Dedicated rocker arm assembly for engine exhaust braking

Abstract

An embodiment of a rocker arm may include a hydraulic unit comprising: a hydraulic unit housing; a valve pin configured to move between an initial position and a lifted position in response to pressurized fluid in an upper chamber; a control valve assembly in a lower chamber, configured to selectively place the upper chamber and the lower chamber in fluid communication; a brake plunger configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; and a reset assembly coupled to the housing, the reset assembly comprising: a retaining sleeve comprising (i) an outer peripheral wall configured to lock to an exterior surface of the housing and (ii) a bottom wall with an opening configured for the brake plunger to pass through, and a return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

Description

ATTORNEY DOCKET PATENT APPLICATION 006976.23691 of 29Dedicated Rocker Arm Assembly for Engine Exhaust BrakingTECHNICAL FIELD

[0001] This disclosure relates to a rocker arm assembly in an engine valvetrain system, and more particularly to an engine-brake rocker arm that includes an integral hydraulic capsule.BACKGROUND

[0002] Engines typically use mechanical, electronic, or hydraulic valve actuation systems to actuate engine valves. Such systems may include combinations of camshafts, rocker arms, and pushrods, which are driven by rotation of the engine crankshaft. When a camshaft is used to actuate engine valves, the timing of valve actuation is determined by the size and position of cam lobes on the camshaft.

[0003] For each complete revolution of the camshaft, the engine completes a full cycle consisting of four strokes (i.e., expansion, exhaust, intake, and compression). During most of the expansion stroke, in which the piston moves away from the cylinder head (i.e., the volume between the cylinder head and the piston crown increases), both the intake valve and the exhaust valve are closed and remain closed. In a driving mode, fuel is combusted during the expansion stroke, enabling the engine to deliver positive power. The expansion stroke ends at bottom dead center, at which point the piston reverses direction and the exhaust valve may be opened to perform a main exhaust event. As the piston travels upward, the cam lobe on the camshaft operates in synchronization to open the exhaust valve during the main exhaust event, thereby forcing combustion gases out of the cylinder.

[0004] When the engine operates in the driving mode, the above-described main exhaust valve event is required. In addition, it may sometimes be desirable to have additional auxiliary valve events, although such events are not strictly required. For example, it may be desirable to actuate the exhaust valve for compression-release engine braking or for other auxiliary valve events to switch the engine into a braking mode, which is a particularly important and beneficial function when a commercial vehicle equipped with such an engine is traveling on long downhill grades.ATTORNEY DOCKET PATENT APPLICATION 006976.23692 of 29

[0005] During compression-release engine braking, the exhaust valve may be selectively opened to at least temporarily convert a power-producing internal combustion engine into a power-absorbing air compressor. During the compression stroke, as the piston moves upward, gas trapped within the cylinder is compressed. The compressed gas resists the upward movement of the piston. When the piston approaches top dead center, at least one exhaust valve may be opened to release the compressed gas from the cylinder into the exhaust manifold, thereby preventing the energy stored in the compressed gas from being returned to the engine during the subsequent expansion downstroke. In this process, the engine generates a decelerating force that assists in slowing the vehicle.

[0006] As a valve rocker arm assembly for implementing compression-release engine braking, U.S. Pat. No. US5564385 discloses a method and apparatus for engine deceleration in a multicylinder internal combustion engine. The apparatus includes a hydraulic lash adjuster that adjusts lash in a valve controller in response to hydraulic fluid pressure below a predetermined maximum value. The angular position of the engine crankshaft (at which an exhaust valve in one of the engine cylinders is actuated by an additional lobe on the camshaft) is determined by the lash in the valve controller. A pressure relief valve maintains hydraulic fluid pressure below the predetermined maximum value, and the controller progressively reduces the lash to zero while maintaining the hydraulic fluid pressure in the valve controller below the predetermined maximum value, thereby substantially reducing the risk of actuating the exhaust valve during periods when cylinder pressure exceeds a predetermined elevated cylinder pressure.

[0007] As an improvement to the above-described engine braking apparatus, Chinese Patent Application Publication No. CN 102414403 A discloses a swing-type engine brake. The engine brake mechanism includes a rocker shaft having a control fluid supply passage, and an exhaust rocker arm pivotally mounted on the rocker shaft. A cam for applying a main exhaust valve actuation operation to the exhaust rocker arm contacts a cam roller associated with the exhaust rocker arm. A valve bridge may be disposed between the exhaust rocker arm and first and second engine valves. A sliding pin may be provided in the valve bridge, with the sliding pin contacting the first engine valve. An engine brake rocker arm may be pivotally mounted on the rocker shaft adjacent to the exhaust rocker arm. The engine brake rocker arm may include a central opening, a hydraulic passage connecting the central opening to a control valve, and a fluid passage connecting the control valve to an actuating piston assembly. The actuating pistonATTORNEY DOCKET PATENT APPLICATION 006976.23693 of 29assembly includes an actuating piston adapted to contact the sliding pin during an engine braking operation. A bushing may be disposed between the engine brake rocker arm and the rocker shaft, the bushing having ports aligned with the hydraulic passages. A cam is provided to apply an engine braking actuation operation to the engine brake rocker arm. A plate is fastened to a rear end of the engine brake rocker arm, and a spring biases the plate and the engine brake rocker arm into contact with the cam.

[0008] The above-described engine braking devices are capable of reliably switching between a main exhaust valve event and auxiliary valve events, such as engine braking events, under hydraulic system control. However, known designs still suffer from the following drawbacks:

[0009] In known engine braking devices, the hydraulic actuating mechanism requires an oil control valve (OCV) to be integrated within the rocker arm, which increases manufacturing cost and assembly complexity of the rocker arm. Moreover, such integrated OCVs are believed to adversely increase the likelihood of failure during long-term operation of the rocker arm.

[0010] In known engine braking devices, the plunger of the hydraulic actuating mechanism is not provided with a retention mechanism. That is, when high hydraulic oil pressure required to maintain the plunger in an extended state is absent, the plunger remains in a default “floating” extended condition. As a result, even when the braking device is deactivated, undesired contact with the valve bridge may occur, leading to wear within the system and shortening the service life of the components.

