enable the expulsion of combustion products. The valve actuation system can also include an actuation mechanism for fuel injectors in the engine. Similar configurations are typically used for fuel injectors and engine valve actuation mechanisms, such as a tappet with a roller on one end that rotates in contact with a lobe on a camshaft. As the cam lobes rotate, they move the tappet up and down, which in turn actuates a push rod that is in turn coupled with a rocker arm.

[0003] In the case of intake and exhaust valves, the rocker arm pivots in response to linear travel of the push rod to open the respective valve, and then typically reverses pivot in cooperation with a return spring to allow the respective valve to close. In the case of actuating fuel injectors, a similar configuration is used in certain systems employing a push rod with an actuating rocker arm, where an injector rocker arm is employed to exert a downward force on a tappet or associated pump of the fuel injector, which pressurizes fuel in the fuel injector for injection.

[0004] Engineers have been working in recent years to increase fuel injection pressure. Increasing fuel injection pressure is associated with reduced emissions of certain emissions and can be used for various purposes, such as so-called "rate shaping." Relatively high fuel injection pressure also enables relatively larger amounts of fuel to be combusted in each engine cycle, ultimately allowing engines to be built with relatively greater power density, at least in theory. However, actuation systems associated with engine valves and fuel injectors can have various drawbacks. In one aspect, space constraints can limit the size, scale, and type of components that can be employed. In a related aspect, increasing injection pressure can subject actuation system components to greater stress and accelerate certain wear phenomena. U.S. Patent No. 5,673,661 to Jesel is directed to a valve lifter that is said to be configured to increase the available space for certain features of an internal combustion push rod overhead valve engine. The Jesel design proposes a push rod seat that is offset in the direction required. Offsetting various components away from adjacent intake ports apparently allows for additional space for increasing the size and area of the intake ports to increase breathing and power of the engine. While the Jesel set forth design can have certain applications, there is always room for improvement and alternative strategies. SUMMARY

[0005] In one aspect, a valve actuation system for an engine includes a camshaft having a plurality of cam lobes and rotatable about a camshaft axis. The system also includes an injector actuation linkage having an injector lifter having an injector roller in contact with a first cam lobe of the plurality of cam lobes. The system also includes a valve actuation linkage having a valve lifter defining a longitudinal center axis, a push rod seat centered on the longitudinal center axis, and a lifter roller in contact with a second cam lobe of the plurality of cam lobes adjacent the first cam lobe of the plurality of cam lobes. The valve actuation linkage also includes a valve rocker arm configured to be coupled with an engine valve, and a valve push rod coupled between the valve lifter and the valve rocker arm and in contact with the push rod seat. The valve rocker arm defines a pivot axis and a rocker arm center plane extending through a center point of the pivot axis. The lifter roller defines a rotation axis and a lifter roller center plane extending through a center point of the rotation axis. The valve push rod defines a push rod axis extending through the valve push rod, the valve lifter, and the valve rocker arm. At least one of the rocker arm center plane or the lifter roller center plane is spaced apart from the push rod axis in a direction parallel to the camshaft axis by an offset distance within the respective rocker arm or valve lifter.

[0006] In another aspect, a valve tappet for a valve actuation system in an engine includes an elongate tappet body defining a longitudinal center axis and including an end section having a longitudinally extending push rod bore formed therein, a push rod seat centered on the longitudinal center axis within the longitudinally extending push rod bore, a clevis having an inboard leg and an outboard leg, and an intermediate section transitioning between the end section and the clevis. The inboard leg is spaced from the outboard leg to form a roller slot, and the inboard leg and the outboard leg form a coaxial pin bore configured to receive a roller pin for supporting a roller in the roller slot. A central plane is defined between the inboard leg and the outboard leg and spaced an offset distance from the longitudinal center axis.

