Variable displacement valve control systems with rocker arm shaft porting and insert sleeves for engine cylinder deactivation

Abstract

A valve train control system comprises a rocker arm shaft mounted to an engine assembly and featuring an internal bore that receives hydraulic fluid. An oil control valve (OCV) is mounted on the rocker arm shaft and is fluid-connected to the internal bore to receive hydraulic fluid. A rocker arm is pivotally mounted on the rocker arm shaft, its opposite ends mating with a pushrod and a valve. The rocker arm includes a spring-loaded locking assembly attached to the pushrod and fluid-connected to the OCV to receive hydraulic fluid and thereby release the rocker arm from the pushrod. An insert sleeve mounted in the internal bore receives hydraulic fluid from the rocker arm shaft. The insert sleeve includes a feed port that transfers hydraulic fluid from the insert sleeve to the OCV and a feed pocket that transfers hydraulic fluid from the OCV to the spring-loaded locking assembly.

Description

Technical field

[0001] The present disclosure relates generally to internal combustion engines. More specifically, aspects of this disclosure relate to variable displacement valve train systems for cylinder deactivation in reciprocating internal combustion engine arrangements. introduction

[0002] Today's production vehicles, such as modern automobiles, are originally equipped with a powertrain that propels the vehicle and supplies power to its onboard electronics. In motor vehicles, for example, the powertrain typically consists of a drive motor that transmits the drive torque to the vehicle's drive system (e.g., differential, axles, camshafts, wheels, etc.) via an automatic or manual transmission. Historically, motor vehicles were powered by internal combustion engines (ICEs) because these were readily available, relatively inexpensive, lightweight, and highly efficient. These engines include compression-ignition (CI) diesel engines, spark-ignition (SI) gasoline engines, two-, four-, and six-stroke engines, and rotary engines, to name just a few.Hybrid electric vehicles (HEVs) and fully electric vehicles (FEVs), on the other hand, use alternative energy sources to power the vehicle, thus minimizing or eliminating dependence on a fossil fuel-based engine for traction.

[0003] A typical overhead valve (OHV) engine consists of an engine block containing a series of internal cylinder bores, each containing a piston that moves back and forth. A cylinder head is mounted on the engine block, and this head interacts with each cylinder bore-piston pair to form a variable-volume combustion chamber. These reciprocating pistons convert the pressure generated by the ignition of a fuel-air mixture in the combustion chamber into rotational forces that drive an engine crankshaft. The cylinder head has intake ports through which air, supplied by an intake manifold, is drawn into each combustion chamber. Exhaust gases and combustion byproducts from each combustion chamber are routed through exhaust ports in the cylinder head to an exhaust manifold.This exhaust manifold, in turn, collects and bundles the exhaust gases for metered recirculation into the intake manifold, for feeding to a turbine-driven turbocharger, or for extraction from the vehicle through an exhaust system.

[0004] Four-stroke internal combustion engines typically operate—as the name suggests—in four distinct stages or "strokes" to drive the engine's crankshaft. In the first stage, known as the "intake stroke," a metered fuel mixture (or just air in compression-ignition diesel engines) is introduced into each cylinder as the piston moves in a straight line from top to bottom through the entire length of the bore. The engine's intake valves open, allowing the vacuum created by the downward-moving piston to draw air into the chamber. In direct injection systems, a metered amount of finely atomized fuel is injected into the chamber via an injector. In the subsequent (second) stage, known as the "compression stroke," the intake and exhaust valves close as the piston moves from bottom to top, compressing the fuel-air mixture.After the compression stroke is complete, the next (third) stage, or "power stroke," begins when a spark plug (or pure compression in diesel engines) ignites the compressed fuel and air, with the resulting expansion of the gases pushing the piston back to bottom dead center (BDC). In a further stage—the so-called "exhaust stroke"—the piston returns to top dead center (TDC) again with the exhaust valves open; the moving piston expels the spent fuel-air mixture from the combustion chamber.

[0005] During the operation of multi-cylinder engines, one or more cylinders can be deactivated to improve fuel efficiency during periods of low demand. The deactivation of selected cylinders—commonly referred to as "variable displacement"—can be achieved in several ways, including the use of a variable valve lift (VVL) unit with an electronically or hydraulically controlled locking device that can be unlocked to detach the pushrod from the rocker arm during operation. Real-time VVL switching can be controlled by an electronic solenoid valve that, upon command from an engine control module (ECM), selectively directs oil from a hydraulic distributor to the switchable locking elements of the VVL unit.ECM activation of the solenoid valve increases the hydraulic pressure in the VVL unit; when the internal hydraulic pressure reaches a threshold for the locking device's spring force, the VVL unit releases the pushrod from the rocker arm, thus preventing the rocker arm from actuating the intake valve. Variable displacement valve train systems employ an oil pressure control system to maintain operating oil pressure at a relatively low level to allow ignition in all cylinders, and at a relatively high level to deactivate ignition in certain cylinders.

[0006] WO 2021 / 121 667 A1 describes a rocker arm shaft assembly configured to hold a rocker arm and supply oil to it, as well as an associated manufacturing process. The rocker arm shaft assembly comprises a core shaft and a sleeve. The core shaft has a core body with a main oil supply channel formed on it. The sleeve has through-passages formed on it. The sleeve is arranged around the core shaft. The main oil supply channel is aligned with at least one of the through-passages on the sleeve. The main oil supply channel is milled into the core shaft.

[0007] DE 10 2010 005 296 A1 describes a method for purging air from an oil passage in a machine arrangement, wherein the machine arrangement comprises a machine structure defining the oil passage, a first cam boss rotatably mounted by the machine structure and comprising a base region and a stroke region, a first tappet arrangement supported by the machine structure and in fluid communication with the oil passage, and a first valve supported by the machine structure and which can be moved from a seated position to a stroke position by the first tappet arrangement, wherein the first tappet arrangement is switched from an activated mode to a deactivated mode by pressurized oil supplied to the oil passage from a pressurized oil source, wherein the activated mode comprises the first valve being in the seated position.when the base region is engaged with the first tappet assembly, and is displaced from the seated position by the first tappet assembly when the lift region is engaged with the first tappet assembly, wherein the off mode includes the first valve remaining in the seated position when the lift region of the first cam boss is engaged with the first tappet assembly. The method includes: isolating the oil passage from the pressurized oil source while the first tappet assembly is engaged with the base region of the first cam boss to operate the first tappet assembly in the activated mode; supplying the pressurized oil to the first tappet assembly via the oil passage after isolation when the first tappet assembly is engaged with the lift region of the cam boss.wherein the first plunger assembly is held in activated mode after being supplied; and air is purged from the oil passage based on the pressurized oil supplied to the oil passage.