[0011] Accordingly, there is a need to provide a rocker arm assembly that is easier to assemble and manufacture, that has a more simplified overall structure and reduced weight, and that includes a plunger retention function to effectively prevent undesired contact with the valve bridge.SUMMARY OF PARTICULAR EMBODIMENTS

[0012] This disclosure presents in general a valvetrain system configured with an engine brake hydraulic unit for achieving engine braking functionality. Accordingly, an object of the present disclosure is to provide a rocker arm assembly for engine exhaust braking, thereby overcoming the deficiencies of the prior art described above.ATTORNEY DOCKET PATENT APPLICATION 006976.23694 of 29

[0013] The following clauses provide summaries of particular embodiments described in this application. These summaries are intended to facilitate understanding of the disclosed concepts and are not exhaustive or limiting. Additional features, alternatives, and variations are described elsewhere in the specification, and any embodiment may be combined with others unless expressly stated otherwise.

[0014] Clause 1. A rocker arm assembly for engine exhaust braking, the rocker arm assembly comprising: a rocker arm having (i) an actuation side configured to engage with a cam and (ii) a valve side opposite the actuation side; and a hydraulic unit disposed in a hydraulic unit receiving bore on the valve side of the rocker arm, the hydraulic unit comprising: a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upper chamber; a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber; a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position; a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; and a reset assembly coupled to the hydraulic unit housing, the reset assembly comprising: a retaining sleeve comprising (i) an outer peripheral wall configured to lock to an exterior surface of the hydraulic unit housing and (ii) a bottom wall with an opening configured for the brake plunger to pass through; and a return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

[0015] Clause 2. The rocker arm assembly of clause 1, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridge is greater than a maximum valve lift of the cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

[0016] Clause 3. The rocker arm assembly of any one of the preceding clauses, wherein the outer peripheral wall of the retaining sleeve is configured to be clamped between the hydraulic unit housing and the hydraulic unit receiving bore.

[0017] Clause 4. The rocker arm assembly of any one of the preceding clauses, wherein the reset assembly further comprises a snap ring disposed on an inner wall of the hydraulic unitATTORNEY DOCKET PATENT APPLICATION 006976.23695 of 29housing between the first and second ends of the return spring, the snap ring being configured to prevent the brake plunger from extending beyond the extended position.

[0018] Clause 5. The rocker arm assembly of any one of the preceding clauses, wherein the outer peripheral wall of the retaining sleeve includes a plurality of inwardly protruding retention tabs, wherein when the retaining sleeve is installed between the hydraulic unit housing and the hydraulic unit receiving bore of the valve side, the inwardly protruding retention tabs engage with annular grooves on the exterior surface of the hydraulic unit housing, thereby securing the retaining sleeve between the hydraulic unit housing and the hydraulic unit receiving bore.

[0019] Clause 6. The rocker arm assembly of any one of the preceding clauses, further comprising a shim plate disposed in the upper chamber of the hydraulic unit housing and a retaining ring axially securing the shim plate in the upper chamber, wherein a spring is disposed between the shim plate and the valve pin to maintain the valve pin in its initial position, and wherein the shim plate is configured to adjust an elastic force applied by the spring to the valve pin.

[0020] Clause 7. The rocker arm assembly of any one of the preceding clauses, further comprising a lock nut engaged above the shim plate to an exterior of the hydraulic unit housing, wherein the lock nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm.

[0021] Clause 8. The rocker arm assembly of any one of the preceding clauses, wherein the lock nut includes a nut portion and a threaded portion to engage an exterior of the hydraulic unit housing, wherein a maximum outer diameter of the nut portion is smaller than an outer diameter of the threaded portion.

[0022] Clause 9. The rocker arm assembly of any one of the preceding clauses, wherein the control valve assembly comprises: a check ball cage disposed below an opening between the upper chamber and the lower chamber; a check ball disposed within the check ball cage, wherein the check ball has a diameter larger than the opening; and a check ball spring disposed between check ball and a bottom of the check ball cage, the check ball spring configured to bias the check ball toward the opening.

[0023] Clause 10. A hydraulic unit configured to be disposed in a hydraulic unit receiving bore on a valve side of a rocker arm for engine exhaust braking, the hydraulic unit comprising: a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upperATTORNEY DOCKET PATENT APPLICATION 006976.23696 of 29chamber; a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber; a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position; a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; and a reset assembly coupled to the hydraulic unit housing, the reset assembly comprising: a retaining sleeve comprising (i) an outer peripheral wall configured to lock to an exterior surface of the hydraulic unit housing and (ii) a bottom wall with an opening configured for the brake plunger to pass through; and a return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

[0024] Clause 11. The hydraulic unit of clause 10, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridge is greater than a maximum valve lift of a cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

[0025] Clause 12. The hydraulic unit of any one of clauses 10 to 11, wherein the outer peripheral wall of the retaining sleeve is configured to be clamped between the hydraulic unit housing and the hydraulic unit receiving bore.

[0026] Clause 13. The hydraulic unit of any one of clauses 10 to 12, wherein the reset assembly further comprises a snap ring disposed on an inner wall of the hydraulic unit housing between the first and second ends of the return spring, the snap ring being configured to prevent the brake plunger from extending beyond the extended position.

[0027] Clause 14. The hydraulic unit of any one of clauses 10 to 13, wherein the outer peripheral wall of the retaining sleeve includes a plurality of inwardly protruding retention tabs, wherein when the retaining sleeve is installed between the hydraulic unit housing and the hydraulic unit receiving bore of the valve side, the inwardly protruding retention tabs engage with annular grooves on the exterior surface of the hydraulic unit housing, thereby securing the retaining sleeve between the hydraulic unit housing and the hydraulic unit receiving bore.

[0028] Clause 15. The hydraulic unit of any one of clauses 10 to 14, further comprising a lock nut engaged to an exterior of the hydraulic unit housing, wherein the lock nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm, wherein theATTORNEY DOCKET PATENT APPLICATION 006976.23697 of 29lock nut includes a nut portion and a threaded portion to engage an exterior of the hydraulic unit housing, wherein a maximum outer diameter of the nut portion is smaller than an outer diameter of the threaded portion.

[0029] Clause 16. A rocker arm assembly for engine exhaust braking, the rocker arm assembly comprising: a rocker arm having (i) an actuation side configured to engage with a cam and (ii) a valve side opposite the actuation side; and a hydraulic unit disposed in a hydraulic unit receiving bore on the valve side of the rocker arm, the hydraulic unit comprising: a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upper chamber; a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber; a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position; a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; and a reset assembly coupled to the hydraulic unit housing, the reset assembly comprising: a snap ring engaged with an inner wall of the hydraulic unit housing; a retaining sleeve comprising (i) an outer peripheral wall configured to engage an inner wall of the hydraulic unit housing by abutting the snap ring and (ii) a bottom wall with an opening configured for the brake plunger to pass through; and a return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

[0030] Clause 17. The rocker arm assembly of clause 16, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridge is greater than a maximum valve lift of the cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

[0031] Clause 18. The rocker arm assembly of any one of clauses 16 to 17, wherein the reset assembly prevents the brake plunger from extending beyond the extended position.

