An engine brake assembly

Abstract

An engine brake rocker arm assembly (RA) including a rocker arm (11) arranged to rock in response to a cam supported by a cam shaft in order to press down at least an exhaust valve, a shaft (20) slidingly arranged in an end of the rocker arm, having a first end provided of an interface (16, 21) towards said exhaust valve and a second end, opposite to the first one, provided of a travel stop (24). Castellation members (30, 40, 50) include frontal teeth suitable to mesh reciprocally, such that the capsule is suitable to assume an extended configuration and a collapsed configuration respectively according to a tooth-to-tooth or tooth- to-valley meshing, under the action of an actuator (70) suitable to rotate at least a member of the castellation capsule with respect to another in such a way to force the castellation capsule in said extended and collapsed conditions, a resilient element (60) arranged to bias the castellation members away from each other, wherein the rocker arm includes a seat (90) filled with oil to define a cushion capable to dampen the travel stop (24).

Description

[0001] DESCRIPTION

[0002] "AN ENGINE BRAKE ASSEMBLY"

[0003] Field of the invention

[0004] The present invention relates to the field of engine brake actuation systems, in the field of medium and heavy- duty vehicles .

[0005] Description of the prior art

[0006] Compression engine brakes can be used as auxiliary brakes, in addition to wheel brakes, on relatively large vehicles, for example trucks, powered by heavy or medium duty diesel engines. During engine brake operation, the engine is not fueled and a compression engine braking strategy is actuated, to provide an additional opening of an engine cylinder's exhaust valve when the piston in that cylinder is near to a top-dead-center position of its compression stroke so that compressed air is released through the exhaust valve.

[0007] This causes that the air trapped in the cylinder cannot return the compression energy accumulated during compression. Thus, the engine works as an air compressor and the torque consumed slows the vehicle.

[0008] In a typical valve train assembly used with a compression engine brake, the exhaust valve is actuated by a rocker arm which engages the exhaust valve by means of a valve bridge . The rocker arm rocks in response to a cam on a rotating cam shaft and presses down on the valve bridge which in turn presses down on the exhaust valves to open them .

[0009] In several rocker arm assembly, an oil circuit pressuri zes a mechanism which pushes selectively an exhaust valve during engine brake .

[0010] EATON INTELLIGENT POWER LTD has developed several solutions , commercially available on the market .

[0011] The Eaton® solution is mainly based on a castellation assembly as disclosed in WO2022248082A1 and WO2019133658 .

[0012] Here an actuator is arranged to rotate a first castellation member in such a way that its axial teeth face the axial teeth of a second castellation member or the valleys between the teeth .

[0013] The first castellation member is rotatably mounted on a shaft fixed with the rocker arm .

[0014] In the first case , teeth-to-teeth, the two castellation members develop the maximal extens ion of the shaft so as to activate the exhaust valve , while in the second case , teeth-to-valleys , the second castellation collapses in the first one . In the last period, EATON developed a new solution disclosed in US 11428127B2 . Here , there are three castellation members mounted on a shaft .

[0015] The third castellation member biases the first and second castellation members apart . The engine brake rocker arm assembly selectively opens first and second exhaust valves and includes an exhaust rocker arm configured to rotate about the rocker shaft . An engine brake capsule assembly is movable between a locked position and is configured to perform an engine braking operation, and an unlocked position that does not perform the engine braking operation, and a hydraulically controlled actuator assembly is configured to selectively move the engine brake capsule assembly between the first and second configurations .

[0016] The actuator assembly includes a pin arranged to rotate the first castellation member of the engine brake capsule assembly . In the fired condition, namely when the engine brake operation is deactivated, the castellation shaft is configured to slide within the lash adj ustment screw .

[0017] Figures la and lb of the prior art , corresponding to figures 3a and 3b of US 11428127B2 , disclose two configurations of the castellation shaft with respect to the rocker arm . Here the engine brake capsule can be af fixed to the same rocker arm operating the valve bridges as disclosed in WO2019133658 , or can be af fixed to a secondary rocker arm as in W02021164950 .

