Patent Description:
Internal combustion engines can utilize a Miller cycle to reduce parasitic pumping losses and fuel consumption rate. A Miller cycle can be performed by controlling the intake valve closing using an early intake valve closing (EIVC) or late intake valve closing (LIVC) strategy. One example of EIVC, LIVC and a variable valve timing (VVT) assembly and method is disclosed in <CIT>. However, further improvements in this technology area to improve the intake valve operations in response to an extended intake valve opening duration event are desired.

The present application incorporates a VVT assembly for LIVC and/or EIVC of the intake valve in response to an extended intake valve opening duration event, such as a transient operating condition of internal combustion engine. The VVT assembly includes a lever extension extending from a modified intake rocker that is operable by a cam shaft to open and close an intake valve of a cylinder of the internal combustion engine. The lever extension of the intake rocker is in contact with a holding member that is operable to extend the open duration of the intake valve during the intake stroke of the piston in the combustion chamber. The holding member is normally unlocked and/or held in a retracted position in the pedestal of the intake rocker to allow the intake rocker to pivot to close the intake valve after the cam lobe passes the rocker roller during a standard Miller cycle mode of operation.

In response to an extended duration mode of operation, the holding member is actuated to extend from the pedestal to contact the lever extension and hold the intake rocker in a pivoted position that corresponds to the intake valve opening, and therefore does not allow the intake valve to close even after the cam lobe passes the rocker roller. The VVT assembly also includes a reset pin extending from the pedestal that is contacted by the cam lobe to release the actuated holding member to allow it to retract back into the pedestal, which in turn releases the intake rocker and allows the intake valve to close. The reset pin is located so the intake valve closing can be completed after bottom-dead-center of the intake stroke.

The present application further describes various embodiments of hydraulic circuits that include a solenoid selectively pressurizing fluid in the hydraulic circuit for releasing the reset pin to extend from the pedestal to contact the cam. Flow paths and components are also provided that control the flow of fluid between the reset pin and the holding member to actuate the holding member from the pedestal, lock the holding member in an extended position in contact with the lever extension of the intake rocker, and to release the locked holding member.

This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein.

In one embodiment of the present application, <FIG> depicts a segment of a cam shaft and intake/exhaust valve assembly <NUM>, which comprises a cam shaft <NUM> that includes one or more cams <NUM> having one or more cam lobes <NUM> extending from a base circle <NUM> (<FIG>. ) The assembly <NUM> also includes first and second intake rockers 20a, 20b (collectively and individually referred to as intake rockers <NUM>) that operate respective pairs of intake valves (not shown), and first and second exhaust rockers 22a, 22b (collectively and individually referred to as exhaust rockers <NUM>) that operate respective pairs of exhaust valves (not shown). The intake valve pairs control air flow into a combustion chamber (not shown) of a cylinder of an internal combustion engine (not shown), and the exhaust valves control exhaust flow out of the cylinder. It should be understood that <FIG> depicts an arrangement for two cylinders of an internal combustion engine, but additional segments can be provided for additional cylinders. In addition, each of the segments can be arranged for two cylinders as shown, arranged for a single cylinder, or arranged for more than two cylinders.

Referring further to <FIG>, the rockers <NUM>, <NUM> are mounted on a pedestal <NUM> which includes a hydraulic circuit <NUM> (discussed further below, see <FIG>) for controlling operation of the rockers <NUM>, <NUM> and of a variable valve timing assembly <NUM>. The hydraulic circuit <NUM> includes a solenoid <NUM> operable to selectively pressurize the fluid in the hydraulic circuit. Operation of the hydraulic circuit <NUM> according to various embodiments will be discussed further below. Another solenoid 29a can be provided with an accumulator 29b for operation of a hydraulic circuit for brake actuation.

Each of the intake rockers <NUM> includes a rocker roller <NUM> that is normally in contact with a respective cam <NUM> of the cam shaft <NUM>. During a normal or nominal mode of operation, the intake valves are opened and closed by the cam <NUM> operating on the respective intake rocker <NUM> through rocker roller <NUM> using a standard Miller cycle mode of operation.

The present disclosure includes VVT assembly <NUM> to provide an extended duration mode of operation in which the opening of the intake valves is extended from the normal or nominal Miller cycle opening duration, such as shown in <FIG>. The extended duration mode can occur, for example, in response to one or more operating conditions indicating a transient condition, such as an accelerator tip-in, is occurring or about to occur. However, initiation of the extended duration mode may be initiated in response to any desired operating condition in which a performance benefit is desired.

