Automatic lash adjuster for use with high compression internal combustion engines

A hydraulic lash adjuster for use in diesel engines including a cylinder head having a first valve, a second valve, and a valve bridge extending between and in contact with both the first valve and the second valve. Where the diesel engine includes a first rocker arm, and where at least one of the first valve and the second valve undergo an oil can valve deflection rate. The hydraulic lash is configured to selectively transmit force between the first rocker arm and the valve bridge, and where the hydraulic lash adjuster is normally in the open configuration, and where the hydraulic lash adjuster changes from the open configuration to a closed configuration at a critical velocity that is greater than the oil can valve deflection rate.

FIELD OF THE INVENTION

The present invention relates to a high compression internal combustion engine, and more specifically a high compression internal combustion engine having a valve train with a normally open automatic lash adjuster.

BACKGROUND

High compression internal combustion engines, such as heavy duty diesel engines, use normally closed lash adjusters in their valve trains which can transmit potentially damaging forces through the valve train when valves deform as a result of “oil canning.”

SUMMARY

In one aspect, an internal combustion engine including an engine block at least partially defining a cylinder, a piston at least partially positioned within the cylinder and movable with respect thereto, a cylinder head coupled to the engine block and at least partially enclosing the cylinder, the cylinder head defining a first runner open to the cylinder and a second runner open to the cylinder, a first valve mounted to the cylinder head and movable with respect thereto between an open position, in which the first runner is in fluid communication with the cylinder, and a closed position, in which the first runner is fluidly isolated from the cylinder, a second valve mounted to the cylinder head and movable with respect thereto between an open position, in which the second runner is in fluid communication with the cylinder, and a closed position, in which the second runner is fluidly isolated from the cylinder, a valve bridge extending between and in contact with the first valve and the second valve, a first cam lobe with a profile corresponding to positive power operation, a second cam lobe with a profile corresponding to engine braking operation, a first input in operable communication with the first cam lobe and the valve bridge, a second input in operable communication with the second cam lobe and the valve bridge, and a hydraulic lash adjuster positioned between and configured to selectively transmit force between one of the first input and the second input and the valve bridge, and wherein the hydraulic lash adjuster is a normally open lash adjuster.

In another aspect, an internal combustion engine including an engine block defining a cylinder, a piston at least partially positioned within the cylinder and movable with respect thereto, a cylinder head coupled to the engine block and at least partially enclosing the cylinder, the cylinder head defining a first runner open to the cylinder, a first valve mounted to the cylinder head and movable with respect thereto between an open position, in which the first runner is in fluid communication with the cylinder, and a closed position, in which the first runner is fluidly isolated from the cylinder, and where the first valve undergoes an oil can valve deflection rate when the first valve is in the closed position, a first cam lobe, a first input in operable communication with the first cam lobe, and a hydraulic lash adjuster configured to selectively transmit force between the first input and the first valve, wherein the hydraulic lash adjuster is a normally open lash adjuster, and wherein the hydraulic lash adjuster includes a critical velocity greater than the oil can valve deflection rate.

In another aspect, a hydraulic lash adjuster for use in diesel engines including a cylinder head having a first valve, a second valve, and a valve bridge extending between and in contact with both the first valve and the second valve, where the diesel engine includes a first rocker arm, and where at least one of the first valve and the second valve undergo an oil can valve deflection rate, the hydraulic lash adjuster including a body having a first end operably connected to the first rocker arm and a second end opposite the first end operatively connected to the valve bridge, and where the body is configured to selectively transmit force between the first rocker arm and the valve bridge, and where the hydraulic lash adjuster is adjustable between an open configuration and a closed configuration, where the hydraulic lash adjuster is normally in the open configuration, and where the hydraulic lash adjuster changes from the open configuration to the closed configuration at a critical velocity that is greater than the oil can valve deflection rate.

DETAILED DESCRIPTION

Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of the formation and arrangement of components set forth in the following description or illustrated in the accompanying drawings. The disclosure is capable of supporting other implementations and of being practiced or of being carried out in various ways.