[0008] DE 21 2016 000 178 U1 describes a diesel engine system comprising: a selectively actuated cylinder deactivation mechanism designed to raise and lower a valve and to deactivate the valve, comprising: a bushing comprising recesses; and a controllable latch that can be moved between a locked state to engage the latch in the recesses and an unlocked state to retract the latch out of the recesses; and a pushrod coupled to the bushing, wherein the pushrod is designed to raise and lower the valve when the latch is in the locked state, and wherein the pushrod is further designed to move back and forth within the bushing to deactivate the valve when the latch is in the unlocked state.

[0009] DE 103 60 293 A1 describes an assembly and anti-rotation device (assembly aid) for roller tappets of a valve train of an internal combustion engine, in which gas exchange valves are actuated by roller tappets. The roller tappets, which essentially consist of a cylindrical tappet body, are held in receiving chambers within the plastic assembly aid. Parallel, opposing anti-rotation surfaces, arranged symmetrically with respect to the longitudinal axis of the roller tappet and attached to the end of the tappet body furthest from a roller, guide the roller tappets against rotation within the assembly aid during operation of the internal combustion engine. This is achieved by matching the inner profile of the receiving chambers to the outer profile of the roller tappets.To avoid confusion during the assembly of switchable and non-switchable roller plungers, the distances between the anti-rotation surfaces on the different plungers, and thus also the inner contours of the corresponding receiving spaces, are selected to be significantly different. To ensure the correct orientation of the switchable roller plungers, e.g., with respect to an oil gallery, the anti-rotation surfaces of the switchable roller plungers and the corresponding receiving spaces of the assembly aid are positioned asymmetrically with respect to the longitudinal axis of the plunger body.

[0010] WO 2024 / 132 215 A1 describes a valve train assembly comprising a rocker arm with a cam end near a cam and a valve end opposite the cam end and near one or more valves, an engine brake capsule coupled to the cam end, and a cylinder deactivation capsule coupled to the cam end. The engine brake capsule comprises an actuating pin assembly, a check valve assembly, and a piston, and is configured to switch between a retracted and an extended position. The cylinder deactivation capsule comprises an outer body, an inner body, and a locking mechanism, and is configured to switch between a locked and an unlocked position. In this way, the valve train assembly can perform both engine braking and cylinder deactivation functions, for example, on the cam side of the valve train assembly.

[0011] US Patent 12,180,866 B1 describes a cylinder deactivation system for an engine. The cylinder deactivation system includes an engine block that defines one cylinder. A valve opens and closes an orifice to the cylinder. A rocker arm pivots to actuate the valve. A camshaft has a cam lift, and a cam-rocker arm input system transmits the cam lift to the valve via the rocker arm. A deactivation assembly is located in the rocker arm and responds to fluid pressure to alternately activate and deactivate the valve. Description

[0012] The invention is defined by the claims.

[0013] The following describes variable displacement valvetrain (VDV) systems with rocker arm shaft fluid porting and insert sleeves for deactivating engine cylinders, methods for manufacturing and using such VDV systems, and motor vehicles with such VDV systems. In a non-restrictive example, control systems and methods for deactivating engine cylinders are presented that utilize a pressurized switching oil channel within the rocker arm shaft in combination with a tappet disengagement at the rocker arm-tappet interface (as opposed to the tappet-valve lifter interface). The oil flow gallery of the valvetrain control system directs oil from a supply channel in the cylinder head into and through the rocker arm shaft and an insert sleeve in the rocker arm shaft to an oil control valve (OCV) mounted on a manifold surrounding the rocker arm shaft.The OCV is selectively activated to direct oil to a worm gear embedded in the outer surface of the insert sleeve. The worm gear directs the oil through a feed port in the rocker arm shaft to a spring-lock deactivation unit (DEAC unit) integrated into a tappet mating end of the rocker arm. Pressurizing the spring-lock deactivation unit disengages the rocker arm from the pushrod, thus preventing the transmission of motion / load from the pushrod to the rocker arm. This deactivates the rocker arm and any inlet / exhaust valve mating to that rocker arm.

[0014] To regulate the oil flow through the rocker arm shaft, an outer diameter surface (OD surface) of the insert sleeve can be flush with an inner diameter surface (ID surface) of the rocker arm shaft, sealing it. Switching oil can flow from the pressurized oil bore in the rocker arm shaft through open longitudinal ends of the insert sleeve; an oil supply port in the circumferential wall of the insert sleeve directs oil into an inlet port of the overrun valve (OCV). Upon activation, the OCV transfers the oil flow from the OCV inlet port to an OCV control port; this control port redirects the oil flow, for example, via a control passage in the OCV distributor, through a sleeve track pocket to a worm gear in the sleeve. The worm gear directs the oil flow through an inlet channel in the rocker arm to the spring locking unit.The OCV features a pressure-regulating port and a floating check valve that maintains a minimal "start-up pressure" in the control passage. This start-up pressure is sufficient to allow the VDV system to switch quickly, but low enough to ensure that the VDV system does not inadvertently disable the rocker arms when not needed.

[0015] Among the advantages offered by at least some of the presented concepts is a simplified and more cost-effective VVL system, in which the switching oil is routed through the rocker arm shafts to the rocker arm spring locking elements. Using this arrangement allows for minimal modifications to the existing engine architecture and eliminates unnecessary hoses, seals, valves, etc. Further advantages of the VVL system include minimizing the amount of oil drawn from the existing engine oil system while simultaneously providing the necessary oil and pressure to actuate the cylinder deactivation system and maintaining oil supply to the tappet-rocker arm interface and between the rocker arm and rocker arm shaft.

[0016] Aspects of this disclosure relate to optimized VDV systems with fluid-connected rocker arm shafts and rocker arm shaft insert sleeves for deactivating engine cylinders (or two-stage valve lift). An example presents a valve train control system for an engine assembly comprising multiple cylinders, intake and exhaust valves for opening and closing the intake and exhaust ports to each cylinder, a camshaft rotatably mounted near the valves, and multiple pushrods (e.g., with pushrod lifters), each seated on a corresponding cam lobe of the camshaft. The valve train control system includes a rocker arm shaft attached to the engine assembly, which has an inner shaft bore for receiving hydraulic fluid. An oil control valve assembly is attached to the rocker arm shaft and fluidically connected to the inner shaft bore to receive a portion of the hydraulic fluid.Several rocker arms are pivotally mounted on the rocker arm shaft; one end of each rocker arm is connected to a corresponding pushrod, while the opposite end of the rocker arm is connected to a corresponding valve. Each subset of rocker arms comprises a hydraulically actuated spring locking unit, which is mounted to, integrally formed with, or otherwise attached to the pushrod end of the rocker arm. Each spring locking unit secures its rocker arm to the pushrod and is in fluid communication with the OCV unit. The supply of hydraulic fluid from the OCV unit causes the spring locking unit to release the rocker arm from the pushrod. An insert sleeve is fitted in the inner bore of the rocker arm shaft, which receives hydraulic fluid from the rocker arm shaft.The insert sleeve includes a feed port that directs hydraulic fluid from the rocker arm shaft and insert sleeve to an OCV inlet port of the OCV unit, and a feed pocket that directs hydraulic fluid from an OCV outlet port of the OCV unit to each spring locking unit.