[0007] In yet another aspect, a rocker arm for a valve actuation system in an engine includes a rocker arm body having a lever end, a valve end, a center section, and each of a first lateral side and a second lateral side extending between the lever end and the valve end. The rocker arm body further has a pivot pin bore formed in the center section and extending horizontally through the rocker arm body between the first lateral side and the second lateral side and defining a pivot axis. A rocker arm center plane extends through a center point of the pivot axis and equidistantly between the first lateral side and the second lateral side. The valve end further has a first bore formed therein and symmetrically between the first lateral side and the second lateral side such that the first bore is bisected by the rocker arm center plane. The lever end further has a second bore formed therein and asymmetrically between the first lateral side and the second lateral side such that the second bore is offset relative to the rocker arm center plane and positioned relatively closer to the first lateral side than to the second lateral side. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a partial sectional pictorial view of an internal combustion engine system according to one embodiment;

[0009] Figure 2 is a perspective sectional pictorial view of a valve actuation system in an engine according to one embodiment;

[0010] Figure 3 is a top elevational view of a valve actuation system according to one embodiment;

[0011] Figure 4 is Figure 2 and 3 are sectional pictorial views of a portion of a valve actuation system of

[0012] Figure 5 is a pictorial view of a rocker arm according to one embodiment;

[0013] Figure 6 This is a schematic view of a rocker arm according to one embodiment;

[0014] Figure 7 This is a cross-sectional schematic view of a portion of a valve actuation system for an engine according to one embodiment;

[0015] Figure 8 This is a side view of a valve tappet according to one embodiment;

[0016] Figure 9 This is a perspective view of a valve tappet according to one embodiment;

[0017] Figure 10 It is relative to Figure 8 Another side view of the valve tappet rotated 45°; and

[0018] Figure 11 yes Figures 8-10 End view of the valve tappet. Detailed Implementation

[0019] refer to Figure 1 The diagram illustrates a valve actuation system 28 in an internal combustion engine 10. The internal combustion engine 10 includes an engine housing 12 having cylinders 14 formed therein, and a piston 16 movable within the cylinders 14. The piston 16 is coupled to a crankshaft 18 in a generally conventional manner. The engine 10 also includes a plurality of engine valves 20, 22, each associated with a cylinder 14 and including two intake valves, two exhaust valves, or one intake valve and one exhaust valve. In the illustrated embodiment, the engine valves 20, 22 are of the same type and are coupled together via a valve bridge 24. The valve actuation system 28 (hereinafter referred to as "system 28") is configured to open and close the engine valves 20, 22 in response to rotation of the camshaft 30 about the camshaft axis 38. The cylinders 14 can be one of many cylinders arranged in the engine 10 in any suitable configuration (e.g., V-type, inline, etc.). The engine 10 may include a direct injection compression ignition engine configured to operate with a liquid fuel (e.g., diesel distillate fuel). However, this disclosure is not limited thereto, and the engine 10 may be a mouth-injector type, supplied with a premixed fuel and air mixture introduced upstream of the engine 10, may be spark-ignited, or may have various features and functions different from those specifically discussed herein. As will become further apparent from the following description, the valve actuation system 28 may be configured to provide a relatively increased power density to the engine 10.

[0020] Still referencing Figure 2Further features of the valve actuation system 28, mounted in or on the engine cylinder head 26 of the engine 10, are shown. The camshaft 30 includes a plurality of cam lobes 32, 34, 36 rotatable together with the camshaft 30 about a camshaft axis 38. The camshaft 30 can be rotated via an engine gear train coupled to the camshaft 30. The valve actuation system 28 includes an injector actuation linkage 40 configured to operate a fuel injector, for example, by moving a tappet in the fuel injector in response to rotation of the camshaft 30 to pressurize fuel. The injector actuation linkage 40 includes an injector tappet 42 having an injector roller 44 that contacts a first cam lob 32 of the plurality of cam lobes. The injector actuation linkage 40 also includes an injector rocker arm 46 and an injector pushrod 48 connected between the injector tappet 42 and the injector rocker arm 46. The injector roller pin 50 is supported in the injector tappet 42 and positions the injector roller 44 for rotation. An oil passage 52 extends through the injector tappet 42 to supply lubricating oil to the contact surfaces of the injector roller 44, the injector roller pin 50, and the cam lobe 32. An oil supply passage 54 is formed in the engine cylinder head 26 and supplies oil to the injector actuation linkage 40 and the valve actuation linkage, which are discussed further herein.