The disclosure generally relates to a high compression internal combustion engine (e.g., a heavy duty diesel engine) having a valve train assembly operable in both a positive power and engine braking modes of operation. The valve train of the engine includes a valve mounted within a cylinder head that undergoes deformation when the valve is in the closed position, a condition known as oil canning. The deformation is the result of the valve being subject to large pressure forces occurring within the compression chamber due to the relatively high firing or combustion pressures present in diesel engines. In light of this deflection, the valve train includes a normally open hydraulic lash adjuster (HLA) in operable communication with the first valve that has a critical velocity that is greater than the oil can deflection rate but less than the deflection rate produced by the cam as it opens the valve. By doing so, the lash adjuster remains in its open configuration as the oil canning occurs but closes when the valve is opened by the cam. Therefore, the HLA does not transmit the potentially damaging forces generated from the oil canning into the valve train, but does transmit the forces necessary to open the valve for positive power and engine braking operations. This capability is in contrast to existing high compression diesel internal combustion engines where normally closed hydraulic lifters are used that transmit the potentially damaging forces generated during oil canning into the valve train—resulting in excessive wear and premature failure of the engine. Furthermore, existing normally open HLA designs have not been used in high compression engines with engine braking capabilities as the deflection of the valve during oil canning activates the lash adjuster, causing it to become rigid and transmit the undesirable forces into the valve train.

FIG. 1illustrates an internal combustion engine (ICE)10for use with an improved valve train14installed thereon. The ICE10includes a block18, a cylinder head22coupled to the block18to define a cylinder26therebetween, and a crank shaft30rotatably coupled to the block18for rotation bout a crank axis34. The ICE10also includes an improved valve train14configured to selectively open and close a plurality of valves40a,40b,40cin fluid communication with the cylinder26.

As shown inFIG. 1, the cylinder head22of the ICE10includes a body46coupled to the block18to at least partially enclose the cylinder26therebetween. The body46defines an intake runner50extending between and in fluid communication with an intake manifold (not shown) and the cylinder26, and an exhaust runner54extending between and in fluid communication with an exhaust manifold (not shown) and the cylinder26. Although not all are shown, each runner50,54, also forms a pair of seats58a,58b,58copen to the cylinder26and configured to interact with a corresponding valve40a,40b,40c. In the illustrated implementation, each runner50,54has a two seats58a,58b,58copen to the cylinder26(e.g., to produce a four valve head), however in alternative implementations, more or fewer runners and/or seats may be present.

The ICE10also includes a piston36and a connecting rod62as is well known in the art (seeFIG. 1). During use, the piston36is positioned and reciprocally travels within the cylinder26between a top dead center position (TDC), in which the cylinder26is located proximate the cylinder head22, and a bottom dead center position (BDC), in which the cylinder26is located away from the cylinder head22. As is well known in the art, the reciprocating motion of the piston36rotates the crank shaft30about the crank axis34in a first direction of rotation66(seeFIG. 1). In the illustrated implementation, the ICE10is a four-stroke design having an intake stroke70, a compression stroke74, an expansion or power stroke78, and an exhaust stroke82as is well known in the art (seeFIG. 5A).

During operation, the ICE10is operable in a positive power condition (see valve travel path100inFIG. 5D), in which the ICE10drives the crank shaft30in the first direction of rotation66(e.g., applies torque to the crank shaft30in the first direction66), and a negative power condition (see valve travel path104inFIG. 5D), in which the ICE10resists the rotation of the crank shaft30and acts as a brake (e.g., applies torque to the crank shaft30in a second direction86opposite the first direction66). Stated differently, the positive power condition of the ICE10generally correspond with combustion cycle operations while the negative power condition generally corresponds with compression release engine braking operations.

As shown inFIGS. 1-3, the valve train14of the ICE10includes an intake assembly90configured to control the flow of gasses between the cylinder26and the intake runner50, and an exhaust/brake assembly (EBA)94configured to control the flow of gasses between the cylinder26and the exhaust runner54. For the purposes of this application, only the EBA94will be described in detail herein.