[0017] Other aspects of this disclosure relate to motor vehicles equipped with variable displacement valve train systems and rocker shafts with fluid ports and rocker shaft insert sleeves for cylinder / valve deactivation. As used herein, the terms "vehicle" and "motor vehicle" may be used interchangeably and synonymously to include any relevant vehicle platform, such as passenger cars (e.g., ICE, HEV, FCHEV, fully and partially autonomous vehicles, etc.), commercial vehicles, industrial vehicles, tracked vehicles, all-terrain and off-road vehicles (ATVs), motorcycles, agricultural equipment, aircraft, watercraft, spacecraft, etc. By way of example, a motor vehicle comprises a vehicle body with a passenger compartment, several wheels attached to the vehicle body (e.g., via corner modules coupled to a unibody or body-on-frame chassis), and other standard equipment.An internal combustion engine assembly is attached to the vehicle body (e.g. on engine mounts in an engine compartment) and is designed to drive one or more of the wheels and thus propel the motor vehicle.

[0018] Continuing the discussion of the preceding vehicle example, the internal combustion engine assembly (ICE assembly) comprises an engine block with multiple cylinder bores, a cylinder head mounted on the engine block and covering the cylinder bores, and multiple pistons, each capable of reciprocating within one of the cylinder bores. Multiple intake valves are movably attached to the cylinder head, each configured to open and close an intake port to one of the cylinder bores. The ICE assembly also includes a camshaft rotatably mounted to the engine block, carrying a set of lobes; a set of pushrods with pushrod lifters is each slidably mounted on one of the lobes of the camshaft. A rocker arm shaft, rigidly mounted to the cylinder head, has an inner bore that receives hydraulic fluid from a supply passage in the cylinder head.An OCV unit is mounted on the rocker arm shaft and connected to the inner shaft bore to receive some of the hydraulic fluid.

[0019] Several rocker arms are pivotally mounted on the rocker arm shaft; each rocker arm is connected at one end to a corresponding pushrod and at the opposite end to a valve stem of a corresponding intake (or exhaust) valve. A subset of rocker arms each has a spring-locking assembly attached to the pushrod end of the rocker arm. Each spring-locking assembly connects the rocker arm to the corresponding pushrod and is in fluid communication with the OCV unit. The intake of high-pressure hydraulic fluid from the OCV unit causes the spring-locking assembly to decouple the rocker arm from the pushrod. An insert sleeve for receiving the hydraulic fluid is fitted in the inner bore of the rocker arm shaft.The insert sleeve has a supply port that transfers hydraulic fluid from the insert sleeve to an OCV inlet port of the OCV unit, and a supply pocket that transfers hydraulic fluid from an OCV outlet port of the OCV unit to the spring locking units of the rocker arm subgroup.

[0020] Aspects of this disclosure also relate to methods for manufacturing and methods for operating the valve train systems, engine assemblies, and / or motor vehicles described herein. An example presents a method for assembling a valve train control system of an engine assembly. The engine assembly has multiple cylinders, multiple valves for opening and closing ports to the cylinders, a camshaft rotatably mounted near the valves, and multiple pushrods with lifters seated on cams of the camshaft. This representative method includes, in any order and in any combination with any of the options and features disclosed above and below, attaching a rocker arm shaft to the engine assembly, the rocker arm shaft having an inner bore configured to receive hydraulic fluid; attaching an OCV unit to the rocker arm shaft;Fluid coupling of the OCV unit with the inner bore of the rocker arm shaft to receive the hydraulic fluid; pivoting mounting of a rocker arm on the rocker arm shaft; connecting a first end of the rocker arm to the pushrod; connecting a second end of the rocker arm to the valve; attaching a spring locking unit, which is attached to the first end of the rocker arm, to the pushrod; fluid coupling of the spring locking unit with the OCV unit to obtain hydraulic fluid from it, thereby actuating the release of the rocker arm from the pushrod;and fitting an insert sleeve inside the inner shaft bore to obtain the hydraulic fluid from the rocker arm shaft, the insert sleeve comprising a supply port for transferring hydraulic fluid from the inner shaft bore and the insert sleeve to an OCV inlet port of the OCV unit and a supply pocket for transferring hydraulic fluid from an OCV outlet port of the OCV unit to the spring locking unit.

[0021] In all disclosed VDV systems, vehicles, and methods, the insert sleeve has an elongated and hollow sleeve body, e.g., a rectangular cylinder made of carbon steel. The feed port is a through-hole extending through a side wall of the sleeve body, while the feed pocket is an elongated channel recessed into the outer surface of the sleeve body. The insert sleeve also has an elongated and straight worm track recessed into the outer surface of the sleeve body, in fluid communication with the feed pocket, and extending longitudinally along the insert sleeve. The rocker arm has an inlet channel in fluid communication with a feed orifice extending through a circumferential wall of the rocker arm shaft.In this case, the worm gear connects the inlet channel and feed orifice to the feed pocket and OCV outlet to transfer hydraulic fluid from the OCV to the spring-lock assembly. It may be desirable for the insert sleeve to be pressed, inserted, or transition-fitted into the rocker arm shaft so that the sleeve's outer surface is flush with the rocker arm shaft's inner surface, thus creating a seal. Furthermore, the insert sleeve can be cast and precision-machined as a single-piece cylindrical structure, made entirely or partially of a metallic material or a rigid polymer.

[0022] In all disclosed VDV systems, vehicles, and methods, the OCV unit may comprise a protective valve body with an inlet chamber, a control tube, and a check valve. The inlet chamber is in fluid communication with the OCV inlet port, the control tube is in fluid communication with the OCV outlet port, and the check valve is inserted between the inlet chamber and the control tube. The OCV unit is selectively switchable (e.g., via a command signal from the ECM) to change between an OFF state and an ON state. In the OFF state, the check valve restricts the flow of hydraulic fluid from the OCV inlet port to the OCV outlet port. In the ON state, the check valve allows unimpeded flow of hydraulic fluid from the OCV inlet port to the OCV outlet port. The check valve may include a solenoid-operated check ball bearing against a valve seat.When the OCV unit is switched off, the check ball may be at least partially detached from the valve seat to maintain a predefined start-up pressure in the hydraulic fluid. The OCV unit may also include a pressure relief valve that regulates the start-up pressure when the OCV unit is switched off (e.g., to ensure that the start-up pressure does not reach a deactivation pressure of the valve).