[0021] System 28 also includes a first valve actuation linkage mechanism 60 having a valve tappet 62 defining a longitudinal central axis 64, a push rod seat 66 centered on the longitudinal central axis 64, and a tappet roller 68. A pin 70 is positioned and supported in the valve tappet 62, and the push rod roller 68 is rotatable about the pin 70 and contacts a second cam ...

[0022] The valve actuation system 28 also includes a second valve actuation linkage 76, which is a mirror image of the first valve actuation linkage 60 and is positioned relative to the injector actuation linkage 40. The second valve actuation linkage 76 includes a tappet roller 78 that contacts a third cam cam cam 36 of a plurality of cam cams, and a valve rocker arm 80. The operation of the second valve actuation linkage 76 can be substantially the same as that of the valve actuation linkage 60, except that one of the corresponding linkages can operate the intake valve and the other can operate the exhaust valve. Describing the corresponding linkages as mirror images refers to the arrangement and construction of the corresponding components, including the construction of the rocker arms 72, 80 in the illustrated embodiment. Relative adjustments between the components of the corresponding linkages can be made based on the operational differences between the intake and exhaust valves, for example, to compensate for different tolerance overlaps or to obtain different valve opening distances.

[0023] Also refer to Figure 3 It will be noted that valve actuation linkages 60 and 76 are positioned adjacent to injector actuation linkage 40. As discussed further herein, in some earlier designs, it was desirable, for example, to increase fuel injection pressure, which is associated with increased wear or performance degradation of the injector actuation linkage, by using a steeper and / or larger cam lob angle. This disclosure provides solutions to increase the contact area between the injector roller 44 and the cam lob angle 32 relative to such earlier systems without unduly affecting packaging or other considerations. These solutions, together or independently, move the position of rollers 68 and 78 outward relative to the cam lob angle 32 to provide a relatively large contact width between the injector roller 44 and the cam lob angle 32. In one embodiment, the described positional movement is made possible at least in part by a feature of the valve rocker arm.

[0024] Therefore, we are now also referring to Figure 4 and 5The valve rocker arm 72 defines a pivot axis 84 and a rocker arm center plane 86 extending between the center point 88 of the pivot axis 84. In the illustrated embodiment, a rocker arm pin 90 is also shown and extends through each of the rocker arms 72, 80, and the injector rocker arm 46. The rocker arm 72 includes a rocker arm body 98 having a rod end 100, a valve end 102, a central section 104, and each of a first lateral side 106 and a second lateral side 108 extending between the rod end 100 and the valve end 102. The rocker arm body 98 also has a pivot pin hole 109 formed in the central section 104 to receive the rocker arm pin 90 and extends horizontally through the rocker arm body 98 between the first lateral side 106 and the second lateral side 108. The rocker arm center plane 86 can be seen to longitudinally bisect the rocker arm body 98 between the rod end 100 and the valve end 102. The valve end 102, configured to connect with the engine valve, also has a first hole 110 formed therein and symmetrically located between the first lateral side 106 and the second lateral side 108. In the illustrated embodiment, the first hole 110 is formed in the enlarged head 112 of the valve end 102. The rod end 100 also includes a second hole 116 formed therein and asymmetrically located between the first lateral side 106 and the second lateral side 108, such that the second hole 116 is offset relative to the rocker arm center plane 86 and positioned closer to the first lateral side 106 than the second lateral side 108. Furthermore, in the illustrated embodiment, the second hole 116 is formed in the enlarged head 118 of the rod end 100.

