Patent Description:
Valvetrains can comprise switchable components for enabling variable valve actuation (VVA) such as lost motion, added motion, among others. One such valvetrain component is a rocker arm. Rocker arms such as switching roller finger followers (SRFFs) can comprise a device for locking and unlocking relative motion of the components of the rocker arm. The response time of the device confines the implementation of the WA. If the device cannot lock and unlock quickly enough, the functionality of the rocker arm cannot be used as engine speeds increase above the response time of the device. So, it is desired to have fast actuation for locking and unlocking the valvetrain components. Examples of such valvetrains are disclosed by <CIT> or <CIT>.

The devices disclosed herein overcome the above disadvantages and improve the art by way of a ventilated latch assembly for a hydraulically actuated switching rocker arm.

A latch assembly comprises a latch pin and a cage biased by a spring. The latch pin comprises a latch nose and a pin body connected to the latch nose. The pin body comprises an outer surface and an inner compartment. The inner compartment comprises a first inner wall defining a portion of the inner compartment and a second inner wall defining a second portion of the inner compartment The cage comprises a stepped base and a shaft extending from the stepped base into the inner compartment. The shaft comprises a first exterior flat formed on a portion of the shaft and adjoining the first inner wall and a second exterior flat formed on a portion of the shaft and adjoining the second inner wall. The stepped base comprises a first end flat parallel to the first exterior flat and a second end flat parallel to the second exterior flat. A spring is biased against the latch pin and the cage. The latch assembly can be used in a latching device of a valvetrain such as a switching roller finger follower or other rocker arm.

The shaft can further comprise a first exterior arc surface and a second exterior arc surface. The inner compartment can comprise an inner circumference segmented into a first arc, a first chord, a second arc, and a second chord. The first chord is part of the first inner wall, and the second chord is part of the second inner wall. The first arc surface can be opposite to the second arc surface about a long axis of the latch pin. The first exterior arc surface can adjoin the first arc surface and the second exterior arc surface can adjoin the second arc surface.

The stepped base can form a travel limit for the pin body. Alternatively, the shaft can form a travel limit for the pin body. Additionally, the stepped base can be solid. And, the shaft can comprise a hollow portion. A solid spring cup can be between the stepped base and the hollow portion.

A latching device can comprise the latch assembly. The latching device can comprise a housing comprising a latch bore comprising a main inner circumference. The latch pin can be configured to slide in the latch bore with the outer surface adjacent the main inner circumference. The stepped base can be fitted to a portion of the main inner circumference.

The stepped base can comprise a first end flat parallel to the first flat and a second end flat parallel to the second flat. The stepped base can span across the main inner circumference to fit to opposed sides of the main inner circumference. The first end flat and the second end flat can be spaced away from the main inner circumference.

The housing can further comprise an outer end surface through which the latch bore passes. The stepped base can comprise a first step and a second step positioned against the outer end surface.

The latching device can further comprising an oil feed through the housing and connected to the latch bore. The latching device is configured so that oil fed via the oil feed can vent out of the latch bore and out of the spaces between the first end flat and the second end flat that can be spaced away from the main inner circumference.

A rocker arm can comprise the latching device and latch assembly. The rocker arm can comprise a pair of outer arms integrated with the housing. An inner arm can be coupled to the pair of outer arms. The inner arm can be configured to selectively move relative to the latch pin when the latch pin is retracted into the latch bore and the inner arm can be configured to selectively abut the latch nose when the latch pin protrudes from the latch bore.

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 may 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.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention.

Reference will now be made in detail to the examples which are illustrated in the accompanying drawings.

The disclosure provides a system and device for increased ventilation for a latching mechanism. A latch assembly <NUM> can constitute a ventilated latching mechanism for a hydraulically-actuated switching rocker arm <NUM> or other variable valvetrain component. The latch assembly <NUM> is designed to allow for improved response time of the latch pin <NUM>. A non-round latch cage <NUM> increases the flow area <NUM> which is exposed to atmospheric pressure, thus improving switching performance.

