Patent Description:
Some internal combustion engines can utilize rocker arms to transfer rotational motion of cams to linear motion appropriate for opening and closing engine valves. Deactivating rocker arms incorporate mechanisms that allow for selective activation and deactivation of the rocker arm. In a deactivated state, the rocker arm may exhibit lost motion movement. However, conventional valve train carrier assemblies may typically be concerned with contact stress issues, high stiffness issues, high cycle fatigue requirements, and compact packaging requirements. Accordingly, while conventional valve train carrier assemblies with deactivating rocker arms work well for their intended purpose, there remains a need for improvement in the relative art.

The present invention is a latch assembly for a switchable rocker arm as it is defined in claim <NUM> and a rocker arm assembly as it is defined in claim <NUM>.

In one aspect, a rocker arm assembly for a Type III valvetrain arranged for cooperation with a cylinder head is provided. The rocker arm assembly includes a rocker arm having an outer arm configured to rotate about a rocker shaft, an inner arm at least partially disposed within the outer arm and configured to rotate about a rocker shaft, and a latch pin movable between an activated position and a deactivated position. In the activated position, rotation of the inner arm about the rocker shaft is transferred to the outer arm via the latch pin. In the deactivated position, rotation of the inner arm about the rocker shaft is not transferred to the outer arm.

The latch assembly for a switchable rocker arm comprises a latch bore comprising a first bore end, a second bore end, and a lost motion gap. A latch pin is configured to reciprocate in the latch bore. The latch pin comprises a main body comprising a first plug end in the first bore end, a second plug end in the second bore end, and a clearance between the first plug end and the second plug end. The latch pin is configured to selectively move in the latch bore between an activated position and a deactivated position. A latch pin assembly is for instance disclosed in <CIT>, <CIT> or <CIT>.

The rocker arm assembly comprises the latch assembly. An outer arm is configured to rotate about a rocker shaft and comprises the latch bore. An inner arm is at least partially disposed within the outer arm and configured to rotate. When the latch pin is in the activated position, the inner arm is configured to transfer force to the outer arm via the latch pin. When the latch pin is in the deactivated position, the inner arm is configured to move in the clearance and in the lost motion gap.

As an operational example of a rocker arm assembly, described herein is a heavy duty Type III rocker arm assembly with cylinder deactivation (CDA) with high stiffness and low mass moment of inertia. In such a valvetrain, CDA is achieved through a round latch pin engagement between two rocker arm bodies to transfer load and disengage in lost motion. An inner arm, an outer arm, and a latch pin are designed to reduce stress, reduce deformations, and yield high fatigue life. The inner and outer arms are designed to resist bending shear and tensile stresses, while the latch pin is designed and arranged such that contact does not create sharp or singular contact/Hertzian stresses, which can lead to wear and tear and prevent intended functionality to transfer full lift or no lift. In another aspect, a latch assembly is disclosed for use in this and other rocker arm assemblies. The latch assembly is particularly suited for "scissor" type III rocker arm assemblies and other switchable rocker arm assemblies such as switching roller finger followers for type II valvetrains.

With initial reference to <FIG>, a Type III valvetrain arrangement is configured to be positioned on a cylinder block (not shown) of an engine. A rotating cam <NUM> is shown schematically and rotating cam <NUM> can impart a valve lift profile to the rocker arm assembly. It will be appreciated that while shown in a Type III arrangement, it is within the scope of the present disclosure for the various features described herein to be used in other arrangements. In this regard, the features described herein associated with the valvetrain arrangement can be suitable to a wide variety of applications. In the example embodiment, the valvetrain arrangement is supported in a carrier (not shown) and each cylinder can include an intake valve rocker arm assembly and an exhaust valve rocker arm assembly <NUM>. The intake valve rocker arm assembly is configured to control motion of intake valves of an associated engine.

In the example embodiment, the rocker arm assembly <NUM> generally includes a rocker arm <NUM> configured to rotate about a rocker shaft <NUM>. The rocker arm <NUM> generally includes an inner arm <NUM> (<FIG>), an outer arm <NUM> (<FIG>), and a latch pin <NUM> (<FIG>). A roller <NUM> is rotatably coupled to inner arm <NUM> by a pivot pin <NUM>. As will be described in greater detail herein, the inner arm <NUM> rotates around the rocker shaft <NUM> based on a lift profile of a cam <NUM> of a camshaft (not shown) contacting the roller <NUM>.