[0025] from Figure 4 It can also be seen that the rocker arm 72 can be equipped with means for connection to the valve bridge 24, including a socket assembly 94, and can be connected to one or more engine valves in any suitable manner. An oil passage 92 extends through the rocker arm body 98 and can receive an oil supply, for example, through pin 90. Figure 4 The diagram also shows a device for connecting the rocker arm 72 to the push rod 74, including a screw assembly 96. A second hole 116 may include a screw hole, wherein an internal thread 120 is configured to mate with an external thread 124 on an adjusting screw 122. A socket 128, etc., of the push rod 74 or connected to the push rod may engage with the adjusting screw 122. The adjusting screw 122 can be rotated to change the connection between the rocker arm 72 and the push rod 74 and is secured with a nut 126.

[0026] It should be noted that the rocker arm's construction can provide the desired displacement or offset to provide an optimized contact width between the injector roller 44 and the cam lobe 32. Asymmetrically positioning the second bore 116 between the first lateral side 106 and the second lateral side 108 provides a lateral position offset for the second bore 116. The second bore 116 defines a central axis 129, which can be offset by a distance 107 from the rocker arm's central plane 86.

[0027] Turn now Figure 6 The image shows rocker arm 80. It is reminiscent that the components of the corresponding valve actuation linkage mechanism can be mirror images of each other, as are the rocker arms 72 and 80 based on the positions of their respective screw holes. Rocker arm 80 defines a rocker arm center plane 87 and includes a first hole 111 and a second hole 117 (screw holes) similar to the first hole 110 and the second hole 116, except for the direction of offset of the second hole 117 relative to the rocker arm center plane 87. By comparison... Figure 5 and Figure 6 As can be seen, rocker arm 72 offsets the second hole 116 to the right of the rocker arm center plane 86, while in rocker arm 80, the second hole 117 is offset to the left of the rocker arm center plane 87. In the illustrated embodiment, each of holes 116, 117 intersects the corresponding center plane; however, this disclosure is not limited thereto, and the rocker arm may be configured such that the second hole or screw hole is located entirely on one side or the other side of the corresponding rocker arm center plane.

[0028] return Figure 2 It can be seen that the tappet roller 68 defines the rotation axis 130 and the tappet roller center plane 132 extending through the center point 134 of the rotation axis 130. The push rod 74 defines the push rod axis, which, in the case shown, is collinear with and jointly marked with the longitudinal center axis 64, wherein the axis 64 extends through the valve push rod 74, the valve tappet 62, and the valve rocker arm 72. It should be recalled that... Figure 2 In the embodiments, the desired offset is obtained based on the construction of the rocker arms 72, 80. Additionally or alternatively, and as further discussed below, the offset can be obtained based on the construction of the valve tappet. Therefore, this disclosure contemplates at least one of the rocker arm center plane 86 or the tappet roller center plane 132 being offset from the axis 64 by a distance within the corresponding rocker arm 72 or valve tappet 62, in a direction parallel to the camshaft axis 38. Similarly, in Figure 2 In one embodiment, the rocker arm center plane 86 is offset from the axis 64 by a distance in the inward direction. In an embodiment where the offset is obtained based on the valve tappet construction, the tappet roller center plane is offset from the longitudinal center axis of the valve tappet by a distance in the outward direction. "Outward" means away from the injector actuation linkage 40 in a direction parallel to the camshaft axis 38. "Inward" means the opposite direction.

[0029] Now for reference Figure 7The diagram illustrates a valve actuation system 228, which includes an injector actuation linkage 240, a first valve actuation linkage 260, and a second valve actuation linkage 276. Valve actuation linkages 260 and 276 may be mirror images of each other and may be configured to actuate each of one or more exhaust valves, or each of one or more intake valves. Injector actuation linkage 240 may be substantially the same as the injector actuation linkage 40 discussed above; however, in the case of valve actuation system 228, instead of providing a relatively increased injector roller width using a rocker arm-based offset, the offset is based on a valve tappet configuration. Figure 7 As can be seen, the injector roller width is shown as 305, and the offset distance is shown as 307. The injector roller width 305 can exceed the offset distance 307 by a factor greater than 10. Similar roller widths and offset distances can be provided by the rocker arm configuration in the previous embodiment of the valve actuation system 28.