An optimized latch pin <NUM> response time can be achieved for switching rocker arm <NUM> engine applications which have low available pressure. A rocker arm <NUM> can be configured to switch between a latched condition, shown in <FIG>, and an unlatched condition, shown in <FIG>. In the latched condition, the inner arm <NUM> is held in place relative to a pair of outer arms <NUM>, <NUM>. An overhead cam <NUM> can press a roller assembly <NUM> which in turn transfers a lift profile to a valve. When the cam <NUM> positions base circle <NUM> at the roller assembly <NUM> is the usual location where latch assembly <NUM> can be actuated to withdraw latch pin <NUM> into latch bore <NUM>. <FIG> shows this unlatched condition where the latch pin <NUM> is withdrawn into latch bore <NUM>. A valve lift profile <NUM> is lost when the inner arm <NUM> pivots around pivot axle <NUM> in pivot bores <NUM>, <NUM>. Latch seat <NUM> swings past the latch nose <NUM> and no actuation force is transferred to the valve stem <NUM>.

A latch assembly <NUM> comprises a latch pin <NUM> and a cage <NUM> biased by a spring <NUM>. Spring <NUM> can be seated in a spring seat <NUM> of the latch pin <NUM>. Spring seat <NUM> can comprise a cup, rim, stake or the like.

The latch pin <NUM> comprises a latch nose <NUM>. A latch step <NUM> can be included on the latch nose <NUM>. Latch step <NUM> and latch nose <NUM> can comprise a crown, flat, chamfer, among other features for catching against or furthering sliding of the inner arm <NUM> and latch seat <NUM>.

Pin body <NUM> is connected to the latch nose <NUM>. The pin body <NUM> comprises an outer surface <NUM> and an inner compartment <NUM>. The inner compartment <NUM> comprises a first inner wall <NUM> segmented by a first slot <NUM> and a second inner wall <NUM> segmented by a second slot <NUM>. The first slot <NUM> and the second slot <NUM> vent out of the inner compartment <NUM>. Actuation fluid can traverse the first and second slot <NUM>, <NUM> while the first inner wall <NUM> and second inner wall <NUM> can form a keyed structure with the cage <NUM>. The keyed structure can prevent rotation of the latch pin <NUM> in the latch bore <NUM>, which improves the seating of the latch seat <NUM> against the step <NUM> of latch nose <NUM>. The size of the first and second slot <NUM>, <NUM> can be sized for the response time of the latch assembly <NUM>. The first and second slot <NUM>, <NUM> can function like controlled orifices so that when the spring <NUM> pushes the latch pin <NUM> to protrude out of the latch bore <NUM> to return to the latched condition, the actuation fluid that is venting out of the latching device <NUM> can be suctioned through the first and second slots <NUM>, <NUM>. This suction can be controlled to tailor the resistance to the motion of the latch pin <NUM> and can be used to control the speed of the response time. Having little resistance at flow area <NUM>, it is easy for the venting actuation fluid to be suctioned to fill the space in the latch bore <NUM> as the latch pin <NUM> moves from the unlatched condition to the latched condition.

The cage <NUM> comprises a stepped base <NUM> and a shaft <NUM> extending from the stepped base <NUM> into the inner compartment <NUM>. The shaft <NUM> can have a complementary keyed structure with the inner compartment <NUM>. The shaft <NUM> comprises a first exterior flat <NUM> adjoining the first inner wall <NUM> and a second exterior flat <NUM> adjoining the second inner wall <NUM>. A spring <NUM> is biased against the latch pin <NUM> and the cage <NUM>. The latch assembly <NUM> can be used in a latching device <NUM> of a valvetrain such as a switching roller finger follower or other rocker arm <NUM>.