[0023] In all disclosed VDV systems, vehicles, and methods, the spring-loaded locking unit may comprise an outer locking housing, a pushrod piston that is slidable within the locking housing, and a spring-loaded locking pin that locks the pushrod piston to the locking housing. The pushrod piston may have a pushrod seat that receives one end of the pushrod. A return spring may be arranged in the locking housing to bias the pushrod piston against the pushrod. Hydraulic fluid, directed from the OCV unit through the insert sleeve and into the locking housing, for example, upon reaching the valve deactivation pressure, releases the spring-loaded locking pin, thereby unlocking the pushrod piston from the locking housing and disengaging the pushrod from the rocker arm.By releasing the spring-loaded locking pin, the pushrod piston and pushrod can move against a return spring in the locking housing. The locking housing can be integrated with the plunger end of the rocker arm as a single unit.

[0024] In all disclosed VDV systems, vehicles, and methods, each OCV unit can be physically mounted directly onto and enclose the OD surface of the rocker arm shaft (e.g., eliminating unnecessary piping between the OCV and rocker arm shaft). Similarly, each rocker arm and spring-locking unit can be mounted directly onto and enclose the outer surface of the rocker arm shaft (e.g., to avoid unnecessary piping between the OCV and rocker arm). One end of the rocker arm shaft can have an inlet port extending through a side wall of the rocker arm shaft and connecting to a supply channel in the engine cylinder head, receiving hydraulic fluid from there. The rocker arm shaft can also have a shaft outlet port extending through a side wall of the rocker arm shaft and communicating with the shaft inlet port via the inner shaft bore.The outlet opening of the rocker arm shaft is aligned with the inlet opening of the OCV unit and the supply opening of the insert sleeve and is in direct fluid contact with them.

[0025] The above summary does not represent every embodiment or aspect of the present disclosure. Rather, the preceding summary merely provides an overview of some of the novel concepts and features set forth herein. The features and advantages mentioned above, as well as other features and associated advantages of this disclosure, will be readily apparent from the following detailed description of illustrated examples and representative modes of carrying out the disclosure, when considered in conjunction with the accompanying drawings and claims. Furthermore, this disclosure expressly includes all combinations and subcombinations of the elements and features described above and below. Brief description of the drawings Fig. Figure 1 is a perspective front view of a representative motor vehicle with an inserted schematic representation of a representative reciprocating internal combustion engine assembly which may use a variable displacement valve train system for deactivating engine cylinders according to the aspects of the present disclosure. Fig. Figure 2 is a partially cutaway, perspective view of part of a representative variable displacement valve train system with a rocker arm shaft with oil connection and a rocker arm shaft insert sleeve in accordance with aspects of the present disclosure. Fig. Figure 3 is an enlarged and partially cut-out perspective view of the rocker arm shaft, the VDV rocker arms, the rocker arm spring locking unit, the insert sleeve, and the oil control valve of the representative variable displacement valve train system. Fig. 2. Fig. 4A and Fig. Figure 4B shows perspective views of the rocker arm shaft insert sleeve of the representative variable displacement valve train system. Fig. 2.

[0026] The present disclosure is suitable for various modifications and alternative forms, and some representative embodiments of the disclosure are illustrated by way of example in the drawings and are described in detail herein. It should be understood, however, that the novel aspects of this disclosure are not limited to the particular forms illustrated in the drawings listed above. Rather, this disclosure encompasses all modifications, equivalents, combinations, permutations, groupings, and alternatives that fall within the scope of this disclosure, such as those covered, for example, by the attached claims. Detailed description

[0027] This disclosure can be implemented in many different forms. Representative embodiments of the disclosure are shown in the drawings and are described in detail herein, whereby it is assumed that these embodiments serve as examples of the disclosed principles and do not represent limitations of the general aspects of the disclosure. Therefore, elements and limitations described, for example, in the sections "Summary," "Introduction," "Description," "Brief Description of Drawings," and "Detailed Description," but not expressly included in the claims, should not be considered to be incorporated into the claims, either individually or collectively, either implicitly or by inference or otherwise. Furthermore, the mention of "first," "second," "third," etc., serves no purpose other than to provide a general basis for the disclosure.The terms used in the description or the claims do not per se establish a serial or numerical limitation; unless expressly stated otherwise, these designations may be used for easier reference to similar features in the description and the drawings and for distinguishing between similar elements in the claims.

[0028] For the purposes of this disclosure, unless expressly excluded, the singular includes the plural and vice versa (e.g., the indefinite articles "a" and "an" are to be understood as meaning "one or more"); the words "and" and "or" apply in both the subjunctive and disjunctive moods; the words "every" and "all" mean "every and all"; and the words "including," "containing," "comprising," "having," and the like each mean "including without limitation." Furthermore, words of approximation, such as "about," "almost," "essentially," "generally," "nearly," and the like, may be used here to denote, for example, "at, close to, or almost at," or "within 0-5% of," or "within acceptable manufacturing tolerances," or any logical combination thereof.Finally, directional adjectives and adverbs such as forward, backward, inside, outside, starboard, port, vertical, horizontal, upward, downward, front, back, left, right, etc. can refer to a motor vehicle, e.g., to the forward movement of a motor vehicle when the vehicle is set up on a horizontal roadway.

[0029] Now, with reference to the drawings, where the same reference symbols refer to the same features in the different views, it is in Fig. Figure 1 shows a perspective view of a representative motor vehicle, generally designated 10, which is shown here for discussion purposes as a gasoline-powered, sedan-like passenger vehicle. The motor vehicle 10 shown—here also referred to simply as the “motor vehicle” or “vehicle”—is merely an exemplary application with which new aspects of this disclosure can be put into practice. Likewise, the implementation of the present concepts in a four-stroke spark-ignition gasoline engine of an internal combustion engine-based powertrain should be understood as an exemplary application of the new concepts disclosed herein. It is understood that the features of this disclosure can also be applied to other engine configurations, integrated into alternative powertrain architectures, and used for any logically relevant type of motor vehicle.Finally, only selected components of the motor vehicle and engine assembly have been shown and are described in detail here. However, the vehicles, engines, and valve trains described below may include numerous additional and alternative features and other available peripheral components for carrying out the various procedures and functions of this disclosure.