In the example embodiment, the latch pin <NUM> is configured to be moved by an actuator. One example of an actuator is shown in <FIG>. Alternative actuators not according to the appended claims can comprise, for example, devices to enable pneumatic, electric, mechanical, etc. movement of the latch pin <NUM> between an activated position (<FIG>) and a deactivated position (<FIG>). In the activated position, rotational motion of inner arm <NUM> about rocker shaft <NUM> is transferred to outer arm <NUM> via the latch pin <NUM>, thereby causing rotational movement of the outer arm <NUM> about the rocker shaft <NUM>. In this way, outer arm <NUM> is configured to transfer motion to another component such as, for example, a valve bridge and/or engine valve. In the deactivated position, rotation of inner arm <NUM> about rocker shaft <NUM> does not contact latch pin <NUM>. As such, rotational motion of inner arm <NUM> is not transferred to outer arm <NUM>.

With additional reference to <FIG>, inner arm <NUM> will be described in more detail. In the example embodiment, inner arm <NUM> includes a main body <NUM> having a first aperture <NUM>, and second aperture <NUM>, and a contact arm <NUM>. The first aperture <NUM> is configured to receive rocker shaft <NUM>, and the second aperture <NUM> is configured to receive pivot pin <NUM>. The contact arm <NUM> is configured to engage the latch pin <NUM> as by comprising a contact surface <NUM>.

With additional reference to <FIG>, outer arm <NUM> will be described in more detail. In the example embodiment, outer arm <NUM> includes a main body <NUM> having opposed flanges <NUM>, a latch bore <NUM>, and a capsule bore <NUM> (see <FIG>, <FIG>). The opposed flanges <NUM> are spaced apart from each other to provide clearance for inner arm <NUM> to be received therebetween. The opposed flanges <NUM> each define an aperture <NUM> configured to receive the rocker shaft <NUM>. The latch bore <NUM> is configured to receive the latch pin <NUM>. Capsule bore <NUM> is configured to receive a valve actuation capsule or valve actuation component such as, for example, a switchable capsule <NUM>, hydraulic lash adjuster, mechanical lash adjuster, or spigot, among others, configured to engage an e-foot, valve stem, valve bridge, among others.

With additional reference to <FIG>, <FIG>, <FIG>, latch pin <NUM> will be described in more detail. In the example embodiment, latch pin <NUM> includes a generally cylindrical main body <NUM> having a first end <NUM> and a second end <NUM>. The latch pin <NUM> is received within the latch bore <NUM> in an orientation parallel to or substantially parallel to the rocker shaft <NUM> and transverse to or substantially transverse to a main (longitudinal) axis of the inner and outer arms <NUM>, <NUM>. Each end <NUM>, <NUM> includes a keyway such as a through-hole, recess, or slot <NUM> configured to receive a key <NUM> (e.g., see <FIG>, <FIG>). The main body <NUM> defines a clearance <NUM> for lost motion of the inner arm <NUM>, such clearance comprising a recess, groove, or notch, for example.

In the deactivated position (<FIG>), latch pin <NUM> is moved to a position where contact arm <NUM> is received within, and can alternatively pass through, the clearance <NUM>. In this configuration, inner arm <NUM> does not transfer motion to outer arm <NUM> via latch pin <NUM>. The extent of the motion of the contact arm <NUM> within the clearance <NUM> is a function of the lift profile transferred from the cam <NUM>.

In the activated position (<FIG>), latch pin <NUM> is moved to a position where contact arm <NUM> will contact main body <NUM> when rotating about rocker shaft <NUM> to thereby transfer rotational motion to outer arm <NUM> via the latch pin <NUM>.

Latch assembly <NUM>, <NUM> can be configured for use in a switchable rocker arm. Latch assembly <NUM> comprises a key <NUM> and can comprise a return spring <NUM> biasing the latch pin <NUM>, while latch assembly <NUM> can comprise key <NUM> and second key <NUM> with the latch pin <NUM> biased by return springs <NUM>, <NUM>.

Latch assembly <NUM>, <NUM> comprises a latch bore <NUM> formed in a body of material, in this example, in a portion of main body <NUM> of outer arm <NUM>. Latch bore <NUM> comprises a first bore end <NUM>, a second bore end <NUM>, and a lost motion gap <NUM>. Lost motion gap <NUM> can be formed between shoulders <NUM>, <NUM> extending from the main body <NUM> of the outer arm <NUM>. Shoulders <NUM>, <NUM> can seat biasing mechanisms <NUM>, <NUM>. In other rocker arm variations, the lost motion gap <NUM> can be formed by a notch, groove, divot or other indentation that enables the inner arm <NUM> to move in lost motion.

