Rocker arms

A rocker arm assembly can include an outer arm having an outer rocker shaft bore configured to receive a rocker shaft and an inner arm having an inner rocker shaft bore configured to receive the rocker shaft. The inner arm can be configured to selectively rotate. A latch pin can be movably seated in the outer arm and configured to move between a latched position and an unlatched position. The rocker arm assembly can further include a lost motion spring. The lost motion spring can include a first end connected to a connecting portion of the inner arm above the inner rocker shaft bore and a second end connected to the outer arm. The inner arm can include an inner arm stop member configured contact with a corresponding outer arm stop member of the outer arm.

FIELD

This application relates to rocker arm assemblies, and more particularly to a switchable rocker arm assembly for use in, for example, a valve train of an internal combustion engine. Deactivation and other variable valve actuation techniques can be accomplished.

DESCRIPTION OF RELATED ART

An internal combustion engine includes a valve train assembly. A valve train assembly includes rocker arms for controlling opening and closing of intake and exhaust valves. A rocker arm is a reciprocating lever that translates radial motion of a rotating camshaft lobe into linear motion that controls the opening and closing of a valve. A rocker arm is mounted on a rocker shaft with one end in direct or indirect contact with the rotating camshaft lobe and the other end being structurally interfaced with a valve.

Variable valve actuation mechanisms, such as cylinder deactivation and variable valve lift, have been introduced to improve engine performance, fuel economy and/or emissions of an internal combustion engine during periods of light engine load. To support a variable valve actuation mechanism, a switchable rocker arm can be used. A switchable rocker arm includes a pair of arms that are rotatably coupled to one another. The pair of arms are switchable between a latched state, in which they are prevented from rotating relative to one another, and an unlatched state, in which they are permitted to rotate relative to one another.

SUMMARY

To attain the advantages and in accordance with the purpose of the disclosure, as embodied and broadly described herein, one aspect of the disclosure can provide that a rocker arm assembly can include an outer arm comprising an outer rocker shaft bore configured to receive a rocker shaft and an inner arm comprising an inner rocker shaft bore configured to receive the rocker shaft. The inner arm can be configured to selectively rotate relative to the outer arm via the rocker shaft extended through the outer rocker shaft bore and the inner rocker shaft bore. The rocker arm assembly can also include a latch pin movably seated in the outer arm and configured to move between a latched position, in which the latch pin engages with the inner arm to lock the relative rotation between the inner arm and the outer arm, and an unlatched position, in which the latch pin disengages with the inner arm to allow the relative rotation between the inner arm and the outer arm. The rocker arm assembly can further include a lost motion spring. The lost motion spring can include a first end connected to a connecting portion of the inner arm above the inner rocker shaft bore and a second end connected to the outer arm. The inner arm can include an inner arm stop member configured contact with a corresponding outer arm stop member of the outer arm, where the inner arm stop member extends below the inner rocker shaft bore from a side substantially opposite to the portion of the inner arm above the inner rocker shaft bore.

According to another exemplary aspect, the outer arm can comprise a roller configured to interface with a camshaft lobe of a type III valve train assembly. The roller can be located laterally from the rocker shaft, and the latch pin can be located above the roller. In some exemplary aspects, the second end of the lost motion spring can be connected to a portion of the outer arm that is located approximately between the roller and the rocker shaft. In another exemplary aspect, the second end of the lost motion spring can be connected to a portion of the outer arm that is located approximately between the rocker shaft and the latch pin.

In still another exemplary aspect, the outer arm can comprise a latch pin seat for receiving the latch pin, where the latch pin seat can comprise a flange fixed thereto on a side away from the inner arm and a return spring disposed between the flange and the latch pin to bias the latch pin towards the inner arm.

According to yet another exemplary aspect, the latch pin can comprise an indented flat surface configured to engage with the inner arm.