[0032] Clause 19. The rocker arm assembly of any one of clauses 16 to 18, further comprising a cover disposed in the upper chamber of the hydraulic unit housing and a second snap ring axially retaining the cover in the upper chamber, wherein a spring is disposed between the cover and the valve pin below it to maintain the valve pin in its initial position, and wherein the cover is configured to adjust an elastic force applied by the spring to the valve pin.ATTORNEY DOCKET PATENT APPLICATION 006976.23698 of 29

[0033] Clause 20. The rocker arm assembly of any one of clauses 16 to 19, further comprising a nut screwed onto an outer periphery of the cover and an exterior of the hydraulic unit housing, wherein the nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm.BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings, in which:

[0035] FIG. 1 is a perspective view of an embodiment of a hydraulic unit in a rocker arm assembly according to the present disclosure, in which components of the hydraulic unit of the rocker arm assembly are shown in an exploded manner for more detailed illustration.

[0036] FIG. 2 is a perspective view of an embodiment of a rocker arm assembly according to particular embodiments, in which the hydraulic unit is presented in a cross-sectional view.

[0037] FIG. 3 is a cross-sectional side view of the embodiment of the rocker arm assembly shown in FIG. 2, in which the engine is in a main exhaust valve event and the hydraulic unit is in a deactivated state.

[0038] FIG. 4 is an enlarged view of the hydraulic unit outlined by a dashed box in FIG. 3, showing the components of the hydraulic unit in greater detail.

[0039] FIG. 5 is a cross-sectional side view of the embodiment of the rocker arm assembly shown in FIG. 2, in which the engine is in an auxiliary valve event and the hydraulic unit is in an activated state.

[0040] FIG. 6 is an enlarged view of the hydraulic unit outlined by a dashed box in FIG. 5, showing the components of the hydraulic unit in greater detail.

[0041] FIG. 7 is a cross-sectional view of another embodiment of a hydraulic unit applicable to the rocker arm assembly of the present disclosure, showing the components of the hydraulic unit in detail.

[0042] FIGS. 8 and 9 are structural views of a plurality of components of the hydraulic unit shown in FIG. 7, respectively.

[0043] The following reference numerals are used in the accompanying drawings to facilitate a complete understanding of the preferred embodiments of the present invention:

[0044] 100 - Hydraulic unit

[0045] 101 - Hydraulic unit housingATTORNEY DOCKET PATENT APPLICATION 006976.23699 of 29

[0046] 102 - Valve pin

[0047] 103 - Check ball

[0048] 104 - Check ball spring

[0049] 105 - Check ball cage

[0050] 106 - Brake plunger

[0051] 107 - Return spring

[0052] 108 - Retaining sleeve

[0053] 1081 - Retention tab (Snap foot)

[0054] 109 - Locknut

[0055] 110 - Retaining ring (e.g., Snap ring)

[0056] 111 - Shim plate (e.g., Backing plate)

[0057] 112 - Spring

[0058] 113 - Retaining ring (e.g., Snap ring)

[0059] 200 - Rocker arm

[0060] 201 - Rocker shaft bore

[0061] 202 - Oil passage

[0062] 203 - Roller

[0063] 204 -Spring

[0064] 205 - Actuation side

[0065] 206 - Valve side

[0066] 300 - Valve bridge assembly

[0067] 301 - Valve bridge

[0068] 302 - Valve pin

[0069] G - Clearance or Gap

[0070] 109 A - Nut

[0071] 110A - Gland (e.g., Cover)

[0072] 111 A - Snap ring (e.g., Circlip)DESCRIPTION OF EXAMPLE EMBODIMENTS

[0073] Referring now to the accompanying drawings, illustrative embodiments of the dedicated rocker arm assembly disclosed in the present disclosure are described in detail. Although the drawings are provided to illustrate certain embodiments of the present disclosure,ATTORNEY DOCKET PATENT APPLICATION 006976.236910 of 29the drawings are not necessarily drawn to scale, and certain features may be enlarged, omitted, or shown in partial cross-section to better illustrate and explain the disclosure of the present disclosure. Components shown in the drawings may be repositioned as required in practice without affecting the technical effects. Phrases such as “in the drawings,” “in the figures,” or similar expressions appearing in the specification are not intended to refer to all drawings or all examples.

[0074] Certain directional terms used below to describe the drawings, such as “front,” “rear,” “inner,” “outer,” “upper,” “lower,” and other directional terms, are to be understood as having their ordinary meanings and as referring to the directions involved when the drawings are viewed normally. Unless otherwise specified, the directional terms used herein are generally consistent with the conventional directions as understood by those skilled in the art.

[0075] The terms “first,” “second,” and the like, as used in the present disclosure, do not denote any order, quantity, or importance, but are used merely to distinguish one component from another.

[0076] To facilitate a further understanding of the objects, structures, features, and functions of the present disclosure, detailed descriptions are provided below in conjunction with the embodiments.

[0077] Reference will now be made in detail to the embodiments illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Directional references such as “upper,” “lower,” “right,” and “left” are made solely for convenience in referring to the drawings and are not intended to limit the scope of the present disclosure.

[0078] In the detailed description below, the dedicated rocker arm assembly illustrated as a non-limiting embodiment is configured to achieve a specific desired function of engine operation, namely, as part of an engine exhaust braking system (compression-release type). Specifically, when the dedicated rocker arm assembly is enabled, the engine exhaust braking system may cause an exhaust valve to open earlier and / or additionally during an engine cycle relative to normal operation (i.e., engine driving mode), thereby providing a vehicledecelerating capability. In some embodiments, a specific exhaust valve of a valvetrain having engine braking capability may be designated as an engine braking valve. In particular embodiments, the engine braking valve is selectively engageable to perform normal exhaust valve operation (e.g., when in a driving mode), or to operate under a specific valve timing scheme to provide engine braking (when in an engine braking mode).ATTORNEY DOCKET PATENT APPLICATION 006976.236911 of 29

[0079] Referring to FIGS. 1 and 2, the detailed structure of a dedicated rocker arm assembly according to one embodiment of the present disclosure and a hydraulic unit 100 for use therein are illustrated. Preferably, as shown in FIG. 2, the dedicated rocker arm assembly is provided as a rocker arm assembly equipped with a dedicated actuating cam and its actuating camshaft (not shown).

[0080] Specifically, in the illustrated embodiment, the dedicated rocker arm assembly with hydraulic unit 100 may be positioned in the engine cylinder head between an actuating cam of the engine and a valve bridge 301 of the engine. More particularly, the dedicated rocker arm assembly comprises two main portions: a rocker arm 200 and a hydraulic unit 100 integrated into one side of the rocker arm 200.