[0030] Fig. Figure 1 illustrates an example of an internal combustion engine assembly 100 (also ICE assembly or engine assembly) in a V-configuration with overhead valves (OHV) installed in an engine compartment 14 of a vehicle body 16 of the motor vehicle 10. The ICE assembly 100 shown is a four-stroke reciprocating piston engine configured to drive one or more wheels 22 of the vehicle to propel the vehicle 10, for example as a gasoline engine with direct injection (DI) or port fuel injection (PFI), including variants for flexible fuel vehicles (FFV) and hybrid electric vehicles (HEV). The engine assembly 100 can optionally be configured in one of the selectable combustion modes, including a homogeneous charge compression ignition (HCI) combustion mode.Homogeneous Charge Compression Ignition (HCCI) and a combustion mode with variable stroke (active fuel management (AFM)) and spark ignition (SI). Although in . Fig. Unless explicitly shown, the vehicle's drivetrain can assume any available configuration, including front-wheel drive (FWD), rear-wheel drive (RWD), all-wheel drive (AWD), four-wheel drive (4WD), etc.

[0031] The illustrated engine assembly 100 comprises a cast metal engine block 105 with a staggered sequence of cylinder bores, for example, a first cylinder bore (or set of cylinder bores) 104 and a second cylinder bore (or set of cylinder bores) 106. A ring-bearing piston 108 and 110 is movable back and forth in each cylinder bore (or, in short, "cylinder") 104, 106, i.e., it can move linearly from a top dead center (TDC) position to a bottom dead center (BDC) position. A torque-transmitting engine crankshaft 112 is rotatably mounted in an engine crankcase 102, which is attached to the underside of the engine block 105. Each piston 108, 110 is connected to the crankshaft 112 via a bearing-mounted connecting rod 114 and 116. Pistons in 108 and 110 engines are typically installed in even numbers of 4, 6, 8, etc.The cylinders are provided and arranged in a V or I configuration; however, the disclosed concepts are similarly applicable to other numbers of cylinders (e.g., 3, 5, etc.) and arrangements (e.g., H-type, flat, etc.). The upper surface of each piston 108, 110 interacts with the inner circumference of the corresponding cylinder 104, 106 and a corresponding chamber area of ​​a cylinder head 126 and 128 to form a variable-volume combustion chamber. The crankshaft 112, in turn, converts the linear reciprocating motion of the pistons 108, 110 into a rotary motion, which is transmitted, for example, as a number of revolutions per minute (rpm) to a power transmission system (not shown) to drive one or more wheels 22.

[0032] With continued reference to the detailed view of Fig. Figure 1 uses a valve train system 124 of an engine, employing a set of one or more intake valves 120 and one or more exhaust valves 122 for each cylinder 104, 106 to regulate the intake and exhaust of its variable-volume combustion chamber. A pair of cylinder heads 126, 128 are mounted on the engine block 105 to form a V-engine configuration with two banks of cylinders 104, 106 arranged at an angle to each other. An air intake system (not shown) directs the intake air via an intake manifold to the cylinders 104, 106, which directs and distributes the air through the respective intake ports and intake openings of the cylinder head 126, 128 into the individual combustion chambers. The engine's air intake system includes airflow tubes and various electronic devices for monitoring and controlling the incoming airflow.The airflow from the intake manifold into the individual combustion chambers is controlled by one or more of the intake valves 120 of the engine, while the discharge of the exhaust gases and combustion by-products from the individual combustion chambers to an exhaust manifold of an engine exhaust system is controlled by one or more of the exhaust valves 122 of the engine.

[0033] The valve train system 124 uses a time-synchronized camshaft 130, which is rotatably mounted in a camshaft pocket in a cylinder bank of the engine block 105, to selectively activate the intake and exhaust valves 120 and 122. The camshaft 130 carries and rotates a series of cams, such as intake and exhaust cams 144 and 146, respectively. A cam-to-rocker drive system (CtR drive system) 142 can engage the intake and exhaust cams 144 and 146 with corresponding rocker arms 138 and 140 to pivot the rocker arms 138 and 140, thereby opening the intake and exhaust valves 120 and 122. The CtR drive system 142 can comprise valve lifters 150 and 152 that act on the cams, each of which is attached to a distal (lower) end of a corresponding pushrod 154 and 156 of the engine and is slidably mounted on a corresponding cam 144, 146.The valve lifters 150, 152 transmit input forces from the cams 144, 146 of the camshaft 130 to the pushrods 154, 156 to convert the rotary motion of the camshaft 130 into a linear motion of the pushrods 154, 156. The valve lifters 150, 152 can each include a roller tappet 158 ​​and 160 (as shown) or a round-point tappet, which can have solid or hydraulic form factors.

[0034] During engine operation, the rotation of the camshaft 130 causes the intake and exhaust cams 144, 146 to press against the valve lifters 158, 160 and the pushrods 154, 156, resulting in a mutual linear displacement. The pushrods 154, 156, in turn, strike the corresponding ends of the rocker arms 138, 140; this causes the rocker arms 138, 140 to pivot against and press against the valve stems of the intake and exhaust valves 120, 122. It is also conceivable that the CtR drive system 142 uses other types of valve lift configurations, including both continuous and discrete variable valve lift (VVL) devices. For example, the activation of the engine valves 120, 122 can be modulated by the control of the variable exhaust and intake camshaft adjustment / variable lift control (VCP / VLC).It is also possible to replace the valve lifters 150, 152 with hydraulic lash adjusters or solid valve lifters. These engine valves 120, 122 are shown here as spring-loaded poppet valves; however, other commercially available types of engine valves can also be used.

[0035] The following discusses variable displacement valvetrain (VDV) systems and methods with rocker arm shaft oil porting and rocker arm shaft insert sleeves that enable cylinder deactivation for internal combustion engines, such as the OHV-ICE 100 assembly. As a non-restrictive example, rocker arm switching oil is routed from the cylinder head into the rocker arm shaft, through an insert sleeve within the rocker arm shaft to an electromagnetically actuated valve, which then routes oil from the valve back through the insert sleeve to a subset of rocker arms. The rocker arm shaft insert sleeve simplifies the control system and the method for routing the oil through the feed ports in the rocker arm shaft to the intake ports of the rocker arms. This helps to avoid the addition of more complex oil passages (e.g.,Precision bores, piping, seals, manifolds, and other hydraulic auxiliary components become unnecessary. This helps to reduce the size, weight, cost, and warranty-related issues of the engine assembly. Furthermore, the disclosed VDV systems allow the oil flowing to the rocker arm to operate at a different pressure level than the oil in the rocker shaft, which is maintained at the level of the engine oil pressure.