In various exemplary aspects, the rocker arm assembly can further comprise a push pin seated in the inner arm. The push pin can be configured to selectively push the latch pin from the latched position to the unlatched position to allow the outer arm to rotate relative to the inner arm. According to one exemplary aspect, the inner arm can comprise an inner bore for movably receiving the push pin. The inner bore can be located in a stepped portion of the inner arm, where the stepped portion can define an inner latch surface configured to engage with the latch pin in the latched position.

According to another exemplary aspect, the movement of the push pin can be controlled hydraulically, and the inner arm can define a hydraulic passageway for supplying a control fluid from an oil gallery adjacent the rocker shaft to the push pin in the inner bore.

In still another exemplary aspect, the connecting portion can comprise a connector tab extending from a top surface of the inner arm in a direction away from the inner rocker shaft bore.

In some exemplary aspects, the outer arm can comprise a pair of side walls extending substantially parallel to each other in a direction substantially perpendicular to a rotating axis of the rocker shaft, where the inner arm can be rotatably disposed at least partially between the pair of side walls. Accordingly, the lost motion spring can comprise a pair of lost motion springs each connecting between the connecting portion of the inner arm and each of the side walls of the outer arm.

Various exemplary aspects of the present disclosure can also provide a rocker arm assembly including an outer arm and an inner arm. The outer arm can comprise an outer rocker shaft bore configured to receive a rocker shaft and a roller configured to interface with a camshaft lobe of a type III valve train assembly, where the roller can be located laterally from the outer rocker shaft bore. The inner arm can comprise an inner rocker shaft bore configured to receive the rocker shaft. The inner arm can be configured to selectively rotate relative to the outer arm via the rocker shaft extended through the outer rocker shaft bore and the inner rocker shaft bore. The rocker arm assembly can also comprise a latch pin movably seated in the outer arm above the roller and configured to move between a latched position, in which the latch pin engages with the inner arm to lock the relative rotation between the inner arm and the outer arm, and an unlatched position, in which the latch pin disengages with the inner arm to allow the relative rotation between the inner arm and the outer arm.

The rocker arm assembly can further comprise a lost motion spring comprising a first end connected to a connecting portion of the inner arm located above the inner rocker shaft bore and a second end connected to the outer arm at a location between the outer rocker shaft bore and the latch pin.

According to one exemplary aspect, the rocker arm assembly can further comprise a push pin seated in the inner arm, where the push pin can be configured to selectively push the latch pin from the latched position to the unlatched position to allow the outer arm to rotate relative to the inner arm. The inner arm can comprise an inner bore for movably receiving the push pin. In another exemplary aspect, the movement of the push pin can be controlled hydraulically, and the inner arm can define a hydraulic passageway for supplying a control fluid from an oil gallery adjacent the rocker shaft to the push pin in the inner bore.

According to still another exemplary aspect, the outer arm comprises a pair of side walls extending substantially parallel to each other in a direction substantially perpendicular to a rotating axis of the rocker shaft, wherein the inner arm is rotatably disposed at least partially between the pair of side walls. In yet still another exemplary aspect, the lost motion spring can comprise a pair of lost motion springs each connecting between the connecting portion of the inner arm and each of the side walls of the outer arm.

Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

DETAILED DESCRIPTION

Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as “left,” “right,” “above,” and “below” are for ease of reference to the figures.

FIGS.1-3illustrate a switchable rocker arm assembly1for an internal combustion engine, according to one exemplary embodiment of the present disclosure. Rocker arm assembly1of the present disclosure can be configured to support various variable valve actuation mechanisms in internal combustion engines. While the exemplary embodiment of the present disclosure will be described in connection with a particular cylinder deactivation mechanism, the present disclosure can be applied to a variable valve lift system or any other suitable variable valve actuation mechanism. Further, while the disclosed embodiment will be described in connection with a particular type III valve train architecture (e.g., a single overhead camshaft configuration), the present disclosure can be applied to, or used in connection with, many other types of valve train systems and configurations.