VVT assembly <NUM> includes a lever extension <NUM> (<FIG>) extending from intake rocker <NUM> that is contactable by a holding member <NUM>, such as an actuator piston or the like, that is extendable into and out of the pedestal <NUM>. The holding member <NUM> is lockable in the extended position via hydraulic circuit <NUM> to prevent intake rocker <NUM> from pivoting on pedestal <NUM> to close the intake valve. VVT assembly <NUM> also includes a reset pin <NUM> in the pedestal <NUM> that is actuatable by the cam lobe <NUM> to release the holding member <NUM> and allow the intake valve to close.

<FIG> though 5F reflect the configuration of the VVT assembly <NUM> at each of the positions <NUM> through <NUM> depicted on the valve opening diagram of <FIG>. In <FIG>, position <NUM> on <FIG> is shown in which the roller <NUM> resides on the base circle <NUM> of cam <NUM>. In this position, holding member <NUM> is retracted into, or movable into and out of, the pedestal <NUM>. If an extended duration operating mode is initiated, reset pin <NUM> may be actuated by fluid pressure from hydraulic circuit <NUM> to project outwardly from the pedestal <NUM> at initiation of the extended duration mode of operation to contact the base circle <NUM>. Prior to its actuation, or during a normal or stand Miller cycle mode of operation, the reset pin <NUM> can be retracted into pedestal <NUM> so that it is normally spaced from base circle <NUM>, while cam lobe <NUM> may slightly contact reset pin <NUM> as it passes by.

In <FIG>, position <NUM> on <FIG> is shown in which the roller <NUM> resides on the cam lobe <NUM> of cam <NUM> to provide peak lift of the intake valve connected to intake rocker <NUM>. In this position, holding member <NUM> is extended from the pedestal <NUM> and locked in this position by fluid pressure in the hydraulic circuit <NUM>. In the extended position, holding member <NUM> contacts the lever extension <NUM> extending from intake rocker <NUM>. Reset pin <NUM> remains actuated to project outwardly from the pedestal <NUM> and in contact with the base circle <NUM>.

In <FIG>, position <NUM> on <FIG> is shown in which the roller <NUM> is spaced from cam <NUM> to maintain peak lift of the intake valve. In this position, holding member <NUM> remains locked in an extended position from the pedestal <NUM> and remains in contact with the lever extension <NUM> of intake rocker <NUM>. Reset pin <NUM> also remains actuated to project outwardly from the pedestal <NUM> and in contact with the base circle <NUM> of cam <NUM>.

In <FIG>, position <NUM> on <FIG> is shown in which the roller <NUM> remains spaced from cam <NUM> to maintain peak lift of the intake valve. The cam <NUM> has now rotated sufficiently so that cam lobe <NUM> contacts the reset pin <NUM> and depresses reset pin <NUM> into pedestal <NUM>. This in turn causes a release of the fluid pressure in hydraulic circuit <NUM> that is locking holding member <NUM> in the extended position, allowing holding member <NUM> to retract into pedestal <NUM>, as shown in <FIG> corresponding to position <NUM> on <FIG>. The reset pin <NUM> is moved back into pedestal <NUM> for re-engagement in the retracted position.

In position <NUM> in which the holding member <NUM> is movable, intake rocker <NUM> is allowed to pivot to close the intake valve and so that roller <NUM> contacts base circle <NUM> of cam <NUM>. Reset pin <NUM> is also maintained in the retracted position in the pedestal <NUM> by an actuating member that is actuated by the hydraulic pressure, and remains locked in the retracted position until re-actuated with hydraulic circuit <NUM> in response to a determination to enter the extended duration mode of operation.

In <FIG>, one embodiment of hydraulic circuit <NUM> is shown. As shown in <FIG>, hydraulic circuit <NUM> includes an actuating member <NUM> that is normally biased into engagement in a groove <NUM> of reset pin <NUM>. In one embodiment, a spring assembly <NUM> is provided that extends between an actuator piston <NUM> and a snap ring <NUM> around a vent plug <NUM>. The actuator piston <NUM> fits in groove <NUM> around reset pin <NUM> to prevent reset pin <NUM> from being extended from pedestal <NUM> via fluid pressure in the hydraulic circuit <NUM>. The ball <NUM> and spring <NUM> form a valve assembly <NUM> that can be closed against a seat <NUM> to prevent fluid flow to and from the overhead fluid supply <NUM> from fluid cavity <NUM>. Spring <NUM> can be retained in pedestal <NUM> using a plug <NUM> that seals the fluid cavity <NUM> in which the valve assembly <NUM> resides.