Latch pin <NUM> is configured to reciprocate in the latch bore <NUM>. Latch pin <NUM> comprises a main body <NUM>, which can be cylindrical. Latch pin <NUM> comprises a first plug end <NUM> in the first bore end <NUM>, a second plug end <NUM> in the second bore end <NUM>, and a clearance <NUM> between the first plug end <NUM> and the second plug end <NUM>. The latch pin is configured to selectively move in the latch bore <NUM> between the activated position and the deactivated position. When the latch pin <NUM> is in the activated position, one of the first plug end <NUM> and the second plug end <NUM> is positioned in the lost motion gap <NUM>. The inner arm <NUM>, in this example, the contact arm <NUM> and contact surface <NUM>, cannot move in lost motion. The inner arm <NUM> transfers a lift profile from the cam <NUM> to the valve end of the outer arm <NUM>. But, when the latch pin <NUM> is in the deactivated position, the clearance <NUM> is in the lost motion gap <NUM>. Then, the inner arm can move in lost motion. A lift profile from the cam <NUM> does not transfer to the valve end of the outer arm <NUM> because the inner arm moves in the space provided by the clearance <NUM> and the lost motion gap <NUM>. It is possible, by so designing the cam lobe profile, to have the inner arm <NUM> move past the latch pin <NUM> altogether so that it moves from above to below the latch pin <NUM>.

The latch assembly <NUM> comprises a key <NUM> in the latch bore <NUM>. The key <NUM> is configured to guide the latch pin <NUM> in the latch bore <NUM>. The key <NUM> comprises a post <NUM>. The latch pin <NUM> comprises a slot <NUM>. The key <NUM> is configured with the post <NUM> to guide the latch pin <NUM> via the slot <NUM>. In alternatives not according to the appended claims, the latch bore <NUM> can be configured with a mating clocking or keying feature, and the key can be substituted with a plug, cap, blind bore, or other latch bore sealing component. As illustrated, the key <NUM> comprises a head <NUM> that can function to press to the latch bore <NUM>. The post <NUM> extends from the head <NUM>. And, a return spring <NUM> is coiled around the post <NUM> and is biased against the head <NUM> and the first plug end <NUM> to bias the latch pin <NUM> in the latch bore <NUM>. The return spring <NUM> can push the plug body <NUM> so that it blocks the inner arm <NUM> from moving in the lost motion gap <NUM>. If a blind bore were placed at the second bore end <NUM>, a hydraulic supply pressure could be controlled to opposed the force of the return spring <NUM> to push the clearance <NUM> into alignment with the lost motion gap <NUM>. Hydraulic supply pressure could be supplied via supply port <NUM> in rocker shaft <NUM>. A second supply port <NUM> can function as another pressure control conduit, including a return path.

According to the appended claims, controlling hydraulic supply pressures is supplied to both ends <NUM>, <NUM> of the latch bore. Instead of one hydraulic port <NUM> in the previous example, two hydraulic ports <NUM>, <NUM> can extend in the flanges <NUM> and in the main body <NUM> between the rocker shaft <NUM> and the latch bore <NUM> so that oil pressure control can direct the latch pin <NUM> between the deactivated and activation positions. Hydraulic supply pressure could be supplied via control of the positions of supply ports <NUM>, <NUM> in rocker shaft <NUM>. It can be said that the latch bore <NUM> is configured to receive hydraulic control via one or more hydraulic ports <NUM>, <NUM> in one or both of the first bore end <NUM> and the second bore end <NUM> to move the latch pin <NUM>. Having a plug shape to the plug bodies <NUM>, <NUM> allows pressure to build against the latch pin <NUM> for oil control. But, with modification to the latch pin <NUM> and latch bore, other reciprocation control techniques can be achieved.

The latch assembly <NUM> can comprise a second return spring <NUM> biased against the second plug end <NUM>. A rim, lip, post, stake, or other spring guide can optionally be included in the latch bore <NUM>. Additionally, and alternative to having a blind bore at the second bore end <NUM>, a through-hole can be used at the second bore end <NUM>. Then, a second key <NUM> can be pressed to the through-hole to secure the latch pin <NUM> in the latch bore <NUM>. Second key <NUM>, and its alternatives, can comprise any one of the alternatives that key <NUM> can comprise, including head <NUM> & post <NUM>. Second return spring <NUM> can bias against the second plug end <NUM> and the head <NUM> of second key <NUM>.