Rocker arm assembly1can be positioned between a rotating camshaft lobe and a stem of a valve (or a lash adjuster) to control the lifting profile of the valve. For illustration purposes, one side of rocker arm assembly1that is configured to interface with the rotating camshaft lobe is referred to as a cam side3, and the opposite side of rocker arm assembly1that is configured to interface with the valve stem is referred to as a valve side7.

Rocker arm assembly1can comprise an outer arm10, an inner arm30, a latching mechanism70, and a lost motion assembly40. Outer arm10and inner arm30can be rotatably coupled to one another via a rocker shaft25having a rocker shaft axis. Rocker shaft25can be a free-floating axle to minimize wear and friction losses. Rocker shaft25can comprise a bushing or another structure to alleviate shear or wear or to provide alignment. Outer arm10can comprise a pair of side walls11,19extending substantially parallel to each other. Side walls11and19can be connected to one another via a lateral surface extending therebetween. Lateral surface can comprise material connected to outer arm stop members17or material forming outer rocker shaft bore15, for example. Inner arm30can be seated, at least partially, between side walls11and19, as best shown inFIG.1. Outer arm10can define an outer rocker shaft bore15in each of side walls11and19, and inner arm30can define an inner rocker shaft bore34. Rocker shaft25passes through, in sequence, outer rocker shaft bore15of side11, inner rocker shaft bore34, and outer rocker shaft bore15of side19to rotatably engage with outer arm10and inner arm30.

Inner arm30can comprise a head portion31in cam side3and a tail portion39in valve side7. Inner rocker shaft bore34can be located near the midpoint between head portion31and tail portion39. Inner arm30can have a generally elongated body with its dimensional profile decreasing from inner rocker shaft bore34to tail portion39. An elephant foot28can be coupled to tail portion39for directly or indirectly interfacing with a valve stem or any other suitable structure associated with a valve. Elephant foot28can be connected to a threaded rod27extending through a hole (not shown) defined inside tail portion39. Threaded rod27can then be secured to tail portion39via a nut29. Any other suitable coupling mechanism known in the art can be used alternatively or additionally. In some exemplary embodiments, tail portion39can also include a lash adjuster or other capsule associated with elephant foot28. A switchable device, such as a castellation device, can be installed in the tail portion39. An oil feed can be installed on or within inner arm30to provide control to the lash adjuster or switchable device or other capsule installed in tail portion39. Such examples are not exhaustive and other variable valve actuation or lash adjusting capsules or other assemblies can be included on inner arm30.

Outer arm10can comprise a roller22for interfacing with the rotating camshaft lobe of a valve train to impart a valve lift profile to rocker arm assembly1. In the disclosed embodiment shown inFIG.1, roller22is configured to interface with a camshaft lobe of a type III valve train assembly. Roller22is rotatably supported by a bearing shaft24, which can be fixed to outer arm10between the pair of side walls11and19. Bearing shaft24can include a needle bearing and/or a bushing bearing to minimize friction losses and wear. Side walls11and19each can define a bearing bore14to receive the ends of bearing shaft24. In some exemplary embodiments, a sliding surface can be used instead of roller22.

Latching mechanism70can be located above roller22for selectively locking and unlocking the relative rotational motion between outer arm10and inner arm30. For example, as best shown inFIG.1, roller22can be attached to one end of outer arm10, which is located laterally with respect to rocker shaft25, and latching mechanism70can be located above roller22. Placing latching mechanism70directly above roller22can require less latching force over the prior art to operate latching mechanism70. Yet, transfer of force from head portion31to tail portion39through the latching mechanism70remains efficient during a locked state. Being above roller22and laterally positioned away from the rocker shaft25, instead of being over the rocker shaft25or nearer to the tail portion39yields a favorable balance of forces for switching between the locked state and the unlocked state. It can be said that the latching mechanism is laterally located so that the lost motion spring45is seated, as by connecting pin49, between the outer rocker shaft bore15and the latching mechanism70. In the locked state, outer arm10is prevented from rotating relative to inner arm30, such that outer arm10and inner arm30can act as a single unit and directly translating the radial motion of the rotating camshaft lobe to a valve. In an unlocked state, outer arm10is allowed to rotate relative to inner arm30, such that the radial motion of the rotating camshaft lobe transferred to outer arm10can be dissipated and lost.