[0030] The valve actuation linkage mechanism 260 includes a valve tappet 262 defining a longitudinal central axis 264. The valve tappet 262 includes a pushrod seat 266 centered on axis 264. A tappet roller, shown at 268, is positioned on a pin 270, and a pushrod 274 is coupled to the valve tappet 262 to actuate a rocker arm (not shown), generally similar to the operation described in the foregoing embodiment of the engine valve actuation system 28. The pushrod 274 defines a pushrod axis that is collinear with and therefore commonly labeled with axis 264. Reference is also made to... Figures 8-11 The valve tappet 262 includes an elongated tappet body 263 defining an axis 264 and having an end section 265 with a longitudinally extending push rod hole 267 formed therein, and a push rod seat 266 centered on the axis 264 and received in the push rod hole 267. The elongated tappet body 263 also includes a fork 269 having an inner leg 271 and an outer leg 273, and an intermediate section 275 transitioning between the end section 265 and the fork 269. The inner leg 271 and the outer leg 273 are spaced apart to form a roller groove 277. The inner leg 271 and the outer leg 273 respectively form coaxial pin holes 279 and 281 and receive a roller pin 270. The roller pin 270 supports a tappet roller 268 rotatable about a rotation axis 330. The central plane 332 is defined between the inner leg 271 and the outer leg 273, and is offset from the longitudinal central axis 264 by a distance of 307.

[0031] from Figures 8-11 It can also be seen that the intermediate section 275 may include a necked-down section 285 adjacent to the end section 265. The intermediate section 275 may also include a transition section 287 adjacent to the fork-shaped member 269. For example... Figure 11As best depicted, both end section 265 and transition section 287 may be generally cylindrical, or include generally cylindrical features extending circumferentially around axis 264, such that end section 265 and transition section 287 define a common cylinder centered on axis 264. Outer leg 273 is at least partially located outside the common cylinder. Valve stem 262 may also include, as... Figure 7 The oil passage 289, as best shown, extends from the intermediate section 275 to the fork member 269 via the tappet body 263. In the illustrated embodiment, a step 291 is formed between the necked-down section 285 and the transition section 287, and the oil passage 289 extends from an inlet 293 formed in the step 291 to an outlet 295 formed in the fork member 269, particularly in the outer leg 273. When positioned for maintenance in the engine, the necked-down section 285 receives and delivers oil flow around the valve tappet 262 and supplies it to the inlet 293. Oil is then delivered through the oil passage 289 to lubricate the pin 270 and roller 268, as well as the associated cam lobe 234.

[0032] For example Figures 8-11 As shown, the strut body 263 may further include an inner surface 299 and an outer surface 301. The inner surface 299 may be partially formed on the inner leg 271 and partially formed on the transition section 287. The inner surface 299 may be planar and step into relative to the intermediate section 275. The outer surface 301 may be planar and step out relative to the intermediate section 275. A curved and inclined surface 303 transitions between the intermediate section 275 and the inner leg 271 and the outer leg 273. Figure 7 As shown, the center point 334 of the rotation axis 330 is shown as being offset from the central plane 264 by a distance 307 in the outward direction. Figure 7 It can also be seen that the inner surface 299 and the injector tappet 242 are in a spaced-apart facing relationship. By positioning the fork-shaped member 269 offset from the axis 262, the injector tappet 242 can be slightly positioned within the spatial envelope defined by the valve tappet 262. Therefore, Figures 7-11 The embodiments described herein can be understood as providing a solution for increased injector roller-cam cam contact width based on a valve tappet construction, while in the aforementioned embodiments of system 28, a rocker arm-based construction provides offset. In either case, in Figure 7 The offset distance shown as 307 is likely between 2.5 mm and 3.5 mm, more particularly between 2.8 and 3.0 mm. In summary, in any embodiment contemplated herein, the offset provided on the outside of the injector tappet enables the roller width 305 to increase by between 5 mm and 7 mm, more particularly between 5.7 and 5.9 mm.