In <FIG> the hydraulic circuit <NUM> is non-active and actuating member <NUM> is engaged to reset pin <NUM> in groove <NUM> to hold reset pin <NUM> retracted into pedestal <NUM>. The holding member <NUM> can also be retracted in pedestal <NUM> or allowed to move into and out of pedestal <NUM> as intake rocker <NUM> pivots so that the holding member <NUM> follows the extension lever <NUM> of intake rocker <NUM> at all times.

In <FIG> the hydraulic circuit <NUM> is active and pressurized control fluid is supplied to groove <NUM> from a control fluid supply <NUM> connected to solenoid <NUM>. The pressurized control fluid displaces actuating member <NUM> out of groove <NUM>. This in turn allows reset pin <NUM> to be forced out of pedestal <NUM> into an extended position as shown in <FIG> due to the force from the pressurized fluid in cavity <NUM> behind the inner end of reset pin <NUM>. In the extended position, the outer end of reset pin <NUM> contacts cam <NUM> on base circle <NUM>. The pressurized fluid in cavity <NUM> also flows to chamber <NUM> in which holding member <NUM> resides so that holding member <NUM> is locked in an extended position against lever extension <NUM>, maintaining it in a peak lift position <NUM>'.

In <FIG> the ball <NUM> of valve assembly <NUM> is allowed to move due to the extension of reset pin <NUM> and seats against seat <NUM>. This isolates the pressurized fluid in chamber <NUM> and locks holding member <NUM> in the extended position, therefore holding intake rocker <NUM> at the peak holding position <NUM>'. As shown in <FIG>, the fluid is trapped in fluid cavity <NUM> and chamber <NUM> to prevent the holding member <NUM> from moving. In <FIG>, the cam shaft <NUM> has rotated so that cam lobe <NUM> is in contact with reset pin <NUM>, which forces reset pin <NUM> into pedestal <NUM> and opens valve assembly <NUM> by unseating ball <NUM> from seat <NUM>. This allows fluid to flow back into the hydraulic circuit from cavity <NUM> and chamber <NUM> through overhead fluid supply <NUM> and into a fluid accumulator. The holding member <NUM> therefore can retract into pedestal <NUM> in response to the intake valve spring force normally biasing the intake rocker <NUM> and intake valve to the closed position.

In <FIG> the fluid in chamber <NUM> has passed through a flow control orifice <NUM> of holding member <NUM> and into cavity <NUM> to allow retraction of the holding member <NUM>. This allows the closing force of the intake valve to be controlled from its peak lift position. In addition, reset pin <NUM> has retracted sufficiently into pedestal <NUM> to align actuating member <NUM> with groove <NUM>. As shown in <FIG>, solenoid <NUM> is de-energized and the actuator piston <NUM> re-engages the reset pin <NUM> in groove <NUM> to lock it in the retracted position. In this position the reset pin <NUM> also holds ball <NUM> off of seat <NUM> to prevent high pressure from building in cavity <NUM> and chamber <NUM>, allowing fluid flow to and from the cavity <NUM> as holding member <NUM> follows the intake rocker <NUM>.

In <FIG>, another embodiment of the hydraulic circuit is shown that is similar to <FIG> and designated at <NUM>. Hydraulic circuit <NUM> provides an overhead fluid supply is controlled through a modified actuating member <NUM>. Corresponding elements are therefore labelled with the same reference numerals as <FIG>.

When the hydraulic circuit <NUM> is inactive as shown in <FIG>, there is no oil pressure in cavity <NUM> or chamber <NUM>. This allows holding member <NUM> to stay retracted and not follow extending lever extension <NUM> during normal operation. Actuating piston <NUM> of actuating member <NUM> blocks the overhead oil supply <NUM> from supplying pressurized fluid into cavity <NUM> through passage <NUM>. In <FIG>, the solenoid <NUM> is energized and control fluid is suppled to groove <NUM> via control fluid supply <NUM>. This displaces actuating member <NUM> out of groove <NUM>, while simultaneously opening passage <NUM> to receive pressurized fluid from overhead fluid supply <NUM>.

As shown in <FIG> the pressurized fluid is provided to cavity <NUM> behind reset pin <NUM> to force it out of pedestal <NUM> and into contact with base circle <NUM> of cam <NUM>. The pressurized fluid is also provided to chamber <NUM> to force holding member <NUM> out of pedestal <NUM> and into contact with the lever extension <NUM> in the peak lift position <NUM>'. In <FIG> the valve assembly <NUM> closes to trap the fluid in cavity <NUM> and chamber <NUM>, as shown in <FIG>, to lock holding member <NUM> in the extended position.