[0018] According to those solutions , the main problem is in the fact that the nut arranged to adj ust the position of the shaft , often named as "travel stop" , impacts on the seat of the capsule in each swinging operation of the rocker arm in the fired condition .

[0019] These impacts produce noise and lead to the damaging of the assembly rocker / capsule .

[0020] Therefore , it is possible to summari ze the present context as an engine brake capsule assembly comprising at least two castellation members provided with axial teeth . One of the castellation members is arranged to rotate in such a way that the axial teeth face the axial teeth of the other castellation member or the corresponding valleys . Therefore , the two possible conf igurations are "tooth-to- tooth" or " tooth-to-valley" .

[0021] An actuator is arranged to tangentially contact and rotate the rotating castellation member to control the angular position of it with respect to the other castellation member . The castellation members are arranged on a shaft provided of a nut of the lash adj ustment screw . In fired operating conditions , the nut alternately departs and approaches the rocker arm, due to the fact that the castellation capsule can collapse . This alternate movement leads to producing impacts , noise and damages .

[0022] US 11428127B2 and WO2021164950 are herewith included by reference .

[0023] Unless speci fically excluded in the detailed description that follows , what is described in this chapter is to be considered as an integral part of the present detailed description .

[0024] Summary of the invention

[0025] The main obj ect of the present invention is to overcome the above problems / drawbacks in the solution proposed and commerciali zed by EATON® .

[0026] The main principle of the invention is the implementation of an oil cushion to dampen the adj ustment screw .

[0027] In particular, in the rocker arm where the brake capsule is housed, a seat is reali zed filled with oil coming from an oil source . A channel reali zed in the rocker arm supplies the seat with oil . The channel has at least one outlet in the seat , which represents an oi l inlet for the seat . In addition, the seat has at least one oil outlet .

[0028] While the seat oil inlet is closed by the nut , when the nut is seated in the seat , the oil outlet is always open in order to permit the oil to outflow even during the approaching motion of the nut to the seat .

[0029] Preferably, the seat has a circa cylindrical shape and the outlet is reali zed through at least one lateral wall inclined from the base of the seat , such that the oil can escape from the seat due to the approaching movement of the nut .

[0030] It should be considered that the valvetrain is arranged in a closed compartment defined in the head of the engine and that the oil supplied to the valvetrain flows to the oil sump, from where a pump withdraws the oil and pumps it in the main gallery connected hydraulically with the valvetrain and, in particular, with the rocker arm supporting the brake capsule .

[0031] These and further obj ects are achieved by means of the attached claims , which describe preferred embodiments of the invention, forming an integral part of the present description .

[0032] Brief description of the drawings

[0033] The invention will become fully clear from the following detailed description, given by way of a mere exempli fying and non limiting example , to be read with reference to the attached drawing figures , wherein :

[0034] Figs , la and lb of the prior art disclose an example of brake, switchable, capsule from EATON® in two opposites conditions while the engine is operated not in braking mode, namely it is fired or dragged;

[0035] Fig. 2 discloses a perspective view of an example of rocker arm supporting a brake, switchable, capsule;

[0036] Figs. 3a - 3c disclose a portion of a valvetrain, including cross-sections of a rocker arm assembly together with a switchable capsule of a rocker arm, according to different operating conditions;

[0037] Fig. 4 discloses a top view of the rocker assembly of figure 3 centered on the nut of the brake switchable capsule ;

[0038] Fig. 5 discloses a longitudinal section of the portion of the valvetrain of the previous figures.

[0039] The same reference numerals and letters in the figures designate the same or functionally equivalent parts.

[0040] According to the present invention, the term "second element" does not imply the presence of a "first element", first, second, etc.. are used only for improving the clarity of the description and they should not be interpreted in a limiting way.

[0041] Detailed description of the preferred embodiments

[0042] As disclosed above, the present invention aims at solving the impacts between the nut of the lash adjustment screw against the upper portion of the rocker arm .

