Patent ID: 12188384

DETAILED DESCRIPTION

A latch assembly500can comprise at least one main latch pin assembly531and at least one secondary latch piston541. Several Figures show first and second main latch pin assemblies531,532working together with first and second secondary latch pistons541,561. While a receptacle wall can be used to form a system for the single main latch pin assembly531and single secondary latch piston541, the illustration comprising pairs can reduce the spring force of pin springs519,529and actuation force of actuation fluid to a pair of secondary latch pistons541,561. For convenience, the first and second main latch pin assemblies531,532can be referred to as outer latch pins while the secondary latch pistons541,561can be referred to as inner pistons.

First and second main latch pin assemblies531,532can comprise first and second latch pins501,502with pin bodies511,521comprising a first diameter D1on a first main pin face512,522. Secondary latch pistons541,561can comprise piston bodies542,562comprising a second diameter D2on a secondary piston face543,563. The first diameter D1can be greater than the second diameter D2(D1>D2). This relationship can be true even if the main latch pin assemblies531,532comprise a main pin body511,521that is stepped from an outer diameter OD1to the first diameter. Outer step514,524can be formed. Several optional benefits can be implemented: the primary latch bores105,125can have a greater diameter than the first diameter to give stability to the primary latch pin assemblies; the pin springs519,529can be wider to yield flexibility in the spring force k; and, the outer steps514,524can serve to set lash for the rocker arm assembly10. Additional features on the main pin bodies511,521can comprise at least one anti-rotation flat515,525. Also, a spring cup516,526can guide the pin springs519,529as they expand and collapse against the bushing or snap ring517,527seated in guide grooves135,136of the primary arm latch bores105,125. Additional spring guides518,528, as necks or grooves, can be formed in the bushing or snap ring517,527. The travel of the main pin bodies511,521in the primary latch bores105,125can be restricted by the placement of the bushings or snap rings517,527.

The secondary latch pistons541,561can be configured to selectively act on the main latching pin assemblies531,532. In the Figures, this is accomplished via actuation fluid from a rocker shaft to the rocker bores. The main latch pin assemblies531,532, by the pin springs519,529, can be biased to oppose the secondary latch pistons541,561.

The secondary latch pistons541,561can comprise piston bodies542,562cupped to receive an actuation fluid. A cavity544,564can be formed in each piston body542,562to receive the actuation fluid. The piston bodies542,562can be crenelated or gapped to form an actuation fluid passage548,568. Teeth545,565spaced with gaps are one way to form the actuation fluid passages548,568. An optional piston spring546can push the secondary latch pistons541,561apart by a preset amount that is typically overcome by the pin springs519,529. But, the optional piston spring546can prime the motion of the secondary latch pistons541,561. The optional piston spring546can push the piston facings543,563to contact the main pin facings512,522.

A rocker arm assembly10can comprise the latch assembly500. A primary arm100can be configured to receive one or both main latch pin assembly531,532. A secondary arm300can be configured to receive one or both secondary latch piston541,562. By splitting the primary rocker arm body101to comprise a pivot slot102, the secondary arm300can pivot around a rocker shaft (with or without optional bushing200) in the pivot slot102. The split primary rocker arm100can also form mirror image portions for housing the first and second main latch pin assemblies531,532. The mirror image portions can flank a portion of the secondary rocker arm body301. So, a latch shelf104can be formed as part of the primary rocker arm body101. The latch shelf104can comprise a pair of primary latch bores105,125. A portion of the latch shelf104can comprise a primary travel limit107.

The primary arm100can comprise the latch shelf104proximal a primary rocker shaft bore108. The main latch pin assembly531,532can be installed in a primary latch bores105,125in the latch shelf104. Lubrication ports to the primary latch bores105,125from the primary rocker shaft bore108are optional.

The secondary arm300can comprise a latch extension304proximal a secondary rocker shaft bore308. The secondary latch pistons541,561can be installed in a secondary latch bore305in the latch extension304.

The primary arm100can comprise a primary travel limit107. The secondary arm300can comprise a secondary travel limit307. The secondary travel limit307can contact the primary travel limit107when the latch assembly500is latched (FIG.4). But, the secondary travel limit307can be configured to swing away from the primary travel limit107when the latch assembly is unlatched (FIGS.5-7). The primary travel limit107can comprise a wall or prong or finger of material of the latch shelf104. A complementary wall or prong or finger of material on the latch extension304can be shaped to abut the primary travel limit107. Lightweighting and durability can be factors in the size and shape of the complementing primary travel limit107and secondary travel limit307. In another aspect, the cooperation of the primary travel limit107and secondary travel limit307serve to smooth latching and unlatching of the latch assembly500. By restricting overtravel of the primary arm100relative to the secondary arm300, the primary latch bore105,125aligns readily with the secondary latch bore305. By forming bore steps351,352in the secondary latch bore305, lash take-up can be designed into the rocker arm assembly10. Lash take-up can also be designed into the rocker arm assembly10by way of the outer step514,524on the pin bodies511,521.