As shown in <FIG>, the cam lobe <NUM> contacts the reset pin <NUM> to force it back into pedestal <NUM>, which in turn opens the valve assembly <NUM> and allows the fluid to flow back into overhead fluid supply <NUM> from cavity <NUM> and chamber <NUM> through the passage <NUM>, allowing the holding member <NUM> to retract as shown in <FIG>. The flow control orifice <NUM> catches the retracting holding member <NUM> to slow its retraction. In <FIG> the fluid pressure has drained from chamber <NUM> and cavity <NUM>, and the solenoid <NUM> is de-energized. This allows actuating piston <NUM> to re-engage reset pin <NUM> in groove <NUM> to lock it in a retracted position in pedestal <NUM>. In addition, the reset pin holds the valve assembly <NUM> in an open position during standard Miller cycle operation.

<FIG> show another embodiment hydraulic circuit <NUM>. Hydraulic circuit <NUM> operates similar to hydraulic circuits <NUM>, <NUM>, and like elements are designated with like reference numerals. In addition, hydraulic circuit <NUM> includes a modified holding member <NUM>' and modified reset pin <NUM>' that are configured to be spring biased to a retracted position with return springs <NUM>, <NUM>, respectively. The return springs <NUM>, <NUM> can be positioned around stems <NUM>, <NUM> of holding member <NUM>' and reset pin <NUM>' respectively. In addition, return springs <NUM>, <NUM> can be positioned against a support <NUM> such as a spring plate or snap ring that is engaged to pedestal <NUM>. The return springs <NUM>, <NUM> maintain the holding member <NUM>' and reset pin <NUM>' out of contact with the lever extension <NUM> and cam lobe <NUM>, respectively, until actuated with fluid pressure. It should be understood, however, the return springs <NUM>, <NUM> are optional and <FIG> may utilize holding member <NUM> and reset pin <NUM> as describe above.

<FIG> also employ another embodiment actuating member <NUM> with an actuating piston <NUM> that does not directly contact the reset pin <NUM>'. As shown in <FIG> actuating piston <NUM> is displaced with control fluid pressurized in control fluid supply <NUM> to compress the spring <NUM> and open overhead fluid supply <NUM> to passage <NUM> and isolate the vent <NUM> through the vent plug of the actuating member around which spring <NUM> is positioned. This unlocks the reset pin <NUM>' and allows high pressure fluid to fill cavity <NUM> behind reset pin <NUM>', as shown in <FIG>. Fluid continues to flow to pressurize chamber <NUM> around holding member <NUM>' as shown in <FIG>. This forces the holding member <NUM>' outwardly to contact the lever extension <NUM> of the intake rocker <NUM>.

Displacement of the reset pin <NUM>' to extend outwardly from the pedestal <NUM> to contact base circle <NUM> of the cam <NUM> also allows valve assembly <NUM> to close on seat <NUM>, as shown in <FIG>. This traps the fluid in cavity <NUM> and chamber <NUM> and locks holding member <NUM>' into position against the lever extension <NUM> at its peak lift position <NUM>', as shown in <FIG>.

As shown in <FIG>, the cam lobe <NUM> contacts the reset pin <NUM>' to force it back into pedestal <NUM>, which in turn opens the valve assembly <NUM> and allows the fluid to flow back into overhead fluid supply <NUM> from cavity <NUM> and chamber <NUM> through the passage <NUM> as shown in <FIG>. The flow control orifice <NUM> catches the retracting holding member <NUM>' to slow its retraction. In <FIG> the solenoid <NUM> is de-energized and the fluid pressure has drained from behind actuator piston <NUM>, allowing the spring <NUM> to displace the actuator piston back to close the overhead fluid supply <NUM>. In <FIG>, the fluid drains from cavity <NUM> and chamber <NUM> through a vent <NUM> of actuating member <NUM>. This allows the holding member <NUM>' and reset pin <NUM>' to retract into pedestal <NUM>, as shown in <FIG>.