A rocker arm assembly <NUM> can comprise an outer arm <NUM> configured to rotate about a rocker shaft <NUM>. Outer arm <NUM> can comprise main body <NUM> defining opposed flanges <NUM> each defining an aperture (rocker bore) <NUM> to receive the rocker shaft <NUM>. The outer arm <NUM> can comprise the latch bore <NUM>. The latch bore <NUM> can be between the rocker shaft <NUM> and the valve end. The valve end can comprise a cleat, e-foot, or other structure to couple to a valve or valve bridge, or valve end can comprise a capsule <NUM> such as a lost motion capsule, engine braking capsule, among others.

Inner arm <NUM> can be at least partially disposed within the outer arm <NUM> and can be configured to selectively move within the outer arm <NUM>. While the inner arm <NUM> is illustrated as rotating about the rocker shaft <NUM> as by surrounding the rocker shaft <NUM> with first aperture (rocker bore) <NUM>, other pivot locations can be had, as by including a pivot pin to link the inner arm <NUM> to the outer arm <NUM>. The inner arm <NUM> can rotate relative to the rocker shaft <NUM> via these alternative pivot arrangements.

The latch assembly <NUM>, <NUM> can be positioned to move between the activated position and the deactivated position, as by reciprocating in the latch bore <NUM>. When the latch pin <NUM> is in the activated position (<FIG> & <FIG>), the inner arm <NUM> is configured to transfer force to the outer arm <NUM> via the latch pin <NUM>. When the latch pin <NUM> is in the deactivated position, the inner arm <NUM> is configured to move in the clearance <NUM> and in the lost motion gap <NUM>.

The inner arm can comprise a main body <NUM> defining a first aperture (rocker bore) <NUM> to receive the rocker shaft <NUM>. A second aperture or pair of apertures <NUM> can be formed across a forked roller end <NUM> and can be configured to rotatably support a roller <NUM>. Roller <NUM> can be seated via a pivot pin <NUM>. Or, roller <NUM> can be substituted with a tappet. Tappet or roller can be configured to receive a lift profile from cam <NUM>. Inner arm <NUM> can also comprise a contact arm <NUM> configured to selectively contact the latch pin <NUM> when the latch pin is in the activated position. The contact arm <NUM> can comprise a contoured contact surface <NUM> to distribute pressure on the latch pin <NUM>.

One or more biasing mechanisms <NUM>, <NUM> (e.g., springs) can be disposed between the inner arm <NUM> and the outer arm <NUM> to bias the inner and outer arms into a desired position relative to each other.

Described herein is a heavy duty Type III rocker arm assembly with cylinder deactivation (CDA). The rocker arm assembly includes an inner arm, outer arm, and latch pin designed for high stiffness and low mass moment of inertia. The design is configured to provide no contact stress singularity issues at edges of the latch pin/rocker arm hole ID due to tangent/throughout contact of the latch pin maintained with the rocker arm hole. Further, the inner arm, outer arm, and latch pin are designed to reduce tensile stress to provide improved fatigue life. Additional modifications can provide further improvement to assembly stiffness.

Claim 1:
A latch assembly (<NUM>; <NUM>) for a switchable rocker arm (<NUM>), comprising:
a latch bore (<NUM>) comprising a first bore end (<NUM>), a second bore end (<NUM>), and a lost motion gap (<NUM>);
a latch pin (<NUM>) configured to reciprocate in the latch bore (<NUM>), the latch pin (<NUM>) comprising a main body (<NUM>) comprising a first plug end (<NUM>) in the first bore end (<NUM>), a second plug end (<NUM>) in the second bore end (<NUM>), and a clearance (<NUM>) between the first plug end (<NUM>) and the second plug end (<NUM>), wherein the latch pin (<NUM>) is configured to selectively move in the latch bore (<NUM>) between an activated position and a deactivated position, wherein, when the latch pin (<NUM>) is in the activated position, one of the first plug end (<NUM>) and the second plug end (<NUM>) is positioned in the lost motion gap (<NUM>), and wherein, when the latch pin (<NUM>) is in the deactivated position, the clearance (<NUM>) is in the lost motion gap (<NUM>);
a key (<NUM>) in the latch bore (<NUM>), the key configured to guide the latch pin (<NUM>) in the latch bore (<NUM>), wherein the key (<NUM>) comprises a post (<NUM>), wherein the latch pin (<NUM>) comprises a slot (<NUM>), and wherein the key (<NUM>) guides the latch pin (<NUM>) via the slot (<NUM>), and
wherein the latch bore (<NUM>) is configured to receive hydraulic control in both of the first bore end (<NUM>) and the second bore end (<NUM>) to move the latch pin (<NUM>).