[0033] Industrial applicability

[0034] Referring generally to the accompanying drawings, it is anticipated that the valve actuation system according to this disclosure will provide increased power density in an engine system based on offsets in the arrangement of components within the respective valve actuation system. Figure 2 In this embodiment, rotation of the camshaft 30 causes rocker arms 72, 80 to move to open and close the intake and exhaust valves, while the injector rocker arm 46 reciprocates to pressurize fuel for injection. The injector roller 44 rotates in contact with the cam lobe 32, where forces between the corresponding components are transmitted in a contact "block" that experiences a contact pressure per unit area based on the contact width. Figure 7 In the case of the embodiments, the operation will be largely similar.

[0035] In some earlier designs that did not provide offsets based on rocker arm or valve tappet configurations, it was observed that the contact width might not be large enough to distribute contact pressure in a way that would avoid excessive wear on the injector roller, cam lobe, or both. Although this disclosure presents valve tappet and rocker arm configurations as separate solutions, it should be understood that these embodiments can be combined with some offsets provided by one or more valve tappets and some offsets provided by one or more rocker arms. In other cases, unlike the valve tappet or rocker arm providing the desired offset to achieve sufficient injector roller width, the push rod in the valve actuation system can be tilted toward the reciprocating axis of the valve tappet. In other words, embodiments are envisioned in which at least one of the rocker arm center plane or the tappet roller center plane is offset from the push rod axis by a distance in a direction parallel to the camshaft axis, without any asymmetric features of the valve tappet or rocker arm, and any misalignment of the tilted arrangement of the push rod is simply tolerated or otherwise compensated for.

[0036] This specification is for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Therefore, those skilled in the art will recognize that various modifications can be made to the embodiments disclosed herein without departing from the full and reasonable scope and spirit of this disclosure. Other aspects, features, and advantages will become apparent from the accompanying drawings and claims. As used herein, the articles “a” and “an” are intended to include one or more articles and are interchangeable with “one or more”. The term “one” or similar language is used when it is desired to indicate that there is only one article. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Additionally, the phrase “based on” is intended to mean “at least partially based on” unless otherwise expressly stated.

Claims

1. A valve actuation system for an engine, comprising: A camshaft, the camshaft including a plurality of cam lobes and rotatable about a camshaft axis; An injector actuation linkage mechanism, the injector actuation linkage mechanism including an injector push rod, the injector push rod having an injector roller that contacts a first cam ... The first valve actuation linkage mechanism includes a valve tappet defining a reciprocating axis, a push rod seat centered on the reciprocating axis, and a tappet roller that contacts a second cam ... The first valve actuation linkage mechanism further includes a valve rocker arm configured to connect with the engine valve, and a valve push rod connected between the valve tappet and the valve rocker arm and in contact with the push rod seat; The valve rocker arm defines a pivot axis and a rocker arm center plane extending through the center point of the pivot axis; The push rod roller defines a rotation axis and a push rod roller center plane extending through the center point of the rotation axis; The valve push rod defines a push rod axis extending through the valve push rod, the valve tappet, and the valve rocker arm; and At least one of the center plane of the rocker arm or the center plane of the tappet roller is offset from the axis of the push rod by a distance in a direction parallel to the axis of the camshaft within the corresponding rocker arm or valve tappet.