[0081] As shown in FIG. 2, the rocker arm 200 includes a rocker shaft bore 201 located at its midsection for receiving a rocker shaft (not shown), an actuation side 205 on one side of the rocker arm 200 (the right side in FIG. 2) configured to abuttingly engage the actuating cam, and a valve side 206 opposite the actuation side 205 and disposed adjacent to the valve bridge 301. More specifically, a roller 203 is arranged on the actuation side 205 of the rocker arm 200 to engage the contoured profile of the actuating cam. As the actuating cam rotates with the actuating shaft, the roller 203 receives pivoting motion from the actuating cam and converts it into pivoting motion of the rocker arm 200 about a pivot axis defined by the rocker shaft received in the rocker shaft bore 201.

[0082] Meanwhile, a receiving bore is formed in the valve side 206 of the rocker arm 200 to accommodate the hydraulic unit 100, and an oil passage 202 is provided in the body of the rocker arm 200 to communicate between the rocker shaft bore 201 and the receiving bore. As a result, pressurized fluid from an external source can be delivered to the hydraulic unit 100 within the receiving bore via the oil passage 202 and the oil passage in the rocker shaft, in correspondence with pivoting of the rocker arm 200 about the rocker shaft. This arrangement allows the hydraulic unit 100 in the receiving bore to be selectively activated or deactivated. Fluid communication between the oil passage in the rocker shaft and the oil passage 202 in the body of the rocker arm 200 is well known to those skilled in the art and is not described in further detail herein.

[0083] In some embodiments, preferably, a spring 204 is provided above the roller 203 on the actuation side 205 of the rocker arm 200. The upper end of the spring 204 may be fixed to a stationary portion of the engine, such as the cylinder head, while the lower end abuts the actuation side 205 of the rocker arm 200. The spring 204 serves to continuously bias theATTORNEY DOCKET PATENT APPLICATION 006976.236912 of 29rocker arm 200 downward into close contact with the actuating cam, for example, to accommodate mechanical clearances. Consequently, during operation of the dedicated rocker arm assembly, the rocker arm 200 remains in tight contact with the actuating cam, thereby preventing undesired mechanical impacts, noise, and wear. This arrangement improves the operational stability and smoothness of the dedicated rocker arm assembly. Of course, those skilled in the art will understand that the dedicated rocker arm assembly can operate without the spring 204, or alternatively, other suitable damping or idle elements known in the art may be used, without departing from the scope of the present disclosure.

[0084] As shown in FIG.2, the hydraulic unit 100 detailed in FIG. 1 is accommodated within the receiving bore of the valve side 206 of the rocker arm 200. The hydraulic unit 100 is used to enable engagement between the dedicated rocker arm assembly and a valve pin 302 of the valve bridge 301 in a valve bridge assembly. As a non-limiting example, the valve bridge assembly 300 is used to facilitate engagement with the exhaust valves of a multicylinder engine, in which the valve bridge 301 can actuate multiple exhaust valves simultaneously via a suitable valve actuation mechanism (e.g., during the driving mode). Meanwhile, the valve pin 302 on the right side of the valve bridge 301 in FIG. 2 is configured to be associated with an exhaust valve used for engine exhaust braking, allowing the engine to actuate this valve independently of the other exhaust valves when in the braking mode, thereby performing compression-release exhaust braking.

[0085] As will be described in detail below, this is achieved by transitioning a brake plunger 106 of the hydraulic unit 100, located above the valve pin 302 and spaced from it by a clearance G, from its reset position to an extended position forcefully engaging the valve pin 302.

[0086] To enable switching of the engine between driving mode and braking mode, the hydraulic unit 100 illustrated in FIG. 1 is integrated into the receiving bore of the valve side 206, adjacent to the valve bridge 301. The hydraulic unit 100 is configured to be in fluid communication with the oil passage 202 in the rocker arm 200, and is thus controlled in response to the pressure of pressurized fluid within the oil passage 202.

[0087] More specifically, FIG. 1 shows an exploded view of the hydraulic unit 100 accommodated in the receiving bore on the valve side 206. As shown in FIGS. 1-4, the hydraulic unit 100 may include a hydraulic unit housing 101 generally configured as a hollow cylinder. In the embodiment shown in FIG. 1, the hydraulic unit housing 101 may include an upper chamber located above and a lower chamber located below. In the embodimentATTORNEY DOCKET PATENT APPLICATION 006976.236913 of 29illustrated in FIGS, l^t, the upper and lower chambers may be formed as a single monolithic piece, the monolithic piece defining the hydraulic unit housing 101 that accommodates and / or contains the various components of the hydraulic unit 100 in a stacked arrangement.

[0088] For example, the upper chamber can accommodate a valve pin 102, while the lower chamber can accommodate a control valve assembly composed of a check ball 103, a check ball cage 105, and a check ball spring 104, as well as a brake plunger 106 that is actuated in response to the control valve assembly being enabled. By containing these components within the hydraulic unit housing 101, embodiments of the present disclosure can achieve a compact yet simplified hydraulic unit 100, thereby reducing the overall complexity and cost of the system. Additionally, the cylindrical symmetry of the hydraulic unit 100 provides further beneficial technical effects, such as ease of assembly.

[0089] Preferably, as shown in FIG. 4, the upper chamber may include one or more fluid passages, for example arranged circumferentially along the side wall of the upper chamber, and configured to receive pressurized fluid (e.g., engine oil) supplied via the oil passage 202 of the rocker arm 200. The lower chamber is located beneath the upper chamber and is configured to be in fluid communication with the upper chamber through an opening provided between the upper and lower chambers. In this way, pressurized fluid introduced into the upper chamber via the fluid passages connected to oil passage 202 can flow into the lower chamber through the opening between the upper and lower chambers, for example in a selective manner under the control of the control valve assembly, the details of which will be explained more clearly below.

[0090] As further shown in FIG. 4, the upper chamber of the hydraulic unit 100 accommodates a valve pin 102. The valve pin 102 is configured to move between an initial position (e.g., as shown in FIG. 4) and a lifted position (e.g., as shown in FIG. 6) in response to the pressure of pressurized fluid entering the upper chamber via the oil passage 202.