The EBA94of the valve train14includes a pair of exhaust valves40a,40bselectively engagable with corresponding valve seats58a,58bof the exhaust runner54, a first cam lobe98having a first lift profile102, a second cam lobe106having a second lift profile110different than the first lift profile102, and a fulcrum bridge114extending between and engaging both exhaust valves40a,40b. The EBA94also includes a first input118in operable communication with the first cam lobe98, a second input122in operable communication with the second cam lobe106, and a lash adjuster (HLA)124. In the illustrated implementation, the EBA94forms a Type III valve train assembly. However, in alternative implementations, the capabilities described herein may be applied to alternative styles of valve train assemblies including, but not limited, to Type I, Type II, Type IV, and Type V.

Both exhaust valves40a,40bof the EBA94are substantially similar and include a head126configured to selectively engage a corresponding seat58a,58bof the exhaust runner54, and a stem130extending from the head126to produce a distal end134. Each exhaust valve40a,40balso includes a valve axis138extending therethrough. During operation, each exhaust valve40a,40bis movably mounted to the cylinder head22for movement with respect thereto along the valve axis138between a closed position (seeFIG. 1), in which the head126of the valve40a,40bengages and forms a seal with the corresponding seat58a,58bof the exhaust runner54(e.g., to fluidly isolate the cylinder26from the exhaust runner54), and an open position (seeFIG. 2), in which the head126of the valve40a,40bdoes not engage the corresponding seat58a,58b(e.g., allowing gasses to flow between the cylinder26and the exhaust runner54). Each exhaust valve40a,40balso includes an exhaust valve spring142coupled thereto and configured to bias the valve40a,40btoward the closed position.

During operation, each exhaust valve40a,40balso undergoes a process called “oil canning.” Oil canning is where the valve40a,40bis deformed from its natural shape such as a result of the high pressure forces present in the cylinder26during the positive power process (e.g., combustion) that cause the distal end134to become displaced. More specifically, only the perimeter146of the head126is in contact with its corresponding seat58a,58bwhen the exhaust valves40a,40bare in the closed position. As such, the center150of the head126, which is unsupported and spaced away from the perimeter146, deforms and deflects relative to the perimeter146as the pressure (P) acting on the inner surface152of the head126increases (e.g., during the engine braking process). This deflection, in turn, causes the distal end134of the stem130to move in a first direction A along the valve axis138at a first or oil can valve deflection rate154(seeFIG. 5D). For the purposes of this application, the oil can valve deflection rate154is defined as the rate of speed that the distal end134is displaced during the oil canning event. In the illustrated implementation, the exhaust valves40a,40bproduce an oil can valve deflection rate154of approximately 34 mm/sec, or approximately 35 mm/sec, or approximately 36 mm/sec. However, in alternative implementations, the oil can valve deflection rate154may range between approximately 34 mm/sec and approximately 50 mm/sec. In still other implementations, the oil can valve deflection rate154may range between approximately 38 mm/sec and approximately 42 mm/sec.

While the illustrated EBA94includes two exhaust valves40a,40b. It is to be understood that in alternative implementations one exhaust valve may be present (not shown), or more than two present.

As shown inFIGS. 5A-5D, the first cam lobe98of the EBA94is in operable communication with the first input118and includes a first lift profile102. The first lift profile102, in turn, includes timing, duration, and lift that are configured to produce positive power during operation of the ICE10(e.g., the first profile102accommodates the combustion cycle operations). More specifically, the first cam lobe98is configured to cause the first input118to open the exhaust valves40a,40bnear the beginning of the exhaust stroke82and close the exhaust valves40a,40bnear the conclusion of the exhaust stroke82(seeFIG. 5B). In the illustrated implementation, the first lift profile102produces a second valve deflection rate158. The second valve deflection rate158is generally defined as the rate at which the exhaust valves40a,40bopens as a result of the first cam lobe98(e.g., how fast the valves40a,40bopen at the beginning of the exhaust stroke82). In the illustrated implementation, the second valve deflection rate158is greater than the oil can valve deflection rate154. More specifically, the first cam lobe98is configured to produce a second valve deflection rate158of approximately 600 mm/sec. In still other implementations, the second valve deflection rate158is between approximately 500 mm/sec and 650 mm/sec.