[0036] The solenoid-operated oil control valve (OCV) is located in the fluid path with the inner oil bore of the rocker arm shaft and controls the oil pressure to the VDV rocker arms. An inner fluid channel in the rocker arm shaft insert guides the oil from the rocker arm shaft to the OCV, while a separate outer fluid channel on the insert guides the oil from the OCV to the VDV rocker arms. The OCV may include a pressure regulating valve assembly to allow low-pressure oil to flow to the rocker arms during normal engine operation, for example, to lubricate the contact points between the pushrods and rocker arm, as well as the bore between the rocker arm and rocker arm shaft. If the OCV is controlled by the engine's electronic control unit (ECU), such as a dedicated engine control module (ECM), the pressure may be reduced by the ECU.When activated by the Engine Control Module (ECM), the overrun valve (OCV) deactivates a selected subset of engine cylinders by diverting the high-pressure oil flow to the VDV rocker arms to disable valve lift. The ECU / ECM signal activates the overrun valve (OCV) solenoid, allowing a ball valve of an inner one-way valve assembly to disengage from a control seat. Simultaneously, the OCV solenoid moves the ball valve to seat on a regulator seat, sealing off oil flow to the pressure regulating valve assembly. When the OCV is deactivated, the one-way OCV assembly partially opens to maintain a minimum pressure in the supply port to prepare the control galleries and minimize oil venting.

[0037] When the OCV is activated, pressurized oil is directed to a dead-travel spring-locking assembly mounted on or integrated into each of the VDV shift rocker arms. The high-pressure oil pushes against a spring-loaded locking pin, compressing a locking pin return spring to force the locking pin into an unlocked position. This allows a pushrod piston, located at the proximal (top) end of a pushrod, to move against a dead-travel return spring within the spring-locking assembly. In the unlocked position, the spring-locking assembly releases the pushrod from the rocker arm, so that each time the cam rotates to lift the pushrod, the pushrod's linear force is directed against the dead-travel return spring.The pushrod, pushrod piston, and spring-loaded locking pin move while the rocker arm assembly remains stationary on the rocker arm shaft. As the cam rotates out of its lift position, the dead-end return spring pushes the pushrod piston, and thus the pushrod and spring-loaded locking pin, back toward the camshaft to ensure that the pushrod remains in contact with the camshaft throughout the entire effective lift cycle.

[0038] It may be desirable for the rocker arm shaft insert sleeve to be made of carbon steel, typically a grade with a coefficient of thermal expansion as close as possible to that of the rocker arm shaft. In alternative embodiments, other metallic, polymer, and composite materials may be used to manufacture the insert sleeve; however, differences in coefficients of thermal expansion and strength should be optimized to avoid deformations that could lead to seizing or mechanical failure of the system. It may be desirable for the insert sleeve to be press-fitted, fitted, or transition-fitted into the rocker arm shaft so that the outer surface of the sleeve is flush with the inner surface of the rocker arm shaft. Alternative system architectures may include the use of seals to minimize or eliminate system leakage and associated pressure losses.The combination of insert sleeve and rocker arm can be optimized to minimize the overall volume of the control gallery, achieve maximum acceptable ventilation, and attain an acceptable system response time. VDV rocker arms can be mounted directly on the rocker shaft or indirectly using a plain bearing, bushing, roller bearing, etc., ensuring adequate lubrication between the rocker shaft and rocker arm to prevent welding.

[0039] Fig. Figure 2 shows a representative valve train system 200 with variable displacement and a rocker arm shaft 202 and an insert sleeve 204 of the rocker arm shaft 202 for deactivating selected valves and cylinders of an engine assembly, such as the intake valve(s) 120 and the cylinder(s) 104 of the engine of Fig. 1. The rocker arm shaft 202 is functionally mounted on an engine assembly and carries one or more valve actuation devices on it. According to the example shown, the rocker arm shaft 202 is rigidly attached to a top surface of an engine cylinder head 206 (e.g., cylinder heads 126, 128 of Fig. 1) The rocker arm shaft 202 is mounted and pivotably supports a series of rocker arms 208 of the valve train (e.g., rocker arms 138, 140). The opposing longitudinal ends of the rocker arm shaft 202 can be inserted into the respective base brackets 210 of the cylinder head 206 and rigidly fastened thereto by means of hexagonal screws 212. To simplify the design and manufacture, the rocker arm shaft 202 can be an elongated and hollow, rectangular cylinder formed as a one-piece structure from a rigid and elastic material (e.g., machined stainless steel tubing). The rocker arm shaft 202 is designed to be mounted at alternative locations on the cylinder head or engine block and to support any number of rocker arms 208, depending, for example, on the arrangement and size of the engine assembly.

[0040] For the lubrication and control of the valve activation devices of the VDV system, the rocker arm shaft 202 is provided with a pressurized inner bore (“inner shaft bore”) 201, which receives hydraulic fluid from a fluid collection volume and directs the hydraulic fluid to the rocker arm arms 208. As shown in the detailed view of Fig. As can be seen best in Figure 2, the rocker arm shaft 202 includes, for example, an inlet opening 203 of the rocker arm shaft 202, which protrudes through a side wall of the rocker arm shaft 202 and is connected to a fluid supply passage 205 that runs through the cylinder head 206. This fluid supply passage 205 can draw pressurized engine oil from an engine oil pan via an engine oil pump (not visible in the views shown) and supply the oil via the inlet opening 203 of the rocker arm shaft 202. An outlet opening 207 ( Fig. 3) The rocker arm shaft 202 projects through a side wall of the rocker arm shaft 202 and is in fluid communication with the inlet port 203 of the rocker arm shaft 202 via the inner shaft bore 201 and the insert sleeve 204. The outlet port 207 of the rocker arm shaft 202 is directly fluidically connected to an OCV inlet port 209 of an OCV unit 214 and a supply port 211 of the insert sleeve 204 (i.e., without any intervening piping, valves, etc.). Optional end seals 216 can be inserted into the open longitudinal ends of the rocker arm shaft 202 to fluidly seal the rocker arm shaft 202 and the insert sleeve 204.

[0041] The variable displacement valve train system 200 Fig. 2 and Fig. Figure 3 uses an active flow control valve to regulate the flow of hydraulic fluid to the valve activation devices of the VDV system. According to the illustrated example, a control-automated OCV unit 214 is operationally mounted on the rocker arm shaft 202 and fluidically connected to the outlet port 207 of the rocker arm shaft 202 to receive a portion of the fluid flowing through the inner shaft bore 201. The OCV unit 214 is mounted directly on the rocker arm shaft 202 and encloses a surface with an outside diameter (OD) that is positioned between two of the rocker arm arms 208. Although the OCV unit 214 is shown as an electromagnetically actuated valve, it can also assume other valve designs, including pneumatically actuated and motor-driven devices.Furthermore, a single OCV unit 214 can regulate the oil supply to several rocker arms 208 (as shown) or be intended for the oil supply to a single rocker arm 208.