[0091] In the embodiment illustrated in FIGS. 1 and 4, the hydraulic unit 100 further includes a shim plate 111 disposed within the upper chamber of the hydraulic unit housing 101, and a retaining ring 110 configured to hold the shim plate 111 axially fixed within the upper chamber. Between the shim plate 111 and the valve pin 102 positioned below, a spring 112 is provided to bias the valve pin 102 downward toward its initial position in the absence of external forces. At the initial position, the valve pin 102 pushes downwards against the check ball 103, unseating it against the passageway between the upper and lower chambers, therebyATTORNEY DOCKET PATENT APPLICATION 006976.236914 of 29allowing fluid communication between the two chambers. The shim plate 111 is configured to adjust the biasing force applied to the valve pin 102 by the spring 112.

[0092] Preferably, the upper portion of the hydraulic unit 100 further includes a locknut 109 threaded onto the exterior of the hydraulic unit housing 101 above the shim plate 111. The locknut 109 is configured to apply a clamping force to the hydraulic unit housing 101, thereby securing the hydraulic unit 100 within the rocker arm body.

[0093] Advantageously, the locknut 109 includes an upper nut portion and a lower threaded portion, wherein a maximum outer diameter of the nut portion is smaller than an outer diameter of the threaded portion. The nut portion and the threaded portion can have independent sizes. With this configuration, the threaded portion is able to threadably engage the exterior of the hydraulic unit housing 101, while the nut portion may be designed to be sufficiently small to be engaged by standard, commercially available tools. By way of example, the outer diameter of the hydraulic unit housing 101 may exceed the maximum size accommodated by standard tooling. In such cases, the alternative nut 109 A design shown and described below with reference to FIG. 7 may require the use of larger, specialized tools for installation, adjustment, or servicing of the hydraulic unit housing 101. In contrast, the locknut 109 shown in FIGS. 1, 4, and 6 is configured such that, regardless of the size of the hydraulic unit housing 101, the nut portion remains compatible with standard tools. In operation, valve lash may be adjusted by first loosening the locknut 109 using a standard tool, thereby permitting rotation of the hydraulic unit housing 101 relative to the rocker arm. A second tool may then be inserted into and engaged with a hexagonal opening formed in an internal shim positioned within the hydraulic unit housing, allowing the capsule to be rotated within the threaded rocker arm bore to increase or decrease lash as desired. Once the lash is set to a target value, the locknut 109 is retightened to secure the hydraulic unit housing 101 in position and prevent further rotation. As a result, valve lash may be set, adjusted, or serviced using existing tooling, thereby eliminating the need for customers to purchase dedicated or custom tools.

[0094] When pressurized fluid from the oil passage 202 flows into and accumulates in the upper chamber, the resulting hydraulic pressure can overcome the downward biasing force of the spring 112, thereby pushing the valve pin 102 upward to the lifted position. As previously mentioned, the control valve assembly downstream of the valve pin 102 can be configured to selectively fluidly connect the upper chamber and the lower chamber in response to the position of the valve pin 102. When the valve pin 102 is in the lifted position, it no longerATTORNEY DOCKET PATENT APPLICATION 006976.236915 of 29applies a downward force on the check ball 103. This allows the check ball spring 104 to bias the check ball 103 upward against a seat defined around the passage between the lower and upper chambers, thereby closing it.

[0095] The embodiment shown in FIG. 4 shows the control valve assembly in more detail. The assembly includes the check ball 103 configured to seal an opening between the upper and lower chambers. During operation, the check ball 103 is typically held against the opening by a check ball spring 104, which biases the check ball upward. The check ball spring 104 is positioned between the check ball 103 and a check ball cage 105, which is fluid-permeable and located beneath the check ball 103, thereby securing the check ball spring 104 and check ball 103 in place.

[0096] When the valve pin 102 is in the initial position (e.g., pressure within the upper chamber is below a threshold amount and cannot overcome the force of the spring 112), its lower end presses downward on the check ball 103 to unseat it, opening the fluid passage through the opening, as shown in FIG. 4. In this configuration, the brake plunger 106 is not rigid, as hydraulic pressure within the lower chamber can escape through the upper chamber.

[0097] When the valve pin 102 is in the lifted position (e.g., pressure within the upper chamber is above the threshold amount, overcoming the spring 112), the valve pin 102 does not exert any force against the check ball 103, as shown in FIG. 6. In this configuration, the check ball 103 functions as a check valve within the hydraulic unit 100: it permits fluid to flow from the upper chamber to the lower chamber while preventing reverse flow back into the upper chamber. This allows pressure to build within the lower chamber, making the brake plunger to stay rigid. When the valve pin 102 returns to its initial position, its lower end can engage and unseat the check ball 103, allowing fluid to flow into the lower chamber, and vice versa.

[0098] As previously described, the lower chamber can further accommodate a brake plunger 106. For example, the brake plunger 106 can be disposed beneath and aligned with the control valve assembly. In the illustrated embodiment, the brake plunger 106 is configured to translate within the lower chamber between an extended position and a reset position in response to pressurized fluid introduced into the lower chamber.

[0099] For instance, as shown in FIG. 6, when the lower chamber is filled with pressurized fluid and the check ball 103 is in the closed position, the brake plunger 106 can be hydraulically actuated downward to an extended position where its lower end protrudes from the bottom of the hydraulic unit 100 by a sufficient distance. This distance is at least equal toATTORNEY DOCKET PATENT APPLICATION 006976.236916 of 29the gap or clearance G between the brake plunger 106 and the valve pin 302. In this configuration, as the rocker arm 200 rotates, the brake plunger 106 can engage the valve pin 302 in the valve bridge 301, thereby transferring motion to the associated engine braking exhaust valve and opening it.

[0100] As shown in FIGS. 1 and 4, the hydraulic unit 100 further includes a reset assembly disposed within the receiving bore on the valve side 206, which is coupled or force-fitted to the hydraulic unit housing 101 and force-transmissively engaged with the brake plunger 106. Preferably, as illustrated in FIGS. 1, 4, and 6, the reset assembly includes a retaining sleeve 108 generally configured as a cylinder, and a return spring 107 disposed between the retaining sleeve 108 and the brake plunger 106. As shown in FIG. 4 and FIG. 6, the retaining sleeve 108 includes an outer peripheral wall configured to be clamped between the hydraulic unit housing 101 and the receiving bore of the valve side 206, and a centered opening in the middle of its inner bottom wall through which the brake plunger 106 passes. The return spring 107 is configured as a compression spring, comprising a first end (lower end, as shown in FIGS. 1, 4, and 6) disposed around the centered opening of the bottom wall, and a second end (upper end, above the first end) in force-transmissive engagement with the brake plunger 106. The opening in the bottom wall may be formed with an upward bend to create a spring seat that aligns and supports the return spring 107. The reset force applied by the return spring 107 to the brake plunger 106 is defined by the compression stroke between the spring’s first and second ends. The brake plunger 106 may include a wider upper portion and a narrower lower portion. The wider upper portion has a diameter substantially matching the interior diameter of the lower chamber so that it can translate axially within the chamber while maintaining lateral alignment. The narrower lower portion of the brake plunger 106 may extend through the center of the return spring 107 along the spring’s axis and project outward through the opening in the bottom wall of the retaining sleeve 108.