In <FIG>, another embodiment of the hydraulic circuit <NUM> is shown that is similar to hydraulic circuit <NUM> of <FIG>. Elements in <FIG> that are like the embodiment of <FIG> are designated with the same reference numerals. As shown in <FIG> and <FIG>, hydraulic circuit <NUM> includes a valve assembly <NUM> that includes a disc <NUM> that is engageable against seat <NUM> rather than a ball <NUM> to act as a check valve. A stem <NUM> extends from the disc <NUM> and is slidingly received in a bore <NUM> of plug <NUM>. Spring <NUM> is positioned around stem <NUM> in contact with plug <NUM> and disc <NUM>.

In addition, a holding member <NUM> is provided that differs in structure and operation from holding member <NUM>' but performs a similar function. Holding member <NUM> includes a second check valve <NUM> that is received in a passage <NUM> of holding member <NUM>. Holding member <NUM> includes a head <NUM> that defines an outer chamber <NUM>, bores <NUM>, and an inner chamber <NUM> that is in flow communication with outer chamber <NUM> through bores <NUM>. Second check valve <NUM> includes an end member <NUM> with a flow control orifice <NUM> extending from inner chamber <NUM> to a cavity <NUM> in pedestal <NUM> that houses holding member <NUM>. A spring <NUM> in cavity <NUM> biases the second check valve <NUM> into passage <NUM>.

Further, a reset pin <NUM> is provided that differs from reset pin <NUM>'. Reset pin <NUM> is not spring biased, but includes a foot <NUM> outside of pedestal <NUM> that is normally in contact with and follows the profile of the cam <NUM>. Reset pin <NUM> also includes a stem <NUM> that moves with the reset pin <NUM> via cam lobe <NUM> to contact disc <NUM> of valve assembly <NUM> to open the valve assembly <NUM>.

Referring to <FIG>, the control fluid supply <NUM> is deenergized, and disc <NUM> is spring biased into position against seat <NUM>. In <FIG> the control fluid supply <NUM> is energized, which displaces actuating piston <NUM> so that the control fluid is in fluid communication with passage <NUM>, as shown in <FIG>. The control fluid then flows into the passage <NUM> containing reset pin <NUM> as shown in <FIG>, which unseats disc <NUM> from seat <NUM>, and control fluid flows into cavity <NUM>, as shown in <FIG>.

In <FIG> the control fluid has flowed into outer chamber <NUM>, through bores <NUM>, and into inner chamber <NUM>. This displaces the holding member <NUM> away from the second check valve <NUM> so the holding member <NUM> can extend from the pedestal to contact the lever extension <NUM> extending from intake rocker <NUM> while the intake valve is at peek lift, as shown in <FIG>. The pressure of the control fluid then equalizes and seats disc <NUM> against seat <NUM>, as shown in <FIG>. The second check valve <NUM> then seats against head <NUM> of holding member <NUM>, which hydraulically locks the system, as indicated in <FIG> with the darkened control fluid in cavity <NUM>, to maintain the intake valve opening.

In <FIG>, the cam lobe <NUM> is in contact with foot <NUM> of reset pin <NUM>, which pushes stem <NUM> against disc <NUM> to open the valve assembly <NUM>. The pressure of the control fluid is relieved to the accumulator and the holding member <NUM> retracts along with second check valve <NUM> in cavity <NUM>, as shown in <FIG> and <FIG>. The seating velocity of the holding member <NUM> is controlled by the flow of control fluid through the flow control orifice <NUM>. In <FIG> the control fluid supply <NUM> is deenergized, which allows actuating piston <NUM> to be displaced by the spring and isolate passage <NUM> from the control fluid supply <NUM>. The control fluid pressure is vented through vent <NUM> and a vent port <NUM> as shown in <FIG>.

Various aspects of the present disclosure are contemplated as disclosed herein and as recited in the claims below. For example, a selectively activatable VVT assembly for one or more cylinders of an internal combustion engine is provided that is configured to operatively engage an intake valve to extend a duration of the intake valve in an open position in response to an extended duration mode of operation. The VVT assembly includes an intake rocker mounted on a pedestal and operable by a cam lobe to open and close the intake valve, and the intake rocker includes a lever extension. The assembly also includes a holding member in the pedestal lockable in position by a hydraulic circuit in the pedestal to contact the lever extension of the intake rocker and hold the intake valve in the open position. A reset pin in the pedestal is actuatable by the cam lobe to release the holding member to allow the intake valve to close.

In one embodiment, the internal combustion engine operates using a Miller cycle when the VVT assembly is not selected for activation.