[0043] In FIGS . 1A and IB, a first castellation device 1 constitutes a mechanical capsule comprising an annular shroud 80 coupled to a rack 75 of an actuator 70 . This mechanical capsule can be drop-in assembled in a capsule bore 17 ( see fig . 2 ) . A bore end 171 comprises a lash bore 172 through hole , through which the shaft 20 can slide . Rocker arm 11 is shown to comprise the capsule bore 17 with a positioning washer 18 and snap ring 19 to hold the castellation device 1 within . Return spring 60 and the castellation members 30 , 50 , 40 can be dropped into the capsule bore 17 , with shaft 20 threaded therethrough . Washer 18 and snap ring 19 , or other locking device such as a set screw, pressed bushing, among others , prevents the castellation device 1 from falling out of the capsule bore 17 . Washer 18 or snap ring 19 or other locking device can serve as a travel limit for shaft 20 , as by obstructing the travel of press foot 21 or e- foot ( elephant foot ) 16 .

[0044] A bias spring 60 is disposed between the second castellation member and the third castellation member and is configured to bias the second castellation member away from the third castellation member such that the castellation capsule assumes an extended configuration .

[0045] A lash sleeve 23 , or lash adj ustment screw is fitted or fixed, as by threading or press- f itting, to a lash end 22 of shaft 20 . Lash sleeve 23 can be positioned on shaft 20 to control the lash of the castel lation device 1 . A travel stop 24 can be included to catch on the lash bore 172 or bore end 171 . Shaft 20 comprises a press foot 21 configured to press on a valve stem, valve bridge , other rocker arm, or other valvetrain component , to reali ze the compressed air release of the engine brake operation . An e- foot arrangement 16 can also be accomplished on the shaft 20 as by attaching the appropriate socket arrangement to the shaft 20 .

[0046] When the castellation members are collapsed, in the tooth- to-valley configuration, the shaft 20 is free to slide within the bore . In particular, when the rocker arm tries to push down the stem of the exhaust valve , the spring of the exhaust valve is more rigid than the spring 60 of the castellation capsule 1 , therefore , the castellation capsule collapses and the shaft 20 sl ides axially within the capsule in response to the approaching of the rocker arm to the exhaust valve stem as clear from the comparison of figures la and lb .

[0047] In contrast , when the castellation members are extended, in the tooth-to-tooth configuration, the e- foot is forced to depart from the rocker arm, thus the approaching movement of the rocker arm is such that to push down the exhaust valve stem as disclosed in figure la .

[0048] The rack 75 of an actuator 70 is coupled to one of the castellation members .

[0049] The actuator 70 defines "rack and pinion" type arrangement such as an axial movement of the actuator forces one of the castellation members to rotate . Being the EATON product already on the market and wel l disclosed in several patents , no further details are needed .

[0050] With reference to figure 3 , the rocker arm 11 is provided also of

[0051] A seat 90 , complementary with the lash end 22 of shaft 20 ; an oil channel 93 arranged to fi ll the seat 90 with hydraulic oil ; and the seat comprises an outlet opening 92 arranged to discharge the oil at least when the lash end 22 approaches the seat .

[0052] The outlet opening 92 is shaped-calibrated so as the oil in the seat defines a cushion capable to dampen the end 22 approaching, and at the same time to permit the lash end to interpenetrate the seat .

[0053] Preferably, the end 22 of the shaft defines a sort of nut with flat shaped faces in order to be screwed on the shaft 20 to permit the lash adj usting .

[0054] The lower portion 24 of the end 22 of the shaft 20 that interpenetrate the seat is preferably cylindrical shaped .

[0055] The lower portion 24 of the end 22 is shaped in such a way that when approaching the seat 90 , it closes the inlet opening 91 communicating with the channel 93 .

[0056] Therefore , in a first approaching phase , the lower portion 24 closes the inlet 91 , and then it pushes the oil outside through the outlet 92 .

[0057] The top view of figure 4 discloses the end portion 22 defined by a hexagonal nut and three outlet opening 92 reali zed in the peripheral wall of the seat .