[0101] In particular embodiments, the retaining sleeve 108 has an outer peripheral wall with multiple inwardly protruding retention tabs 1081 distributed circumferentially, which in FIG.1 are illustrated as 4-6 inwardly bent tabs. The retention tabs 1081 lock the retaining sleeve 108 relative to the hydraulic unit housing 101.

[0102] With this design, during assembly of the hydraulic unit 100 into the receiving bore of the valve side 206 of the rocker arm 200, the return spring 107 can first be fitted around the lower end of the brake plunger 106. Subsequently, the retaining sleeve 108 can be coaxially fitted over the exterior of the hydraulic unit housing 101, such that the lower end of the brakeATTORNEY DOCKET PATENT APPLICATION 006976.236917 of 29plunger 106 passes through the centered opening of the retaining sleeve 108, and the retention tabs 1081 engage with multiple external annular grooves on the hydraulic unit housing 101, thereby immovably securing the retaining sleeve 108 to the housing 101. Finally, the hydraulic unit housing 101 with the retaining sleeve 108 can be inserted into the receiving bore of the valve side 206 of the rocker arm 200. The interference fit between the retaining sleeve 108, the inner wall of the receiving bore, and the exterior of the hydraulic unit housing 101 ensures that the retaining sleeve 108 remains immovably held between the hydraulic unit housing 101 and the receiving bore.

[0103] Preferably, to prevent the brake plunger 106 from overextending beyond its intended extended position, the reset assembly further includes a retaining ring 113 disposed on the inner wall of the hydraulic unit housing 101 between the first and second ends of the return spring 107. With the retaining ring 113 positioned beneath the brake plunger 106 at a preset location, even if the pressure of the fluid in the lower chamber is excessively high, the brake plunger 106 cannot extend beyond the maximum stroke defined by the retaining ring 113. At the maximum stroke, the lower edge of the wider upper portion of the brake plunger 106 will abut the retaining ring 113, which prevents the brake plunger 106 from further extending.

[0104] With this design, the return spring 107 can exert a biasing force on the brake plunger 106, for example near its lower end. The return spring 107 can be supported upwardly by the retaining sleeve 108 attached to or fixed relative to the lower chamber. As shown in FIG. 4, the return spring 107 provides an upward spring force to the brake plunger 106, so that when pressurized fluid in the lower chamber is removed, the brake plunger 106 returns to its reset position (i.e., retracted position). In this reset position, most or all of the brake plunger 106 is substantially contained within the lower chamber, preventing contact with the valve pin 302 in the valve bridge 301 even during rotation of the rocker arm 200. This avoids the “floating” condition of the brake plunger 106 observed in prior designs and prevents undesired mechanical impact, as well as associated noise and wear.

[0105] Thus, compared with the prior art, the hydraulic unit 100 in the present embodiment allows the brake plunger 106 to be default-maintained in the reset position during periods when engine braking is inactive, via the return spring 107, thereby preventing any unintended contact between the hydraulic unit 100 and the valve bridge 301. In other words, the reset position is designed so that the gap or clearance G between the brake plunger 106 and the valve pin 302 in the valve bridge 301 is at least equal to the maximum valve lift of the actuating cam, thereby ensuring that the brake plunger 106 does not engage the valve pin 302ATTORNEY DOCKET PATENT APPLICATION 006976.236918 of 29during rotation of the rocker arm 200. This design protects the system from undesired wear and reduces the risk of damage to movable components.

[0106] Notably, the retaining sleeve 108 is configured to be mounted on an exterior surface of the hydraulic unit housing 101. This external retainer configuration is advantageous because it permits the brake plunger 106 to have a larger diameter than would otherwise be possible with an internal retainer design. By contrast, in the alternative embodiment shown in FIG. 7, the retaining sleeve 108A is affixed to an interior surface of the hydraulic unit housing 101. Assuming the hydraulic unit housing 101 in FIGS. 4 and 7 has the same outer dimensions, positioning the retaining sleeve 108 on the exterior of the housing provides greater internal clearance for the brake plunger 106. In the internal retainer configuration, the wall thickness of the retaining sleeve 108 A reduces the available internal volume of the hydraulic unit housing 101, thereby limiting the maximum achievable diameter of the brake plunger 106. The external retainer configuration avoids this constraint and thus enables a larger-diameter brake plunger 106. This is advantageous because the brake plunger 106 is configured to transmit substantial load to the valve pin 302. As will be appreciated by one of ordinary skill in the art, increasing the load transfer area reduces contact stress by distributing the applied load over a larger surface area, thereby reducing wear and improving durability of the interacting components.

[0107] The switching process of the dedicated rocker arm assembly will now be explained in more detail with reference to FIGS. 3-6, where FIGS. 3^1 depict the dedicated rocker arm assembly with the hydraulic unit 100 in the reset position during normal main exhaust operation, with the engine in drive mode, and FIGS. 5-6 depict the dedicated rocker arm assembly with the hydraulic unit 100 in the extended position during engine exhaust braking, with the engine in brake mode.

[0108] Referring now to FIGS. 3 and 4, during the normal operating mode of the engine valve system (i.e., drive mode), the hydraulic unit 100 can be deactivated. Without hydraulic pressure in the upper chamber, the spring 112 is biased downward, opening the check ball 103 and allowing fluid communication between the upper and lower chambers. In this state, pressure cannot build within the lower chamber to overcome the spring force of the return spring 107. Thus, the return spring 107 biases the brake plunger 106 upward, causing it to remain in its reset position. In this reset position, the lower end of the brake plunger 106 is separated from the valve pin 302 in the valve bridge 301 by a predetermined clearance G, so that it does not contact the valve pin 302 regardless of any rotation of the dedicated rockerATTORNEY DOCKET PATENT APPLICATION 006976.236919 of 29arm assembly. In other words, the brake plunger 106 is biased upward by the spring force of the return spring 107, thereby preventing any contact between the hydraulic unit 100 and the valve pin 302 when the braking mode is inactive. This also prevents wear caused by unintended mechanical contact.

[0109] When engine exhaust braking is required, pressurized fluid is delivered to the hydraulic unit 100 via the oil passage 202 in the rocker arm 200. The pressurized fluid first enters the upper chamber, pushing the valve pin 102 upward to its lifted position. The applied pressure further pushes downward on the check ball 103 of the control valve assembly, thereby opening the fluid passage between the upper and lower chambers and allowing fluid to flow into the lower chamber.