The shaft <NUM> can further comprise a first exterior arc surface <NUM> and a second exterior arc surface <NUM>. The inner compartment <NUM> can comprise an inner circumference F segmented into a first arc AB, a first chord BC, a second arc CD, and a second chord DA. The first chord BC is part of the first inner wall <NUM>, and the second chord DA is part of the second inner wall <NUM>. The first arc AB can be part of a first arc surface <NUM>. The second arc CD can be part of a second arc surface <NUM>. The first arc AB can be opposite to the second arc CD relative to a center point of the circumference F. The first arc surface <NUM> can be opposite to the second arc surface <NUM> about a long axis of the latch pin <NUM>. The first exterior arc surface <NUM> can adjoin the first arc surface <NUM> and the second exterior arc surface <NUM> can adjoin the second arc surface <NUM>.

The stepped base <NUM> can form a travel limit for the pin body <NUM>. The latch pin <NUM> could be configured so that it travels into the latch bore <NUM> until it abuts the stepped base <NUM>. Alternatively, the shaft <NUM> can form a travel limit for the pin body <NUM>. The latch pin <NUM> could be configured so that it travels into the latch bore <NUM> until it abuts the end of shaft <NUM>. Additionally, the stepped base <NUM> can be solid. By solid, the stepped base <NUM> can have no hole for oil to flow through. This is a departure from prior art cages where the base of the cage forms a controlled orifice for releasing actuation fluid out of the latch bore. Instead, the shaft <NUM> can comprise a hollow portion <NUM>. Yet actuation fluid cannot vent out the solid stepped base <NUM> through the hollow portion <NUM>. A solid spring cup <NUM> can be formed by adding or including material inside the shaft <NUM> between the stepped base <NUM> and the hollow portion <NUM>. The spring cup <NUM>, being solid, does not permit actuation fluid to pass through the inside of the shaft <NUM>. The inside of the shaft instead guides the spring <NUM> and forms a pocket <NUM> with the inner compartment <NUM> for cushioning against the actuation fluid. Actuation fluid that is trapped in the pocket <NUM> can pressurize against the solid spring cup <NUM> or solid stepped base <NUM>. In order to vent from the pocket <NUM>, the actuation fluid must travel in the space between the adjoining inner compartment <NUM> and shaft <NUM>, including travel in the first and second slots <NUM>, <NUM>. The keyed structure between the cage <NUM> and latch pin <NUM> can thus also be controlled to tailor the response time of the latch assembly <NUM>, with fluid trapped in the pocket <NUM> forming a controllable resistance to actuation fluid acting on outer surface <NUM>. A smooth, controlled actuation can be achieved by balancing the actuation pressure from oil feed <NUM> to latch bore <NUM>, the leaking of trapped actuation fluid from pocket <NUM>, and the venting out of flow area <NUM>.

A latching device <NUM> can comprise the latch assembly <NUM>. The latching device <NUM> can comprise a housing <NUM> through which a latch bore <NUM> passes. Latch bore <NUM> can be a through-hole in the housing <NUM>. Latch bore <NUM> can be stepped to follow some exterior profiles on the latch pin <NUM> so as to guide the latch pin <NUM> and prevent rotation of the latch pin <NUM> relative to the device to be latched, such as rocker arm <NUM>. Latch bore <NUM> can comprise a main inner circumference G. The latch pin <NUM> can be configured to slide in the latch bore <NUM> with the outer surface <NUM> adjacent the main inner circumference G. The stepped base <NUM> can be fitted to a portion of the main inner circumference G.

The stepped base <NUM> comprises a first end flat <NUM> parallel to the first exterior flat <NUM> and a second end flat <NUM> parallel to the second exterior flat <NUM>. The stepped base <NUM> can span across the main inner circumference G to fit to opposed sides of the main inner circumference G. The first end flat <NUM> and the second end flat <NUM> can be spaced away from the main inner circumference G.

The housing <NUM> can further comprise an outer end surface <NUM> through which the latch bore <NUM> passes. The stepped base <NUM> can comprise a first step <NUM> and a second step <NUM> positioned against the outer end surface <NUM>. The stepped base <NUM> can be press-fit to or otherwise grip the latch bore <NUM> via the first and second steps <NUM>, <NUM>.