As best shown inFIG.3, latching mechanism70can comprise a pair of latch pins74seated in outer arm10and a pair of push pins76seated in inner arm30. Each of side walls11and19can define a latch pin seat12to accommodate each latch pin74. Latch pin seat12can be a hollow cylinder and include a flange72fixed near an outer end of the hollow cylinder away from inner arm30. Latch pin74can have a shape of a cap having an internal recess79. A return spring75can be disposed between flange72and latch pin74and at least partially received inside internal recess79. Return spring75can be configured to bias latch pin74towards inner arm30.

Latch pin74can form an outer latch surface71configured to engage with an inner latch surface84formed in inner arm30. In one exemplary embodiment, outer latch surface71can comprise an indented flat surface on a side facing inner latch surface84, as shown inFIG.3. The indented flat surface, formed by, for example, machining the side facing inner latch surface84, may reduce contact stress and/or avoid concentricity issues. In an alternative embodiment, outer latch surface71can comprise a circumferentially stepped portion at the outer surface of latch pin74. In another alternative embodiment, latch pin74can form a rounded pin shape without an indented flat surface or a stepped portion, and the rounded outer surface of latch pin74can serve as outer latch surface71for engaging with inner latch surface84.

Head portion31of inner arm30can include a stepped portion82, defining inner latch surface84configured to engage with outer latch surface71of latch pin74. In stepped portion82, inner arm30can form an inner bore32extending through the entire width of stepped portion82in a direction parallel to the rotating axis of rocker shaft25. The pair of push pins76can be seated inside inner bore32. Each push pin76can form an internal recess on the side facing the other push pin76, such that the pair of push pins76can collectively form a pressure chamber73therebetween. Each push pin76can be configured to selectively extend out of inner bore32and push corresponding latch pin74into latch pin seat12of outer arm, so that outer arm10can rotate relative to inner arm30.

In some exemplary embodiments, a push pin spring77can be disposed inside pressure chamber73to exert outwardly spring force against the pair of push pins76. The spring force of push pin spring77(e.g., spring constant) can be less than that of return springs75, so that push pins76can be normally kept retracted inside inner bore32of inner arm30. In another exemplary embodiment, push pin spring77can be completely omitted.

The movement of push pins76can be hydraulically controlled. For example, as best shown inFIG.2, inner arm30can define a hydraulic passageway80for supplying a control fluid (e.g., engine oil) from an oil gallery on rocker shaft25and/or inner rocker shaft bore34to pressure chamber73. Inner arm30can use one or more valves, plugs, and/or flow diverters85to define hydraulic passageway80and seal off any unintended leakage paths.

FIGS.4&5andFIGS.6&7schematically illustrate exemplary operational characteristics of rocker arm assembly1when latching mechanism70is in a latched state and an unlatched state, respectively. According to one exemplary aspect, the latched state can represent a normal, steady condition, where latching mechanism70locks outer arm10from rotating relative to inner arm30. In this latched state, the radial motion of a rotating camshaft lobe90can be transmitted to a valve100via rocker arm assembly1, as illustrated inFIG.5. On the other hand, the unlatched state can represent a special, deactivated condition, where latching mechanism70allows outer arm10to rotate relative to inner arm30. In this unlatched state, the radial motion of rotating camshaft lobe90is not transmitted to valve100, as illustrated inFIG.7.