The latch shelf104can comprise one or more anti-rotation bore106and one or more anti-rotation pin551,552installed in the anti-rotation bores106. Then, the outer steps514,524can assuredly align with the bore steps351,352when outer flats515,525are aligned with the anti-rotation pins551,552. When the first and second secondary latch pistons541,561act on the first and second main latch pin assemblies531,532, the at least one anti-rotation outer flat515,525is configured to reciprocate (slide) across the anti-rotation pin551,552.

The secondary latch bore305can be stepped from a first inner diameter ID1guiding the piston bodies542,562or the secondary latch pistons541,561to a second inner diameter ID2that is larger than the first inner diameter (ID2>ID1). The main latch pin assembly531,532can comprise the main latch pins501,502with main pin bodies511,512stepped from an outer diameter to the first diameter D1. The outer step514,524so formed can abut the second inner diameter ID2when the secondary latch piston541,561is passive. The primary latch pin assembly512,522can be biased to abut the second inner diameter ID2when the secondary latch piston541,561is passive. No actuation fluid pressure is supplied to the cavity544,564in the passive condition. But, actuation fluid is supplied from a rocker shaft to one of the bushing ports201of optional bushing200or is supplied directly to a latch oil actuation port306in the secondary body301to cause the first and second secondary latch pistons541,561to act on the first and second main latch pin assemblies531,532. Optionally, a rocker shaft can supply lubrication fluid to oil ports309to lubricate a roller bearing312on a bearing pin313installed in bearing mounts311. Bearing end310can optionally include a cross-drill or vent315connected to oil ports309. Bearing end310can alternatively comprise a tappet or other sliding surface.

The rocker arm assembly10can comprise a lost motion spring assembly400spanning from the primary arm100to the secondary arm300. The lost motion spring assembly400can bias the latch extension304towards the latch shelf104so that the primary travel limit107contacts the secondary travel limit307during a portion of the valve cycle. The lost motion spring assembly400can comprise a spring guide413and plunger424secured by mounting pins401,402at one of pivot knees103,303. A swivel end411can comprise a pin hole412for mounting pin401while stay end422comprises pin slot423for mounting pin402. Lost motion spring403pushes the swivel end411and stay end422apart to return the rocker arm assembly to a position where the latch assembly500is aligned for latching or unlatching. But, lost motion spring403can be compressed when the latch assembly500is unlatched so that a lift profile is absorbed therein.

The rocker arm assembly10can comprise a bearing end310on the secondary arm300and a valve end110,120on the primary arm100. The bearing end310, the valve end110,120, and the latch assembly500can be configured to surround a rocker shaft in a triangular distribution. The rocker shaft being mountable in the primary rocker shaft bore108and the secondary rocker shaft bore308, this can also be phrased that the bearing end310, the valve end110,120, and the latch assembly500can be configured to surround the primary rocker shaft bore108and the secondary rocker shaft bore308in a triangular distribution. Said yet another way, while the lost motion spring assembly400is balanced over the primary rocker shaft bore108and the secondary rocker shaft bore308and the bearing end310, the latch assembly500is balanced under the primary rocker shaft bore108and the secondary rocker shaft bore308. The actuation fluid and latch assembly500do not interfere with actuation fluid to any capsule or actuation in the valve end110,120, nor do they interfere with ordinary lubrication circuits. The location under the primary rocker shaft bore108and the secondary rocker shaft bore308yields a low-conflict area of the rocker arm assembly10to add deactivation mechanisms.

As an option, the valve end110can comprise a capsule bore111. An actuation capsule such as a castellation capsule, a hydraulic lash adjuster, a switching capsule, among many options can be installed in the capsule bore111. InFIG.1, a mechanical lash device is shown to comprise a spigot assembly112with a lash nut113, a lash pin116, and an elephant foot (e-foot)114. An optional vent115is included in the valve end110. InFIG.3, the primary body101is more simply illustrated with a valve end120comprising a knurl124to actuate on a valve stem or valve bridge.

The primary arm100can comprise an optional lubrication port to the main latch pin assemblies501,502. The secondary arm300can comprise an actuation port306to the secondary latch pistons541,561. The secondary latch pistons541,561can comprise a piston body542,562cupped to receive actuation fluid. The actuation fluid can be, for example, hydraulic fluid such as pressurized oil.