[0110] As the lower chamber fills with pressurized fluid, the brake plunger 106 is correspondingly actuated downward to its extended position, in which the lower end of the brake plunger 106 moves to eliminate the gap or clearance G with the valve pin 302 and force-transmissively engages the valve pin 302. In this state, the system is activated, as shown in FIGS. 5-6.

[0111] During brake mode, due to the control characteristics of the control valve assembly that prevent upward fluid backflow, pressurized fluid is retained in the lower chamber.Simultaneously, the valve pin 102 is maintained in the lifted position by the pressurized fluid, keeping it away from the check ball 103, ensuring that the check ball 103 remains seated against the opening in a closed position, effectively maintaining the lower chamber in a pressure-sealed state and allowing the brake plunger 106 to remain rigidly extended. In this configuration, as the dedicated rocker arm assembly rotates, the brake plunger 106 in its extended position engages the valve pin 302, pushing the corresponding engine exhaust valve associated with the valve pin 302 to open, thereby achieving compression braking action.

[0112] When switching back to drive mode, the system can be depressurized, allowing fluid in the upper chamber to, for example, exit via the fluid passages. With hydraulic pressure no longer present in the upper chamber, the valve pin 102 can return to its initial position under the downward bias applied by the spring 112. In this state, the valve pin 102 can push the check ball 103 downward, thereby opening the control valve assembly. Once open, the fluid previously retained in the lower chamber can be depressurized through the opening. As a result, the hydraulic pressure that overcomes the bias of the return spring 107 is removed, allowing the brake plunger 106 to be pushed upward by the return spring 107 and return to its resetATTORNEY DOCKET PATENT APPLICATION 006976.236920 of 29position, so that throughout the rotation of the dedicated rocker arm assembly, the brake plunger 106 does not engage the valve pin 302.

[0113] FIGS. 7-9 illustrate another feasible embodiment of the hydraulic unit 100 according to the present invention. This hydraulic unit 100 has a design largely similar to the hydraulic unit 100 shown in FIGS. 1-6, with the primary differences being in the configuration of certain components in the upper chamber and the design of the reset assembly in the lower chamber. For clarity, identical reference numerals in FIGS. 7-9 denote the same components as in FIGS.1-6.

[0114] Unlike the hydraulic unit 100 shown in FIGS. 1-6, in the embodiment shown in FIG.7, the reset assembly includes: a retaining ring 113 engaged with the inner wall of the hydraulic unit housing 101 ; a retaining sleeve 108A, which comprises an outer peripheral wall configured to engage the inner wall of the hydraulic unit housing 101 and a centered opening in the middle of its inner bottom wall through which the brake plunger 106 passes. The outer peripheral wall abuts the retaining ring 113, preventing downward movement of the retaining sleeve 108 A relative to the hydraulic unit housing 101. The reset assembly further includes a return spring 107, which is a compression spring having a first end arranged around the centered opening and a second end above the first end that engages the brake plunger 106 in a force-transmitting manner. Here, the retaining sleeve 108A is prevented from downward movement by the retaining ring 113 and from upward movement by the return spring 107, thereby immovably securing the retaining sleeve 108A within the hydraulic unit housing 101. This design achieves the resetting function of the brake plunger 106 with fewer components.

[0115] Further, as shown in FIGS. 7-9, the hydraulic unit 100 also includes a cover 110A disposed in the upper chamber and a snap ring 111 A that axially retains the cover 110A in the upper chamber. The snap ring 111 A is configured as a C-shaped snap ring. Between the cover 110A and the valve pin 102 below it is a spring 112 for maintaining the valve pin 102 in its initial position. The cover 110A is configured to adjust the elastic force applied by the spring 112 to the valve pin 102.

[0116] Preferably, the upper portion of the hydraulic unit 100 further includes a nut 109A screwed onto the outer periphery of the cover 110A and engaging the outer side of the hydraulic unit housing 101, which applies a locking force to secure the hydraulic unit 100 to the rocker arm body.

[0117] From the foregoing, the present invention provides the following advantages over the prior art. The brake plunger of the dedicated rocker arm assembly can be maintained in theATTORNEY DOCKET PATENT APPLICATION 006976.236921 of 29reset position by the reset assembly when engine braking is inactive, thereby avoiding any contact between the hydraulic unit and the valve pin. This protects the system from undesired wear and reduces the risk of damage and noise to movable components. The hydraulic unit achieves reduced component cost because the reset assembly can be implemented using standardized or commonly available parts, lowering manufacturing and procurement costs. The hydraulic unit has reduced engineering cost, because the present design does not require fully redesigned engine braking hardware; only modification of certain components is sufficient to implement it on the engine cylinder head and / or valvetrain.

[0118] It should be understood that although the specification describes various embodiments, each embodiment does not necessarily represent a single, separate technical solution. This presentation is for clarity. A person skilled in the art will recognize that the technical features of the embodiments can be appropriately combined to form other embodiments within the scope of the invention.

[0119] The above-described embodiments are only illustrative of the invention and are not intended to limit its scope. Any equivalent modifications, adaptations, or combinations made by a person skilled in the art, without departing from the inventive concept and principles, are intended to fall within the scope of the present invention.

[0120] Although this disclosure describes an engine brake capsule with a particular plunger pad having a particular latching assembly in a particular manner, this disclosure contemplates engine brake capsules with plunger pads having any suitable latching assemblies in any suitable manner. As an example, other latch members in addition or alternative to the ball may be provided, such as a pin, a block, a tab, or the like may be provided for achieving the desired function of this disclosure.

[0121] Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.

[0122] The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although thisATTORNEY DOCKET PATENT APPLICATION 006976.236922 of 29disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.

Claims

ATTORNEY DOCKET PATENT APPLICATION 006976.236923 of 29CLAIMSWhat is claimed is:

1. A rocker arm assembly for engine exhaust braking, the rocker arm assembly comprising:a rocker arm having (i) an actuation side configured to engage with a cam and (ii) a valve side opposite the actuation side; anda hydraulic unit disposed in a hydraulic unit receiving bore on the valve side of the rocker arm, the hydraulic unit comprising:a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upper chamber;a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber;a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position;a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; anda reset assembly coupled to the hydraulic unit housing, the reset assembly comprising:a retaining sleeve comprising (i) an outer peripheral wall configured to lock to an exterior surface of the hydraulic unit housing and (ii) a bottom wall with an opening configured for the brake plunger to pass through; anda return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

2. The rocker arm assembly of claim 1, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridgeATTORNEY DOCKET PATENT APPLICATION 006976.236924 of 29is greater than a maximum valve lift of the cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

3. The rocker arm assembly of claim 1, wherein the outer peripheral wall of the retaining sleeve is configured to be clamped between the hydraulic unit housing and the hydraulic unit receiving bore.