The latching device <NUM> can further comprising an oil feed <NUM> through the housing <NUM>. The oil feed <NUM> can be connected to the latch bore <NUM> so that pressurized actuation fluid acts on the outer surface <NUM> of the latch pin <NUM> to move the latch pin <NUM>. The oil feed <NUM> can be fed, for example, via a feed port <NUM> and flow path <NUM> of a hydraulic lash adjuster (HLA) <NUM>. The latching device <NUM> is configured so that oil fed via the oil feed <NUM> can vent out of the latch bore <NUM> and out of the flow areas <NUM> formed by spaces between the first end flat <NUM> and the second end flat <NUM>. The first and second end flats <NUM>, <NUM> can be spaced away from the main inner circumference G thereby forming the flow areas <NUM>. The large area and exposure to atmospheric pressure allows for fast venting of the actuation fluid. And, the design of the adjoining shaft <NUM> and inner compartment <NUM> can control the pressure needed to actuate the latch assembly <NUM>. How quickly the actuation fluid can build pressure and subsequently vent out controls the response time of the latch assembly <NUM> and latching device <NUM>. The design of the stepped base, with the first and second end flats <NUM>, <NUM> permits a high surface area exposure to atmospheric pressure for flow areas <NUM>.

A rocker arm <NUM> can comprise the latching device <NUM> and latch assembly <NUM>. The rocker arm <NUM> can comprise a pair of outer arms <NUM> integrated with the housing <NUM>. An inner arm <NUM> can be coupled to the pair of outer arms <NUM>. The inner arm <NUM> can be configured to selectively move relative to the latch pin <NUM> when the latch pin <NUM> is retracted into the latch bore <NUM> and the inner arm <NUM> can be configured to selectively abut the latch nose <NUM> when the latch pin <NUM> protrudes from the latch bore <NUM>. The rocker arm <NUM> can comprise numerous alternatives for the inner and outer arm configurations, including rollers, slider pads, cantilevered posts, among others. The pivot location of the inner and outer arms, or valve seating configuration, or location of the latch assembly over the valve side or over the pivot side, can be varied, with the latch assembly <NUM> being movable and usable in place of other rocker arm latch mechanisms.

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

For example, it is possible to implement a method for actuating a switching rocker arm <NUM> comprising an optimized latch pin <NUM> response time for a switching rocker arm <NUM> engine application which has a low available pressure.

As another example, a system can be built, such as a variable valvetrain, for a switching rocker arm <NUM> comprising a latched switching rocker arm <NUM> connected to a hydraulic control circuit, and the latched switching rocker arm <NUM> comprises a latch cage <NUM> configured with oil leakage paths so as to form flow areas <NUM>.

As another example, a latch cage <NUM> can be configured in a switching rocker arm <NUM> to comprise oil leakage paths such as first and second end flats <NUM>, <NUM> to form flow areas <NUM>.

Claim 1:
A latch assembly (<NUM>), comprising:
a latch pin (<NUM>), comprising:
a latch nose (<NUM>); and
a pin body (<NUM>) connected to the latch nose (<NUM>), the pin body (<NUM>) comprising an outer surface (<NUM>) and an inner compartment (<NUM>), the inner compartment (<NUM>) comprising:
a first inner wall (<NUM>) defining a portion of the inner compartment (<NUM>); and
a second inner wall (<NUM>) defining a second portion of the inner compartment (<NUM>);
a cage (<NUM>), comprising:
a stepped base (<NUM>); and
a shaft (<NUM>) extending from the stepped base (<NUM>) into the inner compartment (<NUM>), the shaft (<NUM>) comprising:
a first exterior flat (<NUM>) formed on a portion of the shaft and adjoining the first inner wall (<NUM>); and
a second exterior flat (<NUM>) formed on a second portion of the shaft and adjoining the second inner wall (<NUM>);
wherein the stepped base (<NUM>) comprises a first end flat (<NUM>) parallel to the first exterior flat (<NUM>) and a second end flat (<NUM>) parallel to the second exterior flat (<NUM>); and
a spring (<NUM>) biased against the latch pin (<NUM>) and the cage (<NUM>).