[0042] With reference to Fig. 3 The OCV unit 214 comprises a protective valve housing (or “can”) 218 ​​with an internal cavity 213 extending through the valve housing 218 from a first (upper) end to a second (lower) end. Inside the valve housing 218 are an annular polymer coil former 222 and an electromagnetic coil 220, which is wound coaxially with and around the coil former 222. A magnetic armature assembly, which is in Fig. The valve assembly 224, generally designated as 224, is a three-part assembly that moves as a single unit within the valve body 218, for example, along a generally straight path. This valve assembly 224 generally consists of a cylindrical valve 226, which is circumscribed by the coil 220, an elongated valve arm 228, which is attached to a distal (lower) end of the valve 226 and projects axially from it, and a check ball 230, which bears against a distal (lower) end of the valve arm 228. The valve 226 is located immediately adjacent to a pole piece 232 of the valve, with a helical return spring 234 that biases the valve 226 away from the pole piece 232. The valve 226 is made of a metal or a metal alloy, such as... B. steel or iron, manufactured and slides selectively in the inner cavity 213 (e.g. vertically upwards in Fig. 3) in response to the active excitation of coil 220.

[0043] At a distal (lower) end of the valve housing 218 is an inlet chamber 215 of the OCV, which is in fluid communication with the inlet port 209 of the OCV and, via the inlet port 209, with the outlet port 207 of the rocker arm shaft. Downstream of the inlet chamber 215 is a control tube 217 of the OCV, which is in fluid communication with the inlet chamber 215 and an outlet port 219 of the OCV. A check valve, e.g., a check ball 230, is arranged between the inlet chamber 215 and the control tube 217 and throttles the flow of the hydraulic fluid. The check ball 230 is movable such that it rests against a first (inlet) valve seat 238 and separately against a second (relief) valve seat 240. A vehicle ECU / ECM is programmed to selectively switch the OCV unit 214 between an OFF state and an ON state.When the OCV unit 214 is in the OFF state, the check ball 230 rests at least partially against the first valve seat 238 to limit the flow of hydraulic fluid from the OCV inlet port 209 to the OCV outlet port 219. It may be desirable for the solenoid assembly 224 to partially lift the check ball 230 from the first valve seat 238 to maintain a predefined suction pressure in the hydraulic fluid when the OCV unit 214 is off. When the OCV unit 214 is switched to the ON state by the ECU / ECM, the solenoid assembly 224 fully lifts the check ball 230 from the first valve seat 238 to allow a generally unimpeded flow of hydraulic fluid from the OCV inlet port 209 to the OCV outlet port 219.The magnetic valve assembly 224 can move upwards so that the check ball 230 can rest against the second valve seat 240 to limit the flow of fluid to a spring-loaded, ball-shaped pressure relief valve 258 when the OCV unit 214 is in the zero position.

[0044] Each rocker arm 208 is pivotably mounted on the rocker shaft 202, with a first (rocker arm) end 221 of the rocker arm 208 being functionally equipped with a corresponding pushrod 242 and a second (rocker arm) end 223 of the rocker arm 208 being functionally equipped with a corresponding valve 260. A selected subgroup of the rocker arms 208, namely those that are not suitable for selective deactivation, can be connected with their respective pushrods 242 and valves 260 to the rocker arms 138, 140 described above. Fig. 1 interact in the manner described. Conversely, another selected subgroup of the rocker arms 208 (in Fig. 3 designated with 208'), namely those which are eligible for selected ‘variable displacement’ deactivation (also referred to here as ‘VDV shift rocker arms’), each a corresponding spring locking unit (or ‘deactivation (DEAC) unit’) 244 ( Fig. 3), which is attached to the first end 221 of the rocker arm 208 to actuate and decouple this rocker arm 208 with its pushrod 242. Each spring locking unit 244 has a protective locking housing (or “DEAC housing”) 246 with a pushrod seat 247 in which a complementary pushrod ball sits at a proximal (upper) end of the respective pushrod 242. The rocker arm 208 and the locking housing 246 can be formed integrally or manufactured as separate parts that are then rigidly connected to each other (as shown).

[0045] To detach the rocker arms 208 from the pushrods 242, the OCV unit 214 couples and supplies a metered portion of the hydraulic fluid to each of the spring locking units 244. As in Fig. As can be best seen in Figure 3, for example, each of the VDV shift rocker arms 208' includes an inner inlet channel 225, which is in fluid communication with a feed orifice 227 of the rocker shaft 202, extending through a circumferential side wall of the rocker shaft 202. The rocker inlet channel 225 is in fluid communication with the feed orifice 227 and a piston chamber 229 in the locking housing 246 of the spring locking unit 244. A pushrod piston (or "bolt housing") 248, when unlocked, is slid back and forth within the locking housing 246 to move along a linear path (e.g., from top to bottom) in response to the pressure forces exerted by the pushrod 242. Fig. 3) to move. The pushrod seat 247 is recessed into a (lower) end of the pushrod piston 248 to receive one end of the pushrod 242. A return spring 250, which may be designed as a helical compression spring, is arranged inside the locking housing 246 and presses against a proximal (upper) surface of the pushrod piston 248 to bias the piston 248 towards a distal (lower) end of the locking housing 246.

[0046] For selective locking of the pushrod piston 248 with the locking housing 246, a spring-loaded locking pin 252 is arranged inside the locking housing 246. This locking pin slides into a complementary locking pin slot 231, which is recessed into a side of the pushrod piston 248. A return spring 254 of the locking pin 252, which may be designed as a helical compression spring, is located inside the locking pin slot 231 and is compressed between the locking pin 252 and the pushrod piston 248. If no hydraulic fluid with sufficient pressure is present to compress the return spring 254, the return spring 254 of the locking pin 252 pushes the locking pin 252 laterally out of an open end of the locking pin slot 231 and into stop contact with a complementary recess in a side wall of the locking housing 246.This locks the pushrod piston 248 with the locking housing 246, so that the driving forces exerted by the pushrod 242 on the pushrod piston 248 are transmitted from the pushrod piston 248 and the locking pin 252 via the locking housing 246 to the rocker arm 208'.

[0047] When hydraulic fluid with sufficient pressure to overcome the spring force of the return spring 254 is present, the locking pin 252 is pressed against the return spring 254 and compressed. Simultaneously, the locking pin 252 slides out of the stop contact with the complementary recess in the locking housing 246. This releases the spring-loaded locking pin 252 and unlocks the pushrod piston 248, allowing it to move freely against the dead-travel return spring 250. In the unlocked state, the driving forces and movements exerted by the pushrod 242 on the pushrod piston 248 are not transmitted from the pushrod piston 248 to the rocker arm 208', but are instead dissipated by the dead-travel return spring 250.