4. The rocker arm assembly of claim 1 , wherein the reset assembly further comprises a snap ring disposed on an inner wall of the hydraulic unit housing between the first and second ends of the return spring, the snap ring being configured to prevent the brake plunger from extending beyond the extended position.

5. The rocker arm assembly of claim 1, wherein the outer peripheral wall of the retaining sleeve includes a plurality of inwardly protruding retention tabs, wherein when the retaining sleeve is installed between the hydraulic unit housing and the hydraulic unit receiving bore of the valve side, the inwardly protruding retention tabs engage with annular grooves on the exterior surface of the hydraulic unit housing, thereby securing the retaining sleeve between the hydraulic unit housing and the hydraulic unit receiving bore.

6. The rocker arm assembly of claim 1, further comprising a shim plate disposed in the upper chamber of the hydraulic unit housing and a retaining ring axially securing the shim plate in the upper chamber, wherein a spring is disposed between the shim plate and the valve pin to maintain the valve pin in its initial position, and wherein the shim plate is configured to adjust an elastic force applied by the spring to the valve pin.

7. The rocker arm assembly of claim 6, further comprising a lock nut engaged above the shim plate to an exterior of the hydraulic unit housing, wherein the lock nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm.ATTORNEY DOCKET PATENT APPLICATION 006976.236925 of 298. The rocker arm assembly of claim 7, wherein the lock nut includes a nut portion and a threaded portion to engage an exterior of the hydraulic unit housing, wherein a maximum outer diameter of the nut portion is smaller than an outer diameter of the threaded portion.

9. The rocker arm assembly of claim 1, wherein the control valve assembly comprises: a check ball cage disposed below an opening between the upper chamber and the lower chamber;a check ball disposed within the check ball cage, wherein the check ball has a diameter larger than the opening; anda check ball spring disposed between check ball and a bottom of the check ball cage, the check ball spring configured to bias the check ball toward the opening.

10. A hydraulic unit configured to be disposed in a hydraulic unit receiving bore on a valve side of a rocker arm for engine exhaust braking, the hydraulic unit comprising:a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upper chamber;a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber;a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position;a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; anda reset assembly coupled to the hydraulic unit housing, the reset assembly comprising:a retaining sleeve comprising (i) an outer peripheral wall configured to lock to an exterior surface of the hydraulic unit housing and (ii) a bottom wall with an opening configured for the brake plunger to pass through; anda return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.ATTORNEY DOCKET PATENT APPLICATION 006976.236926 of 2911. The hydraulic unit of claim 10, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridge is greater than a maximum valve lift of a cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

12. The hydraulic unit of claim 10, wherein the outer peripheral wall of the retaining sleeve is configured to be clamped between the hydraulic unit housing and the hydraulic unit receiving bore.

13. The hydraulic unit of claim 10, wherein the reset assembly further comprises a snap ring disposed on an inner wall of the hydraulic unit housing between the first and second ends of the return spring, the snap ring being configured to prevent the brake plunger from extending beyond the extended position.

14. The hydraulic unit of claim 10, wherein the outer peripheral wall of the retaining sleeve includes a plurality of inwardly protruding retention tabs, wherein when the retaining sleeve is installed between the hydraulic unit housing and the hydraulic unit receiving bore of the valve side, the inwardly protruding retention tabs engage with annular grooves on the exterior surface of the hydraulic unit housing, thereby securing the retaining sleeve between the hydraulic unit housing and the hydraulic unit receiving bore.

15. The hydraulic unit of claim 10, further comprising a lock nut engaged to an exterior of the hydraulic unit housing, wherein the lock nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm, wherein the lock nut includes a nut portion and a threaded portion to engage an exterior of the hydraulic unit housing, wherein a maximum outer diameter of the nut portion is smaller than an outer diameter of the threaded portion.

16. A rocker arm assembly for engine exhaust braking, the rocker arm assembly comprising:ATTORNEY DOCKET PATENT APPLICATION 006976.236927 of 29a rocker arm having (i) an actuation side configured to engage with a cam and (ii) a valve side opposite the actuation side; anda hydraulic unit disposed in a hydraulic unit receiving bore on the valve side of the rocker arm, the hydraulic unit comprising:a hydraulic unit housing, comprising an upper chamber configured to receive pressurized fluid and a lower chamber configured to be in selective fluid communication with the upper chamber;a valve pin disposed in the upper chamber and configured to move between an initial position and a lifted position in response to pressurized fluid in the upper chamber;a control valve assembly, disposed in the lower chamber and configured to selectively place the upper chamber and the lower chamber in fluid communication in response the valve pin being in the initial position or the lifted position;a brake plunger, at least partially disposed in the lower chamber and configured to move between an extended position and a reset position in response to pressurized fluid in the lower chamber; anda reset assembly coupled to the hydraulic unit housing, the reset assembly comprising:a snap ring engaged with an inner wall of the hydraulic unit housing;a retaining sleeve comprising (i) an outer peripheral wall configured to engage an inner wall of the hydraulic unit housing by abutting the snap ring and (ii) a bottom wall with an opening configured for the brake plunger to pass through; anda return spring, having a first end arranged around the opening and a second end engaging with the brake plunger.

17. The rocker arm assembly of claim 16, wherein in a drive mode, the brake plunger is maintained in the reset position by a biasing force of the return spring, wherein the reset position is designed so that a gap between the brake plunger and a valve pin of a valve bridge is greater than a maximum valve lift of the cam, thereby preventing the brake plunger from engaging the valve pin during rotation of the rocker arm.

18. The rocker arm assembly of claim 16, wherein the reset assembly prevents the brake plunger from extending beyond the extended position.ATTORNEY DOCKET PATENT APPLICATION 006976.236928 of 2919. The rocker arm assembly of claim 16, further comprising a cover disposed in the upper chamber of the hydraulic unit housing and a second snap ring axially retaining the cover in the upper chamber, wherein a spring is disposed between the cover and the valve pin below it to maintain the valve pin in its initial position, and wherein the cover is configured to adjust an elastic force applied by the spring to the valve pin.

20. The rocker arm assembly of claim 19, further comprising a nut screwed onto an outer periphery of the cover and an exterior of the hydraulic unit housing, wherein the nut is configured to apply a locking force to the hydraulic unit housing, securing it to the rocker arm.

Images