As shown inFIGS. 5A-5D, the second cam lobe106of the EBA94is in operable communication with the second input122and includes a second lift profile110that is different than the first lift profile102. The second lift profile110, in turn, includes timing, duration, and lift, all of which are configured to produce negative power during operation of the ICE10(e.g., the second profile110accommodates the compression release engine braking operations). For example, the second lift profile110is configured to cause the second input122to open one or more of the exhaust valves40a,40bin the later stages of the compression stroke74and close the one or more exhaust valves40a,40bat approximately the beginning of the expansion stroke78(seeFIG. 5C). In the illustrated implementation, the second lift profile110produces a third valve deflection rate162. The third valve deflection rate162is generally defined as the rate at which the exhaust valves40a,40bopen as a result of the second cam lobe106(e.g., how fast the valves40a,40bopen at the end of the compression stroke74). In the illustrated implementation, the third valve deflection rate162is greater than the oil can valve deflection rate154. More specifically, the second cam lobe106is configured to produce a third valve deflection rate162of approximately 450 mm/sec. In still other implementations, the third valve deflection rate162is between approximately 400 mm/sec and 500 mm/sec.

As shown inFIGS. 1-3, the first input118is in operable communication with and extends between the first cam lobe98and the fulcrum bridge114to transmit forces therebetween. More specifically, the first input118includes a first rocker arm166having an elongated body170with a first contact point174, a second contact point178opposite the first contact point174, and a pivot182located between the first contact point174and the second contact point178. When assembled, the first rocker arm166is coupled to the cylinder head22at the pivot182such that the first contact point174is operatively engaged with the first cam lobe98(e.g., in contact with) and the second contact point178is operatively engaged with the fulcrum bridge114(e.g., via the HLA124).

During use, inputs from the first cam lobe98(e.g., changes in cam diameter) are transmitted to the exhaust valves40a,40b(e.g., via the fulcrum bridge114) by pivoting the first rocker arm166about its pivot182. More specifically, the first rocker arm166is configured to interact with the fulcrum bridge114such that inputs from the first cam lobe98actuate both exhaust valves40a,40btogether (described below). While the illustrated rocker arm166acts on the both valves40a,40bvia the HLA124and fulcrum bridge114, in alternative implementations, the second contact point178of the first rocker arm166may operably interact with the valves40a,40bdirectly or through other type of linkage (not shown).

As shown inFIGS. 2 and 3, the second input122is in operable communication with and extends between the second cam lobe106and the fulcrum bridge114to transmit forces therebetween. More specifically, the second input122includes a second rocker arm186having an elongated body190with a first contact point194, a second contact point198opposite the first contact point194, and a pivot202located between the first contact point194and the second contact point198. When assembled, the second rocker arm186is pivotally coupled to the cylinder head22at the pivot202such that the first contact point194is operatively engaged with the second cam lobe106(e.g., in contact with) and the second contact point198is operatively engaged with the fulcrum bridge114. During use, inputs from the second cam lobe106(e.g., changes in cam diameter) are transmitted to one of the two exhaust valves40a,40b(e.g., via the fulcrum bridge114) by pivoting the second rocker arm186about its pivot202. While the illustrated rocker arm186acts on a single exhaust valve40avia a fulcrum bridge114, in alternative implementations, the second end198of the second rocker arm186may operably interact with the valve40aeither directly or through other types of linkage (not shown). For example, the rocker arm186may include a hydraulic plunger252to transmit force between the rocker arm186and the fulcrum bridge114. In still other implementations, the hydraulic plunger252may be replaced with a normally open HLA124(not shown) as described below. Furthermore, in alternative implementations, the second rocker arm186may be configured to actuate both exhaust valves40a,40b.

As shown inFIGS. 2 and 3, the fulcrum bridge114of the EBA94includes an elongated and rigid body206having a first contact point210, a second contact point214, a third contact point218positioned between the first contact point210and the second contact point214, and a fourth contact point222that is not positioned between the first contact point210and the second contact point214(e.g., outside the region between the first contact point210and the second contact point214). When the EBA94is assembled, the first contact point210directly engages the distal end134of the first exhaust valve40aand the second contact point214directly engages the distal end134of the second exhaust valve40b. Furthermore, the third contact point218is in operable communication with the first input118(e.g., via the HLA124, described below), and the fourth contact point222is in operable communication with the second input122. During use, the relative locations of the four contact points210,214,218,222are configured such that applying force to the third contact point218causes both exhaust valves40a,40bto open while applying force to the fourth contact point222causes only the first exhaust valve40ato open. Furthermore, the fourth contact point222is located such that applying a force thereto causes a reaction force (F1) to be applied to the first input118via the third contact point218(e.g. via the HLA124; seeFIG. 2).