[0048] Unlike other available variable displacement valve train systems, the VDV system 200 uses Fig. 2 and Fig. 3 a fluid-supplied rocker arm shaft 202 with an inner rocker arm shaft insert sleeve 204 to direct hydraulic fluid from the OCV unit 214 to the spring locking unit 244 to enable selective deactivation of the engine cylinders. According to the illustrated example, one or more insert sleeves 204 are rigidly mounted in the inner shaft bore 201 to receive hydraulic fluid from the supply passage 205 of the cylinder head through the rocker arm shaft 202. To simplify design and manufacture, each insert sleeve 204 can be cast and precision-machined as an elongated and hollow one-piece structure made entirely or partially of a metallic material. Alternatively, the sleeve can also be formed from a rigid plastic material. The insert sleeve 204 of Fig. Although not inherently limited, 3 has a tubular sleeve body 256 with an open end, made of carbon steel and having a right-angled cylindrical shape. It should be noted that the number, shape, size and / or position of the insert sleeve(s) 204 may differ from those shown in the drawings.

[0049] As in Fig. 4A and Fig. As shown in Figure 4B, the opposing first and second longitudinal ends 233 and 235, respectively, of the sleeve body 256 can be open and unobstructed, allowing hydraulic fluid to flow freely through the insert sleeve 204. As mentioned above, a through-hole-like supply opening 211 extends through a side wall of the sleeve body 256 and is in fluid communication with the outlet opening 207 of the rocker arm shaft and the inlet opening 209 of the OCV to direct hydraulic fluid from the insert sleeve 204 to the OCV unit 214. Downstream of the outlet opening 207, the inlet opening 209, and the supply opening 211 is a supply pocket 237, which is in communication with the outlet opening 219 of the OCV and directs the fluid received from the OCV to the VDV shift rocker arms 208'. This feed pocket 237 is shown as a narrow channel recessed into the outer surface of the sleeve body 256, as shown in the Fig. 4A and Fig. 4B can be seen. The insert sleeve 204 of the Fig. 4A and Fig.Figure 4B also includes an elongated and essentially straight helical path 239, which is recessed into the OD sleeve surface of the sleeve body 256 and is in fluid communication with the feed pocket 237 (e.g., by forming a single, arc-shaped channel that transfers fluid over the outer circumference of the sleeve 204). This helical path 239 is shown as a narrow channel recessed into the outer surface of the sleeve body 256 and extending longitudinally along the insert sleeve 204. The helical path 239 establishes a fluid connection between the feed pocket 237 of the sleeve and the outlet port 219 of the OCV, the feed port 227 of the rocker arm shaft, and the inlet port 225 of the rocker arm. It may be desirable for the outer surface of the sleeve of the insert sleeve body 256 to be substantially flush with an inner surface (ID) of the rocker arm shaft 202 and thus to seal.In this arrangement, the oil inlet flow passes through the interior of the rocker arm shaft 202 and the insert sleeve 204 to the OCV unit 214 and from the OCV unit 214 via the inner surface of the rocker arm shaft 202 and the outside of the sleeve 204.

Claims

[1] Valve train control system for an engine assembly (100) comprising a cylinder (104, 106), a valve (120, 122, 260) for opening and closing an opening to the cylinder (104, 106), a camshaft (130) rotatably mounted near the valve (120, 122, 260), and a pushrod (154, 156, 242) seated on a cam (144, 146) of the camshaft (130), the valve train control system comprising: a rocker arm shaft (202) configured to be attached to the engine assembly and having an inner shaft bore (201) configured to receive hydraulic fluid; an oil control valve unit, also called OCV unit (214), which is attached to the rocker arm shaft (202) and is in fluid communication with the inner shaft bore (201) in order to receive the hydraulic fluid from there; a rocker arm (138, 140, 208, 208') pivotably mounted on the rocker shaft (202) and having a first rocker end (221) configured to fit the pushrod (154, 156, 242) and a second rocker end (223) configured to fit the valve (120, 122, 260); a spring locking unit (244) attached to the first rocker arm end (221) and configured to secure the pushrod (242), the spring locking unit (244) being in fluid communication with the OCV unit (214) to receive hydraulic fluid from it in order to actuate the rocker arm (208, 208') away from the pushrod (242); and a sleeve insert (204) which is fitted in the inner shaft bore (201) to receive the hydraulic fluid from the rocker arm shaft (202), the sleeve insert (204) comprising a supply port (211) which transfers the hydraulic fluid from the sleeve insert (204) to an OCV inlet port (209) of the OCV unit (214), and a supply pocket (237) which transfers the hydraulic fluid from an OCV outlet port (219) of the OCV unit (214) to the spring locking unit (244); wherein the insert sleeve (204) further comprises an elongated and hollow sleeve body (256), wherein the feed opening (211) extends through a sleeve wall of the sleeve body (256), and wherein the feed pocket (237) is recessed into an outer sleeve surface of the sleeve body (256); wherein the insert sleeve (204) further comprises a worm track (239) which is embedded in the outer sleeve surface of the sleeve body (256), is in fluid communication with the feed pocket (237), and extends longitudinally over the length of the insert sleeve (204); wherein the rocker arm (208') has an inlet channel (225) which brings the spring locking unit (244) into fluid communication with a feed orifice (227) which extends through a circumferential shaft wall of the rocker shaft (202), wherein the worm track (239) brings the inlet channel (255) and the feed orifice (227) into fluid communication with the feed pocket (237) and the OCV outlet opening (219) of the OCV unit (214). [2] Valve train control system according to claim 1, wherein the outer sleeve surface of the insert sleeve (204) is flush with an inner shaft surface of the rocker arm shaft (202) and seals it. [3] Valve train control system according to claim 1, wherein the insert sleeve (204) is a one-piece cylindrical structure made of a metallic material. [4] Valve train control system according to claim 1, wherein the OCV unit (214) further comprises an inlet chamber (215) which is in fluid communication with the OCV inlet port (209), a control tube (217) which is in fluid communication with the OCV outlet port (219), and a check valve arranged between the inlet chamber (215) and the control tube (217), wherein the OCV unit (214) is selectively switchable between an OFF state in which the check valve restricts the flow of hydraulic fluid from the OCV inlet port (209) to the OCV outlet port (219) and an ON state in which the check valve allows the flow of hydraulic fluid from the OCV inlet port (209) to the OCV outlet port (219). [5] Valve train control system according to claim 4, wherein the check valve has a check ball (230) and a valve seat (238), wherein the check ball (230) is at least partially detached from the valve seat (238) to maintain a predefined start-up pressure in the hydraulic fluid when the OCV unit (214) is in the OFF state.

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