2. The system according to claim 1, wherein: The valve tappet rocker arm includes a rod end, a valve end, an inner lateral side and an outer lateral side extending between the rod end and the valve end, and a pivot pin hole defining the pivot axis; The valve tappet rocker arm further includes a screw hole formed in the end of the rod, and an adjusting screw inside the screw hole and connected to the push rod; and The screw hole is offset relative to the center plane of the rocker arm, so that the adjusting screw is supported in the valve tappet rocker arm and is closer to the outer lateral side than the inner lateral side.

3. The system according to claim 1 or 2 further includes a second valve actuation linkage mechanism, the second valve actuation linkage mechanism being a mirror image of the first valve actuation linkage mechanism and positioned relative to the injector actuation linkage mechanism and the first valve actuation linkage mechanism.

4. The system according to claim 1 or 2, wherein: The valve tappet includes a fork-shaped member having an inner leg and an outer leg, a pin received in the inner leg and the outer leg and supporting the tappet roller for rotation, and an oil passage extending through the outer leg. The valve tappet further includes an end section having a push rod hole formed therein, and a middle section including a step having an inlet formed therein leading to the oil passage; and The valve stem also includes an inner surface and an outer surface, the inner surface being planar and partially formed on each of the intermediate section and the inner leg, and the outer surface being planar and formed on the outer leg and stepping out relative to the intermediate section.

5. A valve tappet for a valve actuation system in an engine, comprising: An elongated push rod body defining a longitudinal central axis and including an end section having a longitudinally extending push rod hole formed therein, a push rod seat centered on the longitudinal central axis within the longitudinally extending push rod hole, a fork-shaped member having an inner leg and an outer leg, and an intermediate section transitioning between the end section and the fork-shaped member; The inner leg is spaced from the outer leg to form a roller groove, and the inner leg and the outer leg form a coaxial pin hole configured to receive a roller pin for supporting a roller in the roller groove; and The central plane is defined between the inner leg and the outer leg and is offset from the longitudinal central axis by a distance.

6. The valve tappet according to claim 5, wherein: The intermediate section includes a necked section adjacent to the end section and a transition section adjacent to the fork-shaped member; The slender strut body also includes an inner surface and an outer surface, the inner surface being planar and entering relative to the middle section, and the outer surface extending relative to the middle section; and The coaxial pin hole includes a first pin hole formed in the inner leg and opening in the inner surface, and a second pin hole formed in the outer leg and opening in the outer surface.

7. The valve tappet according to claim 6, wherein: The end section and the transition section define a common cylinder centered on the longitudinally extending central axis, and the outer leg is at least partially located outside the common cylinder; The oil passage extends from the middle section to the fork-shaped member through the valve tappet body; The valve tappet body further includes a step formed between the necked-out section and the transition section, and the oil passage extends from an inlet formed in the step to an outlet; and The outlet is formed in the outer leg.

8. The valve tappet according to any one of claims 5-7, further comprising a roller pin supported in the fork member, and a roller positioned on the roller pin and defining a roller axis of rotation having a center point located in the central plane.

9. A rocker arm for a valve actuation system in an engine, comprising: A rocker arm body, the rocker arm body including a rod end, a valve end, a central section, and each of a first lateral side and a second lateral side extending between the rod end and the valve end; The rocker arm body also has a pivot pin hole formed in the central section and extends horizontally through the rocker arm body between the first lateral side and the second lateral side, defining a pivot axis. The center plane of the rocker arm extends through the center point of the pivot axis and is equidistant between the first lateral side and the second lateral side; The valve end also has a first hole, which is formed therein and symmetrically located between the first lateral side and the second lateral side, such that the first hole is equally bisected by the central plane of the rocker arm; and The rod end also has a second hole formed therein and asymmetrically located between the first lateral side and the second lateral side, such that the second hole is offset relative to the center plane of the rocker arm and positioned relatively closer to the first lateral side than the second lateral side.

10. The rocker arm according to claim 9, wherein: The second hole includes an internally threaded screw hole; and The second hole intersects the center plane of the rocker arm and defines a central axis that is offset from the center plane of the rocker arm by a distance.

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