As shown inFIGS. 2-4, the HLA124is positioned between and configured to selectively transmit forces between the second contact point178of the first input118and the exhaust valves40a,40bvia the fulcrum bridge114. More specifically, the HLA124is a normally-open lash adjuster having a body226with a first end230, and a second end234opposite the first end230. Together, the first end230and the second end234define a lash adjuster length238therebetween.

The HLA124is adjustable between a closed configuration, in which the first end230is fixed relative to the second end234(e.g., the adjuster length238is fixed), and an open configuration, in which the first end230is movable relative to the second end234(e.g., the adjuster length238is variable). During use, the HLA124is normally in the open configuration and only transitions to the closed configuration when the relative velocity between the first end230and the second end234(hereinafter the “HLA velocity”) exceeds a pre-determined value—herein referred to as the critical velocity. In the illustrated implementation, the critical velocity of the HLA124is greater than the oil can deflection rate154but less than the second valve deflection rate158of the first cam lobe98. By placing the critical velocity within the above described range, the HLA124remains open when oil canning occurs but closes when the valve30a,40bis required to open. Therefore the potentially damaging forces produced by oil canning are not transmitted back into the valve train14but the valves40a,40bcan still be opened as required for positive power and engine braking operations. In the illustrated implementation, the critical velocity of the HLA124is approximately 40 mm/sec at 130° C. engine oil temperature. In still other implementations, the critical velocity is between approximately 34 mm/sec and approximately 44 mm/sec. In still other implementations, the critical velocity is greater than approximately 34 mm/sec.

In the illustrated implementation, the body226of the HLA124includes a first body portion250at least partially defining a chamber254therein, a second body portion258at least partially positioned and movable within the chamber254, and a check valve262to selectively control the flow of fluid (e.g., oil) into and out of the chamber254. As shown inFIG. 4, the first body portion250defines the first end230, the second body portion258defines the second end234, and relative movement between the first body portion250and the second body portion258cause the size of the chamber254and the adjuster length238to change. More specifically, removing the second body portion258from the chamber254causes the chamber size to increase and the adjuster length238to increase while inserting the second body portion258further into the chamber254causes the chambers size to decrease and the adjuster length238to decrease.

The check valve262of the HLA124is adjustable between an open position, in which a check ball is not engaged with its corresponding seat such that fluid can enter and exit the chamber254, and a closed position, in which the check ball is engaged with its corresponding seat and fluid generally does not enter and exit the chamber254. The check valve262also includes a biasing member266(e.g., a spring) configured to bias the check valve262in the open position. Furthermore, the attributes of the biasing member266are such that they produce the desired critical velocity. When the check valve262is in the closed position, as a result the first body portion250is fixed relative to the second body portion258causing the adjuster length238to be effectively fixed (e.g., the HLA124is in the closed configuration). In contrast, when the check valve262is in the open position (e.g., fluid is able to enter and exit the chamber254), the first body portion250is movable relative to the second body portion258causing the adjust length238to be variable (e.g., the HLA124is in the closed configuration).

While the illustrated implementation discloses a normally open HLA124positioned between the first rocker arm166and the fulcrum bridge114, it is to be understood that the HLA124may be re-positioned within the valve train14as necessary to accommodate different valve train types. For example, in instances where no fulcrum bridge114is present, the HLA124may extend between the first rocker arm166and the valve40a,40b(not shown). In still other implementations where no rocker arms are present, the HLA124may be positioned between the first cam lobe98and the valves40a,40bor the first cam lobe98and the fulcrum bridge114.

Still further, while the illustrated second input122acts directly on the fulcrum bridge114with no HLA124present, it is to be understood that in alternative implementations, an HLA124may be used to selectively transmit forces therebetween as well. In such implementations, the HLA124would have a critical velocity that is greater than the oil can valve deflection rate154and less than the third valve deflection rate162.