In one embodiment, a cylinder head is provided that includes the intake valve and an intake port. The intake valve is moveable between an open position allowing intake gas to enter the cylinder through the intake port and a closed position that prevents intake gas from entering the cylinder through the intake port. A camshaft is rotatably mounted and includes an intake cam with the cam lobe. The cam lobe is operatively connected to the intake valve to periodically move the intake valve into the open and closed positions and shaped such that a timing of the closed position occurs at or before bottom dead center BDC of a compression stroke of a piston in the cylinder during a Miller cycle mode of operation. In one embodiment, the intake valve is held open until after BDC of the compression stroke of the piston during the extended duration mode of operation.

In one embodiment, the holding member includes a flow control orifice to control a fluid flow from a chamber housing the holding member into the hydraulic circuit.

In one embodiment, the hydraulic circuit is connected to a solenoid that is operable to pressurize a fluid in the hydraulic circuit to operate an actuating member that is displaced to allow the reset pin to extend from the pedestal to contact the cam lobe.

In one embodiment, the pressurized fluid locks the holding member in position during the extended duration mode of operation. In one embodiment, the reset pin contacts a valve assembly to hold the valve assembly open while the actuating member is positioned to maintain the reset pin in a retracted position in the pedestal.

In one embodiment, the valve assembly closes in response to the extension of the reset pin from the pedestal to isolate the pressurized fluid in a chamber containing the holding member while the holding member is in the extended position. In one embodiment, the valve assembly includes one of a ball and a disc that is spring biased to engage a seat in response to the reset pin being released to isolate the fluid in the chamber of the holding member.

In one embodiment, in response to the cam lobe actuating the reset pin, the reset pin is retracted into the pedestal to displace the one of the ball and the disc from the seat and release the pressurized fluid from the chamber of the holding member. In one embodiment, the solenoid is de-energized to de-pressurize the fluid and allow the actuating member to re-engage the reset pin in the retracted position.

In one embodiment, the actuating member isolates the fluid in the hydraulic circuit from the holding member when not in the extended duration mode of operation and the actuating member is displaced to open a fluid flow path to the holding member during the extended duration mode of operation.

In one embodiment, the holding member and the reset pin are normally biased into a retracted position in the pedestal.

Another exemplary aspect includes a selectively activatable VVT assembly that includes a pedestal for mounting adjacent to a cylinder of on an internal combustion engine and an intake rocker mounted on the pedestal and operable by a cam lobe to open and close an intake valve of the cylinder. The intake rocker includes a lever extension. The assembly includes a holding member extendable from the pedestal to contact the lever extension of the intake rocker and hold the intake valve in the open position. A reset pin is movable into the pedestal by the cam lobe to release the holding member to allow the intake valve to close.

In one embodiment, the holding member and the reset pin are normally biased into a retracted position in the pedestal. In one embodiment, the holding member includes a flow control orifice to control a fluid flow from a chamber housing the holding member into a hydraulic circuit in the pedestal.

In one embodiment, the reset pin contacts a valve assembly in the hydraulic circuit to hold the valve assembly open wwhile the reset pin is in a retracted position in the pedestal. In one embodiment, the valve assembly closes in response to extension of the reset pin from the pedestal to isolate pressurized fluid in the chamber containing the holding member while the holding member is extended from the pedestal.

In one embodiment, the valve assembly includes one of a ball and a disc that is spring biased to engage a seat in response to the reset pin being extended from the pedestal to isolate the fluid in the chamber of the holding member. In response to the cam lobe moving the reset pin into the pedestal, the reset pin displaces the one of the ball and the disc from the seat and releases the pressurized fluid from the chamber of the holding member.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claim 1:
A selectively activatable variable valve timing (VVT) assembly (<NUM>) for one or more cylinders of an internal combustion engine that includes a pedestal (<NUM>), the VVT assembly <NUM> configured to operatively engage an intake valve to extend a duration of the intake valve in an open position in response to an extended duration mode of operation, wherein the VVT assembly (<NUM>) includes:
an intake rocker (<NUM>) mounted on the pedestal (<NUM>), the intake rocker operable by a cam lobe (<NUM>) to open and close the intake valve;
a lever extension (<NUM>, <NUM>) extending from the intake rocker;
a holding member (<NUM>, <NUM>', <NUM>) extendable from the pedestal (<NUM>) and lockable in position by a hydraulic circuit in the pedestal (<NUM>) to contact the lever extension (<NUM>, <NUM>) and hold the intake valve in the open position during the extended duration mode of operation; and
a reset pin (<NUM>, <NUM>' <NUM>) movable in the pedestal and actuatable by the cam lobe (<NUM>) to release the holding member (<NUM>, <NUM>', <NUM>) to allow the intake valve to close.