A latch assembly500disclosed herein provides a more reliable latching and unlatching function in a rocker arm assembly10such as a deactivating roller rocker arm (RRA) when the loads could otherwise cause the latching pins to stick.

Hydraulic activation of the latching function can be ported through the rocker arm assembly10by way of a rocker shaft with the hydraulic activation contained in the rocker arm assembly10. Then, external hoses and actuators are not mandatory. The main latch pin assemblies531,532are in a normally latched condition thanks to the reaction of the pin springs519,529. Since the function activation is not directly applied on them, this allows a longer guided length of the pin bodies511,521. The first and second secondary latch pistons541,561do not receive the latching load but do receive the force of the oil during activation of the deactivation function of the RRA. With no latching load applied, these first and second secondary latch pistons541,561can be smaller. The combination of the two latching systems to form the latch assembly500allows the rocker arm assembly10to transmit the cam lift to the valve when the latch assembly500is engaged (latched) and allows the rocker arm assembly500to not transmit motion to the valve when the first and second secondary latch pistons541,561receive hydraulic pressure to disengage the main latch pin assemblies531,532.

The rocker arm assembly10can be made by the primary arm100that provides the case for the main latch pin assemblies531,532and the pin springs519,529and the secondary arm300that provides the case for the first and second secondary latch pistons541,561and the oil gallery for the function activation. The secondary arm can also provide a latching feature for the main latch pin assemblies531,532, as by diameter changes to the secondary latch bore305.

DRIVE MODE:FIG.4shows that in this condition the main latch pin assemblies531,532are pushed to jut out of the primary arm100thanks to the pin springs519,529and they are latched on the secondary latch bore305(which can include the second inner diameter ID2latching feature on the secondary arm300). The secondary latch pistons541,561are retracted inside the secondary arm300since they do not receive any pressure from the oil actuation port306. In this configuration, when a cam rotates from base circle to a lift lobe, the motion is transmitted to the valve thanks to the connection provided by the main latch pin assemblies531,532on the secondary arm300.

FUNCTION ACTIVATION: when the deactivation of the rocker arm assembly10is selected, an oil input is sent to the oil actuation port306in the secondary arm300. This allows the secondary latch pistons541,561to expand and push against the main latch pin assemblies531,532. When the cam is on base circle, a geometrical lash between the main latch pin assemblies531,532and the latching feature on the secondary arm300is provided. The geometrical lash can be a designed—for gap between the main latch pin assemblies531,532and the second inner diameter ID2. When included, this can be a designed—for gap between outer step514,524and inner diameter ID2. In this condition, it is possible for the secondary latch pistons541,561to compress the main latch pin assemblies531,532and disengage the primary arm100from the secondary arm300. This is shown inFIG.5. As for timing, when the cam is on a lift lobe, if the main latch pin assemblies531,532are still engaged, the force between the main latch pin assemblies531,532and the secondary arm300latching feature is higher than the force from the actuation oil on the secondary latch pistons541,561and the disengagement is not provided. The latch assembly500does not convert from latched to unlatched if the actuation oil is provided during lift, but it can convert on base circle when the geometrical lash takes pressure from the secondary arm300off of main latch pin assemblies531,532. Functions for the rocker arm assembly10can include various variable valve actuation (VVA) techniques such as cylinder deactivation, braking, internal exhaust gas recirculation, early or late valve opening or closing, etc. Additional inner diameters can be included as the additional latching features to enable the other VVA techniques. For example, instead of valve deactivation, a different valve lift can be supplied as the VVA technique by stepping the main latch pin assemblies531,532from an initial smaller inner diameter to a larger inner diameter. Deactivation mode is the working example, but it is not exclusive.

DEACTIVATION MODE: when the secondary latch pistons541,561are fully extended, the main latch pin assemblies531,532are not able to engage with the latching feature on the secondary arm300. This allows a relative motion between the secondary arm300and the primary arm100that can be seen inFIGS.6&7. When the cam rotates on the lift lobe, the secondary arm300starts its rocking, but it does not transmit the motion to the primary arm100. The secondary arm300instead rocks in the pivot slot102while the primary arm100stays steady and the valve(s) remains closed. To avoid lift-off of the secondary arm300from the cam, a spring based lost motion assembly400can provide enough load from the secondary arm300to the cam. The spring force of lost motion spring403can be small enough so that it does not transmit motion to the valve. The balance of the lost motion assembly400over the cam end310, and the placement of the primary pivot knees103anterior to the latch assembly500and secondary rocker shaft bore308, can concentrate the weight and force of the lost motion assembly400over the cam end310. The cam end can follow the cam and can return to the contacting of primary travel limit107and secondary travel limit307.

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