While not described in detail herein, it is to be understood that an HLA124as described above may also be incorporated into the intake assembly90to aid the opening and closing of the intake valves40c(seeFIG. 1). In such implementations, the layout of the intake assembly90would be substantially similar to the layout of the EBA94. The intake valves40cwould define an “intake oil can valve deflection rate” specific to the intake valve40cdesigns and an “intake second valve deflection rate” specific to the cam profile of the intake cam lobe270. Furthermore, the HLA124incorporated into the intake assembly90would have a critical velocity that is greater than the intake oil cam valve deflection rate and less than the intake second valve deflection rate.

During positive power operation of the ICE10, the ICE undergoes standard four-stroke combustion cycle as is well known in the art (seeFIG. 5Aand valve travel path100inFIG. 5D). More specifically, the piston36reciprocally travels within the cylinder26between TDC and BDC during the intake stroke70, compression stroke74, power stroke78, and exhaust stroke82causing the crank shaft30to rotate about the crank axis34in the first direction of rotation66. Only the aspects of the combustion process relevant to the operation of the HLA124will be described in detail herein.

During the compression stroke74, the exhaust valves40a,40bare in the closed position. As the piston36travels from BDC toward TDC, the piston36compresses the air within the cylinder26causing the pressure within the cylinder26to increase. As the pressure increases within the cylinder26, the pressure is exerted against the inner surface152of both valves40a,40bcausing them to deform (e.g., undergo the oil canning process; described above). More specifically, the center150of the head126deflects relative to the perimeter146causing the distal end134of the stem130of both valves40a,40bto move in the first direction A at the oil can valve deflection rate154(seeFIG. 5D).

The resulting movement of the distal ends134of both exhaust valves40a,40bare exerted against the fulcrum bridge114at the first and second contact points210,214. This causes the fulcrum bridge114to also travel at the oil can valve deflection rate154in the first direction A. As a result, the fulcrum bridge114exerts the force and motion into the HLA124via the third contact point218, again at the oil can valve deflection rate154. Since the oil can valve deflection rate154is below the critical velocity of the HLA124(described above), the HLA124remains in the open position (e.g., the check valve262remains open). Since the HLA124is open, the second end234in contact with the fulcrum bridge114is able to move relative to the first end230in contact with the first input118such that little to no force is transmitted to the first input118. As such, the movement and force created by the oil canning process is not transmitted to the first input118or the remainder of the valve train14.

During the exhaust stroke82, the exhaust valves40a,40bbegin in the closed position. As the first cam lobe98rotates the first lift profile102is configured to provide an input (e.g., lift) to the first rocker arm166(e.g., the first input118). This input, in turn, causes the first rocker arm166to rotate about its pivot182and exert a force against the third contact point218of the fulcrum bridge114via the HLA124. As described above, the first lift profile102is configured to bias the valves40a,40btoward the open position at the second valve deflection rate. Since the second valve deflection rate is greater than the critical velocity, the HLA124transitions into the closed configuration (e.g., the check valve262closes). By doing so, the first end230of the HLA124is fixed relative to the second end234and the movement of the first rocker arm166is directly transmitted to the fulcrum bridge114. As such, the movement and force created by the first cam lobe98to open the exhaust valves40a,40bare transmitted to the valves themselves.

During engine braking operation of the ICE10(see valve travel path104ofFIG. 5D), the second cam lobe106provides inputs to the valve train14. More specifically, late in the compression stroke74the second lift profile110is configured to provide an input (e.g., lift) to the second rocker arm186(e.g., the second input122). This input, in turn, causes the second rocker arm186to rotate about its pivot202and exert a force against the fourth contact point222of the fulcrum bridge114. Due to the relative position of the fourth contact point222(e.g., not between the first and second contact points210,214), the force applied by the second rocker arm186causes only the first exhaust valve40ato open and exerts a reaction force (F1) against the HLA124via the third contact point218(seeFIG. 2). By doing so, the HLA124remains under compression even during the engine braking operations and therefore does not inadvertently extend, a process known as “jacking.”