[0058] It is clear that preferably the seat is defined by a blind cylindrical opening with a through hole in its center in order to permit the accommodation of the shaft 20 , and the lower portion 24 of the end 22 of the shaft 20 has also a cylindrical shape complementary with the seat , with the exception of the outlet openings 92 .

[0059] The section of the outlet openings 92 reduces towards the base face of the cylindrical shape of the seat , in such a way to slow down the oil flow in the last phase of the end 22 approaching the seat .

[0060] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those skilled in the art . Numerous speci fic details are set forth such as examples of speci fic components , devices , and methods , to provide a thorough understanding of embodiments of the present disclosure . It will be apparent to those skilled in the art that speci f ic details need not be described, that example embodiments may be embodied in many di f ferent forms and that neither should be construed to limit the scope of the disclosure . In some example embodiments , well known processes , well-known device structures , and well known technologies are not described in detail .

[0061] Many changes , modi fications , variations and other uses and applications of the subj ect invention will become apparent to those skilled in the art after considering the speci fication and the accompanying drawings which disclose preferred embodiments thereof as described in the appended claims .

[0062] The features disclosed in the prior art background are introduced only in order to better understand the invention and not as a declaration about the existence of known prior art . In addition, said features define the context of the present invention, thus such features shall be considered in common with the detailed description .

[0063] Further implementation details will not be described, as the man skilled in the art is able to carry out the invention starting from the teaching of the above description .

Claims

CLAIMS1 . An engine brake assembly (RA) including- a rocker arm ( 11) arranged to rock in response to a cam supported by a cam shaft in order to press down at least an exhaust valve,- a shaft (20) slidingly arranged in an end of the rocker arm, having a first end provided of an interface (16, 21 ) towards said exhaust valve and a second end, opposite to the first one, provided of a travel stop (24 ) , the shaft being supported by a- castellation capsule ( 1 ) comprising castellation members (30, 40, 50) including frontal teeth suitable to mesh reciprocally, such that the capsule is suitable to assume an extended configuration and a collapsed configuration respectively according to a tooth-to-tooth or tooth-to-valley meshing, under the action of- an actuator (70) suitable to rotate at least a member of the castellation capsule with respect to another in such a way to force the castellation capsule in said extended and collapsed conditions,- a resilient element ( 60) arranged to bias the castellation members away from each other,Wherein the rocker arm includes+ a seat ( 90 ) , complementary with the travel stop ( 24 ) , arranged in such a way that the travel ( 24 ) stop of theshaft (20) interpenetrates the seat during rocker arm departing from the exhaust valve, and+ an oil channel (93) arranged within the rocker arm to fill the seat (90) with hydraulic oil and wherein the seat includes at least an outlet opening (92) , shaped-calibrated to permit oil outflow so as the oil in the seat defines a cushion capable to dampen the travel stop (24) approaching.

2. Assembly according to claim 1, wherein the seat includes at least an outlet opening (92) shaped-calibrated to permit the oil to escape the seat during the travel stop approaching .

3. Assembly according to claim 2, wherein the travel stop is shaped as a hexagonal nut and three outlet opening (92) realized in the peripheral wall of the seat.

4. Assembly according to claim 2 or 3, wherein a section of the outlet opening (92) reduces towards the bottom face of the cylindrical shape of the seat, in such a way to slow down the oil flow in a last phase of the travel stop (24) approaching the bottom face of the seat.

5. Assembly according to anyone of the previous claims, wherein said oil channel (93) has on outlet opening (91) and wherein the travel stop (24) is arranged to close the outlet (91) while approaching the bottom face of the seat.6 . Assembly according to claim 5 depending on claim 4 , wherein the at least one outlet opening and the inlet opening ( 91 ) are arranged in such a way that the travel stop closes the inlet opening before the end of the approaching movement towards the bottom face of the seat .7 . Combustion engine comprising an engine brake system including the assembly of anyone o f the previous claims 1 -6 .

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