During the latched state, the hydraulic pressure of the control fluid is kept below a threshold pressure required to overcome the force of return springs75. Consequently, return springs75can keep latch pins74extended from outer arm10and into stepped portion82of inner arm30with outer latch surfaces71of latch pins74engaging inner latch surfaces84of inner arm30, as shown inFIG.4. To transition from the latched state to the unlatched state, the hydraulic pressure of the control fluid can be increased above the threshold pressure to overcome the force of return springs75. The increased hydraulic pressure increases the pressure inside pressure chamber73, which in turn can extend push pins76out of inner bore32and push latch pins74out of stepped portion82and into a retracted position inside outer arm10, as shown inFIG.6, thereby permitting the rotation of outer arm10relative to inner arm30.

As mentioned above, rocker arm assembly1can comprise lost motion assembly40that biases outer arm10away from inner arm30in order to maintain contact between roller22and camshaft lobe90during an unlatched state. To provide a rotational stop mechanism, of outer arm10can comprise one or more outer arm stop members17, and inner arm30can comprise one or more inner arm stop members37, as shown inFIG.1. One or both side walls11,19of outer arm10can comprise an outer arm stop member17or outer arm stop member can comprise a body portion that connects side walls11,19for coordinated rotation.

Each outer arm stop member17is aligned to contact with a corresponding inner arm stop member37. In an unlatched state, outer arm10is no longer locked with inner arm30and is allowed to rotate relative to inner arm30in a first rotational direction. During this unlatched state, inner arm stop member37and outer arm stop member17can prevent outer arm10from rotating in a second rotational direction opposite to the first rotational direction past a predetermined position.

According to some exemplary aspects, outer arm stop members17and inner arm stop members37can be positioned right below rocker shaft25in a space often regarded as dead space. For example, one or more outer arm stop members17can extend below from the periphery of outer rocker shaft bore15, and one or more corresponding inner arm stop members37can extend below from the periphery of inner rocker shaft bore34.

Referring toFIG.1, rocker arm assembly1can comprise a pair of lost motion assemblies40each connecting inner arm30to each of side walls11and19of outer arm10. In some alternative embodiments, rocker arm assembly1can include only one lost motion assembly40connecting inner arm30to only one of side walls11and19.

Lost motion assembly40can comprise a header42, a footer48, and a lost motion spring45disposed between header42and footer48. Header42can be coupled to inner arm30, and footer48can be coupled to outer arm10. To facilitate the coupling, inner arm30can comprise a connector tab36extending upwardly from its top surface35. Header42can be coupled to connector tab36via a connector pin41which extends through header42in a direction parallel to the rotating axis of rocker shaft25. Connector pin41can be a pivot pin allowing header42to rotate in a radial direction substantially perpendicular to the rotating axis of rocker shaft25. Like header42, footer48can be rotatably coupled to outer arm10via a connecting pin49. The portion of outer arm10to which footer48is connected can be located approximately between roller22and rocker shaft25and between rocker shaft25and latch pin seat12. According to one exemplary aspect of the present disclosure, connector tab36is located above inner rocker shaft bore34, and inner arm step member37extends below inner rocker shaft bore34from a side substantially opposite to connector tab36with respect to inner rocker shaft bore34. Connector tab36can be centered over the inner rocker shaft bore34with the lost motion spring45being tangent to the outer rocker shaft bore15.

According to another exemplary aspect, a header stem43extends from header42, and a footer stem47extends from footer48. Header stem43can be a tubular member sized and configured to slidably receive footer stem47therein. Lost motion spring45is positioned over header stem43and footer stem47. Accordingly, the inner diameter of lost motion spring45can be greater than the outer diameter of header stem43and less than the footprints of header42and footer48. When outer arm10is rotated relative to inner arm30during an unlatched state, the distance between header42and footer48can be reduced, causing lost motion spring45to exert spring force against outer arm10. This spring force can maintain reliable contact between roller22and camshaft lobe90during the movement of outer arm10relative to inner arm30, while compensating the inertia force of moving inner arm10.

Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein.